HomeDocs changes
Documentation changes
What the docs quietly changed.
Anthropic's published documentation, fetched on a schedule and diffed against the last copy. Every edit dated, including the ones that never made a release note.
Last poll read all 4 cleanly: Claude Code CLI, Claude Developer Platform, Claude Documentation, Model Context Protocol. A date here is when this site noticed, not when Anthropic edited.
Claude Developer Platform
821pages tracked
774 changed this week · last read 23 Oct 2026
Claude Code CLI
228pages tracked
148 changed this week · last read 23 Oct 2026
Claude Documentation
280pages tracked
82 changed this week · last read 23 Oct 2026
Model Context Protocol
357pages tracked
171 changed this week · last read 23 Oct 2026
100 on this page
ReadSourcePageWhatLines
22 Sep 2026
274 pages
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api
managed-agents/sessions
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managed-agents/sessions
"model": {"id": "claude-opus-5", "inference_geo": "us"}
"model": {"id": "claude-opus-5-5", "inference_geo": "us"}
id: claude-opus-5
id: claude-opus-5-5
"model": {"id": "claude-opus-5", "inference_geo": "us"},
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api
managed-agents/self-hosted-sandboxes
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managed-agents/self-hosted-sandboxes
# yaml-language-server: $schema=https://platform.claude.com/schemas/ant/beta/environment.json
VERSION=1.33.0
VERSION=1.35.0
ARG ANT_VERSION=1.33.0
ARG ANT_VERSION=1.35.0
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api
managed-agents/reference
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managed-agents/reference
| Type | Description
| ---------------- | -----------------------------------------------------------------------------------------------------------------------------------------------------------
| `system.message` | Append privileged system-level context that applies to the accompanying turn and all subsequent turns. Supported on Claude Fable 5.1, Claude Mythos 5.1, Cl
| Type | Description
| ---------------- | -----------------------------------------------------------------------------------------------------------------------------------------------------------
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api
managed-agents/quickstart
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managed-agents/quickstart
VERSION=1.33.0
VERSION=1.35.0
implementation("com.anthropic:anthropic-java:2.63.0")
implementation("com.anthropic:anthropic-java:2.65.0")
"model": "claude-opus-5",
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api
managed-agents/permission-policies
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managed-agents/permission-policies
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
model="claude-opus-5",
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api
managed-agents/multiagent-orchestration
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managed-agents/multiagent-orchestration
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
model="claude-opus-5",
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api
managed-agents/migration
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managed-agents/migration
model="claude-opus-5",
model="claude-opus-5-5",
model: "claude-opus-5",
model: "claude-opus-5-5",
Model = Model.ClaudeOpus5,
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api
managed-agents/memory
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managed-agents/memory
# yaml-language-server: $schema=https://platform.claude.com/schemas/ant/beta/memory_store.json
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api
managed-agents/mcp-connector
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managed-agents/mcp-connector
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
model="claude-opus-5",
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api
managed-agents/github
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managed-agents/github
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
model="claude-opus-5",
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api
managed-agents/events-and-streaming
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managed-agents/events-and-streaming
`system.message` is supported by Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, Claude Opus 5, and Claude Opus 4.8. If the agent's primary model does not s
`system.message` is supported by Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, Claude Opus 5.5, Claude Opus 5, and Claude Opus 4.8. If the agent's primary
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api
managed-agents/environments
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managed-agents/environments
# yaml-language-server: $schema=https://platform.claude.com/schemas/ant/beta/environment.json
# yaml-language-server: $schema=https://platform.claude.com/schemas/ant/beta/environment.json
# yaml-language-server: $schema=https://platform.claude.com/schemas/ant/beta/environment.json
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api
managed-agents/agent-setup
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managed-agents/agent-setup
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
model="claude-opus-5",
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api
manage-claude/workspaces
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manage-claude/workspaces
"model": "claude-opus-5",
"model": "claude-opus-5-5",
--model claude-opus-5 \
--model claude-opus-5-5 \
model="claude-opus-5",
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api
manage-claude/workload-identity-federation
