[bug] Agent run stops when leaving playground page

[ashrafchowdury]

When an agent run is in progress in the playground, navigating away from the page and then returning causes the run to stop.

Expected behavior is for the run to continue in the background so long-running runs are not interrupted by page navigation.

Reproduced on production.

[linear-code]

AGE-4070

[dosubot]

This is a known gap in how the agent playground manages SSE connections. The root cause is that the Vercel AI SDK's useChat hook aborts the in-flight SSE stream as part of its teardown when the component unmounts [1]. Navigating away from the playground unmounts the AgentChatPanel, which triggers this abort.

A partial fix was landed in PR #4997 — it prevents unmount during revision switches by rendering with a stable component key and using an "agent surface latch" to keep the panel mounted through brief load gaps [1]. However, that fix only applies to navigation within the playground page. Full page navigation still unmounts everything and kills the stream.

Additionally, in-progress streaming turns are deliberately excluded from localStorage persistence, so when the component remounts after navigating back, useChat re-seeds from localStorage and the partial turn is lost [1].

There are several related issues tracking different facets of this:

• #5624 — polling gaps cause stale transcripts; proposes focus-based refetch and a lightweight records-count endpoint for background convergence
• #5530 — second browser tab gets stuck on a stale transcript because there's no live-following signal
• #5542 — refreshing while paused on an approval gate loses the gate and renders "No response"

Fixing this fully would likely require decoupling the run lifecycle from the React component lifecycle — e.g., tracking active runs server-side and letting the client re-adopt/poll for the current state on remount, rather than relying solely on the SSE connection staying alive.

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