Pinned reference-browser revisions

Every implementation decision that touches CSS, DOM, JS, layout, or paint semantics must cite a path in one of these trees, plus the pinned revision below. The reference trees are large; pinning prevents non-reproducible consultations ("latest main" drifts).

These pinned revisions are the canonical reference set for Vixen's implementation work. Update a pin deliberately with the corresponding toolchain/ architecture change so citations continue to name an exact tree state.

Pin table (reviewed 2026-07-14)

How to consult each

Firefox / Servo Stylo subtree (firefox/ checkout)

The Firefox checkout is large. For Vixen, use a sparse checkout containing the Rust-facing pieces we can cite directly plus the Firefox C++ seams that show API contracts:

firefox/servo/components/style/                    ← Stylo. Read this for CSS cascade/computed values.
firefox/servo/components/selectors/                ← selector engine used by Stylo.
firefox/dom/bindings/                              ← WebIDL binding and wrapping discipline.
firefox/dom/webidl/                                ← DOM API surface contracts.
firefox/dom/base/                                  ← DOM API behavior and selector delegation.

Current Firefox HEAD (46e9f12a8f9b) does not include servo/components/layout_2020/, servo/components/layout/, or servo/components/script/. Do not cite those removed historical paths. Vixen's Flutter-hosted formatter may use current Firefox formatting behavior and Ladybird's readable box-tree architecture as references; neither provides code ownership or a second renderer.

When in doubt about a CSS computed value, search firefox/servo/components/style/properties/ for the property name — longhands, shorthands, and computed-value logic all live there.

Ladybird (ladybird/)

Use Ladybird when a question is architectural ("how do other engines seam X from Y?") rather than specification-level. Vixen's Dart formatter may follow its box/formatting-context decomposition, not its C++ ownership model.

ladybird/Libraries/LibWeb/                         ← DOM, CSS, layout, paint (cleanly seamed)
ladybird/Libraries/LibWeb/CSS/                     ← cascade + stylesheet model
ladybird/Libraries/LibWeb/Layout/TreeBuilder.cpp   ← styled DOM → layout tree seam
ladybird/Libraries/LibWeb/Layout/                  ← formatting contexts
ladybird/Libraries/LibWeb/Painting/                ← display-list construction
ladybird/Libraries/LibGfx/                         ← rasteriser fallback

Flutter (flutter/)

Consult for dart:ui Paragraph/Canvas/Picture/Scene, Impeller, the rendering pipeline, Semantics, platform-channel, native-runner, lifecycle, capture, and test behavior. The SDK pin is a substrate reference, not evidence of Vixen CSS or platform support.

flutter/packages/flutter/lib/                     ← widgets, services, Semantics
flutter/engine/src/flutter/lib/ui/                 ← dart:ui Canvas/Paragraph/scene implementation
flutter/engine/src/flutter/flow/                   ← layer/scene composition
flutter/engine/src/flutter/impeller/               ← required graphics backend
flutter/packages/flutter_test/                    ← widget/test harness patterns
flutter/packages/flutter_tools/templates/app/linux.tmpl/ ← Linux runner boundary
flutter/examples/                                 ← focused framework examples

GNOME Web (gnome-web/)

Consult only for Linux browser metadata, portal expectations, and Flatpak conventions. It is not a GUI architecture reference; Vixen renders its sole GUI with Flutter.

gnome-web/data/                                    ← gschema, metainfo, desktop
gnome-web/flatpak/                                 ← runtime/portal conventions useful for the FlatPark submission

Obscura (obscura/)

Consult for CDP/session and CLI ergonomics only. Rendered automation uses Vixen's chrome-less Flutter host and does not inherit another renderer or CLI verbatim.

Deno (deno/)

Consult Deno for JS runtime embedding and Rust host packaging, per ADR-014. The target crate is deno_core. Use this tree for extension/op organization, resource-table shape, permission checks near host boundaries, bootstrap script packaging, and feature-family test layout. Do not cite Deno for DOM/Web API semantics over Firefox/specs; Deno is the runtime substrate reference, while Web-facing behavior remains WPT/spec-gated.

Import-map matching uses Deno's import_map 0.25.0 resolver with default logging disabled. Vixen owns parser ordering, bounds, diagnostics, scheme/policy checks, and a bounded exact-URL integrity table because the crate has no integrity model. Vixen also owns current-standard first-wins merging, parser-position snapshots, and the bounded successful-resolution set because the crate only parses and resolves individual maps.

deno/core/                                         ← op/extension/runtime core patterns
deno/runtime/                                      ← permissions, workers, bootstrap packaging
deno/ext/                                          ← feature-family JS/Rust extension layout
deno/cli/                                          ← integration tests and permission plumbing examples

Re-cloning fresh

If .tmp/ref/ is unavailable, clone each at the pinned revision:

mkdir -p .tmp/ref && cd .tmp/ref

git clone --depth 1 --filter=blob:none --sparse --branch main https://github.com/mozilla-firefox/firefox.git
git -C firefox sparse-checkout set servo gfx/wr gfx/layers/wr gfx/webrender_bindings dom/webidl dom/base dom/bindings js/public
git -C firefox checkout 46e9f12a8f9b

git clone --depth 1 --filter=blob:none --sparse --branch master https://github.com/LadybirdBrowser/ladybird.git
git -C ladybird sparse-checkout set Libraries/LibWeb Libraries/LibGfx
git -C ladybird checkout 0de15a5dd2a9

git clone --depth 1 --filter=blob:none --sparse --branch stable https://github.com/flutter/flutter.git
git -C flutter sparse-checkout set packages/flutter packages/flutter_test packages/flutter_tools/templates/app/linux.tmpl engine/src/flutter/lib/ui engine/src/flutter/flow engine/src/flutter/impeller examples
git -C flutter checkout 6655482ec06e547f90abf8ae7590466f4415978d

git clone --depth 1 --filter=blob:none --sparse --branch main https://gitlab.gnome.org/GNOME/epiphany.git gnome-web
git -C gnome-web sparse-checkout set data flatpak
git -C gnome-web checkout 21e02b9a272d

git clone --depth 1 --filter=blob:none --branch main https://github.com/h4ckf0r0day/obscura.git
git -C obscura checkout ca71ce3c2da9

git clone --depth 1 --filter=blob:none --sparse --branch main https://github.com/denoland/deno.git
git -C deno sparse-checkout set core runtime ext cli
git -C deno checkout 83c50b1da61e

Disk budget depends on sparse settings. Keep the checkouts in .tmp/ref/ or another ignored workspace; avoid committing reference trees.

Citation discipline

Vixen's tick-tock rules (each phase is a tick — capability lands; the post-phase cleanup is a tock — dead-code removal, ≤ 1 kLOC modules, reference citations):

• Every implementation commit cites at least one path + commit hash from a reference tree explaining why the behaviour is correct.
• Every tock (post-phase hardening) cites at least four reference paths.
• Commit hashes are the short form of the pin above (46e9f12a8f, 0de15a5dd2, etc.), never HEAD or main.
• When a reference path goes stale, refresh the affected checkout to the current branch HEAD and update this file in the same change; do not leave implementation comments pointing at historical paths that no longer exist.