errors changedapi/errors
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3131* 529 - `overloaded_error`: The API is temporarily overloaded.
3232
3333 <Warning>
34 529 errors can occur when the API experiences high traffic across all users.
34 A 529 error can occur when the API experiences high traffic across all users.
3535
36 In rare cases, if your organization has a sharp increase in usage, you might see 429 errors because of acceleration limits on the API. To avoid hitting acceleration limits, ramp up your traffic gradually and maintain consistent usage patterns.
36 In rare cases, if your organization has a sharp increase in usage, you might see 429 errors because of acceleration limits on the API. To avoid hitting acceleration limits, increase your traffic gradually and maintain consistent usage patterns.
3737 </Warning>
3838
3939The official SDK automatically retries transient failures (such as connection errors, rate limits, and 5xx server errors) with exponential backoff, twice by default, honoring the `retry-after` header when present. The SDK client accepts `max_retries` (typescript, java, php: `maxRetries`; csharp: `MaxRetries`; go: `option.WithMaxRetries`) to configure or disable this behavior.
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260260
261261Avoid setting a large `max_tokens` value without using the [streaming Messages API](https://platform.claude.com/docs/en/build-with-claude/streaming) or [Message Batches API](https://platform.claude.com/docs/en/api/messages/batches/create):
262262
263* Some networks may drop idle connections after a variable period of time, which can cause the request to fail or time out without receiving a response from Anthropic.
263* Some networks might drop idle connections after a variable period of time, which can cause the request to fail or time out without receiving a response from Anthropic.
264264* Networks differ in reliability. The [Message Batches API](https://platform.claude.com/docs/en/api/messages/batches/create) can help you manage the risk of network issues by allowing you to poll for results rather than requiring an uninterrupted network connection.
265265
266266If you are building a direct API integration, setting a [TCP socket keep-alive](https://tldp.org/HOWTO/TCP-Keepalive-HOWTO/programming.html) can reduce the impact of idle connection timeouts on some networks.
267267
268The [SDKs](https://platform.claude.com/docs/en/cli-sdks-libraries/overview) validate that your non-streaming Messages API requests are not expected to exceed a 10-minute timeout. They also set a socket option for TCP keep-alive.
268The [Claude SDK](https://platform.claude.com/docs/en/cli-sdks-libraries/overview) validates that your non-streaming Messages API requests are not expected to exceed a 10-minute timeout. It also sets a socket option for TCP keep-alive.
269269
270270If you don't need to process events incrementally, the SDK can consume the stream for you and return the complete `Message` object, identical to what a non-streaming call returns:
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422422 ```
423423</CodeGroup>
424424
425See [Streaming Messages](https://platform.claude.com/docs/en/build-with-claude/streaming#get-the-final-message-without-handling-events) for more details.
425See [Streaming messages](https://platform.claude.com/docs/en/build-with-claude/streaming#get-the-final-message-without-handling-events) for more details.
426426
427427## Common validation errors
428428
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450450`thinking` or `redacted_thinking` blocks in the latest assistant message cannot be modified. These blocks must remain as they were in the original response.
451451```
452452
453With tool use, every `thinking` and `redacted_thinking` block from the assistant turn must be passed back exactly as received, including blocks whose `thinking` field is empty. Pass thinking blocks back unchanged, and if your application filters content blocks by type before resending, include both `thinking` and `redacted_thinking`. See [Troubleshooting thinking](https://platform.claude.com/docs/en/build-with-claude/thinking-troubleshooting#error-thinking-blocks-modified), [Preserving thinking blocks](https://platform.claude.com/docs/en/build-with-claude/thinking#preserving-thinking-blocks), and [Preserved thinking](https://platform.claude.com/docs/en/build-with-claude/thinking#preserved-thinking).
