diff --git a/.changeset/fix-3344-gemini-agent-tool.md b/.changeset/fix-3344-gemini-agent-tool.md
new file mode 100644
index 000000000..e297e3e51
--- /dev/null
+++ b/.changeset/fix-3344-gemini-agent-tool.md
@@ -0,0 +1,5 @@
+---
+type: Fixed
+pr: 3349
+---
+Gemini and Antigravity agent conversion now drops Claude-only agent dispatcher tools instead of emitting invalid `agent` permissions.
diff --git a/bin/install.js b/bin/install.js
index 1fa5a91ae..9e349fc6f 100755
--- a/bin/install.js
+++ b/bin/install.js
@@ -1240,7 +1240,7 @@ function convertToolName(claudeTool) {
  * Convert a Claude Code tool name to Gemini CLI format
  * - Applies Claude→Gemini mapping (Read→read_file, Bash→run_shell_command, etc.)
  * - Filters out MCP tools (mcp__*) — they are auto-discovered at runtime in Gemini
- * - Filters out Task — agents are auto-registered as tools in Gemini
+ * - Filters out Task/Agent — agents are auto-registered as tools in Gemini
  * @returns {string|null} Gemini tool name, or null if tool should be excluded
  */
 function convertGeminiToolName(claudeTool) {
@@ -1248,8 +1248,8 @@ function convertGeminiToolName(claudeTool) {
   if (claudeTool.startsWith('mcp__')) {
     return null;
   }
-  // Task: exclude — agents are auto-registered as callable tools
-  if (claudeTool === 'Task') {
+  // Task/Agent: exclude — agents are auto-registered as callable tools
+  if (claudeTool === 'Task' || claudeTool === 'Agent') {
     return null;
   }
   // Check for explicit mapping
diff --git a/tests/runtime-converters.test.cjs b/tests/runtime-converters.test.cjs
index dcffa9924..ad47e6bea 100644
--- a/tests/runtime-converters.test.cjs
+++ b/tests/runtime-converters.test.cjs
@@ -264,6 +264,28 @@ Use \${PHASE} in shell examples.
     assert.ok(result.includes('$PHASE'), 'escapes ${PHASE} shell variable for Gemini');
     assert.ok(!result.includes('${PHASE}'), 'removes Gemini template-string pattern');
   });
+
+  test('excludes Claude agent dispatcher tools from Gemini frontmatter', () => {
+    const input = `---
+name: gsd-debug-session-manager
+description: Manages debug sessions.
+tools: Read, Task, Agent, AskUserQuestion
+---
+
+<role>
+Coordinate debugger agents.
+</role>`;
+
+    const result = convertClaudeToGeminiAgent(input);
+    const frontmatter = result.split('---')[1] || '';
+
+    assert.ok(frontmatter.includes('  - read_file'), 'maps Read -> read_file');
+    assert.ok(frontmatter.includes('  - ask_user'), 'maps AskUserQuestion -> ask_user');
+    assert.ok(!frontmatter.includes('  - task'), 'does not emit invalid Gemini task tool');
+    assert.ok(!frontmatter.includes('  - agent'), 'does not emit invalid Gemini agent tool');
+    assert.ok(!frontmatter.includes('Task'), 'does not preserve Claude-only Task tool');
+    assert.ok(!frontmatter.includes('Agent'), 'does not preserve Claude-only Agent tool');
+  });
 });
 
 // ─── neutralizeAgentReferences (#766) ─────────────────────────────────────────