diff --git a/app/components/prompt-editor/ConfigEditorPane.tsx b/app/components/prompt-editor/ConfigEditorPane.tsx
index 73397c6..721115b 100644
--- a/app/components/prompt-editor/ConfigEditorPane.tsx
+++ b/app/components/prompt-editor/ConfigEditorPane.tsx
@@ -1,11 +1,16 @@
 import { useEffect, useRef, useState } from "react";
 import { guardrailsFetch } from "@/app/lib/guardrailsClient";
 import { ConfigEditorPaneProps, Tool } from "@/app/lib/types/promptEditor";
-import { CompletionConfig, CompletionParams } from "@/app/lib/types/configs";
-import { ConfigType, MODEL_OPTIONS, getModelsForType } from "@/app/lib/models";
+import {
+  CompletionConfig,
+  CompletionParams,
+  ProviderType,
+} from "@/app/lib/types/configs";
+import { ConfigType, getModelsForType } from "@/app/lib/models";
 import { PROVIDER_TYPES } from "@/app/lib/constants";
 import {
   getAllProviders,
+  getCompletionTypesForProvider,
   getModelSchema,
   getParamLabel,
   getProviderLabel,
@@ -87,6 +92,10 @@ export default function ConfigEditorPane({
     value: p,
     label: getProviderLabel(p),
   }));
+  const availableTypes = getCompletionTypesForProvider(provider);
+  const typeOptions = PROVIDER_TYPES.filter((t) =>
+    availableTypes.includes(t.value as ConfigType),
+  );
 
   const selectedConfig = savedConfigs.find((c) => c.id === selectedConfigId);
   const isBoundToSavedConfig = !!boundConfigId;
@@ -110,35 +119,14 @@ export default function ConfigEditorPane({
     });
   };
 
-  const handleProviderChange = (newProvider: string) => {
-    const candidates = getModelsForType(newProvider, currentType);
-    const fallback = MODEL_OPTIONS[newProvider]?.[0]?.value ?? "";
-    const nextModel = candidates[0]?.value ?? fallback;
-    handleConfigChange({
-      completion: { provider: newProvider as CompletionConfig["provider"] },
-      params: { model: nextModel },
-    });
-  };
-
-  const handleTypeChange = (newType: ConfigType) => {
-    const provider = configBlob.completion.provider;
-    const candidates = getModelsForType(provider, newType);
-    const stillValid = candidates.some((m) => m.value === params.model);
-    const nextModel = stillValid
-      ? params.model
-      : (candidates[0]?.value ??
-        MODEL_OPTIONS[provider]?.[0]?.value ??
-        params.model);
-    handleConfigChange({
-      completion: { type: newType },
-      params: { model: nextModel },
-    });
-  };
-
-  const handleModelChange = (model: string) => {
-    const nextSchema = getModelSchema(provider, model);
+  const applyProviderTypeModel = (
+    nextProvider: string,
+    nextType: ConfigType,
+    nextModel: string,
+  ) => {
+    const nextSchema = getModelSchema(nextProvider, nextModel);
     const nextSchemaParams = nextSchema
-      ? reconcileParamsForModel(provider, model, params)
+      ? reconcileParamsForModel(nextProvider, nextModel, params)
       : {};
     const oldSchemaKeys = modelSchema ? Object.keys(modelSchema.config) : [];
     const carryover = { ...params };
@@ -148,11 +136,33 @@ export default function ConfigEditorPane({
       ...configBlob,
       completion: {
         ...configBlob.completion,
-        params: { ...carryover, model, ...nextSchemaParams },
+        provider: nextProvider as ProviderType,
+        type: nextType,
+        params: { ...carryover, model: nextModel, ...nextSchemaParams },
       },
     });
   };
 
