diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3180a8f6..9fad61b3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@ Games go live on Summer's automatic checks, with Summer's review afterwards: `su
   - A sent-back page's decision comes from the review's `latestReview`; while the platform lacks it, from `/approval` when it answers; else the page still reports `needs_changes` and points at `store.status`. On a platform without `/review`, a first-launch hold reports as Summer's, as before. The waiting answer no longer carries `approvalState`.
 - **Platforms a hosted release left out: `notIncluded` and `notUsed`.** `summer_go_live` reads `droppedTargets` from the release, answers `notIncluded` (one entry per platform: the reason, `checkErrorCode` and the line to tell the creator, such as "iOS isn't included: this build couldn't be checked for iPhone.") and goes live on the platforms the release kept instead of waiting for the others. `notUsed` names a newer client the release did not use (that platform stays live with its current client). The live answer's `next` names both.
 - **`playable_release_required` answers `blocked`** with the platform's own message, or "Upload a build that includes your game's apps so they can be checked against the new server."
+- **Setup names an older `summer` on PATH.** After `npx -y summer-engine@latest setup`, a stale global `summer` (3.1.0) first on PATH ran on the next `summer login`. Setup now says which one it is and how to update it (`npm install -g summer-engine@latest`, or `brew upgrade summerengine/tap/summer`), and to use `npx -y summer-engine@latest login` until then; `--json` lists it in `warnings`.
 - **"Summer is still checking this; nothing to do on your side."** When a publish's checks have run over an hour, `summer_go_live`'s waiting answer and `summer_publish_build`'s hold say so, with the time (`stillCheckingSince`).
 - **`summer_publish_build`'s hold** reads the review too: on hold (with the changes to make), taken down, or Summer's own hold. `approval_denied` now reads "This game was taken down, so it can't take new builds."
 - **Copy:** the README, `AGENTS.md`, the project `AGENTS.md` block and the `publish-your-game` skill say a game is live once the automatic checks pass, with staff review afterwards, and tell an automatic-check rejection from a staff hold and a take-down.
diff --git a/src/cli/commands/setup.ts b/src/cli/commands/setup.ts
index 4e8e7d0c..aaa19ecd 100644
--- a/src/cli/commands/setup.ts
+++ b/src/cli/commands/setup.ts
@@ -22,6 +22,7 @@ import { brandLine, c, sym, tildeify } from "../../core/format.js";
 
 import { TOOLKIT_VERSION as cliVersion } from "../../core/version.js";
 import { listsSummerEngine, resolveDefaultChannel } from "../../installer/version-check.js";
+import { findShadowingSummer, shadowWarning } from "../../installer/path-shadow.js";
 import { agentLabel, agentSpec, cliSetupRefusal, defaultPathContext } from "../../installer/agent-table.js";
 import { addAllowRules, allowRulesPath, removeAllowRules, supportsAllowRules, type AllowRulesResult } from "../../installer/cli-permissions.js";
 import { PROFILES, parseProfile, type Profile } from "../../core/tool-profiles.js";
@@ -271,6 +272,7 @@ async function setupAgent(agentArg: string | undefined, opts: SetupCommandOption
   const projectFiles = projectStep.value;
 
   const doctor = await runDoctor({ quiet: true });
+  const shadow = opts.print ? null : staleSummerOnPath();
 
   if (json) {
     const steps: SetupStep[] = [
@@ -281,12 +283,12 @@ async function setupAgent(agentArg: string | undefined, opts: SetupCommandOption
       doctorStep(doctor),
     ];
     const ok = steps.every((step) => step.ok);
-    console.log(JSON.stringify({ ok, agent, scope, steps, config, games, skills, projectFiles, doctor }, null, 2));
+    console.log(JSON.stringify({ ok, agent, scope, steps, config, games, skills, projectFiles, doctor, ...(shadow ? { warnings: [shadow] } : {}) }, null, 2));
     if (!ok) process.exit(1);
     return;
   }
 
-  printSetupResult(config!, games, skills, doctor, projectFiles);
+  printSetupResult(config!, games, skills, doctor, projectFiles, shadow);
   if (!doctor.ok || skills.status === "failed") {
     process.exit(1);
   }
@@ -390,6 +392,8 @@ async function setupCliOnly(agent: SupportedAgent, scope: ConfigScope, opts: Set
   if (existing) {
     warnings.push(`${tildeify(existing)} still lists the summer-engine MCP server from an earlier setup. Remove that entry to use the CLI only.`);
   }
+  const shadow = staleSummerOnPath();
+  if (shadow) warnings.push(shadow);
 
   const dryRun = Boolean(opts.dryRun);
   const skills = setupSkills(agent, {
@@ -511,6 +515,16 @@ function printProjectFiles(project: ProjectFiles | null): void {
   }
 }
 
