Summary

Adds the private main-realm executor for the isolated parser worker selected in
ADR 0004.

• Lazily creates at most one authoritative worker generation.
• Serializes requests through a bounded FIFO queue with independent request-count
  and retained UTF-16 text limits.
• Enforces startup, queue-wait, and posted-execution safety deadlines.
• Settles caller cancellation promptly while draining already-posted work.
• Retires crashed, timed-out, malformed, or poisoned generations without
  replaying posted work.
• Preserves never-posted queued work across eligible generation replacement.
• Rejects reused worker identities and serializes retirement across hostile
  cleanup/settlement reentrancy.
• Keeps the worker factory, executor, protocol, and implementation types private;
  there is no root or /vnext public API change.

Risk classification

Medium: concurrency, cancellation, worker lifecycle, resource accounting, and
packaging boundaries.

The principal risks are double settlement, stale-generation authority, physical
worker overlap, posted-work replay, unbounded retention, and browser bundler
regressions. The implementation mutates ownership before every external cleanup
or settlement boundary, uses an iterative pump trampoline, and tests hostile
synchronous callbacks at each boundary.

Evidence

• Full Node suite: 1,246 passed, 1 expected failure.
• Focused deterministic executor suite: 84 passed.
• Chromium: 4 files / 7 tests, including real worker, crash, silent-worker
  deadline, recovery, and default static Worker URL behavior.
• Changed executor coverage:
  • Statements: 95.51%
  • Branches: 95.37%
  • Functions: 100%
  • Lines: 95.49%
• All TypeScript project checks, oxlint, test-integrity, and diff checks pass.
• Packed-package smoke test passes and asserts the executor artifact.
• The post-rebase executor patch ID exactly matches the twice-reviewed pre-rebase
  patch.

Adversarial review ledger

The review loop found and fixed:

• cancellation and FIFO reentrancy during promotion;
• preventDefault running before generation retirement;
• listener installation continuing after synchronous retirement;
• recursive synchronous worker responses overflowing the stack;
• startup-failure queue transfer and ready-failure ownership errors;
• postMessage accessor disposal/forged-response races;
• a P1 physical-worker overlap during cleanup-triggered nested submission; and
• same-worker identity reuse after termination.

Two independent reviewers approved the corrected pre-rebase patch. Two fresh
independent audits also approved the exact rebased head after rerunning Node,
Chromium, package, coverage, type, lint, integrity, placement, and demo gates.

API and rollout

This is implementation infrastructure only. It is not wired to sessions,
completion, diagnostics, or other public features. No compatibility or migration
work is required in this slice. The next consuming coordinator must preserve the
same bounded ownership and no-replay rules.

Summary by cubic

Adds a private, single-lane browser executor for the isolated SQL parser worker with bounded queueing, strict deadlines, and safe lifecycle handling. Internal only; no public or /vnext API changes. Hardened to fail closed on retirement errors with explicit terminal states.

• New Features

  • Lazily creates at most one worker generation; posts one request at a time.
  • Bounded FIFO queue with request-count and UTF‑16 text limits; startup/queue/execution deadlines and prompt caller cancellation.
  • Retires crashed/timed-out/poisoned generations without replay; preserves never-posted queued work across replacement.
  • Rejects reused worker identities; retirement is serialized and atomic to avoid reentrancy races.
  • Executor, worker factory, protocol, and types remain private; docs updated and scripts/package-smoke.mjs asserts executor artifacts.

• Bug Fixes

  • Fails closed if worker retirement throws to prevent accepting new work in an unsafe state.
  • Makes terminal states explicit to avoid resurrection and double settlement.

^{Written for commit 1cb7105. Summary will update on new commits.}