diff --git a/src/lib/amber.ts b/src/lib/amber.ts
index 1c61c96..23ef2fc 100644
--- a/src/lib/amber.ts
+++ b/src/lib/amber.ts
@@ -300,24 +300,44 @@ function buildCallbackUrl(): string {
 /**
  * Navigate to an Amber nostrsigner: URL.
  *
- * Per NIP-55, web clients must navigate directly to the nostrsigner: URI
- * using window.location.href. This fires an Android intent that Amber
- * intercepts via its registered nostrsigner: scheme handler.
+ * For web apps the correct Android intent format is:
+ *   intent:<payload>#Intent;scheme=nostrsigner;S.<key>=<value>;...;end
  *
- * DO NOT use window.open(..., '_blank') — that opens a new tab/window
- * instead of firing the intent, which is what caused "malformed request".
+ * This is the format Amber's GitHub README documents for web clients.
+ * The nostrsigner: URL format (without intent: wrapper) causes the
+ * "malformed request" error because Android doesn't route it correctly
+ * from a browser context.
+ *
+ * Reference: https://github.com/greenart7c3/Amber (Web Applications section)
  */
 function openAmberUrl(url: string): void {
   window.location.href = url;
 }
 
+/**
+ * Build an Android intent URL for Amber web usage.
+ * Converts nostrsigner: params into the intent: format Amber expects from browsers.
+ *
+ * Format: intent:<payload>#Intent;scheme=nostrsigner;S.<key>=<val>;...;end
+ */
+function buildIntentUrl(payload: string, params: Record<string, string>): string {
+  const extras = Object.entries(params)
+    .map(([k, v]) => `S.${k}=${encodeURIComponent(v)}`)
+    .join(';');
+  return `intent:${payload}#Intent;scheme=nostrsigner;${extras};end`;
+}
+
 /**
  * Open Amber for get_public_key WITHOUT a callback URL.
  * Used in PWA/Capacitor mode: Amber copies pubkey to clipboard,
  * the app reads it on visibilitychange.
  */
 export function openAmberForLoginNoCallback(): void {
-  const amberUrl = 'nostrsigner:?compressionType=none&returnType=signature&type=get_public_key';
+  const amberUrl = buildIntentUrl('', {
+    compressionType: 'none',
+    returnType: 'signature',
+    type: 'get_public_key',
+  });
   openAmberUrl(amberUrl);
 }
 
@@ -343,10 +363,15 @@ export function openAmberForLogin(): void {
   const currentPath = window.location.hash.replace(/^#/, '') || '/';
   localStorage.setItem('amber_return_path', currentPath);
 
-  // NIP-55 nostrsigner: URI — Amber opens, user approves, Amber calls callbackUrl
-  const amberUrl = `nostrsigner:?compressionType=none&returnType=signature&type=get_public_key&callbackUrl=${encodeURIComponent(callbackUrl)}`;
+  // Android intent format for web → Amber communication (per Amber README)
+  const amberUrl = buildIntentUrl('', {
+    compressionType: 'none',
+    returnType: 'signature',
+    type: 'get_public_key',
+    callbackUrl: callbackUrl,
+  });
 
-  console.log('[Amber] Opening Amber for login, callback:', callbackUrl);
+  console.log('[Amber] Opening Amber for login, intent:', amberUrl);
   openAmberUrl(amberUrl);
 }
 
@@ -386,9 +411,13 @@ export function openAmberForSignEvent(event: Omit<NostrEvent, 'id' | 'sig'>): vo
     timestamp: Date.now(),
   });
   
-  const encodedEvent = encodeURIComponent(eventJson);
-  const amberUrl = `nostrsigner:${encodedEvent}?compressionType=none&returnType=event&type=sign_event&callbackUrl=${encodeURIComponent(callbackUrl)}`;
-  
+  const amberUrl = buildIntentUrl(encodeURIComponent(eventJson), {
+    compressionType: 'none',
+    returnType: 'event',
+    type: 'sign_event',
+    callbackUrl: callbackUrl,
+  });
+
   openAmberUrl(amberUrl);
 }
 
@@ -407,9 +436,14 @@ export function openAmberForNip04Encrypt(pubkey: string, plaintext: string): voi
     timestamp: Date.now(),
   });
   
-  const encodedText = encodeURIComponent(plaintext);
-  const amberUrl = `nostrsigner:${encodedText}?pubkey=${pubkey}&compressionType=none&returnType=signature&type=nip04_encrypt&callbackUrl=${encodeURIComponent(callbackUrl)}`;
-  
+  const amberUrl = buildIntentUrl(encodeURIComponent(plaintext), {
+    pubKey: pubkey,
+    compressionType: 'none',
+    returnType: 'signature',
+    type: 'nip04_encrypt',
+    callbackUrl: callbackUrl,
+  });
+
   openAmberUrl(amberUrl);
 }
 
@@ -428,9 +462,14 @@ export function openAmberForNip04Decrypt(pubkey: string, ciphertext: string): vo
     timestamp: Date.now(),
   });
   
-  const encodedText = encodeURIComponent(ciphertext);
-  const amberUrl = `nostrsigner:${encodedText}?pubkey=${pubkey}&compressionType=none&returnType=signature&type=nip04_decrypt&callbackUrl=${encodeURIComponent(callbackUrl)}`;
-  
+  const amberUrl = buildIntentUrl(encodeURIComponent(ciphertext), {
+    pubKey: pubkey,
+    compressionType: 'none',
+    returnType: 'signature',
+    type: 'nip04_decrypt',
+    callbackUrl: callbackUrl,
+  });
+
   openAmberUrl(amberUrl);
 }
 
@@ -449,9 +488,14 @@ export function openAmberForNip44Encrypt(pubkey: string, plaintext: string): voi
     timestamp: Date.now(),
   });
   
-  const encodedText = encodeURIComponent(plaintext);
-  const amberUrl = `nostrsigner:${encodedText}?pubkey=${pubkey}&compressionType=none&returnType=signature&type=nip44_encrypt&callbackUrl=${encodeURIComponent(callbackUrl)}`;
-  
+  const amberUrl = buildIntentUrl(encodeURIComponent(plaintext), {
+    pubKey: pubkey,
+    compressionType: 'none',
+    returnType: 'signature',
+    type: 'nip44_encrypt',
+    callbackUrl: callbackUrl,
+  });
+
   openAmberUrl(amberUrl);
 }
 
@@ -470,9 +514,14 @@ export function openAmberForNip44Decrypt(pubkey: string, ciphertext: string): vo
     timestamp: Date.now(),
   });
   
-  const encodedText = encodeURIComponent(ciphertext);
-  const amberUrl = `nostrsigner:${encodedText}?pubkey=${pubkey}&compressionType=none&returnType=signature&type=nip44_decrypt&callbackUrl=${encodeURIComponent(callbackUrl)}`;
-  
+  const amberUrl = buildIntentUrl(encodeURIComponent(ciphertext), {
+    pubKey: pubkey,
+    compressionType: 'none',
+    returnType: 'signature',
+    type: 'nip44_decrypt',
+    callbackUrl: callbackUrl,
+  });
+
   openAmberUrl(amberUrl);
 }