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Merged
ngxson merged 2 commits into from
Jun 28, 2026
+80 −24
Merged

jinja, chat: add --reasoning-preserve flag #25105

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6989cb1
jinja, chat: add --reasoning-preserve flag
ngxson Jun 28, 2026
fcf66c1
correct help message
ngxson Jun 28, 2026
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14 changes: 14 additions & 0 deletions common/arg.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3296,6 +3296,20 @@ common_params_context common_params_parser_init(common_params & params, llama_ex
params.sampling.reasoning_budget_message = value;
}
).set_examples({LLAMA_EXAMPLE_SERVER, LLAMA_EXAMPLE_COMPLETION, LLAMA_EXAMPLE_CLI}).set_env("LLAMA_ARG_THINK_BUDGET_MESSAGE"));
add_opt(common_arg(
{"--reasoning-preserve"},
{"--no-reasoning-preserve"},
"preserve reasoning trace in the full history, not just the last assistant message (default: template default)\n"
"compatible with certain templates having 'supports_preserve_reasoning' capability\n"
"example: https://docs.z.ai/guides/capabilities/thinking-mode#preserved-thinking",
[](common_params & params, bool value) {
if (value) {
params.default_template_kwargs["preserve_reasoning"] = "true";
} else {
params.default_template_kwargs["preserve_reasoning"] = "false";
}
}
).set_examples({LLAMA_EXAMPLE_SERVER, LLAMA_EXAMPLE_COMPLETION, LLAMA_EXAMPLE_CLI}).set_env("LLAMA_ARG_REASONING_PRESERVE"));
add_opt(common_arg(
{"--chat-template"}, "JINJA_TEMPLATE",
string_format(
Expand Down
4 changes: 4 additions & 0 deletions common/chat.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -912,6 +912,10 @@ static std::string common_chat_template_direct_apply_impl(
if (inputs.add_generation_prompt) {
inp["add_generation_prompt"] = true;
}
if (inp.contains("preserve_reasoning") && inp["preserve_reasoning"].is_boolean()) {
bool enabled = inp["preserve_reasoning"].get<bool>();
jinja::caps_apply_preserve_reasoning(ctx, enabled);
}

jinja::global_from_json(ctx, inp, inputs.mark_input);

Expand Down
67 changes: 44 additions & 23 deletions common/jinja/caps.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -16,22 +16,34 @@ using json = nlohmann::ordered_json;
namespace jinja {

using caps_json_fn = std::function<json()>;
using caps_analyze_fn = std::function<void(bool, value &, value &)>;
using caps_ctx_fn = std::function<void(context &)>;
using caps_analyze_fn = std::function<void(bool, value &, value &, const std::string &)>;

void caps_apply_preserve_reasoning(jinja::context & ctx, bool enabled) {
ctx.set_val("preserve_thinking", mk_val<value_bool>(enabled));
ctx.set_val("clear_thinking", mk_val<value_bool>(!enabled));
ctx.set_val("truncate_history_thinking", mk_val<value_bool>(!enabled));
}

static void caps_try_execute(jinja::program & prog,
const caps_json_fn & messages_fn,
const caps_ctx_fn & ctx_fn,
const caps_json_fn & tools_fn,
const caps_analyze_fn & analyze_fn) {
context ctx;
ctx.is_get_stats = true;
jinja::global_from_json(ctx, json{
{"messages", messages_fn()},
{"tools", tools_fn()},
{"tools", tools_fn ? tools_fn() : json::array()},
{"bos_token", ""},
{"eos_token", ""},
{"add_generation_prompt", true}
}, true);

if (ctx_fn) {
ctx_fn(ctx);
}

auto messages = ctx.get_val("messages");
auto tools = ctx.get_val("tools");

Expand All @@ -49,7 +61,7 @@ static void caps_try_execute(jinja::program & prog,
// ignore exceptions during capability analysis
}

analyze_fn(success, messages, tools);
analyze_fn(success, messages, tools, result);
}

