diff --git a/public/my.js b/public/my.js
index d329bbc..6549641 100644
--- a/public/my.js
+++ b/public/my.js
@@ -319,6 +319,9 @@
       const eth=await window.RMCWallet.pick();
       if(!eth){err.textContent='No wallet found in this browser. On a phone, open your wallet app (SafePal, Phantom, MetaMask, Trust, Coinbase…), go to its Browser or DApp tab, and type this page\'s address there — your wallet connects automatically.';return;}
       const accs=await eth.request({method:'eth_requestAccounts'});const account=accs[0];
+      // Match the wallet's active chain to the SIWE message's Chain ID (137),
+      // or the wallet rejects the signature ("chain ID does not match").
+      try{await window.RMCWallet.ensureChain(eth);}catch(ce){err.textContent='Please switch your wallet to the Polygon network, then tap Connect again. (Your wallet blocks sign-in when it\'s on a different network.)';return;}
       const ch=await(await fetch('/api/public/msg-challenge',{method:'POST',headers:{'Content-Type':'application/json'},body:JSON.stringify({address:account})})).json();
       if(!ch.message)throw new Error(ch.error||'Could not start sign-in.');
       let hex='0x';for(const b of new TextEncoder().encode(ch.message))hex+=b.toString(16).padStart(2,'0');
diff --git a/public/rmc-wallet.js b/public/rmc-wallet.js
index 8d408b9..b1c945c 100644
--- a/public/rmc-wallet.js
+++ b/public/rmc-wallet.js
@@ -77,6 +77,22 @@
         }, 220);
       });
     },
-    list:function(){ return probeInjected(found.slice()); }
+    list:function(){ return probeInjected(found.slice()); },
+    // Switch the wallet to Polygon (137) so a SIWE sign-in whose message says
+    // "Chain ID: 137" matches the wallet's active chain — otherwise wallets
+    // refuse the signature with a "chain ID does not match" error. Adds Polygon
+    // if the wallet doesn't have it. Returns a Promise.
+    ensureChain:function(eth){
+      var POLY='0x89';
+      return eth.request({method:'eth_chainId'}).then(function(cid){
+        if(cid===POLY) return true;
+        return eth.request({method:'wallet_switchEthereumChain',params:[{chainId:POLY}]}).then(function(){return true;}).catch(function(e){
+          if(e&&e.code===4902){
+            return eth.request({method:'wallet_addEthereumChain',params:[{chainId:POLY,chainName:'Polygon Mainnet',nativeCurrency:{name:'POL',symbol:'POL',decimals:18},rpcUrls:['https://polygon-rpc.com'],blockExplorerUrls:['https://polygonscan.com']}]}).then(function(){return true;});
+          }
+          throw e;
+        });
+      });
+    }
   };
 })();
diff --git a/public/training.js b/public/training.js
index e46fa80..03b9aa5 100644
--- a/public/training.js
+++ b/public/training.js
@@ -63,6 +63,7 @@ if(tid&&/^\d+$/.test(tid))document.querySelectorAll('a[href^="/tools"]').forEach
       const eth=await window.RMCWallet.pick();
       if(!eth){err.textContent='No wallet in this browser. On a phone, open this page inside your wallet app\'s browser — or use the Telegram Mini App.';btn.disabled=false;btn.textContent=UNLOCK_LABEL;return;}
       const accs=await eth.request({method:'eth_requestAccounts'});const account=accs[0];
+      try{await window.RMCWallet.ensureChain(eth);}catch(ce){err.textContent='Switch your wallet to the Polygon network, then tap unlock again.';btn.disabled=false;btn.textContent=UNLOCK_LABEL;return;}
       const ch=await(await fetch('/api/public/msg-challenge',{method:'POST',headers:{'Content-Type':'application/json'},body:JSON.stringify({address:account})})).json();
       if(!ch.message)throw new Error(ch.error||'Could not start sign-in.');
       let hex='0x';for(const b2 of new TextEncoder().encode(ch.message))hex+=b2.toString(16).padStart(2,'0');