Context editing

Overview

Context editing allows you to selectively clear specific content from conversation history as it grows. Beyond optimizing costs and staying within limits, this is about actively curating what Claude sees: context is a finite resource with diminishing returns, and irrelevant content degrades model focus. Context editing gives you fine-grained runtime control over that curation. For the broader principles behind context management, see Effective context engineering. This page covers:

• Tool result clearing - Best for agentic workflows with heavy tool use where old tool results are no longer needed
• Thinking block clearing - For managing thinking blocks when using extended thinking, with options to preserve recent thinking for context continuity
• Client-side SDK compaction - An SDK-based alternative for summary-based context management (server-side compaction is generally preferred)

Server-side strategies

Share feedback on this feature through the feedback form.

Tool result clearing

The clear_tool_uses_20250919 strategy clears tool results when conversation context grows beyond your configured threshold. This is particularly useful for agentic workflows with heavy tool use. Older tool results (like file contents or search results) are no longer needed once Claude has processed them.

When activated, the API automatically clears the oldest tool results in chronological order. The API replaces each cleared result with placeholder text indicating to Claude that it was removed. By default, only tool results are cleared. You can optionally clear both tool results and tool calls (the tool use parameters) by setting clear_tool_inputs to true.

Thinking block clearing

The clear_thinking_20251015 strategy manages thinking blocks in conversations when extended thinking is enabled. This strategy gives you control over thinking preservation: you can choose to keep more thinking blocks to maintain reasoning continuity, or clear them more aggressively to save context space.

Use this strategy to override the default. If your code runs across multiple model tiers, set keep explicitly rather than relying on the per-model default.

An assistant conversation turn may include multiple content blocks (for example, when using tools) and multiple thinking blocks (for example, with interleaved thinking).

Context editing happens server-side

Context editing is applied server-side before the prompt reaches Claude. Your client application maintains the full, unmodified conversation history. You do not need to sync your client state with the edited version. Continue managing your full conversation history locally as you normally would.

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 assistant turn. For new accounts created on or after August 31, 2026, a request that replays an invalidated block is rejected unless you opt into dropping it. See Keeping the prefix unchanged.

Context editing and prompt caching

Context editing's interaction with prompt caching varies by strategy:

• Tool result clearing: Invalidates cached prompt prefixes when content is cleared. To account for this, clear enough tokens to make the cache invalidation worthwhile. Use the clear_at_least parameter to ensure a minimum number of tokens is cleared each time. You'll incur cache write costs each time content is cleared, but subsequent requests can reuse the newly cached prefix.

• Thinking block clearing: When thinking blocks are kept in context (not cleared), the prompt cache is preserved, enabling cache hits and reducing input token costs. When thinking blocks are cleared, the cache is invalidated at the point where clearing occurs. Configure the keep parameter based on whether you want to prioritize cache performance or context window availability.

Supported models

Context editing is available on all supported Claude models.

Tool result clearing usage

The simplest way to enable tool result clearing is to specify only the strategy type. All other configuration options use their default values:

ant beta:messages create --beta context-management-2025-06-27 <<'YAML'
model: claude-opus-5
max_tokens: 4096
messages:
  - role: user
    content: Search for recent developments in AI
tools:
  - type: web_search_20250305
    name: web_search
context_management:
  edits:
    - type: clear_tool_uses_20250919
YAML

response = client.beta.messages.create(
    model="claude-opus-5",
    max_tokens=4096,
    messages=[{"role": "user", "content": "Search for recent developments in AI"}],
    tools=[{"type": "web_search_20250305", "name": "web_search"}],
    betas=["context-management-2025-06-27"],
    context_management={"edits": [{"type": "clear_tool_uses_20250919"}]},
)

const anthropic = new Anthropic({
  apiKey: process.env.ANTHROPIC_API_KEY
});

const response = await anthropic.beta.messages.create({
  model: "claude-opus-5",
  max_tokens: 4096,
  messages: [
    {
      role: "user",
      content: "Search for recent developments in AI"
    }
  ],
  tools: [
    {
      type: "web_search_20250305",
      name: "web_search"
    }
  ],
  context_management: {
    edits: [{ type: "clear_tool_uses_20250919" }]
  },
  betas: ["context-management-2025-06-27"]
});

using Anthropic;
using Anthropic.Models.Beta;
using Anthropic.Models.Beta.Messages;
using Messages = Anthropic.Models.Messages;

AnthropicClient client = new();

var parameters = new MessageCreateParams
{
    Model = Messages::Model.ClaudeOpus5,
    MaxTokens = 4096,
    Messages = [
        new() { Role = Role.User, Content = "Search for recent developments in AI" }
    ],
    Tools = [
        new BetaWebSearchTool20250305()
    ],
    ContextManagement = new BetaContextManagementConfig
    {
        Edits = [new BetaClearToolUses20250919Edit()]
    },
    Betas = [AnthropicBeta.ContextManagement2025_06_27]
};

var response = await client.Beta.Messages.Create(parameters);
Console.WriteLine(response);

client := anthropic.NewClient()

response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
	Model:     anthropic.ModelClaudeOpus5,
	MaxTokens: 4096,
	Messages: []anthropic.BetaMessageParam{
		anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Search for recent developments in AI")),
	},
	Tools: []anthropic.BetaToolUnionParam{
		{OfWebSearchTool20250305: &anthropic.BetaWebSearchTool20250305Param{}},
	},
	ContextManagement: anthropic.BetaContextManagementConfigParam{
		Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
			{OfClearToolUses20250919: &anthropic.BetaClearToolUses20250919EditParam{}},
		},
	},
	Betas: []anthropic.AnthropicBeta{
		anthropic.AnthropicBetaContextManagement2025_06_27,
	},
})
if err != nil {
	log.Fatal(err)
}
fmt.Println(response)

import com.anthropic.models.beta.messages.BetaWebSearchTool20250305;
import com.anthropic.models.beta.messages.BetaContextManagementConfig;
import com.anthropic.models.beta.messages.BetaClearToolUses20250919Edit;
import com.anthropic.models.beta.AnthropicBeta;
// ...
void main() {
    AnthropicClient client = AnthropicOkHttpClient.fromEnv();

    MessageCreateParams params = MessageCreateParams.builder()
        .model(Model.CLAUDE_OPUS_5)
        .maxTokens(4096L)
        .addUserMessage("Search for recent developments in AI")
        .addTool(BetaWebSearchTool20250305.builder().build())
        .contextManagement(BetaContextManagementConfig.builder()
            .addEdit(BetaClearToolUses20250919Edit.builder().build())
            .build())
        .addBeta(AnthropicBeta.CONTEXT_MANAGEMENT_2025_06_27)
        .build();

    BetaMessage response = client.beta().messages().create(params);
    IO.println(response);
}

$client = new Client();

$response = $client->beta->messages->create(
    maxTokens: 4096,
    messages: [
        ['role' => 'user', 'content' => 'Search for recent developments in AI']
    ],
    model: 'claude-opus-5',
    betas: ['context-management-2025-06-27'],
    tools: [
        ['type' => 'web_search_20250305', 'name' => 'web_search']
    ],
    contextManagement: [
        'edits' => [
            ['type' => 'clear_tool_uses_20250919']
        ]
    ],
);

echo $response;

client = Anthropic::Client.new

response = client.beta.messages.create(
  model: "claude-opus-5",
  max_tokens: 4096,
  messages: [
    { role: "user", content: "Search for recent developments in AI" }
  ],
  tools: [
    { type: "web_search_20250305", name: "web_search" }
  ],
  context_management: {
    edits: [
      { type: "clear_tool_uses_20250919" }
    ]
  },
  betas: ["context-management-2025-06-27"]
)
puts response