// for debugging only
Expand Down Expand Up @@ -109,11 +121,9 @@ caps caps_get(jinja::program & prog) {
}
});
},
[&]() {
// tools
return json{nullptr};
},
[&](bool success, value & messages, value &) {
nullptr, // ctx_fn
nullptr, // tools_fn
[&](bool success, value & messages, value &, const std::string &) {
auto & content = messages->at(0)->at("content");
caps_print_stats(content, "messages[0].content");
if (has_op(content, "selectattr") || has_op(content, "array_access")) {
Expand Down Expand Up @@ -145,11 +155,9 @@ caps caps_get(jinja::program & prog) {
},
});
},
[&]() {
// tools
return json::array();
},
[&](bool, value & messages, value &) {
nullptr, // ctx_fn
nullptr, // tools_fn
[&](bool, value & messages, value &, const std::string &) {
auto & content = messages->at(0)->at("content");
caps_print_stats(content, "messages[0].content");
if (!content->stats.used) {
Expand Down Expand Up @@ -201,6 +209,7 @@ caps caps_get(jinja::program & prog) {
},
});
},
nullptr, // ctx_fn
[&]() {
// tools
return json::array({
Expand All @@ -224,7 +233,7 @@ caps caps_get(jinja::program & prog) {
},
});
},
[&](bool success, value & messages, value & tools) {
[&](bool success, value & messages, value & tools, const std::string &) {
if (!success) {
return; // Nothing can be inferred
}
Expand Down Expand Up @@ -293,6 +302,7 @@ caps caps_get(jinja::program & prog) {
},
});
},
nullptr, // ctx_fn
[&]() {
// tools
return json::array({
Expand All @@ -316,7 +326,7 @@ caps caps_get(jinja::program & prog) {
},
});
},
[&](bool success, value & messages, value & tools) {
[&](bool success, value & messages, value & tools, const std::string &) {
if (!success) {
result.supports_tool_calls = false;
result.supports_tools = false;
Expand Down Expand Up @@ -394,6 +404,7 @@ caps caps_get(jinja::program & prog) {
},
});
},
nullptr, // ctx_fn
[&]() {
// tools
return json::array({
Expand All @@ -417,7 +428,7 @@ caps caps_get(jinja::program & prog) {
},
});
},
[&](bool success, value & messages, value & /*tools*/) {
[&](bool success, value & messages, value &, const std::string &) {
if (!success) {
result.supports_parallel_tool_calls = false;
return;
Expand All @@ -438,11 +449,22 @@ caps caps_get(jinja::program & prog) {
JJ_DEBUG("%s\n", ">>> Running capability check: preserve reasoning");

// case: preserve reasoning content in chat history
const std::string reasoning_placeholder = "<REASONING_CONTENT_PLACEHOLDER>";
caps_try_execute(
prog,
[&]() {
// messages
return json::array({
{
{"role", "user"},
{"content", "User message"}
},
{
{"role", "assistant"},
{"content", "Assistant message"},
// check of reasoning_content deeper in the history, not just the last assistant message
{"reasoning_content", reasoning_placeholder}
},
{
{"role", "user"},
{"content", "User message"}
Expand All @@ -458,14 +480,13 @@ caps caps_get(jinja::program & prog) {
},
});
},
[&]() {
// tools
return json::array();
[&](context & ctx) {
caps_apply_preserve_reasoning(ctx, true);
},
[&](bool, value & messages, value &) {
auto & content = messages->at(1)->at("reasoning_content");
caps_print_stats(content, "messages[1].reasoning_content");
if (content->stats.used) {
nullptr, // tools_fn
[&](bool, value &, value &, const std::string & output) {
// note: we cannot use stats here because the reasoning_content may be used for "if" condition test, but not actually outputted in the final result
if (output.find(reasoning_placeholder) != std::string::npos) {
result.supports_preserve_reasoning = true;
}
}
Expand Down
6 changes: 5 additions & 1 deletion common/jinja/caps.h
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Original file line number Diff line number Diff line change
Expand Up @@ -12,7 +12,9 @@ struct caps {
bool supports_tool_calls = true;
bool supports_system_role = true;
bool supports_parallel_tool_calls = true;
bool supports_preserve_reasoning = false; // support assistant message with reasoning_content

// supports preserve reasoning trace in the full history, not just the last assistant message
bool supports_preserve_reasoning = false;

// one of the 2 content capabilities must be true
bool supports_string_content = true;
Expand All @@ -29,4 +31,6 @@ struct caps {

caps caps_get(jinja::program & prog);

void caps_apply_preserve_reasoning(jinja::context & ctx, bool enabled);

} // namespace jinja
13 changes: 13 additions & 0 deletions tools/server/server-context.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1538,6 +1538,19 @@ struct server_context_impl {
/* media_path */ params_base.media_path,
/* force_pure_content */ params_base.force_pure_content_parser
};

{
auto caps = common_chat_templates_get_caps(chat_params.tmpls.get());
auto it = params_base.default_template_kwargs.find("preserve_reasoning");
bool supported = caps.at("supports_preserve_reasoning");
bool enabled = it != params_base.default_template_kwargs.end();
if (supported && !enabled) {
SRV_INF("%s", "chat template supports preserving reasoning, consider enabling it via --reasoning-preserve\n");
}
Comment on lines +1547 to +1549

@CISC CISC Jun 28, 2026

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nit: I suppose it would be useful if this reflected the default state.

@ngxson ngxson Jun 28, 2026

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all known templates have it disabled by default, so I think we are temporary ok here

if (!supported && enabled) {
SRV_WRN("%s", "chat template does NOT support preserving reasoning, --reasoning-preserve has no effect\n");
}
}
}

return true;
Expand Down