Browser Runtime

Phase 6 browser runtime boundary for Flow Player.

Current scope:

• Worker protocol for init, play, pause, push-chunk, and graceful destroy/destroyed shutdown.
• Capability probing for WebCodecs, MSE, WebGL2, WebGPU, OffscreenCanvas, and Worker support.
• WebGL2 renderer baseline for hard-decoded VideoFrame and soft-decoded I420 planes.
• Runtime metrics helpers for chunk ingest, first frame marking, and decode/upload/render A/B sampling summaries.
• WASM playback event bridge for FLV H264/HEVC demux, WebCodecs decode, and WebGL2 render.

The metrics helpers are intentionally small building blocks for browser A/B sampling reports. They do not start automatic browser collection by themselves.

The runtime intentionally has no npm dependencies. Vite is used only as a dev/build dependency for producing the npm-grade package output, while TypeScript declarations are shipped beside the ESM implementation so the Jessibuca-compatible API layer and direct runtime consumers can use this package without taking extra runtime dependencies.

Frontend projects consume @flow-player/browser-runtime as an npm/browser runtime package. The public package surface is the ESM entrypoint, TypeScript declarations, and the module worker script exposed at @flow-player/browser-runtime/worker.

The Rust flow-player-wasm crate is the backend boundary for the WASM build and dist pipeline. Business frontend code should not operate on that crate directly, and the package exports still do not expose a .wasm bundle.

Raw WASM artifact build:

npm --prefix packages/browser-runtime run build:wasm

This builds flow-player-wasm for wasm32-unknown-unknown without wasm-bindgen, then copies the artifact to target/browser-runtime/flow_player_wasm.wasm. Use -- --out-dir <path> or -- --profile dev|release to override the output directory or profile. If the Rust target is missing, install it with rustup target add wasm32-unknown-unknown.

Deployable dist build:

npm --prefix packages/browser-runtime run build:dist

This creates dist/browser-runtime with the runtime sources, declarations, bundled delivery docs, manifest, and wasm/flow_player_wasm.wasm. Use -- --wasm-path <path> to package an already-built WASM artifact without running cargo. The dist manifest records sourceCommit and sourceDirty so release jobs can reject dirty source builds.

NPM-grade package build:

npm --prefix packages/browser-runtime run build:package

This creates dist/browser-runtime-package, an npm pack-ready package root. Its package exports point at built dist/index.js, dist/index.d.ts, dist/worker/player-worker.js, and dist/worker/player-worker.d.ts; the WASM artifact is included at wasm/flow_player_wasm.wasm for static deployment, but remains outside package exports. The default release profile minifies the ESM output through Vite. Use -- --profile dev when you need readable output for debugging package path issues. The package build requires Node.js ^20.19.0 || >=22.12.0, matching the Vite 8 runtime requirement.

Package publish check:

npm --prefix packages/browser-runtime run publish:check

This rebuilds the ESM package and verifies publish metadata, exports, TypeScript declarations, worker entry, WASM artifact, bundled docs, npm pack --dry-run, and a clean source manifest. It does not run npm publish.

Smoke check:

npm --prefix packages/browser-runtime run test:smoke

Benchmark baseline:

npm --prefix packages/browser-runtime run benchmark
npm --silent --prefix packages/browser-runtime run benchmark -- --json --iterations 10 --warmup 2

Reference:

• Delivery artifacts
• Agent integration wiki
• Performance benchmark guide