I have inspected the 9router Claude provider and model configuration to identify accepted model IDs, auth requirements, and compatibility modes for Claude Code requests.

### Key Findings
- **9Router Integration**: The 9Router infrastructure is designed to act as a translation layer. It does not natively "speak" Claude Code's protocol; instead, it uses a set of `mitm` (Man-in-the-Middle) handlers and translators to normalize requests.
- **Provider Aliases**:
    - `claude` (alias `cc`): This is the primary provider identifier for official Anthropic connections.
    - `anthropic-compatible-*`: This prefix is used for third-party gateways that follow the Anthropic Messages API spec.
- **Model IDs**:
    - Accepted models are defined in `/app/open-sse/providers/registry/claude.js`.
    - Current models: `claude-fable-5`, `claude-sonnet-5`, `claude-opus-4-8`, `claude-opus-4-7`, `claude-haiku-4-5-20251001`.
- **Compatibility Requirements**:
    - **Base URL**: Set `ANTHROPIC_BASE_URL` to `http://127.0.0.1:20128/v1` (for local 9router instances).
    - **Headers**: Claude Code expects specific headers (e.g., `Anthropic-Version`, `Anthropic-Beta`) which 9router's `claude.js` provider and `prepareClaudeRequest` logic handle automatically.
    - **Authentication**: When routing via 9router, you must use the API key provided by 9router as the `x-api-key` (passed as `ANTHROPIC_AUTH_TOKEN`).
    - **Passthrough Mode**: If using a native client (like the Claude CLI), the system attempts `normalizeClaudePassthrough` to scrub beta-specific shapes (like adaptive thinking or mid-conversation system prompts) that generic Anthropic-compatible gateways may reject.

### Actions Taken
- Inspected `/app/open-sse/providers/registry/claude.js` to identify model IDs and headers.
- Investigated `/app/open-sse/translator/formats/claude.js` for compatibility logic and request preparation (including thinking block handling).
- Verified the core routing logic in `/app/open-sse/executors/base.js` and `/app/open-sse/services/provider.js`.
- Confirmed that 9router auto-manages the translation between internal formats and the Claude Messages API via the `claude` provider registration.

No files were modified; this was an inspection-only task. No issues were encountered during the investigation.