diff --git a/src/DevSecOpsSentinel.Api/Endpoints/WorkflowEndpoints.cs b/src/DevSecOpsSentinel.Api/Endpoints/WorkflowEndpoints.cs
index 4fa5205..1559312 100644
--- a/src/DevSecOpsSentinel.Api/Endpoints/WorkflowEndpoints.cs
+++ b/src/DevSecOpsSentinel.Api/Endpoints/WorkflowEndpoints.cs
@@ -26,6 +26,11 @@ public static WebApplication MapWorkflowEndpoints(this WebApplication app, int m
             IWorkflowAnalysisService service,
             CancellationToken cancellationToken) =>
         {
+            if (request is null)
+            {
+                return MissingOrInvalidRequest();
+            }
+            
             IResult? validationFailure =
                 ValidateWorkflowRequest(
                     request,
@@ -39,7 +44,7 @@ public static WebApplication MapWorkflowEndpoints(this WebApplication app, int m
             WorkflowAnalysisResult result =
                 await service.AnalyzeAsync(
                     new WorkflowDocument(
-                        request!.FileName,
+                        request.FileName,
                         request.Content),
                     cancellationToken);
 
@@ -70,6 +75,11 @@ await service.AnalyzeAsync(
             IRemediationReportService service,
             CancellationToken cancellationToken) =>
         {
+            if (request is null)
+            {
+                return MissingOrInvalidRequest();
+            }
+            
             IResult? validationFailure =
                 ValidateWorkflowRequest(
                     request,
@@ -83,7 +93,7 @@ await service.AnalyzeAsync(
             RemediationReport report =
                 await service.BuildAsync(
                     new WorkflowDocument(
-                        request!.FileName,
+                        request.FileName,
                         request.Content),
                     cancellationToken);
 
@@ -107,6 +117,11 @@ await service.BuildAsync(
             IRemediationReportService service,
             CancellationToken cancellationToken) =>
         {
+            if (request is null)
+            {
+                return MissingOrInvalidRequest();
+            }
+            
             IResult? validationFailure =
                 ValidateWorkflowRequest(
                     request,
@@ -120,7 +135,7 @@ await service.BuildAsync(
             RemediationReport report =
                 await service.BuildAsync(
                     new WorkflowDocument(
-                        request!.FileName,
+                        request.FileName,
                         request.Content),
                     cancellationToken);
 
@@ -184,13 +199,16 @@ await service.BuildAsync(
             CallerAuthentication caller,
             CancellationToken cancellationToken) =>
         {
+            if (request is null)
+            {
+                return MissingOrInvalidRequest();
+            }
+
             IResult? validationFailure =
                 ValidateWorkflowRequest(
-                    request is null
-                        ? null
-                        : new AnalyzeWorkflowRequest(
-                            request.FileName,
-                            request.Content),
+                    new AnalyzeWorkflowRequest(
+                        request.FileName,
+                        request.Content),
                     maximumWorkflowCharacters);
 
             if (validationFailure is not null)
@@ -201,7 +219,7 @@ request is null
             WorkflowExplanationResult result =
                 await service.ExplainAsync(
                     new WorkflowDocument(
-                        request!.FileName,
+                        request.FileName,
                         request.Content),
                     request.UseAi,
                     caller.AiAccess == AiAccess.Full
@@ -232,20 +250,28 @@ await service.ExplainAsync(
         return app;
     }
 
+    /// <summary>
+    /// A missing body and an invalid one produce the same problem response, but they are
+    /// checked in different places: the null test lives at each call site so the compiler —
+    /// and the analyzer — can see the proof, instead of a null-forgiving operator asserting
+    /// what a helper established somewhere else.
+    /// </summary>
+    private static IResult MissingOrInvalidRequest() =>
+        Results.BadRequest(new ProblemDetails
+        {
+            Title = "Invalid workflow request",
+            Detail = "Both fileName and content are required.",
+            Status = StatusCodes.Status400BadRequest
+        });
+
     private static IResult? ValidateWorkflowRequest(
-        AnalyzeWorkflowRequest? request,
+        AnalyzeWorkflowRequest request,
         int maximumCharacters)
     {
-        if (request is null ||
-            string.IsNullOrWhiteSpace(request.FileName) ||
+        if (string.IsNullOrWhiteSpace(request.FileName) ||
             string.IsNullOrWhiteSpace(request.Content))
         {
-            return Results.BadRequest(new ProblemDetails
-            {
-                Title = "Invalid workflow request",
-                Detail = "Both fileName and content are required.",
-                Status = StatusCodes.Status400BadRequest
-            });
+            return MissingOrInvalidRequest();
         }
 
         if (request.Content.Length > maximumCharacters)
diff --git a/src/DevSecOpsSentinel.Api/Security/ApiKeyAuthenticationMiddleware.cs b/src/DevSecOpsSentinel.Api/Security/ApiKeyAuthenticationMiddleware.cs
index 4d271c5..5264081 100644
--- a/src/DevSecOpsSentinel.Api/Security/ApiKeyAuthenticationMiddleware.cs
+++ b/src/DevSecOpsSentinel.Api/Security/ApiKeyAuthenticationMiddleware.cs
@@ -60,14 +60,10 @@ private bool IsOpenRequest(PathString path, ApiSecurityOptions options)
             return true;
         }
 
