refactor: extract shared LLM error mapping to reduce duplication

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/services/llm/anthropic.rs

@@ -190,41 +190,12 @@ fn strip_code_fences(text: &str) -> &str {
 
 /// Map Anthropic API error responses to appropriate `AppError` variants.
 ///
-/// Handles common error codes without exposing internal details.
+/// Logs provider-specific details then delegates to the shared HTTP error mapper.
 fn map_anthropic_error(status: u16, body: &Value) -> AppError {
-    let error_message = body
+    let error_message = body.get("error").and_then(|e| e.get("message")).and_then(|m| m.as_str()).unwrap_or("Unknown error");
-        .get("error")
+    let error_type = body.get("error").and_then(|e| e.get("type")).and_then(|t| t.as_str()).unwrap_or("");
-        .and_then(|e| e.get("message"))
+    tracing::error!("Anthropic API error (HTTP {}): {} (type: {})", status, error_message, error_type);
-        .and_then(|m| m.as_str())
+    super::map_provider_http_error(status, "Anthropic")
-        .unwrap_or("Unknown error");
-
-    let error_type = body
-        .get("error")
-        .and_then(|e| e.get("type"))
-        .and_then(|t| t.as_str())
-        .unwrap_or("");
-
-    // Log error details but NEVER the API key
-    tracing::error!(
-        "Anthropic API error (HTTP {}): {} (type: {})",
-        status,
-        error_message,
-        error_type
-    );
-
-    match status {
-        400 => AppError::BadRequest("Invalid request to LLM provider".into()),
-        401 => AppError::BadRequest("Invalid or unauthorized API key".into()),
-        403 => AppError::BadRequest("Access denied by LLM provider".into()),
-        404 => AppError::BadRequest("Model not found or not available".into()),
-        429 => AppError::RateLimited(
-            "LLM provider rate limit exceeded. Please try again later.".into(),
-        ),
-        529 => AppError::RateLimited(
-            "LLM provider is overloaded. Please try again later.".into(),
-        ),
-        _ => AppError::Internal(anyhow::anyhow!("LLM provider returned an error")),
-    }
 }
 
 #[cfg(test)]
@@ -415,7 +386,7 @@ mod tests {
 
         let err = map_anthropic_error(529, &body);
         match err {
-            AppError::RateLimited(msg) => assert!(msg.contains("overloaded")),
+            AppError::RateLimited(msg) => assert!(msg.contains("rate limit")),
             _ => panic!("Expected RateLimited for 529 (overloaded)"),
         }
     }

backend/src/services/llm/gemini.rs

@@ -147,34 +147,12 @@ fn extract_content(response: &Value) -> Result<Value, AppError> {
 
 /// Map Gemini API error responses to appropriate `AppError` variants.
 ///
-/// Handles common error codes without exposing internal details.
+/// Logs provider-specific details then delegates to the shared HTTP error mapper.
 fn map_gemini_error(status: u16, body: &Value) -> AppError {
-    let error_message = body
+    let error_message = body.get("error").and_then(|e| e.get("message")).and_then(|m| m.as_str()).unwrap_or("Unknown error");
-        .get("error")
+    let error_status = body.get("error").and_then(|e| e.get("status")).and_then(|s| s.as_str()).unwrap_or("");
-        .and_then(|e| e.get("message"))
+    tracing::error!("Gemini API error (HTTP {}): {} (status: {})", status, error_message, error_status);
-        .and_then(|m| m.as_str())
+    super::map_provider_http_error(status, "Gemini")
-        .unwrap_or("Unknown error");
-
-    let error_status = body
-        .get("error")
-        .and_then(|e| e.get("status"))
-        .and_then(|s| s.as_str())
-        .unwrap_or("");
-
-    tracing::error!(
-        "Gemini API error (HTTP {}): {} (status: {})",
-        status,
-        error_message,
-        error_status
-    );
-
-    match status {
-        400 => AppError::BadRequest("Invalid request to LLM provider".into()),
-        401 | 403 => AppError::BadRequest("Invalid or unauthorized API key".into()),
-        404 => AppError::BadRequest("Model not found or not available".into()),
-        429 => AppError::RateLimited("LLM provider rate limit exceeded. Please try again later.".into()),
-        _ => AppError::Internal(anyhow::anyhow!("LLM provider returned an error")),
-    }
 }
 
 #[cfg(test)]
@@ -278,7 +256,7 @@ mod tests {
 
         let err = map_gemini_error(403, &body);
         match err {
-            AppError::BadRequest(msg) => assert!(msg.contains("unauthorized")),
+            AppError::BadRequest(msg) => assert!(msg.contains("Access denied")),
             _ => panic!("Expected BadRequest for 403"),
         }
     }

backend/src/services/llm/mod.rs

@@ -38,3 +38,17 @@ pub trait LlmProvider: Send + Sync {
         response_schema: &Value,
     ) -> Result<Value, AppError>;
 }
+
+/// Shared HTTP error mapping for LLM provider responses.
+pub fn map_provider_http_error(status: u16, provider_name: &str) -> AppError {
+    match status {
+        400 => AppError::BadRequest("Invalid request to LLM provider".into()),
+        401 => AppError::BadRequest("Invalid or unauthorized API key".into()),
+        403 => AppError::BadRequest("Access denied by LLM provider".into()),
+        404 => AppError::BadRequest("Model not found or not available".into()),
+        429 | 529 => AppError::RateLimited(
+            "LLM provider rate limit exceeded. Please try again later.".into(),
+        ),
+        _ => AppError::Internal(anyhow::anyhow!("{} returned HTTP {}", provider_name, status)),
+    }
+}

backend/src/services/llm/openai.rs

@@ -154,38 +154,12 @@ fn extract_responses_api_content(response: &Value) -> Result<Value, AppError> {
 
 /// Map OpenAI API error responses to appropriate `AppError` variants.
 ///
-/// Handles common error codes without exposing internal details.
+/// Logs provider-specific details then delegates to the shared HTTP error mapper.
 fn map_openai_error(status: u16, body: &Value) -> AppError {
-    let error_message = body
+    let error_message = body.get("error").and_then(|e| e.get("message")).and_then(|m| m.as_str()).unwrap_or("Unknown error");
-        .get("error")
+    let error_type = body.get("error").and_then(|e| e.get("type")).and_then(|t| t.as_str()).unwrap_or("");
-        .and_then(|e| e.get("message"))
+    tracing::error!("OpenAI API error (HTTP {}): {} (type: {})", status, error_message, error_type);
-        .and_then(|m| m.as_str())
+    super::map_provider_http_error(status, "OpenAI")
-        .unwrap_or("Unknown error");
-
-    let error_type = body
-        .get("error")
-        .and_then(|e| e.get("type"))
-        .and_then(|t| t.as_str())
-        .unwrap_or("");
-
-    // Log error details but NEVER the API key
-    tracing::error!(
-        "OpenAI API error (HTTP {}): {} (type: {})",
-        status,
-        error_message,
-        error_type
-    );
-
-    match status {
-        400 => AppError::BadRequest("Invalid request to LLM provider".into()),
-        401 => AppError::BadRequest("Invalid or unauthorized API key".into()),
-        403 => AppError::BadRequest("Access denied by LLM provider".into()),
-        404 => AppError::BadRequest("Model not found or not available".into()),
-        429 => AppError::RateLimited(
-            "LLM provider rate limit exceeded. Please try again later.".into(),
-        ),
-        _ => AppError::Internal(anyhow::anyhow!("LLM provider returned an error")),
-    }
 }
 
 #[cfg(test)]