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AI release notes

Anthropic's official release notes. Claude apps: the website, desktop and phone apps. Claude Code: Claude's coding assistant. Claude API: what developers use to build Claude into their own products.

Compiled by the Toolstash team · Updated

  1. Claude Code

    Claude Code 2.1.292

    8 new64 fixes20 other

    Added --marketplace <source> to claude plugin install: adds the marketplace if needed, under the same policy checks as claude plugin marketplace add, then installs the plugin from it. Added an effort parameter to the Agent tool, so Claude runs a sub-agent at the effort level you ask for.

  2. Claude Code

    Claude Code 2.1.291

    2 fixes

    Fixed a regression in 2.1.290 where cloud sessions could drop answers to permission prompts. Fixed a regression in 2.1.288 where the last messages of a session could be lost when quitting.

  3. Claude API

    We’ve added capabilities.server_tools to the Models API

    GET /v1/models and GET /v1/models/{model_id} now report whether each model accepts the web search and code execution tools. To check whether a model accepts the code execution tool, read capabilities.server_tools.code_execution. The top-level capabilities.code_execution reports whether code can call your request’s other tools.

  4. Claude Code

    Claude Code 2.1.290

    15 new130 fixes45 other

    Added serverToolUses to the result of a mod's turn.step hook: the tool calls the API ran itself (the advisor), each with its id, name, input, start and end. Added agentId to the tool.check event of plugin hooks, so a hook can tell a subagent's permission check from the main session's.

  5. Claude API

    We’ve added capabilities.thinking.types.disabled to the Models API

    GET /v1/models and GET /v1/models/{model_id} now report whether each model accepts thinking: {type: "disabled"}, which turns thinking off.

  6. Claude Code

    Claude Code 2.1.289

    1 new23 fixes3 other

    Added agent.spawn for teammates, one agent id across plugin hook events, and idle and waiting states in $.agent.list().

  7. Claude Code

    Claude Code 2.1.288

    7 new64 fixes18 other

    Added $.ui.selection() for mods: returns the text you last selected in fullscreen mode and, when the selection lies within one transcript row, that row. Added a built-in gh api to cloud sessions whose image has no GitHub CLI, and fixed the built-in sending control characters from file names, jq filters or GitHub errors to the terminal.

  8. Claude Code

    Claude Code 2.1.287

    8 new66 fixes32 other

    Added Claude Mods: plugins may now modify deeper behavior. Added You should know, a built-in mod where a side agent watches your back and flags things you or Claude might miss. Turn it on with /plugin enable cc-plugin-you-should-know@builtin (for first-party sessions with telemetry on).

  9. Claude API

    We’ve added a line field to the Models API

    GET /v1/models and GET /v1/models/{model_id} now return the model line each model belongs to. Claude Opus 4.5 and Claude Opus 4.6 both report opus, for example. Use line to group models without parsing their IDs. line is null for a model that belongs to no line. Dreams (research preview) now supports Claude Opus 5.5, Claude Fable 5.1, and Claude Sonnet 5.5.

  10. Claude Code

    Claude Code 2.1.286

    7 new49 fixes32 other

    Added a count such as "2 of 5" to the permission prompt when several permission requests stack up. Added mouse support for the "N more" rows of lists in fullscreen mode: click one to jump to that end of the list, with hover and pressed states.

  11. Claude API

    In Python SDK 1.10.0, TypeScript SDK 0.130.0, C# SDK 12.52.0, Go SDK 1.77.0, Java SDK 2.67.0, PHP SDK…

    These releases also keep client.beta.organization and ant beta:organization. We announced the deprecation of the Claude Sonnet 4.5 model (claude-sonnet-4-5-20250929), with retirement on the Claude API scheduled for November 30, 2026.

  12. Claude Code

    Claude Code 2.1.285

    10 new86 fixes40 other

    Added CLAUDE_CODE_DISABLE_WEB_FETCH environment variable to turn off the WebFetch tool. Added claude --desktop to open the Claude desktop app on the current directory, or on a session with --continue / --resume <id>.

  13. Claude Code

    Claude Code 2.1.284

    14 new57 fixes29 other

    Added Claude Sonnet 5.5 (claude-sonnet-5-5), now the default Sonnet model on the Anthropic API — 1M context, $2/$10 per Mtok with $0.20/Mtok cache reads. Added a "Yes, but ask again next time" answer to auto mode's prompt before a read outside the working directories, so you can allow that one read and still be asked about later ones.

  14. Claude API

    Code written for Claude Sonnet 5 can break on Claude Sonnet 5.5 in five ways

    To turn off up-front thinking, send thinking: {"type": "between_tools"} instead of "disabled", at high effort or below. Forced tool use (tool_choice types any and tool) returns a 400 error. Thinking blocks are tied to the model and the conversation. On the Claude API and Google Cloud, the earlier computer_20251124 computer use tool isn’t accepted. The advisor tool rejects Claude Opus 4.8, Claude Opus 4.7, and Claude Sonnet 5 as advisors. For model-specific prompting patterns, see Prompting Claude Sonnet 5.5. Thinking blocks that Claude Sonnet 5.5 produces work only in the account that produced them, or in an account linked to it.

  15. Claude appsAnnouncement

    Claude Sonnet 5.5 launch

    We just launched Claude Sonnet 5.5, the second model in our Claude 5.5 family. Sonnet 5.5 is a faster, lower-cost complement to Claude Opus 5.5.

