overview

 ### August 5, 2026
 
 * **Inference hooks** are now in beta for Claude Enterprise organizations. Point Claude at your organization's AI security server, and each governed prompt across claude.ai, Cowork, and Claude Code is held for the server's allow or deny verdict before inference proceeds. Requests are signed, failure handling is configurable, and every denial is recorded in the compliance [Activity Feed](https://platform.claude.com/docs/en/manage-claude/compliance-activity-feed). See [Inference hooks](https://platform.claude.com/docs/en/manage-claude/inference-hooks).
-* We've retired the Claude Opus 4.1 model (`claude-opus-4-1-20250805`). All requests to this model on the Claude API will now return an error. We recommend upgrading to [Claude Opus 5](https://platform.claude.com/docs/en/about-claude/models/overview#latest-models-comparison). Researchers can request ongoing access through the [External Researcher Access Program](https://support.claude.com/en/articles/9125743-what-is-the-external-researcher-access-program).
+* We've retired the Claude Opus 4.1 model (`claude-opus-4-1-20250805`). All requests to this model on the Claude API will now return an error. We recommend upgrading to [Claude Opus 5](https://platform.claude.com/docs/en/models/overview#latest-models-comparison). Researchers can request ongoing access through the [External Researcher Access Program](https://support.claude.com/en/articles/9125743-what-is-the-external-researcher-access-program).
 
 ### August 3, 2026
 

 
 ### July 24, 2026
 
-* We've launched **Claude Opus 5** (`claude-opus-5`), a step-change improvement over Claude Opus 4.8. Claude Opus 5 supports a [1M token context window](https://platform.claude.com/docs/en/build-with-claude/context-windows) (both the default and the maximum), 128k max output tokens, and [thinking](https://platform.claude.com/docs/en/build-with-claude/thinking) on by default, at $5 / $25 USD per MTok, the same pricing as Claude Opus 4.8. It's available on the Claude API, [Claude in Amazon Bedrock](https://platform.claude.com/docs/en/build-with-claude/claude-in-amazon-bedrock), [Claude Platform on AWS](https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws), [Claude on Google Cloud](https://platform.claude.com/docs/en/build-with-claude/claude-on-vertex-ai), and [Claude in Microsoft Foundry](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry). See [What's new in Claude Opus 5](https://platform.claude.com/docs/en/about-claude/models/whats-new-opus-5) for new features, behavior changes, and migration guidance, and the [models overview](https://platform.claude.com/docs/en/about-claude/models/overview) for complete specs.
-* On Claude Opus 5, disabling thinking is allowed only at effort `high` or below: `thinking: {"type": "disabled"}` with effort `xhigh` or `max` returns a 400 error, a breaking change from Claude Opus 4.8. See [What's new in Claude Opus 5](https://platform.claude.com/docs/en/about-claude/models/whats-new-opus-5#behavior-changes).
+* We've launched **Claude Opus 5** (`claude-opus-5`), a step-change improvement over Claude Opus 4.8. Claude Opus 5 supports a [1M token context window](https://platform.claude.com/docs/en/build-with-claude/context-windows) (both the default and the maximum), 128k max output tokens, and [thinking](https://platform.claude.com/docs/en/build-with-claude/thinking) on by default, at $5 / $25 USD per MTok, the same pricing as Claude Opus 4.8. It's available on the Claude API, [Claude in Amazon Bedrock](https://platform.claude.com/docs/en/build-with-claude/claude-in-amazon-bedrock), [Claude Platform on AWS](https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws), [Claude on Google Cloud](https://platform.claude.com/docs/en/build-with-claude/claude-on-vertex-ai), and [Claude in Microsoft Foundry](https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry). See [What's new in Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/whats-new-opus-5) for new features, behavior changes, and migration guidance, and the [models overview](https://platform.claude.com/docs/en/models/overview) for complete specs.
+* On Claude Opus 5, disabling thinking is allowed only at effort `high` or below: `thinking: {"type": "disabled"}` with effort `xhigh` or `max` returns a 400 error, a breaking change from Claude Opus 4.8. See [What's new in Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/whats-new-opus-5#behavior-changes).
 * [Effort](https://platform.claude.com/docs/en/build-with-claude/effort) is the primary control for steering Claude Opus 5: the model supports the full ladder (`low`, `medium`, `high`, `xhigh`, `max`), with `max` for capability-critical work.
 * Mid-conversation tool changes are now in beta on Claude Fable 5, Claude Mythos 5, Claude Opus 4.8, and Claude Opus 5: add or remove tools between turns of a conversation while preserving the prompt cache. Include the `mid-conversation-tool-changes-2026-07-01` beta header in your requests.
 * The `fallbacks` parameter now supports a `"default"` mode, which applies Anthropic's recommended fallback models by refusal category. Server-side fallback is in beta, and the `"default"` mode requires the `server-side-fallback-2026-07-01` beta header. See [Refusals and fallback](https://platform.claude.com/docs/en/build-with-claude/refusals-and-fallback).

