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LegacyClient

pub struct LegacyClient {
  client_name : String
  client_version : String
  transport : LegacyTransport
  next_id : Int
  server_name : String
  server_version : String
}

LegacyClient::LegacyClient

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fn LegacyClient::LegacyClient(name~ : String, version~ : String, transport~ : @colmugx/mcp/transport.AnyTransport
AnyTransport) -> LegacyClient

LegacyClient::close

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async fn LegacyClient::close(self : LegacyClient) -> Unit

Close the underlying transport. For the HTTP session transport this also sends a best-effort DELETE to terminate the session.

LegacyClient::connect_http

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async fn LegacyClient::connect_http(url~ : String, name~ : String, version~ : String, auth_token? : String, extra_headers? : Array[(String, String)]) -> Result[LegacyClient, @colmugx/mcp/protocol/types.MCPError
MCPError]

Create a legacy client connected over the 2025-11-25 Streamable HTTP session transport and complete the initialize handshake. extra_headers are applied to every request, mirroring the modern HttpClientTransport.

LegacyClient::initialize

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async fn LegacyClient::initialize(self : LegacyClient) -> Result[@colmugx/mcp/protocol/types.ServerInfo
ServerInfo, @colmugx/mcp/protocol/types.MCPError
MCPError]

Perform the legacy initialize handshake: send initialize, parse serverInfo/protocolVersion from the response, then send notifications/initialized. Returns the server identity on success.

The legacy client advertises empty client capabilities: it has no inbound request handlers (roots/listChanged and sampling are provided by the modern client after the 2026-07-28 migration), so claiming them here would be a lie.

LegacyClient::ping

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async fn LegacyClient::ping(self : LegacyClient) -> Result[Unit, @colmugx/mcp/protocol/types.MCPError
MCPError]

Send a legacy ping request and wait for a response. Returns Ok(()) if the response contains no JSON-RPC error.

LegacyClient::send_raw

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async fn LegacyClient::send_raw(self : LegacyClient, request : String) -> Result[String, @colmugx/mcp/protocol/types.MCPError
MCPError]

Send a raw JSON-RPC request string and wait for the response (legacy synchronous send/receive). Callers build the request body themselves.

LegacyHttpSessionTransport

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pub struct LegacyHttpSessionTransport {
  base_url : String
  auth_token : String?
  session_id : String?
  closed : Bool
  pending_responses : @moonbitlang/async/aqueue.Queue
Queue[String]
  extra_headers : Array[(String, String)]
}

2025-11-25 Streamable HTTP session-aware client transport.

This transport is intentionally separate from the modern @transport.AnyTransport enum: it holds a Mcp-Session-Id returned during initialize and re-sends it on every subsequent POST. It also terminates the session with an HTTP DELETE in close. The legacy GET long-poll SSE channel and Last-Event-ID resumability are not implemented.

LegacyHttpSessionTransport::LegacyHttpSessionTransport

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fn LegacyHttpSessionTransport::LegacyHttpSessionTransport(url~ : String, auth_token? : String, extra_headers? : Array[(String, String)]) -> LegacyHttpSessionTransport

LegacyHttpSessionTransport::close

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async fn LegacyHttpSessionTransport::close(self : LegacyHttpSessionTransport) -> Unit

Best-effort session termination. If a session id is held, sends an HTTP DELETE to the MCP endpoint with the Mcp-Session-Id header. Errors are ignored.

LegacyHttpSessionTransport::receive

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fn LegacyHttpSessionTransport::receive(self : LegacyHttpSessionTransport) -> String?

Drain the next response message queued by send. Returns None when the queue is empty.

LegacyHttpSessionTransport::send

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async fn LegacyHttpSessionTransport::send(self : LegacyHttpSessionTransport, message : String) -> Unit

POST a JSON-RPC request to the legacy MCP endpoint. If the server returns an Mcp-Session-Id header, it is stored for all later requests. Responses may be a single JSON object or an SSE stream; every JSON-RPC payload is queued for receive. SSE tokenization is shared with the modern transport via @transport.SseEventReader.

LegacyHttpSessionTransport::send_notification

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async fn LegacyHttpSessionTransport::send_notification(self : LegacyHttpSessionTransport, notification : @colmugx/mcp/protocol/types.Notification
Notification) -> Unit

Send a JSON-RPC notification (no id, fire-and-forget). Per the 2025-11-25 spec the server answers with HTTP 202 Accepted and no body.

LegacyTransport

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pub enum LegacyTransport {
  Wrapped(@colmugx/mcp/transport.AnyTransport
AnyTransport)
  HttpSession(LegacyHttpSessionTransport)
}

Internal transport wrapper for LegacyClient.

LegacyClient must be able to accept a modern @transport.AnyTransport (for callers that already have one) or the legacy session-aware HTTP transport (for connect_http). This private enum keeps both shapes inside the legacy package without adding a variant to the closed AnyTransport enum in the transport package.