Compaction
Server-side context compaction for managing long conversations that approach context window limits.
Note
This feature is eligible for Zero Data Retention (ZDR). When your organization has a ZDR arrangement, data sent through this feature is not stored after the API response is returned.
Tip
Server-side compaction is the recommended strategy for managing context in long-running conversations and agentic workflows. It handles context management automatically with minimal integration work.
Compaction extends the effective context length for long-running conversations and tasks by automatically summarizing older context when approaching the context window limit. This isn't just about staying under a token cap. As conversations get longer, models struggle to maintain focus across the full history. Compaction keeps the active context focused and performant by replacing stale content with concise summaries.
Tip
For a deeper look at why long contexts degrade and how compaction helps, see Effective context engineering.
This is ideal for:
- Chat-based, multi-turn conversations where you want users to use one chat for a long period of time
- Task-oriented prompts that require a lot of follow-up work (often tool use) that may exceed the context window
Note
Compaction is in beta. Include the beta header compact-2026-01-12 in your API requests to use this feature.
Supported models
Compaction is supported on the following models:
- Claude Mythos Preview (
claude-mythos-preview) - Claude Opus 4.7 (
claude-opus-4-7) - Claude Opus 4.6 (
claude-opus-4-6) - Claude Sonnet 4.6 (
claude-sonnet-4-6)
How compaction works
When compaction is enabled, Claude automatically summarizes your conversation when it approaches the configured token threshold. The API:
- Detects when input tokens exceed your specified trigger threshold.
- Generates a summary of the current conversation.
- Creates a
compactionblock containing the summary. - Continues the response with the compacted context.
On subsequent requests, append the response to your messages. The API automatically drops all message blocks prior to the compaction block, continuing the conversation from the summary.
Basic usage
Enable compaction by adding the compact_20260112 strategy to context_management.edits in your Messages API request.
curl https://api.anthropic.com/v1/messages \
--header "x-api-key: $ANTHROPIC_API_KEY" \
--header "anthropic-version: 2023-06-01" \
--header "anthropic-beta: compact-2026-01-12" \
--header "content-type: application/json" \
--data \
'{
"model": "claude-opus-4-7",
"max_tokens": 4096,
"messages": [
{
"role": "user",
"content": "Help me build a website"
}
],
"context_management": {
"edits": [
{
"type": "compact_20260112"
}
]
}
}'
ant beta:messages create --beta compact-2026-01-12 <<'YAML'
model: claude-opus-4-7
max_tokens: 4096
messages:
- role: user
content: Help me build a website
context_management:
edits:
- type: compact_20260112
YAML
import anthropic
client = anthropic.Anthropic()
messages = [{"role": "user", "content": "Help me build a website"}]
response = client.beta.messages.create(
betas=["compact-2026-01-12"],
model="claude-opus-4-7",
max_tokens=4096,
messages=messages,
context_management={"edits": [{"type": "compact_20260112"}]},
)
# Append the response (including any compaction block) to continue the conversation
messages.append({"role": "assistant", "content": response.content})
import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const messages: Anthropic.Beta.Messages.BetaMessageParam[] = [
{ role: "user", content: "Help me build a website" }
];
const response = await client.beta.messages.create({
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages,
context_management: {
edits: [
{
type: "compact_20260112"
}
]
}
});
// Append the response (including any compaction block) to continue the conversation
messages.push({
role: "assistant",
content: response.content
});
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Anthropic;
using Anthropic.Models.Beta.Messages;
class Program
{
static async Task Main(string[] args)
{
AnthropicClient client = new();
var messages = new List<BetaMessageParam>
{
new() { Role = Role.User, Content = "Help me build a website" }
};
var parameters = new MessageCreateParams
{
Betas = ["compact-2026-01-12"],
Model = "claude-opus-4-7",
MaxTokens = 4096,
Messages = messages,
ContextManagement = new BetaContextManagementConfig
{
Edits = [new BetaCompact20260112Edit()]
}
};
var response = await client.Beta.Messages.Create(parameters);
// Append the response (including any compaction block) to continue the conversation
messages.Add(new BetaMessageParam
{
Role = Role.Assistant,
Content = response.Content.Select(b => new BetaContentBlockParam(b.Json)).ToList()
});
Console.WriteLine(response);
}
}
package main
import (
"context"
"fmt"
"log"
"github.com/anthropics/anthropic-sdk-go"
)
func main() {
client := anthropic.NewClient()
messages := []anthropic.BetaMessageParam{
anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Help me build a website")),
}
response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
Model: anthropic.ModelClaudeOpus4_7,
MaxTokens: 4096,
Messages: messages,
ContextManagement: anthropic.BetaContextManagementConfigParam{
Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
{OfCompact20260112: &anthropic.BetaCompact20260112EditParam{}},
},
},
Betas: []anthropic.AnthropicBeta{"compact-2026-01-12"},
})
if err != nil {
log.Fatal(err)
}
// Append the response (including any compaction block) to continue the conversation
messages = append(messages, response.ToParam())
fmt.Println(response)
}
import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.beta.messages.MessageCreateParams;
import com.anthropic.models.beta.messages.BetaMessage;
import com.anthropic.models.beta.messages.BetaContextManagementConfig;
import com.anthropic.models.beta.messages.BetaCompact20260112Edit;
public class CompactionExample {
public static void main(String[] args) {
AnthropicClient client = AnthropicOkHttpClient.fromEnv();
MessageCreateParams params = MessageCreateParams.builder()
.addBeta("compact-2026-01-12")
.model("claude-opus-4-7")
.maxTokens(4096L)
.addUserMessage("Help me build a website")
.contextManagement(BetaContextManagementConfig.builder()
.addEdit(BetaCompact20260112Edit.builder().build())
.build())
.build();
BetaMessage response = client.beta().messages().create(params);
// Append the response (including any compaction block) to continue the conversation
// by including it in the next request's messages
System.out.println(response);
}
}
<?php
use Anthropic\Client;
$client = new Client(apiKey: getenv("ANTHROPIC_API_KEY"));
$messages = [
['role' => 'user', 'content' => 'Help me build a website']
];
$response = $client->beta->messages->create(
maxTokens: 4096,
messages: $messages,
model: 'claude-opus-4-7',
betas: ['compact-2026-01-12'],
contextManagement: [
'edits' => [
['type' => 'compact_20260112']
]
]
);
// Append the response (including any compaction block) to continue the conversation
$messages[] = ['role' => 'assistant', 'content' => $response->content];
echo $response->content[0]->text;
require "anthropic"
client = Anthropic::Client.new
messages = [
{ role: "user", content: "Help me build a website" }
]
response = client.beta.messages.create(
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages: messages,
context_management: {
edits: [{ type: "compact_20260112" }]
}
)
# Append the response (including any compaction block) to continue the conversation
messages << { role: "assistant", content: response.content }
puts response
Parameters
| Parameter | Type | Default | Description |
|---|---|---|---|
type | string | Required | Must be "compact_20260112" |
trigger | object | 150,000 tokens | When to trigger compaction. Must be at least 50,000 tokens. |
pause_after_compaction | boolean | false | Whether to pause after generating the compaction summary |
instructions | string | null | Custom summarization prompt. Completely replaces the default prompt when provided. |
Trigger configuration
Configure when compaction triggers using the trigger parameter:
ant beta:messages create --beta compact-2026-01-12 <<'YAML'
model: claude-opus-4-7
max_tokens: 4096
messages:
- role: user
content: Hello, Claude
context_management:
edits:
- type: compact_20260112
trigger:
type: input_tokens
value: 150000
YAML
import anthropic
client = anthropic.Anthropic()
messages = [{"role": "user", "content": "Hello, Claude"}]
response = client.beta.messages.create(
betas=["compact-2026-01-12"],
model="claude-opus-4-7",
max_tokens=4096,
messages=messages,
context_management={
"edits": [
{
"type": "compact_20260112",
"trigger": {"type": "input_tokens", "value": 150000},
}
]
},
)
import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const messages: Anthropic.Beta.Messages.BetaMessageParam[] = [];
const response = await client.beta.messages.create({
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages,
context_management: {
edits: [
{
type: "compact_20260112",
trigger: {
type: "input_tokens",
value: 150000
}
}
]
}
});
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Anthropic;
using Anthropic.Models.Beta.Messages;
class Program
{
static async Task Main(string[] args)
{
AnthropicClient client = new();
List<BetaMessageParam> messages = [new() { Role = Role.User, Content = "Hello" }];
var parameters = new MessageCreateParams
{
Model = "claude-opus-4-7",
MaxTokens = 4096,
Betas = ["compact-2026-01-12"],
Messages = messages,
ContextManagement = new BetaContextManagementConfig
{
Edits = [new BetaCompact20260112Edit
{
Trigger = new BetaInputTokensTrigger(150000)
}]
}
};
var message = await client.Beta.Messages.Create(parameters);
Console.WriteLine(message);
}
}
package main
import (
"context"
"fmt"
"log"
"github.com/anthropics/anthropic-sdk-go"
)
func main() {
client := anthropic.NewClient()
messages := []anthropic.BetaMessageParam{anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Hello, Claude"))}
response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
Model: anthropic.ModelClaudeOpus4_7,
MaxTokens: 4096,
Messages: messages,
ContextManagement: anthropic.BetaContextManagementConfigParam{
Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
{OfCompact20260112: &anthropic.BetaCompact20260112EditParam{
Trigger: anthropic.BetaInputTokensTriggerParam{Value: 150000},
}},
},
},
Betas: []anthropic.AnthropicBeta{"compact-2026-01-12"},
})
if err != nil {
log.Fatal(err)
}
fmt.Println(response)
}
import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.beta.messages.MessageCreateParams;
import com.anthropic.models.beta.messages.BetaMessage;
import com.anthropic.models.beta.messages.BetaContextManagementConfig;
import com.anthropic.models.beta.messages.BetaCompact20260112Edit;
import com.anthropic.models.beta.messages.BetaInputTokensTrigger;
public class CompactionExample {
public static void main(String[] args) {
AnthropicClient client = AnthropicOkHttpClient.fromEnv();
MessageCreateParams params = MessageCreateParams.builder()
.model("claude-opus-4-7")
.maxTokens(4096L)
.addBeta("compact-2026-01-12")
.addUserMessage("Hello, Claude")
.contextManagement(BetaContextManagementConfig.builder()
.addEdit(BetaCompact20260112Edit.builder()
.trigger(BetaInputTokensTrigger.builder()
.value(150000L)
.build())
.build())
.build())
.build();
BetaMessage response = client.beta().messages().create(params);
System.out.println(response);
}
}
<?php
use Anthropic\Client;
$client = new Client(apiKey: getenv("ANTHROPIC_API_KEY"));
$messages = [['role' => 'user', 'content' => 'Hello, Claude']];
$message = $client->beta->messages->create(
maxTokens: 4096,
messages: $messages,
model: 'claude-opus-4-7',
betas: ['compact-2026-01-12'],
contextManagement: [
'edits' => [
[
'type' => 'compact_20260112',
'trigger' => [
'type' => 'input_tokens',
'value' => 150000
]
]
]
]
);
echo $message;
require "anthropic"
client = Anthropic::Client.new
messages = [{ role: "user", content: "Hello, Claude" }]
response = client.beta.messages.create(
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages: messages,
context_management: {
edits: [
{
type: "compact_20260112",
trigger: {
type: "input_tokens",
value: 150000
}
}
]
}
)
puts response
Custom summarization instructions
By default, compaction uses the following summarization prompt:
You have written a partial transcript for the initial task above. Please write a summary of the transcript. The purpose of this summary is to provide continuity so you can continue to make progress towards solving the task in a future context, where the raw history above may not be accessible and will be replaced with this summary. Write down anything that would be helpful, including the state, next steps, learnings etc. You must wrap your summary in a <summary></summary> block.
