[BUG] Forked skill's agent id is not correct.

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Main agent get wrong agentId for forked skill. So it fails when resume the forked skill.

Main agent get acf6fe7 for agentId

{"parentUuid":"ba7534a1-ca99-45cd-b34a-288a9f71e631","isSidechain":false,"userType":"external","cwd":"/Users/jayce/team-attention/cops","sessionId":"0221b20f-f53d-483e-aa25-547434785a58","version":"2.1.4","gitBranch":"main","slug":"linked-soaring-feigenbaum","type":"user","message":{"role":"user","content":[{"type":"tool_result","tool_use_id":"toolu_012y3m6dhSAmV9qwVEZiGbNu","content":"Skill \"plan-workflow\" completed (forked execution).\n\nResult:\nThe temp file has been created at:\n\n```\n.agent/tmp/20260112-010306-plan-review\n```"}]},"uuid":"e98fcc0a-3e83-44cd-856d-9f77ebdc30cf","timestamp":"2026-01-11T16:03:09.506Z","toolUseResult":{"success":true,"commandName":"plan-workflow","status":"forked","agentId":"acf6fe7","result":"The temp file has been created at:\n\n```\n.agent/tmp/20260112-010306-plan-review\n```"},"sourceToolAssistantUUID":"ba7534a1-ca99-45cd-b34a-288a9f71e631"}

Actual agent that runs forked skill is af5b8d7

{"parentUuid":"0ef1ece9-33c6-4996-8426-ebc676f6546d","isSidechain":true,"userType":"external","cwd":"/Users/jayce/team-attention/cops","sessionId":"0221b20f-f53d-483e-aa25-547434785a58","version":"2.1.4","gitBranch":"main","agentId":"af5b8d7","slug":"linked-soaring-feigenbaum","message":{"model":"claude-opus-4-5-20251101","id":"msg_014cYvGWdtkrDerQ87vNh6ji","type":"message","role":"assistant","content":[{"type":"text","text":"The temp file has been created at:\n\n```\n.agent/tmp/20260112-010306-plan-review\n```"}],"stop_reason":null,"stop_sequence":null,"usage":{"input_tokens":1,"cache_creation_input_tokens":132,"cache_read_input_tokens":54894,"cache_creation":{"ephemeral_5m_input_tokens":132,"ephemeral_1h_input_tokens":0},"output_tokens":1,"service_tier":"standard"}},"requestId":"req_011CX1sb3SDvVUCLMjEcXzD8","type":"assistant","uuid":"ade4ac8f-4929-4115-b2ae-1e8b7ae0e235","timestamp":"2026-01-11T16:03:09.459Z"}

acf6fe7 log file doesn't exist. forked skill cannot resume after quit.

What Should Happen?

Maybe main agent should get correct agent id for forked skill.

Error Messages/Logs

Steps to Reproduce

1. Run forked skill
2. See the log files for the session.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.4 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

I use Ghostty for terminal