diff --git a/frontend/src/routes/auth.$provider.callback.tsx b/frontend/src/routes/auth.$provider.callback.tsx
index 5026d67f..4ee8f9a4 100644
--- a/frontend/src/routes/auth.$provider.callback.tsx
+++ b/frontend/src/routes/auth.$provider.callback.tsx
@@ -1,9 +1,9 @@
 import { createFileRoute, useNavigate, Link } from "@tanstack/react-router";
-import { useEffect, useState, useRef } from "react";
+import { useEffect, useState, useRef, useCallback } from "react";
 import { useOpenSecret } from "@opensecret/react";
 import { AlertDestructive } from "@/components/AlertDestructive";
 import { Card, CardContent, CardHeader, CardTitle } from "@/components/ui/card";
-import { Loader2 } from "lucide-react";
+import { Loader2, Copy, Check, ExternalLink } from "lucide-react";
 import { Button } from "@/components/ui/button";
 import { getBillingService } from "@/billing/billingService";
 
@@ -28,11 +28,29 @@ function formatProviderName(provider: string): string {
 function OAuthCallback() {
   const [isProcessing, setIsProcessing] = useState(true);
   const [error, setError] = useState<string | null>(null);
+  const [showCopyFallback, setShowCopyFallback] = useState(false);
+  const [copied, setCopied] = useState(false);
+  const [authCode, setAuthCode] = useState<string | null>(null);
   const [nativeRedirectUrl, setNativeRedirectUrl] = useState<string | null>(null);
   const navigate = useNavigate();
   const { handleGitHubCallback, handleGoogleCallback, handleAppleCallback } = useOpenSecret();
   const processedRef = useRef(false);
 
+  const handleCopyCode = useCallback(async () => {
+    if (!authCode) return;
+    try {
+      await navigator.clipboard.writeText(authCode);
+      setCopied(true);
+      setTimeout(() => setCopied(false), 2000);
+    } catch {
+      // Fallback: select the text in the input for manual copy
+      const input = document.querySelector<HTMLInputElement>("[data-auth-code]");
+      if (input) {
+        input.select();
+      }
+    }
+  }, [authCode]);
+
   // Helper functions for the callback process
   const handleSuccessfulAuth = () => {
     // Check if this is a Tauri app auth flow (desktop or mobile)
@@ -46,6 +64,13 @@ function OAuthCallback() {
       const accessToken = localStorage.getItem("access_token") || "";
       const refreshToken = localStorage.getItem("refresh_token");
 
+      // Generate the fallback auth code for copy/paste flow
+      const codePayload = JSON.stringify({
+        access_token: accessToken,
+        refresh_token: refreshToken || ""
+      });
+      setAuthCode(btoa(codePayload));
+
       let deepLinkUrl = `cloud.opensecret.maple://auth?access_token=${encodeURIComponent(accessToken)}`;
 
       if (refreshToken) {
@@ -60,6 +85,11 @@ function OAuthCallback() {
         window.location.href = deepLinkUrl;
       }, 1000);
 
+      // Show the copy fallback after a few seconds in case the redirect doesn't work
+      setTimeout(() => {
+        setShowCopyFallback(true);
+      }, 3000);
+
       return;
     }
 
@@ -168,9 +198,41 @@ function OAuthCallback() {
           <p className="mb-4">
             Authentication successful! Tap the button below to return to Maple.
           </p>
-          <div className="flex justify-center">
+          <div className="flex justify-center mb-4">
             <Button onClick={() => (window.location.href = nativeRedirectUrl)}>Open Maple</Button>
           </div>
+          {showCopyFallback && authCode && (
+            <div className="border-t pt-4 mt-2">
+              <p className="text-sm text-muted-foreground mb-3">
+                <ExternalLink className="inline h-4 w-4 mr-1" />
+                Trouble opening the app? Copy the code below and paste it in the Maple app.
+              </p>
+              <div className="flex gap-2">
+                <input
+                  type="text"
+                  readOnly
+                  value={authCode}
+                  data-auth-code
+                  className="flex-1 rounded-md border bg-muted px-3 py-2 text-xs font-mono truncate"
+                  onClick={(e) => (e.target as HTMLInputElement).select()}
+                />
+                <Button onClick={handleCopyCode} variant="outline" size="sm" className="shrink-0">
+                  {copied ? (
+                    <>
+                      <Check className="h-4 w-4 mr-1" /> Copied
+                    </>
+                  ) : (
+                    <>
+                      <Copy className="h-4 w-4 mr-1" /> Copy
+                    </>
+                  )}
+                </Button>
+              </div>
+              <p className="text-xs text-muted-foreground mt-2">
+                Switch to the Maple app and paste the code into the login code input.
+              </p>
+            </div>
+          )}
         </CardContent>
       </Card>
     );
diff --git a/frontend/src/routes/login.tsx b/frontend/src/routes/login.tsx
index 47822ae7..f92ec62f 100644
--- a/frontend/src/routes/login.tsx
+++ b/frontend/src/routes/login.tsx
@@ -33,7 +33,7 @@ export const Route = createFileRoute("/login")({
   })
 });
 
