diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
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@@ -1,9 +1,277 @@
 # Changelog
 
-## v0.4.0
+All notable changes to this project will be documented in this file.
+
+The format is based on Keep a Changelog and this project follows Semantic Versioning.
+
+---
+
+# v0.5.0 - General Availability (GA)
+
+Release Date: 2026-06-19
+
+BZOD v0.5.0 is the largest release since project inception, transforming BZOD from a single-user URL shortener into a complete multi-user redirector, landing page, analytics, and administration platform.
+
+---
+
+## Added
+
+### Multi-User Platform
+
+* Multi-user architecture with isolated tenant databases
+* Standard user accounts
+* Administrator accounts
+* User provisioning and lifecycle management
+* User enable/disable operations
+* User deletion workflows
+* Password reset functionality
+* User quota management
+* User database isolation
+
+### Authentication & Security
+
+* Session-based authentication
+* CSRF protection
+* Role-Based Access Control (RBAC)
+* Password hashing and verification
+* Session invalidation
+* Login/logout workflows
+* Administrative privilege separation
+* Audit logging
+
+### User Self-Service Portal
+
+* User dashboard
+* My Links management
+* My Pages management
+* User analytics dashboard
+* API token management
+* Password management
+* Profile management
+
+### Administration
+
+* User management dashboard
+* User detail pages
+* User creation forms
+* User editing interface
+* Session administration
+* Quota administration
+* Moderation dashboard
+* Slug management dashboard
+* Audit event viewer
+* Backup management interface
+* System health dashboard
+
+### Analytics
+
+* Per-user analytics
+* URL analytics dashboards
+* Landing page analytics dashboards
+* Browser statistics
+* Referrer tracking
+* Visit logging
+* Geographic analytics framework
+* Analytics aggregation jobs
+
+### Content Management
+
+* Landing page builder
+* URL registry management
+* Global slug namespace
+* Slug ownership tracking
+* Slug transfer workflows
+* Soft delete support
+* Moderation controls
+
+### Operations
+
+* Backup CLI
+* Restore CLI
+* User backup support
+* User restore support
+* Database diagnostics
+* Health checks
+* Quota reconciliation jobs
+* Retention jobs
+* Expiry jobs
+* Aggregation workers
+
+### Documentation
+
+* Installation Guide
+* Upgrade Guide
+* Multi-User Guide
+* Administration Guide
+* Security Guide
+* Backup & Restore Guide
+* Database Documentation
+* Architecture Documentation
+* CLI Documentation
+* API Documentation
+* Testing Documentation
+
+---
+
+## Changed
+
+### Architecture
+
+* Migrated from single-user storage model to tenant-isolated storage model
+* Introduced users.db as central identity store
+* Introduced system.db as global platform metadata store
+* Introduced per-user content databases
+* Introduced per-user analytics databases
+
+### Routing
+
+* Unified global slug resolution
+* Centralized slug ownership tracking
+* Improved redirect handling
+* Improved landing page routing
+
+### Analytics
+
+* Improved aggregation performance
+* Improved reporting consistency
+* Improved analytics isolation
+
+### Administration
+
+* Expanded administrative tooling
+* Improved dashboard coverage
+* Added operational visibility
+
+---
+
+## Security
 
 ### Added
 
+* CSRF validation
+* Session management
+* RBAC enforcement
+* Audit event logging
+* User isolation controls
+* Slug ownership validation
+
+### Hardened
+
+* Authentication flows
+* Session validation
+* Administrative authorization
+* User lifecycle operations
+
+---
+
+## Database
+
+### Added
+
+* users.db
+* system.db
+* Per-user content.db
+* Per-user analytics.db
+* Migration framework
+
+### Improved
+
+* WAL mode support
+* Upgrade migrations
+* Backup compatibility
+* Recovery workflows
+
+---
+
+## Testing
+
+### Added
+
+Comprehensive automated validation covering:
+
+* Authentication tests
+* Authorization tests
+* Migration tests
+* Upgrade validation tests
+* User isolation tests
+* Slug namespace tests
+* Slug transfer tests
+* Moderation tests
+* Backup and restore tests
+* Disaster recovery tests
+* Analytics tests
+* Concurrency tests
+* HTTP end-to-end tests
+* Business workflow tests
+* Security regression tests
+
+### Coverage
+
+* 90+ unit and integration tests
+* HTTP workflow validation
+* Upgrade path verification
+* Multi-user isolation verification
+* Backup and recovery validation
+
+---
+
+## Fixed
+
+### Authentication
+
+* Multi-user migration login regressions
+* Session validation issues
+* Administrative account migration edge cases
+
+### Routing
+
+* Redirect handling consistency
+* Slug ownership synchronization
+* Landing page resolution issues
+
+### Analytics
+
+* Aggregation edge cases
+* Reporting consistency
+* Isolation validation
+
+### Concurrency
+
+* Fixed mutex deadlock conditions discovered during E2E testing
+* Improved lock scoping around audit logging
+
+### Administration
+
+* Improved slug transfer workflows
+* Improved user lifecycle operations
+* Improved dashboard consistency
+
+---
+
+## Upgrade Notes
+
+### From v0.4.0
+
+BZOD v0.5.0 introduces a new multi-user architecture.
+
+Existing installations are automatically migrated during startup.
+
+Migration includes:
+
+* Legacy administrator migration
+* Global slug index generation
+* User database creation
+* Analytics preservation
+* Content preservation
+
+Backups are strongly recommended before upgrading.
+
+---
+
+# v0.4.0
+
+## Added
+
 * Raw visitor activity logs
 * Analytics drill-down pages
 * Date-range analytics filters
@@ -12,13 +280,13 @@
 * Advanced pagination
 * Visitor log tables
 
-### Improved
+## Improved
 
 * Registry pagination
 * Analytics navigation
 * Export performance
 
-### Fixed
+## Fixed
 
 * Pagination edge cases
-* Analytics sorting consistency
\ No newline at end of file
+* Analytics sorting consistency