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manage-claude/workload-identity-federation
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model="claude-opus-5",
model="claude-opus-5-5",
model: "claude-opus-5",
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api
manage-claude/wif-providers/spiffe
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manage-claude/wif-providers/spiffe
"model": "claude-opus-5",
"model": "claude-opus-5-5",
--model claude-opus-5 \
--model claude-opus-5-5 \
model="claude-opus-5",
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api
manage-claude/wif-providers/okta
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manage-claude/wif-providers/okta
-d '{"model": "claude-opus-5", "max_tokens": 1024, "messages": [{"role": "user", "content": "Hello, Claude"}]}' \
-d '{"model": "claude-opus-5-5", "max_tokens": 1024, "messages": [{"role": "user", "content": "Hello, Claude"}]}' \
model="claude-opus-5",
model="claude-opus-5-5",
model: "claude-opus-5",
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api
manage-claude/wif-providers/kubernetes
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manage-claude/wif-providers/kubernetes
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model="claude-opus-5",
model="claude-opus-5-5",
model: "claude-opus-5",
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api
manage-claude/wif-providers/github-actions
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manage-claude/wif-providers/github-actions
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model="claude-opus-5",
model="claude-opus-5-5",
model: "claude-opus-5",
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api
manage-claude/wif-providers/gcp
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manage-claude/wif-providers/gcp
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model="claude-opus-5",
model="claude-opus-5-5",
model: "claude-opus-5",
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api
manage-claude/wif-providers/azure
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manage-claude/wif-providers/azure
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model="claude-opus-5",
model="claude-opus-5-5",
model: "claude-opus-5",
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api
manage-claude/wif-providers/aws
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manage-claude/wif-providers/aws
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model="claude-opus-5",
model="claude-opus-5-5",
model: "claude-opus-5",
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api
manage-claude/usage-cost-api
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manage-claude/usage-cost-api
models[]=claude-opus-5&\
models[]=claude-opus-5-5&\
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api
manage-claude/rate-limits-api
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manage-claude/rate-limits-api
"models": ["claude-opus-5"],
"models": ["claude-opus-5-5"],
"models": ["claude-opus-5"],
"models": ["claude-opus-5-5"],
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api
manage-claude/data-residency
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manage-claude/data-residency
"model": "claude-opus-5",
"model": "claude-opus-5-5",
--model claude-opus-5 \
--model claude-opus-5-5 \
model="claude-opus-5",
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api
manage-claude/compliance-sessions
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manage-claude/compliance-sessions
"model": "claude-opus-5",
"model": "claude-opus-5-5",
"model": "claude-opus-5",
"model": "claude-opus-5-5",
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api
manage-claude/compliance-content-data
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manage-claude/compliance-content-data
"model": "claude-opus-5",
"model": "claude-opus-5-5",
"model": "claude-opus-5",
"model": "claude-opus-5-5",
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api
manage-claude/cmek-google-cloud-kms
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manage-claude/cmek-google-cloud-kms
Open **Settings > Workspaces**, choose the workspace, and open its **Security** tab. Under **Encryption key**, select the key, click **Save**, and confirm. Attaching a
In the Claude Console, go to [Manage > Security](https://platform.claude.com/settings/workspaces/default/security-compliance) and select the workspace in the workspace
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api
manage-claude/cmek-azure-key-vault
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manage-claude/cmek-azure-key-vault
Open **Settings > Workspaces**, choose the workspace, and open its **Security** tab. Under **Encryption key**, select the key, click **Save**, and confirm. Attaching a
In the Claude Console, go to [Manage > Security](https://platform.claude.com/settings/workspaces/default/security-compliance) and select the workspace in the workspace
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api
manage-claude/cmek-aws-kms
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manage-claude/cmek-aws-kms
**Finding your compartment ID:** Each workspace has a compartment ID that scopes its CMEK data. Find it in the Claude Console under **Workspace > Security**, under **Encrypti
**Finding your compartment ID:** Each workspace has a compartment ID that scopes its CMEK data. To find it in the Claude Console, go to [Manage > Security](https://platform.c
Open **Settings > Workspaces**, choose the workspace, and open its **Security** tab. Under **Encryption key**, select the key, click **Save**, and confirm. Attaching a
