Claude API vs Beam 1.0

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.

Beam 1.0

The Reflection API is OpenAI-compatible, with an OpenAPI document, strict structured outputs and tool calls, and error codes that say when to retry, and the weights are Apache-2.0. It is a free public beta with unpublished daily limits and no per-token price, reasoning can't be turned off, and three API incidents were posted between 14 and 16 October 2026.

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

Beam 1.0

1. Send reasoning_effort low or medium for short tasks. The default is max, and none or minimal return 400 unsupported_value
2. Return every assistant message with its reasoning_content unchanged. If a turn comes back without it, start a new conversation, since later requests fail with missing_required_parameter
3. Don't rely on stop or seed. Both are accepted and ignored, so truncate output in your own code
4. Honour x-should-retry: false on a 429. It means a daily limit is spent and Retry-After counts to 00:00 UTC
5. Set max_completion_tokens yourself on long prompts. The default budget isn't reduced to fit the prompt and includes reasoning tokens