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Fix GLM tool-call argument tag parsing #59

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Fix GLM tool-call argument tag parsing #59

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b0ff557
fix: handle GLM tool argument tags
aarongiuffre Oct 23, 2026
1f38c71
Fix array tool-argument coercion for GLM
aarongiuffre Oct 23, 2026
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104 changes: 90 additions & 14 deletions helios/src/output/argument_tags.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,7 @@ use serde_json::{Map, Value};
use crate::output::tagged::{OutputConfig, TaggedOutput};

pub struct ArgumentTags;

impl ToolDialect for ArgumentTags {
const NAME: &'static str = "GLM";
const TRIM_NEWLINES: bool = false;
Expand All @@ -20,47 +21,96 @@ impl ToolDialect for ArgumentTags {
let body = body.trim();
let split = body.find("<arg_key>").unwrap_or(body.len());
let name = body[..split].trim();

if name.is_empty() {
return Err("tool function name is empty".into());
}

let mut rest = &body[split..];

let function = tools
.iter()
.filter_map(|tool| tool.get("function"))
.find(|function| function.get("name").and_then(Value::as_str) == Some(name));
.find(|function| {
function.get("name").and_then(Value::as_str) == Some(name)
});

let properties = function
.and_then(|function| function.get("parameters"))
.and_then(|parameters| parameters.get("properties"))
.and_then(Value::as_object);

let mut arguments = Map::new();

while !rest.trim().is_empty() {
let key = rest
.trim_start()
.strip_prefix("<arg_key>")
.ok_or("GLM tool call requires an argument key")?;
let remaining = rest.trim_start();

let key = remaining.strip_prefix("<arg_key>").ok_or_else(|| {
let marker = if remaining.starts_with("</arg_value>") {
"closing-arg-value"
} else if remaining.starts_with("</tool_call>") {
"closing-tool-call"
} else if remaining.starts_with("<arg_value>") {
"arg-value-without-key"
} else if remaining.starts_with("<arg_key") {
"malformed-arg-key"
} else if remaining.starts_with('<') {
"unexpected-tag"
} else {
"unexpected-text"
};

format!(
"GLM tool call requires an argument key \
(remaining_bytes={}, next_marker={marker})",
remaining.len()
)
})?;

let (key, tail) = key
.split_once("</arg_key>")
.ok_or("unterminated GLM argument key")?;

if key.is_empty() || arguments.contains_key(key) {
return Err("GLM argument names must be nonempty and unique".into());
}

let value = tail
.trim_start()
.strip_prefix("<arg_value>")
.ok_or("GLM argument requires a value tag")?;

let (value, tail) = value
.split_once("</arg_value>")
.ok_or("unterminated GLM argument value")?;
arguments.insert(
key.to_owned(),
parameter_value(value, properties.and_then(|p| p.get(key)))?,
);

let schema = properties.and_then(|properties| properties.get(key));
let declared_type = schema
.and_then(|schema| schema.get("type"))
.map(Value::to_string)
.unwrap_or_else(|| "<missing-or-union>".into());

let converted = parameter_value(value, schema).map_err(|error| {
crate::FrontendError::Input(crate::Failure::caused_by(
format!(
"GLM argument '{key}' (declared type {declared_type}) \
failed conversion: {error}"
),
error,
))
})?;

arguments.insert(key.to_owned(), converted);
rest = tail;
}

Ok(vec![(
name.to_owned(),
serde_json::to_string(&arguments).map_err(|error| {
crate::FrontendError::Input(crate::Failure::caused_by(error.to_string(), error))
crate::FrontendError::Input(crate::Failure::caused_by(
error.to_string(),
error,
))
})?,
)])
}
Expand Down Expand Up @@ -93,13 +143,15 @@ mod tests {
#[test]
fn split_streams_preserve_reasoning_and_decode_typed_tool_arguments() {
let text = "\nreason α\n</think>\nAnswer\n<tool_call>run<arg_key>text</arg_key><arg_value>\nhello α\n</arg_value><arg_key>count</arg_key><arg_value>2</arg_value><arg_key>enabled</arg_key><arg_value>true</arg_value><arg_key>items</arg_key><arg_value>[1,2]</arg_value><arg_key>options</arg_key><arg_value>{\"x\":1}</arg_value><arg_key>empty</arg_key><arg_value>null</arg_value></tool_call><tool_call>run</tool_call>\nend";

