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chat-parser: handle whitespace around JSON in tool call parsing #4

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chat-parser: handle whitespace around JSON in tool call parsing #4

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11 changes: 11 additions & 0 deletions common/chat-parser.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -488,13 +488,24 @@ std::optional<common_chat_msg_parser::find_regex_result> common_chat_msg_parser:
}

std::optional<common_json> common_chat_msg_parser::try_consume_json() {
// Skip leading whitespace - JSON values never start with whitespace, and models often
// output newlines/spaces between tags and JSON content (e.g., "<function=name>\n {...}")
auto saved_pos = pos_;
consume_spaces();

auto it = input_.cbegin() + pos_;
const auto end = input_.cend();
common_json result;
if (!common_json_parse(it, end, healing_marker_, result)) {
// Restore position if parsing failed - don't consume whitespace without a successful parse
pos_ = saved_pos;
return std::nullopt;
}
pos_ = std::distance(input_.cbegin(), it);

// Consume trailing whitespace after successful JSON parse
consume_spaces();

if (result.healing_marker.marker.empty()) {
// No healing marker, just return the parsed json
return result;
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9 changes: 9 additions & 0 deletions tests/test-chat.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1018,6 +1018,15 @@ static void test_template_output_parsers() {
"<function=special_function>{\"arg1\": 1}</function>",
/* is_partial= */ false,
{COMMON_CHAT_FORMAT_HERMES_2_PRO}));
// Test <function=name> with whitespace before JSON (issue: model outputs newline+spaces before JSON)
assert_msg_equals(
message_assist_call,
common_chat_parse(
"<function=special_function>\n"
" {\"arg1\": 1}\n"
"</function>",
/* is_partial= */ false,
{COMMON_CHAT_FORMAT_HERMES_2_PRO}));
assert_msg_equals(
message_assist_call,
common_chat_parse(
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