fix: strip unsupported Gemini agent skills frontmatter (#971)

bin/install.js

@@ -757,6 +757,7 @@ function stripSubTags(content) {
  * - tools: must be a YAML array (not comma-separated string)
  * - tool names: must use Gemini built-in names (read_file, not Read)
  * - color: must be removed (causes validation error)
+ * - skills: must be removed (causes validation error)
  * - mcp__* tools: must be excluded (auto-discovered at runtime)
  */
 function convertClaudeToGeminiAgent(content) {
@@ -771,11 +772,19 @@ function convertClaudeToGeminiAgent(content) {
   const lines = frontmatter.split('\n');
   const newLines = [];
   let inAllowedTools = false;
+  let inSkippedArrayField = false;
   const tools = [];
 
   for (const line of lines) {
     const trimmed = line.trim();
 
+    if (inSkippedArrayField) {
+      if (!trimmed || trimmed.startsWith('- ')) {
+        continue;
+      }
+      inSkippedArrayField = false;
+    }
+
     // Convert allowed-tools YAML array to tools list
     if (trimmed.startsWith('allowed-tools:')) {
       inAllowedTools = true;
@@ -801,6 +810,12 @@ function convertClaudeToGeminiAgent(content) {
     // Strip color field (not supported by Gemini CLI, causes validation error)
     if (trimmed.startsWith('color:')) continue;
 
+    // Strip skills field (not supported by Gemini CLI, causes validation error)
+    if (trimmed.startsWith('skills:')) {
+      inSkippedArrayField = true;
+      continue;
+    }
+
     // Collect allowed-tools/tools array items
     if (inAllowedTools) {
       if (trimmed.startsWith('- ')) {
@@ -2414,6 +2429,7 @@ function installAllRuntimes(runtimes, isGlobal, isInteractive) {
 if (process.env.GSD_TEST_MODE) {
   module.exports = {
     getCodexSkillAdapterHeader,
+    convertClaudeToGeminiAgent,
     convertClaudeAgentToCodexAgent,
     generateCodexAgentToml,
     generateCodexConfigBlock,

tests/gemini-config.test.cjs

@@ -0,0 +1,47 @@
+/**
+ * GSD Tools Tests - Gemini agent conversion
+ *
+ * Verifies Gemini-specific agent frontmatter conversion removes
+ * unsupported fields while preserving converted tools and body text.
+ */
+
+process.env.GSD_TEST_MODE = '1';
+
+const { test, describe } = require('node:test');
+const assert = require('node:assert');
+
+const { convertClaudeToGeminiAgent } = require('../bin/install.js');
+
+describe('convertClaudeToGeminiAgent', () => {
+  test('drops unsupported skills frontmatter while keeping converted tools', () => {
+    const input = `---
+name: gsd-codebase-mapper
+description: Explores codebase and writes structured analysis documents.
+tools: Read, Bash, Grep, Glob, Write
+color: cyan
+skills:
+  - gsd-mapper-workflow
+---
+
+<role>
+Use \${PHASE} in shell examples.
+</role>`;
+
+    const result = convertClaudeToGeminiAgent(input);
+    const frontmatter = result.split('---')[1] || '';
+
+    assert.ok(frontmatter.includes('name: gsd-codebase-mapper'), 'keeps name');
+    assert.ok(frontmatter.includes('description: Explores codebase and writes structured analysis documents.'), 'keeps description');
+    assert.ok(frontmatter.includes('tools:'), 'adds Gemini tools array');
+    assert.ok(frontmatter.includes('  - read_file'), 'maps Read -> read_file');
+    assert.ok(frontmatter.includes('  - run_shell_command'), 'maps Bash -> run_shell_command');
+    assert.ok(frontmatter.includes('  - search_file_content'), 'maps Grep -> search_file_content');
+    assert.ok(frontmatter.includes('  - glob'), 'maps Glob -> glob');
+    assert.ok(frontmatter.includes('  - write_file'), 'maps Write -> write_file');
+    assert.ok(!frontmatter.includes('color:'), 'drops unsupported color field');
+    assert.ok(!frontmatter.includes('skills:'), 'drops unsupported skills field');
+    assert.ok(!frontmatter.includes('gsd-mapper-workflow'), 'drops skills list items');
+    assert.ok(result.includes('$PHASE'), 'escapes ${PHASE} shell variable for Gemini');
+    assert.ok(!result.includes('${PHASE}'), 'removes Gemini template-string pattern');
+  });
+});