[thekevinbot]

Final step of the one-function-per-file ratchet opened in #1042. Every split that step needed has landed (#1045 distcheck, #1046 checks-B1, #1047 python, #1048 the 16 -> 15 config step, #1049 ts, #1050 checks-B2), so this PR is the ceiling drop and nothing else.

Fixes #1042

The change

Five max_lines values, 15 -> 12. No code changes.

File	Table	Before	After
testing-conventions.toml	[python]	15	12
testing-conventions.toml	[typescript]	15	12
packages/python/testing-conventions.toml	[python]	15	12
packages/ts/testing-conventions.toml	[typescript]	15	12
internals/checks/testing-conventions.toml	[python]	15	12

plugins/dirsql-plugin-embeddings/testing-conventions.toml stays at 10 -- it was already ahead of the campaign and raising it to 12 would loosen the rule for that package.

Why 12 and not 10

#1042 proposed the ladder down to 10; the campaign stops at 12. That is a decision, not an abandonment -- 12 is Kevin's explicit call, and it matches the issue's own recommendation.

Per #1042's analysis, the remaining four moves to reach 10 are the gate rearranging cohesive modules rather than finding real problems:

• packages/ts/src/resolve-config-extensions.ts -- resolveConfigsExtensionSpecs, 11 lines
• packages/python/dirsql/resolve_config_extensions.py -- _resolve_entries, 12 lines
• internals/checks/src/checks/artifact_completeness/gate.py -- run, 11 lines
• packages/ts/src/resolve-extension.ts -- resolveExtensionPath, 10 lines

Each is a marginal private helper or a run orchestrator flagged only because a slightly longer sibling sits above it in the file. Parent issue #1020 (ratchet toward the default of 1) stays open and carries the remaining distance.

Verification

testing-conventions@0.0.111 pinned explicitly (a bare npx testing-conventions resolves engine-aware and can silently pick an older release, #1018). Every scan root CI runs this gate on, at the value set here:

Scan root	Language	Config read	Exit
internals/checks/src	python	internals/checks/testing-conventions.toml (12)	0
packages/python/dirsql	python	packages/python/testing-conventions.toml (12)	0
packages/ts/src	typescript	packages/ts/testing-conventions.toml (12)	0
internals/distcheck/src	python	root testing-conventions.toml (12; passes no config:)	0
plugins/dirsql-plugin-embeddings/src	python	plugins/dirsql-plugin-embeddings/testing-conventions.toml (10)	0

Zero violations, zero exemptions -- the exemption count for this gate stays at zero. Harness sanity-checked by re-running internals/checks/src at max_lines = 8, which correctly reports 5 violations.

just preflight (derives the (source, gate) pairs from the CI workflows) finishes preflight: 0 failing pair(s), 3 skipped -- the three skips are the packaging pairs, which need a built artifact. The three e2e-verify pairs that run locally (packages/ts, internals/checks, plugins/dirsql-plugin-embeddings) all pass with no receipt in the diff, which is the gate agreeing that none is owed.

Red / green

Not applicable. This is a config tightening with no behavior change and no new functionality -- there is nothing to assert red. Per AGENTS.md, red/green governs adding or changing behavior; the gate's own CI run is the proof, and every affected root was verified clean locally before push.

Obligations

Re-confirmed against the repo, not assumed:

• Changelog fragment: not required. internals/checks/src/checks/changelog_gate/decide.py sets _ROOTS = ("packages", "plugins"), so the root and internals/checks files are outside the gate entirely. For the two package files that are inside it, _is_exempt waives <pkg>/testing-conventions.toml by exact match (re.fullmatch(rf"{p}/testing-conventions\.toml", path)) -- gate config that ships in no published artifact.
• E2E attestation: not required. No lane's e2e scope is touched. The python lane walks packages/python/dirsql plus [e2e] extra_scope = ["packages/rust/src", "packages/python/src"]; the ts lane packages/ts/src plus ["packages/rust/src", "packages/ts/napi"]; internals/checks its own internals/checks/src. A package-root testing-conventions.toml is in none of them, and internals/distcheck declares no e2e-verify gate at all.
• Migration fragment: not required. No public API change, no removed deprecation, no runtime behavior change. The only behavior change is which diffs a CI gate rejects.
• PARITY.md: no change. No SDK API surface is added, removed, or renamed; no drift introduced and none restored.

Changelog / Migrations

• Changelog fragment added under <root>/<pkg>/changelog.d/ for each changed package (or: skip-changelog trailer on a commit with reason) -- not required: both package files are _is_exempt matches (see Obligations)
• Migration fragment added under <root>/<pkg>/migrations.d/ (or: not required -- additive/bugfix only) -- not required

E2E Verification

N/A - CI gate config only, no source change in any scoped lane.

• Ran e2e suites locally for every affected SDK: N/A
• Python SDK e2e: N/A
• TypeScript SDK e2e: N/A
• Rust core e2e (if applicable): N/A
• packages/python/e2e-attestations/<branch>.json receipt written if packages/python changed (just e2e-attest-python) -- not owed: no scoped source change
• packages/ts/e2e-attestations/<branch>.json receipt written if packages/ts changed (just e2e-attest-ts) -- not owed: no scoped source change
• Command(s) run: npx -y testing-conventions@0.0.111 unit one-function-per-file across all five scan roots; just preflight
• Result summary: all five roots exit 0; preflight green