test: add comprehensive tests for Linux user bin directory resolution

- Add dedicated tests for resolveLinuxUserBinDirs() function
- Test path ordering (extraDirs > user dirs > system dirs)
- Test buildMinimalServicePath() with HOME set/unset
- Test platform-specific behavior (Linux vs macOS vs Windows)

Test count: 7 → 20 (+13 tests)

src/daemon/service-env.test.ts

@@ -4,8 +4,136 @@ import {
   buildMinimalServicePath,
   buildNodeServiceEnvironment,
   buildServiceEnvironment,
+  getMinimalServicePathParts,
+  resolveLinuxUserBinDirs,
 } from "./service-env.js";
 
+describe("resolveLinuxUserBinDirs", () => {
+  it("returns correct paths when HOME is provided", () => {
+    const dirs = resolveLinuxUserBinDirs("/home/testuser");
+
+    expect(dirs).toEqual([
+      "/home/testuser/.local/bin",
+      "/home/testuser/.npm-global/bin",
+      "/home/testuser/bin",
+      "/home/testuser/.nvm/current/bin",
+      "/home/testuser/.fnm/current/bin",
+      "/home/testuser/.volta/bin",
+      "/home/testuser/.asdf/shims",
+      "/home/testuser/.local/share/pnpm",
+      "/home/testuser/.bun/bin",
+    ]);
+  });
+
+  it("returns empty array when HOME is undefined", () => {
+    const dirs = resolveLinuxUserBinDirs(undefined);
+    expect(dirs).toEqual([]);
+  });
+
+  it("returns empty array when HOME is empty string", () => {
+    const dirs = resolveLinuxUserBinDirs("");
+    expect(dirs).toEqual([]);
+  });
+
+  it("handles root home directory correctly", () => {
+    const dirs = resolveLinuxUserBinDirs("/root");
+
+    expect(dirs).toContain("/root/.local/bin");
+    expect(dirs).toContain("/root/.npm-global/bin");
+    expect(dirs).toContain("/root/.nvm/current/bin");
+    expect(dirs.length).toBe(9);
+  });
+});
+
+describe("getMinimalServicePathParts - Linux user directories", () => {
+  it("includes user bin directories when HOME is set on Linux", () => {
+    const result = getMinimalServicePathParts({
+      platform: "linux",
+      home: "/home/testuser",
+    });
+
+    // Should include all common user bin directories
+    expect(result).toContain("/home/testuser/.local/bin");
+    expect(result).toContain("/home/testuser/.npm-global/bin");
+    expect(result).toContain("/home/testuser/bin");
+    expect(result).toContain("/home/testuser/.nvm/current/bin");
+    expect(result).toContain("/home/testuser/.fnm/current/bin");
+    expect(result).toContain("/home/testuser/.volta/bin");
+    expect(result).toContain("/home/testuser/.asdf/shims");
+    expect(result).toContain("/home/testuser/.local/share/pnpm");
+    expect(result).toContain("/home/testuser/.bun/bin");
+  });
+
+  it("excludes user bin directories when HOME is undefined on Linux", () => {
+    const result = getMinimalServicePathParts({
+      platform: "linux",
+      home: undefined,
+    });
+
+    // Should only include system directories
+    expect(result).toEqual(["/usr/local/bin", "/usr/bin", "/bin"]);
+
+    // Should not include any user-specific paths
+    expect(result.some((p) => p.includes(".local"))).toBe(false);
+    expect(result.some((p) => p.includes(".npm-global"))).toBe(false);
+    expect(result.some((p) => p.includes(".nvm"))).toBe(false);
+  });
+
+  it("places user directories before system directories on Linux", () => {
+    const result = getMinimalServicePathParts({
+      platform: "linux",
+      home: "/home/testuser",
+    });
+
+    const userDirIndex = result.indexOf("/home/testuser/.local/bin");
+    const systemDirIndex = result.indexOf("/usr/bin");
+
+    expect(userDirIndex).toBeGreaterThan(-1);
+    expect(systemDirIndex).toBeGreaterThan(-1);
+    expect(userDirIndex).toBeLessThan(systemDirIndex);
+  });
+
+  it("places extraDirs before user directories on Linux", () => {
+    const result = getMinimalServicePathParts({
+      platform: "linux",
+      home: "/home/testuser",
+      extraDirs: ["/custom/bin"],
+    });
+
+    const extraDirIndex = result.indexOf("/custom/bin");
+    const userDirIndex = result.indexOf("/home/testuser/.local/bin");
+
+    expect(extraDirIndex).toBeGreaterThan(-1);
+    expect(userDirIndex).toBeGreaterThan(-1);
+    expect(extraDirIndex).toBeLessThan(userDirIndex);
+  });
+
+  it("does not include Linux user directories on macOS", () => {
+    const result = getMinimalServicePathParts({
+      platform: "darwin",
+      home: "/Users/testuser",
+    });
+
+    // Should not include Linux-specific user dirs even with HOME set
+    expect(result.some((p) => p.includes(".npm-global"))).toBe(false);
+    expect(result.some((p) => p.includes(".nvm"))).toBe(false);
+
+    // Should only include macOS system directories
+    expect(result).toContain("/opt/homebrew/bin");
+    expect(result).toContain("/usr/local/bin");
+  });
+
+  it("does not include Linux user directories on Windows", () => {
+    const result = getMinimalServicePathParts({
+      platform: "win32",
+      home: "C:\\Users\\testuser",
+    });
+
+    // Windows returns empty array (uses existing PATH)
+    expect(result).toEqual([]);
+  });
+});
+
 describe("buildMinimalServicePath", () => {
   it("includes Homebrew + system dirs on macOS", () => {
     const result = buildMinimalServicePath({
@@ -26,6 +154,51 @@ describe("buildMinimalServicePath", () => {
     expect(result).toBe("C:\\\\Windows\\\\System32");
   });
 
