HttpSse

Category: Mcp_client

Source: http_sse.dart

Streamable HTTP transport for MCP (2025-03-26 spec).

Single endpoint. Each client→server message is one POST. The server responds with either: • Content-Type: application/json — a single JSON-RPC message • Content-Type: text/event-stream — zero or more JSON-RPC messages in SSE events (data: {...})

Authentication is via Authorization: Bearer <token>. Session state across requests uses the Mcp-Session-Id header (captured from the initialize response, sent back on every subsequent request).

Out of scope for v1: • Standalone GET-SSE channel for server-initiated notifications. For HTTP-bound servers, tools/list_changed lands in B7 alongside the rest of the ACP integration.

Classes

McpHttpTransport

Constructor

McpHttpTransport({
    required this.endpoint,
    this.bearerToken,
    http.Client? httpClient,
  })

Properties

Property	Type	Description
endpoint	Uri
bearerToken	String?	Optional bearer token. When set, every request carries Authorization: Bearer <token>.
incoming	Stream<JsonRpcMessage> get
incoming	Stream<JsonRpcMessage> get

Methods

void send(JsonRpcMessage message)

Future<void> close()

McpHttpTransportError

Surfaced via the [JsonRpcTransport.incoming] stream's error channel when the server returns a non-2xx HTTP status. The [McpClient] in turn maps it to an [McpCallFailure] for the agent loop.

On 401 responses the [wwwAuthenticate] header (if any) is captured — the pool consumes it to discover OAuth metadata per RFC 9728.

Constructor

const McpHttpTransportError({
    required this.statusCode,
    required this.body,
    this.wwwAuthenticate,
  })

Properties

Property	Type	Description
statusCode	int
body	String
wwwAuthenticate	String?	Raw WWW-Authenticate header from the response. Populated when the server returns 401. null for other failure statuses.

Methods

String toString()

Functions

`String? resolveMcpBearerToken(

McpAuthSpec auth, CredentialStore credentials, String serverId, )`

Resolves the bearer token for an MCP server, honouring: • [McpBearerAuth] — literal token from config, falling back to mcp:<server-id>:bearer in the credential store. • [McpOAuthAuth] — current oauth_access field from the credential store (populated by glue mcp auth login <server>). • [McpNoAuth] — null (no Authorization header).

Returns null when no token is available. Callers send no header in that case; the server may 401, which the pool surfaces as McpServerAuthRequiredEvent so the user knows to log in.