diff --git a/tests/scanners/accurate-tokens.test.mjs b/tests/scanners/accurate-tokens.test.mjs
index 5d7e92a..ee919c7 100644
--- a/tests/scanners/accurate-tokens.test.mjs
+++ b/tests/scanners/accurate-tokens.test.mjs
@@ -4,6 +4,7 @@ import { resolve } from 'node:path';
 import { fileURLToPath } from 'node:url';
 import { execFile } from 'node:child_process';
 import { promisify } from 'node:util';
+import { hermeticEnv } from '../helpers/hermetic-home.mjs';
 
 const exec = promisify(execFile);
 const __dirname = fileURLToPath(new URL('.', import.meta.url));
@@ -14,7 +15,8 @@ const FIXTURE = resolve(REPO, 'tests/fixtures/marketplace-large');
 
 describe('--accurate-tokens (no API key)', () => {
   it('skips API calibration and reports calibration.skipped === "no-api-key"', async () => {
-    const env = { ...process.env };
+    // Isolate HOME (TOK reads the CLAUDE.md cascade) while dropping the API key.
+    const env = hermeticEnv();
     delete env.ANTHROPIC_API_KEY;
     const { stdout, stderr } = await exec(
       'node',
@@ -30,6 +32,7 @@ describe('--accurate-tokens (no API key)', () => {
     const { stdout } = await exec('node', [CLI, FIXTURE, '--json'], {
       timeout: 30000,
       cwd: REPO,
+      env: hermeticEnv(),
     });
     const json = JSON.parse(stdout);
     assert.equal(json.calibration, undefined);
diff --git a/tests/scanners/drift-cli.test.mjs b/tests/scanners/drift-cli.test.mjs
index f7c7ade..2e44bec 100644
--- a/tests/scanners/drift-cli.test.mjs
+++ b/tests/scanners/drift-cli.test.mjs
@@ -4,24 +4,28 @@ import { resolve, join } from 'node:path';
 import { fileURLToPath } from 'node:url';
 import { execFileSync } from 'node:child_process';
 import { deleteBaseline } from '../../scanners/lib/baseline.mjs';
+import { hermeticEnv, withHermeticHome } from '../helpers/hermetic-home.mjs';
 
 const __dirname = fileURLToPath(new URL('.', import.meta.url));
 const FIXTURES = resolve(__dirname, '../fixtures');
 const HEALTHY = resolve(FIXTURES, 'healthy-project');
 const DRIFT_CLI = resolve(__dirname, '../../scanners/drift-cli.mjs');
 
+// Isolate HOME: drift runs a full scan (HOME-scoped SKL/COL) AND writes its
+// baselines under ~/.claude. Without this, the CLI would pollute the real
+// ~/.claude during the run. See tests/helpers/hermetic-home.mjs.
+const RUN = { encoding: 'utf-8', timeout: 30000, env: hermeticEnv() };
+
 const TEST_BASELINE = `_drift_test_${Date.now()}`;
 
 afterEach(async () => {
-  await deleteBaseline(TEST_BASELINE);
+  // Cleanup must look in the SAME hermetic HOME the CLI wrote to.
+  await withHermeticHome(() => deleteBaseline(TEST_BASELINE));
 });
 
 describe('drift-cli --save', () => {
   it('saves a baseline and confirms', () => {
-    const result = execFileSync('node', [DRIFT_CLI, HEALTHY, '--save', '--name', TEST_BASELINE, '--json'], {
-      encoding: 'utf-8',
-      timeout: 30000,
-    });
+    const result = execFileSync('node', [DRIFT_CLI, HEALTHY, '--save', '--name', TEST_BASELINE, '--json'], RUN);
     const output = JSON.parse(result);
     assert.equal(output.saved, true);
     assert.equal(output.name, TEST_BASELINE);
@@ -32,15 +36,9 @@ describe('drift-cli --save', () => {
 describe('drift-cli --list', () => {
   it('lists baselines including saved one', async () => {
     // Save first
-    execFileSync('node', [DRIFT_CLI, HEALTHY, '--save', '--name', TEST_BASELINE], {
-      encoding: 'utf-8',
-      timeout: 30000,
-    });
+    execFileSync('node', [DRIFT_CLI, HEALTHY, '--save', '--name', TEST_BASELINE], RUN);
 
