Update Session

post /v1/sessions/{session_id}

Update Session

Path Parameters

• session_id: string

Header Parameters

• "anthropic-beta": optional array of AnthropicBeta

  Optional header to specify the beta version(s) you want to use.

  • string

  • "message-batches-2024-09-24" or "prompt-caching-2024-07-31" or "computer-use-2024-10-22" or 22 more

    • "message-batches-2024-09-24"

    • "prompt-caching-2024-07-31"

    • "computer-use-2024-10-22"

    • "computer-use-2025-01-24"

    • "pdfs-2024-09-25"

    • "token-counting-2024-11-01"

    • "token-efficient-tools-2025-02-19"

    • "output-128k-2025-02-19"

    • "files-api-2025-04-14"

    • "mcp-client-2025-04-04"

    • "mcp-client-2025-11-20"

    • "dev-full-thinking-2025-05-14"

    • "interleaved-thinking-2025-05-14"

    • "code-execution-2025-05-22"

    • "extended-cache-ttl-2025-04-11"

    • "context-1m-2025-08-07"

    • "context-management-2025-06-27"

    • "model-context-window-exceeded-2025-08-26"

    • "skills-2025-10-02"

    • "fast-mode-2026-02-01"

    • "output-300k-2026-03-24"

    • "user-profiles-2026-03-24"

    • "advisor-tool-2026-03-01"

    • "managed-agents-2026-04-01"

    • "cache-diagnosis-2026-04-07"

Body Parameters

• agent: optional BetaManagedAgentsSessionAgentUpdate

  Mid-session agent configuration update. Only tools and mcp_servers are updatable. Full replacement: the provided array becomes the new value. To preserve existing entries, GET the session, modify the array, and POST it back.

  • mcp_servers: optional array of BetaManagedAgentsURLMCPServerParams

    Replacement MCP server list. Full replacement: the provided array becomes the new value. Send an empty array to clear; omit to preserve.

    • name: string

      Unique name for this server, referenced by mcp_toolset configurations. 1-255 characters.

    • type: "url"

      • "url"

    • url: string

      Endpoint URL for the MCP server.

  • tools: optional array of BetaManagedAgentsAgentToolset20260401Params or BetaManagedAgentsMCPToolsetParams or BetaManagedAgentsCustomToolParams

    Replacement tool list. Full replacement: the provided array becomes the new value. Send an empty array to clear; omit to preserve.

    • BetaManagedAgentsAgentToolset20260401Params object { type, configs, default_config }

      Configuration for built-in agent tools. Use this to enable or disable groups of tools available to the agent.

      • type: "agent_toolset_20260401"

        • "agent_toolset_20260401"

      • configs: optional array of BetaManagedAgentsAgentToolConfigParams

        Per-tool configuration overrides.

        • name: "bash" or "edit" or "read" or 5 more

          Built-in agent tool identifier.

          • "bash"

          • "edit"

          • "read"

          • "write"

          • "glob"

          • "grep"

          • "web_fetch"

          • "web_search"

        • enabled: optional boolean

          Whether this tool is enabled and available to Claude. Overrides the default_config setting.

        • permission_policy: optional BetaManagedAgentsAlwaysAllowPolicy or BetaManagedAgentsAlwaysAskPolicy

          Permission policy for tool execution.

          • BetaManagedAgentsAlwaysAllowPolicy object { type }

            Tool calls are automatically approved without user confirmation.

            • type: "always_allow"

              • "always_allow"

          • BetaManagedAgentsAlwaysAskPolicy object { type }

            Tool calls require user confirmation before execution.

            • type: "always_ask"

              • "always_ask"

      • default_config: optional BetaManagedAgentsAgentToolsetDefaultConfigParams

        Default configuration for all tools in a toolset.

        • enabled: optional boolean

          Whether tools are enabled and available to Claude by default. Defaults to true if not specified.

        • permission_policy: optional BetaManagedAgentsAlwaysAllowPolicy or BetaManagedAgentsAlwaysAskPolicy

          Permission policy for tool execution.

