diff --git a/src/RedShirt.Example.JobWorker.Common.Aws.SsmSecretManager/Services/SsmSecretManagerService.cs b/src/RedShirt.Example.JobWorker.Common.Aws.SsmSecretManager/Services/SsmSecretManagerService.cs
index 03e5cc6..4c7f51a 100644
--- a/src/RedShirt.Example.JobWorker.Common.Aws.SsmSecretManager/Services/SsmSecretManagerService.cs
+++ b/src/RedShirt.Example.JobWorker.Common.Aws.SsmSecretManager/Services/SsmSecretManagerService.cs
@@ -1,11 +1,13 @@
 using Amazon.SimpleSystemsManagement;
 using Amazon.SimpleSystemsManagement.Model;
 using RedShirt.Example.JobWorker.Common.Aws.SsmSecretManager.Services.Resilience;
+using RedShirt.Example.JobWorker.Common.SecretManagers.Core.Exceptions;
 using RedShirt.Example.JobWorker.Common.SecretManagers.Core.Services;
+using System.Text.RegularExpressions;
 
 namespace RedShirt.Example.JobWorker.Common.Aws.SsmSecretManager.Services;
 
-internal sealed class SsmSecretManagerService(
+internal sealed partial class SsmSecretManagerService(
     IAmazonSimpleSystemsManagement ssm,
     ISsmRetryWrapperService retryWrapperService) : ISecretManagerService
 {
@@ -14,8 +16,28 @@ internal sealed class SsmSecretManagerService(
     /// </summary>
     private const int MaxNamesPerRequest = 10;
 
+    /// <summary>
+    ///     Regular expression for AWS Systems Manager Parameter Store hierarchical paths.
+    ///     Paths must start with /, use only a-zA-Z0-9_.- in each segment, contain at most 15
+    ///     hierarchy levels, and be at most 2048 characters.
+    ///     Source: https://docs.aws.amazon.com/systems-manager/latest/userguide/sysman-paramstore-su-create.html
+    /// </summary>
+    [GeneratedRegex(@"^(?=.{1,2048}$)(/[a-zA-Z0-9_.-]+){1,15}$")]
+    private static partial Regex ValidKeyRegex();
+
+    private static void ThrowIfInvalidKey(string key)
+    {
+        if (string.IsNullOrWhiteSpace(key) || !ValidKeyRegex().IsMatch(key))
+        {
+            throw new WorkerSecretManagerException($"Invalid secret path: {key}")
+                {CouldBeTransient = false, IsHandled = false, CouldBeExternallySolvable = false};
+        }
+    }
+
     public async Task<string> GetSecretAsync(string key, CancellationToken cancellationToken = default)
     {
+        ThrowIfInvalidKey(key);
+
         var response = await retryWrapperService.RunAsync(ct =>
             ssm.GetParameterAsync(new GetParameterRequest
             {
@@ -29,6 +51,11 @@ public async Task<string> GetSecretAsync(string key, CancellationToken cancellat
     public async Task<Dictionary<string, string>> GetSecretsAsync(List<string> keys,
         CancellationToken cancellationToken = default)
     {
+        foreach (var key in keys)
+        {
+            ThrowIfInvalidKey(key);
+        }
+
         var result = new Dictionary<string, string>();
         var remaining = keys.Distinct().ToList();
 
diff --git a/src/RedShirt.Example.JobWorker.Common.Azure.KeyVaultSecretManager/Services/AzureKeyVaultService.cs b/src/RedShirt.Example.JobWorker.Common.Azure.KeyVaultSecretManager/Services/AzureKeyVaultService.cs
index 743cb01..ea8b3e3 100644
--- a/src/RedShirt.Example.JobWorker.Common.Azure.KeyVaultSecretManager/Services/AzureKeyVaultService.cs
+++ b/src/RedShirt.Example.JobWorker.Common.Azure.KeyVaultSecretManager/Services/AzureKeyVaultService.cs
@@ -11,9 +11,13 @@ internal sealed partial class AzureKeyVaultService(
     IAzureRetryWrapperService retryWrapperService,
     IAzureKeyVaultClientSource clientSource) : ISecretManagerService
 {
-    private static bool IsValidKey(string key)
+    private static void ThrowIfInvalidKey(string key)
     {
-        return ValidKeyRegex().IsMatch(key);
+        if (string.IsNullOrWhiteSpace(key) || !ValidKeyRegex().IsMatch(key))
+        {
+            throw new WorkerSecretManagerException($"Invalid secret path: {key}")
+                {CouldBeTransient = false, IsHandled = false, CouldBeExternallySolvable = false};
+        }
     }
 
