diff --git a/sgl-router/src/routers/grpc/common/responses/utils.rs b/sgl-router/src/routers/grpc/common/responses/utils.rs
index 24d6cb847..3fbe20efb 100644
--- a/sgl-router/src/routers/grpc/common/responses/utils.rs
+++ b/sgl-router/src/routers/grpc/common/responses/utils.rs
@@ -7,7 +7,7 @@ use axum::{
     response::{IntoResponse, Response},
 };
 use serde_json::{json, to_value};
-use tracing::{debug, warn};
+use tracing::{debug, error, warn};
 
 use crate::{
     core::WorkerRegistry,
@@ -44,6 +44,10 @@ pub async fn ensure_mcp_connection(
                 .await
                 .is_none()
             {
+                error!(
+                    function = "ensure_mcp_connection",
+                    "Failed to connect to MCP server"
+                );
                 return Err(error::failed_dependency(
                     "Failed to connect to MCP server. Check server_url and authorization.",
                 ));
diff --git a/sgl-router/src/routers/grpc/common/stages/client_acquisition.rs b/sgl-router/src/routers/grpc/common/stages/client_acquisition.rs
index d2b912ee2..c6fea0635 100644
--- a/sgl-router/src/routers/grpc/common/stages/client_acquisition.rs
+++ b/sgl-router/src/routers/grpc/common/stages/client_acquisition.rs
@@ -2,6 +2,7 @@
 
 use async_trait::async_trait;
 use axum::response::Response;
+use tracing::error;
 
 use super::PipelineStage;
 use crate::routers::grpc::{
@@ -15,11 +16,13 @@ pub struct ClientAcquisitionStage;
 #[async_trait]
 impl PipelineStage for ClientAcquisitionStage {
     async fn execute(&self, ctx: &mut RequestContext) -> Result<Option<Response>, Response> {
-        let workers = ctx
-            .state
-            .workers
-            .as_ref()
-            .ok_or_else(|| error::internal_error("Worker selection not completed"))?;
+        let workers = ctx.state.workers.as_ref().ok_or_else(|| {
+            error!(
+                function = "ClientAcquisitionStage::execute",
+                "Worker selection stage not completed"
+            );
+            error::internal_error("Worker selection not completed")
+        })?;
 
         let clients = match workers {
             WorkerSelection::Single { worker } => {
diff --git a/sgl-router/src/routers/grpc/common/stages/dispatch_metadata.rs b/sgl-router/src/routers/grpc/common/stages/dispatch_metadata.rs
index 2cbfd1b47..d7b811dd0 100644
--- a/sgl-router/src/routers/grpc/common/stages/dispatch_metadata.rs
+++ b/sgl-router/src/routers/grpc/common/stages/dispatch_metadata.rs
@@ -4,6 +4,7 @@ use std::time::{SystemTime, UNIX_EPOCH};
 
 use async_trait::async_trait;
 use axum::response::Response;
+use tracing::error;
 
 use super::PipelineStage;
 use crate::routers::grpc::{
@@ -17,11 +18,13 @@ pub struct DispatchMetadataStage;
 #[async_trait]
 impl PipelineStage for DispatchMetadataStage {
     async fn execute(&self, ctx: &mut RequestContext) -> Result<Option<Response>, Response> {
-        let proto_request = ctx
-            .state
-            .proto_request
-            .as_ref()
-            .ok_or_else(|| error::internal_error("Proto request not built"))?;
+        let proto_request = ctx.state.proto_request.as_ref().ok_or_else(|| {
+            error!(
+                function = "DispatchMetadataStage::execute",
+                "Proto request not built"
+            );
+            error::internal_error("Proto request not built")
+        })?;
 
         let request_id = proto_request.request_id.clone();
         let model = match &ctx.input.request_type {
diff --git a/sgl-router/src/routers/grpc/common/stages/request_execution.rs b/sgl-router/src/routers/grpc/common/stages/request_execution.rs
index ef9818f1b..8b26879e9 100644
--- a/sgl-router/src/routers/grpc/common/stages/request_execution.rs
+++ b/sgl-router/src/routers/grpc/common/stages/request_execution.rs
@@ -2,6 +2,7 @@
 
 use async_trait::async_trait;
 use axum::response::Response;
+use tracing::error;
 
 use super::PipelineStage;
 use crate::{
@@ -35,17 +36,21 @@ impl RequestExecutionStage {
 #[async_trait]
 impl PipelineStage for RequestExecutionStage {
     async fn execute(&self, ctx: &mut RequestContext) -> Result<Option<Response>, Response> {
-        let proto_request = ctx
-            .state
-            .proto_request
-            .take()
-            .ok_or_else(|| error::internal_error("Proto request not built"))?;
+        let proto_request = ctx.state.proto_request.take().ok_or_else(|| {
+            error!(
+                function = "RequestExecutionStage::execute",
+                "Proto request not built"
+            );
+            error::internal_error("Proto request not built")
+        })?;
 
-        let clients = ctx
-            .state
-            .clients
-            .as_mut()
-            .ok_or_else(|| error::internal_error("Client acquisition not completed"))?;
+        let clients = ctx.state.clients.as_mut().ok_or_else(|| {
+            error!(
+                function = "RequestExecutionStage::execute",
+                "Client acquisition not completed"
+            );
+            error::internal_error("Client acquisition not completed")
+        })?;
 
         let result = match self.mode {
             ExecutionMode::Single => self.execute_single(proto_request, clients).await?,
@@ -70,14 +75,22 @@ impl RequestExecutionStage {
         proto_request: proto::GenerateRequest,
         clients: &mut ClientSelection,
     ) -> Result<ExecutionResult, Response> {
-        let client = clients
-            .single_mut()
-            .ok_or_else(|| error::internal_error("Expected single client but got dual"))?;
+        let client = clients.single_mut().ok_or_else(|| {
+            error!(
+                function = "execute_single",
+                "Expected single client but got dual"
+            );
+            error::internal_error("Expected single client but got dual")
+        })?;
 
-        let stream = client
-            .generate(proto_request)
-            .await
-            .map_err(|e| error::internal_error(format!("Failed to start generation: {}", e)))?;
+        let stream = client.generate(proto_request).await.map_err(|e| {
+            error!(
+                function = "execute_single",
+                error = %e,
+                "Failed to start generation"
+            );
+            error::internal_error(format!("Failed to start generation: {}", e))
+        })?;
 