In the Claude Console, go to [Manage > Security](https://platform.claude.com/settings/workspaces/default/security-compliance) and select the workspace in the workspace
If you plan to use the optional `EncryptionContext` condition shown here, create the workspace first (without a key) and copy its compartment ID from the Claude Console under **Wor
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api
manage-claude/claude-code-analytics-api
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manage-claude/claude-code-analytics-api
"model": "claude-opus-5",
"model": "claude-opus-5-5",
"amount": 141
"amount": 113
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api
manage-claude/authentication
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manage-claude/authentication
"model": "claude-opus-5",
"model": "claude-opus-5-5",
"model": "claude-opus-5",
"model": "claude-opus-5-5",
--model claude-opus-5 \
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api
intro
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intro
If you're unsure which model to use, start with [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview) for most workloads. Use [Claude Fable 5.1](https://platf
If you're unsure which model to use, start with [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) for most workloads. Use [Claude Fable 5.1](https://p
* [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview) (`claude-opus-5`) — *For complex agentic coding and enterprise work* — Complex projects · Agents · Cod
* [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) (`claude-opus-5-5`) — New — *For long-running agentic coding and knowledge work* — Complex project
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api
home
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home
* [Claude Opus 5](https://platform.claude.com/docs/en/models/opus-5/overview) (`claude-opus-5`) — *For complex agentic coding and enterprise work* — Complex projects · Agents ·
* [Claude Opus 5.5](https://platform.claude.com/docs/en/models/opus-5-5/overview) (`claude-opus-5-5`) — New — *For long-running agentic coding and knowledge work* — Complex pro
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api
get-started
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get-started
"model": "claude-opus-5",
"model": "claude-opus-5-5",
"model": "claude-opus-5",
"model": "claude-opus-5-5",
--model claude-opus-5 \
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api
cli-sdks-libraries/sdks/typescript
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cli-sdks-libraries/sdks/typescript
model: "claude-opus-5"
model: "claude-opus-5-5"
model: "claude-opus-5"
model: "claude-opus-5-5"
model: "claude-opus-5",
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api
cli-sdks-libraries/sdks/ruby
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cli-sdks-libraries/sdks/ruby
model: :"claude-opus-5"
model: :"claude-opus-5-5"
model: :"claude-opus-5"
model: :"claude-opus-5-5"
model: :"claude-opus-5"
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api
cli-sdks-libraries/sdks/python
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cli-sdks-libraries/sdks/python
model="claude-opus-5",
model="claude-opus-5-5",
model="claude-opus-5",
model="claude-opus-5-5",
model="claude-opus-5",
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api
cli-sdks-libraries/sdks/php
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cli-sdks-libraries/sdks/php
model: 'claude-opus-5',
model: 'claude-opus-5-5',
model: 'claude-opus-5',
model: 'claude-opus-5-5',
model: 'claude-opus-5',
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api
cli-sdks-libraries/sdks/java
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cli-sdks-libraries/sdks/java
implementation("com.anthropic:anthropic-java:2.63.0")
implementation("com.anthropic:anthropic-java:2.65.0")
<version>2.63.0</version>
<version>2.65.0</version>
.model(Model.CLAUDE_OPUS_5)
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api
cli-sdks-libraries/sdks/go
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cli-sdks-libraries/sdks/go
Model: anthropic.ModelClaudeOpus5,
Model: anthropic.ModelClaudeOpus5_5,
Model: anthropic.ModelClaudeOpus5,
Model: anthropic.ModelClaudeOpus5_5,
Model: anthropic.ModelClaudeOpus5,
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api
cli-sdks-libraries/sdks/csharp
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cli-sdks-libraries/sdks/csharp
Model = Model.ClaudeOpus5,
Model = Model.ClaudeOpus5_5,
Model = Model.ClaudeOpus5,
Model = Model.ClaudeOpus5_5,
IChatClient chatClient = client.AsIChatClient("claude-opus-5")
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api
cli-sdks-libraries/libraries/openai-sdk
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cli-sdks-libraries/libraries/openai-sdk
model="claude-opus-5", # Claude model name
model="claude-opus-5-5", # Claude model name
model: "claude-opus-5" // Claude model name
model: "claude-opus-5-5" // Claude model name
model: "claude-opus-5", // Claude model name
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api
cli-sdks-libraries/libraries/apple-foundation-models
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cli-sdks-libraries/libraries/apple-foundation-models
ClaudeLanguageModel(name: .opus5, auth: auth)
ClaudeLanguageModel(name: .opus5_5, auth: auth)
ClaudeLanguageModel(name: .opus5, auth: auth, fixedEffort: .xhigh)
ClaudeLanguageModel(name: .opus5_5, auth: auth, fixedEffort: .xhigh)
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api
cli-sdks-libraries/cli/using
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cli-sdks-libraries/cli/using
ant messages create --model claude-opus-5 --max-tokens 1024 ...
