Model board / Claude Sonnet 5.5

Verified 2026-10-01 against the pages listed below. Prices are USD per 1M tokens, list rate — no committed-use, enterprise or volume discount.

released 2026-09-28 at Sonnet 5's price. 1h cache write $4.00

full 1M window at standard rates; 128K max output per request, 300K on the Batch API with a beta header

read 0.1x input; 5m write 1.25x, 1h write 2x; caches from 512 tokens, half Sonnet 5's 1,024

Watch out

Not a drop-in swap for Sonnet 5 code: forced tool use (tool_choice any or tool) returns 400; thinking cannot be switched off — the lowest setting, between_tools, only drops the up-front pass; text between tool calls now arrives in thinking blocks; and on the Claude API the earlier computer_20251124 tool is refused

What we would use it for

Anthropic's balance of speed and capability, at the price Sonnet 5 set

What this has cost, week by week

Output price at each refresh since 2026-10-01. A vendor change is the provider changing its price. Our correction means this board changed what it prints and the provider's charge did not move — the two are never merged, because publishing the second as the first would be a price rise that never happened.

Nothing has moved since we started tracking it.

Where these numbers came from

• https://platform.claude.com/docs/en/about-claude/pricing
• https://platform.claude.com/docs/en/about-claude/models/overview
• https://platform.claude.com/docs/en/models/sonnet-5-5/overview
• https://platform.claude.com/docs/en/build-with-claude/prompt-caching
• https://platform.claude.com/docs/en/release-notes/overview

No number on this page was written that was not read from one of those pages on 2026-10-01. If one is wrong, send us the source URL and it is corrected in the next weekly refresh, with a changelog line saying what was wrong — contact@naderu.com.

Jobs this is one of our picks for

• Content writing — Drafting and rewriting to a house style (content-writing)
• Agentic coding — Long tool-use loops over whole repos (agentic-coding)
• RAG and grounded answers — Answers built on passages you retrieved (rag-grounded-answers)

Discussed in Naderu Weekly

• Same price, new rules — 2026-10-01

The rest of the board

This row sits alongside 66 others on the model board, refreshed every week. The same data as JSON, and the terms for using it, are at /board-data.