          • BetaManagedAgentsAlwaysAllowPolicy object { type }

            Tool calls are automatically approved without user confirmation.

          • BetaManagedAgentsAlwaysAskPolicy object { type }

            Tool calls require user confirmation before execution.

    • BetaManagedAgentsMCPToolsetParams object { mcp_server_name, type, configs, default_config }

      Configuration for tools from an MCP server defined in mcp_servers.

      • mcp_server_name: string

        Name of the MCP server. Must match a server name from the mcp_servers array. 1-255 characters.

      • type: "mcp_toolset"

        • "mcp_toolset"

      • configs: optional array of BetaManagedAgentsMCPToolConfigParams

        Per-tool configuration overrides.

        • name: string

          Name of the MCP tool to configure. 1-128 characters.

        • enabled: optional boolean

          Whether this tool is enabled. Overrides the default_config setting.

        • permission_policy: optional BetaManagedAgentsAlwaysAllowPolicy or BetaManagedAgentsAlwaysAskPolicy

          Permission policy for tool execution.

          • BetaManagedAgentsAlwaysAllowPolicy object { type }

            Tool calls are automatically approved without user confirmation.

          • BetaManagedAgentsAlwaysAskPolicy object { type }

            Tool calls require user confirmation before execution.

      • default_config: optional BetaManagedAgentsMCPToolsetDefaultConfigParams

        Default configuration for all tools from an MCP server.

        • enabled: optional boolean

          Whether tools are enabled by default. Defaults to true if not specified.

        • permission_policy: optional BetaManagedAgentsAlwaysAllowPolicy or BetaManagedAgentsAlwaysAskPolicy

          Permission policy for tool execution.

          • BetaManagedAgentsAlwaysAllowPolicy object { type }

            Tool calls are automatically approved without user confirmation.

          • BetaManagedAgentsAlwaysAskPolicy object { type }

            Tool calls require user confirmation before execution.

    • BetaManagedAgentsCustomToolParams object { description, input_schema, name, type }

      A custom tool that is executed by the API client rather than the agent. When the agent calls this tool, an agent.custom_tool_use event is emitted and the session goes idle, waiting for the client to provide the result via a user.custom_tool_result event.

      • description: string

        Description of what the tool does, shown to the agent to help it decide when to use the tool. 1-1024 characters.

      • input_schema: BetaManagedAgentsCustomToolInputSchema

        JSON Schema for custom tool input parameters.

        • properties: optional map[unknown]

          JSON Schema properties defining the tool's input parameters.

        • required: optional array of string

          List of required property names.

        • type: optional "object"

          Must be 'object' for tool input schemas.

          • "object"

      • name: string

        Unique name for the tool. 1-128 characters; letters, digits, underscores, and hyphens.

      • type: "custom"

        • "custom"

• metadata: optional map[string]

  Metadata patch. Set a key to a string to upsert it, or to null to delete it. Omit the field to preserve.

• title: optional string

  Human-readable session title.

• vault_ids: optional array of string

  Vault IDs (vlt_*) to attach to the session. Not yet supported; requests setting this field are rejected. Reserved for future use.

Returns

• BetaManagedAgentsSession object { id, agent, archived_at, 12 more }

  A Managed Agents session.

  • id: string

  • agent: BetaManagedAgentsSessionAgent

    Resolved agent definition for a session. Snapshot of the agent at session creation time.

    • id: string

    • description: string

    • mcp_servers: array of BetaManagedAgentsMCPServerURLDefinition

      • name: string

      • type: "url"

        • "url"

      • url: string

    • model: BetaManagedAgentsModelConfig

      Model identifier and configuration.

      • id: BetaManagedAgentsModel

        The model that will power your agent.

        See models for additional details and options.

        • "claude-opus-4-7" or "claude-opus-4-6" or "claude-sonnet-4-6" or 6 more

          The model that will power your agent.

          See models for additional details and options.

