Allow previous_response_id after server-side compaction#4682
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Allow previous_response_id after server-side compaction#4682
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The stateful marker (previous_response_id) continues to work after server-side compaction. The server retains the compacted context and the response ID chain remains valid, so there is no need to skip the marker when compaction data is present in the message history.
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Summary
Remove the guard that prevented using
previous_response_id(stateful marker) when compaction data was present in the message history.Server-side compaction is transparent to the response ID chain — after compaction, the server retains the compacted context tied to the response ID, so
previous_response_idremains valid and avoids re-sending the full history (including the compaction blob).Session Context
Key decisions from the development session:
gpt-5.4thatprevious_response_idchaining works across compaction boundaries. Turn 3 triggered compaction and turn 4 succeeded usingprevious_response_idfrom turn 3.previous_response_id. When the stateful marker is set (WebSocket reuse or HTTP with marker), the server already has the compacted context.latestCompactionMessageIndex === undefinedguard from the condition. The compaction slicing logic before it is still correct for the HTTP fallback path.Changes
src/platform/endpoint/node/responsesApi.ts: Removed check that blockedprevious_response_idwhen compaction data existed in message history.