+  it("includes Linux user directories when HOME is set in env", () => {
+    const result = buildMinimalServicePath({
+      platform: "linux",
+      env: { HOME: "/home/alice" },
+    });
+    const parts = result.split(path.delimiter);
+
+    // Verify user directories are included
+    expect(parts).toContain("/home/alice/.local/bin");
+    expect(parts).toContain("/home/alice/.npm-global/bin");
+    expect(parts).toContain("/home/alice/.nvm/current/bin");
+
+    // Verify system directories are also included
+    expect(parts).toContain("/usr/local/bin");
+    expect(parts).toContain("/usr/bin");
+    expect(parts).toContain("/bin");
+  });
+
+  it("excludes Linux user directories when HOME is not in env", () => {
+    const result = buildMinimalServicePath({
+      platform: "linux",
+      env: {},
+    });
+    const parts = result.split(path.delimiter);
+
+    // Should only have system directories
+    expect(parts).toEqual(["/usr/local/bin", "/usr/bin", "/bin"]);
+
+    // No user-specific paths
+    expect(parts.some((p) => p.includes("home"))).toBe(false);
+  });
+
+  it("ensures user directories come before system directories on Linux", () => {
+    const result = buildMinimalServicePath({
+      platform: "linux",
+      env: { HOME: "/home/bob" },
+    });
+    const parts = result.split(path.delimiter);
+
+    const firstUserDirIdx = parts.indexOf("/home/bob/.local/bin");
+    const firstSystemDirIdx = parts.indexOf("/usr/local/bin");
+
+    expect(firstUserDirIdx).toBeLessThan(firstSystemDirIdx);
+  });
+
   it("includes extra directories when provided", () => {
     const result = buildMinimalServicePath({
       platform: "linux",

src/daemon/service-env.ts

@@ -38,7 +38,7 @@ function resolveSystemPathDirs(platform: NodeJS.Platform): string[] {
  * Resolve common user bin directories for Linux.
  * These are paths where npm global installs and node version managers typically place binaries.
  */
-function resolveLinuxUserBinDirs(home: string | undefined): string[] {
+export function resolveLinuxUserBinDirs(home: string | undefined): string[] {
   if (!home) return [];
 
   const dirs: string[] = [];