Fix Verdict:Error from prose-wrapped AI responses

src/SpamGuard/Services/EmailClassifier.cs

@@ -8,38 +8,43 @@ using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 using SpamGuard.Configuration;
 using SpamGuard.Models;
+using SpamGuard.State;
 
 public sealed partial class EmailClassifier
 {
     private readonly SpamGuardOptions _options;
     private readonly ILogger<EmailClassifier> _logger;
     private readonly HttpClient _httpClient;
+    private readonly OverrideStore _overrideStore;
 
-    private const string SystemPrompt = """
+    private const string BaseSystemPrompt = """
         You are an email spam classifier. Analyze the following email and determine if it is spam or legitimate.
 
         Spam includes:
         - Unsolicited marketing or promotional emails the recipient never signed up for
         - AI-generated emails designed to look like legitimate correspondence
-        - Newsletter signups the recipient didn't request
+        - Newsletter signups the recipient did not request
 
         Legitimate includes:
         - Emails from known contacts or businesses the recipient has a relationship with
         - Transactional emails (receipts, shipping notifications, password resets)
         - Emails the recipient would expect to receive
 
-        Respond with JSON only:
+        YOU MUST respond with ONLY a JSON object. No explanation, no preamble, no markdown fencing.
+        Output exactly this structure and nothing else:
         {"classification": "spam" | "legitimate", "confidence": 0.0-1.0, "reason": "brief explanation"}
         """;
 
     public EmailClassifier(
         IOptions<SpamGuardOptions> options,
         ILogger<EmailClassifier> logger,
-        HttpClient httpClient)
+        HttpClient httpClient,
+        OverrideStore overrideStore)
     {
         _options = options.Value;
         _logger = logger;
         _httpClient = httpClient;
+        _overrideStore = overrideStore;
     }
 
     public string BuildPrompt(EmailSummary email)
@@ -62,11 +67,13 @@ public sealed partial class EmailClassifier
 
         _logger.LogDebug("Classifying email UID={Uid} from {From}", email.Uid, email.From);
 
+        var systemPrompt = BaseSystemPrompt + _overrideStore.BuildFewShotText(10);
+
         var requestBody = new
         {
             model = _options.Claude.Model,
             max_tokens = 256,
-            system = SystemPrompt,
+            system = systemPrompt,
             messages = new[]
             {
                 new { role = "user", content = userMessage }
@@ -78,11 +85,27 @@ public sealed partial class EmailClassifier
         {
             Content = new StringContent(json, Encoding.UTF8, "application/json")
         };
+
+        var isAnthropic = _options.Claude.BaseUrl.Contains("anthropic.com", StringComparison.OrdinalIgnoreCase);
+        if (isAnthropic)
+        {
             request.Headers.Add("x-api-key", _options.Claude.ApiKey);
             request.Headers.Add("anthropic-version", "2023-06-01");
+        }
+        else
+        {
+            request.Headers.Authorization =
+                new System.Net.Http.Headers.AuthenticationHeaderValue("Bearer", _options.Claude.ApiKey);
+        }
 
         var response = await _httpClient.SendAsync(request, ct);
-        response.EnsureSuccessStatusCode();
+
+        if (!response.IsSuccessStatusCode)
+        {
+            var errorBody = await response.Content.ReadAsStringAsync(ct);
+            _logger.LogError("Claude API returned {StatusCode}: {Error}", (int)response.StatusCode, errorBody);
+            return null;
+        }
 
         var responseJson = await response.Content.ReadAsStringAsync(ct);
         using var doc = JsonDocument.Parse(responseJson);
@@ -108,18 +131,32 @@ public sealed partial class EmailClassifier
         // Strip markdown code fencing if present
         var cleaned = StripMarkdownFencing().Replace(text, "$1").Trim();
 
+        // Try direct parse first (happy path)
+        var result = TryParseJson(cleaned);
+        if (result != null) return result;
+
+        // Fall back: extract first {...} block from prose-wrapped responses
+        var start = cleaned.IndexOf('{');
+        var end = cleaned.LastIndexOf('}');
+        if (start >= 0 && end > start)
+            return TryParseJson(cleaned[start..(end + 1)]);
+
+        return null;
+    }
+
+    private static ClassificationResult? TryParseJson(string json)
+    {
         try
         {
-            using var doc = JsonDocument.Parse(cleaned);
+            using var doc = JsonDocument.Parse(json);
             var root = doc.RootElement;
-
             return new ClassificationResult(
                 Classification: root.GetProperty("classification").GetString() ?? "unknown",
                 Confidence: root.GetProperty("confidence").GetDouble(),
                 Reason: root.GetProperty("reason").GetString() ?? ""
             );
         }
-        catch (Exception)
+        catch
         {
             return null;
         }