-type LoginMethod = "email" | "github" | "google" | "apple" | "guest" | null;
+type LoginMethod = "email" | "github" | "google" | "apple" | "guest" | "paste-code" | null;
 
 function LoginPage() {
   const navigate = useNavigate();
@@ -43,10 +43,26 @@ function LoginPage() {
   const [error, setError] = useState<string | null>(null);
   const [isLoading, setIsLoading] = useState(false);
 
+  const [pasteCodeValue, setPasteCodeValue] = useState("");
+  const [oauthProvider, setOauthProvider] = useState<string | null>(null);
+  const [showPasteInput, setShowPasteInput] = useState(false);
+
   // Use platform detection functions
   const isIOSPlatform = isIOS();
   const isTauriEnv = isTauri();
 
+  // Show paste code input after a delay when auto-navigated from OAuth
+  useEffect(() => {
+    if (loginMethod === "paste-code" && oauthProvider) {
+      setShowPasteInput(false);
+      const timer = setTimeout(() => setShowPasteInput(true), 3000);
+      return () => clearTimeout(timer);
+    }
+    if (loginMethod === "paste-code" && !oauthProvider) {
+      setShowPasteInput(true);
+    }
+  }, [loginMethod, oauthProvider]);
+
   // Redirect if already logged in
   useEffect(() => {
     if (os.auth.user) {
@@ -105,6 +121,49 @@ function LoginPage() {
     }
   };
 
+  const handlePasteCode = async () => {
+    setIsLoading(true);
+    setError(null);
+    try {
+      const decoded = atob(pasteCodeValue.trim());
+      const parsed = JSON.parse(decoded) as { access_token?: string; refresh_token?: string };
+
+      if (!parsed.access_token) {
+        throw new Error("Invalid login code: missing token");
+      }
+
+      // Store tokens in localStorage (clear old refresh token to prevent stale mismatch)
+      localStorage.setItem("access_token", parsed.access_token);
+      localStorage.removeItem("refresh_token");
+      if (parsed.refresh_token) {
+        localStorage.setItem("refresh_token", parsed.refresh_token);
+      }
+
+      // Clear any existing billing token
+      try {
+        getBillingService().clearToken();
+      } catch (billingError) {
+        console.warn("Failed to clear billing token:", billingError);
+      }
+
+      // Reload the app to pick up the new tokens
+      window.location.href = "/";
+    } catch (err) {
+      if (
+        err instanceof SyntaxError ||
+        (err instanceof DOMException && err.name === "InvalidCharacterError")
+      ) {
+        setError("Invalid login code. Please copy the code from the browser and try again.");
+      } else if (err instanceof Error) {
+        setError(err.message);
+      } else {
+        setError("Failed to process login code. Please try again.");
+      }
+    } finally {
+      setIsLoading(false);
+    }
+  };
+
   const handleGitHubLogin = async () => {
     try {
       console.log("[OAuth] Using", isTauriEnv ? "Tauri" : "web", "flow");
@@ -130,6 +189,11 @@ function LoginPage() {
           console.error("[OAuth] Failed to open external browser:", error);
           setError("Failed to open authentication page in browser");
         });
+
+        // Navigate to paste-code screen so user sees it while browser is open
+        setError(null);
+        setOauthProvider("GitHub");
+        setLoginMethod("paste-code");
       } else {
         // Web flow remains unchanged
         const { auth_url } = await os.initiateGitHubAuth("");
@@ -172,6 +236,11 @@ function LoginPage() {
           console.error("[OAuth] Failed to open external browser:", error);
           setError("Failed to open authentication page in browser");
         });
+
+        // Navigate to paste-code screen so user sees it while browser is open
+        setError(null);
+        setOauthProvider("Google");
+        setLoginMethod("paste-code");
       } else {
         // Web flow remains unchanged
         const { auth_url } = await os.initiateGoogleAuth("");
@@ -336,6 +405,11 @@ function LoginPage() {
           console.error("[OAuth] Failed to open external browser:", error);
           setError("Failed to open authentication page in browser");
         });
+
+        // Navigate to paste-code screen so user sees it while browser is open
+        setError(null);
+        setOauthProvider("Apple");
+        setLoginMethod("paste-code");
       } else {
         // Web flow - use AppleAuthProvider component which will initiate the flow
         console.log("[OAuth] Using web flow for Apple Sign In (Web only)");
@@ -401,6 +475,79 @@ function LoginPage() {
     );
   }
 
