common : consume trailing channel markers in Gemma 4 tool grammar (#25072)

Author: rodboev

common/chat.cpp

@@ -1392,7 +1392,7 @@ static common_chat_params common_chat_params_init_gemma4(const common_chat_templ
             auto scan_to_toolcall = p.rule("scan-to-toolcall", p.until("<|tool_call>"));
             auto content = p.rule("content", p.content(p.until_one_of({"<|channel>", "<channel|>", "<|tool_call>"})));
             auto message = p.rule("message", thought + content);
-            return start + p.zero_or_more(message) + scan_to_toolcall + tool_call;
+            return start + p.zero_or_more(message) + scan_to_toolcall + tool_call + consume_empty_channels;
         }
 
         // Gemma 4 may emit an extra <|channel>thought\n<channel|> at the end of the content. It may

tests/test-chat.cpp

@@ -3070,6 +3070,14 @@ static void test_template_output_peg_parsers(bool detailed_debug) {
             .expect(message_with_tool_calls("amount", R"({"orig": 1.5e10})"))
             .run();
 
+        // Tool call with trailing <|channel> fragment (#25072)
+        tst.test(
+                "<|tool_call>call:get_time{city:<|\"|>London<|\"|>}<tool_call|><|channel> ")
+            .tools({ get_time_tool })
+            .is_partial(true)
+            .expect(message_with_tool_calls("get_time", R"({"city": "London"})"))
+            .run();
+
         // Edge cases
         tst.test(
                 "<|channel>thought\n<channel|>Hello, world!\nWhat's up?<channel|>")