diff --git a/tests/check-gap-analysis-plan-post-e2e.test.cjs b/tests/check-gap-analysis-plan-post-e2e.test.cjs
index 3a3044539..282c1501f 100644
--- a/tests/check-gap-analysis-plan-post-e2e.test.cjs
+++ b/tests/check-gap-analysis-plan-post-e2e.test.cjs
@@ -23,7 +23,7 @@ const path = require('path');
 const os = require('os');
 const { spawnSync } = require('child_process');
 
-const { runGsdTools, createTempProject, cleanup } = require('./helpers.cjs');
+const { runGsdTools, createTempProject, cleanup, installSpawnEnv, withAmbientCapabilityHome } = require('./helpers.cjs');
 const { LOOP_HOOK_POINT_CLI_TIMEOUT_MS } = require('./helpers/timeouts.cjs');
 
 const GSD_TOOLS = path.join(__dirname, '..', 'gsd-core', 'bin', 'gsd-tools.cjs');
@@ -77,7 +77,7 @@ function spawnRenderHooks(point, cwd) {
     cwd,
     encoding: 'utf8',
     timeout: LOOP_HOOK_POINT_CLI_TIMEOUT_MS,
-    env: { ...process.env, GSD_SESSION_KEY: '', CODEX_THREAD_ID: '', CLAUDE_SESSION_ID: '' },
+    env: installSpawnEnv({ GSD_SESSION_KEY: '', CODEX_THREAD_ID: '', CLAUDE_SESSION_ID: '' }),
   });
   return {
     status: result.status,
@@ -137,6 +137,15 @@ describe('render-hooks plan:post — gate discovery', () => {
     assert.ok(envelope.rendered.includes('gap-analysis.plan-post'), 'rendered must include check query');
   });
 
+  test('#4485: render-hooks ignores capabilities installed in ambient user locations', (t) => {
+    withAmbientCapabilityHome(t, 'gsd-ambient-plan-post-', 'ambient-plan-post', 'plan:post');
+
+    const result = spawnRenderHooks('plan:post', tmpDir);
+    assert.strictEqual(result.status, 0, `exit non-zero: ${result.stderr}`);
+    const activeHooks = JSON.parse(result.stdout).activeHooks;
+    assert.deepStrictEqual(activeHooks.map((hook) => [hook.capId, hook.check?.query]), [['gap-analysis', 'gap-analysis.plan-post']]);
+  });
+
   test('[negative] render-hooks plan:post returns empty activeHooks when workflow.post_planning_gaps=false (gate deactivated)', () => {
     fs.writeFileSync(
       path.join(tmpDir, '.planning', 'config.json'),
diff --git a/tests/execute-wave-post-gate-pipeline-e2e.test.cjs b/tests/execute-wave-post-gate-pipeline-e2e.test.cjs
index 1643d7fde..46920c61e 100644
--- a/tests/execute-wave-post-gate-pipeline-e2e.test.cjs
+++ b/tests/execute-wave-post-gate-pipeline-e2e.test.cjs
@@ -29,7 +29,7 @@ const os = require('node:os');
 const path = require('node:path');
 const { spawnSync } = require('node:child_process');
 
-const { cleanup } = require('./helpers.cjs');
+const { cleanup, installSpawnEnv, withAmbientCapabilityHome } = require('./helpers.cjs');
 const { gitOrThrow } = require('./helpers/git-fixture.cjs');
 const { LOOP_HOOK_POINT_CLI_TIMEOUT_MS } = require('./helpers/timeouts.cjs');
 
