[BUG] No small/fast model in APAC

Environment

• Platform (select one):
• [ ] Anthropic API
• [x] AWS Bedrock
• [ ] Google Vertex AI
• [ ] Other: <!-- specify -->
• Claude CLI version: 1.0.102
• Operating System: ubuntu 20.04
• Terminal: vscode embedded terminal

Bug Description

It appears that claude code will not use the small/fast model if the region is an APAC one

Steps to Reproduce

1. CLAUDE_CODE_USE_BEDROCK=1 AWS_REGION=ap-southeast-2 ANTHROPIC_MODEL=apac.anthropic.claude-sonnet-4-20250514-v1:0 ANTHROPIC_SMALL_FAST_MODEL_REGION=ap-southeast-2 ANTHROPIC_SMALL_FAST_MODEL=apac.anthropic.claude-3-haiku-20240307-v1:0 claude
2. "Is my README.md up to date?"
3. /cost

Expected Behavior

I expected to see some usage by model for claude-sonnet, and some for haiku

Actual Behavior

I only see usage for claude-sonnet

Additional Context

If I use CLAUDE_CODE_USE_BEDROCK=1 AWS_REGION=us-west-2 claude, I do get a split in usage by model.

I also get a split in usage if I use CLAUDE_CODE_USE_BEDROCK=1 AWS_REGION=us-west-2 ANTHROPIC_MODEL=us.anthropic.claude-sonnet-4-20250514-v1:0 ANTHROPIC_SMALL_FAST_MODEL_REGION=us-west-2 ANTHROPIC_SMALL_FAST_MODEL=us.anthropic.claude-3-haiku-20240307-v1:0 claude

I cannot use CLAUDE_CODE_USE_BEDROCK=1 AWS_REGION=ap-southeast-2 claude, as claude code assumes the model starts with "us.", when in that region it starts with "apac.".

I have confirmed I have access to all the models being used, both in Model Access and IAM.