[router] fix chat template loading and tokenizer path (#10999)

sgl-router/src/tokenizer/factory.rs

@@ -134,6 +134,36 @@ fn is_likely_sentencepiece(buffer: &[u8]) -> bool {
             || buffer.windows(4).any(|w| w == b"</s>"))
 }
 
+/// Helper function to discover chat template files in a directory
+pub fn discover_chat_template_in_dir(dir: &Path) -> Option<String> {
+    use std::fs;
+
+    // Priority 1: Look for chat_template.json (contains Jinja in JSON format)
+    let json_template_path = dir.join("chat_template.json");
+    if json_template_path.exists() {
+        return json_template_path.to_str().map(|s| s.to_string());
+    }
+
+    // Priority 2: Look for chat_template.jinja (standard Jinja file)
+    let jinja_path = dir.join("chat_template.jinja");
+    if jinja_path.exists() {
+        return jinja_path.to_str().map(|s| s.to_string());
+    }
+
+    // Priority 3: Look for any .jinja file (for models with non-standard naming)
+    if let Ok(entries) = fs::read_dir(dir) {
+        for entry in entries.flatten() {
+            if let Some(name) = entry.file_name().to_str() {
+                if name.ends_with(".jinja") && name != "chat_template.jinja" {
+                    return entry.path().to_str().map(|s| s.to_string());
+                }
+            }
+        }
+    }
+
+    None
+}
+
 /// Factory function to create tokenizer from a model name or path (async version)
 pub async fn create_tokenizer_async(
     model_name_or_path: &str,
@@ -161,14 +191,32 @@ pub async fn create_tokenizer_async(
             // Look for tokenizer.json in the cache directory
             let tokenizer_path = cache_dir.join("tokenizer.json");
             if tokenizer_path.exists() {
-                create_tokenizer_from_file(tokenizer_path.to_str().unwrap())
+                // Try to find a chat template file in the cache directory
+                let chat_template_path = discover_chat_template_in_dir(&cache_dir);
+                let tokenizer_path_str = tokenizer_path.to_str().ok_or_else(|| {
+                    Error::msg(format!(
+                        "Tokenizer path is not valid UTF-8: {:?}",
+                        tokenizer_path
+                    ))
+                })?;
+                create_tokenizer_with_chat_template(
+                    tokenizer_path_str,
+                    chat_template_path.as_deref(),
+                )
             } else {
                 // Try other common tokenizer file names
                 let possible_files = ["tokenizer_config.json", "vocab.json"];
                 for file_name in &possible_files {
                     let file_path = cache_dir.join(file_name);
                     if file_path.exists() {
-                        return create_tokenizer_from_file(file_path.to_str().unwrap());
+                        let chat_template_path = discover_chat_template_in_dir(&cache_dir);
+                        let file_path_str = file_path.to_str().ok_or_else(|| {
+                            Error::msg(format!("File path is not valid UTF-8: {:?}", file_path))
+                        })?;
+                        return create_tokenizer_with_chat_template(
+                            file_path_str,
+                            chat_template_path.as_deref(),
+                        );
                     }
                 }
                 Err(Error::msg(format!(

sgl-router/src/tokenizer/hub.rs

@@ -40,6 +40,13 @@ fn is_tokenizer_file(filename: &str) -> bool {
         || filename.ends_with("merges.txt")
         || filename.ends_with(".model")  // SentencePiece models
         || filename.ends_with(".tiktoken")
+        || is_chat_template_file(filename) // Include chat template files
+}
+
+/// Checks if a file is a chat template file
+fn is_chat_template_file(filename: &str) -> bool {
+    filename.ends_with(".jinja")  // Direct Jinja files
+        || filename == "chat_template.json" // JSON file containing Jinja template
 }
 
 /// Attempt to download tokenizer files from Hugging Face
@@ -123,7 +130,13 @@ pub async fn download_tokenizer_from_hf(model_id: impl AsRef<Path>) -> anyhow::R
     }
 
     match cache_dir {
-        Some(dir) => Ok(dir),
+        Some(dir) => {
+            // Ensure we return the correct model directory, not a subfolder
+            // Some models have an "original" subfolder for PyTorch weights
+            // We want the main model directory that contains tokenizer files
+            let final_dir = resolve_model_cache_dir(&dir, &model_name);
+            Ok(final_dir)
+        }
         None => Err(anyhow::anyhow!(
             "Invalid HF cache path for model '{}'",
             model_name
@@ -206,11 +219,76 @@ pub async fn from_hf(name: impl AsRef<Path>, ignore_weights: bool) -> anyhow::Re
     }
 
     match p.parent() {
-        Some(p) => Ok(p.to_path_buf()),
+        Some(p) => {
+            let final_dir = resolve_model_cache_dir(p, &model_name);
+            Ok(final_dir)
+        }
         None => Err(anyhow::anyhow!("Invalid HF cache path: {}", p.display())),
     }
 }
 
