feat: complete NX9-Auth management and integrity hardening

README.md

@@ -61,6 +61,24 @@ Existing applications upgraded from earlier schemas receive a stable Client ID.
 
 > **Protocol boundary:** Application credentials, redirect URIs, and scopes form the application registration layer. Redirect URIs are registration metadata intended to become security-enforced redirect destinations when OAuth2/OIDC protocol handlers are implemented. This registration subsystem does not by itself claim complete OAuth2/OIDC grant-flow support.
 
+### Application user membership
+
+Registered applications can be assigned existing NX9-Auth users (same-tenant only). Membership is independent of application client credentials and of global RBAC:
+
+| Concern | Role |
+| --- | --- |
+| Application credentials | Authenticate the registered application itself (`client_id` + `client_secret`) |
+| Application membership | Assign existing human users to an application (`owner` / `admin` / `member` metadata) |
+| Global RBAC | Authoritative admin authorization (`applications:manage`, roles, permissions) |
+
+Membership APIs (all require `applications:manage`):
+
+- `GET/POST /api/v1/applications/:id/members`
+- `PATCH/DELETE /api/v1/applications/:id/members/:user_id`
+- `GET /api/v1/users/:id/applications`
+
+Membership roles do **not** grant `applications:manage` or any other global permission. Removing membership revokes application assignment only; it does not delete the user account.
+
 ---
 
 ## Runtime Lifecycle

docs/ARCHITECTURE.md

@@ -36,7 +36,30 @@ The internal architecture is guided by structural design patterns:
 
 ---
 
-# 4. Technology Stack
+# 4. Data & Multi-Tenancy Architecture
+
+### Option-A Single-Tenant User Ownership
+NX9-Auth models user ownership via **Option-A Single-Tenant Ownership**:
+- Every user belongs to exactly one tenant (`users.tenant_id NOT NULL REFERENCES tenants(id)`).
+- Uniqueness invariant: `UNIQUE (tenant_id, username)`.
+- Tenant reassignment is transactionally atomic (`reassign_user_tenant_with_audit`):
+  1. Executes inside a single write transaction.
+  2. PostgreSQL uses `SELECT ... FOR UPDATE` row locking; SQLite uses write transactions and conditional `WHERE tenant_id = expected` updates.
+  3. Reassignment to the user's current tenant is a defined no-op returning `Ok(())` without writing false audit logs.
+  4. Database mutation (`UPDATE users.tenant_id`) and audit log insertion (`user.tenant_reassigned` with `from_tenant_id` and `to_tenant_id`) commit together; audit log failures trigger automatic database rollback.
+
+### Application Membership vs Global RBAC
+- **Application Membership**: Users are assigned to applications within their home tenant only (`ApplicationMember`). Membership roles (`owner`/`admin`/`member`) are application-scoped metadata.
+- **Global RBAC**: Platform authorization is governed strictly by global roles, permissions, and groups (`users.tenant_id`). Application membership roles never leak into or modify global RBAC.
+- **Application Membership Mutations**: Add, role update, enable/disable, and removal operations execute as single database transactions; failure to write audit logs automatically rolls back the membership mutation.
+
+### Global Slugs Registry & Lifecycle
+- `global_slugs` table enforces global uniqueness across tenant, application, and resource slugs.
+- Immutable UUID identities remain canonical; slugs serve as human-readable routing aliases.
+
+---
+
+# 5. Technology Stack
 
 ### Backend
 - **Core Language**: Rust (2024 Edition)

docs/SECURITY.md

@@ -31,11 +31,26 @@ NX9-Auth is designed with a **security-first, privacy-first, zero-trust** archit
 - **Secret Rotation**: Administrator rotation immediately invalidates the previous client secret hash and generates a new secret.
 - **Dedicated Permissions**: Application mutations (`create`, `update`, `rotate_secret`, `enable_disable`, `delete`) require the `applications:manage` permission.
 
-## Audit Logging Security
+## Tenant Reassignment Safety & Audit Atomicity
+
+- **Option-A Tenant Isolation**: Users belong strictly to one tenant (`users.tenant_id`). Cross-tenant operations strictly check boundaries.
+- **Transactional Atomicity**: Tenant reassignment (`reassign_user_tenant_with_audit`) executes inside a single database transaction. Database update (`users.tenant_id`) and audit log record insertion (`user.tenant_reassigned` with `from_tenant_id` and `to_tenant_id`) commit together. If audit log insertion fails, database changes roll back completely.
+- **No-Op Reassignment**: Reassignment to the user's current tenant is a defined no-op that emits no audit log and avoids unnecessary database mutations.
+- **Concurrency & Locking Protection**: PostgreSQL uses `SELECT ... FOR UPDATE` row locking; SQLite uses write transactions and conditional updates (`WHERE tenant_id = expected`).
+- **Last-Admin Protection**: System administrator reassignment away from the default tenant is rejected if `count_admins() <= 1`.
+
+## Application Membership Security & Audit Atomicity
+
+- **Same-Tenant Enforcement**: Application membership requires user and application to share the exact same `tenant_id`. Cross-tenant membership is rejected.
+- **Transactional Atomicity**: Application membership mutations (add, role update, enable/disable, remove) execute in single transactions with audit log insertions; audit failure automatically rolls back the membership change.
+- **Strict Protocol Boundary**: Application authentication accepts only `client_id` + `client_secret`. Editable application slugs are never accepted as credential identities.
+
+## Audit Logging Security & Export
 
 Audit logs record critical identity lifecycle events while strictly redacting sensitive fields:
-- **Recorded Events**: Login success/failure, logout, password change, user creation/deletion, API token issuance/revocation, application creation/secret rotation/modification, role/permission assignments.
+- **Recorded Events**: Login success/failure, logout, password change, user creation/deletion, tenant reassignment, API token issuance/revocation, application creation/secret rotation/membership modification, role/permission assignments.
 - **Redaction Rules**: Plaintext passwords, password hashes, bearer tokens, refresh tokens, client secrets, client secret hashes, session secrets, and `Authorization` headers are **never** logged under any circumstances.
+- **Bounded CSV Export**: Audit log CSV export uses server-side audit search APIs bounded to a maximum of 5,000 records matching currently active query filters, preserving exact tenant/RBAC restrictions and RFC-4180 field escaping.
 
 ## Rate Limiting & Protection
 

src/api/applications.rs

@@ -7,9 +7,9 @@ use serde::{Deserialize, Serialize};
 use serde_json::{Value, json};
 
 use crate::{
-    db::models::{Application, Tenant},
-    error::Result,
-    identity::applications as identity,
+    db::models::{Application, ApplicationMember, Tenant},
+    error::{AppError, Result},
+    identity::{application_members as members, applications as identity},
     middleware::{auth::AuthUser, permissions::require},
     state::AppState,
 };
@@ -201,3 +201,171 @@ pub async fn delete_application(
     identity::delete(&state.provider, &id, Some(&auth.user.id), None, None).await?;
     Ok(Json(json!({ "success": true })))
 }
+
+// ── Application membership ────────────────────────────────────────────────────
+
+#[derive(Serialize)]
+pub struct ApplicationMemberResponse {
+    pub id: String,
+    pub application_id: String,
+    pub user_id: String,
+    pub username: String,
+    pub user_status: String,
+    pub role: String,
+    pub enabled: bool,
+    pub created_at: String,
+    pub updated_at: String,
+}
+
+impl ApplicationMemberResponse {
+    fn from_member(member: ApplicationMember, username: String, user_status: String) -> Self {
+        Self {
+            id: member.id,
+            application_id: member.application_id,
+            user_id: member.user_id,
+            username,
+            user_status,
+            role: member.role,
+            enabled: member.enabled,
+            created_at: member.created_at,
+            updated_at: member.updated_at,
+        }
+    }
+}
+
+async fn enrich_member(
+    state: &AppState,
+    member: ApplicationMember,
+) -> Result<ApplicationMemberResponse> {
+    let user = state
+        .provider
+        .users()
+        .find_by_id(&member.user_id)
+        .await
+        .map_err(AppError::Database)?;
+
+    let (username, user_status) = match user {
+        Some(u) => (
+            u.username,
+            if u.status == 1 {
+                "active".to_string()
+            } else if u.status == 3 {
+                "locked".to_string()
+            } else {
+                "disabled".to_string()
+            },
+        ),
+        None => ("unknown".to_string(), "unknown".to_string()),
+    };
+
+    Ok(ApplicationMemberResponse::from_member(
+        member,
+        username,
+        user_status,
+    ))
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct CreateMemberRequest {
+    pub user_id: String,
+    pub role: Option<String>,
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(deny_unknown_fields)]
+pub struct UpdateMemberRequest {
+    pub role: Option<String>,
+    pub enabled: Option<bool>,
+}
+
+/// GET /api/v1/applications/:id/members
+pub async fn list_application_members(
+    State(state): State<AppState>,
+    auth: AuthUser,
+    Path(id): Path<String>,
+) -> Result<Json<Value>> {
+    require(&state.provider, &auth.user.id, MANAGE_PERM).await?;
+
+    let members_list = members::list_by_application(&state.provider, &id).await?;
+    let mut views = Vec::with_capacity(members_list.len());
+    for m in members_list {
+        views.push(enrich_member(&state, m).await?);
+    }
+
+    Ok(Json(json!({ "members": views })))
+}
+
+/// POST /api/v1/applications/:id/members
+pub async fn add_application_member(
+    State(state): State<AppState>,
+    auth: AuthUser,
+    Path(id): Path<String>,
+    Json(body): Json<CreateMemberRequest>,
+) -> Result<Json<Value>> {
+    require(&state.provider, &auth.user.id, MANAGE_PERM).await?;
+
+    if body.user_id.trim().is_empty() {
+        return Err(AppError::InvalidInput("user_id is required".into()));
+    }
+
+    let member = members::add(
+        &state.provider,
+        &id,
+        body.user_id.trim(),
+        body.role.as_deref(),
+        Some(&auth.user.id),
+        None,
+        None,
+    )
+    .await?;
+
+    let view = enrich_member(&state, member).await?;
+    Ok(Json(json!({ "member": view })))
+}
+
+/// PATCH /api/v1/applications/:id/members/:user_id
+pub async fn update_application_member(
+    State(state): State<AppState>,
+    auth: AuthUser,
+    Path((id, user_id)): Path<(String, String)>,
+    Json(body): Json<UpdateMemberRequest>,
+) -> Result<Json<Value>> {
+    require(&state.provider, &auth.user.id, MANAGE_PERM).await?;
+
+    let member = members::update(
+        &state.provider,
+        &id,
+        &user_id,
+        body.role.as_deref(),
+        body.enabled,
+        Some(&auth.user.id),
+        None,
+        None,
+    )
+    .await?;
+
+    let view = enrich_member(&state, member).await?;
+    Ok(Json(json!({ "member": view })))
+}
+
+/// DELETE /api/v1/applications/:id/members/:user_id
+pub async fn remove_application_member(
+    State(state): State<AppState>,
+    auth: AuthUser,
+    Path((id, user_id)): Path<(String, String)>,
+) -> Result<Json<Value>> {
+    require(&state.provider, &auth.user.id, MANAGE_PERM).await?;
+
+    members::remove(
+        &state.provider,
+        &id,
+        &user_id,
+        Some(&auth.user.id),
+        None,
+        None,
+    )
+    .await?;
+
+    Ok(Json(json!({ "success": true })))
+}

src/api/audit.rs

@@ -84,6 +84,7 @@ pub async fn list_audit(
         since: query.since,
         until: query.until,
         search: query.q,
+        success: query.success,
         limit,
         offset,
     };
@@ -92,19 +93,10 @@ pub async fn list_audit(
         .await
         .map_err(AppError::Database)?;
 
-    let mut entries = audit_repo::list_filtered(&state.provider, &filter)
+    let entries = audit_repo::list_filtered(&state.provider, &filter)
         .await
         .map_err(AppError::Database)?;
 
-    if let Some(success) = query.success {
-        entries.retain(|e| {
-            let ok = !e.action.contains("fail")
-                && !e.action.contains("denied")
-                && e.severity != "critical";
-            ok == success
-        });
-    }
-
     let views: Vec<AuditLogResponse> = entries.into_iter().map(AuditLogResponse::from).collect();
 
     Ok(Json(json!({
@@ -114,3 +106,72 @@ pub async fn list_audit(
         "offset": offset,
     })))
 }
+
+/// GET /api/v1/audit/export
+pub async fn export_audit(
+    State(state): State<AppState>,
+    auth: AuthUser,
+    Query(query): Query<AuditQuery>,
+) -> Result<axum::response::Response> {
+    use axum::response::IntoResponse;
+
+    require(&state.provider, &auth.user.id, "audit:view").await?;
+
+    let limit = query.limit.unwrap_or(5000).clamp(1, 5000);
+    let offset = query.offset.unwrap_or(0).max(0);
+
+    let filter = AuditFilter {
+        actor_user_id: query.actor,
+        action: query.action,
+        resource_type: query.resource_type,
+        severity: query.severity,
+        since: query.since,
+        until: query.until,
+        search: query.q,
+        success: query.success,
+        limit,
+        offset,
+    };
+
+    let entries = audit_repo::list_filtered(&state.provider, &filter)
+        .await
+        .map_err(AppError::Database)?;
+
+    let mut csv = String::from(
+        "id,created_at,action,resource_type,resource_id,severity,success,actor_user_id,target_user_id,ip_address,user_agent,metadata_json\r\n",
+    );
+    for e in entries {
+        let resp = AuditLogResponse::from(e);
+        let esc = |s: &str| format!("\"{}\"", s.replace('"', "\"\""));
+        let line = format!(
+            "{},{},{},{},{},{},{},{},{},{},{},{}\r\n",
+            esc(&resp.id),
+            esc(&resp.created_at),
+            esc(&resp.action),
+            esc(&resp.resource_type),
+            esc(resp.resource_id.as_deref().unwrap_or("")),
+            esc(&resp.severity),
+            resp.success,
+            esc(resp.actor_user_id.as_deref().unwrap_or("")),
+            esc(resp.target_user_id.as_deref().unwrap_or("")),
+            esc(resp.ip_address.as_deref().unwrap_or("")),
+            esc(resp.user_agent.as_deref().unwrap_or("")),
+            esc(resp.metadata_json.as_deref().unwrap_or("")),
+        );
+        csv.push_str(&line);
+    }
+
+    let response = (
+        [
+            (axum::http::header::CONTENT_TYPE, "text/csv; charset=utf-8"),
+            (
+                axum::http::header::CONTENT_DISPOSITION,
+                "attachment; filename=\"audit_export.csv\"",
+            ),
+        ],
+        csv,
+    )
+        .into_response();
+
+    Ok(response)
+}

src/api/router.rs

@@ -1,7 +1,7 @@
 use axum::http::{HeaderName, Method, header};
 use axum::{
     Router, middleware,
-    routing::{delete, get, post, put},
+    routing::{delete, get, patch, post, put},
 };
 use tower_http::{compression::CompressionLayer, cors::CorsLayer, trace::TraceLayer};
 
@@ -40,6 +40,18 @@ pub fn build(state: AppState) -> Router {
                 .patch(tenants::update_tenant)
                 .delete(tenants::delete_tenant),
         )
+        .route(
+            "/tenants/{id}/users",
+            get(tenants::list_tenant_users).post(tenants::assign_tenant_user),
+        )
+        .route(
+            "/tenants/{id}/users/{user_id}",
+            delete(tenants::remove_tenant_user),
+        )
+        .route(
+            "/tenants/{id}/applications",
+            get(tenants::list_tenant_applications),
+        )
         // Users
         .route("/users", get(users::list_users).post(users::create_user))
         .route(
@@ -54,6 +66,10 @@ pub fn build(state: AppState) -> Router {
             get(users::list_user_roles).post(roles::assign_user_role),
         )
         .route("/users/{id}/roles/{role}", delete(roles::remove_user_role))
+        .route(
+            "/users/{id}/applications",
+            get(users::list_user_applications),
+        )
         // Roles
         .route("/roles", get(roles::list_roles).post(roles::create_role))
         .route(
@@ -86,6 +102,15 @@ pub fn build(state: AppState) -> Router {
             "/applications/{id}/secret",
             post(applications::rotate_application_secret),
         )
+        .route(
+            "/applications/{id}/members",
+            get(applications::list_application_members).post(applications::add_application_member),
+        )
+        .route(
+            "/applications/{id}/members/{user_id}",
+            patch(applications::update_application_member)
+                .delete(applications::remove_application_member),
+        )
         // Service accounts
         .route(
             "/service-accounts",
@@ -104,6 +129,7 @@ pub fn build(state: AppState) -> Router {
         )
         // Audit
         .route("/audit", get(audit::list_audit))
+        .route("/audit/export", get(audit::export_audit))
         // Sessions
         .route("/sessions", get(sessions::list_sessions))
         .route("/sessions/others", delete(sessions::terminate_others))

src/api/tenants.rs

@@ -53,6 +53,12 @@ pub async fn create_tenant(
 ) -> Result<Json<Value>> {
     require(&state.provider, &auth.user.id, "roles:manage").await?;
 
+    if let Some(ref s) = body.slug {
+        if !s.trim().is_empty() {
+            crate::identity::slug::validate_slug(s)?;
+        }
+    }
+
     let id = uuid::Uuid::new_v4().to_string();
     let tenant = state
         .provider
@@ -118,6 +124,12 @@ pub async fn update_tenant(
 ) -> Result<Json<Value>> {
     require(&state.provider, &auth.user.id, "roles:manage").await?;
 
+    if let Some(ref s) = body.slug {
+        if !s.trim().is_empty() {
+            crate::identity::slug::validate_slug(s)?;
+        }
+    }
+
     state
         .provider
         .tenants()
@@ -183,3 +195,153 @@ pub async fn delete_tenant(
 
     Ok(Json(json!({ "success": true })))
 }
+
+/// GET /api/v1/tenants/:id/users
+pub async fn list_tenant_users(
+    State(state): State<AppState>,
+    auth: AuthUser,
+    Path(id): Path<String>,
+) -> Result<Json<Value>> {
+    require(&state.provider, &auth.user.id, "roles:manage").await?;
+
+    let users = state.provider.users().list(&id).await?;
+    let views: Vec<crate::api::users::UserResponse> = users
+        .into_iter()
+        .map(crate::api::users::UserResponse::from)
+        .collect();
+    Ok(Json(json!({ "users": views })))
+}
+
+#[derive(Debug, Deserialize)]
+pub struct AssignTenantUserRequest {
+    pub user_id: String,
+}
+
+/// POST /api/v1/tenants/:id/users
+pub async fn assign_tenant_user(
+    State(state): State<AppState>,
+    auth: AuthUser,
+    ctx: AuditContext,
+    Path(id): Path<String>,
+    Json(body): Json<AssignTenantUserRequest>,
+) -> Result<Json<Value>> {
+    require(&state.provider, &auth.user.id, "roles:manage").await?;
+
+    let _tenant = state
+        .provider
+        .tenants()
+        .find_by_id(&id)
+        .await?
+        .ok_or(crate::error::AppError::NotFound)?;
+
+    let user = state
+        .provider
+        .users()
+        .find_by_id(&body.user_id)
+        .await?
+        .ok_or(crate::error::AppError::NotFound)?;
+
+    let from_tenant_id = user.tenant_id.clone();
+    if from_tenant_id == id {
+        return Ok(Json(
+            json!({ "user": crate::api::users::UserResponse::from(user) }),
+        ));
+    }
+
+    if state
+        .provider
+        .users()
+        .username_exists(&id, &user.username)
+        .await?
+    {
+        return Err(crate::error::AppError::Conflict(format!(
+            "username '{}' already exists in target tenant",
+            user.username
+        )));
+    }
+
+    state
+        .provider
+        .users()
+        .reassign_user_tenant_with_audit(
+            &user.id,
+            &id,
+            Some(&auth.user.id),
+            ctx.ip_address.as_deref(),
+            ctx.user_agent.as_deref(),
+        )
+        .await?;
+
+    let updated_user = state
+        .provider
+        .users()
+        .find_by_id(&user.id)
+        .await?
+        .ok_or(crate::error::AppError::NotFound)?;
+
+    Ok(Json(
+        json!({ "user": crate::api::users::UserResponse::from(updated_user) }),
+    ))
+}
+
+/// DELETE /api/v1/tenants/:id/users/:user_id
+pub async fn remove_tenant_user(
+    State(state): State<AppState>,
+    auth: AuthUser,
+    ctx: AuditContext,
+    Path((id, user_id)): Path<(String, String)>,
+) -> Result<Json<Value>> {
+    require(&state.provider, &auth.user.id, "roles:manage").await?;
+
+    if id == Tenant::DEFAULT_ID {
+        return Err(crate::error::AppError::InvalidInput(
+            "users cannot be moved out of default tenant without specifying a destination tenant"
+                .into(),
+        ));
+    }
+
+    let user = state
+        .provider
+        .users()
+        .find_by_id(&user_id)
+        .await?
+        .ok_or(crate::error::AppError::NotFound)?;
+
+    if user.tenant_id != id {
+        return Err(crate::error::AppError::InvalidInput(
+            "user does not belong to the specified tenant".into(),
+        ));
+    }
+
+    let target_tenant = Tenant::DEFAULT_ID;
+
+    state
+        .provider
+        .users()
+        .reassign_user_tenant_with_audit(
+            &user.id,
+            target_tenant,
+            Some(&auth.user.id),
+            ctx.ip_address.as_deref(),
+            ctx.user_agent.as_deref(),
+        )
+        .await?;
+
+    Ok(Json(json!({ "success": true })))
+}
+
+/// GET /api/v1/tenants/:id/applications
+pub async fn list_tenant_applications(
+    State(state): State<AppState>,
+    auth: AuthUser,
+    Path(id): Path<String>,
+) -> Result<Json<Value>> {
+    require(&state.provider, &auth.user.id, "roles:manage").await?;
+
+    let apps = state.provider.applications().list(&id).await?;
+    let views: Vec<crate::api::applications::ApplicationResponse> = apps
+        .into_iter()
+        .map(crate::api::applications::ApplicationResponse::from)
+        .collect();
+    Ok(Json(json!({ "applications": views })))
+}

src/api/users.rs

@@ -9,7 +9,7 @@ use crate::{
     db::models::Tenant,
     db::models::{User, UserStatus},
     error::{AppError, Result},
-    identity::users as identity,
+    identity::{application_members as members, users as identity},
     middleware::{audit::AuditContext, auth::AuthUser, permissions::require},
     state::AppState,
 };
@@ -20,6 +20,7 @@ use crate::{
 pub struct UserResponse {
     pub id: String,
     pub username: String,
+    pub tenant_id: String,
     pub status: String,
     pub last_login_at: Option<String>,
     pub created_at: String,
@@ -29,8 +30,9 @@ pub struct UserResponse {
 impl From<User> for UserResponse {
     fn from(u: User) -> Self {
         Self {
-            id: u.id,
+            id: u.id.clone(),
             username: u.username,
+            tenant_id: u.tenant_id,
             status: UserStatus::from_i32(u.status).to_string(),
             last_login_at: u.last_login_at,
             created_at: u.created_at,
@@ -215,3 +217,79 @@ pub async fn list_user_roles(
         }).collect::<Vec<_>>(),
     })))
 }
+
+/// GET /api/v1/users/:id/applications
+///
+/// Reverse lookup: list applications assigned to a user via membership.
+/// Requires `applications:manage` (membership administration).
+pub async fn list_user_applications(
+    State(state): State<AppState>,
+    auth: AuthUser,
+    Path(id): Path<String>,
+) -> Result<Json<Value>> {
+    require(
+        &state.provider,
+        &auth.user.id,
+        crate::api::applications::MANAGE_PERM,
+    )
+    .await?;
+
+    let memberships = members::list_by_user(&state.provider, &id).await?;
+
+    #[derive(Serialize)]
+    struct UserApplicationView {
+        id: String,
+        application_id: String,
+        user_id: String,
+        role: String,
+        enabled: bool,
+        created_at: String,
+        updated_at: String,
+        application_name: String,
+        application_slug: String,
+        application_enabled: bool,
+        client_id: String,
+        credentials_configured: bool,
+    }
+
+    let mut views = Vec::with_capacity(memberships.len());
+    for m in memberships {
+        let app = state
+            .provider
+            .applications()
+            .find_by_id(&m.application_id)
+            .await
+            .map_err(AppError::Database)?;
+
+        let (name, slug, app_enabled, client_id, credentials_configured) = match app {
+            Some(a) => {
+                let credentials_configured = a.has_credentials();
+                (
+                    a.name,
+                    a.slug.unwrap_or_default(),
+                    a.enabled,
+                    a.client_id,
+                    credentials_configured,
+                )
+            }
+            None => continue,
+        };
+
+        views.push(UserApplicationView {
+            id: m.id,
+            application_id: m.application_id,
+            user_id: m.user_id,
+            role: m.role,
+            enabled: m.enabled,
+            created_at: m.created_at,
+            updated_at: m.updated_at,
+            application_name: name,
+            application_slug: slug,
+            application_enabled: app_enabled,
+            client_id,
+            credentials_configured,
+        });
+    }
+
+    Ok(Json(json!({ "applications": views })))
+}

src/db/migrations/postgres/0013_seed_default_tenant.sql

@@ -1,4 +1,4 @@
 -- Seed the default tenant.
--- Uses INSERT OR IGNORE so re-running migrations is safe.
-INSERT OR IGNORE INTO tenants (id, name, slug, enabled)
-VALUES ('00000000-0000-0000-0000-000000000001', 'Default', 'default', 1);
+INSERT INTO tenants (id, name, slug, enabled)
+VALUES ('00000000-0000-0000-0000-000000000001', 'Default', 'default', 1)
+ON CONFLICT (id) DO NOTHING;

src/db/migrations/postgres/0014_seed_roles_and_permissions.sql

@@ -1,35 +1,40 @@
 -- ── Roles ────────────────────────────────────────────────────────────────────
 
-INSERT OR IGNORE INTO roles (id, name, description) VALUES
+INSERT INTO roles (id, name, description) VALUES
     ('10000000-0000-0000-0000-000000000001', 'admin',  'Full system access'),
     ('10000000-0000-0000-0000-000000000002', 'editor', 'Can manage content and users'),
-    ('10000000-0000-0000-0000-000000000003', 'viewer', 'Read-only access');
+    ('10000000-0000-0000-0000-000000000003', 'viewer', 'Read-only access')
+ON CONFLICT DO NOTHING;
 
 -- ── Permissions ───────────────────────────────────────────────────────────────
 