     /// <summary>
@@ -28,11 +32,7 @@ private static bool IsValidKey(string key)
 
     public async Task<string> GetSecretAsync(string key, CancellationToken cancellationToken = default)
     {
-        if (!IsValidKey(key))
-        {
-            throw new WorkerSecretManagerException($"Invalid secret path: {key}")
-                {CouldBeTransient = false, IsHandled = false, CouldBeExternallySolvable = false};
-        }
+        ThrowIfInvalidKey(key);
 
         try
         {
@@ -57,10 +57,9 @@ public async Task<string> GetSecretAsync(string key, CancellationToken cancellat
     public async Task<Dictionary<string, string>> GetSecretsAsync(List<string> keys,
         CancellationToken cancellationToken = default)
     {
-        if (keys.FirstOrDefault(key => !IsValidKey(key)) is { } badKey)
+        foreach (var key in keys)
         {
-            throw new WorkerSecretManagerException($"Invalid secret path: {badKey}")
-                {CouldBeTransient = false, IsHandled = false, CouldBeExternallySolvable = false};
+            ThrowIfInvalidKey(key);
         }
 
         var items = new Dictionary<string, string>();
diff --git a/test/RedShirt.Example.JobWorker.Common.Aws.SsmSecretManager.UnitTests/Tests/Services/SsmSecretManagerServiceTests.cs b/test/RedShirt.Example.JobWorker.Common.Aws.SsmSecretManager.UnitTests/Tests/Services/SsmSecretManagerServiceTests.cs
index 56678f4..29518f3 100644
--- a/test/RedShirt.Example.JobWorker.Common.Aws.SsmSecretManager.UnitTests/Tests/Services/SsmSecretManagerServiceTests.cs
+++ b/test/RedShirt.Example.JobWorker.Common.Aws.SsmSecretManager.UnitTests/Tests/Services/SsmSecretManagerServiceTests.cs
@@ -2,11 +2,19 @@
 using Amazon.SimpleSystemsManagement.Model;
 using RedShirt.Example.JobWorker.Common.Aws.SsmSecretManager.Services;
 using RedShirt.Example.JobWorker.Common.Aws.SsmSecretManager.Services.Resilience;
+using RedShirt.Example.JobWorker.Common.SecretManagers.Core.Exceptions;
 
 namespace RedShirt.Example.JobWorker.Common.Aws.SsmSecretManager.UnitTests.Tests.Services;
 
 public class SsmSecretManagerServiceTests
 {
+    private static string NewPath(string? prefix = null)
+    {
+        return string.IsNullOrEmpty(prefix)
+            ? $"/{Guid.NewGuid():N}"
+            : $"{prefix}/{Guid.NewGuid():N}";
+    }
+
     private sealed class PassthroughRetryWrapper : ISsmRetryWrapperService
     {
         public Task<T> RunAsync<T>(Func<CancellationToken, Task<T>> func, CancellationToken cancellationToken = default)
@@ -17,11 +25,52 @@ public Task<T> RunAsync<T>(Func<CancellationToken, Task<T>> func, CancellationTo
 
