fix(launcher): strip extras from the pip constraints file

[cdeust]

The bug

ensure_all_deps passes BASE_PACKAGES verbatim as the -c constraints file (launcher_deps.py:318), and one entry carries an extra — psycopg[binary]==3.3.4 (launcher_pins.py:89). pip has always documented constraints files as version-only and now rejects extras outright, so the entire ML resolve aborts:

ERROR: Constraints cannot have extras
[cortex-launcher] dependency install failed for sentence-transformers==5.6.1, flashrank==0.2.10

sentence-transformers and flashrank never install.

Why it went unnoticed

Only the ML install passes constraints. The base stack installs clean, so nothing fails visibly — the FlashRank re-ranker is simply absent, and recall silently degrades to first-stage-only scores. Same observable shape as the 2026-07-10 FlashRank incident.

Hit on a real plugin install (fresh hypermnesia-mcp@cortex-plugins 4.17.1, macOS).

The fix

pip_install normalizes each constraint through the new constraint_without_extras before writing the file.

This restores the parameter's own documented contract rather than changing it — its docstring already promised name==ver. A constraint pins the VERSION a shared transitive resolves to (numpy, via sentence-transformers), and pip applies it to the distribution however its extras were requested. Extras belong on the install target, which still carries [binary].

Version range — not pip-26-only

I first attributed this to pip 26. That was wrong: pip 25.2 rejects it too, found while validating against the project venv. The affected population is considerably wider than the pip-26 leading edge. Both measurements are now in the source comment and CHANGELOG.

Verification — external signals

pip itself judges the generated file:

	verdict
before	ERROR: Constraints cannot have extras
after	0 occurrences

Command: pip install --dry-run --no-index -c <BASE_PACKAGES> flashrank==0.2.10, run on pip 26.0.1/py3.14 and pip 25.2/py3.13.

• Regression test fails without the fix, passes with it — it asserts the bytes written to the constraints file (what pip actually parses), not the helper: a correct helper wired in at the wrong place would still ship the bug.
• A third test locks the real BASE_PACKAGES list so a future extra cannot reintroduce this.
• tests_py/scripts/: 578 passed, 121 subtests.
• ruff check + ruff format --check: clean.
• launcher_deps_install.py stays within the repo's 300-line cap (300/300).

Note for release

Per CLAUDE.md, this delivers nothing to installs until the marketplace pins move — the fix needs a release + .claude-plugin/marketplace.json bump with scripts/check_marketplace_pins.py exiting 0.

🤖 Generated with Claude Code