fix(server): prefer LAN remote addresses over public IPs

packages/server/src/server/__tests__/network-addresses.test.ts

@@ -43,6 +43,38 @@ describe("resolveRemoteAddresses", () => {
       assert.equal(result.primaryRemoteUrl, "https://192.168.1.128:9898")
     })
   })
+
+  it("prefers private LAN addresses over public addresses", () => {
+    const addresses = [
+      { address: "203.0.113.40", family: "IPv4", internal: false },
+      { address: "192.168.1.128", family: "IPv4", internal: false },
+      { address: "8.8.8.8", family: "IPv4", internal: false },
+    ]
+
+    usingMockedNetworkInterfaces(addresses, () => {
+      const result = resolveRemoteAddresses({ host: "0.0.0.0", protocol: "https", port: 9898 })
+
+      assert.deepEqual(
+        result.userVisible.map((entry) => entry.ip),
+        ["192.168.1.128", "203.0.113.40", "8.8.8.8"],
+      )
+      assert.equal(result.primaryRemoteUrl, "https://192.168.1.128:9898")
+    })
+  })
+
+  it("uses a public address when no private LAN address is available", () => {
+    const addresses = [
+      { address: "169.254.10.20", family: "IPv4", internal: false },
+      { address: "203.0.113.40", family: "IPv4", internal: false },
+    ]
+
+    usingMockedNetworkInterfaces(addresses, () => {
+      const result = resolveRemoteAddresses({ host: "0.0.0.0", protocol: "https", port: 9898 })
+
+      assert.deepEqual(result.userVisible.map((entry) => entry.ip), ["203.0.113.40", "169.254.10.20"])
+      assert.equal(result.primaryRemoteUrl, "https://203.0.113.40:9898")
+    })
+  })
 })
 
 function usingMockedNetworkInterfaces(

packages/server/src/server/network-addresses.ts

@@ -88,7 +88,9 @@ function sortUserVisibleAddresses(addresses: NetworkAddress[]): NetworkAddress[]
 }
 
 function getUserVisiblePriority(ip: string): number {
-  return isLinkLocalIPv4(ip) ? 1 : 0
+  if (isPrivateIPv4(ip)) return 0
+  if (isLinkLocalIPv4(ip)) return 2
+  return 1
 }
 
 function isLinkLocalIPv4(ip: string): boolean {
@@ -98,6 +100,16 @@ function isLinkLocalIPv4(ip: string): boolean {
   return first === 169 && second === 254
 }
 
+function isPrivateIPv4(ip: string): boolean {
+  const octets = parseIPv4(ip)
+  if (!octets) return false
+  const [first, second] = octets
+
+  if (first === 10) return true
+  if (first === 192 && second === 168) return true
+  return first === 172 && second >= 16 && second <= 31
+}
+
 function parseIPv4(value: string): number[] | null {
   if (!isIPv4Address(value)) return null
   return value.split(".").map((part) => Number(part))