feat: task-aware model routing via x-char-task header (#4145)

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: yujonglee

Cargo.lock

@@ -172,6 +172,49 @@
         }
       }
     },
+    "/llm/chat/completions": {
+      "post": {
+        "tags": [
+          "llm"
+        ],
+        "operationId": "llm_chat_completions",
+        "parameters": [
+          {
+            "name": "x-char-task",
+            "in": "header",
+            "description": "Task type for model selection",
+            "required": false,
+            "schema": {
+              "oneOf": [
+                {
+                  "type": "null"
+                },
+                {
+                  "$ref": "#/components/schemas/CharTask"
+                }
+              ]
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "description": "Chat completion response (streaming or non-streaming)"
+          },
+          "401": {
+            "description": "Unauthorized"
+          },
+          "429": {
+            "description": "Rate limit exceeded"
+          },
+          "502": {
+            "description": "Upstream provider failed"
+          },
+          "504": {
+            "description": "Request timeout"
+          }
+        }
+      }
+    },
     "/nango/connect-session": {
       "post": {
         "tags": [
@@ -881,6 +924,14 @@
           }
         }
       },
+      "CharTask": {
+        "type": "string",
+        "enum": [
+          "chat",
+          "enhance",
+          "title"
+        ]
+      },
       "ConnectSessionResponse": {
         "type": "object",
         "required": [
@@ -1759,12 +1810,6 @@
         "scheme": "bearer",
         "bearerFormat": "JWT",
         "description": "Supabase JWT token"
-      },
-      "device_fingerprint": {
-        "type": "apiKey",
-        "in": "header",
-        "name": "x-device-fingerprint",
-        "description": "Optional device fingerprint for analytics"
       }
     }
   },

apps/api/openapi.gen.json

@@ -1,9 +1,7 @@
 use std::collections::BTreeMap;
 
 use utoipa::openapi::path::{Operation, PathItem};
-use utoipa::openapi::security::{
-    ApiKey, ApiKeyValue, Http, HttpAuthScheme, SecurityRequirement, SecurityScheme,
-};
+use utoipa::openapi::security::{Http, HttpAuthScheme, SecurityRequirement, SecurityScheme};
 use utoipa::{Modify, OpenApi};
 
 #[derive(OpenApi)]
@@ -71,13 +69,6 @@ impl Modify for SecurityAddon {
                         .build(),
                 ),
             );
-            components.add_security_scheme(
-                "device_fingerprint",
-                SecurityScheme::ApiKey(ApiKey::Header(ApiKeyValue::with_description(
-                    "x-device-fingerprint",
-                    "Optional device fingerprint for analytics",
-                ))),
-            );
         }
     }
 }

apps/api/src/openapi.rs

@@ -213,7 +213,7 @@ function useTransport(
   systemPromptOverride?: string,
 ) {
   const registry = useToolRegistry();
-  const configuredModel = useLanguageModel();
+  const configuredModel = useLanguageModel("chat");
   const model = modelOverride ?? configuredModel;
   const language = main.UI.useValue("ai_language", main.STORE_ID) ?? "en";
   const [systemPrompt, setSystemPrompt] = useState<string | undefined>();

apps/desktop/src/components/chat/session.tsx

@@ -18,7 +18,7 @@ export function ChatView() {
     currentTab?.type === "sessions" ? currentTab.id : undefined;
 
   const stableSessionId = useStableSessionId(groupId);
-  const model = useLanguageModel();
+  const model = useLanguageModel("chat");
 
   const { handleSendMessage } = useChatActions({
     groupId,

apps/desktop/src/components/chat/view.tsx

@@ -62,7 +62,7 @@ export function OptionsMenu({
   const { user_id } = main.UI.useValues(main.STORE_ID);
   const updateSessionTabState = useTabs((state) => state.updateSessionTabState);
   const createEnhancedNote = useCreateEnhancedNote();
-  const model = useLanguageModel();
+  const model = useLanguageModel("enhance");
   const generate = useAITask((state) => state.generate);
   const selectedTemplateId = settings.UI.useValue(
     "selected_template_id",

apps/desktop/src/components/main/body/sessions/floating/options-menu.tsx

@@ -16,7 +16,7 @@ export function EnhanceError({
   enhancedNoteId: string;
   error: Error | undefined;
 }) {
-  const model = useLanguageModel();
+  const model = useLanguageModel("enhance");
   const generate = useAITask((state) => state.generate);
   const templateId =
     (main.UI.useCell(

apps/desktop/src/components/main/body/sessions/note-input/enhanced/enhance-error.tsx

