Keep a named Cloud machine's prompt name instead of flipping to its slug

[teamleaderleo]

Summary

A Cloud machine created or renamed with a display name shows cmux@<that name> in its prompt at first. Within about 30 seconds the prompt switches to the generated slug (cmux@hardy-pink-jay).

Cause: two writers of /etc/cmux/vm-name disagree.

• Create and rename write vmPromptIdentity(row).name, which is the display name as a slug, falling back to the generated slug.
• The guest's cmux-prompt-sync re-fetches GET /api/vm/reflection/name every 30 s and writes that answer. The route returned reflectionMachineName(vm), which is always the generated slug.

Both now use one function, vmPromptName. The change is server-side only, so it reaches running machines without a guest upgrade. Machines without a display name are unchanged: they still get their slug.

Evidence

Found by the Cloud dogfood journey on staging (run 36402933616). The same terminal, captured before pause and after resume:

cmux@dogfood-d8e45d in ~ λ echo dogfood-14578b34-$((1+1))
dogfood-14578b34-2
cmux@hardy-pink-jay in ~ λ echo dogfood-14578b34-$((1+2))
dogfood-14578b34-3

Testing

• New web/tests/vm-reflection-name-route.test.ts, committed first and red: the route answered hardy-pink-jay for a machine named "Dogfood Box". It is green after the fix. The unnamed case still answers the slug.
• bun test passes across the new route test and tests/vm-guest-prompt.test.ts and tests/vm-reflection.test.ts (32 tests).
• bun run typecheck and bun run lint:complexity are clean. eslint on the touched files is clean.
• After merge and deploy, the staging journey rerun should show one name before and after resume.

Changelog

Fixed: a named Cloud machine's terminal prompt no longer switches back to its generated name after about 30 seconds.

🤖 Generated with Claude Code

---

^{Need help on this PR? Tag @codesmith-bot with what you need. Autofix is disabled.}

---

Summary by cubic

Keeps a named Cloud machine's prompt (cmux@<name>) stable instead of flipping to its generated slug after about 30 seconds.

• The guest's cmux-prompt-sync re-fetches /api/vm/reflection/name every 30 seconds, and that route answered the slug while create and rename write the display name. Both writers now use vmPromptName(vm).
• vmPromptName lives in its own module so the polled route no longer loads guestPrompt's bashrc and prompt assets.
• Server-side only, so existing machines pick up the fix without a guest upgrade; unnamed machines are unchanged.
• Adds a route test covering named and unnamed cases.

^{Written for commit 9e7035c. Summary will update on new commits.}

[coderabbitai]

Warning

Review limit reached

Next included review available in 3 minutes.

Check out review usage here.

View limit details

Limit details: You’ve used all 10 included reviews currently available.

You've used all free OSS reviews for now. Wait for the free limit to reset to keep reviewing this public repository.

Learn how review limits work.

Review configuration:

⚙️ Run configuration

Configuration used: Repository: manaflow-ai/cmux/.coderabbit.yaml

Review profile: ASSERTIVE

Plan: Advanced

Run ID: 53538130-e6bf-4420-ba2c-d2ee1b1cc702

📥 Commits

Reviewing files that changed from the base of the PR and between b36339a and 9e7035c.

📒 Files selected for processing (4)

• web/app/api/vm/reflection/name/route.ts
• web/services/vms/guestPrompt.ts
• web/services/vms/promptName.ts
• web/tests/vm-reflection-name-route.test.ts

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[teamleaderleo]

Review (subagent, correctness first): nothing serious.

Checked:

• Only one reader of this route: cmux-prompt-sync, which only writes vm-name. Hostnames, routing and peers still use reflectionMachineName (reflection index, /machine, the machines list), unchanged.
• The name always passes the guest's NAME regex: [a-z0-9-], at most 63 characters, cmux when empty.
• Rename still pushes the same name. It uses vmPromptIdentity, which now shares vmPromptName. A guest fetch that races a rename heals within 30 s.
• The test is isolated: its mock delegates to the real function when inactive.

Fixed:

• Optional tidy-up: vmPromptName now lives in services/vms/promptName.ts, so the route every VM polls each 30 s does not read the bashrc and prompt assets at cold start. guestPrompt.ts re-exports it.

Left:

• Rows with no slug: the route now answers cmux, the same as create and rename write, where it used to answer the provider id. This is intended.
• Stale wording: cmux@<slug> in a workflows.ts comment is a nit and left as is.

After the change: route and prompt tests pass (17), bun run typecheck and eslint are clean, and the complexity gate is unchanged.

[github-actions]

Merge receipt for 9e7035c808: every check was green at merge (21 verified; 16 skipped by policy). Full suite runs on main after merge.