Claude API
The Claude model API service provided by Anthropic, which allows developers to call Claude series models through interfaces for application development, billed by usage.
Core Facts
Timeline (last 90 days)
Older accounts can send the thinking-binding-controls-2026-08-01 beta header and not set prefix_mismatch_behavior, in which case failed blocks still reach the model, and the response lists thinking_mismatch_allowed in input_transformations.
The agent framework patterns listed in the documentation that break thinking block binding include: re-rendering the system prompt, editing tools mid-conversation, disabling tool use by removing tools, cutting out turns from the middle, writing your own keep-tail summary, and serializers that skip empty blocks.
Appending messages always works, and modifications to effort, max_tokens, tool_choice, metadata, and cache_control markers likewise work, and server-side compression also does not trigger the problem.
Enforcement depends on account creation time: more recently created accounts have prefix checking enabled by default and receive a 400 error; on older accounts the check still runs, but it is only actually enforced for requests that set a specific parameter.
The API performs two checks on each thinking or redacted_thinking block: the model must be able to read the block (otherwise it is silently discarded), and the content preceding the thinking block (the top-level system prompt, the tools array, and every message before that block) must have no changes whatsoever.
When an integration rewrites its own conversation history, the Claude API may return a 400 error beginning with `messages.1.content.0: Invalid \`signature\` in \`thinking\` block`, indicating that the thinking block was bound to a different conversation.
By setting block_binding.prefix_mismatch_behavior to drop_block, the request can be made to succeed, and the API will discard each failed block and all blocks after it.
Claude API credits are a prepaid balance independent of the subscription, used to deduct charges by token when calling the Claude API.
When running a workflow in n8n fails, priority should be given to checking API Key validity, account quota, and model name availability.
The Claude API adds two commands, `/claude-api build-eval` and `/claude-api hillclimb`, used respectively to generate an evaluation test set and to iteratively optimize prompts, model settings, and test harness code, with an API-first integration that does not lock you into a framework.
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All Facts (20)
The Claude API supports a Prompt Caching mechanism, where content is billed at full price on the first request, and subsequent tokens that hit the cache cost approximately 10% of the original price
80%UnverifiedAnthropic承诺所有新功能在原生Claude API上线的同一天也会同步部署到Managed Agents服务中
85%UnverifiedClaude Code SDK在Anthropic产品矩阵中连接底层Claude API与上层应用场景
80%UnverifiedBy setting block_binding.prefix_mismatch_behavior to drop_block, the request can be made to succeed, and the API will discard each failed block and all blocks after it.
50%UnverifiedWhen an integration rewrites its own conversation history, the Claude API may return a 400 error beginning with `messages.1.content.0: Invalid \`signature\` in \`thinking\` block`, indicating that the thinking block was bound to a different conversation.
50%UnverifiedThe API performs two checks on each thinking or redacted_thinking block: the model must be able to read the block (otherwise it is silently discarded), and the content preceding the thinking block (the top-level system prompt, the tools array, and every message before that block) must have no changes whatsoever.
50%UnverifiedEnforcement depends on account creation time: more recently created accounts have prefix checking enabled by default and receive a 400 error; on older accounts the check still runs, but it is only actually enforced for requests that set a specific parameter.
50%UnverifiedAppending messages always works, and modifications to effort, max_tokens, tool_choice, metadata, and cache_control markers likewise work, and server-side compression also does not trigger the problem.
50%UnverifiedThe agent framework patterns listed in the documentation that break thinking block binding include: re-rendering the system prompt, editing tools mid-conversation, disabling tool use by removing tools, cutting out turns from the middle, writing your own keep-tail summary, and serializers that skip empty blocks.
50%UnverifiedOlder accounts can send the thinking-binding-controls-2026-08-01 beta header and not set prefix_mismatch_behavior, in which case failed blocks still reach the model, and the response lists thinking_mismatch_allowed in input_transformations.
50%UnverifiedClaude API credits are a prepaid balance independent of the subscription, used to deduct charges by token when calling the Claude API.
50%UnverifiedWhen running a workflow in n8n fails, priority should be given to checking API Key validity, account quota, and model name availability.
50%UnverifiedThe Claude API adds two commands, `/claude-api build-eval` and `/claude-api hillclimb`, used respectively to generate an evaluation test set and to iteratively optimize prompts, model settings, and test harness code, with an API-first integration that does not lock you into a framework.
50%UnverifiedThe approach forces Claude to return structured JSON (containing reply, confidence, source_ids) by defining a tool answerTool and pointing tool_choice at it.
50%UnverifiedThe approach uses Next.js and the Claude API, and runs with three files.
50%Unverifiedai-newtab's architecture sends the user's browsing history to a third-party Claude API, meaning control over the handling of sensitive information shifts from the user side to the server side, and browsing history can reflect sensitive information such as health, finances, political leanings, and personal relationships.
50%UnverifiedThe $1,000 in API credits is aimed at developers, used for programmatic calls to the model interface, billed by token consumption, and typically integrated into the backend of one's own product.
50%UnverifiedTeams using the Claude API or Claude Code should prepare backup models or backup providers for important tasks to avoid single-point dependency.
50%UnverifiedThe scope of the problem covered five product lines: Claude API, Claude.ai, Claude Code, Claude Security and Claude Cowork.
50%UnverifiedTeams using the Claude API or Claude Code should add error monitoring and alerting for 4xx/5xx rejection requests in critical business processes, distinguishing "quota issues" from "network issues".
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