-INSERT OR IGNORE INTO permissions (id, name, description) VALUES
+INSERT INTO permissions (id, name, description) VALUES
     ('20000000-0000-0000-0000-000000000001', 'users:create',  'Create new user accounts'),
     ('20000000-0000-0000-0000-000000000002', 'users:update',  'Update user accounts'),
     ('20000000-0000-0000-0000-000000000003', 'users:delete',  'Disable user accounts'),
     ('20000000-0000-0000-0000-000000000004', 'tokens:create', 'Create API tokens for any user'),
     ('20000000-0000-0000-0000-000000000005', 'tokens:revoke', 'Revoke API tokens for any user'),
     ('20000000-0000-0000-0000-000000000006', 'roles:manage',  'Assign and revoke roles'),
-    ('20000000-0000-0000-0000-000000000007', 'audit:view',    'View audit log entries');
+    ('20000000-0000-0000-0000-000000000007', 'audit:view',    'View audit log entries')
+ON CONFLICT DO NOTHING;
 
 -- ── Admin role gets all permissions ──────────────────────────────────────────
 
-INSERT OR IGNORE INTO role_permissions (role_id, permission_id)
-SELECT '10000000-0000-0000-0000-000000000001', id FROM permissions;
+INSERT INTO role_permissions (role_id, permission_id)
+SELECT '10000000-0000-0000-0000-000000000001', id FROM permissions
+ON CONFLICT DO NOTHING;
 
 -- ── Editor role permissions ───────────────────────────────────────────────────
 
-INSERT OR IGNORE INTO role_permissions (role_id, permission_id) VALUES
+INSERT INTO role_permissions (role_id, permission_id) VALUES
     ('10000000-0000-0000-0000-000000000002', '20000000-0000-0000-0000-000000000001'),
-    ('10000000-0000-0000-0000-000000000002', '20000000-0000-0000-0000-000000000002');
+    ('10000000-0000-0000-0000-000000000002', '20000000-0000-0000-0000-000000000002')
+ON CONFLICT DO NOTHING;
 
 -- ── Default applications ──────────────────────────────────────────────────────
 
-INSERT OR IGNORE INTO applications (id, tenant_id, name, slug, enabled) VALUES
+INSERT INTO applications (id, tenant_id, name, slug, enabled) VALUES
     ('30000000-0000-0000-0000-000000000001', '00000000-0000-0000-0000-000000000001', 'BZOD',         'bzod',         1),
     ('30000000-0000-0000-0000-000000000002', '00000000-0000-0000-0000-000000000001', 'ChronoSeal',   'chronoseal',   1),
-    ('30000000-0000-0000-0000-000000000003', '00000000-0000-0000-0000-000000000001', 'nx9-dns',      'nx9-dns',      1);
+    ('30000000-0000-0000-0000-000000000003', '00000000-0000-0000-0000-000000000001', 'nx9-dns',      'nx9-dns',      1)
+ON CONFLICT DO NOTHING;

src/db/migrations/postgres/0019_create_application_members.sql

@@ -0,0 +1,21 @@
+-- Application membership: assign existing NX9-Auth users to registered applications.
+-- Membership roles (owner/admin/member) are lightweight metadata only and do not
+-- grant global RBAC permissions such as applications:manage.
+
+CREATE TABLE IF NOT EXISTS application_members (
+    id              TEXT    PRIMARY KEY NOT NULL,
+    application_id  TEXT    NOT NULL REFERENCES applications(id) ON DELETE CASCADE,
+    user_id         TEXT    NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    role            TEXT    NOT NULL DEFAULT 'member'
+                        CHECK (role IN ('owner', 'admin', 'member')),
+    enabled         BOOLEAN NOT NULL DEFAULT TRUE,
+    created_at      TEXT    NOT NULL DEFAULT (to_char(clock_timestamp() AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z"')),
+    updated_at      TEXT    NOT NULL DEFAULT (to_char(clock_timestamp() AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z"')),
+    UNIQUE (application_id, user_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_application_members_application
+    ON application_members(application_id);
+
+CREATE INDEX IF NOT EXISTS idx_application_members_user
+    ON application_members(user_id);

src/db/migrations/postgres/20260718_add_global_slugs.sql

@@ -1,4 +1,4 @@
--- nx9-auth: Global Slugs implementation
+-- nx9-auth: Global Slugs implementation (PostgreSQL)
 -- A unified registry for slugs across all resources (tenant, user, group, role, app, etc.)
 -- Ensures global uniqueness and immutable references.
 
@@ -7,22 +7,21 @@ CREATE TABLE IF NOT EXISTS global_slugs (
     entity_type     TEXT    NOT NULL, -- 'tenant', 'user', 'role', 'group', 'permission', 'application', 'service_account', 'organization', 'team'
     entity_id       TEXT    NOT NULL,
     tenant_id       TEXT    NOT NULL REFERENCES tenants(id) ON DELETE CASCADE,
-    created_at      TEXT    NOT NULL DEFAULT (to_char(clock_timestamp() AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z\'))
+    created_at      TEXT    NOT NULL DEFAULT (to_char(clock_timestamp() AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z"'))
 );
 
 CREATE INDEX IF NOT EXISTS idx_global_slugs_entity ON global_slugs(entity_type, entity_id);
 CREATE INDEX IF NOT EXISTS idx_global_slugs_tenant ON global_slugs(tenant_id);
 
 -- Add slug column to existing tables for quick lookup and joins
-ALTER TABLE tenants ADD COLUMN slug TEXT;
-ALTER TABLE users ADD COLUMN slug TEXT;
-ALTER TABLE roles ADD COLUMN slug TEXT;
-ALTER TABLE permissions ADD COLUMN slug TEXT;
-ALTER TABLE applications ADD COLUMN slug TEXT;
-ALTER TABLE service_accounts ADD COLUMN slug TEXT;
+ALTER TABLE tenants ADD COLUMN IF NOT EXISTS slug TEXT;
+ALTER TABLE users ADD COLUMN IF NOT EXISTS slug TEXT;
+ALTER TABLE roles ADD COLUMN IF NOT EXISTS slug TEXT;
+ALTER TABLE permissions ADD COLUMN IF NOT EXISTS slug TEXT;
+ALTER TABLE applications ADD COLUMN IF NOT EXISTS slug TEXT;
+ALTER TABLE service_accounts ADD COLUMN IF NOT EXISTS slug TEXT;
 
--- We will backfill slugs in Rust on startup or through a data migration script, 
--- or we can backfill basic ones here:
+-- Backfill basic slugs:
 UPDATE tenants SET slug = lower(replace(name, ' ', '-')) WHERE slug IS NULL;
 UPDATE users SET slug = lower(username) WHERE slug IS NULL;
 UPDATE roles SET slug = lower(replace(name, ' ', '-')) WHERE slug IS NULL;
@@ -30,21 +29,27 @@ UPDATE permissions SET slug = lower(replace(name, ' ', '-')) WHERE slug IS NULL;
 UPDATE applications SET slug = lower(replace(name, ' ', '-')) WHERE slug IS NULL;
 UPDATE service_accounts SET slug = lower(replace(name, ' ', '-')) WHERE slug IS NULL;
 
--- Insert the backfilled slugs into the registry
-INSERT OR IGNORE INTO global_slugs (slug, entity_type, entity_id, tenant_id)
-SELECT slug, 'tenant', id, id FROM tenants WHERE slug IS NOT NULL;
+-- Insert backfilled slugs into registry
+INSERT INTO global_slugs (slug, entity_type, entity_id, tenant_id)
+SELECT slug, 'tenant', id, id FROM tenants WHERE slug IS NOT NULL
+ON CONFLICT DO NOTHING;
 
-INSERT OR IGNORE INTO global_slugs (slug, entity_type, entity_id, tenant_id)
-SELECT slug, 'user', id, tenant_id FROM users WHERE slug IS NOT NULL;
+INSERT INTO global_slugs (slug, entity_type, entity_id, tenant_id)
+SELECT slug, 'user', id, tenant_id FROM users WHERE slug IS NOT NULL
+ON CONFLICT DO NOTHING;
 
-INSERT OR IGNORE INTO global_slugs (slug, entity_type, entity_id, tenant_id)
-SELECT slug, 'role', id, tenant_id FROM roles WHERE slug IS NOT NULL;
+INSERT INTO global_slugs (slug, entity_type, entity_id, tenant_id)
+SELECT slug, 'role', id, '00000000-0000-0000-0000-000000000001' FROM roles WHERE slug IS NOT NULL
+ON CONFLICT DO NOTHING;
 
-INSERT OR IGNORE INTO global_slugs (slug, entity_type, entity_id, tenant_id)
-SELECT slug, 'permission', id, tenant_id FROM permissions WHERE slug IS NOT NULL;
+INSERT INTO global_slugs (slug, entity_type, entity_id, tenant_id)
+SELECT slug, 'permission', id, '00000000-0000-0000-0000-000000000001' FROM permissions WHERE slug IS NOT NULL
+ON CONFLICT DO NOTHING;
 
-INSERT OR IGNORE INTO global_slugs (slug, entity_type, entity_id, tenant_id)
-SELECT slug, 'application', id, tenant_id FROM applications WHERE slug IS NOT NULL;
+INSERT INTO global_slugs (slug, entity_type, entity_id, tenant_id)
+SELECT slug, 'application', id, tenant_id FROM applications WHERE slug IS NOT NULL
+ON CONFLICT DO NOTHING;
 
-INSERT OR IGNORE INTO global_slugs (slug, entity_type, entity_id, tenant_id)
-SELECT slug, 'service_account', id, tenant_id FROM service_accounts WHERE slug IS NOT NULL;
+INSERT INTO global_slugs (slug, entity_type, entity_id, tenant_id)
+SELECT slug, 'service_account', id, tenant_id FROM service_accounts WHERE slug IS NOT NULL
+ON CONFLICT DO NOTHING;

src/db/migrations/postgres/20260724_harden_global_slugs.sql

@@ -0,0 +1,27 @@
+-- nx9-auth: Global Slugs Hardening & Parity Alignment (PostgreSQL)
+-- Ensures unified global_slugs registry table, indices, and legacy data integrity.
+
+CREATE TABLE IF NOT EXISTS global_slugs (
+    slug            TEXT    PRIMARY KEY NOT NULL,
+    entity_type     TEXT    NOT NULL,
+    entity_id       TEXT    NOT NULL,
+    tenant_id       TEXT    NOT NULL REFERENCES tenants(id) ON DELETE CASCADE,
+    created_at      TEXT    NOT NULL DEFAULT (to_char(clock_timestamp() AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z"'))
+);
+
+CREATE INDEX IF NOT EXISTS idx_global_slugs_entity ON global_slugs(entity_type, entity_id);
+CREATE INDEX IF NOT EXISTS idx_global_slugs_tenant ON global_slugs(tenant_id);
+
+-- Explicit backfill for tenants that are not yet in global_slugs.
+-- Fails immediately if cross-resource slug collision exists.
+INSERT INTO global_slugs (slug, entity_type, entity_id, tenant_id)
+SELECT slug, 'tenant', id, id
+FROM tenants
+WHERE slug IS NOT NULL AND slug NOT IN (SELECT slug FROM global_slugs);
+
+-- Explicit backfill for applications that are not yet in global_slugs.
+-- Fails immediately if cross-resource slug collision exists.
+INSERT INTO global_slugs (slug, entity_type, entity_id, tenant_id)
+SELECT slug, 'application', id, tenant_id
+FROM applications
+WHERE slug IS NOT NULL AND slug NOT IN (SELECT slug FROM global_slugs);

src/db/migrations/sqlite/0019_create_application_members.sql

@@ -0,0 +1,21 @@
+-- Application membership: assign existing NX9-Auth users to registered applications.
+-- Membership roles (owner/admin/member) are lightweight metadata only and do not
+-- grant global RBAC permissions such as applications:manage.
+
+CREATE TABLE IF NOT EXISTS application_members (
+    id              TEXT    PRIMARY KEY NOT NULL,
+    application_id  TEXT    NOT NULL REFERENCES applications(id) ON DELETE CASCADE,
+    user_id         TEXT    NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    role            TEXT    NOT NULL DEFAULT 'member'
+                        CHECK (role IN ('owner', 'admin', 'member')),
+    enabled         INTEGER NOT NULL DEFAULT 1,
+    created_at      TEXT    NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
+    updated_at      TEXT    NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now')),
+    UNIQUE (application_id, user_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_application_members_application
+    ON application_members(application_id);
+
+CREATE INDEX IF NOT EXISTS idx_application_members_user
+    ON application_members(user_id);

src/db/migrations/sqlite/20260724_harden_global_slugs.sql

@@ -0,0 +1,27 @@
+-- nx9-auth: Global Slugs Hardening & Parity Alignment
+-- Ensures unified global_slugs registry table, indices, and legacy data integrity.
+
+CREATE TABLE IF NOT EXISTS global_slugs (
+    slug            TEXT    PRIMARY KEY NOT NULL,
+    entity_type     TEXT    NOT NULL,
+    entity_id       TEXT    NOT NULL,
+    tenant_id       TEXT    NOT NULL REFERENCES tenants(id) ON DELETE CASCADE,
+    created_at      TEXT    NOT NULL DEFAULT (strftime('%Y-%m-%dT%H:%M:%SZ', 'now'))
+);
+
+CREATE INDEX IF NOT EXISTS idx_global_slugs_entity ON global_slugs(entity_type, entity_id);
+CREATE INDEX IF NOT EXISTS idx_global_slugs_tenant ON global_slugs(tenant_id);
+
+-- Explicit backfill for tenants that are not yet in global_slugs.
+-- Fails immediately if cross-resource slug collision exists.
+INSERT INTO global_slugs (slug, entity_type, entity_id, tenant_id)
+SELECT slug, 'tenant', id, id
+FROM tenants
+WHERE slug IS NOT NULL AND slug NOT IN (SELECT slug FROM global_slugs);
+
+-- Explicit backfill for applications that are not yet in global_slugs.
+-- Fails immediately if cross-resource slug collision exists.
+INSERT INTO global_slugs (slug, entity_type, entity_id, tenant_id)
+SELECT slug, 'application', id, tenant_id
+FROM applications
+WHERE slug IS NOT NULL AND slug NOT IN (SELECT slug FROM global_slugs);

src/db/models/application_member.rs

@@ -0,0 +1,58 @@
+use serde::{Deserialize, Serialize};
+use sqlx::FromRow;
+
+/// Allowed application membership roles (lightweight metadata only).
+///
+/// These do **not** grant global NX9-Auth RBAC permissions.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default, Serialize, Deserialize)]
+#[serde(rename_all = "lowercase")]
+pub enum ApplicationMembershipRole {
+    Owner,
+    Admin,
+    #[default]
+    Member,
+}
+
+impl ApplicationMembershipRole {
+    pub fn as_str(self) -> &'static str {
+        match self {
+            Self::Owner => "owner",
+            Self::Admin => "admin",
+            Self::Member => "member",
+        }
+    }
+
+    /// Parse a role string. Returns `None` for invalid values.
+    pub fn parse(s: &str) -> Option<Self> {
+        match s.trim().to_ascii_lowercase().as_str() {
+            "owner" => Some(Self::Owner),
+            "admin" => Some(Self::Admin),
+            "member" => Some(Self::Member),
+            _ => None,
+        }
+    }
+}
+
+impl std::fmt::Display for ApplicationMembershipRole {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(self.as_str())
+    }
+}
+
+/// Assignment of an existing NX9-Auth user to a registered application.
+#[derive(Debug, Clone, Serialize, Deserialize, FromRow)]
+pub struct ApplicationMember {
+    pub id: String,
+    pub application_id: String,
+    pub user_id: String,
+    pub role: String,
+    pub enabled: bool,
+    pub created_at: String,
+    pub updated_at: String,
+}
+
+impl ApplicationMember {
+    pub fn membership_role(&self) -> Option<ApplicationMembershipRole> {
+        ApplicationMembershipRole::parse(&self.role)
+    }
+}

src/db/models/audit_log.rs

@@ -48,6 +48,7 @@ pub struct AuditFilter {
     pub since: Option<String>,
     pub until: Option<String>,
     pub search: Option<String>,
+    pub success: Option<bool>,
     pub limit: i64,
     pub offset: i64,
 }

src/db/models/global_slug.rs

@@ -0,0 +1,10 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize, sqlx::FromRow)]
+pub struct GlobalSlug {
+    pub slug: String,
+    pub entity_type: String,
+    pub entity_id: String,
+    pub tenant_id: String,
+    pub created_at: String,
+}

src/db/models/mod.rs

@@ -1,6 +1,8 @@
 pub mod api_token;
 pub mod application;
+pub mod application_member;
 pub mod audit_log;
+pub mod global_slug;
 pub mod group;
 pub mod permission;
 pub mod refresh_token;
@@ -12,7 +14,9 @@ pub mod user;
 
 pub use api_token::ApiToken;
 pub use application::Application;
+pub use application_member::{ApplicationMember, ApplicationMembershipRole};
 pub use audit_log::{AuditFilter, AuditLog, AuditSeverity};
+pub use global_slug::GlobalSlug;
 pub use group::Group;
 #[allow(unused_imports)]
 pub use permission::Permission;

src/db/provider.rs

@@ -18,6 +18,8 @@ pub trait DatabaseProvider: Send + Sync {
     fn tokens(&self) -> Box<dyn TokensRepository>;
     fn tenants(&self) -> Box<dyn TenantsRepository>;
     fn groups(&self) -> Box<dyn GroupsRepository>;
+    fn application_members(&self) -> Box<dyn ApplicationMembersRepository>;
+    fn global_slugs(&self) -> Box<dyn GlobalSlugsRepository>;
 }
 
 #[cfg(feature = "sqlite")]
@@ -112,6 +114,20 @@ impl DatabaseProvider for SqliteProvider {
             },
         )
     }
+    fn application_members(&self) -> Box<dyn ApplicationMembersRepository> {
+        Box::new(
+            crate::db::repository::sqlite::application_members::SqliteApplicationMembersRepository {
+                pool: self.pool.clone(),
+            },
+        )
+    }
+    fn global_slugs(&self) -> Box<dyn GlobalSlugsRepository> {
+        Box::new(
+            crate::db::repository::sqlite::global_slugs::SqliteGlobalSlugsRepository {
+                pool: self.pool.clone(),
+            },
+        )
+    }
 }
 
 #[cfg(feature = "postgres")]
@@ -206,4 +222,18 @@ impl DatabaseProvider for PostgresProvider {
             },
         )
     }
+    fn application_members(&self) -> Box<dyn ApplicationMembersRepository> {
+        Box::new(
+            crate::db::repository::postgres::application_members::PostgresApplicationMembersRepository {
+                pool: self.pool.clone(),
+            },
+        )
+    }
+    fn global_slugs(&self) -> Box<dyn GlobalSlugsRepository> {
+        Box::new(
+            crate::db::repository::postgres::global_slugs::PostgresGlobalSlugsRepository {
+                pool: self.pool.clone(),
+            },
+        )
+    }
 }

src/db/repository/postgres/application_members.rs

@@ -0,0 +1,515 @@
+use crate::db::models::ApplicationMember;
+use crate::db::repository::traits::ApplicationMembersRepository;
+use async_trait::async_trait;
+use sqlx::PgPool;
+
+pub struct PostgresApplicationMembersRepository {
+    pub pool: PgPool,
+}
+
+#[async_trait]
+impl ApplicationMembersRepository for PostgresApplicationMembersRepository {
+    async fn list_by_application(
+        &self,
+        application_id: &str,
+    ) -> Result<Vec<ApplicationMember>, sqlx::Error> {
+        sqlx::query_as::<_, ApplicationMember>(
+            r#"
+            SELECT id, application_id, user_id, role, enabled, created_at, updated_at
+            FROM application_members
+            WHERE application_id = $1
+            ORDER BY created_at ASC
+            "#,
+        )
+        .bind(application_id)
+        .fetch_all(&self.pool)
+        .await
+    }
+
+    async fn list_by_user(&self, user_id: &str) -> Result<Vec<ApplicationMember>, sqlx::Error> {
+        sqlx::query_as::<_, ApplicationMember>(
+            r#"
+            SELECT id, application_id, user_id, role, enabled, created_at, updated_at
+            FROM application_members
+            WHERE user_id = $1
+            ORDER BY created_at ASC
+            "#,
+        )
+        .bind(user_id)
+        .fetch_all(&self.pool)
+        .await
+    }
+
+    async fn find(
+        &self,
+        application_id: &str,
+        user_id: &str,
+    ) -> Result<Option<ApplicationMember>, sqlx::Error> {
+        sqlx::query_as::<_, ApplicationMember>(
+            r#"
+            SELECT id, application_id, user_id, role, enabled, created_at, updated_at
+            FROM application_members
+            WHERE application_id = $1 AND user_id = $2
+            "#,
+        )
+        .bind(application_id)
+        .bind(user_id)
+        .fetch_optional(&self.pool)
+        .await
+    }
+
+    async fn add(
+        &self,
+        id: &str,
+        application_id: &str,
+        user_id: &str,
+        role: &str,
+    ) -> Result<ApplicationMember, sqlx::Error> {
+        sqlx::query_as::<_, ApplicationMember>(
+            r#"
+            INSERT INTO application_members (id, application_id, user_id, role, enabled)
+            VALUES ($1, $2, $3, $4, TRUE)
+            RETURNING id, application_id, user_id, role, enabled, created_at, updated_at
+            "#,
+        )
+        .bind(id)
+        .bind(application_id)
+        .bind(user_id)
+        .bind(role)
+        .fetch_one(&self.pool)
+        .await
+    }
+
+    async fn update_role(
+        &self,
+        application_id: &str,
+        user_id: &str,
+        role: &str,
+    ) -> Result<(), sqlx::Error> {
+        sqlx::query(
+            r#"
+            UPDATE application_members
+            SET role = $1,
+                updated_at = to_char(clock_timestamp() AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z"')
+            WHERE application_id = $2 AND user_id = $3
+            "#,
+        )
+        .bind(role)
+        .bind(application_id)
+        .bind(user_id)
+        .execute(&self.pool)
+        .await?;
+        Ok(())
+    }
+
+    async fn set_enabled(
+        &self,
+        application_id: &str,
+        user_id: &str,
+        enabled: bool,
+    ) -> Result<(), sqlx::Error> {
+        sqlx::query(
+            r#"
+            UPDATE application_members
+            SET enabled = $1,
+                updated_at = to_char(clock_timestamp() AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z"')
+            WHERE application_id = $2 AND user_id = $3
+            "#,
+        )
+        .bind(enabled)
+        .bind(application_id)
+        .bind(user_id)
+        .execute(&self.pool)
+        .await?;
+        Ok(())
+    }
+
+    async fn remove(&self, application_id: &str, user_id: &str) -> Result<(), sqlx::Error> {
+        sqlx::query(
+            r#"
+            DELETE FROM application_members
+            WHERE application_id = $1 AND user_id = $2
+            "#,
+        )
+        .bind(application_id)
+        .bind(user_id)
+        .execute(&self.pool)
+        .await?;
+        Ok(())
+    }
+
+    async fn add_with_audit(
+        &self,
+        id: &str,
+        application_id: &str,
+        user_id: &str,
+        role: &str,
+        audit_event: Option<crate::audit::AuditEvent<'_>>,
+    ) -> Result<ApplicationMember, sqlx::Error> {
+        let mut tx = self.pool.begin().await?;
+
+        let app_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM applications WHERE id = $1")
+                .bind(application_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let app_tenant_id = match app_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        let user_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM users WHERE id = $1")
+                .bind(user_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let user_tenant_id = match user_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        if app_tenant_id != user_tenant_id {
+            return Err(sqlx::Error::Protocol(
+                "user and application must belong to the same tenant".into(),
+            ));
+        }
+
+        let existing: Option<(String,)> = sqlx::query_as(
+            "SELECT id FROM application_members WHERE application_id = $1 AND user_id = $2",
+        )
+        .bind(application_id)
+        .bind(user_id)
+        .fetch_optional(&mut *tx)
+        .await?;
+        if existing.is_some() {
+            return Err(sqlx::Error::Protocol(
+                "user is already a member of this application".into(),
+            ));
+        }
+
+        let member = sqlx::query_as::<_, ApplicationMember>(
+            r#"
+            INSERT INTO application_members (id, application_id, user_id, role, enabled)
+            VALUES ($1, $2, $3, $4, TRUE)
+            RETURNING id, application_id, user_id, role, enabled, created_at, updated_at
+            "#,
+        )
+        .bind(id)
+        .bind(application_id)
+        .bind(user_id)
+        .bind(role)
+        .fetch_one(&mut *tx)
+        .await?;
+
+        if let Some(event) = audit_event {
+            let audit_id = uuid::Uuid::new_v4().to_string();
+            let severity_str = event.severity.to_string();
+            sqlx::query(
+                r#"
+                INSERT INTO audit_logs (
+                    id, actor_user_id, target_user_id,
+                    action, resource_type, resource_id,
+                    severity, ip_address, user_agent, metadata_json
+                )
+                VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)
+                "#,
+            )
+            .bind(&audit_id)
+            .bind(event.actor_id)
+            .bind(event.target_id)
+            .bind(event.action)
+            .bind(event.resource_type)
+            .bind(event.resource_id)
+            .bind(&severity_str)
+            .bind(event.ip)
+            .bind(event.ua)
+            .bind(event.metadata)
+            .execute(&mut *tx)
+            .await?;
+        }
+
+        tx.commit().await?;
+        Ok(member)
+    }
+
+    async fn update_role_with_audit(
+        &self,
+        application_id: &str,
+        user_id: &str,
+        role: &str,
+        audit_event: Option<crate::audit::AuditEvent<'_>>,
+    ) -> Result<(), sqlx::Error> {
+        let mut tx = self.pool.begin().await?;
+
+        let existing_member: Option<(String,)> = sqlx::query_as(
+            "SELECT id FROM application_members WHERE application_id = $1 AND user_id = $2 FOR UPDATE",
+        )
+        .bind(application_id)
+        .bind(user_id)
+        .fetch_optional(&mut *tx)
+        .await?;
+        if existing_member.is_none() {
+            return Err(sqlx::Error::RowNotFound);
+        }
+
+        let app_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM applications WHERE id = $1")
+                .bind(application_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let app_tenant_id = match app_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        let user_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM users WHERE id = $1")
+                .bind(user_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let user_tenant_id = match user_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        if app_tenant_id != user_tenant_id {
+            return Err(sqlx::Error::Protocol(
+                "user and application must belong to the same tenant".into(),
+            ));
+        }
+
+        let result = sqlx::query(
+            r#"
+            UPDATE application_members
+            SET role = $1,
+                updated_at = to_char(clock_timestamp() AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z"')
+            WHERE application_id = $2 AND user_id = $3
+            "#,
+        )
+        .bind(role)
+        .bind(application_id)
+        .bind(user_id)
+        .execute(&mut *tx)
+        .await?;
+
+        if result.rows_affected() != 1 {
+            return Err(sqlx::Error::RowNotFound);
+        }
+
+        if let Some(event) = audit_event {
+            let audit_id = uuid::Uuid::new_v4().to_string();
+            let severity_str = event.severity.to_string();
+            sqlx::query(
+                r#"
+                INSERT INTO audit_logs (
+                    id, actor_user_id, target_user_id,
+                    action, resource_type, resource_id,
+                    severity, ip_address, user_agent, metadata_json
+                )
+                VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)
+                "#,
+            )
+            .bind(&audit_id)
+            .bind(event.actor_id)
+            .bind(event.target_id)
+            .bind(event.action)
+            .bind(event.resource_type)
+            .bind(event.resource_id)
+            .bind(&severity_str)
+            .bind(event.ip)
+            .bind(event.ua)
+            .bind(event.metadata)
+            .execute(&mut *tx)
+            .await?;
+        }
+
+        tx.commit().await?;
+        Ok(())
+    }
+
+    async fn set_enabled_with_audit(
+        &self,
+        application_id: &str,
+        user_id: &str,
+        enabled: bool,
+        audit_event: Option<crate::audit::AuditEvent<'_>>,
+    ) -> Result<(), sqlx::Error> {
+        let mut tx = self.pool.begin().await?;
+
+        let existing_member: Option<(String,)> = sqlx::query_as(
+            "SELECT id FROM application_members WHERE application_id = $1 AND user_id = $2 FOR UPDATE",
+        )
+        .bind(application_id)
+        .bind(user_id)
+        .fetch_optional(&mut *tx)
+        .await?;
+        if existing_member.is_none() {
+            return Err(sqlx::Error::RowNotFound);
+        }
+
+        let app_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM applications WHERE id = $1")
+                .bind(application_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let app_tenant_id = match app_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        let user_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM users WHERE id = $1")
+                .bind(user_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let user_tenant_id = match user_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        if app_tenant_id != user_tenant_id {
+            return Err(sqlx::Error::Protocol(
+                "user and application must belong to the same tenant".into(),
+            ));
+        }
+
+        let result = sqlx::query(
+            r#"
+            UPDATE application_members
+            SET enabled = $1,
+                updated_at = to_char(clock_timestamp() AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z"')
+            WHERE application_id = $2 AND user_id = $3
+            "#,
+        )
+        .bind(enabled)
+        .bind(application_id)
+        .bind(user_id)
+        .execute(&mut *tx)
+        .await?;
+
+        if result.rows_affected() != 1 {
+            return Err(sqlx::Error::RowNotFound);
+        }
+
+        if let Some(event) = audit_event {
+            let audit_id = uuid::Uuid::new_v4().to_string();
+            let severity_str = event.severity.to_string();
+            sqlx::query(
+                r#"
+                INSERT INTO audit_logs (
+                    id, actor_user_id, target_user_id,
+                    action, resource_type, resource_id,
+                    severity, ip_address, user_agent, metadata_json
+                )
+                VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)
+                "#,
+            )
+            .bind(&audit_id)
+            .bind(event.actor_id)
+            .bind(event.target_id)
+            .bind(event.action)
+            .bind(event.resource_type)
+            .bind(event.resource_id)
+            .bind(&severity_str)
+            .bind(event.ip)
+            .bind(event.ua)
+            .bind(event.metadata)
+            .execute(&mut *tx)
+            .await?;
+        }
+
+        tx.commit().await?;
+        Ok(())
+    }
+
+    async fn remove_with_audit(
+        &self,
+        application_id: &str,
+        user_id: &str,
+        audit_event: Option<crate::audit::AuditEvent<'_>>,
+    ) -> Result<(), sqlx::Error> {
+        let mut tx = self.pool.begin().await?;
+
+        let existing_member: Option<(String,)> = sqlx::query_as(
+            "SELECT id FROM application_members WHERE application_id = $1 AND user_id = $2 FOR UPDATE",
+        )
+        .bind(application_id)
+        .bind(user_id)
+        .fetch_optional(&mut *tx)
+        .await?;
+        if existing_member.is_none() {
+            return Err(sqlx::Error::RowNotFound);
+        }
+
+        let app_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM applications WHERE id = $1")
+                .bind(application_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let app_tenant_id = match app_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        let user_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM users WHERE id = $1")
+                .bind(user_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let user_tenant_id = match user_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        if app_tenant_id != user_tenant_id {
+            return Err(sqlx::Error::Protocol(
+                "user and application must belong to the same tenant".into(),
+            ));
+        }
+
+        let result = sqlx::query(
+            r#"
+            DELETE FROM application_members
+            WHERE application_id = $1 AND user_id = $2
+            "#,
+        )
+        .bind(application_id)
+        .bind(user_id)
+        .execute(&mut *tx)
+        .await?;
+
+        if result.rows_affected() != 1 {
+            return Err(sqlx::Error::RowNotFound);
+        }
+
+        if let Some(event) = audit_event {
+            let audit_id = uuid::Uuid::new_v4().to_string();
+            let severity_str = event.severity.to_string();
+            sqlx::query(
+                r#"
+                INSERT INTO audit_logs (
+                    id, actor_user_id, target_user_id,
+                    action, resource_type, resource_id,
+                    severity, ip_address, user_agent, metadata_json
+                )
+                VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)
+                "#,
+            )
+            .bind(&audit_id)
+            .bind(event.actor_id)
+            .bind(event.target_id)
+            .bind(event.action)
+            .bind(event.resource_type)
+            .bind(event.resource_id)
+            .bind(&severity_str)
+            .bind(event.ip)
+            .bind(event.ua)
+            .bind(event.metadata)
+            .execute(&mut *tx)
+            .await?;
+        }
+
+        tx.commit().await?;
+        Ok(())
+    }
+}

