936 pages for error.

compaction-background Claude Developer Platform · in the page build-with-claude/compaction-background …demand#continue-from-the-summary) and [Handle a missing summary or an error](https://platform.claude.com/docs/en/build-with-claude/compaction-on-demand#when-no-summary-comes-back) apply unchanged. ##… compaction-on-demand Claude Developer Platform · in the page build-with-claude/compaction-on-demand …sages. If any remain in front of the block, the request returns a 400 error (`compaction_block_misplaced`). * Send exactly one `compaction` block on every later request. <Warning> Two mistakes in t… compaction-thinking-blocks Claude Developer Platform · in the page build-with-claude/compaction-thinking-blocks …ep, because a model that can’t read a thinking block drops it with no error. 2. Compact the older turns, and keep at least one turn that holds a thinking block. 3. Send the next request, with the bloc… compaction-threshold Claude Developer Platform · in the page build-with-claude/compaction-threshold …conversation messages.append({"role": "user", "content": "Now add error handling"}) response = client.beta.messages.create( betas=["compact-2026-01-12"], model="claude-opus-5-… context-editing Claude Developer Platform · in the page build-with-claude/context-editing …, "content": "Search for the latest developments in quantum error correction and summarize the key breakthroughs." } ], "tools": [ { "type": "web_search… context-windows Claude Developer Platform · in the page build-with-claude/context-windows …ds the model’s context window, the API returns a 400 `invalid_request_error` (“prompt is too long”) on every model. On Claude 4.5 models and newer, if input tokens plus `max_tokens` exceeds the conte… effort Claude Developer Platform · in the page build-with-claude/effort …osts. Requests that set `thinking: {"type": "disabled"}` return a 400 error at every effort level. Run an effort sweep on your own evals rather than carrying settings over from an earlier model. At `… effort-per-message Claude Developer Platform · in the page build-with-claude/effort-per-message …azon-bedrock-legacy#mid-conversation-system-messages-on-bedrock). ## Errors * Without the beta header, a per-message `output_config` returns a 400 error: `messages.N.output_config: Extra inputs are… This will automatically use the environment variable VOYAGE_API_KEY. Claude Developer Platform · in the page build-with-claude/embeddings …ors by dividing each row by its Euclidean norm. Raises a ValueError if any row has a norm of zero to prevent division by zero. """ row_norms = np.linalg.norm(v, axis=1, keepdim… extended-thinking Claude Developer Platform · in the page build-with-claude/extended-thinking …ls do not support it and reject requests that use it, returning a 400 error. * Recommended alternative: [Adaptive thinking](https://platform.claude.com/docs/en/build-with-claude/thinking-steering-a… fallback-credit Claude Developer Platform · in the page build-with-claude/fallback-credit …Google Cloud (Google managed) and Amazon Bedrock, which return a 400 error for that header. The `fallback-credit-2026-06-01` header is accepted and grants the same fields. </Step> <Step title="R… fast-mode Claude Developer Platform · in the page build-with-claude/fast-mode …al, requests to `claude-opus-4-8` with `speed: "fast"` will return an error. To continue using fast mode, migrate to Claude Opus 5.5. See [Migrating to Claude Opus 5.5 from Claude Opus 4.8](https://pl… files Claude Developer Platform · in the page build-with-claude/files …```go Go func downloadFile(client anthropic.Client, fileID string) error { resp, err := client.Files.Download(context.TODO(), fileID, anthropic.FileDownloadParams{}) if err != nil { retur… handling-stop-reasons Claude Developer Platform · in the page build-with-claude/handling-stop-reasons …ason` field is part of every successful Messages API response. Unlike errors, which indicate failures in processing your request, `stop_reason` tells you why Claude completed its response generation.… message-threads Claude Developer Platform · in the page build-with-claude/message-threads …I can no longer continue the thread, a continue request returns a 404 error. Send the full conversation again in a new create request, and continue from that response’s `id`. The SDK thread helper doe… mid-conversation-effort-example Claude Developer Platform · in the page build-with-claude/mid-conversation-effort-example …"context" "crypto/sha256" "encoding/hex" "encoding/json" "errors" "fmt" "log" "os" "os/exec" "path/filepath" "strings" "sync" "time" "github.com/anthropics/anth… mid-conversation-system-messages Claude Developer Platform · in the page build-with-claude/mid-conversation-system-messages …e`). Referencing a name that is not declared in `tools` returns a 400 error (on the