+  if (loginMethod === "paste-code") {
+    return (
+      <AuthMain
+        title={oauthProvider ? `Logging in with ${oauthProvider}` : "Paste Login Code"}
+        description={
+          oauthProvider
+            ? `Complete your ${oauthProvider} login in the browser that just opened.`
+            : "Paste the code from your browser to complete authentication."
+        }
+      >
+        {oauthProvider && !showPasteInput && (
+          <div className="flex justify-center py-4">
+            <Loader2 className="h-8 w-8 animate-spin text-muted-foreground" />
+          </div>
+        )}
+        {error && <AlertDestructive title="Error" description={error} />}
+        {showPasteInput && (
+          <>
+            {oauthProvider && (
+              <p className="text-sm text-muted-foreground text-center">
+                Having trouble? Paste the login code from the browser below.
+              </p>
+            )}
+            <div className="grid gap-2">
+              <Label htmlFor="auth-code">Login Code</Label>
+              <Input
+                id="auth-code"
+                type="text"
+                placeholder="Paste your login code here"
+                value={pasteCodeValue}
+                onChange={(e) => setPasteCodeValue(e.target.value)}
+                className="font-mono text-xs"
+                autoFocus
+              />
+              <p className="text-xs text-muted-foreground">
+                After signing in with your browser, copy the code shown on the success page and
+                paste it here.
+              </p>
+            </div>
+            <Button
+              onClick={handlePasteCode}
+              className="w-full"
+              disabled={isLoading || !pasteCodeValue.trim()}
+            >
+              {isLoading ? (
+                <>
+                  <Loader2 className="mr-2 h-4 w-4 animate-spin" />
+                  Verifying...
+                </>
+              ) : (
+                "Complete Login"
+              )}
+            </Button>
+          </>
+        )}
+        <Button
+          type="button"
+          variant="outline"
+          onClick={() => {
+            setLoginMethod(null);
+            setOauthProvider(null);
+            setPasteCodeValue("");
+            setShowPasteInput(false);
+            setError(null);
+          }}
+          className="w-full"
+        >
+          Back
+        </Button>
+      </AuthMain>
+    );
+  }
+
   if (loginMethod === "guest") {
     return (
       <form onSubmit={handleGuestSubmit}>
diff --git a/frontend/src/routes/signup.tsx b/frontend/src/routes/signup.tsx
index 7fc581cb..140340e3 100644
--- a/frontend/src/routes/signup.tsx
+++ b/frontend/src/routes/signup.tsx
@@ -36,7 +36,7 @@ export const Route = createFileRoute("/signup")({
   })
 });
 
-type SignUpMethod = "email" | "github" | "google" | "apple" | "guest" | null;
+type SignUpMethod = "email" | "github" | "google" | "apple" | "guest" | "paste-code" | null;
 
 function SignupPage() {
   const navigate = useNavigate();
@@ -49,10 +49,26 @@ function SignupPage() {
   const [showGuestCredentials, setShowGuestCredentials] = useState(false);
   const [guestUuid, setGuestUuid] = useState<string | null>(null);
 
+  const [pasteCodeValue, setPasteCodeValue] = useState("");
+  const [oauthProvider, setOauthProvider] = useState<string | null>(null);
+  const [showPasteInput, setShowPasteInput] = useState(false);
+
   // Use platform detection functions
   const isIOSPlatform = isIOS();
   const isTauriEnv = isTauri();
 
+  // Show paste code input after a delay when auto-navigated from OAuth
+  useEffect(() => {
+    if (signUpMethod === "paste-code" && oauthProvider) {
+      setShowPasteInput(false);
+      const timer = setTimeout(() => setShowPasteInput(true), 3000);
+      return () => clearTimeout(timer);
+    }
+    if (signUpMethod === "paste-code" && !oauthProvider) {
+      setShowPasteInput(true);
+    }
+  }, [signUpMethod, oauthProvider]);
+
   // Redirect if already logged in (but not if we're showing guest credentials)
   useEffect(() => {
     if (os.auth.user && !showGuestCredentials) {
@@ -116,6 +132,49 @@ function SignupPage() {
     }
   };
 
