Claude API vs Fireworks AI Inference

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.

Fireworks AI Inference

Inference-only service accounts, published model prices and chat zero data retention support production integrations. Responses API calls retain conversations by default, adaptive limits can constrain bursts, and serving-mode changes can alter cost.

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 Opus 5.5, Sonnet 5.5 or Fable 5.1. 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
6. Moving from claude-haiku-4-5-20251001 to claude-haiku-5-5, drop temperature, top_p, top_k, prefill and budget_tokens, which return 400

Fireworks AI Inference

1. Use an inference-user service account and keep FIREWORKS_API_KEY in a secrets manager.
2. Use https://api.fireworks.ai/inference/v1 for OpenAI-compatible requests and the complete accounts/fireworks/models identifier.
3. Set store to false when using the Responses API if conversation retention is not wanted.
4. Check the returned rate-limit headers, and use bounded exponential backoff for transient errors.
5. Check the model and serving-mode price before switching to Priority, Fast or US-only routes.