 
 ### June 30, 2026
 
-* We've launched **Claude Sonnet 5** (`claude-sonnet-5`), the next generation of our Sonnet model family, at introductory pricing of $2 / $10 per MTok (made the standard price on August 10, 2026). Claude Sonnet 5 supports a [1M token context window](https://platform.claude.com/docs/en/build-with-claude/context-windows), 128k max output tokens, and the same set of tools and platform features as Claude Sonnet 4.6, except [Priority Tier](https://platform.claude.com/docs/en/api/service-tiers#supported-models), which is not available on Claude Sonnet 5. Three behavior changes apply when migrating: [adaptive thinking](https://platform.claude.com/docs/en/build-with-claude/thinking) is now on by default; manual extended thinking (`thinking: {type: "enabled", budget_tokens: N}`) is removed and returns a 400 error (it was deprecated on Sonnet 4.6); and setting sampling parameters (`temperature`, `top_p`, `top_k`) to non-default values returns a 400 error. Claude Sonnet 5 also uses a new tokenizer that produces approximately 30% more tokens for the same text. The exact increase depends on the content and workload shape. See [What's new in Claude Sonnet 5](https://platform.claude.com/docs/en/about-claude/models/whats-new-sonnet-5) for details and migration guidance. For behavioral differences and model-specific prompting patterns, see [Prompting Claude Sonnet 5](https://platform.claude.com/docs/en/build-with-claude/prompt-engineering/prompting-claude-sonnet-5).
+* We've launched **Claude Sonnet 5** (`claude-sonnet-5`), the next generation of our Sonnet model family, at introductory pricing of $2 / $10 per MTok (made the standard price on August 10, 2026). Claude Sonnet 5 supports a [1M token context window](https://platform.claude.com/docs/en/build-with-claude/context-windows), 128k max output tokens, and the same set of tools and platform features as Claude Sonnet 4.6, except [Priority Tier](https://platform.claude.com/docs/en/api/service-tiers#supported-models), which is not available on Claude Sonnet 5. Three behavior changes apply when migrating: [adaptive thinking](https://platform.claude.com/docs/en/build-with-claude/thinking) is now on by default; manual extended thinking (`thinking: {type: "enabled", budget_tokens: N}`) is removed and returns a 400 error (it was deprecated on Sonnet 4.6); and setting sampling parameters (`temperature`, `top_p`, `top_k`) to non-default values returns a 400 error. Claude Sonnet 5 also uses a new tokenizer that produces approximately 30% more tokens for the same text. The exact increase depends on the content and workload shape. See [What's new in Claude Sonnet 5](https://platform.claude.com/docs/en/models/sonnet-5/whats-new-sonnet-5) for details and migration guidance. For behavioral differences and model-specific prompting patterns, see [Prompting Claude Sonnet 5](https://platform.claude.com/docs/en/build-with-claude/prompt-engineering/prompting-claude-sonnet-5).
 * Claude Managed Agents session event streams now support [event deltas](https://platform.claude.com/docs/en/managed-agents/events-and-streaming#event-deltas). Opt in with the `event_deltas[]` query parameter on `GET /v1/sessions/{session_id}/events/stream`. The `event_start` and `event_delta` events preview an agent message's text as it's generated, before the complete `agent.message` event arrives.
 * [Listing sessions](https://platform.claude.com/docs/en/managed-agents/session-operations#listing-sessions) for Claude Managed Agents now supports backward pagination. `GET /v1/sessions` returns a `prev_page` cursor alongside `next_page`; pass it as the `page` parameter to return to the previous page. See [Pagination](https://platform.claude.com/docs/en/api/overview#pagination).
 * When creating a Claude Managed Agents session, you can now [override the agent's configuration for that session](https://platform.claude.com/docs/en/managed-agents/sessions#override-agent-configuration-for-a-session). Pass `agent` with `type: "agent_with_overrides"` to replace the model, system prompt, tools, MCP servers, or skills for a single session. The agent itself is unchanged.

