feat(v1.81.0-stable-agentcore): major release with agent-to-agent protocol, lazy imports, and comprehensive feature expansion

[busla]

What

This is the stable v1.81.0-agentcore release branch containing 401 commits and 290K+ lines of new features, fixes, and documentation. Major changes include A2A (agent-to-agent) protocol implementation, lazy import system refactoring for performance, comprehensive proxy server updates with enhanced team/key management, 8+ LLM provider integrations, extensive dashboard component refactoring, and 1026+ bug fixes across the codebase.

Key Architectural Improvements

Core SDK Enhancements

• Lazy import system (_lazy_imports.py, _lazy_imports_registry.py) for faster module initialization
• Agent-to-agent communication protocol (a2a_protocol/) with streaming and cost calculation
• Comprehensive architecture documentation (ARCHITECTURE.md) for contributor guidance

AI Gateway (Proxy) Improvements

• Enhanced team management with deleted teams tracking and status management
• New deleted keys endpoint with audit trail capabilities
• Improved authentication and API key validation for pass-through endpoints
• MCP server REST endpoint extensions
• Dashboard UI refactoring with 453+ component updates

Provider Ecosystem

• Azure Model Router with regional endpoint routing
• Enhanced Anthropic/Bedrock integration with prompt caching
• VertexAI pass-through improvements with header forwarding fixes
• Tool Search support on /messages API
• Claude Code integration with WebSearch capabilities

Performance & Reliability

• Removed CPU usage bottlenecks under heavy load
• Optimized hot-path request handling
• Fixed SIGTERM handling with separate health-check processes
• Enhanced PostgreSQL error handling during rolling deployments
• Improved mid-stream fallback support

Testing & Quality

• 692 test files updated with 12K+ lines of new test code
• New comprehensive test suites: team endpoints (820 lines), VertexAI load balancing (449 lines), public endpoints (256 lines), fallback management (494 lines)
• Expanded provider-specific tests for Gemini, WatsonX, and other integrations
• Enhanced exception header preservation and response normalization tests

Documentation

• 335+ documentation files updated in /docs/my-website/
• New Azure Model Router guide with detailed reference images
• MCP troubleshooting guide added
• Claude Code quickstart cookbook
• Enhanced VertexAI pass-through documentation

Files Modified

Core Changes: litellm/__init__.py, litellm/proxy/proxy_server.py, litellm/proxy/management_endpoints/team_endpoints.py

New Modules: litellm/_lazy_imports.py, litellm/_lazy_imports_registry.py, litellm/a2a_protocol/ (8 files)

UI/Dashboard: 453 files in ui/litellm-dashboard/ with test coverage expansion

Tests: 692 test files across tests/ directory with 12,153 insertions

Documentation: 335+ files including architecture guide, provider docs, troubleshooting guides

Total Impact: 2,433 files changed, +290,524 lines added, -48,770 lines removed

Testing

This release includes:

• make test-unit should pass with all 85+ test suites
• Proxy server tests for team/key management endpoints
• Provider-specific integration tests for new LLM support
• Load balancing and fallback scenario tests
• Exception handling and response normalization tests

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