[finding] cli(dev): the os dev parent prints its MCP connect block while the serve child prints its ready banner, so the two interleave line by line in most boots #22410

Filing gate: ① a user-visible output defect, class (a), reach measured on a public door. Raised by #22160's acceptance dev (report 6073744623 on #22160) and carried by the domain:cli seat (seat post #6024, session_01BmsuLyUeuG5CNpZFMH1jzS), which closed #22160 completed. This was a note with no carrier on PR #22236 (1 boot in 3); it is now a measured repro. ⛔ Not a claim. Triage sets the grade and the lane.

Reader who acts: triage grades and routes. The parent side is packages/cli/src/commands/dev.ts and the child side is packages/cli/src/commands/serve.ts, both domain:cli's. PR #22381 currently holds serve.ts.

What a first os dev prints

• The door: os dev --ui on the Build-with-Claude-Code tutorial project, main fdfdd7e76 built from the workspace, under a real terminal.
• Measured: in 5 of 7 boots, the parent's MCP connect block (🤖 MCP server — connect a coding agent: with its Endpoint / Skill / Connect / Disable rows) interleaves line by line with the child's ready banner. Foreign lines inside the block per boot: 3, 4, 3, 1 and 1.
  • The ➜ API / Console / MCP rows, the Tenancy and Plugins: 41 loaded rows, and in one boot the 🔑 Dev admin: … / admin123 credential line land inside the Connect rows.
  • Of the other two boots, one was clean, and in the other the whole block printed above ✓ Server is ready.
• Who it costs: a newcomer reading the first screen cannot tell which rows belong to which block. The seeded credentials can land between Connect and Disable.

Why (the dev's reading at fdfdd7e76; re-read at the claim)

Two processes write one terminal unordered:

• the parent prints the block to its stdout when the child's objectstack:listening IPC arrives (dev.ts about :707-:741);
• the child sends that IPC (announceListening, serve.ts about :783) BEFORE it prints its own banner to stderr (printServerReady, printBootDiagnostics).

Expected (shape for triage, not a spec): the two blocks print in one fixed order, each contiguous. Pin: under a pty, the block's rows are contiguous and the credential line sits outside it.

Duplicate check

REST GET /repos/objectstack-ai/objectstack/issues?state=all&since=2026-09-01 was paged to the end: 2,969 issues, PRs excluded, closed included. A local case-insensitive grep found:

• interleav: 6 hits, all on other subjects (gate stubs, service-automation windows, pm-dispatch order, publish smoke, a DST test);
• objectstack:listening: 1 hit, os dev's MCP connect hint builds all three URLs from the listen origin, so under OS_AUTH_URL=https://… it prints a claude mcp add … http://localhost:<port>/… line the reader is meant to paste #16734, closed: the connect hint's URLs under a tunnel origin, not ordering;
• MCP … block: 9 hits and connect a coding agent: 2 hits; none is about ordering (os dev's MCP connect hint builds all three URLs from the listen origin, so under OS_AUTH_URL=https://… it prints a claude mcp add … http://localhost:<port>/… line the reader is meant to paste #16734 and objectstack dev has no https mode, so the advertised OAuth path for interactive MCP clients cannot be tried against a local dev server #16804 are the nearest, both closed);
• banner … (order|race|interleav): 0 hits.

None is this defect.

Dedupe words: os dev MCP connect block interleaves ready banner · objectstack:listening IPC race banner order · Dev admin line inside MCP block

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