ant messages create --model claude-opus-5-5 --max-tokens 1024 ...
ant models retrieve --model-id claude-opus-5 --format yaml
ant models retrieve --model-id claude-opus-5-5 --format yaml
id: claude-opus-5
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cli-sdks-libraries/cli/scripting
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cli-sdks-libraries/cli/scripting
"model": "claude-opus-5",
"model": "claude-opus-5-5",
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api
cli-sdks-libraries/cli/quickstart
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cli-sdks-libraries/cli/quickstart
VERSION=1.33.0
VERSION=1.35.0
--model claude-opus-5 \
--model claude-opus-5-5 \
"model": "claude-opus-5",
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cli-sdks-libraries/cli/authentication
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cli-sdks-libraries/cli/authentication
--model claude-opus-5 \
--model claude-opus-5-5 \
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cli-sdks-libraries/cli/apply
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cli-sdks-libraries/cli/apply
model: claude-opus-5
model: claude-opus-5-5
model: claude-opus-5
model: claude-opus-5-5
model: claude-opus-5
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api
claude_api_primer
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claude_api_primer
Recommended default for most work, including complex agentic coding: Claude Opus 5: claude-opus-5
Step up for the hardest long-running agentic and research tasks, at 2x Claude Opus 5 pricing: Claude Fable 5.1: claude-fable-5-1
Previous Opus model: Claude Opus 4.8: claude-opus-4-8
Recommended default for most work, including complex agentic coding: Claude Opus 5.5: claude-opus-5-5
Step up for the hardest long-running agentic and research tasks, at 2.5x Claude Opus 5.5 pricing: Claude Fable 5.1: claude-fable-5-1
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api
build-with-claude/working-with-messages
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build-with-claude/working-with-messages
"model": "claude-opus-5",
"model": "claude-opus-5-5",
--model claude-opus-5 \
--model claude-opus-5-5 \
model="claude-opus-5",
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api
build-with-claude/vision
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build-with-claude/vision
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
model="claude-opus-5",
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api
build-with-claude/token-counting
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build-with-claude/token-counting
"model": "claude-opus-5",
"model": "claude-opus-5-5",
--model claude-opus-5 \
--model claude-opus-5-5 \
model="claude-opus-5",
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api
build-with-claude/thinking-troubleshooting
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build-with-claude/thinking-troubleshooting
| Claude Opus 5.5 | Adaptive only | Always on | `"enabled"`, `"disabled"` |
*2 Claude Opus 5 accepts `"disabled"` at [effort](https://platform.claude.com/docs/en/build-with-claude/effort) `high` or below; combining it with effort `xhigh` or `max` returns a
*2 Claude Opus 5 accepts `"disabled"` at [effort](https://platform.claude.com/docs/en/build-with-claude/effort) `high` or below; combining it with effort `xhigh` or `max` returns a
The request fails with a 400 error. On Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, and Claude Mythos 5, the message reads:
The request fails with a 400 error. On Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Opus 5.5, and Claude Mythos 5, the message reads:
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api
build-with-claude/thinking-steering-and-cost
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build-with-claude/thinking-steering-and-cost
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model="claude-opus-5",
model="claude-opus-5-5",
model="claude-opus-5",
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api
build-with-claude/thinking
±changed
+16−15
apichanged
build-with-claude/thinking
On Claude Opus 5, Claude Sonnet 5, Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, and Claude Mythos Preview, thinking is already on and needs no configuratio
On Claude Opus 5.5, Claude Opus 5, Claude Sonnet 5, Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, and Claude Mythos Preview, thinking is already on and need
Claude Opus 5 also has thinking on by default and accepts `thinking: {type: "disabled"}` at [effort](https://platform.claude.com/docs/en/build-with-claude/effort) `high` or below.
Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, and Claude Mythos Preview reject `thinking: {type: "disabled"}`. Thinking can't be turned off on these models.