 
 ### June 15, 2026
 
-* We've retired the Claude Sonnet 4 model (`claude-sonnet-4-20250514`) and the Claude Opus 4 model (`claude-opus-4-20250514`). All requests to these models on the Claude API will now return an error. We recommend upgrading to [Claude Sonnet 4.6](https://platform.claude.com/docs/en/about-claude/models/overview#latest-models-comparison) and [Claude Opus 4.8](https://platform.claude.com/docs/en/about-claude/models/overview#latest-models-comparison) respectively. Researchers can request ongoing access through the [External Researcher Access Program](https://support.claude.com/en/articles/9125743-what-is-the-external-researcher-access-program).
+* We've retired the Claude Sonnet 4 model (`claude-sonnet-4-20250514`) and the Claude Opus 4 model (`claude-opus-4-20250514`). All requests to these models on the Claude API will now return an error. We recommend upgrading to [Claude Sonnet 4.6](https://platform.claude.com/docs/en/models/overview#latest-models-comparison) and [Claude Opus 4.8](https://platform.claude.com/docs/en/models/overview#latest-models-comparison) respectively. Researchers can request ongoing access through the [External Researcher Access Program](https://support.claude.com/en/articles/9125743-what-is-the-external-researcher-access-program).
 
 ### June 11, 2026
 

 
 ### June 9, 2026
 
-* We've launched **Claude Fable 5** (`claude-fable-5`), our most capable widely released model, alongside **Claude Mythos 5** (`claude-mythos-5`) for Project Glasswing participants. Both models support a [1M token context window](https://platform.claude.com/docs/en/build-with-claude/context-windows) by default, 128k max output tokens, and always-on [adaptive thinking](https://platform.claude.com/docs/en/build-with-claude/thinking). See [Introducing Claude Fable 5 and Claude Mythos 5](https://platform.claude.com/docs/en/about-claude/models/introducing-claude-fable-5-and-claude-mythos-5) for capabilities, API changes, and availability.
+* We've launched **Claude Fable 5** (`claude-fable-5`), our most capable widely released model, alongside **Claude Mythos 5** (`claude-mythos-5`) for Project Glasswing participants. Both models support a [1M token context window](https://platform.claude.com/docs/en/build-with-claude/context-windows) by default, 128k max output tokens, and always-on [adaptive thinking](https://platform.claude.com/docs/en/build-with-claude/thinking). See [Introducing Claude Fable 5 and Claude Mythos 5](https://platform.claude.com/docs/en/models/fable-5/introducing-claude-fable-5-and-claude-mythos-5) for capabilities, API changes, and availability.
 * Claude Fable 5 and Claude Mythos 5 use the tokenizer introduced with Claude Opus 4.7. Compared to models before Claude Opus 4.7, the same text produces roughly 30% more tokens. The exact increase depends on the content and workload shape. Use the [token counting API](https://platform.claude.com/docs/en/build-with-claude/token-counting#token-counts-on-claude-fable-5) with `model: "claude-fable-5"` to measure your prompts under the new tokenizer.
 * Claude Fable 5 runs safety classifiers on requests and during response generation. When a classifier declines a request, the Messages API returns `stop_reason: "refusal"`. You are not billed for a request refused before any output is generated. An opt-in `fallbacks` parameter (in beta on the Claude API and Claude Platform on AWS; not supported on the Message Batches API) re-runs refused requests on another model, billed at the fallback model's rates. See [Handling stop reasons](https://platform.claude.com/docs/en/build-with-claude/handling-stop-reasons).
 * The [`stop_details.category`](https://platform.claude.com/docs/en/build-with-claude/refusals-and-fallback#refusal-response) field on refusal responses now includes `"reasoning_extraction"` on Claude Fable 5, returned when a request is blocked under Anthropic's Terms of Service restrictions on reverse engineering or duplicating model outputs. The existing `"cyber"` and `"bio"` categories are unchanged. No beta header is required.

