[ENHANCEMENT] Allow AWS Bedrock Custom ARN users to supply their own ARN without restriction

[wisestmumbler]

Problem (one or two sentences)

AWS Bedrock has valid ARNs that don't conform to what Roo is trying to enforce. It may be best for the plugin to not try to keep up with all of the changes there.

If users are going through the trouble of using a custom ARN the plugin should allow them freedom to try things out.

Here's an example of the plugin being too heavy handed in this case:
#9481
#10040

I've also tried to set the settings close to what I want and then export, edit, and reimport. I am not blocked on reimport (thankfully) but still can't run with an ARN that I know is valid but the plugin doesn't allow.

Context (who is affected and when)

Any custom ARN user

Desired behavior (conceptual, not technical)

If a aws bedrock user is using a custom ARN you should give them all of the options and not limit them with potentially overlimiting validation regexes and reduced option sets.

Constraints / preferences (optional)

No response

Request checklist

• I've searched existing Issues and Discussions for duplicates
• This describes a specific problem with clear context and impact

Roo Code Task Links (optional)

No response

Acceptance criteria (optional)

No response

Proposed approach (optional)

No response

Trade-offs / risks (optional)

No response

[mrubens]

I agree with this

[roomote]

I've analyzed this issue and here's my proposed implementation plan:

Problem Summary

There are two related issues affecting custom ARN users:

1. ARN validation is too strict - The regex in validateBedrockArn() only allows arn:aws: prefix but doesn't support other AWS partitions like arn:aws-us-gov: (GovCloud) or arn:aws-cn: (China regions). This blocks users with valid ARNs from using the service.

2. Missing model options for custom ARNs - When using a custom ARN, the UI doesn't show model-specific options like "Enable Reasoning" because the model capabilities (e.g., supportsReasoningBinary) are unknown for custom ARNs. The referenced issue [BUG] Bedrock Custom ARNs to have "Enable Reasoning" checkbox #10040 describes this exact problem.

Proposed Changes

1. Fix ARN Validation (webview-ui/src/utils/validate.ts)

Update the ARN regex from:

/^arn:aws:(?:bedrock|sagemaker):([^:]+):([^:]*):(?:([^/]+)\/([\w.\-:]+)|([^/]+))$/

To support all AWS partitions:

/^arn:aws(?:-us-gov|-cn)?:(?:bedrock|sagemaker):([^:]+):([^:]*):(?:([^/]+)\/([\w.\-:]+)|([^/]+))$/

This allows:

• arn:aws:bedrock:... (commercial)
• arn:aws-us-gov:bedrock:... (GovCloud)
• arn:aws-cn:bedrock:... (China)

2. Add Model Capability Options for Custom ARNs (webview-ui/src/components/settings/providers/BedrockCustomArn.tsx)

Add UI controls to let users configure model capabilities when using a custom ARN:

• Enable Reasoning checkbox - allows users to enable/disable reasoning (thinking) for their custom ARN model
• This would set a new provider setting that the ThinkingBudget component can use to determine if reasoning options should be shown

This approach gives users full control over their custom ARN configuration rather than trying to detect or restrict capabilities.

Files to Modify:

• webview-ui/src/utils/validate.ts - Update ARN validation regex
• webview-ui/src/components/settings/providers/BedrockCustomArn.tsx - Add model capability options
• packages/types/src/provider-settings.ts - Add new setting for custom ARN model capabilities (if needed)
• Tests for the above changes

Please mention @roomote in a comment saying that you approve this plan, and I'll proceed with the implementation.

[mrubens]

@roomote why not just get rid of the regex? To @wisestmumbler's point the user is already pretty advanced if they're trying to enter an ARN.

[roomote]

Thanks for the feedback @mrubens. I agree - removing the regex validation entirely makes sense for custom ARN users since they are advanced users who know what they are doing. I will explore implementing this simpler approach and open a PR shortly.

[roomote]

Opened a PR with my attempt at addressing this: #10110

The change removes the strict regex validation entirely as suggested. Users entering custom ARNs are now trusted to provide valid ARNs without restriction. The region mismatch warning is preserved as a helpful hint.

Feedback welcome!