          • "claude-opus-4-7"

            Frontier intelligence for long-running agents and coding

          • "claude-opus-4-6"

            Most intelligent model for building agents and coding

          • "claude-sonnet-4-6"

            Best combination of speed and intelligence

          • "claude-haiku-4-5"

            Fastest model with near-frontier intelligence

          • "claude-haiku-4-5-20251001"

            Fastest model with near-frontier intelligence

          • "claude-opus-4-5"

            Premium model combining maximum intelligence with practical performance

          • "claude-opus-4-5-20251101"

            Premium model combining maximum intelligence with practical performance

          • "claude-sonnet-4-5"

            High-performance model for agents and coding

          • "claude-sonnet-4-5-20250929"

            High-performance model for agents and coding

        • string

      • speed: optional "standard" or "fast"

        Inference speed mode. fast provides significantly faster output token generation at premium pricing. Not all models support fast; invalid combinations are rejected at create time.

        • "standard"

        • "fast"

    • multiagent: BetaManagedAgentsSessionMultiagentCoordinator

      Resolved coordinator topology with full agent definitions for each roster member.

      • agents: array of BetaManagedAgentsSessionThreadAgent

        Full agent definitions the coordinator may spawn as session threads.

        • id: string

        • description: string

        • mcp_servers: array of BetaManagedAgentsMCPServerURLDefinition

          • name: string

          • type: "url"

          • url: string

        • model: BetaManagedAgentsModelConfig

          Model identifier and configuration.

        • name: string

        • skills: array of BetaManagedAgentsAnthropicSkill or BetaManagedAgentsCustomSkill

          • BetaManagedAgentsAnthropicSkill object { skill_id, type, version }

            A resolved Anthropic-managed skill.

            • skill_id: string

            • type: "anthropic"

              • "anthropic"

            • version: string

          • BetaManagedAgentsCustomSkill object { skill_id, type, version }

            A resolved user-created custom skill.

            • skill_id: string

            • type: "custom"

              • "custom"

            • version: string

        • system: string

        • tools: array of BetaManagedAgentsAgentToolset20260401 or BetaManagedAgentsMCPToolset or BetaManagedAgentsCustomTool

          • BetaManagedAgentsAgentToolset20260401 object { configs, default_config, type }

            • configs: array of BetaManagedAgentsAgentToolConfig

              • enabled: boolean

              • name: "bash" or "edit" or "read" or 5 more

                Built-in agent tool identifier.

                • "bash"

                • "edit"

                • "read"

                • "write"

                • "glob"

                • "grep"

                • "web_fetch"

                • "web_search"

              • permission_policy: BetaManagedAgentsAlwaysAllowPolicy or BetaManagedAgentsAlwaysAskPolicy

                Permission policy for tool execution.

                • BetaManagedAgentsAlwaysAllowPolicy object { type }

                  Tool calls are automatically approved without user confirmation.

                  • type: "always_allow"

                    • "always_allow"

                • BetaManagedAgentsAlwaysAskPolicy object { type }

                  Tool calls require user confirmation before execution.

                  • type: "always_ask"

                    • "always_ask"

            • default_config: BetaManagedAgentsAgentToolsetDefaultConfig

              Resolved default configuration for agent tools.

              • enabled: boolean

              • permission_policy: BetaManagedAgentsAlwaysAllowPolicy or BetaManagedAgentsAlwaysAskPolicy

                Permission policy for tool execution.

                • BetaManagedAgentsAlwaysAllowPolicy object { type }

                  Tool calls are automatically approved without user confirmation.

                • BetaManagedAgentsAlwaysAskPolicy object { type }

                  Tool calls require user confirmation before execution.

            • type: "agent_toolset_20260401"

              • "agent_toolset_20260401"

          • BetaManagedAgentsMCPToolset object { configs, default_config, mcp_server_name, type }

            • configs: array of BetaManagedAgentsMCPToolConfig

              • enabled: boolean

              • name: string

              • permission_policy: BetaManagedAgentsAlwaysAllowPolicy or BetaManagedAgentsAlwaysAskPolicy

                Permission policy for tool execution.

