diff --git a/.changeset/green-owls-jump.md b/.changeset/green-owls-jump.md
new file mode 100644
index 0000000..aee39d7
--- /dev/null
+++ b/.changeset/green-owls-jump.md
@@ -0,0 +1,16 @@
+---
+"layne": patch
+---
+
+fix(config-validator): accept scanner keys in $global and validate removeOnException label key
+
+`KNOWN_GLOBAL_KEYS` was missing `semgrep`, `trufflehog`, `claude`, and
+`piAgent`, so using `$global.semgrep` (functional since the previous
+config-inheritance fix) would cause `npm run validate-config` to report
+an unknown key error. Added all four scanner keys and wired their
+respective validators (`validateScanner`, `validateClaude`,
+`validatePiAgent`) inside `validateGlobal`.
+
+`validateLabels` was also missing `removeOnException` from its checked
+key list, even though the worker reads and applies it. The key is now
+validated alongside the other five label keys.
diff --git a/src/__tests__/config-validator.test.ts b/src/__tests__/config-validator.test.ts
new file mode 100644
index 0000000..7aad123
--- /dev/null
+++ b/src/__tests__/config-validator.test.ts
@@ -0,0 +1,83 @@
+import { describe, it, expect } from 'vitest';
+import { validateConfig } from '../config-validator.js';
+
+describe('validateConfig()', () => {
+  describe('$global scanner keys', () => {
+    it('accepts $global.semgrep without flagging it as an unknown key', () => {
+      const result = validateConfig({
+        '$global': { semgrep: { extraArgs: ['--config', 'p/owasp-top-ten'] } },
+      });
+      expect(result.valid).toBe(true);
+    });
+
+    it('accepts $global.trufflehog without flagging it as an unknown key', () => {
+      const result = validateConfig({
+        '$global': { trufflehog: { enabled: false } },
+      });
+      expect(result.valid).toBe(true);
+    });
+
+    it('accepts $global.claude without flagging it as an unknown key', () => {
+      const result = validateConfig({
+        '$global': { claude: { enabled: true, model: 'claude-sonnet-4-6' } },
+      });
+      expect(result.valid).toBe(true);
+    });
+
+    it('accepts $global.piAgent without flagging it as an unknown key', () => {
+      const result = validateConfig({
+        '$global': { piAgent: { enabled: false, model: 'claude-opus-4-6' } },
+      });
+      expect(result.valid).toBe(true);
+    });
+
+    it('still rejects a genuinely unknown key in $global', () => {
+      const result = validateConfig({
+        '$global': { typo_key: true },
+      });
+      expect(result.valid).toBe(false);
+      expect((result as { valid: false; errors: string[] }).errors[0]).toMatch(/unknown key/);
+    });
+
+    it('validates the contents of $global.semgrep (rejects bad extraArgs)', () => {
+      const result = validateConfig({
+        '$global': { semgrep: { extraArgs: [123] } },
+      });
+      expect(result.valid).toBe(false);
+      expect((result as { valid: false; errors: string[] }).errors[0]).toMatch(/extraArgs/);
+    });
+
+    it('validates the contents of $global.claude (rejects non-claude model)', () => {
+      const result = validateConfig({
+        '$global': { claude: { enabled: true, model: 'gpt-4o' } },
+      });
+      expect(result.valid).toBe(false);
+      expect((result as { valid: false; errors: string[] }).errors[0]).toMatch(/model/);
+    });
+  });
+
+  describe('validateLabels — removeOnException', () => {
+    it('accepts labels.removeOnException as a valid key', () => {
+      const result = validateConfig({
+        'acme/app': { labels: { removeOnException: ['security-exception'] } },
+      });
+      expect(result.valid).toBe(true);
+    });
+
+    it('rejects labels.removeOnException when not an array', () => {
+      const result = validateConfig({
+        'acme/app': { labels: { removeOnException: 'security-exception' } },
+      });
+      expect(result.valid).toBe(false);
+      expect((result as { valid: false; errors: string[] }).errors[0]).toMatch(/removeOnException/);
+    });
+
+    it('rejects labels.removeOnException when items are not strings', () => {
+      const result = validateConfig({
+        'acme/app': { labels: { removeOnException: [42] } },
+      });
+      expect(result.valid).toBe(false);
+      expect((result as { valid: false; errors: string[] }).errors[0]).toMatch(/removeOnException/);
+    });
+  });
+});
diff --git a/src/config-validator.ts b/src/config-validator.ts
index a0d99fc..d349aa9 100644
--- a/src/config-validator.ts
+++ b/src/config-validator.ts
@@ -9,7 +9,7 @@
  */
 
 const KNOWN_REPO_KEYS    = new Set(['mode', 'contextLines', 'timeoutMinutes', 'semgrep', 'trufflehog', 'claude', 'piAgent', 'notifications', 'labels', 'trigger', 'comment', 'exceptionApprovers']);
-const KNOWN_GLOBAL_KEYS  = new Set(['mode', 'contextLines', 'timeoutMinutes', 'notifications', 'labels', 'trigger', 'comment', 'exceptionApprovers']);
+const KNOWN_GLOBAL_KEYS  = new Set(['mode', 'contextLines', 'timeoutMinutes', 'semgrep', 'trufflehog', 'claude', 'piAgent', 'notifications', 'labels', 'trigger', 'comment', 'exceptionApprovers']);
 const VALID_MODES        = new Set(['changed_files', 'diff_only']);
 const VALID_TRIGGER_ONS  = new Set(['pull_request', 'workflow_run', 'workflow_job']);
 const VALID_CONCLUSIONS  = new Set(['success', 'failure', 'neutral', 'cancelled', 'skipped', 'timed_out', 'action_required']);
@@ -57,6 +57,10 @@ function validateGlobal(block: Record<string, unknown>, ctx: string, errors: str
     }
   }
   validateScanMode(block, ctx, errors);
+  if (block['semgrep']       !== undefined) validateScanner(block['semgrep'],    `${ctx}.semgrep`,    errors);
+  if (block['trufflehog']    !== undefined) validateScanner(block['trufflehog'], `${ctx}.trufflehog`, errors);
+  if (block['claude']        !== undefined) validateClaude(block['claude'],       `${ctx}.claude`,     errors);
+  if (block['piAgent']       !== undefined) validatePiAgent(block['piAgent'],    `${ctx}.piAgent`,    errors);
   if (block['notifications'] !== undefined) validateNotifications(block['notifications'], `${ctx}.notifications`, errors);
   if (block['labels']        !== undefined) validateLabels(block['labels'], `${ctx}.labels`, errors);
   if (block['trigger']       !== undefined) validateTrigger(block['trigger'], `${ctx}.trigger`, errors);
@@ -251,7 +255,7 @@ function validateComment(block: unknown, ctx: string, errors: string[]): void {
 function validateLabels(block: unknown, ctx: string, errors: string[]): void {
   if (typeof block !== 'object' || block === null) { errors.push(`${ctx}: must be an object`); return; }
   const b = block as Record<string, unknown>;
-  for (const key of ['onFailure', 'removeOnFailure', 'onSuccess', 'removeOnSuccess', 'onException']) {
+  for (const key of ['onFailure', 'removeOnFailure', 'onSuccess', 'removeOnSuccess', 'onException', 'removeOnException']) {
     if (b[key] === undefined) continue;
     if (!Array.isArray(b[key]))
       errors.push(`${ctx}.${key}: must be an array`);