diff --git a/src/app/(dashboard)/dashboard/playground/components/StudioConfigPane.tsx b/src/app/(dashboard)/dashboard/playground/components/StudioConfigPane.tsx
index decb51ed73..20440a705a 100644
--- a/src/app/(dashboard)/dashboard/playground/components/StudioConfigPane.tsx
+++ b/src/app/(dashboard)/dashboard/playground/components/StudioConfigPane.tsx
@@ -8,11 +8,14 @@ import type { PlaygroundEndpoint } from "@/lib/playground/codeExport";
 import { endpointToPath } from "@/lib/playground/codeExport";
 import PresetPicker from "./PresetPicker";
 import ImprovePromptButton from "./ImprovePromptButton";
+import { useProviderOptions } from "@/app/(dashboard)/dashboard/translator/hooks/useProviderOptions";
+import { useAvailableModels } from "@/app/(dashboard)/dashboard/translator/hooks/useAvailableModels";
 
 export interface ConfigState {
   endpoint: PlaygroundEndpoint;
   baseUrl: string;
   model: string;
+  provider?: string;
   systemPrompt: string;
   params: PlaygroundParams;
 }
@@ -46,6 +49,10 @@ const ENDPOINT_OPTIONS: Array<{ value: PlaygroundEndpoint; label: string }> = [
  */
 export default function StudioConfigPane({ configState, setConfigState }: StudioConfigPaneProps) {
   const [collapsed, setCollapsed] = useState(false);
+  const { provider, setProvider, providerOptions, loading: loadingProviders } = useProviderOptions(
+    configState.provider ?? ""
+  );
+  const { availableModels, loading: loadingModels } = useAvailableModels();
 
   function update<K extends keyof ConfigState>(key: K, value: ConfigState[K]) {
     setConfigState({ ...configState, [key]: value });
@@ -108,18 +115,56 @@ export default function StudioConfigPane({ configState, setConfigState }: Studio
           </select>
         </div>
 
+        {/* Provider */}
+        <div className="flex flex-col gap-1.5">
+          <label className="text-xs font-medium text-text-muted uppercase tracking-wider">
+            Provider
+          </label>
+          <select
+            value={provider}
+            onChange={(e) => {
+              setProvider(e.target.value);
+              update("provider", e.target.value);
+            }}
+            disabled={loadingProviders}
+            className="w-full text-xs bg-surface border border-border rounded px-2 py-1.5 focus:outline-none focus:ring-1 focus:ring-primary text-text-main"
+          >
+            <option value="">Auto</option>
+            {providerOptions.map((opt) => (
+              <option key={opt.value} value={opt.value}>
+                {opt.label}
+              </option>
+            ))}
+          </select>
+        </div>
+
         {/* Model */}
         <div className="flex flex-col gap-1.5">
           <label className="text-xs font-medium text-text-muted uppercase tracking-wider">
             Model
           </label>
-          <input
-            type="text"
-            value={configState.model}
-            onChange={(e) => update("model", e.target.value)}
-            placeholder="e.g. openai/gpt-4o"
-            className="w-full text-xs bg-surface border border-border rounded px-2 py-1.5 focus:outline-none focus:ring-1 focus:ring-primary text-text-main"
-          />
+          {availableModels.length > 0 ? (
+            <select
+              value={configState.model}
+              onChange={(e) => update("model", e.target.value)}
+              disabled={loadingModels}
+              className="w-full text-xs bg-surface border border-border rounded px-2 py-1.5 focus:outline-none focus:ring-1 focus:ring-primary text-text-main"
+            >
+              {availableModels.map((m) => (
+                <option key={m} value={m}>
+                  {m}
+                </option>
+              ))}
+            </select>
+          ) : (
+            <input
+              type="text"
+              value={configState.model}
+              onChange={(e) => update("model", e.target.value)}
+              placeholder="e.g. openai/gpt-4o"
+              className="w-full text-xs bg-surface border border-border rounded px-2 py-1.5 focus:outline-none focus:ring-1 focus:ring-primary text-text-main"
+            />
+          )}
         </div>
 
         {/* System prompt */}
diff --git a/src/app/(dashboard)/dashboard/playground/components/tabs/BuildTab.tsx b/src/app/(dashboard)/dashboard/playground/components/tabs/BuildTab.tsx
index 40bfb78c98..a3a5c521a1 100644
--- a/src/app/(dashboard)/dashboard/playground/components/tabs/BuildTab.tsx
+++ b/src/app/(dashboard)/dashboard/playground/components/tabs/BuildTab.tsx
@@ -6,9 +6,8 @@ import { useRef, useState } from "react";
 import { useTranslations } from "next-intl";
 import { useToolsBuilder } from "../../hooks/useToolsBuilder";
