feat: Claude Code provider — AWS Bedrock support

[dafzthomas]

Summary

This issue proposes adding AWS Bedrock as an auth path for Claude Code in T3 Code, as a scoped contribution on top of the Claude Code provider work tracked in #991.

This is also related to #759 (AWS Bedrock feature request). A contributor on that issue noted:

When Claude Code support lands this should be covered fully, as Claude Code can natively support Bedrock.

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Problem

Many teams and enterprises access Claude via AWS Bedrock rather than a direct Anthropic subscription:

• AWS billing and IAM is the source of truth
• Direct Anthropic API keys are not permitted
• Credentials come from AWS credential chains (instance roles, SSO, named profiles)

Claude Code already supports Bedrock natively via CLAUDE_CODE_USE_BEDROCK=1 — T3 Code just needs to surface the config and pass it through when spawning the claude subprocess.

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What's already done (PR #1018)

The frontend scaffolding is complete:

• Contracts: claudeCode in ProviderKind, ClaudeCodeProviderStartOptions, Claude model catalog
• Settings UI: "Claude Code" section with Bedrock toggle, AWS region/profile fields, per-model ARN override fields (Haiku/Sonnet/Opus), reset button
• Model picker: "Claude Code" and "Claude Code Bedrock" show as "Coming soon" — blocked until the server adapter exists

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What still needs to be built (server-side)

This is the part that requires team ownership. A ClaudeCodeAdapter needs to be added to apps/server/src/provider/:

1. Register claudeCode in ProviderAdapterRegistry alongside the existing CodexAdapter
2. Spawn claude app-server as a subprocess (analogous to how CodexAdapter spawns codex)
3. Set env vars from ClaudeCodeProviderStartOptions:
   • CLAUDE_CODE_USE_BEDROCK=1
   • AWS_REGION from awsRegion
   • AWS_PROFILE from awsProfile (optional)
   • Model ARN overrides via Claude Code's settings.json modelOverrides field
4. Wire subprocess stdin/stdout to the existing provider session protocol
5. Handle session lifecycle (start, stop, interrupt) consistently with CodexAdapter

Once the adapter exists, the picker gating (currently hardcoded to false) can be switched to settings.claudeCodeUseBedrock.

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Notes on Bedrock + Claude Code

• Set CLAUDE_CODE_USE_BEDROCK=1
• Standard AWS credential chain is used automatically (instance roles, SSO, named profiles)
• AWS_PROFILE overrides the active profile
• No ARNs required for standard Claude models — ARN fields are optional overrides for inference profiles
• modelOverrides in Claude Code's settings.json maps model slugs to inference profile ARNs

There are no known ToS restrictions on using Bedrock through a third-party GUI — Bedrock is a standard AWS service, billing flows through AWS, and Anthropic's usage policies apply at the API level.

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Draft PR

#1018 — frontend scaffolding only, explicitly excludes the server adapter.