chat: only treat [tool_name( as tool-call start in LFM2.5 parser

common/chat.cpp

@@ -1762,7 +1762,13 @@ static common_chat_params common_chat_params_init_lfm2_5(const common_chat_templ
             )
         );
 
-        auto content = p.content(p.until_one_of({"<|tool_call_start|>", "["}));
+        // A bare '[' in ordinary content (a list, an index, a type hint, etc.) is not a tool call;
+        // treating it as one would fail the parse and surface as an HTTP 500.
+        std::vector<std::string> content_stops = { "<|tool_call_start|>" };
+        foreach_function(inputs.tools, [&](const json & tool) {
+            content_stops.push_back("[" + tool.at("function").at("name").get<std::string>() + "(");
+        });
+        auto content = p.content(p.until_one_of(content_stops));
         auto maybe_start = p.optional(p.literal("<|tool_call_start|>"));
         return generation_prompt + reasoning + content + maybe_start + tool_calls + end;
     });

tests/test-chat.cpp

@@ -4177,6 +4177,29 @@ static void test_template_output_peg_parsers(bool detailed_debug) {
             ))
             .run();
 
+        // Bare-bracket content must not abort the request. LFM2.5 has no tool-call wrapper
+        // token; content must only stop at an actual "[{tool_name}(" prefix (matching the
+        // grammar triggers). A '[' that doesn't start a defined tool call (a list/index/
+        // type hint) used to fail the final parse and surface as an HTTP 500.
+        tst.test("Here is a Python list: [1, 2, 3] and that is all.")
+            .tools({ special_function_tool })
+            .expect_content("Here is a Python list: [1, 2, 3] and that is all.")
+            .run();
+
+        // The reported production shape: a code-mode reply that ends up as content
+        // containing a bracketed data structure.
+        tst.test("trades = [\n    {\"timestamp\": \"09:30:00\", \"price\": 150.10, \"size\": 100}\n]")
+            .tools({ special_function_tool })
+            .expect_content("trades = [\n    {\"timestamp\": \"09:30:00\", \"price\": 150.10, \"size\": 100}\n]")
+            .run();
+
+        // Streaming: a bare '[' mid-content must not retract previously streamed content.
+        tst.test("Here is a Python list: [1, 2")
+            .tools({ special_function_tool })
+            .is_partial(true)
+            .expect_content("Here is a Python list: [1, 2")
+            .run();
+
         // Partial tool call (streaming)
         tst.test("[special_function(arg1=")
             .tools({ special_function_tool })