 import { useStructuredOutput } from "../../hooks/useStructuredOutput";
-import ToolsBuilder from "../ToolsBuilder";
-import StructuredOutputEditor from "../StructuredOutputEditor";
 import MarkdownMessage from "../MarkdownMessage";
+import BuildWizard from "./build/BuildWizard";
 import type { ConfigState } from "../StudioConfigPane";
 
 interface BuildTabProps {
@@ -225,177 +224,104 @@ export default function BuildTab({ configState }: BuildTabProps) {
     await runRequest(newMessages);
   }
 
-  function clearConversation() {
-    setMessages([]);
-    setToolCalls([]);
-    setToolResultDrafts([]);
-    setValidationResult(null);
-    setPrompt("");
-  }
-
-  return (
-    <div className="flex h-full overflow-hidden">
-      {/* Left panel: conversation + run */}
-      <div className="flex-1 flex flex-col overflow-hidden">
-        {/* Toolbar */}
-        <div className="flex items-center gap-2 px-4 py-2 border-b border-border bg-bg-alt shrink-0">
-          <button
-            onClick={() => void handleRun()}
-            disabled={running || (!prompt.trim() && messages.length === 0)}
-            className="flex items-center gap-1.5 text-xs px-3 py-1.5 rounded bg-primary text-white hover:bg-primary/90 transition-colors disabled:opacity-40 disabled:cursor-not-allowed"
+  // Result area: conversation history + tool-call UI + validation badge
+  const resultArea = (
+    <div className="space-y-3">
+      {messages.map((msg, idx) => (
+        <div key={idx} className={`flex ${msg.role === "user" ? "justify-end" : "justify-start"}`}>
+          <div
+            className={`max-w-[80%] rounded-xl px-3 py-2 text-sm ${
+              msg.role === "user"
+                ? "bg-primary text-white"
+                : msg.role === "tool"
+                  ? "bg-yellow-500/10 border border-yellow-500/30 text-text-main"
+                  : "bg-bg-alt border border-border text-text-main"
+            }`}
           >
-            <span className="material-symbols-outlined text-[14px]">play_arrow</span>
-            {running ? t("running") : t("runLabel")}
-          </button>
-
-          {messages.length > 0 && (
-            <button
-              onClick={clearConversation}
-              className="text-xs px-2.5 py-1.5 rounded border border-border text-text-muted hover:text-text-main hover:bg-black/5 dark:hover:bg-white/5 transition-colors"
-            >
-              {t("clearAll")}
-            </button>
-          )}
-
-          <div className="ml-auto flex items-center gap-2 text-[11px] text-text-muted">
-            {toolsBuilder.tools.length > 0 && (
-              <span className="px-1.5 py-0.5 rounded bg-primary/10 text-primary">
-                {toolsBuilder.tools.length} tool{toolsBuilder.tools.length !== 1 ? "s" : ""}
-              </span>
-            )}
-            {structuredOutput.enabled && (
-              <span className="px-1.5 py-0.5 rounded bg-green-500/10 text-green-600 dark:text-green-400">
-                JSON mode
-              </span>
+            {msg.role === "user" ? (
+              <span className="whitespace-pre-wrap">{msg.content}</span>
+            ) : (
+              <MarkdownMessage content={msg.content} />
             )}
           </div>
         </div>
+      ))}
 
-        {/* Conversation history */}
-        <div className="flex-1 overflow-y-auto px-4 py-3 space-y-3">
-          {messages.map((msg, idx) => (
-            <div key={idx} className={`flex ${msg.role === "user" ? "justify-end" : "justify-start"}`}>
+      {/* Tool call UI */}
+      {toolCalls.length > 0 && (
+        <div className="space-y-2">
+          {toolCalls.map((tc) => {
+            const draft = toolResultDrafts.find((d) => d.toolCallId === tc.id);
+            return (
               <div
-                className={`max-w-[80%] rounded-xl px-3 py-2 text-sm ${
-                  msg.role === "user"
-                    ? "bg-primary text-white"
-                    : msg.role === "tool"
-                      ? "bg-yellow-500/10 border border-yellow-500/30 text-text-main"
-                      : "bg-bg-alt border border-border text-text-main"
-                }`}
+                key={tc.id}
+                className="border border-amber-500/40 rounded-lg p-3 bg-amber-500/5"
               >
-                {msg.role === "user" ? (
-                  <span className="whitespace-pre-wrap">{msg.content}</span>
-                ) : (
-                  <MarkdownMessage content={msg.content} />
-                )}
-              </div>
-            </div>
-          ))}
-
-          {/* Tool call UI */}
-          {toolCalls.length > 0 && (
-            <div className="space-y-2">
