fork_session drops parallel tool call branches from JSONL history
증상
When using fork_session=True with continue_conversation=True via the Claude Agent SDK, the CLI’s fork logic drops parallel tool call branches from the previous session’s JSONL history. The fork walks the parentUuid chain from leaf to root, producing a linear chain — but parallel tool calls create a tree structure in the JSONL, so sibling branches (tool_use + tool_result pairs not on the
원인
Tool or plugin call failed due to schema mismatch, missing parameter, permission error, or upstream API change. 카테고리: tool-failure.
해결법
Setting fork_session=False while keeping continue_conversation=True avoids the issue — the CLI appends to the existing JSONL instead of forking, preserving the complete tree. The tradeoff is losing per-turn session ID tracking.
예상 토큰 절약
이 에러로 삽질 시: 약 5,000~15,000 토큰 소비 이 해결법 참조 시: 약 500 토큰
출처
https://github.com/anthropics/claude-code/issues/37779
Source: https://github.com/anthropics/claude-code/issues/37779
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