fix(host-cloudflare): route toolkit MCP endpoints

apps/cloud/src/mcp/agent-handler.ts

@@ -254,14 +254,19 @@ export const makeCloudMcpAgentHandler = () => {
       });
     }
 
+    const resource = resourceFromPath(request);
+
     if (sessionId) {
       let owner: "ok" | "not_found" | "forbidden" | "terminated";
       // oxlint-disable-next-line executor/no-try-catch-or-throw -- adapter boundary: a Durable Object stub RPC rejects with a plain platform Error, never a typed failure
       try {
-        owner = await mcpSessionStub(env.MCP_SESSION, sessionId).validateMcpSessionOwner({
-          accountId: outcome.principal.accountId,
-          organizationId: outcome.principal.organizationId,
-        });
+        owner = await mcpSessionStub(env.MCP_SESSION, sessionId).validateMcpSessionOwner(
+          {
+            accountId: outcome.principal.accountId,
+            organizationId: outcome.principal.organizationId,
+          },
+          resource,
+        );
       } catch (error) {
         // The sibling stub touchpoints in this handler are both guarded — the
         // `_cf_scheduleDestroy` call above with `Effect.ignore`, the
@@ -290,7 +295,6 @@ export const makeCloudMcpAgentHandler = () => {
       }
     }
 
-    const resource = resourceFromPath(request);
     const props = await runTraced(request, propsForPrincipal(request, outcome.principal, resource));
     (ctx as ExecutionContext & { props?: McpSessionProps }).props = props;
     const forwarded = withOrgWriteAccess(

apps/host-cloudflare/src/mcp/agent-handler.ts

@@ -3,10 +3,10 @@ import { Effect, Predicate } from "effect";
 import {
   McpAuthProvider,
   jsonRpcErrorBody,
-  defaultMcpResource,
   orgWriteAccessForPrincipal,
   withOrgWriteAccess,
   type AuthOutcome,
+  type McpResource,
   type Principal,
 } from "@executor-js/host-mcp";
 import {
@@ -22,6 +22,7 @@ import { mcpSessionStub } from "@executor-js/cloudflare/mcp/session-stub";
 
 import type { CloudflareConfig, CloudflareEnv } from "../config";
 import { cloudflareAccessMcpAuth } from "./auth";
+import { mcpResourceFromPath } from "./resource";
 import { McpSessionDO } from "./session-durable-object";
 
 const corsPreflightResponse = (): Response =>
@@ -75,6 +76,7 @@ const authenticate = (request: Request, config: CloudflareConfig) =>
 const propsForPrincipal = (
   request: Request,
   principal: Principal,
+  resource: McpResource,
 ): Effect.Effect<McpSessionProps> =>
   Effect.gen(function* () {
     const propagation = yield* currentPropagationHeaders(request);
@@ -86,21 +88,20 @@ const propsForPrincipal = (
         elicitationMode: readElicitationMode(request),
         artifactsEnabled: readArtifactsEnabled(request),
         searchToolsEnabled: readSearchToolsEnabled(request),
-        // host-cloudflare only routes the bare `/mcp` endpoint to the Agent
-        // bridge (see worker.ts), so the session always serves the default
-        // resource.
-        resource: defaultMcpResource,
+        resource,
         webOrigin: new URL(request.url).origin,
       },
       propagation,
     };
   });
 
 export const makeCloudflareMcpAgentHandler = (config: CloudflareConfig) => {
-  const serve = McpSessionDO.serve("/mcp", {
+  const serveOptions = {
     binding: "MCP_SESSION",
     transport: "streamable-http",
-  });
+  } as const;
+  const serveDefault = McpSessionDO.serve("/mcp", serveOptions);
+  const serveToolkit = McpSessionDO.serve("/mcp/toolkits/:slug", serveOptions);
 
   return async (request: Request, env: CloudflareEnv, ctx: ExecutionContext): Promise<Response> => {
     if (request.method === "OPTIONS") return corsPreflightResponse();
@@ -120,15 +121,23 @@ export const makeCloudflareMcpAgentHandler = (config: CloudflareConfig) => {
       return renderAuthError(auth, request, outcome);
     }
 