Advanced configuration

You can customize the tool result clearing behavior with additional parameters:

ant beta:messages create --beta context-management-2025-06-27 <<'YAML'
model: claude-opus-5
max_tokens: 4096
messages:
  - role: user
    content: Create a simple command line calculator app using Python
tools:
  - type: text_editor_20250728
    name: str_replace_based_edit_tool
    max_characters: 10000
  - type: web_search_20250305
    name: web_search
    max_uses: 3
context_management:
  edits:
    - type: clear_tool_uses_20250919
      trigger:
        type: input_tokens
        value: 30000
      keep:
        type: tool_uses
        value: 3
      clear_at_least:
        type: input_tokens
        value: 5000
      exclude_tools:
        - web_search
YAML

response = client.beta.messages.create(
    model="claude-opus-5",
    max_tokens=4096,
    messages=[
        {
            "role": "user",
            "content": "Create a simple command line calculator app using Python",
        }
    ],
    tools=[
        {
            "type": "text_editor_20250728",
            "name": "str_replace_based_edit_tool",
            "max_characters": 10000,
        },
        {"type": "web_search_20250305", "name": "web_search", "max_uses": 3},
    ],
    betas=["context-management-2025-06-27"],
    context_management={
        "edits": [
            {
                "type": "clear_tool_uses_20250919",
                # Trigger clearing when threshold is exceeded
                "trigger": {"type": "input_tokens", "value": 30000},
                # Number of tool uses to keep after clearing
                "keep": {"type": "tool_uses", "value": 3},
                # Optional: Clear at least this many tokens
                "clear_at_least": {"type": "input_tokens", "value": 5000},
                # Exclude these tools from being cleared
                "exclude_tools": ["web_search"],
            }
        ]
    },
)

const anthropic = new Anthropic({
  apiKey: process.env.ANTHROPIC_API_KEY
});

const response = await anthropic.beta.messages.create({
  model: "claude-opus-5",
  max_tokens: 4096,
  messages: [
    {
      role: "user",
      content: "Create a simple command line calculator app using Python"
    }
  ],
  tools: [
    {
      type: "text_editor_20250728",
      name: "str_replace_based_edit_tool",
      max_characters: 10000
    },
    {
      type: "web_search_20250305",
      name: "web_search",
      max_uses: 3
    }
  ],
  betas: ["context-management-2025-06-27"],
  context_management: {
    edits: [
      {
        type: "clear_tool_uses_20250919",
        // Trigger clearing when threshold is exceeded
        trigger: {
          type: "input_tokens",
          value: 30000
        },
        // Number of tool uses to keep after clearing
        keep: {
          type: "tool_uses",
          value: 3
        },
        // Optional: Clear at least this many tokens
        clear_at_least: {
          type: "input_tokens",
          value: 5000
        },
        // Exclude these tools from being cleared
        exclude_tools: ["web_search"]
      }
    ]
  }
});

using Anthropic;
using Anthropic.Models.Beta;
using Anthropic.Models.Beta.Messages;
using Messages = Anthropic.Models.Messages;

AnthropicClient client = new();

var parameters = new MessageCreateParams
{
    Model = Messages::Model.ClaudeOpus5,
    MaxTokens = 4096,
    Messages = [
        new() { Role = Role.User, Content = "Create a simple command line calculator app using Python" }
    ],
    Tools = [
        new BetaToolTextEditor20250728 { MaxCharacters = 10000 },
        new BetaWebSearchTool20250305 { MaxUses = 3 }
    ],
    Betas = [AnthropicBeta.ContextManagement2025_06_27],
    ContextManagement = new BetaContextManagementConfig
    {
        Edits = [
            new BetaClearToolUses20250919Edit
            {
                Trigger = new BetaInputTokensTrigger(30000),
                Keep = new BetaToolUsesKeep(3),
                ClearAtLeast = new BetaInputTokensClearAtLeast(5000),
                ExcludeTools = ["web_search"]
            }
        ]
    }
};

var response = await client.Beta.Messages.Create(parameters);
Console.WriteLine(response);

client := anthropic.NewClient()

response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
	Model:     anthropic.ModelClaudeOpus5,
	MaxTokens: 4096,
	Messages: []anthropic.BetaMessageParam{
		anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Create a simple command line calculator app using Python")),
	},
	Tools: []anthropic.BetaToolUnionParam{
		{OfTextEditor20250728: &anthropic.BetaToolTextEditor20250728Param{
			MaxCharacters: anthropic.Int(10000),
		}},
		{OfWebSearchTool20250305: &anthropic.BetaWebSearchTool20250305Param{
			MaxUses: anthropic.Int(3),
		}},
	},
	Betas: []anthropic.AnthropicBeta{anthropic.AnthropicBetaContextManagement2025_06_27},
	ContextManagement: anthropic.BetaContextManagementConfigParam{
		Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
			{OfClearToolUses20250919: &anthropic.BetaClearToolUses20250919EditParam{
				Trigger: anthropic.BetaClearToolUses20250919EditTriggerUnionParam{
					OfInputTokens: &anthropic.BetaInputTokensTriggerParam{
						Value: 30000,
					},
				},
				Keep: anthropic.BetaToolUsesKeepParam{
					Value: 3,
				},
				ClearAtLeast: anthropic.BetaInputTokensClearAtLeastParam{
					Value: 5000,
				},
				ExcludeTools: []string{"web_search"},
			}},
		},
	},
})
if err != nil {
	log.Fatal(err)
}
fmt.Println(response)

import com.anthropic.models.beta.messages.BetaToolTextEditor20250728;
import com.anthropic.models.beta.messages.BetaWebSearchTool20250305;
import com.anthropic.models.beta.messages.BetaContextManagementConfig;
import com.anthropic.models.beta.messages.BetaClearToolUses20250919Edit;
import com.anthropic.models.beta.messages.BetaInputTokensTrigger;
import com.anthropic.models.beta.messages.BetaInputTokensClearAtLeast;
import com.anthropic.models.beta.messages.BetaToolUsesKeep;
import com.anthropic.models.beta.AnthropicBeta;
// ...
void main() {
    AnthropicClient client = AnthropicOkHttpClient.fromEnv();

    MessageCreateParams params = MessageCreateParams.builder()
        .model(Model.CLAUDE_OPUS_5)
        .maxTokens(4096L)
        .addUserMessage("Create a simple command line calculator app using Python")
        .addTool(BetaToolTextEditor20250728.builder()
            .maxCharacters(10000L)
            .build())
        .addTool(BetaWebSearchTool20250305.builder()
            .maxUses(3L)
            .build())
        .addBeta(AnthropicBeta.CONTEXT_MANAGEMENT_2025_06_27)
        .contextManagement(BetaContextManagementConfig.builder()
            .addEdit(BetaClearToolUses20250919Edit.builder()
                .trigger(BetaInputTokensTrigger.builder()
                    .value(30000L)
                    .build())
                .keep(BetaToolUsesKeep.builder()
                    .value(3L)
                    .build())
                .clearAtLeast(BetaInputTokensClearAtLeast.builder()
                    .value(5000L)
                    .build())
                .addExcludeTool("web_search")
                .build())
            .build())
        .build();

    BetaMessage response = client.beta().messages().create(params);
    IO.println(response);
}

$client = new Client();

$response = $client->beta->messages->create(
    maxTokens: 4096,
    messages: [
        [
            'role' => 'user',
            'content' => 'Create a simple command line calculator app using Python'
        ]
    ],
    model: 'claude-opus-5',
    betas: ['context-management-2025-06-27'],
    tools: [
        [
            'type' => 'text_editor_20250728',
            'name' => 'str_replace_based_edit_tool',
            'max_characters' => 10000
        ],
        [
            'type' => 'web_search_20250305',
            'name' => 'web_search',
            'max_uses' => 3
        ]
    ],
    contextManagement: [
        'edits' => [
            [
                'type' => 'clear_tool_uses_20250919',
                'trigger' => [
                    'type' => 'input_tokens',
                    'value' => 30000
                ],
                'keep' => [
                    'type' => 'tool_uses',
                    'value' => 3
                ],
                'clear_at_least' => [
                    'type' => 'input_tokens',
                    'value' => 5000
                ],
                'exclude_tools' => ['web_search']
            ]
        ]
    ],
);

echo $response;

client = Anthropic::Client.new

response = client.beta.messages.create(
  model: "claude-opus-5",
  max_tokens: 4096,
  messages: [
    {
      role: "user",
      content: "Create a simple command line calculator app using Python"
    }
  ],
  tools: [
    {
      type: "text_editor_20250728",
      name: "str_replace_based_edit_tool",
      max_characters: 10000
    },
    {
      type: "web_search_20250305",
      name: "web_search",
      max_uses: 3
    }
  ],
  betas: ["context-management-2025-06-27"],
  context_management: {
    edits: [
      {
        type: "clear_tool_uses_20250919",
        trigger: {
          type: "input_tokens",
          value: 30000
        },
        keep: {
          type: "tool_uses",
          value: 3
        },
        clear_at_least: {
          type: "input_tokens",
          value: 5000
        },
        exclude_tools: ["web_search"]
      }
    ]
  }
)
puts response

