Function installTraceparentFetch

e2e/src/surfaces/mcp.ts:51–92

(mcpUrl: string, runDir: string)

};

const installTraceparentFetch = (mcpUrl: string, runDir: string): void => {
  traceSink = { mcpUrl, runDir };
  if (traceFetchInstalled) return;
  traceFetchInstalled = true;
  const original = globalThis.fetch;
  globalThis.fetch = async (input, init) => {
    const url = typeof input === "string" ? input : input instanceof URL ? input.href : input.url;
    const method = (
      init?.method ?? (input instanceof Request ? input.method : "GET")
    ).toUpperCase();
    const sink = traceSink;
    if (!sink || method !== "POST" || !url.startsWith(sink.mcpUrl)) {
      return original(input, init);
    }
    const traceId = randomBytes(16).toString("hex");
    const headers = new Headers(init?.headers ?? (input instanceof Request ? input.headers : {}));
    headers.set("traceparent", `00-${traceId}-${randomBytes(8).toString("hex")}-01`);
    const at = Date.now();
    const finish = (status?: number) =>
      appendTraces(sink.runDir, [
        {
          id: traceId,
          at,
          url,
          ms: Date.now() - at,
          ...(status === undefined ? {} : { status }),
          source: "terminal" as const,
          label: rpcLabel(init?.body),
        },
      ]);
    try {
      const response = await original(input, { ...init, headers });
      finish(response.status);
      return response;
      // oxlint-disable-next-line executor/no-try-catch-or-throw -- fetch adapter boundary
    } catch (error) {
      finish();
      // oxlint-disable-next-line executor/no-try-catch-or-throw -- fetch adapter boundary
      throw error;
    }
  };
};

export interface McpCallResult {
  readonly raw: unknown;