@@ -61,14 +61,13 @@ function gitAddCommit(dir, message) {
  * When raw=true the tool emits JSON; parsed is set on success.
  */
 function runTool(args, { cwd, env = {} } = {}) {
-  const childEnv = {
-    ...process.env,
+  const childEnv = installSpawnEnv({
     GSD_SESSION_KEY: '',
     CODEX_THREAD_ID: '',
     CLAUDE_SESSION_ID: '',
     CLAUDE_CODE_SSE_PORT: '',
     ...env,
-  };
+  });
   const r = spawnSync(process.execPath, [GSD_TOOLS, ...args], {
     cwd: cwd || os.tmpdir(),
     encoding: 'utf8',
@@ -97,6 +96,18 @@ after(() => { for (const d of tmpDirs) { try { cleanup(d); } catch { /* best-eff
 
 describe('A. loop render-hooks execute:wave:post — resolution', () => {
 
+  test('#4485: render-hooks ignores capabilities installed in ambient user locations', (t) => {
+    withAmbientCapabilityHome(t, 'gsd-ambient-wave-post-', 'ambient-wave-post', 'execute:wave:post');
+
+    const dir = makeTmpDir();
+    const result = runTool(['loop', 'render-hooks', 'execute:wave:post', '--raw'], { cwd: dir });
+    assert.strictEqual(result.status, 0, result.stderr);
+    assert.deepStrictEqual(
+      result.parsed.activeHooks.map((hook) => [hook.capId, hook.check?.query]),
+      [['drift', 'verify.schema-drift'], ['drift', 'verify.codebase-drift'], ['ui', 'ui.safety-gate']],
+    );
+  });
+
   test('[happy] full resolution: all 3 gates present with default config', () => {
     const dir = makeTmpDir();
     fs.mkdirSync(path.join(dir, '.planning'), { recursive: true });
diff --git a/tests/helpers.cjs b/tests/helpers.cjs
index a55d96cd6..c03e47c50 100644
--- a/tests/helpers.cjs
+++ b/tests/helpers.cjs
@@ -1251,7 +1251,50 @@ function writePackageSourceMarkerFixture(configDir) {
   return configDir;
 }
 
-module.exports = { runGsdTools, createTempDir, createTempProject, createTempGitProject, cleanup, tmpRootCandidates, readFileNormalized, readWorkflowCombined, parseFrontmatter, isUsageOutput, captureConsole, toPosixPath, absPlanningPath, runNpm, isolatedNpmEnv, withIsolatedProcessState, delay, waitFor, resetRuntimeWarningCaches, SESSION_ENV_KEYS, saveSessionEnv, restoreSessionEnv, clearSessionEnv, isolateWorkstreamEnv, restoreWorkstreamEnv, TOOLS_PATH, SESSION_IDENTITY_ENV_KEYS, scrubConfigLocationEnv, installSpawnEnv, installSpawnHome, sandboxHome, writePackageSourceMarkerFixture, TEST_HOME_SANDBOX_MARKER, mockPartialWriteThenThrow, captureFdSync, suppressFdAsync };
+/** Write one valid third-party gate into a synthetic user capability home. */
+function writeAmbientCapabilityGate(home, id, point) {
+  const capDir = path.join(home, '.gsd', 'capabilities', id);
+  fs.mkdirSync(capDir, { recursive: true });
+  fs.writeFileSync(path.join(capDir, 'capability.json'), JSON.stringify({
+    id,
+    title: 'Ambient test capability',
+    version: '1.0.0',
+    role: 'feature',
+    tier: 'full',
+    description: 'Capability outside the test fixture that must remain invisible.',
+    engines: { gsd: '>=1.7.0' },
+    requires: [],
+    runtimeCompat: { supported: ['claude'], unsupported: [] },
+    skills: [],
+    agents: [],
+    config: {},
+    steps: [],
+    contributions: [],
+    gates: [{ point, check: { query: 'ambient.check' }, blocking: false, onError: 'skip' }],
+  }), 'utf8');
+}
+
+/**
+ * Put a capability in the parent process's ambient home for one serial test.
+ * The child must still receive installSpawnEnv()'s different sandbox home.
+ */
+function withAmbientCapabilityHome(t, prefix, id, point) {
+  const home = createTempDir(prefix);
+  writeAmbientCapabilityGate(home, id, point);
+  const previous = { HOME: process.env.HOME, USERPROFILE: process.env.USERPROFILE };
+  process.env.HOME = home;
+  process.env.USERPROFILE = home;
+  t.after(() => {
+    for (const [key, value] of Object.entries(previous)) {
+      if (value === undefined) delete process.env[key];
+      else process.env[key] = value;
+    }
+    cleanup(home);
+  });
+  return home;
+}
+
+module.exports = { runGsdTools, createTempDir, createTempProject, createTempGitProject, cleanup, tmpRootCandidates, readFileNormalized, readWorkflowCombined, parseFrontmatter, isUsageOutput, captureConsole, toPosixPath, absPlanningPath, runNpm, isolatedNpmEnv, withIsolatedProcessState, delay, waitFor, resetRuntimeWarningCaches, SESSION_ENV_KEYS, saveSessionEnv, restoreSessionEnv, clearSessionEnv, isolateWorkstreamEnv, restoreWorkstreamEnv, TOOLS_PATH, SESSION_IDENTITY_ENV_KEYS, scrubConfigLocationEnv, installSpawnEnv, installSpawnHome, sandboxHome, writePackageSourceMarkerFixture, writeAmbientCapabilityGate, withAmbientCapabilityHome, TEST_HOME_SANDBOX_MARKER, mockPartialWriteThenThrow, captureFdSync, suppressFdAsync };
 
