diff --git a/.changeset/not-installed.md b/.changeset/not-installed.md
new file mode 100644
index 0000000..c001305
--- /dev/null
+++ b/.changeset/not-installed.md
@@ -0,0 +1,5 @@
+---
+"uptide": patch
+---
+
+`fix` and `check` in a checkout whose dependencies are not installed now stop before any analysis with `PACKAGE_NOT_INSTALLED` (exit 2), name the `package.json` that declares the package, say whether nothing is installed or only that package is missing, and give the frozen install for the lockfile (`npm ci`, `pnpm install --frozen-lockfile`, `yarn install --frozen-lockfile`, `yarn install --immutable`). Before, a `node_modules` in a directory above the project counted as the project's install, so a fresh clone under such a directory got past the check and `fix` failed with a misleading "has no upgrade". Uptide still installs nothing in your checkout. `check --json` now answers every refusal on stdout with `{"error": {"code", "message"}}`, as `fix --json` does. When the package is already at or past the target, `fix` says "<package> is already at <version> (target <target>)".
diff --git a/docs/commands/check.md b/docs/commands/check.md
index 9b6ac70..266a6a2 100644
--- a/docs/commands/check.md
+++ b/docs/commands/check.md
@@ -28,7 +28,7 @@ whole-repository budgeted mode or `--max-time` flag. Install dependencies first.
 | `--all-deps` | also analyze `@types/*` and dependencies the repository never imports |
 | `--html [path]`, `--open` | a shareable report (below) |
 | `--cwd <dir>` | repository to work on |
-| `--json` | the full report as JSON on stdout |
+| `--json` | the full report as JSON on stdout; when the run stops before a report, `{"error": {"code", "message"}}` instead (exit 2) |
 | `--ci` | plain log output: no color, no spinner (`NO_COLOR` is respected too) |
 
 While it runs, a terminal shows one live line with the current phase, which disappears when
diff --git a/docs/troubleshooting.md b/docs/troubleshooting.md
index 93dea0c..868adf2 100644
--- a/docs/troubleshooting.md
+++ b/docs/troubleshooting.md
@@ -23,6 +23,19 @@ classic/Berry with the node-modules linker. Deno is not supported.
 lockfile` once (bun's own flag) so the repository has `bun.lock`, and `check` can read the
 installed versions.
 
+## "declared in package.json but not installed"
+
+`check` and `fix` compile your code against the version installed in `node_modules`, so
+they stop before any analysis when the package is not there, with the code `PACKAGE_NOT_INSTALLED`
+(exit 2; `--json` carries it in `error.code`). "nothing is installed (no node_modules)"
+means a fresh clone: install the dependencies, then run the same command again. "node_modules
+is there, without it" means a partial install, for example a workspace package installed on
+its own. The message names the `package.json` that declares the package, and the next
+command is the frozen install for the repository's lockfile: `npm ci`, `pnpm install
+--frozen-lockfile`, `yarn install --frozen-lockfile` or `yarn install --immutable`. Uptide
+never installs into your checkout. Only the project's own `node_modules` counts: a copy in a
+directory above the project root (a stray `~/node_modules`) is not its install.
+
 ## Package manager not available, or the wrong version
 
 `fix` runs the package manager the repository names in `packageManager` (corepack's choice),
diff --git a/packages/cli/src/__snapshots__/failures.test.ts.snap b/packages/cli/src/__snapshots__/failures.test.ts.snap
index 994cd57..1ac2077 100644
--- a/packages/cli/src/__snapshots__/failures.test.ts.snap
+++ b/packages/cli/src/__snapshots__/failures.test.ts.snap
@@ -1,11 +1,23 @@
 // Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
 
+exports[`friendly failures: each says what to run next > a copy above the project root is not its install (UPT-136) 1`] = `
+[
+  "  Next: pnpm install --frozen-lockfile",
+]
+`;
+
 exports[`friendly failures: each says what to run next > a dependency asked for by name that is not there: exit 2 1`] = `
 [
   "  Next: npx uptide",
 ]
 `;
 
