not connecting through open router

➜ ~ export ANTHROPIC_AUTH_TOKEN="sk-or-v1-"
➜ ~ export ANTHROPIC_BASE_URL="https://openrouter.ai/api/v1"
➜ ~ export ANTHROPIC_MODEL="openai/gpt-oss-20b"

➜ ~ claude --model openai/gpt-oss-20b

╭────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ │
│ Do you trust the files in this folder? │
│ │
│ /home/o │
│ │
│ Claude Code may read files in this folder. Reading untrusted files may lead Claude Code to behave in unexpected ways. │
│ │
│ With your permission Claude Code may execute files in this folder. Executing untrusted code is unsafe. │
│ │
│ https://docs.anthropic.com/s/claude-code-security │
│ │
│ ❯ 1. Yes, proceed │
│ 2. No, exit │
│ │
╰────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯
Enter to confirm · Esc to exit
╭───────────────────────────────────────────────────╮
│ ✻ Welcome to Claude Code! │
│ │
│ /help for help, /status for your current setup │
│ │
│ cwd: /home/o │
│ │
│ ─────────────────────────────────────────────── │
│ │
│ Overrides (via env): │
│ │
│ • API Base URL: https://openrouter.ai/api/v1 │
╰───────────────────────────────────────────────────╯

> hi
⎿  API Error: 405 status code (no body)

Reproduce the issue with the shown ANTHROPIC_AUTH_TOKEN, ANTHROPIC_BASE_URL, ANTHROPIC_MODEL, and claude command, then inspect the request path and method used for the configured API base URL. Compare that request with OpenRouter's compatibility requirements. Done means the example connection no longer returns HTTP 405 and the relevant behavior is covered by a regression check.

Written by the indexing model from the issue text.