     public class GetSecretAsync
     {
+        [Theory]
+        [InlineData("")]
+        [InlineData(" ")]
+        [InlineData("flat-name")]
+        [InlineData("bad key")]
+        [InlineData("/bad key")]
+        [InlineData("/bad$key")]
+        [InlineData("/trailing/")]
+        [InlineData("/empty//segment")]
+        [InlineData("/a/b/c/d/e/f/g/h/i/j/k/l/m/n/o/p")]
+        public async Task InvalidKey_ThrowsSecretManagerExceptionWithoutCallingSsm(string key)
+        {
+            var ssm = new Mock<IAmazonSimpleSystemsManagement>(MockBehavior.Strict);
+            var service = new SsmSecretManagerService(ssm.Object, new PassthroughRetryWrapper());
+
+            var thrown = await Assert.ThrowsAsync<WorkerSecretManagerException>(() =>
+                service.GetSecretAsync(key, TestContext.Current.CancellationToken));
+
+            Assert.Equal($"Invalid secret path: {key}", thrown.Message);
+            Assert.False(thrown.CouldBeTransient);
+            Assert.False(thrown.IsHandled);
+            Assert.False(thrown.CouldBeExternallySolvable);
+            ssm.VerifyNoOtherCalls();
+        }
+
+        [Fact]
+        public async Task KeyLongerThan2048Characters_ThrowsSecretManagerException()
+        {
+            var key = "/" + new string('a', 2048);
+            var ssm = new Mock<IAmazonSimpleSystemsManagement>(MockBehavior.Strict);
+            var service = new SsmSecretManagerService(ssm.Object, new PassthroughRetryWrapper());
+
+            var thrown = await Assert.ThrowsAsync<WorkerSecretManagerException>(() =>
+                service.GetSecretAsync(key, TestContext.Current.CancellationToken));
+
+            Assert.Equal($"Invalid secret path: {key}", thrown.Message);
+            Assert.False(thrown.CouldBeTransient);
+            Assert.False(thrown.IsHandled);
+            ssm.VerifyNoOtherCalls();
+        }
+
         [Fact]
         public async Task PassesCancellationTokenToSsm()
         {
             using var cts = CancellationTokenSource.CreateLinkedTokenSource(TestContext.Current.CancellationToken);
-            var name = Guid.NewGuid().ToString("N");
+            var name = NewPath();
             var value = Guid.NewGuid().ToString("N");
 
             var ssm = new Mock<IAmazonSimpleSystemsManagement>(MockBehavior.Strict);
@@ -47,7 +96,7 @@ public async Task PassesCancellationTokenToSsm()
         [Fact]
         public async Task PropagatesSsmException()
         {
-            var name = Guid.NewGuid().ToString("N");
+            var name = NewPath();
 
             var ssm = new Mock<IAmazonSimpleSystemsManagement>(MockBehavior.Strict);
             ssm.Setup(s => s.GetParameterAsync(It.IsAny<GetParameterRequest>(), It.IsAny<CancellationToken>()))
@@ -62,7 +111,7 @@ await Assert.ThrowsAsync<AmazonSimpleSystemsManagementException>(() =>
         [Fact]
         public async Task ReturnsDecryptedParameterValue()
         {
-            var name = Guid.NewGuid().ToString("N");
+            var name = NewPath();
             var value = Guid.NewGuid().ToString("N");
 
             var ssm = new Mock<IAmazonSimpleSystemsManagement>(MockBehavior.Strict);
@@ -88,6 +137,36 @@ public async Task ReturnsDecryptedParameterValue()
                 TestContext.Current.CancellationToken), Times.Once);
             ssm.VerifyNoOtherCalls();
         }
+
+        [Theory]
+        [InlineData("/a")]
+        [InlineData("/common/redis")]
+        [InlineData("/Dev/DBServer/MySQL/db-string13")]
+        [InlineData("/path.with-dots_and-dashes/value")]
+        [InlineData("/a/b/c/d/e/f/g/h/i/j/k/l/m/n/o")]
+        public async Task ValidKey_ReturnsDecryptedParameterValue(string key)
+        {
+            var value = Guid.NewGuid().ToString("N");
+
+            var ssm = new Mock<IAmazonSimpleSystemsManagement>(MockBehavior.Strict);
+            ssm.Setup(s => s.GetParameterAsync(
+                    It.Is<GetParameterRequest>(r => r.Name == key && r.WithDecryption == true),
+                    It.IsAny<CancellationToken>()))
+                .ReturnsAsync(new GetParameterResponse
+                {
+                    Parameter = new Parameter {Name = key, Value = value}
+                });
+
+            var service = new SsmSecretManagerService(ssm.Object, new PassthroughRetryWrapper());
+
+            var result = await service.GetSecretAsync(key, TestContext.Current.CancellationToken);
+
+            Assert.Equal(value, result);
+            ssm.Verify(s => s.GetParameterAsync(
+                It.Is<GetParameterRequest>(r => r.Name == key && r.WithDecryption == true),
+                TestContext.Current.CancellationToken), Times.Once);
+            ssm.VerifyNoOtherCalls();
+        }
     }
 