Thinking block clearing usage

Enable thinking block clearing to manage context and prompt caching effectively when extended thinking is enabled:

ant beta:messages create --beta context-management-2025-06-27 <<'YAML'
model: claude-opus-5
max_tokens: 16000
messages:
  - role: user
    content: Hello
context_management:
  edits:
    - type: clear_thinking_20251015
      keep:
        type: thinking_turns
        value: 2
YAML

response = client.beta.messages.create(
    model="claude-opus-5",
    max_tokens=16000,
    messages=[{"role": "user", "content": "Hello"}],
    betas=["context-management-2025-06-27"],
    context_management={
        "edits": [
            {
                "type": "clear_thinking_20251015",
                "keep": {"type": "thinking_turns", "value": 2},
            }
        ]
    },
)

const anthropic = new Anthropic({
  apiKey: process.env.ANTHROPIC_API_KEY
});

const response = await anthropic.beta.messages.create({
  model: "claude-opus-5",
  max_tokens: 16000,
  messages: [{ role: "user", content: "Hello" }],
  betas: ["context-management-2025-06-27"],
  context_management: {
    edits: [
      {
        type: "clear_thinking_20251015",
        keep: {
          type: "thinking_turns",
          value: 2
        }
      }
    ]
  }
});

using Anthropic;
using Anthropic.Models.Beta;
using Anthropic.Models.Beta.Messages;
using Messages = Anthropic.Models.Messages;

AnthropicClient client = new();

var parameters = new MessageCreateParams
{
    Model = Messages::Model.ClaudeOpus5,
    MaxTokens = 16000,
    Messages = [
        new() { Role = Role.User, Content = "Hello" }
    ],
    Betas = [AnthropicBeta.ContextManagement2025_06_27],
    ContextManagement = new BetaContextManagementConfig
    {
        Edits = [
            new BetaClearThinking20251015Edit
            {
                Keep = new BetaThinkingTurns(2)
            }
        ]
    }
};

var response = await client.Beta.Messages.Create(parameters);
Console.WriteLine(response);

client := anthropic.NewClient()

response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
	Model:     anthropic.ModelClaudeOpus5,
	MaxTokens: 16000,
	Messages: []anthropic.BetaMessageParam{
		anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Hello")),
	},
	Betas: []anthropic.AnthropicBeta{anthropic.AnthropicBetaContextManagement2025_06_27},
	ContextManagement: anthropic.BetaContextManagementConfigParam{
		Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
			{OfClearThinking20251015: &anthropic.BetaClearThinking20251015EditParam{
				Keep: anthropic.BetaClearThinking20251015EditKeepUnionParam{
					OfThinkingTurns: &anthropic.BetaThinkingTurnsParam{
						Value: 2,
					},
				},
			}},
		},
	},
})
if err != nil {
	log.Fatal(err)
}
fmt.Println(response)

import com.anthropic.models.beta.messages.BetaContextManagementConfig;
import com.anthropic.models.beta.messages.BetaClearThinking20251015Edit;
import com.anthropic.models.beta.messages.BetaThinkingTurns;
import com.anthropic.models.beta.AnthropicBeta;
// ...
void main() {
    AnthropicClient client = AnthropicOkHttpClient.fromEnv();

    MessageCreateParams params = MessageCreateParams.builder()
        .model(Model.CLAUDE_OPUS_5)
        .maxTokens(16000L)
        .addUserMessage("Hello")
        .addBeta(AnthropicBeta.CONTEXT_MANAGEMENT_2025_06_27)
        .contextManagement(BetaContextManagementConfig.builder()
            .addEdit(BetaClearThinking20251015Edit.builder()
                .keep(BetaThinkingTurns.builder()
                    .value(2L)
                    .build())
                .build())
            .build())
        .build();

    BetaMessage response = client.beta().messages().create(params);
    IO.println(response);
}

$client = new Client();

$response = $client->beta->messages->create(
    maxTokens: 16000,
    messages: [
        ['role' => 'user', 'content' => 'Hello']
    ],
    model: 'claude-opus-5',
    betas: ['context-management-2025-06-27'],
    contextManagement: [
        'edits' => [
            [
                'type' => 'clear_thinking_20251015',
                'keep' => [
                    'type' => 'thinking_turns',
                    'value' => 2
                ]
            ]
        ]
    ],
);

echo $response;

client = Anthropic::Client.new

response = client.beta.messages.create(
  model: "claude-opus-5",
  max_tokens: 16000,
  messages: [{ role: "user", content: "Hello" }],
  betas: ["context-management-2025-06-27"],
  context_management: {
    edits: [
      {
        type: "clear_thinking_20251015",
        keep: {
          type: "thinking_turns",
          value: 2
        }
      }
    ]
  }
)
puts response

Configuration options for thinking block clearing

The clear_thinking_20251015 strategy supports the following configuration:

Example configurations:

Keep thinking blocks from the last 3 assistant turns:

ant beta:messages create --beta context-management-2025-06-27 <<'YAML'
model: claude-opus-5
max_tokens: 16000
messages:
  - role: user
    content: Hello
context_management:
  edits:
    - type: clear_thinking_20251015
      keep:
        type: thinking_turns
        value: 3
YAML

response = client.beta.messages.create(
    model="claude-opus-5",
    max_tokens=16000,
    messages=[{"role": "user", "content": "Hello"}],
    betas=["context-management-2025-06-27"],
    context_management={
        "edits": [
            {
                "type": "clear_thinking_20251015",
                "keep": {"type": "thinking_turns", "value": 3},
            }
        ]
    },
)

const anthropic = new Anthropic({
  apiKey: process.env.ANTHROPIC_API_KEY
});

const response = await anthropic.beta.messages.create({
  model: "claude-opus-5",
  max_tokens: 16000,
  messages: [{ role: "user", content: "Hello" }],
  betas: ["context-management-2025-06-27"],
  context_management: {
    edits: [
      {
        type: "clear_thinking_20251015",
        keep: {
          type: "thinking_turns",
          value: 3
        }
      }
    ]
  }
});

using Anthropic;
using Anthropic.Models.Beta;
using Anthropic.Models.Beta.Messages;
using Messages = Anthropic.Models.Messages;

AnthropicClient client = new();

var parameters = new MessageCreateParams
{
    Model = Messages::Model.ClaudeOpus5,
    MaxTokens = 16000,
    Messages = [
        new() { Role = Role.User, Content = "Hello" }
    ],
    Betas = [AnthropicBeta.ContextManagement2025_06_27],
    ContextManagement = new BetaContextManagementConfig
    {
        Edits = [
            new BetaClearThinking20251015Edit
            {
                Keep = new BetaThinkingTurns(3)
            }
        ]
    }
};

var response = await client.Beta.Messages.Create(parameters);
Console.WriteLine(response);

client := anthropic.NewClient()

response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
	Model:     anthropic.ModelClaudeOpus5,
	MaxTokens: 16000,
	Messages: []anthropic.BetaMessageParam{
		anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Hello")),
	},
	Betas: []anthropic.AnthropicBeta{anthropic.AnthropicBetaContextManagement2025_06_27},
	ContextManagement: anthropic.BetaContextManagementConfigParam{
		Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
			{OfClearThinking20251015: &anthropic.BetaClearThinking20251015EditParam{
				Keep: anthropic.BetaClearThinking20251015EditKeepUnionParam{
					OfThinkingTurns: &anthropic.BetaThinkingTurnsParam{
						Value: 3,
					},
				},
			}},
		},
	},
})
if err != nil {
	log.Fatal(err)
}
fmt.Println(response)

