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chat: fix LFM2/LFM2.5 ignoring json_schema (#24377)

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The LFM2 specialized template handler only built a grammar for tool-calling,
silently ignoring json_schema from response_format.
This commit is contained in:
Tarek Dakhran
2026-06-10 14:41:41 +02:00
committed by GitHub
parent fb83cc9a07
commit d2462f8f7a
1 changed files with 12 additions and 3 deletions
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15
common/chat.cpp
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@@ -1647,11 +1647,12 @@ static common_chat_params common_chat_params_init_lfm2(const common_chat_templat
data.thinking_start_tag = THINK_START;
data.thinking_end_tag = THINK_END;
auto has_tools = inputs.tools.is_array() && !inputs.tools.empty();
auto has_tools = inputs.tools.is_array() && !inputs.tools.empty();
auto has_response_format = !inputs.json_schema.is_null() && inputs.json_schema.is_object();
// Gate by reasoning format and whether the template supports <think>
auto extract_reasoning = inputs.reasoning_format != COMMON_REASONING_FORMAT_NONE &&
tmpl.source().find(THINK_START) != std::string::npos;
auto include_grammar = has_tools && inputs.tool_choice != COMMON_CHAT_TOOL_CHOICE_NONE;
auto include_grammar = has_response_format || (has_tools && inputs.tool_choice != COMMON_CHAT_TOOL_CHOICE_NONE);
if (inputs.has_continuation()) {
const auto & msg = inputs.continue_msg;
@@ -1674,6 +1675,10 @@ static common_chat_params common_chat_params_init_lfm2(const common_chat_templat
}
if (!has_tools || inputs.tool_choice == COMMON_CHAT_TOOL_CHOICE_NONE) {
if (has_response_format) {
auto response_format = p.content(p.schema(p.json(), "response-format-schema", inputs.json_schema));
return generation_prompt + reasoning + response_format + end;
}
return generation_prompt + reasoning + p.content(p.rest()) + end;
}
auto tool_calls = p.rule("tool-calls",
@@ -1692,13 +1697,17 @@ static common_chat_params common_chat_params_init_lfm2(const common_chat_templat
data.parser = parser.save();
if (include_grammar) {
data.grammar_lazy = inputs.tool_choice == COMMON_CHAT_TOOL_CHOICE_AUTO;
data.grammar_lazy = !(has_response_format || (has_tools && inputs.tool_choice == COMMON_CHAT_TOOL_CHOICE_REQUIRED));
data.grammar = build_grammar([&](const common_grammar_builder & builder) {
foreach_function(inputs.tools, [&](const json & tool) {
const auto & function = tool.at("function");
auto schema = function.at("parameters");
builder.resolve_refs(schema);
});
if (has_response_format) {
auto schema = inputs.json_schema;
builder.resolve_refs(schema);
}
parser.build_grammar(builder, data.grammar_lazy);
});