+    const resource = mcpResourceFromPath(new URL(request.url).pathname);
+    if (resource === null) {
+      return jsonRpcResponse(404, -32001, "MCP route not found");
+    }
+
     if (!sessionId && request.method === "DELETE") {
       return new Response(null, { status: 204, headers: { "access-control-allow-origin": "*" } });
     }
 
     if (sessionId) {
-      const owner = await mcpSessionStub(env.MCP_SESSION, sessionId).validateMcpSessionOwner({
-        accountId: outcome.principal.accountId,
-        organizationId: outcome.principal.organizationId,
-      });
+      const owner = await mcpSessionStub(env.MCP_SESSION, sessionId).validateMcpSessionOwner(
+        {
+          accountId: outcome.principal.accountId,
+          organizationId: outcome.principal.organizationId,
+        },
+        resource,
+      );
       if (owner === "not_found") {
         return jsonRpcResponse(404, -32001, "Session not found");
       }
@@ -142,7 +151,7 @@ export const makeCloudflareMcpAgentHandler = (config: CloudflareConfig) => {
       }
     }
 
-    const props = await Effect.runPromise(propsForPrincipal(request, outcome.principal));
+    const props = await Effect.runPromise(propsForPrincipal(request, outcome.principal, resource));
     (ctx as ExecutionContext & { props?: McpSessionProps }).props = props;
     const forwarded = withOrgWriteAccess(
       withVerifiedIdentityHeaders(
@@ -151,10 +160,11 @@ export const makeCloudflareMcpAgentHandler = (config: CloudflareConfig) => {
           accountId: outcome.principal.accountId,
           organizationId: outcome.principal.organizationId,
         },
-        defaultMcpResource,
+        resource,
       ),
       orgWriteAccessForPrincipal(outcome.principal),
     );
-    return serve.fetch(forwarded, env, ctx);
+    const target = resource.kind === "toolkit" ? serveToolkit : serveDefault;
+    return target.fetch(forwarded, env, ctx);
   };
 };

apps/host-cloudflare/src/mcp/resource.test.ts

@@ -0,0 +1,29 @@
+import { describe, expect, it } from "@effect/vitest";
+
+import { mcpResourceFromPath } from "./resource";
+
+describe("mcpResourceFromPath", () => {
+  it("classifies the default MCP path", () => {
+    expect(mcpResourceFromPath("/mcp")).toEqual({ kind: "default" });
+  });
+
+  it("classifies a toolkit MCP path", () => {
+    expect(mcpResourceFromPath("/mcp/toolkits/calendar-tools")).toEqual({
+      kind: "toolkit",
+      slug: "calendar-tools",
+    });
+  });
+
+  it.each([
+    "/",
+    "/mcp/",
+    "/mcp/toolkits",
+    "/mcp/toolkits/",
+    "/mcp//toolkits/calendar-tools",
+    "/mcp/toolkits//calendar-tools",
+    "/mcp/toolkits/calendar-tools/extra",
+    "/api/toolkits/calendar-tools",
+  ])("rejects the non-serving path %s", (pathname) => {
+    expect(mcpResourceFromPath(pathname)).toBeNull();
+  });
+});

apps/host-cloudflare/src/mcp/resource.ts

@@ -0,0 +1,8 @@
+import { defaultMcpResource, type McpResource } from "@executor-js/host-mcp";
+
+export const mcpResourceFromPath = (pathname: string): McpResource | null => {
+  if (pathname === "/mcp") return defaultMcpResource;
+
+  const toolkitMatch = /^\/mcp\/toolkits\/([^/]+)$/.exec(pathname);
+  return toolkitMatch?.[1] ? { kind: "toolkit", slug: toolkitMatch[1] } : null;
+};

apps/host-cloudflare/src/worker.e2e.node.test.ts

@@ -302,6 +302,77 @@ describe("cloudflare host e2e (workerd/miniflare)", () => {
     expect(toolNames).toContain("execute");
   }, 60_000);
 