 // Lazy, for the reason builtLib() is lazy: reading either of these is what
 // forces the built-lib require, so a test file that needs neither can still
diff --git a/tests/plan-pre-hook-e2e.test.cjs b/tests/plan-pre-hook-e2e.test.cjs
index a0411a316..9265324e8 100644
--- a/tests/plan-pre-hook-e2e.test.cjs
+++ b/tests/plan-pre-hook-e2e.test.cjs
@@ -29,7 +29,7 @@ const os = require('node:os');
 const path = require('node:path');
 const { spawnSync } = require('node:child_process');
 
-const { cleanup } = require('./helpers.cjs');
+const { cleanup, installSpawnEnv, withAmbientCapabilityHome } = require('./helpers.cjs');
 
 const GSD_TOOLS = path.join(__dirname, '..', 'gsd-core', 'bin', 'gsd-tools.cjs');
 
@@ -66,7 +66,7 @@ const CLEAN_ENV = {
 
 /**
  * Run gsd-tools via spawnSync. Returns { status, stdout, stderr }.
- * Passes env overrides merged on top of process.env + CLEAN_ENV.
+ * Passes env overrides through the canonical sandboxed child environment.
  */
 function runTools(args, cwd, envOverrides = {}) {
   return spawnSync(
@@ -76,7 +76,7 @@ function runTools(args, cwd, envOverrides = {}) {
       cwd: cwd || process.cwd(),
       encoding: 'utf8',
       timeout: PLAN_PRE_HOOK_CLI_TIMEOUT_MS,
-      env: { ...process.env, ...CLEAN_ENV, ...envOverrides },
+      env: installSpawnEnv({ ...CLEAN_ENV, ...envOverrides }),
     },
   );
 }
@@ -278,11 +278,20 @@ describe('plan:pre all-off — empty resolution', () => {
     assert.strictEqual(result.status, 0, `exit non-zero. stderr=${result.stderr?.slice(0, 300)}`);
     const envelope = parseEnvelope(result, 'all-off');
 
-    assert.deepEqual(envelope.activeHooks, [],
+    assert.deepStrictEqual(envelope.activeHooks, [],
       `activeHooks must be empty when all flags false. Got: ${JSON.stringify(envelope.activeHooks.map(h=>h.capId))}`);
     assert.strictEqual(envelope.rendered, '_No active hooks at plan:pre._',
       'rendered must be placeholder when no active hooks');
   });
+
+  test('#4485: an ambient plan:pre capability cannot perturb the empty resolution', (t) => {
+    withAmbientCapabilityHome(t, 'gsd-ambient-plan-pre-', 'ambient-plan-pre', 'plan:pre');
+
+    const result = runTools(['loop', 'render-hooks', 'plan:pre', '--cwd', tmpDir, '--raw'], tmpDir);
+    assert.strictEqual(result.status, 0, `exit non-zero. stderr=${result.stderr?.slice(0, 300)}`);
+    const envelope = parseEnvelope(result, 'all-off-ambient');
+    assert.deepStrictEqual(envelope.activeHooks, []);
+  });
 });
 
 // ─── 6. check ui.plan-gate: frontend + no-spec → block:true ──────────────────