release: 0.51.0

[stainless-app]

Automated Release PR

0.51.0 (2026-09-22)

Full Changelog: v0.50.0...v0.51.0

Features

• api: add support for claude-opus-5-5, inline tool definitions and MCP tool-list pinning (beta) (0d6ea88)
• php: add static with() constructors to discriminated unions (ca8fa1f)
• tools: add compactBeforeNextTurn() to the tool runner (#228) (1501659)

Bug Fixes

• api: share one evaluated_permission enum across Managed Agents events (dc060c1)
• client: read tool definitions into the class their type names (761c22d)
• php: limit static with() constructors to unions used in request params (d826535)
• tools: addTools() takes effect straight away (#235) (e277760)
• tools: leave reply-only params off the tool runner's compaction request (#234) (a65dec2)

Chores

• docs: add descriptions to the Dreams API reference (a3fa7d2)
• docs: add descriptions to the User Profiles API reference (a3fa7d2)
• docs: add memory store descriptions to the Managed Agents API reference (a3fa7d2)
• docs: improve descriptions in the Dreams API reference (ee3a9c9)
• docs: remove placeholder parameter descriptions (8d16eb8)
• docs: simplify the session thread agent type description (35d8451)
• docs: update diagnostics field descriptions on beta messages (35c8916)

Documentation

• add path and header parameter descriptions (801a12b)

---

This pull request is managed by Stainless's GitHub App.

The semver version number is based on included commit messages. Alternatively, you can manually set the version number in the title of this pull request.

🔗 Stainless website
📚 Read the docs
🙋 Reach out for help or questions

[stainless-app]

🤖 Release is at https://github.com/anthropics/anthropic-sdk-php/releases/tag/v0.51.0 🌻