### Preflight Checklist - [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) 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? When using `/model opusplan` with AWS Bedrock, Claude Code falls back to Sonnet 4.5 (`us.anthropic.claude-sonnet-4-5-20250929-v1:0`) instead of using Sonn

[BUG] Opusplan mode falls back to Sonnet 4.5 instead of 4.6 on AWS Bedrock

Status Fixed / completed

Reported on v2.1.76

Maintainer reply None cached

Activity 4 comments · opened Mar 17, 2026 · closed Mar 18, 2026

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?

When using /model opusplan with AWS Bedrock, Claude Code falls back to Sonnet 4.5
(us.anthropic.claude-sonnet-4-5-20250929-v1:0) instead of using Sonnet 4.6 as expected.
Individual model selections (/model opus and /model sonnet) correctly use the 4.6 versions.

What Should Happen?

Opusplan mode should display:
Set model to Opus 4.6 in plan mode, else Sonnet 4.6

And the statusline should show claude-sonnet-4-6 (or the Bedrock equivalent) when not in plan mode.

Error Messages/Logs

Steps to Reproduce

Configure Claude Code for AWS Bedrock with a profile that has access to both Opus 4.6 and Sonnet 4.6
Run /model opusplan
Observe the model shown in the statusline

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.76

Platform

AWS Bedrock

Operating System

macOS

Terminal/Shell

Other

Additional Information

View original on GitHub ↗

4 Comments

github-actions[bot] · 7 months ago

Found 1 possible duplicate issue:

https://github.com/anthropics/claude-code/issues/27237

This issue will be automatically closed as a duplicate in 3 days.

If your issue is a duplicate, please close it and 👍 the existing issue instead
To prevent auto-closure, add a comment or 👎 this comment

🤖 Generated with Claude Code

East-rayyy · 7 months ago

@crierr — the Bedrock model version fallback issue is caused by the alias resolver not consulting your ANTHROPIC_DEFAULT_*_MODEL env vars properly. I built claude-alias-patch that fixes the resolver — it patches 6 locations in cli.js including the env var whitelist and a fallback resolver so your Bedrock model IDs are used correctly.

Set ANTHROPIC_DEFAULT_SONNET_MODEL to your exact Bedrock ARN for Sonnet 4.6 in ~/.claude/settings.json and the alias will resolve to it instead of falling back to 4.5. Single install script — auto-patches your Claude instance.

crierr · 7 months ago

Hey @East-rayyy, I set ‎ANTHROPIC_DEFAULT_SONNET_MODEL as you suggested and it fixed the issue — thanks a ton for the clear explanation

github-actions[bot] · 6 months ago

This issue has been automatically locked since it was closed and has not had any activity for 7 days. If you're experiencing a similar issue, please file a new issue and reference this one if it's relevant.