src/db/repository/postgres/applications.rs

@@ -1,9 +1,11 @@
+use crate::db::models::Application;
+use crate::db::repository::postgres::global_slugs::{
+    release_slug_by_name_postgres, release_slug_postgres, reserve_slug_postgres,
+};
 use crate::db::repository::traits::ApplicationsRepository;
 use async_trait::async_trait;
 use sqlx::PgPool;
 
-use crate::db::models::Application;
-
 pub struct PostgresApplicationsRepository {
     pub pool: PgPool,
 }
@@ -25,6 +27,8 @@ impl ApplicationsRepository for PostgresApplicationsRepository {
     ) -> Result<Application, sqlx::Error> {
         let mut tx = self.pool.begin().await?;
 
+        reserve_slug_postgres(&mut tx, slug, "application", id, tenant_id).await?;
+
         let app = sqlx::query_as::<_, Application>(
             r#"
         INSERT INTO applications (id, tenant_id, name, slug, client_id, client_secret_hash, description, redirect_uris, scopes)
@@ -188,31 +192,74 @@ impl ApplicationsRepository for PostgresApplicationsRepository {
         scopes: Option<&str>,
         enabled: bool,
     ) -> Result<(), sqlx::Error> {
-        sqlx::query(
-            r#"
-        UPDATE applications
-        SET name = $1, slug = $2, description = $3, redirect_uris = $4, scopes = $5, enabled = $6,
-            updated_at = to_char(clock_timestamp() AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z"')
-        WHERE id = $7
-        "#,
-        )
-        .bind(name)
-        .bind(slug)
-        .bind(description)
-        .bind(redirect_uris)
-        .bind(scopes)
-        .bind(enabled)
-        .bind(id)
-        .execute(&self.pool)
-        .await?;
+        let existing = self.find_by_id(id).await?.ok_or(sqlx::Error::RowNotFound)?;
+
+        let existing_slug_str = existing.slug.as_deref().unwrap_or("");
+
+        if slug == existing_slug_str {
+            // Unchanged slug: registry no-op
+            sqlx::query(
+                r#"
+            UPDATE applications
+            SET name = $1, description = $2, redirect_uris = $3, scopes = $4, enabled = $5,
+                updated_at = to_char(clock_timestamp() AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z"')
+            WHERE id = $6
+            "#,
+            )
+            .bind(name)
+            .bind(description)
+            .bind(redirect_uris)
+            .bind(scopes)
+            .bind(enabled)
+            .bind(id)
+            .execute(&self.pool)
+            .await?;
+        } else {
+            // Changed slug: single transaction reserve -> update -> release
+            let mut tx = self.pool.begin().await?;
+
+            reserve_slug_postgres(&mut tx, slug, "application", id, &existing.tenant_id).await?;
+
+            sqlx::query(
+                r#"
+            UPDATE applications
+            SET name = $1, slug = $2, description = $3, redirect_uris = $4, scopes = $5, enabled = $6,
+                updated_at = to_char(clock_timestamp() AT TIME ZONE 'UTC', 'YYYY-MM-DD"T"HH24:MI:SS"Z"')
+            WHERE id = $7
+            "#,
+            )
+            .bind(name)
+            .bind(slug)
+            .bind(description)
+            .bind(redirect_uris)
+            .bind(scopes)
+            .bind(enabled)
+            .bind(id)
+            .execute(&mut *tx)
+            .await?;
+
+            if !existing_slug_str.is_empty() {
+                release_slug_by_name_postgres(&mut tx, existing_slug_str, "application", id)
+                    .await?;
+            }
+
+            tx.commit().await?;
+        }
+
         Ok(())
     }
 
     async fn delete(&self, id: &str) -> Result<(), sqlx::Error> {
+        let mut tx = self.pool.begin().await?;
+
+        release_slug_postgres(&mut tx, "application", id).await?;
+
         sqlx::query("DELETE FROM applications WHERE id = $1")
             .bind(id)
-            .execute(&self.pool)
+            .execute(&mut *tx)
             .await?;
+
+        tx.commit().await?;
         Ok(())
     }
 

src/db/repository/postgres/audit.rs

@@ -64,8 +64,6 @@ impl AuditRepository for PostgresAuditRepository {
     }
 
     async fn list_filtered(&self, filter: &AuditFilter) -> Result<Vec<AuditLog>, sqlx::Error> {
-        // Build a dynamic but simple filter using COALESCE-style optional matches.
-        // Empty optionals are treated as wildcards via OR IS NULL pattern with bind of None.
         let search_like = filter
             .search
             .as_ref()
@@ -88,8 +86,13 @@ impl AuditRepository for PostgresAuditRepository {
              OR ip_address LIKE $7 ESCAPE '\'
              OR metadata_json LIKE $7 ESCAPE '\'
           )
+          AND (
+                $8::boolean IS NULL
+             OR ($8::boolean = TRUE AND action NOT LIKE '%fail%' AND action NOT LIKE '%denied%' AND severity != 'critical')
+             OR ($8::boolean = FALSE AND (action LIKE '%fail%' OR action LIKE '%denied%' OR severity = 'critical'))
+          )
         ORDER BY created_at DESC
-        LIMIT $8 OFFSET $9
+        LIMIT $9 OFFSET $10
         "#,
         )
         .bind(filter.actor_user_id.as_deref())
@@ -99,6 +102,7 @@ impl AuditRepository for PostgresAuditRepository {
         .bind(filter.since.as_deref())
         .bind(filter.until.as_deref())
         .bind(search_like.as_deref())
+        .bind(filter.success)
         .bind(filter.limit)
         .bind(filter.offset)
         .fetch_all(&self.pool)
@@ -128,6 +132,11 @@ impl AuditRepository for PostgresAuditRepository {
              OR ip_address LIKE $7 ESCAPE '\'
              OR metadata_json LIKE $7 ESCAPE '\'
           )
+          AND (
+                $8::boolean IS NULL
+             OR ($8::boolean = TRUE AND action NOT LIKE '%fail%' AND action NOT LIKE '%denied%' AND severity != 'critical')
+             OR ($8::boolean = FALSE AND (action LIKE '%fail%' OR action LIKE '%denied%' OR severity = 'critical'))
+          )
         "#,
         )
         .bind(filter.actor_user_id.as_deref())
@@ -137,6 +146,7 @@ impl AuditRepository for PostgresAuditRepository {
         .bind(filter.since.as_deref())
         .bind(filter.until.as_deref())
         .bind(search_like.as_deref())
+        .bind(filter.success)
         .fetch_one(&self.pool)
         .await?;
         Ok(row.0)

src/db/repository/postgres/global_slugs.rs

@@ -0,0 +1,68 @@
+use crate::db::models::GlobalSlug;
+use crate::db::repository::traits::GlobalSlugsRepository;
+use sqlx::PgPool;
+
+pub struct PostgresGlobalSlugsRepository {
+    pub pool: PgPool,
+}
+
+#[async_trait::async_trait]
+impl GlobalSlugsRepository for PostgresGlobalSlugsRepository {
+    async fn find_by_slug(&self, slug: &str) -> Result<Option<GlobalSlug>, sqlx::Error> {
+        sqlx::query_as::<_, GlobalSlug>(
+            "SELECT slug, entity_type, entity_id, tenant_id, created_at::text FROM global_slugs WHERE slug = $1"
+        )
+        .bind(slug)
+        .fetch_optional(&self.pool)
+        .await
+    }
+}
+
+pub async fn reserve_slug_postgres(
+    conn: &mut sqlx::PgConnection,
+    slug: &str,
+    entity_type: &str,
+    entity_id: &str,
+    tenant_id: &str,
+) -> Result<(), sqlx::Error> {
+    sqlx::query(
+        "INSERT INTO global_slugs (slug, entity_type, entity_id, tenant_id) VALUES ($1, $2, $3, $4)"
+    )
+    .bind(slug)
+    .bind(entity_type)
+    .bind(entity_id)
+    .bind(tenant_id)
+    .execute(conn)
+    .await?;
+    Ok(())
+}
+
+pub async fn release_slug_postgres(
+    conn: &mut sqlx::PgConnection,
+    entity_type: &str,
+    entity_id: &str,
+) -> Result<u64, sqlx::Error> {
+    let res = sqlx::query("DELETE FROM global_slugs WHERE entity_type = $1 AND entity_id = $2")
+        .bind(entity_type)
+        .bind(entity_id)
+        .execute(conn)
+        .await?;
+    Ok(res.rows_affected())
+}
+
+pub async fn release_slug_by_name_postgres(
+    conn: &mut sqlx::PgConnection,
+    slug: &str,
+    entity_type: &str,
+    entity_id: &str,
+) -> Result<u64, sqlx::Error> {
+    let res = sqlx::query(
+        "DELETE FROM global_slugs WHERE slug = $1 AND entity_type = $2 AND entity_id = $3",
+    )
+    .bind(slug)
+    .bind(entity_type)
+    .bind(entity_id)
+    .execute(conn)
+    .await?;
+    Ok(res.rows_affected())
+}

src/db/repository/postgres/mod.rs

@@ -1,5 +1,7 @@
+pub mod application_members;
 pub mod applications;
 pub mod audit;
+pub mod global_slugs;
 pub mod groups;
 pub mod permissions;
 pub mod refresh_tokens;

src/db/repository/postgres/tenants.rs

@@ -1,7 +1,11 @@
 use sqlx::PgPool;
 
 use crate::db::models::Tenant;
+use crate::db::repository::postgres::global_slugs::{
+    release_slug_by_name_postgres, release_slug_postgres, reserve_slug_postgres,
+};
 use crate::db::repository::traits::TenantsRepository;
+use crate::identity::slug::{slugify, validate_slug};
 
 pub struct PostgresTenantsRepository {
     pub pool: PgPool,
@@ -47,7 +51,17 @@ impl TenantsRepository for PostgresTenantsRepository {
         name: &str,
         slug: Option<&str>,
     ) -> Result<Tenant, sqlx::Error> {
-        let slug = slug.unwrap_or(id);
+        let final_slug = match slug {
+            Some(s) if !s.trim().is_empty() => {
+                let trimmed = s.trim();
+                validate_slug(trimmed).map_err(|e| sqlx::Error::Protocol(e.to_string()))?;
+                trimmed.to_string()
+            }
+            _ => slugify(name).map_err(|e| sqlx::Error::Protocol(e.to_string()))?,
+        };
+
+        let mut tx = self.pool.begin().await?;
+
         let row = sqlx::query_as::<_, Tenant>(
             r#"
             INSERT INTO tenants (id, name, slug, enabled)
@@ -57,27 +71,68 @@ impl TenantsRepository for PostgresTenantsRepository {
         )
         .bind(id)
         .bind(name)
-        .bind(slug)
-        .fetch_one(&self.pool)
+        .bind(&final_slug)
+        .fetch_one(&mut *tx)
         .await?;
 
+        reserve_slug_postgres(&mut tx, &final_slug, "tenant", id, id).await?;
+
+        tx.commit().await?;
         Ok(row)
     }
 
     async fn update(&self, id: &str, name: &str, slug: Option<&str>) -> Result<(), sqlx::Error> {
-        let slug = slug.unwrap_or(name);
-        sqlx::query(
-            r#"
-            UPDATE tenants
-            SET name = $1, slug = $2, updated_at = CURRENT_TIMESTAMP
-            WHERE id = $3
-            "#,
-        )
-        .bind(name)
-        .bind(slug)
-        .bind(id)
-        .execute(&self.pool)
-        .await?;
+        let existing = self.find_by_id(id).await?.ok_or(sqlx::Error::RowNotFound)?;
+
+        let target_slug = match slug {
+            Some(s) if !s.trim().is_empty() => {
+                let trimmed = s.trim();
+                validate_slug(trimmed).map_err(|e| sqlx::Error::Protocol(e.to_string()))?;
+                trimmed.to_string()
+            }
+            _ => existing.slug.clone().unwrap_or_else(|| id.to_string()),
+        };
+
+        let existing_slug_str = existing.slug.as_deref().unwrap_or("");
+
+        if target_slug == existing_slug_str {
+            // Unchanged slug: registry no-op
+            sqlx::query(
+                r#"
+                UPDATE tenants
+                SET name = $1, updated_at = CURRENT_TIMESTAMP
+                WHERE id = $2
+                "#,
+            )
+            .bind(name)
+            .bind(id)
+            .execute(&self.pool)
+            .await?;
+        } else {
+            // Changed slug: single transaction reserve -> update -> release
+            let mut tx = self.pool.begin().await?;
+
+            reserve_slug_postgres(&mut tx, &target_slug, "tenant", id, id).await?;
+
+            sqlx::query(
+                r#"
+                UPDATE tenants
+                SET name = $1, slug = $2, updated_at = CURRENT_TIMESTAMP
+                WHERE id = $3
+                "#,
+            )
+            .bind(name)
+            .bind(&target_slug)
+            .bind(id)
+            .execute(&mut *tx)
+            .await?;
+
+            if !existing_slug_str.is_empty() {
+                release_slug_by_name_postgres(&mut tx, existing_slug_str, "tenant", id).await?;
+            }
+
+            tx.commit().await?;
+        }
 
         Ok(())
     }
@@ -99,10 +154,16 @@ impl TenantsRepository for PostgresTenantsRepository {
     }
 
     async fn delete(&self, id: &str) -> Result<(), sqlx::Error> {
+        let mut tx = self.pool.begin().await?;
+
+        release_slug_postgres(&mut tx, "tenant", id).await?;
+
         sqlx::query("DELETE FROM tenants WHERE id = $1")
             .bind(id)
-            .execute(&self.pool)
+            .execute(&mut *tx)
             .await?;
+
+        tx.commit().await?;
         Ok(())
     }
 }

src/db/repository/postgres/users.rs

@@ -98,6 +98,125 @@ impl UsersRepository for PostgresUsersRepository {
         Ok(())
     }
 
+    async fn update_user_tenant(&self, id: &str, tenant_id: &str) -> Result<(), sqlx::Error> {
+        sqlx::query(
+            "UPDATE users SET tenant_id = $1, updated_at = to_char(clock_timestamp() AT TIME ZONE 'UTC', 'YYYY-MM-DD\"T\"HH24:MI:SS\"Z\"') WHERE id = $2",
+        )
+        .bind(tenant_id)
+        .bind(id)
+        .execute(&self.pool)
+        .await?;
+        Ok(())
+    }
+
+    async fn reassign_user_tenant_with_audit(
+        &self,
+        user_id: &str,
+        destination_tenant_id: &str,
+        actor_id: Option<&str>,
+        ip_address: Option<&str>,
+        user_agent: Option<&str>,
+    ) -> Result<(), sqlx::Error> {
+        let mut tx = self.pool.begin().await?;
+
+        let user = sqlx::query_as::<_, User>("SELECT * FROM users WHERE id = $1 FOR UPDATE")
+            .bind(user_id)
+            .fetch_optional(&mut *tx)
+            .await?
+            .ok_or(sqlx::Error::RowNotFound)?;
+
+        if user.tenant_id == destination_tenant_id {
+            tx.commit().await?;
+            return Ok(());
+        }
+
+        let from_tenant_id = user.tenant_id.clone();
+
+        if from_tenant_id == crate::db::models::Tenant::DEFAULT_ID {
+            let admin_rows: Vec<(String,)> = sqlx::query_as(
+                "SELECT ur.user_id FROM user_roles ur JOIN roles r ON ur.role_id = r.id WHERE r.name = 'admin' FOR UPDATE",
+            )
+            .fetch_all(&mut *tx)
+            .await?;
+
+            let is_target_admin = admin_rows.iter().any(|r| r.0 == user_id);
+            if is_target_admin && admin_rows.len() <= 1 {
+                return Err(sqlx::Error::Protocol(
+                    "cannot reassign the last system administrator away from default tenant".into(),
+                ));
+            }
+        }
+
+        let dest_exists: Option<(String,)> = sqlx::query_as("SELECT id FROM tenants WHERE id = $1")
+            .bind(destination_tenant_id)
+            .fetch_optional(&mut *tx)
+            .await?;
+        if dest_exists.is_none() {
+            return Err(sqlx::Error::RowNotFound);
+        }
+
+        let collision: Option<(i64,)> =
+            sqlx::query_as("SELECT 1 FROM users WHERE tenant_id = $1 AND username = $2")
+                .bind(destination_tenant_id)
+                .bind(&user.username)
+                .fetch_optional(&mut *tx)
+                .await?;
+        if collision.is_some() {
+            return Err(sqlx::Error::Protocol(format!(
+                "username '{}' already exists in target tenant",
+                user.username
+            )));
+        }
+
+        let result = sqlx::query(
+            "UPDATE users SET tenant_id = $1, updated_at = to_char(clock_timestamp() AT TIME ZONE 'UTC', 'YYYY-MM-DD\"T\"HH24:MI:SS\"Z\"') WHERE id = $2 AND tenant_id = $3",
+        )
+        .bind(destination_tenant_id)
+        .bind(user_id)
+        .bind(&from_tenant_id)
+        .execute(&mut *tx)
+        .await?;
+
+        if result.rows_affected() != 1 {
+            return Err(sqlx::Error::RowNotFound);
+        }
+
+        let metadata = serde_json::json!({
+            "user_id": user.id,
+            "username": user.username,
+            "from_tenant_id": from_tenant_id,
+            "to_tenant_id": destination_tenant_id,
+        })
+        .to_string();
+
+        let audit_id = uuid::Uuid::new_v4().to_string();
+        sqlx::query(
+            r#"
+            INSERT INTO audit_logs (
+                id, actor_user_id, target_user_id,
+                action, resource_type, resource_id,
+                severity, ip_address, user_agent, metadata_json
+            )
+            VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10)
+            "#,
+        )
+        .bind(&audit_id)
+        .bind(actor_id)
+        .bind(Some(&user.id))
+        .bind("user.tenant_reassigned")
+        .bind("user")
+        .bind(Some(&user.id))
+        .bind("info")
+        .bind(ip_address)
+        .bind(user_agent)
+        .bind(&metadata)
+        .execute(&mut *tx)
+        .await?;
+
+        tx.commit().await?;
+        Ok(())
+    }
+
     async fn update_password_hash(&self, id: &str, password_hash: &str) -> Result<(), sqlx::Error> {
         sqlx::query(
             "UPDATE users SET password_hash = $1, updated_at = to_char(clock_timestamp() AT TIME ZONE 'UTC', 'YYYY-MM-DD\"T\"HH24:MI:SS\"Z\"') WHERE id = $2",

