diff --git a/src/GmRelay.Bot/Infrastructure/Logging/SecretRedactor.cs b/src/GmRelay.Bot/Infrastructure/Logging/SecretRedactor.cs
new file mode 100644
index 0000000..680e66f
--- /dev/null
+++ b/src/GmRelay.Bot/Infrastructure/Logging/SecretRedactor.cs
@@ -0,0 +1,47 @@
+using System.Text.RegularExpressions;
+using Npgsql;
+
+namespace GmRelay.Bot.Infrastructure.Logging;
+
+public static partial class SecretRedactor
+{
+    public static string RedactConnectionString(string? connectionString)
+    {
+        if (string.IsNullOrWhiteSpace(connectionString))
+        {
+            return string.Empty;
+        }
+
+        try
+        {
+            var builder = new NpgsqlConnectionStringBuilder(connectionString);
+            if (!string.IsNullOrWhiteSpace(builder.Password))
+            {
+                builder.Password = "***";
+            }
+
+            return builder.ToString();
+        }
+        catch (ArgumentException)
+        {
+            return RedactText(connectionString);
+        }
+    }
+
+    public static string RedactText(string? text)
+    {
+        if (string.IsNullOrWhiteSpace(text))
+        {
+            return string.Empty;
+        }
+
+        return SecretKeyValueRegex().Replace(
+            text,
+            static match => $"{match.Groups["key"].Value}={GetRedactedValue()}");
+    }
+
+    private static string GetRedactedValue() => "***";
+
+    [GeneratedRegex(@"(?<key>password|pwd|passwd|token|secret|api[-_]?key)\s*=\s*(?<value>[^;\s,]+)", RegexOptions.IgnoreCase | RegexOptions.CultureInvariant)]
+    private static partial Regex SecretKeyValueRegex();
+}
diff --git a/src/GmRelay.Bot/Program.cs b/src/GmRelay.Bot/Program.cs
index 5f8a7bb..9cba23f 100644
--- a/src/GmRelay.Bot/Program.cs
+++ b/src/GmRelay.Bot/Program.cs
@@ -4,6 +4,7 @@ using GmRelay.Bot.Features.Reminders.SendJoinLink;
 using GmRelay.Bot.Features.Sessions.CreateSession;
 using GmRelay.Bot.Features.Sessions.RescheduleSession;
 using GmRelay.Bot.Infrastructure.Database;
+using GmRelay.Bot.Infrastructure.Logging;
 using GmRelay.Bot.Infrastructure.Scheduling;
 using GmRelay.Bot.Infrastructure.Telegram;
 using Npgsql;
@@ -20,11 +21,16 @@ builder.AddServiceDefaults();
 builder.Services.AddSingleton<NpgsqlDataSource>(sp =>
 {
     var config = sp.GetRequiredService<IConfiguration>();
+    var loggerFactory = sp.GetRequiredService<ILoggerFactory>();
     var connectionString = config.GetConnectionString("gmrelaydb")
         ?? throw new InvalidOperationException(
             "ConnectionStrings:gmrelaydb is required. Set via environment variable ConnectionStrings__gmrelaydb.");
-    
-    Console.WriteLine($"[DBG] Master ConnectionString => {connectionString}");
+
+    var logger = loggerFactory.CreateLogger("GmRelay.Bot.Startup");
+    logger.LogInformation(
+        "Configured PostgreSQL data source with connection string {ConnectionString}",
+        SecretRedactor.RedactConnectionString(connectionString));
+
     return NpgsqlDataSource.Create(connectionString);
 });
 
diff --git a/tests/GmRelay.Bot.Tests/Infrastructure/Logging/SecretRedactorTests.cs b/tests/GmRelay.Bot.Tests/Infrastructure/Logging/SecretRedactorTests.cs
new file mode 100644
index 0000000..c031700
--- /dev/null
+++ b/tests/GmRelay.Bot.Tests/Infrastructure/Logging/SecretRedactorTests.cs
@@ -0,0 +1,31 @@
+using GmRelay.Bot.Infrastructure.Logging;
+
+namespace GmRelay.Bot.Tests.Infrastructure.Logging;
+
+public sealed class SecretRedactorTests
+{
+    [Fact]
+    public void RedactConnectionString_ShouldMaskDatabasePassword()
+    {
+        var result = SecretRedactor.RedactConnectionString(
+            "Host=localhost;Port=5432;Database=gmrelay;Username=gmrelay;Password=super-secret");
+
+        Assert.Contains("Password=***", result);
+        Assert.DoesNotContain("super-secret", result);
+        Assert.Contains("Host=localhost", result);
+    }
+
+    [Fact]
+    public void RedactText_ShouldMaskKnownSecretKeys()
+    {
+        var result = SecretRedactor.RedactText(
+            "Password=super-secret Token=telegram-token apiKey=service-key");
+
+        Assert.DoesNotContain("super-secret", result);
+        Assert.DoesNotContain("telegram-token", result);
+        Assert.DoesNotContain("service-key", result);
+        Assert.Contains("Password=***", result);
+        Assert.Contains("Token=***", result);
+        Assert.Contains("apiKey=***", result);
+    }
+}