[BUG] Task Tool Fails to Spawn Agents in AWS GovCloud

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?

Environment

• Claude Code Version: 2.1.29
• Node Version: v24.13.0
• Platform: macOS 26.2 (Build 25C56)
• AWS Region: us-gov-west-1
• AWS Profile: bedrock (GovCloud)

Summary

The Task tool cannot spawn specialized agents (code-reviewer, Explore, Plan, etc.) in AWS GovCloud environments. The tool incorrectly resolves model identifiers by stripping the GovCloud-specific prefix, causing API authentication failures.

Root Cause

The Task tool extracts the model ID from the ARN but incorrectly normalizes us-gov.anthropic to us.anthropic, which is invalid for GovCloud regions.

Expected Model ID: us-gov.anthropic.claude-sonnet-4-5-20250929-v1:0
Actual Model ID Sent: us.anthropic.claude-sonnet-4-5-20250929-v1:0

Configuration Tested

~/.claude/settings.json

{
  "model": "arn:aws-us-gov:bedrock:us-gov-west-1:414305825600:inference-profile/us-gov.anthropic.claude-sonnet-4-5-20250929-v1:0",
  "alwaysThinkingEnabled": true
}

Environment Variables (.zshrc)

export CLAUDE_CODE_USE_BEDROCK=1
export AWS_PROFILE=bedrock
export AWS_REGION=us-gov-west-1
export AWS_DEFAULT_REGION=us-gov-west-1
export ANTHROPIC_MODEL='arn:aws-us-gov:bedrock:us-gov-west-1:414305825600:inference-profile/us-gov.anthropic.claude-sonnet-4-5-20250929-v1:0'

Agent Configuration (~/.claude/agents/code-reviewer.md)

Tested with:

1. Full ARN
2. Model ID with us-gov. prefix
3. Shorthand (sonnet, haiku)
4. No model spec (inherit from parent)

All configurations fail with the same error.

Attempted Workarounds (All Failed)

Test 1: Full ARN in agent config

model: arn:aws-us-gov:bedrock:us-gov-west-1:414305825600:inference-profile/us-gov.anthropic.claude-sonnet-4-5-20250929-v1:0

Result: ❌ Still sends us.anthropic...

Test 2: Model ID with us-gov prefix

model: us-gov.anthropic.claude-sonnet-4-5-20250929-v1:0

Result: ❌ Still sends us.anthropic...

Test 3: Shorthand model names

model: sonnet
model: haiku

Result: ❌ Resolves to commercial AWS IDs

Test 4: No model specified (inherit)

# No model field

Result: ❌ Still sends us.anthropic...

Impact

• Severity: HIGH
• Users Affected: All AWS GovCloud users
• Workaround: None available
• Functionality Lost: Cannot spawn any specialized agents (code-reviewer, Explore, Plan, etc.)
• Main Claude Code Session: Works fine (only Task tool is affected)

Proposed Fix

Location

The Task tool's model resolution logic (likely in the Claude Code agent spawning code)

Current Logic (incorrect)

// Pseudo-code
const modelId = arn.split('/').pop();  // Gets "us-gov.anthropic.claude-..."
const normalizedId = modelId.replace(/^us-gov\./, 'us.');

Corrected Logic

// Pseudo-code
const modelId = arn.split('/').pop();  // Gets "us-gov.anthropic.claude-..."
// Don't normalize - use as-is for GovCloud
return modelId;

Alternative Fix

Respect the AWS_REGION environment variable:

if (process.env.AWS_REGION?.startsWith('us-gov-')) {
  // Use us-gov. prefix
} else {
  // Use us. prefix
}

Additional Context

• Main Claude Code session works perfectly with GovCloud ARN
• Only the Task tool (agent spawning) has this issue
• Manual code reviews were used as workaround
• Issue is blocking agent-based workflows in government environments
• This affects all federal agencies and contractors using Claude Code in GovCloud

Files for Reference

I can provide:

• Complete bug report with detailed analysis
• Configuration files used
• Error logs from multiple test attempts
• Examples of working main session vs failing agent spawning

---

Would you like me to provide any additional information?

What Should Happen?

The Task tool should spawn specialized agents (code-reviewer, Explore, Plan, etc.) in AWS GovCloud environments. The tool should correctly resolves model identifiers by not stripping the GovCloud-specific prefix, which is causing API authentication failures.

Error Messages/Logs

API Error (us.anthropic.claude-sonnet-4-5-20250929-v1:0): 400 The provided model identifier is invalid.

Steps to Reproduce

1. Configure Claude Code for AWS GovCloud with full ARN in settings.json
2. Attempt to invoke any agent using the Task tool:

``javascript
Task(subagent_type="code-reviewer", prompt="Review code")
``

1. Observe error: The provided model identifier is invalid

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.29

Platform

AWS Bedrock

Operating System

macOS

Terminal/Shell

IntelliJ IDEA terminal

Additional Information

_No response_