diff --git a/src/application/Setup.ts b/src/application/Setup.ts
index 271908a7a..441ce207f 100644
--- a/src/application/Setup.ts
+++ b/src/application/Setup.ts
@@ -48,7 +48,10 @@ export interface SetupHost {
   hopperPath(): Promise<string | undefined>;
   installHopper(): Promise<boolean>;
   detectedClients(): Promise<readonly SetupClient[]>;
-  configureClient(client: SetupClient): Promise<ClientConfigurationResult>;
+  configureClient(
+    client: SetupClient,
+    hopperPath: string,
+  ): Promise<ClientConfigurationResult>;
   installSkill(): Promise<"installed" | "unchanged" | "failed">;
   doctor(): Promise<Awaited<ReturnType<typeof runDoctor>>>;
 }
@@ -97,16 +100,22 @@ export const runSetup = async (
       );
     actions.push("installed_homebrew");
   }
-  if ((await host.hopperPath()) === undefined) {
+  let hopperPath = await host.hopperPath();
+  if (hopperPath === undefined) {
     if (!yes) return fail("Re-run with --yes to install Hopper.");
     if (!(await host.installHopper()))
       return fail(
         "Hopper installation was interrupted; resolve the system prompt and re-run setup.",
       );
     actions.push("installed_hopper");
+    hopperPath = await host.hopperPath();
+    if (hopperPath === undefined)
+      return fail(
+        "Hopper installation completed but its launcher was not found.",
+      );
   }
   for (const client of await host.detectedClients()) {
-    const result = await host.configureClient(client);
+    const result = await host.configureClient(client, hopperPath);
     clients[client.name] = result;
     if (result.status === "failed")
       return fail(
@@ -188,6 +197,7 @@ const detectJsonClients = async (
 /** Back up, atomically update, and semantically read back one JSON MCP configuration. */
 export const configureJsonClient = async (
   client: SetupClient,
+  hopperPath?: string,
 ): Promise<ClientConfigurationResult> => {
   let document: Record<string, unknown> = {};
   let original: string | undefined;
@@ -206,6 +216,9 @@ export const configureJsonClient = async (
   const desired = {
     command: "npx",
     args: ["-y", PRODUCT_IDENTITY.packageName, "mcp"],
+    ...(hopperPath === undefined
+      ? {}
+      : { env: { HOPPER_LAUNCHER_PATH: hopperPath } }),
   };
   if (
     JSON.stringify(servers[PRODUCT_IDENTITY.mcpServerKey]) ===
diff --git a/tests/setup.test.ts b/tests/setup.test.ts
index da55b5a1a..04cfb9f74 100644
--- a/tests/setup.test.ts
+++ b/tests/setup.test.ts
@@ -22,6 +22,7 @@ class FakeSetupHost implements SetupHost {
   homebrewInstalls = 0;
   hopperInstalls = 0;
   configurations = 0;
+  configuredHopperPaths: string[] = [];
 
   macosVersion = (): Promise<string | undefined> =>
     Promise.resolve(this.version);
@@ -41,8 +42,10 @@ class FakeSetupHost implements SetupHost {
     Promise.resolve(this.clients);
   configureClient = (
     client: SetupClient,
+    hopperPath: string,
   ): Promise<ClientConfigurationResult> => {
     this.configurations += 1;
+    this.configuredHopperPaths.push(hopperPath);
     return Promise.resolve(
       this.clientResults.get(client.name) ?? {
         status: "configured",
@@ -99,6 +102,7 @@ describe("setup workflow", () => {
     host.hopper = "/Applications/Manual Hopper";
     expect((await runSetup(true, host)).actions).toEqual(["installed_skill"]);
     expect(host.hopperInstalls).toBe(0);
+    expect(host.configuredHopperPaths).toEqual([]);
   });
 
   it.each(["homebrew", "hopper"] as const)(
@@ -127,6 +131,7 @@ describe("setup workflow", () => {
     const result = await runSetup(true, host);
     expect(Object.keys(result.clients)).toEqual(["claude", "cursor"]);
     expect(host.configurations).toBe(2);
+    expect(host.configuredHopperPaths).toEqual(["/Hopper", "/Hopper"]);
   });
 
   it.each(["backup", "write", "readback"] as const)(
diff --git a/tests/setupConfig.test.ts b/tests/setupConfig.test.ts
index 048bd1449..57510adc7 100644
--- a/tests/setupConfig.test.ts
+++ b/tests/setupConfig.test.ts
@@ -49,6 +49,28 @@ describe("JSON client configuration transaction", () => {
     ).rejects.toThrow();
   });
 
+  it("persists a custom Hopper launcher and remains idempotent", async () => {
+    directory = await mkdtemp(join(tmpdir(), "rea-setup-"));
+    const configPath = join(directory, "mcp.json");
+    const hopperPath = "/Applications/Hopper v6.app/Contents/MacOS/hopper";
+    const client = { name: "cursor", configPath };
+    expect(await configureJsonClient(client, hopperPath)).toMatchObject({
+      status: "configured",
+    });
+    expect(JSON.parse(await readFile(configPath, "utf8"))).toMatchObject({
+      mcpServers: {
+        rea: {
+          command: "npx",
+          args: ["-y", "@morluto/rea", "mcp"],
+          env: { HOPPER_LAUNCHER_PATH: hopperPath },
+        },
+      },
+    });
+    expect(await configureJsonClient(client, hopperPath)).toEqual({
+      status: "unchanged",
+    });
+  });
+
   it("refuses malformed existing JSON without overwriting it", async () => {
     directory = await mkdtemp(join(tmpdir(), "rea-setup-"));
     const configPath = join(directory, "mcp.json");