Claude API, with `error.details.error_code` set to `tool_reference_unresolved`). A `tool_addition` block can instead… overview Claude Developer Platform · in the page build-with-claude/overview …ecline a request; the decline comes back as a normal response, not an error. | | ↳ [Client-side fallback](https://platform.claude.com/docs/en/build-wit… preserved-thinking Claude Developer Platform · in the page build-with-claude/preserved-thinking …odels. The API drops a block the current model can’t read, without an error, so [keep sending the full history when you switch models](https://platform.claude.com/docs/en/build-with-claude/preserved-t… change-tools-or-instructions Claude Developer Platform · in the page build-with-claude/preserved-thinking/change-tools-or-instructions …ctions-details). A system message with text or tool blocks gets a 400 error right after Claude’s turn or right before a user message. So when Claude’s turn is last, wait until the next user message is… fix-bound-to-a-different-conversation Claude Developer Platform · in the page build-with-claude/preserved-thinking/fix-bound-to-a-different-conversation …onversation description: Get a conversation going again after the 400 error that says a thinking block is bound to a different conversation, find what your code changed, and test that the change is go… prefix-checks Claude Developer Platform · in the page build-with-claude/preserved-thinking/prefix-checks …n it, what happens when a request fails it, and how to handle the 400 error and the case with no error. featureMetadata: status: stable supportedModels: - claude-fable-5-2 - claude-mythos-… Request 2 caches its request content (not the response) Claude Developer Platform · in the page build-with-claude/prompt-caching …explicit `cache_control` with a different TTL, the API returns a 400 error. * If 4 explicit block-level breakpoints already exist, the API returns a 400 error (no slots left for automatic caching). *… claude-prompting-best-practices Claude Developer Platform · in the page build-with-claude/prompt-engineering/claude-prompting-best-practices …quests with prefilled assistant messages to these models return a 400 error. Model intelligence and instruction following have advanced such that most use cases of prefill no longer require it. Earlie… prompting-claude-fable-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-fable-5 …id premature abstraction and half-finished implementations. Don't add error handling, fallbacks, or validation for scenarios that cannot happen. Trust internal code and framework guarantees. Only vali… Delivering work Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-fable-5-1 …"content": f"File not found: {path}", "is_error": True, } ) # Send the tool results as the user turn, then a fresh copy of the… Finishing work Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-fable-5-2 …ith-claude/preserved-thinking/prefix-checks#prefix-check) gets a [400 error](https://platform.claude.com/docs/en/api/errors#thinking-block-conversation-mismatch). If you resume a stored conversation a… prompting-claude-haiku-5-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-haiku-5-5 …rompt and send its thinking blocks back, the request can return a 400 error. To change instructions partway through a conversation, [put them in the newest turn](https://platform.claude.com/docs/en/bu… prompting-claude-opus-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-opus-5 …that matter: ```text wrap Only correct an earlier statement when the error would change the user's code, conclusions, or decisions. State corrections plainly and briefly, then continue the task. For… prompting-claude-opus-5-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-opus-5-5 …al model and one-page summary for a transaction or finding and fixing errors in a valuation workbook, and it catches details that are easy to miss in large inputs, such as a date in a long planning th… prompting-claude-sonnet-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-sonnet-5 …et_tokens: N}`) is not supported on Claude Sonnet 5 and returns a 400 error. It was deprecated on Claude Sonnet 4.6 and is now removed. Use adaptive thinking with the effort parameter instead. <Note>… prompting-claude-sonnet-5-5 Claude Developer Platform · in the page build-with-claude/prompt-engineering/prompting-claude-sonnet-5-5 …anges need adaptive thinking. With `between_tools`, they return a 400 error, as [Running without up-front thinking](https://platform.claude.com/docs/en/build-with-claude/prompt-engineering/prompting-c… refusals-and-fallback Claude Developer Platform · in the page build-with-claude/refusals-and-fallback …e a request. When that happens, you receive a normal response, not an error, with `stop_reason: "refusal"`. Its `stop_details.category` names the policy area (see [What a refusal