-        if (environment.IsDevelopment() ||
-            environment.IsEnvironment("Testing"))
+        if ((environment.IsDevelopment() || environment.IsEnvironment("Testing")) &&
+            (path.StartsWithSegments("/openapi") || path.StartsWithSegments("/scalar")))
         {
-            if (path.StartsWithSegments("/openapi") ||
-                path.StartsWithSegments("/scalar"))
-            {
-                return true;
-            }
+            return true;
         }
 
         // Everything the deterministic engine serves. It parses text and
diff --git a/src/DevSecOpsSentinel.Infrastructure/Ai/OpenAiWorkflowAiProvider.cs b/src/DevSecOpsSentinel.Infrastructure/Ai/OpenAiWorkflowAiProvider.cs
index b3586af..cfa45c2 100644
--- a/src/DevSecOpsSentinel.Infrastructure/Ai/OpenAiWorkflowAiProvider.cs
+++ b/src/DevSecOpsSentinel.Infrastructure/Ai/OpenAiWorkflowAiProvider.cs
@@ -30,6 +30,12 @@ public async Task<WorkflowAiExplanation> ExplainAsync(
         string sanitizedContent,
         CancellationToken cancellationToken)
     {
+        // The file name arrives in the request, and a value containing a line break would
+        // let a caller forge extra lines in any text log sink. Structured logging keeps it a
+        // property in JSON sinks, but the console rendering is still a text line. One control
+        // character is enough to matter; none survive this.
+        string safeFileName = new([.. analysis.FileName.Where(c => !char.IsControl(c))]);
+
         if (_client is null)
         {
             return AiExplanationFactory.CreateFallback(
@@ -113,7 +119,7 @@ public async Task<WorkflowAiExplanation> ExplainAsync(
             _logger.LogWarning(
                 exception,
                 "OpenAI request timed out for workflow {FileName}.",
-                analysis.FileName);
+                safeFileName);
 
             return AiExplanationFactory.CreateFallback(
                 analysis,
@@ -125,7 +131,7 @@ public async Task<WorkflowAiExplanation> ExplainAsync(
             _logger.LogWarning(
                 exception,
                 "OpenAI request failed for workflow {FileName}.",
-                analysis.FileName);
+                safeFileName);
 
             return AiExplanationFactory.CreateFallback(
                 analysis,
diff --git a/tests/DevSecOpsSentinel.Evals/ContainmentReplayEval.cs b/tests/DevSecOpsSentinel.Evals/ContainmentReplayEval.cs
index 27cda96..b13e43e 100644
--- a/tests/DevSecOpsSentinel.Evals/ContainmentReplayEval.cs
+++ b/tests/DevSecOpsSentinel.Evals/ContainmentReplayEval.cs
@@ -131,15 +131,15 @@ public void Write_replay_scoreboard()
                 + $"| {verdict(accepted)} | {(accepted == entry.ShouldBeAccepted ? "pass" : "**FAIL**")} |");
         }
 
-        File.WriteAllLines(Path.Combine(AppContext.BaseDirectory, "replay-scoreboard.md"), lines);
+        File.WriteAllLines(Path.Join(AppContext.BaseDirectory, "replay-scoreboard.md"), lines);
         Assert.True(true);
     }
 
-    private static string ResponsesDirectory => Path.Combine(AppContext.BaseDirectory, "Responses");
+    private static string ResponsesDirectory => Path.Join(AppContext.BaseDirectory, "Responses");
 
     private static OpenAiWorkflowAiProvider.OpenAiExplanationPayload Load(string responseFile)
     {
-        string json = File.ReadAllText(Path.Combine(ResponsesDirectory, responseFile));
+        string json = File.ReadAllText(Path.Join(ResponsesDirectory, responseFile));
         return JsonSerializer.Deserialize<OpenAiWorkflowAiProvider.OpenAiExplanationPayload>(json, JsonOptions)
             ?? throw new InvalidOperationException($"{responseFile} did not deserialise.");
     }
diff --git a/tests/DevSecOpsSentinel.Evals/CorpusEval.cs b/tests/DevSecOpsSentinel.Evals/CorpusEval.cs
index ab304b6..d6522f4 100644
--- a/tests/DevSecOpsSentinel.Evals/CorpusEval.cs
+++ b/tests/DevSecOpsSentinel.Evals/CorpusEval.cs
@@ -89,7 +89,7 @@ public void Corpus_entries_all_have_a_file_on_disk()
     {
         string[] missing = [.. GoldenCorpus.Entries
             .Select(entry => entry.FileName)
-            .Where(name => !File.Exists(Path.Combine(CorpusDirectory, name)))];
+            .Where(name => !File.Exists(Path.Join(CorpusDirectory, name)))];
 
