[BUG] subagents do not respect AWS_REGION/ANTHROPIC_SMALL_FAST_MODEL_AWS_REGION

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?

https://github.com/anthropics/claude-code/issues/16594 was auto-closed, and other reports keep getting closed as duplicate of it, but the bug still exists. If you use bedrock with a non us region, various skills/subagent contexts just don't work b/c they do not respect the configured region and try to use models that are not available.

What Should Happen?

All skills and subagents should respect the given AWS Region for the provided credentials.

Error Messages/Logs

● I see the issue. The main model uses EU region (eu.anthropic.claude-opus-4-5-20251101-v1:0), but WebFetch is trying to use a US region Haiku model (us.anthropic.claude-haiku-4-5-20251001-v1:0).

Steps to Reproduce

1. export AWS_REGION=eu-west-1 and or whichever bedrock region, and CLAUDE_CODE_USE_BEDROCK=1.
2. Login (or set your AWS_BEARER_TOKEN_BEDROCK)
3. Run various skills/subagents until you hit one trying to use a us model and it breaks. e.g. webfetch

Claude Model

Not sure / Multiple models

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.90 (Claude Code)

Platform

AWS Bedrock

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_