         Ok(ExecutionResult::Single { stream })
     }
@@ -87,9 +100,13 @@ impl RequestExecutionStage {
         proto_request: proto::GenerateRequest,
         clients: &mut ClientSelection,
     ) -> Result<ExecutionResult, Response> {
-        let (prefill_client, decode_client) = clients
-            .dual_mut()
-            .ok_or_else(|| error::internal_error("Expected dual clients but got single"))?;
+        let (prefill_client, decode_client) = clients.dual_mut().ok_or_else(|| {
+            error!(
+                function = "execute_dual_dispatch",
+                "Expected dual clients but got single"
+            );
+            error::internal_error("Expected dual clients but got single")
+        })?;
 
         let prefill_request = proto_request.clone();
         let decode_request = proto_request;
@@ -103,6 +120,11 @@ impl RequestExecutionStage {
         let prefill_stream = match prefill_result {
             Ok(s) => s,
             Err(e) => {
+                error!(
+                    function = "execute_dual_dispatch",
+                    error = %e,
+                    "Prefill worker failed to start"
+                );
                 return Err(error::internal_error(format!(
                     "Prefill worker failed to start: {}",
                     e
@@ -114,6 +136,11 @@ impl RequestExecutionStage {
         let decode_stream = match decode_result {
             Ok(s) => s,
             Err(e) => {
+                error!(
+                    function = "execute_dual_dispatch",
+                    error = %e,
+                    "Decode worker failed to start"
+                );
                 return Err(error::internal_error(format!(
                     "Decode worker failed to start: {}",
                     e
diff --git a/sgl-router/src/routers/grpc/common/stages/worker_selection.rs b/sgl-router/src/routers/grpc/common/stages/worker_selection.rs
index 554ccc47f..d52819374 100644
--- a/sgl-router/src/routers/grpc/common/stages/worker_selection.rs
+++ b/sgl-router/src/routers/grpc/common/stages/worker_selection.rs
@@ -4,7 +4,7 @@ use std::sync::Arc;
 
 use async_trait::async_trait;
 use axum::response::Response;
-use tracing::warn;
+use tracing::{error, warn};
 
 use super::PipelineStage;
 use crate::{
@@ -47,11 +47,13 @@ impl WorkerSelectionStage {
 #[async_trait]
 impl PipelineStage for WorkerSelectionStage {
     async fn execute(&self, ctx: &mut RequestContext) -> Result<Option<Response>, Response> {
-        let prep = ctx
-            .state
-            .preparation
-            .as_ref()
-            .ok_or_else(|| error::internal_error("Preparation stage not completed"))?;
+        let prep = ctx.state.preparation.as_ref().ok_or_else(|| {
+            error!(
+                function = "WorkerSelectionStage::execute",
+                "Preparation stage not completed"
+            );
+            error::internal_error("Preparation stage not completed")
+        })?;
 
         // For Harmony, use selection_text produced during Harmony encoding
         // Otherwise, use original_text from regular preparation
@@ -66,6 +68,12 @@ impl PipelineStage for WorkerSelectionStage {
                 match self.select_single_worker(ctx.input.model_id.as_deref(), text) {
                     Some(w) => WorkerSelection::Single { worker: w },
                     None => {
+                        error!(
+                            function = "WorkerSelectionStage::execute",
+                            mode = "Regular",
+                            model_id = ?ctx.input.model_id,
+                            "No available workers for model"
+                        );
                         return Err(error::service_unavailable(format!(
                             "No available workers for model: {:?}",
                             ctx.input.model_id
@@ -77,6 +85,12 @@ impl PipelineStage for WorkerSelectionStage {
                 match self.select_pd_pair(ctx.input.model_id.as_deref(), text) {
                     Some((prefill, decode)) => WorkerSelection::Dual { prefill, decode },
                     None => {
+                        error!(
+                            function = "WorkerSelectionStage::execute",
+                            mode = "PrefillDecode",
+                            model_id = ?ctx.input.model_id,
+                            "No available PD worker pairs for model"
+                        );
                         return Err(error::service_unavailable(format!(
                             "No available PD worker pairs for model: {:?}",
                             ctx.input.model_id
diff --git a/sgl-router/src/routers/grpc/error.rs b/sgl-router/src/routers/grpc/error.rs
index 3dbfc6210..b6c4a1fbc 100644
--- a/sgl-router/src/routers/grpc/error.rs
+++ b/sgl-router/src/routers/grpc/error.rs
@@ -9,7 +9,6 @@ use axum::{
     Json,
 };
 use serde_json::json;
-use tracing::{error, warn};
 
 /// Create a 500 Internal Server Error response
 ///
@@ -21,7 +20,6 @@ use tracing::{error, warn};
 /// ```
 pub fn internal_error(message: impl Into<String>) -> Response {
     let msg = message.into();
-    error!("{}", msg);
     (
         StatusCode::INTERNAL_SERVER_ERROR,
         Json(json!({
@@ -45,7 +43,6 @@ pub fn internal_error(message: impl Into<String>) -> Response {
 /// ```
 pub fn bad_request(message: impl Into<String>) -> Response {
     let msg = message.into();
-    error!("{}", msg);
     (
         StatusCode::BAD_REQUEST,
         Json(json!({
@@ -69,7 +66,6 @@ pub fn bad_request(message: impl Into<String>) -> Response {
 /// ```
 pub fn not_found(message: impl Into<String>) -> Response {
     let msg = message.into();
-    warn!("{}", msg);
     (
         StatusCode::NOT_FOUND,
         Json(json!({
@@ -93,7 +89,6 @@ pub fn not_found(message: impl Into<String>) -> Response {
 /// ```
 pub fn service_unavailable(message: impl Into<String>) -> Response {
     let msg = message.into();
-    warn!("{}", msg);
     (
         StatusCode::SERVICE_UNAVAILABLE,
         Json(json!({
@@ -117,7 +112,6 @@ pub fn service_unavailable(message: impl Into<String>) -> Response {
 /// ```
 pub fn failed_dependency(message: impl Into<String>) -> Response {
     let msg = message.into();
-    warn!("{}", msg);
     (
         StatusCode::FAILED_DEPENDENCY,
         Json(json!({
diff --git a/sgl-router/src/routers/grpc/harmony/processor.rs b/sgl-router/src/routers/grpc/harmony/processor.rs
index c4255220c..3cbc80fa2 100644
--- a/sgl-router/src/routers/grpc/harmony/processor.rs
+++ b/sgl-router/src/routers/grpc/harmony/processor.rs
@@ -4,6 +4,7 @@ use std::sync::Arc;
 
 use axum::response::Response;
 use proto::generate_complete::MatchedStop::{MatchedStopStr, MatchedTokenId};
+use tracing::error;
 
 use super::HarmonyParserAdapter;
 use crate::{
@@ -63,6 +64,11 @@ impl HarmonyResponseProcessor {
 
             // Parse Harmony channels with HarmonyParserAdapter
             let mut parser = HarmonyParserAdapter::new().map_err(|e| {
+                error!(
+                    function = "process_non_streaming_chat_response",
+                    error = %e,
+                    "Failed to create Harmony parser"
+                );
                 error::internal_error(format!("Failed to create Harmony parser: {}", e))
             })?;
 
@@ -73,7 +79,14 @@ impl HarmonyResponseProcessor {
                     complete.finish_reason.clone(),
                     matched_stop.clone(),
                 )
-                .map_err(|e| error::internal_error(format!("Harmony parsing failed: {}", e)))?;
+                .map_err(|e| {
+                    error!(
+                        function = "process_non_streaming_chat_response",
+                        error = %e,
+                        "Harmony parsing failed on complete response"
+                    );
+                    error::internal_error(format!("Harmony parsing failed: {}", e))
+                })?;
 
