[router] add tool parser base structure and partial json parser (#9482)

sgl-router/Cargo.toml

@@ -48,6 +48,7 @@ metrics = "0.24.2"
 metrics-exporter-prometheus = "0.17.0"
 uuid = { version = "1.10", features = ["v4", "serde"] }
 thiserror = "2.0.12"
+regex = "1.10"
 url = "2.5.4"
 tokio-stream = { version = "0.1", features = ["sync"] }
 anyhow = "1.0"

sgl-router/benches/tokenizer_benchmark.rs

@@ -100,7 +100,8 @@ fn bench_encode_throughput(c: &mut Criterion) {
         let tokenizer_clone = tokenizer.clone();
 
         // Get token count once
-        let token_count = tokenizer.encode(prompt).unwrap().token_ids().len();
+        let encoding = tokenizer.encode(prompt).unwrap();
+        let token_count = encoding.token_ids().len();
 
         // Track if metrics have been printed for this test case
         let printed = Arc::new(AtomicBool::new(false));
@@ -157,7 +158,8 @@ fn bench_batch_encode(c: &mut Criterion) {
     let batch_sizes = vec![1, 8, 16, 32, 64, 128];
     let prompt = MEDIUM_PROMPT;
     let prompt_len = prompt.len();
-    let token_count = tokenizer.encode(prompt).unwrap().token_ids().len();
+    let encoding = tokenizer.encode(prompt).unwrap();
+    let token_count = encoding.token_ids().len();
 
     let mut group = c.benchmark_group("batch_encode");
 
@@ -303,7 +305,8 @@ fn bench_decode_performance(c: &mut Criterion) {
     );
 
     let test_text = "The quick brown fox jumps over the lazy dog. ".repeat(10);
-    let tokens = tokenizer.encode(&test_text).unwrap().token_ids();
+    let encoding = tokenizer.encode(&test_text).unwrap();
+    let tokens = encoding.token_ids();
     let num_tokens = tokens.len();
 
     let mut group = c.benchmark_group("decode_performance");
@@ -313,12 +316,11 @@ fn bench_decode_performance(c: &mut Criterion) {
     group.bench_function("direct_decode", |b| {
         let printed = printed_direct.clone();
         let tokenizer = tokenizer.clone();
-        let tokens = tokens.clone();
 
         b.iter_custom(|iters| {
             let start = Instant::now();
             for _ in 0..iters {
-                black_box(tokenizer.decode(&tokens, false).unwrap());
+                black_box(tokenizer.decode(tokens, false).unwrap());
             }
             let duration = start.elapsed();
 
@@ -344,14 +346,13 @@ fn bench_decode_performance(c: &mut Criterion) {
     group.bench_function("decode_stream", |b| {
         let printed = printed_stream.clone();
         let tokenizer = tokenizer.clone();
-        let tokens = tokens.clone();
 
         b.iter_custom(|iters| {
             let start = Instant::now();
             for _ in 0..iters {
                 let mut decoder = DecodeStream::new(tokenizer.clone(), &[], false);
                 let mut output = String::new();
-                for token in &tokens {
+                for token in tokens {
                     if let Some(text) = decoder.step(*token).unwrap() {
                         output.push_str(&text);
                     }
@@ -382,14 +383,13 @@ fn bench_decode_performance(c: &mut Criterion) {
     group.bench_function("sequence_decode", |b| {
         let printed = printed_seq.clone();
         let tokenizer = tokenizer.clone();
-        let tokens = tokens.clone();
 
         b.iter_custom(|iters| {
             let start = Instant::now();
             for _ in 0..iters {
                 let mut sequence = Sequence::new(tokenizer.clone());
                 let mut output = String::new();
-                for token in &tokens {
+                for token in tokens {
                     let text = sequence.append_token(*token).unwrap();
                     output.push_str(&text);
                 }
@@ -424,7 +424,8 @@ fn bench_streaming_decode_100k(c: &mut Criterion) {
     );
 
     let sample_text = "The quick brown fox jumps over the lazy dog. ".repeat(1000);
-    let all_tokens = tokenizer.encode(&sample_text).unwrap().token_ids();
+    let encoding = tokenizer.encode(&sample_text).unwrap();
+    let all_tokens = encoding.token_ids();
 
     let mut group = c.benchmark_group("streaming_100k");
     group.measurement_time(Duration::from_secs(1));
@@ -434,7 +435,6 @@ fn bench_streaming_decode_100k(c: &mut Criterion) {
     group.bench_function("decode_stream_100k", |b| {
         let printed = printed_stream.clone();
         let tokenizer = tokenizer.clone();
-        let tokens = all_tokens.clone();
 
         b.iter_custom(|_iters| {
             let start = Instant::now();
@@ -442,7 +442,7 @@ fn bench_streaming_decode_100k(c: &mut Criterion) {
             let mut output = String::new();
             let mut tokens_processed = 0u64;
 
-            for token in tokens.iter().cycle() {
+            for token in all_tokens.iter().cycle() {
                 if start.elapsed() >= Duration::from_millis(500) {
                     break;
                 }
@@ -486,7 +486,6 @@ fn bench_streaming_decode_100k(c: &mut Criterion) {
     group.bench_function("sequence_100k", |b| {
         let printed = printed_seq.clone();
         let tokenizer = tokenizer.clone();
-        let tokens = all_tokens.clone();
 
         b.iter_custom(|_iters| {
             let start = Instant::now();
@@ -494,7 +493,7 @@ fn bench_streaming_decode_100k(c: &mut Criterion) {
             let mut output = String::new();
             let mut tokens_processed = 0u64;
 