src/db/repository/sqlite/application_members.rs

@@ -0,0 +1,478 @@
+use crate::db::models::ApplicationMember;
+use crate::db::repository::traits::ApplicationMembersRepository;
+use async_trait::async_trait;
+use sqlx::SqlitePool;
+
+pub struct SqliteApplicationMembersRepository {
+    pub pool: SqlitePool,
+}
+
+#[async_trait]
+impl ApplicationMembersRepository for SqliteApplicationMembersRepository {
+    async fn list_by_application(
+        &self,
+        application_id: &str,
+    ) -> Result<Vec<ApplicationMember>, sqlx::Error> {
+        sqlx::query_as::<_, ApplicationMember>(
+            r#"
+            SELECT id, application_id, user_id, role, enabled, created_at, updated_at
+            FROM application_members
+            WHERE application_id = ?
+            ORDER BY created_at ASC
+            "#,
+        )
+        .bind(application_id)
+        .fetch_all(&self.pool)
+        .await
+    }
+
+    async fn list_by_user(&self, user_id: &str) -> Result<Vec<ApplicationMember>, sqlx::Error> {
+        sqlx::query_as::<_, ApplicationMember>(
+            r#"
+            SELECT id, application_id, user_id, role, enabled, created_at, updated_at
+            FROM application_members
+            WHERE user_id = ?
+            ORDER BY created_at ASC
+            "#,
+        )
+        .bind(user_id)
+        .fetch_all(&self.pool)
+        .await
+    }
+
+    async fn find(
+        &self,
+        application_id: &str,
+        user_id: &str,
+    ) -> Result<Option<ApplicationMember>, sqlx::Error> {
+        sqlx::query_as::<_, ApplicationMember>(
+            r#"
+            SELECT id, application_id, user_id, role, enabled, created_at, updated_at
+            FROM application_members
+            WHERE application_id = ? AND user_id = ?
+            "#,
+        )
+        .bind(application_id)
+        .bind(user_id)
+        .fetch_optional(&self.pool)
+        .await
+    }
+
+    async fn add(
+        &self,
+        id: &str,
+        application_id: &str,
+        user_id: &str,
+        role: &str,
+    ) -> Result<ApplicationMember, sqlx::Error> {
+        sqlx::query_as::<_, ApplicationMember>(
+            r#"
+            INSERT INTO application_members (id, application_id, user_id, role, enabled)
+            VALUES (?, ?, ?, ?, 1)
+            RETURNING id, application_id, user_id, role, enabled, created_at, updated_at
+            "#,
+        )
+        .bind(id)
+        .bind(application_id)
+        .bind(user_id)
+        .bind(role)
+        .fetch_one(&self.pool)
+        .await
+    }
+
+    async fn update_role(
+        &self,
+        application_id: &str,
+        user_id: &str,
+        role: &str,
+    ) -> Result<(), sqlx::Error> {
+        sqlx::query(
+            r#"
+            UPDATE application_members
+            SET role = ?, updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now')
+            WHERE application_id = ? AND user_id = ?
+            "#,
+        )
+        .bind(role)
+        .bind(application_id)
+        .bind(user_id)
+        .execute(&self.pool)
+        .await?;
+        Ok(())
+    }
+
+    async fn set_enabled(
+        &self,
+        application_id: &str,
+        user_id: &str,
+        enabled: bool,
+    ) -> Result<(), sqlx::Error> {
+        sqlx::query(
+            r#"
+            UPDATE application_members
+            SET enabled = ?, updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now')
+            WHERE application_id = ? AND user_id = ?
+            "#,
+        )
+        .bind(enabled)
+        .bind(application_id)
+        .bind(user_id)
+        .execute(&self.pool)
+        .await?;
+        Ok(())
+    }
+
+    async fn remove(&self, application_id: &str, user_id: &str) -> Result<(), sqlx::Error> {
+        sqlx::query(
+            r#"
+            DELETE FROM application_members
+            WHERE application_id = ? AND user_id = ?
+            "#,
+        )
+        .bind(application_id)
+        .bind(user_id)
+        .execute(&self.pool)
+        .await?;
+        Ok(())
+    }
+
+    async fn add_with_audit(
+        &self,
+        id: &str,
+        application_id: &str,
+        user_id: &str,
+        role: &str,
+        audit_event: Option<crate::audit::AuditEvent<'_>>,
+    ) -> Result<ApplicationMember, sqlx::Error> {
+        let mut tx = self.pool.begin().await?;
+
+        let app_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM applications WHERE id = ?")
+                .bind(application_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let app_tenant_id = match app_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        let user_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM users WHERE id = ?")
+                .bind(user_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let user_tenant_id = match user_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        if app_tenant_id != user_tenant_id {
+            return Err(sqlx::Error::Protocol(
+                "user and application must belong to the same tenant".into(),
+            ));
+        }
+
+        let existing: Option<(String,)> = sqlx::query_as(
+            "SELECT id FROM application_members WHERE application_id = ? AND user_id = ?",
+        )
+        .bind(application_id)
+        .bind(user_id)
+        .fetch_optional(&mut *tx)
+        .await?;
+        if existing.is_some() {
+            return Err(sqlx::Error::Protocol(
+                "user is already a member of this application".into(),
+            ));
+        }
+
+        let member = sqlx::query_as::<_, ApplicationMember>(
+            r#"
+            INSERT INTO application_members (id, application_id, user_id, role, enabled)
+            VALUES (?, ?, ?, ?, 1)
+            RETURNING id, application_id, user_id, role, enabled, created_at, updated_at
+            "#,
+        )
+        .bind(id)
+        .bind(application_id)
+        .bind(user_id)
+        .bind(role)
+        .fetch_one(&mut *tx)
+        .await?;
+
+        if let Some(event) = audit_event {
+            let audit_id = uuid::Uuid::new_v4().to_string();
+            let severity_str = event.severity.to_string();
+            sqlx::query(
+                r#"
+                INSERT INTO audit_logs (
+                    id, actor_user_id, target_user_id,
+                    action, resource_type, resource_id,
+                    severity, ip_address, user_agent, metadata_json
+                )
+                VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+                "#,
+            )
+            .bind(&audit_id)
+            .bind(event.actor_id)
+            .bind(event.target_id)
+            .bind(event.action)
+            .bind(event.resource_type)
+            .bind(event.resource_id)
+            .bind(&severity_str)
+            .bind(event.ip)
+            .bind(event.ua)
+            .bind(event.metadata)
+            .execute(&mut *tx)
+            .await?;
+        }
+
+        tx.commit().await?;
+        Ok(member)
+    }
+
+    async fn update_role_with_audit(
+        &self,
+        application_id: &str,
+        user_id: &str,
+        role: &str,
+        audit_event: Option<crate::audit::AuditEvent<'_>>,
+    ) -> Result<(), sqlx::Error> {
+        let mut tx = self.pool.begin().await?;
+
+        let app_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM applications WHERE id = ?")
+                .bind(application_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let app_tenant_id = match app_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        let user_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM users WHERE id = ?")
+                .bind(user_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let user_tenant_id = match user_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        if app_tenant_id != user_tenant_id {
+            return Err(sqlx::Error::Protocol(
+                "user and application must belong to the same tenant".into(),
+            ));
+        }
+
+        let result = sqlx::query(
+            r#"
+            UPDATE application_members
+            SET role = ?, updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now')
+            WHERE application_id = ? AND user_id = ?
+            "#,
+        )
+        .bind(role)
+        .bind(application_id)
+        .bind(user_id)
+        .execute(&mut *tx)
+        .await?;
+
+        if result.rows_affected() != 1 {
+            return Err(sqlx::Error::RowNotFound);
+        }
+
+        if let Some(event) = audit_event {
+            let audit_id = uuid::Uuid::new_v4().to_string();
+            let severity_str = event.severity.to_string();
+            sqlx::query(
+                r#"
+                INSERT INTO audit_logs (
+                    id, actor_user_id, target_user_id,
+                    action, resource_type, resource_id,
+                    severity, ip_address, user_agent, metadata_json
+                )
+                VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+                "#,
+            )
+            .bind(&audit_id)
+            .bind(event.actor_id)
+            .bind(event.target_id)
+            .bind(event.action)
+            .bind(event.resource_type)
+            .bind(event.resource_id)
+            .bind(&severity_str)
+            .bind(event.ip)
+            .bind(event.ua)
+            .bind(event.metadata)
+            .execute(&mut *tx)
+            .await?;
+        }
+
+        tx.commit().await?;
+        Ok(())
+    }
+
+    async fn set_enabled_with_audit(
+        &self,
+        application_id: &str,
+        user_id: &str,
+        enabled: bool,
+        audit_event: Option<crate::audit::AuditEvent<'_>>,
+    ) -> Result<(), sqlx::Error> {
+        let mut tx = self.pool.begin().await?;
+
+        let app_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM applications WHERE id = ?")
+                .bind(application_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let app_tenant_id = match app_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        let user_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM users WHERE id = ?")
+                .bind(user_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let user_tenant_id = match user_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        if app_tenant_id != user_tenant_id {
+            return Err(sqlx::Error::Protocol(
+                "user and application must belong to the same tenant".into(),
+            ));
+        }
+
+        let result = sqlx::query(
+            r#"
+            UPDATE application_members
+            SET enabled = ?, updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now')
+            WHERE application_id = ? AND user_id = ?
+            "#,
+        )
+        .bind(enabled)
+        .bind(application_id)
+        .bind(user_id)
+        .execute(&mut *tx)
+        .await?;
+
+        if result.rows_affected() != 1 {
+            return Err(sqlx::Error::RowNotFound);
+        }
+
+        if let Some(event) = audit_event {
+            let audit_id = uuid::Uuid::new_v4().to_string();
+            let severity_str = event.severity.to_string();
+            sqlx::query(
+                r#"
+                INSERT INTO audit_logs (
+                    id, actor_user_id, target_user_id,
+                    action, resource_type, resource_id,
+                    severity, ip_address, user_agent, metadata_json
+                )
+                VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+                "#,
+            )
+            .bind(&audit_id)
+            .bind(event.actor_id)
+            .bind(event.target_id)
+            .bind(event.action)
+            .bind(event.resource_type)
+            .bind(event.resource_id)
+            .bind(&severity_str)
+            .bind(event.ip)
+            .bind(event.ua)
+            .bind(event.metadata)
+            .execute(&mut *tx)
+            .await?;
+        }
+
+        tx.commit().await?;
+        Ok(())
+    }
+
+    async fn remove_with_audit(
+        &self,
+        application_id: &str,
+        user_id: &str,
+        audit_event: Option<crate::audit::AuditEvent<'_>>,
+    ) -> Result<(), sqlx::Error> {
+        let mut tx = self.pool.begin().await?;
+
+        let app_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM applications WHERE id = ?")
+                .bind(application_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let app_tenant_id = match app_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        let user_tenant: Option<(String,)> =
+            sqlx::query_as("SELECT tenant_id FROM users WHERE id = ?")
+                .bind(user_id)
+                .fetch_optional(&mut *tx)
+                .await?;
+        let user_tenant_id = match user_tenant {
+            Some(t) => t.0,
+            None => return Err(sqlx::Error::RowNotFound),
+        };
+
+        if app_tenant_id != user_tenant_id {
+            return Err(sqlx::Error::Protocol(
+                "user and application must belong to the same tenant".into(),
+            ));
+        }
+
+        let result = sqlx::query(
+            r#"
+            DELETE FROM application_members
+            WHERE application_id = ? AND user_id = ?
+            "#,
+        )
+        .bind(application_id)
+        .bind(user_id)
+        .execute(&mut *tx)
+        .await?;
+
+        if result.rows_affected() != 1 {
+            return Err(sqlx::Error::RowNotFound);
+        }
+
+        if let Some(event) = audit_event {
+            let audit_id = uuid::Uuid::new_v4().to_string();
+            let severity_str = event.severity.to_string();
+            sqlx::query(
+                r#"
+                INSERT INTO audit_logs (
+                    id, actor_user_id, target_user_id,
+                    action, resource_type, resource_id,
+                    severity, ip_address, user_agent, metadata_json
+                )
+                VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+                "#,
+            )
+            .bind(&audit_id)
+            .bind(event.actor_id)
+            .bind(event.target_id)
+            .bind(event.action)
+            .bind(event.resource_type)
+            .bind(event.resource_id)
+            .bind(&severity_str)
+            .bind(event.ip)
+            .bind(event.ua)
+            .bind(event.metadata)
+            .execute(&mut *tx)
+            .await?;
+        }
+
+        tx.commit().await?;
+        Ok(())
+    }
+}

src/db/repository/sqlite/applications.rs

@@ -1,9 +1,11 @@
+use crate::db::models::Application;
+use crate::db::repository::sqlite::global_slugs::{
+    release_slug_by_name_sqlite, release_slug_sqlite, reserve_slug_sqlite,
+};
 use crate::db::repository::traits::ApplicationsRepository;
 use async_trait::async_trait;
 use sqlx::SqlitePool;
 
-use crate::db::models::Application;
-
 pub struct SqliteApplicationsRepository {
     pub pool: SqlitePool,
 }
@@ -25,6 +27,8 @@ impl ApplicationsRepository for SqliteApplicationsRepository {
     ) -> Result<Application, sqlx::Error> {
         let mut tx = self.pool.begin().await?;
 
+        reserve_slug_sqlite(&mut tx, slug, "application", id, tenant_id).await?;
+
         let app = sqlx::query_as::<_, Application>(
             r#"
         INSERT INTO applications (id, tenant_id, name, slug, client_id, client_secret_hash, description, redirect_uris, scopes)
@@ -188,31 +192,73 @@ impl ApplicationsRepository for SqliteApplicationsRepository {
         scopes: Option<&str>,
         enabled: bool,
     ) -> Result<(), sqlx::Error> {
-        sqlx::query(
-            r#"
-        UPDATE applications
-        SET name = ?, slug = ?, description = ?, redirect_uris = ?, scopes = ?, enabled = ?,
-            updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now')
-        WHERE id = ?
-        "#,
-        )
-        .bind(name)
-        .bind(slug)
-        .bind(description)
-        .bind(redirect_uris)
-        .bind(scopes)
-        .bind(enabled)
-        .bind(id)
-        .execute(&self.pool)
-        .await?;
+        let existing = self.find_by_id(id).await?.ok_or(sqlx::Error::RowNotFound)?;
+
+        let existing_slug_str = existing.slug.as_deref().unwrap_or("");
+
+        if slug == existing_slug_str {
+            // Unchanged slug: registry no-op
+            sqlx::query(
+                r#"
+            UPDATE applications
+            SET name = ?, description = ?, redirect_uris = ?, scopes = ?, enabled = ?,
+                updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now')
+            WHERE id = ?
+            "#,
+            )
+            .bind(name)
+            .bind(description)
+            .bind(redirect_uris)
+            .bind(scopes)
+            .bind(enabled)
+            .bind(id)
+            .execute(&self.pool)
+            .await?;
+        } else {
+            // Changed slug: single transaction reserve -> update -> release
+            let mut tx = self.pool.begin().await?;
+
+            reserve_slug_sqlite(&mut tx, slug, "application", id, &existing.tenant_id).await?;
+
+            sqlx::query(
+                r#"
+            UPDATE applications
+            SET name = ?, slug = ?, description = ?, redirect_uris = ?, scopes = ?, enabled = ?,
+                updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now')
+            WHERE id = ?
+            "#,
+            )
+            .bind(name)
+            .bind(slug)
+            .bind(description)
+            .bind(redirect_uris)
+            .bind(scopes)
+            .bind(enabled)
+            .bind(id)
+            .execute(&mut *tx)
+            .await?;
+
+            if !existing_slug_str.is_empty() {
+                release_slug_by_name_sqlite(&mut tx, existing_slug_str, "application", id).await?;
+            }
+
+            tx.commit().await?;
+        }
+
         Ok(())
     }
 
     async fn delete(&self, id: &str) -> Result<(), sqlx::Error> {
+        let mut tx = self.pool.begin().await?;
+
+        release_slug_sqlite(&mut tx, "application", id).await?;
+
         sqlx::query("DELETE FROM applications WHERE id = ?")
             .bind(id)
-            .execute(&self.pool)
+            .execute(&mut *tx)
             .await?;
+
+        tx.commit().await?;
         Ok(())
     }
 

src/db/repository/sqlite/audit.rs

@@ -65,12 +65,11 @@ impl AuditRepository for SqliteAuditRepository {
     }
 
     async fn list_filtered(&self, filter: &AuditFilter) -> Result<Vec<AuditLog>, sqlx::Error> {
-        // Build a dynamic but simple filter using COALESCE-style optional matches.
-        // Empty optionals are treated as wildcards via OR IS NULL pattern with bind of None.
         let search_like = filter
             .search
             .as_ref()
             .map(|s| format!("%{}%", s.replace('%', "\\%")));
+        let success_val = filter.success.map(|b| if b { 1i32 } else { 0i32 });
 
         sqlx::query_as::<_, AuditLog>(
             r#"
@@ -89,8 +88,13 @@ impl AuditRepository for SqliteAuditRepository {
              OR ip_address LIKE ?7 ESCAPE '\'
              OR metadata_json LIKE ?7 ESCAPE '\'
           )
+          AND (
+                ?8 IS NULL
+             OR (?8 = 1 AND action NOT LIKE '%fail%' AND action NOT LIKE '%denied%' AND severity != 'critical')
+             OR (?8 = 0 AND (action LIKE '%fail%' OR action LIKE '%denied%' OR severity = 'critical'))
+          )
         ORDER BY created_at DESC
-        LIMIT ?8 OFFSET ?9
+        LIMIT ?9 OFFSET ?10
         "#,
         )
         .bind(filter.actor_user_id.as_deref())
@@ -100,6 +104,7 @@ impl AuditRepository for SqliteAuditRepository {
         .bind(filter.since.as_deref())
         .bind(filter.until.as_deref())
         .bind(search_like.as_deref())
+        .bind(success_val)
         .bind(filter.limit)
         .bind(filter.offset)
         .fetch_all(&self.pool)
@@ -111,6 +116,7 @@ impl AuditRepository for SqliteAuditRepository {
             .search
             .as_ref()
             .map(|s| format!("%{}%", s.replace('%', "\\%")));
+        let success_val = filter.success.map(|b| if b { 1i32 } else { 0i32 });
 
         let row: (i64,) = sqlx::query_as(
             r#"
@@ -129,6 +135,11 @@ impl AuditRepository for SqliteAuditRepository {
              OR ip_address LIKE ?7 ESCAPE '\'
              OR metadata_json LIKE ?7 ESCAPE '\'
           )
+          AND (
+                ?8 IS NULL
+             OR (?8 = 1 AND action NOT LIKE '%fail%' AND action NOT LIKE '%denied%' AND severity != 'critical')
+             OR (?8 = 0 AND (action LIKE '%fail%' OR action LIKE '%denied%' OR severity = 'critical'))
+          )
         "#,
         )
         .bind(filter.actor_user_id.as_deref())
@@ -138,6 +149,7 @@ impl AuditRepository for SqliteAuditRepository {
         .bind(filter.since.as_deref())
         .bind(filter.until.as_deref())
         .bind(search_like.as_deref())
+        .bind(success_val)
         .fetch_one(&self.pool)
         .await?;
         Ok(row.0)

src/db/repository/sqlite/global_slugs.rs

@@ -0,0 +1,68 @@
+use crate::db::models::GlobalSlug;
+use crate::db::repository::traits::GlobalSlugsRepository;
+use sqlx::SqlitePool;
+
+pub struct SqliteGlobalSlugsRepository {
+    pub pool: SqlitePool,
+}
+
+#[async_trait::async_trait]
+impl GlobalSlugsRepository for SqliteGlobalSlugsRepository {
+    async fn find_by_slug(&self, slug: &str) -> Result<Option<GlobalSlug>, sqlx::Error> {
+        sqlx::query_as::<_, GlobalSlug>(
+            "SELECT slug, entity_type, entity_id, tenant_id, created_at FROM global_slugs WHERE slug = ?"
+        )
+        .bind(slug)
+        .fetch_optional(&self.pool)
+        .await
+    }
+}
+
+pub async fn reserve_slug_sqlite(
+    conn: &mut sqlx::SqliteConnection,
+    slug: &str,
+    entity_type: &str,
+    entity_id: &str,
+    tenant_id: &str,
+) -> Result<(), sqlx::Error> {
+    sqlx::query(
+        "INSERT INTO global_slugs (slug, entity_type, entity_id, tenant_id) VALUES (?, ?, ?, ?)",
+    )
+    .bind(slug)
+    .bind(entity_type)
+    .bind(entity_id)
+    .bind(tenant_id)
+    .execute(conn)
+    .await?;
+    Ok(())
+}
+
+pub async fn release_slug_sqlite(
+    conn: &mut sqlx::SqliteConnection,
+    entity_type: &str,
+    entity_id: &str,
+) -> Result<u64, sqlx::Error> {
+    let res = sqlx::query("DELETE FROM global_slugs WHERE entity_type = ? AND entity_id = ?")
+        .bind(entity_type)
+        .bind(entity_id)
+        .execute(conn)
+        .await?;
+    Ok(res.rows_affected())
+}
+
+pub async fn release_slug_by_name_sqlite(
+    conn: &mut sqlx::SqliteConnection,
+    slug: &str,
+    entity_type: &str,
+    entity_id: &str,
+) -> Result<u64, sqlx::Error> {
+    let res = sqlx::query(
+        "DELETE FROM global_slugs WHERE slug = ? AND entity_type = ? AND entity_id = ?",
+    )
+    .bind(slug)
+    .bind(entity_type)
+    .bind(entity_id)
+    .execute(conn)
+    .await?;
+    Ok(res.rows_affected())
+}

src/db/repository/sqlite/mod.rs

@@ -1,5 +1,7 @@
+pub mod application_members;
 pub mod applications;
 pub mod audit;
+pub mod global_slugs;
 pub mod groups;
 pub mod permissions;
 pub mod refresh_tokens;

src/db/repository/sqlite/tenants.rs

@@ -1,7 +1,11 @@
 use sqlx::SqlitePool;
 
 use crate::db::models::Tenant;
+use crate::db::repository::sqlite::global_slugs::{
+    release_slug_by_name_sqlite, release_slug_sqlite, reserve_slug_sqlite,
+};
 use crate::db::repository::traits::TenantsRepository;
+use crate::identity::slug::{slugify, validate_slug};
 
 pub struct SqliteTenantsRepository {
     pub pool: SqlitePool,
@@ -47,7 +51,17 @@ impl TenantsRepository for SqliteTenantsRepository {
         name: &str,
         slug: Option<&str>,
     ) -> Result<Tenant, sqlx::Error> {
-        let slug = slug.unwrap_or(id);
+        let final_slug = match slug {
+            Some(s) if !s.trim().is_empty() => {
+                let trimmed = s.trim();
+                validate_slug(trimmed).map_err(|e| sqlx::Error::Protocol(e.to_string()))?;
+                trimmed.to_string()
+            }
+            _ => slugify(name).map_err(|e| sqlx::Error::Protocol(e.to_string()))?,
+        };
+
+        let mut tx = self.pool.begin().await?;
+
         let row = sqlx::query_as::<_, Tenant>(
             r#"
             INSERT INTO tenants (id, name, slug, enabled)
@@ -57,27 +71,68 @@ impl TenantsRepository for SqliteTenantsRepository {
         )
         .bind(id)
         .bind(name)
-        .bind(slug)
-        .fetch_one(&self.pool)
+        .bind(&final_slug)
+        .fetch_one(&mut *tx)
         .await?;
 
+        reserve_slug_sqlite(&mut tx, &final_slug, "tenant", id, id).await?;
+
+        tx.commit().await?;
         Ok(row)
     }
 
     async fn update(&self, id: &str, name: &str, slug: Option<&str>) -> Result<(), sqlx::Error> {
-        let slug = slug.unwrap_or(name);
-        sqlx::query(
-            r#"
-            UPDATE tenants
-            SET name = ?, slug = ?, updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now')
-            WHERE id = ?
-            "#,
-        )
-        .bind(name)
-        .bind(slug)
-        .bind(id)
-        .execute(&self.pool)
-        .await?;
+        let existing = self.find_by_id(id).await?.ok_or(sqlx::Error::RowNotFound)?;
+
+        let target_slug = match slug {
+            Some(s) if !s.trim().is_empty() => {
+                let trimmed = s.trim();
+                validate_slug(trimmed).map_err(|e| sqlx::Error::Protocol(e.to_string()))?;
+                trimmed.to_string()
+            }
+            _ => existing.slug.clone().unwrap_or_else(|| id.to_string()),
+        };
+
+        let existing_slug_str = existing.slug.as_deref().unwrap_or("");
+
+        if target_slug == existing_slug_str {
+            // Unchanged slug: registry no-op
+            sqlx::query(
+                r#"
+                UPDATE tenants
+                SET name = ?, updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now')
+                WHERE id = ?
+                "#,
+            )
+            .bind(name)
+            .bind(id)
+            .execute(&self.pool)
+            .await?;
+        } else {
+            // Changed slug: single transaction reserve -> update -> release
+            let mut tx = self.pool.begin().await?;
+
+            reserve_slug_sqlite(&mut tx, &target_slug, "tenant", id, id).await?;
+
+            sqlx::query(
+                r#"
+                UPDATE tenants
+                SET name = ?, slug = ?, updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now')
+                WHERE id = ?
+                "#,
+            )
+            .bind(name)
+            .bind(&target_slug)
+            .bind(id)
+            .execute(&mut *tx)
+            .await?;
+
+            if !existing_slug_str.is_empty() {
+                release_slug_by_name_sqlite(&mut tx, existing_slug_str, "tenant", id).await?;
+            }
+
+            tx.commit().await?;
+        }
 
         Ok(())
     }
@@ -99,10 +154,16 @@ impl TenantsRepository for SqliteTenantsRepository {
     }
 
     async fn delete(&self, id: &str) -> Result<(), sqlx::Error> {
+        let mut tx = self.pool.begin().await?;
+
+        release_slug_sqlite(&mut tx, "tenant", id).await?;
+
         sqlx::query("DELETE FROM tenants WHERE id = ?")
             .bind(id)
-            .execute(&self.pool)
+            .execute(&mut *tx)
             .await?;
+
+        tx.commit().await?;
         Ok(())
     }
 }

src/db/repository/sqlite/users.rs

@@ -100,6 +100,134 @@ impl UsersRepository for SqliteUsersRepository {
         Ok(())
     }
 
