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fix: preserve reasoning in assistant tool-call conversion #393

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Merged
jamiepine merged 4 commits into from
Mar 12, 2026
Merged

fix: preserve reasoning in assistant tool-call conversion #393

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dfe45f6
fix: preserve reasoning in assistant tool-call conversion
skulldogged Mar 11, 2026
ebdbee6
Merge upstream/main into fix/reasoning-tool-call-serialization
skulldogged Mar 11, 2026
1e89e96
fix: address reasoning serialization review follow-ups
skulldogged Mar 11, 2026
b4a66e4
Merge branch 'main' into fix/reasoning-tool-call-serialization
jamiepine Mar 12, 2026
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142 changes: 138 additions & 4 deletions src/llm/model.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -9,8 +9,8 @@ use crate::llm::routing::{
use futures::StreamExt as _;
use rig::completion::{self, CompletionError, CompletionModel, CompletionRequest, GetTokenUsage};
use rig::message::{
AssistantContent, DocumentSourceKind, Image, Message, MimeType, Text, ToolCall, ToolFunction,
UserContent,
AssistantContent, DocumentSourceKind, Image, Message, MimeType, ReasoningContent, Text,
ToolCall, ToolFunction, UserContent,
};
use rig::one_or_many::OneOrMany;
use rig::streaming::{RawStreamingChoice, RawStreamingToolCall, StreamingCompletionResponse};
Expand Down Expand Up @@ -1369,13 +1369,19 @@ fn convert_messages_to_openai(messages: &OneOrMany<Message>) -> Vec<serde_json::
}
Message::Assistant { content, .. } => {
let mut text_parts = Vec::new();
let mut reasoning_parts = Vec::new();
let mut saw_reasoning = false;
let mut tool_calls = Vec::new();

for item in content.iter() {
match item {
AssistantContent::Text(t) => {
text_parts.push(t.text.clone());
}
AssistantContent::Reasoning(reasoning) => {
saw_reasoning = true;
reasoning_parts.extend(collect_reasoning_text_parts(reasoning));
}
AssistantContent::ToolCall(tc) => {
// OpenAI expects arguments as a JSON string.
// Prefer call_id (set when replaying Responses-API tool calls
Expand Down Expand Up @@ -1403,6 +1409,11 @@ fn convert_messages_to_openai(messages: &OneOrMany<Message>) -> Vec<serde_json::
let mut msg = serde_json::json!({"role": "assistant"});
if !text_parts.is_empty() {
msg["content"] = serde_json::json!(text_parts.join("\n"));
} else if !tool_calls.is_empty() || saw_reasoning {
msg["content"] = serde_json::Value::Null;
}
if saw_reasoning {
msg["reasoning_content"] = serde_json::json!(reasoning_parts.join("\n"));
}
if !tool_calls.is_empty() {
msg["tool_calls"] = serde_json::json!(tool_calls);
Expand All @@ -1415,6 +1426,22 @@ fn convert_messages_to_openai(messages: &OneOrMany<Message>) -> Vec<serde_json::
result
}

fn collect_reasoning_text_parts(reasoning: &rig::message::Reasoning) -> Vec<String> {
reasoning
.content
.iter()
.filter_map(|content| match content {
ReasoningContent::Text { text, .. } => (!text.trim().is_empty()).then(|| text.clone()),
ReasoningContent::Summary(summary) => {
(!summary.trim().is_empty()).then(|| summary.clone())
}
ReasoningContent::Encrypted(_) | ReasoningContent::Redacted { .. } => None,
#[allow(unreachable_patterns)]
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_ => None,
})
.collect()
}
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fn convert_messages_to_openai_responses(messages: &OneOrMany<Message>) -> Vec<serde_json::Value> {
let mut result = Vec::new();

Expand Down Expand Up @@ -1461,6 +1488,9 @@ fn convert_messages_to_openai_responses(messages: &OneOrMany<Message>) -> Vec<se
}
Message::Assistant { content, .. } => {
let mut text_parts = Vec::new();
let mut reasoning_parts = Vec::new();
let mut saw_reasoning = false;
let mut function_calls = Vec::new();