     public class GetSecretsAsync
@@ -95,7 +174,7 @@ public class GetSecretsAsync
         [Fact]
         public async Task DeduplicatesNamesBeforeCallingSsm()
         {
-            var name = Guid.NewGuid().ToString("N");
+            var name = NewPath();
             var value = Guid.NewGuid().ToString("N");
 
             var ssm = new Mock<IAmazonSimpleSystemsManagement>(MockBehavior.Strict);
@@ -138,7 +217,7 @@ public async Task EmptyList_DoesNotCallSsm()
         [Fact]
         public async Task ExactlyTenNames_IsSingleRequest()
         {
-            var names = Enumerable.Range(0, 10).Select(i => $"/{i}/{Guid.NewGuid():N}").ToList();
+            var names = Enumerable.Range(0, 10).Select(i => NewPath($"/{i}")).ToList();
             var values = names.ToDictionary(n => n, _ => Guid.NewGuid().ToString("N"));
 
             var ssm = new Mock<IAmazonSimpleSystemsManagement>(MockBehavior.Strict);
@@ -165,7 +244,7 @@ public async Task ExactlyTenNames_IsSingleRequest()
         [Fact]
         public async Task ExactlyTwentyNames_IsTwoFullBatches()
         {
-            var names = Enumerable.Range(0, 20).Select(i => $"/{i}/{Guid.NewGuid():N}").ToList();
+            var names = Enumerable.Range(0, 20).Select(i => NewPath($"/{i}")).ToList();
             var values = names.ToDictionary(n => n, _ => Guid.NewGuid().ToString("N"));
             var seenBatchSizes = new List<int>();
 
@@ -193,10 +272,48 @@ public async Task ExactlyTwentyNames_IsTwoFullBatches()
             ssm.VerifyNoOtherCalls();
         }
 
+        [Fact]
+        public async Task InvalidKey_ReportsFirstInvalidKeyInListOrder()
+        {
+            var ssm = new Mock<IAmazonSimpleSystemsManagement>(MockBehavior.Strict);
+            var service = new SsmSecretManagerService(ssm.Object, new PassthroughRetryWrapper());
+
+            var thrown = await Assert.ThrowsAsync<WorkerSecretManagerException>(() =>
+                service.GetSecretsAsync(["/ok-key", "bad key", "/also-bad!"],
+                    TestContext.Current.CancellationToken));
+
+            Assert.Equal("Invalid secret path: bad key", thrown.Message);
+            Assert.False(thrown.CouldBeTransient);
+            Assert.False(thrown.IsHandled);
+            ssm.VerifyNoOtherCalls();
+        }
+
+        [Theory]
+        [InlineData("")]
+        [InlineData(" ")]
+        [InlineData("flat-name")]
+        [InlineData("bad key")]
+        [InlineData("/bad$key")]
+        public async Task InvalidKey_ThrowsBeforeCallingSsm(string badKey)
+        {
+            var validKey = NewPath();
+            var ssm = new Mock<IAmazonSimpleSystemsManagement>(MockBehavior.Strict);
+            var service = new SsmSecretManagerService(ssm.Object, new PassthroughRetryWrapper());
+
+            var thrown = await Assert.ThrowsAsync<WorkerSecretManagerException>(() =>
+                service.GetSecretsAsync([validKey, badKey], TestContext.Current.CancellationToken));
+
+            Assert.Equal($"Invalid secret path: {badKey}", thrown.Message);
+            Assert.False(thrown.CouldBeTransient);
+            Assert.False(thrown.IsHandled);
+            Assert.False(thrown.CouldBeExternallySolvable);
+            ssm.VerifyNoOtherCalls();
+        }
+
         [Fact]
         public async Task MoreThanTenNames_IsChunkedAcrossRequests()
         {
-            var names = Enumerable.Range(0, 11).Select(i => $"/{i}/{Guid.NewGuid():N}").ToList();
+            var names = Enumerable.Range(0, 11).Select(i => NewPath($"/{i}")).ToList();
             var values = names.ToDictionary(n => n, _ => Guid.NewGuid().ToString("N"));
 