@@ -301,7 +301,7 @@ function CreateOtherFormatButton({
     main.STORE_ID,
   );
   const createEnhancedNote = useCreateEnhancedNote();
-  const model = useLanguageModel();
+  const model = useLanguageModel("enhance");
   const openNew = useTabs((state) => state.openNew);
 
   const store = main.UI.useStore(main.STORE_ID);
@@ -611,7 +611,7 @@ function labelForEditorView(view: EditorView): string {
 }
 
 function useEnhanceLogic(sessionId: string, enhancedNoteId: string) {
-  const model = useLanguageModel();
+  const model = useLanguageModel("enhance");
   const llmStatus = useLLMConnectionStatus();
   const taskId = createTaskId(enhancedNoteId, "enhance");
   const [missingModelError, setMissingModelError] = useState<Error | null>(

apps/desktop/src/components/main/body/sessions/note-input/header.tsx

@@ -30,7 +30,7 @@ export function useAutoEnhanceRunner(
   isEnhancing: boolean;
 } {
   const sessionId = tab.id;
-  const model = useLanguageModel();
+  const model = useLanguageModel("enhance");
   const { conn: llmConn } = useLLMConnection();
   const { updateSessionTabState } = useTabs();
   const createEnhancedNote = useCreateEnhancedNote();

apps/desktop/src/hooks/autoEnhance/runner.ts

@@ -7,6 +7,7 @@ import { fetch as tauriFetch } from "@tauri-apps/plugin-http";
 import { extractReasoningMiddleware, wrapLanguageModel } from "ai";
 import { useMemo } from "react";
 
+import type { CharTask } from "@hypr/api-client";
 import type { AIProviderStorage } from "@hypr/store";
 
 import { useAuth } from "../auth";
@@ -22,7 +23,7 @@ import {
 } from "../components/settings/ai/shared/eligibility";
 import { env } from "../env";
 import * as settings from "../store/tinybase/store/settings";
-import { tracedFetch } from "../utils/traced-fetch";
+import { createTracedFetch, tracedFetch } from "../utils/traced-fetch";
 
 type LanguageModelV3 = Parameters<typeof wrapLanguageModel>[0]["model"];
 
@@ -52,9 +53,12 @@ type LLMConnectionResult = {
   status: LLMConnectionStatus;
 };
 
-export const useLanguageModel = (): LanguageModelV3 | null => {
+export const useLanguageModel = (task?: CharTask): LanguageModelV3 | null => {
   const { conn } = useLLMConnection();
-  return useMemo(() => (conn ? createLanguageModel(conn) : null), [conn]);
+  return useMemo(
+    () => (conn ? createLanguageModel(conn, task) : null),
+    [conn, task],
+  );
 };
 
 export const useLLMConnection = (): LLMConnectionResult => {
@@ -227,11 +231,14 @@ const wrapWithThinkingMiddleware = (
   });
 };
 
-const createLanguageModel = (conn: LLMConnectionInfo): LanguageModelV3 => {
+const createLanguageModel = (
+  conn: LLMConnectionInfo,
+  task?: CharTask,
+): LanguageModelV3 => {
   switch (conn.providerId) {
     case "hyprnote": {
       const provider = createOpenRouter({
-        fetch: tracedFetch,
+        fetch: task ? createTracedFetch(task) : tracedFetch,
         baseURL: conn.baseUrl,
         apiKey: conn.apiKey,
       });