[dmitry-tokarev-nv]

Linear: OPS-9049

Overview

The flake8 hook takes 17 to 27 s of each CI pre-commit run, but it enforces nothing. YAML splits its args list at every comma, so flake8 receives only --select=C. This PR removes the hook. Ruff is then the only Python linter, so this PR also moves the ruff hook from 0.5.2 to 0.17.3. It pins the old rule set, so nothing that passed before fails now, and it adds two rules that have no findings on main.

Key Changes

Core logic: none. The change is configuration only.

• .pre-commit-config.yaml: the flake8 hook is gone. ruff-pre-commit moves from v0.5.2 to v0.17.3, and the hook id from ruff to ruff-check. In v0.17.3, ruff is a legacy alias.
• pyproject.toml: [tool.ruff.lint] select = ["E4", "E7", "E9", "F", "W605", "PLW0602"]. The first four are the default rule set of ruff 0.5.2. W605 flags invalid escape sequences, and PLW0602 flags a global name that is never assigned. A TODO records the next step: enable flake8-bugbear (B) after its findings on main are fixed.
• .ai/python-guidelines.md, a docstring in docs/fern/scripts/tests/test_gen_python_api.py, and a comment in lib/bindings/python/codegen/src/gen_python_prometheus_names.rs mentioned flake8. They now name ruff or drop the mention.
• lib/bindings/kvbm/python/kvbm/__init__.py: the file-level # flake8: noqa becomes # ruff: noqa, which ruff treats the same way. The kvbm package is deprecated, so this PR does not clean it up.
• lib/bindings/python/src/dynamo/llm/exceptions.py: the file-level directive is removed, because it suppressed nothing. Ruff now checks that file.
• lib/bindings/python/src/dynamo/llm/__init__.py: the file-level directive is removed, and the 5 F401 findings it hid are fixed. Four are public re-exports (EngineType, make_engine, run_input, HttpError), now written as X as X like the other re-exports in the file. The fifth, import logging, was unused and is gone.

Validation

flake8 enforced nothing

The args line was [--max-line-length=88, --select=C,E,F,W,B,B950, --extend-ignore = E203,E501]. PyYAML, which pre-commit uses, parses it into --select=C, E, F, W, B, B950, --extend-ignore = E203, and E501. With only C selected and no --max-complexity, flake8 has nothing to report. The line has not changed since df90e29eba.

Check before this PR	Result
pre-commit run flake8 on a planted unused import and a planted syntax error	Passed
pre-commit run ruff on the same two files	Failed: it reports the syntax error and fixes the unused import
flake8 7.3.0 with the parsed arguments on all 1,947 .py files of main a5c73615d0	exit 0, no output
flake8 with the intended arguments on the two planted files	E999 and F401

Fixing the arguments instead is not a real option. The intended rules flag about 3,250 lines on main, and 2,758 of them are W503, which conflicts with black. In the rule families that ruff also covers (F, E4, E7, E9), they flag 149 more lines than ruff. All 149 follow conventions that ruff accepts on purpose. Of the 123 late imports, 110 follow pytest.importorskip and 13 follow other allowed setup code. The other 26 are 12 import X as X re-exports, 7 unused names that start with _, 6 duplicate imports, and 1 import inside a loop.

The ruff upgrade does not change enforcement

Ruff run on the 1,958 files the hook checks	Result
0.5.2, the old hook	60 rules, exit 0, no findings
0.17.3 with the repository configuration before this PR	407 rules by default, 9,238 findings (2,991 UP045, 1,313 UP006, 699 I001, 569 BLE001, and more)
0.17.3 with the pinned select	59 rules, exit 0, no findings

The only rule that drops out is E999. Newer ruff removed it as a rule, because it always reports syntax errors. No nested pyproject.toml has a [tool.ruff] table, so the root pin applies to the whole repository.

The upgraded hook, run through pre-commit:

• It passes on all files.
• It fails a planted unused import (and fixes it) and a planted syntax error.
• It passes a 116-character line, so it does not select E501.
• It fails an import after code with E402.

These results also keep the two rewritten sentences true. pre-commit run --all-files passes locally with 40 hooks.

Two added rules and a TODO

These two rules close the gaps between the intended flake8 rules and ruff that cost nothing today:

Rule	Covers	Findings on main	Planted bad case	Planted good case
W605	pycodestyle W605, an invalid escape sequence such as "\d+"	0	fails, and the hook fixes it	r"\d+" passes
PLW0602	pyflakes F824, which ruff does not have: a global name that the function never assigns	0	fails	an assigned global passes

The TODO is for flake8-bugbear (B), which never ran here because the hook never installed the plugin. On main, ruff check --select B reports 254 findings, among them 23 B023 (a closure that captures a loop variable). Those need their own PR. Ruff has no B950, so the TODO names E501 (line too long) as the closest ruff rule.