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api
build-with-claude/task-budgets
±changed
+19−17
apichanged
build-with-claude/task-budgets
- claude-opus-5-5
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
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api
build-with-claude/structured-outputs
±changed
+68−67
apichanged
build-with-claude/structured-outputs
- claude-opus-5-5
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
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api
build-with-claude/streaming
±changed
+46−46
apichanged
build-with-claude/streaming
--model claude-opus-5 \
--model claude-opus-5-5 \
model="claude-opus-5",
model="claude-opus-5-5",
model: "claude-opus-5",
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api
build-with-claude/skills-guide
±changed
+117−117
apichanged
build-with-claude/skills-guide
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
model="claude-opus-5",
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api
build-with-claude/search-results
±changed
+18−18
apichanged
build-with-claude/search-results
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
model="claude-opus-5",
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api
build-with-claude/refusals-and-fallback
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apichanged
build-with-claude/refusals-and-fallback
Claude Fable 5.1, Claude Fable 5, and Claude Opus 5 include safety classifiers that can decline a request. When that happens, you receive a normal response, not an error, with `sto
Claude Fable 5.1, Claude Fable 5, Claude Opus 5.5, and Claude Opus 5 include safety classifiers that can decline a request. When that happens, you receive a normal response, not an
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api
build-with-claude/prompt-engineering/prompting-claude-fable-5-1
±changed
+1−1
apichanged
build-with-claude/prompt-engineering/prompting-claude-fable-5-1
Append each assistant turn to the history exactly as the API returned it, thinking blocks included, and don't edit earlier turns between requests. For new accounts created on or af
Append each assistant turn to the history exactly as the API returned it, thinking blocks included, and don't edit earlier turns between requests. For new accounts created on or af
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api
build-with-claude/prompt-engineering/claude-prompting-best-practices
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build-with-claude/prompt-engineering/claude-prompting-best-practices
This is the reference for prompt engineering with current Claude models, including Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, Claude Opus 5, Claude Opus
This is the reference for prompt engineering with current Claude models, including Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, Claude Opus 5.5, Claude Opu
For an overview of model capabilities, see the [models overview](https://platform.claude.com/docs/en/models/overview). For Claude Fable 5.1 capabilities and API changes, see [Wha
For an overview of model capabilities, see the [models overview](https://platform.claude.com/docs/en/models/overview). For Claude Fable 5.1 capabilities and API changes, see [Wha
| Claude Opus 5.5 | [Prompting Claude Opus 5.5](https://platform.claude.com/docs/en/build-with-claude/prompt-engineering/prompting-claude-opus-5-5) | Diffe
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api
build-with-claude/prompt-caching
±changed
+95−88
apichanged
build-with-claude/prompt-caching
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
model="claude-opus-5",
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api
build-with-claude/preserved-thinking
±changed
+62−23
apichanged
build-with-claude/preserved-thinking
* **The model is the one that produced the block, or a newer one.** A model reads its own thinking blocks and those of earlier models. Claude Fable 5.1 reads blocks from Claude Opu
* **The model can read the block.** Each model reads its own thinking blocks and those of a fixed set of other models. Claude Fable 5.1 reads blocks from Claude Opus 5 and, on the
The model check applies to every account. The API enforces the prefix check by default for accounts created on or after August 31, 2026, 00:00 UTC. On older accounts, it enforces t
The model check applies to every account. The API enforces the prefix check by default for accounts created on or after August 31, 2026, 00:00 UTC. On older accounts, it enforces t
* **A conversation that moves up to Claude Fable 5.1 keeps its reasoning.** The earlier model's thinking blocks stay readable, so the model thinks as usual from the first turn afte
