Summary

Implements browser_execute — the single tool for all browser interaction (decisions.md §3.2). Three-level shape with minimal upstream-opencode diff.

What's added

Level 1 — packages/bcode-browser/src/

• browser-execute.ts (~85 lines) — Effect factory. Spawns uv run --project <HARNESS_DIR> python run.py -c <code> via Effect's ChildProcessSpawner. BU_NAME = ctx.sessionID for daemon isolation (parallel sub-agents get isolated browsers). ENOENT on uv → one-line install hint per decisions.md §4.4.
• harness.ts (5 lines) — HARNESS_DIR resolved from import.meta.url. Phase-C TODO when binary packaging lands.

Level 2 — packages/opencode/src/tool/

• browser-execute.ts (~25 lines) — Tool.define adapter. Passes parameters through, translates Tool.Context.sessionID for the Level-1 factory, Effect.orDie for opencode's never-error contract.
• browser-execute.txt — tool description shown to the model.
• registry.ts — 4-line additions (import + init + builtin entry).

Workspace wiring

• packages/opencode/package.json — one line: "@browser-use/bcode-browser": "workspace:*".

Total upstream-opencode diff: 6 lines (tool import, init line, builtin entry, package.json dep). Everything else lives in our package.

Replaces ROADMAP A3

The original A3 plan was to bootstrap ~/.cache/bcode/venv/ on first bcode run with a manifest. Replaced 2026-04-26 (decisions.md §4.4 update): uv run --project <HARNESS_DIR> builds a per-package venv at packages/bcode-browser/harness/.venv/ (gitignored) on first call, caches every subsequent call.

• Cold call: ~3s (uv resolves + builds venv)
• Warm call: ~50ms

No bootstrap step, no manifest, no first-run code path. Single source of truth for Python deps: harness/pyproject.toml. "Is uv on PATH?" is the only check, lazily evaluated via spawn ENOENT.

Verification

Typecheck: bun run typecheck (filtered F4) — 5/5 packages pass in ~5s. Pre-push hook runs clean without --no-verify.

End-to-end smoke test (no Chrome required):

const proc = ChildProcess.make('uv',
  ['run', '--project', HARNESS_DIR, 'python', '-c', 'print(42)'],
  { cwd: HARNESS_DIR, extendEnv: true, stdin: 'ignore' })
const handle = yield* spawner.spawn(proc)
const [out, code] = yield* Effect.all([
  Stream.mkString(Stream.decodeText(handle.all)),
  handle.exitCode
])
// out: "42\n", code: 0

Verifies the spawn pipeline: TS → uv → cached venv → python → captured stdout/exit-code.

A Chrome-required integration test (actually invoking goto(...)) is deferred; that needs the cloud-browser or a headed local Chrome and is the right thing for E1 (evals) to drive.

Out of scope (next PRs)

• A5 (permission gating — session-level allow per decisions.md §9 leaning).
• Screenshot → attachment plumbing. Will need a helpers.py divergence to surface the screenshot path; design after permission gating lands.
• helpers.py editing protection (path allowlist for daemon.py/admin.py). Decisions §3.7/§4.5 — needs a hook in opencode's permission rules.
• Streaming stdout/stderr to TUI (deferred per discussion thread).