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fix(google): handle thoughtSignature differently for Gemini 2.5 vs 3 #6890

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Merged
alexhancock merged 1 commit into from
Feb 2, 2026
Merged

fix(google): handle thoughtSignature differently for Gemini 2.5 vs 3 #6890

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95 changes: 82 additions & 13 deletions crates/goose/src/providers/formats/google.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -232,6 +232,25 @@ pub fn process_response_part(
process_response_part_impl(part, last_signature, handling)
}

/// Gemini 2.x includes thoughtSignature on first chunk as metadata, not actual thinking.
fn process_response_part_for_model(
part: &Value,
last_signature: &mut Option<String>,
model_version: Option<&str>,
) -> Option<MessageContent> {
let is_gemini_2 = model_version
.map(|m| m.starts_with("gemini-2"))
.unwrap_or(false);

let has_signature = part.get(THOUGHT_SIGNATURE_KEY).is_some();
let handling = if has_signature && !is_gemini_2 {
SignedTextHandling::SignedTextAsThinking
} else {
SignedTextHandling::SignedTextAsRegularText
};
process_response_part_impl(part, last_signature, handling)
}

fn process_response_part_non_streaming(
part: &Value,
last_signature: &mut Option<String>,
Expand Down Expand Up @@ -461,6 +480,8 @@ where
}
}

let model_version = chunk.get("modelVersion").and_then(|v| v.as_str());

let parts = chunk
.get("candidates")
.and_then(|v| v.as_array())
Expand All @@ -471,7 +492,7 @@ where

if let Some(parts) = parts {
for part in parts {
if let Some(content) = process_response_part(part, &mut last_signature) {
if let Some(content) = process_response_part_for_model(part, &mut last_signature, model_version) {
let message = Message::new(
Role::Assistant,
chrono::Utc::now().timestamp(),
Expand Down Expand Up @@ -1072,18 +1093,71 @@ mod tests {
async fn test_streaming_with_thought_signature() {
use futures::StreamExt;

let signed_stream = concat!(
let gemini3_stream = concat!(
r#"data: {"candidates": [{"content": {"role": "model", "#,
r#""parts": [{"text": "Begin", "thoughtSignature": "sig123"}]}}]}"#,
r#""parts": [{"text": "Begin", "thoughtSignature": "sig123"}]}}], "#,
r#""modelVersion": "gemini-3-pro"}"#,
"\n",
r#"data: {"candidates": [{"content": {"role": "model", "#,
r#""parts": [{"text": " middle"}]}}]}"#,
r#""parts": [{"text": " end"}]}}], "modelVersion": "gemini-3-pro"}"#
);
let lines: Vec<Result<String, anyhow::Error>> =
gemini3_stream.lines().map(|l| Ok(l.to_string())).collect();
let stream = Box::pin(futures::stream::iter(lines));
let mut message_stream = std::pin::pin!(response_to_streaming_message(stream));

let mut text_parts = Vec::new();
let mut thinking_parts = Vec::new();

while let Some(result) = message_stream.next().await {
let (message, _usage) = result.unwrap();
if let Some(msg) = message {
match msg.content.first() {
Some(MessageContent::Text(text)) => text_parts.push(text.text.clone()),
Some(MessageContent::Thinking(t)) => thinking_parts.push(t.thinking.clone()),
_ => {}
}
}
}

assert_eq!(thinking_parts, vec!["Begin"]);
assert_eq!(text_parts, vec![" end"]);

let gemini25_stream = concat!(
r#"data: {"candidates": [{"content": {"role": "model", "#,
r#""parts": [{"text": "Begin", "thoughtSignature": "sig123"}]}}], "#,
r#""modelVersion": "gemini-2.5-pro"}"#,
"\n",
r#"data: {"candidates": [{"content": {"role": "model", "#,
r#""parts": [{"text": " end"}]}}], "modelVersion": "gemini-2.5-pro"}"#
);
let lines: Vec<Result<String, anyhow::Error>> =
gemini25_stream.lines().map(|l| Ok(l.to_string())).collect();
let stream = Box::pin(futures::stream::iter(lines));
let mut message_stream = std::pin::pin!(response_to_streaming_message(stream));

let mut text_parts = Vec::new();

while let Some(result) = message_stream.next().await {
let (message, _usage) = result.unwrap();
if let Some(msg) = message {
if let Some(MessageContent::Text(text)) = msg.content.first() {
text_parts.push(text.text.clone());
}
}
}

assert_eq!(text_parts, vec!["Begin", " end"]);

let unknown_stream = concat!(
r#"data: {"candidates": [{"content": {"role": "model", "#,
r#""parts": [{"text": "Begin", "thoughtSignature": "sig123"}]}}]}"#,
"\n",
r#"data: {"candidates": [{"content": {"role": "model", "#,
r#""parts": [{"text": " end"}]}}]}"#
);
let lines: Vec<Result<String, anyhow::Error>> =
signed_stream.lines().map(|l| Ok(l.to_string())).collect();
unknown_stream.lines().map(|l| Ok(l.to_string())).collect();
let stream = Box::pin(futures::stream::iter(lines));
let mut message_stream = std::pin::pin!(response_to_streaming_message(stream));

Expand All @@ -1094,20 +1168,15 @@ mod tests {
let (message, _usage) = result.unwrap();
if let Some(msg) = message {
match msg.content.first() {
Some(MessageContent::Text(text)) => {
text_parts.push(text.text.clone());
}
Some(MessageContent::Thinking(thinking)) => {
thinking_parts.push(thinking.thinking.clone());
assert_eq!(thinking.signature, "sig123");
}
Some(MessageContent::Text(text)) => text_parts.push(text.text.clone()),
Some(MessageContent::Thinking(t)) => thinking_parts.push(t.thinking.clone()),
_ => {}
}
}
}

assert_eq!(thinking_parts, vec!["Begin"]);
assert_eq!(text_parts, vec![" middle", " end"]);
assert_eq!(text_parts, vec![" end"]);
}

#[tokio::test]
Expand Down