fix(#222): enforce research synthesizer write-only summary contract (#240)

tests/bug-222-research-synthesizer-write-contract.test.cjs

@@ -0,0 +1,56 @@
+// allow-test-rule: source-text-is-the-product
+'use strict';
+
+const { test, describe } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const REPO_ROOT = path.resolve(__dirname, '..');
+const SYNTHESIZER_PATH = path.join(REPO_ROOT, 'agents', 'gsd-research-synthesizer.md');
+
+function readSynthesizerPrompt() {
+  return fs.readFileSync(SYNTHESIZER_PATH, 'utf8');
+}
+
+describe('bug #222: research synthesizer must write SUMMARY.md via Write tool', () => {
+  test('step 6 has explicit hard-rule block forbidding return-message content fallback', () => {
+    const prompt = readSynthesizerPrompt();
+
+    assert.match(
+      prompt,
+      /canonical output of this agent[\s\S]*existing on disk after you return/i,
+      'Step 6 must define SUMMARY.md-on-disk as canonical output.'
+    );
+    assert.match(
+      prompt,
+      /Hard rules \(must follow\):/i,
+      'Step 6 must contain explicit hard rules block.'
+    );
+    assert.match(
+      prompt,
+      /Use the `Write` tool[\s\S]*there are no restrictions/i,
+      'Rule 1 must force Write tool usage and reject hallucinated restrictions.'
+    );
+    assert.match(
+      prompt,
+      /Do NOT return the SUMMARY\.md content in your response/i,
+      'Rule 2 must forbid returning SUMMARY content in the response body.'
+    );
+    assert.match(
+      prompt,
+      /Do NOT ask permission to write/i,
+      'Rule 3 must forbid write-permission asks for this agent.'
+    );
+    assert.match(
+      prompt,
+      /Do NOT use `Bash\(cat << 'EOF'\)` or heredoc/i,
+      'Rule 4 must forbid heredoc/Bash file creation fallback.'
+    );
+    assert.match(
+      prompt,
+      /If the Write tool errors[\s\S]*Do not silently fall back to returning content/i,
+      'Rule 5 must force explicit error reporting for Write failures.'
+    );
+  });
+});