fix(security): redact delegated token in formatted output

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+- Redact plaintext sandbox access tokens from response string output to prevent accidental disclosure in logs.
 - Set the next NuGet version and default user agent to `0.1.3`.
 - Added delegated sandbox access token lifecycle methods and a separate token scoped sandbox handle.
 

src/CreateOS.Sandbox/Models.cs

@@ -131,7 +131,10 @@ public sealed record SandboxData
 public sealed record SandboxAccessTokenCreateResponse(
     string Token, bool Enabled,
     [property: JsonPropertyName("created_at")] DateTimeOffset CreatedAt,
-    [property: JsonPropertyName("rotated_at")] DateTimeOffset? RotatedAt = null);
+    [property: JsonPropertyName("rotated_at")] DateTimeOffset? RotatedAt = null)
+{
+    public override string ToString() => "SandboxAccessTokenCreateResponse { Token = [REDACTED] }";
+}
 
 /// <summary>Delegated token state without plaintext credential material.</summary>
 public sealed record SandboxAccessTokenMetadata(

tests/CreateOS.Sandbox.Tests/SandboxInstanceTests.cs

@@ -91,6 +91,7 @@ public async Task AccessTokenLifecycleUsesScopedCredential()
         var owner = Instance(transport, ingress: false);
         var created = await owner.CreateAccessTokenAsync();
         Assert.Equal("skp_sb_first", created.Token);
+        Assert.DoesNotContain(created.Token, created.ToString());
         Assert.Equal("skp_sb...irst", (await owner.GetAccessTokenAsync()).TokenHint);
         var worker = owner.WithAccessToken(created.Token);
         Assert.NotSame(owner.Files, worker.Files);