diff --git a/README.md b/README.md
index 5053726..16cf1c7 100644
--- a/README.md
+++ b/README.md
@@ -20,6 +20,28 @@ If Pi is already running, use `/reload`.
 
 Requires Node.js `>=22.20.0`.
 
+### npm prefix permissions
+
+Pi global package installs use `npm install -g`. If `npm_config_prefix` points at an
+unwritable prefix such as `/usr/local`, install or reload can fail with `EACCES`.
+Use a writable npm prefix, configure Pi's `npmCommand` setting for your Node
+version manager, or install project-local with `pi install npm:pi-extmgr -l`.
+
+`npmCommand` examples for `~/.pi/agent/settings.json`:
+
+```jsonc
+{
+  // mise: run npm through Node 22
+  // "npmCommand": ["mise", "exec", "node@22", "--", "npm"]
+
+  // bun: use Bun as Pi's package-manager command
+  // "npmCommand": ["bun"]
+
+  // nvm: start Pi from an nvm-enabled shell and use npm on PATH
+  // "npmCommand": ["npm"]
+}
+```
+
 ## Features
 
 - **Unified manager UI**
diff --git a/src/packages/extensions.ts b/src/packages/extensions.ts
index e89ad87..8f5e11d 100644
--- a/src/packages/extensions.ts
+++ b/src/packages/extensions.ts
@@ -19,7 +19,7 @@ import {
   normalizeRelativePath,
   resolveRelativePathSelection,
 } from "../utils/relative-path-selection.js";
-import { resolveNpmCommand } from "../utils/npm-exec.js";
+import { resolveConfiguredNpmRootCommand } from "../utils/npm-exec.js";
 
 interface PackageSettingsObject {
   source: string;
@@ -39,7 +39,7 @@ export interface PackageManifest {
 }
 
 const execFileAsync = promisify(execFile);
-let globalNpmRootCache: string | null | undefined;
+let globalNpmRootCache: { key: string; root: string | null } | undefined;
 
 function normalizeSource(source: string): string {
   return source
@@ -58,24 +58,32 @@ function normalizePackageRootCandidate(candidate: string): string {
   return resolved;
 }
 
-async function getGlobalNpmRoot(): Promise<string | undefined> {
-  if (globalNpmRootCache !== undefined) {
-    return globalNpmRootCache ?? undefined;
+async function getGlobalNpmRoot(cwd: string): Promise<string | undefined> {
+  let npmCommand: ReturnType<typeof resolveConfiguredNpmRootCommand>;
+  try {
+    npmCommand = resolveConfiguredNpmRootCommand(cwd);
+  } catch {
+    return undefined;
+  }
+
+  const cacheKey = [npmCommand.command, ...npmCommand.args].join("\0");
+
+  if (globalNpmRootCache?.key === cacheKey) {
+    return globalNpmRootCache.root ?? undefined;
   }
 
   try {
-    const npmCommand = resolveNpmCommand(["root", "-g"]);
     const { stdout } = await execFileAsync(npmCommand.command, npmCommand.args, {
       timeout: 2_000,
       windowsHide: true,
     });
-    const root = stdout.trim();
-    globalNpmRootCache = root || null;
+    const root = npmCommand.getRoot(stdout);
+    globalNpmRootCache = { key: cacheKey, root: root || null };
   } catch {
-    globalNpmRootCache = null;
+    globalNpmRootCache = { key: cacheKey, root: null };
   }
 
-  return globalNpmRootCache ?? undefined;
+  return globalNpmRootCache.root ?? undefined;
 }
 
 async function resolveNpmPackageRoot(
@@ -96,7 +104,7 @@ async function resolveNpmPackageRoot(
   const packageDir = process.env.PI_PACKAGE_DIR || join(homedir(), ".pi", "agent");
   const globalCandidates = [join(packageDir, "npm", "node_modules", packageName)];
 