             // Build response message (assistant)
             let message = ChatCompletionMessage {
@@ -171,6 +184,11 @@ impl HarmonyResponseProcessor {
 
         // Parse Harmony channels
         let mut parser = HarmonyParserAdapter::new().map_err(|e| {
+            error!(
+                function = "process_responses_iteration",
+                error = %e,
+                "Failed to create Harmony parser"
+            );
             error::internal_error(format!("Failed to create Harmony parser: {}", e))
         })?;
 
@@ -190,7 +208,14 @@ impl HarmonyResponseProcessor {
                 complete.finish_reason.clone(),
                 matched_stop,
             )
-            .map_err(|e| error::internal_error(format!("Harmony parsing failed: {}", e)))?;
+            .map_err(|e| {
+                error!(
+                    function = "process_responses_iteration",
+                    error = %e,
+                    "Harmony parsing failed on complete response"
+                );
+                error::internal_error(format!("Harmony parsing failed: {}", e))
+            })?;
 
         // VALIDATION: Check if model incorrectly generated Tool role messages
         // This happens when the model copies the format of tool result messages
diff --git a/sgl-router/src/routers/grpc/harmony/responses.rs b/sgl-router/src/routers/grpc/harmony/responses.rs
index e669ca5b0..ae0aaf2de 100644
--- a/sgl-router/src/routers/grpc/harmony/responses.rs
+++ b/sgl-router/src/routers/grpc/harmony/responses.rs
@@ -39,7 +39,7 @@ use axum::response::Response;
 use bytes::Bytes;
 use serde_json::{from_str, from_value, json, to_string, to_value, Value};
 use tokio::sync::mpsc;
-use tracing::{debug, warn};
+use tracing::{debug, error, warn};
 use uuid::Uuid;
 
 use crate::{
@@ -324,6 +324,12 @@ async fn execute_with_mcp_loop(
 
         // Safety check: prevent infinite loops
         if iteration_count > MAX_TOOL_ITERATIONS {
+            error!(
+                function = "execute_with_mcp_loop",
+                iteration_count = iteration_count,
+                max_iterations = MAX_TOOL_ITERATIONS,
+                "Maximum tool iterations exceeded"
+            );
             return Err(error::internal_error(format!(
                 "Maximum tool iterations ({}) exceeded",
                 MAX_TOOL_ITERATIONS
@@ -1157,6 +1163,13 @@ async fn execute_mcp_tools(
         // Parse tool arguments from JSON string
         let args_str = tool_call.function.arguments.as_deref().unwrap_or("{}");
         let args: Value = from_str(args_str).map_err(|e| {
+            error!(
+                function = "execute_mcp_tools",
+                tool_name = %tool_call.function.name,
+                call_id = %tool_call.id,
+                error = %e,
+                "Failed to parse tool arguments JSON"
+            );
             error::internal_error(format!(
                 "Invalid tool arguments JSON for tool '{}': {}",
                 tool_call.function.name, e
@@ -1519,6 +1532,12 @@ async fn load_previous_messages(
         .get_response_chain(&prev_id, None)
         .await
         .map_err(|e| {
+            error!(
+                function = "load_previous_messages",
+                prev_id = %prev_id_str,
+                error = %e,
+                "Failed to load previous response chain from storage"
+            );
             error::internal_error(format!(
                 "Failed to load previous response chain for {}: {}",
                 prev_id_str, e
diff --git a/sgl-router/src/routers/grpc/harmony/stages/preparation.rs b/sgl-router/src/routers/grpc/harmony/stages/preparation.rs
index b8d8919df..c370514cb 100644
--- a/sgl-router/src/routers/grpc/harmony/stages/preparation.rs
+++ b/sgl-router/src/routers/grpc/harmony/stages/preparation.rs
@@ -3,6 +3,7 @@
 use async_trait::async_trait;
 use axum::response::Response;
 use serde_json::json;
+use tracing::error;
 
 use super::super::HarmonyBuilder;
 use crate::{
@@ -56,6 +57,10 @@ impl PipelineStage for HarmonyPreparationStage {
             let request_arc = ctx.responses_request_arc();
             self.prepare_responses(ctx, &request_arc).await?;
         } else {
+            error!(
+                function = "HarmonyPreparationStage::execute",
+                "Unsupported request type for Harmony pipeline"
+            );
             return Err(error::bad_request(
                 "Only Chat and Responses requests supported in Harmony pipeline".to_string(),
             ));
@@ -78,6 +83,10 @@ impl HarmonyPreparationStage {
     ) -> Result<Option<Response>, Response> {
         // Validate - reject logprobs
         if request.logprobs {
+            error!(
+                function = "prepare_chat",
+                "logprobs requested but not supported for Harmony models"
+            );
             return Err(error::bad_request(
                 "logprobs are not supported for Harmony models".to_string(),
             ));
@@ -94,10 +103,14 @@ impl HarmonyPreparationStage {
         };
 
         // Step 3: Build via Harmony
-        let build_output = self
-            .builder
-            .build_from_chat(&body_ref)
-            .map_err(|e| error::bad_request(format!("Harmony build failed: {}", e)))?;
+        let build_output = self.builder.build_from_chat(&body_ref).map_err(|e| {
+            error!(
+                function = "prepare_chat",
+                error = %e,
+                "Harmony build failed for chat request"
+            );
+            error::bad_request(format!("Harmony build failed: {}", e))
+        })?;
 
         // Step 4: Store results
         ctx.state.preparation = Some(PreparationOutput {
@@ -154,6 +167,10 @@ impl HarmonyPreparationStage {
         };
 
         if tool_constraint.is_some() && text_constraint.is_some() {
+            error!(
+                function = "prepare_responses",
+                "Conflicting constraints: both tool_choice and text format specified"
+            );
             return Err(error::bad_request(
                 "Cannot use both tool_choice (required/function) and text format (json_object/json_schema) simultaneously".to_string(),
             ));
@@ -162,10 +179,14 @@ impl HarmonyPreparationStage {
         let constraint = tool_constraint.or(text_constraint);
 
         // Step 3: Build via Harmony from responses API request
-        let build_output = self
-            .builder
-            .build_from_responses(request)
-            .map_err(|e| error::bad_request(format!("Harmony build failed: {}", e)))?;
+        let build_output = self.builder.build_from_responses(request).map_err(|e| {
+            error!(
+                function = "prepare_responses",
+                error = %e,
+                "Harmony build failed for responses request"
+            );
+            error::bad_request(format!("Harmony build failed: {}", e))
+        })?;
 