-    const result = execFileSync('node', [DRIFT_CLI, '--list', '--json'], {
-      encoding: 'utf-8',
-      timeout: 30000,
-    });
+    const result = execFileSync('node', [DRIFT_CLI, '--list', '--json'], RUN);
     const output = JSON.parse(result);
     assert.ok(Array.isArray(output.baselines));
     const found = output.baselines.find(b => b.name === TEST_BASELINE);
@@ -51,16 +49,10 @@ describe('drift-cli --list', () => {
 describe('drift-cli compare', () => {
   it('outputs valid JSON with --json flag', () => {
     // Save baseline first
-    execFileSync('node', [DRIFT_CLI, HEALTHY, '--save', '--name', TEST_BASELINE], {
-      encoding: 'utf-8',
-      timeout: 30000,
-    });
+    execFileSync('node', [DRIFT_CLI, HEALTHY, '--save', '--name', TEST_BASELINE], RUN);
 
     // Compare same fixture against itself
-    const result = execFileSync('node', [DRIFT_CLI, HEALTHY, '--baseline', TEST_BASELINE, '--json'], {
-      encoding: 'utf-8',
-      timeout: 30000,
-    });
+    const result = execFileSync('node', [DRIFT_CLI, HEALTHY, '--baseline', TEST_BASELINE, '--json'], RUN);
     const diff = JSON.parse(result);
     assert.ok('newFindings' in diff);
     assert.ok('resolvedFindings' in diff);
@@ -71,15 +63,9 @@ describe('drift-cli compare', () => {
   });
 
   it('shows stable trend when comparing same fixture', () => {
-    execFileSync('node', [DRIFT_CLI, HEALTHY, '--save', '--name', TEST_BASELINE], {
-      encoding: 'utf-8',
-      timeout: 30000,
-    });
+    execFileSync('node', [DRIFT_CLI, HEALTHY, '--save', '--name', TEST_BASELINE], RUN);
 
-    const result = execFileSync('node', [DRIFT_CLI, HEALTHY, '--baseline', TEST_BASELINE, '--json'], {
-      encoding: 'utf-8',
-      timeout: 30000,
-    });
+    const result = execFileSync('node', [DRIFT_CLI, HEALTHY, '--baseline', TEST_BASELINE, '--json'], RUN);
     const diff = JSON.parse(result);
     assert.equal(diff.summary.trend, 'stable');
     assert.equal(diff.summary.newCount, 0);
@@ -88,10 +74,7 @@ describe('drift-cli compare', () => {
 
   it('exits with code 1 when baseline not found', () => {
     assert.throws(() => {
-      execFileSync('node', [DRIFT_CLI, HEALTHY, '--baseline', `nonexistent_${Date.now()}`, '--json'], {
-        encoding: 'utf-8',
-        timeout: 30000,
-      });
+      execFileSync('node', [DRIFT_CLI, HEALTHY, '--baseline', `nonexistent_${Date.now()}`, '--json'], RUN);
     }, (err) => {
       assert.equal(err.status, 1);
       return true;
diff --git a/tests/scanners/posture.test.mjs b/tests/scanners/posture.test.mjs
index 40d6a4f..5821252 100644
--- a/tests/scanners/posture.test.mjs
+++ b/tests/scanners/posture.test.mjs
@@ -4,6 +4,7 @@ import { resolve } from 'node:path';
 import { fileURLToPath } from 'node:url';
 import { execFile } from 'node:child_process';
 import { promisify } from 'node:util';
+import { hermeticEnv } from '../helpers/hermetic-home.mjs';
 