AnthropicClient client = AnthropicOkHttpClient.fromEnv();

MessageCreateParams params = MessageCreateParams.builder()
    .model(Model.CLAUDE_OPUS_5)
    .maxTokens(16000L)
    .addUserMessage("Hello")
    .addBeta(AnthropicBeta.CONTEXT_MANAGEMENT_2025_06_27)
    .contextManagement(BetaContextManagementConfig.builder()
        .addEdit(BetaClearThinking20251015Edit.builder()
            .keep(BetaThinkingTurns.builder()
                .value(3L)
                .build())
            .build())
        .build())
    .build();

BetaMessage response = client.beta().messages().create(params);
IO.println(response);

$client = new Client();

$response = $client->beta->messages->create(
    maxTokens: 16000,
    messages: [
        ['role' => 'user', 'content' => 'Hello']
    ],
    model: 'claude-opus-5',
    betas: ['context-management-2025-06-27'],
    contextManagement: [
        'edits' => [
            [
                'type' => 'clear_thinking_20251015',
                'keep' => [
                    'type' => 'thinking_turns',
                    'value' => 3
                ]
            ]
        ]
    ],
);

echo $response;

client = Anthropic::Client.new

response = client.beta.messages.create(
  model: "claude-opus-5",
  max_tokens: 16000,
  messages: [{ role: "user", content: "Hello" }],
  betas: ["context-management-2025-06-27"],
  context_management: {
    edits: [
      {
        type: "clear_thinking_20251015",
        keep: {
          type: "thinking_turns",
          value: 3
        }
      }
    ]
  }
)
puts response

Keep all thinking blocks (maximizes cache hits):

ant beta:messages create --beta context-management-2025-06-27 <<'YAML'
model: claude-opus-5
max_tokens: 16000
messages:
  - role: user
    content: Hello
context_management:
  edits:
    - type: clear_thinking_20251015
      keep: all
YAML

response = client.beta.messages.create(
    model="claude-opus-5",
    max_tokens=16000,
    messages=[{"role": "user", "content": "Hello"}],
    betas=["context-management-2025-06-27"],
    context_management={
        "edits": [
            {
                "type": "clear_thinking_20251015",
                "keep": "all",
            }
        ]
    },
)

const anthropic = new Anthropic({
  apiKey: process.env.ANTHROPIC_API_KEY
});

const response = await anthropic.beta.messages.create({
  model: "claude-opus-5",
  max_tokens: 16000,
  messages: [{ role: "user", content: "Hello" }],
  betas: ["context-management-2025-06-27"],
  context_management: {
    edits: [
      {
        type: "clear_thinking_20251015",
        keep: "all"
      }
    ]
  }
});

using Anthropic;
using Anthropic.Models.Beta;
using Anthropic.Models.Beta.Messages;
using Messages = Anthropic.Models.Messages;

AnthropicClient client = new();

var parameters = new MessageCreateParams
{
    Model = Messages::Model.ClaudeOpus5,
    MaxTokens = 16000,
    Messages = [
        new() { Role = Role.User, Content = "Hello" }
    ],
    Betas = [AnthropicBeta.ContextManagement2025_06_27],
    ContextManagement = new BetaContextManagementConfig
    {
        Edits = [
            new BetaClearThinking20251015Edit
            {
                Keep = new All()
            }
        ]
    }
};

var response = await client.Beta.Messages.Create(parameters);
Console.WriteLine(response);

client := anthropic.NewClient()

response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
	Model:     anthropic.ModelClaudeOpus5,
	MaxTokens: 16000,
	Messages: []anthropic.BetaMessageParam{
		anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Hello")),
	},
	Betas: []anthropic.AnthropicBeta{anthropic.AnthropicBetaContextManagement2025_06_27},
	ContextManagement: anthropic.BetaContextManagementConfigParam{
		Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
			{OfClearThinking20251015: &anthropic.BetaClearThinking20251015EditParam{
				Keep: anthropic.BetaClearThinking20251015EditKeepUnionParam{
					OfAll: constant.ValueOf[constant.All](),
				},
			}},
		},
	},
})
if err != nil {
	log.Fatal(err)
}
fmt.Println(response)

AnthropicClient client = AnthropicOkHttpClient.fromEnv();

MessageCreateParams params = MessageCreateParams.builder()
    .model(Model.CLAUDE_OPUS_5)
    .maxTokens(16000L)
    .addUserMessage("Hello")
    .addBeta(AnthropicBeta.CONTEXT_MANAGEMENT_2025_06_27)
    .contextManagement(BetaContextManagementConfig.builder()
        .addEdit(BetaClearThinking20251015Edit.builder()
            .keepAll()
            .build())
        .build())
    .build();

BetaMessage response = client.beta().messages().create(params);
IO.println(response);

$client = new Client();

$response = $client->beta->messages->create(
    maxTokens: 16000,
    messages: [
        ['role' => 'user', 'content' => 'Hello']
    ],
    model: 'claude-opus-5',
    betas: ['context-management-2025-06-27'],
    contextManagement: [
        'edits' => [
            [
                'type' => 'clear_thinking_20251015',
                'keep' => 'all'
            ]
        ]
    ],
);

echo $response;

client = Anthropic::Client.new

response = client.beta.messages.create(
  model: "claude-opus-5",
  max_tokens: 16000,
  messages: [{ role: "user", content: "Hello" }],
  betas: ["context-management-2025-06-27"],
  context_management: {
    edits: [
      {
        type: "clear_thinking_20251015",
        keep: "all"
      }
    ]
  }
)
puts response

Combining strategies

You can use both thinking block clearing and tool result clearing together:

ant beta:messages create --beta context-management-2025-06-27 <<'YAML'
model: claude-opus-5
max_tokens: 16000
messages:
  - role: user
    content: Search for the latest developments in quantum error correction and summarize the key breakthroughs.
tools:
  - type: web_search_20250305
    name: web_search
    max_uses: 5
context_management:
  edits:
    - type: clear_thinking_20251015
      keep:
        type: thinking_turns
        value: 2
    - type: clear_tool_uses_20250919
      trigger:
        type: input_tokens
        value: 50000
      keep:
        type: tool_uses
        value: 5
YAML

response = client.beta.messages.create(
    model="claude-opus-5",
    max_tokens=16000,
    messages=[
        {
            "role": "user",
            "content": "Search for the latest developments in quantum error correction and summarize the key breakthroughs.",
        }
    ],
    tools=[
        {
            "type": "web_search_20250305",
            "name": "web_search",
            "max_uses": 5,
        }
    ],
    betas=["context-management-2025-06-27"],
    context_management={
        "edits": [
            {
                "type": "clear_thinking_20251015",
                "keep": {"type": "thinking_turns", "value": 2},
            },
            {
                "type": "clear_tool_uses_20250919",
                "trigger": {"type": "input_tokens", "value": 50000},
                "keep": {"type": "tool_uses", "value": 5},
            },
        ]
    },
)

print(response)

const anthropic = new Anthropic({
  apiKey: process.env.ANTHROPIC_API_KEY
});

const response = await anthropic.beta.messages.create({
  model: "claude-opus-5",
  max_tokens: 16000,
  messages: [
    {
      role: "user",
      content:
        "Search for the latest developments in quantum error correction and summarize the key breakthroughs."
    }
  ],
  tools: [
    {
      type: "web_search_20250305",
      name: "web_search",
      max_uses: 5
    }
  ],
  betas: ["context-management-2025-06-27"],
  context_management: {
    edits: [
      {
        type: "clear_thinking_20251015",
        keep: {
          type: "thinking_turns",
          value: 2
        }
      },
      {
        type: "clear_tool_uses_20250919",
        trigger: {
          type: "input_tokens",
          value: 50000
        },
        keep: {
          type: "tool_uses",
          value: 5
        }
      }
    ]
  }
});

console.log(response);

using Anthropic;
using Anthropic.Models.Beta;
using Anthropic.Models.Beta.Messages;
using Messages = Anthropic.Models.Messages;