-            for token in tokens.iter().cycle() {
+            for token in all_tokens.iter().cycle() {
                 if start.elapsed() >= Duration::from_millis(500) {
                     break;
                 }
@@ -693,7 +692,8 @@ fn bench_concurrent_streaming(c: &mut Criterion) {
     let tokens_per_sequence = 10_000;
 
     let sample_text = "The quick brown fox jumps over the lazy dog. ".repeat(100);
-    let token_batch = tokenizer.encode(&sample_text).unwrap().token_ids();
+    let encoding = tokenizer.encode(&sample_text).unwrap();
+    let token_batch: Vec<u32> = encoding.token_ids().to_vec();
 
     let mut group = c.benchmark_group("concurrent_streaming");
     group.measurement_time(Duration::from_secs(2));
@@ -775,7 +775,8 @@ fn bench_stop_sequences(c: &mut Criterion) {
         .with_stop_token(2);
 
     let sample_text = "Hello world! This is a test. ### Stop here. Continue after.".repeat(100);
-    let tokens = tokenizer.encode(&sample_text).unwrap().token_ids();
+    let encoding = tokenizer.encode(&sample_text).unwrap();
+    let tokens = encoding.token_ids();
 
     let mut group = c.benchmark_group("stop_sequences");
 
@@ -784,7 +785,6 @@ fn bench_stop_sequences(c: &mut Criterion) {
     group.bench_function("no_stops", |b| {
         let printed_clone = printed_no_stop.clone();
         let tokenizer = tokenizer.clone();
-        let tokens = tokens.clone();
 
         b.iter_custom(|iters| {
             let start = Instant::now();
@@ -796,7 +796,7 @@ fn bench_stop_sequences(c: &mut Criterion) {
                     StopSequenceConfig::default(),
                     false,
                 );
-                for token in &tokens {
+                for token in tokens {
                     let _ = decoder.process_token(*token).unwrap();
                     total_tokens += 1;
                 }
@@ -826,7 +826,6 @@ fn bench_stop_sequences(c: &mut Criterion) {
     group.bench_function("with_stops", |b| {
         let printed_clone = printed_with_stops.clone();
         let tokenizer = tokenizer.clone();
-        let tokens = tokens.clone();
         let config = config.clone();
 
         b.iter_custom(|iters| {
@@ -839,7 +838,7 @@ fn bench_stop_sequences(c: &mut Criterion) {
                     StopSequenceDecoder::new(tokenizer.clone(), config.clone(), false);
                 let mut sequence_tokens = 0u64;
 
-                for token in &tokens {
+                for token in tokens {
                     let result = decoder.process_token(*token).unwrap();
                     sequence_tokens += 1;
 
@@ -986,7 +985,8 @@ fn bench_multithreaded_decode(c: &mut Criterion) {
 
     // Generate tokens for decoding
     let test_text = "The quick brown fox jumps over the lazy dog. ".repeat(100);
-    let test_tokens = tokenizer.encode(&test_text).unwrap().token_ids();
+    let encoding = tokenizer.encode(&test_text).unwrap();
+    let test_tokens: Vec<u32> = encoding.token_ids().to_vec();
 
     let mut group = c.benchmark_group("multithreaded_decode");
     group.measurement_time(Duration::from_secs(2));
@@ -1130,7 +1130,7 @@ fn bench_memory_efficiency(c: &mut Criterion) {
         b.iter_custom(|iters| {
             let start = Instant::now();
             for _ in 0..iters {
-                let _ = black_box(encoding.token_ids_ref());
+                let _ = black_box(encoding.token_ids());
             }
             let duration = start.elapsed();
 

sgl-router/src/lib.rs

@@ -14,6 +14,7 @@ pub mod routers;
 pub mod server;
 pub mod service_discovery;
 pub mod tokenizer;
+pub mod tool_parser;
 pub mod tree;
 use crate::metrics::PrometheusConfig;
 

sgl-router/src/tool_parser/errors.rs

@@ -0,0 +1,32 @@
+use thiserror::Error;
+
+/// Result type for tool parser operations
+pub type ToolParserResult<T> = Result<T, ToolParserError>;
+
+/// Errors that can occur during tool parsing
+#[derive(Debug, Error)]
+pub enum ToolParserError {
+    #[error("Parsing failed: {0}")]
+    ParsingFailed(String),
+
+    #[error("Model not supported: {0}")]
+    ModelNotSupported(String),
+
+    #[error("Parse depth exceeded: max {0}")]
+    DepthExceeded(usize),
+
+    #[error("Invalid JSON: {0}")]
+    JsonError(#[from] serde_json::Error),
+
+    #[error("Regex error: {0}")]
+    RegexError(#[from] regex::Error),
+
+    #[error("Incomplete tool call")]
+    Incomplete,
+
+    #[error("Invalid tool name: {0}")]
+    InvalidToolName(String),
+
+    #[error("Token not found: {0}")]
+    TokenNotFound(String),
+}

sgl-router/src/tool_parser/mod.rs

@@ -0,0 +1,20 @@
+/// Tool parser module for handling function/tool calls in model outputs
+///
+/// This module provides infrastructure for parsing tool calls from various model formats.
+/// Phase 1 focuses on core infrastructure: types, traits, registry, and partial JSON parsing.
+pub mod errors;
+pub mod partial_json;
+pub mod registry;
+pub mod state;
+pub mod traits;
+pub mod types;
+
+#[cfg(test)]
+mod tests;
+
+// Re-export commonly used types
+pub use errors::{ToolParserError, ToolParserResult};
+pub use registry::ParserRegistry;
+pub use state::{ParsePhase, ParseState};
+pub use traits::{PartialJsonParser, ToolParser};
+pub use types::{FunctionCall, PartialToolCall, StreamResult, TokenConfig, ToolCall};