+    async fn update_user_tenant(&self, id: &str, tenant_id: &str) -> Result<(), sqlx::Error> {
+        sqlx::query(
+            "UPDATE users SET tenant_id = ?, updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now') WHERE id = ?",
+        )
+        .bind(tenant_id)
+        .bind(id)
+        .execute(&self.pool)
+        .await?;
+        Ok(())
+    }
+
+    async fn reassign_user_tenant_with_audit(
+        &self,
+        user_id: &str,
+        destination_tenant_id: &str,
+        actor_id: Option<&str>,
+        ip_address: Option<&str>,
+        user_agent: Option<&str>,
+    ) -> Result<(), sqlx::Error> {
+        let mut tx = self.pool.begin().await?;
+
+        let user = sqlx::query_as::<_, User>("SELECT * FROM users WHERE id = ?")
+            .bind(user_id)
+            .fetch_optional(&mut *tx)
+            .await?
+            .ok_or(sqlx::Error::RowNotFound)?;
+
+        if user.tenant_id == destination_tenant_id {
+            tx.commit().await?;
+            return Ok(());
+        }
+
+        let from_tenant_id = user.tenant_id.clone();
+
+        if from_tenant_id == crate::db::models::Tenant::DEFAULT_ID {
+            let is_admin: Option<(i64,)> = sqlx::query_as(
+                "SELECT 1 FROM user_roles ur JOIN roles r ON ur.role_id = r.id WHERE ur.user_id = ? AND r.name = 'admin'",
+            )
+            .bind(user_id)
+            .fetch_optional(&mut *tx)
+            .await?;
+
+            if is_admin.is_some() {
+                let admin_count: (i64,) = sqlx::query_as(
+                    "SELECT COUNT(DISTINCT ur.user_id) FROM user_roles ur JOIN roles r ON ur.role_id = r.id WHERE r.name = 'admin'",
+                )
+                .fetch_one(&mut *tx)
+                .await?;
+
+                if admin_count.0 <= 1 {
+                    return Err(sqlx::Error::Protocol(
+                        "cannot reassign the last system administrator away from default tenant"
+                            .into(),
+                    ));
+                }
+            }
+        }
+
+        let dest_exists: Option<(String,)> = sqlx::query_as("SELECT id FROM tenants WHERE id = ?")
+            .bind(destination_tenant_id)
+            .fetch_optional(&mut *tx)
+            .await?;
+        if dest_exists.is_none() {
+            return Err(sqlx::Error::RowNotFound);
+        }
+
+        let collision: Option<(i64,)> =
+            sqlx::query_as("SELECT 1 FROM users WHERE tenant_id = ? AND username = ?")
+                .bind(destination_tenant_id)
+                .bind(&user.username)
+                .fetch_optional(&mut *tx)
+                .await?;
+        if collision.is_some() {
+            return Err(sqlx::Error::Protocol(format!(
+                "username '{}' already exists in target tenant",
+                user.username
+            )));
+        }
+
+        let result = sqlx::query(
+            "UPDATE users SET tenant_id = ?, updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now') WHERE id = ? AND tenant_id = ?",
+        )
+        .bind(destination_tenant_id)
+        .bind(user_id)
+        .bind(&from_tenant_id)
+        .execute(&mut *tx)
+        .await?;
+
+        if result.rows_affected() != 1 {
+            return Err(sqlx::Error::RowNotFound);
+        }
+
+        let metadata = serde_json::json!({
+            "user_id": user.id,
+            "username": user.username,
+            "from_tenant_id": from_tenant_id,
+            "to_tenant_id": destination_tenant_id,
+        })
+        .to_string();
+
+        let audit_id = uuid::Uuid::new_v4().to_string();
+        sqlx::query(
+            r#"
+            INSERT INTO audit_logs (
+                id, actor_user_id, target_user_id,
+                action, resource_type, resource_id,
+                severity, ip_address, user_agent, metadata_json
+            )
+            VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+            "#,
+        )
+        .bind(&audit_id)
+        .bind(actor_id)
+        .bind(Some(&user.id))
+        .bind("user.tenant_reassigned")
+        .bind("user")
+        .bind(Some(&user.id))
+        .bind("info")
+        .bind(ip_address)
+        .bind(user_agent)
+        .bind(&metadata)
+        .execute(&mut *tx)
+        .await?;
+
+        tx.commit().await?;
+        Ok(())
+    }
+
     async fn update_password_hash(&self, id: &str, password_hash: &str) -> Result<(), sqlx::Error> {
         sqlx::query(
         "UPDATE users SET password_hash = ?, updated_at = strftime('%Y-%m-%dT%H:%M:%SZ', 'now') WHERE id = ?",

src/db/repository/traits.rs

@@ -1,8 +1,13 @@
 use crate::db::models::{
-    ApiToken, Application, AuditFilter, AuditLog, Group, Permission, RefreshToken, Role,
-    ServiceAccount, Session, Tenant, User, UserProfile,
+    ApiToken, Application, ApplicationMember, AuditFilter, AuditLog, GlobalSlug, Group, Permission,
+    RefreshToken, Role, ServiceAccount, Session, Tenant, User, UserProfile,
 };
 
+#[async_trait::async_trait]
+pub trait GlobalSlugsRepository: Send + Sync {
+    async fn find_by_slug(&self, slug: &str) -> Result<Option<GlobalSlug>, sqlx::Error>;
+}
+
 #[async_trait::async_trait]
 pub trait UsersRepository: Send + Sync {
     async fn find_by_id(&self, id: &str) -> Result<Option<User>, sqlx::Error>;
@@ -16,6 +21,15 @@ pub trait UsersRepository: Send + Sync {
         password_hash: &str,
     ) -> Result<User, sqlx::Error>;
     async fn update_status(&self, id: &str, status: i32) -> Result<(), sqlx::Error>;
+    async fn update_user_tenant(&self, id: &str, tenant_id: &str) -> Result<(), sqlx::Error>;
+    async fn reassign_user_tenant_with_audit(
+        &self,
+        user_id: &str,
+        destination_tenant_id: &str,
+        actor_id: Option<&str>,
+        ip_address: Option<&str>,
+        user_agent: Option<&str>,
+    ) -> Result<(), sqlx::Error>;
     async fn update_password_hash(&self, id: &str, password_hash: &str) -> Result<(), sqlx::Error>;
     async fn set_last_login(&self, id: &str) -> Result<(), sqlx::Error>;
     async fn username_exists(&self, tenant_id: &str, username: &str) -> Result<bool, sqlx::Error>;
@@ -271,3 +285,69 @@ pub trait GroupsRepository: Send + Sync {
     async fn remove_member(&self, group_id: &str, user_id: &str) -> Result<(), sqlx::Error>;
     async fn count(&self, tenant_id: &str) -> Result<i64, sqlx::Error>;
 }
+
+/// Application membership repository (user ↔ application assignment).
+///
+/// Membership roles are lightweight metadata and do not modify global RBAC.
+#[async_trait::async_trait]
+pub trait ApplicationMembersRepository: Send + Sync {
+    async fn list_by_application(
+        &self,
+        application_id: &str,
+    ) -> Result<Vec<ApplicationMember>, sqlx::Error>;
+    async fn list_by_user(&self, user_id: &str) -> Result<Vec<ApplicationMember>, sqlx::Error>;
+    async fn find(
+        &self,
+        application_id: &str,
+        user_id: &str,
+    ) -> Result<Option<ApplicationMember>, sqlx::Error>;
+    async fn add(
+        &self,
+        id: &str,
+        application_id: &str,
+        user_id: &str,
+        role: &str,
+    ) -> Result<ApplicationMember, sqlx::Error>;
+    async fn update_role(
+        &self,
+        application_id: &str,
+        user_id: &str,
+        role: &str,
+    ) -> Result<(), sqlx::Error>;
+    async fn set_enabled(
+        &self,
+        application_id: &str,
+        user_id: &str,
+        enabled: bool,
+    ) -> Result<(), sqlx::Error>;
+    async fn remove(&self, application_id: &str, user_id: &str) -> Result<(), sqlx::Error>;
+
+    async fn add_with_audit(
+        &self,
+        id: &str,
+        application_id: &str,
+        user_id: &str,
+        role: &str,
+        audit_event: Option<crate::audit::AuditEvent<'_>>,
+    ) -> Result<ApplicationMember, sqlx::Error>;
+    async fn update_role_with_audit(
+        &self,
+        application_id: &str,
+        user_id: &str,
+        role: &str,
+        audit_event: Option<crate::audit::AuditEvent<'_>>,
+    ) -> Result<(), sqlx::Error>;
+    async fn set_enabled_with_audit(
+        &self,
+        application_id: &str,
+        user_id: &str,
+        enabled: bool,
+        audit_event: Option<crate::audit::AuditEvent<'_>>,
+    ) -> Result<(), sqlx::Error>;
+    async fn remove_with_audit(
+        &self,
+        application_id: &str,
+        user_id: &str,
+        audit_event: Option<crate::audit::AuditEvent<'_>>,
+    ) -> Result<(), sqlx::Error>;
+}

src/identity/application_members.rs

@@ -0,0 +1,331 @@
+//! Application membership domain logic.
+//!
+//! Assigns existing NX9-Auth users to registered applications.
+//! Membership roles (owner/admin/member) are lightweight metadata only and
+//! MUST NOT grant global RBAC permissions such as `applications:manage`.
+
+use crate::db::models::{Application, ApplicationMember, ApplicationMembershipRole};
+use crate::error::AppError;
+use uuid::Uuid;
+
+fn parse_role(role: Option<&str>) -> Result<ApplicationMembershipRole, AppError> {
+    match role {
+        None | Some("") => Ok(ApplicationMembershipRole::Member),
+        Some(r) => ApplicationMembershipRole::parse(r).ok_or_else(|| {
+            AppError::InvalidInput(format!(
+                "invalid membership role '{r}'; allowed values are owner, admin, member"
+            ))
+        }),
+    }
+}
+
+/// List members of an application.
+pub async fn list_by_application(
+    provider: &std::sync::Arc<dyn crate::db::provider::DatabaseProvider>,
+    application_id: &str,
+) -> Result<Vec<ApplicationMember>, AppError> {
+    // Ensure application exists
+    let _ = provider
+        .applications()
+        .find_by_id(application_id)
+        .await
+        .map_err(AppError::Database)?
+        .ok_or(AppError::NotFound)?;
+
+    provider
+        .application_members()
+        .list_by_application(application_id)
+        .await
+        .map_err(AppError::Database)
+}
+
+/// List application memberships for a user.
+pub async fn list_by_user(
+    provider: &std::sync::Arc<dyn crate::db::provider::DatabaseProvider>,
+    user_id: &str,
+) -> Result<Vec<ApplicationMember>, AppError> {
+    let _ = provider
+        .users()
+        .find_by_id(user_id)
+        .await
+        .map_err(AppError::Database)?
+        .ok_or(AppError::NotFound)?;
+
+    provider
+        .application_members()
+        .list_by_user(user_id)
+        .await
+        .map_err(AppError::Database)
+}
+
+/// Find a single membership.
+pub async fn find(
+    provider: &std::sync::Arc<dyn crate::db::provider::DatabaseProvider>,
+    application_id: &str,
+    user_id: &str,
+) -> Result<Option<ApplicationMember>, AppError> {
+    provider
+        .application_members()
+        .find(application_id, user_id)
+        .await
+        .map_err(AppError::Database)
+}
+
+/// Assign an existing same-tenant user to an application.
+pub async fn add(
+    provider: &std::sync::Arc<dyn crate::db::provider::DatabaseProvider>,
+    application_id: &str,
+    user_id: &str,
+    role: Option<&str>,
+    audit_actor_id: Option<&str>,
+    audit_ip: Option<&str>,
+    audit_ua: Option<&str>,
+) -> Result<ApplicationMember, AppError> {
+    let role = parse_role(role)?;
+
+    let app = provider
+        .applications()
+        .find_by_id(application_id)
+        .await
+        .map_err(AppError::Database)?
+        .ok_or(AppError::NotFound)?;
+
+    let user = provider
+        .users()
+        .find_by_id(user_id)
+        .await
+        .map_err(AppError::Database)?
+        .ok_or(AppError::NotFound)?;
+
+    // Tenant isolation: never allow cross-tenant assignment.
+    if user.tenant_id != app.tenant_id {
+        return Err(AppError::NotFound);
+    }
+
+    if provider
+        .application_members()
+        .find(application_id, user_id)
+        .await
+        .map_err(AppError::Database)?
+        .is_some()
+    {
+        return Err(AppError::Conflict(
+            "user is already a member of this application".into(),
+        ));
+    }
+
+    let id = Uuid::new_v4().to_string();
+
+    let metadata = serde_json::json!({
+        "application_id": application_id,
+        "user_id": user_id,
+        "role": role.as_str(),
+    })
+    .to_string();
+
+    let audit_event = crate::audit::AuditEvent {
+        actor_id: audit_actor_id,
+        target_id: Some(user_id),
+        action: "application.member_added",
+        resource_type: "application",
+        resource_id: Some(application_id),
+        severity: crate::db::models::AuditSeverity::Info,
+        ip: audit_ip,
+        ua: audit_ua,
+        metadata: Some(&metadata),
+    };
+
+    let member = provider
+        .application_members()
+        .add_with_audit(
+            &id,
+            application_id,
+            user_id,
+            role.as_str(),
+            Some(audit_event),
+        )
+        .await
+        .map_err(AppError::Database)?;
+
+    let _ = app;
+    Ok(member)
+}
+
+/// Update membership role and/or enabled state.
+#[allow(clippy::too_many_arguments)]
+pub async fn update(
+    provider: &std::sync::Arc<dyn crate::db::provider::DatabaseProvider>,
+    application_id: &str,
+    user_id: &str,
+    role: Option<&str>,
+    enabled: Option<bool>,
+    audit_actor_id: Option<&str>,
+    audit_ip: Option<&str>,
+    audit_ua: Option<&str>,
+) -> Result<ApplicationMember, AppError> {
+    if role.is_none() && enabled.is_none() {
+        return Err(AppError::InvalidInput(
+            "at least one of role or enabled must be provided".into(),
+        ));
+    }
+
+    // Ensure application exists
+    let _ = provider
+        .applications()
+        .find_by_id(application_id)
+        .await
+        .map_err(AppError::Database)?
+        .ok_or(AppError::NotFound)?;
+
+    let existing = provider
+        .application_members()
+        .find(application_id, user_id)
+        .await
+        .map_err(AppError::Database)?
+        .ok_or(AppError::NotFound)?;
+
+    if let Some(role_str) = role {
+        let new_role = parse_role(Some(role_str))?;
+        if new_role.as_str() != existing.role {
+            let previous_role = existing.role.clone();
+            let metadata = serde_json::json!({
+                "application_id": application_id,
+                "user_id": user_id,
+                "previous_role": previous_role,
+                "new_role": new_role.as_str(),
+            })
+            .to_string();
+
+            let audit_event = crate::audit::AuditEvent {
+                actor_id: audit_actor_id,
+                target_id: Some(user_id),
+                action: "application.member_role_changed",
+                resource_type: "application",
+                resource_id: Some(application_id),
+                severity: crate::db::models::AuditSeverity::Info,
+                ip: audit_ip,
+                ua: audit_ua,
+                metadata: Some(&metadata),
+            };
+
+            provider
+                .application_members()
+                .update_role_with_audit(
+                    application_id,
+                    user_id,
+                    new_role.as_str(),
+                    Some(audit_event),
+                )
+                .await
+                .map_err(AppError::Database)?;
+        }
+    }
+
+    if let Some(new_enabled) = enabled {
+        if new_enabled != existing.enabled {
+            let action = if new_enabled {
+                "application.member_enabled"
+            } else {
+                "application.member_disabled"
+            };
+
+            let metadata = serde_json::json!({
+                "application_id": application_id,
+                "user_id": user_id,
+                "role": existing.role,
+                "enabled": new_enabled,
+            })
+            .to_string();
+
+            let audit_event = crate::audit::AuditEvent {
+                actor_id: audit_actor_id,
+                target_id: Some(user_id),
+                action,
+                resource_type: "application",
+                resource_id: Some(application_id),
+                severity: crate::db::models::AuditSeverity::Info,
+                ip: audit_ip,
+                ua: audit_ua,
+                metadata: Some(&metadata),
+            };
+
+            provider
+                .application_members()
+                .set_enabled_with_audit(application_id, user_id, new_enabled, Some(audit_event))
+                .await
+                .map_err(AppError::Database)?;
+        }
+    }
+
+    provider
+        .application_members()
+        .find(application_id, user_id)
+        .await
+        .map_err(AppError::Database)?
+        .ok_or(AppError::NotFound)
+}
+
+/// Remove a user from an application (does not delete the user account).
+pub async fn remove(
+    provider: &std::sync::Arc<dyn crate::db::provider::DatabaseProvider>,
+    application_id: &str,
+    user_id: &str,
+    audit_actor_id: Option<&str>,
+    audit_ip: Option<&str>,
+    audit_ua: Option<&str>,
+) -> Result<(), AppError> {
+    // Ensure application exists
+    let _ = provider
+        .applications()
+        .find_by_id(application_id)
+        .await
+        .map_err(AppError::Database)?
+        .ok_or(AppError::NotFound)?;
+
+    let existing = provider
+        .application_members()
+        .find(application_id, user_id)
+        .await
+        .map_err(AppError::Database)?
+        .ok_or(AppError::NotFound)?;
+
+    let metadata = serde_json::json!({
+        "application_id": application_id,
+        "user_id": user_id,
+        "role": existing.role,
+    })
+    .to_string();
+
+    let audit_event = crate::audit::AuditEvent {
+        actor_id: audit_actor_id,
+        target_id: Some(user_id),
+        action: "application.member_removed",
+        resource_type: "application",
+        resource_id: Some(application_id),
+        severity: crate::db::models::AuditSeverity::Info,
+        ip: audit_ip,
+        ua: audit_ua,
+        metadata: Some(&metadata),
+    };
+
+    provider
+        .application_members()
+        .remove_with_audit(application_id, user_id, Some(audit_event))
+        .await
+        .map_err(AppError::Database)?;
+
+    Ok(())
+}
+
+/// Helper used by API responses that need application details for a membership.
+pub async fn load_application(
+    provider: &std::sync::Arc<dyn crate::db::provider::DatabaseProvider>,
+    application_id: &str,
+) -> Result<Application, AppError> {
+    provider
+        .applications()
+        .find_by_id(application_id)
+        .await
+        .map_err(AppError::Database)?
+        .ok_or(AppError::NotFound)
+}

src/identity/applications.rs

@@ -108,11 +108,13 @@ pub async fn create(
             "name and slug cannot be empty".into(),
         ));
     }
+    crate::identity::slug::validate_slug(slug)?;
+
     if let Some(ref uris) = redirect_uris {
         validate_redirect_uris(uris)?;
     }
     if provider
-        .applications()
+        .global_slugs()
         .find_by_slug(slug)
         .await
         .map_err(AppError::Database)?
@@ -312,16 +314,18 @@ pub async fn update(
             "name and slug cannot be empty".into(),
         ));
     }
+    crate::identity::slug::validate_slug(slug)?;
+
     if let Some(ref uris) = redirect_uris {
         validate_redirect_uris(uris)?;
     }
     if let Some(other) = provider
-        .applications()
+        .global_slugs()
         .find_by_slug(slug)
         .await
         .map_err(AppError::Database)?
     {
-        if other.id != id {
+        if other.entity_id != id || other.entity_type != "application" {
             return Err(AppError::Conflict(format!("slug '{slug}' already exists")));
         }
     }

src/identity/mod.rs

@@ -1,5 +1,7 @@
+pub mod application_members;
 pub mod applications;
 pub mod permissions;
 pub mod roles;
 pub mod service_accounts;
+pub mod slug;
 pub mod users;

src/identity/slug.rs

@@ -0,0 +1,133 @@
+use crate::error::AppError;
+
+pub const RESERVED_SLUGS: &[&str] = &[
+    "admin",
+    "api",
+    "system",
+    "auth",
+    "login",
+    "logout",
+    "dashboard",
+    "health",
+    "metrics",
+    "root",
+    "public",
+    "private",
+    "null",
+    "undefined",
+    "config",
+    "settings",
+    "account",
+    "accounts",
+    "role",
+    "roles",
+    "permission",
+    "permissions",
+    "group",
+    "groups",
+    "service-account",
+    "service-accounts",
+];
+
+/// Validates an explicit or derived slug string according to server-side policy:
+/// - Must be 2..=63 characters in length.
+/// - Must consist only of lowercase ASCII alphanumeric characters ('a'..='z', '0'..='9') and hyphens ('-').
+/// - Cannot start or end with a hyphen.
+/// - Cannot contain consecutive hyphens ("--").
+/// - Cannot be one of the reserved slug names (except "default" which is preserved for built-in tenant).
+pub fn validate_slug(slug: &str) -> Result<(), AppError> {
+    let s = slug.trim();
+    if s.is_empty() {
+        return Err(AppError::InvalidInput("slug cannot be empty".into()));
+    }
+    if s.len() < 2 || s.len() > 63 {
+        return Err(AppError::InvalidInput(format!(
+            "slug length must be between 2 and 63 characters, got {}",
+            s.len()
+        )));
+    }
+    if s.starts_with('-') || s.ends_with('-') {
+        return Err(AppError::InvalidInput(
+            "slug cannot start or end with a hyphen".into(),
+        ));
+    }
+    if s.contains("--") {
+        return Err(AppError::InvalidInput(
+            "slug cannot contain consecutive hyphens".into(),
+        ));
+    }
+    for ch in s.chars() {
+        if !ch.is_ascii_lowercase() && !ch.is_ascii_digit() && ch != '-' {
+            return Err(AppError::InvalidInput(format!(
+                "slug contains invalid character '{ch}'; only lowercase alphanumeric characters and hyphens are allowed"
+            )));
+        }
+    }
+    if RESERVED_SLUGS.contains(&s) {
+        return Err(AppError::InvalidInput(format!(
+            "slug '{s}' is reserved by system"
+        )));
+    }
+    Ok(())
+}
+
+/// Slugifies a display name when CREATE omits an explicit slug.
+/// Converts non-alphanumeric characters to hyphens, lowercases the string,
+/// collapses repeated hyphens, and validates the result.
+pub fn slugify(input: &str) -> Result<String, AppError> {
+    let mut slug = String::with_capacity(input.len());
+    let mut prev_hyphen = false;
+
+    for ch in input.chars() {
+        if ch.is_ascii_alphanumeric() {
+            slug.push(ch.to_ascii_lowercase());
+            prev_hyphen = false;
+        } else if !prev_hyphen && !slug.is_empty() {
+            slug.push('-');
+            prev_hyphen = true;
+        }
+    }
+
+    let trimmed = slug.trim_matches('-');
+    if trimmed.is_empty() {
+        return Err(AppError::InvalidInput(
+            "unable to generate valid slug from provided name".into(),
+        ));
+    }
+
+    validate_slug(trimmed)?;
+    Ok(trimmed.to_string())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_valid_slugs() {
+        assert!(validate_slug("default").is_ok());
+        assert!(validate_slug("my-app-1").is_ok());
+        assert!(validate_slug("acme-corp").is_ok());
+        assert!(validate_slug("xy").is_ok());
+    }
+
+    #[test]
+    fn test_invalid_slugs() {
+        assert!(validate_slug("").is_err());
+        assert!(validate_slug("a").is_err());
+        assert!(validate_slug("-app").is_err());
+        assert!(validate_slug("app-").is_err());
+        assert!(validate_slug("my--app").is_err());
+        assert!(validate_slug("My-App").is_err());
+        assert!(validate_slug("my_app").is_err());
+        assert!(validate_slug("admin").is_err());
+        assert!(validate_slug("api").is_err());
+    }
+
+    #[test]
+    fn test_slugify() {
+        assert_eq!(slugify("Acme Corp!").unwrap(), "acme-corp");
+        assert_eq!(slugify("My   App 123").unwrap(), "my-app-123");
+        assert!(slugify("!!!").is_err());
+    }
+}

tests/application_members_test.rs

@@ -0,0 +1,194 @@
+#![cfg(feature = "sqlite")]
+
+use nx9_auth::db::{
+    self,
+    models::Tenant,
+    provider::{DatabaseProvider, SqliteProvider},
+};
+use nx9_auth::identity::{application_members, applications, users};
+use std::sync::Arc;
+
+async fn setup_test_provider() -> (Arc<SqliteProvider>, String) {
+    let db_id = uuid::Uuid::new_v4().to_string();
+    let db_path = format!("target/test_app_members_{}.db", db_id);
+    let pool = db::create_pool(&db_path)
+        .await
+        .expect("Failed to create test pool");
+    db::run_migrations(&pool)
+        .await
+        .expect("Failed to run migrations");
+    (Arc::new(SqliteProvider::new(pool)), db_path)
+}
+
+async fn teardown_test_db(path: String) {
+    let _ = std::fs::remove_file(path);
+}
+
+#[tokio::test]
+async fn test_application_membership_add_update_remove_transactions() {
+    let (provider, db_path) = setup_test_provider().await;
+    let provider_dyn: Arc<dyn DatabaseProvider> = provider.clone();
+    let dummy_cfg = nx9_auth::config::SecurityConfig::default();
+
+    // Create user and application in Default Tenant
+    let user = users::create_user(
+        &provider_dyn,
+        &dummy_cfg,
+        Tenant::DEFAULT_ID,
+        "app_user_1",
+        "X9#mK$9qL!2zP0",
+        None,
+        None,
+        None,
+    )
+    .await
+    .unwrap();
+
+    let (app, _) = applications::create(
+        &provider_dyn,
+        Tenant::DEFAULT_ID,
+        "Portal App",
+        "portal-app",
+        None,
+        None,
+        None,
+        None,
+        None,
+        None,
+    )
+    .await
+    .unwrap();
+
+    // 1. Add membership atomically with audit log
+    let member = application_members::add(
+        &provider_dyn,
+        &app.id,
+        &user.id,
+        Some("member"),
+        Some(&user.id),
+        Some("127.0.0.1"),
+        Some("TestRunner"),
+    )
+    .await
+    .unwrap();
+
+    assert_eq!(member.application_id, app.id);
+    assert_eq!(member.user_id, user.id);
+    assert_eq!(member.role, "member");
+
+    let audit_add = provider
+        .audit()
+        .list_filtered(&nx9_auth::db::models::AuditFilter {
+            resource_type: Some("application".to_string()),
+            limit: 10,
+            ..Default::default()
+        })
+        .await
+        .unwrap();
+
+    let add_event = audit_add
+        .into_iter()
+        .find(|e| e.action == "application.member_added")
+        .expect("member_added audit record must exist");
+    assert_eq!(add_event.target_user_id.as_deref(), Some(user.id.as_str()));
+
+    // 2. Update membership role atomically with audit log
+    let updated_member = application_members::update(
+        &provider_dyn,
+        &app.id,
+        &user.id,
+        Some("admin"),
+        None,
+        Some(&user.id),
+        Some("127.0.0.1"),
+        Some("TestRunner"),
+    )
+    .await
+    .unwrap();
+
+    assert_eq!(updated_member.role, "admin");
+
+    // 3. Remove membership atomically with audit log
+    application_members::remove(
+        &provider_dyn,
+        &app.id,
+        &user.id,
+        Some(&user.id),
+        Some("127.0.0.1"),
+        Some("TestRunner"),
+    )
+    .await
+    .unwrap();
+
+    let remaining_members = provider
+        .application_members()
+        .list_by_application(&app.id)
+        .await
+        .unwrap();
+    assert_eq!(remaining_members.len(), 0);
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_application_membership_same_tenant_isolation() {
+    let (provider, db_path) = setup_test_provider().await;
+    let provider_dyn: Arc<dyn DatabaseProvider> = provider.clone();
+    let dummy_cfg = nx9_auth::config::SecurityConfig::default();
+
+    let tenant_b = uuid::Uuid::new_v4().to_string();
+    provider
+        .tenants()
+        .create(&tenant_b, "Tenant B", Some("tenant-b-app"))
+        .await
+        .unwrap();
+
+    // Create user in Default Tenant
+    let user_a = users::create_user(
+        &provider_dyn,
+        &dummy_cfg,
+        Tenant::DEFAULT_ID,
+        "user_tenant_a",
+        "X9#mK$9qL!2zP0",
+        None,
+        None,
+        None,
+    )
+    .await
+    .unwrap();
+
+    // Create application in Tenant B
+    let (app_b, _) = applications::create(
+        &provider_dyn,
+        &tenant_b,
+        "App Tenant B",
+        "app-tenant-b",
+        None,
+        None,
+        None,
+        None,
+        None,
+        None,
+    )
+    .await
+    .unwrap();
+
+    // Attempting to assign user_a (Tenant Default) to app_b (Tenant B) MUST be rejected
+    let res = application_members::add(
+        &provider_dyn,
+        &app_b.id,
+        &user_a.id,
+        Some("member"),
+        None,
+        None,
+        None,
+    )
+    .await;
+
+    assert!(
+        res.is_err(),
+        "Cross-tenant application membership assignment MUST be rejected"
+    );
+
+    teardown_test_db(db_path).await;
+}

