diff --git a/src/Authority/StellaOps.Authority/StellaOps.Authority/Audit/AuthorityAuditSink.cs b/src/Authority/StellaOps.Authority/StellaOps.Authority/Audit/AuthorityAuditSink.cs
index 9aa598483..0d5a517c2 100644
--- a/src/Authority/StellaOps.Authority/StellaOps.Authority/Audit/AuthorityAuditSink.cs
+++ b/src/Authority/StellaOps.Authority/StellaOps.Authority/Audit/AuthorityAuditSink.cs
@@ -1,5 +1,6 @@
 
 using Microsoft.Extensions.Logging;
+using StellaOps.Audit.Emission;
 using StellaOps.Authority.Persistence.Documents;
 using StellaOps.Authority.Persistence.InMemory.Stores;
 using StellaOps.Cryptography.Audit;
@@ -18,13 +19,16 @@ internal sealed class AuthorityAuditSink : IAuthEventSink
 
     private readonly IAuthorityLoginAttemptStore loginAttemptStore;
     private readonly ILogger<AuthorityAuditSink> logger;
+    private readonly IAuditEventEmitter? timelineEmitter;
 
     public AuthorityAuditSink(
         IAuthorityLoginAttemptStore loginAttemptStore,
-        ILogger<AuthorityAuditSink> logger)
+        ILogger<AuthorityAuditSink> logger,
+        IAuditEventEmitter? timelineEmitter = null)
     {
         this.loginAttemptStore = loginAttemptStore ?? throw new ArgumentNullException(nameof(loginAttemptStore));
         this.logger = logger ?? throw new ArgumentNullException(nameof(logger));
+        this.timelineEmitter = timelineEmitter;
     }
 
     public async ValueTask WriteAsync(AuthEventRecord record, CancellationToken cancellationToken)
@@ -42,6 +46,80 @@ internal sealed class AuthorityAuditSink : IAuthEventSink
 
         var document = MapToDocument(record);
         await loginAttemptStore.InsertAsync(document, cancellationToken).ConfigureAwait(false);
+
+        // DEPRECATE-001: dual-write to Timeline unified audit sink. Fire-and-forget;
+        // any failure is already logged by HttpAuditEventEmitter and must never
+        // affect the local write or calling endpoint.
+        if (timelineEmitter is not null)
+        {
+            try
+            {
+                var payload = MapToTimelinePayload(record);
+                await timelineEmitter.EmitAsync(payload, cancellationToken).ConfigureAwait(false);
+            }
+            catch (Exception ex)
+            {
+                logger.LogWarning(ex, "Failed to emit authority audit event to Timeline (local write succeeded)");
+            }
+        }
+    }
+
+    private static AuditEventPayload MapToTimelinePayload(AuthEventRecord record)
+    {
+        var outcome = NormalizeOutcome(record.Outcome);
+        var severity = record.Outcome switch
+        {
+            AuthEventOutcome.Failure => "warning",
+            AuthEventOutcome.LockedOut => "warning",
+            AuthEventOutcome.Error => "error",
+            _ => "info"
+        };
+
+        var subjectId = record.Subject?.SubjectId.Value ?? record.Subject?.Username.Value ?? "authority-system";
+        var subjectName = record.Subject?.DisplayName.Value ?? record.Subject?.Username.Value ?? subjectId;
+
+        var details = new Dictionary<string, object?>(OrdinalComparer)
+        {
+            ["outcome"] = outcome,
+            ["eventType"] = record.EventType
+        };
+        if (!string.IsNullOrWhiteSpace(record.Reason))
+        {
+            details["reason"] = record.Reason;
+        }
+        if (record.Client is { } client)
+        {
+            details["client.id"] = client.ClientId.Value;
+            details["client.provider"] = client.Provider.Value;
+        }
+
+        return new AuditEventPayload
+        {
+            Id = $"authority-{Guid.NewGuid():N}",
+            Timestamp = record.OccurredAt,
+            Module = "authority",
+            Action = record.EventType ?? "unknown",
+            Severity = severity,
+            Actor = new AuditActorPayload
+            {
+                Id = subjectId,
+                Name = subjectName,
+                Type = "user",
+                IpAddress = record.Network?.RemoteAddress.Value ?? record.Network?.ForwardedFor.Value,
+                UserAgent = record.Network?.UserAgent.Value
+            },
+            Resource = new AuditResourcePayload
+            {
+                Type = "authority_session",
+                Id = record.CorrelationId ?? subjectId,
+                Name = subjectName
+            },
+            Description = $"Authority {record.EventType} ({outcome})",
+            Details = details,
+            CorrelationId = record.CorrelationId,
+            TenantId = record.Tenant.HasValue ? record.Tenant.Value : null,
+            Tags = new[] { "authority", outcome }
+        };
     }
 
     private static AuthorityLoginAttemptDocument MapToDocument(AuthEventRecord record)