Function handlerFor

packages/hosts/mcp/src/envelope.ts:300–338

(resource: McpResource)

    (signingKey ??= crypto.getRandomValues(new Uint8Array(32)));

  const handlerFor = (resource: McpResource): McpHttpHandler => {
    const key = mcpResourceKey(resource);
    const cached = handlers.get(key);
    if (cached) return cached;

    const handler = createMcpHandler(
      (context: McpRequestContext) => {
        const request = context.requestInfo;
        const inputs = request ? requestInputs.get(request) : undefined;
        if (!request || !inputs) {
          // oxlint-disable-next-line executor/no-effect-escape-hatch -- boundary: the third-party McpServerFactory Promise contract has no typed failure channel; missing documented request context is an SDK defect
          return Effect.runPromise(Effect.die("Modern MCP request has no authenticated context"));
        }
        return Effect.runPromise(
          Effect.gen(function* () {
            const clientCapabilities = yield* clientCapabilitiesFromRequest(request);
            const requestStatePrincipal = mcpRequestStatePrincipal(inputs.principal);
            const requestStateBinding = yield* Effect.promise(() =>
              mcpRequestStateBindingFromBody({
                body: inputs.parsedBody,
                principal: requestStatePrincipal,
                resource,
              }),
            );
            return yield* inputs.builder.build(inputs.principal, {
              resource,
              appsEnabled: appsEnabledForClientCapabilities(clientCapabilities),
              requestStateSigningKey: getSigningKey(),
              requestStatePrincipal,
              ...(requestStateBinding === null ? {} : { requestStateBinding }),
            });
          }),
        );
      },
      { legacy: "reject" },
    );
    handlers.set(key, handler);
    return handler;
  };

  return {
    fetch: async (request, principal, resource, builder) => {