-              {toolCalls.map((tc) => {
-                const draft = toolResultDrafts.find((d) => d.toolCallId === tc.id);
-                return (
-                  <div
-                    key={tc.id}
-                    className="border border-amber-500/40 rounded-lg p-3 bg-amber-500/5"
+                <div className="flex items-center gap-2 mb-2">
+                  <span className="material-symbols-outlined text-[14px] text-amber-500">
+                    function
+                  </span>
+                  <code className="text-xs font-mono text-text-main">
+                    {tc.function.name}
+                  </code>
+                </div>
+                <pre className="text-[11px] font-mono text-text-muted bg-bg-alt rounded p-2 overflow-x-auto mb-2 whitespace-pre-wrap break-all">
+                  {tc.function.arguments}
+                </pre>
+                <div className="flex flex-col gap-2">
+                  <label className="text-[10px] text-text-muted uppercase tracking-wider">
+                    Tool result
+                  </label>
+                  <textarea
+                    value={draft?.draft ?? ""}
+                    onChange={(e) =>
+                      setToolResultDrafts((prev) =>
+                        prev.map((d) =>
+                          d.toolCallId === tc.id ? { ...d, draft: e.target.value } : d,
+                        ),
+                      )
+                    }
+                    rows={3}
+                    placeholder={t("enterToolResult")}
+                    className="text-xs font-mono bg-bg-alt border border-border rounded px-2 py-1.5 focus:outline-none focus:ring-1 focus:ring-primary text-text-main resize-y"
+                  />
+                  <button
+                    onClick={() => void sendToolResult(tc.id)}
+                    className="text-xs px-2.5 py-1 rounded bg-primary text-white hover:bg-primary/90 transition-colors self-start"
                   >
-                    <div className="flex items-center gap-2 mb-2">
-                      <span className="material-symbols-outlined text-[14px] text-amber-500">
-                        function
-                      </span>
-                      <code className="text-xs font-mono text-text-main">
-                        {tc.function.name}
-                      </code>
-                    </div>
-                    <pre className="text-[11px] font-mono text-text-muted bg-bg-alt rounded p-2 overflow-x-auto mb-2 whitespace-pre-wrap break-all">
-                      {tc.function.arguments}
-                    </pre>
-                    <div className="flex flex-col gap-2">
-                      <label className="text-[10px] text-text-muted uppercase tracking-wider">
-                        Tool result
-                      </label>
-                      <textarea
-                        value={draft?.draft ?? ""}
-                        onChange={(e) =>
-                          setToolResultDrafts((prev) =>
-                            prev.map((d) =>
-                              d.toolCallId === tc.id ? { ...d, draft: e.target.value } : d,
-                            ),
-                          )
-                        }
-                        rows={3}
-                        placeholder="Enter tool result…"
-                        className="text-xs font-mono bg-bg-alt border border-border rounded px-2 py-1.5 focus:outline-none focus:ring-1 focus:ring-primary text-text-main resize-y"
-                      />
-                      <button
-                        onClick={() => void sendToolResult(tc.id)}
-                        className="text-xs px-2.5 py-1 rounded bg-primary text-white hover:bg-primary/90 transition-colors self-start"
-                      >
-                        Send tool result
-                      </button>
-                    </div>
-                  </div>
-                );
-              })}
-            </div>
-          )}
-
-          {/* Structured output validation */}
-          {validationResult != null && (
-            <div
-              className={`text-xs rounded-lg px-3 py-2 border ${
-                validationResult.valid
-                  ? "border-green-500/40 bg-green-500/5 text-green-600 dark:text-green-400"
-                  : "border-destructive/40 bg-destructive/5 text-destructive"
-              }`}
-            >
-              {validationResult.valid ? "✅ Valid JSON schema response" : `❌ ${validationResult.error}`}
-            </div>
-          )}
+                    Send tool result
+                  </button>
+                </div>
+              </div>
