Contributing via Pull Requests

This guide walks through the PR workflow: title format, labels, CI pipeline, and getting your changes merged.

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PR Title Format (Required)

Every PR targeting main must start with a type tag in square brackets. This is checked by Mergify before any merge is allowed.

Format:

[type] Short description of the change

Valid type tags:

Tag	When to use
[feat] or [feature]	New feature or capability
[bugfix] or [fix]	Bug fix
[refactor]	Code restructuring with no behavior change
[perf]	Performance improvement
[ci]	CI/CD or build tooling changes
[doc] or [docs]	Documentation only
[misc] or [chore]	Housekeeping, dependency bumps, minor cleanup
[kernel]	CUDA kernel changes in fastvideo-kernel/
[new-model]	Adding a new model or pipeline

Examples:

[feat] Add causal Wan 2.2 I2V pipeline
[bugfix] Fix VAE temporal tiling corruption on H100
[refactor] Restructure distributed attention dispatch
[docs] Add LoRA finetuning guide
[new-model] Port HunyuanVideo 1.5 to FastVideo

If your title is missing the tag, Mergify will post a comment listing the valid formats. Update the title and the check will re-evaluate automatically.

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Labels

Labels are applied automatically based on your PR title and the files you changed. You don't need to set them manually.

Type label — set from the [tag] in your title: type: feat, type: bugfix, type: refactor, type: perf, type: ci, type: docs, type: misc, type: new-model

Scope labels — set from which files you modified (multiple labels can apply): scope: training, scope: inference, scope: attention, scope: kernel, scope: data, scope: infra, scope: distributed, scope: docs, scope: ui, scope: model

Process labels — set during review and merge:

Label	Who sets it	Meaning
ready	You (/merge comment) or a maintainer	Triggers Full Suite and enables auto-merge
needs-rebase	Mergify (automatic)	Your PR has conflicts; rebase against main
do-not-merge	Maintainer	Blocks merge regardless of CI status

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CI Pipeline

Three tiers run automatically on every PR.

Tier 1: Pre-commit (~2 min) — runs on every push

GitHub Actions checks formatting, linting, type correctness, and spelling using pre-commit hooks: yapf, ruff, mypy, codespell, pymarkdown, actionlint, and check-filenames.

Tier 2: Fastcheck (~10-20 min) — runs on every push, path-filtered

Buildkite runs GPU tests only for the components you changed. If you only modified fastvideo/models/vaes/, only VAE Tests run. Tests run in parallel.

Tier 3: Full Suite (~60-90 min) — triggered by the ready label

When you comment /merge (or a maintainer adds the ready label), Buildkite runs the complete test suite on your PR branch: SSIM regression, LoRA inference and training, distillation, self-forcing, VSA, VMoBA, performance benchmarks, and API server tests.

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Getting Your PR Merged

Step-by-step:

1. Open a PR with a title that starts with a valid [type] tag.
2. Push your changes. Pre-commit and Fastcheck run automatically.
3. Fix any pre-commit failures locally (pre-commit run --all-files) and push again.
4. Wait for at least one approving review.
5. Once approved and pre-commit is green, comment /merge on the PR.
6. The ready label is added, which triggers the Full Suite on your PR branch.
7. Mergify also auto-rebases your branch against main if it is behind and conflict-free.
8. If all Full Suite tests pass and all merge conditions are met (approval, valid title, pre-commit green, fastcheck green, no draft, no conflicts), Mergify squash-merges to main automatically. Your branch is deleted.
9. If a Full Suite test fails, check the Buildkite build log for the failing step. Fix the issue, push, and comment /merge again. You can also re-run individual failed tests with /test <name> — see below.

Note

Only contributors with write permission to the repository can trigger slash commands. If you're an external contributor, ask a maintainer to run /merge or add the ready label for you.

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Running Tests On Demand

Comment on your PR to trigger specific tests independently of the auto-merge flow.

Trigger the entire Full Suite:

/test full

Trigger the Fastcheck suite:

/test fastcheck

Trigger individual tests:

/test encoder          # Encoder component tests
/test vae              # VAE component tests
/test transformer      # Transformer / DiT tests
/test kernel           # CUDA kernel tests
/test unit             # Unit tests

/test ssim             # SSIM regression tests
/test training         # Training pipeline tests
/test lora-inference   # LoRA inference tests
/test lora-training    # LoRA training tests
/test distillation     # DMD distillation tests
/test self-forcing     # Self-Forcing distillation tests
/test vsa              # VSA training tests
/test vmoba            # VMoBA inference tests
/test performance      # Performance benchmarks
/test api              # API server integration tests
/test pre-commit       # Pre-commit checks on PR code

The workflow reacts with a 🚀 emoji to confirm the command was received.

When you re-run an individual test with /test <name>, the new result overwrites the original failed check (same Buildkite check name). Once all tests in a tier pass, the fastcheck-passed or full-suite-passed status is automatically updated.

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Troubleshooting

Pre-commit fails

Run locally to reproduce and auto-fix:

# Install pre-commit if needed
uv pip install pre-commit
pre-commit install

# Run all checks on all files
pre-commit run --all-files

Common quick fixes:

• yapf: yapf -i <file> (Python formatting)
• ruff: ruff check --fix <file> (linting)
• codespell: codespell --write-changes <file> (spelling)

PR title format check fails

Update your title to start with a valid type tag. The Mergify merge protection check re-evaluates automatically after you save the title.

Valid tags: feat, feature, bugfix, fix, refactor, perf, ci, doc, docs, misc, chore, kernel, new-model

My PR has merge conflicts (needs-rebase label)

Rebase against main and force-push:

git fetch origin main
git rebase origin/main
# Resolve any conflicts, then:
git push --force-with-lease

Mergify removes the needs-rebase label automatically once conflicts are resolved.

Full Suite failed after /merge

The Full Suite found a regression. Check the failing Buildkite step's output for assertion errors or tracebacks.

Common causes:

• Test failures caused by your code changes
• Missing dependency in pyproject.toml
• GPU memory issue (some tests require specific hardware like L40S or H100)
• Kernel build failure (if you changed fastvideo-kernel/)

After fixing, push and comment /merge again.

I'm an external contributor without write permission

You can't use slash commands directly. After your PR is approved, ask a maintainer to comment /merge or add the ready label.