+/** An older summer-engine first on PATH would run instead of this one after setup (`summer login`). */
+function staleSummerOnPath(): string | null {
+  try {
+    const found = findShadowingSummer(cliVersion);
+    return found ? shadowWarning(found, cliVersion) : null;
+  } catch {
+    return null;
+  }
+}
+
 /** The config file that already lists summer-engine for this agent and scope, or null. */
 async function recordedMcpEntry(agent: SupportedAgent, scope: ConfigScope): Promise<string | null> {
   try {
@@ -540,7 +554,8 @@ function printSetupResult(
   games: Awaited<ReturnType<typeof configureSummerGamesMcp>>,
   skills: SkillSetupResult,
   doctor: DoctorResult,
-  projectFiles: ProjectFiles | null
+  projectFiles: ProjectFiles | null,
+  shadow: string | null = null
 ): void {
   if (config.print) {
     console.log(config.snippet.trimEnd());
@@ -593,7 +608,7 @@ function printSetupResult(
   printSkillsLine(skills, config.dryRun);
   printProjectFiles(projectFiles);
 
-  for (const warning of config.warnings) {
+  for (const warning of shadow ? [...config.warnings, shadow] : config.warnings) {
     console.log(`  ${sym.warn()}  ${c.yellow(warning)}`);
   }
 
