ci: skip backend unit tests on ui-only PRs without stranding required checks

[devin-ai-integration]

Relevant issues

Re-does #32422 correctly and supersedes the straight revert in #32530

Linear ticket

Pre-Submission checklist

Please complete all items before asking a LiteLLM maintainer to review your PR

• I have added meaningful tests
• My PR passes all CI/CD checks (e.g., lint, format, unit tests)
• My PR's scope is as isolated as possible; it only solves 1 specific problem
• I have received a Greptile Confidence Score of at least 4/5 before requesting a maintainer review

Screenshots / Proof of Fix

This is a CI trigger change, so there is no proxy or LLM surface to curl; the proof is the workflow config plus how the checks behave

The classification is the exact same script CircleCI uses (.circleci/scripts/classify_changes.sh backend), so the skip set is identical to CircleCI. Verified locally at HEAD:

$ printf 'ui/litellm-dashboard/src/x.tsx\n' | bash .circleci/scripts/classify_changes.sh backend
skip
$ printf 'README.md\ndocs/x.mdx\n'          | bash .circleci/scripts/classify_changes.sh backend
skip
$ printf 'ui/x.tsx\nlitellm/main.py\n'       | bash .circleci/scripts/classify_changes.sh backend
run

This PR itself only touches .github/, which classifies as run, so every test-unit-* job on this PR executes the full suite; that is the regression proof that backend PRs are unaffected. A UI-only PR like #32502 will now run each job, hit decision=skip, and report the required check green in seconds instead of leaving it stuck on "Expected; waiting for status to be reported"

Type

🚄 Infrastructure

Changes

#32422 added paths-ignore: [ui/**, **.md, **.mdx] to the pull_request trigger of the 12 test-unit-*.yml workflows so UI-only and docs-only PRs would not pay for the backend suites. The problem is that those job names (core-utils / Run tests, auth-checks / Run tests, and so on) are configured as required status checks in branch protection. paths-ignore stops the whole workflow from ever starting, so on a UI-only PR the required contexts are never reported and the PR sits forever on "Expected; waiting for status to be reported" (see #32502). GitHub only treats a required check as satisfied when the job actually runs and reports a conclusion; a workflow that never triggers is not the same as a skipped job

This is exactly the difference from CircleCI, where the equivalent filter runs inside the job (.circleci/scripts/path_filter.sh calls circleci-agent step halt), so the job still completes green. Mirroring that, this PR drops paths-ignore from all 12 workflows and instead short-circuits the expensive steps inside each job:

• new composite action .github/actions/detect-backend-changes diffs the PR against github.event.pull_request.base.sha and pipes the changed files through the same classify_changes.sh backend script CircleCI uses, exposing decision=run|skip. It defaults to run for non pull_request events or whenever the base or diff cannot be resolved, so tests are never skipped when classification is uncertain
• _test-unit-base.yml (the reusable base behind 10 of the workflows) runs the detect step right after checkout and gates Install dependencies, Generate Prisma client, Run tests and coverage on decision != 'skip'; the upload-coverage job is gated the same way
• test-unit-documentation.yml and test-unit-proxy-legacy.yml do not use the reusable base, so they get the same detect step and step-level guards inline

The net effect is that the jobs always start and always report a conclusion, so required checks are satisfied on every PR, but on a UI-only or docs-only PR they skip the uv sync, prisma generate and pytest steps and finish in seconds. Backend PRs behave exactly as before

Link to Devin session: https://app.devin.ai/sessions/01543c7d72924959bdd52dc138bb4a20
Requested by: @mateo-berri

[devin-ai-integration]

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[greptile-apps]

Greptile Summary

This PR fixes a branch-protection deadlock introduced by #32422: removing paths-ignore from all 12 test-unit-*.yml workflows and replacing it with a new composite action (.github/actions/detect-backend-changes) that classifies changed files inside the job using the same classify_changes.sh backend logic CircleCI uses. Jobs always start and always report a conclusion, so required status checks are never left in "Expected; waiting…" limbo, but expensive steps (uv sync, prisma generate, pytest) are gated on decision != 'skip' so UI-only and docs-only PRs still finish in seconds.

• New composite action fetches the PR base SHA, diffs it against HEAD, and pipes the result through .circleci/scripts/classify_changes.sh backend; every failure path (non-PR event, unreachable base SHA, empty diff, script error) defaults to decision=run so tests are never incorrectly skipped.
• _test-unit-base.yml propagates decision as a job output so the downstream upload-coverage job is also gated, and the two standalone workflows (test-unit-documentation.yml, test-unit-proxy-legacy.yml) receive inline copies of the same detect step.

Confidence Score: 5/5

Safe to merge — changes are confined to CI configuration, with no production code or test logic altered.

All 12 workflows are updated consistently: 10 via the reusable base and 2 inline. Every error path in the composite action defaults to run, so tests can never be silently skipped due to a classification failure. The fallback logic is also exercised by this PR itself (.github/** is classified as backend, so all jobs run normally). The upload-coverage gating via job outputs is wired correctly in the base workflow. No application code is touched.

No files require special attention; the most critical logic lives in .github/actions/detect-backend-changes/action.yml and .github/workflows/_test-unit-base.yml, both of which look correct.

Important Files Changed

Filename	Overview
.github/actions/detect-backend-changes/action.yml	New composite action that classifies PR changes via classify_changes.sh and exposes decision=run
.github/workflows/_test-unit-base.yml	Adds detect-backend-changes step after checkout, gates Install dependencies / Generate Prisma / Run tests / Save coverage on decision != skip, and gates upload-coverage job via job outputs
.github/workflows/test-unit-documentation.yml	Removes paths-ignore and adds inline detect-backend-changes step with step-level guards on install, prisma, and test steps
.github/workflows/test-unit-proxy-legacy.yml	Removes paths-ignore and adds inline detect-backend-changes step with step-level guards; matrix jobs each independently run the detection
.github/workflows/test-unit-core-utils.yml	paths-ignore block removed; skipping logic now lives entirely in the reusable _test-unit-base.yml
.github/workflows/test-unit-proxy-db.yml	paths-ignore block removed; inherits skip logic from reusable base workflow

_{Reviews (1): Last reviewed commit: "ci: skip backend unit tests on ui-only P..." | Re-trigger Greptile}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[codspeed-hq]

Merging this PR will not alter performance

✅ 30 untouched benchmarks

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_{Comparing litellm_ci_skip_backend_tests_ui_only (557770e) with litellm_internal_staging (b00877c)}

[mateo-berri]

LGTM; thanks!