What this read moved
51–69 of 69This capture is too large to show at once. Changes 51-69 of 69 are below, significant first; the rest are on the following screens.
build-with-claude/files Changed · +2 / -0 lines
from line 940
940940 A file is downloadable only when its metadata shows `"downloadable": true`, which is the case for files created by skills or the code execution tool. Downloading a file you uploaded returns a 400 error.
941941</Note>
942942
943On the Claude API, supported image and video files that Claude produces with the code execution tool, including files created by skills, carry signed C2PA Content Credentials when you download them. See [Content Credentials on generated files](https://platform.claude.com/docs/en/agents-and-tools/tool-use/code-execution-tool#content-credentials-on-generated-files) for what the credential contains and how to verify it.
944
943945## File storage and limits
944946
945947### Storage limits
build-with-claude/handling-stop-reasons Changed · +1 / -1 lines
from line 1915
19151915
19161916On a refusal, the `stop_details` object identifies the policy category that triggered it. The categories and the full refusal response shape are covered on [Refusals and fallback](https://platform.claude.com/docs/en/build-with-claude/refusals-and-fallback#refusal-response). `stop_details` is `null` for all stop reasons other than `refusal`.
19171917
1918A refused request on Claude Fable 5 or Claude Opus 5 can usually be served by retrying on another Claude model, and [Refusals and fallback](https://platform.claude.com/docs/en/build-with-claude/refusals-and-fallback) shows how to set up that retry, server-side or in your client. [Fallback credit](https://platform.claude.com/docs/en/build-with-claude/fallback-credit) covers how to avoid paying the prompt-cache cost twice when you build the retry yourself.
1918A refused request on Claude Fable 5.1, Claude Fable 5, or Claude Opus 5 can usually be served by retrying on another Claude model. [Refusals and fallback](https://platform.claude.com/docs/en/build-with-claude/refusals-and-fallback) shows how to set up that retry, server-side or in your client. If you build the retry yourself from Claude Fable 5.1, Claude Fable 5, or Claude Opus 5, [fallback credit](https://platform.claude.com/docs/en/build-with-claude/fallback-credit) covers how to avoid paying the prompt-cache cost twice.
19191919
19201920### model\_context\_window\_exceeded
19211921
build-with-claude/overview Changed · +1 / -1 lines
from line 109
109109| ------------------------------------------------------------------------ | --------------------------------------------------------------------------------------------------------------------------------- | ---------------- | --------------------------------------------------------------------- |
110110| [Files API](https://platform.claude.com/docs/en/build-with-claude/files) | Upload and manage files to use with Claude without re-uploading content with each request. Supports PDFs, images, and text files. | Not ZDR eligible | <PlatformAvailability claudeApi claudePlatformAwsBeta azureAiBeta />† |
111111
112\* **Structured outputs:** Your prompts and Claude's outputs are not stored. Only JSON schemas are cached, for up to 24 hours since last use. **Web search and web fetch:** ZDR-eligible except when [dynamic filtering](https://platform.claude.com/docs/en/agents-and-tools/tool-use/web-search-tool#dynamic-filtering) is enabled. **Fallback credit and server-side fallback:** The features retain no message content, but both handle refusals from Claude Fable 5, which [is not available under ZDR](https://platform.claude.com/docs/en/manage-claude/api-and-data-retention#model-specific-data-retention-requirements). See [ZDR details](https://platform.claude.com/docs/en/manage-claude/api-and-data-retention#feature-eligibility).
112\* **Structured outputs:** Your prompts and Claude's outputs are not stored. Only JSON schemas are cached, for up to 24 hours since last use. **Web search and web fetch:** ZDR-eligible except when [dynamic filtering](https://platform.claude.com/docs/en/agents-and-tools/tool-use/web-search-tool#dynamic-filtering) is enabled. **Fallback credit and server-side fallback:** The features retain no message content, but they handle refusals from the Claude Fable models, which [are not available under ZDR](https://platform.claude.com/docs/en/manage-claude/api-and-data-retention#model-specific-data-retention-requirements). See [ZDR details](https://platform.claude.com/docs/en/manage-claude/api-and-data-retention#feature-eligibility).
113113
114114† On Microsoft Foundry, feature availability differs by [hosting option](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry#hosting-options). These features are available on Hosted on Anthropic deployments, and not on Hosted on Azure deployments.