tests/audit_export_test.rs

@@ -0,0 +1,226 @@
+#![cfg(feature = "sqlite")]
+
+use nx9_auth::db::{
+    self,
+    provider::{DatabaseProvider, SqliteProvider},
+};
+use std::sync::Arc;
+
+async fn setup_test_provider() -> (Arc<SqliteProvider>, String) {
+    let db_id = uuid::Uuid::new_v4().to_string();
+    let db_path = format!("target/test_audit_export_{}.db", db_id);
+    let pool = db::create_pool(&db_path)
+        .await
+        .expect("Failed to create test pool");
+    db::run_migrations(&pool)
+        .await
+        .expect("Failed to run migrations");
+    (Arc::new(SqliteProvider::new(pool)), db_path)
+}
+
+async fn teardown_test_db(path: String) {
+    let _ = std::fs::remove_file(path);
+}
+
+#[tokio::test]
+async fn test_audit_list_remains_clamped_to_500() {
+    let (provider, db_path) = setup_test_provider().await;
+
+    // Insert 600 audit events
+    for i in 0..600 {
+        let audit_id = uuid::Uuid::new_v4().to_string();
+        provider
+            .audit()
+            .insert(
+                &audit_id,
+                None,
+                None,
+                "user.login",
+                "user",
+                None,
+                "info",
+                Some("127.0.0.1"),
+                Some("TestRunner"),
+                Some(&format!("{{\"index\": {i}}}")),
+            )
+            .await
+            .unwrap();
+    }
+
+    // Normal list filter with limit=1000 MUST be clamped to 500 by backend API logic
+    let filter = nx9_auth::db::models::AuditFilter {
+        limit: 1000,
+        ..Default::default()
+    };
+    let clamped_limit = filter.limit.clamp(1, 500);
+    assert_eq!(clamped_limit, 500);
+
+    let entries = provider
+        .audit()
+        .list_filtered(&nx9_auth::db::models::AuditFilter {
+            limit: clamped_limit,
+            ..Default::default()
+        })
+        .await
+        .unwrap();
+
+    assert_eq!(
+        entries.len(),
+        500,
+        "Normal audit listing must be bounded to 500 records max"
+    );
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_audit_export_can_return_more_than_500_up_to_5000() {
+    let (provider, db_path) = setup_test_provider().await;
+
+    // Insert 600 audit events
+    for i in 0..600 {
+        let audit_id = uuid::Uuid::new_v4().to_string();
+        provider
+            .audit()
+            .insert(
+                &audit_id,
+                None,
+                None,
+                "user.login",
+                "user",
+                None,
+                "info",
+                Some("127.0.0.1"),
+                Some("TestRunner"),
+                Some(&format!("{{\"index\": {i}}}")),
+            )
+            .await
+            .unwrap();
+    }
+
+    // Export query path with limit=5000 returns all 600 records (>500)
+    let export_filter = nx9_auth::db::models::AuditFilter {
+        limit: 5000,
+        ..Default::default()
+    };
+
+    let entries = provider
+        .audit()
+        .list_filtered(&export_filter)
+        .await
+        .unwrap();
+
+    assert_eq!(
+        entries.len(),
+        600,
+        "Export query path must return >500 records when available"
+    );
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_audit_export_hard_bounded_at_5000() {
+    let (_provider, db_path) = setup_test_provider().await;
+
+    // Request limit 999999 must be clamped to hard maximum 5000
+    let requested_limit = 999999i64;
+    let export_limit = requested_limit.clamp(1, 5000);
+    assert_eq!(export_limit, 5000);
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_server_side_success_filtering_before_limit_and_count() {
+    let (provider, db_path) = setup_test_provider().await;
+
+    // Insert 10 success events and 10 failure events
+    for _ in 0..10 {
+        let audit_id = uuid::Uuid::new_v4().to_string();
+        provider
+            .audit()
+            .insert(
+                &audit_id,
+                None,
+                None,
+                "user.login",
+                "user",
+                None,
+                "info",
+                Some("127.0.0.1"),
+                Some("TestRunner"),
+                None,
+            )
+            .await
+            .unwrap();
+    }
+
+    for _ in 0..10 {
+        let audit_id = uuid::Uuid::new_v4().to_string();
+        provider
+            .audit()
+            .insert(
+                &audit_id,
+                None,
+                None,
+                "auth.failed",
+                "user",
+                None,
+                "warning",
+                Some("127.0.0.1"),
+                Some("TestRunner"),
+                None,
+            )
+            .await
+            .unwrap();
+    }
+
+    // Server-side filter success = true
+    let success_filter = nx9_auth::db::models::AuditFilter {
+        success: Some(true),
+        limit: 50,
+        ..Default::default()
+    };
+
+    let count = provider
+        .audit()
+        .count_filtered(&success_filter)
+        .await
+        .unwrap();
+    let entries = provider
+        .audit()
+        .list_filtered(&success_filter)
+        .await
+        .unwrap();
+
+    assert_eq!(count, 10);
+    assert_eq!(entries.len(), 10);
+    assert!(entries.iter().all(|e| !e.action.contains("fail")));
+
+    // Server-side filter success = false
+    let fail_filter = nx9_auth::db::models::AuditFilter {
+        success: Some(false),
+        limit: 50,
+        ..Default::default()
+    };
+
+    let fail_count = provider.audit().count_filtered(&fail_filter).await.unwrap();
+    let fail_entries = provider.audit().list_filtered(&fail_filter).await.unwrap();
+
+    assert_eq!(fail_count, 10);
+    assert_eq!(fail_entries.len(), 10);
+    assert!(fail_entries.iter().all(|e| e.action.contains("fail")));
+
+    teardown_test_db(db_path).await;
+}
+
+#[test]
+fn test_rfc4180_csv_escaping_rules() {
+    let esc = |s: &str| format!("\"{}\"", s.replace('"', "\"\""));
+
+    assert_eq!(esc("simple"), "\"simple\"");
+    assert_eq!(esc("with,comma"), "\"with,comma\"");
+    assert_eq!(esc("with \"quotes\""), "\"with \"\"quotes\"\"\"");
+    assert_eq!(esc("multi\nline"), "\"multi\nline\"");
+}

tests/postgres_migration_test.rs

@@ -0,0 +1,34 @@
+#![cfg(feature = "postgres")]
+
+use sqlx::postgres::PgPoolOptions;
+use std::time::Duration;
+
+#[tokio::test]
+async fn test_postgres_fresh_migration_from_0001_to_latest() {
+    let database_url = "postgres://postgres@127.0.0.1:5433/nx9_auth_test_fresh";
+
+    let pool = match PgPoolOptions::new()
+        .acquire_timeout(Duration::from_secs(1))
+        .connect(database_url)
+        .await
+    {
+        Ok(p) => p,
+        Err(e) => {
+            println!("Skipping PostgreSQL live connection test (server not running): {e}");
+            return;
+        }
+    };
+
+    let migrator = sqlx::migrate!("src/db/migrations/postgres");
+    let res = migrator.run(&pool).await;
+
+    assert!(res.is_ok(), "Fresh PostgreSQL migration failed: {:?}", res);
+
+    // Test idempotency (re-running on migrated database)
+    let res_idempotent = migrator.run(&pool).await;
+    assert!(
+        res_idempotent.is_ok(),
+        "Re-running PostgreSQL migrations failed: {:?}",
+        res_idempotent
+    );
+}

tests/slug_management_test.rs

@@ -0,0 +1,335 @@
+#![cfg(feature = "sqlite")]
+
+use nx9_auth::db::{
+    self,
+    models::Tenant,
+    provider::{DatabaseProvider, SqliteProvider},
+};
+use nx9_auth::identity::{applications, slug};
+use std::sync::Arc;
+
+async fn setup_test_provider() -> (Arc<SqliteProvider>, String) {
+    let db_id = uuid::Uuid::new_v4().to_string();
+    let db_path = format!("target/test_slug_{}.db", db_id);
+    let pool = db::create_pool(&db_path)
+        .await
+        .expect("Failed to create test pool");
+    db::run_migrations(&pool)
+        .await
+        .expect("Failed to run migrations");
+    (Arc::new(SqliteProvider::new(pool)), db_path)
+}
+
+async fn teardown_test_db(path: String) {
+    let _ = std::fs::remove_file(path);
+}
+
+#[tokio::test]
+async fn test_canonical_slug_validation_and_policy() {
+    // Valid slugs
+    assert!(slug::validate_slug("default").is_ok());
+    assert!(slug::validate_slug("my-app-1").is_ok());
+    assert!(slug::validate_slug("acme-tenant").is_ok());
+    assert!(slug::validate_slug("ab").is_ok());
+
+    // Invalid length
+    assert!(slug::validate_slug("a").is_err());
+    let long_slug = "a".repeat(64);
+    assert!(slug::validate_slug(&long_slug).is_err());
+
+    // Invalid formatting
+    assert!(slug::validate_slug("-invalid").is_err());
+    assert!(slug::validate_slug("invalid-").is_err());
+    assert!(slug::validate_slug("in--valid").is_err());
+    assert!(slug::validate_slug("Invalid").is_err());
+    assert!(slug::validate_slug("in_valid").is_err());
+
+    // Reserved names
+    assert!(slug::validate_slug("admin").is_err());
+    assert!(slug::validate_slug("api").is_err());
+    assert!(slug::validate_slug("system").is_err());
+}
+
+#[tokio::test]
+async fn test_explicit_invalid_slug_rejection_no_silent_slugify() {
+    let (provider, db_path) = setup_test_provider().await;
+
+    // Explicit invalid slug must be rejected directly and NOT silently slugified
+    let tenant_id = uuid::Uuid::new_v4().to_string();
+    let res = provider
+        .tenants()
+        .create(&tenant_id, "My Organization", Some("INVALID SLUG!"))
+        .await;
+
+    assert!(res.is_err(), "Explicit invalid slug should be rejected");
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_omitted_slug_generation_on_create() {
+    let (provider, db_path) = setup_test_provider().await;
+
+    let tenant_id = uuid::Uuid::new_v4().to_string();
+    let tenant = provider
+        .tenants()
+        .create(&tenant_id, "Acme Corporation Inc!", None)
+        .await
+        .expect("Should derive slug from name when omitted");
+
+    assert_eq!(tenant.slug.as_deref(), Some("acme-corporation-inc"));
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_same_resource_duplicate_rejection() {
+    let (provider, db_path) = setup_test_provider().await;
+
+    let id1 = uuid::Uuid::new_v4().to_string();
+    provider
+        .tenants()
+        .create(&id1, "Tenant One", Some("tenant-one"))
+        .await
+        .expect("First tenant creation should succeed");
+
+    let id2 = uuid::Uuid::new_v4().to_string();
+    let res = provider
+        .tenants()
+        .create(&id2, "Tenant Two", Some("tenant-one"))
+        .await;
+
+    assert!(res.is_err(), "Duplicate tenant slug must be rejected");
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_cross_resource_collision_rejection() {
+    let (provider, db_path) = setup_test_provider().await;
+    let provider_dyn: Arc<dyn nx9_auth::db::provider::DatabaseProvider> = provider.clone();
+
+    // Create a tenant with slug "shared-identifier"
+    let t_id = uuid::Uuid::new_v4().to_string();
+    provider
+        .tenants()
+        .create(&t_id, "Shared Tenant", Some("shared-identifier"))
+        .await
+        .expect("Tenant creation should succeed");
+
+    // Attempting to create an application with the SAME slug "shared-identifier" must fail
+    let app_res = applications::create(
+        &provider_dyn,
+        Tenant::DEFAULT_ID,
+        "Colliding Application",
+        "shared-identifier",
+        None,
+        None,
+        None,
+        None,
+        None,
+        None,
+    )
+    .await;
+
+    assert!(
+        app_res.is_err(),
+        "Cross-resource slug collision (app vs tenant) must be rejected"
+    );
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_unchanged_slug_update_no_op() {
+    let (provider, db_path) = setup_test_provider().await;
+
+    let id = uuid::Uuid::new_v4().to_string();
+    provider
+        .tenants()
+        .create(&id, "Original Name", Some("stable-slug"))
+        .await
+        .expect("Tenant creation should succeed");
+
+    // Updating tenant name while keeping the exact same slug must succeed (no-op for registry)
+    let update_res = provider
+        .tenants()
+        .update(&id, "Updated Name", Some("stable-slug"))
+        .await;
+
+    assert!(
+        update_res.is_ok(),
+        "Unchanged slug update should succeed as no-op"
+    );
+
+    let updated = provider.tenants().find_by_id(&id).await.unwrap().unwrap();
+    assert_eq!(updated.name, "Updated Name");
+    assert_eq!(updated.slug.as_deref(), Some("stable-slug"));
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_rename_and_old_slug_release() {
+    let (provider, db_path) = setup_test_provider().await;
+
+    let id = uuid::Uuid::new_v4().to_string();
+    provider
+        .tenants()
+        .create(&id, "Alpha Tenant", Some("old-alpha-slug"))
+        .await
+        .expect("Tenant creation should succeed");
+
+    // Rename to new-alpha-slug
+    provider
+        .tenants()
+        .update(&id, "Alpha Tenant", Some("new-alpha-slug"))
+        .await
+        .expect("Rename should succeed");
+
+    // Verify old-alpha-slug is released and can be claimed by another resource
+    let id2 = uuid::Uuid::new_v4().to_string();
+    let claim_res = provider
+        .tenants()
+        .create(&id2, "Beta Tenant", Some("old-alpha-slug"))
+        .await;
+
+    assert!(
+        claim_res.is_ok(),
+        "Released old slug should be claimable by new resource"
+    );
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_slug_release_ownership_verification() {
+    let (provider, db_path) = setup_test_provider().await;
+
+    let id1 = uuid::Uuid::new_v4().to_string();
+    provider
+        .tenants()
+        .create(&id1, "Tenant One", Some("tenant-slug-1"))
+        .await
+        .expect("Tenant 1 creation should succeed");
+
+    // Attempting to release tenant-slug-1 using a wrong entity_id (id2) directly via sqlite helper
+    let mut tx = provider.pool.begin().await.unwrap();
+    let rows = db::repository::sqlite::global_slugs::release_slug_by_name_sqlite(
+        &mut tx,
+        "tenant-slug-1",
+        "tenant",
+        "wrong-entity-id",
+    )
+    .await
+    .unwrap();
+    tx.commit().await.unwrap();
+
+    assert_eq!(
+        rows, 0,
+        "Release with wrong entity_id ownership must affect 0 rows"
+    );
+
+    // Verify tenant-slug-1 is still registered in global_slugs
+    let existing_slug = provider
+        .global_slugs()
+        .find_by_slug("tenant-slug-1")
+        .await
+        .unwrap();
+    assert!(
+        existing_slug.is_some(),
+        "Registration must remain intact when release ownership fails"
+    );
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_deletion_slug_release() {
+    let (provider, db_path) = setup_test_provider().await;
+
+    let id = uuid::Uuid::new_v4().to_string();
+    provider
+        .tenants()
+        .create(&id, "Temporary Tenant", Some("temp-tenant-slug"))
+        .await
+        .expect("Tenant creation should succeed");
+
+    // Delete tenant
+    provider
+        .tenants()
+        .delete(&id)
+        .await
+        .expect("Tenant deletion should succeed");
+
+    // Verify temp-tenant-slug is released from global_slugs
+    let found = provider
+        .global_slugs()
+        .find_by_slug("temp-tenant-slug")
+        .await
+        .unwrap();
+    assert!(
+        found.is_none(),
+        "Slug must be removed from global_slugs after deletion"
+    );
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_application_slug_never_authenticates_as_client_id() {
+    let (provider, db_path) = setup_test_provider().await;
+    let provider_dyn: Arc<dyn nx9_auth::db::provider::DatabaseProvider> = provider.clone();
+
+    let (app, raw_secret) = applications::create(
+        &provider_dyn,
+        Tenant::DEFAULT_ID,
+        "Auth App",
+        "auth-app-slug",
+        None,
+        None,
+        None,
+        None,
+        None,
+        None,
+    )
+    .await
+    .expect("App creation should succeed");
+
+    // Authenticating using canonical client_id must succeed
+    let auth_ok =
+        applications::validate_client_credentials(&provider_dyn, app.get_client_id(), &raw_secret)
+            .await;
+    assert!(
+        auth_ok.is_ok(),
+        "Authentication with client_id must succeed"
+    );
+
+    // Authenticating using application SLUG as client_id MUST FAIL
+    let auth_slug_fail =
+        applications::validate_client_credentials(&provider_dyn, "auth-app-slug", &raw_secret)
+            .await;
+    assert!(
+        auth_slug_fail.is_err(),
+        "Application slug MUST NEVER authenticate as client_id"
+    );
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_dual_migration_paths_sqlite() {
+    let db_id = uuid::Uuid::new_v4().to_string();
+    let db_path = format!("target/test_migration_path_{}.db", db_id);
+    let pool = db::create_pool(&db_path).await.unwrap();
+
+    // Fresh migration
+    let res = db::run_migrations(&pool).await;
+    assert!(res.is_ok(), "Fresh migration must succeed");
+
+    // Idempotent re-run
+    let res2 = db::run_migrations(&pool).await;
+    assert!(res2.is_ok(), "Re-running migrations must succeed");
+
+    let _ = std::fs::remove_file(db_path);
+}

tests/tenant_management_ui_test.rs

@@ -0,0 +1,570 @@
+#![cfg(feature = "sqlite")]
+
+use nx9_auth::db::{
+    self,
+    models::Tenant,
+    provider::{DatabaseProvider, SqliteProvider},
+};
+use nx9_auth::identity::{applications, users};
+use std::sync::Arc;
+
+async fn setup_test_provider() -> (Arc<SqliteProvider>, String) {
+    let db_id = uuid::Uuid::new_v4().to_string();
+    let db_path = format!("target/test_tenant_mgmt_{}.db", db_id);
+    let pool = db::create_pool(&db_path)
+        .await
+        .expect("Failed to create test pool");
+    db::run_migrations(&pool)
+        .await
+        .expect("Failed to run migrations");
+    (Arc::new(SqliteProvider::new(pool)), db_path)
+}
+
+async fn teardown_test_db(path: String) {
+    let _ = std::fs::remove_file(path);
+}
+
+#[tokio::test]
+async fn test_tenant_user_listing_and_assignment() {
+    let (provider, db_path) = setup_test_provider().await;
+    let provider_dyn: Arc<dyn DatabaseProvider> = provider.clone();
+
+    // Create a new tenant
+    let tenant_id = uuid::Uuid::new_v4().to_string();
+    provider
+        .tenants()
+        .create(&tenant_id, "Acme Org", Some("acme-org"))
+        .await
+        .expect("Tenant creation should succeed");
+
+    let dummy_cfg = nx9_auth::config::SecurityConfig::default();
+
+    let user = users::create_user(
+        &provider_dyn,
+        &dummy_cfg,
+        Tenant::DEFAULT_ID,
+        "employee_1",
+        "X9#mK$9qL!2zP0",
+        None,
+        None,
+        None,
+    )
+    .await
+    .expect("User creation should succeed");
+
+    assert_eq!(user.tenant_id, Tenant::DEFAULT_ID);
+
+    // Reassign user to Acme Org
+    provider
+        .users()
+        .update_user_tenant(&user.id, &tenant_id)
+        .await
+        .expect("Tenant assignment should succeed");
+
+    let tenant_users = provider
+        .users()
+        .list(&tenant_id)
+        .await
+        .expect("Listing tenant users should succeed");
+
+    assert_eq!(tenant_users.len(), 1);
+    assert_eq!(tenant_users[0].username, "employee_1");
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_assign_user_username_collision_rejection() {
+    let (provider, db_path) = setup_test_provider().await;
+    let provider_dyn: Arc<dyn DatabaseProvider> = provider.clone();
+
+    let dummy_cfg = nx9_auth::config::SecurityConfig::default();
+
+    let tenant_id = uuid::Uuid::new_v4().to_string();
+    provider
+        .tenants()
+        .create(&tenant_id, "Beta Corp", Some("beta-corp"))
+        .await
+        .unwrap();
+
+    // Create user in Default tenant named "common_user"
+    let u1 = users::create_user(
+        &provider_dyn,
+        &dummy_cfg,
+        Tenant::DEFAULT_ID,
+        "common_user",
+        "X9#mK$9qL!2zP0",
+        None,
+        None,
+        None,
+    )
+    .await
+    .unwrap();
+
+    // Create user in Beta Corp also named "common_user"
+    let _u2 = users::create_user(
+        &provider_dyn,
+        &dummy_cfg,
+        &tenant_id,
+        "common_user",
+        "X9#mK$9qL!2zP0",
+        None,
+        None,
+        None,
+    )
+    .await
+    .unwrap();
+
+    // Attempting to move u1 into Beta Corp must collide because "common_user" already exists in Beta Corp
+    let exists = provider
+        .users()
+        .username_exists(&tenant_id, &u1.username)
+        .await
+        .unwrap();
+
+    assert!(
+        exists,
+        "Username existence check must return true for colliding username in destination tenant"
+    );
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_tenant_application_listing_isolation() {
+    let (provider, db_path) = setup_test_provider().await;
+    let provider_dyn: Arc<dyn DatabaseProvider> = provider.clone();
+
+    let tenant_a = uuid::Uuid::new_v4().to_string();
+    let tenant_b = uuid::Uuid::new_v4().to_string();
+
+    provider
+        .tenants()
+        .create(&tenant_a, "Tenant A", Some("tenant-a"))
+        .await
+        .unwrap();
+
+    provider
+        .tenants()
+        .create(&tenant_b, "Tenant B", Some("tenant-b"))
+        .await
+        .unwrap();
+
+    // Create application in Tenant A
+    let (app_a, _) = applications::create(
+        &provider_dyn,
+        &tenant_a,
+        "App A",
+        "app-a-slug",
+        None,
+        None,
+        None,
+        None,
+        None,
+        None,
+    )
+    .await
+    .unwrap();
+
+    // Create application in Tenant B
+    let (app_b, _) = applications::create(
+        &provider_dyn,
+        &tenant_b,
+        "App B",
+        "app-b-slug",
+        None,
+        None,
+        None,
+        None,
+        None,
+        None,
+    )
+    .await
+    .unwrap();
+
+    let apps_a = provider.applications().list(&tenant_a).await.unwrap();
+    let apps_b = provider.applications().list(&tenant_b).await.unwrap();
+
+    assert_eq!(apps_a.len(), 1);
+    assert_eq!(apps_a[0].id, app_a.id);
+
+    assert_eq!(apps_b.len(), 1);
+    assert_eq!(apps_b[0].id, app_b.id);
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_session_identity_immediately_reflects_tenant_reassignment() {
+    let (provider, db_path) = setup_test_provider().await;
+    let provider_dyn: Arc<dyn DatabaseProvider> = provider.clone();
+    let dummy_cfg = nx9_auth::config::SecurityConfig::default();
+
+    let tenant_b = uuid::Uuid::new_v4().to_string();
+    provider
+        .tenants()
+        .create(&tenant_b, "Tenant B", Some("tenant-b-session"))
+        .await
+        .unwrap();
+
+    // 1. Create user in Default Tenant
+    let user = users::create_user(
+        &provider_dyn,
+        &dummy_cfg,
+        Tenant::DEFAULT_ID,
+        "session_user",
+        "X9#mK$9qL!2zP0",
+        None,
+        None,
+        None,
+    )
+    .await
+    .unwrap();
+
+    // 2. Create active session for user
+    let session_id = uuid::Uuid::new_v4().to_string();
+    let token_hash = "hash_123456";
+    let expires_at = "2030-01-01T00:00:00Z";
+
+    provider
+        .sessions()
+        .create(
+            &session_id,
+            &user.id,
+            token_hash,
+            Some("127.0.0.1"),
+            Some("TestAgent"),
+            expires_at,
+        )
+        .await
+        .unwrap();
+
+    // 3. Resolve user identity via session user_id -> tenant_id must be Default Tenant
+    let session_user_before = provider
+        .users()
+        .find_by_id(&user.id)
+        .await
+        .unwrap()
+        .unwrap();
+    assert_eq!(session_user_before.tenant_id, Tenant::DEFAULT_ID);
+
+    // 4. Reassign user to Tenant B
+    provider
+        .users()
+        .update_user_tenant(&user.id, &tenant_b)
+        .await
+        .unwrap();
+
+    // 5. Subsequent request resolving user identity for the same active session MUST immediately yield Tenant B
+    let session_user_after = provider
+        .users()
+        .find_by_id(&user.id)
+        .await
+        .unwrap()
+        .unwrap();
+    assert_eq!(session_user_after.tenant_id, tenant_b);
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_prevent_last_admin_reassignment_validation() {
+    let (provider, db_path) = setup_test_provider().await;
+    let provider_dyn: Arc<dyn DatabaseProvider> = provider.clone();
+    let dummy_cfg = nx9_auth::config::SecurityConfig::default();
+
+    // Create an admin user
+    let admin_user = users::create_user(
+        &provider_dyn,
+        &dummy_cfg,
+        Tenant::DEFAULT_ID,
+        "admin_user",
+        "X9#mK$9qL!2zP0",
+        None,
+        None,
+        None,
+    )
+    .await
+    .unwrap();
+
+    let admin_role = provider
+        .roles()
+        .find_by_name("admin")
+        .await
+        .unwrap()
+        .expect("admin role must exist");
+    provider
+        .roles()
+        .assign_to_user(&admin_user.id, &admin_role.id)
+        .await
+        .unwrap();
+
+    // Check system admin count
+    let admin_count = provider.users().count_admins().await.unwrap();
+    assert_eq!(admin_count, 1, "Should count 1 system admin user");
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_reassignment_audit_event_metadata_invariants() {
+    let (provider, db_path) = setup_test_provider().await;
+    let provider_dyn: Arc<dyn DatabaseProvider> = provider.clone();
+    let dummy_cfg = nx9_auth::config::SecurityConfig::default();
+
+    let user = users::create_user(
+        &provider_dyn,
+        &dummy_cfg,
+        Tenant::DEFAULT_ID,
+        "audit_user",
+        "X9#mK$9qL!2zP0",
+        None,
+        None,
+        None,
+    )
+    .await
+    .unwrap();
+
+    let audit_id = uuid::Uuid::new_v4().to_string();
+    let from_tenant_id = Tenant::DEFAULT_ID;
+    let to_tenant_id = uuid::Uuid::new_v4().to_string();
+
+    let metadata = serde_json::json!({
+        "user_id": user.id,
+        "from_tenant_id": from_tenant_id,
+        "to_tenant_id": to_tenant_id,
+    })
+    .to_string();
+
+    provider
+        .audit()
+        .insert(
+            &audit_id,
+            Some(&user.id),
+            Some(&user.id),
+            "user.tenant_reassigned",
+            "user",
+            Some(&user.id),
+            "info",
+            Some("127.0.0.1"),
+            Some("TestRunner"),
+            Some(&metadata),
+        )
+        .await
+        .unwrap();
+
+    let entries = provider
+        .audit()
+        .list_filtered(&nx9_auth::db::models::AuditFilter {
+            resource_type: Some("user".to_string()),
+            limit: 10,
+            ..Default::default()
+        })
+        .await
+        .unwrap();
+
+    let event = entries
+        .into_iter()
+        .find(|e| e.id == audit_id)
+        .expect("Audit event must exist");
+
+    assert_eq!(event.action, "user.tenant_reassigned");
+    let parsed_meta: serde_json::Value =
+        serde_json::from_str(event.metadata_json.as_deref().unwrap()).unwrap();
+    assert_eq!(parsed_meta["from_tenant_id"], from_tenant_id);
+    assert_eq!(parsed_meta["to_tenant_id"], to_tenant_id);
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_reassign_user_tenant_with_audit_atomic_success() {
+    let (provider, db_path) = setup_test_provider().await;
+    let provider_dyn: Arc<dyn DatabaseProvider> = provider.clone();
+    let dummy_cfg = nx9_auth::config::SecurityConfig::default();
+
+    let tenant_dest = uuid::Uuid::new_v4().to_string();
+    provider
+        .tenants()
+        .create(&tenant_dest, "Dest Tenant", Some("dest-tenant"))
+        .await
+        .unwrap();
+
+    let user = users::create_user(
+        &provider_dyn,
+        &dummy_cfg,
+        Tenant::DEFAULT_ID,
+        "atomic_user",
+        "X9#mK$9qL!2zP0",
+        None,
+        None,
+        None,
+    )
+    .await
+    .unwrap();
+
+    // Call atomic reassign
+    provider
+        .users()
+        .reassign_user_tenant_with_audit(
+            &user.id,
+            &tenant_dest,
+            Some(&user.id),
+            Some("127.0.0.1"),
+            Some("TestRunner"),
+        )
+        .await
+        .unwrap();
+
+    // Verify tenant update
+    let updated_user = provider
+        .users()
+        .find_by_id(&user.id)
+        .await
+        .unwrap()
+        .unwrap();
+    assert_eq!(updated_user.tenant_id, tenant_dest);
+
+    // Verify audit record was inserted inside transaction
+    let audit_entries = provider
+        .audit()
+        .list_filtered(&nx9_auth::db::models::AuditFilter {
+            resource_type: Some("user".to_string()),
+            limit: 10,
+            ..Default::default()
+        })
+        .await
+        .unwrap();
+
+    let audit_event = audit_entries
+        .into_iter()
+        .find(|e| {
+            e.action == "user.tenant_reassigned" && e.target_user_id.as_deref() == Some(&user.id)
+        })
+        .expect("Atomic reassignment audit event must exist");
+
+    let meta: serde_json::Value =
+        serde_json::from_str(audit_event.metadata_json.as_deref().unwrap()).unwrap();
+    assert_eq!(meta["from_tenant_id"], Tenant::DEFAULT_ID);
+    assert_eq!(meta["to_tenant_id"], tenant_dest);
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_reassign_user_tenant_no_op_behavior() {
+    let (provider, db_path) = setup_test_provider().await;
+    let provider_dyn: Arc<dyn DatabaseProvider> = provider.clone();
+    let dummy_cfg = nx9_auth::config::SecurityConfig::default();
+
+    let user = users::create_user(
+        &provider_dyn,
+        &dummy_cfg,
+        Tenant::DEFAULT_ID,
+        "noop_user",
+        "X9#mK$9qL!2zP0",
+        None,
+        None,
+        None,
+    )
+    .await
+    .unwrap();
+
+    // Reassigning to SAME tenant must be a defined no-op
+    provider
+        .users()
+        .reassign_user_tenant_with_audit(
+            &user.id,
+            Tenant::DEFAULT_ID,
+            Some("actor_1"),
+            Some("127.0.0.1"),
+            Some("TestRunner"),
+        )
+        .await
+        .unwrap();
+
+    // Audit logs MUST NOT contain a false tenant_reassigned event
+    let audit_entries = provider
+        .audit()
+        .list_filtered(&nx9_auth::db::models::AuditFilter {
+            resource_type: Some("user".to_string()),
+            limit: 10,
+            ..Default::default()
+        })
+        .await
+        .unwrap();
+
+    let noop_audit = audit_entries.into_iter().find(|e| {
+        e.action == "user.tenant_reassigned" && e.target_user_id.as_deref() == Some(&user.id)
+    });
+
+    assert!(
+        noop_audit.is_none(),
+        "No-op reassignment must NOT write a false audit log entry"
+    );
+
+    teardown_test_db(db_path).await;
+}
+
+#[tokio::test]
+async fn test_concurrent_admin_reassignment_cannot_remove_all_system_admins() {
+    let (provider, db_path) = setup_test_provider().await;
+    let provider_dyn: Arc<dyn DatabaseProvider> = provider.clone();
+    let dummy_cfg = nx9_auth::config::SecurityConfig::default();
+
+    let dest_tenant = uuid::Uuid::new_v4().to_string();
+    provider
+        .tenants()
+        .create(&dest_tenant, "Dest", Some("dest"))
+        .await
+        .unwrap();
+
+    // Create single system admin in Default Tenant
+    let admin_user = users::create_user(
+        &provider_dyn,
+        &dummy_cfg,
+        Tenant::DEFAULT_ID,
+        "single_admin",
+        "X9#mK$9qL!2zP0",
+        None,
+        None,
+        None,
+    )
+    .await
+    .unwrap();
+
+    let admin_role = provider
+        .roles()
+        .find_by_name("admin")
+        .await
+        .unwrap()
+        .unwrap();
+    provider
+        .roles()
+        .assign_to_user(&admin_user.id, &admin_role.id)
+        .await
+        .unwrap();
+
+    // Single system admin reassignment away from Default Tenant MUST be rejected
+    let res = provider
+        .users()
+        .reassign_user_tenant_with_audit(
+            &admin_user.id,
+            &dest_tenant,
+            Some(&admin_user.id),
+            Some("127.0.0.1"),
+            Some("TestRunner"),
+        )
+        .await;
+
+    assert!(
+        res.is_err(),
+        "Moving the last system admin away from Default Tenant MUST fail"
+    );
+
+    // Invariant check: system admin count MUST remain >= 1 in Default Tenant
+    let admin_count = provider.users().count_admins().await.unwrap();
+    assert_eq!(admin_count, 1, "System admin count must never drop to 0");
+
+    teardown_test_db(db_path).await;
+}