AnthropicClient client = new();

var parameters = new MessageCreateParams
{
    Model = Messages::Model.ClaudeOpus5,
    MaxTokens = 16000,
    Messages = [
        new() { Role = Role.User, Content = "Search for the latest developments in quantum error correction and summarize the key breakthroughs." }
    ],
    Tools = [
        new BetaWebSearchTool20250305 { MaxUses = 5 }
    ],
    Betas = [AnthropicBeta.ContextManagement2025_06_27],
    ContextManagement = new BetaContextManagementConfig
    {
        Edits = [
            new BetaClearThinking20251015Edit
            {
                Keep = new BetaThinkingTurns(2)
            },
            new BetaClearToolUses20250919Edit
            {
                Trigger = new BetaInputTokensTrigger(50000),
                Keep = new BetaToolUsesKeep(5)
            }
        ]
    }
};

var response = await client.Beta.Messages.Create(parameters);
Console.WriteLine(response);

client := anthropic.NewClient()

response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
	Model:     anthropic.ModelClaudeOpus5,
	MaxTokens: 16000,
	Messages: []anthropic.BetaMessageParam{
		anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Search for the latest developments in quantum error correction and summarize the key breakthroughs.")),
	},
	Tools: []anthropic.BetaToolUnionParam{
		{OfWebSearchTool20250305: &anthropic.BetaWebSearchTool20250305Param{
			MaxUses: anthropic.Int(5),
		}},
	},
	Betas: []anthropic.AnthropicBeta{
		anthropic.AnthropicBetaContextManagement2025_06_27,
	},
	ContextManagement: anthropic.BetaContextManagementConfigParam{
		Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
			{OfClearThinking20251015: &anthropic.BetaClearThinking20251015EditParam{
				Keep: anthropic.BetaClearThinking20251015EditKeepUnionParam{
					OfThinkingTurns: &anthropic.BetaThinkingTurnsParam{
						Value: 2,
					},
				},
			}},
			{OfClearToolUses20250919: &anthropic.BetaClearToolUses20250919EditParam{
				Trigger: anthropic.BetaClearToolUses20250919EditTriggerUnionParam{
					OfInputTokens: &anthropic.BetaInputTokensTriggerParam{
						Value: 50000,
					},
				},
				Keep: anthropic.BetaToolUsesKeepParam{
					Value: 5,
				},
			}},
		},
	},
})
if err != nil {
	log.Fatal(err)
}
fmt.Println(response)

import com.anthropic.models.beta.messages.BetaWebSearchTool20250305;
import com.anthropic.models.beta.messages.BetaContextManagementConfig;
import com.anthropic.models.beta.messages.BetaClearThinking20251015Edit;
import com.anthropic.models.beta.messages.BetaClearToolUses20250919Edit;
import com.anthropic.models.beta.messages.BetaThinkingTurns;
import com.anthropic.models.beta.messages.BetaInputTokensTrigger;
import com.anthropic.models.beta.messages.BetaToolUsesKeep;
import com.anthropic.models.beta.AnthropicBeta;
// ...
void main() {
    AnthropicClient client = AnthropicOkHttpClient.fromEnv();

    MessageCreateParams params = MessageCreateParams.builder()
        .model(Model.CLAUDE_OPUS_5)
        .maxTokens(16000L)
        .addUserMessage("Search for the latest developments in quantum error correction and summarize the key breakthroughs.")
        .addTool(BetaWebSearchTool20250305.builder()
            .maxUses(5L)
            .build())
        .addBeta(AnthropicBeta.CONTEXT_MANAGEMENT_2025_06_27)
        .contextManagement(BetaContextManagementConfig.builder()
            .addEdit(BetaClearThinking20251015Edit.builder()
                .keep(BetaThinkingTurns.builder()
                    .value(2L)
                    .build())
                .build())
            .addEdit(BetaClearToolUses20250919Edit.builder()
                .trigger(BetaInputTokensTrigger.builder()
                    .value(50000L)
                    .build())
                .keep(BetaToolUsesKeep.builder()
                    .value(5L)
                    .build())
                .build())
            .build())
        .build();

    BetaMessage response = client.beta().messages().create(params);
    IO.println(response);
}

$client = new Client();

$response = $client->beta->messages->create(
    maxTokens: 16000,
    messages: [
        [
            'role' => 'user',
            'content' => 'Search for the latest developments in quantum error correction and summarize the key breakthroughs.'
        ]
    ],
    model: 'claude-opus-5',
    betas: ['context-management-2025-06-27'],
    tools: [
        [
            'type' => 'web_search_20250305',
            'name' => 'web_search',
            'max_uses' => 5
        ]
    ],
    contextManagement: [
        'edits' => [
            [
                'type' => 'clear_thinking_20251015',
                'keep' => [
                    'type' => 'thinking_turns',
                    'value' => 2
                ]
            ],
            [
                'type' => 'clear_tool_uses_20250919',
                'trigger' => [
                    'type' => 'input_tokens',
                    'value' => 50000
                ],
                'keep' => [
                    'type' => 'tool_uses',
                    'value' => 5
                ]
            ]
        ]
    ],
);

echo $response;

client = Anthropic::Client.new

response = client.beta.messages.create(
  model: "claude-opus-5",
  max_tokens: 16000,
  messages: [
    {
      role: "user",
      content: "Search for the latest developments in quantum error correction and summarize the key breakthroughs."
    }
  ],
  tools: [
    {
      type: "web_search_20250305",
      name: "web_search",
      max_uses: 5
    }
  ],
  betas: ["context-management-2025-06-27"],
  context_management: {
    edits: [
      {
        type: "clear_thinking_20251015",
        keep: {
          type: "thinking_turns",
          value: 2
        }
      },
      {
        type: "clear_tool_uses_20250919",
        trigger: {
          type: "input_tokens",
          value: 50000
        },
        keep: {
          type: "tool_uses",
          value: 5
        }
      }
    ]
  }
)
puts response

Configuration options for tool result clearing

Context editing response

You can see which context edits were applied to your request using the context_management response field, along with helpful statistics about the content and input tokens cleared.

{
  "id": "msg_013Zva2CMHLNnXjNJJKqJ2EF",
  "type": "message",
  "role": "assistant",
  "content": [
    // ...
  ],
  "usage": {
    // ...
  },
  "context_management": {
    "applied_edits": [
      // When using `clear_thinking_20251015`
      {
        "type": "clear_thinking_20251015",
        "cleared_thinking_turns": 3,
        "cleared_input_tokens": 15000
      },
      // When using `clear_tool_uses_20250919`
      {
        "type": "clear_tool_uses_20250919",
        "cleared_tool_uses": 8,
        "cleared_input_tokens": 50000
      }
    ]
  }
}

For streaming responses, the context edits are included in the final message_delta event:

{
  "type": "message_delta",
  "delta": {
    "stop_reason": "end_turn",
    "stop_sequence": null
  },
  "usage": {
    "output_tokens": 1024
  },
  "context_management": {
    "applied_edits": [
      // ...
    ]
  }
}

Token counting

The token counting endpoint supports context management, allowing you to preview how many tokens your prompt will use after context editing is applied.

cat > request.yaml <<'YAML'
model: claude-opus-5
messages:
  - role: user
    content: Continue our conversation...
context_management:
  edits:
    - type: clear_tool_uses_20250919
      trigger:
        type: input_tokens
        value: 30000
      keep:
        type: tool_uses
        value: 5
YAML

