From b5fa4af9f37590dd0111c2ae737be6c9fe1267eb Mon Sep 17 00:00:00 2001
From: Eshwar Sundar <eshwar.sundar@glean.com>
Date: Wed, 28 Oct 2026 17:25:27 +0530
Subject: [PATCH] fix: stop sending Glean internal-service headers from the
 plugin

---
 shared/glean/mcp/src/remote-client.ts        |  7 +----
 shared/glean/mcp/tests/remote-client.test.ts | 33 ++++++++++++++++++++
 2 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/shared/glean/mcp/src/remote-client.ts b/shared/glean/mcp/src/remote-client.ts
index cb19530..6b24ecc 100644
--- a/shared/glean/mcp/src/remote-client.ts
+++ b/shared/glean/mcp/src/remote-client.ts
@@ -153,16 +153,11 @@ function buildTransport(
   chatSessionId?: string,
 ): StreamableHTTPClientTransport {
   const parsedUrl = new URL(serverUrl);
+  // External clients must not send Glean internal-service headers; the edge WAF rejects them.
   const headers: Record<string, string> = {
-    "X-Glean-Internal-Service": "true",
     "X-Glean-Gateway-Request-Metadata": buildGatewayMetadataHeader(chatSessionId),
   };
 
-  const scParam = parsedUrl.searchParams.get("sc");
-  if (scParam) {
-    headers["X-Glean-Request-ScParams"] = scParam;
-  }
-
   const transportOpts: ConstructorParameters<typeof StreamableHTTPClientTransport>[1] = {
     requestInit: { headers },
     fetch: opts.fetch ?? loggingFetch,
diff --git a/shared/glean/mcp/tests/remote-client.test.ts b/shared/glean/mcp/tests/remote-client.test.ts
index c500bc2..840e4d5 100644
--- a/shared/glean/mcp/tests/remote-client.test.ts
+++ b/shared/glean/mcp/tests/remote-client.test.ts
@@ -211,3 +211,36 @@ describe("remote elicitation bridge", () => {
     }
   });
 });
+
+describe("remote transport headers", () => {
+  it("keeps gateway metadata without forwarding internal headers or removing sc", async () => {
+    const handler = createMcpHandler(
+      () => new McpServer({ name: "test", version: "1.0.0" }),
+    );
+    const requests: Request[] = [];
+    const client = await createRemoteClient(
+      "http://test.local/mcp?sc=request-scope",
+      {
+        fetch: (url, init) => {
+          const request = new Request(url, init);
+          requests.push(request);
+          return handler.fetch(request);
+        },
+      },
+    );
+
+    try {
+      expect(requests.length).toBeGreaterThan(0);
+      for (const request of requests) {
+        expect(new URL(request.url).searchParams.get("sc")).toBe("request-scope");
+        expect(request.headers.has("X-Glean-Internal-Service")).toBe(false);
+        expect(request.headers.has("X-Glean-Request-ScParams")).toBe(false);
+        expect(request.headers.has("X-Glean-Forced-ScParams")).toBe(false);
+        expect(request.headers.has("X-Glean-Gateway-Request-Metadata")).toBe(true);
+      }
+    } finally {
+      await client.close();
+      await handler.close();
+    }
+  });
+});