+exports[`friendly failures: each says what to run next > a partial install names the package and the workspace that declares it 1`] = `
+[
+  "  Next: pnpm install --frozen-lockfile",
+]
+`;
+
 exports[`friendly failures: each says what to run next > a registry error thrown by the engine is the same failure 1`] = `
 [
   "  Next: run the same command again in a minute",
@@ -16,6 +28,18 @@ exports[`friendly failures: each says what to run next > a repository without zo
 
 exports[`friendly failures: each says what to run next > breaking found and a dependency failed: breaking is the answer (exit 1) 1`] = `[]`;
 
+exports[`friendly failures: each says what to run next > check --json answers a refusal with its code on stdout 1`] = `
+[
+  "  Next: pnpm install --frozen-lockfile",
+]
+`;
+
+exports[`friendly failures: each says what to run next > check --json answers a refusal with its code on stdout 2`] = `
+[
+  "  Next: npx uptide --json",
+]
+`;
+
 exports[`friendly failures: each says what to run next > declared but missing from the lockfile 1`] = `
 [
   "  Next: npm install",
@@ -42,6 +66,18 @@ exports[`friendly failures: each says what to run next > fix outside git, below
 ]
 `;
 
+exports[`friendly failures: each says what to run next > fix stops before any work when nothing is installed 1`] = `
+[
+  "  Next: pnpm install --frozen-lockfile",
+]
+`;
+
+exports[`friendly failures: each says what to run next > fix stops before any work when nothing is installed 2`] = `
+[
+  "  Next: pnpm install --frozen-lockfile",
+]
+`;
+
 exports[`friendly failures: each says what to run next > missing ANTHROPIC_API_KEY: fix still runs with the rules 1`] = `
 [
   "  Next: npx uptide fix zod   (set ANTHROPIC_API_KEY, OPENAI_API_KEY or GEMINI_API_KEY in your environment first)",
diff --git a/packages/cli/src/cli.ts b/packages/cli/src/cli.ts
index 372b48d..377e4e2 100644
--- a/packages/cli/src/cli.ts
+++ b/packages/cli/src/cli.ts
@@ -220,7 +220,7 @@ export async function run(
       } else {
         if (err instanceof CliError && err.options.next)
           err.options.next = suggest(err.options.next);
-        // `fix --json` answers on every exit, a failure included (UPT-107).
+        // `fix --json` and `check --json` answer on every exit, a failure included (UPT-107, UPT-136).
         if (flags.json && options.jsonErrors)
           emit({
             ...(err instanceof ReportedError ? err.report : {}),
@@ -736,7 +736,7 @@ ${EXIT_CODES(
             }
             return EXIT.ok;
           },
-          { quiet: !flags.verbose },
+          { quiet: !flags.verbose, jsonErrors: true },
         ),
     );
 
diff --git a/packages/cli/src/errors.ts b/packages/cli/src/errors.ts
index 0f38479..b8cd849 100644
--- a/packages/cli/src/errors.ts
+++ b/packages/cli/src/errors.ts
@@ -1,4 +1,5 @@
 import {
+  type ErrorCode,
   IntegrityError,
   NoTypesError,
   PackageNotFoundError,
@@ -13,6 +14,8 @@ export const EXIT = { ok: 0, breaking: 1, error: 2 } as const;
 /** A failure the user can act on. `next` is the exact command to run, when there is one. */
 export class CliError extends Error {
   override readonly name = 'CliError';
+  /** What `--json` reports; ANALYSIS_FAILED when unset. */
+  readonly code: ErrorCode | undefined;
   constructor(
     message: string,
     readonly options: {
@@ -20,9 +23,11 @@ export class CliError extends Error {
       next?: string;
       literalNext?: boolean;
       exitCode?: number;
+      code?: ErrorCode;
     } = {},
   ) {
     super(message);
+    this.code = options.code;
   }
 }
 
