* fix(channels): keep IM runs alive when the creating request disconnects
The channel manager holds a `runs.wait` / `runs.stream` request open for
the whole run, and that request dies with the Gateway instance that
received the IM message: a leader hand-off, a rolling restart, a crash.
The Gateway cancels a run whose creating request disconnects unless the
request asked for `on_disconnect: continue`, so every IM run in flight
was cancelled on failover.
Channel runs now ask for `continue`, like scheduled-task and MCP-task
runs already do. The run finishes on the Gateway executing it and its
thread state is persisted, so the answer stays readable in the web UI
even though the IM reply is lost with the old transport. The key is set
after the fire-and-forget branch because the SDK's `runs.create` has no
`on_disconnect` parameter.
Docs: CONFIGURATION.md and the Helm/deployment guides no longer list
"failover cancels IM runs" as a known limit; IM_CHANNEL_CONNECTIONS.md
and the channels AGENTS.md describe the policy.
* docs(changelog): link #6876
* fix(channels): keep the inbound dedupe key once a run may be executing
With `on_disconnect: continue` a run outlives the manager worker that
requested it, but the worker loop released the inbound dedupe key on
cancellation, so a provider redelivery on the replacement instance
admitted the same event again and executed the turn twice (review on
#6876).
Each inbound message now carries an admission record: `requested`
flips before the run request leaves the manager, `confirmed` once the
Gateway proved it admitted the run (a run id, a stream frame, a
completed response). The generic release paths (worker cancellation,
worker/handler exceptions, a broken stream) keep the key when the run
may continue: after confirmation, on cancellation after the request
was sent, and on post-request transport failures (read timeout, read
error, protocol error). Pre-request failures, Gateway rejections
(busy thread, stale pin, status errors, connection failures) and the
stream's terminal `error` frame still release it so the redelivery
can retry.