sgl-router/src/tool_parser/partial_json.rs

@@ -0,0 +1,527 @@
+use crate::tool_parser::{
+    errors::{ToolParserError, ToolParserResult},
+    traits::PartialJsonParser,
+};
+use serde_json::{Map, Value};
+
+/// Parser for incomplete JSON
+pub struct PartialJson {
+    /// Maximum depth for nested structures
+    max_depth: usize,
+    /// Whether to allow incomplete values
+    allow_incomplete: bool,
+}
+
+impl PartialJson {
+    /// Create a new partial JSON parser
+    pub fn new(max_depth: usize, allow_incomplete: bool) -> Self {
+        Self {
+            max_depth,
+            allow_incomplete,
+        }
+    }
+
+    /// Parse potentially incomplete JSON, returning parsed value and consumed bytes
+    pub fn parse_value(&self, input: &str) -> ToolParserResult<(Value, usize)> {
+        let mut parser = Parser::new(input, self.max_depth, self.allow_incomplete);
+        let value = parser.parse_value(0)?;
+        Ok((value, parser.position))
+    }
+}
+
+impl Default for PartialJson {
+    fn default() -> Self {
+        Self::new(32, true)
+    }
+}
+
+impl PartialJsonParser for PartialJson {
+    fn parse(&self, input: &str) -> ToolParserResult<(Value, usize)> {
+        self.parse_value(input)
+    }
+
+    fn is_complete(&self, input: &str) -> bool {
+        // Try to parse as complete JSON
+        serde_json::from_str::<Value>(input).is_ok()
+    }
+
+    fn max_depth(&self) -> usize {
+        self.max_depth
+    }
+}
+
+/// Internal parser state
+struct Parser<'a> {
+    chars: std::iter::Peekable<std::str::Chars<'a>>,
+    position: usize,
+    max_depth: usize,
+    allow_incomplete: bool,
+}
+
+impl<'a> Parser<'a> {
+    fn new(input: &'a str, max_depth: usize, allow_incomplete: bool) -> Self {
+        Self {
+            chars: input.chars().peekable(),
+            position: 0,
+            max_depth,
+            allow_incomplete,
+        }
+    }
+
+    fn peek(&mut self) -> Option<char> {
+        self.chars.peek().copied()
+    }
+
+    fn advance(&mut self) {
+        if self.chars.next().is_some() {
+            self.position += 1;
+        }
+    }
+
+    fn skip_whitespace(&mut self) {
+        while let Some(ch) = self.peek() {
+            if ch.is_whitespace() {
+                self.advance();
+            } else {
+                break;
+            }
+        }
+    }
+
+    fn parse_value(&mut self, depth: usize) -> ToolParserResult<Value> {
+        if depth > self.max_depth {
+            return Err(ToolParserError::DepthExceeded(self.max_depth));
+        }
+
+        self.skip_whitespace();
+
+        match self.peek() {
+            Some('{') => self.parse_object(depth + 1),
+            Some('[') => self.parse_array(depth + 1),
+            Some('"') => self.parse_string(),
+            Some('t') | Some('f') => self.parse_bool(),
+            Some('n') => self.parse_null(),
+            Some(c) if c == '-' || c.is_ascii_digit() => self.parse_number(),
+            _ => {
+                if self.allow_incomplete {
+                    Ok(Value::Null)
+                } else {
+                    Err(ToolParserError::ParsingFailed(
+                        "Unexpected character".into(),
+                    ))
+                }
+            }
+        }
+    }
+
+    fn parse_object(&mut self, depth: usize) -> ToolParserResult<Value> {
+        if depth > self.max_depth {
+            return Err(ToolParserError::DepthExceeded(self.max_depth));
+        }
+
+        let mut object = Map::new();
+
+        // Consume '{'
+        self.advance();
+        self.skip_whitespace();
+
+        // Check for empty object
+        if self.peek() == Some('}') {
+            self.advance();
+            return Ok(Value::Object(object));
+        }
+
+        loop {
+            // Parse key
+            let key = match self.parse_string() {
+                Ok(Value::String(s)) => s,
+                Err(_) if self.allow_incomplete => {
+                    // Incomplete object
+                    return Ok(Value::Object(object));
+                }
+                Err(e) => return Err(e),
+                _ => return Err(ToolParserError::ParsingFailed("Expected string key".into())),
+            };
+
+            self.skip_whitespace();
+
+            // Expect ':'
+            if self.peek() != Some(':') {
+                if self.allow_incomplete {
+                    // Add null value for incomplete pair
+                    object.insert(key, Value::Null);
+                    return Ok(Value::Object(object));
+                }
+                return Err(ToolParserError::ParsingFailed("Expected ':'".into()));
+            }
+            self.advance();
+            self.skip_whitespace();
+
+            // Parse value (keep same depth - we already incremented in parse_object)
+            let value = match self.parse_value(depth) {
+                Ok(v) => v,
+                Err(_) if self.allow_incomplete => {
+                    // Add null for incomplete value
+                    object.insert(key, Value::Null);
+                    return Ok(Value::Object(object));
+                }
+                Err(e) => return Err(e),
+            };
+
+            object.insert(key, value);
+            self.skip_whitespace();
+
+            match self.peek() {
+                Some(',') => {
+                    self.advance();
+                    self.skip_whitespace();
+                    // Check for trailing comma
+                    if self.peek() == Some('}') {
+                        self.advance();
+                        return Ok(Value::Object(object));
+                    }
+                }
+                Some('}') => {
+                    self.advance();
+                    return Ok(Value::Object(object));
+                }
+                None if self.allow_incomplete => {
+                    return Ok(Value::Object(object));
+                }
+                _ => {
+                    if self.allow_incomplete {
+                        return Ok(Value::Object(object));
+                    }
+                    return Err(ToolParserError::ParsingFailed("Expected ',' or '}'".into()));
+                }
+            }
+        }
+    }
+
+    fn parse_array(&mut self, depth: usize) -> ToolParserResult<Value> {
+        if depth > self.max_depth {
+            return Err(ToolParserError::DepthExceeded(self.max_depth));
+        }
+
+        let mut array = Vec::new();
+
+        // Consume '['
+        self.advance();
+        self.skip_whitespace();
+
+        // Check for empty array
+        if self.peek() == Some(']') {
+            self.advance();
+            return Ok(Value::Array(array));
+        }
+
+        loop {
+            // Parse value (keep same depth - we already incremented in parse_object)
+            let value = match self.parse_value(depth) {
+                Ok(v) => v,
+                Err(_) if self.allow_incomplete => {
+                    return Ok(Value::Array(array));
+                }
+                Err(e) => return Err(e),
+            };
+
+            array.push(value);
+            self.skip_whitespace();
+
+            match self.peek() {
+                Some(',') => {
+                    self.advance();
+                    self.skip_whitespace();
+                    // Check for trailing comma
+                    if self.peek() == Some(']') {
+                        self.advance();
+                        return Ok(Value::Array(array));
+                    }
+                }
+                Some(']') => {
+                    self.advance();
+                    return Ok(Value::Array(array));
+                }
+                None if self.allow_incomplete => {
+                    return Ok(Value::Array(array));
+                }
+                _ => {
+                    if self.allow_incomplete {
+                        return Ok(Value::Array(array));
+                    }
+                    return Err(ToolParserError::ParsingFailed("Expected ',' or ']'".into()));
+                }
+            }
+        }
+    }
+
+    fn parse_string(&mut self) -> ToolParserResult<Value> {
+        if self.peek() != Some('"') {
+            return Err(ToolParserError::ParsingFailed("Expected '\"'".into()));
+        }
+
+        // Consume opening quote
+        self.advance();
+
+        let mut string = String::new();
+        let mut escaped = false;
