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Chromium Fork Workflow

This chapter covers Chromium-fork specific workflow for CBF contributors.

1. Scope

CBF requires a Chromium fork with CBF integration. Do not assume stock Chromium has equivalent behavior.

Relevant locations:

  • CBF Chromium code: chromium/src/chrome/browser/cbf/
  • Bridge implementation: chromium/src/chrome/browser/cbf/bridge
  • Exported patch queue: chromium/patches/cbf

2. Build and test targets

You should use autoninja to build Chromium targets from chromium/src:

autoninja -C out/Default chrome
autoninja -C out/Default cbf_bridge

From the repository root, you can also execute the following command:
This command will automatically add ./depot_tools to PATH.

uv run tool build -t chrome -t cbf_bridge

# If you activated venv with uv, you can also use:
python3 tool build -t chrome -t cbf_bridge

These targets are relevant for CBF development:

  • chrome: Chromium-fork build target with CBF integration.
  • cbf_bridge: CBF bridge library target. It is used from cbf-chrome-sys.
  • cbf_tests, browser_tests, unit_tests: Chromium-side test targets covering different test scopes and types. See their respective BUILD.gn files for details.

3. Patch queue policy

Changes to Chromium are exported as patches using Git’s format-patch and stored in the cbf repository. You should maintain a clean with the following principles:

  • Keep CBF-specific changes traceable in chromium/patches/cbf.
  • Curate chromium/src commit stack, then export patches.
  • Fold refinements with fixup/squash rather than appending noisy fix patches.

Patch-splitting principles:

  • Keep one primary responsibility per patch.
  • Keep dependency direction explicit in patch ordering.
  • Prefer mechanical moves/refactors before behavior changes.
  • Keep each patch buildable in the target Chromium output directory.
  • Use short imperative English subjects for exported patches; do not use Conventional Commits in patch titles.
  • When refining an existing patch, prefer fixup / squash into that patch instead of adding a follow-up fix patch.

Common tooling flow:

uv run tool apply
uv run tool export
uv run tool git <...args>
uv run tool commit -m "<message>"

Patch files live in chromium/patches/cbf/.

4. Runtime constraints

  • CBF runtime behavior depends on --enable-features=Cbf.
  • IPC bootstrap uses inherited endpoint + session token injected by start_chromium.
  • start_chromium should be the default runtime path; manual launch is primarily for debugging.