         // Step 4: Store results with constraint
         ctx.state.preparation = Some(PreparationOutput {
@@ -200,12 +221,25 @@ impl HarmonyPreparationStage {
             TextFormat::Text => Ok(None),
             TextFormat::JsonObject => {
                 let tag = build_text_format_structural_tag(&serde_json::json!({"type": "object"}))
-                    .map_err(|e| Box::new(error::internal_error(e)))?;
+                    .map_err(|e| {
+                        error!(
+                            function = "generate_text_format_constraint",
+                            error = %e,
+                            "Failed to build text format structural tag for JsonObject"
+                        );
+                        Box::new(error::internal_error(e))
+                    })?;
                 Ok(Some(("structural_tag".to_string(), tag)))
             }
             TextFormat::JsonSchema { schema, .. } => {
-                let tag = build_text_format_structural_tag(schema)
-                    .map_err(|e| Box::new(error::internal_error(e)))?;
+                let tag = build_text_format_structural_tag(schema).map_err(|e| {
+                    error!(
+                        function = "generate_text_format_constraint",
+                        error = %e,
+                        "Failed to build text format structural tag for JsonSchema"
+                    );
+                    Box::new(error::internal_error(e))
+                })?;
                 Ok(Some(("structural_tag".to_string(), tag)))
             }
         }
@@ -266,11 +300,19 @@ impl HarmonyPreparationStage {
         };
 
         // Validate specific function exists
-        if specific_function.is_some() && tools_to_use.is_empty() {
-            return Err(Box::new(error::bad_request(format!(
-                "Tool '{}' not found in tools list",
-                specific_function.unwrap()
-            ))));
+        match specific_function {
+            Some(tool_name) if tools_to_use.is_empty() => {
+                error!(
+                    function = "generate_tool_call_constraint",
+                    tool_name = %tool_name,
+                    "Specified tool not found in tools list"
+                );
+                return Err(Box::new(error::bad_request(format!(
+                    "Tool '{}' not found in tools list",
+                    tool_name
+                ))));
+            }
+            _ => {}
         }
 
         // Build tags for each tool - need two patterns per tool for reasoning on/off
@@ -312,6 +354,11 @@ impl HarmonyPreparationStage {
         });
 
         serde_json::to_string(&structural_tag).map_err(|e| {
+            error!(
+                function = "generate_tool_call_constraint",
+                error = %e,
+                "Failed to serialize structural tag"
+            );
             Box::new(error::internal_error(format!(
                 "Failed to serialize structural tag: {}",
                 e
diff --git a/sgl-router/src/routers/grpc/harmony/stages/request_building.rs b/sgl-router/src/routers/grpc/harmony/stages/request_building.rs
index 5e63aab67..b5f31183b 100644
--- a/sgl-router/src/routers/grpc/harmony/stages/request_building.rs
+++ b/sgl-router/src/routers/grpc/harmony/stages/request_building.rs
@@ -2,7 +2,7 @@
 
 use async_trait::async_trait;
 use axum::response::Response;
-use tracing::debug;
+use tracing::{debug, error};
 use uuid::Uuid;
 
 use crate::routers::grpc::{
@@ -30,18 +30,22 @@ impl HarmonyRequestBuildingStage {
 impl PipelineStage for HarmonyRequestBuildingStage {
     async fn execute(&self, ctx: &mut RequestContext) -> Result<Option<Response>, Response> {
         // Get preparation output
-        let prep = ctx
-            .state
-            .preparation
-            .as_ref()
-            .ok_or_else(|| error::internal_error("Preparation not completed"))?;
+        let prep = ctx.state.preparation.as_ref().ok_or_else(|| {
+            error!(
+                function = "HarmonyRequestBuildingStage::execute",
+                "Preparation stage not completed"
+            );
+            error::internal_error("Preparation not completed")
+        })?;
 
         // Get clients
-        let clients = ctx
-            .state
-            .clients
-            .as_ref()
-            .ok_or_else(|| error::internal_error("Client acquisition not completed"))?;
+        let clients = ctx.state.clients.as_ref().ok_or_else(|| {
+            error!(
+                function = "HarmonyRequestBuildingStage::execute",
+                "Client acquisition stage not completed"
+            );
+            error::internal_error("Client acquisition not completed")
+        })?;
         let builder_client = match clients {
             ClientSelection::Single { client } => client,
             ClientSelection::Dual { prefill, .. } => prefill,
@@ -52,6 +56,10 @@ impl PipelineStage for HarmonyRequestBuildingStage {
             RequestType::Chat(_) => format!("chatcmpl-{}", Uuid::new_v4()),
             RequestType::Responses(_) => format!("responses-{}", Uuid::new_v4()),
             RequestType::Generate(_) => {
+                error!(
+                    function = "HarmonyRequestBuildingStage::execute",
+                    "Generate request type not supported for Harmony models"
+                );
                 return Err(error::bad_request(
                     "Generate requests are not supported with Harmony models".to_string(),
                 ));
@@ -75,7 +83,14 @@ impl PipelineStage for HarmonyRequestBuildingStage {
                         None,
                         prep.tool_constraints.clone(),
                     )
-                    .map_err(|e| error::bad_request(format!("Invalid request parameters: {}", e)))?
+                    .map_err(|e| {
+                        error!(
+                            function = "HarmonyRequestBuildingStage::execute",
+                            error = %e,
+                            "Failed to build generate request from chat"
+                        );
+                        error::bad_request(format!("Invalid request parameters: {}", e))
+                    })?
             }
             RequestType::Responses(request) => builder_client
                 .build_generate_request_from_responses(
@@ -86,7 +101,14 @@ impl PipelineStage for HarmonyRequestBuildingStage {
                     prep.harmony_stop_ids.clone(),
                     prep.tool_constraints.clone(),
                 )
-                .map_err(|e| error::bad_request(format!("Invalid request parameters: {}", e)))?,
+                .map_err(|e| {
+                    error!(
+                        function = "HarmonyRequestBuildingStage::execute",
+                        error = %e,
+                        "Failed to build generate request from responses"
+                    );
+                    error::bad_request(format!("Invalid request parameters: {}", e))
+                })?,
             _ => unreachable!(),
         };
 
diff --git a/sgl-router/src/routers/grpc/harmony/stages/response_processing.rs b/sgl-router/src/routers/grpc/harmony/stages/response_processing.rs
index bc640efb5..924556e34 100644
--- a/sgl-router/src/routers/grpc/harmony/stages/response_processing.rs
+++ b/sgl-router/src/routers/grpc/harmony/stages/response_processing.rs
@@ -4,6 +4,7 @@ use std::sync::Arc;
 
 use async_trait::async_trait;
 use axum::response::Response;
+use tracing::error;
 
 use super::super::{HarmonyResponseProcessor, HarmonyStreamingProcessor};
 use crate::routers::grpc::{
@@ -46,19 +47,24 @@ impl PipelineStage for HarmonyResponseProcessingStage {
         match &ctx.input.request_type {
             RequestType::Chat(_) => {
                 // Get execution result (output tokens from model)
-                let execution_result = ctx
-                    .state
-                    .response
-                    .execution_result
-                    .take()
-                    .ok_or_else(|| error::internal_error("No execution result"))?;
+                let execution_result =
+                    ctx.state.response.execution_result.take().ok_or_else(|| {
+                        error!(
+                            function = "HarmonyResponseProcessingStage::execute",
+                            request_type = "Chat",
+                            "No execution result available"
+                        );
+                        error::internal_error("No execution result")
+                    })?;
 