ui/src/components/navigation/mod.rs

@@ -12,13 +12,22 @@ pub fn Header() -> Element {
     let auth = state.auth;
     let theme = state.theme;
     let mut menu_open = use_signal(|| false);
-    let mut tenant_menu_open = use_signal(|| false);
+    let mut quick_create_open = use_signal(|| false);
     let mut mobile = state.mobile_nav_open;
 
     let username = auth().username().to_string();
     let theme_icon = theme().icon();
     let theme_label = theme().label();
 
+    let auth_state = state.auth.read();
+    let can_create_user = auth_state.has_permission("users:create") || auth_state.is_adminish();
+    let can_create_tenant = auth_state.has_permission("roles:manage") || auth_state.is_adminish();
+    let can_create_app = auth_state.has_permission("applications:manage") || auth_state.is_adminish();
+    let can_create_role = auth_state.has_permission("roles:manage") || auth_state.is_adminish();
+    let can_create_sa = auth_state.has_permission("service_accounts:manage") || auth_state.has_permission("roles:manage") || auth_state.is_adminish();
+    let has_any_create = can_create_user || can_create_tenant || can_create_app || can_create_role || can_create_sa;
+    drop(auth_state);
+
     rsx! {
         header { class: "app-header",
             button {
@@ -36,66 +45,97 @@ pub fn Header() -> Element {
                 span { "nx9-auth" }
             }
 
-            // Tenant Switcher
-            div { class: "dropdown", style: "margin-left: 1rem;",
-                button {
-                    class: "btn btn-ghost",
-                    r#type: "button",
-                    "aria-haspopup": "menu",
-                    "aria-expanded": "{tenant_menu_open()}",
-                    onclick: move |_| tenant_menu_open.set(!tenant_menu_open()),
-                    span { class: "icon", "🏢" }
-                    span { style: "margin-left: 0.4rem; font-weight: 500;",
-                        {(state.tenant)().map(|t| t.name).unwrap_or("Default Tenant".to_string())}
-                    }
-                    span { style: "margin-left: 0.25rem; opacity: 0.6;", "▾" }
+            // Tenant Indicator & Management Link
+            div { class: "tenant-badge", style: "margin-left: 1rem; display: flex; align-items: center; gap: 0.5rem;",
+                span { class: "icon", "🏢" }
+                span { style: "font-weight: 500; font-size: 13px;",
+                    {(state.tenant)().map(|t| t.name).unwrap_or("Default Tenant".to_string())}
                 }
-                if tenant_menu_open() {
-                    div { class: "dropdown-menu", role: "menu",
-                        button { class: "dropdown-item", r#type: "button", "Default Tenant" }
-                        div { class: "dropdown-divider" }
-                        Link {
-                            class: "dropdown-item text-primary",
-                            to: Route::TenantsPage {},
-                            onclick: move |_| tenant_menu_open.set(false),
-                            "Manage tenants…"
+                Link {
+                    class: "btn btn-xs btn-ghost text-primary",
+                    to: Route::TenantsPage {},
+                    "Manage tenants…"
+                }
+            }
+
+            div { style: "flex: 1;" }
+
+            div { class: "header-actions",
+                if has_any_create {
+                    div { class: "dropdown", style: "position: relative; margin-right: 0.5rem;",
+                        button {
+                            class: "btn btn-primary btn-sm",
+                            r#type: "button",
+                            title: "Quick Create",
+                            "aria-haspopup": "menu",
+                            "aria-expanded": "{quick_create_open()}",
+                            onclick: move |_| quick_create_open.set(!quick_create_open()),
+                            onkeydown: move |evt: KeyboardEvent| {
+                                if evt.key() == Key::Escape {
+                                    quick_create_open.set(false);
+                                }
+                            },
+                            "➕ New ▾"
+                        }
+                        if quick_create_open() {
+                            div {
+                                class: "dropdown-backdrop",
+                                style: "position: fixed; top: 0; left: 0; right: 0; bottom: 0; z-index: 999; background: transparent;",
+                                onclick: move |_| quick_create_open.set(false),
+                            }
+                            div {
+                                class: "dropdown-menu",
+                                role: "menu",
+                                style: "display: block; position: absolute; right: 0; top: 100%; z-index: 1000;",
+                                onkeydown: move |evt: KeyboardEvent| {
+                                    if evt.key() == Key::Escape {
+                                        quick_create_open.set(false);
+                                    }
+                                },
+                                if can_create_user {
+                                    Link {
+                                        class: "dropdown-item",
+                                        to: "/users?create=1",
+                                        onclick: move |_| quick_create_open.set(false),
+                                        "👤 Create User"
+                                    }
+                                }
+                                if can_create_tenant {
+                                    Link {
+                                        class: "dropdown-item",
+                                        to: "/tenants?create=1",
+                                        onclick: move |_| quick_create_open.set(false),
+                                        "🏢 Create Tenant"
+                                    }
+                                }
+                                if can_create_app {
+                                    Link {
+                                        class: "dropdown-item",
+                                        to: "/applications?create=1",
+                                        onclick: move |_| quick_create_open.set(false),
+                                        "🚀 Create Application"
+                                    }
+                                }
+                                if can_create_role {
+                                    Link {
+                                        class: "dropdown-item",
+                                        to: "/roles?create=1",
+                                        onclick: move |_| quick_create_open.set(false),
+                                        "🛡️ Create Role"
+                                    }
+                                }
+                                if can_create_sa {
+                                    Link {
+                                        class: "dropdown-item",
+                                        to: "/service-accounts?create=1",
+                                        onclick: move |_| quick_create_open.set(false),
+                                        "🤖 Create Service Account"
+                                    }
+                                }
+                            }
                         }
                     }
                 }
-            }
-
-            // Global Search (Ctrl+K)
-            div { class: "search", style: "flex: 1; max-width: 400px; margin: 0 2rem;",
-                div { style: "position: relative;",
-                    span { style: "position: absolute; left: 0.75rem; top: 50%; transform: translateY(-50%); opacity: 0.5;", "🔍" }
-                    input {
-                        class: "form-control",
-                        style: "padding-left: 2rem; width: 100%;",
-                        r#type: "search",
-                        placeholder: "Search… (Ctrl+K)",
-                        "aria-label": "Global search",
-                    }
-                }
-            }
-            
-            div { class: "header-actions",
-                // Quick Create
-                button {
-                    class: "btn btn-primary btn-sm",
-                    style: "margin-right: 0.5rem;",
-                    r#type: "button",
-                    title: "Quick Create",
-                    "➕ New"
-                }
-
-                // Notifications
-                button {
-                    class: "btn btn-ghost btn-icon",
-                    r#type: "button",
-                    title: "Notifications",
-                    "aria-label": "Notifications",
-                    "🔔"
-                }
 
                 // Theme
                 button {

ui/src/components/tables/datatable.rs

@@ -60,7 +60,6 @@ pub fn DataTable(
                                     input {
                                         r#type: "checkbox",
                                         checked: col.visible,
-                                        // TODO: emit event
                                     }
                                     span { "{col.label}" }
                                 }
@@ -68,14 +67,6 @@ pub fn DataTable(
                         }
                     }
                 }
-                
-                // CSV Export (future ready)
-                button {
-                    class: "btn btn-outline",
-                    r#type: "button",
-                    title: "Export to CSV (Coming Soon)",
-                    "⬇ Export"
-                }
             }
             
             div { class: "table-wrap",

ui/src/models/mod.rs

@@ -21,6 +21,8 @@ pub struct TenantsResponse {
 pub struct UserView {
     pub id: String,
     pub username: String,
+    #[serde(default)]
+    pub tenant_id: Option<String>,
     pub status: String,
     #[serde(default)]
     pub last_login_at: Option<String>,
@@ -156,6 +158,60 @@ pub struct RotateSecretResponse {
     pub client_secret: String,
 }
 
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize, Default)]
+pub struct ApplicationMemberView {
+    pub id: String,
+    pub application_id: String,
+    pub user_id: String,
+    #[serde(default)]
+    pub username: String,
+    #[serde(default)]
+    pub user_status: String,
+    pub role: String,
+    #[serde(default)]
+    pub enabled: bool,
+    #[serde(default)]
+    pub created_at: String,
+    #[serde(default)]
+    pub updated_at: String,
+}
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize, Default)]
+pub struct ApplicationMembersResponse {
+    #[serde(default)]
+    pub members: Vec<ApplicationMemberView>,
+}
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize, Default)]
+pub struct UserApplicationMembershipView {
+    pub id: String,
+    pub application_id: String,
+    pub user_id: String,
+    pub role: String,
+    #[serde(default)]
+    pub enabled: bool,
+    #[serde(default)]
+    pub created_at: String,
+    #[serde(default)]
+    pub updated_at: String,
+    #[serde(default)]
+    pub application_name: String,
+    #[serde(default)]
+    pub application_slug: String,
+    #[serde(default)]
+    pub application_enabled: bool,
+    #[serde(default)]
+    pub client_id: String,
+    #[serde(default)]
+    pub credentials_configured: bool,
+}
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize, Default)]
+pub struct UserApplicationsResponse {
+    #[serde(default)]
+    pub applications: Vec<UserApplicationMembershipView>,
+}
+
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize, Default)]
 pub struct ServiceAccountView {
     pub id: String,

ui/src/pages/audit/mod.rs

@@ -84,10 +84,38 @@ pub fn AuditPage() -> Element {
             }
             div { class: "row",
                 button {
-                    class: "btn btn-outline", r#type: "button",
-                    title: "Export is a placeholder",
-                    onclick: move |_| {},
-                    "Export (soon)"
+                    class: "btn btn-outline",
+                    r#type: "button",
+                    title: "Export filtered audit log records as CSV",
+                    onclick: move |_| {
+                        let mut parts = vec!["limit=5000".to_string(), "offset=0".to_string()];
+                        if !query().is_empty() { parts.push(format!("q={}", urlencoding_lite(&query()))); }
+                        if !action().is_empty() { parts.push(format!("action={}", urlencoding_lite(&action()))); }
+                        if !resource().is_empty() { parts.push(format!("resource_type={}", urlencoding_lite(&resource()))); }
+                        if severity() != "all" { parts.push(format!("severity={}", severity())); }
+                        if success() == "true" { parts.push("success=true".to_string()); }
+                        else if success() == "false" { parts.push("success=false".to_string()); }
+                        if !since().is_empty() { parts.push(format!("since={}", urlencoding_lite(&since()))); }
+                        if !until().is_empty() { parts.push(format!("until={}", urlencoding_lite(&until()))); }
+                        let qs = parts.join("&");
+                        let export_url = format!("/api/v1/audit/export?{qs}");
+                        #[cfg(target_arch = "wasm32")]
+                        {
+                            use wasm_bindgen::JsCast;
+                            if let Some(window) = web_sys::window() {
+                                if let Some(document) = window.document() {
+                                    if let Ok(element) = document.create_element("a") {
+                                        let _ = element.set_attribute("href", &export_url);
+                                        let _ = element.set_attribute("download", "audit_export.csv");
+                                        if let Ok(html_elem) = element.dyn_into::<web_sys::HtmlElement>() {
+                                            html_elem.click();
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    },
+                    "Export CSV"
                 }
                 button { class: "btn btn-outline", r#type: "button", onclick: move |_| load.call(()), "Refresh" }
             }
@@ -231,3 +259,44 @@ fn urlencoding_lite(s: &str) -> String {
         })
         .collect()
 }
+
+fn export_audit_csv(entries: &[crate::models::AuditEntry]) {
+    let mut csv = String::from("id,created_at,action,resource_type,resource_id,severity,success,actor_user_id,target_user_id,ip_address,user_agent,metadata_json\n");
+    for e in entries {
+        let esc = |s: &str| format!("\"{}\"", s.replace('"', "\"\""));
+        let line = format!(
+            "{},{},{},{},{},{},{},{},{},{},{},{}\n",
+            esc(&e.id),
+            esc(&e.created_at),
+            esc(&e.action),
+            esc(&e.resource_type),
+            esc(e.resource_id.as_deref().unwrap_or("")),
+            esc(&e.severity),
+            e.success,
+            esc(e.actor_user_id.as_deref().unwrap_or("")),
+            esc(e.target_user_id.as_deref().unwrap_or("")),
+            esc(e.ip_address.as_deref().unwrap_or("")),
+            esc(e.user_agent.as_deref().unwrap_or("")),
+            esc(e.metadata_json.as_deref().unwrap_or("")),
+        );
+        csv.push_str(&line);
+    }
+
+    #[cfg(target_arch = "wasm32")]
+    {
+        use wasm_bindgen::JsCast;
+        if let Some(window) = web_sys::window() {
+            if let Some(document) = window.document() {
+                let encoded = urlencoding_lite(&csv);
+                let data_url = format!("data:text/csv;charset=utf-8,{}", encoded);
+                if let Ok(element) = document.create_element("a") {
+                    let _ = element.set_attribute("href", &data_url);
+                    let _ = element.set_attribute("download", "audit_export.csv");
+                    if let Ok(html_elem) = element.dyn_into::<web_sys::HtmlElement>() {
+                        html_elem.click();
+                    }
+                }
+            }
+        }
+    }
+}

ui/src/pages/auth/mod.rs

@@ -74,6 +74,10 @@ pub fn LoginPage() -> Element {
                                             .and_then(|v| v.as_str())
                                             .unwrap_or("")
                                             .to_string(),
+                                        tenant_id: user_val
+                                            .get("tenant_id")
+                                            .and_then(|v| v.as_str())
+                                            .map(|s| s.to_string()),
                                         status: user_val
                                             .get("status")
                                             .and_then(|v| v.as_str())

ui/src/pages/dashboard/mod.rs

@@ -303,16 +303,6 @@ fn AdminSummary(admin: Value) -> Element {
                     }
                 }
             }
-
-            div { class: "card mt-2",
-                div { class: "card-body row", style: "justify-content:space-between;",
-                    span {
-                        strong { "System health: " }
-                        span { class: "badge badge-success", "{health}" }
-                    }
-                    span { class: "text-muted", "Placeholder probe — expand in a future release" }
-                }
-            }
         }
     }
 }

ui/src/pages/profile/mod.rs

@@ -177,7 +177,7 @@ pub fn ProfilePage() -> Element {
                 }
 
                 div { class: "card",
-                    div { class: "card-header", h3 { "Coming soon" } }
+                    div { class: "card-header", h3 { "Planned security features" } }
                     div { class: "card-body stack",
                         div { class: "row", style: "justify-content:space-between;",
                             span { "Avatar upload" }

ui/src/pages/roles/mod.rs

@@ -52,7 +52,16 @@ pub fn RolesPage() -> Element {
             }
         });
     });
-    use_effect(move || { reload.call(()); });
+    use_effect(move || {
+        reload.call(());
+    });
+
+    let can_create = state.auth.read().has_permission("roles:manage") || state.auth.read().is_adminish();
+    use_effect(move || {
+        if can_create && crate::utils::check_and_clear_create_intent() {
+            show_create.set(true);
+        }
+    });
 
     let mut filtered: Vec<RoleView> = roles()
         .into_iter()

ui/src/pages/service_accounts/mod.rs

@@ -46,6 +46,13 @@ pub fn ServiceAccountsPage() -> Element {
     });
     use_effect(move || { reload.call(()); });
 
+    let can_create = state.auth.read().has_permission("service_accounts:manage") || state.auth.read().is_adminish();
+    use_effect(move || {
+        if can_create && crate::utils::check_and_clear_create_intent() {
+            show_create.set(true);
+        }
+    });
+
     let mut filtered: Vec<_> = items()
         .into_iter()
         .filter(|s| {

ui/src/pages/tenants/mod.rs

@@ -2,7 +2,7 @@ use crate::components::feedback::{ConfirmDialog, EmptyState, ErrorState, Loading
 use crate::components::forms::TextInput;
 use crate::components::navigation::Breadcrumb;
 use crate::components::tables::{DataTable, ColumnDef};
-use crate::models::TenantView;
+use crate::models::{ApplicationView, AuditEntry, TenantView, UserView};
 use crate::routes::Route;
 use crate::services::api;
 use crate::state::{AppState, ToastKind};
@@ -38,6 +38,13 @@ pub fn TenantsPage() -> Element {
 
     use_effect(move || { reload.call(()); });
 
+    let can_create = state.auth.read().has_permission("roles:manage") || state.auth.read().is_adminish();
+    use_effect(move || {
+        if can_create && crate::utils::check_and_clear_create_intent() {
+            show_create.set(true);
+        }
+    });
+
     let filtered = {
         let q = query();
         let sk = sort_key();
@@ -227,21 +234,44 @@ pub fn TenantDetailPage(id: String) -> Element {
     let mut error = use_signal(|| Option::<String>::None);
     let mut loading = use_signal(|| true);
 
+    let mut tab = use_signal(|| "overview".to_string());
     let mut edit_name = use_signal(String::new);
     let mut edit_slug = use_signal(String::new);
 
+    let mut tenant_users = use_signal(Vec::<UserView>::new);
+    let mut all_users = use_signal(Vec::<UserView>::new);
+    let mut tenant_apps = use_signal(Vec::<ApplicationView>::new);
+    let mut activity = use_signal(Vec::<AuditEntry>::new);
+
+    let mut user_query = use_signal(String::new);
+    let mut show_assign_modal = use_signal(|| false);
+    let mut selected_assign_user_id = use_signal(String::new);
+
+    let mut confirm_reassign_user = use_signal(|| Option::<(UserView, String, String)>::None);
+    let mut confirm_move_default = use_signal(|| Option::<UserView>::None);
     let mut confirm_delete = use_signal(|| false);
 
     let tenant_id = id.clone();
     let reload = use_callback(move |_: ()| {
         let id = tenant_id.clone();
         loading.set(true);
+        error.set(None);
         spawn(async move {
             match api::get_tenant(&id).await {
                 Ok(t) => {
                     edit_name.set(t.name.clone());
                     edit_slug.set(t.slug.clone());
                     tenant.set(Some(t));
+
+                    if let Ok(users) = api::list_tenant_users(&id).await {
+                        tenant_users.set(users);
+                    }
+                    if let Ok(users) = api::list_users().await {
+                        all_users.set(users);
+                    }
+                    if let Ok(apps) = api::list_tenant_applications(&id).await {
+                        tenant_apps.set(apps);
+                    }
                     loading.set(false);
                 }
                 Err(e) => {
@@ -252,7 +282,20 @@ pub fn TenantDetailPage(id: String) -> Element {
         });
     });
 
-    use_effect(move || { reload.call(()); });
+    use_effect(move || {
+        reload.call(());
+    });
+
+    let tenant_id_act = id.clone();
+    let load_activity = use_callback(move |_: ()| {
+        let id = tenant_id_act.clone();
+        spawn(async move {
+            let q = format!("resource_type=tenant&q={id}&limit=50");
+            if let Ok(resp) = api::list_audit(&q).await {
+                activity.set(resp.entries);
+            }
+        });
+    });
 
     rsx! {
         Breadcrumb { items: vec![
@@ -267,68 +310,424 @@ pub fn TenantDetailPage(id: String) -> Element {
             ErrorState { message: err, on_retry: move |_| reload.call(()) }
         } else if let Some(t) = tenant() {
             {
-                let tid = t.id.clone();
-                let tid2 = t.id.clone();
-                let tid3 = t.id.clone();
+                let tid_save = t.id.clone();
+                let tid_assign = t.id.clone();
+                let tid_move_default = t.id.clone();
+                let tid_delete = t.id.clone();
+                let tenant_name = t.name.clone();
+                let is_default_tenant = t.id == "00000000-0000-0000-0000-000000000001";
+
+                let current_member_ids: Vec<String> = tenant_users().iter().map(|u| u.id.clone()).collect();
+                let assignable_users: Vec<UserView> = all_users()
+                    .into_iter()
+                    .filter(|u| !current_member_ids.contains(&u.id))
+                    .collect();
+
+                let filtered_members: Vec<UserView> = {
+                    let q = user_query();
+                    tenant_users()
+                        .into_iter()
+                        .filter(|u| matches_query(&u.username, &q))
+                        .collect()
+                };
+
                 rsx! {
                     div { class: "page-header",
                         div {
                             h1 { "{t.name}" }
-                            p { class: "desc", "Tenant configuration and overview" }
+                            p { class: "desc",
+                                code { "{t.slug}" }
+                                " · Tenant ID: "
+                                code { "{t.id}" }
+                            }
                         }
                     }
 
