diff --git a/packages/cli/__tests__/lib/preflight.test.ts b/packages/cli/__tests__/lib/preflight.test.ts
index 36446ea46..dc7536ce4 100644
--- a/packages/cli/__tests__/lib/preflight.test.ts
+++ b/packages/cli/__tests__/lib/preflight.test.ts
@@ -97,24 +97,14 @@ describe("preflight.checkTmux", () => {
     expect(mockExec).toHaveBeenCalledWith("tmux", ["-V"]);
   });
 
-  it("attempts auto-install when tmux is missing", async () => {
-    // First call: tmux -V fails (not installed)
-    // Second call: auto-install attempt (brew/apt/dnf)
-    // Third call: tmux -V succeeds (installed now)
-    mockExec
-      .mockRejectedValueOnce(new Error("ENOENT")) // tmux -V
-      .mockResolvedValueOnce({ stdout: "", stderr: "" }) // install command
-      .mockResolvedValueOnce({ stdout: "tmux 3.3a", stderr: "" }); // verify
-    await expect(preflight.checkTmux()).resolves.toBeUndefined();
-  });
-
-  it("throws with install instructions when auto-install fails", async () => {
-    // All attempts fail
+  it("throws with install instructions when tmux is missing", async () => {
     mockExec.mockRejectedValue(new Error("ENOENT"));
     const err = await preflight.checkTmux().catch((e: Error) => e);
     expect(err).toBeInstanceOf(Error);
     expect(err.message).toContain("tmux is not installed");
     expect(err.message).toContain("Install it:");
+    expect(mockExec).toHaveBeenCalledTimes(1);
+    expect(mockExec).toHaveBeenCalledWith("tmux", ["-V"]);
   });
 });
 
diff --git a/packages/cli/src/lib/preflight.ts b/packages/cli/src/lib/preflight.ts
index 7b424ddfc..0f7721f85 100644
--- a/packages/cli/src/lib/preflight.ts
+++ b/packages/cli/src/lib/preflight.ts
@@ -66,22 +66,17 @@ function findPackageUp(startDir: string, ...segments: string[]): string | null {
 }
 
 /**
- * Check that tmux is installed. If missing, attempt auto-install.
- * Falls back to a clear error with platform-appropriate instructions
- * if auto-install is not possible.
+ * Check that tmux is installed.
+ * Throws with platform-appropriate manual install instructions when missing.
  */
 async function checkTmux(): Promise<void> {
   try {
     await exec("tmux", ["-V"]);
     return;
   } catch {
-    // tmux not found — try to install it
+    // tmux not found
   }
 
-  // Attempt auto-install based on platform
-  const installed = await autoInstallTmux();
-  if (installed) return;
-
   const hint =
     process.platform === "darwin"
       ? "brew install tmux"
@@ -91,36 +86,6 @@ async function checkTmux(): Promise<void> {
   throw new Error(`tmux is not installed. Install it: ${hint}`);
 }
 
-/**
- * Try to auto-install tmux. Returns true if successful.
- * Tries brew (macOS), apt-get, then dnf (Linux). Silent on failure.
- */
-async function autoInstallTmux(): Promise<boolean> {
-  const attempts: Array<{ cmd: string; args: string[] }> =
-    process.platform === "darwin"
-      ? [{ cmd: "brew", args: ["install", "tmux"] }]
-      : process.platform === "linux"
-        ? [
-            { cmd: "sudo", args: ["apt-get", "install", "-y", "tmux"] },
-            { cmd: "sudo", args: ["dnf", "install", "-y", "tmux"] },
-          ]
-        : [];
-
-  for (const { cmd, args } of attempts) {
-    try {
-      const label = [cmd, ...args].join(" ");
-      console.log(`  Attempting: ${label}`);
-      await exec(cmd, args);
-      // Verify it actually worked
-      await exec("tmux", ["-V"]);
-      return true;
-    } catch {
-      // Try next method
-    }
-  }
-  return false;
-}
-
 /**
  * Check that the GitHub CLI is installed and authenticated.
  * Distinguishes between "not installed" and "not authenticated"