fix(acp): prevent assistant message fragmentation on background tool updates & filter leaked harness telemetry - #13137
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…updates & filter leaked harness telemetry Fixes pingdotgg#13133 - Only close active assistant segments on new tool calls (isNew: previous === undefined) instead of on every in-flight tool progress or completion event. - Prevent duplicate `assistant:assistant:` message IDs in ProviderRuntimeIngestion. - Add streaming filter to strip echoed <SYSTEM_MESSAGE> blocks and harness preambles from Antigravity session chunks. - Add negative constraint to buildRuntimeInstructions preventing models from quoting harness telemetry.
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ApprovabilityVerdict: Not approved Macroscope's review found this PR not approvable — This PR changes live ACP streaming behavior and the shared default runtime prompt used across multiple providers. Its stateful telemetry filter also has an unresolved High-severity edge case involving delimiters split across chunks, so the production behavior requires human review. Not approved because:
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Included review availability: Your plan provides up to 10 included reviews per hour; 8 remain after this review. 📝 WalkthroughWalkthroughThe changes update ACP assistant segment handling, filter system telemetry from Antigravity session updates, add runtime instructions about system messages, and normalize assistant message IDs. ChangesACP stream handling and message cleanup
Priority: ➖ Normal Estimated code review effort: 3 (Moderate) | ~25 minutes Change: Bug fix · Severity of issue fixed: Medium Sequence Diagram(s)sequenceDiagram
participant AcpSessionRuntime
participant AntigravitySessionUpdateTransformer
participant MessageFilter
participant AssistantStream
AcpSessionRuntime->>AntigravitySessionUpdateTransformer: transform session update
AntigravitySessionUpdateTransformer->>MessageFilter: filter assistant or thought chunk
MessageFilter-->>AntigravitySessionUpdateTransformer: return sanitized chunk
AntigravitySessionUpdateTransformer-->>AssistantStream: deliver filtered session update
AcpSessionRuntime->>AntigravitySessionUpdateTransformer: reset at prompt boundary
Merge Risk: 🔵 Low · up to A narrow ACP session-ID edge case can leave duplicate assistant prefixes in message metadata; the PR is otherwise low risk but this should be fixed or explicitly accepted. 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
✨ Finishing Touches🧪 Generate unit tests (beta)
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Actionable comments posted: 3
- 🪄 Fix CodeRabbit comments on this PR
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Inline comments:
In `@apps/server/src/provider/acp/AntigravityProtocol.ts`:
- Around line 282-284: Update the streaming filter branch around nextIndex in
AntigravityProtocol so it retains the longest trailing suffix that could begin a
telemetry preamble or tag instead of emitting it as assistant text. Carry that
suffix into the next chunk for detection, and add regressions covering split
opening tags and split preambles.
- Line 290: Update the `afterPreamble` lookup to search for a separate opening
tag only after `preambleText`, so it does not match the tag embedded in the
preamble. If no separate tag is found, discard only through the next newline and
preserve subsequent assistant text.
- Around line 312-342: Update makeAntigravitySessionUpdateTransformer so both
filterMessage and filterThought reset at each new prompt boundary, before
processing that prompt’s updates. Keep the filters independent and preserve
their existing per-channel behavior.
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apps/server/src/orchestration/Layers/ProviderRuntimeIngestion.test.tsapps/server/src/orchestration/Layers/ProviderRuntimeIngestion.tsapps/server/src/provider/RuntimeInstructions.tsapps/server/src/provider/acp/AcpSessionRuntime.tsapps/server/src/provider/acp/AntigravityAcpSupport.tsapps/server/src/provider/acp/AntigravityProtocol.test.tsapps/server/src/provider/acp/AntigravityProtocol.ts
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… reset filters at prompt boundaries
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Actionable comments posted: 1
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Inline comments:
In `@apps/server/src/provider/acp/AntigravityProtocol.ts`:
- Around line 306-307: Update the filtering logic around SYSTEM_MESSAGE_PREAMBLE
and OPEN_SYSTEM_MESSAGE_TAG so an incomplete preamble containing the embedded
opening tag is buffered rather than treated as a standalone system-message
block. Preserve the buffered prefix across chunks, then emit the complete
legitimate text after the closing preamble context is resolved; add regression
coverage for the two-chunk input described in the review.
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apps/server/src/orchestration/Layers/ProviderRuntimeIngestion.tsapps/server/src/provider/acp/AcpSessionRuntime.tsapps/server/src/provider/acp/AntigravityProtocol.test.tsapps/server/src/provider/acp/AntigravityProtocol.ts
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- apps/server/src/orchestration/Layers/ProviderRuntimeIngestion.ts
- apps/server/src/provider/acp/AcpSessionRuntime.ts
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Thanks for pinning down the segment-close bug. #13386 carries that part with you as co-author, plus a regression test through the real runtime. The |
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Superseded by #13386 (takes the segment change; rest not carried). |
2 participants
Fixes #13133
Summary of Changes
This pull request addresses assistant message fragmentation and leaked harness telemetry observed during background tool executions in ACP sessions (specifically reproduced and analyzed in Antigravity harness sessions):
Prevent premature assistant segment severing on background tool updates:
AcpSessionRuntime.ts,closeActiveAssistantSegmentwas previously called unconditionally on everyToolCallUpdatednotification.completed/failedwhile the model is actively streaming an assistant response, this severed the assistant segment mid-token and created an unexpected split message bubble with a truncated initial bubble.isNew: previous === undefined) before closing preceding assistant segments.Normalize assistant message IDs:
ProviderRuntimeIngestion.ts,assistantSegmentMessageIdprependedassistant:even ifbaseKeywas already prefixed (yieldingassistant:assistant:...).assistantSegmentMessageIdand routing assistant completion and checkpoint IDs throughcanonicalAssistantMessageId.Filter leaked harness telemetry from assistant text & thoughts:
AntigravityProtocol.ts, addedcreateAntigravityMessageFilterandmakeAntigravitySessionUpdateTransformerto filter<SYSTEM_MESSAGE>...</SYSTEM_MESSAGE>tags and harness notification preambles that the model may inadvertently echo intoagent_message_chunkoragent_thought_chunk.AcpSessionRuntime.ts, empty content deltas resulting from sanitized chunks are skipped without creating phantom segments.Prompt instructions:
RuntimeInstructions.ts, added instructions informing models that internal<SYSTEM_MESSAGE>tags and task notifications are strictly for internal awareness and should not be quoted back to the user.Verification
<SYSTEM_MESSAGE>filtering across single and fragmented chunk boundaries inAntigravityProtocol.test.ts.RuntimeInstructions.test.ts.ProviderRuntimeIngestion.test.ts.Summary by CodeRabbit