453With tool use, every `thinking` and `redacted_thinking` block from the assistant turn must be passed back exactly as received, including blocks whose `thinking` field is empty. Pass thinking blocks back unchanged, and if your application filters content blocks by type before resending, include both `thinking` and `redacted_thinking`. See the [fix for modified thinking blocks](https://platform.claude.com/docs/en/build-with-claude/thinking-troubleshooting#error-thinking-blocks-modified) in Troubleshooting thinking, and also [Preserving thinking blocks](https://platform.claude.com/docs/en/build-with-claude/thinking#preserving-thinking-blocks) and [Preserved thinking](https://platform.claude.com/docs/en/build-with-claude/thinking#preserved-thinking).
454454
455455### Extended thinking not supported
456456
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460460"thinking.type.enabled" is not supported for this model. Use "thinking.type.adaptive" and "output_config.effort" to control thinking behavior.
461461```
462462
463Use [adaptive thinking](https://platform.claude.com/docs/en/build-with-claude/thinking) instead. [Migrating to adaptive thinking](https://platform.claude.com/docs/en/build-with-claude/extended-thinking#migrating-to-adaptive-thinking) shows the parameter mapping, and [Troubleshooting thinking](https://platform.claude.com/docs/en/build-with-claude/thinking-troubleshooting#error-thinking-type-enabled) covers the symptom-first fix.
463Use [adaptive thinking](https://platform.claude.com/docs/en/build-with-claude/thinking) instead. [Migrating to adaptive thinking](https://platform.claude.com/docs/en/build-with-claude/extended-thinking#migrating-to-adaptive-thinking) shows the parameter mapping, and Troubleshooting thinking covers the [symptom-first fix for the extended thinking error](https://platform.claude.com/docs/en/build-with-claude/thinking-troubleshooting#error-thinking-type-enabled).
464464
465465### Adaptive thinking not supported
466466
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470470adaptive thinking is not supported on this model
471471```
472472
473Use `thinking: {"type": "enabled", "budget_tokens": N}` on these models; see [Extended thinking](https://platform.claude.com/docs/en/build-with-claude/extended-thinking) for the configuration and [Troubleshooting thinking](https://platform.claude.com/docs/en/build-with-claude/thinking-troubleshooting#error-thinking-type-adaptive) for the symptom-first fix.
473Use `thinking: {"type": "enabled", "budget_tokens": N}` on these models; see [Extended thinking](https://platform.claude.com/docs/en/build-with-claude/extended-thinking) for the configuration and the [symptom-first fix for the adaptive thinking error](https://platform.claude.com/docs/en/build-with-claude/thinking-troubleshooting#error-thinking-type-adaptive) in Troubleshooting thinking.
474474
475475### Thinking cannot be disabled
476476
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506506
507507Claude Haiku 5.5 accepts `thinking: {"type": "disabled"}` and holds it to the same two effort limits that apply to `between_tools`: at `xhigh` or `max` effort, or with a per-message `output_config.effort` that differs from the level in effect, the request returns a 400 `invalid_request_error` with the matching message shown earlier.
508508
509In both messages, "enable thinking" means adaptive thinking: omit the `thinking` field or send `thinking: {"type": "adaptive"}`. Claude Sonnet 5.5 and Claude Haiku 5.5 reject `"enabled"` with a 400 error. To vary effort per turn, use adaptive thinking.
509In both messages, "enable thinking" means adaptive thinking: omit the `thinking` field or send `thinking: {"type": "adaptive"}`. Claude Sonnet 5.5 and Claude Haiku 5.5 reject `"enabled"` with a 400 error. To vary effort for each turn, use adaptive thinking.
510510
511511Sending `thinking: {"type": "between_tools"}` to any model other than Claude Sonnet 5.5 returns a 400 `invalid_request_error`:
512512
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514514"thinking.type.between_tools" is not supported for this model.
515515```
516516
517For the fixes, see [Troubleshooting thinking](https://platform.claude.com/docs/en/build-with-claude/thinking-troubleshooting#error-thinking-type-between-tools), which covers the `between_tools` and effort errors.
