Chat and run observation

Chat on Interchange is mail. People and agents share one mail bus, and a deployed run has an address. Progress is a separate feed.

Pick the feed

Need	Source
Person sends a message	Mail to <deploymentId>@<tenant.domain> (triggerWorkflowRun or the mailbox send)
Agent reply text	The person's inbox: mailbox routes and SSE (@corbits/mailbox)
Status, steps, parked waits	Poll run events (readWorkflowRunEvents, or createRunSession which polls every 2 s)
Tool calls, reasoning	Run events or GET T/workflows/runs/:runId/turns, never mail (mail is plain text)
Human decision for a waiting run	deliverWorkflowSignal with a stable signalId
Tool approval	GET T/approvals, then POST T/approvals/:id/approve or /reject

How a turn flows

1. The first mail to a run address fires the run. The hub treats inbound mail to a run address as the trigger, whether it came from the HTTP route or an agent's mail_send.
2. While the run lives, later mail resumes its onTrigger section as input. A terminal run cannot be re-fired (409).
3. Replies land in the sender's inbox and publish on the mailbox event bus. Threads follow In-Reply-To and References.

What the host must provide

The stock hub has no mailbox routes. The host mounts @corbits/mailbox at T/mailbox, wraps the hub's persistMail so agent mail reaches inboxes, and supplies a deliver that sends run-addressed mail through POST T/workflows/:runId/mail with the caller's session. See use_skill corbits-hub-libs. Workbench apps/hub/src/mailbox-send.ts is the reference. The default event bus is in memory, so use a shared one for multiple replicas.

UI

@corbits/react-ui ChatThread takes messages as a prop: { id, role: "user" | "agent" | "system", parts, createdAt } where parts are text, reasoning, tool, or file. Write the adapter that maps inbox rows to text parts and run events to tool and reasoning parts. A person's address is the auth user id at the tenant domain, lowercased.

Cautions

• onTrigger body runs can silently skip when a second top-level run of the same deployment reaches the section (upstream known limitation, INTR-552). Do not build one run per conversation on onTrigger without testing a second run.
• An untimed park (awaitSignal, or an approval: "ask" tool) inside a childWorkflow is refused. Put human waits in the top-level run or in a loop body.
• Agent model context lives in the sidecar's agent repo. It is not the transcript, and compaction does not touch the mail.

Need more

• Setting up the hub and deploying: use_skill interchange-hub-setup.
• Mounting mailbox, artifacts, memory: use_skill corbits-hub-libs.
• UI components: use_skill corbits-ui-apps.
• Handoff between workflows: use_skill interchange-workflows.