Pin ruff at 0.16.4 to match what the VS Code extension bundles

[lchoquel]

Part of the workspace-wide ruff 0.16.4 rollout (wip/updates/ruff-0.16.4-workspace-rollout-20260814.md). This is repo 1 of the scoped batch of seven; pipelex, conformance, pipelex-sdk-python and mthds-python landed earlier.

Why

Ruff 0.16 lints pyproject.toml itself, and the Ruff VS Code extension syncs config files to the language server. A pre-0.16 binary parses those TOML documents as Python source and paints phantom Ruff(invalid-syntax) diagnostics on lines like requires-python — requires-python = ... gets read as requires - python, an invalid assignment target. The extension runs whatever binary it finds, repo venv first, so the venv pin is what has to move.

The installed extension (charliermarsh.ruff-2026.74.0) bundles ruff 0.16.4, which is why the pin lands there rather than on 0.16.2. Keeping it exact rather than a floor is what stops the editor and the CLI from drifting apart again.

What changed

• pyproject.toml: ruff==0.14.13 → ruff==0.16.4, plus the matching uv.lock update. This was the repo's only ruff pin site.
• .vscode/settings.json: dropped "ruff.configuration": "--config=pyproject.toml". That setting takes a path to a config file, not a CLI flag, so the value never resolved — it only ever worked by falling back to Ruff's normal filesystem discovery, which finds the same pyproject.toml anyway.

Fallout: none

Nothing shipped changes — this is a dev dependency. The upgrade produced no new lint findings and no reformatting, which is what the rollout plan predicted for this repo: the ruff config here uses a narrow select list without preview, so none of the new preview rules or the noqa → ruff: ignore[...] migration that dominated the pipelex sweep applies.

Verification

make agent-check (fix-unused-imports, ruff format, ruff check, pyright, mypy) and make agent-test both pass.

🤖 Generated with Claude Code

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Summary by cubic

Pins ruff to 0.16.4 to align the CLI with the VS Code extension and stop phantom invalid-syntax diagnostics on pyproject.toml. Previously pinned to 0.14.13 (pre-0.16), which parsed TOML as Python; now both editor and CLI use 0.16.4, which lints TOML correctly.

Review notes

• pyproject.toml: ruff==0.14.13 → ruff==0.16.4; updated uv.lock and CHANGELOG.md.
• .vscode/settings.json: removed ruff.configuration (it incorrectly used a CLI flag); rely on normal config discovery.
• Dev-only change; no new lint findings and no reformatting; make agent-check and make agent-test pass.
• Action: run uv sync or recreate your venv to pick up ruff==0.16.4.

^{Written for commit c4537b3. Summary will update on new commits.}

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge with no actionable changed-code defects identified.

The Ruff pin and lockfile remain consistent, the removed editor setting was ineffective, and no runtime dependency or shipped behavior changes.

_{Reviews (1): Last reviewed commit: "Pin ruff at 0.16.4 to match what the VS ..." | Re-trigger Greptile}