+            );
+          })}
         </div>
+      )}
 
-        {/* Prompt input */}
-        <div className="px-4 py-3 border-t border-border shrink-0">
-          <div className="flex items-end gap-2">
-            <textarea
-              value={prompt}
-              onChange={(e) => setPrompt(e.target.value)}
-              onKeyDown={(e) => {
-                if (e.key === "Enter" && !e.shiftKey) {
-                  e.preventDefault();
-                  void handleRun();
-                }
-              }}
-              placeholder="Enter your message… (Enter to send, Shift+Enter for newline)"
-              rows={2}
-              className="flex-1 text-sm bg-surface border border-border rounded-lg px-3 py-2 focus:outline-none focus:ring-1 focus:ring-primary text-text-main resize-none"
-            />
-          </div>
+      {/* Structured output validation */}
+      {validationResult != null && (
+        <div
+          className={`text-xs rounded-lg px-3 py-2 border ${
+            validationResult.valid
+              ? "border-green-500/40 bg-green-500/5 text-green-600 dark:text-green-400"
+              : "border-destructive/40 bg-destructive/5 text-destructive"
+          }`}
+        >
+          {validationResult.valid ? "✅ Valid JSON schema response" : `❌ ${validationResult.error}`}
         </div>
-      </div>
-
-      {/* Right panel: tools + structured output config */}
-      <div className="w-72 shrink-0 border-l border-border bg-bg-alt overflow-y-auto p-4 flex flex-col gap-6">
-        {/* Tools section */}
-        <div>
-          <h3 className="text-xs font-semibold text-text-muted uppercase tracking-wider mb-3">
-            Function calling
-          </h3>
-          <ToolsBuilder toolsBuilder={toolsBuilder} />
-        </div>
-
-        {/* Structured output section */}
-        <div>
-          <h3 className="text-xs font-semibold text-text-muted uppercase tracking-wider mb-3">
-            Structured output
-          </h3>
-          <StructuredOutputEditor structuredOutput={structuredOutput} />
-        </div>
-      </div>
+      )}
     </div>
   );
+
+  return (
+    <BuildWizard
+      toolsBuilder={toolsBuilder}
+      structuredOutput={structuredOutput}
+      running={running}
+      onRun={() => void handleRun()}
+      prompt={prompt}
+      setPrompt={setPrompt}
+      result={resultArea}
+    />
+  );
 }
diff --git a/src/app/(dashboard)/dashboard/playground/components/tabs/CompareTab.tsx b/src/app/(dashboard)/dashboard/playground/components/tabs/CompareTab.tsx
index 6719b7fc40..8f208b8460 100644
--- a/src/app/(dashboard)/dashboard/playground/components/tabs/CompareTab.tsx
+++ b/src/app/(dashboard)/dashboard/playground/components/tabs/CompareTab.tsx
@@ -104,6 +104,13 @@ export default function CompareTab({ configState }: CompareTabProps) {
   // Metrics trackers per column id (plain class instances, no React hooks)
   const metricsTrackersRef = useRef<Map<string, ColumnMetricsTracker>>(new Map());
 
+  // User prompt input
+  const [prompt, setPrompt] = useState("");
+
+  // RAF throttle: pending chunk accumulator and scheduled frame id
+  const pendingRef = useRef<Record<string, string>>({});
+  const rafRef = useRef<number | null>(null);
+
   // Input for model name when adding a column
   const [newModel, setNewModel] = useState("");
   const addInputRef = useRef<HTMLInputElement>(null);
@@ -127,6 +134,30 @@ export default function CompareTab({ configState }: CompareTabProps) {
     return metricsTrackersRef.current.get(id)!;
   }
 
+  /**
+   * Throttle per-column chunk updates via requestAnimationFrame.
+   * Accumulates all deltas that arrive within a single frame and flushes
+   * them with a single setColumns call, preventing hundreds of re-renders/s.
+   */
+  function pushChunk(colId: string, delta: string) {
+    pendingRef.current[colId] = (pendingRef.current[colId] ?? "") + delta;
+
+    if (rafRef.current == null) {
+      rafRef.current = requestAnimationFrame(() => {
+        const snapshot = pendingRef.current;
+        pendingRef.current = {};
+        rafRef.current = null;
+
+        setColumns((prev) =>
+          prev.map((c) => {
+            const extra = snapshot[c.id];
+            return extra != null ? { ...c, response: c.response + extra } : c;
+          })
+        );
+      });
+    }
+  }
+
   function addColumn() {
     if (columns.length >= MAX_COLUMNS) return;
     const model = newModel.trim() || configState.model;
@@ -179,6 +210,7 @@ export default function CompareTab({ configState }: CompareTabProps) {
         ...(configState.systemPrompt
           ? [{ role: "system", content: configState.systemPrompt }]
           : []),
