Claude Platform Updates: New Models, Features, and Deprecations in July 2026
Anthropic has released Claude Sonnet 5, Claude Fable 5, and Claude Mythos 5, featuring expanded context windows and updated tokenizers, impacting prompt token counts. Several enhancements to Claude Managed Agents improve session event streaming, pagination, and configuration overrides. The platform also introduced new tool versions for code execution and web search, alongside API and SDK updates, while deprecating older Opus and Sonnet models and fast mode for certain versions.
- →Launch of Claude Sonnet 5 with 1M token context window
- →Introduction of Claude Fable 5 and Claude Mythos 5
- →Removal of fast mode for Claude Opus 4.6 and deprecation for Claude Opus 4.7
- →Retirement of older Claude Sonnet 4 and Claude Opus 4 models
- →Claude Managed Agents session event streams support deltas
Deprecations (2) ›
- Removal of fast mode for Claude Opus 4.6 and deprecation for Claude Opus 4.7
Fast mode has been removed for Claude Opus 4.6, with requests now running at standard speed and pricing. Fast mode for Claude Opus 4.7 is deprecated, scheduled for removal on July 24, 2026, with migration recommended to Claude Opus 4.8.
- Retirement of older Claude Sonnet 4 and Claude Opus 4 models
The Claude Sonnet 4 (claude-sonnet-4-20250514) and Claude Opus 4 (claude-opus-4-20250514) models have been retired. All requests to these models will now result in an error, and users are advised to upgrade to Claude Sonnet 4.6 and Claude Opus 4.8 respectively.
Features (2) ›
- Launch of Claude Sonnet 5 with 1M token context window
Claude Sonnet 5 is now available with a 1M token context window and 128k max output tokens, at introductory pricing through August 2026. It includes adaptive thinking enabled by default and uses a new tokenizer that increases token counts by approximately 30% for the same text.
- Introduction of Claude Fable 5 and Claude Mythos 5
Claude Fable 5 and Claude Mythos 5 are now available, supporting a 1M token context window and 128k max output tokens with always-on adaptive thinking. These models utilize the tokenizer introduced with Claude Opus 4.7, resulting in roughly 30% more tokens for the same input text.
Enhancements (2) ›
- Claude Managed Agents session event streams support deltas
Session event streams for Claude Managed Agents now support event deltas, allowing developers to preview agent message text as it is generated. This feature can be enabled using the event_deltas[] query parameter on the /v1/sessions/{session_id}/events/stream endpoint.
- New configuration options for Claude Managed Agents
Users can now override an agent's configuration for individual sessions by passing agent with type: "agent_with_overrides" when creating a session. Additionally, Claude Managed Agents vaults support a new injection_location setting for environment variable credentials, controlling their substitution into request headers or body.
https://platform.claude.com/docs/en/release-notes/overview