app: fix desktop app stuck loading when OLLAMA_HOST is an unspecified bind address (#14885)

app/ui/ui.go

@@ -155,7 +155,7 @@ func (s *Server) ollamaProxy() http.Handler {
 					return
 				}
 
-				target := envconfig.Host()
+				target := envconfig.ConnectableHost()
 				s.log().Info("configuring ollama proxy", "target", target.String())
 
 				newProxy := httputil.NewSingleHostReverseProxy(target)

envconfig/config.go

@@ -59,6 +59,29 @@ func Host() *url.URL {
 	}
 }
 
+// ConnectableHost returns Host() with unspecified bind addresses (0.0.0.0, ::)
+// replaced by the corresponding loopback address (127.0.0.1, ::1).
+// Unspecified addresses are valid for binding a server socket but not for
+// connecting as a client, which fails on Windows.
+func ConnectableHost() *url.URL {
+	u := Host()
+	host, port, err := net.SplitHostPort(u.Host)
+	if err != nil {
+		return u
+	}
+
+	if ip := net.ParseIP(host); ip != nil && ip.IsUnspecified() {
+		if ip.To4() != nil {
+			host = "127.0.0.1"
+		} else {
+			host = "::1"
+		}
+		u.Host = net.JoinHostPort(host, port)
+	}
+
+	return u
+}
+
 // AllowedOrigins returns a list of allowed origins. AllowedOrigins can be configured via the OLLAMA_ORIGINS environment variable.
 func AllowedOrigins() (origins []string) {
 	if s := Var("OLLAMA_ORIGINS"); s != "" {

envconfig/config_test.go

@@ -52,6 +52,37 @@ func TestHost(t *testing.T) {
 	}
 }
 
+func TestConnectableHost(t *testing.T) {
+	cases := map[string]struct {
+		value  string
+		expect string
+	}{
+		"empty":                    {"", "http://127.0.0.1:11434"},
+		"localhost":                {"127.0.0.1", "http://127.0.0.1:11434"},
+		"localhost and port":       {"127.0.0.1:1234", "http://127.0.0.1:1234"},
+		"ipv4 unspecified":         {"0.0.0.0", "http://127.0.0.1:11434"},
+		"ipv4 unspecified + port":  {"0.0.0.0:1234", "http://127.0.0.1:1234"},
+		"ipv6 unspecified":         {"[::]", "http://[::1]:11434"},
+		"ipv6 unspecified + port":  {"[::]:1234", "http://[::1]:1234"},
+		"ipv6 localhost":           {"[::1]", "http://[::1]:11434"},
+		"ipv6 localhost + port":    {"[::1]:1234", "http://[::1]:1234"},
+		"specific address":         {"192.168.1.5", "http://192.168.1.5:11434"},
+		"specific address + port":  {"192.168.1.5:8080", "http://192.168.1.5:8080"},
+		"hostname":                 {"example.com", "http://example.com:11434"},
+		"hostname and port":        {"example.com:1234", "http://example.com:1234"},
+		"https unspecified + port": {"https://0.0.0.0:4321", "https://127.0.0.1:4321"},
+	}
+
+	for name, tt := range cases {
+		t.Run(name, func(t *testing.T) {
+			t.Setenv("OLLAMA_HOST", tt.value)
+			if host := ConnectableHost(); host.String() != tt.expect {
+				t.Errorf("%s: expected %s, got %s", name, tt.expect, host.String())
+			}
+		})
+	}
+}
+
 func TestOrigins(t *testing.T) {
 	cases := []struct {
 		value  string