+        { role: "user", content: prompt },
       ],
     };
 
@@ -247,10 +279,8 @@ export default function CompareTab({ configState }: CompareTabProps) {
             accumulated += content;
             tracker.onChunk(1);
 
-            updateColumn(col.id, {
-              response: accumulated,
-              metrics: tracker.getMetrics(),
-            });
+            // Throttled: accumulate delta and flush once per animation frame
+            pushChunk(col.id, content);
           }
 
           const usage = parsed["usage"] as
@@ -269,6 +299,12 @@ export default function CompareTab({ configState }: CompareTabProps) {
       });
     } catch (err) {
       if (controller.signal.aborted) {
+        // Cancel any pending RAF for this column and clean up its pending delta
+        if (rafRef.current != null) {
+          cancelAnimationFrame(rafRef.current);
+          rafRef.current = null;
+        }
+        delete pendingRef.current[col.id];
         updateColumn(col.id, { status: "idle" });
         return;
       }
@@ -303,6 +339,18 @@ export default function CompareTab({ configState }: CompareTabProps) {
 
   return (
     <div className="flex flex-col h-full">
+      {/* Prompt input area */}
+      <div className="px-4 pt-3 pb-2 border-b border-border bg-bg-alt shrink-0">
+        <textarea
+          value={prompt}
+          onChange={(e) => setPrompt(e.target.value)}
+          placeholder="Enter your prompt here…"
+          rows={3}
+          className="w-full text-sm bg-surface border border-border rounded px-3 py-2 focus:outline-none focus:ring-1 focus:ring-primary text-text-main resize-y"
+          aria-label="User prompt"
+        />
+      </div>
+
       {/* Compare toolbar */}
       <div className="flex items-center gap-2 px-4 py-2 border-b border-border bg-bg-alt shrink-0">
         {/* Run / Cancel all */}
@@ -318,7 +366,7 @@ export default function CompareTab({ configState }: CompareTabProps) {
         ) : (
           <button
             onClick={() => void runAll()}
-            disabled={columns.length === 0}
+            disabled={columns.length === 0 || !prompt.trim()}
             className="flex items-center gap-1.5 text-xs px-3 py-1.5 rounded bg-primary text-white hover:bg-primary/90 transition-colors disabled:opacity-40 disabled:cursor-not-allowed"
             aria-label="Run all columns"
           >
diff --git a/src/app/(dashboard)/dashboard/playground/components/tabs/build/BuildWizard.tsx b/src/app/(dashboard)/dashboard/playground/components/tabs/build/BuildWizard.tsx
new file mode 100644
index 0000000000..ee51c1ee4f
--- /dev/null
+++ b/src/app/(dashboard)/dashboard/playground/components/tabs/build/BuildWizard.tsx
@@ -0,0 +1,294 @@
+"use client";
+
+// src/app/(dashboard)/dashboard/playground/components/tabs/build/BuildWizard.tsx
+
+import { useState } from "react";
+import { useTranslations } from "next-intl";
+import ToolsBuilder from "../../ToolsBuilder";
+import StructuredOutputEditor from "../../StructuredOutputEditor";
+import { useToolsBuilder } from "../../../hooks/useToolsBuilder";
+import { useStructuredOutput } from "../../../hooks/useStructuredOutput";
+
+type BuildMode = "tools" | "json" | "both";
+
+interface BuildWizardProps {
+  toolsBuilder: ReturnType<typeof useToolsBuilder>;
+  structuredOutput: ReturnType<typeof useStructuredOutput>;
+  running: boolean;
+  onRun: () => void;
+  prompt: string;
+  setPrompt: (value: string) => void;
+  result: React.ReactNode;
+}
+
+interface StepperProps {
+  currentStep: 1 | 2 | 3;
+}
+
+function Stepper({ currentStep }: StepperProps) {
+  const t = useTranslations("playground.build");
+
+  const steps: Array<{ num: 1 | 2 | 3; label: string }> = [
+    { num: 1, label: t("step1Label") },
+    { num: 2, label: t("step2Label") },
+    { num: 3, label: t("step3Label") },
+  ];
+
+  return (
+    <div className="flex items-center gap-0 px-4 py-3 border-b border-border bg-bg-alt shrink-0">
+      {steps.map((step, idx) => (
+        <div key={step.num} className="flex items-center">
+          {idx > 0 && (
+            <div
+              className={`h-px w-8 mx-2 transition-colors ${
+                currentStep > step.num ? "bg-primary" : "bg-border"
+              }`}
+            />
+          )}
+          <div className="flex items-center gap-1.5">
+            <span
+              className={`flex items-center justify-center w-5 h-5 rounded-full text-[11px] font-semibold transition-colors ${
+                currentStep === step.num
+                  ? "bg-primary text-white"
+                  : currentStep > step.num
+                    ? "bg-primary/20 text-primary"
+                    : "bg-border text-text-muted"