-  const npmGlobalRoot = await getGlobalNpmRoot();
+  const npmGlobalRoot = await getGlobalNpmRoot(cwd);
   if (npmGlobalRoot) {
     globalCandidates.unshift(join(npmGlobalRoot, packageName));
   }
diff --git a/src/utils/npm-exec.ts b/src/utils/npm-exec.ts
index e7dff6d..d6b4f6a 100644
--- a/src/utils/npm-exec.ts
+++ b/src/utils/npm-exec.ts
@@ -1,10 +1,23 @@
+import { existsSync, readFileSync } from "node:fs";
+import { homedir } from "node:os";
 import path from "node:path";
 import { execPath, platform } from "node:process";
-import { type ExtensionAPI } from "@mariozechner/pi-coding-agent";
+import { type ExtensionAPI, getAgentDir, SettingsManager } from "@mariozechner/pi-coding-agent";
 
 interface NpmCommandResolutionOptions {
   platform?: NodeJS.Platform;
   nodeExecPath?: string;
+  npmCommand?: readonly string[] | undefined;
+  cwd?: string;
+}
+
+interface ResolvedNpmCommand {
+  command: string;
+  args: string[];
+}
+
+interface ResolvedNpmRootCommand extends ResolvedNpmCommand {
+  getRoot(stdout: string): string;
 }
 
 interface NpmExecOptions {
@@ -12,15 +25,148 @@ interface NpmExecOptions {
   signal?: AbortSignal;
 }
 
+const settingsManagersByPath = new Map<string, SettingsManager>();
+let warnedAboutBunGlobalDirHeuristic = false;
+
 function getNpmCliPath(nodeExecPath: string, runtimePlatform: NodeJS.Platform): string {
   const pathImpl = runtimePlatform === "win32" ? path.win32 : path;
   return pathImpl.join(pathImpl.dirname(nodeExecPath), "node_modules", "npm", "bin", "npm-cli.js");
 }
 