You can provide custom instructions via the instructions parameter to replace this prompt entirely. Custom instructions don't supplement the default; they completely replace it:
ant beta:messages create --beta compact-2026-01-12 <<'YAML'
model: claude-opus-4-7
max_tokens: 4096
messages:
- role: user
content: Hello, Claude
context_management:
edits:
- type: compact_20260112
instructions: >-
Focus on preserving code snippets, variable names, and
technical decisions.
YAML
import anthropic
client = anthropic.Anthropic()
messages = [{"role": "user", "content": "Hello, Claude"}]
response = client.beta.messages.create(
betas=["compact-2026-01-12"],
model="claude-opus-4-7",
max_tokens=4096,
messages=messages,
context_management={
"edits": [
{
"type": "compact_20260112",
"instructions": "Focus on preserving code snippets, variable names, and technical decisions.",
}
]
},
)
import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const messages: Anthropic.Beta.Messages.BetaMessageParam[] = [];
const response = await client.beta.messages.create({
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages,
context_management: {
edits: [
{
type: "compact_20260112",
instructions:
"Focus on preserving code snippets, variable names, and technical decisions."
}
]
}
});
using System;
using System.Threading.Tasks;
using Anthropic;
using Anthropic.Models.Beta.Messages;
class Program
{
static async Task Main(string[] args)
{
AnthropicClient client = new();
var parameters = new MessageCreateParams
{
Betas = ["compact-2026-01-12"],
Model = "claude-opus-4-7",
MaxTokens = 4096,
Messages =
[
new BetaMessageParam { Role = Role.User, Content = "Help me build a Python web scraper" },
new BetaMessageParam { Role = Role.Assistant, Content = "I'll help you build a web scraper..." },
new BetaMessageParam { Role = Role.User, Content = "Add support for JavaScript-rendered pages" }
],
ContextManagement = new BetaContextManagementConfig
{
Edits = [new BetaCompact20260112Edit
{
Instructions = "Focus on preserving code snippets, variable names, and technical decisions."
}]
}
};
var message = await client.Beta.Messages.Create(parameters);
Console.WriteLine(message);
}
}
package main
import (
"context"
"fmt"
"log"
"github.com/anthropics/anthropic-sdk-go"
)
func main() {
client := anthropic.NewClient()
response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
Model: anthropic.ModelClaudeOpus4_7,
MaxTokens: 4096,
Messages: []anthropic.BetaMessageParam{
anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Help me build a Python web scraper")),
{Role: anthropic.BetaMessageParamRoleAssistant, Content: []anthropic.BetaContentBlockParamUnion{anthropic.NewBetaTextBlock("I'll help you build a web scraper...")}},
anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Add support for JavaScript-rendered pages")),
},
ContextManagement: anthropic.BetaContextManagementConfigParam{
Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
{OfCompact20260112: &anthropic.BetaCompact20260112EditParam{
Instructions: anthropic.String("Focus on preserving code snippets, variable names, and technical decisions."),
}},
},
},
Betas: []anthropic.AnthropicBeta{"compact-2026-01-12"},
})
if err != nil {
log.Fatal(err)
}
fmt.Println(response)
}
import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.beta.messages.MessageCreateParams;
import com.anthropic.models.beta.messages.BetaMessage;
import com.anthropic.models.beta.messages.BetaContextManagementConfig;
import com.anthropic.models.beta.messages.BetaCompact20260112Edit;
public class CompactionExample {
public static void main(String[] args) {
AnthropicClient client = AnthropicOkHttpClient.fromEnv();
MessageCreateParams params = MessageCreateParams.builder()
.addBeta("compact-2026-01-12")
.model("claude-opus-4-7")
.maxTokens(4096L)
.addUserMessage("Help me build a Python web scraper")
.addAssistantMessage("I'll help you build a web scraper...")
.addUserMessage("Add support for JavaScript-rendered pages")
.contextManagement(BetaContextManagementConfig.builder()
.addEdit(BetaCompact20260112Edit.builder()
.instructions("Focus on preserving code snippets, variable names, and technical decisions.")
.build())
.build())
.build();
BetaMessage response = client.beta().messages().create(params);
System.out.println(response);
}
}
<?php
use Anthropic\Client;
$client = new Client(apiKey: getenv("ANTHROPIC_API_KEY"));
$response = $client->beta->messages->create(
maxTokens: 4096,
messages: [
['role' => 'user', 'content' => 'Help me build a Python web scraper'],
['role' => 'assistant', 'content' => "I'll help you build a web scraper..."],
['role' => 'user', 'content' => 'Add support for JavaScript-rendered pages']
],
model: 'claude-opus-4-7',
betas: ['compact-2026-01-12'],
contextManagement: [
'edits' => [
[
'type' => 'compact_20260112',
'instructions' => 'Focus on preserving code snippets, variable names, and technical decisions.'
]
]
]
);
echo $response->content[0]->text;
require "anthropic"
client = Anthropic::Client.new
response = client.beta.messages.create(
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages: [
{ role: "user", content: "Help me build a Python web scraper" },
{ role: "assistant", content: "I'll help you build a web scraper..." },
{ role: "user", content: "Add support for JavaScript-rendered pages" }
],
context_management: {
edits: [
{
type: "compact_20260112",
instructions:
"Focus on preserving code snippets, variable names, and technical decisions."
}
]
}
)
puts response
Pausing after compaction
Use pause_after_compaction to pause the API after generating the compaction summary. This allows you to add additional content blocks (such as preserving recent messages or specific instruction-oriented messages) before the API continues with the response.
