Highlights:
- pyproject.toml replaces setup.py (PEP 621)
- Core deps 23 -> 19 (-17%, CLI/DeepAgent still work out-of-box)
- 20+ fine-grained extras + 8 super-combo extras (agno-style)
- 35+ top-level imports emit DeprecationWarning with migration paths
- @tool decorator supports bare usage
- Anthropic Claude promoted to core provider
- 1349 tests pass, 0 regression, full backward compat

Full details: CHANGELOG.md, docs/API.md, docs/learn_cc/arch_v4.md