115115
build-with-claude/streaming Changed · +2 / -2 lines
from line 297
297297
298298Each stream uses the following event flow:
299299
3001. `message_start`: contains a `Message` object with empty `content`.
3001. `message_start`: contains a `Message` object with empty `content`. Under the [`thinking-binding-controls-2026-08-01`](https://platform.claude.com/docs/en/build-with-claude/thinking#preserved-thinking-controls) beta header, this `Message` object also carries the `input_transformations` array. After a mid-stream [server-side fallback](https://platform.claude.com/docs/en/build-with-claude/refusals-and-fallback#server-side-fallback), the final `message_delta` event carries the array again with the serving model's entries.
3013012. A series of content blocks, each of which has a `content_block_start`, one or more `content_block_delta` events, and a `content_block_stop` event. Each content block has an `index` that corresponds to its index in the final Message `content` array. One exception: during [server-side fallback](https://platform.claude.com/docs/en/build-with-claude/refusals-and-fallback#server-side-fallback) responses, a `fallback` content block arrives at each model boundary as a `content_block_start` and `content_block_stop` pair with no deltas in between.
3023023. One or more `message_delta` events, indicating top-level changes to the final `Message` object.
3033034. A final `message_stop` event.
from line 357
357357
358358For thinking content, a special `signature_delta` event is sent just before the `content_block_stop` event. This signature is used to verify the integrity of the thinking block.
359359
360When `display: "omitted"` is set on the thinking configuration, no `thinking_delta` events are sent. The thinking block opens, receives a single `signature_delta`, and closes. See [Controlling thinking display](https://platform.claude.com/docs/en/build-with-claude/thinking#controlling-thinking-display).
360When `display: "omitted"` is set on the thinking configuration, no `thinking_delta` events are sent. The thinking block opens, receives a single `signature_delta`, and closes. With `display: "updates"` (beta), reasoning blocks stream the same way, and only the [progress updates](https://platform.claude.com/docs/en/build-with-claude/thinking#progress-updates) that some models write between tool calls stream `thinking_delta` events. See [Controlling thinking display](https://platform.claude.com/docs/en/build-with-claude/thinking#controlling-thinking-display).
361361
362362A typical thinking delta looks like:
363363
build-with-claude/structured-outputs Changed · +1 / -1 lines
from line 6
66
77## Compatibility
88- [ZDR](https://platform.claude.com/docs/en/manage-claude/api-and-data-retention): eligible (excludes [Covered Models](https://platform.claude.com/docs/en/manage-claude/api-and-data-retention#model-specific-data-retention-requirements))
9- Supported models: `claude-fable-5`, `claude-mythos-5`, `claude-mythos-preview`, `claude-opus-5`, `claude-opus-4-8`, `claude-opus-4-7`, `claude-opus-4-6`, `claude-sonnet-5`, `claude-sonnet-4-6`, `claude-sonnet-4-5-20250929`, `claude-opus-4-5-20251101`, `claude-haiku-4-5-20251001`
9- Supported models: `claude-fable-5-1`, `claude-mythos-5-1`, `claude-fable-5`, `claude-mythos-5`, `claude-mythos-preview`, `claude-opus-5`, `claude-opus-4-8`, `claude-opus-4-7`, `claude-opus-4-6`, `claude-sonnet-5`, `claude-sonnet-4-6`, `claude-sonnet-4-5-20250929`, `claude-opus-4-5-20251101`, `claude-haiku-4-5-20251001`
1010- Platforms: Claude API, Claude Platform on AWS, Amazon Bedrock [1], Google Cloud, Microsoft Foundry
11111. On Amazon Bedrock, structured outputs are available for Claude Opus 4.6, Claude Sonnet 4.6, Claude Sonnet 4.5, Claude Opus 4.5, and Claude Haiku 4.5.
1212
build-with-claude/working-with-messages Changed · +1 / -1 lines
from line 323
323323
324324### System role in messages
325325
326On Claude Fable 5, [Claude Mythos 5](https://anthropic.com/glasswing), Claude Opus 4.8, and Claude Opus 5, you can include messages with `"role": "system"` after a user turn (subject to [placement rules](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages#limitations)) to add a new system instruction partway through a conversation. A `system` message cannot be the first entry in `messages`; use the top-level `system` field for instructions that apply from the start.
