[BUG] Builtin Agents fail when using bedrock because they cannot be configured to use `model: inherit`

Environment

• Platform (select one):
• [ ] Anthropic API
• [x] AWS Bedrock
• [ ] Google Vertex AI
• [ ] Other: <!-- specify -->
• Claude CLI version: 1.0.77
• Operating System: macOS 15.6
• Terminal: VS Code

Bug Description

Builtin agents (like general-purpose) are hardcoded with specific model configurations and cannot be configured to use model: inherit. This prevents them from working with AWS Bedrock and other model providers that require the inherit setting.

Steps to Reproduce

1. Configure Claude Code to use AWS Bedrock as the model provider
2. Try to use a builtin agent like general-purpose with the Task tool
3. The agent fails because it cannot inherit the global Bedrock model configuration
4. Custom agents with model: inherit in their markdown work correctly

Expected Behavior

Builtin agents should respect the global model configuration when using AWS Bedrock or other providers, either by:

• Automatically using model: inherit by default
• Allowing users to override builtin agent model settings via configuration
• Providing a global setting to make all agents use model: inherit

Actual Behavior

Builtin agents fail to work with Bedrock because they use hardcoded model configurations instead of inheriting the global model settings. Users must recreate all builtin agents as custom agents with model: inherit.

Additional Context

This significantly impacts the Bedrock user experience and creates maintenance overhead. Users in enterprise environments who require specific model providers must:

• Manually recreate each builtin agent as a custom agent
• Maintain duplicate agent definitions
• Miss out on updates to builtin agents
• Spend considerable time on workarounds

Proposed Solutions:

1. Global Override Setting: Add agents.useInheritModel: true to force all agents to use model: inherit
2. Builtin Agent Overrides: Allow per-agent model configuration overrides in settings
3. Default to Inherit: Change builtin agents to use model: inherit by default

Current Workaround: Create custom versions of all needed builtin agents with model: inherit in the markdown.