Fixes anthropics/claude-plugins-official#2071 — on macOS where the
default `python3` is Apple's Command Line Tools Python 3.9.6, the
plugin's agentic commit reviewer silently does not run, even when the
user has a newer Python installed.
Three compounding factors in the bug:
1. `sg-python.sh` only checks the major version (`3`), so it always
picks 3.9 even when 3.10+ is on PATH.
2. `claude_agent_sdk` requires Python >=3.10 — pip install on 3.9
returns "No matching distribution" -> bootstrap returns BUILD_FAILED.
3. Even with a hand-built 3.12 venv, `llm.py` imports the SDK
in-process into the hook's interpreter (still 3.9), which raises
SyntaxError. The existing venv-probe in `ensure_agent_sdk.py` uses
the venv's own Python (3.12) so it reports NOOP_VENV (healthy) while
the consumer fails — misleading telemetry on top of silent feature
degradation.
Per BQ telemetry, 14,073 external macOS users hit
sdk_bootstrap=BUILD_FAILED in the past 4 days (the default-macOS
cohort), out of ~86K total external installed users. Combined with
~20K other users in similar broken-bootstrap states (Windows pre-#2055,
Linux <3.10), about half the installed base has a silently-broken
agentic reviewer.
This PR implements the reporter's items #1, #3, and #4. Item #2
(running the SDK out-of-process) is deferred as a bigger refactor.
Item #1 — hooks/sg-python.sh — prefer >=3.10 binaries via 3-pass probe:
Pass 1: python3.13 / 3.12 / 3.11 / 3.10 (>=3.10 by name, highest wins)
Pass 2: bare python3 / python / py -3 (accept only if reported >=3.10)
Pass 3: bare python3 / python / py -3 (any Python 3, FALLBACK so
pattern checks still work on macOS-default 3.9 — no regression
vs today; SDK-dependent paths detect the version mismatch
inside Python and degrade cleanly via item #4)
Item #4 — ensure_agent_sdk.py — health-check honesty:
Added HOOK_PY_INCOMPATIBLE=6 outcome with short-circuit at top of main():
if sys.version_info < (3, 10):
return HOOK_PY_INCOMPATIBLE, "hook_py", f"py_{...}"
Telemetry consequences after rollout: sdk_bootstrap=6 is a new clean
bucket; some users currently miscounted in sdk_bootstrap=3 BUILD_FAILED
(wasted pip cycles) and sdk_bootstrap=1 NOOP_VENV (falsely-healthy)
move to sdk_bootstrap=6. The remaining NOOP_VENV count becomes
trustworthy.
Item #3 — ensure_agent_sdk.py — one-time user-visible notice:
When outcome == HOOK_PY_INCOMPATIBLE and a marker file at
`~/.claude/security/.agentic_unavailable_notice_v<pv>` doesn't exist,
the SessionStart response includes hookSpecificOutput.additionalContext
+ systemMessage explaining the situation. Marker file is plugin-
version-keyed so a future fix (e.g. shipping out-of-process SDK) can
bump pv and re-notify users.
BUILD_FAILED is intentionally excluded from the notice — it covers
transient causes where a permanent banner would mislead.
Verified locally on macOS Python 3.13:
- py_compile clean on both files.
- Existing 45-test smoke + extensibility suite: 45/45 PASS in 2.50s.
- Unit test of simulated 3.9 path: HOOK_PY_INCOMPATIBLE returned with
correct phase/kind; notice shown on first call, suppressed on
second, reshown on bumped pv; BUILD_FAILED correctly does NOT
trigger notice.
NOT verified: actual Python 3.9 behavior end-to-end (would need a 3.9
install). Worth a follow-up smoke test in a 3.9 venv before next
release. The unit test simulating 3.9 covers the logic but not the
runtime invocation through the shim.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The first round of this PR removed SKIP_WIN32, fixed venv_py to use
Scripts/python.exe, and added Lib/site-packages to the consumer glob —
all necessary. Windows verification (Win11 ARM64, Py 3.13, Git Bash)
showed two more blockers, both addressed here.