+
+        while let Some(ch) = self.peek() {
+            if escaped {
+                // Handle escape sequences
+                let escaped_char = match ch {
+                    '"' | '\\' | '/' => ch,
+                    'b' => '\u{0008}',
+                    'f' => '\u{000C}',
+                    'n' => '\n',
+                    'r' => '\r',
+                    't' => '\t',
+                    'u' => {
+                        // Unicode escape
+                        self.advance();
+                        let hex = self.parse_unicode_escape()?;
+                        string.push(hex);
+                        escaped = false;
+                        continue;
+                    }
+                    _ => ch, // Invalid escape, but be lenient
+                };
+                string.push(escaped_char);
+                escaped = false;
+            } else if ch == '\\' {
+                escaped = true;
+            } else if ch == '"' {
+                // End of string
+                self.advance();
+                return Ok(Value::String(string));
+            } else {
+                string.push(ch);
+            }
+            self.advance();
+        }
+
+        // Incomplete string
+        if self.allow_incomplete {
+            Ok(Value::String(string))
+        } else {
+            Err(ToolParserError::ParsingFailed("Unterminated string".into()))
+        }
+    }
+
+    fn parse_unicode_escape(&mut self) -> ToolParserResult<char> {
+        let mut hex = String::new();
+        for _ in 0..4 {
+            if let Some(ch) = self.peek() {
+                if ch.is_ascii_hexdigit() {
+                    hex.push(ch);
+                    self.advance();
+                } else {
+                    break;
+                }
+            } else {
+                break;
+            }
+        }
+
+        if hex.len() == 4 {
+            u32::from_str_radix(&hex, 16)
+                .ok()
+                .and_then(char::from_u32)
+                .ok_or_else(|| ToolParserError::ParsingFailed("Invalid unicode escape".into()))
+        } else if self.allow_incomplete {
+            Ok('\u{FFFD}') // Replacement character
+        } else {
+            Err(ToolParserError::ParsingFailed(
+                "Incomplete unicode escape".into(),
+            ))
+        }
+    }
+
+    fn parse_number(&mut self) -> ToolParserResult<Value> {
+        let mut number = String::new();
+
+        // Handle negative sign
+        if self.peek() == Some('-') {
+            number.push('-');
+            self.advance();
+        }
+
+        // Parse integer part
+        if self.peek() == Some('0') {
+            number.push('0');
+            self.advance();
+        } else {
+            while let Some(ch) = self.peek() {
+                if ch.is_ascii_digit() {
+                    number.push(ch);
+                    self.advance();
+                } else {
+                    break;
+                }
+            }
+        }
+
+        // Parse decimal part
+        if self.peek() == Some('.') {
+            number.push('.');
+            self.advance();
+
+            while let Some(ch) = self.peek() {
+                if ch.is_ascii_digit() {
+                    number.push(ch);
+                    self.advance();
+                } else {
+                    break;
+                }
+            }
+        }
+
+        // Parse exponent
+        if let Some(ch) = self.peek() {
+            if ch == 'e' || ch == 'E' {
+                number.push(ch);
+                self.advance();
+
+                if let Some(sign) = self.peek() {
+                    if sign == '+' || sign == '-' {
+                        number.push(sign);
+                        self.advance();
+                    }
+                }
+
+                while let Some(ch) = self.peek() {
+                    if ch.is_ascii_digit() {
+                        number.push(ch);
+                        self.advance();
+                    } else {
+                        break;
+                    }
+                }
+            }
+        }
+
+        // Try to parse as integer first, then as float
+        if let Ok(n) = number.parse::<i64>() {
+            Ok(Value::Number(serde_json::Number::from(n)))
+        } else if let Ok(n) = number.parse::<f64>() {
+            Ok(Value::Number(
+                serde_json::Number::from_f64(n).unwrap_or_else(|| serde_json::Number::from(0)),
+            ))
+        } else if self.allow_incomplete {
+            Ok(Value::Number(serde_json::Number::from(0)))
+        } else {
+            Err(ToolParserError::ParsingFailed("Invalid number".into()))
+        }
+    }
+
+    fn parse_bool(&mut self) -> ToolParserResult<Value> {
+        let mut word = String::new();
+
+        // Peek at upcoming characters to validate it looks like a boolean
+        let mut temp_chars = self.chars.clone();
+        while let Some(&ch) = temp_chars.peek() {
+            if ch.is_alphabetic() && word.len() < 5 {
+                // "false" is 5 chars
+                word.push(ch);
+                temp_chars.next();
+            } else {
+                break;
+            }
+        }
+
+        // Check if it's a valid boolean prefix
+        let is_valid = word == "true"
+            || word == "false"
+            || (self.allow_incomplete && ("true".starts_with(&word) || "false".starts_with(&word)));
+
+        if !is_valid {
+            return Err(ToolParserError::ParsingFailed("Invalid boolean".into()));
+        }
+
+        // Now actually consume the characters
+        word.clear();
+        while let Some(ch) = self.peek() {
+            if ch.is_alphabetic() {
+                word.push(ch);
+                self.advance();
+            } else {
+                break;
+            }
+        }
+
+        match word.as_str() {
+            "true" => Ok(Value::Bool(true)),
+            "false" => Ok(Value::Bool(false)),
+            partial if self.allow_incomplete => {
+                if "true".starts_with(partial) {
+                    Ok(Value::Bool(true))
+                } else if "false".starts_with(partial) {
+                    Ok(Value::Bool(false))
+                } else {
+                    Err(ToolParserError::ParsingFailed("Invalid boolean".into()))
+                }
+            }
+            _ => Err(ToolParserError::ParsingFailed("Invalid boolean".into())),
+        }
+    }
+
+    fn parse_null(&mut self) -> ToolParserResult<Value> {
+        let mut word = String::new();
+
+        // Peek at upcoming characters to validate it looks like "null"
+        let mut temp_chars = self.chars.clone();
+        while let Some(&ch) = temp_chars.peek() {
+            if ch.is_alphabetic() && word.len() < 4 {
+                // "null" is 4 chars
+                word.push(ch);
+                temp_chars.next();
+            } else {
+                break;
+            }
+        }
+
+        // Check if it's a valid null prefix
+        let is_valid = word == "null" || (self.allow_incomplete && "null".starts_with(&word));
+
+        if !is_valid {
+            return Err(ToolParserError::ParsingFailed("Invalid null".into()));
+        }
+
+        // Now actually consume the characters
+        word.clear();
+        while let Some(ch) = self.peek() {
+            if ch.is_alphabetic() {
+                word.push(ch);
+                self.advance();
+            } else {
+                break;
+            }
+        }
+
+        if word == "null" || (self.allow_incomplete && "null".starts_with(&word)) {
+            Ok(Value::Null)
+        } else {
+            Err(ToolParserError::ParsingFailed("Invalid null".into()))
+        }
+    }
+}
+
+/// Utility function to check if a string contains complete JSON
+pub fn is_complete_json(input: &str) -> bool {
+    serde_json::from_str::<Value>(input).is_ok()
+}
+
+/// Utility function to find common prefix between two strings
+pub fn find_common_prefix(s1: &str, s2: &str) -> usize {
+    s1.chars()
+        .zip(s2.chars())
+        .take_while(|(a, b)| a == b)
+        .count()
+}
+
+/// Utility function to compute diff between old and new strings
+pub fn compute_diff(old: &str, new: &str) -> String {
+    let common_len = find_common_prefix(old, new);
+    // Convert character count to byte offset
+    new.chars().skip(common_len).collect()
+}

