Bug: --continue flag uses wrong model ID for EU region (Bedrock)

Description

When using Claude Code with AWS Bedrock in eu-central-1 region, the --continue flag fails because it attempts to use the US Haiku model identifier which is not available in EU regions.

Error Message

% claude --continue

▗ ▗   ▖ ▖  Claude Code v2.0.25
           Sonnet 4.5 · API Usage Billing
  ▘▘ ▝▝    ~/Develop/claude-code-stats

> Warmup 
  ⎿  API Error (us.anthropic.claude-3-5-haiku-20241022-v1:0): 400 The provided model identifier is invalid.

% claude           

▗ ▗   ▖ ▖  Claude Code v2.0.25
           Sonnet 4.5 · API Usage Billing
  ▘▘ ▝▝    ~/Develop/claude-code-stats

Expected Behavior

When using --continue with AWS Bedrock in eu-central-1, Claude Code should use the EU-compatible model identifier:

• eu.anthropic.claude-3-5-haiku-20241022-v1:0 (EU Haiku)

Instead of:

• us.anthropic.claude-3-5-haiku-20241022-v1:0 (US Haiku)
• Entire session being lost (won't appear anymore with --resume)

Environment

• Claude Code Version: v2.0.25
• Platform: macOS (Darwin 24.6.0)
• AWS Region: eu-central-1 (confirmed via AWS_DEFAULT_REGION)
• Provider: AWS Bedrock (CLAUDE_CODE_USE_BEDROCK=1)
• Primary Model: Sonnet 4.5 (works fine for new sessions)

Relevant Environment Variables

AWS_DEFAULT_REGION=eu-central-1
CLAUDE_CODE_USE_BEDROCK=1
CLAUDE_CODE_ENTRYPOINT=cli

Steps to Reproduce

1. Configure Claude Code to use AWS Bedrock in eu-central-1 region
2. Set environment: export AWS_DEFAULT_REGION=eu-central-1
3. Set environment: export CLAUDE_CODE_USE_BEDROCK=1
4. Start a new session: claude (works fine)
5. Try to continue the session: claude --continue
6. Error occurs: "The provided model identifier is invalid"

Root Cause

The warmup phase when using --continue appears to be hardcoded to use US model identifiers (us.anthropic.claude-3-5-haiku-20241022-v1:0) regardless of the AWS region configuration.

Impact

• --continue is completely broken for all EU Bedrock users
• No workaround available - users cannot resume previous sessions
• Forces users to start new sessions every time, losing conversation context

Suggested Fix

Claude Code should:

1. Detect the AWS region from environment (AWS_DEFAULT_REGION) or Bedrock configuration
2. Use region-appropriate model identifiers for all operations including --continue
3. Map us.* models to eu.* models when in EU regions
4. Apply this logic consistently across all warmup and model selection code paths

Example Region Mapping

const modelIdByRegion = {
  'us-east-1': 'us.anthropic.claude-3-5-haiku-20241022-v1:0',
  'us-west-2': 'us.anthropic.claude-3-5-haiku-20241022-v1:0',
  'eu-central-1': 'eu.anthropic.claude-3-5-haiku-20241022-v1:0',
  'eu-west-1': 'eu.anthropic.claude-3-5-haiku-20241022-v1:0',
  'eu-west-2': 'eu.anthropic.claude-3-5-haiku-20241022-v1:0',
  // ... other regions
};

Workaround

None available. Users must avoid --continue and start new sessions each time.