+/// Resolve the correct model cache directory
+/// Handles cases where files might be in subfolders (e.g., "original" folder)
+fn resolve_model_cache_dir(path: &Path, model_name: &str) -> PathBuf {
+    // Check if we're in a subfolder like "original"
+    if let Some(parent) = path.parent() {
+        if let Some(folder_name) = path.file_name() {
+            if folder_name == "original" {
+                // We're in the "original" subfolder, go up one level
+                return parent.to_path_buf();
+            }
+        }
+    }
+
+    // Check if the current path contains the model name components
+    // This helps ensure we're at the right directory level
+    let model_parts: Vec<&str> = model_name.split('/').collect();
+    if model_parts.len() >= 2 {
+        let expected_pattern = format!(
+            "models--{}--{}",
+            model_parts[0].replace("-", "--"),
+            model_parts[1].replace("-", "--")
+        );
+
+        if path.to_string_lossy().contains(&expected_pattern) {
+            // We're already at the correct level
+            return path.to_path_buf();
+        }
+
+        let mut current = path.to_path_buf();
+
+        // First check if current path already contains tokenizer files
+        if current.join("tokenizer.json").exists() || current.join("tokenizer_config.json").exists()
+        {
+            return current;
+        }
+
+        // If not, traverse up to find the model root, then look in snapshots
+        while let Some(parent) = current.parent() {
+            if parent.to_string_lossy().contains(&expected_pattern) {
+                let snapshots_dir = parent.join("snapshots");
+                if snapshots_dir.exists() && snapshots_dir.is_dir() {
+                    if let Ok(entries) = std::fs::read_dir(&snapshots_dir) {
+                        for entry in entries.flatten() {
+                            let snapshot_path = entry.path();
+                            if snapshot_path.is_dir()
+                                && (snapshot_path.join("tokenizer.json").exists()
+                                    || snapshot_path.join("tokenizer_config.json").exists())
+                            {
+                                return snapshot_path;
+                            }
+                        }
+                    }
+                }
+                return parent.to_path_buf();
+            }
+            current = parent.to_path_buf();
+        }
+    }
+
+    path.to_path_buf()
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -223,10 +301,24 @@ mod tests {
         assert!(is_tokenizer_file("vocab.json"));
         assert!(is_tokenizer_file("merges.txt"));
         assert!(is_tokenizer_file("spiece.model"));
+        assert!(is_tokenizer_file("chat_template.jinja"));
+        assert!(is_tokenizer_file("template.jinja"));
         assert!(!is_tokenizer_file("model.bin"));
         assert!(!is_tokenizer_file("README.md"));
     }
 
+    #[test]
+    fn test_is_chat_template_file() {
+        assert!(is_chat_template_file("chat_template.jinja"));
+        assert!(is_chat_template_file("template.jinja"));
+        assert!(is_chat_template_file("any_file.jinja"));
+        assert!(is_chat_template_file("chat_template.json"));
+        assert!(!is_chat_template_file("tokenizer.json"));
+        assert!(!is_chat_template_file("other_file.json"));
+        assert!(!is_chat_template_file("chat_template"));
+        assert!(!is_chat_template_file("README.md"));
+    }
+
     #[test]
     fn test_is_weight_file() {
         assert!(is_weight_file("model.bin"));

sgl-router/src/tokenizer/huggingface.rs

@@ -25,7 +25,12 @@ pub struct HuggingFaceTokenizer {
 impl HuggingFaceTokenizer {
     /// Create a tokenizer from a HuggingFace tokenizer JSON file
     pub fn from_file(file_path: &str) -> Result<Self> {
-        Self::from_file_with_chat_template(file_path, None)
+        // Try to auto-discover chat template if not explicitly provided
+        let path = std::path::Path::new(file_path);
+        let chat_template_path = path
+            .parent()
+            .and_then(crate::tokenizer::factory::discover_chat_template_in_dir);
+        Self::from_file_with_chat_template(file_path, chat_template_path.as_deref())
     }
 
     /// Create a tokenizer from a HuggingFace tokenizer JSON file with an optional chat template
@@ -135,13 +140,35 @@ impl HuggingFaceTokenizer {
         None
     }
 
-    /// Load chat template from a .jinja file
+    /// Load chat template from a file (.jinja or .json containing Jinja)
     fn load_chat_template_from_file(template_path: &str) -> Result<Option<String>> {
         use std::fs;
 
         let content = fs::read_to_string(template_path)
             .map_err(|e| Error::msg(format!("Failed to read chat template file: {}", e)))?;
 
+        // Check if it's a JSON file containing a Jinja template
+        if template_path.ends_with(".json") {
+            // Parse JSON and extract the template string
+            let json_value: serde_json::Value = serde_json::from_str(&content)
+                .map_err(|e| Error::msg(format!("Failed to parse chat_template.json: {}", e)))?;
+
+            if let Some(template_str) = json_value.as_str() {
+                return Ok(Some(template_str.to_string()));
+            } else if let Some(obj) = json_value.as_object() {
+                if let Some(template_value) = obj.get("chat_template") {
+                    if let Some(template_str) = template_value.as_str() {
+                        return Ok(Some(template_str.to_string()));
+                    }
+                }
+            }
+
+            return Err(Error::msg(
+                "chat_template.json does not contain a valid template",
+            ));
+        }
+
+        // Otherwise it's a plain .jinja file
         // Clean up the template (similar to Python implementation)
         let template = content.trim().replace("\\n", "\n");