         Assert.True(missing.Length == 0, $"Declared but absent from Corpus/: {Join(missing)}");
     }
@@ -140,12 +140,12 @@ public void Write_scoreboard()
             lines.Add($"| {rule.RuleId} {rule.Title} | {(count == 0 ? "**none**" : count.ToString())} |");
         }
 
-        string path = Path.Combine(AppContext.BaseDirectory, "scoreboard.md");
+        string path = Path.Join(AppContext.BaseDirectory, "scoreboard.md");
         File.WriteAllLines(path, lines);
         Assert.True(File.Exists(path));
     }
 
-    internal static string CorpusDirectory => Path.Combine(AppContext.BaseDirectory, "Corpus");
+    internal static string CorpusDirectory => Path.Join(AppContext.BaseDirectory, "Corpus");
 
     /// <summary>
     /// The scan a recorded reply is measured against. Shared with the replay eval so both
@@ -153,7 +153,7 @@ public void Write_scoreboard()
     /// </summary>
     internal static WorkflowAnalysisResult AnalyzeForReplay(string fileName)
     {
-        string content = File.ReadAllText(Path.Combine(CorpusDirectory, fileName));
+        string content = File.ReadAllText(Path.Join(CorpusDirectory, fileName));
         WorkflowParseResult parsed = Parser.Parse(new WorkflowDocument(fileName, content));
 
         return new WorkflowAnalysisResult(
@@ -166,7 +166,7 @@ internal static WorkflowAnalysisResult AnalyzeForReplay(string fileName)
 
     private static string[] Scan(string fileName)
     {
-        string content = File.ReadAllText(Path.Combine(CorpusDirectory, fileName));
+        string content = File.ReadAllText(Path.Join(CorpusDirectory, fileName));
         WorkflowParseResult parsed = Parser.Parse(new WorkflowDocument(fileName, content));
 
         Assert.True(
diff --git a/tests/DevSecOpsSentinel.Infrastructure.Tests/GitHubPrivateKeySourceTests.cs b/tests/DevSecOpsSentinel.Infrastructure.Tests/GitHubPrivateKeySourceTests.cs
index 83e36b8..21f6764 100644
--- a/tests/DevSecOpsSentinel.Infrastructure.Tests/GitHubPrivateKeySourceTests.cs
+++ b/tests/DevSecOpsSentinel.Infrastructure.Tests/GitHubPrivateKeySourceTests.cs
@@ -22,7 +22,7 @@ private static string CreatePem()
 
     private readonly string _pem = CreatePem();
 
-    private readonly string _keyPath = Path.Combine(
+    private readonly string _keyPath = Path.Join(
         Path.GetTempPath(),
         $"sentinel-key-{Guid.NewGuid():N}.pem");
 
@@ -122,7 +122,7 @@ public void A_missing_file_is_reported_as_unavailable()
     {
         GitHubPrivateKeySource source = new(new GitHubOptions
         {
-            PrivateKeyPath = Path.Combine(Path.GetTempPath(), "does-not-exist.pem")
+            PrivateKeyPath = Path.Join(Path.GetTempPath(), "does-not-exist.pem")
         });
 
         Assert.False(source.IsAvailable);
diff --git a/tests/DevSecOpsSentinel.Infrastructure.Tests/RepositoryWorkflowsTests.cs b/tests/DevSecOpsSentinel.Infrastructure.Tests/RepositoryWorkflowsTests.cs
index 4a4aad3..4d1e78f 100644
--- a/tests/DevSecOpsSentinel.Infrastructure.Tests/RepositoryWorkflowsTests.cs
+++ b/tests/DevSecOpsSentinel.Infrastructure.Tests/RepositoryWorkflowsTests.cs
@@ -59,7 +59,7 @@ private static string WorkflowDirectory()
         DirectoryInfo? directory = new(AppContext.BaseDirectory);
         while (directory is not null)
         {
-            string candidate = Path.Combine(directory.FullName, ".github", "workflows");
+            string candidate = Path.Join(directory.FullName, ".github", "workflows");
             if (Directory.Exists(candidate))
             {
                 return candidate;
@@ -96,7 +96,7 @@ public void There_are_workflows_to_check()
     [MemberData(nameof(WorkflowFiles))]
     public void Our_own_workflows_pass_our_own_rules(string fileName)
     {
-        string path = Path.Combine(WorkflowDirectory(), fileName);
+        string path = Path.Join(WorkflowDirectory(), fileName);
         WorkflowParseResult result = _parser.Parse(
             new WorkflowDocument(fileName, File.ReadAllText(path)));