                • BetaManagedAgentsAlwaysAllowPolicy object { type }

                  Tool calls are automatically approved without user confirmation.

                • BetaManagedAgentsAlwaysAskPolicy object { type }

                  Tool calls require user confirmation before execution.

            • default_config: BetaManagedAgentsMCPToolsetDefaultConfig

              Resolved default configuration for all tools from an MCP server.

              • enabled: boolean

              • permission_policy: BetaManagedAgentsAlwaysAllowPolicy or BetaManagedAgentsAlwaysAskPolicy

                Permission policy for tool execution.

                • BetaManagedAgentsAlwaysAllowPolicy object { type }

                  Tool calls are automatically approved without user confirmation.

                • BetaManagedAgentsAlwaysAskPolicy object { type }

                  Tool calls require user confirmation before execution.

            • mcp_server_name: string

            • type: "mcp_toolset"

              • "mcp_toolset"

          • BetaManagedAgentsCustomTool object { description, input_schema, name, type }

            A custom tool as returned in API responses.

            • description: string

            • input_schema: BetaManagedAgentsCustomToolInputSchema

              JSON Schema for custom tool input parameters.

              • properties: optional map[unknown]

                JSON Schema properties defining the tool's input parameters.

              • required: optional array of string

                List of required property names.

              • type: optional "object"

                Must be 'object' for tool input schemas.

                • "object"

            • name: string

            • type: "custom"

              • "custom"

        • type: "agent"

          • "agent"

        • version: number

      • type: "coordinator"

        • "coordinator"

    • name: string

    • skills: array of BetaManagedAgentsAnthropicSkill or BetaManagedAgentsCustomSkill

      • BetaManagedAgentsAnthropicSkill object { skill_id, type, version }

        A resolved Anthropic-managed skill.

      • BetaManagedAgentsCustomSkill object { skill_id, type, version }

        A resolved user-created custom skill.

    • system: string

    • tools: array of BetaManagedAgentsAgentToolset20260401 or BetaManagedAgentsMCPToolset or BetaManagedAgentsCustomTool

      • BetaManagedAgentsAgentToolset20260401 object { configs, default_config, type }

      • BetaManagedAgentsMCPToolset object { configs, default_config, mcp_server_name, type }

      • BetaManagedAgentsCustomTool object { description, input_schema, name, type }

        A custom tool as returned in API responses.

    • type: "agent"

      • "agent"

    • version: number

  • archived_at: string

    A timestamp in RFC 3339 format

  • created_at: string

    A timestamp in RFC 3339 format

  • environment_id: string

  • metadata: map[string]

  • outcome_evaluations: array of BetaManagedAgentsOutcomeEvaluationResource

    Per-outcome evaluation state. One entry per define_outcome event sent to the session.

    • completed_at: string

      A timestamp in RFC 3339 format

    • description: string

      What the agent should produce.

    • explanation: string

      Grader's verdict text from the most recent evaluation. For satisfied, explains why criteria are met; for needs_revision (intermediate), what's missing; for failed, why unrecoverable.

    • iteration: number

      0-indexed revision cycle the outcome is currently on.

    • outcome_id: string

      Server-generated outc_ ID for this outcome.

    • result: string

      Current evaluation state. pending before the agent begins work; running while producing or revising; evaluating while the grader scores; satisfied/max_iterations_reached/failed/interrupted are terminal.

    • type: "outcome_evaluation"

      • "outcome_evaluation"

  • resources: array of BetaManagedAgentsSessionResource

    • BetaManagedAgentsGitHubRepositoryResource object { id, created_at, mount_path, 4 more }

      • id: string

      • created_at: string

        A timestamp in RFC 3339 format

      • mount_path: string

      • type: "github_repository"

        • "github_repository"

      • updated_at: string

        A timestamp in RFC 3339 format

      • url: string

      • checkout: optional BetaManagedAgentsBranchCheckout or BetaManagedAgentsCommitCheckout

        • BetaManagedAgentsBranchCheckout object { name, type }

          • name: string

            Branch name to check out.

