2026-06-23 06:59 UTC · anthropic/api-release-notes · live page
Summary by fallback. It may be wrong; the diff below is what actually changed. Raw: 33c1c17f37-anthropic-api-release-notes.diff · commit 33c1c17f37
diff --git a/snapshots/anthropic/api-release-notes.md b/snapshots/anthropic/api-release-notes.mdindex 20fcb74..3e07d76 100644--- a/snapshots/anthropic/api-release-notes.md+++ b/snapshots/anthropic/api-release-notes.md@@ -5,4 +5,13 @@ For release notes on Claude Apps, see the Release notes for Claude Apps in the C For updates to Claude Code, see the complete CHANGELOG.md in the `claude-code` repository. +### 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 will now return an error. We recommend upgrading to Claude Sonnet 4.6 and Claude Opus 4.8 respectively. Researchers can request ongoing access through the External Researcher Access Program.++### June 11, 2026++- The code execution tool now supports `code_execution_20260521`, which discloses the 90-second per-cell execution time limit in the tool description so Claude can budget long-running cells. No beta header is required.+- The web search tool and web fetch tool now support `web_search_20260318` and `web_fetch_20260318`, adding a `response_inclusion` parameter to drop consumed result blocks from the API response for agentic workflows. No beta header is required.+ ### June 10, 2026 @@ -14,11 +23,13 @@ For updates to Claude Code, see the complete CHANGELOG.md in the `claude-code` r - 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. Use the token counting API 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.-- The `stop_details.category` 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.-- On Claude Fable 5 and Claude Mythos 5, adaptive thinking is the only thinking mode: `thinking: {"type": "disabled"}` is not supported, and manual extended thinking budgets and assistant prefill are not supported (both return a 400 error). See Migrating from Claude Mythos Preview to Claude Mythos 5.-- On Claude Fable 5 and Claude Mythos 5, `thinking.display` defaults to `"omitted"`, the same as Claude Opus 4.8, Claude Opus 4.7, and Claude Mythos Preview; set `display: "summarized"` to receive readable thinking summaries. The raw chain of thought is never returned; pass thinking blocks back unchanged in multi-turn conversations on the same model. See Thinking output on Claude Fable 5 and Claude Mythos 5.-- Claude Fable 5 requires 30-day data retention on the Claude API and is not available under zero data retention. See Model-specific data retention requirements.-- Claude Managed Agents now supports scheduled deployments, letting you run sessions on a cron schedule without managing your own scheduler.-- Claude Managed Agents vaults now support environment variable credentials, so you can securely inject secrets into the agent's sandbox for CLIs, SDKs, and other services that authenticate through environment variables.-- The `session.thread_*` webhook events now include a `session_thread_id` field identifying the multi-agent thread that triggered the event.+- The+ `stop_details.category`+ 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. ### June 5, 2026