diff --git a/src/components/AuthorizerBasicAuthLogin.tsx b/src/components/AuthorizerBasicAuthLogin.tsx
index 5d4dcd4..81667fb 100644
--- a/src/components/AuthorizerBasicAuthLogin.tsx
+++ b/src/components/AuthorizerBasicAuthLogin.tsx
@@ -167,6 +167,7 @@ export const AuthorizerBasicAuthLogin: FC<{
           is_totp: step.totp,
           offer_webauthn_verify: step.webauthn,
           has_code_factor: step.totp || step.email || step.mobile,
+          has_sms_otp: step.mobile,
         });
         return;
       }
@@ -267,6 +268,7 @@ export const AuthorizerBasicAuthLogin: FC<{
           is_totp: otpData.is_totp || false,
           offerWebauthnVerify: otpData.offer_webauthn_verify || false,
           hasCodeFactor: otpData.has_code_factor || false,
+          hasSmsOtp: otpData.has_sms_otp || false,
           onBack: () => setOtpData({ ...initOtpData }),
         }}
         urlProps={urlProps}
diff --git a/src/components/AuthorizerMFASetup.tsx b/src/components/AuthorizerMFASetup.tsx
index 11ed468..81437b9 100644
--- a/src/components/AuthorizerMFASetup.tsx
+++ b/src/components/AuthorizerMFASetup.tsx
@@ -294,6 +294,7 @@ export const AuthorizerMFASetup: FC<{
           phone_number={loginContext?.phone_number}
           is_totp={false}
           hasCodeFactor
+          hasSmsOtp={otpMethodPending === 'sms_otp'}
           onLogin={(data) => {
             if (loginContext && data && (data as AuthTokenLike).access_token) {
               loginContext.onComplete(data as AuthTokenLike);
diff --git a/src/components/AuthorizerPasskeyLogin.tsx b/src/components/AuthorizerPasskeyLogin.tsx
index 583fc95..d9f068b 100644
--- a/src/components/AuthorizerPasskeyLogin.tsx
+++ b/src/components/AuthorizerPasskeyLogin.tsx
@@ -191,6 +191,7 @@ export const AuthorizerPasskeyLogin: FC<{
         is_totp={mfaStep.totp}
         offerWebauthnVerify={mfaStep.webauthn}
         hasCodeFactor={mfaStep.totp || mfaStep.email || mfaStep.mobile}
+        hasSmsOtp={mfaStep.mobile}
         onBack={() => setMfaStep(null)}
         onLogin={(data) => {
           setAuthData({
diff --git a/src/components/AuthorizerRoot.tsx b/src/components/AuthorizerRoot.tsx
index 298b12e..83078bd 100644
--- a/src/components/AuthorizerRoot.tsx
+++ b/src/components/AuthorizerRoot.tsx
@@ -104,6 +104,7 @@ export const AuthorizerRoot: FC<{
             mfaRedirect.mfaMethods.includes('email_otp') ||
             mfaRedirect.mfaMethods.includes('sms_otp')
           }
+          hasSmsOtp={mfaRedirect.mfaMethods.includes('sms_otp')}
           onBack={onCancelMfa}
           onLogin={(data: any) => {
             if (onLogin) {
diff --git a/src/components/AuthorizerSignup.tsx b/src/components/AuthorizerSignup.tsx
index 023afe9..b4dce2d 100644
--- a/src/components/AuthorizerSignup.tsx
+++ b/src/components/AuthorizerSignup.tsx
@@ -216,6 +216,7 @@ export const AuthorizerSignup: FC<{
           is_totp: step.totp,
           offer_webauthn_verify: step.webauthn,
           has_code_factor: step.totp || step.email || step.mobile,
+          has_sms_otp: step.mobile,
         });
         return;
       }
@@ -382,6 +383,7 @@ export const AuthorizerSignup: FC<{
             is_totp: otpData.is_totp || false,
             offerWebauthnVerify: otpData.offer_webauthn_verify || false,
             hasCodeFactor: otpData.has_code_factor || false,
+            hasSmsOtp: otpData.has_sms_otp || false,
             onBack: () => setOtpData({ ...initOtpData }),
           }}
           urlProps={urlProps}
diff --git a/src/components/AuthorizerVerifyOtp.tsx b/src/components/AuthorizerVerifyOtp.tsx
index 1dc7815..029208d 100644
--- a/src/components/AuthorizerVerifyOtp.tsx
+++ b/src/components/AuthorizerVerifyOtp.tsx
@@ -1,4 +1,4 @@
-import { FC, useEffect, useState } from 'react';
+import { FC, useEffect, useRef, useState } from 'react';
 import {
   VerifyOTPRequest,
   isWebauthnSupported,
@@ -15,6 +15,7 @@ import { AuthorizerTOTPScanner } from './AuthorizerTOTPScanner';
 import { AuthorizerMfaLocked } from './AuthorizerMfaLocked';
 import { IconPasskey } from '../icons/mfa';
 import { resolveAuthStep } from '../utils/mfaTriage';
+import { hasWindow } from '../utils/window';
 