looks like](https://p… search-results Claude Developer Platform · in the page build-with-claude/search-results …type="text", text="If you encounter timeout errors, first check the configuration settings. Common causes include network latency and incorrect timeout values.",… skills-guide Claude Developer Platform · in the page build-with-claude/skills-guide …alidate the cached prefix if it changes the Skill’s description. ### Error handling Handle Skill-related errors gracefully: <CodeGroup exclude="shell:cURL, shell:CLI"> <CodeGroupItem language="cU… streaming Claude Developer Platform · in the page build-with-claude/streaming …s Event streams might also include any number of `ping` events. ### Error events The API might occasionally send [errors](https://platform.claude.com/docs/en/api/errors) in the event stream. For ex… structured-outputs Claude Developer Platform · in the page build-with-claude/structured-outputs …cations. Even with careful prompting, you might encounter: * Parsing errors from invalid JSON syntax * Missing required fields * Inconsistent data types * Schema violations requiring error handling a… task-budgets Claude Developer Platform · in the page build-with-claude/task-budgets …th-claude/task-budgets#feature-support)). Smaller values return a 400 error. ## Interaction with other parameters * **`max_tokens`:** Orthogonal to task budgets. `max_tokens` is a hard per-request c… thinking Claude Developer Platform · in the page build-with-claude/thinking …each model does with each `thinking` value a request can send. A 400 error means the API rejects the request, and [Troubleshooting thinking](https://platform.claude.com/docs/en/build-with-claude/thin… thinking-tool-workflows Claude Developer Platform · in the page build-with-claude/thinking-tool-workflows …pe: "enabled"}`), `tool_choice` options that force tool use return an error. * [Check forced tool use on your model in adaptive mode](https://platform.claude.com/docs/en/build-with-claude/thinking#th… thinking-troubleshooting Claude Developer Platform · in the page build-with-claude/thinking-troubleshooting …g description: "Diagnose and fix thinking failures: configuration 400 errors, empty or missing thinking blocks, max_tokens stops, and cache misses." --- <Note> To learn how zero data retention (ZDR… token-counting Claude Developer Platform · in the page build-with-claude/token-counting …i/messages/count_tokens).) This endpoint returns an `invalid_request_error` for a few inputs that the Messages API accepts: * [Server tools](https://platform.claude.com/docs/en/agents-and-tools/tool… vision Claude Developer Platform · in the page build-with-claude/vision …es exceeding the stricter limit are rejected with an `invalid_request_error` whose message references “many-image requests” and states the current limit in pixels. To stay under the limit on all platf… vision-coordinates Claude Developer Platform · in the page build-with-claude/vision-coordinates …still be rejected when you send it. </Note> ## Turn resizing into an error with `transformations` Pre-resizing only protects your coordinates while your pipeline keeps producing the right sizes. A n… working-with-messages Claude Developer Platform · in the page build-with-claude/working-with-messages …mpling-parameters). Setting them to a non-default value returns a 400 error, and starting with `2026-10-21` any value does. Omit them from request payloads and use prompting to guide the model’s behav… API usage primer for Claude Claude Developer Platform · in the page claude_api_primer …g only, on by default; `thinking: {"type": "disabled"}` returns a 400 error, so send `thinking: {"type": "between_tools"}` to turn off up-front thinking) * Claude Haiku 5.5 (`claude-haiku-5-5`, adapti… apply Claude Developer Platform · in the page cli-sdks-libraries/cli/apply …ould also read as an agent. A path or glob that matches nothing is an error. ```markdown agents/reviewer.md --- name: Code reviewer model: claude-opus-5-5 tools: - type: agent_toolset_20260401… scripting Claude Developer Platform · in the page cli-sdks-libraries/cli/scripting …the benefits of type safety in one sentence. Type safety catches errors at compile time rather than runtime, reducing bugs, improving code clarity, enabling better tooling support, and making cod… using Claude Developer Platform · in the page cli-sdks-libraries/cli/using …| | `--format-error`, `--transform-error` | Same as `--format` and `--transform` but applied to [error responses](https://platform.claude.com/do… apple-foundation-models Claude Developer Platform · in the page cli-sdks-libraries/libraries/apple-foundation-models …est fields to send, because sending a field a model rejects is a hard error. The constants carry the right capabilities. For an ID that isn’t compiled in, declare what the model accepts (there is deli…