feat(core): distill tool

evals/head_entropy.eval.ts

@@ -0,0 +1,44 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { describe, expect } from 'vitest';
+import { appEvalTest } from './app-test-helper.js';
+
+describe('Head Entropy Behavioral Evals', () => {
+  appEvalTest('ALWAYS_PASSES', {
+    name: 'Head Entropy: Model distills a high-noise tool output',
+    configOverrides: {
+      modelSteering: true,
+      continuousSession: true,
+    },
+    files: {
+      'src/big-file.ts': '// NOISE\n'.repeat(100) + 'const SECRET = "SIGNAL";\n' + '// NOISE\n'.repeat(100),
+    },
+    prompt:
+      'Grep for SECRET in src/. If the result is very noisy, use distill_result to replace it with just the signal you found before continuing.',
+    setup: async (rig) => {
+      // Pause on our new tools to observe the workflow
+      rig.setBreakpoint(['grep_search', 'distill_result']);
+    },
+    assert: async (rig) => {
+      // 1. Wait for Grep
+      await rig.waitForPendingConfirmation('grep_search', 45000);
+      await rig.resolveAwaitedTool();
+
+      // 2. Wait for Distillation
+      await rig.waitForPendingConfirmation('distill_result', 45000);
+      await rig.resolveAwaitedTool();
+
+      // 3. Final Verification
+      await rig.waitForOutput(/SIGNAL/i, 60000);
+      await rig.waitForIdle(30000);
+
+      const output = rig.getStaticOutput();
+      expect(output).toContain('SIGNAL');
+      expect(output).not.toContain('NOISE'); // Should be elided/replaced
+    },
+  });
+});