sgl-router/src/tool_parser/registry.rs

@@ -0,0 +1,119 @@
+use crate::tool_parser::traits::ToolParser;
+use std::collections::HashMap;
+use std::sync::Arc;
+
+/// Registry for tool parsers and model mappings
+pub struct ParserRegistry {
+    /// Map of parser name to parser instance
+    parsers: HashMap<String, Arc<dyn ToolParser>>,
+    /// Map of model name/pattern to parser name
+    model_mapping: HashMap<String, String>,
+    /// Default parser to use when no match found
+    default_parser: String,
+}
+
+impl ParserRegistry {
+    /// Create a new parser registry with default mappings
+    pub fn new() -> Self {
+        let mut registry = Self {
+            parsers: HashMap::new(),
+            model_mapping: HashMap::new(),
+            default_parser: "json".to_string(),
+        };
+
+        // Register default model mappings
+        registry.register_default_mappings();
+
+        registry
+    }
+
+    /// Register a parser
+    pub fn register_parser(&mut self, name: impl Into<String>, parser: Arc<dyn ToolParser>) {
+        self.parsers.insert(name.into(), parser);
+    }
+
+    /// Map a model name/pattern to a parser
+    pub fn map_model(&mut self, model: impl Into<String>, parser: impl Into<String>) {
+        self.model_mapping.insert(model.into(), parser.into());
+    }
+
+    /// Get parser for a specific model
+    pub fn get_parser(&self, model: &str) -> Option<Arc<dyn ToolParser>> {
+        // Try exact match first
+        if let Some(parser_name) = self.model_mapping.get(model) {
+            if let Some(parser) = self.parsers.get(parser_name) {
+                return Some(parser.clone());
+            }
+        }
+
+        // Try prefix matching (e.g., "gpt-4" matches "gpt-*")
+        for (pattern, parser_name) in &self.model_mapping {
+            if pattern.ends_with('*') {
+                let prefix = &pattern[..pattern.len() - 1];
+                if model.starts_with(prefix) {
+                    if let Some(parser) = self.parsers.get(parser_name) {
+                        return Some(parser.clone());
+                    }
+                }
+            }
+        }
+
+        // Fall back to default parser if it exists
+        self.parsers.get(&self.default_parser).cloned()
+    }
+
+    /// List all registered parsers
+    pub fn list_parsers(&self) -> Vec<&str> {
+        self.parsers.keys().map(|s| s.as_str()).collect()
+    }
+
+    /// List all model mappings
+    pub fn list_mappings(&self) -> Vec<(&str, &str)> {
+        self.model_mapping
+            .iter()
+            .map(|(k, v)| (k.as_str(), v.as_str()))
+            .collect()
+    }
+
+    /// Register default model mappings
+    fn register_default_mappings(&mut self) {
+        // OpenAI models
+        self.map_model("gpt-4*", "json");
+        self.map_model("gpt-3.5*", "json");
+        self.map_model("gpt-4o*", "json");
+
+        // Anthropic models
+        self.map_model("claude-*", "json");
+
+        // Mistral models
+        self.map_model("mistral-*", "mistral");
+        self.map_model("mixtral-*", "mistral");
+
+        // Qwen models
+        self.map_model("qwen*", "qwen");
+
+        // Llama models
+        self.map_model("llama-*", "llama");
+        self.map_model("meta-llama-*", "llama");
+
+        // Other models default to JSON
+        self.map_model("gemini-*", "json");
+        self.map_model("palm-*", "json");
+    }
+
+    /// Set the default parser
+    pub fn set_default_parser(&mut self, name: impl Into<String>) {
+        self.default_parser = name.into();
+    }
+
+    /// Check if a parser is registered
+    pub fn has_parser(&self, name: &str) -> bool {
+        self.parsers.contains_key(name)
+    }
+}
+
+impl Default for ParserRegistry {
+    fn default() -> Self {
+        Self::new()
+    }
+}

