diff --git a/frontend/src/a2a.js b/frontend/src/a2a.js
index 498212a..3fbfdca 100644
--- a/frontend/src/a2a.js
+++ b/frontend/src/a2a.js
@@ -3,10 +3,17 @@ export const CONFIG_URL = import.meta.env.DEV ? "/config.json" : "./config.json"
 export async function requestJson(url, init = {}) {
   const response = await fetch(url, { credentials: "same-origin", ...init });
   const text = await response.text();
-  const data = text ? JSON.parse(text) : null;
+  let data = null;
+  try {
+    data = text ? JSON.parse(text) : null;
+  } catch {
+    data = { message: text };
+  }
   if (!response.ok) {
-    const detail = data && (data.detail || data.message);
-    throw new Error(detail || `request failed: ${response.status}`);
+    const detail = data && (data.detail || data.message || data.error);
+    const error = new Error(detail || `request failed: ${response.status}`);
+    error.status = response.status;
+    throw error;
   }
   return data;
 }
@@ -20,66 +27,53 @@ export async function loadSession(config) {
 }
 
 export function signInUrl(config) {
-  // Always prefer authorizeUrl. The dashboard's login cookie is host-locked to
-  // the dashboard's own origin, so sending the browser straight to loginUrl
-  // signs the user in *there* and bounces back here still signed out.
-  // authorizeUrl hands this origin a code it trades for its own session.
   const target = config.auth?.authorizeUrl || config.auth?.loginUrl;
   if (!target) return null;
-  const next = encodeURIComponent(
-    window.location.pathname + window.location.search + window.location.hash,
-  );
+  const next = encodeURIComponent(window.location.pathname + window.location.search + window.location.hash);
   return `${target}${target.includes("?") ? "&" : "?"}next=${next}`;
 }
 
-export async function requireSession(config) {
-  const session = await loadSession(config);
-  if (!session?.authenticated) {
-    const target = signInUrl(config);
-    if (target) window.location.assign(target);
-    throw new Error("sign in required");
-  }
-  return session;
-}
-
 export async function callSkill(config, skillName, args) {
-  if (config.auth?.invokeRequiresSession) {
-    await requireSession(config);
-  }
-  return requestJson(
-    `${config.endpoints.invoke}/${encodeURIComponent(skillName)}`,
-    {
-      method: "POST",
-      headers: { "content-type": "application/json" },
-      body: JSON.stringify({ arguments: args }),
-    },
-  );
+  return requestJson(`${config.endpoints.invoke}/${encodeURIComponent(skillName)}`, {
+    method: "POST",
+    headers: { "content-type": "application/json" },
+    body: JSON.stringify({ arguments: args }),
+  });
 }
 
-export function sampleValue(schema) {
-  if (!schema || typeof schema !== "object") return null;
-  if ("default" in schema) return schema.default;
-  if ("const" in schema) return schema.const;
-  if (Array.isArray(schema.enum) && schema.enum.length) return schema.enum[0];
-  const type = Array.isArray(schema.type)
-    ? schema.type.find((item) => item !== "null") || schema.type[0]
-    : schema.type;
-  if (type === "array") return [];
-  if (type === "boolean") return false;
-  if (type === "integer" || type === "number") return 0;
-  if (type === "string") return "";
-  const props = schema.properties || {};
-  if (type === "object" || Object.keys(props).length) {
-    const required = Array.isArray(schema.required) ? schema.required : Object.keys(props);
-    return Object.fromEntries(
-      required.map((key) => [key, sampleValue(props[key])]),
-    );
+export async function callSkillWithSession(config, skillName, args) {
+  try {
+    return await callSkill(config, skillName, args);
+  } catch (error) {
+    if (error.status === 401) {
+      const target = signInUrl(config);
+      if (target) window.location.assign(target);
+      throw new Error("Sign in required to run QuoteJudge.");
+    }
+    throw error;
   }
-  return null;
 }
 
-export function sampleArgs(skill) {
-  const schema = skill?.input_schema || skill?.inputSchema || {};
-  const value = sampleValue(schema);
-  return value && typeof value === "object" && !Array.isArray(value) ? value : {};
+export function fileToBrowserDocument(file) {
+  return new Promise((resolve, reject) => {
+    const reader = new FileReader();
+    reader.onerror = () => reject(new Error(`Could not read ${file.name}`));
+    reader.onload = () => {
+      const result = String(reader.result || "");
+      const comma = result.indexOf(",");
+      resolve({
+        filename: file.name,
+        media_type: file.type || guessMediaType(file.name),
+        data_base64: comma >= 0 ? result.slice(comma + 1) : result,
+      });
+    };
+    reader.readAsDataURL(file);
+  });
+}
+
+function guessMediaType(name) {
+  const lower = name.toLowerCase();
+  if (lower.endsWith(".json")) return "application/json";
+  if (lower.endsWith(".csv")) return "text/csv";
+  return "text/plain";
 }