diff --git a/src/fastcontext/agent/tool/grep.py b/src/fastcontext/agent/tool/grep.py
index 4ee161f..02ea18c 100644
--- a/src/fastcontext/agent/tool/grep.py
+++ b/src/fastcontext/agent/tool/grep.py
@@ -149,7 +149,7 @@ def run_rg(rg_path: str, pattern: str, path: str, **kwargs) -> str:
             command.append("-n")
     elif output_mode == "files_with_matches":
         command.append("--files-with-matches")
-    elif output_mode == "count_matches":
+    elif output_mode == "count":
         command.append("--count-matches")
 
     # --heading and --color never
diff --git a/tests/test_grep_count.py b/tests/test_grep_count.py
new file mode 100644
index 0000000..41d1a9b
--- /dev/null
+++ b/tests/test_grep_count.py
@@ -0,0 +1,21 @@
+import asyncio
+import json
+import tempfile
+from pathlib import Path
+
+from fastcontext.agent.tool.grep import GrepTool
+
+
+def test_grep_count_mode():
+    """output_mode 'count' (the advertised enum value) must emit per-file
+    match counts via rg --count-matches, not fall through to content."""
+    grep = GrepTool()
+    with tempfile.TemporaryDirectory() as cwd:
+        (Path(cwd) / "haystack.txt").write_text("MATCH\nMATCH\nMATCH\nnope\n", encoding="utf-8")
+
+        out = asyncio.run(grep.call(json.dumps({"pattern": "MATCH", "output_mode": "count"}), cwd=cwd))
+
+        # rg --count-matches prints "<path>:<count>"; 3 matches in the file.
+        assert out.strip().endswith(":3"), f"expected a per-file count of 3, got: {out!r}"
+        # It must not be content mode (which would echo the matched line text).
+        assert "MATCH\n" not in out and not out.strip().endswith("MATCH")