When enabled, the API returns a message with the compaction stop reason after generating the compaction block:
ant beta:messages create --beta compact-2026-01-12 \
--transform '{stop_reason,content}' --format jsonl <<'YAML' > resp.json
model: claude-opus-4-7
max_tokens: 4096
messages:
- role: user
content: "Hello, Claude"
context_management:
edits:
- type: compact_20260112
pause_after_compaction: true
YAML
# Check if compaction triggered a pause
if grep -q '"stop_reason":"compaction"' resp.json; then
# Response contains only the compaction block
RESP=$(cat resp.json)
CONTENT="${RESP#*\"content\":}"
printf '%s' "${CONTENT%\}}" > content.json
# Continue the request
ant beta:messages create --beta compact-2026-01-12 <<YAML > /dev/null
model: claude-opus-4-7
max_tokens: 4096
messages:
- role: user
content: "Hello, Claude"
- role: assistant
content: $(cat content.json)
context_management:
edits:
- type: compact_20260112
YAML
fi
import anthropic
client = anthropic.Anthropic()
messages = [{"role": "user", "content": "Hello, Claude"}]
response = client.beta.messages.create(
betas=["compact-2026-01-12"],
model="claude-opus-4-7",
max_tokens=4096,
messages=messages,
context_management={
"edits": [{"type": "compact_20260112", "pause_after_compaction": True}]
},
)
# Check if compaction triggered a pause
if response.stop_reason == "compaction":
# Response contains only the compaction block
messages.append({"role": "assistant", "content": response.content})
# Continue the request
response = client.beta.messages.create(
betas=["compact-2026-01-12"],
model="claude-opus-4-7",
max_tokens=4096,
messages=messages,
context_management={"edits": [{"type": "compact_20260112"}]},
)
import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const messages: Anthropic.Beta.Messages.BetaMessageParam[] = [
{ role: "user", content: "Hello, Claude" }
];
let response = await client.beta.messages.create({
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages,
context_management: {
edits: [
{
type: "compact_20260112",
pause_after_compaction: true
}
]
}
});
// Check if compaction triggered a pause
if (response.stop_reason === "compaction") {
// Response contains only the compaction block
messages.push({
role: "assistant",
content: response.content
});
// Continue the request
response = await client.beta.messages.create({
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages,
context_management: {
edits: [{ type: "compact_20260112" }]
}
});
}
using Anthropic;
using Anthropic.Models.Beta.Messages;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
class Program
{
static async Task Main(string[] args)
{
var client = new AnthropicClient();
var messages = new List<BetaMessageParam>
{
new() { Role = Role.User, Content = "Hello, Claude" }
};
var parameters = new MessageCreateParams
{
Model = "claude-opus-4-7",
MaxTokens = 4096,
Betas = ["compact-2026-01-12"],
Messages = messages,
ContextManagement = new BetaContextManagementConfig
{
Edits = [new BetaCompact20260112Edit
{
PauseAfterCompaction = true
}]
}
};
var response = await client.Beta.Messages.Create(parameters);
if (response.StopReason == BetaStopReason.Compaction)
{
messages.Add(new BetaMessageParam
{
Role = Role.Assistant,
Content = response.Content.Select(b => new BetaContentBlockParam(b.Json)).ToList()
});
parameters = new()
{
Model = "claude-opus-4-7",
MaxTokens = 4096,
Betas = ["compact-2026-01-12"],
Messages = messages,
ContextManagement = new BetaContextManagementConfig
{
Edits = [new BetaCompact20260112Edit()]
}
};
response = await client.Beta.Messages.Create(parameters);
}
Console.WriteLine(response);
}
}
package main
import (
"context"
"fmt"
"log"
"github.com/anthropics/anthropic-sdk-go"
)
func main() {
client := anthropic.NewClient()
messages := []anthropic.BetaMessageParam{anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Hello, Claude"))}
compactEdit := anthropic.BetaContextManagementConfigParam{
Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
{OfCompact20260112: &anthropic.BetaCompact20260112EditParam{
PauseAfterCompaction: anthropic.Bool(true),
}},
},
}
response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
Model: anthropic.ModelClaudeOpus4_7,
MaxTokens: 4096,
Messages: messages,
ContextManagement: compactEdit,
Betas: []anthropic.AnthropicBeta{"compact-2026-01-12"},
})
if err != nil {
log.Fatal(err)
}
if response.StopReason == "compaction" {
messages = append(messages, response.ToParam())
response, err = client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
Model: anthropic.ModelClaudeOpus4_7,
MaxTokens: 4096,
Messages: messages,
ContextManagement: anthropic.BetaContextManagementConfigParam{
Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
{OfCompact20260112: &anthropic.BetaCompact20260112EditParam{}},
},
},
Betas: []anthropic.AnthropicBeta{"compact-2026-01-12"},
})
if err != nil {
log.Fatal(err)
}
}
fmt.Println(response)
}
import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.beta.messages.MessageCreateParams;
import com.anthropic.models.beta.messages.BetaMessage;
import com.anthropic.models.beta.messages.BetaContextManagementConfig;
import com.anthropic.models.beta.messages.BetaCompact20260112Edit;
import com.anthropic.models.beta.messages.BetaStopReason;
public class CompactionPauseExample {
public static void main(String[] args) {
AnthropicClient client = AnthropicOkHttpClient.fromEnv();
MessageCreateParams params = MessageCreateParams.builder()
.model("claude-opus-4-7")
.maxTokens(4096L)
.addBeta("compact-2026-01-12")
.addUserMessage("Help me build a website")
.contextManagement(BetaContextManagementConfig.builder()
.addEdit(BetaCompact20260112Edit.builder()
.pauseAfterCompaction(true)
.build())
.build())
.build();
BetaMessage response = client.beta().messages().create(params);
// Check if compaction triggered a pause
if (response.stopReason().isPresent()
&& response.stopReason().get().equals(BetaStopReason.COMPACTION)) {
// Append the compaction block and continue the request
// by building a new request with the compacted context
MessageCreateParams continueParams = MessageCreateParams.builder()
.model("claude-opus-4-7")
.maxTokens(4096L)
.addBeta("compact-2026-01-12")
.addUserMessage("Help me build a website")
.addMessage(response)
.contextManagement(BetaContextManagementConfig.builder()
.addEdit(BetaCompact20260112Edit.builder().build())
.build())
.build();
response = client.beta().messages().create(continueParams);
}
System.out.println(response);
}
}
<?php
use Anthropic\Client;
// The PHP SDK does not yet expose a typed constant for the `compaction` stop reason; compare the string value directly.
$client = new Client(apiKey: getenv("ANTHROPIC_API_KEY"));
$messages = [['role' => 'user', 'content' => 'Hello, Claude']];
$response = $client->beta->messages->create(
maxTokens: 4096,
messages: $messages,
model: 'claude-opus-4-7',
betas: ['compact-2026-01-12'],
contextManagement: [
'edits' => [
[
'type' => 'compact_20260112',
'pause_after_compaction' => true
]
]
]
);
if ($response->stopReason === 'compaction') {
$messages[] = [
'role' => 'assistant',
'content' => $response->content
];
$response = $client->beta->messages->create(
maxTokens: 4096,
messages: $messages,
model: 'claude-opus-4-7',
betas: ['compact-2026-01-12'],
contextManagement: [
'edits' => [
['type' => 'compact_20260112']
]
]
);
}
echo $response;
require "anthropic"
client = Anthropic::Client.new
messages = [{ role: "user", content: "Hello, Claude" }]
response = client.beta.messages.create(
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages: messages,
context_management: {
edits: [
{
type: "compact_20260112",
pause_after_compaction: true
}
]
}
)
if response.stop_reason == :compaction
messages << { role: "assistant", content: response.content }
response = client.beta.messages.create(
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages: messages,
context_management: {
edits: [{ type: "compact_20260112" }]
}
)
end
puts response
Enforcing a total token budget
When a model works on long tasks with many tool-use iterations, total token consumption can grow significantly. You can combine pause_after_compaction with a compaction counter to estimate cumulative usage and gracefully wrap up the task once a budget is reached:
import anthropic
client = anthropic.Anthropic()
messages = [{"role": "user", "content": "Hello, Claude"}]
TRIGGER_THRESHOLD = 100_000
TOTAL_TOKEN_BUDGET = 3_000_000
n_compactions = 0
response = client.beta.messages.create(
betas=["compact-2026-01-12"],
model="claude-opus-4-7",
max_tokens=4096,
messages=messages,
context_management={
"edits": [
{
"type": "compact_20260112",
"trigger": {"type": "input_tokens", "value": TRIGGER_THRESHOLD},
"pause_after_compaction": True,
}
]
},
)
if response.stop_reason == "compaction":
n_compactions += 1
messages.append({"role": "assistant", "content": response.content})
# Estimate total tokens consumed; prompt wrap-up if over budget
if n_compactions * TRIGGER_THRESHOLD >= TOTAL_TOKEN_BUDGET:
messages.append(
{
"role": "user",
"content": "Please wrap up your current work and summarize the final state.",
}
)
Working with compaction blocks
When compaction is triggered, the API returns a compaction block at the start of the assistant response.
A long-running conversation may result in multiple compactions. The last compaction block reflects the final state of the prompt, replacing content prior to it with the generated summary.
{
"content": [
{
"type": "compaction",
"content": "Summary of the conversation: The user requested help building a web scraper..."
},
{
"type": "text",
"text": "Based on our conversation so far..."
