diff --git a/python/coinbase-agentkit/coinbase_agentkit/action_providers/x402/utils.py b/python/coinbase-agentkit/coinbase_agentkit/action_providers/x402/utils.py
index da85989c2..28c055d28 100644
--- a/python/coinbase-agentkit/coinbase_agentkit/action_providers/x402/utils.py
+++ b/python/coinbase-agentkit/coinbase_agentkit/action_providers/x402/utils.py
@@ -663,11 +663,14 @@ def build_url_with_params(
 def is_service_registered(url: str, registered_services: set[str]) -> bool:
     """Check if a URL is registered for x402 requests.
 
-    Matches by origin (protocol + hostname + port) or prefix.
+    Matches by origin (protocol + hostname + port) or by same-origin path prefix.
+
+    Does **not** use raw ``url.startswith(registered)`` — that allows hostname-suffix
+    and other prefix bypasses (e.g. ``https://good.com.evil.com`` vs ``https://good.com``).
 
     Args:
         url: The URL to check
-        registered_services: Set of registered service URLs
+        registered_services: Set of registered service URLs or origins
 
     Returns:
         True if the service is registered, False otherwise
@@ -678,12 +681,34 @@ def is_service_registered(url: str, registered_services: set[str]) -> bool:
 
     try:
         parsed = urlparse(url)
+        if not parsed.scheme or not parsed.netloc:
+            return False
         origin = f"{parsed.scheme}://{parsed.netloc}"
 
         for registered in registered_services:
-            # Check if origin matches or URL starts with registered prefix
-            if origin == registered or url.startswith(registered):
+            # Bare origin registration: "https://api.example.com"
+            if origin == registered:
                 return True
+
+            reg = urlparse(registered)
+            if not reg.scheme or not reg.netloc:
+                continue
+
+            reg_origin = f"{reg.scheme}://{reg.netloc}"
+            if origin != reg_origin:
+                continue
+
+            # Origin-only URL form ("https://api.example.com/") → any path on that origin
+            reg_path = reg.path or "/"
+            if reg_path == "/" and not reg.query and not reg.fragment:
+                return True
+
+            # Same-origin path match or segment-boundary prefix
+            req_path = parsed.path or "/"
+            reg_prefix = reg_path if reg_path.endswith("/") else f"{reg_path}/"
+            if req_path == reg_path or req_path.startswith(reg_prefix):
+                return True
+
         return False
     except Exception:
         return False
diff --git a/typescript/agentkit/src/action-providers/x402/utils.isServiceRegistered.test.ts b/typescript/agentkit/src/action-providers/x402/utils.isServiceRegistered.test.ts
new file mode 100644
index 000000000..e4a725601
--- /dev/null
+++ b/typescript/agentkit/src/action-providers/x402/utils.isServiceRegistered.test.ts
@@ -0,0 +1,30 @@
+import { isServiceRegistered } from "./utils";
+
+describe("isServiceRegistered", () => {
+  const registered = new Set(["https://api.example.com", "https://pay.example.com/v1"]);
+
+  it("allows exact origin registration for any path on that origin", () => {
+    expect(isServiceRegistered("https://api.example.com/foo", registered)).toBe(true);
+  });
+
+  it("allows same-origin path prefix registrations", () => {
+    expect(isServiceRegistered("https://pay.example.com/v1/charge", registered)).toBe(true);
+    expect(isServiceRegistered("https://pay.example.com/v1", registered)).toBe(true);
+  });
+
+  it("rejects hostname-suffix bypass of prefix matching", () => {
+    expect(isServiceRegistered("https://api.example.com.evil.com/x", registered)).toBe(false);
+  });
+
+  it("rejects different hosts even when the string shares a prefix", () => {
+    expect(isServiceRegistered("https://api.example.com.attacker/x", registered)).toBe(false);
+    expect(isServiceRegistered("https://evil.com/https://api.example.com", registered)).toBe(
+      false,
+    );
+  });
+
+  it("rejects sibling paths outside the registered prefix", () => {
+    expect(isServiceRegistered("https://pay.example.com/v2/charge", registered)).toBe(false);
+    expect(isServiceRegistered("https://pay.example.com/v10", registered)).toBe(false);
+  });
+});
diff --git a/typescript/agentkit/src/action-providers/x402/utils.ts b/typescript/agentkit/src/action-providers/x402/utils.ts
index 356316687..2feedae73 100644
--- a/typescript/agentkit/src/action-providers/x402/utils.ts
+++ b/typescript/agentkit/src/action-providers/x402/utils.ts
@@ -615,10 +615,13 @@ export function buildUrlWithParams(
 
 /**
  * Checks if a URL is registered for x402 requests.
- * Matches by origin (protocol + hostname + port) or prefix.
+ * Matches by origin (protocol + hostname + port) or by same-origin path prefix.
+ *
+ * Does **not** use raw `url.startsWith(registered)` — that allows hostname-suffix
+ * and other prefix bypasses (e.g. `https://good.com.evil.com` vs `https://good.com`).
  *
  * @param url - The URL to check
- * @param registeredServices - Set of registered service URLs
+ * @param registeredServices - Set of registered service URLs or origins
  * @returns True if the service is registered, false otherwise
  */
 export function isServiceRegistered(url: string, registeredServices: Set<string>): boolean {
@@ -628,11 +631,32 @@ export function isServiceRegistered(url: string, registeredServices: Set<string>
 
   try {
     const parsed = new URL(url);
-    const origin = parsed.origin;
 
     for (const registered of registeredServices) {
-      // Check if origin matches or URL starts with registered prefix
-      if (origin === registered || url.startsWith(registered)) {
+      // Bare origin registration: "https://api.example.com"
+      if (parsed.origin === registered) {
+        return true;
+      }
+
+      let reg: URL;
+      try {
+        reg = new URL(registered);
+      } catch {
+        continue;
+      }
+
+      if (parsed.origin !== reg.origin) {
+        continue;
+      }
+
+      // Origin-only URL form ("https://api.example.com/") → any path on that origin
+      if (reg.pathname === "/" && reg.search === "" && reg.hash === "") {
+        return true;
+      }
+
+      // Same-origin path match or segment-boundary prefix
+      const regPrefix = reg.pathname.endsWith("/") ? reg.pathname : `${reg.pathname}/`;
+      if (parsed.pathname === reg.pathname || parsed.pathname.startsWith(regPrefix)) {
         return true;
       }
     }