+              }`}
+            >
+              {currentStep > step.num ? (
+                <span className="material-symbols-outlined text-[12px]">check</span>
+              ) : (
+                step.num
+              )}
+            </span>
+            <span
+              className={`text-xs font-medium transition-colors ${
+                currentStep === step.num ? "text-text-main" : "text-text-muted"
+              }`}
+            >
+              {step.label}
+            </span>
+          </div>
+        </div>
+      ))}
+    </div>
+  );
+}
+
+interface ModeCardProps {
+  icon: string;
+  title: string;
+  description: string;
+  selected: boolean;
+  onClick: () => void;
+}
+
+function ModeCard({ icon, title, description, selected, onClick }: ModeCardProps) {
+  return (
+    <button
+      onClick={onClick}
+      className={`flex flex-col gap-2 p-4 rounded-xl border-2 text-left transition-all hover:shadow-sm ${
+        selected
+          ? "border-primary bg-primary/5"
+          : "border-border bg-surface hover:border-primary/40"
+      }`}
+    >
+      <span className="text-2xl">{icon}</span>
+      <span className={`text-sm font-semibold ${selected ? "text-primary" : "text-text-main"}`}>
+        {title}
+      </span>
+      <span className="text-xs text-text-muted leading-relaxed">{description}</span>
+    </button>
+  );
+}
+
+export default function BuildWizard({
+  toolsBuilder,
+  structuredOutput,
+  running,
+  onRun,
+  prompt,
+  setPrompt,
+  result,
+}: BuildWizardProps) {
+  const t = useTranslations("playground");
+  const tb = useTranslations("playground.build");
+
+  const [step, setStep] = useState<1 | 2 | 3>(1);
+  const [mode, setMode] = useState<BuildMode>("tools");
+
+  const includesTools = mode === "tools" || mode === "both";
+  const includesJson = mode === "json" || mode === "both";
+
+  function goToStep2() {
+    setStep(2);
+  }
+
+  function goToStep3() {
+    setStep(3);
+  }
+
+  function goBack() {
+    if (step === 2) setStep(1);
+    else if (step === 3) setStep(2);
+  }
+
+  return (
+    <div className="flex flex-col h-full overflow-hidden">
+      <Stepper currentStep={step} />
+
+      {/* Step 1: Mode picker */}
+      {step === 1 && (
+        <div className="flex-1 overflow-y-auto p-6 flex flex-col gap-6">
+          <div>
+            <h2 className="text-base font-semibold text-text-main mb-1">{tb("step1Title")}</h2>
+            <p className="text-xs text-text-muted">{tb("step1Subtitle")}</p>
+          </div>
+
+          <div className="grid grid-cols-1 sm:grid-cols-3 gap-3">
+            <ModeCard
+              icon="🔧"
+              title={tb("modeToolsTitle")}
+              description={tb("modeToolsDesc")}
+              selected={mode === "tools"}
+              onClick={() => setMode("tools")}
+            />
+            <ModeCard
+              icon="📋"
+              title={tb("modeJsonTitle")}
+              description={tb("modeJsonDesc")}
+              selected={mode === "json"}
+              onClick={() => setMode("json")}
+            />
+            <ModeCard
+              icon="🔧"
+              title={tb("modeBothTitle")}
+              description={tb("modeBothDesc")}
+              selected={mode === "both"}
+              onClick={() => setMode("both")}
+            />
+          </div>
+
+          <div className="flex justify-end pt-2">
+            <button
+              onClick={goToStep2}
+              className="flex items-center gap-1.5 text-sm px-4 py-2 rounded-lg bg-primary text-white hover:bg-primary/90 transition-colors"
+            >
+              {tb("nextButton")}
+              <span className="material-symbols-outlined text-[16px]">arrow_forward</span>
+            </button>
+          </div>
+        </div>
+      )}
+
+      {/* Step 2: Configure */}
+      {step === 2 && (
+        <div className="flex-1 overflow-y-auto p-6 flex flex-col gap-6">
+          <div>
+            <h2 className="text-base font-semibold text-text-main mb-1">{tb("step2Title")}</h2>
+            <p className="text-xs text-text-muted">{tb("step2Subtitle")}</p>
+          </div>
+
+          {includesTools && (
+            <div>
+              <h3 className="text-xs font-semibold text-text-muted uppercase tracking-wider mb-3">
+                {t("toolsLabel")}
+              </h3>
+              <ToolsBuilder toolsBuilder={toolsBuilder} />
+            </div>
+          )}
+
+          {includesJson && (
+            <div>
+              <h3 className="text-xs font-semibold text-text-muted uppercase tracking-wider mb-3">
+                {t("structuredOutputLabel")}
+              </h3>