}
]
}
Passing compaction blocks back
You must pass the compaction block back to the API on subsequent requests to continue the conversation with the shortened prompt. The simplest approach is to append the entire response content to your messages:
ant beta:messages create --beta compact-2026-01-12 \
--transform content --format jsonl <<'YAML' > content.json
model: claude-opus-4-7
max_tokens: 4096
messages:
- role: user
content: Hello, Claude
context_management:
edits:
- type: compact_20260112
YAML
# After receiving a response with a compaction block, append it as the
# assistant turn and continue the conversation
ant beta:messages create --beta compact-2026-01-12 <<YAML
model: claude-opus-4-7
max_tokens: 4096
messages:
- role: user
content: Hello, Claude
- role: assistant
content: $(cat content.json)
- role: user
content: Now add error handling
context_management:
edits:
- type: compact_20260112
YAML
import anthropic
client = anthropic.Anthropic()
messages = [{"role": "user", "content": "Hello, Claude"}]
response = client.beta.messages.create(
betas=["compact-2026-01-12"],
model="claude-opus-4-7",
max_tokens=4096,
messages=messages,
context_management={"edits": [{"type": "compact_20260112"}]},
)
# After receiving a response with a compaction block
messages.append({"role": "assistant", "content": response.content})
# Continue the conversation
messages.append({"role": "user", "content": "Now add error handling"})
response = client.beta.messages.create(
betas=["compact-2026-01-12"],
model="claude-opus-4-7",
max_tokens=4096,
messages=messages,
context_management={"edits": [{"type": "compact_20260112"}]},
)
import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const messages: Anthropic.Beta.Messages.BetaMessageParam[] = [];
// Assume we already have a response from a previous request
const response = await client.beta.messages.create({
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages,
context_management: {
edits: [{ type: "compact_20260112" }]
}
});
// After receiving a response with a compaction block
messages.push({
role: "assistant",
content: response.content
});
// Continue the conversation
messages.push({ role: "user", content: "Now add error handling" });
const nextResponse = await client.beta.messages.create({
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages,
context_management: {
edits: [{ type: "compact_20260112" }]
}
});
using Anthropic;
using Anthropic.Models.Beta.Messages;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
class Program
{
static async Task Main(string[] args)
{
AnthropicClient client = new();
var messages = new List<BetaMessageParam>
{
new() { Role = Role.User, Content = "Help me build a web scraper" }
};
var response = await client.Beta.Messages.Create(new()
{
Betas = ["compact-2026-01-12"],
Model = "claude-opus-4-7",
MaxTokens = 4096,
Messages = messages,
ContextManagement = new BetaContextManagementConfig
{
Edits = [new BetaCompact20260112Edit()]
}
});
messages.Add(new BetaMessageParam
{
Role = Role.Assistant,
Content = response.Content.Select(b => new BetaContentBlockParam(b.Json)).ToList()
});
messages.Add(new BetaMessageParam { Role = Role.User, Content = "Now add error handling" });
var nextResponse = await client.Beta.Messages.Create(new()
{
Betas = ["compact-2026-01-12"],
Model = "claude-opus-4-7",
MaxTokens = 4096,
Messages = messages,
ContextManagement = new BetaContextManagementConfig
{
Edits = [new BetaCompact20260112Edit()]
}
});
Console.WriteLine(nextResponse);
}
}
package main
import (
"context"
"fmt"
"log"
"github.com/anthropics/anthropic-sdk-go"
)
func main() {
client := anthropic.NewClient()
messages := []anthropic.BetaMessageParam{
anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Help me build a web scraper")),
}
compactEdit := anthropic.BetaContextManagementConfigParam{
Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
{OfCompact20260112: &anthropic.BetaCompact20260112EditParam{}},
},
}
response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
Model: anthropic.ModelClaudeOpus4_7,
MaxTokens: 4096,
Messages: messages,
ContextManagement: compactEdit,
Betas: []anthropic.AnthropicBeta{"compact-2026-01-12"},
})
if err != nil {
log.Fatal(err)
}
messages = append(messages, response.ToParam())
messages = append(messages, anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Now add error handling")))
nextResponse, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
Model: anthropic.ModelClaudeOpus4_7,
MaxTokens: 4096,
Messages: messages,
ContextManagement: compactEdit,
Betas: []anthropic.AnthropicBeta{"compact-2026-01-12"},
})
if err != nil {
log.Fatal(err)
}
fmt.Println(nextResponse)
}
import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.beta.messages.MessageCreateParams;
import com.anthropic.models.beta.messages.BetaMessage;
import com.anthropic.models.beta.messages.BetaContextManagementConfig;
import com.anthropic.models.beta.messages.BetaCompact20260112Edit;
public class CompactionExample {
public static void main(String[] args) {
AnthropicClient client = AnthropicOkHttpClient.fromEnv();
// First request
BetaMessage response = client.beta().messages().create(
MessageCreateParams.builder()
.addBeta("compact-2026-01-12")
.model("claude-opus-4-7")
.maxTokens(4096L)
.addUserMessage("Help me build a web scraper")
.contextManagement(BetaContextManagementConfig.builder()
.addEdit(BetaCompact20260112Edit.builder().build())
.build())
.build());
// After receiving a response with a compaction block, append the full
// content (including compaction blocks) and continue the conversation
BetaMessage nextResponse = client.beta().messages().create(
MessageCreateParams.builder()
.addBeta("compact-2026-01-12")
.model("claude-opus-4-7")
.maxTokens(4096L)
.addUserMessage("Help me build a web scraper")
.addMessage(response)
.addUserMessage("Now add error handling")
.contextManagement(BetaContextManagementConfig.builder()
.addEdit(BetaCompact20260112Edit.builder().build())
.build())
.build());
System.out.println(nextResponse);
}
}
<?php
use Anthropic\Client;
$client = new Client(apiKey: getenv("ANTHROPIC_API_KEY"));
$messages = [
['role' => 'user', 'content' => 'Help me build a web scraper']
];
$response = $client->beta->messages->create(
maxTokens: 4096,
messages: $messages,
model: 'claude-opus-4-7',
betas: ['compact-2026-01-12'],
contextManagement: [
'edits' => [['type' => 'compact_20260112']]
]
);
$messages[] = ['role' => 'assistant', 'content' => $response->content];
$messages[] = ['role' => 'user', 'content' => 'Now add error handling'];
$nextResponse = $client->beta->messages->create(
maxTokens: 4096,
messages: $messages,
model: 'claude-opus-4-7',
betas: ['compact-2026-01-12'],
contextManagement: [
'edits' => [['type' => 'compact_20260112']]
]
);
echo $nextResponse->content[0]->text;
require "anthropic"
client = Anthropic::Client.new
messages = [
{ role: "user", content: "Help me build a web scraper" }
]
response = client.beta.messages.create(
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages: messages,
context_management: {
edits: [{ type: "compact_20260112" }]
}
)
messages << { role: "assistant", content: response.content }
messages << { role: "user", content: "Now add error handling" }
next_response = client.beta.messages.create(
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages: messages,
context_management: {
edits: [{ type: "compact_20260112" }]
}
)
puts next_response.content
When the API receives a compaction block, all content blocks before it are ignored. You can either:
- Keep the original messages in your list and let the API handle removing the compacted content
- Manually drop the compacted messages and only include the compaction block onwards
Streaming
When streaming responses with compaction enabled, you'll receive a content_block_start event when compaction begins. The compaction block streams differently from text blocks. You'll receive a content_block_start event, followed by a single content_block_delta with the complete summary content (no intermediate streaming), and then a content_block_stop event.
ant beta:messages create --stream --format jsonl \
--beta compact-2026-01-12 <<'YAML'
model: claude-opus-4-7
max_tokens: 4096
messages:
- role: user
content: Hello, Claude
context_management:
edits:
- type: compact_20260112
YAML
import anthropic
client = anthropic.Anthropic()
messages = [{"role": "user", "content": "Hello, Claude"}]
with client.beta.messages.stream(
betas=["compact-2026-01-12"],
model="claude-opus-4-7",
max_tokens=4096,
messages=messages,
context_management={"edits": [{"type": "compact_20260112"}]},
) as stream:
for event in stream:
if event.type == "content_block_start":
if event.content_block.type == "compaction":
print("Compaction started...")
elif event.content_block.type == "text":
print("Text response started...")
elif event.type == "content_block_delta":
if event.delta.type == "compaction_delta":
print(f"Compaction complete: {len(event.delta.content or '')} chars")
elif event.delta.type == "text_delta":
print(event.delta.text, end="", flush=True)
# Get the final accumulated message
message = stream.get_final_message()
messages.append({"role": "assistant", "content": message.content})
import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const messages: Anthropic.Beta.Messages.BetaMessageParam[] = [];
const stream = await client.beta.messages.stream({
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages,
context_management: {
edits: [{ type: "compact_20260112" }]
}
});
for await (const event of stream) {
if (event.type === "content_block_start") {
if (event.content_block.type === "compaction") {
console.log("Compaction started...");
} else if (event.content_block.type === "text") {
console.log("Text response started...");
}
} else if (event.type === "content_block_delta") {
if (event.delta.type === "compaction_delta") {
console.log(`Compaction complete: ${event.delta.content?.length ?? 0} chars`);
} else if (event.delta.type === "text_delta") {
process.stdout.write(event.delta.text);
}
}
}
// Get the final accumulated message
const message = await stream.finalMessage();
messages.push({
role: "assistant",
content: message.content
});
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Anthropic;
using Anthropic.Models.Beta.Messages;
class Program
{
static async Task Main(string[] args)
{
var client = new AnthropicClient();
List<BetaMessageParam> messages = [new() { Role = Role.User, Content = "Hello" }];
var parameters = new MessageCreateParams
{
Betas = ["compact-2026-01-12"],
Model = "claude-opus-4-7",
MaxTokens = 4096,
Messages = messages,
ContextManagement = new BetaContextManagementConfig
{
Edits = [new BetaCompact20260112Edit()]
}
};
await foreach (var streamEvent in client.Beta.Messages.CreateStreaming(parameters))
{
if (streamEvent.TryPickContentBlockStart(out var startEvent))
{
if (startEvent.ContentBlock.TryPickBetaCompaction(out _))
{
Console.WriteLine("Compaction started...");
}
else if (startEvent.ContentBlock.TryPickBetaText(out _))
{
Console.WriteLine("Text response started...");
}
}
else if (streamEvent.TryPickContentBlockDelta(out var deltaEvent))
{
if (deltaEvent.Delta.TryPickCompaction(out var compactionDelta))
{
Console.WriteLine({{CONTENT}}quot;Compaction complete: {compactionDelta.Content?.Length ?? 0} chars");
}
else if (deltaEvent.Delta.TryPickText(out var textDelta))
{
Console.Write(textDelta.Text);
}
}
}
}
}
package main
import (
"context"
"fmt"
"log"
"github.com/anthropics/anthropic-sdk-go"
)
func main() {
client := anthropic.NewClient()
messages := []anthropic.BetaMessageParam{anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Hello, Claude"))}
stream := client.Beta.Messages.NewStreaming(context.TODO(), anthropic.BetaMessageNewParams{
Model: anthropic.ModelClaudeOpus4_7,
MaxTokens: 4096,
Messages: messages,
ContextManagement: anthropic.BetaContextManagementConfigParam{
Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
{OfCompact20260112: &anthropic.BetaCompact20260112EditParam{}},
},
},
Betas: []anthropic.AnthropicBeta{"compact-2026-01-12"},
})
for stream.Next() {
event := stream.Current()
switch eventVariant := event.AsAny().(type) {
case anthropic.BetaRawContentBlockStartEvent:
switch eventVariant.ContentBlock.AsAny().(type) {
case anthropic.BetaCompactionBlock:
fmt.Println("Compaction started...")
case anthropic.BetaTextBlock:
fmt.Println("Text response started...")