          • type: "branch"

            • "branch"

        • BetaManagedAgentsCommitCheckout object { sha, type }

          • sha: string

            Full commit SHA to check out.

          • type: "commit"

            • "commit"

    • BetaManagedAgentsFileResource object { id, created_at, file_id, 3 more }

      • id: string

      • created_at: string

        A timestamp in RFC 3339 format

      • file_id: string

      • mount_path: string

      • type: "file"

        • "file"

      • updated_at: string

        A timestamp in RFC 3339 format

    • BetaManagedAgentsMemoryStoreResource object { memory_store_id, type, access, 4 more }

      A memory store attached to an agent session.

      • memory_store_id: string

        The memory store ID (memstore_...). Must belong to the caller's organization and workspace.

      • type: "memory_store"

        • "memory_store"

      • access: optional "read_write" or "read_only"

        Access mode for an attached memory store.

        • "read_write"

        • "read_only"

      • description: optional string

        Description of the memory store, snapshotted at attach time. Rendered into the agent's system prompt. Empty string when the store has no description.

      • instructions: optional string

        Per-attachment guidance for the agent on how to use this store. Rendered into the memory section of the system prompt. Max 4096 chars.

      • mount_path: optional string

        Filesystem path where the store is mounted in the session container, e.g. /mnt/memory/user-preferences. Derived from the store's name. Output-only.

      • name: optional string

        Display name of the memory store, snapshotted at attach time. Later edits to the store's name do not propagate to this resource.

  • stats: BetaManagedAgentsSessionStats

    Timing statistics for a session.

    • active_seconds: optional number

      Cumulative time in seconds the session spent in running status. Excludes idle time.

    • duration_seconds: optional number

      Elapsed time since session creation in seconds. For terminated sessions, frozen at the final update.

  • status: "rescheduling" or "running" or "idle" or "terminated"

    SessionStatus enum

    • "rescheduling"

    • "running"

    • "idle"

    • "terminated"

  • title: string

  • type: "session"

    • "session"

  • updated_at: string

    A timestamp in RFC 3339 format

  • usage: BetaManagedAgentsSessionUsage

    Cumulative token usage for a session across all turns.

    • cache_creation: optional BetaManagedAgentsCacheCreationUsage

      Prompt-cache creation token usage broken down by cache lifetime.

      • ephemeral_1h_input_tokens: optional number

        Tokens used to create 1-hour ephemeral cache entries.

      • ephemeral_5m_input_tokens: optional number

        Tokens used to create 5-minute ephemeral cache entries.

    • cache_read_input_tokens: optional number

      Total tokens read from prompt cache.

    • input_tokens: optional number

      Total input tokens consumed across all turns.

    • output_tokens: optional number

      Total output tokens generated across all turns.

  • vault_ids: array of string

    Vault IDs attached to the session at creation. Empty when no vaults were supplied.

Example

curl https://api.anthropic.com/v1/sessions/$SESSION_ID \
    -H 'Content-Type: application/json' \
    -H 'anthropic-version: 2023-06-01' \
    -H 'anthropic-beta: managed-agents-2026-04-01' \
    -H "X-Api-Key: $ANTHROPIC_API_KEY" \
    -d '{
          "title": "Order #1234 inquiry"
        }'