+function getConfiguredNpmBase(
+  npmCommand?: readonly string[] | undefined
+): ResolvedNpmCommand | undefined {
+  if (!npmCommand || npmCommand.length === 0) {
+    return undefined;
+  }
+
+  const [command, ...args] = npmCommand;
+  if (!command?.trim()) {
+    throw new Error("Invalid npmCommand: first array entry must be a non-empty command");
+  }
+
+  return { command, args: [...args] };
+}
+
+function getSettingsNpmCommand(cwd: string): string[] | undefined {
+  const agentDir = getAgentDir();
+  const cacheKey = `${agentDir}\0${cwd}`;
+  const cached = settingsManagersByPath.get(cacheKey);
+  if (cached) {
+    return cached.getNpmCommand();
+  }
+
+  const settingsManager = SettingsManager.create(cwd, agentDir);
+  settingsManagersByPath.set(cacheKey, settingsManager);
+  return settingsManager.getNpmCommand();
+}
+
+function getCommandName(command: string): string {
+  return (command.split(/[\\/]/).pop() ?? "").replace(/\.(cmd|exe)$/i, "");
+}
+
+function expandHome(input: string): string {
+  if (input === "~") return homedir();
+  if (input.startsWith("~/")) return path.join(homedir(), input.slice(2));
+  return input;
+}
+
+function resolveBunConfigPath(value: string, baseDir: string): string {
+  const expanded = expandHome(value.trim());
+  return path.isAbsolute(expanded) ? expanded : path.resolve(baseDir, expanded);
+}
+
+function stripTomlComment(line: string): string {
+  return line.replace(/\s+#.*$/, "").trim();
+}
+
+function readBunGlobalDirFromBunfig(configPath: string): string | undefined {
+  if (!existsSync(configPath)) return undefined;
+
+  let content: string;
+  try {
+    content = readFileSync(configPath, "utf8");
+  } catch {
+    return undefined;
+  }
+
+  let inInstallSection = false;
+  for (const rawLine of content.split(/\r?\n/)) {
+    const line = stripTomlComment(rawLine);
+    if (!line) continue;
+
+    const sectionMatch = line.match(/^\[([^\]]+)]$/);
+    if (sectionMatch) {
+      inInstallSection = sectionMatch[1]?.trim() === "install";
+      continue;
+    }
+
+    const keyMatch = line.match(/^(install\.)?globalDir\s*=\s*(["'])(.*?)\2/);
+    if (!keyMatch) continue;
+    if (!inInstallSection && !keyMatch[1]) continue;
+
+    const value = keyMatch[3]?.trim();
+    return value ? resolveBunConfigPath(value, path.dirname(configPath)) : undefined;
+  }
+
+  return undefined;
+}
+
+function getBunGlobalDir(cwd?: string): string | undefined {
+  const envGlobalDir = process.env.BUN_INSTALL_GLOBAL_DIR?.trim();
+  if (envGlobalDir) {
+    return resolveBunConfigPath(envGlobalDir, process.cwd());
+  }
+
+  const candidates = [
+    path.join(homedir(), ".bunfig.toml"),
+    ...(process.env.XDG_CONFIG_HOME
+      ? [path.join(process.env.XDG_CONFIG_HOME, ".bunfig.toml")]
+      : []),
+    ...(cwd ? [path.join(cwd, "bunfig.toml")] : []),
+  ];
+
+  let globalDir: string | undefined;
+  for (const configPath of candidates) {
+    globalDir = readBunGlobalDirFromBunfig(configPath) ?? globalDir;
+  }
+  return globalDir;
+}
+
+function warnAboutBunGlobalDirHeuristic(): void {
+  if (warnedAboutBunGlobalDirHeuristic) return;
+  warnedAboutBunGlobalDirHeuristic = true;
+  console.warn(
+    "[extmgr] Could not read Bun globalDir from BUN_INSTALL_GLOBAL_DIR or bunfig.toml; " +
+      "guessing from `bun pm bin -g`. If Bun's globalDir is customized, set BUN_INSTALL_GLOBAL_DIR."
+  );
+}
+
+function getBunNodeModulesRoot(globalBinDir: string, cwd?: string): string {
+  const globalDir = getBunGlobalDir(cwd);
+  if (globalDir) {
+    return path.join(globalDir, "node_modules");
+  }
+
+  // Best-effort fallback for Bun's default layout: globalBinDir is usually
+  // ~/.bun/bin and globalDir is usually ~/.bun/install/global. This may be
+  // wrong when [install].globalDir is customized in bunfig.toml.
+  warnAboutBunGlobalDirHeuristic();
+  return path.join(path.dirname(globalBinDir), "install", "global", "node_modules");
+}
+
 export function resolveNpmCommand(
   npmArgs: string[],
   options?: NpmCommandResolutionOptions
-): { command: string; args: string[] } {
+): ResolvedNpmCommand {
+  const configured = getConfiguredNpmBase(options?.npmCommand);
+  if (configured) {
+    return {
+      command: configured.command,
+      args: [...configured.args, ...npmArgs],
+    };
+  }
+
   const runtimePlatform = options?.platform ?? platform;
 
   if (runtimePlatform === "win32") {
@@ -34,13 +180,44 @@ export function resolveNpmCommand(
   return { command: "npm", args: npmArgs };
 }
 
