Claude API vs OpenRouter

Claude API

Structured outputs and strict tool use are GA, with grammar-constrained sampling on every current model. Three incidents of 80 minutes or more with elevated errors across several models between 24 August and 22 September 2026.

OpenRouter

Public OpenAPI document, llms.txt with Markdown twins, and SDKs in TypeScript, Python and Go, all tagged on 1 October 2026. No machine payment. USDC top-ups go to a prepaid balance.

Claude API

1. Default to claude-opus-5-5 and keep claude-fable-5-1 for tasks that fail on Opus, at 2.5 times the price
2. Don't send tool_choice any or tool to the 5.x models. Use auto with strict: true on the tool
3. Put cache_control on the system prompt and tool list. Reads cost 0.05x input on Opus 5.5
4. Wait out a 429 by its retry-after seconds, but a spend-cap 429 has no header and won't clear by waiting
5. Move off claude-sonnet-4-5-20250929 before 2026-11-30. Retired ids fail, they don't redirect

OpenRouter

1. Set provider.data_collection: "deny" or provider.zdr: true when the prompt holds anything private
2. Pass a models list so a failed provider falls through to the next one
3. Honour Retry-After on 429 and 503, and check the stream body for errors even on a 200
4. Set max_price so a routed request can't land on an expensive provider
5. Free models allow 50 requests a day until $10 of credit has been bought. Check GET /api/v1/key for what's left