sgl-router/src/tool_parser/state.rs

@@ -0,0 +1,181 @@
+use crate::tool_parser::types::{PartialToolCall, ToolCall};
+
+/// Current phase of parsing
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum ParsePhase {
+    /// Looking for start of tool call
+    Searching,
+    /// Parsing function name
+    InName,
+    /// Parsing function arguments
+    InArguments,
+    /// Tool call complete
+    Complete,
+}
+
+/// State for streaming parser
+#[derive(Debug, Clone)]
+pub struct ParseState {
+    /// Buffer for accumulating input
+    pub buffer: String,
+    /// Position of last consumed character
+    pub consumed: usize,
+    /// Current partial tool being parsed
+    pub partial_tool: Option<PartialToolCall>,
+    /// Completed tool calls
+    pub completed_tools: Vec<ToolCall>,
+    /// Current parsing phase
+    pub phase: ParsePhase,
+    /// Bracket/brace depth for JSON parsing
+    pub bracket_depth: i32,
+    /// Whether currently inside a string literal
+    pub in_string: bool,
+    /// Whether next character should be escaped
+    pub escape_next: bool,
+    /// Current tool index (for streaming)
+    pub tool_index: usize,
+}
+
+impl ParseState {
+    /// Create a new parse state
+    pub fn new() -> Self {
+        Self {
+            buffer: String::new(),
+            consumed: 0,
+            partial_tool: None,
+            completed_tools: Vec::new(),
+            phase: ParsePhase::Searching,
+            bracket_depth: 0,
+            in_string: false,
+            escape_next: false,
+            tool_index: 0,
+        }
+    }
+
+    /// Reset state for parsing next tool
+    pub fn reset(&mut self) {
+        self.partial_tool = None;
+        self.phase = ParsePhase::Searching;
+        self.bracket_depth = 0;
+        self.in_string = false;
+        self.escape_next = false;
+    }
+
+    /// Process a single character for JSON parsing
+    pub fn process_char(&mut self, ch: char) {
+        // Handle escape sequences
+        if self.escape_next {
+            self.escape_next = false;
+            self.buffer.push(ch);
+            return;
+        }
+
+        if ch == '\\' && self.in_string {
+            self.escape_next = true;
+            self.buffer.push(ch);
+            return;
+        }
+
+        // Track string boundaries
+        if ch == '"' && !self.escape_next {
+            self.in_string = !self.in_string;
+        }
+
+        // Track bracket depth for JSON
+        if !self.in_string {
+            match ch {
+                '{' | '[' => {
+                    self.bracket_depth += 1;
+                }
+                '}' | ']' => {
+                    self.bracket_depth -= 1;
+                    if self.bracket_depth == 0 && self.partial_tool.is_some() {
+                        // Complete tool call found
+                        self.phase = ParsePhase::Complete;
+                    }
+                }
+                _ => {}
+            }
+        }
+
+        self.buffer.push(ch);
+    }
+
+    /// Check if we have a complete JSON object/array
+    pub fn has_complete_json(&self) -> bool {
+        self.bracket_depth == 0 && !self.in_string && !self.buffer.is_empty()
+    }
+
+    /// Extract content from buffer starting at position
+    pub fn extract_from(&self, start: usize) -> &str {
+        if start >= self.buffer.len() {
+            return "";
+        }
+
+        // Find the nearest character boundary at or after start
+        let mut safe_start = start;
+        while safe_start < self.buffer.len() && !self.buffer.is_char_boundary(safe_start) {
+            safe_start += 1;
+        }
+
+        if safe_start < self.buffer.len() {
+            &self.buffer[safe_start..]
+        } else {
+            ""
+        }
+    }
+
+    /// Mark content as consumed up to position
+    pub fn consume_to(&mut self, position: usize) {
+        if position > self.consumed {
+            self.consumed = position;
+        }
+    }
+
+    /// Get unconsumed content
+    pub fn unconsumed(&self) -> &str {
+        if self.consumed >= self.buffer.len() {
+            return "";
+        }
+
+        // Find the nearest character boundary at or after consumed
+        let mut safe_consumed = self.consumed;
+        while safe_consumed < self.buffer.len() && !self.buffer.is_char_boundary(safe_consumed) {
+            safe_consumed += 1;
+        }
+
+        if safe_consumed < self.buffer.len() {
+            &self.buffer[safe_consumed..]
+        } else {
+            ""
+        }
+    }
+
+    /// Clear consumed content from buffer
+    pub fn clear_consumed(&mut self) {
+        if self.consumed > 0 {
+            // Find the nearest character boundary at or before consumed
+            let mut safe_consumed = self.consumed;
+            while safe_consumed > 0 && !self.buffer.is_char_boundary(safe_consumed) {
+                safe_consumed -= 1;
+            }
+
+            if safe_consumed > 0 {
+                self.buffer.drain(..safe_consumed);
+                self.consumed = self.consumed.saturating_sub(safe_consumed);
+            }
+        }
+    }
+
+    /// Add completed tool
+    pub fn add_completed_tool(&mut self, tool: ToolCall) {
+        self.completed_tools.push(tool);
+        self.tool_index += 1;
+    }
+}
+
+impl Default for ParseState {
+    fn default() -> Self {
+        Self::new()
+    }
+}

