The Anthropic Managed-Agents SSE stream (`/v1/sessions/{id}/events/stream`)
is not guaranteed to stay open for the life of a multi-turn session.
Inter-turn gaps (e.g. while MCP tools or the next model request run) of
~25s+ are common and can trigger upstream / proxy read timeouts; when
that happens, the SDK's `for await` iterator just ends and the proxy
silently closed the downstream response, leaving the browser with only
the events from the first tool batch.
Implement the official 'consolidation' pattern: treat any upstream
end-of-stream that isn't a terminal `session.status_*` as a transient
drop, fetch what we missed via `sessions.events.list()` (deduped by
event.id), reopen the live stream, and keep going — up to a 20 minute
wall-clock budget so a wedged session can't pin the function forever.
Also switch the wire format from inline-markdown-with-status-comments to
NDJSON, so the React side can render in-flight tool activity in a
separate status banner from the streaming brief. The existing zero-width
heartbeat is replaced by an explicit `{"type":"heartbeat"}` line.
Drop the `agent.tool_use` write-tool special case — the agent now
streams the brief directly via `agent.message` text blocks.
Co-Authored-By: alex <alex@semipublic.co>
Devin AI
c283d884cf