The file-level noqa directives

Ruff skips a file that has either # flake8: noqa or # ruff: noqa. Without a directive, ruff reports 4 E402 in the kvbm __init__.py, 5 F401 in dynamo/llm/__init__.py, and nothing in exceptions.py.

• kvbm __init__.py keeps a whole-file # ruff: noqa, because the package is deprecated.
• exceptions.py loses its directive, and the ruff, black, and isort hooks pass on it.
• dynamo/llm/__init__.py loses its directive, and ruff 0.17.3 reports no findings after the fixes. The four re-exports have users: for example, components/src/dynamo/mocker/main.py imports EngineType, make_engine, and run_input from dynamo.llm, and components/src/dynamo/common/utils/guided_json.py imports HttpError. Nothing in the repository uses dynamo.llm.logging. An AST comparison shows that the module binds the same 61 names as before, without logging.

A local import of dynamo.llm was not possible: the compiled dynamo._core on hand predates main's AisPerfConfig, and the original file fails the same way there. The CI test jobs build dynamo._core from this PR and import these names.

CI

This PR edits .pre-commit-config.yaml, so its own pre-commit job starts with an empty hook cache. Such cold runs took 152 to 189 s on 2026-10-28, which is close to the 3-minute step limit that #17532 raises. The cold job 123074777938 of the first commit passed with a 122 s step, and flake8 does not appear in its log. Part of that gap comes from a faster runner: black took 34 s there, against 47 to 55 s in the other runs. The cold job 123083739885 of the second commit passed with a 107 s step, and its ruff check hook ran ruff 0.17.3 and passed.

Issues and Ongoing Work

• Closes OPS-9049
• ci(test): OPS-9045 raise the pre-commit step timeout to 6 minutes #17532 raises the pre-commit step timeout from 3 to 6 minutes.
• A separate follow-up can move black and isort to ruff.

Pull Request Checklist

• I used Dynamo's /pr-checklist skill.

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• Source mode: Auto
• Repository: ai-dynamo/dynamo
• Branch: dtokarev/ops-9049-remove-flake8-hook
• File: .coderabbit.yaml
• Commit: 8bcb684
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Commits

Reviewing files that changed from the base of the PR and between 8a9517c and 8bcb684.

Files selected for processing: 4

• .ai/python-guidelines.md
• .pre-commit-config.yaml
• docs/fern/scripts/tests/test_gen_python_api.py
• lib/bindings/python/codegen/src/gen_python_prometheus_names.rs

Files with no reviewable changes: 1

• .pre-commit-config.yaml

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Walkthrough

The pre-commit configuration no longer includes the Flake8 hook. Related documentation and comments now refer to Ruff or no longer list Flake8.

Changes

Python lint references

Layer / File(s)	Summary
Remove Flake8 references .pre-commit-config.yaml, .ai/python-guidelines.md, docs/fern/scripts/tests/test_gen_python_api.py, lib/bindings/python/codegen/src/gen_python_prometheus_names.rs	The pre-commit configuration removes the Flake8 hook. The guidelines and code comments remove or replace Flake8 references with Ruff.

Priority: Low

Estimated code review effort: 1 (Trivial) | ~5 minutes

Merge Risk: Minimal · up to 8bcb6

The PR removes the Flake8 hook and updates its documentation references without an identified merge-blocking issue.

Pre-merge checks: 5

Check name	Status	Explanation
Docstring Coverage		Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentat…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Description check		The pull request description includes all required sections: Overview, Key Changes, Validation, Issues and Ongoing Work, issue closure, and the checklist. It provides detailed technical context and va…
Title check		The title names the two changes the PR makes: replacing flake8 with ruff in the pre-commit setup, and upgrading the ruff hook to 0.17.3. The changeset removes the flake8 pre-commit hook and updates re…

Full details: Docstring Coverage

Explanation

Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 1 functions across 2 files. (1 skipped: 1 unsupported.)

Full details: Description check

Explanation

The pull request description includes all required sections: Overview, Key Changes, Validation, Issues and Ongoing Work, issue closure, and the checklist. It provides detailed technical context and validation results. The checklist item remains unchecked, but this is non-critical for the description check.

Full details: Title check

Explanation

The title names the two changes the PR makes: replacing flake8 with ruff in the pre-commit setup, and upgrading the ruff hook to 0.17.3. The changeset removes the flake8 pre-commit hook and updates references to flake8 to name ruff or omit it, which matches the first part of the title. The changeset summaries do not mention the ruff version upgrade to 0.17.3, so that part of the title is not visible in the provided file summaries. The title's main point is the flake8-to-ruff replacement, so it is related to the main change.

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[github-actions]

🌿 Fern Docs Preview: https://nvidia-preview-01a1844e-e0f9-7133-b2c0-3214e3e2b816.docs.buildwithfern.com/dynamo/dev

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[harryskim]

Docs changes LGTM.