}
case anthropic.BetaRawContentBlockDeltaEvent:
switch deltaVariant := eventVariant.Delta.AsAny().(type) {
case anthropic.BetaCompactionContentBlockDelta:
fmt.Printf("Compaction complete: %d chars\n", len(deltaVariant.Content))
case anthropic.BetaTextDelta:
fmt.Print(deltaVariant.Text)
}
}
}
if err := stream.Err(); err != nil {
log.Fatal(err)
}
}
import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.beta.messages.MessageCreateParams;
import com.anthropic.models.beta.messages.BetaContextManagementConfig;
import com.anthropic.models.beta.messages.BetaCompact20260112Edit;
public class CompactionStreamingExample {
public static void main(String[] args) {
AnthropicClient client = AnthropicOkHttpClient.fromEnv();
MessageCreateParams params = MessageCreateParams.builder()
.model("claude-opus-4-7")
.maxTokens(4096L)
.addBeta("compact-2026-01-12")
.addUserMessage("Hello, Claude")
.contextManagement(BetaContextManagementConfig.builder()
.addEdit(BetaCompact20260112Edit.builder().build())
.build())
.build();
try (var streamResponse = client.beta().messages().createStreaming(params)) {
streamResponse.stream().forEach(event -> {
event.contentBlockStart().ifPresent(startEvent -> {
startEvent.contentBlock().compaction().ifPresent(c ->
System.out.println("Compaction started...")
);
startEvent.contentBlock().text().ifPresent(t ->
System.out.println("Text response started...")
);
});
event.contentBlockDelta().ifPresent(deltaEvent -> {
deltaEvent.delta().compaction().ifPresent(cd ->
System.out.println("Compaction complete: " + cd.content().map(String::length).orElse(0) + " chars")
);
deltaEvent.delta().text().ifPresent(td ->
System.out.print(td.text())
);
});
});
}
}
}
<?php
use Anthropic\Client;
$client = new Client(apiKey: getenv("ANTHROPIC_API_KEY"));
$messages = [['role' => 'user', 'content' => 'Hello, Claude']];
$stream = $client->beta->messages->createStream(
maxTokens: 4096,
messages: $messages,
model: 'claude-opus-4-7',
betas: ['compact-2026-01-12'],
contextManagement: [
'edits' => [
['type' => 'compact_20260112']
]
]
);
foreach ($stream as $event) {
if ($event->type === 'content_block_start') {
if ($event->contentBlock->type === 'compaction') {
echo "Compaction started...\n";
} elseif ($event->contentBlock->type === 'text') {
echo "Text response started...\n";
}
} elseif ($event->type === 'content_block_delta') {
if ($event->delta->type === 'compaction_delta') {
echo "Compaction complete: " . strlen($event->delta->content ?? '') . " chars\n";
} elseif ($event->delta->type === 'text_delta') {
echo $event->delta->text;
}
}
}
require "anthropic"
client = Anthropic::Client.new
messages = [{ role: "user", content: "Hello, Claude" }]
stream = client.beta.messages.stream(
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages: messages,
context_management: {
edits: [{ type: "compact_20260112" }]
}
)
stream.each do |event|
case event.type
when :content_block_start
if event.content_block.type == :compaction
puts "Compaction started..."
elsif event.content_block.type == :text
puts "Text response started..."
end
when :content_block_delta
if event.delta.type == :compaction_delta
puts "Compaction complete: #{(event.delta.content || "").length} chars"
elsif event.delta.type == :text_delta
print event.delta.text
end
end
end
Prompt caching
Compaction works well with prompt caching. You can add a cache_control breakpoint on compaction blocks to cache the summarized content. The original compacted content is ignored.
{
"role": "assistant",
"content": [
{
"type": "compaction",
"content": "[summary text]",
"cache_control": { "type": "ephemeral" }
},
{
"type": "text",
"text": "Based on our conversation..."
}
]
}
Maximizing cache hits with system prompts
When compaction occurs, the summary becomes new content that needs to be written to the cache. Without additional cache breakpoints, this would also invalidate any cached system prompt, requiring it to be re-cached along with the compaction summary.
To maximize cache hit rates, add a cache_control breakpoint at the end of your system prompt. This keeps the system prompt cached separately from the conversation, so when compaction occurs:
- The system prompt cache remains valid and is read from cache
- Only the compaction summary needs to be written as a new cache entry
ant beta:messages create --beta compact-2026-01-12 <<'YAML'
model: claude-opus-4-7
max_tokens: 4096
system:
- type: text
text: You are a helpful coding assistant...
cache_control:
type: ephemeral
messages:
- role: user
content: Hello, Claude
context_management:
edits:
- type: compact_20260112
YAML
import anthropic
client = anthropic.Anthropic()
messages = [{"role": "user", "content": "Hello, Claude"}]
response = client.beta.messages.create(
betas=["compact-2026-01-12"],
model="claude-opus-4-7",
max_tokens=4096,
system=[
{
"type": "text",
"text": "You are a helpful coding assistant...",
"cache_control": {
"type": "ephemeral"
}, # Cache the system prompt separately
}
],
messages=messages,
context_management={"edits": [{"type": "compact_20260112"}]},
)
import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const messages: Anthropic.Beta.Messages.BetaMessageParam[] = [];
const response = await client.beta.messages.create({
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
system: [
{
type: "text",
text: "You are a helpful coding assistant...",
cache_control: { type: "ephemeral" } // Cache the system prompt separately
}
],
messages,
context_management: {
edits: [{ type: "compact_20260112" }]
}
});
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Anthropic;
using Anthropic.Models.Beta.Messages;
class Program
{
static async Task Main(string[] args)
{
var client = new AnthropicClient();
var parameters = new MessageCreateParams
{
Betas = ["compact-2026-01-12"],
Model = "claude-opus-4-7",
MaxTokens = 4096,
System = new List<BetaTextBlockParam>
{
new()
{
Text = "You are a helpful coding assistant...",
CacheControl = new BetaCacheControlEphemeral()
}
},
Messages = [],
ContextManagement = new BetaContextManagementConfig
{
Edits = [new BetaCompact20260112Edit()]
}
};
var response = await client.Beta.Messages.Create(parameters);
Console.WriteLine(response);
}
}
package main
import (
"context"
"fmt"
"log"
"github.com/anthropics/anthropic-sdk-go"
)
func main() {
client := anthropic.NewClient()
response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
Model: anthropic.ModelClaudeOpus4_7,
MaxTokens: 4096,
System: []anthropic.BetaTextBlockParam{
{
Text: "You are a helpful coding assistant...",
CacheControl: anthropic.NewBetaCacheControlEphemeralParam(),
},
},
Messages: []anthropic.BetaMessageParam{anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Hello, Claude"))},
ContextManagement: anthropic.BetaContextManagementConfigParam{
Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
{OfCompact20260112: &anthropic.BetaCompact20260112EditParam{}},
},
},
Betas: []anthropic.AnthropicBeta{"compact-2026-01-12"},
})
if err != nil {
log.Fatal(err)
}
fmt.Println(response)
}
import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.beta.messages.MessageCreateParams;
import com.anthropic.models.beta.messages.BetaMessage;
import com.anthropic.models.beta.messages.BetaTextBlockParam;
import com.anthropic.models.beta.messages.BetaContextManagementConfig;
import com.anthropic.models.beta.messages.BetaCompact20260112Edit;
import com.anthropic.models.beta.messages.BetaCacheControlEphemeral;
import java.util.List;
public class CompactionExample {
public static void main(String[] args) {
AnthropicClient client = AnthropicOkHttpClient.fromEnv();
MessageCreateParams params = MessageCreateParams.builder()
.model("claude-opus-4-7")
.maxTokens(4096L)
.addBeta("compact-2026-01-12")
.systemOfBetaTextBlockParams(List.of(
BetaTextBlockParam.builder()
.text("You are a helpful coding assistant...")
.cacheControl(BetaCacheControlEphemeral.builder().build())
.build()
))
.addUserMessage("Hello, Claude")
.contextManagement(BetaContextManagementConfig.builder()
.addEdit(BetaCompact20260112Edit.builder().build())
.build())
.build();
BetaMessage response = client.beta().messages().create(params);
System.out.println(response);
}
}
<?php
use Anthropic\Client;
$client = new Client(apiKey: getenv("ANTHROPIC_API_KEY"));
$response = $client->beta->messages->create(
maxTokens: 4096,
messages: [['role' => 'user', 'content' => 'Hello, Claude']],
model: 'claude-opus-4-7',
betas: ['compact-2026-01-12'],
system: [
[
'type' => 'text',
'text' => 'You are a helpful coding assistant...',
'cache_control' => [
'type' => 'ephemeral'
]
]
],
contextManagement: [
'edits' => [
['type' => 'compact_20260112']
]
]
);
echo $response->content[0]->text;
require "anthropic"
client = Anthropic::Client.new
response = client.beta.messages.create(
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
system: [
{
type: "text",
text: "You are a helpful coding assistant...",
cache_control: {
type: "ephemeral"
}
}
],
messages: [],
context_management: {
edits: [{ type: "compact_20260112" }]
}
)
puts response
This approach is particularly beneficial for long system prompts, as they remain cached even across multiple compaction events throughout a conversation.
Understanding usage
Compaction requires an additional sampling step, which contributes to rate limits and billing. The API returns detailed usage information in the response:
{
"usage": {
"input_tokens": 23000,
"output_tokens": 1000,
"iterations": [
{
"type": "compaction",
"input_tokens": 180000,
"output_tokens": 3500
},
{
"type": "message",
"input_tokens": 23000,
"output_tokens": 1000
}
]
}
}
The iterations array shows usage for each sampling iteration. When compaction occurs, you'll see a compaction iteration followed by the main message iteration. The top-level input_tokens and output_tokens match the message iteration exactly in this example because there is only one non-compaction iteration. The final iteration's token counts reflect the effective context size after compaction.
