[BUG] Claude gateway rejects builtinBrowserEnabled in policy desktop block

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?

Claude Code (gateway server) version: 2.1.291
Claude Desktop version: 2.16120.0
Deployment: self-hosted Claude apps gateway, Bedrock, Windows clients

Config (policies[0]):
desktop:
builtinBrowserEnabled: true

Which Claude Code version first accepts builtinBrowserEnabled
(and builtinBrowserDefaultDomainPolicy / AllowedDomains / BlockedDomains)
in a gateway desktop block? Could the gateway docs list this per key?

What Should Happen?

The key is documented for Claude Desktop 3P
(claude.com/docs/third-party/claude-desktop/browser) and added in a recent
Desktop release, so the gateway should accept it in the desktop block.

Error Messages/Logs

Result at boot:
  managed.policies[0].desktop invalid:
    builtinBrowserEnabled: unknown desktop key — fix the typo, or upgrade
    the gateway if this key was added in a newer Claude Desktop release

Steps to Reproduce

# gateway.yaml — minimal repro
listen:
  host: 0.0.0.0
  port: 8080
  public_url: https://claude-gateway.internal.example.com

oidc:
  issuer: https://idp.example.com
  client_id: example-client-id
  client_secret: ${OIDC_CLIENT_SECRET}
  allowed_email_domains: [example.com]

session:
  jwt_secret: ${GATEWAY_JWT_SECRET}

store:
  postgres_url: ${GATEWAY_POSTGRES_URL}

upstreams:
  - provider: bedrock
    region: us-east-1
    auth: {}

managed:
  policies:
    - match: {}
      desktop:
        builtinBrowserEnabled: true   # <- add this line last; boot fails here

Run it with claude gateway --config gateway.yaml

Claude Model

_No response_

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.291

Platform

AWS Bedrock

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_