326On Claude Fable 5.1, [Claude Mythos 5.1](https://anthropic.com/glasswing), Claude Fable 5, [Claude Mythos 5](https://anthropic.com/glasswing), Claude Opus 4.8, and Claude Opus 5, you can include messages with `"role": "system"` after a user turn (subject to [placement rules](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages#limitations)) to add a new system instruction partway through a conversation. A `system` message cannot be the first entry in `messages`. Use the top-level `system` field for instructions that apply from the start.
327327
328328A mid-conversation system message has the same authority as the top-level `system` field, but because it is appended to the end of the message history, it does not invalidate any cached prefix that came before it. Use the top-level `system` field for instructions that should apply from the very first turn, and a mid-conversation system message for instructions that only become relevant later.
329329
intro Changed · +2 / -2 lines
from line 7
77<Tip>
88 The latest generation of Claude models:
99
10 **Claude Fable 5** - Next-generation intelligence for long-running agents. Read the [Claude Fable 5 and Claude Mythos 5 announcement](https://www.anthropic.com/news/claude-fable-5-mythos-5).
10 **Claude Fable 5.1** - For demanding reasoning and long-horizon agentic work. Read the [Claude Fable 5.1 announcement](https://www.anthropic.com/claude/fable/5-1).
1111
12 **Claude Mythos 5** - Shares Claude Fable 5's capabilities without the safety classifiers. Available in limited release through [Project Glasswing](https://anthropic.com/glasswing).
12 **Claude Mythos 5.1** - Offers Claude Fable 5.1's capabilities by invitation through [Project Glasswing](https://anthropic.com/glasswing).
1313
1414 **Claude Opus 5** - For complex agentic coding and enterprise work. Read the [Claude Opus 5 announcement](https://www.anthropic.com/news/claude-opus-5).
1515
managed-agents/dreams Changed · +1 / -1 lines
from line 164
164164 ```
165165</CodeGroup>
166166
167Dreaming inputs include the pre-existing memory store and an array of sessions. The selected model runs the dreaming pipeline; during the research preview `claude-opus-5`, `claude-fable-5`, `claude-opus-4-8`, `claude-opus-4-7`, `claude-sonnet-5`, and `claude-sonnet-4-6` are supported. You can optionally pass `instructions` to steer the dreaming process; see [Steer with instructions](https://platform.claude.com/docs/en/managed-agents/dreams#steer-with-instructions).
167Dreaming inputs include the pre-existing memory store and an array of sessions. The selected model runs the dreaming pipeline. During the research preview, `claude-opus-5`, `claude-fable-5`, `claude-opus-4-8`, `claude-opus-4-7`, `claude-sonnet-5`, and `claude-sonnet-4-6` are supported. You can optionally pass `instructions` to steer the dreaming process. See [Steer with instructions](https://platform.claude.com/docs/en/managed-agents/dreams#steer-with-instructions).
168168
169169The response is the full `dream` resource with `status: "pending"`:
170170
managed-agents/events-and-streaming Changed · +1 / -1 lines
from line 2563
25632563### Sending system messages
25642564
25652565<Note>
2566 `system.message` is currently supported by Claude Opus 4.8, Claude Fable 5, Claude Mythos 5, and Claude Opus 5. If the agent's primary model does not support mid-conversation system injection, the event is rejected with a `model_does_not_support_mid_conversation_system` validation error; subagent models are not checked, because `system.message` lands on the primary thread only.
2566 `system.message` is supported by Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, Claude Opus 5, and Claude Opus 4.8. If the agent's primary model does not support mid-conversation system injection, the event is rejected with a `model_does_not_support_mid_conversation_system` validation error. Subagent models are not checked, because `system.message` lands on the primary thread only.
25672567</Note>
25682568
25692569Send a `system.message` event to give the agent privileged system-level context that applies to the accompanying turn and all subsequent turns. Unlike the `system` field on the agent definition (which sets the top-level system prompt), `system.message` content is appended to the session's system context as a `role: "system"` turn rather than replacing that prompt. Use it when the agent needs updated system-level guidance mid-session: a different persona, revised constraints, or context fetched at runtime that should shape the model's behavior going forward.