 const exec = promisify(execFile);
 const __dirname = fileURLToPath(new URL('.', import.meta.url));
@@ -11,9 +12,13 @@ const FIXTURES = resolve(__dirname, '../fixtures');
 const POSTURE_BIN = resolve(__dirname, '../../scanners/posture.mjs');
 
 async function runPosture(args) {
+  // Isolate HOME: posture runs the HOME-scoped SKL/COL scanners + CLAUDE.md
+  // cascade, so a real ~/.claude would leak the developer's plugins/skills
+  // into grades and counts. See tests/helpers/hermetic-home.mjs.
   const { stdout, stderr } = await exec('node', [POSTURE_BIN, ...args], {
     timeout: 30000,
     cwd: resolve(__dirname, '../..'),
+    env: hermeticEnv(),
   });
   return { stdout, stderr };
 }
diff --git a/tests/scanners/token-hotspots-cli.test.mjs b/tests/scanners/token-hotspots-cli.test.mjs
index f6bfde5..7e2289e 100644
--- a/tests/scanners/token-hotspots-cli.test.mjs
+++ b/tests/scanners/token-hotspots-cli.test.mjs
@@ -5,6 +5,7 @@ import { fileURLToPath } from 'node:url';
 import { execFile } from 'node:child_process';
 import { promisify } from 'node:util';
 import { readFile, unlink } from 'node:fs/promises';
+import { hermeticEnv } from '../helpers/hermetic-home.mjs';
 
 const exec = promisify(execFile);
 const __dirname = fileURLToPath(new URL('.', import.meta.url));
@@ -12,12 +13,16 @@ const REPO = resolve(__dirname, '../..');
 const CLI = resolve(REPO, 'scanners/token-hotspots-cli.mjs');
 const ORCH = resolve(REPO, 'scanners/scan-orchestrator.mjs');
 const FIXTURE = resolve(REPO, 'tests/fixtures/marketplace-large');
+// Isolate HOME: the scan-orchestrator run executes HOME-scoped SKL/COL, and
+// TOK reads the CLAUDE.md cascade (which includes ~/.claude). See hermetic-home.mjs.
+const ENV = hermeticEnv();
 
 describe('token-hotspots-cli', () => {
   it('returns valid JSON with hotspots.length >= 3', async () => {
     const { stdout } = await exec('node', [CLI, FIXTURE, '--json'], {
       timeout: 30000,
       cwd: REPO,
+      env: ENV,
     });
     const json = JSON.parse(stdout);
     assert.equal(json.scanner, 'TOK');
@@ -33,6 +38,7 @@ describe('token-hotspots-cli', () => {
       await exec('node', [CLI, FIXTURE, '--output-file', out], {
         timeout: 30000,
         cwd: REPO,
+        env: ENV,
       });
       const written = await readFile(out, 'utf-8');
       const json = JSON.parse(written);
@@ -47,6 +53,7 @@ describe('token-hotspots-cli', () => {
     const { stdout } = await exec('node', [CLI, FIXTURE, '--json'], {
       timeout: 30000,
       cwd: REPO,
+      env: ENV,
     });
     const json = JSON.parse(stdout);
     assert.equal(json.telemetry_recipe_path, undefined,
@@ -57,6 +64,7 @@ describe('token-hotspots-cli', () => {
     const { stdout } = await exec('node', [CLI, FIXTURE, '--json', '--with-telemetry-recipe'], {
       timeout: 30000,
       cwd: REPO,
+      env: ENV,
     });
     const json = JSON.parse(stdout);
     assert.equal(typeof json.telemetry_recipe_path, 'string');
@@ -75,6 +83,7 @@ describe('scan-orchestrator integration — TOK hotspots survive envelope', () =
       await exec('node', [ORCH, FIXTURE, '--output-file', out], {
         timeout: 60000,
         cwd: REPO,
+        env: ENV,
       });
       const written = await readFile(out, 'utf-8');
       const envelope = JSON.parse(written);