+  const handleProviderChange = (newProvider: string) => {
+    const types = getCompletionTypesForProvider(newProvider);
+    const nextType = types.includes(currentType)
+      ? currentType
+      : (types[0] ?? currentType);
+    const nextModel = getModelsForType(newProvider, nextType)[0]?.value ?? "";
+    applyProviderTypeModel(newProvider, nextType, nextModel);
+  };
+
+  const handleTypeChange = (newType: ConfigType) => {
+    const candidates = getModelsForType(provider, newType);
+    const stillValid = candidates.some((m) => m.value === params.model);
+    const nextModel = stillValid ? params.model : (candidates[0]?.value ?? "");
+    applyProviderTypeModel(provider, newType, nextModel);
+  };
+
+  const handleModelChange = (model: string) => {
+    applyProviderTypeModel(provider, currentType, model);
+  };
+
   const saveDisabled = !configName.trim() || isSaving;
 
   return (
@@ -212,14 +222,14 @@ export default function ConfigEditorPane({
               }
               className={inputClass}
             >
-              {PROVIDER_TYPES.map((option) => (
+              {typeOptions.map((option) => (
                 <option key={option.value} value={option.value}>
                   {option.label}
                 </option>
               ))}
             </select>
             <p className="text-xs mt-1.5 text-text-secondary">
-              {PROVIDER_TYPES.find(
+              {typeOptions.find(
                 (t) => t.value === (configBlob.completion.type || "text"),
               )?.description ?? ""}
             </p>
diff --git a/app/hooks/useConfigPersistence.ts b/app/hooks/useConfigPersistence.ts
index c2ab651..2418086 100644
--- a/app/hooks/useConfigPersistence.ts
+++ b/app/hooks/useConfigPersistence.ts
@@ -94,14 +94,17 @@ export function useConfigPersistence({
         : {};
 
       const acceptsTools = !schema || "max_output_tokens" in schema.config;
+      const completionType = currentConfigBlob.completion.type || "text";
 
       const configBlob: ConfigBlob = {
         completion: {
           provider: completionProvider,
-          type: currentConfigBlob.completion.type || "text",
+          type: completionType,
           params: {
             model,
-            instructions: currentContent,
+            // TTS params forbid `instructions` on the backend; only send it
+            // for types that accept it (text, stt).
+            ...(completionType !== "tts" && { instructions: currentContent }),
             ...modelParams,
             ...(allKnowledgeBaseIds.length > 0 && {
               knowledge_base_ids: allKnowledgeBaseIds,
@@ -177,7 +180,11 @@ export function useConfigPersistence({
       return true;
     } catch (e) {
       console.error("Failed to save config:", e);
-      toast.error("Failed to save configuration. Please try again.");
+      toast.error(
+        e instanceof Error && e.message
+          ? `Failed to save configuration: ${e.message}`
+          : "Failed to save configuration. Please try again.",
+      );
       return false;
     } finally {
       setIsSaving(false);
diff --git a/app/lib/apiClient.ts b/app/lib/apiClient.ts
index 6c0f045..05aa766 100644
--- a/app/lib/apiClient.ts
+++ b/app/lib/apiClient.ts
@@ -63,17 +63,43 @@ export async function apiClient<
   } as ApiClientResponse<TData, TResponseType>;
 }
 
-/** Parse an error body into a readable message string. */
+function stringifyValidationDetail(value: unknown): string {
+  if (!Array.isArray(value)) {
+    return typeof value === "string" ? value : "";
+  }
+  return value
+    .map((item) => {
+      if (typeof item === "string") return item;
+      if (item && typeof item === "object") {
+        const rec = item as Record<string, unknown>;
+        const field = Array.isArray(rec.loc)
+          ? rec.loc.filter((p) => p !== "body").join(".")
+          : (rec.field as string) || "";
+        const msg = (rec.msg as string) || (rec.message as string) || "";
+        return field ? `${field}: ${msg}` : msg;
+      }
+      return "";
+    })
+    .filter(Boolean)
+    .join("; ");
+}
+
 function extractErrorMessage(
   body: Record<string, unknown>,
   fallback: string,
 ): string {
+  const detail =
+    stringifyValidationDetail(body.errors) ||
+    (typeof body.detail === "string"
+      ? ""
+      : stringifyValidationDetail(body.detail));
   const msg =
     (body.error as string) ||
     (body.message as string) ||
-    (body.detail as string) ||
+    (typeof body.detail === "string" ? (body.detail as string) : "") ||
     "";
-  return msg || fallback;
+  const combined = [msg, detail].filter(Boolean).join(" — ");
+  return combined || fallback;
 }
 