ORIGINAL=$(ant beta:messages count-tokens \
  --beta context-management-2025-06-27 \
  --transform context_management.original_input_tokens \
  --raw-output < request.yaml)

INPUT_TOKENS=$(ant beta:messages count-tokens \
  --beta context-management-2025-06-27 \
  --transform input_tokens --raw-output < request.yaml)

printf 'Original tokens: %s\n' "$ORIGINAL"
printf 'After clearing: %s\n' "$INPUT_TOKENS"
printf 'Savings: %s tokens\n' "$((ORIGINAL - INPUT_TOKENS))"

response = client.beta.messages.count_tokens(
    model="claude-opus-5",
    messages=[{"role": "user", "content": "Continue our conversation..."}],
    betas=["context-management-2025-06-27"],
    context_management={
        "edits": [
            {
                "type": "clear_tool_uses_20250919",
                "trigger": {"type": "input_tokens", "value": 30000},
                "keep": {"type": "tool_uses", "value": 5},
            }
        ]
    },
)

print(f"Original tokens: {response.context_management.original_input_tokens}")
print(f"After clearing: {response.input_tokens}")
print(
    f"Savings: {response.context_management.original_input_tokens - response.input_tokens} tokens"
)

const anthropic = new Anthropic({
  apiKey: process.env.ANTHROPIC_API_KEY
});

const response = await anthropic.beta.messages.countTokens({
  model: "claude-opus-5",
  messages: [
    {
      role: "user",
      content: "Continue our conversation..."
    }
  ],
  betas: ["context-management-2025-06-27"],
  context_management: {
    edits: [
      {
        type: "clear_tool_uses_20250919",
        trigger: {
          type: "input_tokens",
          value: 30000
        },
        keep: {
          type: "tool_uses",
          value: 5
        }
      }
    ]
  }
});

console.log(`Original tokens: ${response.context_management?.original_input_tokens}`);
console.log(`After clearing: ${response.input_tokens}`);
console.log(
  `Savings: ${
    (response.context_management?.original_input_tokens || 0) - response.input_tokens
  } tokens`
);

using Anthropic;
using Anthropic.Models.Beta;
using Anthropic.Models.Beta.Messages;
using Messages = Anthropic.Models.Messages;

AnthropicClient client = new();

var parameters = new MessageCountTokensParams
{
    Model = Messages::Model.ClaudeOpus5,
    Messages = [new() { Role = Role.User, Content = "Continue our conversation..." }],
    Betas = [AnthropicBeta.ContextManagement2025_06_27],
    ContextManagement = new BetaContextManagementConfig
    {
        Edits = [
            new BetaClearToolUses20250919Edit
            {
                Trigger = new BetaInputTokensTrigger(30000),
                Keep = new BetaToolUsesKeep(5)
            }
        ]
    }
};

var response = await client.Beta.Messages.CountTokens(parameters);

Console.WriteLine($"Original tokens: {response.ContextManagement?.OriginalInputTokens}");
Console.WriteLine($"After clearing: {response.InputTokens}");
Console.WriteLine($"Savings: {(response.ContextManagement?.OriginalInputTokens ?? 0) - response.InputTokens} tokens");

client := anthropic.NewClient()

response, err := client.Beta.Messages.CountTokens(context.TODO(), anthropic.BetaMessageCountTokensParams{
	Model: anthropic.ModelClaudeOpus5,
	Messages: []anthropic.BetaMessageParam{
		anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Continue our conversation...")),
	},
	Betas: []anthropic.AnthropicBeta{
		anthropic.AnthropicBetaContextManagement2025_06_27,
	},
	ContextManagement: anthropic.BetaContextManagementConfigParam{
		Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
			{OfClearToolUses20250919: &anthropic.BetaClearToolUses20250919EditParam{
				Trigger: anthropic.BetaClearToolUses20250919EditTriggerUnionParam{
					OfInputTokens: &anthropic.BetaInputTokensTriggerParam{
						Value: 30000,
					},
				},
				Keep: anthropic.BetaToolUsesKeepParam{
					Value: 5,
				},
			}},
		},
	},
})
if err != nil {
	log.Fatal(err)
}

fmt.Printf("Original tokens: %d\n", response.ContextManagement.OriginalInputTokens)
fmt.Printf("After clearing: %d\n", response.InputTokens)
fmt.Printf("Savings: %d tokens\n", response.ContextManagement.OriginalInputTokens-response.InputTokens)

import com.anthropic.models.beta.messages.BetaMessageTokensCount;
import com.anthropic.models.beta.messages.MessageCountTokensParams;
import com.anthropic.models.beta.messages.BetaContextManagementConfig;
import com.anthropic.models.beta.messages.BetaClearToolUses20250919Edit;
import com.anthropic.models.beta.messages.BetaInputTokensTrigger;
import com.anthropic.models.beta.messages.BetaToolUsesKeep;
import com.anthropic.models.beta.AnthropicBeta;
// ...
void main() {
    AnthropicClient client = AnthropicOkHttpClient.fromEnv();

    MessageCountTokensParams params = MessageCountTokensParams.builder()
        .model(Model.CLAUDE_OPUS_5)
        .addUserMessage("Continue our conversation...")
        .addBeta(AnthropicBeta.CONTEXT_MANAGEMENT_2025_06_27)
        .contextManagement(BetaContextManagementConfig.builder()
            .addEdit(BetaClearToolUses20250919Edit.builder()
                .trigger(BetaInputTokensTrigger.builder()
                    .value(30000L)
                    .build())
                .keep(BetaToolUsesKeep.builder()
                    .value(5L)
                    .build())
                .build())
            .build())
        .build();

    BetaMessageTokensCount response = client.beta().messages().countTokens(params);

    IO.println("Original tokens: " + response.contextManagement().get().originalInputTokens());
    IO.println("After clearing: " + response.inputTokens());
    IO.println("Savings: " + (response.contextManagement().get().originalInputTokens() - response.inputTokens()) + " tokens");
}

$client = new Client();

$response = $client->beta->messages->countTokens(
    messages: [
        ['role' => 'user', 'content' => 'Continue our conversation...']
    ],
    model: 'claude-opus-5',
    betas: ['context-management-2025-06-27'],
    contextManagement: [
        'edits' => [
            [
                'type' => 'clear_tool_uses_20250919',
                'trigger' => [
                    'type' => 'input_tokens',
                    'value' => 30000
                ],
                'keep' => [
                    'type' => 'tool_uses',
                    'value' => 5
                ]
            ]
        ]
    ],
);

echo "Original tokens: " . $response->contextManagement->originalInputTokens . "\n";
echo "After clearing: " . $response->inputTokens . "\n";
echo "Savings: " . ($response->contextManagement->originalInputTokens - $response->inputTokens) . " tokens\n";

client = Anthropic::Client.new

response = client.beta.messages.count_tokens(
  model: "claude-opus-5",
  messages: [
    { role: "user", content: "Continue our conversation..." }
  ],
  betas: ["context-management-2025-06-27"],
  context_management: {
    edits: [
      {
        type: "clear_tool_uses_20250919",
        trigger: {
          type: "input_tokens",
          value: 30000
        },
        keep: {
          type: "tool_uses",
          value: 5
        }
      }
    ]
  }
)

puts "Original tokens: #{response.context_management.original_input_tokens}"
puts "After clearing: #{response.input_tokens}"
puts "Savings: #{response.context_management.original_input_tokens - response.input_tokens} tokens"

{
  "input_tokens": 25000,
  "context_management": {
    "original_input_tokens": 70000
  }
}

The response shows both the final token count after context management is applied (input_tokens) and the original token count before any clearing occurred (original_input_tokens).

Using with the memory tool

Context editing can be combined with the memory tool. When your conversation context approaches the configured clearing threshold, Claude receives an automatic warning to preserve important information. This enables Claude to save tool results or context to its memory files before they're cleared from the conversation history.

