feat: add Claude Agent SDK as alternative LLM backend

package.json

@@ -41,7 +41,7 @@
     "eval": "npx tsx tests/evals/runner.ts"
   },
   "dependencies": {
-    "@anthropic-ai/claude-agent-sdk": "^0.2.37",
+    "@anthropic-ai/claude-agent-sdk": "^0.2.92",
     "@anthropic-ai/sdk": "^0.71.2",
     "@electron-toolkit/utils": "^4.0.0",
     "@floating-ui/dom": "^1.7.6",
@@ -88,10 +88,10 @@
     "@types/react": "^18.3.12",
     "@types/react-dom": "^18.3.1",
     "@types/semver": "^7.7.1",
-    "@vitejs/plugin-react": "^4.3.4",
-    "autoprefixer": "^10.4.20",
     "@typescript-eslint/eslint-plugin": "^8.57.2",
     "@typescript-eslint/parser": "^8.57.2",
+    "@vitejs/plugin-react": "^4.3.4",
+    "autoprefixer": "^10.4.20",
     "electron": "^39.8.5",
     "electron-builder": "^25.1.8",
     "electron-vite": "^3.0.0",

src/main/index.ts

@@ -389,14 +389,20 @@ ipcMain.handle("default-mail-app:get-pending", () => {
 // Initialize database on startup
 const _db = initDatabase();
 
-// Wire up AnthropicService cost tracking
-import { setAnthropicServiceDb } from "./services/anthropic-service";
+// Wire up AnthropicService cost tracking + LLM backend toggle
+import { setAnthropicServiceDb, setLlmBackendFromConfig } from "./services/anthropic-service";
 setAnthropicServiceDb(_db);
 
-// If no ANTHROPIC_API_KEY in env (e.g. packaged app with no .env), read from stored config
-// so that services using `new Anthropic()` pick it up automatically.
 {
   const config = getConfig();
+
+  // Set LLM backend from persisted config (env var takes precedence inside getLlmBackend())
+  if (config.llmBackend) {
+    setLlmBackendFromConfig(config.llmBackend);
+  }
+
+  // If using Anthropic backend: read stored API key into env so `new Anthropic()` picks it up.
+  // When using claude-sdk backend, API key is not required.
   if (!process.env.ANTHROPIC_API_KEY && config.anthropicApiKey) {
     process.env.ANTHROPIC_API_KEY = config.anthropicApiKey;
   }

src/main/ipc/gmail.ipc.ts

@@ -2,6 +2,7 @@ import { ipcMain } from "electron";
 import { GmailClient } from "../services/gmail-client";
 import { saveEmail, getEmailIds, getInboxEmails, getEmail, saveAccount, getAccounts } from "../db";
 import { getConfig } from "./settings.ipc";
+import { getLlmBackend } from "../services/anthropic-service";
 import type { IpcResponse, DashboardEmail } from "../../shared/types";
 import { DEMO_INBOX_EMAILS, DEMO_EXPECTED_ANALYSIS } from "../demo/fake-inbox";
 import { createLogger } from "../services/logger";
@@ -70,7 +71,10 @@ export function registerGmailIpc(): void {
 
       try {
         const client = new GmailClient();
-        const hasAnthropicKey = !!(process.env.ANTHROPIC_API_KEY || getConfig().anthropicApiKey);
+        // Claude SDK backend doesn't need an API key — the subscription handles auth
+        const hasAnthropicKey =
+          getLlmBackend() === "claude-sdk" ||
+          !!(process.env.ANTHROPIC_API_KEY || getConfig().anthropicApiKey);
         return {
           success: true,
           data: {

src/main/ipc/settings.ipc.ts

@@ -18,7 +18,12 @@ import {
 } from "../../shared/types";
 import { resetAnalyzer } from "./analysis.ipc";
 import { resetArchiveReadyAnalyzer } from "./archive-ready.ipc";
-import { resetClient, getUsageStats, getCallHistory } from "../services/anthropic-service";
+import {
+  resetClient,
+  getUsageStats,
+  getCallHistory,
+  setLlmBackendFromConfig,
+} from "../services/anthropic-service";
 import { prefetchService } from "../services/prefetch-service";
 import { agentCoordinator } from "../agents/agent-coordinator";
 import {
@@ -70,6 +75,7 @@ function getStore(): Store<{ config: Config }> {
           },
           keyboardBindings: "superhuman" as const,
           configVersion: 1,
+          llmBackend: "anthropic" as const,
         },
       },
     });
@@ -272,6 +278,11 @@ export function registerSettingsIpc(): void {
         });
       }
 