1. Pip dependency resolver picks unbuildable cryptography on ARM64.
Without --prefer-binary, pip picks a cryptography version with no
published ARM64 wheel and tries to build it from source. That needs
Rust/Cargo, almost never present on user machines → BUILD_FAILED
with err_kind=other:cryptography. A binary wheel exists for an
adjacent version (cryptography-46.0.3-cp311-abi3-win_arm64.whl);
--prefer-binary tells pip to pick it. Cross-platform safe (no-op
where the latest version already has a wheel).
2. pywin32 .pth files aren't processed by sys.path.insert().
With the venv built, ensure_agent_sdk.py's post-build probe passes
(it runs from venv_py, where Python's site.py at startup processes
pywin32.pth and registers win32/, win32/lib/ plus runs
pywin32_bootstrap.py to set the DLL search dir). But llm.py runs in
the hook's SYSTEM Python and adds the venv via sys.path.insert(),
which doesn't trigger site.py at all. Without the bootstrap, the
SDK's mcp.client.stdio → mcp.os.win32.utilities chain raises
ModuleNotFoundError: pywintypes and the agentic reviewer falls back
to single-shot silently — exactly the symptom this PR is trying to
fix. The probe says NOOP_VENV; the actual consumer fails. Probe and
consumer use different Pythons.
Replicate what site.py would do: after inserting site-packages,
also insert win32/ and win32/lib/, then exec pywin32_bootstrap.py.
Pulled into a shared helper _inject_agent_sdk_venv_into_syspath()
so both consumer sites (3P SDK fallback, agentic_review fallback)
call the same code — Windows handling stays in one place.
Verified on macOS (POSIX path unchanged):
- Helper end-to-end test: POSIX-layout venv detected + fake package
imports successfully via the injected path
- Windows-layout venv also detected; win32 branch correctly skipped
via sys.platform check
- Both files pass py_compile
Credit: @mhegazy verified the previous commit on Win11 ARM64 / Py 3.13
/ Git Bash, surfaced both issues end-to-end, and provided the exact
fix patterns. This commit applies them with the pywin32 part factored
into a shared helper (vs. inlining at both consumer sites).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The agentic reviewer is silently no-op on Windows today. SessionStart
bootstrap (ensure_agent_sdk.py) short-circuits with SKIP_WIN32 because
the consumer glob in llm.py only matches POSIX venv layout
(lib/pythonX.Y/site-packages). On Windows, venvs use Lib/site-packages
(capital L, no pythonX.Y subdir), so even if a venv got built the
glob wouldn't find its contents.
Result: Windows users on default installs (no system-wide
claude_agent_sdk) get layer 1 (pattern warnings) and layer 2 (single-
shot LLM diff review) but not layer 3 — the cross-file agentic review
that catches IDOR, auth-bypass, cross-file SSRF, and other things that
need to read related files. Plugin description claims layer 3 but it
silently doesn't run.
Three changes:
1. llm.py — extend the consumer glob (2 sites: 3P SDK fallback at
~L297, agentic_review fallback at ~L1090) to also match the Windows
Lib/site-packages layout, so a venv built on Windows is actually
discoverable.
2. ensure_agent_sdk.py — remove the sys.platform == 'win32' early-exit
so the SessionStart bootstrap builds the venv on Windows too.
Outcome code 4 (formerly SKIP_WIN32) is retired but not reused so
pre-fix telemetry rows still decode correctly.
3. ensure_agent_sdk.py — venv_py path now branches on sys.platform:
Windows venvs put the interpreter at Scripts\python.exe; POSIX
uses bin/python. Previously assumed POSIX, so even with the glob
fix, the post-build SDK-importability probe would fail on Windows.
Verified locally on macOS:
- glob test: both layouts now match (POSIX venv detected, simulated
Windows venv also detected via the new Lib/site-packages branch)
- both files pass py_compile
- POSIX path unchanged (sys.platform != 'win32' so old branch runs)
Not verified on Windows in this commit — needs an actual Windows
runner to confirm the venv build + SDK import + subprocess plumbing
all work end-to-end. The SDK spawns a child claude.exe; Windows
process plumbing has its own quirks (shell semantics, path escaping)
that may surface separately. Worth a controlled rollout (one-week
soak under env-var opt-in before flipping default).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