+              <StructuredOutputEditor structuredOutput={structuredOutput} />
+            </div>
+          )}
+
+          <div className="flex items-center justify-between pt-2">
+            <button
+              onClick={goBack}
+              className="flex items-center gap-1.5 text-sm px-4 py-2 rounded-lg border border-border text-text-muted hover:text-text-main hover:bg-black/5 dark:hover:bg-white/5 transition-colors"
+            >
+              <span className="material-symbols-outlined text-[16px]">arrow_back</span>
+              {tb("backButton")}
+            </button>
+            <button
+              onClick={goToStep3}
+              className="flex items-center gap-1.5 text-sm px-4 py-2 rounded-lg bg-primary text-white hover:bg-primary/90 transition-colors"
+            >
+              {tb("nextButton")}
+              <span className="material-symbols-outlined text-[16px]">arrow_forward</span>
+            </button>
+          </div>
+        </div>
+      )}
+
+      {/* Step 3: Run */}
+      {step === 3 && (
+        <div className="flex-1 flex flex-col overflow-hidden">
+          {/* Toolbar */}
+          <div className="flex items-center gap-2 px-4 py-2 border-b border-border bg-bg-alt shrink-0">
+            <button
+              onClick={goBack}
+              className="flex items-center gap-1 text-xs px-2.5 py-1.5 rounded border border-border text-text-muted hover:text-text-main hover:bg-black/5 dark:hover:bg-white/5 transition-colors"
+            >
+              <span className="material-symbols-outlined text-[14px]">arrow_back</span>
+              {tb("backButton")}
+            </button>
+
+            <div className="w-px h-4 bg-border mx-1" />
+
+            <button
+              onClick={onRun}
+              disabled={running || (!prompt.trim())}
+              className="flex items-center gap-1.5 text-xs px-3 py-1.5 rounded bg-primary text-white hover:bg-primary/90 transition-colors disabled:opacity-40 disabled:cursor-not-allowed"
+            >
+              <span className="material-symbols-outlined text-[14px]">play_arrow</span>
+              {running ? t("running") : tb("runButton")}
+            </button>
+
+            <div className="ml-auto flex items-center gap-2 text-[11px] text-text-muted">
+              {includesTools && toolsBuilder.tools.length > 0 && (
+                <span className="px-1.5 py-0.5 rounded bg-primary/10 text-primary">
+                  {toolsBuilder.tools.length} tool{toolsBuilder.tools.length !== 1 ? "s" : ""}
+                </span>
+              )}
+              {includesJson && structuredOutput.enabled && (
+                <span className="px-1.5 py-0.5 rounded bg-green-500/10 text-green-600 dark:text-green-400">
+                  JSON mode
+                </span>
+              )}
+            </div>
+          </div>
+
+          {/* Result area (conversation + tool-call UI + validation badge) */}
+          <div className="flex-1 overflow-y-auto px-4 py-3">
+            {result}
+          </div>
+
+          {/* Prompt input */}
+          <div className="px-4 py-3 border-t border-border shrink-0">
+            <div className="flex items-end gap-2">
+              <textarea
+                value={prompt}
+                onChange={(e) => setPrompt(e.target.value)}
+                onKeyDown={(e) => {
+                  if (e.key === "Enter" && !e.shiftKey) {
+                    e.preventDefault();
+                    onRun();
+                  }
+                }}
+                placeholder={tb("promptPlaceholder")}
+                rows={2}
+                className="flex-1 text-sm bg-surface border border-border rounded-lg px-3 py-2 focus:outline-none focus:ring-1 focus:ring-primary text-text-main resize-none"
+              />
+            </div>
+          </div>
+        </div>
+      )}
+    </div>
+  );
+}
diff --git a/src/i18n/messages/en.json b/src/i18n/messages/en.json
index a8cf4cdbca..2c1e537f7d 100644
--- a/src/i18n/messages/en.json
+++ b/src/i18n/messages/en.json
@@ -7540,7 +7540,27 @@
     "invalidJson": "Invalid JSON",
     "running": "Running…",
     "runLabel": "Run",
-    "enterToolResult": "Enter tool result…"
+    "enterToolResult": "Enter tool result…",
+    "build": {
+      "step1Label": "What to test?",
+      "step2Label": "Configure",
+      "step3Label": "Run",
+      "step1Title": "What do you want to test?",
+      "step1Subtitle": "Choose the capability you want to explore in this session.",
+      "step2Title": "Configure",
+      "step2Subtitle": "Set up the tools or JSON schema that will be used in the request.",
+      "step3Title": "Run",
+      "modeToolsTitle": "Tools",