 
 ### April 30, 2026
 
-* We've retired the 1M token context window beta (`context-1m-2025-08-07`) for Claude Sonnet 4.5 and Claude Sonnet 4. The beta header now has no effect on these models, and requests exceeding the standard 200k-token context window return an error. To use the 1M context window, migrate to [Claude Sonnet 4.6](https://platform.claude.com/docs/en/about-claude/models/overview#latest-models-comparison) or [Claude Opus 4.6](https://platform.claude.com/docs/en/about-claude/models/overview#latest-models-comparison), where it's included at standard pricing with no beta header required.
+* We've retired the 1M token context window beta (`context-1m-2025-08-07`) for Claude Sonnet 4.5 and Claude Sonnet 4. The beta header now has no effect on these models, and requests exceeding the standard 200k-token context window return an error. To use the 1M context window, migrate to [Claude Sonnet 4.6](https://platform.claude.com/docs/en/models/overview#latest-models-comparison) or [Claude Opus 4.6](https://platform.claude.com/docs/en/models/overview#latest-models-comparison), where it's included at standard pricing with no beta header required.
 
 ### April 29, 2026
 

 
 ### April 20, 2026
 
-* We've retired the Claude Haiku 3 model (`claude-3-haiku-20240307`). All requests to this model will now return an error. We recommend upgrading to [Claude Haiku 4.5](https://platform.claude.com/docs/en/about-claude/models/overview#latest-models-comparison).
+* We've retired the Claude Haiku 3 model (`claude-3-haiku-20240307`). All requests to this model will now return an error. We recommend upgrading to [Claude Haiku 4.5](https://platform.claude.com/docs/en/models/overview#latest-models-comparison).
 
 ### April 16, 2026
 

 
 ### April 14, 2026
 
-* We announced the deprecation of the Claude Sonnet 4 model (`claude-sonnet-4-20250514`) and the Claude Opus 4 model (`claude-opus-4-20250514`), with retirement on the Claude API scheduled for June 15, 2026. We recommend migrating to [Claude Sonnet 4.6](https://platform.claude.com/docs/en/about-claude/models/overview#latest-models-comparison) and [Claude Opus 4.8](https://platform.claude.com/docs/en/about-claude/models/migration-guide) respectively. Read more in [Model deprecations](https://platform.claude.com/docs/en/about-claude/model-deprecations).
+* We announced the deprecation of the Claude Sonnet 4 model (`claude-sonnet-4-20250514`) and the Claude Opus 4 model (`claude-opus-4-20250514`), with retirement on the Claude API scheduled for June 15, 2026. We recommend migrating to [Claude Sonnet 4.6](https://platform.claude.com/docs/en/models/overview#latest-models-comparison) and [Claude Opus 4.8](https://platform.claude.com/docs/en/about-claude/models/migration-guide) respectively. Read more in [Model deprecations](https://platform.claude.com/docs/en/about-claude/model-deprecations).
 