517For the fixes, see the [`between_tools` and effort errors](https://platform.claude.com/docs/en/build-with-claude/thinking-troubleshooting#error-thinking-type-between-tools) in Troubleshooting thinking.
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519Omit the `thinking` parameter and the request runs with adaptive thinking. To keep thinking content out of responses without turning thinking off, set `display: "omitted"` on the thinking configuration. See [Troubleshooting thinking](https://platform.claude.com/docs/en/build-with-claude/thinking-troubleshooting#error-thinking-type-disabled).
519Omit the `thinking` parameter and the request runs with adaptive thinking. To keep thinking content out of responses without turning thinking off, set `display: "omitted"` on the thinking configuration. See the [fix for the disabled thinking error](https://platform.claude.com/docs/en/build-with-claude/thinking-troubleshooting#error-thinking-type-disabled) in Troubleshooting thinking.
520520
521521### Forced tool use not supported
522522
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546546messages.{i}.content.{j}: Invalid `signature` in `thinking` block. The block is bound to a different conversation. Remove the block, or set `thinking.block_binding.prefix_mismatch_behavior` to "drop_block".
547547```
548548
549Without the `thinking-binding-controls-2026-08-01` beta header the message also names that header. Keep the conversation history append-only, or send the beta header with `prefix_mismatch_behavior: "drop_block"` to drop the block and continue. On Claude Sonnet 5.5 and Claude Haiku 5.5, `block_binding` works only with `thinking: {"type": "adaptive"}`. With `between_tools` on Claude Sonnet 5.5, or `thinking: {"type": "disabled"}` on Claude Haiku 5.5, keep the history append-only, or strip the thinking blocks from the edited turn on. A block from a model the target model can't read is dropped rather than rejected. See [Keeping the prefix unchanged](https://platform.claude.com/docs/en/build-with-claude/preserved-thinking#prefix-check) and [Troubleshooting thinking](https://platform.claude.com/docs/en/build-with-claude/thinking-troubleshooting#error-thinking-block-signature).
549Without the `thinking-binding-controls-2026-08-01` beta header, the message also names that header. Keep the conversation history append-only, or send the beta header with `prefix_mismatch_behavior: "drop_block"` to drop the block and continue. On Claude Sonnet 5.5 and Claude Haiku 5.5, `block_binding` works only with `thinking: {"type": "adaptive"}`. With `between_tools` on Claude Sonnet 5.5, or `thinking: {"type": "disabled"}` on Claude Haiku 5.5, keep the history append-only, or strip the thinking blocks from the edited turn on. A block from a model the target model can't read is dropped rather than rejected. See [Keeping the prefix unchanged](https://platform.claude.com/docs/en/build-with-claude/preserved-thinking#prefix-check) and the [fix for an invalid thinking block signature](https://platform.claude.com/docs/en/build-with-claude/thinking-troubleshooting#error-thinking-block-signature) in Troubleshooting thinking.
550550
551551Sending `thinking.block_binding` without the `thinking-binding-controls-2026-08-01` [beta header](https://platform.claude.com/docs/en/api/beta-headers) returns a 400 `invalid_request_error` whose message ends in:
552552
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558558
559559### Outbound web identity federation disabled (Claude Platform on AWS)
560560
561If every request to [Claude Platform on AWS](https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws) returns `"Outbound web identity federation is disabled for your account"`, run `aws iam enable-outbound-web-identity-federation` once per AWS account. See [Enable outbound web identity federation](https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws#enable-outbound-web-identity-federation) for details.
561If every request to [Claude Platform on AWS](https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws) returns `"Outbound web identity federation is disabled for your account"`, run `aws iam enable-outbound-web-identity-federation` once for each AWS account. See [Enable outbound web identity federation](https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws#enable-outbound-web-identity-federation) for details.
562562
563563## Next steps
564564
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