From cd42a8ec2c5a955d91f3ad7865eb371717d8b5df Mon Sep 17 00:00:00 2001
From: Spencer Twaddle <7374698+stwaddle@users.noreply.github.com>
Date: Sat, 2 May 2026 15:57:13 -0500
Subject: [PATCH] Add ErrorHandlingMiddleware for consistent JSON error
 responses

Catches all unhandled exceptions, logs them, and returns
{ "error": "An unexpected error occurred." } with HTTP 500.
Registered before all other middleware so nothing leaks through.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 src/Budget.Api/Program.cs                     |  1 +
 .../Services/ErrorHandlingMiddleware.cs       | 21 +++++++++++++++++++
 2 files changed, 22 insertions(+)
 create mode 100644 src/Budget.Api/Services/ErrorHandlingMiddleware.cs

diff --git a/src/Budget.Api/Program.cs b/src/Budget.Api/Program.cs
index b07d8bc..2ffe153 100644
--- a/src/Budget.Api/Program.cs
+++ b/src/Budget.Api/Program.cs
@@ -126,6 +126,7 @@ using (var scope = app.Services.CreateScope())
 }
 
 app.UseForwardedHeaders();
+app.UseMiddleware<ErrorHandlingMiddleware>();
 
 app.UseDefaultFiles();
 app.UseStaticFiles();
diff --git a/src/Budget.Api/Services/ErrorHandlingMiddleware.cs b/src/Budget.Api/Services/ErrorHandlingMiddleware.cs
new file mode 100644
index 0000000..c86b9c2
--- /dev/null
+++ b/src/Budget.Api/Services/ErrorHandlingMiddleware.cs
@@ -0,0 +1,21 @@
+using System.Text.Json;
+
+namespace Budget.Api.Services;
+
+public class ErrorHandlingMiddleware(RequestDelegate next, ILogger<ErrorHandlingMiddleware> logger)
+{
+    public async Task InvokeAsync(HttpContext context)
+    {
+        try
+        {
+            await next(context);
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "Unhandled exception");
+            context.Response.StatusCode = StatusCodes.Status500InternalServerError;
+            context.Response.ContentType = "application/json";
+            await context.Response.WriteAsync(JsonSerializer.Serialize(new { error = "An unexpected error occurred." }));
+        }
+    }
+}