models/opus-4-5/overview Changed · +1 / -1 lines
from line 18
1818
1919| Model | Context | Max output | Price / MTok | Thinking | Default effort | Knowledge cutoff |
2020| :-------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------------------- | :------------- | :--------------- |
21| [Claude Fable 5](https://platform.claude.com/docs/en/models/fable-5/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jan 2026 |
21| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun 2026 |
2222| [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview) | 1M | 128K | $5 / $25 | Adaptive | `high` | May 2026 |
2323| **Claude Opus 4.5** (this model) | 200K | 64K | $5 / $25 | Extended | `high` | May 2025 |
2424| [Claude Sonnet 5](https://platform.claude.com/docs/en/models/sonnet-5/overview) | 1M | 128K | $2 / $10 | Adaptive | `high` | Jan 2026 |
models/opus-4-6/overview Changed · +1 / -1 lines
from line 18
1818
1919| Model | Context | Max output | Price / MTok | Thinking | Default effort | Knowledge cutoff |
2020| :-------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :----------------------------- | :------------- | :--------------- |
21| [Claude Fable 5](https://platform.claude.com/docs/en/models/fable-5/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jan 2026 |
21| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun 2026 |
2222| [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview) | 1M | 128K | $5 / $25 | Adaptive | `high` | May 2026 |
2323| **Claude Opus 4.6** (this model) | 1M | 128K | $5 / $25 | Adaptive (extended deprecated) | `high` | May 2025 |
2424| [Claude Sonnet 5](https://platform.claude.com/docs/en/models/sonnet-5/overview) | 1M | 128K | $2 / $10 | Adaptive | `high` | Jan 2026 |
models/opus-4-7/overview Changed · +1 / -1 lines
from line 18
1818
1919| Model | Context | Max output | Price / MTok | Thinking | Default effort | Knowledge cutoff |
2020| :-------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------------------- | :------------- | :--------------- |
21| [Claude Fable 5](https://platform.claude.com/docs/en/models/fable-5/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jan 2026 |
21| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun 2026 |
2222| [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview) | 1M | 128K | $5 / $25 | Adaptive | `high` | May 2026 |
2323| **Claude Opus 4.7** (this model) | 1M | 128K | $5 / $25 | Adaptive | `high` | Jan 2026 |
2424| [Claude Sonnet 5](https://platform.claude.com/docs/en/models/sonnet-5/overview) | 1M | 128K | $2 / $10 | Adaptive | `high` | Jan 2026 |
models/opus-4-8/overview Changed · +1 / -1 lines
from line 16
1616
1717| Model | Context | Max output | Price / MTok | Thinking | Default effort | Knowledge cutoff |
1818| :-------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------------------- | :------------- | :--------------- |
19| [Claude Fable 5](https://platform.claude.com/docs/en/models/fable-5/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jan 2026 |
19| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun 2026 |
2020| [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview) | 1M | 128K | $5 / $25 | Adaptive | `high` | May 2026 |
2121| **Claude Opus 4.8** (this model) | 1M | 128K | $5 / $25 | Adaptive | `high` | Jan 2026 |
2222| [Claude Sonnet 5](https://platform.claude.com/docs/en/models/sonnet-5/overview) | 1M | 128K | $2 / $10 | Adaptive | `high` | Jan 2026 |
models/opus-5/overview Changed · +1 / -1 lines
from line 24
2424
2525| Model | Context | Max output | Price / MTok | Latency | Thinking | Default effort | Knowledge cutoff |
2626| :-------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------- | :------------------- | :------------- | :--------------- |
27| [Claude Fable 5](https://platform.claude.com/docs/en/models/fable-5/overview) | 1M | 128K | $10 / $50 | Slower | Adaptive (always on) | `high` | Jan 2026 |
27| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Slower | Adaptive (always on) | `high` | Jun 2026 |
2828| **Claude Opus 5** (this model) | 1M | 128K | $5 / $25 | Moderate | Adaptive | `high` | May 2026 |
2929| [Claude Sonnet 5](https://platform.claude.com/docs/en/models/sonnet-5/overview) | 1M | 128K | $2 / $10 | Fast | Adaptive | `high` | Jan 2026 |
3030| [Claude Haiku 4.5](https://platform.claude.com/docs/en/models/haiku-4-5/overview) | 200K | 64K | $1 / $5 | Fastest | Extended | — | Feb 2025 |
models/sonnet-4-5/overview Changed · +1 / -1 lines
from line 18
1818