-                let dispatch = ctx
-                    .state
-                    .dispatch
-                    .as_ref()
-                    .cloned()
-                    .ok_or_else(|| error::internal_error("Dispatch metadata not set"))?;
+                let dispatch = ctx.state.dispatch.as_ref().cloned().ok_or_else(|| {
+                    error!(
+                        function = "HarmonyResponseProcessingStage::execute",
+                        request_type = "Chat",
+                        "Dispatch metadata not set"
+                    );
+                    error::internal_error("Dispatch metadata not set")
+                })?;
 
                 // For streaming, delegate to streaming processor and return SSE response
                 if is_streaming {
@@ -92,19 +98,24 @@ impl PipelineStage for HarmonyResponseProcessingStage {
                 }
 
                 // For non-streaming, process normally
-                let execution_result = ctx
-                    .state
-                    .response
-                    .execution_result
-                    .take()
-                    .ok_or_else(|| error::internal_error("No execution result"))?;
+                let execution_result =
+                    ctx.state.response.execution_result.take().ok_or_else(|| {
+                        error!(
+                            function = "HarmonyResponseProcessingStage::execute",
+                            request_type = "Responses",
+                            "No execution result available"
+                        );
+                        error::internal_error("No execution result")
+                    })?;
 
-                let dispatch = ctx
-                    .state
-                    .dispatch
-                    .as_ref()
-                    .cloned()
-                    .ok_or_else(|| error::internal_error("Dispatch metadata not set"))?;
+                let dispatch = ctx.state.dispatch.as_ref().cloned().ok_or_else(|| {
+                    error!(
+                        function = "HarmonyResponseProcessingStage::execute",
+                        request_type = "Responses",
+                        "Dispatch metadata not set"
+                    );
+                    error::internal_error("Dispatch metadata not set")
+                })?;
 
                 let responses_request = ctx.responses_request_arc();
                 let iteration_result = self
@@ -115,9 +126,15 @@ impl PipelineStage for HarmonyResponseProcessingStage {
                 ctx.state.response.responses_iteration_result = Some(iteration_result);
                 Ok(None)
             }
-            RequestType::Generate(_) => Err(error::internal_error(
-                "Generate requests not supported in Harmony pipeline",
-            )),
+            RequestType::Generate(_) => {
+                error!(
+                    function = "HarmonyResponseProcessingStage::execute",
+                    "Generate request type not supported in Harmony pipeline"
+                );
+                Err(error::internal_error(
+                    "Generate requests not supported in Harmony pipeline",
+                ))
+            }
         }
     }
 
diff --git a/sgl-router/src/routers/grpc/pipeline.rs b/sgl-router/src/routers/grpc/pipeline.rs
index a05d6b81a..cb09f2a50 100644
--- a/sgl-router/src/routers/grpc/pipeline.rs
+++ b/sgl-router/src/routers/grpc/pipeline.rs
@@ -219,9 +219,19 @@ impl RequestPipeline {
         match ctx.state.response.final_response {
             Some(FinalResponse::Chat(response)) => axum::Json(response).into_response(),
             Some(FinalResponse::Generate(_)) => {
+                error!(
+                    function = "execute_chat",
+                    "Wrong response type: expected Chat, got Generate"
+                );
                 error::internal_error("Internal error: wrong response type")
             }
-            None => error::internal_error("No response produced"),
+            None => {
+                error!(
+                    function = "execute_chat",
+                    "No response produced by pipeline"
+                );
+                error::internal_error("No response produced")
+            }
         }
     }
 
@@ -260,9 +270,19 @@ impl RequestPipeline {
         match ctx.state.response.final_response {
             Some(FinalResponse::Generate(response)) => axum::Json(response).into_response(),
             Some(FinalResponse::Chat(_)) => {
+                error!(
+                    function = "execute_generate",
+                    "Wrong response type: expected Generate, got Chat"
+                );
                 error::internal_error("Internal error: wrong response type")
             }
-            None => error::internal_error("No response produced"),
+            None => {
+                error!(
+                    function = "execute_generate",
+                    "No response produced by pipeline"
+                );
+                error::internal_error("No response produced")
+            }
         }
     }
 
@@ -285,6 +305,10 @@ impl RequestPipeline {
             match stage.execute(&mut ctx).await {
                 Ok(Some(_response)) => {
                     // Streaming not supported for responses sync mode
+                    error!(
+                        function = "execute_chat_for_responses",
+                        "Streaming attempted in responses context"
+                    );
                     return Err(error::bad_request(
                         "Streaming is not supported in this context".to_string(),
                     ));
@@ -308,9 +332,19 @@ impl RequestPipeline {
         match ctx.state.response.final_response {
             Some(FinalResponse::Chat(response)) => Ok(response),
             Some(FinalResponse::Generate(_)) => {
+                error!(
+                    function = "execute_chat_for_responses",
+                    "Wrong response type: expected Chat, got Generate"
+                );
                 Err(error::internal_error("Internal error: wrong response type"))
             }
-            None => Err(error::internal_error("No response produced")),
+            None => {
+                error!(
+                    function = "execute_chat_for_responses",
+                    "No response produced by pipeline"
+                );
+                Err(error::internal_error("No response produced"))
+            }
         }
     }
 
@@ -376,6 +410,10 @@ impl RequestPipeline {
             .responses_iteration_result
             .take()
             .ok_or_else(|| {
+                error!(
+                    function = "execute_harmony_responses",
+                    "No ResponsesIterationResult produced by pipeline"
+                );
                 error::internal_error("No ResponsesIterationResult produced by pipeline")
             })
     }
@@ -421,10 +459,12 @@ impl RequestPipeline {
         }
 
         // Extract execution_result (the raw stream from workers)
-        ctx.state
-            .response
-            .execution_result
-            .take()
-            .ok_or_else(|| error::internal_error("No ExecutionResult produced by pipeline"))
+        ctx.state.response.execution_result.take().ok_or_else(|| {
+            error!(
+                function = "execute_harmony_responses_streaming",
+                "No ExecutionResult produced by pipeline"
+            );
+            error::internal_error("No ExecutionResult produced by pipeline")
+        })
     }
 }
diff --git a/sgl-router/src/routers/grpc/regular/responses/handlers.rs b/sgl-router/src/routers/grpc/regular/responses/handlers.rs
index 4b6267bef..f90635c0c 100644
--- a/sgl-router/src/routers/grpc/regular/responses/handlers.rs
+++ b/sgl-router/src/routers/grpc/regular/responses/handlers.rs
@@ -43,7 +43,7 @@ use bytes::Bytes;
 use futures_util::StreamExt;
 use serde_json::json;
 use tokio::sync::mpsc;
-use tracing::{debug, warn};
+use tracing::{debug, error, warn};
 use uuid::Uuid;
 use validator::Validate;
 
