Model call failed: unexpected tool_use_id in tool_result blocks (persists after session resume)

[crmitchelmore]

Summary

Copilot CLI repeatedly fails with:

Model call failed: messages.0.content.1: unexpected tool_use_id found in tool_result blocks: toolu_015VQ5FANNzGvtz26zVwRioZ. Each tool_result block must have a corresponding tool_use block in the previous message.

This persisted even after resuming the session.

Environment

• Copilot CLI version: 0.0.382
• OS: macOS (Darwin)
• Observed at: 2026-01-15T07:23:46.722Z

Example occurrences

• Request ID: BF38:3C9E91:12D1420:16F224A:69689578
• Request ID: BF38:3C9E91:12D26BB:16F3886:69689579
• Request ID: BF38:3C9E91:12D3EB7:16F5455:6968957F

Expected

Tool results should always match a preceding tool_use in the prior message; the model call should proceed normally.

Actual

The CLI emits repeated “Model call failed … unexpected tool_use_id …” errors and cannot continue; the error persists through session resume.

Notes

This looks like message assembly/state corruption where tool_result blocks are being sent without the corresponding tool_use blocks, possibly triggered by session resume or streaming retries.

[jakkaj]

I too am having this. Opus 4.5. Version 0.0.383 · Commit b3d398d.

Restarting client fixes it (--continue)

Also, compact fails

Works fine in another sesh ->

[examon]

This was fixed in v0.0.386. The compaction logic that builds conversation history for session resume now correctly handles tool call sequences, preventing the "unexpected tool_use_id in tool_result blocks" error. If you're still seeing this on a newer version, feel free to reopen.