+  const handlePasteCode = async () => {
+    setIsLoading(true);
+    setError(null);
+    try {
+      const decoded = atob(pasteCodeValue.trim());
+      const parsed = JSON.parse(decoded) as { access_token?: string; refresh_token?: string };
+
+      if (!parsed.access_token) {
+        throw new Error("Invalid login code: missing token");
+      }
+
+      // Store tokens in localStorage (clear old refresh token to prevent stale mismatch)
+      localStorage.setItem("access_token", parsed.access_token);
+      localStorage.removeItem("refresh_token");
+      if (parsed.refresh_token) {
+        localStorage.setItem("refresh_token", parsed.refresh_token);
+      }
+
+      // Clear any existing billing token
+      try {
+        getBillingService().clearToken();
+      } catch (billingError) {
+        console.warn("Failed to clear billing token:", billingError);
+      }
+
+      // Reload the app to pick up the new tokens
+      window.location.href = "/";
+    } catch (err) {
+      if (
+        err instanceof SyntaxError ||
+        (err instanceof DOMException && err.name === "InvalidCharacterError")
+      ) {
+        setError("Invalid login code. Please copy the code from the browser and try again.");
+      } else if (err instanceof Error) {
+        setError(err.message);
+      } else {
+        setError("Failed to process login code. Please try again.");
+      }
+    } finally {
+      setIsLoading(false);
+    }
+  };
+
   const handleGitHubSignup = async () => {
     try {
       console.log("[OAuth] Using", isTauriEnv ? "Tauri" : "web", "flow");
@@ -141,6 +200,11 @@ function SignupPage() {
           console.error("[OAuth] Failed to open external browser:", error);
           setError("Failed to open authentication page in browser");
         });
+
+        // Navigate to paste-code screen so user sees it while browser is open
+        setError(null);
+        setOauthProvider("GitHub");
+        setSignUpMethod("paste-code");
       } else {
         // Web flow remains unchanged
         const { auth_url } = await os.initiateGitHubAuth("");
@@ -183,6 +247,11 @@ function SignupPage() {
           console.error("[OAuth] Failed to open external browser:", error);
           setError("Failed to open authentication page in browser");
         });
+
+        // Navigate to paste-code screen so user sees it while browser is open
+        setError(null);
+        setOauthProvider("Google");
+        setSignUpMethod("paste-code");
       } else {
         // Web flow remains unchanged
         const { auth_url } = await os.initiateGoogleAuth("");
@@ -352,6 +421,11 @@ function SignupPage() {
           console.error("[OAuth] Failed to open external browser:", error);
           setError("Failed to open authentication page in browser");
         });
+
+        // Navigate to paste-code screen so user sees it while browser is open
+        setError(null);
+        setOauthProvider("Apple");
+        setSignUpMethod("paste-code");
       } else {
         // Web flow - use AppleAuthProvider component which will initiate the flow
         console.log("[OAuth] Using web flow for Apple Sign In (Web only)");
@@ -426,6 +500,79 @@ function SignupPage() {
     );
   }
 
+  if (signUpMethod === "paste-code") {
+    return (
+      <AuthMain
+        title={oauthProvider ? `Signing up with ${oauthProvider}` : "Paste Login Code"}
+        description={
+          oauthProvider
+            ? `Complete your ${oauthProvider} sign-up in the browser that just opened.`
+            : "Paste the code from your browser to complete authentication."
+        }
+      >
+        {oauthProvider && !showPasteInput && (
+          <div className="flex justify-center py-4">
+            <Loader2 className="h-8 w-8 animate-spin text-muted-foreground" />
+          </div>
+        )}
+        {error && <AlertDestructive title="Error" description={error} />}
+        {showPasteInput && (
+          <>
+            {oauthProvider && (
+              <p className="text-sm text-muted-foreground text-center">
+                Having trouble? Paste the login code from the browser below.
+              </p>
+            )}
+            <div className="grid gap-2">
+              <Label htmlFor="auth-code">Login Code</Label>
+              <Input
+                id="auth-code"
+                type="text"
+                placeholder="Paste your login code here"
+                value={pasteCodeValue}
+                onChange={(e) => setPasteCodeValue(e.target.value)}
+                className="font-mono text-xs"
+                autoFocus
+              />
+              <p className="text-xs text-muted-foreground">
+                After signing in with your browser, copy the code shown on the success page and
+                paste it here.
+              </p>
+            </div>
+            <Button
+              onClick={handlePasteCode}
+              className="w-full"
+              disabled={isLoading || !pasteCodeValue.trim()}
+            >
+              {isLoading ? (
+                <>
+                  <Loader2 className="mr-2 h-4 w-4 animate-spin" />
+                  Verifying...
+                </>
+              ) : (
+                "Complete Sign Up"
+              )}
+            </Button>
+          </>
+        )}
+        <Button
+          type="button"
+          variant="outline"
+          onClick={() => {
+            setSignUpMethod(null);
+            setOauthProvider(null);
+            setPasteCodeValue("");
+            setShowPasteInput(false);
+            setError(null);
+          }}
+          className="w-full"
+        >
+          Back
+        </Button>
+      </AuthMain>
+    );
+  }
+
   if (signUpMethod === "guest") {
     return (
       <>