[dezren39]

Summary

app.send
  serialize broadcast enqueue order
  enqueue to each program FIFO (1 in-flight + up to 16 queued)
    full queue → remove stalled recipient
ProgramHandler Wait
  remove program and stop its dispatcher

Delivery is enqueued rather than called inline, so Update can broadcast to its own program without blocking.

Evidence

• Before: the fail-first ordering probe recorded [second, third, first]; 100 broadcasts to one blocked recipient added 100 goroutines.
• After: the ordering probe confirms both recipients receive the same sequence; the stalled-recipient probe confirms queue overflow prunes the recipient without per-broadcast goroutine growth; self-send is delivered once per update in order without blocking Update.
• go test ./... -count=1 — pass (pkgs/chat).
• go test -race ./... -count=1 — pass (pkgs/chat).
• go vet ./... and git diff --check — pass.

Merge Danger

Door: two-way.

A slow recipient is removed once its fixed 16-message queue fills; other recipients continue receiving broadcasts.

Blast Radius: chat sessions only.

Closes #4389.

---

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• pkgs/chat/main.go
• pkgs/chat/main_test.go

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[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-11-02T18:44:21.637173Z	8a12197	PR opened

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