Note
The top-level input_tokens and output_tokens do not include compaction iteration usage. They reflect the sum of all non-compaction iterations. To calculate total tokens consumed and billed for a request, sum across all entries in the usage.iterations array.
If you previously relied on usage.input_tokens and usage.output_tokens for cost tracking or auditing, you'll need to update your tracking logic to aggregate across usage.iterations when compaction is enabled. The iterations array is only populated when a new compaction is triggered during the request. Re-applying a previous compaction block incurs no additional compaction cost, and the top-level usage fields remain accurate in that case.
Combining with other features
Server tools
When using server tools (like web search), the compaction trigger is checked at the start of each sampling iteration. Compaction may occur multiple times within a single request depending on your trigger threshold and the amount of output generated.
Token counting
The token counting endpoint (/v1/messages/count_tokens) applies existing compaction blocks in your prompt but does not trigger new compactions. Use it to check your effective token count after previous compactions:
cat > request.yaml <<'YAML'
model: claude-opus-4-7
messages:
- role: user
content: Hello, Claude
context_management:
edits:
- type: compact_20260112
YAML
CURRENT=$(ant beta:messages count-tokens \
--beta compact-2026-01-12 \
--transform input_tokens --raw-output < request.yaml)
ORIGINAL=$(ant beta:messages count-tokens \
--beta compact-2026-01-12 \
--transform context_management.original_input_tokens \
--raw-output < request.yaml)
printf 'Current tokens: %s\n' "$CURRENT"
printf 'Original tokens: %s\n' "$ORIGINAL"
import anthropic
client = anthropic.Anthropic()
messages = [{"role": "user", "content": "Hello, Claude"}]
count_response = client.beta.messages.count_tokens(
betas=["compact-2026-01-12"],
model="claude-opus-4-7",
messages=messages,
context_management={"edits": [{"type": "compact_20260112"}]},
)
print(f"Current tokens: {count_response.input_tokens}")
print(f"Original tokens: {count_response.context_management.original_input_tokens}")
import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const messages: Anthropic.Beta.Messages.BetaMessageParam[] = [
{ role: "user", content: "Summarize the key points of our conversation so far." }
];
const countResponse = await client.beta.messages.countTokens({
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
messages,
context_management: {
edits: [{ type: "compact_20260112" }]
}
});
console.log(`Current tokens: ${countResponse.input_tokens}`);
console.log(`Original tokens: ${countResponse.context_management!.original_input_tokens}`);
using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Anthropic;
using Anthropic.Models.Beta.Messages;
class Program
{
static async Task Main(string[] args)
{
AnthropicClient client = new();
List<BetaMessageParam> messages = [new() { Role = Role.User, Content = "Hello" }];
var countParams = new MessageCountTokensParams
{
Model = "claude-opus-4-7",
Messages = messages,
ContextManagement = new BetaContextManagementConfig
{
Edits = [new BetaCompact20260112Edit()]
},
Betas = ["compact-2026-01-12"]
};
var countResponse = await client.Beta.Messages.CountTokens(countParams);
Console.WriteLine({{CONTENT}}quot;Current tokens: {countResponse.InputTokens}");
Console.WriteLine({{CONTENT}}quot;Original tokens: {countResponse.ContextManagement?.OriginalInputTokens}");
}
}
package main
import (
"context"
"fmt"
"log"
"github.com/anthropics/anthropic-sdk-go"
)
func main() {
client := anthropic.NewClient()
messages := []anthropic.BetaMessageParam{anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Hello, Claude"))}
countResponse, err := client.Beta.Messages.CountTokens(context.TODO(), anthropic.BetaMessageCountTokensParams{
Model: anthropic.ModelClaudeOpus4_7,
Messages: messages,
ContextManagement: anthropic.BetaContextManagementConfigParam{
Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
{OfCompact20260112: &anthropic.BetaCompact20260112EditParam{}},
},
},
Betas: []anthropic.AnthropicBeta{"compact-2026-01-12"},
})
if err != nil {
log.Fatal(err)
}
fmt.Printf("Current tokens: %d\n", countResponse.InputTokens)
fmt.Printf("Original tokens: %d\n", countResponse.ContextManagement.OriginalInputTokens)
}
import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
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.BetaCompact20260112Edit;
public class Main {
public static void main(String[] args) {
AnthropicClient client = AnthropicOkHttpClient.fromEnv();
MessageCountTokensParams params = MessageCountTokensParams.builder()
.model("claude-opus-4-7")
.addUserMessage("Hello, Claude")
.contextManagement(BetaContextManagementConfig.builder()
.addEdit(BetaCompact20260112Edit.builder().build())
.build())
.addBeta("compact-2026-01-12")
.build();
BetaMessageTokensCount countResponse = client.beta().messages().countTokens(params);
System.out.println("Current tokens: " + countResponse.inputTokens());
System.out.println("Original tokens: " + countResponse.contextManagement().get().originalInputTokens());
}
}
<?php
use Anthropic\Client;
$client = new Client(apiKey: getenv("ANTHROPIC_API_KEY"));
$messages = [['role' => 'user', 'content' => 'Hello, Claude']];
$countResponse = $client->beta->messages->countTokens(
messages: $messages,
model: 'claude-opus-4-7',
betas: ['compact-2026-01-12'],
contextManagement: [
'edits' => [
['type' => 'compact_20260112']
]
]
);
echo "Current tokens: " . $countResponse->inputTokens . "\n";
echo "Original tokens: " . $countResponse->contextManagement->originalInputTokens . "\n";
require "anthropic"
client = Anthropic::Client.new
messages = [{ role: "user", content: "Hello, Claude" }]
count_response = client.beta.messages.count_tokens(
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
messages: messages,
context_management: {
edits: [{ type: "compact_20260112" }]
}
)
puts "Current tokens: #{count_response.input_tokens}"
puts "Original tokens: #{count_response.context_management.original_input_tokens}"
Examples
Here's a complete example of a long-running conversation with compaction:
# The CLI handles individual turns; maintain the messages array in the
# calling script. See the SDK tabs for the full chat() loop. Single-turn
# request shape:
ant beta:messages create --beta compact-2026-01-12 \
--transform 'content.#(type=="text").text' --raw-output <<'YAML'
model: claude-opus-4-7
max_tokens: 4096
messages:
- role: user
content: Help me build a Python web scraper
context_management:
edits:
- type: compact_20260112
trigger:
type: input_tokens
value: 100000
YAML
import anthropic
client = anthropic.Anthropic()
messages: list[dict] = []
def chat(user_message: str) -> str:
messages.append({"role": "user", "content": user_message})
response = client.beta.messages.create(
betas=["compact-2026-01-12"],
model="claude-opus-4-7",
max_tokens=4096,
messages=messages,
context_management={
"edits": [
{
"type": "compact_20260112",
"trigger": {"type": "input_tokens", "value": 100000},
}
]
},
)
# Append response (compaction blocks are automatically included)
messages.append({"role": "assistant", "content": response.content})
# Return the text content
return next(block.text for block in response.content if block.type == "text")
# Run a long conversation
print(chat("Help me build a Python web scraper"))
print(chat("Add support for JavaScript-rendered pages"))
print(chat("Now add rate limiting and error handling"))
# ... continue as long as needed
import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
const messages: Anthropic.Beta.BetaMessageParam[] = [];
async function chat(userMessage: string): Promise<string> {
messages.push({ role: "user", content: userMessage });
const response = await client.beta.messages.create({
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages,
context_management: {
edits: [
{
type: "compact_20260112",
trigger: { type: "input_tokens", value: 100000 }
}
]
}
});
// Append response (compaction blocks are automatically included)
messages.push({ role: "assistant", content: response.content });
// Return the text content
const textBlock = response.content.find((block) => block.type === "text");
return textBlock?.text ?? "";
}
// Run a long conversation
console.log(await chat("Help me build a Python web scraper"));
console.log(await chat("Add support for JavaScript-rendered pages"));
console.log(await chat("Now add rate limiting and error handling"));
// ... continue as long as needed
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Anthropic;
using Anthropic.Models.Beta.Messages;
public class Program
{
static async Task Main(string[] args)
{
AnthropicClient client = new();
List<BetaMessageParam> messages = new();
Console.WriteLine(await Chat(client, messages, "Help me build a Python web scraper"));
Console.WriteLine(await Chat(client, messages, "Add support for JavaScript-rendered pages"));
Console.WriteLine(await Chat(client, messages, "Now add rate limiting and error handling"));
}
static async Task<string> Chat(AnthropicClient client, List<BetaMessageParam> messages, string userMessage)
{
messages.Add(new() { Role = Role.User, Content = userMessage });
var parameters = new MessageCreateParams
{
Betas = ["compact-2026-01-12"],
Model = "claude-opus-4-7",
MaxTokens = 4096,
Messages = messages,
ContextManagement = new BetaContextManagementConfig
{
Edits = [new BetaCompact20260112Edit
{
Trigger = new BetaInputTokensTrigger(100000)
}]
}
};
var response = await client.Beta.Messages.Create(parameters);
messages.Add(new()
{
Role = Role.Assistant,
Content = response.Content.Select(b => new BetaContentBlockParam(b.Json)).ToList()
});
return response.Content
.Select(b => b.Value)
.OfType<BetaTextBlock>()
.Select(tb => tb.Text)
.FirstOrDefault() ?? "";
}
}
package main
import (
"context"
"fmt"
"log"
"github.com/anthropics/anthropic-sdk-go"
)
var (
client = anthropic.NewClient()
messages []anthropic.BetaMessageParam
)
func chat(userMessage string) string {
messages = append(messages, anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock(userMessage)))
response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
Model: anthropic.ModelClaudeOpus4_7,
MaxTokens: 4096,
Messages: messages,
ContextManagement: anthropic.BetaContextManagementConfigParam{
Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
{OfCompact20260112: &anthropic.BetaCompact20260112EditParam{
Trigger: anthropic.BetaInputTokensTriggerParam{Value: 100000},
}},
},
},
Betas: []anthropic.AnthropicBeta{"compact-2026-01-12"},
})
if err != nil {
log.Fatal(err)
}
messages = append(messages, response.ToParam())
for _, block := range response.Content {
if variant, ok := block.AsAny().(anthropic.BetaTextBlock); ok {
return variant.Text
}
}
return ""
}
func main() {
fmt.Println(chat("Help me build a Python web scraper"))
fmt.Println(chat("Add support for JavaScript-rendered pages"))
fmt.Println(chat("Now add rate limiting and error handling"))
}
import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.beta.messages.MessageCreateParams;