diff --git a/packages/cli/src/failures.test.ts b/packages/cli/src/failures.test.ts
index 278689e..2dbfefc 100644
--- a/packages/cli/src/failures.test.ts
+++ b/packages/cli/src/failures.test.ts
@@ -1,4 +1,4 @@
-import { writeFileSync } from 'node:fs';
+import { rmSync, writeFileSync } from 'node:fs';
 import { join } from 'node:path';
 import { type PackageReport, UptideError } from '@uptide/core';
 import { describe, expect, it } from 'vitest';
@@ -86,11 +86,84 @@ describe('friendly failures: each says what to run next', () => {
     );
     expect(code).toBe(2);
     expect(stderr).toContain('✖ Dependencies');
-    expect(stderr).toContain('error: zod and stripe are in the lockfile but not installed');
+    expect(stderr).toContain(
+      'error: zod and stripe are declared in package.json but not installed: nothing is installed (no node_modules)',
+    );
     expect(stderr).toContain(`Next: ${next}\n`);
     expect(engine.calls).toEqual([]);
   });
 
+  it('a partial install names the package and the workspace that declares it', async () => {
+    const cwd = tempRepo({
+      'package.json': '{"name":"mono"}',
+      'pnpm-lock.yaml': '',
+      'packages/api/package.json': manifest,
+      'node_modules/stripe/package.json': '{}',
+    });
+    const engine = fakeEngine({
+      workspaces: async () => ['.', 'packages/api'],
+      declared: async (dir) =>
+        new Map(dir.endsWith('api') ? [['zod', '^3.23.8']] : [['stripe', '14.25.0']]),
+    });
+    const { code, stderr } = await fail(['check', 'zod'], cwd, engine);
+    expect(code).toBe(2);
+    expect(stderr).toContain(
+      'error: zod is declared in packages/api/package.json but not installed: node_modules is there, without it',
+    );
+    expect(stderr).toContain('Next: pnpm install --frozen-lockfile\n');
+    expect(engine.calls).toEqual([]);
+  });
+
+  it('a copy above the project root is not its install (UPT-136)', async () => {
+    const parent = tempRepo({
+      'node_modules/zod/package.json': '{"name":"zod","version":"4.6.5"}',
+      'shop/package.json': manifest,
+      'shop/pnpm-lock.yaml': '',
+    });
+    const { code, stderr } = await fail(['check', 'zod'], join(parent, 'shop'));
+    expect(code).toBe(2);
+    expect(stderr).toContain(
+      'error: zod is declared in package.json but not installed: nothing is installed (no node_modules)',
+    );
+  });
+
+  it('fix stops before any work when nothing is installed', async () => {
+    const root = pnpmGitRepo();
+    rmSync(join(root, 'node_modules'), { recursive: true });
+    const { code, stderr, engine } = await fail(['fix', '--only', 'zod'], root);
+    expect(code).toBe(2);
+    expect(stderr).toContain('✖ Repository');
+    expect(stderr).toContain(
+      'error: zod is declared in package.json but not installed: nothing is installed (no node_modules)',
+    );
+    expect(stderr).toContain('Next: pnpm install --frozen-lockfile\n');
+    expect(engine.calls).toEqual([]);
+    const json = await fail(['fix', '--only', 'zod', '--json'], root);
+    expect(json.code).toBe(2);
+    expect(JSON.parse(json.stdout).error.code).toBe('PACKAGE_NOT_INSTALLED');
+  });
+
+  it('check --json answers a refusal with its code on stdout', async () => {
+    const missing = await fail(
+      ['check', 'zod', '--json'],
+      tempRepo({ 'package.json': manifest, 'pnpm-lock.yaml': '' }),
+    );
+    expect(missing.code).toBe(2);
+    expect(JSON.parse(missing.stdout)).toEqual({
+      error: {
+        code: 'PACKAGE_NOT_INSTALLED',
+        message:
+          'zod is declared in package.json but not installed: nothing is installed (no node_modules)',
+      },
+    });
+    const engine = fakeEngine({ declared: async () => new Map([['zod', '^3.23.8']]) });
+    const absent = await fail(['check', '--only', 'stripe', '--json'], npmRepo(), engine);
+    expect(absent.code).toBe(2);
+    expect(JSON.parse(absent.stdout)).toEqual({
+      error: { code: 'ANALYSIS_FAILED', message: 'stripe is not a dependency of shop' },
+    });
+  });
+
   it('missing Berry installation names the immutable install command', async () => {
     const { code, stderr } = await fail(
       ['check', 'zod', 'stripe'],
diff --git a/packages/cli/src/failures.ts b/packages/cli/src/failures.ts
index 8b80d1b..4a008d7 100644
--- a/packages/cli/src/failures.ts
+++ b/packages/cli/src/failures.ts
@@ -50,11 +50,23 @@ export function yarnPlugAndPlay(root: string): CliError {
   });
 }
 
