Claude Platform Docs

Send Events

beta.sessions.events.send(strsession_id, EventSendParams**kwargs) -> BetaManagedAgentsSendSessionEvents
POST/v1/sessions/{session_id}/events

Send Events

Parameters
session_id: str

Events to send to the session.

One of the following:
class BetaManagedAgentsUserMessageEventParams:

Parameters for sending a user message to the session.

content: Iterable[Content]

Array of content blocks for the user message.

One of the following:
class BetaManagedAgentsTextBlock:

Regular text content.

text: str

The text content.

minLength1
type: Literal["text"]
class BetaManagedAgentsImageBlock:

Image content specified directly as base64 data or as a reference via a URL.

class BetaManagedAgentsDocumentBlock:

Document content, either specified directly as base64 data, as text, or as a reference via a URL.

class BetaManagedAgentsRedactedBlock:

Placeholder for content withheld by Anthropic model policy.

type: Literal["redacted"]
type: Literal["user.message"]
class BetaManagedAgentsUserInterruptEventParams:

Parameters for sending an interrupt to pause the agent.

type: Literal["user.interrupt"]
session_thread_id: Optional[str]

If absent, interrupts every non-archived thread in a multiagent session (or the primary alone in a single-agent session). If present, interrupts only the named thread.

class BetaManagedAgentsUserToolConfirmationEventParams:

Parameters for confirming or denying a tool execution request.

result: Literal["allow", "deny"]

UserToolConfirmationResult enum

One of the following:
"allow"
"deny"
tool_use_id: str

The id of the agent.tool_use or agent.mcp_tool_use event this result corresponds to, which can be found in the last session.status_idle event's stop_reason.event_ids field.

minLength1
maxLength128
type: Literal["user.tool_confirmation"]
deny_message: Optional[str]

Optional message providing context for a 'deny' decision. Only allowed when result is 'deny'.

maxLength10000
class BetaManagedAgentsUserCustomToolResultEventParams:

Parameters for providing the result of a custom tool execution.

class BetaManagedAgentsUserDefineOutcomeEventParams:

Parameters for defining an outcome the agent should work toward. The agent begins work on receipt.

description: str

What the agent should produce. This is the task specification.

rubric: Rubric

Rubric for grading the quality of an outcome.

One of the following:
class BetaManagedAgentsFileRubricParams:

Rubric referenced by a file uploaded via the Files API.

file_id: str

ID of the rubric file.

type: Literal["file"]
class BetaManagedAgentsTextRubricParams:

Rubric content provided inline as text.

content: str

Rubric content. Plain text or markdown — the grader treats it as freeform text. Maximum 262144 characters.

maxLength262144
type: Literal["text"]
type: Literal["user.define_outcome"]
max_iterations: Optional[int]

Eval→revision cycles before giving up. Default 3, max 20.

formatint32
class BetaManagedAgentsUserToolResultEventParams:

Parameters for providing the result of an agent-toolset tool execution. Only valid on self_hosted environments, where sandbox-routed tools are executed by the client rather than the server.

class BetaManagedAgentsSystemMessageEventParams:

Privileged context for the accompanying turn and all subsequent turns, appended to the session's system context as a role: "system" turn rather than replacing the top-level system prompt. At most one per request: it must be the final event and immediately follow the user.message, user.tool_result, or user.custom_tool_result it accompanies. Only supported on models that accept mid-conversation system messages.

System content blocks to append. Text-only.

text: str

The text content.

minLength1
type: Literal["text"]
type: Literal["system.message"]
betas: Optional[List[AnthropicBetaParam]]

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

One of the following:
str
Literal["message-batches-2024-09-24", "prompt-caching-2024-07-31", "computer-use-2024-10-22", 38 more]
One of the following:
"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"
"user-profiles-2026-08-18"
"advisor-tool-2026-03-01"
"managed-agents-2026-04-01"
"cache-diagnosis-2026-04-07"
"dreaming-2026-04-21"
"thinking-token-count-2026-05-13"
"server-side-fallback-2026-06-01"
"server-side-fallback-2026-07-01"
"fallback-credit-2026-06-01"
"fallback-credit-2026-07-01"
"agent-memory-2026-07-22"
"mid-conversation-tool-changes-2026-07-01"
"compact-2026-01-12"
"computer-use-2025-11-24"
"mcp-tunnels-2026-06-22"
"structured-outputs-2025-11-13"
"task-budgets-2026-03-13"
"thinking-display-updates-2026-08-18"
"ce-user-management-2026-07-13"
Returns
class BetaManagedAgentsSendSessionEvents:

Events that were successfully sent to the session.

Send Events

import os
from anthropic import Anthropic

client = Anthropic(
    api_key=os.environ.get(
        "ANTHROPIC_API_KEY"
    ),  # This is the default and can be omitted
)
beta_managed_agents_send_session_events = client.beta.sessions.events.send(
    session_id="sesn_011CZkZAtmR3yMPDzynEDxu7",
    events=[
        {
            "content": [
                {
                    "text": "Where is my order #1234?",
                    "type": "text",
                }
            ],
            "type": "user.message",
        }
    ],
)
print(beta_managed_agents_send_session_events.data)
{
  "data": [
    {
      "id": "sevt_011CZkZGOp0iBcp4kaQSihUmy",
      "content": [
        {
          "text": "Where is my order #1234?",
          "type": "text"
        }
      ],
      "type": "user.message",
      "processed_at": "2026-03-15T10:00:00Z"
    }
  ]
}
Returns Examples
{
  "data": [
    {
      "id": "sevt_011CZkZGOp0iBcp4kaQSihUmy",
      "content": [
        {
          "text": "Where is my order #1234?",
          "type": "text"
        }
      ],
      "type": "user.message",
      "processed_at": "2026-03-15T10:00:00Z"
    }
  ]
}