Error on session compaction on Opus 4.6

[amannhq]

Description

Getting this error on session compaction

undefined: The model returned the following errors: messages.3.content.1: thinking or redacted_thinking blocks in the latest assistant message cannot be modified. These blocks must remain as they were in the original response.

Plugins

oh-my-openagent

OpenCode version

No response

Steps to reproduce

1. Start the agent install the oh-my-openagent plugin select Sisyphus (Ultraworker) agent.
2. Give a prompt select Opus 4.6 connect via amazon-bedrock.
3. Wait till context window reaches and trigged auto compaction

Screenshot and/or share link

No response

Operating System

macos Tahoe

Terminal

Opencode desktop

[github-actions]

This issue might be a duplicate of existing issues. Please check:

• Amazon Bedrock Opus 4.6 compaction failure #14332: Amazon Bedrock Opus 4.6 compaction failure (same provider and model)
• Claude Opus 4.5 (latest) eventually fails: thinking block cannot be modified #13286: Claude Opus 4.5 (latest) eventually fails: thinking block cannot be modified (same error about thinking blocks)
• normalizeMessages() removes empty text parts between reasoning blocks, invalidating Anthropic thinking block signatures #16748: normalizeMessages() removes empty text parts between reasoning blocks, invalidating Anthropic thinking block signatures (related root cause)

Please review these issues and comment on one of them if your problem is the same, so we can consolidate tracking.

[Jacko1394]

Opus 4.6 works for one Plan pass, but then I always get Bad Request on the Build pass.

[Jacko1394]

Seems the same as: #13217
In the latest v1.3.9, when using Opus 4.6 via GitHub Copilot Enterprise, when the compaction occurs I hear an error sound, but no error shown.
Once that happens I cannot prompt any further, and can't change models either (previously that was a workaround) so the session cannot be used anymore.

@Hona Would you be able to help with this? 🥹

[Jacko1394]

Still blocking me: #11301 (comment)

[Hona]

@Jacko1394 are you using opus 4.6 via github copilot auth?

[Jacko1394]

@Jacko1394 are you using opus 4.6 via github copilot auth?

Yeah, GitHub Copilot Enterprise provider