@@ -644,8 +644,14 @@ async fn execute_without_mcp(
     response_id: Option<String>,
 ) -> Result<ResponsesResponse, Response> {
     // Convert ResponsesRequest → ChatCompletionRequest
-    let chat_request = conversions::responses_to_chat(modified_request)
-        .map_err(|e| error::bad_request(format!("Failed to convert request: {}", e)))?;
+    let chat_request = conversions::responses_to_chat(modified_request).map_err(|e| {
+        error!(
+            function = "execute_without_mcp",
+            error = %e,
+            "Failed to convert ResponsesRequest to ChatCompletionRequest"
+        );
+        error::bad_request(format!("Failed to convert request: {}", e))
+    })?;
 
     // Execute chat pipeline (errors already have proper HTTP status codes)
     let chat_response = ctx
@@ -659,8 +665,14 @@ async fn execute_without_mcp(
         .await?; // Preserve the Response error as-is
 
     // Convert ChatCompletionResponse → ResponsesResponse
-    conversions::chat_to_responses(&chat_response, original_request, response_id)
-        .map_err(|e| error::internal_error(format!("Failed to convert to responses format: {}", e)))
+    conversions::chat_to_responses(&chat_response, original_request, response_id).map_err(|e| {
+        error!(
+            function = "execute_without_mcp",
+            error = %e,
+            "Failed to convert ChatCompletionResponse to ResponsesResponse"
+        );
+        error::internal_error(format!("Failed to convert to responses format: {}", e))
+    })
 }
 
 /// Load conversation history and response chains, returning modified request
@@ -737,7 +749,15 @@ async fn load_conversation_history(
             .conversation_storage
             .get_conversation(&conv_id)
             .await
-            .map_err(|e| error::internal_error(format!("Failed to check conversation: {}", e)))?;
+            .map_err(|e| {
+                error!(
+                    function = "load_conversation_history",
+                    conversation_id = %conv_id_str,
+                    error = %e,
+                    "Failed to check conversation existence in storage"
+                );
+                error::internal_error(format!("Failed to check conversation: {}", e))
+            })?;
 
         if conversation.is_none() {
             return Err(error::not_found(format!(
diff --git a/sgl-router/src/routers/grpc/regular/responses/tool_loop.rs b/sgl-router/src/routers/grpc/regular/responses/tool_loop.rs
index 2a8715805..29e274e87 100644
--- a/sgl-router/src/routers/grpc/regular/responses/tool_loop.rs
+++ b/sgl-router/src/routers/grpc/regular/responses/tool_loop.rs
@@ -16,7 +16,7 @@ use futures_util::StreamExt;
 use serde_json::{json, Value};
 use tokio::sync::mpsc;
 use tokio_stream::wrappers::UnboundedReceiverStream;
-use tracing::{debug, warn};
+use tracing::{debug, error, warn};
 use uuid::Uuid;
 
 use super::conversions;
@@ -250,8 +250,15 @@ pub(super) async fn execute_tool_loop(
 
     loop {
         // Convert to chat request
-        let mut chat_request = conversions::responses_to_chat(&current_request)
-            .map_err(|e| error::bad_request(format!("Failed to convert request: {}", e)))?;
+        let mut chat_request = conversions::responses_to_chat(&current_request).map_err(|e| {
+            error!(
+                function = "tool_loop",
+                iteration = state.iteration,
+                error = %e,
+                "Failed to convert ResponsesRequest to ChatCompletionRequest in tool loop"
+            );
+            error::bad_request(format!("Failed to convert request: {}", e))
+        })?;
 
         // Prepare tools and tool_choice for this iteration
         prepare_chat_tools_and_choice(&mut chat_request, &mcp_chat_tools, state.iteration);
@@ -301,6 +308,13 @@ pub(super) async fn execute_tool_loop(
                     response_id.clone(),
                 )
                 .map_err(|e| {
+                    error!(
+                        function = "tool_loop",
+                        iteration = state.iteration,
+                        error = %e,
+                        context = "function_tool_calls",
+                        "Failed to convert ChatCompletionResponse to ResponsesResponse"
+                    );
                     error::internal_error(format!("Failed to convert to responses format: {}", e))
                 })?;
 
@@ -331,6 +345,13 @@ pub(super) async fn execute_tool_loop(
                     response_id.clone(),
                 )
                 .map_err(|e| {
+                    error!(
+                        function = "tool_loop",
+                        iteration = state.iteration,
+                        error = %e,
+                        context = "max_tool_calls_limit",
+                        "Failed to convert ChatCompletionResponse to ResponsesResponse"
+                    );
                     error::internal_error(format!("Failed to convert to responses format: {}", e))
                 })?;
 
@@ -453,6 +474,13 @@ pub(super) async fn execute_tool_loop(
                 response_id.clone(),
             )
             .map_err(|e| {
+                error!(
+                    function = "tool_loop",
+                    iteration = state.iteration,
+                    error = %e,
+                    context = "final_response",
+                    "Failed to convert ChatCompletionResponse to ResponsesResponse"
+                );
                 error::internal_error(format!("Failed to convert to responses format: {}", e))
             })?;
 
diff --git a/sgl-router/src/routers/grpc/regular/stages/chat/preparation.rs b/sgl-router/src/routers/grpc/regular/stages/chat/preparation.rs
index 6457cec01..09be7f1c6 100644
--- a/sgl-router/src/routers/grpc/regular/stages/chat/preparation.rs
+++ b/sgl-router/src/routers/grpc/regular/stages/chat/preparation.rs
@@ -4,6 +4,7 @@ use std::borrow::Cow;
 
 use async_trait::async_trait;
 use axum::response::Response;
+use tracing::error;
 
 use crate::{
     protocols::chat::ChatCompletionRequest,
@@ -43,18 +44,22 @@ impl ChatPreparationStage {
         let body_ref = utils::filter_chat_request_by_tool_choice(request);
 
         // Step 2: Process messages and apply chat template
-        let processed_messages =
-            match utils::process_chat_messages(&body_ref, &*ctx.components.tokenizer) {
-                Ok(msgs) => msgs,
-                Err(e) => {
-                    return Err(error::bad_request(e));
-                }
-            };
+        let processed_messages = match utils::process_chat_messages(
+            &body_ref,
+            &*ctx.components.tokenizer,
+        ) {
+            Ok(msgs) => msgs,
+            Err(e) => {
+                error!(function = "ChatPreparationStage::execute", error = %e, "Failed to process chat messages");
+                return Err(error::bad_request(e));
+            }
+        };
 
