sessions

managed-agents/sessions First recorded · 1081 lines, first recorded

## Creating a session ### Seed the session with initial events ### Override agent configuration for a session #### Pin the inference geo for a session ### Set a session budget ## MCP authentication through vaults ## Starting the session ## Next steps

The first capture of this source. The page was already there, and this is what it said.

---
title: Start a session
url: https://platform.claude.com/docs/en/managed-agents/sessions
description: Create a session to run your agent and begin executing tasks.
---

A session is an agent instance within an environment. Each session references an [agent](https://platform.claude.com/docs/en/managed-agents/agent-setup) and an [environment](https://platform.claude.com/docs/en/managed-agents/environments) (both created separately), and maintains conversation history across multiple interactions. Sessions follow a two-step lifecycle: first [create the session](https://platform.claude.com/docs/en/managed-agents/sessions#creating-a-session), then [send a user event](https://platform.claude.com/docs/en/managed-agents/sessions#starting-the-session) to start work. You can also collapse both steps into one call with [`initial_events`](https://platform.claude.com/docs/en/managed-agents/sessions#seed-the-session-with-initial-events).

<Note>
  Managed Agents API requests require the `managed-agents-2026-04-01` beta header, except memory store endpoints, which use `agent-memory-2026-07-22` instead. The SDK sets the correct beta header automatically. See [Beta headers](https://platform.claude.com/docs/en/api/beta-headers#endpoint-specific-headers).
</Note>

## Creating a session

A session requires an `agent` ID and an `environment` ID. Agents are versioned resources; passing in the `agent` ID as a string creates the session with the latest agent version.

<CodeGroup defaultLanguage="CLI">
  ```bash cURL
  session=$(curl -fsSL https://api.anthropic.com/v1/sessions \
    -H "x-api-key: $ANTHROPIC_API_KEY" \
    -H "anthropic-version: 2023-06-01" \
    -H "anthropic-beta: managed-agents-2026-04-01" \
    -H "content-type: application/json" \
    -d @- <<EOF
  {
    "agent": "$AGENT_ID",
    "environment_id": "$ENVIRONMENT_ID"
  }
  EOF
  )
  SESSION_ID=$(jq -r '.id' <<< "$session")
  ```

  ```bash CLI
  ant beta:sessions create \
    --agent "$AGENT_ID" \
    --environment-id "$ENVIRONMENT_ID"
  ```

  ```python Python
  session = client.beta.sessions.create(
      agent=agent.id,
      environment_id=environment.id,
  )
  ```

  ```typescript TypeScript
  const session = await client.beta.sessions.create({
    agent: agent.id,
    environment_id: environment.id
  });
  ```

  ```csharp C#
  var session = await client.Beta.Sessions.Create(new()
  {
      Agent = agent.ID,
      EnvironmentID = environment.ID,
  });
  ```

  ```go Go
  session, err := client.Beta.Sessions.New(ctx, anthropic.BetaSessionNewParams{
  	Agent: anthropic.BetaSessionNewParamsAgentUnion{
  		OfString: anthropic.String(agent.ID),
  	},
  	EnvironmentID: environment.ID,
  })
  if err != nil {
  	panic(err)
  }
  ```

  ```java Java
  var session = client.beta().sessions().create(SessionCreateParams.builder()
      .agent(agent.id())
      .environmentId(environment.id())
      .build());
  ```

  ```php PHP
  $session = $client->beta->sessions->create(
      agent: $agent->id,
      environmentID: $environment->id,
  );
  ```

  ```ruby Ruby
  session = client.beta.sessions.create(
    agent: agent.id,
    environment_id: environment.id
  )
  ```
</CodeGroup>

To pin a session to a specific agent version, pass an object. This lets you control exactly which version runs and stage rollouts of new versions independently.

