fix: address PR review comments

- Fix test to verify >=30 bytes detection
- Add fs.existsSync checks for /usr paths

src/shared/services/cliRuntime.ts

@@ -1,4 +1,5 @@
 import fs from "fs/promises";
+import fsSync from "fs";
 import os from "os";
 import path from "path";
 import { spawn, execFileSync } from "child_process";
@@ -419,8 +420,13 @@ const getKnownToolPaths = (toolId: string): string[] => {
       }
 
       paths.push(path.join(home, ".local", "bin", posixName));
-      paths.push(path.join("/usr", "local", "bin", posixName));
-      paths.push(path.join("/usr", "bin", posixName));
+      // Only add system paths if they exist (avoids unnecessary stat calls)
+      if (fsSync.existsSync("/usr/local/bin")) {
+        paths.push(path.join("/usr", "local", "bin", posixName));
+      }
+      if (fsSync.existsSync("/usr/bin")) {
+        paths.push(path.join("/usr", "bin", posixName));
+      }
 
       if (toolId === "opencode") {
         paths.push(path.join(home, ".opencode", "bin", posixName));

tests/unit/cli-runtime-detection.test.mjs

@@ -61,10 +61,27 @@ describe("Size threshold — checkKnownPath", () => {
     fs.rmSync(tmpDir, { recursive: true, force: true });
   });
 
-  it("should reject files under 30 bytes as suspicious_size", async () => {
-    const tinyFile = createFile(tmpDir, "tiny-cmd", "a".repeat(20));
-    const result = await getCliRuntimeStatus("opencode");
-    assert.ok(result.reason !== "suspicious_size" || !result.installed);
+  it("should detect files >= 30 bytes via env var", async () => {
+    const prev = process.env.CLI_DROID_BIN;
+    // Create a valid 30-byte+ script
+    const content =
+      process.platform === "win32"
+        ? "@echo off\r\necho 1.0.0\r\nexit 0\r\n"
+        : "#!/bin/sh\r\necho 1.0.0\r\nexit 0\r\n";
+    const script = createFile(tmpDir, "droid-valid", content);
+    // Verify it's at least 30 bytes
+    const stat = fs.statSync(script);
+    assert.ok(stat.size >= 30, `File should be >= 30 bytes, got ${stat.size}`);
+
+    process.env.CLI_DROID_BIN = script;
+    try {
+      const result = await getCliRuntimeStatus("droid");
+      assert.ok(result.installed, `Expected installed=true, got reason=${result.reason}`);
+      assert.ok(result.commandPath === script, `Expected commandPath=${script}`);
+    } finally {
+      if (prev !== undefined) process.env.CLI_DROID_BIN = prev;
+      else delete process.env.CLI_DROID_BIN;
+    }
   });
 
   it("should detect a valid CLI script (>= 30 bytes) via env var", async () => {