1919| Model | Context | Max output | Price / MTok | Thinking | Default effort | Knowledge cutoff |
2020| :-------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------------------- | :------------- | :--------------- |
21| [Claude Fable 5](https://platform.claude.com/docs/en/models/fable-5/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jan 2026 |
21| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun 2026 |
2222| [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview) | 1M | 128K | $5 / $25 | Adaptive | `high` | May 2026 |
2323| [Claude Sonnet 5](https://platform.claude.com/docs/en/models/sonnet-5/overview) | 1M | 128K | $2 / $10 | Adaptive | `high` | Jan 2026 |
2424| **Claude Sonnet 4.5** (this model) | 200K | 64K | $3 / $15 | Extended | — | Jan 2025 |
models/sonnet-4-6/overview Changed · +1 / -1 lines
from line 18
1818
1919| Model | Context | Max output | Price / MTok | Thinking | Default effort | Knowledge cutoff |
2020| :-------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :----------------------------- | :------------- | :--------------- |
21| [Claude Fable 5](https://platform.claude.com/docs/en/models/fable-5/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jan 2026 |
21| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Adaptive (always on) | `high` | Jun 2026 |
2222| [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview) | 1M | 128K | $5 / $25 | Adaptive | `high` | May 2026 |
2323| [Claude Sonnet 5](https://platform.claude.com/docs/en/models/sonnet-5/overview) | 1M | 128K | $2 / $10 | Adaptive | `high` | Jan 2026 |
2424| **Claude Sonnet 4.6** (this model) | 1M | 128K | $3 / $15 | Adaptive (extended deprecated) | `high` | Aug 2025 |
models/sonnet-5/overview Changed · +1 / -1 lines
from line 24
2424
2525| Model | Context | Max output | Price / MTok | Latency | Thinking | Default effort | Knowledge cutoff |
2626| :-------------------------------------------------------------------------------- | :------ | :--------- | :----------- | :------- | :------------------- | :------------- | :--------------- |
27| [Claude Fable 5](https://platform.claude.com/docs/en/models/fable-5/overview) | 1M | 128K | $10 / $50 | Slower | Adaptive (always on) | `high` | Jan 2026 |
27| [Claude Fable 5.1](https://platform.claude.com/docs/en/models/fable-5-1/overview) | 1M | 128K | $10 / $50 | Slower | Adaptive (always on) | `high` | Jun 2026 |
2828| [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview) | 1M | 128K | $5 / $25 | Moderate | Adaptive | `high` | May 2026 |
2929| **Claude Sonnet 5** (this model) | 1M | 128K | $2 / $10 | Fast | Adaptive | `high` | Jan 2026 |
3030| [Claude Haiku 4.5](https://platform.claude.com/docs/en/models/haiku-4-5/overview) | 200K | 64K | $1 / $5 | Fastest | Extended | — | Feb 2025 |
release-notes/system-prompts/overview Changed · +2 / -0 lines
from line 7
77Claude's web interface ([claude.ai](https://claude.ai)) and mobile apps use a system prompt to provide up-to-date information, such as the current date, to Claude at the start of every conversation. The system prompt also encourages certain behaviors, such as always providing code snippets in Markdown. This prompt is periodically updated to improve Claude's responses. These system prompt updates do not apply to the Claude API. Some models have multiple dated entries on their pages. Starting with the Claude 4.6 generation, each model ID is a [single fixed snapshot](https://platform.claude.com/docs/en/about-claude/models/model-ids-and-versions), so those models have one entry.
88
99<CardGroup cols={3}>
10 <Card id="claude-fable-5-1" title="Claude Fable 5.1" icon="file" href="https://platform.claude.com/docs/en/release-notes/system-prompts/claude-fable-5-1" />
11
1012 <Card id="claude-opus-5" title="Claude Opus 5" icon="file" href="https://platform.claude.com/docs/en/release-notes/system-prompts/claude-opus-5" />
1113
1214 <Card id="claude-fable-5" title="Claude Fable 5" icon="file" href="https://platform.claude.com/docs/en/release-notes/system-prompts/claude-fable-5" />
resources/overview Changed · +4 / -0 lines
from line 5
55---
66
77<CardGroup cols={3}>
8 <Card title="Claude Fable 5.1 and Mythos 5.1 System Card" icon="file" href="https://www.anthropic.com/claude-fable-5-1-mythos-5-1-system-card">
9 Detailed documentation of Claude Fable 5.1 and Claude Mythos 5.1.
10 </Card>
11
812 <Card title="Claude Opus 5 System Card" icon="file" href="https://www.anthropic.com/claude-opus-5-system-card">
913 Detailed documentation of Claude Opus 5.
1014 </Card>