 /** Dispatch the auth-expired event (client-side only). */
diff --git a/app/lib/chatClient.ts b/app/lib/chatClient.ts
index 356f2d9..57e0731 100644
--- a/app/lib/chatClient.ts
+++ b/app/lib/chatClient.ts
@@ -10,6 +10,7 @@ import { apiFetch } from "@/app/lib/apiClient";
 import {
   CompletionParams,
   ConfigBlob,
+  ProviderType,
   SavedConfig,
   Tool,
 } from "@/app/lib/types/configs";
@@ -243,7 +244,7 @@ export function configToBlob(config: SavedConfig): ConfigBlob {
 
   const blob: ConfigBlob = {
     completion: {
-      provider: config.provider as "openai",
+      provider: config.provider as ProviderType,
       type: config.type ?? "text",
       params,
     },
diff --git a/app/lib/modelSchema.ts b/app/lib/modelSchema.ts
index 853a58a..0b195dd 100644
--- a/app/lib/modelSchema.ts
+++ b/app/lib/modelSchema.ts
@@ -19,9 +19,19 @@ export type {
   RawModelEntry,
 } from "@/app/lib/types/models";
 
-export const SUPPORTED_PROVIDERS = ["openai", "google"] as const;
-
-export const SUPPORTED_PARAMS = new Set(["effort", "temperature"]);
+export const SUPPORTED_PROVIDERS = [
+  "openai",
+  "google",
+  "google-aistudio",
+] as const;
+
+export const SUPPORTED_PARAMS = new Set([
+  "effort",
+  "temperature",
+  "summary",
+  "voice",
+  "thinking_level",
+]);
 
 export function flattenGroupedModels(
   grouped: Record<string, RawModelEntry[]>,
@@ -50,6 +60,7 @@ export function flattenGroupedModels(
 export const PROVIDER_LABELS: Record<string, string> = {
   openai: "OpenAI",
   google: "Google",
+  "google-aistudio": "Google AI Studio",
 };
 
 export function getProviderLabel(provider: string): string {
@@ -59,6 +70,9 @@ export function getProviderLabel(provider: string): string {
 export const PARAM_LABELS: Record<string, string> = {
   effort: "Effort",
   temperature: "Temperature",
+  summary: "Summary",
+  voice: "Voice",
+  thinking_level: "Thinking Level",
 };
 
 export const PARAM_VALUE_LABELS: Record<string, Record<string, string>> = {
@@ -106,6 +120,18 @@ export function getModelsForProviderAndType(
   );
 }
 
+export function getCompletionTypesForProvider(
+  provider: string,
+): ModelCompletionType[] {
+  return Array.from(
+    new Set(
+      schemas()
+        .filter((m) => m.provider === provider)
+        .flatMap((m) => m.completion_type),
+    ),
+  );
+}
+
 export function getParamLabel(key: string): string {
   return PARAM_LABELS[key] ?? key;
 }
diff --git a/app/lib/types/assessment/config.ts b/app/lib/types/assessment/config.ts
index a1ea1e5..72ecd8b 100644
--- a/app/lib/types/assessment/config.ts
+++ b/app/lib/types/assessment/config.ts
@@ -3,6 +3,7 @@ import type {
   CompletionConfig,
   ConfigPublic,
   ConfigVersionItems,
+  ProviderType,
 } from "@/app/lib/types/configs";
 import type { LabeledValue, ValueSetter } from "./core";
 
@@ -29,7 +30,7 @@ export interface ConfigParamDefinition {
 }
 
 export interface AssessmentModelConfig {
-  provider: "openai" | "google" | "google-aistudio" | "anthropic";
+  provider: ProviderType;
   model_name: string;
   config: Record<string, ConfigParamDefinition>;
 }
diff --git a/app/lib/types/configs.ts b/app/lib/types/configs.ts
index 68b259d..1ab8a89 100644
--- a/app/lib/types/configs.ts
+++ b/app/lib/types/configs.ts
@@ -1,5 +1,11 @@
 import type { AssessmentTag } from "@/app/lib/types/assessment";
 
+export type ProviderType =
+  | "openai"
+  | "google"
+  | "google-aistudio"
+  | "anthropic";
+
 export interface SavedConfig {
   id: string;
   config_id: string;
@@ -66,7 +72,7 @@ export interface CompletionParams {
 }
 
 export interface CompletionConfig {
-  provider: "openai" | "google" | "google-aistudio" | "anthropic";
+  provider: ProviderType;
   type?: "text" | "stt" | "tts";
   params: CompletionParams;
 }