-export function missingNodeModules(repo: Repo, missing: readonly string[]): CliError {
+/** Each missing dependency with a workspace that declares it. */
+export function missingNodeModules(
+  repo: Repo,
+  missing: readonly { name: string; workspace: string }[],
+): CliError {
+  const and = (list: readonly string[]) => names(list).replace(' or ', ' and ');
+  const one = missing.length === 1;
+  const manifests = [...new Set(missing.map((m) => join(m.workspace, 'package.json')))];
   return new CliError(
-    `${names(missing).replace(' or ', ' and ')} ${missing.length === 1 ? 'is' : 'are'} in the lockfile but not installed in node_modules`,
+    `${and(missing.map((m) => m.name))} ${one ? 'is' : 'are'} declared in ${and(manifests)} but not installed: ${
+      existsSync(join(repo.root, 'node_modules'))
+        ? `node_modules is there, without ${one ? 'it' : 'them'}`
+        : 'nothing is installed (no node_modules)'
+    }`,
     {
-      why: 'The analysis compiles your code against the installed and the target version.',
+      code: 'PACKAGE_NOT_INSTALLED',
+      why: 'Install the dependencies first, then run the same command again. The analysis compiles your code against the installed and the target version.',
       next:
         repo.manager === 'yarn' &&
         (existsSync(join(dirname(repo.lockfile), '.yarnrc.yml')) ||
@@ -133,11 +145,16 @@ export function networkFailure(report: CheckResult): CliError | undefined {
     : undefined;
 }
 
-/** Whether `name` resolves from `dir` the way Node would look it up. */
-function installedIn(dir: string, name: string): boolean {
-  for (let current = dir; ; current = dirname(current)) {
+/**
+ * Whether `name` resolves from workspace `w` the way Node would look it up, up to the
+ * project root: a copy above it (a stray `~/node_modules`) is not this repository's install
+ * (UPT-136).
+ */
+function installedIn(repo: Repo, w: string, name: string): boolean {
+  const top = resolve(repo.root);
+  for (let current = join(top, w); ; current = dirname(current)) {
     if (existsSync(join(current, 'node_modules', name, 'package.json'))) return true;
-    if (dirname(current) === current) return false;
+    if (current === top || dirname(current) === current) return false;
   }
 }
 
@@ -145,9 +162,10 @@ function installedIn(dir: string, name: string): boolean {
 export function requireInstalled(repo: Repo, dependencies: readonly DependencyStatus[]): void {
   for (const dep of dependencies)
     if (dep.workspaces.length > 0 && !dep.installed) throw notInLockfile(repo, dep.name);
-  const missing = dependencies
-    .filter((dep) => dep.workspaces.some((w) => !installedIn(join(repo.root, w), dep.name)))
-    .map((dep) => dep.name);
+  const missing = dependencies.flatMap((dep) => {
+    const workspace = dep.workspaces.find((w) => !installedIn(repo, w, dep.name));
+    return workspace === undefined ? [] : [{ name: dep.name, workspace }];
+  });
   if (missing.length > 0) throw missingNodeModules(repo, missing);
 }
 
