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fix: final assistant content cannot end with trailing whitespace error from Anthropic #5967

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Merged
tlongwell-block merged 1 commit into from
Dec 4, 2025
Merged

fix: final assistant content cannot end with trailing whitespace error from Anthropic #5967

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27 changes: 27 additions & 0 deletions crates/goose/src/conversation/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -202,6 +202,7 @@ pub fn fix_conversation(conversation: Conversation) -> (Conversation, Vec<String
fn fix_messages(messages: Vec<Message>) -> (Vec<Message>, Vec<String>) {
[
merge_text_content_items,
trim_assistant_text_whitespace,
remove_empty_messages,
fix_tool_calling,
merge_consecutive_messages,
Expand Down Expand Up @@ -257,6 +258,32 @@ fn merge_text_content_items(messages: Vec<Message>) -> (Vec<Message>, Vec<String
)
}

fn trim_assistant_text_whitespace(messages: Vec<Message>) -> (Vec<Message>, Vec<String>) {
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@alexhancock alexhancock Dec 3, 2025

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Interesting. I might just add a fn trim which trims both leading and trailing whitespace of all messages. Would be simpler, and in theory doesn't cause any issues. Only makes messages smaller.

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@tlongwell-block tlongwell-block Dec 4, 2025

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Okay, looked into this a bit and tried out some edge cases. We could get into trouble with messages that contain things like ascii art, tables, charts, or other space-dependent content in user message. So, I'm just going to leave this as trimming only the trailing whitespace on assistant messages

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@tlongwell-block tlongwell-block Dec 4, 2025

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I could limit the trimming to only the very latest assistant message since that appears to be the only one Anthropic cares about per that message. Any thoughts there @alexhancock ?

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@DOsinga DOsinga Dec 4, 2025

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this stops things from crashing so that's good and agree, leading whitespace you can't trim in general. do we know where the issue comes from though? it would be better if we could fix it at the source.

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@tlongwell-block tlongwell-block Dec 4, 2025 •
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If the error is to be believed at face value, it's an assistant message causing the issue.

So that rules out tool responses, the moim, and special/control input from the user/client. So my thought is that the LLM itself is generating a trailing whitespace for some reason? They do get weird sometimes once context gets long enough.

tool call seems likely and fits with what I was seeing

let mut issues = Vec::new();

let fixed_messages = messages
.into_iter()
.map(|mut message| {
if message.role == Role::Assistant {
for content in &mut message.content {
if let MessageContent::Text(text) = content {
let trimmed = text.text.trim_end();
if trimmed.len() != text.text.len() {
issues.push(
"Trimmed trailing whitespace from assistant message".to_string(),
);
text.text = trimmed.to_string();
}
}
}
}
message
})
.collect();

(fixed_messages, issues)
}

fn remove_empty_messages(messages: Vec<Message>) -> (Vec<Message>, Vec<String>) {
let mut issues = Vec::new();
let filtered_messages = messages
Expand Down
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