+export function resolveConfiguredNpmCommand(npmArgs: string[], cwd: string): ResolvedNpmCommand {
+  return resolveNpmCommand(npmArgs, { npmCommand: getSettingsNpmCommand(cwd) });
+}
+
+export function resolveNpmRootCommand(
+  options?: NpmCommandResolutionOptions
+): ResolvedNpmRootCommand {
+  const configured = getConfiguredNpmBase(options?.npmCommand);
+
+  if (configured && getCommandName(configured.command) === "bun") {
+    return {
+      command: configured.command,
+      args: [...configured.args, "pm", "bin", "-g"],
+      getRoot: (stdout) => {
+        const binDir = stdout.trim();
+        return binDir ? getBunNodeModulesRoot(binDir, options?.cwd) : "";
+      },
+    };
+  }
+
+  const resolved = resolveNpmCommand(["root", "-g"], options);
+  return {
+    ...resolved,
+    getRoot: (stdout) => stdout.trim(),
+  };
+}
+
+export function resolveConfiguredNpmRootCommand(cwd: string): ResolvedNpmRootCommand {
+  return resolveNpmRootCommand({ npmCommand: getSettingsNpmCommand(cwd), cwd });
+}
+
 export async function execNpm(
   pi: ExtensionAPI,
   npmArgs: string[],
   ctx: { cwd: string },
   options: NpmExecOptions
 ): Promise<{ code: number; stdout: string; stderr: string; killed: boolean }> {
-  const resolved = resolveNpmCommand(npmArgs);
+  const resolved = resolveConfiguredNpmCommand(npmArgs, ctx.cwd);
   return pi.exec(resolved.command, resolved.args, {
     timeout: options.timeout,
     cwd: ctx.cwd,
diff --git a/src/utils/ui-helpers.ts b/src/utils/ui-helpers.ts
index 7e6c18a..c678620 100644
--- a/src/utils/ui-helpers.ts
+++ b/src/utils/ui-helpers.ts
@@ -3,7 +3,7 @@
  */
 import { type ExtensionCommandContext } from "@mariozechner/pi-coding-agent";
 import { UI } from "../constants.js";
-import { notify } from "./notify.js";
+import { error as notifyError, notify } from "./notify.js";
 
 /**
  * Confirm and trigger reload
@@ -20,12 +20,18 @@ export async function confirmReload(
 
   const confirmed = await ctx.ui.confirm("Reload Required", `${reason}\nReload pi now?`);
 
-  if (confirmed) {
+  if (!confirmed) {
+    return false;
+  }
+
+  try {
     await ctx.reload();
     return true;
+  } catch (error) {
+    const message = error instanceof Error ? error.message : String(error);
+    notifyError(ctx, `Reload failed: ${message}`);
+    return false;
   }
-
-  return false;
 }
 
 /**
diff --git a/test/npm-exec.test.ts b/test/npm-exec.test.ts
index 8340423..a29d45e 100644
--- a/test/npm-exec.test.ts
+++ b/test/npm-exec.test.ts
@@ -1,6 +1,6 @@
 import assert from "node:assert/strict";
 import test from "node:test";
-import { resolveNpmCommand } from "../src/utils/npm-exec.js";
+import { resolveNpmCommand, resolveNpmRootCommand } from "../src/utils/npm-exec.js";
 