 ### April 9, 2026
 

 ### March 30, 2026
 
 * We've raised the `max_tokens` cap to 300k on the [Message Batches API](https://platform.claude.com/docs/en/build-with-claude/batch-processing#extended-output-beta) for Claude Opus 4.6 and Sonnet 4.6. Include the `output-300k-2026-03-24` beta header to generate longer single-turn outputs for long-form content, structured data, and large code generation tasks.
-* We're retiring the 1M token context window beta for Claude Sonnet 4.5 and Claude Sonnet 4 on **April 30, 2026**. After that date, the `context-1m-2025-08-07` beta header will have no effect on these models, and requests that exceed the standard 200k-token context window will return an error. To continue using 1M context windows, migrate to [Claude Sonnet 4.6](https://platform.claude.com/docs/en/about-claude/models/overview#latest-models-comparison) or [Claude Opus 4.6](https://platform.claude.com/docs/en/about-claude/models/overview#latest-models-comparison), which support the full 1M token context window at standard pricing with no beta header required.
+* We're retiring the 1M token context window beta for Claude Sonnet 4.5 and Claude Sonnet 4 on **April 30, 2026**. After that date, the `context-1m-2025-08-07` beta header will have no effect on these models, and requests that exceed the standard 200k-token context window will return an error. To continue using 1M context windows, migrate to [Claude Sonnet 4.6](https://platform.claude.com/docs/en/models/overview#latest-models-comparison) or [Claude Opus 4.6](https://platform.claude.com/docs/en/models/overview#latest-models-comparison), which support the full 1M token context window at standard pricing with no beta header required.
 
 ### March 18, 2026
 

 ### February 19, 2026
 
 * We've launched **automatic caching** for the Messages API. Add a single `cache_control` field to your request body and the system automatically caches the last cacheable block, moving the cache point forward as conversations grow. No manual breakpoint management required. Works alongside existing block-level cache control for fine-grained optimization. Available on the Claude API and Microsoft Foundry (preview). Learn more in [Prompt caching](https://platform.claude.com/docs/en/build-with-claude/prompt-caching#automatic-caching).
-* We've retired the Claude Sonnet 3.7 model (`claude-3-7-sonnet-20250219`) and the Claude Haiku 3.5 model (`claude-3-5-haiku-20241022`). All requests to Claude Sonnet 3.7 will now return an error. Requests to Claude Haiku 3.5 on the Claude API will now return an error; it remains available on Amazon Bedrock and Google Cloud. We recommend upgrading to [Claude Sonnet 4.6](https://platform.claude.com/docs/en/about-claude/models/overview#latest-models-comparison) and [Claude Haiku 4.5](https://platform.claude.com/docs/en/about-claude/models/overview#latest-models-comparison) respectively. Researchers can request ongoing access through the [External Researcher Access Program](https://support.claude.com/en/articles/9125743-what-is-the-external-researcher-access-program).
-* We announced the deprecation of the Claude Haiku 3 model (`claude-3-haiku-20240307`), with retirement scheduled for April 20, 2026. We recommend migrating to [Claude Haiku 4.5](https://platform.claude.com/docs/en/about-claude/models/overview#latest-models-comparison). Read more in [Model deprecations](https://platform.claude.com/docs/en/about-claude/model-deprecations).
+* We've retired the Claude Sonnet 3.7 model (`claude-3-7-sonnet-20250219`) and the Claude Haiku 3.5 model (`claude-3-5-haiku-20241022`). All requests to Claude Sonnet 3.7 will now return an error. Requests to Claude Haiku 3.5 on the Claude API will now return an error; it remains available on Amazon Bedrock and Google Cloud. We recommend upgrading to [Claude Sonnet 4.6](https://platform.claude.com/docs/en/models/overview#latest-models-comparison) and [Claude Haiku 4.5](https://platform.claude.com/docs/en/models/overview#latest-models-comparison) respectively. Researchers can request ongoing access through the [External Researcher Access Program](https://support.claude.com/en/articles/9125743-what-is-the-external-researcher-access-program).
+* We announced the deprecation of the Claude Haiku 3 model (`claude-3-haiku-20240307`), with retirement scheduled for April 20, 2026. We recommend migrating to [Claude Haiku 4.5](https://platform.claude.com/docs/en/models/overview#latest-models-comparison). Read more in [Model deprecations](https://platform.claude.com/docs/en/about-claude/model-deprecations).
 