         // Step 3: Tokenize the processed text
         let encoding = match ctx.components.tokenizer.encode(&processed_messages.text) {
             Ok(encoding) => encoding,
             Err(e) => {
+                error!(function = "ChatPreparationStage::execute", error = %e, "Tokenization failed");
                 return Err(error::internal_error(format!("Tokenization failed: {}", e)));
             }
         };
@@ -64,7 +69,10 @@ impl ChatPreparationStage {
         // Step 4: Build tool constraints if needed
         let tool_call_constraint = if let Some(tools) = body_ref.tools.as_ref() {
             utils::generate_tool_constraints(tools, &request.tool_choice, &request.model)
-                .map_err(|e| error::bad_request(format!("Invalid tool configuration: {}", e)))?
+                .map_err(|e| {
+                    error!(function = "ChatPreparationStage::execute", error = %e, "Invalid tool configuration");
+                    error::bad_request(format!("Invalid tool configuration: {}", e))
+                })?
         } else {
             None
         };
diff --git a/sgl-router/src/routers/grpc/regular/stages/chat/request_building.rs b/sgl-router/src/routers/grpc/regular/stages/chat/request_building.rs
index e91c8b64e..efdab648a 100644
--- a/sgl-router/src/routers/grpc/regular/stages/chat/request_building.rs
+++ b/sgl-router/src/routers/grpc/regular/stages/chat/request_building.rs
@@ -2,6 +2,7 @@
 
 use async_trait::async_trait;
 use axum::response::Response;
+use tracing::error;
 use uuid::Uuid;
 
 use crate::routers::grpc::{
@@ -26,17 +27,21 @@ impl ChatRequestBuildingStage {
 #[async_trait]
 impl PipelineStage for ChatRequestBuildingStage {
     async fn execute(&self, ctx: &mut RequestContext) -> Result<Option<Response>, Response> {
-        let prep = ctx
-            .state
-            .preparation
-            .as_ref()
-            .ok_or_else(|| error::internal_error("Preparation not completed"))?;
+        let prep = ctx.state.preparation.as_ref().ok_or_else(|| {
+            error!(
+                function = "ChatRequestBuildingStage::execute",
+                "Preparation not completed"
+            );
+            error::internal_error("Preparation not completed")
+        })?;
 
-        let clients = ctx
-            .state
-            .clients
-            .as_ref()
-            .ok_or_else(|| error::internal_error("Client acquisition not completed"))?;
+        let clients = ctx.state.clients.as_ref().ok_or_else(|| {
+            error!(
+                function = "ChatRequestBuildingStage::execute",
+                "Client acquisition not completed"
+            );
+            error::internal_error("Client acquisition not completed")
+        })?;
 
         let chat_request = ctx.chat_request_arc();
 
@@ -63,7 +68,10 @@ impl PipelineStage for ChatRequestBuildingStage {
                     .clone(),
                 prep.tool_constraints.clone(),
             )
-            .map_err(|e| error::bad_request(format!("Invalid request parameters: {}", e)))?;
+            .map_err(|e| {
+                error!(function = "ChatRequestBuildingStage::execute", error = %e, "Failed to build generate request");
+                error::bad_request(format!("Invalid request parameters: {}", e))
+            })?;
 
         // Inject PD metadata if needed
         if self.inject_pd_metadata {
diff --git a/sgl-router/src/routers/grpc/regular/stages/chat/response_processing.rs b/sgl-router/src/routers/grpc/regular/stages/chat/response_processing.rs
index 1d3a20220..410ee817b 100644
--- a/sgl-router/src/routers/grpc/regular/stages/chat/response_processing.rs
+++ b/sgl-router/src/routers/grpc/regular/stages/chat/response_processing.rs
@@ -7,6 +7,7 @@ use std::sync::Arc;
 
 use async_trait::async_trait;
 use axum::response::Response;
+use tracing::error;
 
 use crate::routers::grpc::{
     common::stages::PipelineStage,
@@ -54,19 +55,26 @@ impl ChatResponseProcessingStage {
         let is_streaming = ctx.is_streaming();
 
         // Extract execution result
-        let execution_result = ctx
-            .state
-            .response
-            .execution_result
-            .take()
-            .ok_or_else(|| error::internal_error("No execution result"))?;
+        let execution_result = ctx.state.response.execution_result.take().ok_or_else(|| {
+            error!(
+                function = "ChatResponseProcessingStage::execute",
+                "No execution result"
+            );
+            error::internal_error("No execution result")
+        })?;
 
         // Get dispatch metadata (needed by both streaming and non-streaming)
         let dispatch = ctx
             .state
             .dispatch
             .as_ref()
-            .ok_or_else(|| error::internal_error("Dispatch metadata not set"))?
+            .ok_or_else(|| {
+                error!(
+                    function = "ChatResponseProcessingStage::execute",
+                    "Dispatch metadata not set"
+                );
+                error::internal_error("Dispatch metadata not set")
+            })?
             .clone();
 
         if is_streaming {
@@ -85,12 +93,13 @@ impl ChatResponseProcessingStage {
 
         let chat_request = ctx.chat_request_arc();
 
-        let stop_decoder = ctx
-            .state
-            .response
-            .stop_decoder
-            .as_mut()
-            .ok_or_else(|| error::internal_error("Stop decoder not initialized"))?;
+        let stop_decoder = ctx.state.response.stop_decoder.as_mut().ok_or_else(|| {
+            error!(
+                function = "ChatResponseProcessingStage::execute",
+                "Stop decoder not initialized"
+            );
+            error::internal_error("Stop decoder not initialized")
+        })?;
 
         let response = self
             .processor
diff --git a/sgl-router/src/routers/grpc/regular/stages/generate/preparation.rs b/sgl-router/src/routers/grpc/regular/stages/generate/preparation.rs
index 95f2b2ef8..ebd4fdf12 100644
--- a/sgl-router/src/routers/grpc/regular/stages/generate/preparation.rs
+++ b/sgl-router/src/routers/grpc/regular/stages/generate/preparation.rs
@@ -4,6 +4,7 @@ use std::sync::Arc;
 
 use async_trait::async_trait;
 use axum::response::Response;
+use tracing::error;
 
 use crate::{
     protocols::{common::InputIds, generate::GenerateRequest},
@@ -44,6 +45,7 @@ impl GeneratePreparationStage {
         let (original_text, token_ids) = match self.resolve_generate_input(ctx, request) {
             Ok(res) => res,
             Err(msg) => {
+                error!(function = "GeneratePreparationStage::execute", error = %msg, "Failed to resolve generate input");
                 return Err(error::bad_request(msg));
             }
         };
diff --git a/sgl-router/src/routers/grpc/regular/stages/generate/request_building.rs b/sgl-router/src/routers/grpc/regular/stages/generate/request_building.rs
index 956a21ec9..020195fe6 100644
--- a/sgl-router/src/routers/grpc/regular/stages/generate/request_building.rs
+++ b/sgl-router/src/routers/grpc/regular/stages/generate/request_building.rs
@@ -2,6 +2,7 @@
 
 use async_trait::async_trait;
 use axum::response::Response;
+use tracing::error;
 use uuid::Uuid;
 
 use crate::routers::grpc::{
@@ -26,17 +27,21 @@ impl GenerateRequestBuildingStage {
 #[async_trait]
 impl PipelineStage for GenerateRequestBuildingStage {
     async fn execute(&self, ctx: &mut RequestContext) -> Result<Option<Response>, Response> {
-        let prep = ctx
-            .state
-            .preparation
-            .as_ref()
-            .ok_or_else(|| error::internal_error("Preparation not completed"))?;
+        let prep = ctx.state.preparation.as_ref().ok_or_else(|| {
+            error!(
+                function = "GenerateRequestBuildingStage::execute",
+                "Preparation not completed"
+            );
+            error::internal_error("Preparation not completed")
+        })?;
 