+      // Propagate LLM backend change
+      if ("llmBackend" in config && newConfig.llmBackend) {
+        setLlmBackendFromConfig(newConfig.llmBackend);
+      }
+
       // Append any new extra PATH directories so they take effect without restart
       if ("extraPathDirs" in config) {
         const pathEntries = new Set((process.env.PATH || "").split(":"));
@@ -283,9 +294,9 @@ export function registerSettingsIpc(): void {
         }
       }
 
-      // Reset cached analyzer/service instances when model config or API key changes,
+      // Reset cached analyzer/service instances when model config, API key, or backend changes,
       // since they hold Anthropic client instances that capture the key at construction.
-      if ("modelConfig" in config || "anthropicApiKey" in config) {
+      if ("modelConfig" in config || "anthropicApiKey" in config || "llmBackend" in config) {
         resetClient();
         resetAnalyzer();
         resetArchiveReadyAnalyzer();

src/main/services/anthropic-service.ts

@@ -15,6 +15,7 @@ import type {
 } from "@anthropic-ai/sdk/resources/messages";
 import { createLogger } from "./logger";
 import { randomUUID } from "crypto";
+import { createMessageViaSdk } from "./claude-sdk-service";
 
 const log = createLogger("anthropic");
 
@@ -86,6 +87,28 @@ interface CreateOptions {
   timeoutMs?: number;
 }
 
+// LLM backend toggle — env var takes precedence, then persisted config
+export type LlmBackend = "anthropic" | "claude-sdk";
+
+let _configBackend: LlmBackend | null = null;
+
+/**
+ * Set the LLM backend from persisted config (called during app init).
+ */
+export function setLlmBackendFromConfig(backend: LlmBackend): void {
+  _configBackend = backend;
+}
+
+/**
+ * Get the active LLM backend.
+ * Priority: LLM_BACKEND env var > persisted config > default ("anthropic").
+ */
+export function getLlmBackend(): LlmBackend {
+  const envVal = process.env.LLM_BACKEND;
+  if (envVal === "anthropic" || envVal === "claude-sdk") return envVal;
+  return _configBackend ?? "anthropic";
+}
+
 // Anthropic client — singleton for production, replaceable for testing
 let _anthropicClient: Anthropic | null = null;
 let _defaultClient: Anthropic | null = null;
@@ -273,11 +296,17 @@ function getRetryCategory(error: unknown): string | null {
 
 /**
  * Create a message using Claude API with retry and cost tracking.
+ * When LLM_BACKEND=claude-sdk, delegates to the Claude Agent SDK adapter.
  */
 export async function createMessage(
   params: MessageCreateParamsNonStreaming,
   options: CreateOptions,
 ): Promise<Message> {
+  // Delegate to Claude Agent SDK if configured
+  if (getLlmBackend() === "claude-sdk") {
+    return createMessageViaClaudeSdk(params, options);
+  }
+
   const { caller, emailId, accountId, timeoutMs } = options;
   const model = params.model;
   const startTime = Date.now();
@@ -452,3 +481,46 @@ export function getCallHistory(limit: number = 50): LlmCallRecord[] {
     .prepare("SELECT * FROM llm_calls ORDER BY created_at DESC LIMIT ?")
     .all(limit) as LlmCallRecord[];
 }
+
+/**
+ * Bridge: delegate createMessage to the Claude Agent SDK adapter,
+ * then record cost in the same llm_calls table.
+ */
+async function createMessageViaClaudeSdk(
+  params: MessageCreateParamsNonStreaming,
+  options: CreateOptions,
+): Promise<Message> {
+  const { caller, emailId, accountId, timeoutMs } = options;
+  const model = params.model;
+  const startTime = Date.now();
+
+  try {
+    const { message, durationMs, inputTokens, outputTokens } = await createMessageViaSdk(params, {
+      caller,
+      emailId,
+      accountId,
+      timeoutMs,
+    });
+
+    // Record to llm_calls for unified cost tracking
+    recordCall(
+      model,
+      caller,
+      emailId || null,
+      accountId || null,
+      inputTokens,
+      outputTokens,
+      0, // cache_read — not applicable for SDK
+      0, // cache_create — not applicable for SDK
+      durationMs,
+      true,
+      null,
+    );
+
+    return message;
+  } catch (error) {
+    const errMsg = error instanceof Error ? error.message : String(error);
+    recordCall(model, caller, emailId || null, accountId || null, 0, 0, 0, 0, Date.now() - startTime, false, errMsg);
+    throw error;
+  }
+}