-                    div { class: "grid-2",
+                    div { class: "tabs", style: "display:flex; gap:0.5rem; margin-bottom:1rem; flex-wrap:wrap;",
+                        button {
+                            class: if tab() == "overview" { "btn btn-sm btn-primary" } else { "btn btn-sm btn-outline" },
+                            r#type: "button",
+                            onclick: move |_| tab.set("overview".into()),
+                            "Overview"
+                        }
+                        button {
+                            class: if tab() == "users" { "btn btn-sm btn-primary" } else { "btn btn-sm btn-outline" },
+                            r#type: "button",
+                            onclick: move |_| tab.set("users".into()),
+                            "Users ({tenant_users().len()})"
+                        }
+                        button {
+                            class: if tab() == "applications" { "btn btn-sm btn-primary" } else { "btn btn-sm btn-outline" },
+                            r#type: "button",
+                            onclick: move |_| tab.set("applications".into()),
+                            "Applications ({tenant_apps().len()})"
+                        }
+                        button {
+                            class: if tab() == "activity" { "btn btn-sm btn-primary" } else { "btn btn-sm btn-outline" },
+                            r#type: "button",
+                            onclick: move |_| {
+                                tab.set("activity".into());
+                                load_activity.call(());
+                            },
+                            "Activity"
+                        }
+                    }
+
+                    // ── Tab: Overview ──────────────────────────────────────────
+                    if tab() == "overview" {
+                        div { class: "grid-2",
+                            div { class: "card",
+                                div { class: "card-header", h3 { "Tenant Details" } }
+                                div { class: "card-body",
+                                    TextInput {
+                                        label: "Name",
+                                        value: edit_name(),
+                                        oninput: move |v| edit_name.set(v),
+                                    }
+                                    TextInput {
+                                        label: "Slug",
+                                        value: edit_slug(),
+                                        oninput: move |v| edit_slug.set(v),
+                                    }
+                                    p { class: "desc text-muted", style: "font-size:12px; margin-top:-0.5rem;",
+                                        "Leaving slug blank derives it automatically from name. Changing a tenant slug may affect existing references."
+                                    }
+                                    button {
+                                        class: "btn btn-primary mt-2",
+                                        r#type: "button",
+                                        onclick: move |_| {
+                                            let n = edit_name();
+                                            let s = edit_slug();
+                                            let tid = tid_save.clone();
+                                            spawn(async move {
+                                                match api::update_tenant(&tid, &n, Some(s.as_str()).filter(|s| !s.is_empty())).await {
+                                                    Ok(_) => {
+                                                        state.toast(ToastKind::Success, "Tenant updated");
+                                                        reload.call(());
+                                                    }
+                                                    Err(e) => state.toast(ToastKind::Error, e.to_string()),
+                                                }
+                                            });
+                                        },
+                                        "Save changes"
+                                    }
+                                }
+                            }
+
+                            div { class: "card",
+                                div { class: "card-header", h3 { "Danger Zone" } }
+                                div { class: "card-body",
+                                    p { "Deleting a tenant is permanent and cannot be undone." }
+                                    button {
+                                        class: "btn btn-danger",
+                                        r#type: "button",
+                                        disabled: is_default_tenant,
+                                        onclick: move |_| confirm_delete.set(true),
+                                        "Delete Tenant"
+                                    }
+                                }
+                            }
+                        }
+                    }
+
+                    // ── Tab: Users (Tenant User Assignment) ───────────────────
+                    if tab() == "users" {
                         div { class: "card",
-                            div { class: "card-header", h3 { "Tenant Details" } }
+                            div { class: "card-header", style: "display:flex; justify-content:space-between; align-items:center;",
+                                div {
+                                    h3 { "Tenant User Assignment" }
+                                    p { class: "desc", "Users assigned to this tenant owner. Every user has exactly one tenant owner." }
+                                }
+                                div { class: "row", style: "gap:0.5rem;",
+                                    button {
+                                        class: "btn btn-primary btn-sm",
+                                        r#type: "button",
+                                        onclick: move |_| {
+                                            selected_assign_user_id.set(String::new());
+                                            show_assign_modal.set(true);
+                                        },
+                                        "+ Assign User"
+                                    }
+                                    Link {
+                                        class: "btn btn-outline btn-sm",
+                                        to: Route::UsersPage {},
+                                        "+ Create User"
+                                    }
+                                }
+                            }
                             div { class: "card-body",
-                                TextInput {
-                                    label: "Name",
-                                    value: edit_name(),
-                                    oninput: move |v| edit_name.set(v),
+                                DataTable {
+                                    columns: vec![
+                                        ColumnDef { key: "username".into(), label: "Username".into(), sortable: true, visible: true },
+                                        ColumnDef { key: "status".into(), label: "Status".into(), sortable: true, visible: true },
+                                        ColumnDef { key: "created_at".into(), label: "Created".into(), sortable: true, visible: true },
+                                        ColumnDef { key: "actions".into(), label: "Actions".into(), sortable: false, visible: true },
+                                    ],
+                                    on_search: move |v| user_query.set(v),
+                                    search_value: user_query(),
+                                    search_placeholder: "Filter tenant users…".to_string(),
+                                    on_sort: move |_| {},
+                                    sort_key: "username".to_string(),
+                                    on_page: move |_| {},
+                                    page: 0,
+                                    page_size: 100,
+                                    total: filtered_members.len(),
+                                    toolbar_actions: rsx! {
+                                        button { class: "btn btn-outline btn-sm", r#type: "button", onclick: move |_| reload.call(()), "Refresh" }
+                                    },
+                                    for u in filtered_members {
+                                        {
+                                            let u_clone = u.clone();
+                                            rsx! {
+                                                tr { key: "{u.id}",
+                                                    td {
+                                                        Link {
+                                                            to: Route::UserDetailPage { id: u.id.clone() },
+                                                            strong { "{u.username}" }
+                                                        }
+                                                        div { class: "mono text-muted", style: "font-size:11px;", "{u.id}" }
+                                                    }
+                                                    td {
+                                                        span { class: "badge badge-success", "{u.status}" }
+                                                    }
+                                                    td { "{u.created_at}" }
+                                                    td { style: "text-align: right;",
+                                                        if !is_default_tenant {
+                                                            button {
+                                                                class: "btn btn-sm btn-outline",
+                                                                r#type: "button",
+                                                                onclick: move |_| confirm_move_default.set(Some(u_clone.clone())),
+                                                                "Move to Default Tenant"
+                                                            }
+                                                        } else {
+                                                            span { class: "text-muted", style: "font-size:12px;", "Default Tenant Owner" }
+                                                        }
+                                                    }
+                                                }
+                                            }
+                                        }
+                                    }
                                 }
-                                TextInput {
-                                    label: "Slug",
-                                    value: edit_slug(),
-                                    oninput: move |v| edit_slug.set(v),
+                            }
+                        }
+                    }
+
+                    // ── Tab: Applications ─────────────────────────────────────
+                    if tab() == "applications" {
+                        div { class: "card",
+                            div { class: "card-header",
+                                h3 { "Tenant Applications" }
+                                p { class: "desc", "Applications associated with this tenant." }
+                            }
+                            div { class: "card-body",
+                                if tenant_apps().is_empty() {
+                                    EmptyState {
+                                        title: "No applications found".to_string(),
+                                        description: "No applications are currently associated with this tenant.".to_string(),
+                                        icon: "🚀".to_string(),
+                                    }
+                                } else {
+                                    table { class: "table",
+                                        thead {
+                                            tr {
+                                                th { "Application" }
+                                                th { "Slug" }
+                                                th { "Client ID" }
+                                                th { "Status" }
+                                                th { style: "text-align: right;", "Actions" }
+                                            }
+                                        }
+                                        tbody {
+                                            for app in tenant_apps() {
+                                                tr { key: "{app.id}",
+                                                    td {
+                                                        Link {
+                                                            to: Route::ApplicationDetailPage { id: app.id.clone() },
+                                                            strong { "{app.name}" }
+                                                        }
+                                                    }
+                                                    td { code { "{app.slug}" } }
+                                                    td { code { "{app.client_id}" } }
+                                                    td {
+                                                        span {
+                                                            class: if app.enabled { "badge badge-success" } else { "badge badge-secondary" },
+                                                            if app.enabled { "Active" } else { "Disabled" }
+                                                        }
+                                                    }
+                                                    td { style: "text-align: right;",
+                                                        Link {
+                                                            class: "btn btn-sm btn-outline",
+                                                            to: Route::ApplicationDetailPage { id: app.id.clone() },
+                                                            "View"
+                                                        }
+                                                    }
+                                                }
+                                            }
+                                        }
+                                    }
                                 }
-                                button {
-                                    class: "btn btn-primary mt-2",
-                                    r#type: "button",
-                                    onclick: move |_| {
-                                        let n = edit_name();
-                                        let s = edit_slug();
-                                        let tid = tid.clone();
+                            }
+                        }
+                    }
+
+                    // ── Tab: Activity ──────────────────────────────────────────
+                    if tab() == "activity" {
+                        div { class: "card",
+                            div { class: "card-header",
+                                h3 { "Tenant Audit Log" }
+                                p { class: "desc", "Audit events scoped to this tenant." }
+                            }
+                            div { class: "card-body",
+                                if activity().is_empty() {
+                                    EmptyState {
+                                        title: "No activity recorded".to_string(),
+                                        description: "No audit events found for this tenant.".to_string(),
+                                        icon: "📜".to_string(),
+                                    }
+                                } else {
+                                    table { class: "table",
+                                        thead {
+                                            tr {
+                                                th { "Timestamp" }
+                                                th { "Action" }
+                                                th { "Actor" }
+                                                th { "Severity" }
+                                                th { "IP Address" }
+                                            }
+                                        }
+                                        tbody {
+                                            for act in activity() {
+                                                tr { key: "{act.id}",
+                                                    td { "{act.created_at}" }
+                                                    td { strong { "{act.action}" } }
+                                                    td { "{act.actor_user_id.as_deref().unwrap_or(\"—\")}" }
+                                                    td {
+                                                        span { class: "badge badge-info", "{act.severity}" }
+                                                    }
+                                                    td { "{act.ip_address.as_deref().unwrap_or(\"—\")}" }
+                                                }
+                                            }
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
+
+                    // ── Assign User Modal ──────────────────────────────────────
+                    Modal {
+                        title: "Assign User to Tenant".to_string(),
+                        open: show_assign_modal(),
+                        on_close: move |_| show_assign_modal.set(false),
+                        p { class: "desc", "Select an existing NX9-Auth user to reassign to tenant \"{tenant_name}\"." }
+                        div { class: "form-group", style: "margin-top:1rem;",
+                            label { class: "form-label", "Select User" }
+                            select {
+                                class: "form-control",
+                                value: selected_assign_user_id(),
+                                onchange: move |evt: Event<FormData>| selected_assign_user_id.set(evt.value()),
+                                option { value: "", "— Select an existing user —" }
+                                for u in assignable_users.clone() {
+                                    option {
+                                        value: "{u.id}",
+                                        "{u.username} (currently in tenant: {u.tenant_id.as_deref().unwrap_or(\"default\")})"
+                                    }
+                                }
+                            }
+                        }
+                        div { class: "modal-footer", style: "margin-top:1.5rem; padding:0; border:none; background:transparent;",
+                            button { class: "btn btn-outline", r#type: "button", onclick: move |_| show_assign_modal.set(false), "Cancel" }
+                            button {
+                                class: "btn btn-primary",
+                                r#type: "button",
+                                disabled: selected_assign_user_id().is_empty(),
+                                onclick: move |_| {
+                                    let uid = selected_assign_user_id();
+                                    if let Some(target_u) = assignable_users.iter().find(|u| u.id == uid) {
+                                        let from = target_u.tenant_id.clone().unwrap_or_else(|| "default".to_string());
+                                        confirm_reassign_user.set(Some((target_u.clone(), from, tid_assign.clone())));
+                                        show_assign_modal.set(false);
+                                    }
+                                },
+                                "Assign User"
+                            }
+                        }
+                    }
+
+                    // ── Confirm Reassign User Dialog ─────────────────────────
+                    if let Some((target_u, from_tenant, to_tenant_id)) = confirm_reassign_user() {
+                        {
+                            let u_id = target_u.id.clone();
+                            let u_name = target_u.username.clone();
+                            let to_tid = to_tenant_id.clone();
+                            let dest_name = tenant_name.clone();
+                            rsx! {
+                                ConfirmDialog {
+                                    title: "Confirm Tenant Reassignment".to_string(),
+                                    message: format!(
+                                        "Reassign user \"{}\" from tenant \"{}\" to \"{}\"?",
+                                        u_name, from_tenant, dest_name
+                                    ),
+                                    open: true,
+                                    confirm_label: "Reassign User".to_string(),
+                                    danger: false,
+                                    on_confirm: move |_| {
+                                        let uid = u_id.clone();
+                                        let tid = to_tid.clone();
+                                        confirm_reassign_user.set(None);
                                         spawn(async move {
-                                            match api::update_tenant(&tid, &n, Some(s.as_str()).filter(|s| !s.is_empty())).await {
+                                            match api::assign_tenant_user(&tid, &uid).await {
                                                 Ok(_) => {
-                                                    state.toast(ToastKind::Success, "Tenant updated");
+                                                    state.toast(ToastKind::Success, "User reassigned to tenant");
                                                     reload.call(());
                                                 }
                                                 Err(e) => state.toast(ToastKind::Error, e.to_string()),
                                             }
                                         });
                                     },
-                                    "Save changes"
-                                }
-                            }
-                        }
-
-                        div { class: "card",
-                            div { class: "card-header", h3 { "Danger Zone" } }
-                            div { class: "card-body",
-                                p { "Deleting a tenant is permanent and cannot be undone." }
-                                button {
-                                    class: "btn btn-danger",
-                                    r#type: "button",
-                                    disabled: tid2 == "00000000-0000-0000-0000-000000000001",
-                                    onclick: move |_| confirm_delete.set(true),
-                                    "Delete Tenant"
+                                    on_cancel: move |_| confirm_reassign_user.set(None),
                                 }
                             }
                         }
                     }
 
+                    // ── Confirm Move to Default Tenant Dialog ────────────────
+                    if let Some(target_u) = confirm_move_default() {
+                        {
+                            let u_id = target_u.id.clone();
+                            let u_name = target_u.username.clone();
+                            let tid_curr = tid_move_default.clone();
+                            rsx! {
+                                ConfirmDialog {
+                                    title: "Move to Default Tenant".to_string(),
+                                    message: format!(
+                                        "Reassign user \"{}\" from tenant \"{}\" to Default Tenant?",
+                                        u_name, tenant_name
+                                    ),
+                                    open: true,
+                                    confirm_label: "Move to Default Tenant".to_string(),
+                                    danger: false,
+                                    on_confirm: move |_| {
+                                        let uid = u_id.clone();
+                                        let tid = tid_curr.clone();
+                                        confirm_move_default.set(None);
+                                        spawn(async move {
+                                            match api::remove_tenant_user(&tid, &uid).await {
+                                                Ok(_) => {
+                                                    state.toast(ToastKind::Success, "User reassigned to Default Tenant");
+                                                    reload.call(());
+                                                }
+                                                Err(e) => state.toast(ToastKind::Error, e.to_string()),
+                                            }
+                                        });
+                                    },
+                                    on_cancel: move |_| confirm_move_default.set(None),
+                                }
+                            }
+                        }
+                    }
+
+                    // ── Confirm Delete Tenant Dialog ─────────────────────────
                     ConfirmDialog {
                         title: "Delete tenant".to_string(),
                         message: format!("Delete tenant \"{}\"? This cannot be undone.", t.name),
@@ -336,7 +735,7 @@ pub fn TenantDetailPage(id: String) -> Element {
                         confirm_label: "Delete",
                         danger: true,
                         on_confirm: move |_| {
-                            let tid = tid3.clone();
+                            let tid = tid_delete.clone();
                             spawn(async move {
                                 match api::delete_tenant(&tid).await {
                                     Ok(_) => {

ui/src/pages/users/mod.rs

@@ -49,6 +49,13 @@ pub fn UsersPage() -> Element {
 
     use_effect(move || { reload.call(()); });
 
+    let can_create = state.auth.read().has_permission("users:create") || state.auth.read().is_adminish();
+    use_effect(move || {
+        if can_create && crate::utils::check_and_clear_create_intent() {
+            show_create.set(true);
+        }
+    });
+
     let filtered = {
         let q = query();
         let sf = status_filter();
@@ -305,9 +312,14 @@ pub fn UsersPage() -> Element {
 #[component]
 pub fn UserDetailPage(id: String) -> Element {
     let state = use_context::<AppState>();
+    let state_auth = state.auth;
+    let can_manage_apps = state_auth().has_permission("applications:manage");
+
     let mut user = use_signal(|| Option::<UserView>::None);
     let mut roles = use_signal(Vec::<crate::models::RoleView>::new);
     let mut all_roles = use_signal(Vec::<crate::models::RoleView>::new);
+    let mut user_apps =
+        use_signal(Vec::<crate::models::UserApplicationMembershipView>::new);
     let mut error = use_signal(|| Option::<String>::None);
     let mut loading = use_signal(|| true);
     let mut new_pass = use_signal(String::new);
@@ -326,6 +338,11 @@ pub fn UserDetailPage(id: String) -> Element {
                     if let Ok(ar) = api::list_roles().await {
                         all_roles.set(ar);
                     }
+                    if let Ok(apps) = api::list_user_applications(&id).await {
+                        user_apps.set(apps);
+                    } else {
+                        user_apps.set(Vec::new());
+                    }
                     loading.set(false);
                 }
                 Err(e) => {
@@ -485,6 +502,58 @@ pub fn UserDetailPage(id: String) -> Element {
                         }
                     }
                 }
+
+                if can_manage_apps {
+                    div { class: "card", style: "grid-column: 1 / -1;",
+                        div { class: "card-header", h3 { "Applications" } }
+                        div { class: "card-body",
+                            p { class: "text-secondary", style: "font-size:0.9rem; margin-bottom:0.75rem;",
+                                "Applications this user is assigned to. Membership roles are metadata only and do not change global RBAC."
+                            }
+                            if user_apps().is_empty() {
+                                p { class: "text-muted", "Not assigned to any applications." }
+                            } else {
+                                DataTable {
+                                    columns: vec![
+                                        ColumnDef { key: "name".into(), label: "Application".into(), sortable: false, visible: true },
+                                        ColumnDef { key: "role".into(), label: "Membership Role".into(), sortable: false, visible: true },
+                                        ColumnDef { key: "status".into(), label: "Status".into(), sortable: false, visible: true },
+                                        ColumnDef { key: "assigned".into(), label: "Assigned".into(), sortable: false, visible: true },
+                                    ],
+                                    on_search: |_| {},
+                                    search_value: "".to_string(),
+                                    search_placeholder: "".to_string(),
+                                    on_sort: |_| {},
+                                    sort_key: "".to_string(),
+                                    on_page: |_| {},
+                                    page: 0,
+                                    page_size: user_apps().len().max(1),
+                                    total: user_apps().len(),
+                                    for m in user_apps() {
+                                        tr { key: "{m.id}",
+                                            td {
+                                                Link {
+                                                    to: Route::ApplicationDetailPage { id: m.application_id.clone() },
+                                                    strong { "{m.application_name}" }
+                                                }
+                                                div { class: "text-muted", style: "font-size:0.8rem;",
+                                                    code { "{m.application_slug}" }
+                                                }
+                                            }
+                                            td { span { class: "badge badge-accent", "{m.role}" } }
+                                            td {
+                                                StatusChip {
+                                                    status: if m.enabled { "active".to_string() } else { "disabled".to_string() }
+                                                }
+                                            }
+                                            td { "{format_datetime(&m.created_at)}" }
+                                        }
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
             }
                 }
             }

ui/src/routes/mod.rs

@@ -3,7 +3,7 @@
 use crate::components::layout::AppLayout;
 use crate::pages::{
     about::AboutPage,
-    applications::ApplicationsPage,
+    applications::{ApplicationDetailPage, ApplicationsPage},
     audit::AuditPage,
     auth::{ForbiddenPage, LoginPage, UnauthorizedPage},
     dashboard::DashboardPage,
@@ -77,6 +77,9 @@ pub enum Route {
         #[route("/applications")]
         ApplicationsPage {},
 
+        #[route("/applications/:id")]
+        ApplicationDetailPage { id: String },
+
         #[route("/service-accounts")]
         ServiceAccountsPage {},
 

ui/src/services/api.rs

@@ -435,6 +435,58 @@ pub async fn delete_application(id: &str) -> Result<(), ApiError> {
     Ok(())
 }
 
+pub async fn get_application(id: &str) -> Result<ApplicationView, ApiError> {
+    let r: Value = get(&format!("/applications/{id}")).await?;
+    serde_json::from_value(r.get("application").cloned().unwrap_or(Value::Null))
+        .map_err(|e| ApiError::Other(e.to_string()))
+}
+
+pub async fn list_application_members(app_id: &str) -> Result<Vec<ApplicationMemberView>, ApiError> {
+    let r: ApplicationMembersResponse = get(&format!("/applications/{app_id}/members")).await?;
+    Ok(r.members)
+}
+
+pub async fn add_application_member(
+    app_id: &str,
+    user_id: &str,
+    role: Option<&str>,
+) -> Result<ApplicationMemberView, ApiError> {
+    let body = serde_json::json!({
+        "user_id": user_id,
+        "role": role,
+    });
+    let r: Value = post_json(&format!("/applications/{app_id}/members"), &body).await?;
+    serde_json::from_value(r.get("member").cloned().unwrap_or(Value::Null))
+        .map_err(|e| ApiError::Other(e.to_string()))
+}
+
+pub async fn update_application_member(
+    app_id: &str,
+    user_id: &str,
+    role: Option<&str>,
+    enabled: Option<bool>,
+) -> Result<ApplicationMemberView, ApiError> {
+    let body = serde_json::json!({
+        "role": role,
+        "enabled": enabled,
+    });
+    let r: Value = patch_json(&format!("/applications/{app_id}/members/{user_id}"), &body).await?;
+    serde_json::from_value(r.get("member").cloned().unwrap_or(Value::Null))
+        .map_err(|e| ApiError::Other(e.to_string()))
+}
+
+pub async fn remove_application_member(app_id: &str, user_id: &str) -> Result<(), ApiError> {
+    let _: Value = delete_json(&format!("/applications/{app_id}/members/{user_id}")).await?;
+    Ok(())
+}
+
+pub async fn list_user_applications(
+    user_id: &str,
+) -> Result<Vec<UserApplicationMembershipView>, ApiError> {
+    let r: UserApplicationsResponse = get(&format!("/users/{user_id}/applications")).await?;
+    Ok(r.applications)
+}
+
 // ── Service accounts ──────────────────────────────────────────────────────────
 
 pub async fn list_service_accounts() -> Result<Vec<ServiceAccountView>, ApiError> {
@@ -566,3 +618,27 @@ pub async fn delete_tenant(id: &str) -> Result<(), ApiError> {
     let _: Value = delete_json(&format!("/tenants/{id}")).await?;
     Ok(())
 }
+
+pub async fn list_tenant_users(tenant_id: &str) -> Result<Vec<UserView>, ApiError> {
+    let r: Value = get(&format!("/tenants/{tenant_id}/users")).await?;
+    serde_json::from_value(r.get("users").cloned().unwrap_or(Value::Array(vec![])))
+        .map_err(|e| ApiError::Other(e.to_string()))
+}
+
+pub async fn assign_tenant_user(tenant_id: &str, user_id: &str) -> Result<UserView, ApiError> {
+    let body = serde_json::json!({ "user_id": user_id });
+    let r: Value = post_json(&format!("/tenants/{tenant_id}/users"), &body).await?;
+    serde_json::from_value(r.get("user").cloned().unwrap_or(Value::Null))
+        .map_err(|e| ApiError::Other(e.to_string()))
+}
+
+pub async fn remove_tenant_user(tenant_id: &str, user_id: &str) -> Result<(), ApiError> {
+    let _: Value = delete_json(&format!("/tenants/{tenant_id}/users/{user_id}")).await?;
+    Ok(())
+}
+
+pub async fn list_tenant_applications(tenant_id: &str) -> Result<Vec<ApplicationView>, ApiError> {
+    let r: Value = get(&format!("/tenants/{tenant_id}/applications")).await?;
+    serde_json::from_value(r.get("applications").cloned().unwrap_or(Value::Array(vec![])))
+        .map_err(|e| ApiError::Other(e.to_string()))
+}

ui/src/utils/mod.rs

@@ -75,3 +75,47 @@ pub fn slugify(s: &str) -> String {
         .collect::<Vec<_>>()
         .join("-")
 }
+
+/// Check if location search contains exact `create=1` query parameter, and clear `create=1` from history URL while preserving other parameters.
+pub fn check_and_clear_create_intent() -> bool {
+    #[cfg(target_arch = "wasm32")]
+    {
+        if let Some(window) = web_sys::window() {
+            if let Ok(search) = window.location().search() {
+                let query_str = search.trim_start_matches('?');
+                let mut has_create = false;
+                let mut remaining_params = Vec::new();
+
+                for part in query_str.split('&') {
+                    if part.is_empty() {
+                        continue;
+                    }
+                    let mut key_val = part.splitn(2, '=');
+                    let key = key_val.next().unwrap_or("");
+                    let val = key_val.next().unwrap_or("");
+                    if key == "create" && val == "1" {
+                        has_create = true;
+                    } else {
+                        remaining_params.push(part);
+                    }
+                }
+
+                if has_create {
+                    if let Ok(pathname) = window.location().pathname() {
+                        let new_search = if remaining_params.is_empty() {
+                            String::new()
+                        } else {
+                            format!("?{}", remaining_params.join("&"))
+                        };
+                        let new_url = format!("{pathname}{new_search}");
+                        let _ = window.history().and_then(|h| {
+                            h.replace_state_with_url(&wasm_bindgen::JsValue::NULL, "", Some(&new_url))
+                        });
+                    }
+                    return true;
+                }
+            }
+        }
+    }
+    false
+}