diff --git a/src/installer/path-shadow.test.ts b/src/installer/path-shadow.test.ts
new file mode 100644
index 00000000..289d9150
--- /dev/null
+++ b/src/installer/path-shadow.test.ts
@@ -0,0 +1,60 @@
+import { delimiter, join } from "node:path";
+import { describe, expect, it } from "vitest";
+import { findShadowingSummer, shadowWarning, type PathShadowDeps } from "./path-shadow.js";
+
+/** A fake disk: files with contents, and links (path -> target). */
+function disk(files: Record<string, string>, links: Record<string, string> = {}): PathShadowDeps {
+  return {
+    exists: (path) => path in files || path in links,
+    realpath: (path) => links[path] ?? path,
+    readFile: (path) => {
+      if (!(path in files)) throw new Error(`ENOENT ${path}`);
+      return files[path];
+    },
+    platform: "darwin",
+    packageRoot: "/npx/abc/node_modules/summer-engine",
+  };
+}
+
+const pkg = (version: string) => JSON.stringify({ name: "summer-engine", version });
+const npx = {
+  "/npx/abc/node_modules/summer-engine/package.json": pkg("4.8.0"),
+  "/npx/abc/node_modules/summer-engine/dist/bin/summer.js": "",
+};
+const npxLink = { "/npx/abc/node_modules/.bin/summer": "/npx/abc/node_modules/summer-engine/dist/bin/summer.js" };
+const globalOld = {
+  "/usr/local/lib/node_modules/summer-engine/package.json": pkg("3.1.0"),
+  "/usr/local/lib/node_modules/summer-engine/dist/bin/summer.js": "",
+};
+const globalLink = { "/usr/local/bin/summer": "/usr/local/lib/node_modules/summer-engine/dist/bin/summer.js" };
+const path = (...dirs: string[]) => ({ PATH: dirs.join(delimiter) });
+
+describe("findShadowingSummer", () => {
+  it("names an older global summer behind npx's own copy", () => {
+    const found = findShadowingSummer("4.8.0", path("/npx/abc/node_modules/.bin", "/usr/local/bin"), disk({ ...npx, ...globalOld }, { ...npxLink, ...globalLink }));
+    expect(found).toEqual({ path: "/usr/local/bin/summer", version: "3.1.0", homebrew: false });
+    expect(shadowWarning(found!, "4.8.0")).toContain("npm install -g summer-engine@latest");
+  });
+
+  it("says nothing when the global summer is as new, or there is none", () => {
+    const current = { ...globalOld, "/usr/local/lib/node_modules/summer-engine/package.json": pkg("4.8.0") };
+    expect(findShadowingSummer("4.8.0", path("/npx/abc/node_modules/.bin", "/usr/local/bin"), disk({ ...npx, ...current }, { ...npxLink, ...globalLink }))).toBeNull();
+    expect(findShadowingSummer("4.8.0", path("/npx/abc/node_modules/.bin", "/usr/bin"), disk(npx, npxLink))).toBeNull();
+  });
+
+  it("says nothing when the first summer is another program", () => {
+    const other = { "/opt/bin/summer": "#!/bin/sh" };
+    expect(findShadowingSummer("4.8.0", path("/opt/bin", "/usr/local/bin"), disk({ ...other, ...globalOld }, globalLink))).toBeNull();
+  });
+
+  it("tells a Homebrew install to upgrade with brew", () => {
+    const cellar = "/opt/homebrew/Cellar/summer/3.1.0/libexec/lib/node_modules/summer-engine";
+    const found = findShadowingSummer(
+      "4.8.0",
+      path("/opt/homebrew/bin"),
+      disk({ [join(cellar, "package.json")]: pkg("3.1.0"), [join(cellar, "dist/bin/summer.js")]: "" }, { "/opt/homebrew/bin/summer": join(cellar, "dist/bin/summer.js") })
+    );
+    expect(found?.homebrew).toBe(true);
+    expect(shadowWarning(found!, "4.8.0")).toContain("brew upgrade summerengine/tap/summer");
+  });
+});
diff --git a/src/installer/path-shadow.ts b/src/installer/path-shadow.ts
new file mode 100644
index 00000000..0251d424
--- /dev/null
+++ b/src/installer/path-shadow.ts
@@ -0,0 +1,106 @@
+/**
+ * An older `summer` first on PATH. After `npx -y summer-engine@latest setup`,
+ * the person's next `summer login` runs whatever `summer` their shell finds
+ * first, which can be a stale global install (3.1.0 while setup ran 4.8.0).
+ * Setup names it and says how to update it.
+ */
+
+import { existsSync, readFileSync, realpathSync } from "node:fs";
+import { delimiter, dirname, join, sep } from "node:path";
+import { PACKAGE_ROOT } from "../core/package-root.js";
+import { compareSemver, parseSemver } from "./version-check.js";
+
+export interface ShadowingSummer {
+  /** The `summer` the shell runs, as found on PATH. */
+  path: string;
+  version: string;
+  /** Installed by Homebrew (its Cellar), so brew updates it. */
+  homebrew: boolean;
+}
+
+export interface PathShadowDeps {
+  exists?: (path: string) => boolean;
+  realpath?: (path: string) => string;
+  readFile?: (path: string) => string;
+  platform?: NodeJS.Platform;
+  packageRoot?: string;
+}
+
+/** The summer-engine package a `summer` launcher belongs to: up from where its link points, or the
+ *  npm prefix beside a Windows `summer.cmd`. Null for any other program named summer. */
+function owningPackage(bin: string, deps: Required<PathShadowDeps>): { root: string; version: string } | null {
+  const candidates: string[] = [];
+  let dir = dirname(deps.realpath(bin));
+  for (let i = 0; i < 6; i += 1) {
+    candidates.push(dir);
+    const up = dirname(dir);
+    if (up === dir) break;
+    dir = up;
+  }
+  candidates.push(join(dirname(bin), "node_modules", "summer-engine"));
+  for (const root of candidates) {
+    const manifest = join(root, "package.json");
+    if (!deps.exists(manifest)) continue;
+    try {
+      const pkg = JSON.parse(deps.readFile(manifest)) as { name?: string; version?: string };
+      if (pkg.name === "summer-engine" && pkg.version) return { root, version: pkg.version };
+    } catch {
+      // not a package we can read: keep looking
+    }
+  }
+  return null;
+}
+
+/**
+ * The first `summer` on PATH that is not this package, when it is an older summer-engine.
+ * npx puts its own copy (this package) first while setup runs; that copy is gone afterwards,
+ * so the next one is what the person's shell runs.
+ */
+export function findShadowingSummer(
+  runningVersion: string,
+  env: NodeJS.ProcessEnv = process.env,
+  overrides: PathShadowDeps = {}
+): ShadowingSummer | null {
+  const deps: Required<PathShadowDeps> = {
+    exists: overrides.exists ?? existsSync,
+    realpath: overrides.realpath ?? ((path) => realpathSync(path)),
+    readFile: overrides.readFile ?? ((path) => readFileSync(path, "utf-8")),
+    platform: overrides.platform ?? process.platform,
+    packageRoot: overrides.packageRoot ?? PACKAGE_ROOT,
+  };
+  const running = parseSemver(runningVersion);
+  if (!running) return null;
+  const names = deps.platform === "win32" ? ["summer.cmd", "summer.exe", "summer"] : ["summer"];
+  const ours = safeRealpath(deps.packageRoot, deps);
+  for (const dir of (env.PATH ?? env.Path ?? "").split(delimiter)) {
+    if (!dir) continue;
+    const bin = names.map((name) => join(dir, name)).find((path) => deps.exists(path));
+    if (!bin) continue;
+    let owner: { root: string; version: string } | null;
+    try {
+      owner = owningPackage(bin, deps);
+    } catch {
+      continue;
+    }
+    if (owner && safeRealpath(owner.root, deps) === ours) continue;
+    if (!owner) return null;
+    const found = parseSemver(owner.version);
+    if (!found || compareSemver(found, running) >= 0) return null;
+    return { path: bin, version: owner.version, homebrew: safeRealpath(bin, deps).includes(`${sep}Cellar${sep}`) };
+  }
+  return null;
+}
+
+function safeRealpath(path: string, deps: Required<PathShadowDeps>): string {
+  try {
+    return deps.realpath(path);
+  } catch {
+    return path;
+  }
+}
+
+/** The one warning line: which `summer` the shell runs, and the command that updates it. */
+export function shadowWarning(found: ShadowingSummer, runningVersion: string): string {
+  const update = found.homebrew ? "brew upgrade summerengine/tap/summer" : "npm install -g summer-engine@latest";
+  return `The summer command in your shell is ${found.version} (${found.path}), older than this setup (${runningVersion}), so summer login would run the old CLI. Update it: ${update}. Until then: npx -y summer-engine@latest login`;
+}