-        let clients = ctx
-            .state
-            .clients
-            .as_ref()
-            .ok_or_else(|| error::internal_error("Client acquisition not completed"))?;
+        let clients = ctx.state.clients.as_ref().ok_or_else(|| {
+            error!(
+                function = "GenerateRequestBuildingStage::execute",
+                "Client acquisition not completed"
+            );
+            error::internal_error("Client acquisition not completed")
+        })?;
 
         let generate_request = ctx.generate_request_arc();
 
@@ -59,7 +64,10 @@ impl PipelineStage for GenerateRequestBuildingStage {
                 prep.original_text.clone(),
                 prep.token_ids.clone(),
             )
-            .map_err(error::bad_request)?;
+            .map_err(|e| {
+                error!(function = "GenerateRequestBuildingStage::execute", error = %e, "Failed to build generate request");
+                error::bad_request(e)
+            })?;
 
         // Inject PD metadata if needed
         if self.inject_pd_metadata {
diff --git a/sgl-router/src/routers/grpc/regular/stages/generate/response_processing.rs b/sgl-router/src/routers/grpc/regular/stages/generate/response_processing.rs
index 29bb69eda..3f325ac0d 100644
--- a/sgl-router/src/routers/grpc/regular/stages/generate/response_processing.rs
+++ b/sgl-router/src/routers/grpc/regular/stages/generate/response_processing.rs
@@ -4,6 +4,7 @@ use std::{sync::Arc, time::Instant};
 
 use async_trait::async_trait;
 use axum::response::Response;
+use tracing::error;
 
 use crate::routers::grpc::{
     common::stages::PipelineStage,
@@ -52,19 +53,26 @@ impl GenerateResponseProcessingStage {
         let is_streaming = ctx.is_streaming();
 
         // Extract execution result
-        let execution_result = ctx
-            .state
-            .response
-            .execution_result
-            .take()
-            .ok_or_else(|| error::internal_error("No execution result"))?;
+        let execution_result = ctx.state.response.execution_result.take().ok_or_else(|| {
+            error!(
+                function = "GenerateResponseProcessingStage::execute",
+                "No execution result"
+            );
+            error::internal_error("No execution result")
+        })?;
 
         // Get dispatch metadata (needed by both streaming and non-streaming)
         let dispatch = ctx
             .state
             .dispatch
             .as_ref()
-            .ok_or_else(|| error::internal_error("Dispatch metadata not set"))?
+            .ok_or_else(|| {
+                error!(
+                    function = "GenerateResponseProcessingStage::execute",
+                    "Dispatch metadata not set"
+                );
+                error::internal_error("Dispatch metadata not set")
+            })?
             .clone();
 
         if is_streaming {
@@ -82,12 +90,13 @@ impl GenerateResponseProcessingStage {
         let request_logprobs = ctx.generate_request().return_logprob.unwrap_or(false);
         let generate_request = ctx.generate_request_arc();
 
-        let stop_decoder = ctx
-            .state
-            .response
-            .stop_decoder
-            .as_mut()
-            .ok_or_else(|| error::internal_error("Stop decoder not initialized"))?;
+        let stop_decoder = ctx.state.response.stop_decoder.as_mut().ok_or_else(|| {
+            error!(
+                function = "GenerateResponseProcessingStage::execute",
+                "Stop decoder not initialized"
+            );
+            error::internal_error("Stop decoder not initialized")
+        })?;
 
         let result_array = self
             .processor
diff --git a/sgl-router/src/routers/grpc/regular/stages/response_processing.rs b/sgl-router/src/routers/grpc/regular/stages/response_processing.rs
index 71e885be4..1df4f0805 100644
--- a/sgl-router/src/routers/grpc/regular/stages/response_processing.rs
+++ b/sgl-router/src/routers/grpc/regular/stages/response_processing.rs
@@ -4,6 +4,7 @@ use std::sync::Arc;
 
 use async_trait::async_trait;
 use axum::response::Response;
+use tracing::error;
 
 use super::{chat::ChatResponseProcessingStage, generate::GenerateResponseProcessingStage};
 use crate::routers::grpc::{
@@ -40,9 +41,15 @@ impl PipelineStage for ResponseProcessingStage {
         match &ctx.input.request_type {
             RequestType::Chat(_) => self.chat_stage.execute(ctx).await,
             RequestType::Generate(_) => self.generate_stage.execute(ctx).await,
-            RequestType::Responses(_) => Err(error::bad_request(
-                "Responses API processing must be handled by responses handler".to_string(),
-            )),
+            RequestType::Responses(_) => {
+                error!(
+                    function = "ResponseProcessingStage::execute",
+                    "Responses API not supported in regular pipeline"
+                );
+                Err(error::bad_request(
+                    "Responses API processing must be handled by responses handler".to_string(),
+                ))
+            }
         }
     }
 
diff --git a/sgl-router/src/routers/grpc/utils.rs b/sgl-router/src/routers/grpc/utils.rs
index df74c3bf0..3731c3dc7 100644
--- a/sgl-router/src/routers/grpc/utils.rs
+++ b/sgl-router/src/routers/grpc/utils.rs
@@ -43,8 +43,14 @@ pub async fn get_grpc_client_from_worker(
     let client_arc = worker
         .get_grpc_client()
         .await
-        .map_err(|e| error::internal_error(format!("Failed to get gRPC client: {}", e)))?
-        .ok_or_else(|| error::internal_error("Selected worker is not configured for gRPC"))?;
+        .map_err(|e| {
+            error!(function = "get_grpc_client_from_worker", error = %e, "Failed to get gRPC client");
+            error::internal_error(format!("Failed to get gRPC client: {}", e))
+        })?
+        .ok_or_else(|| {
+            error!(function = "get_grpc_client_from_worker", "Selected worker not configured for gRPC");
+            error::internal_error("Selected worker is not configured for gRPC")
+        })?;
 
     Ok((*client_arc).clone())
 }
@@ -596,7 +602,7 @@ pub async fn collect_stream_responses(
                         all_responses.push(complete);
                     }
                     Some(Error(err)) => {
-                        error!("{} error: {}", worker_name, err.message);
+                        error!(function = "collect_stream_responses", worker = %worker_name, error = %err.message, "Worker generation error");
                         // Don't mark as completed - let Drop send abort for error cases
                         return Err(error::internal_error(format!(
                             "{} generation failed: {}",
@@ -612,7 +618,7 @@ pub async fn collect_stream_responses(
                 }
             }
             Err(e) => {
-                error!("{} stream error: {:?}", worker_name, e);
+                error!(function = "collect_stream_responses", worker = %worker_name, error = ?e, "Worker stream error");
                 // Don't mark as completed - let Drop send abort for error cases
                 return Err(error::internal_error(format!(
                     "{} stream failed: {}",