Summary

• Strip malformed tool_use blocks from assistant messages during transcript repair to fix permanent session corruption
• Malformed blocks (missing id, missing name, or with partialJson field) are now detected and removed before pairing repair runs
• Sessions that would previously require manual JSONL surgery now auto-recover
• Added logging when malformed blocks are stripped for observability

Problem

When tool calls are interrupted (by error, timeout, content filtering, or process termination), sessions become permanently corrupted. Every subsequent API request fails with:

• unexpected tool_use_id found in tool_result blocks
• tool result's tool id not found (2013)

Root cause: extractToolCallsFromAssistant() skips malformed tool_use blocks (lines 22-23 in the old code) but leaves them in the message content. The blocks remain in the transcript causing API rejections.

Solution

1. Add isValidToolUseBlock() to detect malformed blocks
2. Add stripMalformedToolUseBlocks() to remove them from assistant messages
3. Call the strip function before pairing repair to prevent creating synthetic results for invalid blocks
4. Track droppedMalformedToolUseCount in the repair report for observability
5. Log a warning when malformed blocks are stripped

Test plan

• All 13 unit tests pass (4 existing + 9 new)
• New test "recovers from interrupted tool call (session corruption scenario)" reproduces the exact failure mode
• Lint passes
• Build succeeds

Future suggestions

These are not blockers but could improve robustness:

1. Consolidate validation logic - extractToolCallsFromAssistant() has similar but not identical validation. Could extract shared validation to reduce duplication.

2. Provider-specific partial data fields - Currently only checks for partialJson. Other providers might use different field names for partial/streaming data.

3. Consider logging in stripMalformedToolUseBlocks directly - Currently only logs in google.ts. Other call sites via sanitizeToolUseResultPairing() don't get the warning.

Fixes #5497, #5481, #5430, #5518

🤖 Generated with Claude Code

Greptile Overview

Greptile Summary

This PR improves session transcript repair by stripping malformed assistant toolCall blocks (e.g., missing/empty id or containing partialJson) before attempting to re-pair toolResult messages. The repair report now exposes droppedMalformedToolUseCount, and the Google embedded runner logs a warning when malformed tool blocks are removed. A new test suite reproduces the “interrupted tool call causes permanent session corruption” scenario and validates the new behavior.

Confidence Score: 4/5

• This PR looks safe to merge and should improve recovery from corrupted transcripts, with low behavioral risk outside transcript sanitization.
• Changes are localized to transcript-repair logic and the Google runner’s sanitization pipeline, with comprehensive new unit tests covering key malformed-block scenarios. Minor edge-case risk remains around provider-specific malformed tool-call shapes not covered (beyond partialJson/missing id).
• src/agents/session-transcript-repair.ts