Case Study: API Error 400 due to tool use concurrency issues#1189
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Case Study: API Error 400 due to tool use concurrency issues#1189
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Adding CLAUDE.md with task information for AI processing. This file will be removed when the task is complete. Issue: #1188
This case study analyzes the "API Error: 400 due to tool use concurrency issues" that occurs in Claude Code when parallel Edit tool calls target the same file. Key findings: - Root cause: Race condition when multiple Edit tools modify same file - Existing issue: anthropics/claude-code#11421 (OPEN) - Workaround: Serialize same-file Edit operations - Solution: Use Anthropic's Tool Runner SDK helpers Includes: - Full log from the failed session (4685 lines) - Timeline reconstruction of the failure sequence - Proposed solutions and workarounds - References to related GitHub issues Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
konard
changed the title
This reverts commit b9c41b5.
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Summary
This PR adds a comprehensive case study analyzing the "API Error: 400 due to tool use concurrency issues" that occurs in Claude Code when multiple parallel Edit tool calls target the same file.
Fixes #1188
Key Findings
Root Cause
Race condition when multiple Edit tool calls modify the same file in parallel:
old_stringpatterns no longer exist (file already modified)"tool_use" ids were found without "tool_result" blocks immediately afterRelated Issues (Anthropic)
Proposed Solutions
Files Added
docs/case-studies/issue-1188/CASE-STUDY.mddocs/case-studies/issue-1188/solution-draft-log.txtActions Taken
References