fix(confidence-engine): sanitize reasoning error responses

app/api/analyse/route.js

@@ -26,7 +26,7 @@ async function post(request) {
 
     if (!result.success) {
       return Response.json(
-        { ...result, reconstruction: result.reconstruction || null },
+        { error: "Reasoning request could not be completed." },
         { status: Number(result.statusCode) || 500 },
       );
     }
@@ -42,9 +42,25 @@ async function post(request) {
       promptVersion: result.promptVersion,
     });
   } catch (e) {
+    if (e.code === "PROVIDER_UNAVAILABLE") {
+      return Response.json(
+        { error: "Reasoning service is temporarily unavailable." },
+        { status: 503 },
+      );
+    }
+
+    const validationFailed = e?.validationFailed || e?.code === "VALIDATION_FAILED";
+    if (validationFailed) {
+      return Response.json(
+        { success: false, error: "Reasoning request could not be completed." },
+        { status: Number(e.statusCode) || 500 },
+      );
+    }
+
+    const statusCode = Number(e.statusCode) || 500;
     return Response.json(
-      { error: e.message || "Unknown server error", responseDurationMs: 0 },
-      { status: 500 },
+      { error: "Reasoning request could not be completed." },
+      { status: statusCode },
     );
   }
 }

app/api/cases/overview/route.js

@@ -55,7 +55,9 @@ async function post(request) {
         {
           success: false,
           stage: error.statusCode === 400 ? "request_validation" : "provider",
-          error: error.message ?? "Overview synthesis failed",
+          error: error.statusCode === 400
+            ? "Invalid overview request"
+            : "Reasoning request could not be completed.",
         },
         { status: error.statusCode }
       );

app/api/cases/start/route.js

@@ -48,14 +48,8 @@ async function post(request) {
     return Response.json(
       {
         success: false,
-        error: diagnostics.error,
-        validationErrors: result.validationErrors,
-        diagnostics: result.diagnostics,
-        analysisErrors: result.analysisErrors,
-        validationIssues: result.validationIssues,
-        providerApiPath: result.providerApiPath,
-        providerExecution: result.providerExecution,
-        rawResponse: result.rawResponse ?? undefined,
+        error: status === 400 ? diagnostics.error : "Reasoning request could not be completed.",
+        ...(status === 400 ? { validationErrors: result.validationErrors } : {}),
       },
       { status },
     );

app/api/cases/synthesis/route.js

@@ -57,7 +57,9 @@ async function post(request) {
         {
           success: false,
           stage: error.statusCode === 400 ? "request_validation" : "provider",
-          error: error.message ?? "Synthesis failed",
+          error: error.statusCode === 400
+            ? "Invalid synthesis request"
+            : "Reasoning request could not be completed.",
         },
         { status: error.statusCode }
       );

app/api/focused-investigation/deconstruct/route.js

@@ -154,7 +154,7 @@ async function post(request) {
       );
     }
     return Response.json(
-      { error: e.message || "Unknown server error" },
+      { error: "Reasoning request could not be completed." },
       { status: 500 },
     );
   }