import com.anthropic.models.beta.messages.BetaMessage;
import com.anthropic.models.beta.messages.BetaMessageParam;
import com.anthropic.models.beta.messages.BetaContextManagementConfig;
import com.anthropic.models.beta.messages.BetaCompact20260112Edit;
import com.anthropic.models.beta.messages.BetaInputTokensTrigger;
import java.util.ArrayList;
import java.util.List;
public class CompactionExample {
private static final AnthropicClient client = AnthropicOkHttpClient.fromEnv();
private static final List<BetaMessageParam> messages = new ArrayList<>();
public static void main(String[] args) {
System.out.println(chat("Help me build a Python web scraper"));
System.out.println(chat("Add support for JavaScript-rendered pages"));
System.out.println(chat("Now add rate limiting and error handling"));
}
private static String chat(String userMessage) {
messages.add(BetaMessageParam.builder()
.role(BetaMessageParam.Role.USER)
.content(userMessage)
.build());
MessageCreateParams params = MessageCreateParams.builder()
.addBeta("compact-2026-01-12")
.model("claude-opus-4-7")
.maxTokens(4096L)
.messages(messages)
.contextManagement(BetaContextManagementConfig.builder()
.addEdit(BetaCompact20260112Edit.builder()
.trigger(BetaInputTokensTrigger.builder()
.value(100000L)
.build())
.build())
.build())
.build();
BetaMessage response = client.beta().messages().create(params);
// Append response (compaction blocks are automatically included)
messages.add(response.toParam());
return response.content().stream()
.filter(block -> block.text().isPresent())
.map(block -> block.text().get().text())
.findFirst()
.orElse("");
}
}
<?php
use Anthropic\Client;
$client = new Client(apiKey: getenv("ANTHROPIC_API_KEY"));
$messages = [];
function chat($client, &$messages, $userMessage) {
$messages[] = ['role' => 'user', 'content' => $userMessage];
$response = $client->beta->messages->create(
maxTokens: 4096,
messages: $messages,
model: 'claude-opus-4-7',
betas: ['compact-2026-01-12'],
contextManagement: [
'edits' => [
[
'type' => 'compact_20260112',
'trigger' => ['type' => 'input_tokens', 'value' => 100000]
]
]
]
);
$messages[] = ['role' => 'assistant', 'content' => $response->content];
foreach ($response->content as $block) {
if ($block->type === 'text') {
return $block->text;
}
}
return '';
}
echo chat($client, $messages, "Help me build a Python web scraper") . "\n";
echo chat($client, $messages, "Add support for JavaScript-rendered pages") . "\n";
echo chat($client, $messages, "Now add rate limiting and error handling") . "\n";
require "anthropic"
client = Anthropic::Client.new
messages = []
def chat(client, messages, user_message)
messages << { role: "user", content: user_message }
response = client.beta.messages.create(
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages: messages,
context_management: {
edits: [
{
type: "compact_20260112",
trigger: { type: "input_tokens", value: 100000 }
}
]
}
)
messages << { role: "assistant", content: response.content }
response.content.find { |block| block.type == :text }&.text || ""
end
puts chat(client, messages, "Help me build a Python web scraper")
puts chat(client, messages, "Add support for JavaScript-rendered pages")
puts chat(client, messages, "Now add rate limiting and error handling")
Here's an example that uses pause_after_compaction to preserve the prior exchange and the current user message (three messages total) verbatim instead of summarizing them:
# The CLI handles individual turns; maintain the messages array in the
# calling script. See the SDK tabs for the full chat() loop with
# pause-and-preserve handling. Single-turn request shape:
ant beta:messages create --beta compact-2026-01-12 \
--transform 'content.#(type=="text").text' --raw-output <<'YAML'
model: claude-opus-4-7
max_tokens: 4096
messages:
- role: user
content: Help me build a Python web scraper
context_management:
edits:
- type: compact_20260112
trigger:
type: input_tokens
value: 100000
pause_after_compaction: true
YAML
import anthropic
from typing import Any
client = anthropic.Anthropic()
messages: list[dict[str, Any]] = []
def chat(user_message: str) -> str:
messages.append({"role": "user", "content": user_message})
response = client.beta.messages.create(
betas=["compact-2026-01-12"],
model="claude-opus-4-7",
max_tokens=4096,
messages=messages,
context_management={
"edits": [
{
"type": "compact_20260112",
"trigger": {"type": "input_tokens", "value": 100000},
"pause_after_compaction": True,
}
]
},
)
# Check if compaction occurred and paused
if response.stop_reason == "compaction":
# Get the compaction block from the response
compaction_block = response.content[0]
# Preserve the prior exchange + current user message (3 messages)
# by including them after the compaction block
preserved_messages = messages[-3:] if len(messages) >= 3 else messages
# Build new message list: compaction + preserved messages
new_assistant_content = [compaction_block]
messages_after_compaction = [
{"role": "assistant", "content": new_assistant_content}
] + preserved_messages
# Continue the request with the compacted context + preserved messages
response = client.beta.messages.create(
betas=["compact-2026-01-12"],
model="claude-opus-4-7",
max_tokens=4096,
messages=messages_after_compaction,
context_management={"edits": [{"type": "compact_20260112"}]},
)
# Update our message list to reflect the compaction
messages.clear()
messages.extend(messages_after_compaction)
# Append the final response
messages.append({"role": "assistant", "content": response.content})
# Return the text content
return next(block.text for block in response.content if block.type == "text")
# Run a long conversation
print(chat("Help me build a Python web scraper"))
print(chat("Add support for JavaScript-rendered pages"))
print(chat("Now add rate limiting and error handling"))
# ... continue as long as needed
import Anthropic from "@anthropic-ai/sdk";
const client = new Anthropic();
let messages: Anthropic.Beta.BetaMessageParam[] = [];
async function chat(userMessage: string): Promise<string> {
messages.push({ role: "user", content: userMessage });
let response = await client.beta.messages.create({
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages,
context_management: {
edits: [
{
type: "compact_20260112",
trigger: { type: "input_tokens", value: 100000 },
pause_after_compaction: true
}
]
}
});
// Check if compaction occurred and paused
if (response.stop_reason === "compaction") {
// Get the compaction block from the response
const compactionBlock = response.content[0];
// Preserve the prior exchange + current user message (3 messages)
// by including them after the compaction block
const preservedMessages = messages.length >= 3 ? messages.slice(-3) : [...messages];
// Build new message list: compaction + preserved messages
const messagesAfterCompaction: Anthropic.Beta.BetaMessageParam[] = [
{ role: "assistant", content: [compactionBlock] },
...preservedMessages
];
// Continue the request with the compacted context + preserved messages
response = await client.beta.messages.create({
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages: messagesAfterCompaction,
context_management: {
edits: [{ type: "compact_20260112" }]
}
});
// Update our message list to reflect the compaction
messages = messagesAfterCompaction;
}
// Append the final response
messages.push({ role: "assistant", content: response.content });
// Return the text content
const textBlock = response.content.find((block) => block.type === "text");
return textBlock?.text ?? "";
}
// Run a long conversation
console.log(await chat("Help me build a Python web scraper"));
console.log(await chat("Add support for JavaScript-rendered pages"));
console.log(await chat("Now add rate limiting and error handling"));
// ... continue as long as needed
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Anthropic;
using Anthropic.Models.Beta.Messages;
public class CompactionExample
{
private static AnthropicClient client = new();
private static List<BetaMessageParam> messages = new();
static async Task<string> Chat(string userMessage)
{
messages.Add(new() { Role = Role.User, Content = userMessage });
var response = await client.Beta.Messages.Create(new()
{
Betas = ["compact-2026-01-12"],
Model = "claude-opus-4-7",
MaxTokens = 4096,
Messages = messages,
ContextManagement = new BetaContextManagementConfig
{
Edits = [new BetaCompact20260112Edit
{
Trigger = new BetaInputTokensTrigger(100000),
PauseAfterCompaction = true
}]
}
});
if (response.StopReason == BetaStopReason.Compaction)
{
if (!response.Content[0].TryPickCompaction(out var cb))
throw new InvalidOperationException("Expected compaction block");
var preserved = messages.Count >= 3
? messages.Skip(messages.Count - 3).ToList()
: new List<BetaMessageParam>(messages);
var messagesAfterCompaction = new List<BetaMessageParam>
{
new()
{
Role = Role.Assistant,
Content = new List<BetaContentBlockParam> { new BetaCompactionBlockParam(cb.Content) }
}
};
messagesAfterCompaction.AddRange(preserved);
response = await client.Beta.Messages.Create(new()
{
Betas = ["compact-2026-01-12"],
Model = "claude-opus-4-7",
MaxTokens = 4096,
Messages = messagesAfterCompaction,
ContextManagement = new BetaContextManagementConfig
{
Edits = [new BetaCompact20260112Edit()]
}
});
messages = messagesAfterCompaction;
}
messages.Add(new()
{
Role = Role.Assistant,
Content = response.Content.Select(b => new BetaContentBlockParam(b.Json)).ToList()
});
return response.Content
.Select(b => b.Value)
.OfType<BetaTextBlock>()
.Select(tb => tb.Text)
.FirstOrDefault() ?? "";
}
static async Task Main()
{
Console.WriteLine(await Chat("Help me build a Python web scraper"));
Console.WriteLine(await Chat("Add support for JavaScript-rendered pages"));
Console.WriteLine(await Chat("Now add rate limiting and error handling"));
}
}
package main
import (
"context"
"fmt"
"log"
"github.com/anthropics/anthropic-sdk-go"
)
var (
client = anthropic.NewClient()
messages []anthropic.BetaMessageParam
)
func chat(userMessage string) string {
messages = append(messages, anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock(userMessage)))
compactEdit := anthropic.BetaContextManagementConfigParam{
Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
{OfCompact20260112: &anthropic.BetaCompact20260112EditParam{
Trigger: anthropic.BetaInputTokensTriggerParam{Value: 100000},
PauseAfterCompaction: anthropic.Bool(true),
}},
},
}
response, err := client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
Model: anthropic.ModelClaudeOpus4_7,
MaxTokens: 4096,
Messages: messages,
ContextManagement: compactEdit,
Betas: []anthropic.AnthropicBeta{"compact-2026-01-12"},
})
if err != nil {
log.Fatal(err)
}
if response.StopReason == "compaction" {
compactionParam := response.Content[0].ToParam()
var preserved []anthropic.BetaMessageParam
if len(messages) >= 3 {
preserved = messages[len(messages)-3:]
} else {
preserved = messages
}
messagesAfterCompaction := []anthropic.BetaMessageParam{
{Role: anthropic.BetaMessageParamRoleAssistant, Content: []anthropic.BetaContentBlockParamUnion{compactionParam}},
}
messagesAfterCompaction = append(messagesAfterCompaction, preserved...)