for item in content.iter() {
match item {
Expand All @@ -1470,6 +1500,10 @@ fn convert_messages_to_openai_responses(messages: &OneOrMany<Message>) -> Vec<se
"text": text.text,
}));
}
AssistantContent::Reasoning(reasoning) => {
saw_reasoning = true;
reasoning_parts.extend(collect_reasoning_text_parts(reasoning));
}
AssistantContent::ToolCall(tool_call) => {
let arguments = serde_json::to_string(&tool_call.function.arguments)
.unwrap_or_else(|_| "{}".to_string());
Expand All @@ -1478,7 +1512,7 @@ fn convert_messages_to_openai_responses(messages: &OneOrMany<Message>) -> Vec<se
.as_deref()
.filter(|call_id| !call_id.is_empty())
.unwrap_or(&tool_call.id);
result.push(serde_json::json!({
function_calls.push(serde_json::json!({
"type": "function_call",
"name": tool_call.function.name,
"arguments": arguments,
Expand All @@ -1490,11 +1524,24 @@ fn convert_messages_to_openai_responses(messages: &OneOrMany<Message>) -> Vec<se
}

if !text_parts.is_empty() {
result.push(serde_json::json!({
let mut message = serde_json::json!({
"role": "assistant",
"content": text_parts,
});
if saw_reasoning {
message["reasoning_content"] =
serde_json::json!(reasoning_parts.join("\n"));
}
result.push(message);
} else if saw_reasoning {
result.push(serde_json::json!({
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"role": "assistant",
"content": [],
"reasoning_content": reasoning_parts.join("\n"),
}));
}

result.extend(function_calls);
}
}
}
Expand Down Expand Up @@ -3110,6 +3157,93 @@ mod tests {
}
}

#[test]
fn convert_messages_to_openai_preserves_reasoning_for_tool_calls() {
let messages = OneOrMany::one(Message::Assistant {
id: None,
content: OneOrMany::many(vec![
AssistantContent::Reasoning(rig::message::Reasoning::multi(vec![
"step one".to_string(),
"step two".to_string(),
])),
AssistantContent::tool_call(
"call_1",
"file",
serde_json::json!({"operation": "list", "path": "."}),
),
])
.expect("non-empty assistant content"),
});

let converted = convert_messages_to_openai(&messages);
assert_eq!(converted.len(), 1);
assert_eq!(converted[0]["role"], "assistant");
assert!(converted[0]["content"].is_null());
assert_eq!(converted[0]["reasoning_content"], "step one\nstep two");
assert_eq!(converted[0]["tool_calls"][0]["function"]["name"], "file");
assert_eq!(
converted[0]["tool_calls"][0]["function"]["arguments"],
"{\"operation\":\"list\",\"path\":\".\"}"
);
}

#[test]
fn convert_messages_to_openai_responses_preserves_reasoning_for_tool_calls() {
let messages = OneOrMany::one(Message::Assistant {
id: None,
content: OneOrMany::many(vec![
AssistantContent::Reasoning(rig::message::Reasoning::new("inspect identity files")),
AssistantContent::tool_call(
"call_1",
"file",
serde_json::json!({"operation": "list", "path": "."}),
),
])
.expect("non-empty assistant content"),
});

let converted = convert_messages_to_openai_responses(&messages);
assert_eq!(converted.len(), 2);
assert_eq!(converted[0]["role"], "assistant");
assert_eq!(converted[0]["content"], serde_json::json!([]));
assert_eq!(converted[0]["reasoning_content"], "inspect identity files");
assert_eq!(converted[1]["type"], "function_call");
assert_eq!(converted[1]["name"], "file");
}

#[test]
fn convert_messages_to_openai_preserves_empty_reasoning_content_for_redacted_reasoning() {
let messages = OneOrMany::one(Message::Assistant {
id: None,
content: OneOrMany::many(vec![AssistantContent::Reasoning(
rig::message::Reasoning::redacted("hidden").with_id("rs_123".to_string()),
)])
.expect("non-empty assistant content"),
});

let converted = convert_messages_to_openai(&messages);
assert_eq!(converted.len(), 1);
assert!(converted[0]["content"].is_null());
assert_eq!(converted[0]["reasoning_content"], "");
}

#[test]
fn convert_messages_to_openai_responses_preserves_empty_reasoning_content_for_redacted_reasoning()
{
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let messages = OneOrMany::one(Message::Assistant {
id: None,
content: OneOrMany::many(vec![AssistantContent::Reasoning(
rig::message::Reasoning::encrypted("ciphertext").with_id("rs_456".to_string()),
)])
.expect("non-empty assistant content"),
});

let converted = convert_messages_to_openai_responses(&messages);
assert_eq!(converted.len(), 1);
assert_eq!(converted[0]["content"], serde_json::json!([]));
assert_eq!(converted[0]["reasoning_content"], "");
}

#[test]
fn parse_openai_response_empty_error_includes_provider_and_finish_reason() {
let body = serde_json::json!({
Expand Down
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