[ScriptedAlchemy]

Why

Every host session launches its own hauler MCP server from the same installed pack, and only one of them can own the pack's event-runtime Unix socket. On 0.4.8 the second server exited before answering initialize (EventRuntimeTransportError: Event runtime endpoint already has a live server.), which is why the hauler_* tools were invisible in a second concurrent Claude Code / Codex / Cursor session.

agent-bundle fixed this in #561 (closes #559), squash cd0b4a62c: the generated server starts in the standby role when the socket is owned, serves its own MCP session, probes ~1 s (jittered), and takes the socket over when the owner exits. Both transitions, and any takeover failure other than "still owned", go to stderr only.

What changed

• package.json: agent-bundle and @agent-bundle/runtime re-pinned from the c2ffe5ec5 pkg.pr.new preview to cd0b4a62cd92b3fbced6742b3cead32d9639c3e4 (the way this repo already consumes the framework — pkg.pr.new tarballs pinned by full SHA in devDependencies); pnpm-lock.yaml regenerated.
• pnpm-workspace.yaml: blockExoticSubdeps: false, with a comment. The only change the new framework needed: the cd0b4a62c @agent-bundle/runtime preview depends on the same-commit preview tarball of rsc-markdown-stream (behind MarkdownContent; not on npm), and pnpm 11 rejects URL-resolved transitive dependencies by default (ERR_PNPM_EXOTIC_SUBDEP). Neither a direct devDependency on the same URL nor an overrides entry satisfies the check (both probed), so the setting is the fix the diagnostic names. Development-only: the published package still declares no dependencies.
• README.md: the pinned-commit note.
• .changeset/repin-cd0b4a62c-standby.md (patch).

No source, generated-file, or diagnostic changes were needed: agent-bundle validate/build pass clean on the new framework (no AB7014/AB7015), Claude host validation passes (Claude Code 2.1.260).

Verification

• pnpm check: validate, build, typecheck, Effect diagnostics (0 errors, 0 warnings), rstest 811/811, route-unit 45/45.

• pnpm prepack: Prepack validated 77 file(s) for cargo-hauler; npm pack → 77 files, dependencies absent.

• Standby proof in the built artifact — two node artifact/claude/mcp/mcp-hauler-2b8242f9.mjs processes from the same install root, same env and cwd, each fed a JSON-RPC initialize on stdin (harness and full transcripts under /tmp/hauler-standby/).

  Before, 0.4.8 as installed from npm (before-0.4.8/transcript.log):

  +   350ms A stdout: id=1 result serverInfo={"name":"cargo-hauler","version":"0.4.8"}
  +  1915ms B: spawned pid 3044137
  +  2227ms B stderr: EventRuntimeTransportError: Event runtime endpoint already has a live server.
  +  2227ms B stderr:   code: 'runtime-failed'
  +  2264ms B: exited code=1 signal=null
  +  5996ms summary: … B initialize=NO REPLY tools/list#2=NO REPLY
  

  After, this branch's build (after-cd0b4a62c/transcript.log):

  +  1965ms B: spawned pid 3715500
  +  2249ms B stderr: agent-bundle event runtime: /tmp/agent-bundle-1000/event-c39012e1204575401879b1f2f08980c4.sock is owned by another process; standing by
  +  2289ms B stdout: id=1 result serverInfo={"name":"cargo-hauler","version":"0.4.8"} protocolVersion=2025-06-18
  +  2329ms B stdout: id=2 result tools=[hauler_await, hauler_kill, hauler_last, hauler_log, hauler_request, hauler_result, hauler_status]
  +  5651ms B stdout: id=10 result content[0]="cargo-hauler · daemon running (pid 132023) · 1/5 permits, 4 queued · …"
  +  5670ms killing A with SIGTERM
  +  5703ms A: exited code=143 signal=null
  +  6562ms B stderr: agent-bundle event runtime: /tmp/agent-bundle-1000/event-c39012e1204575401879b1f2f08980c4.sock was released by its owner; took it over
  +  6585ms B stdout: id=3 result tools=[hauler_await, hauler_kill, hauler_last, hauler_log, hauler_request, hauler_result, hauler_status]
  +  6715ms B stdout: id=11 result content[0]="cargo-hauler · daemon running (pid 132023) · …"
  

  The second server answers initialize, tools/list, and a real hauler_status call while standing by, takes the socket over ~0.9 s after the owner exits, and keeps answering afterwards. The socket file is removed on exit; no stray processes.

• CLI smoke from the build: node dist/bin/hauler.js status --json → daemon running, state dir /fast/cache/cargo-hauler.

Self-review

Reviewed the diff against origin/master by hand (no second-model reviewer was run for this dependency re-pin):

• Lockfile: only the two pins move plus the new transitive closure of the cd0b4a62c previews (rsc-markdown-stream preview, npm-package-arg, hosted-git-info, lru-cache, proc-log, validate-npm-package-name); nothing else changes.
• blockExoticSubdeps: false widens what transitive dependencies may come from URLs. Accepted: the repo already trusts the same pkg.pr.new namespace for its direct pins, the setting is dev-only, and the comment ties it to the preview pin so it goes when agent-bundle is on npm.
• Version string: the build still reports 0.4.8 because the version bump lands through the Version Packages PR (Version Packages #84), as for every release here.

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[changeset-bot]

🦋 Changeset detected

Latest commit: 2de28b7

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
cargo-hauler	Patch

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