sgl-router/src/tool_parser/tests.rs

@@ -0,0 +1,249 @@
+use super::*;
+use crate::tool_parser::partial_json::{
+    compute_diff, find_common_prefix, is_complete_json, PartialJson,
+};
+
+#[test]
+fn test_parse_state_new() {
+    let state = ParseState::new();
+    assert_eq!(state.phase, ParsePhase::Searching);
+    assert_eq!(state.buffer, "");
+    assert_eq!(state.consumed, 0);
+    assert_eq!(state.bracket_depth, 0);
+    assert!(!state.in_string);
+    assert!(!state.escape_next);
+}
+
+#[test]
+fn test_parse_state_process_char() {
+    let mut state = ParseState::new();
+
+    // Test bracket tracking
+    state.process_char('{');
+    assert_eq!(state.bracket_depth, 1);
+
+    state.process_char('}');
+    assert_eq!(state.bracket_depth, 0);
+
+    // Test string tracking
+    state.process_char('"');
+    assert!(state.in_string);
+
+    state.process_char('"');
+    assert!(!state.in_string);
+
+    // Test escape handling
+    state.process_char('"');
+    state.process_char('\\');
+    assert!(state.escape_next);
+
+    state.process_char('"');
+    assert!(!state.escape_next);
+    assert!(state.in_string); // Still in string because quote was escaped
+}
+
+#[test]
+fn test_token_config() {
+    let config = TokenConfig {
+        start_tokens: vec!["<start>".to_string(), "[".to_string()],
+        end_tokens: vec!["</end>".to_string(), "]".to_string()],
+        separator: ", ".to_string(),
+    };
+
+    let pairs: Vec<_> = config.iter_pairs().collect();
+    assert_eq!(pairs.len(), 2);
+    assert_eq!(pairs[0], ("<start>", "</end>"));
+    assert_eq!(pairs[1], ("[", "]"));
+}
+
+#[test]
+fn test_parser_registry() {
+    let registry = ParserRegistry::new();
+
+    // Test has default mappings
+    assert!(!registry.list_mappings().is_empty());
+
+    // Test model pattern matching
+    let mappings = registry.list_mappings();
+    let has_gpt = mappings.iter().any(|(m, _)| m.starts_with("gpt"));
+    assert!(has_gpt);
+}
+
+#[test]
+fn test_parser_registry_pattern_matching() {
+    let mut registry = ParserRegistry::new();
+
+    // Test that model mappings work by checking the list
+    registry.map_model("test-model", "json");
+
+    // Verify through list_mappings
+    let mappings = registry.list_mappings();
+    let has_test = mappings
+        .iter()
+        .any(|(m, p)| *m == "test-model" && *p == "json");
+    assert!(has_test);
+}
+
+#[test]
+fn test_tool_call_serialization() {
+    let tool_call = ToolCall {
+        id: "call-123".to_string(),
+        r#type: "function".to_string(),
+        function: FunctionCall {
+            name: "search".to_string(),
+            arguments: r#"{"query": "rust programming"}"#.to_string(),
+        },
+    };
+
+    let json = serde_json::to_string(&tool_call).unwrap();
+    assert!(json.contains("call-123"));
+    assert!(json.contains("search"));
+    assert!(json.contains("rust programming"));
+
+    let parsed: ToolCall = serde_json::from_str(&json).unwrap();
+    assert_eq!(parsed.id, "call-123");
+    assert_eq!(parsed.function.name, "search");
+}
+
+#[test]
+fn test_partial_json_parser() {
+    let parser = PartialJson::default();
+
+    // Test complete JSON
+    let input = r#"{"name": "test", "value": 42}"#;
+    let (value, consumed) = parser.parse_value(input).unwrap();
+    assert_eq!(value["name"], "test");
+    assert_eq!(value["value"], 42);
+    assert_eq!(consumed, input.len());
+
+    // Test incomplete JSON object
+    let input = r#"{"name": "test", "value": "#;
+    let (value, _consumed) = parser.parse_value(input).unwrap();
+    assert_eq!(value["name"], "test");
+    assert!(value["value"].is_null());
+
+    // Test incomplete string
+    let input = r#"{"name": "tes"#;
+    let (value, _consumed) = parser.parse_value(input).unwrap();
+    assert_eq!(value["name"], "tes");
+
+    // Test incomplete array
+    let input = r#"[1, 2, "#;
+    let (value, _consumed) = parser.parse_value(input).unwrap();
+    assert!(value.is_array());
+    assert_eq!(value[0], 1);
+    assert_eq!(value[1], 2);
+}
+
+#[test]
+fn test_partial_json_depth_limit() {
+    // max_depth of 3 allows nesting up to 3 levels
+    // Set allow_incomplete to false to get errors instead of partial results
+    let parser = PartialJson::new(3, false);
+
+    // This should work (simple object)
+    let input = r#"{"a": 1}"#;
+    let result = parser.parse_value(input);
+    assert!(result.is_ok());
+
+    // This should work (nested to depth 3)
+    let input = r#"{"a": {"b": {"c": 1}}}"#;
+    let result = parser.parse_value(input);
+    assert!(result.is_ok());
+
+    // This should fail (nested to depth 4, exceeds limit)
+    let input = r#"{"a": {"b": {"c": {"d": 1}}}}"#;
+    let result = parser.parse_value(input);
+    assert!(result.is_err());
+}
+
+#[test]
+fn test_is_complete_json() {
+    assert!(is_complete_json(r#"{"name": "test"}"#));
+    assert!(is_complete_json(r#"[1, 2, 3]"#));
+    assert!(is_complete_json(r#""string""#));
+    assert!(is_complete_json("42"));
+    assert!(is_complete_json("true"));
+    assert!(is_complete_json("null"));
+
+    assert!(!is_complete_json(r#"{"name": "#));
+    assert!(!is_complete_json(r#"[1, 2, "#));
+    assert!(!is_complete_json(r#""unclosed"#));
+}
+
+#[test]
+fn test_find_common_prefix() {
+    assert_eq!(find_common_prefix("hello", "hello"), 5);
+    assert_eq!(find_common_prefix("hello", "help"), 3);
+    assert_eq!(find_common_prefix("hello", "world"), 0);
+    assert_eq!(find_common_prefix("", "hello"), 0);
+    assert_eq!(find_common_prefix("hello", ""), 0);
+}
+
+#[test]
+fn test_compute_diff() {
+    assert_eq!(compute_diff("hello", "hello world"), " world");
+    assert_eq!(compute_diff("", "hello"), "hello");
+    assert_eq!(compute_diff("hello", "hello"), "");
+    assert_eq!(compute_diff("test", "hello"), "hello");
+}
+
+#[test]
+fn test_stream_result_variants() {
+    // Test Incomplete
+    let result = StreamResult::Incomplete;
+    matches!(result, StreamResult::Incomplete);
+
+    // Test ToolName
+    let result = StreamResult::ToolName {
+        index: 0,
+        name: "test".to_string(),
+    };
+    if let StreamResult::ToolName { index, name } = result {
+        assert_eq!(index, 0);
+        assert_eq!(name, "test");
+    } else {
+        panic!("Expected ToolName variant");
+    }
+
+    // Test ToolComplete
+    let tool = ToolCall {
+        id: "123".to_string(),
+        r#type: "function".to_string(),
+        function: FunctionCall {
+            name: "test".to_string(),
+            arguments: "{}".to_string(),
+        },
+    };
+    let result = StreamResult::ToolComplete(tool.clone());
+    if let StreamResult::ToolComplete(t) = result {
+        assert_eq!(t.id, "123");
+    } else {
+        panic!("Expected ToolComplete variant");
+    }
+}
+
+#[test]
+fn test_partial_tool_call() {
+    let mut partial = PartialToolCall {
+        name: None,
+        arguments_buffer: String::new(),
+        start_position: 0,
+        name_sent: false,
+        streamed_args: String::new(),
+    };
+
+    // Set name
+    partial.name = Some("test_function".to_string());
+    assert_eq!(partial.name.as_ref().unwrap(), "test_function");
+
+    // Append arguments
+    partial.arguments_buffer.push_str(r#"{"key": "value"}"#);
+    assert_eq!(partial.arguments_buffer, r#"{"key": "value"}"#);
+
+    // Update streaming state
+    partial.name_sent = true;
+    partial.streamed_args = r#"{"key": "#.to_string();
+    assert!(partial.name_sent);
+    assert_eq!(partial.streamed_args, r#"{"key": "#);
+}