@@ -159,12 +177,12 @@ export function requireInstalled(repo: Repo, dependencies: readonly DependencySt
 export function requireNodeModules(repo: Repo, dependencies: readonly DependencyStatus[]): void {
   const declared = dependencies.filter((dep) => dep.workspaces.length > 0);
   const missing = declared.filter((dep) =>
-    dep.workspaces.every((w) => !installedIn(join(repo.root, w), dep.name)),
+    dep.workspaces.every((w) => !installedIn(repo, w, dep.name)),
   );
   if (declared.length > 0 && missing.length === declared.length)
     throw missingNodeModules(
       repo,
-      missing.slice(0, 3).map((dep) => dep.name),
+      missing.slice(0, 3).map((dep) => ({ name: dep.name, workspace: dep.workspaces[0] ?? '.' })),
     );
 }
 
diff --git a/packages/core/src/fix/isolate.test.ts b/packages/core/src/fix/isolate.test.ts
index e40bb8c..e1ab187 100644
--- a/packages/core/src/fix/isolate.test.ts
+++ b/packages/core/src/fix/isolate.test.ts
@@ -1291,6 +1291,36 @@ describe('preflight refusals become agent-led drafts with an agent (UPT-78)', ()
     expect(result.agentFallback?.join(';')).toContain('the check returned nothing to analyze');
   });
 
+  it('an empty check without an install says so, not "has no upgrade" (UPT-136)', async () => {
+    const { root, services } = zodFixture(scratch);
+    const empty = async () => ({ ...(await services.check({ cwd: root })), packages: [] });
+    rmSync(join(root, 'node_modules'), { recursive: true });
+    const error = await isolatedFix(
+      { cwd: root, ...agent },
+      { ...services, check: empty, agentRunner: runner() },
+    ).catch((e: unknown) => e);
+    expect(error).toMatchObject({
+      code: 'PACKAGE_NOT_INSTALLED',
+      message:
+        'zod is declared in package.json but not installed. Install the dependencies first: pnpm install --frozen-lockfile, then run uptide fix zod again.',
+    });
+  });
+
+  it('a package already at the target says so', async () => {
+    const { root, services } = zodFixture(scratch);
+    const empty = async () => ({ ...(await services.check({ cwd: root })), packages: [] });
+    writeFileSync(
+      join(root, 'node_modules/zod/package.json'),
+      JSON.stringify({ name: 'zod', version: '4.6.5', types: 'index.d.ts' }),
+    );
+    await expect(
+      isolatedFix(
+        { cwd: root, only: 'zod', fixer: null, tool: TOOL },
+        { ...services, check: empty },
+      ),
+    ).rejects.toThrow(/^zod is already at 4\.6\.5 \(target 4\.6\.5\)$/);
+  });
+
   it('never falls back on a safety refusal', async () => {
     const { root, services } = zodFixture(scratch);
     const planner = vi
diff --git a/packages/core/src/fix/managers/manager.test.ts b/packages/core/src/fix/managers/manager.test.ts
index f4b555f..dbf841d 100644
--- a/packages/core/src/fix/managers/manager.test.ts
+++ b/packages/core/src/fix/managers/manager.test.ts
@@ -4,7 +4,7 @@ import { join } from 'node:path';
 import { afterAll, expect, it } from 'vitest';
 import { versionRange } from '../versions.js';
 import { assertLockScope } from './lock-guard.js';
-import { berrySkipBuild, packageManager, updateArgs } from './manager.js';
+import { berrySkipBuild, frozenInstall, packageManager, updateArgs } from './manager.js';
 import { pnpmGraph, yarnGraph } from './text-lock.js';
 