+      "modeToolsDesc": "Test function calling — define tools and see how the model invokes them.",
+      "modeJsonTitle": "JSON",
+      "modeJsonDesc": "Test structured output — constrain the response to a JSON schema.",
+      "modeBothTitle": "Tools + JSON",
+      "modeBothDesc": "Combine function calling and structured output in a single request.",
+      "backButton": "Back",
+      "nextButton": "Next",
+      "runButton": "Run",
+      "promptPlaceholder": "Enter your message… (Enter to send, Shift+Enter for newline)"
+    }
   },
   "miniPlayground": {
     "endpoint": "Endpoint",
diff --git a/src/i18n/messages/pt-BR.json b/src/i18n/messages/pt-BR.json
index 561439fe28..d7fd1d774c 100644
--- a/src/i18n/messages/pt-BR.json
+++ b/src/i18n/messages/pt-BR.json
@@ -4301,7 +4301,27 @@
     "invalidJson": "JSON inválido",
     "running": "Executando…",
     "runLabel": "Executar",
-    "enterToolResult": "Insira o resultado da ferramenta…"
+    "enterToolResult": "Insira o resultado da ferramenta…",
+    "build": {
+      "step1Label": "O que testar?",
+      "step2Label": "Configurar",
+      "step3Label": "Rodar",
+      "step1Title": "O que você quer testar?",
+      "step1Subtitle": "Escolha a funcionalidade que deseja explorar nesta sessão.",
+      "step2Title": "Configurar",
+      "step2Subtitle": "Configure as ferramentas ou o esquema JSON que serão usados na requisição.",
+      "step3Title": "Rodar",
+      "modeToolsTitle": "Ferramentas",
+      "modeToolsDesc": "Teste function calling — defina ferramentas e veja como o modelo as invoca.",
+      "modeJsonTitle": "JSON",
+      "modeJsonDesc": "Teste saída estruturada — restrinja a resposta a um esquema JSON.",
+      "modeBothTitle": "Ferramentas + JSON",
+      "modeBothDesc": "Combine function calling e saída estruturada em uma única requisição.",
+      "backButton": "Voltar",
+      "nextButton": "Próximo",
+      "runButton": "Executar",
+      "promptPlaceholder": "Digite sua mensagem… (Enter para enviar, Shift+Enter para nova linha)"
+    }
   },
   "pricingModal": {
     "title": "Configuração de preços",
diff --git a/tests/unit/v388-phase4-playground.test.ts b/tests/unit/v388-phase4-playground.test.ts
new file mode 100644
index 0000000000..40530c5196
--- /dev/null
+++ b/tests/unit/v388-phase4-playground.test.ts
@@ -0,0 +1,41 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+
+// Regression guards for v3.8.8 Playground screen fixes (Phase 4).
+const root = join(import.meta.dirname, "../..");
+const read = (p: string) => readFileSync(join(root, p), "utf8");
+
+test("playground config: adds Provider + Model selects reusing translator hooks", () => {
+  const src = read("src/app/(dashboard)/dashboard/playground/components/StudioConfigPane.tsx");
+  assert.ok(src.includes("useProviderOptions"), "reuses useProviderOptions");
+  assert.ok(src.includes("useAvailableModels"), "reuses useAvailableModels");
+  assert.ok(src.includes('update("provider"'), "writes provider into ConfigState");
+  assert.ok(src.includes("provider?: string"), "ConfigState gains provider");
+});
+
+test("playground compare: prompt input + rAF throttle + user message in request", () => {
+  const src = read("src/app/(dashboard)/dashboard/playground/components/tabs/CompareTab.tsx");
+  assert.ok(src.includes("requestAnimationFrame"), "throttles stream updates via rAF");
+  assert.ok(/role:\s*"user"/.test(src), "request body includes a user message");
+  assert.ok(src.includes("setPrompt"), "has a prompt input control");
+});
+
+test("playground build: wizard with 3 modes reusing editors; BuildTab keeps handlers", () => {
+  const wiz = read("src/app/(dashboard)/dashboard/playground/components/tabs/build/BuildWizard.tsx");
+  assert.ok(wiz.includes('"tools"') && wiz.includes('"json"') && wiz.includes('"both"'), "three modes");
+  assert.ok(wiz.includes("ToolsBuilder") && wiz.includes("StructuredOutputEditor"), "reuses both editors");
+  const tab = read("src/app/(dashboard)/dashboard/playground/components/tabs/BuildTab.tsx");
+  assert.ok(tab.includes("<BuildWizard"), "BuildTab mounts BuildWizard");
+  assert.ok(tab.includes("runRequest") && tab.includes("sendToolResult"), "BuildTab preserves run/tool handlers");
+});
+
+test("playground build i18n: playground.build keys present with en/pt parity", () => {
+  const en = JSON.parse(read("src/i18n/messages/en.json"));
+  const pt = JSON.parse(read("src/i18n/messages/pt-BR.json"));
+  const ek = Object.keys(en.playground?.build ?? {});
+  const pk = Object.keys(pt.playground?.build ?? {});
+  assert.ok(ek.length >= 10, `expected >=10 build keys, got ${ek.length}`);
+  assert.deepEqual(ek.sort(), pk.sort(), "en/pt-BR playground.build keys must match");
+});