  16. New modelAnnouncement

    New model: Claude Sonnet 5.5

    We’ve launched Claude Sonnet 5.5 (claude-sonnet-5-5). It’s available on the Claude API, Claude in Amazon Bedrock, Claude Platform on AWS, Claude on Google Cloud, and Claude in Microsoft Foundry. For its context window, output limits, and prices, see the Claude Sonnet 5.5 model page.

  17. Claude Code

    Claude Code 2.1.283

    11 new53 fixes30 other

    Added x-claude-code-prompt-id to the gateway hint headers so LLM gateways can group the requests that serve one user prompt; opt in with CLAUDE_CODE_GATEWAY_HINT_HEADERS=1. Added availableModelsMatch managed setting: with "exact", an availableModels entry allows only the model version it names, so new releases stay blocked until listed.

  18. Claude appsAnnouncement

    Build plugins for Claude

    You can now submit plugins to the Claude directory through a new developer portal, track them through review, and see usage analytics once they’re live.

  19. Claude Code

    Claude Code 2.1.282

    8 new58 fixes20 other

    Added a maxProseWidth setting that caps the width of Claude's prose in wide terminals while tables and code blocks keep the full width. Added a startup notice, and /status and claude doctor entries, listing telemetry variables in a project's settings files that were ignored or that turned telemetry off.

  20. Claude API

    We’re resuming billing for refusals that arrive before any output when stop_details.category is "bio",…

    Mid-stream refusals were already billed. Refusals billed under this change are charged like any other request, at the rates of the model that ran it. Refusals before any output in other categories are still not billed, and fallback credit is unchanged. This change applies on all platforms. The Compliance API local session endpoints are out of beta for Claude for Microsoft 365 sessions in Excel, PowerPoint, Word, and Outlook (product_surface values beginning with office_agents). The Compliance API Activity Feed no longer returns file names, project document names, or artifact titles.

  21. Claude Code

    Claude Code 2.1.281

    13 new112 fixes51 other

    Added Claude apps gateway support for newer Claude Desktop keys in desktop policy blocks, including blockReadsOutsideWorkingDirectories and disableBypassPermissionsMode. Added assume_role on Claude apps gateway Bedrock upstreams: the gateway calls Bedrock as an IAM role it assumes through STS, in another AWS account if needed, optionally one session per developer.

  22. Claude API

    Cache diagnostics is out of beta on the Claude API and no longer requires the cache-diagnosis-2026-04-07…

    Include the diagnostics object on a Messages request to opt in; requests that still send the header work as before. Responses from POST /v1/messages now always include the diagnostics field, which is null when the request did not include the diagnostics object.

  23. Claude Code

    Claude Code 2.1.280

    12 new67 fixes35 other

    Added Claude Opus 5.5 (claude-opus-5-5), now the default Opus model — 1M context, $4/$20 per Mtok with $0.20/Mtok cache reads. Added mouse support to more lists in fullscreen mode: the wheel scrolls the /skills list, and a skill's state options in /plugin can be clicked.

  24. Claude API

    On Claude Opus 5.5, thinking can’t be disabled: thinking: {"type": "disabled"} and thinking: {"type":…

    Omit the thinking field and control thinking depth with the effort parameter. tool_choice types any and tool also return a 400 error, as on Claude Fable 5.1; use auto with strict tool use. On the Claude API and Google Cloud, computer use on this model requires the computer_toolset_20260801 toolset and the earlier computer_20251124 tool returns a 400 error; on Amazon Bedrock, computer_20251124 keeps working. Fast mode (research preview) is available for Claude Opus 5.5 on the Claude API. Tools can now be defined inside a mid-conversation system message, in beta on the Claude API with the inline-tools-2026-09-15 beta header.

  25. Claude appsAnnouncement

    Claude Opus 5.5 launch

    We just launched Claude Opus 5.5, the first model in our new Claude 5.5 family. It performs at the level of Claude Fable 5.1 on most work and costs 40% less to run than Opus 5.

  26. New modelAnnouncement

    New model: Claude Opus 5.5

    We’ve launched Claude Opus 5.5 (claude-opus-5-5), a model for long-running agentic coding and knowledge work. It has a 1M token context window by default, 128k max output tokens, and always-on adaptive thinking, at $4 / $20 USD per MTok (Claude Opus 5 is $5 / $25 USD). Claude Opus 5.5 is available on the Claude API, Claude in Amazon Bedrock, Claude Platform on AWS, Claude on Google Cloud, and Claude in Microsoft Foundry.

  27. Claude Code

    Claude Code 2.1.278

    1 new1 other

    Added an Auto mode server row to /status showing whether this session's auto mode classifier runs on the server.

  28. Claude Code

    Claude Code 2.1.277

    10 new57 fixes20 other

    Added AGENTS.md support: in a project with no CLAUDE.md, Claude Code reads AGENTS.md instead; change it under "Project instructions" in /config (not yet on Bedrock, Vertex or Foundry). Added CLAUDE_GATEWAY_PROXY_IS_EGRESS_BOUNDARY=1 for Claude apps gateways whose only egress is a forward proxy: every outbound request hands the proxy the hostname instead of resolving it locally.

  29. Claude Code

    Claude Code 2.1.276

    1 fix

    Fixed every request failing with 400 … Input tag 'advisor_20260301' when ANTHROPIC_BASE_URL points at a proxy or gateway (2.1.275 regression).

  30. Claude API

    For cache diagnostics, a response to a request that sends the cache-diagnosis-2026-04-07 beta header now…

    The field is null when the request did not include the diagnostics object. Previously the field was omitted in that case. The Compliance API local session endpoints now also return transcripts of Claude in Chrome sessions (product_surface value claude_in_chrome), in beta for Claude Enterprise organizations, with your existing Compliance Access Key and the read:compliance_user_data scope.