diff --git a/apps/web/src/App.tsx b/apps/web/src/App.tsx
index 8f54c0b..18a472b 100644
--- a/apps/web/src/App.tsx
+++ b/apps/web/src/App.tsx
@@ -1,6 +1,6 @@
 import { useState } from "react";
 import type { RiskAssessment } from "@custos/core";
-import { requiresFriction, requiresHardBlock } from "@custos/core";
+import { requiresFriction, requiresHardBlock, detectChainNetwork } from "@custos/core";
 import { analyzeSendIntent } from "./compositionRoot.js";
 
 export function App() {
@@ -9,12 +9,21 @@ export function App() {
   const [context, setContext] = useState("");
   const [assessment, setAssessment] = useState<RiskAssessment | null>(null);
   const [busy, setBusy] = useState(false);
+  const [unrecognizedNetwork, setUnrecognizedNetwork] = useState(false);
 
   async function handleCheck() {
+    const network = detectChainNetwork(address);
+    if (network === "other") {
+      setUnrecognizedNetwork(true);
+      setAssessment(null);
+      return;
+    }
+
+    setUnrecognizedNetwork(false);
     setBusy(true);
     try {
       const result = await analyzeSendIntent.execute({
-        destination: { value: address, network: "tron" },
+        destination: { value: address, network },
         amountUsdt: Number(amount) || 0,
         context: context ? { text: context } : undefined,
       });
@@ -62,6 +71,12 @@ export function App() {
         {busy ? "Analyzing on-device..." : "Check before sending"}
       </button>
 
+      {unrecognizedNetwork && (
+        <p style={{ marginTop: 12, color: "#c0392b" }}>
+          Unrecognized address format — doesn't match Tron or Ethereum. Double-check it before sending.
+        </p>
+      )}
+
       {assessment && (
         <div
           style={{
diff --git a/packages/core/src/domain/services/__tests__/detectChainNetwork.test.ts b/packages/core/src/domain/services/__tests__/detectChainNetwork.test.ts
new file mode 100644
index 0000000..b3f439b
--- /dev/null
+++ b/packages/core/src/domain/services/__tests__/detectChainNetwork.test.ts
@@ -0,0 +1,32 @@
+import { describe, expect, it } from "vitest";
+import { detectChainNetwork } from "../detectChainNetwork.js";
+
+describe("detectChainNetwork", () => {
+  it("detects a Tron base58 address", () => {
+    expect(detectChainNetwork("TAbc123456789abcdefghjkmnpqrstuvwx")).toBe("tron");
+  });
+
+  it("detects an Ethereum hex address", () => {
+    expect(detectChainNetwork("0x1234567890abcdef1234567890abcdef12345678")).toBe("ethereum");
+  });
+
+  it("detects an Ethereum hex address with uppercase digits", () => {
+    expect(detectChainNetwork("0xABCDEF1234567890ABCDEF1234567890ABCDEF12")).toBe("ethereum");
+  });
+
+  it("returns other for an address matching neither format", () => {
+    expect(detectChainNetwork("not-a-real-address")).toBe("other");
+  });
+
+  it("returns other for a Tron-like address of the wrong length", () => {
+    expect(detectChainNetwork("TAbc123")).toBe("other");
+  });
+
+  it("returns other for an Ethereum-like address missing the 0x prefix", () => {
+    expect(detectChainNetwork("1234567890abcdef1234567890abcdef12345678")).toBe("other");
+  });
+
+  it("returns other for an empty string", () => {
+    expect(detectChainNetwork("")).toBe("other");
+  });
+});
diff --git a/packages/core/src/domain/services/detectChainNetwork.ts b/packages/core/src/domain/services/detectChainNetwork.ts
new file mode 100644
index 0000000..3f6f78e
--- /dev/null
+++ b/packages/core/src/domain/services/detectChainNetwork.ts
@@ -0,0 +1,16 @@
+import type { ChainNetwork } from "../entities/Address.js";
+
+const TRON_ADDRESS = /^T[1-9A-HJ-NP-Za-km-z]{33}$/;
+const ETHEREUM_ADDRESS = /^0x[0-9a-fA-F]{40}$/;
+
+/**
+ * Infers the chain network from an address's format alone. Returns "other"
+ * for anything matching neither Tron base58 nor Ethereum hex — callers must
+ * not treat "other" as a safe default, since `RiskListPort.lookup` keys on
+ * `network:value` and a wrong network silently skips the real risk list.
+ */
+export function detectChainNetwork(value: string): ChainNetwork {
+  if (TRON_ADDRESS.test(value)) return "tron";
+  if (ETHEREUM_ADDRESS.test(value)) return "ethereum";
+  return "other";
+}
diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
index 626d9b0..a95c01e 100644
--- a/packages/core/src/index.ts
+++ b/packages/core/src/index.ts
@@ -13,6 +13,7 @@ export * from "./domain/ports/WalletPort.js";
 export * from "./domain/ports/RiskListPort.js";
 export * from "./domain/ports/AuditLogPort.js";
 export * from "./domain/services/detectAddressPoisoning.js";
+export * from "./domain/services/detectChainNetwork.js";
 
 // Application
 export * from "./application/use-cases/AnalyzeSendIntent.js";