Combining with other features

Server tools

When using server tools (such as web search), the compaction trigger is checked at the start of each sampling iteration. Compaction might 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:

curl https://api.anthropic.com/v1/messages/count_tokens \
  -H "x-api-key: $ANTHROPIC_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "anthropic-beta: compact-2026-01-12" \
  -H "content-type: application/json" \
  -d '{
    "model": "claude-opus-5",
    "messages": [
      {
        "role": "user",
        "content": "Hello, Claude"
      }
    ],
    "context_management": {
      "edits": [
        {
          "type": "compact_20260112"
        }
      ]
    }
  }'

cat > request.yaml <<'YAML'
model: claude-opus-5
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"

client = anthropic.Anthropic()
messages = [{"role": "user", "content": "Hello, Claude"}]
count_response = client.beta.messages.count_tokens(
    betas=["compact-2026-01-12"],
    model="claude-opus-5",
    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}")

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-5",
  messages,
  context_management: {
    edits: [{ type: "compact_20260112" }]
  }
});

console.log(`Current tokens: ${countResponse.input_tokens}`);
console.log(`Original tokens: ${countResponse.context_management!.original_input_tokens}`);

AnthropicClient client = new();
List<BetaMessageParam> messages = [new() { Role = Role.User, Content = "Hello" }];

var countParams = new MessageCountTokensParams
{
    Model = "claude-opus-5",
    Messages = messages,
    ContextManagement = new BetaContextManagementConfig
    {
        Edits = [new BetaCompact20260112Edit()]
    },
    Betas = ["compact-2026-01-12"]
};

var countResponse = await client.Beta.Messages.CountTokens(countParams);
Console.WriteLine($"Current tokens: {countResponse.InputTokens}");
Console.WriteLine($"Original tokens: {countResponse.ContextManagement?.OriginalInputTokens}");

client := anthropic.NewClient()
messages := []anthropic.BetaMessageParam{anthropic.NewBetaUserMessage(anthropic.NewBetaTextBlock("Hello, Claude"))}

countResponse, err := client.Beta.Messages.CountTokens(context.TODO(), anthropic.BetaMessageCountTokensParams{
	Model:    anthropic.ModelClaudeOpus5,
	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.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;
// ...
        AnthropicClient client = AnthropicOkHttpClient.fromEnv();

        MessageCountTokensParams params = MessageCountTokensParams.builder()
            .model("claude-opus-5")
            .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());

$client = new Client();
$messages = [['role' => 'user', 'content' => 'Hello, Claude']];

$countResponse = $client->beta->messages->countTokens(
    messages: $messages,
    model: 'claude-opus-5',
    betas: ['compact-2026-01-12'],
    contextManagement: [
        'edits' => [
            ['type' => 'compact_20260112']
        ]
    ]
);

echo "Current tokens: " . $countResponse->inputTokens . "\n";
echo "Original tokens: " . $countResponse->contextManagement->originalInputTokens . "\n";

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-5",
  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}"