 void test("resolveNpmCommand uses npm directly on non-windows", () => {
   const resolved = resolveNpmCommand(["view", "pi-extmgr", "version", "--json"], {
@@ -25,3 +25,59 @@ void test("resolveNpmCommand uses node + npm-cli.js on windows", () => {
     "pi-extmgr",
   ]);
 });
+
+void test("resolveNpmCommand honors Pi npmCommand settings", () => {
+  const resolved = resolveNpmCommand(["view", "pi-extmgr", "version", "--json"], {
+    npmCommand: ["mise", "exec", "node@22", "--", "npm"],
+  });
+
+  assert.equal(resolved.command, "mise");
+  assert.deepEqual(resolved.args, [
+    "exec",
+    "node@22",
+    "--",
+    "npm",
+    "view",
+    "pi-extmgr",
+    "version",
+    "--json",
+  ]);
+});
+
+void test("resolveNpmRootCommand detects path-qualified bun commands", () => {
+  const oldGlobalDir = process.env.BUN_INSTALL_GLOBAL_DIR;
+  process.env.BUN_INSTALL_GLOBAL_DIR = "/opt/bun/global";
+
+  try {
+    const resolved = resolveNpmRootCommand({ npmCommand: ["/usr/local/bin/bun"] });
+
+    assert.equal(resolved.command, "/usr/local/bin/bun");
+    assert.deepEqual(resolved.args, ["pm", "bin", "-g"]);
+    assert.equal(resolved.getRoot("/home/alice/.bun/bin\n"), "/opt/bun/global/node_modules");
+  } finally {
+    if (oldGlobalDir === undefined) {
+      delete process.env.BUN_INSTALL_GLOBAL_DIR;
+    } else {
+      process.env.BUN_INSTALL_GLOBAL_DIR = oldGlobalDir;
+    }
+  }
+});
+
+void test("resolveNpmRootCommand detects bun.cmd commands", () => {
+  const oldGlobalDir = process.env.BUN_INSTALL_GLOBAL_DIR;
+  process.env.BUN_INSTALL_GLOBAL_DIR = "/opt/bun/global";
+
+  try {
+    const resolved = resolveNpmRootCommand({ npmCommand: ["bun.cmd"] });
+
+    assert.equal(resolved.command, "bun.cmd");
+    assert.deepEqual(resolved.args, ["pm", "bin", "-g"]);
+    assert.equal(resolved.getRoot("/home/alice/.bun/bin\n"), "/opt/bun/global/node_modules");
+  } finally {
+    if (oldGlobalDir === undefined) {
+      delete process.env.BUN_INSTALL_GLOBAL_DIR;
+    } else {
+      process.env.BUN_INSTALL_GLOBAL_DIR = oldGlobalDir;
+    }
+  }
+});
diff --git a/test/ui-helpers.test.ts b/test/ui-helpers.test.ts
new file mode 100644
index 0000000..2db285f
--- /dev/null
+++ b/test/ui-helpers.test.ts
@@ -0,0 +1,76 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import { type ExtensionCommandContext } from "@mariozechner/pi-coding-agent";
+import { confirmReload } from "../src/utils/ui-helpers.js";
+
+void test("confirmReload returns false without reloading when user cancels", async () => {
+  const notifications: { message: string; level: string | undefined }[] = [];
+  let reloadCalls = 0;
+  const ctx = {
+    hasUI: true,
+    ui: {
+      confirm: () => Promise.resolve(false),
+      notify: (message: string, level?: string) => {
+        notifications.push({ message, level });
+      },
+    },
+    reload: () => {
+      reloadCalls += 1;
+      return Promise.resolve();
+    },
+  } as unknown as ExtensionCommandContext;
+
+  const reloaded = await confirmReload(ctx, "Package updated.");
+
+  assert.equal(reloaded, false);
+  assert.equal(reloadCalls, 0);
+  assert.deepEqual(notifications, []);
+});
+
+void test("confirmReload returns true after a successful reload", async () => {
+  const notifications: { message: string; level: string | undefined }[] = [];
+  let reloadCalls = 0;
+  const ctx = {
+    hasUI: true,
+    ui: {
+      confirm: () => Promise.resolve(true),
+      notify: (message: string, level?: string) => {
+        notifications.push({ message, level });
+      },
+    },
+    reload: () => {
+      reloadCalls += 1;
+      return Promise.resolve();
+    },
+  } as unknown as ExtensionCommandContext;
+
+  const reloaded = await confirmReload(ctx, "Package updated.");
+
+  assert.equal(reloaded, true);
+  assert.equal(reloadCalls, 1);
+  assert.deepEqual(notifications, []);
+});
+
+void test("confirmReload reports reload failures without throwing", async () => {
+  const notifications: { message: string; level: string | undefined }[] = [];
+  const ctx = {
+    hasUI: true,
+    ui: {
+      confirm: () => Promise.resolve(true),
+      notify: (message: string, level?: string) => {
+        notifications.push({ message, level });
+      },
+    },
+    reload: () => Promise.reject(new Error("npm install -g pi-extmgr failed with code 243")),
+  } as unknown as ExtensionCommandContext;
+
+  const reloaded = await confirmReload(ctx, "Package updated.");
+
+  assert.equal(reloaded, false);
+  assert.deepEqual(notifications, [
+    {
+      message: "Reload failed: npm install -g pi-extmgr failed with code 243",
+      level: "error",
+    },
+  ]);
+});