             var ssm = new Mock<IAmazonSimpleSystemsManagement>(MockBehavior.Strict);
@@ -229,8 +346,8 @@ public async Task MoreThanTenNames_IsChunkedAcrossRequests()
         [Fact]
         public async Task OmitsInvalidParametersFromResult()
         {
-            var foundName = Guid.NewGuid().ToString("N");
-            var missingName = Guid.NewGuid().ToString("N");
+            var foundName = NewPath("/found");
+            var missingName = NewPath("/missing");
             var foundValue = Guid.NewGuid().ToString("N");
 
             var ssm = new Mock<IAmazonSimpleSystemsManagement>(MockBehavior.Strict);
@@ -265,7 +382,7 @@ public async Task OmitsInvalidParametersFromResult()
         public async Task PassesCancellationTokenToSsm()
         {
             using var cts = CancellationTokenSource.CreateLinkedTokenSource(TestContext.Current.CancellationToken);
-            var name = Guid.NewGuid().ToString("N");
+            var name = NewPath();
             var value = Guid.NewGuid().ToString("N");
 
             var ssm = new Mock<IAmazonSimpleSystemsManagement>(MockBehavior.Strict);
@@ -302,8 +419,8 @@ await Assert.ThrowsAsync<AmazonSimpleSystemsManagementException>(() =>
         [Fact]
         public async Task ReturnsDecryptedParameterValues()
         {
-            var nameA = Guid.NewGuid().ToString("N");
-            var nameB = Guid.NewGuid().ToString("N");
+            var nameA = NewPath("/a");
+            var nameB = NewPath("/b");
             var valueA = Guid.NewGuid().ToString("N");
             var valueB = Guid.NewGuid().ToString("N");
 
@@ -338,5 +455,33 @@ public async Task ReturnsDecryptedParameterValues()
                 Times.Once);
             ssm.VerifyNoOtherCalls();
         }
+
+        [Theory]
+        [InlineData("/a")]
+        [InlineData("/common/redis")]
+        [InlineData("/Dev/DBServer/MySQL/db-string13")]
+        public async Task ValidKeys_ReturnDecryptedParameterValues(string key)
+        {
+            var value = Guid.NewGuid().ToString("N");
+
+            var ssm = new Mock<IAmazonSimpleSystemsManagement>(MockBehavior.Strict);
+            ssm.Setup(s => s.GetParametersAsync(
+                    It.Is<GetParametersRequest>(r =>
+                        r.WithDecryption == true && r.Names.Count == 1 && r.Names[0] == key),
+                    It.IsAny<CancellationToken>()))
+                .ReturnsAsync(new GetParametersResponse
+                {
+                    Parameters = [new Parameter {Name = key, Value = value}]
+                });
+
+            var service = new SsmSecretManagerService(ssm.Object, new PassthroughRetryWrapper());
+
+            var result = await service.GetSecretsAsync([key], TestContext.Current.CancellationToken);
+
+            Assert.Equal(new Dictionary<string, string> {[key] = value}, result);
+            ssm.Verify(s => s.GetParametersAsync(It.IsAny<GetParametersRequest>(), It.IsAny<CancellationToken>()),
+                Times.Once);
+            ssm.VerifyNoOtherCalls();
+        }
     }
 }
\ No newline at end of file