fix: handle null tool_response fallback

tests/hooks/hooks.test.js

@@ -63,6 +63,29 @@ function runScript(scriptPath, input = '', env = {}) {
   });
 }
 
+function runShellScript(scriptPath, args = [], input = '', env = {}, cwd = process.cwd()) {
+  return new Promise((resolve, reject) => {
+    const proc = spawn('bash', [scriptPath, ...args], {
+      cwd,
+      env: { ...process.env, ...env },
+      stdio: ['pipe', 'pipe', 'pipe']
+    });
+
+    let stdout = '';
+    let stderr = '';
+
+    if (input) {
+      proc.stdin.write(input);
+    }
+    proc.stdin.end();
+
+    proc.stdout.on('data', data => stdout += data);
+    proc.stderr.on('data', data => stderr += data);
+    proc.on('close', code => resolve({ code, stdout, stderr }));
+    proc.on('error', reject);
+  });
+}
+
 // Create a temporary test directory
 function createTestDir() {
   const testDir = path.join(os.tmpdir(), `hooks-test-${Date.now()}`);
@@ -1777,6 +1800,43 @@ async function runTests() {
     assert.ok(stdout.trim().length > 0, 'CLV2_PYTHON_CMD should export a resolved interpreter path');
   })) passed++; else failed++;
 
+  if (await asyncTest('observe.sh falls back to legacy output fields when tool_response is null', async () => {
+    const homeDir = createTestDir();
+    const projectDir = createTestDir();
+    const observePath = path.join(__dirname, '..', '..', 'skills', 'continuous-learning-v2', 'hooks', 'observe.sh');
+    const payload = JSON.stringify({
+      tool_name: 'Bash',
+      tool_input: { command: 'echo hello' },
+      tool_response: null,
+      tool_output: 'legacy output',
+      session_id: 'session-123',
+      cwd: projectDir
+    });
+
+    try {
+      const result = await runShellScript(observePath, ['post'], payload, {
+        HOME: homeDir,
+        CLAUDE_PROJECT_DIR: projectDir
+      }, projectDir);
+
+      assert.strictEqual(result.code, 0, `observe.sh should exit successfully, stderr: ${result.stderr}`);
+
+      const projectsDir = path.join(homeDir, '.claude', 'homunculus', 'projects');
+      const projectIds = fs.readdirSync(projectsDir);
+      assert.strictEqual(projectIds.length, 1, 'observe.sh should create one project-scoped observation directory');
+
+      const observationsPath = path.join(projectsDir, projectIds[0], 'observations.jsonl');
+      const observations = fs.readFileSync(observationsPath, 'utf8').trim().split('\n').filter(Boolean);
+      assert.ok(observations.length > 0, 'observe.sh should append at least one observation');
+
+      const observation = JSON.parse(observations[0]);
+      assert.strictEqual(observation.output, 'legacy output', 'observe.sh should fall back to legacy tool_output when tool_response is null');
+    } finally {
+      cleanupTestDir(homeDir);
+      cleanupTestDir(projectDir);
+    }
+  })) passed++; else failed++;
+
   if (await asyncTest('matches .tsx extension for type checking', async () => {
     const testDir = createTestDir();
     const testFile = path.join(testDir, 'component.tsx');