fix: stop __version__ drift (#85) and mypy [no-redef] in optional mcp import (#87)

[dgenio]

Fixes #85 and #87 — the two remaining infra/correctness defects from the #85–#88 triage batch (the other two, #86 and #88, were already fixed in d83609d).

What changed

#85 — agent_kernel.__version__ drifted from pyproject.toml

• src/agent_kernel/__init__.py: __version__ is now derived from installed distribution metadata via importlib.metadata.version("weaver-kernel") (single source of truth), with a PackageNotFoundError → "0.0.0+local" fallback for source trees without dist metadata. The hardcoded "0.5.0" literal is gone.
• tests/test_version.py (new): asserts __version__ == importlib.metadata.version("weaver-kernel") and that __version__ stays in __all__.

#87 — optional McpError import triggered mypy [no-redef] when mcp was absent

• src/agent_kernel/drivers/mcp.py: replaced the annotate-then-import ... as _McpError pattern with a _load_mcp_error() helper that imports through importlib.import_module (mirroring the existing mcp_support.import_optional idiom). _McpError is now declared exactly once, so the [no-redef] is gone.
• tests/test_mcp_driver.py: added two regression tests covering both branches of _load_mcp_error (mcp present → returns McpError; mcp absent → returns None).

Docs

• CHANGELOG.md: added ### Fixed entries for agent_kernel.__version__ reports "0.5.0" but pyproject.toml declares 0.7.0 #85 and _McpError annotation+import pattern triggers mypy [no-redef] when mcp is unavailable #87 under [Unreleased], matching the existing issue-referenced style.

Why

• agent_kernel.__version__ reports "0.5.0" but pyproject.toml declares 0.7.0 #85: __version__ reported 0.5.0 while the package shipped 0.7.0/0.8.0. RELEASE.md only ever documented bumping pyproject.toml, so the literal was a latent drift bug; deriving from metadata aligns the code with the documented release process and makes future drift impossible.
• _McpError annotation+import pattern triggers mypy [no-redef] when mcp is unavailable #87: the old pattern declared _McpError twice (annotation + import as), which mypy reads as a redefinition once the mcp import resolves to Any under ignore_missing_imports (i.e. on a base install without the [mcp] extra).

How verified

All commands run in a clean dev venv (pip install -e ".[dev,mcp]"):

• Reproduced before fixing:
  • agent_kernel.__version__ reports "0.5.0" but pyproject.toml declares 0.7.0 #85: metadata: 0.8.0 | module: 0.5.0
  • _McpError annotation+import pattern triggers mypy [no-redef] when mcp is unavailable #87 (with mcp uninstalled): mcp.py:28: error: Name "_McpError" already defined on line 26 [no-redef]
• After fix:
  • agent_kernel.__version__ reports "0.5.0" but pyproject.toml declares 0.7.0 #85: metadata: 0.8.0 | module: 0.8.0
  • _McpError annotation+import pattern triggers mypy [no-redef] when mcp is unavailable #87: python -m mypy src/agent_kernel/drivers/mcp.py → Success both with and without the mcp extra installed.
• make ci → exit 0: ruff format --check clean, ruff check All checks passed!, mypy Success: no issues found in 41 source files, 564 passed / 1 skipped, coverage 94%, examples ran.
• New tests: tests/test_version.py (2) + _load_mcp_error cases (2) all pass; the mcp-absent branch is covered.

Scope notes (Mode B)

Strictly limited to #85 and #87. Diffstat: 5 files, +62/−10 (4 tracked + 1 new test). No back-compat shims (per request — none needed; both are internal/diagnostic surfaces). Other open triage issues (#92–#96, #99, #94) are independent feature/docs work and intentionally not bundled here.

Risks / caveats

• importlib.metadata.version() must use the distribution name (weaver-kernel), not the import name (agent_kernel) — handled and covered by test_version.py. In an uninstalled raw source tree the value is 0.0.0+local; in editable/CI installs it reflects the real dist version.

https://claude.ai/code/session_0185WabrTuoL3jCNZiER7ES6

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Generated by Claude Code

[Copilot]

Pull request overview

Fixes two infra/correctness issues: preventing agent_kernel.__version__ from drifting from the packaged distribution version, and removing a mypy [no-redef] error caused by an optional mcp import pattern.

Changes:

• Derive agent_kernel.__version__ from importlib.metadata.version("weaver-kernel") with a local fallback when dist metadata is unavailable.
• Refactor optional McpError loading into a _load_mcp_error() helper to avoid mypy redefinition errors.
• Add regression tests and document both fixes in the changelog.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/test_version.py	New tests pin __version__ to distribution metadata and ensure it remains exported.
tests/test_mcp_driver.py	Adds regression tests for _load_mcp_error() when mcp is present vs missing.
src/agent_kernel/drivers/mcp.py	Introduces _load_mcp_error() and resolves _McpError once to avoid mypy [no-redef].
src/agent_kernel/init.py	Replaces hardcoded __version__ with importlib.metadata-derived version + fallback.
CHANGELOG.md	Adds Unreleased “Fixed” entries for issues #85 and #87.