Anthropic API 2026-10-07

Code written for Claude Haiku 4.5 can break on Claude Haiku 5.5. Manual extended thinking (`budget_tokens`), the sampling parameters `temperature`, `top_p`, and `top_k`, and assistant message prefill can each return a 400 error. `computer_20250124` also returns a 400 error: use the `computer_toolset_20260801` toolset on the Claude API and Google Cloud, or `computer_20251124` on Amazon Bedrock. A request that sends thinking blocks back after a change to `system`, `tools`, or earlier turns can also return a 400 error. Adaptive thinking is on by default, so a response can begin with `thinking` blocks, and their text is omitted unless you set `thinking.display` to `"summarized"`. The same text also counts as more tokens. See the migration guide for each change. For model-specific prompting patterns, see Prompting Claude Haiku 5.5.

We've launched **Claude Haiku 5.5** (`claude-haiku-5-5`), our most capable model tuned for high-volume and latency-sensitive work. It has a 1M token context window, 128k max output tokens, and adaptive thinking with the effort parameter. It's available on the Claude API, Claude in Amazon Bedrock, Claude Platform on AWS, Claude on Google Cloud, and Claude in Microsoft Foundry. See What's new in Claude Haiku 5.5.

We've lowered the price of prompt cache reads on Claude Sonnet 5.5 from $0.20 USD to $0.10 USD per million tokens: 0.05x the base input price instead of 0.1x. Cache writes and all other prices are unchanged. See Prompt caching pricing.

The Python and TypeScript SDKs now include classes, in beta, for the browser use tool and the computer use tool. You subclass one and write one method per tool against your own browser or desktop automation. The SDK runs the tool loop, the URL and file policies you set for the browser, and your approval callback. See Browser and computer use with the SDK toolsets.

Claude Max and Team plans now include monthly API credits. To learn how to claim them, see API credits for Max and Team plans.

In Claude Managed Agents, a cloud environment with `limited` networking now also applies its `allowed_hosts` to the `web_search` and `web_fetch` tools. A `web_fetch` call for a URL on a host that `allowed_hosts` does not match returns a `url_not_allowed` error result to the agent. `web_search` omits results from such hosts. When `allowed_hosts` lists no hosts, neither tool returns a page or a search result. `allow_package_managers` and `allow_mcp_servers` add no hosts for these tools. To let the tools reach a host, add it to `allowed_hosts`, which also opens it to the sandbox. `unrestricted` networking and self-hosted environments do not limit these tools. See Environment networking.

In Claude Managed Agents, the `web_fetch` tool now fetches only URLs that have already appeared in the session, for example in the text of a user message, in a `web_search` result, or in a page that `web_fetch` returned earlier. This reduces the risk of data exfiltration. A URL that appears only in Claude's own output, the agent's system prompt, an attached document, or the output of a tool such as `bash`, `read`, or an MCP tool does not count: a `web_fetch` call for it returns a `url_not_in_prior_context` error result to the agent. To let the agent fetch a URL, send it in the text of a `user.message` event.

With `limited` networking, creating a session fails with a 400 error when an enabled web tool's `allowed_domains` has an entry not within `allowed_hosts`. So does a session update that adds such an entry. An `allowed_hosts` entry matches one exact host unless it starts with `*.`, so `docs.example.com` is not within `["example.com"]`. To fix the error, add the host to `allowed_hosts` or remove the entry from `allowed_domains`. See Restrict web search and web fetch domains.