diff --git a/common/parsers/muse-glimmer.cpp b/common/parsers/muse-glimmer.cpp
index add95697eb..d03bf2d58f 100644
--- a/common/parsers/muse-glimmer.cpp
+++ b/common/parsers/muse-glimmer.cpp
@@ -130,7 +130,7 @@ common_chat_params common_chat_params_init_muse_glimmer(const common_chat_templa
         });
         data.grammar_triggers = {
             { COMMON_GRAMMAR_TRIGGER_TYPE_PATTERN,
-              "<\\|start\\|>assistant( to=(?!self<\\|message\\|>)(?!user<\\|message\\|>)[^<]*?<\\|message\\|>)" },
+              "(?:^|<\\|start\\|>assistant)( to=(?!self<\\|message\\|>)(?!user<\\|message\\|>)[^<]*?<\\|message\\|>)" },
         };
     }
 
diff --git a/tests/test-chat.cpp b/tests/test-chat.cpp
index 13733c1d9c..f2728f7cca 100644
--- a/tests/test-chat.cpp
+++ b/tests/test-chat.cpp
@@ -6357,6 +6357,14 @@ static void test_template_output_peg_parsers(bool detailed_debug) {
             .expect(message_assist)
             .run();
 
+        // A tool call as the first message of the turn: "<|start|>assistant" is the
+        // generation prompt, so the output starts at " to=".
+        tst.test(" to=special_function<|message|>" + call_markup)
+            .tools({ special_function_tool })
+            .reasoning_format(COMMON_REASONING_FORMAT_AUTO)
+            .expect(message_assist_call)
+            .run();
+
         // "Inform then act": the model answers the user and calls a tool in ONE generation,
         // closing the answer with <|eom|>. The answer must stop there rather than swallow it.
         tst.test(" to=user<|message|>Hello, world!\nWhat's up?<|eom|>"