Add feature-gated js_repl polling flow

[fjord-oai]

Summary

Adds a feature-gated polling mode for js_repl.

With js_repl_polling enabled, js_repl can submit async JS executions and immediately return an exec_id / session_id, while js_repl_poll provides incremental logs and final results for that execution.

What Changed

Feature flag and tool exposure

• Added js_repl_polling
• Gated it behind js_repl
• Added js_repl_poll to the tool spec only when polling is enabled
• Allowed direct js_repl_poll calls in js_repl_tools_only mode when polling is enabled

Polling API

• js_repl now accepts polling-related first-line pragma args:
  • poll=true
  • session_id=<id>
• Added js_repl_poll
  • takes exec_id
  • optionally takes yield_time_ms
  • returns JSON with exec_id, session_id, status, logs, output, and error
• Extended js_repl_reset
  • {"session_id":"..."} resets a single polling session
  • {} resets all js_repl kernels

Polling runtime

• Added session-based polling support in JsReplManager
• Enforces one active exec per polling session
• Allows multiple polling sessions in parallel
• Buffers incremental logs for polling and retains completed execs for replay for a bounded window
• Emits output delta events while a polled exec is running

Semantics and robustness

• Polling mode does not support timeout_ms; callers must use js_repl_poll.yield_time_ms
• Omitted or short poll waits clamp to the intended idle long-poll behavior
• Keeps poll semantics aligned with background-terminal expectations:
  • return early when logs or completion are available
  • keep polling the same exec_id until status becomes completed or error
• Releases a polling session for reuse before async completion-event emission
• Replaced non-polling timeout string matching with a typed local execute error
• Removed redundant kernel-side log buffering in streaming mode and used host-side buffered logs for final poll output fallback

Parsing / guidance

• Updated freeform js_repl parsing to support polling pragma args
• Keeps comma-separated pragma args tolerant for compatibility, while preferring space-separated args in guidance
• Added feature-aware error/help text so polling-specific guidance only appears when polling is enabled
• Updated project-doc and docs/js_repl.md guidance for the polling flow

git stack

• ✅ 01 Add feature-gated freeform js_repl core runtime #10674
• ✅ 02 Add js_repl host helpers and exec end events #10672
• ✅ 03 Add js_repl_tools_only model and routing restrictions #10671
• ✅ 04 Add js_repl kernel crash diagnostics #11666
• ✅ 05 Fix js_repl view_image test runtime panic #11796
• ✅ 06 Fix js_repl in-flight tool-call waiter race #11800
• ✅ 07 Stop filtering model tools in js_repl_tools_only mode #12069
• ✅ 08 Add optional js_repl isolation and vendored Node runtime #10670
• ✅ 09 js_repl: canonicalize paths for node_modules boundary checks #12177
• ✅ 10 js_repl: block wrapped payload prefixes in grammar #12300
• ✅ 11 js_repl: remove codex.state helper references #12275
• ✅ 12 ci(bazel): install Node from node-version.txt in remote image #12205
• ✅ 13 tests(js_repl): stabilize CI runtime test execution #12407
• ✅ 14 feat: update Docker image digest to reflect #12205 #12372
• ✅ 15 tests(js_repl): remove node-related skip paths from js_repl tests #12185
• 👉 16 Add feature-gated js_repl polling flow #10673
• ⏳ 17 Add multimodal outputs to js_repl polling #13081
• ⏳ 18 refactor js_repl to reuse managed child process infra #13266

[jif-oai]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Keep it up!

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".