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api
build-with-claude/pdf-support
±changed
+55−55
apichanged
build-with-claude/pdf-support
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
model="claude-opus-5",
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api
build-with-claude/multilingual-support
±changed
+9−9
apichanged
build-with-claude/multilingual-support
"model": "claude-opus-5",
"model": "claude-opus-5-5",
--model claude-opus-5 \
--model claude-opus-5-5 \
model="claude-opus-5",
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api
build-with-claude/mid-conversation-system-messages
±changed
+1196−26
apichanged
build-with-claude/mid-conversation-system-messages
This feature is available on Claude Fable 5.1, [Claude Mythos 5.1](https://anthropic.com/glasswing), Claude Fable 5, [Claude Mythos 5](https://anthropic.com/glasswing), Claude Op
[Mid-conversation tool changes](https://platform.claude.com/docs/en/build-with-claude/mid-conversation-system-messages#mid-conversation-tool-changes) are in beta and require the
This feature is available on Claude Fable 5.1, [Claude Mythos 5.1](https://anthropic.com/glasswing), Claude Fable 5, [Claude Mythos 5](https://anthropic.com/glasswing), Claude Op
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api
build-with-claude/mid-conversation-effort-example
±changed
+9−9
apichanged
build-with-claude/mid-conversation-effort-example
MODEL = "claude-opus-5"
MODEL = "claude-opus-5-5"
const MODEL = "claude-opus-5";
const MODEL = "claude-opus-5-5";
const Model model = Model.ClaudeOpus5;
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api
build-with-claude/handling-stop-reasons
±changed
+141−141
apichanged
build-with-claude/handling-stop-reasons
"model": "claude-opus-5",
"model": "claude-opus-5-5",
--model claude-opus-5 \
--model claude-opus-5-5 \
model="claude-opus-5",
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api
build-with-claude/files
±changed
+18−18
apichanged
build-with-claude/files
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
model="claude-opus-5",
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api
build-with-claude/fast-mode
±changed
+33−31
apichanged
build-with-claude/fast-mode
Fast mode delivers up to 2.5x higher output tokens per second from Claude Opus 5 and Claude Opus 4.8 at premium pricing. Set `speed: "fast"` with the `fast-mode-2026-02-01` beta he
Fast mode delivers up to 2.5x higher output tokens per second from Claude Opus 5.5, Claude Opus 5, and Claude Opus 4.8 at premium pricing. Set `speed: "fast"` with the `fast-mode-2
* Claude Opus 5.5 (claude-opus-5-5)
Fast mode for Claude Opus 5 and Claude Opus 4.8 is available as a research preview on the Claude API, including [Claude Managed Agents](https://platform.claude.com/docs/en/manage
Fast mode for Claude Opus 5.5, Claude Opus 5, and Claude Opus 4.8 is available as a research preview on the Claude API, including [Claude Managed Agents](https://platform.claude.
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api
build-with-claude/fallback-credit
±changed
+1−1
apichanged
build-with-claude/fallback-credit
On models that include the 1M token context window by default, such as Claude Fable 5.1, Claude Fable 5, Claude Opus 5, and Claude Opus 4.8, the `context-1m-2025-08-07` beta he
On models that include the 1M token context window by default, such as Claude Fable 5.1, Claude Fable 5, Claude Opus 5.5, Claude Opus 5, and Claude Opus 4.8, the `context-1m-20
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api
build-with-claude/extended-thinking
±changed
+1−1
apichanged
build-with-claude/extended-thinking
* You are moving to Claude Opus 4.7, Claude Opus 4.8, Claude Opus 5, Claude Sonnet 5, Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, or Claude Mythos 5, where `type: "enabled
* You are moving to Claude Opus 4.7, Claude Opus 4.8, Claude Opus 5, Claude Opus 5.5, Claude Sonnet 5, Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, or Claude Mythos 5, wher
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api
build-with-claude/effort
±changed
+25−20
apichanged
build-with-claude/effort
- claude-opus-5-5
"model": "claude-opus-5",
"model": "claude-opus-5-5",
--model claude-opus-5 \
--model claude-opus-5-5 \
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api
build-with-claude/context-windows
±changed
+1−1
apichanged
build-with-claude/context-windows
Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, Claude Opus 5, Claude Opus 4.8, Claude Opus 4.7, Claude Opus 4.6, Claude Sonnet 5, Claude Sonnet 4.6, and [Cla
Claude Fable 5.1, Claude Mythos 5.1, Claude Fable 5, Claude Mythos 5, Claude Opus 5.5, Claude Opus 5, Claude Opus 4.8, Claude Opus 4.7, Claude Opus 4.6, Claude Sonnet 5, Claude Son