 ### February 17, 2026
 

 
 ### January 5, 2026
 
-* We've retired the Claude Opus 3 model (`claude-3-opus-20240229`). All requests to this model will now return an error. We recommend upgrading to [Claude Opus 4.5](https://platform.claude.com/docs/en/about-claude/models/overview#latest-models-comparison), which offers significantly improved intelligence at a third of the cost. Researchers can request ongoing access to Claude Opus 3 on the API through the [External Researcher Access Program](https://support.claude.com/en/articles/9125743-what-is-the-external-researcher-access-program).
+* We've retired the Claude Opus 3 model (`claude-3-opus-20240229`). All requests to this model will now return an error. We recommend upgrading to [Claude Opus 4.5](https://platform.claude.com/docs/en/models/overview#latest-models-comparison), which offers significantly improved intelligence at a third of the cost. Researchers can request ongoing access to Claude Opus 3 on the API through the [External Researcher Access Program](https://support.claude.com/en/articles/9125743-what-is-the-external-researcher-access-program).
 
 ### December 19, 2025
 

 
 ### September 29, 2025
 
-* We've launched [Claude Sonnet 4.5](https://www.anthropic.com/news/claude-sonnet-4-5), our best model for complex agents and coding, with the highest intelligence across most tasks. Learn more in the [models overview](https://platform.claude.com/docs/en/about-claude/models/overview).
+* We've launched [Claude Sonnet 4.5](https://www.anthropic.com/news/claude-sonnet-4-5), our best model for complex agents and coding, with the highest intelligence across most tasks. Learn more in the [models overview](https://platform.claude.com/docs/en/models/overview).
 * We've introduced [global endpoint pricing](https://platform.claude.com/docs/en/about-claude/pricing#cloud-platform-pricing) for Amazon Bedrock and Vertex AI. The Claude API (1P) pricing is unaffected.
 * We've introduced a new stop reason `model_context_window_exceeded` that allows you to request the maximum possible tokens without calculating input size. Learn more in [Handling stop reasons](https://platform.claude.com/docs/en/build-with-claude/handling-stop-reasons).
 * We've launched the memory tool in beta, enabling Claude to store and consult information across conversations. Learn more in [Memory tool](https://platform.claude.com/docs/en/agents-and-tools/tool-use/memory-tool).

 
 The following features are now available in the Claude API without a beta header:
 
-* [Models API](https://platform.claude.com/docs/en/api/models/list): Query available models, validate model IDs, and resolve [model aliases](https://platform.claude.com/docs/en/about-claude/models/overview) to their canonical model IDs.
+* [Models API](https://platform.claude.com/docs/en/api/models/list): Query available models, validate model IDs, and resolve [model aliases](https://platform.claude.com/docs/en/models/overview) to their canonical model IDs.
 * [Message Batches API](https://platform.claude.com/docs/en/build-with-claude/batch-processing): Process large batches of messages asynchronously at 50% of the standard API cost.
 * [Token counting API](https://platform.claude.com/docs/en/build-with-claude/token-counting): Calculate token counts for Messages before sending them to Claude.
 * [Prompt Caching](https://platform.claude.com/docs/en/build-with-claude/prompt-caching): Reduce costs by up to 90% and latency by up to 80% by caching and reusing prompt content.