Retrieve Conversation Stream
Resume the stream for the most recent active run in a conversation.
This endpoint allows you to reconnect to an active background stream for a conversation, enabling recovery from network interruptions.
Agent-direct mode: Pass conversation_id=“default” with agent_id in request body to retrieve the stream for the agent’s most recent active run.
Direct run access: Pass run_id directly to skip run lookup entirely. Useful for recovery from duplicate request 409 errors.
OTID lookup: Pass otid to look up the run_id from Redis. Useful when you have the otid from a 409 error response.
Deprecated: Passing an agent ID as conversation_id still works but will be removed.
ParametersExpand Collapse
conversationID: string
The conversation identifier. Can be a conversation ID (‘conv-
body: MessageStreamParams { agent_id, batch_size, include_pings, 4 more }
agent_id?: string | null
Agent ID for agent-direct mode with ‘default’ conversation. Use with conversation_id=‘default’ in the URL path.
include_pings?: boolean | null
Whether to include periodic keepalive ping messages in the stream to prevent connection timeouts.
otid?: string | null
Offline threading ID to look up the run_id. Bypasses active run lookup if run_id not provided.
ReturnsExpand Collapse
LettaStreamingResponse = SystemMessage { id, content, date, 8 more } | UserMessage { id, content, date, 8 more } | ReasoningMessage { id, date, reasoning, 10 more } | 10 more
Streaming response type for Server-Sent Events (SSE) endpoints. Each event in the stream will be one of these types.
SystemMessage { id, content, date, 8 more }
A message generated by the system. Never streamed back on a response, only used for cursor pagination.
Args: id (str): The ID of the message date (datetime): The date the message was created in ISO format name (Optional[str]): The name of the sender of the message content (str): The message content sent by the system
UserMessage { id, content, date, 8 more }
A message sent by the user. Never streamed back on a response, only used for cursor pagination.
Args: id (str): The ID of the message date (datetime): The date the message was created in ISO format name (Optional[str]): The name of the sender of the message content (Union[str, List[LettaUserMessageContentUnion]]): The message content sent by the user (can be a string or an array of multi-modal content parts)
The message content sent by the user (can be a string or an array of multi-modal content parts)
Array<LettaUserMessageContentUnion>
ImageContent { source, type }
source: URLImage { url, type } | Base64Image { data, media_type, detail, type } | LettaImage { file_id, data, detail, 2 more }
ReasoningMessage { id, date, reasoning, 10 more }
Representation of an agent’s internal reasoning.
Args: id (str): The ID of the message date (datetime): The date the message was created in ISO format name (Optional[str]): The name of the sender of the message source (Literal[“reasoner_model”, “non_reasoner_model”]): Whether the reasoning content was generated natively by a reasoner model or derived via prompting reasoning (str): The internal reasoning of the agent signature (Optional[str]): The model-generated signature of the reasoning step
otid?: string | null
The offline threading id (OTID). Set by the client to deduplicate requests. Used for idempotency in background streaming mode — each message in a request must have a unique OTID. Retries of the same request should reuse the same OTIDs.
HiddenReasoningMessage { id, date, state, 9 more }
Representation of an agent’s internal reasoning where reasoning content has been hidden from the response.
Args: id (str): The ID of the message date (datetime): The date the message was created in ISO format name (Optional[str]): The name of the sender of the message state (Literal[“redacted”, “omitted”]): Whether the reasoning content was redacted by the provider or simply omitted by the API hidden_reasoning (Optional[str]): The internal reasoning of the agent
ToolCallMessage { id, date, tool_call, 9 more }
A message representing a request to call a tool (generated by the LLM to trigger tool execution).
Args: id (str): The ID of the message date (datetime): The date the message was created in ISO format name (Optional[str]): The name of the sender of the message tool_call (Union[ToolCall, ToolCallDelta]): The tool call
Deprecatedtool_call: ToolCall { arguments, name, tool_call_id } | ToolCallDelta { arguments, name, tool_call_id }
otid?: string | null
The offline threading id (OTID). Set by the client to deduplicate requests. Used for idempotency in background streaming mode — each message in a request must have a unique OTID. Retries of the same request should reuse the same OTIDs.
tool_calls?: Array<ToolCall { arguments, name, tool_call_id } > | ToolCallDelta { arguments, name, tool_call_id } | null
Array<ToolCall { arguments, name, tool_call_id } >
ToolReturnMessage { id, date, status, 13 more }
A message representing the return value of a tool call (generated by Letta executing the requested tool).