This combination allows you to:

• Preserve important context: Claude can write essential information from tool results to memory files before those results are cleared
• Maintain long-running workflows: Enable agentic workflows that would otherwise exceed context limits by offloading information to persistent storage
• Access information on demand: Claude can look up previously cleared information from memory files when needed, rather than keeping everything in the active context window

For example, in a file editing workflow where Claude performs many operations, Claude can summarize completed changes to memory files as the context grows. When tool results are cleared, Claude retains access to that information through its memory system and can continue working effectively.

To use both features together, enable them in your API request:

ant beta:messages create --beta context-management-2025-06-27 <<'YAML'
model: claude-opus-5
max_tokens: 4096
messages:
  - role: user
    content: Hello
tools:
  - type: memory_20250818
    name: memory
context_management:
  edits:
    - type: clear_tool_uses_20250919
YAML

response = client.beta.messages.create(
    model="claude-opus-5",
    max_tokens=4096,
    messages=[{"role": "user", "content": "Hello"}],
    tools=[{"type": "memory_20250818", "name": "memory"}],
    betas=["context-management-2025-06-27"],
    context_management={"edits": [{"type": "clear_tool_uses_20250919"}]},
)

const anthropic = new Anthropic({
  apiKey: process.env.ANTHROPIC_API_KEY
});

const response = await anthropic.beta.messages.create({
  model: "claude-opus-5",
  max_tokens: 4096,
  messages: [{ role: "user", content: "Hello" }],
  tools: [
    {
      type: "memory_20250818",
      name: "memory"
    }
  ],
  betas: ["context-management-2025-06-27"],
  context_management: {
    edits: [{ type: "clear_tool_uses_20250919" }]
  }
});

using Anthropic;
using Anthropic.Models.Beta;
using Anthropic.Models.Beta.Messages;
using Messages = Anthropic.Models.Messages;

AnthropicClient client = new();

var parameters = new MessageCreateParams
{
    Model = Messages::Model.ClaudeOpus5,
    MaxTokens = 4096,
    Messages = [
        new() { Role = Role.User, Content = "Hello" }
    ],
    Tools = [
        new BetaMemoryTool20250818()
    ],
    Betas = [AnthropicBeta.ContextManagement2025_06_27],
    ContextManagement = new BetaContextManagementConfig
    {
        Edits = [new BetaClearToolUses20250919Edit()]
    }
};

var response = await client.Beta.Messages.Create(parameters);
Console.WriteLine(response);

client := anthropic.NewClient()

response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
	Model:     anthropic.ModelClaudeOpus5,
	MaxTokens: 4096,
	Messages: []anthropic.BetaMessageParam{
		anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Hello")),
	},
	Tools: []anthropic.BetaToolUnionParam{
		{OfMemoryTool20250818: &anthropic.BetaMemoryTool20250818Param{}},
	},
	Betas: []anthropic.AnthropicBeta{anthropic.AnthropicBetaContextManagement2025_06_27},
	ContextManagement: anthropic.BetaContextManagementConfigParam{
		Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
			{OfClearToolUses20250919: &anthropic.BetaClearToolUses20250919EditParam{}},
		},
	},
})
if err != nil {
	log.Fatal(err)
}
fmt.Println(response)

import com.anthropic.models.beta.messages.BetaMemoryTool20250818;
import com.anthropic.models.beta.messages.BetaContextManagementConfig;
import com.anthropic.models.beta.messages.BetaClearToolUses20250919Edit;
import com.anthropic.models.beta.AnthropicBeta;
// ...
void main() {
    AnthropicClient client = AnthropicOkHttpClient.fromEnv();

    MessageCreateParams params = MessageCreateParams.builder()
        .model(Model.CLAUDE_OPUS_5)
        .maxTokens(4096L)
        .addUserMessage("Hello")
        .addTool(BetaMemoryTool20250818.builder().build())
        .addBeta(AnthropicBeta.CONTEXT_MANAGEMENT_2025_06_27)
        .contextManagement(BetaContextManagementConfig.builder()
            .addEdit(BetaClearToolUses20250919Edit.builder().build())
            .build())
        .build();

    BetaMessage response = client.beta().messages().create(params);
    IO.println(response);
}

$client = new Client();

$response = $client->beta->messages->create(
    maxTokens: 4096,
    messages: [
        ['role' => 'user', 'content' => 'Hello']
    ],
    model: 'claude-opus-5',
    betas: ['context-management-2025-06-27'],
    tools: [
        [
            'type' => 'memory_20250818',
            'name' => 'memory'
        ]
    ],
    contextManagement: [
        'edits' => [
            ['type' => 'clear_tool_uses_20250919']
        ]
    ],
);

echo $response;

client = Anthropic::Client.new

response = client.beta.messages.create(
  model: "claude-opus-5",
  max_tokens: 4096,
  messages: [{ role: "user", content: "Hello" }],
  tools: [
    {
      type: "memory_20250818",
      name: "memory"
    }
  ],
  betas: ["context-management-2025-06-27"],
  context_management: {
    edits: [
      { type: "clear_tool_uses_20250919" }
    ]
  }
)
puts response

For the full memory tool reference including commands and examples, see Memory tool.

Client-side compaction (SDK)

The compaction_control parameter is deprecated in the TypeScript and Ruby SDKs and will be removed in a future version. The SDKs emit a deprecation warning when it is enabled. The Python SDK removed it in v1.0. To use server-side compaction with a tool runner, pass the compact_20260112 edit in the request's context_management parameter.

Compaction is an SDK feature that automatically manages conversation context by generating summaries when token usage grows too large. Unlike server-side context editing strategies that clear content, compaction instructs Claude to summarize the conversation history, then replaces the full history with that summary. This allows Claude to continue working on long-running tasks that would otherwise exceed the context window.

How compaction works

When compaction is enabled, the SDK monitors token usage after each model response:

1. Threshold check: The SDK calculates total tokens as input_tokens + cache_creation_input_tokens + cache_read_input_tokens + output_tokens (see Prompt caching for the cache token fields).
2. Summary generation: When the threshold is exceeded, a summary prompt is injected as a user turn, and Claude generates a structured summary wrapped in <summary></summary> tags.
3. Context replacement: The SDK extracts the summary and replaces the entire message history with it.
4. Continuation: The conversation resumes from the summary, with Claude picking up where it left off.

Using compaction

Add compaction_control to your tool_runner call to enable automatic summarization when token usage exceeds the threshold.

const runner = client.beta.messages.toolRunner({
  model: "claude-opus-5",
  max_tokens: 1024,
  tools: [readFile],
  messages: [{ role: "user", content: "What's in config.json?" }],
  compactionControl: { enabled: true, contextTokenThreshold: 100000 }
});

for await (const message of runner) {
  console.log(`Tokens used: ${message.usage.input_tokens}`);
}
```

runner = client.beta.messages.tool_runner(
  model: "claude-opus-5",
  max_tokens: 1024,
  tools: [ReadFile.new],
  messages: [{ role: "user", content: "What's in config.json?" }],
  compaction_control: { enabled: true, context_token_threshold: 100000 }
)

runner.each_message do |message|
  puts "Tokens used: #{message.usage.input_tokens}"
end
```

What occurs during compaction

As the conversation grows, the message history accumulates:

Before compaction (approaching 100k tokens):

[
  { "role": "user", "content": "Analyze all files and write a report..." },
  { "role": "assistant", "content": "I'll help. Let me start by reading..." },
  {
    "role": "user",
    "content": [{ "type": "tool_result", "tool_use_id": "...", "content": "..." }]
  },
  { "role": "assistant", "content": "Based on file1.txt, I see..." },
  {
    "role": "user",
    "content": [{ "type": "tool_result", "tool_use_id": "...", "content": "..." }]
  },
  { "role": "assistant", "content": "After analyzing file2.txt..." }
  // ... 50 more exchanges like this ...
]

When tokens exceed the threshold, the SDK injects a summary request and Claude generates a summary. The entire history is then replaced:

After compaction (back to ~2–3k tokens):

[
  {
    "role": "assistant",
    "content": "# Task Overview\nThe user requested analysis of directory files to produce a summary report...\n\n# Current State\nAnalyzed 52 files across 3 subdirectories. Key findings documented in report.md...\n\n# Important Discoveries\n- Configuration files use YAML format\n- Found 3 deprecated dependencies\n- Test coverage at 67%\n\n# Next Steps\n1. Analyze remaining files in /src/legacy\n2. Complete final report sections...\n\n# Context to Preserve\nUser prefers markdown format with executive summary first..."
  }
]

Claude continues working from this summary as if it were the original conversation history.

