🤖 fix: add heartbeat pattern to onChat for reliable stall detection #1909
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Previously, stall detection used a 60s timeout while checking if a stream was active. This caused false positives during long tool operations (bash with 5+ min timeout, subagent calls) where it's normal to have no events. The retry would reset chat state and cause full UI repaints. Now the server sends heartbeats every 5s unconditionally, and the client expects *any* event within 10s. If 10s pass with no events (including heartbeats), the connection is dead and we resubscribe. Long operations no longer trigger false stalls since heartbeats keep flowing.
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ammario
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Jan 26, 2026
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Summary
Adds a heartbeat pattern to the
onChatsubscription to reliably distinguish dead connections from intentionally idle streams during long operations.Background
The previous stall detection used a 60s timeout while checking if a stream was active. This caused false positives during long tool operations (bash with 5+ min timeout, subagent calls) where it's normal to have no events for extended periods. The retry would call
resetChatStateForReplay()which clears the aggregator and triggers a full UI repaint—noticeable and disruptive to users.Implementation
heartbeatevent every 5s unconditionally in theonChathandlerNow if 10s pass with no events (including heartbeats), the connection is genuinely dead → resubscribe. Long operations no longer trigger false stalls since heartbeats keep flowing.
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