+  it("serves toolkit MCP sessions and rejects cross-resource session reuse", async () => {
+    const createToolkit = await worker.fetch("/api/toolkits", {
+      method: "POST",
+      headers: { "content-type": "application/json" },
+      body: JSON.stringify({
+        owner: "org",
+        name: `Cloudflare Toolkit ${runId}`,
+        slug: `cloudflare-toolkit-${runId}`,
+      }),
+    });
+    expect(createToolkit.status).toBe(200);
+    const toolkit = (await createToolkit.json()) as { id: string; slug: string };
+
+    const addConnection = await worker.fetch(`/api/toolkits/${toolkit.id}/connections`, {
+      method: "POST",
+      headers: { "content-type": "application/json" },
+      body: JSON.stringify({ pattern: "executor.*" }),
+    });
+    expect(addConnection.status).toBe(200);
+
+    const accept = "application/json, text/event-stream";
+    const toolkitPath = `/mcp/toolkits/${toolkit.slug}`;
+    const rpc = (path: string, sessionId: string | null, body: unknown) =>
+      worker.fetch(path, {
+        method: "POST",
+        headers: {
+          "content-type": "application/json",
+          accept,
+          ...(sessionId ? { "mcp-session-id": sessionId } : {}),
+        },
+        body: JSON.stringify(body),
+      });
+
+    const init = await rpc(toolkitPath, null, {
+      jsonrpc: "2.0",
+      id: 1,
+      method: "initialize",
+      params: {
+        protocolVersion: "2025-03-26",
+        capabilities: {},
+        clientInfo: { name: "toolkit-route-test", version: "1" },
+      },
+    });
+    expect(init.status).toBe(200);
+    const sessionId = init.headers.get("mcp-session-id");
+    expect(sessionId).toBeTruthy();
+
+    await rpc(toolkitPath, sessionId, {
+      jsonrpc: "2.0",
+      method: "notifications/initialized",
+    });
+
+    const list = await rpc(toolkitPath, sessionId, {
+      jsonrpc: "2.0",
+      id: 2,
+      method: "tools/list",
+    });
+    expect(list.status).toBe(200);
+    const listed = await readMcpJson<{
+      result?: { tools?: ReadonlyArray<{ name: string }> };
+    }>(list);
+    expect(listed.result?.tools?.map((tool) => tool.name)).toContain("execute");
+
+    const reusedOnDefault = await rpc("/mcp", sessionId, {
+      jsonrpc: "2.0",
+      id: 3,
+      method: "tools/list",
+    });
+    expect(reusedOnDefault.status).toBe(403);
+  }, 60_000);
+
   it("serves streamable HTTP GET only for initialized sessions", async () => {
     const missing = await worker.fetch("/mcp", {
       method: "GET",

apps/host-cloudflare/src/worker.ts

@@ -4,16 +4,17 @@ import {
   missingCloudflareAccessVars,
   type CloudflareEnv,
 } from "./config";
+import { mcpResourceFromPath } from "./mcp/resource";
 
 // The MCP Durable Object classes, bound in wrangler.jsonc. They must be exported
 // at the Worker entry module scope for the runtime to find them.
 export { McpExecutionOwnerDirectoryDO, McpSessionDO } from "./mcp";
 
 // ---------------------------------------------------------------------------
 // The Worker fetch entry. Most requests go to `ExecutorApp.make`'s Effect web
-// handler. `/mcp` stays at this edge boundary because `McpAgent.serve()` needs
-// the Cloudflare `ExecutionContext` to pass authenticated session props into the
-// hibernatable Durable Object bridge.
+// handler. `/mcp` and `/mcp/toolkits/:slug` stay at this edge boundary because
+// `McpAgent.serve()` needs the Cloudflare `ExecutionContext` to pass
+// authenticated session props into the hibernatable Durable Object bridge.
 // ---------------------------------------------------------------------------
 
 let handlerPromise: Promise<{
@@ -48,7 +49,8 @@ export default {
     }
 
     const serve = await resolveHandler(env);
-    if (new URL(request.url).pathname === "/mcp") {
+    const resource = mcpResourceFromPath(new URL(request.url).pathname);
+    if (resource !== null) {
       return serve.mcp(request, env, ctx);
     }
     return serve.app(request);