 interface InputDataType {
   otp: string | null;
@@ -38,6 +39,10 @@ export const AuthorizerVerifyOtp: FC<{
   is_totp?: boolean;
   offerWebauthnVerify?: boolean;
   hasCodeFactor?: boolean;
+  // True specifically when the pending code factor is SMS-delivered (as
+  // opposed to email OTP or TOTP) - gates the WebOTP auto-fill call, which
+  // only makes sense for an actual incoming SMS.
+  hasSmsOtp?: boolean;
   // When present, a "Back" link lets the user leave this challenge (e.g.
   // return to the login screen) instead of being stuck once a factor is
   // being verified.
@@ -51,6 +56,7 @@ export const AuthorizerVerifyOtp: FC<{
   is_totp,
   offerWebauthnVerify,
   hasCodeFactor,
+  hasSmsOtp,
   onBack,
 }) => {
   const [error, setError] = useState(``);
@@ -151,8 +157,64 @@ export const AuthorizerVerifyOtp: FC<{
     setFormData({ ...formData, [field]: value });
   };
 
+  // WebOTP: races navigator.credentials.get() against the user manually
+  // typing/pasting the SMS code, so the code auto-fills where the platform
+  // supports it. autoComplete="one-time-code" on the input below is only a
+  // declarative hint - browsers require this explicit call to actually
+  // fill the field. Scoped to SMS-OTP alone (not TOTP/email-OTP), since
+  // those codes never arrive by SMS. Feature-detected via
+  // window.OTPCredential, matching what the autocomplete hint already
+  // implies; unsupported platforms simply never resolve/reject here.
+  const otpAbortControllerRef = useRef<AbortController | null>(null);
+  useEffect(() => {
+    if (
+      !hasCodeFactor ||
+      is_totp ||
+      !hasSmsOtp ||
+      totpData.is_screen_visible ||
+      webauthnLocked ||
+      !hasWindow() ||
+      !('OTPCredential' in window)
+    ) {
+      return;
+    }
+
+    const controller = new AbortController();
+    otpAbortControllerRef.current = controller;
+
+    (
+      navigator.credentials.get({
+        otp: { transport: ['sms'] },
+        signal: controller.signal,
+      } as any) as Promise<{ code?: string } | null>
+    )
+      .then((otpCredential) => {
+        if (otpCredential?.code) {
+          setFormData((prev) => ({ ...prev, otp: otpCredential.code as string }));
+        }
+      })
+      .catch(() => {
+        // Aborted on unmount/submit, or the platform declined - the user
+        // can still type/paste the code manually, so this isn't an error.
+      });
+
+    return () => {
+      controller.abort();
+    };
+  }, [
+    hasCodeFactor,
+    is_totp,
+    hasSmsOtp,
+    totpData.is_screen_visible,
+    webauthnLocked,
+  ]);
+
   const onSubmit = async (e: any) => {
     e.preventDefault();
+    // Stop racing WebOTP once the user (or an auto-filled value) submits -
+    // otherwise a late resolution could overwrite formData.otp after the
+    // fact on a re-shown form (e.g. a failed attempt).
+    otpAbortControllerRef.current?.abort();
     setSuccessMessage(``);
     try {
       setLoading(true);
diff --git a/src/types/index.ts b/src/types/index.ts
index da1676c..38f66b1 100644
--- a/src/types/index.ts
+++ b/src/types/index.ts
@@ -95,6 +95,10 @@ export type OtpDataType = {
   // a verified email/SMS OTP factor (is_totp false) alongside webauthn, and
   // that code path must stay reachable even when a passkey is also offered.
   has_code_factor?: boolean;
+  // True specifically for a verified SMS-OTP factor (as opposed to email
+  // OTP) - drives AuthorizerVerifyOtp's WebOTP (navigator.credentials.get)
+  // auto-fill, which only makes sense for an SMS-delivered code.
+  has_sms_otp?: boolean;
 };
 
 export type TotpDataType = {