<CodeGroup defaultLanguage="CLI">
  ```bash cURL
  pinned_session=$(curl -fsSL https://api.anthropic.com/v1/sessions \
    -H "x-api-key: $ANTHROPIC_API_KEY" \
    -H "anthropic-version: 2023-06-01" \
    -H "anthropic-beta: managed-agents-2026-04-01" \
    -H "content-type: application/json" \
    -d @- <<EOF
  {
    "agent": {"type": "agent", "id": "$AGENT_ID", "version": 1},
    "environment_id": "$ENVIRONMENT_ID"
  }
  EOF
  )
  PINNED_SESSION_ID=$(jq -r '.id' <<< "$pinned_session")
  ```

  ```bash CLI
  ant beta:sessions create <<YAML
  agent:
    type: agent
    id: $AGENT_ID
    version: 1
  environment_id: $ENVIRONMENT_ID
  YAML
  ```

  ```python Python
  pinned_session = client.beta.sessions.create(
      agent={"type": "agent", "id": agent.id, "version": 1},
      environment_id=environment.id,
  )
  ```

  ```typescript TypeScript
  const pinnedSession = await client.beta.sessions.create({
    agent: { type: "agent", id: agent.id, version: 1 },
    environment_id: environment.id
  });
  ```

  ```csharp C#
  var pinnedSession = await client.Beta.Sessions.Create(new()
  {
      Agent = new BetaManagedAgentsAgentParams
      {
          Type = BetaManagedAgentsAgentParamsType.Agent,
          ID = agent.ID,
          Version = 1,
      },
      EnvironmentID = environment.ID,
  });
  ```

  ```go Go
  pinnedSession, err := client.Beta.Sessions.New(ctx, anthropic.BetaSessionNewParams{
  	Agent: anthropic.BetaSessionNewParamsAgentUnion{
  		OfBetaManagedAgentsAgents: &anthropic.BetaManagedAgentsAgentParams{
  			Type:    anthropic.BetaManagedAgentsAgentParamsTypeAgent,
  			ID:      agent.ID,
  			Version: anthropic.Int(1),
  		},
  	},
  	EnvironmentID: environment.ID,
  })
  if err != nil {
  	panic(err)
  }
  ```

  ```java Java
  var pinnedSession = client.beta().sessions().create(SessionCreateParams.builder()
      .agent(BetaManagedAgentsAgentParams.builder()
          .type(BetaManagedAgentsAgentParams.Type.AGENT)
          .id(agent.id())
          .version(1)
          .build())
      .environmentId(environment.id())
      .build());
  ```

  ```php PHP
  $pinnedSession = $client->beta->sessions->create(
      agent: ['type' => 'agent', 'id' => $agent->id, 'version' => 1],
      environmentID: $environment->id,
  );
  ```

  ```ruby Ruby
  pinned_session = client.beta.sessions.create(
    agent: {type: :agent, id: agent.id, version: 1},
    environment_id: environment.id
  )
  ```
</CodeGroup>

### Seed the session with initial events

You can create a session and start its work in one call. `initial_events` is an optional array of initial [events](https://platform.claude.com/docs/en/managed-agents/reference#event-types) to send to the session at creation, processed in order. It supports `user.message` and [`user.define_outcome`](https://platform.claude.com/docs/en/managed-agents/define-outcomes) events, and accepts a maximum of 50 events. A non-empty list starts the agent loop in the same call: the session is created directly in the `running` status, with no further request.

The following example creates a session with a single `user.message` in `initial_events`:

<CodeGroup defaultLanguage="CLI">
  ```bash cURL
  seeded_session=$(curl -fsSL https://api.anthropic.com/v1/sessions \
    -H "x-api-key: $ANTHROPIC_API_KEY" \
    -H "anthropic-version: 2023-06-01" \
    -H "anthropic-beta: managed-agents-2026-04-01" \
    -H "content-type: application/json" \
    -d @- <<EOF
  {
    "agent": "$AGENT_ID",
    "environment_id": "$ENVIRONMENT_ID",
    "initial_events": [
      {
        "type": "user.message",
        "content": [{"type": "text", "text": "List the files in the working directory."}]
      }
    ]
  }
  EOF
  )
  SEEDED_SESSION_ID=$(jq -r '.id' <<< "$seeded_session")

  # initial_events aren't echoed on the create response; list the session's
  # events to see the seeded message.
  seeded_events=$(curl -fsSL \
    "https://api.anthropic.com/v1/sessions/$SEEDED_SESSION_ID/events" \
    -H "x-api-key: $ANTHROPIC_API_KEY" \
    -H "anthropic-version: 2023-06-01" \
    -H "anthropic-beta: managed-agents-2026-04-01")
  echo "Seeded event: $(jq -r \
    '.data[] | select(.type == "user.message") | .content[0].text' <<< "$seeded_events")"
  ```

  ```bash CLI
  SEEDED_SESSION_ID=$(ant beta:sessions create \
    --transform id --raw-output <<YAML
  agent: $AGENT_ID
  environment_id: $ENVIRONMENT_ID
  initial_events:
    - type: user.message
      content:
        - type: text
          text: List the files in the working directory.
  YAML
  )

  # initial_events aren't echoed on the create response; list the session's
  # events to see the seeded message.
  echo "Seeded event: $(ant beta:sessions:events list \
    --session-id "$SEEDED_SESSION_ID" \
    --format raw \
    --transform 'data.#(type=="user.message").content.0.text' --raw-output)"
  ```

  ```python Python
  seeded_session = client.beta.sessions.create(
      agent=agent.id,
      environment_id=environment.id,
      initial_events=[
          {
              "type": "user.message",
              "content": [
                  {"type": "text", "text": "List the files in the working directory."}
              ],
          },
      ],
  )
  # initial_events are not echoed on the create response; read them back
  # from the session's event list.
  for event in client.beta.sessions.events.list(seeded_session.id):
      if event.type == "user.message":
          for block in event.content:
              if block.type == "text":
                  print(f"Seeded event: {block.text}")
  ```

  ```typescript TypeScript
  const seededSession = await client.beta.sessions.create({
    agent: agent.id,
    environment_id: environment.id,
    initial_events: [
      {
        type: "user.message",
        content: [{ type: "text", text: "List the files in the working directory." }]
      }
    ]
  });

  // initial_events are not echoed on the create response; list the session's
  // events to read the seeded message back.
  for await (const event of client.beta.sessions.events.list(seededSession.id)) {
    if (event.type === "user.message") {
      for (const block of event.content) {
        if (block.type === "text") {
          console.log(`Seeded event: ${block.text}`);
        }
      }
    }
  }
  ```

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