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api
build-with-claude/context-editing
±changed
+82−82
apichanged
build-with-claude/context-editing
On Claude Fable 5.1, server-side context management never invalidates thinking blocks. Client-side edits to earlier turns can invalidate the thinking blocks in every later assistan
On Claude Fable 5.1 and Claude Opus 5.5, server-side context management never invalidates thinking blocks. Client-side edits to earlier turns can invalidate the thinking blocks in
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
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api
build-with-claude/compaction-threshold
±changed
+122−121
apichanged
build-with-claude/compaction-threshold
- claude-opus-5-5
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
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api
build-with-claude/compaction-thinking-blocks
±changed
+2−1
apichanged
build-with-claude/compaction-thinking-blocks
- claude-opus-5-5
Mid-conversation system messages inside the summarized turns are summarized too, so their instructions and tool changes stop applying after the swap. To keep one in force, state it
Mid-conversation system messages inside the summarized turns are summarized too, so their text instructions stop applying after the swap. To keep one in force, state it again in a
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api
build-with-claude/compaction-on-demand
±changed
+26−25
apichanged
build-with-claude/compaction-on-demand
- claude-opus-5-5
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
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api
build-with-claude/compaction-keep-recent-turns
±changed
+16−15
apichanged
build-with-claude/compaction-keep-recent-turns
- claude-opus-5-5
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model="claude-opus-5",
model="claude-opus-5-5",
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api
build-with-claude/compaction-background
±changed
+13−12
apichanged
build-with-claude/compaction-background
- claude-opus-5-5
model="claude-opus-5",
model="claude-opus-5-5",
model="claude-opus-5",
model="claude-opus-5-5",
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api
build-with-claude/claude-platform-on-aws
±changed
+25−24
apichanged
build-with-claude/claude-platform-on-aws
implementation("com.anthropic:anthropic-java:2.63.0")
implementation("com.anthropic:anthropic-java-aws:2.63.0")
implementation("com.anthropic:anthropic-java:2.65.0")
implementation("com.anthropic:anthropic-java-aws:2.65.0")
<version>2.63.0</version>
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api
build-with-claude/claude-on-vertex-ai
±changed
+31−30
apichanged
build-with-claude/claude-on-vertex-ai
implementation("com.anthropic:anthropic-java:2.63.0")
implementation("com.anthropic:anthropic-java-vertex:2.63.0")
implementation("com.anthropic:anthropic-java:2.65.0")
implementation("com.anthropic:anthropic-java-vertex:2.65.0")
<version>2.63.0</version>
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api
build-with-claude/claude-on-amazon-bedrock-legacy
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+7−7
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build-with-claude/claude-on-amazon-bedrock-legacy
implementation("com.anthropic:anthropic-java:2.63.0")
implementation("com.anthropic:anthropic-java-bedrock:2.63.0")
implementation("com.anthropic:anthropic-java:2.65.0")
implementation("com.anthropic:anthropic-java-bedrock:2.65.0")
<version>2.63.0</version>
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api
build-with-claude/claude-in-microsoft-foundry
±changed
+24−23
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build-with-claude/claude-in-microsoft-foundry
This guide shows you how to set up and make API calls to Claude in Microsoft Foundry using one of Anthropic's client SDKs or direct HTTP requests. When you access Claude in Microso
This guide shows you how to set up and make API calls to Claude in Microsoft Foundry using one of Anthropic's client SDKs or direct HTTP requests. When you access Claude in Microso
implementation("com.anthropic:anthropic-java:2.63.0")
implementation("com.anthropic:anthropic-java-foundry:2.63.0")
implementation("com.anthropic:anthropic-java:2.65.0")
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api
build-with-claude/claude-in-amazon-bedrock
±changed
+15−14
apichanged
build-with-claude/claude-in-amazon-bedrock
implementation("com.anthropic:anthropic-java:2.63.0")
implementation("com.anthropic:anthropic-java-bedrock:2.63.0")
implementation("com.anthropic:anthropic-java:2.65.0")
implementation("com.anthropic:anthropic-java-bedrock:2.65.0")