for boundary in text
.char_indices()
.map(|(index, _)| index)
.chain([text.len()])
{
let mut parser = ArgumentTagOutput::new(config());
let mut output = Accumulator::new("test".into());

output
.apply(parser.push(Input::Text(&text[..boundary])).unwrap())
.unwrap();
Expand All @@ -109,19 +161,34 @@ mod tests {
output
.apply(parser.finish(Termination::Eos).unwrap())
.unwrap();

output.finish().unwrap();
let message = output.message();

assert_eq!(message["reasoning_content"], "\nreason α\n");
assert_eq!(message["content"], "\nAnswer\n\nend");

let calls = message["tool_calls"].as_array().unwrap();
assert_eq!(calls.len(), 2);
assert_eq!(calls[0]["function"]["name"], "run");
let arguments: Value =
serde_json::from_str(calls[0]["function"]["arguments"].as_str().unwrap()).unwrap();

let arguments: Value = serde_json::from_str(
calls[0]["function"]["arguments"].as_str().unwrap(),
)
.unwrap();

assert_eq!(
arguments,
json!({"text":"\nhello α\n", "count":2, "enabled":true, "items":[1,2], "options":{"x":1}, "empty":null})
json!({
"text":"\nhello α\n",
"count":2,
"enabled":true,
"items":[1,2],
"options":{"x":1},
"empty":null
})
);

assert_eq!(calls[1]["function"]["arguments"], "{}");
}
}
Expand All @@ -146,15 +213,24 @@ mod tests {
#[test]
fn truncation_and_structured_output_keep_protocol_semantics() {
let mut parser = ArgumentTagOutput::new(config());

parser
.push(Input::Text("</think><tool_call>run<arg_key>text</arg_key>"))
.unwrap();
assert!(parser.finish(Termination::OutputLimit).unwrap().is_empty());

assert!(
parser
.finish(Termination::OutputLimit)
.unwrap()
.is_empty()
);

let mut parser = ArgumentTagOutput::new(OutputConfig {
structured: true,
start: crate::output::tagged::OutputStart::Content,
..config()
});

assert_eq!(
parser
.push(Input::Text("<think>{\"x\":1}</think>"))
Expand Down
29 changes: 28 additions & 1 deletion helios/src/output/tagged.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -556,7 +556,7 @@ pub(crate) fn parameter_value(raw: &str, schema: Option<&Value>) -> Result<Value
_ => return Err("invalid tool parameter type declaration".into()),
};
let parsed: std::result::Result<Value, _> = serde_json::from_str(raw);
for kind in kinds {
for &kind in &kinds {
if kind == "string" {
return Ok(Value::String(raw.into()));
}
Expand All @@ -575,5 +575,32 @@ pub(crate) fn parameter_value(raw: &str, schema: Option<&Value>) -> Result<Value
}
}
}

// coercion fallback for array
if kinds.contains(&"array") {
if let Ok(Value::Array(_)) = &parsed {
return Ok(parsed.unwrap());
}
if let Ok(Value::String(s)) = &parsed {
if let Ok(Value::Array(a)) = serde_json::from_str(s) {
return Ok(Value::Array(a));
}
}
let trimmed = raw.trim();
if !trimmed.is_empty() && !trimmed.starts_with('[') {
let parts: Vec<Value> = trimmed
.split(',')
.map(|p| Value::String(p.trim().trim_matches('"').to_string()))
.filter(|v| !v.as_str().unwrap_or("").is_empty())
.collect();
if !parts.is_empty() {
return Ok(Value::Array(parts));
}
}
if !trimmed.is_empty() {
return Ok(Value::Array(vec![Value::String(trimmed.to_string())]));
}
}

Err("tool parameter value does not match its declared JSON type".into())
}