diff --git a/agent/prompt_builder.py b/agent/prompt_builder.py
index 80af3b64d..0a2cbe374 100644
--- a/agent/prompt_builder.py
+++ b/agent/prompt_builder.py
@@ -187,7 +187,7 @@ TOOL_USE_ENFORCEMENT_GUIDANCE = (
 
 # Model name substrings that trigger tool-use enforcement guidance.
 # Add new patterns here when a model family needs explicit steering.
-TOOL_USE_ENFORCEMENT_MODELS = ("gpt", "codex", "gemini", "gemma")
+TOOL_USE_ENFORCEMENT_MODELS = ("gpt", "codex", "gemini", "gemma", "grok")
 
 # OpenAI GPT/Codex-specific execution guidance.  Addresses known failure modes
 # where GPT models abandon work on partial results, skip prerequisite lookups,
diff --git a/tests/agent/test_prompt_builder.py b/tests/agent/test_prompt_builder.py
index ce8084709..17e3523c0 100644
--- a/tests/agent/test_prompt_builder.py
+++ b/tests/agent/test_prompt_builder.py
@@ -1018,6 +1018,9 @@ class TestToolUseEnforcementGuidance:
     def test_enforcement_models_includes_codex(self):
         assert "codex" in TOOL_USE_ENFORCEMENT_MODELS
 
+    def test_enforcement_models_includes_grok(self):
+        assert "grok" in TOOL_USE_ENFORCEMENT_MODELS
+
     def test_enforcement_models_is_tuple(self):
         assert isinstance(TOOL_USE_ENFORCEMENT_MODELS, tuple)