<version>2.63.0</version>
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api
build-with-claude/citations
±changed
+63−63
apichanged
build-with-claude/citations
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
model="claude-opus-5",
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api
build-with-claude/cache-diagnostics
±changed
+34−34
apichanged
build-with-claude/cache-diagnostics
"model": "claude-opus-5",
"model": "claude-opus-5-5",
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
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api
build-with-claude/batch-processing
±changed
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build-with-claude/batch-processing
| Claude Opus 5.5 | $2 / MTok | $10 / MTok |
"model": "claude-opus-5",
"model": "claude-opus-5-5",
"model": "claude-opus-5",
"model": "claude-opus-5-5",
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api
api/service-tiers
±changed
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apichanged
api/service-tiers
Priority Tier is supported on all available Claude models except Claude Fable 5.1, Claude Mythos 5.1, Claude Mythos 5, [Claude Mythos Preview](https://anthropic.com/glasswing), Cla
Priority Tier is supported on all available Claude models except Claude Fable 5.1, Claude Mythos 5.1, Claude Mythos 5, [Claude Mythos Preview](https://anthropic.com/glasswing), Cla
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api
api/rate-limits
±changed
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apichanged
api/rate-limits
| Claude Opus 5.5 | 1,000 | 2,
| Claude Opus 5.5 | 5,000 | 5,
| Claude Opus 5.5 | 10,000 | 10
*2 Opus rate limit is a total limit that applies to combined traffic across Claude Opus 4.8, Opus 4.7, Opus 4.6, and Opus 4.5. Claude Opus 5 has a separate rate limit and is not pa
*2 Opus rate limit is a total limit that applies to combined traffic across Claude Opus 4.8, Opus 4.7, Opus 4.6, and Opus 4.5. Claude Opus 5.5 and Claude Opus 5 each have a separat
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api
api/errors
±changed
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apichanged
api/errors
On Claude Fable 5.1, [Claude Mythos 5.1](https://anthropic.com/glasswing), Claude Fable 5, [Claude Mythos 5](https://anthropic.com/glasswing), and [Claude Mythos Preview](https://a
On Claude Fable 5.1, [Claude Mythos 5.1](https://anthropic.com/glasswing), Claude Fable 5, [Claude Mythos 5](https://anthropic.com/glasswing), Claude Opus 5.5, and [Claude Mythos P
Claude Fable 5.1 and [Claude Mythos 5.1](https://anthropic.com/glasswing) don't support forced tool use. Sending `tool_choice: {"type": "any"}` or `tool_choice: {"type": "tool", "n
Claude Opus 5.5, Claude Fable 5.1, and [Claude Mythos 5.1](https://anthropic.com/glasswing) don't support forced tool use. Sending `tool_choice: {"type": "any"}` or `tool_choice: {
### Computer use tool version not supported
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api
api/beta-headers
±changed
+9−9
apichanged
api/beta-headers
"model": "claude-opus-5",
"model": "claude-opus-5-5",
--model claude-opus-5 \
--model claude-opus-5-5 \
model="claude-opus-5",
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api
agents-and-tools/tool-use/web-search-tool
±changed
+18−18
apichanged
agents-and-tools/tool-use/web-search-tool
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
model="claude-opus-5",
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api
agents-and-tools/tool-use/tool-search-tool
±changed
+10−9
apichanged
agents-and-tools/tool-use/tool-search-tool
| Claude Opus 5.5 (claude-opus-5-5) | `tool_search_tool_regex_20251119`, `tool_search_tool_bm25_20251119` |
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
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api
agents-and-tools/tool-use/tool-runner
±changed
+37−37
apichanged
agents-and-tools/tool-use/tool-runner
model="claude-opus-5",
model="claude-opus-5-5",
model: "claude-opus-5",
model: "claude-opus-5-5",
model: "claude-opus-5",
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api
agents-and-tools/tool-use/text-editor-tool
±changed
+39−39
apichanged
agents-and-tools/tool-use/text-editor-tool
"model": "claude-opus-5",
"model": "claude-opus-5-5",
--model claude-opus-5 \
--model claude-opus-5-5 \
model="claude-opus-5",
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api
agents-and-tools/tool-use/strict-tool-use
±changed
+27−27
apichanged
agents-and-tools/tool-use/strict-tool-use
"model": "claude-opus-5",
"model": "claude-opus-5-5",
model: claude-opus-5
model: claude-opus-5-5
model="claude-opus-5",
+27 −27 lines
Recorded here 22 Sep 2026 16:37 UTC
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