 const roots: string[] = [];
@@ -18,6 +18,14 @@ function fixture(files: Record<string, string | undefined>) {
   for (const [f, t] of Object.entries(files)) if (t !== undefined) writeFileSync(join(root, f), t);
   return root;
 }
+it.each([
+  [{ 'package-lock.json': '{"lockfileVersion":3}' }, 'npm ci'],
+  [{ 'pnpm-lock.yaml': '' }, 'pnpm install --frozen-lockfile'],
+  [{ 'yarn.lock': '' }, 'yarn install --frozen-lockfile'],
+  [{ 'yarn.lock': '__metadata:\n  version: 8\n' }, 'yarn install --immutable'],
+])('the install a person runs for %j is %s', (files, command) => {
+  expect(frozenInstall(packageManager(fixture(files)))).toBe(command);
+});
 it.each(['^', '~', ''])('preserves the %s range style', (style) => {
   expect(versionRange(`${style}3.23.8`, '4.6.5')).toBe(`${style}4.6.5`);
 });
diff --git a/packages/core/src/fix/managers/manager.ts b/packages/core/src/fix/managers/manager.ts
index 1e9c611..4d106d8 100644
--- a/packages/core/src/fix/managers/manager.ts
+++ b/packages/core/src/fix/managers/manager.ts
@@ -102,6 +102,15 @@ export function packageManager(root: string): PackageManager {
     'fix supports npm (lockfile v2/v3), pnpm, and Yarn classic/Berry; no supported lockfile found',
   );
 }
+/** The install a person runs to get exactly what the lockfile pins. */
+export function frozenInstall(pm: PackageManager): string {
+  return {
+    npm: 'npm ci',
+    pnpm: 'pnpm install --frozen-lockfile',
+    'yarn-classic': 'yarn install --frozen-lockfile',
+    'yarn-berry': 'yarn install --immutable',
+  }[pm.kind];
+}
 /** Manifests have already been updated, so npm can preserve dependency sections with no add/save flags. */
 export function updateArgs(pm: PackageManager, root: string, workspaces: string[]): string[] {
   const args = managerArgs(pm, root, workspaces);
diff --git a/packages/core/src/fix/run.ts b/packages/core/src/fix/run.ts
index bd833d3..46e6ea0 100644
--- a/packages/core/src/fix/run.ts
+++ b/packages/core/src/fix/run.ts
@@ -123,6 +123,7 @@ import {
   assertNoDowngrades,
   bumpVersions,
   declareLead,
+  frozenInstall,
   install,
   packageManager,
   removeDeclarations,
@@ -496,10 +497,23 @@ async function fixPackage(options: FixOptions, services: FixServices): Promise<F
   );
   if (!packages.length) {
     // Installed below the target, yet the check returned nothing to work from: say that.
-    const behind = fallbackReport(root, pack.name, target, '').packages.filter(
-      (p) => p.installed !== 'unknown' && compareVersions(p.installed, target) < 0,
-    );
-    if (!behind.length) throw new Error(`${pack.name} has no upgrade to ${target}`);
+    const declared = fallbackReport(root, pack.name, target, '').packages;
+    // Nothing installed reads as nothing to upgrade; the cause is the install (UPT-136).
+    const missing = declared.find((p) => p.installed === 'unknown');
+    if (missing)
+      throw new UptideError(
+        'PACKAGE_NOT_INSTALLED',
+        `${pack.name} is declared in ${join(missing.workspace, 'package.json')} but not installed. Install the dependencies first: ${frozenInstall(packageManager(root))}, then run uptide fix ${pack.name} again.`,
+      );
+    const behind = declared.filter((p) => compareVersions(p.installed, target) < 0);
+    // Everything declared is at or past the target (an alternate lead declares nothing here).
+    const at = declared.map((p) => p.installed).sort(compareVersions)[0];
+    if (!behind.length)
+      throw new Error(
+        at
+          ? `${pack.name} is already at ${at} (target ${target})`
+          : `${pack.name} is not declared in any package.json of this repository`,
+      );
     const reason = `the check returned nothing to analyze for ${pack.name} ${behind[0]?.installed} → ${target} (no import or pack site found)`;
     if (!canAssist) throw new UptideError('INCOMPLETE_CHECK', `${reason}. Nothing was changed.`);
     fallback.push(`Planner refused: ${reason}`);
diff --git a/packages/core/src/fix/versions.ts b/packages/core/src/fix/versions.ts
index 7db8f59..d17f0d9 100644
--- a/packages/core/src/fix/versions.ts
+++ b/packages/core/src/fix/versions.ts
@@ -2,7 +2,7 @@ import { assertManagerAvailable } from './managers/availability.js';
 import { isolatedUpgrade } from './managers/isolated-install.js';
 import type { InstallReport, Upgrade } from './managers/upgrade.js';
 
-export { packageManager } from './managers/manager.js';
+export { frozenInstall, packageManager } from './managers/manager.js';
 
 import { readFileSync, writeFileSync } from 'node:fs';
 import { join, relative } from 'node:path';