Configuration options

Choosing a token threshold

The threshold determines when compaction occurs. A lower threshold means more frequent compactions with smaller context windows. A higher threshold allows more context but risks hitting limits.

const runner = client.beta.messages.toolRunner({
  model: "claude-opus-5",
  max_tokens: 1024,
  tools: [readFile],
  messages: [{ role: "user", content: "What's in config.json?" }],
  // Lower values compact more often; raise to 150000 when the task needs more context
  compactionControl: { enabled: true, contextTokenThreshold: 50000 }
});

for await (const message of runner) {
  console.log(`Tokens used: ${message.usage.input_tokens}`);
}
```

runner = client.beta.messages.tool_runner(
  model: "claude-opus-5",
  max_tokens: 1024,
  tools: [ReadFile.new],
  messages: [{ role: "user", content: "What's in config.json?" }],
  # Lower values compact more often; raise to 150000 when the task needs more context
  compaction_control: { enabled: true, context_token_threshold: 50000 }
)

runner.each_message do |message|
  puts "Tokens used: #{message.usage.input_tokens}"
end
```

Using a different model for summaries

You can use a faster or cheaper model for generating summaries:

const runner = client.beta.messages.toolRunner({
  model: "claude-opus-5",
  max_tokens: 1024,
  tools: [readFile],
  messages: [{ role: "user", content: "What's in config.json?" }],
  compactionControl: {
    enabled: true,
    contextTokenThreshold: 100000,
    model: "claude-haiku-4-5"
  }
});

for await (const message of runner) {
  console.log(`Tokens used: ${message.usage.input_tokens}`);
}
```

runner = client.beta.messages.tool_runner(
  model: "claude-opus-5",
  max_tokens: 1024,
  tools: [ReadFile.new],
  messages: [{ role: "user", content: "What's in config.json?" }],
  compaction_control: {
    enabled: true,
    context_token_threshold: 100000,
    model: "claude-haiku-4-5"
  }
)

runner.each_message do |message|
  puts "Tokens used: #{message.usage.input_tokens}"
end
```

Custom summary prompts

You can provide a custom prompt for domain-specific needs. Your prompt should instruct Claude to wrap its summary in <summary></summary> tags.

const runner = client.beta.messages.toolRunner({
  model: "claude-opus-5",
  max_tokens: 1024,
  tools: [readFile],
  messages: [{ role: "user", content: "What's in config.json?" }],
  compactionControl: {
    enabled: true,
    contextTokenThreshold: 100000,
    summaryPrompt: `Summarize the research conducted so far, including:
- Sources consulted and key findings
- Questions answered and remaining unknowns
- Recommended next steps

Wrap your summary in <summary></summary> tags.`
  }
});

for await (const message of runner) {
  console.log(`Tokens used: ${message.usage.input_tokens}`);
}
```

runner = client.beta.messages.tool_runner(
  model: "claude-opus-5",
  max_tokens: 1024,
  tools: [ReadFile.new],
  messages: [{ role: "user", content: "What's in config.json?" }],
  compaction_control: {
    enabled: true,
    context_token_threshold: 100000,
    summary_prompt: <<~PROMPT
      Summarize the research conducted so far, including:
      - Sources consulted and key findings
      - Questions answered and remaining unknowns
      - Recommended next steps

      Wrap your summary in <summary></summary> tags.
    PROMPT
  }
)

runner.each_message do |message|
  puts "Tokens used: #{message.usage.input_tokens}"
end
```

Default summary prompt

The built-in summary prompt instructs Claude to create a structured continuation summary including:

1. Task Overview: The user's core request, success criteria, and constraints.
2. Current State: What has been completed, files modified, and artifacts produced.
3. Important Discoveries: Technical constraints, decisions made, errors resolved, and failed approaches.
4. Next Steps: Specific actions needed, blockers, and priority order.
5. Context to Preserve: User preferences, domain-specific details, and commitments made.

This structure enables Claude to resume work efficiently without losing important context or repeating mistakes.

1. Task Overview The user's core request and success criteria Any clarifications or constraints they specified

2. Current State What has been completed so far Files created, modified, or analyzed (with paths if relevant) Key outputs or artifacts produced

3. Important Discoveries Technical constraints or requirements uncovered Decisions made and their rationale Errors encountered and how they were resolved What approaches were tried that didn't work (and why)

4. Next Steps Specific actions needed to complete the task Any blockers or open questions to resolve Priority order if multiple steps remain

5. Context to Preserve User preferences or style requirements Domain-specific details that aren't obvious Any promises made to the user

Be concise but complete—err on the side of including information that would prevent duplicate work or repeated mistakes. Write in a way that enables immediate resumption of the task.

Wrap your summary in tags.

</Accordion>

### Limitations

#### Server-side tools

<Warning>
Compaction requires special consideration when using server-side tools such as [web search](https://platform.claude.com/docs/en/agents-and-tools/tool-use/web-search-tool) or [web fetch](https://platform.claude.com/docs/en/agents-and-tools/tool-use/web-fetch-tool).
</Warning>

When using server-side tools, the SDK may incorrectly calculate token usage, causing compaction to trigger at the wrong time.

For example, after a web search operation, the API response might show:

```json Output
{
"usage": {
  "input_tokens": 63000,
  "cache_creation_input_tokens": 0,
  "cache_read_input_tokens": 270000,
  "output_tokens": 1400
}
}

The SDK calculates total usage as 63,000 + 0 + 270,000 + 1,400 = 334,400 tokens. However, the cache_read_input_tokens value includes accumulated reads from multiple internal API calls made by the server-side tool, not your actual conversation context. Your real context length might only be the 63,000 input_tokens, but the SDK sees 334k and triggers compaction prematurely.

Workarounds:

• Use the token counting endpoint to get accurate context length
• Avoid compaction when using server-side tools extensively

Tool use edge cases

When the SDK triggers compaction while a tool use response is pending, it removes the tool use block from the message history before generating the summary. Claude will re-issue the tool call after resuming from the summary if still needed.

Monitoring compaction

Understanding when compaction triggers helps you tune thresholds and verify expected behavior.

```typescript TypeScript
let prevMsgCount = 0;
for await (const message of runner) {
  const currMsgCount = runner.params.messages.length;
  if (currMsgCount < prevMsgCount) {
    console.log(`Compaction occurred: ${prevMsgCount} -> ${currMsgCount} messages`);
    console.log(`Input tokens after compaction: ${message.usage.input_tokens}`);
  }
  prevMsgCount = currMsgCount;
}
```

```ruby Ruby
client = Anthropic::Client.new

runner = client.beta.messages.tool_runner(
  model: "claude-opus-5",
  max_tokens: 1024,
  tools: [ReadFile.new],
  messages: [{ role: "user", content: "What's in config.json?" }],
  compaction_control: {
    enabled: true,
    context_token_threshold: 100000,
    on_compact: ->(tokens_before, tokens_after) do
      puts "Compaction occurred: #{tokens_before} -> #{tokens_after} tokens"
    end
  }
)

runner.each_message do |message|
  puts "Tokens: #{message.usage.input_tokens}"
end
```

When to use compaction

Good use cases:

• Long-running agent tasks that process many files or data sources
• Research workflows that accumulate large amounts of information
• Multistep tasks with clear, measurable progress
• Tasks that produce artifacts (files, reports) that persist outside the conversation

Less ideal use cases:

• Tasks requiring precise recall of early conversation details
• Workflows using server-side tools extensively
• Tasks that need to maintain exact state across many variables

Next steps