response, err = client.Beta.Messages.New(context.TODO(), anthropic.BetaMessageNewParams{
Model: anthropic.ModelClaudeOpus4_7,
MaxTokens: 4096,
Messages: messagesAfterCompaction,
ContextManagement: anthropic.BetaContextManagementConfigParam{
Edits: []anthropic.BetaContextManagementConfigEditUnionParam{
{OfCompact20260112: &anthropic.BetaCompact20260112EditParam{}},
},
},
Betas: []anthropic.AnthropicBeta{"compact-2026-01-12"},
})
if err != nil {
log.Fatal(err)
}
messages = messagesAfterCompaction
}
messages = append(messages, response.ToParam())
for _, block := range response.Content {
if textBlock, ok := block.AsAny().(anthropic.BetaTextBlock); ok {
return textBlock.Text
}
}
return ""
}
func main() {
fmt.Println(chat("Help me build a Python web scraper"))
fmt.Println(chat("Add support for JavaScript-rendered pages"))
fmt.Println(chat("Now add rate limiting and error handling"))
}
import com.anthropic.client.AnthropicClient;
import com.anthropic.client.okhttp.AnthropicOkHttpClient;
import com.anthropic.models.beta.messages.MessageCreateParams;
import com.anthropic.models.beta.messages.BetaMessage;
import com.anthropic.models.beta.messages.BetaMessageParam;
import com.anthropic.models.beta.messages.BetaContextManagementConfig;
import com.anthropic.models.beta.messages.BetaCompact20260112Edit;
import com.anthropic.models.beta.messages.BetaInputTokensTrigger;
import com.anthropic.models.beta.messages.BetaStopReason;
import java.util.ArrayList;
import java.util.List;
public class CompactionExample {
private static final AnthropicClient client = AnthropicOkHttpClient.fromEnv();
private static final List<BetaMessageParam> messages = new ArrayList<>();
public static String chat(String userMessage) {
messages.add(BetaMessageParam.builder()
.role(BetaMessageParam.Role.USER)
.content(userMessage)
.build());
MessageCreateParams params = MessageCreateParams.builder()
.addBeta("compact-2026-01-12")
.model("claude-opus-4-7")
.maxTokens(4096L)
.messages(messages)
.contextManagement(BetaContextManagementConfig.builder()
.addEdit(BetaCompact20260112Edit.builder()
.trigger(BetaInputTokensTrigger.builder()
.value(100000L)
.build())
.pauseAfterCompaction(true)
.build())
.build())
.build();
BetaMessage response = client.beta().messages().create(params);
// Check if compaction occurred and paused
if (response.stopReason().isPresent()
&& response.stopReason().get().equals(BetaStopReason.COMPACTION)) {
// Preserve the prior exchange + current user message (3 messages)
List<BetaMessageParam> preservedMessages = messages.size() >= 3
? new ArrayList<>(messages.subList(messages.size() - 3, messages.size()))
: new ArrayList<>(messages);
// Build new message list: compaction + preserved messages
List<BetaMessageParam> messagesAfterCompaction = new ArrayList<>();
messagesAfterCompaction.add(response.toParam());
messagesAfterCompaction.addAll(preservedMessages);
// Continue the request with the compacted context + preserved messages
MessageCreateParams continueParams = MessageCreateParams.builder()
.addBeta("compact-2026-01-12")
.model("claude-opus-4-7")
.maxTokens(4096L)
.messages(messagesAfterCompaction)
.contextManagement(BetaContextManagementConfig.builder()
.addEdit(BetaCompact20260112Edit.builder().build())
.build())
.build();
response = client.beta().messages().create(continueParams);
// Update our message list to reflect the compaction
messages.clear();
messages.addAll(messagesAfterCompaction);
}
// Append the final response
messages.add(response.toParam());
return response.content().stream()
.filter(block -> block.text().isPresent())
.map(block -> block.text().get().text())
.findFirst()
.orElse("");
}
public static void main(String[] args) {
System.out.println(chat("Help me build a Python web scraper"));
System.out.println(chat("Add support for JavaScript-rendered pages"));
System.out.println(chat("Now add rate limiting and error handling"));
}
}
<?php
use Anthropic\Client;
// The PHP SDK does not yet expose a typed constant for the `compaction` stop reason; compare the string value directly.
$client = new Client(apiKey: getenv("ANTHROPIC_API_KEY"));
$messages = [];
function chat($client, &$messages, $userMessage) {
$messages[] = ['role' => 'user', 'content' => $userMessage];
$response = $client->beta->messages->create(
maxTokens: 4096,
messages: $messages,
model: 'claude-opus-4-7',
betas: ['compact-2026-01-12'],
contextManagement: [
'edits' => [
[
'type' => 'compact_20260112',
'trigger' => ['type' => 'input_tokens', 'value' => 100000],
'pause_after_compaction' => true
]
]
]
);
if ($response->stopReason === 'compaction') {
$compactionBlock = $response->content[0];
$preserved = count($messages) >= 3
? array_slice($messages, -3)
: $messages;
$messagesAfterCompaction = array_merge(
[['role' => 'assistant', 'content' => [$compactionBlock]]],
$preserved
);
$response = $client->beta->messages->create(
maxTokens: 4096,
messages: $messagesAfterCompaction,
model: 'claude-opus-4-7',
betas: ['compact-2026-01-12'],
contextManagement: [
'edits' => [['type' => 'compact_20260112']]
]
);
$messages = $messagesAfterCompaction;
}
$messages[] = ['role' => 'assistant', 'content' => $response->content];
foreach ($response->content as $block) {
if ($block->type === 'text') {
return $block->text;
}
}
return '';
}
echo chat($client, $messages, "Help me build a Python web scraper") . "\n";
echo chat($client, $messages, "Add support for JavaScript-rendered pages") . "\n";
echo chat($client, $messages, "Now add rate limiting and error handling") . "\n";
require "anthropic"
client = Anthropic::Client.new
messages = []
def chat(client, messages, user_message)
messages << { role: "user", content: user_message }
response = client.beta.messages.create(
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages: messages,
context_management: {
edits: [
{
type: "compact_20260112",
trigger: { type: "input_tokens", value: 100000 },
pause_after_compaction: true
}
]
}
)
if response.stop_reason == :compaction
compaction_block = response.content[0]
preserved = messages.length >= 3 ? messages[-3..-1] : messages.dup
messages_after_compaction = [
{ role: "assistant", content: [compaction_block] }
] + preserved
response = client.beta.messages.create(
betas: ["compact-2026-01-12"],
model: "claude-opus-4-7",
max_tokens: 4096,
messages: messages_after_compaction,
context_management: {
edits: [{ type: "compact_20260112" }]
}
)
messages.clear
messages.concat(messages_after_compaction)
end
messages << { role: "assistant", content: response.content }
response.content.find { |block| block.type == :text }&.text || ""
end
puts chat(client, messages, "Help me build a Python web scraper")
puts chat(client, messages, "Add support for JavaScript-rendered pages")
puts chat(client, messages, "Now add rate limiting and error handling")
Current limitations
-
Same model for summarization: The model specified in your request is used for summarization. There is no option to use a different (for example, cheaper) model for the summary.
-
Compaction might fail when tools are defined: When your request includes
tools, the model occasionally calls a tool during the internal summarization step instead of writing a summary. When this occurs, the response contains acompactionblock withcontent: null. To prevent this, setinstructionsto a prompt that explicitly tells the model not to call tools, for example:Summarize the transcript inside <summary></summary> tags. Include relevant information in the summary for continuing the task in the next context window. Do not call any tools while writing this summary; respond with text only.
Next steps
Session memory compaction cookbook
Explore a practical implementation that manages long-running conversations with instant session memory compaction using background threading and prompt caching.
Context windows
Learn about context window sizes and management strategies.
Context editing
Explore other strategies for managing conversation context like tool result clearing and thinking block clearing.