Auto-compact fails for Bedrock-hosted Claude models due to incorrect context limit

[nathanl]

Problem

I'm using Opus 4.6 via Amazon Bedrock in OpenCode. Auto-compaction is not happening, resulting in broken sessions.
Claude suggests this is an issue with models.dev reporting the Anthropic token limit rather than the Bedrock one.

In a session, at the top of the sidebar I see "200,084 tokens" and "20% used", indicating a 1M token limit.

But at this point the session has the error undefined: The model returned the following errors: prompt is too long: 200148 tokens > 200000 maximum.
If I try to manually /compact, that fails too: undefined: The model returned the following errors: messages.5.content.6: thinkingorredacted_thinking blocks in the latest assistant message cannot be modified. These blocks must remain as they were in the original response.
The only thing I can do is abandon the session.

Expected Behavior

OpenCode should use the correct 200k token limit that Bedrock uses (maybe by fixing what models.dev reports).

Workaround

Override the limit in ~/.config/opencode/opencode.json:

{
  "provider": {
    "amazon-bedrock": {
      "models": {
        "us.anthropic.claude-opus-4-6-v1": {
          "limit": {
            "context": 200000,
            "output": 32000
          }
        }
      }
    }
  }
}

With this, in a new session I see 20k tokens and "10% used".

Plugins

None

OpenCode version

1.2.20

Steps to reproduce

1. Use Claude Opus 4.6 via Amazon Bedrock
2. Continue session until 200k tokens are used

Screenshot and/or share link

Operating System

MacOS Tahoe 26.3

Terminal

iTerm2 3.6.8

[github-actions]

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

• Prompt too long when using Claude Opus 4.6 (Global) Amazon Bedrock #12688: Same error (prompt is too long: ... > 200000 maximum) with Claude Opus 4.6 (Global) on Amazon Bedrock — incorrect context limit causing session failures
• Split Bedrock Claude Opus 4.6 into 200K + 1M models and set 1M beta flag #13199: Proposes splitting Bedrock Opus 4.6 into 200K and 1M variants to fix exactly this problem
• 1M tokens for Opus 4.6 #12338: Same root cause — 1M context window incorrectly reported for Opus 4.6 on Bedrock, causing overflow errors

[nathanl]

I do think this is a duplicate issue, so I'm closing it.