Args: id (str): The ID of the message date (datetime): The date the message was created in ISO format name (Optional[str]): The name of the sender of the message tool_return (str): The return value of the tool (deprecated, use tool_returns) status (Literal[“success”, “error”]): The status of the tool call (deprecated, use tool_returns) tool_call_id (str): A unique identifier for the tool call that generated this message (deprecated, use tool_returns) stdout (Optional[List(str)]): Captured stdout (e.g. prints, logs) from the tool invocation (deprecated, use tool_returns) stderr (Optional[List(str)]): Captured stderr from the tool invocation (deprecated, use tool_returns) tool_returns (Optional[List[ToolReturn]]): List of tool returns for multi-tool support
otid?: string | null
The offline threading id (OTID). Set by the client to deduplicate requests. Used for idempotency in background streaming mode — each message in a request must have a unique OTID. Retries of the same request should reuse the same OTIDs.
The tool return value - either a string or list of content parts (text/image)
Array<TextContent { text, signature, type } | ImageContent { source, type } >
ImageContent { source, type }
source: URLImage { url, type } | Base64Image { data, media_type, detail, type } | LettaImage { file_id, data, detail, 2 more }
AssistantMessage { id, content, date, 8 more }
A message sent by the LLM in response to user input. Used in the LLM context.
Args: id (str): The ID of the message date (datetime): The date the message was created in ISO format name (Optional[str]): The name of the sender of the message content (Union[str, List[LettaAssistantMessageContentUnion]]): The message content sent by the agent (can be a string or an array of content parts)
The message content sent by the agent (can be a string or an array of content parts)
Array<LettaAssistantMessageContentUnion { text, signature, type } >
ApprovalRequestMessage { id, date, tool_call, 9 more }
A message representing a request for approval to call a tool (generated by the LLM to trigger tool execution).
Args: id (str): The ID of the message date (datetime): The date the message was created in ISO format name (Optional[str]): The name of the sender of the message tool_call (ToolCall): The tool call
Deprecatedtool_call: ToolCall { arguments, name, tool_call_id } | ToolCallDelta { arguments, name, tool_call_id }
otid?: string | null
The offline threading id (OTID). Set by the client to deduplicate requests. Used for idempotency in background streaming mode — each message in a request must have a unique OTID. Retries of the same request should reuse the same OTIDs.
tool_calls?: Array<ToolCall { arguments, name, tool_call_id } > | ToolCallDelta { arguments, name, tool_call_id } | null
The tool calls that have been requested by the llm to run, which are pending approval
Array<ToolCall { arguments, name, tool_call_id } >
ApprovalResponseMessage { id, date, approval_request_id, 11 more }
A message representing a response form the user indicating whether a tool has been approved to run.
Args: id (str): The ID of the message date (datetime): The date the message was created in ISO format name (Optional[str]): The name of the sender of the message approve: (bool) Whether the tool has been approved approval_request_id: The ID of the approval request reason: (Optional[str]) An optional explanation for the provided approval status
approvals?: Array<ApprovalReturn { approve, tool_call_id, reason, type } | ToolReturn { status, tool_call_id, tool_return, 3 more } > | null
The list of approval responses
ToolReturn { status, tool_call_id, tool_return, 3 more }
The tool return value - either a string or list of content parts (text/image)
Array<TextContent { text, signature, type } | ImageContent { source, type } >
ImageContent { source, type }
source: URLImage { url, type } | Base64Image { data, media_type, detail, type } | LettaImage { file_id, data, detail, 2 more }
LettaPing { id, date, is_err, 7 more }
A ping message used as a keepalive to prevent SSE streams from timing out during long running requests.
Args: id (str): The ID of the message date (datetime): The date the message was created in ISO format
message_type?: "ping"
The type of the message. Ping messages are a keep-alive to prevent SSE streams from timing out during long running requests.
LettaErrorMessage { error_type, message, message_type, 3 more }
Error messages are used to notify the client of an error that occurred during the agent’s execution.
LettaStopReason { stop_reason, message_type }
LettaUsageStatistics { cache_write_tokens, cached_input_tokens, completion_tokens, 7 more }
Usage statistics for the agent interaction.
Attributes: completion_tokens (int): The number of tokens generated by the agent. prompt_tokens (int): The number of tokens in the prompt. total_tokens (int): The total number of tokens processed by the agent. step_count (int): The number of steps taken by the agent. cached_input_tokens (Optional[int]): The number of input tokens served from cache. None if not reported. cache_write_tokens (Optional[int]): The number of input tokens written to cache. None if not reported. reasoning_tokens (Optional[int]): The number of reasoning/thinking tokens generated. None if not reported.
cache_write_tokens?: number | null
The number of input tokens written to cache (Anthropic only). None if not reported by provider.
cached_input_tokens?: number | null
The number of input tokens served from cache. None if not reported by provider.
Retrieve Conversation Stream
import Letta from '@letta-ai/letta-client';
const client = new Letta({
apiKey: process.env['LETTA_API_KEY'], // This is the default and can be omitted
});
const response = await client.conversations.messages.stream('default');
console.log(response);{}Returns Examples
{}