sgl-router/src/tool_parser/traits.rs

@@ -0,0 +1,35 @@
+use crate::tool_parser::{
+    errors::ToolParserResult,
+    state::ParseState,
+    types::{StreamResult, ToolCall},
+};
+use async_trait::async_trait;
+
+/// Core trait for all tool parsers
+#[async_trait]
+pub trait ToolParser: Send + Sync {
+    /// Parse complete tool calls from final output
+    async fn parse_complete(&self, output: &str) -> ToolParserResult<Vec<ToolCall>>;
+
+    /// Parse tool calls from model output (streaming)
+    async fn parse_incremental(
+        &self,
+        chunk: &str,
+        state: &mut ParseState,
+    ) -> ToolParserResult<StreamResult>;
+
+    /// Check if text contains tool calls in this parser's format
+    fn detect_format(&self, text: &str) -> bool;
+}
+
+/// Trait for partial JSON parsing
+pub trait PartialJsonParser: Send + Sync {
+    /// Parse potentially incomplete JSON
+    fn parse(&self, input: &str) -> ToolParserResult<(serde_json::Value, usize)>;
+
+    /// Check if JSON is complete
+    fn is_complete(&self, input: &str) -> bool;
+
+    /// Get the maximum parsing depth
+    fn max_depth(&self) -> usize;
+}

sgl-router/src/tool_parser/types.rs

@@ -0,0 +1,73 @@
+use serde::{Deserialize, Serialize};
+
+/// Parsed tool call from model output (OpenAI format)
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+pub struct ToolCall {
+    /// Unique identifier for the tool call
+    pub id: String,
+    /// Type of tool call (currently always "function")
+    #[serde(rename = "type")]
+    pub r#type: String,
+    /// Function call details
+    pub function: FunctionCall,
+}
+
+/// Function call within a tool call
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq)]
+pub struct FunctionCall {
+    /// Name of the function to call
+    pub name: String,
+    /// Arguments as JSON string
+    pub arguments: String,
+}
+
+/// Streaming parse result
+#[derive(Debug, Clone)]
+pub enum StreamResult {
+    /// Need more data to continue parsing
+    Incomplete,
+    /// Found a tool name (for streaming)
+    ToolName { index: usize, name: String },
+    /// Found incremental arguments (for streaming)
+    ToolArguments { index: usize, arguments: String },
+    /// Completed parsing a tool
+    ToolComplete(ToolCall),
+    /// Normal text (not part of tool call)
+    NormalText(String),
+}
+
+/// Token configuration for parsing
+#[derive(Debug, Clone)]
+pub struct TokenConfig {
+    /// Start tokens for tool calls
+    pub start_tokens: Vec<String>,
+    /// End tokens for tool calls
+    pub end_tokens: Vec<String>,
+    /// Separator between multiple tool calls
+    pub separator: String,
+}
+
+impl TokenConfig {
+    /// Iterate over start/end token pairs
+    pub fn iter_pairs(&self) -> impl Iterator<Item = (&str, &str)> {
+        self.start_tokens
+            .iter()
+            .zip(self.end_tokens.iter())
+            .map(|(s, e)| (s.as_str(), e.as_str()))
+    }
+}
+
+/// Simple partial tool call for streaming
+#[derive(Debug, Clone)]
+pub struct PartialToolCall {
+    /// Tool name (if parsed)
+    pub name: Option<String>,
+    /// Buffer for accumulating arguments
+    pub arguments_buffer: String,
+    /// Start position in the input buffer
+    pub start_position: usize,
+    /// Whether the name has been sent (for streaming)
+    pub name_sent: bool,
+    /// Arguments already streamed
+    pub streamed_args: String,
+}