Response

{
  "id": "sesn_011CZkZAtmR3yMPDzynEDxu7",
  "agent": {
    "id": "agent_011CZkYpogX7uDKUyvBTophP",
    "description": "A general-purpose starter agent.",
    "mcp_servers": [
      {
        "name": "example-mcp",
        "type": "url",
        "url": "https://example-server.modelcontextprotocol.io/sse"
      }
    ],
    "model": {
      "id": "claude-sonnet-4-6",
      "speed": "standard"
    },
    "multiagent": {
      "agents": [
        {
          "id": "agent_011CZkYqphY8vELVzwCUpqiQ",
          "description": "A focused research subagent.",
          "mcp_servers": [
            {
              "name": "example-mcp",
              "type": "url",
              "url": "https://example-server.modelcontextprotocol.io/sse"
            }
          ],
          "model": {
            "id": "claude-sonnet-4-6",
            "speed": "standard"
          },
          "name": "Researcher",
          "skills": [
            {
              "skill_id": "xlsx",
              "type": "anthropic",
              "version": "1"
            }
          ],
          "system": "You are a research subagent that gathers and summarises sources for the coordinating agent.",
          "tools": [
            {
              "configs": [
                {
                  "enabled": true,
                  "name": "bash",
                  "permission_policy": {
                    "type": "always_allow"
                  }
                }
              ],
              "default_config": {
                "enabled": true,
                "permission_policy": {
                  "type": "always_ask"
                }
              },
              "type": "agent_toolset_20260401"
            }
          ],
          "type": "agent",
          "version": 1
        }
      ],
      "type": "coordinator"
    },
    "name": "My First Agent",
    "skills": [
      {
        "skill_id": "xlsx",
        "type": "anthropic",
        "version": "1"
      },
      {
        "skill_id": "skill_011CZkZFNu9hAbo3jZPRgTlx",
        "type": "custom",
        "version": "2"
      }
    ],
    "system": "You are a general-purpose agent that can research, write code, run commands, and use connected tools to complete the user's task end to end.",
    "tools": [
      {
        "configs": [
          {
            "enabled": true,
            "name": "bash",
            "permission_policy": {
              "type": "always_allow"
            }
          }
        ],
        "default_config": {
          "enabled": true,
          "permission_policy": {
            "type": "always_ask"
          }
        },
        "type": "agent_toolset_20260401"
      }
    ],
    "type": "agent",
    "version": 1
  },
  "archived_at": null,
  "created_at": "2026-03-15T10:00:00Z",
  "environment_id": "env_011CZkZ9X2dpNyB7HsEFoRfW",
  "metadata": {},
  "outcome_evaluations": [
    {
      "completed_at": "2026-03-15T10:02:31Z",
      "description": "Produce a 2-page summary as summary.md",
      "explanation": "All five sections present with inline citations.",
      "iteration": 0,
      "outcome_id": "outc_011CZkZRSw2kEfs6ncTVljxP",
      "result": "satisfied",
      "type": "outcome_evaluation"
    }
  ],
  "resources": [
    {
      "id": "sesrsc_011CZkZBJq5dWxk9fVLNcPht",
      "created_at": "2026-03-15T10:00:00Z",
      "file_id": "file_011CNha8iCJcU1wXNR6q4V8w",
      "mount_path": "/uploads/receipt.pdf",
      "type": "file",
      "updated_at": "2026-03-15T10:00:00Z"
    },
    {
      "id": "sesrsc_011CZkZCKr6eXyl0gWMOdQiu",
      "created_at": "2026-03-15T10:00:00Z",
      "mount_path": "/workspace/example-repo",
      "type": "github_repository",
      "updated_at": "2026-03-15T10:00:00Z",
      "url": "https://github.com/example-org/example-repo",
      "checkout": {
        "name": "main",
        "type": "branch"
      }
    }
  ],
  "stats": {
    "active_seconds": 0,
    "duration_seconds": 0
  },
  "status": "idle",
  "title": "Order #1234 inquiry",
  "type": "session",
  "updated_at": "2026-03-15T10:00:00Z",
  "usage": {
    "cache_creation": {
      "ephemeral_1h_input_tokens": 0,
      "ephemeral_5m_input_tokens": 0
    },
    "cache_read_input_tokens": 0,
    "input_tokens": 0,
    "output_tokens": 0
  },
  "vault_ids": [
    "vlt_011CZkZDLs7fYzm1hXNPeRjv"
  ]
}