diff --git a/src/PostHog.AspNetCore/README.md b/src/PostHog.AspNetCore/README.md
index ad52fcd..0eae1e5 100644
--- a/src/PostHog.AspNetCore/README.md
+++ b/src/PostHog.AspNetCore/README.md
@@ -65,6 +65,18 @@ The available options are:
 > When that number is reached, the client will start dropping older events. `MaxBatchSize` ensures that the `/batch` 
 > request doesn't get too large.
 
+### Local Evaluation
+
+If you want to evaluate feature flags locally, you'll need to provide a personal API key for the PostHog API. 
+
+For local development, you can set the `PostHog:PersonalApiKey` setting in your user secrets:
+
+```bash
+$ dotnet user-secrets set PostHog:PersonalApiKey YOUR_PERSONAL_API_KEY
+```
+
+For production, we recommend using a secrets manager or environment variables to set the `PostHog:PersonalApiKey` setting.
+
 ## Docs
 
 More detailed docs for using this library can be found at [PostHog Docs for the .NET Client SDK](https://posthog.com/docs/libraries/dotnet).
diff --git a/src/PostHog/Api/PostHogApiClient.cs b/src/PostHog/Api/PostHogApiClient.cs
index 06b260c..bab5a65 100644
--- a/src/PostHog/Api/PostHogApiClient.cs
+++ b/src/PostHog/Api/PostHogApiClient.cs
@@ -151,7 +151,7 @@ public async Task<ApiResult> SendEventAsync(
         try
         {
             return await GetAuthenticatedResponseAsync<LocalEvaluationApiResult>(
-                $"/api/feature_flag/local_evaluation/?token={options.ProjectApiKey}&send_cohorts",
+                $"/api/feature_flag/local_evaluation/?send_cohorts",
                 cancellationToken);
         }
         catch (ApiException e) when (e.ErrorType is "quota_limited")
diff --git a/src/PostHog/Library/HttpClientExtensions.cs b/src/PostHog/Library/HttpClientExtensions.cs
index 06890f3..49370c3 100644
--- a/src/PostHog/Library/HttpClientExtensions.cs
+++ b/src/PostHog/Library/HttpClientExtensions.cs
@@ -45,11 +45,17 @@ public static async Task EnsureSuccessfulApiCall(
         this HttpResponseMessage response,
         CancellationToken cancellationToken)
     {
-        // TODO: Is there any error status codes that we should allow the exception to propagate here?
         if (response.IsSuccessStatusCode)
         {
             return;
         }
+
+        if (response.StatusCode == HttpStatusCode.NotFound)
+        {
+            // Allow 404 exception to propagate up.
+            response.EnsureSuccessStatusCode();
+        }
+
         var (error, exception) = await ReadApiErrorResultAsync();
 
         throw response.StatusCode switch
diff --git a/tests/TestLibrary/Fakes/FakeHttpMessageHandlerExtensions.cs b/tests/TestLibrary/Fakes/FakeHttpMessageHandlerExtensions.cs
index 8128ba5..8264cf9 100644
--- a/tests/TestLibrary/Fakes/FakeHttpMessageHandlerExtensions.cs
+++ b/tests/TestLibrary/Fakes/FakeHttpMessageHandlerExtensions.cs
@@ -73,15 +73,9 @@ public static FakeHttpMessageHandler.RequestHandler AddLocalEvaluationResponse(
 
     public static FakeHttpMessageHandler.RequestHandler AddLocalEvaluationResponse(
         this FakeHttpMessageHandler handler,
-        LocalEvaluationApiResult responseBody)
-        => handler.AddLocalEvaluationResponse("fake-project-api-key", responseBody);
-
-    public static FakeHttpMessageHandler.RequestHandler AddLocalEvaluationResponse(
-        this FakeHttpMessageHandler handler,
-        string projectApiKey,
         LocalEvaluationApiResult responseBody) =>
         handler.AddResponse(
-            new Uri($"https://us.i.posthog.com/api/feature_flag/local_evaluation/?token={projectApiKey}&send_cohorts"),
+            new Uri("https://us.i.posthog.com/api/feature_flag/local_evaluation/?send_cohorts"),
             HttpMethod.Get,
             responseBody: responseBody);
 
diff --git a/tests/UnitTests/Features/FeatureFlagsTests.cs b/tests/UnitTests/Features/FeatureFlagsTests.cs
index c5bf706..491d31b 100644
--- a/tests/UnitTests/Features/FeatureFlagsTests.cs
+++ b/tests/UnitTests/Features/FeatureFlagsTests.cs
@@ -3228,7 +3228,7 @@ public async Task ReturnsEmptyDictionaryWhenPersonalApiKeyIncorrect()
             FeatureFlagPayloads = new Dictionary<string, string>(),
         });
         container.FakeHttpMessageHandler.AddResponse(
-            new Uri("https://us.i.posthog.com/api/feature_flag/local_evaluation/?token=fake-project-api-key&send_cohorts"),
+            new Uri("https://us.i.posthog.com/api/feature_flag/local_evaluation/?send_cohorts"),
             HttpMethod.Get,
             new HttpResponseMessage(HttpStatusCode.Unauthorized)
             {
@@ -3384,7 +3384,7 @@ public async Task ReturnsEmptyDictionaryWhenLocalEvaluationQuotaExceeded()
         // When local evaluation is quota limited, we do not want to fallback to /decide.
         var decideHandler = container.FakeHttpMessageHandler.AddDecideResponseException(new InvalidOperationException());
         container.FakeHttpMessageHandler.AddResponse(
-            new Uri("https://us.i.posthog.com/api/feature_flag/local_evaluation/?token=fake-project-api-key&send_cohorts"),
+            new Uri("https://us.i.posthog.com/api/feature_flag/local_evaluation/?send_cohorts"),
             HttpMethod.Get,
             new HttpResponseMessage(HttpStatusCode.PaymentRequired)
             {
@@ -3416,7 +3416,7 @@ public async Task ReturnsFalseWhenSingleFlagLocalEvaluationRequestQuotaExceeded(
         var container = new TestContainer("fake-personal-api-key");
         var decideHandler = container.FakeHttpMessageHandler.AddDecideResponseException(new InvalidOperationException());
         container.FakeHttpMessageHandler.AddResponse(
-            new Uri("https://us.i.posthog.com/api/feature_flag/local_evaluation/?token=fake-project-api-key&send_cohorts"),
+            new Uri("https://us.i.posthog.com/api/feature_flag/local_evaluation/?send_cohorts"),
             HttpMethod.Get,
             new HttpResponseMessage(HttpStatusCode.PaymentRequired)
             {