[router][grpc] Consolidate parser checks for chat completions (#11439)

sgl-router/src/tool_parser/parsers/mod.rs

@@ -11,6 +11,7 @@ pub mod json_parser;
 pub mod kimik2_parser;
 pub mod llama_parser;
 pub mod mistral_parser;
+pub mod passthrough_parser;
 pub mod pythonic_parser;
 pub mod qwen_parser;
 pub mod step3_parser;
@@ -27,6 +28,7 @@ pub use json_parser::JsonParser;
 pub use kimik2_parser::KimiK2Parser;
 pub use llama_parser::LlamaParser;
 pub use mistral_parser::MistralParser;
+pub use passthrough_parser::PassthroughParser;
 pub use pythonic_parser::PythonicParser;
 pub use qwen_parser::QwenParser;
 pub use step3_parser::Step3Parser;

sgl-router/src/tool_parser/parsers/passthrough_parser.rs

@@ -0,0 +1,50 @@
+//! Passthrough parser that returns text unchanged
+//!
+//! This parser is used as a fallback for unknown models where no specific
+//! tool call parsing should be performed. It simply returns the input text
+//! with no tool calls detected.
+
+use crate::protocols::spec::Tool;
+use crate::tool_parser::errors::ParserResult;
+use crate::tool_parser::traits::ToolParser;
+use crate::tool_parser::types::{StreamingParseResult, ToolCall, ToolCallItem};
+use async_trait::async_trait;
+
+/// Passthrough parser that returns text unchanged with no tool calls
+#[derive(Default)]
+pub struct PassthroughParser;
+
+impl PassthroughParser {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+#[async_trait]
+impl ToolParser for PassthroughParser {
+    async fn parse_complete(&self, output: &str) -> ParserResult<(String, Vec<ToolCall>)> {
+        // Return text unchanged with no tool calls
+        Ok((output.to_string(), vec![]))
+    }
+
+    async fn parse_incremental(
+        &mut self,
+        chunk: &str,
+        _tools: &[Tool],
+    ) -> ParserResult<StreamingParseResult> {
+        // Return chunk unchanged with no tool calls
+        Ok(StreamingParseResult {
+            normal_text: chunk.to_string(),
+            calls: vec![],
+        })
+    }
+
+    fn has_tool_markers(&self, _text: &str) -> bool {
+        // Passthrough never detects tool calls
+        false
+    }
+
+    fn get_unstreamed_tool_args(&self) -> Option<Vec<ToolCallItem>> {
+        None
+    }
+}