diff --git a/frontend-react/src/App.tsx b/frontend-react/src/App.tsx
index ef54c8b..88d33e0 100644
--- a/frontend-react/src/App.tsx
+++ b/frontend-react/src/App.tsx
@@ -1,4 +1,4 @@
-import { useMemo } from "react";
+import { useEffect, useMemo, useState } from "react";
 import { analyze, autoLayout, compile, tidyLayout } from "./api/client";
 import { CanvasArea } from "./components/CanvasArea";
 import { LeftPanel } from "./components/LeftPanel";
@@ -40,6 +40,23 @@ function toCompileFromAnalyze(result: Awaited<ReturnType<typeof analyze>>): Reco
   };
 }
 
+function sortKeysDeep(value: unknown): unknown {
+  if (Array.isArray(value)) {
+    return value.map((item) => sortKeysDeep(item));
+  }
+  if (value && typeof value === "object") {
+    const record = value as Record<string, unknown>;
+    const sorted = Object.keys(record)
+      .sort((a, b) => a.localeCompare(b))
+      .reduce<Record<string, unknown>>((acc, key) => {
+        acc[key] = sortKeysDeep(record[key]);
+        return acc;
+      }, {});
+    return sorted;
+  }
+  return value;
+}
+
 export function App() {
   const store = useMemo(() => createSchemetaStore({ model: SAMPLE_PAYLOAD }), []);
   const actionsApi = useSchemetaActions(store);
@@ -48,6 +65,13 @@ export function App() {
   const compileResult = useSchemetaSelector(store, (state) => state.compileResult);
   const lifecycle = useSchemetaSelector(store, (state) => state.lifecycle);
   const jsonError = useSchemetaSelector(store, (state) => state.uiFlags.jsonError);
+  const [jsonEditorText, setJsonEditorText] = useState(() => JSON.stringify(SAMPLE_PAYLOAD, null, 2));
+
+  useEffect(() => {
+    if (model) {
+      setJsonEditorText(JSON.stringify(model, null, 2));
+    }
+  }, [model]);
   const lastApiVersion = useSchemetaSelector(store, (state) => {
     const apiVersion = state.compileResult && typeof state.compileResult.api_version === "string" ? state.compileResult.api_version : null;
     return apiVersion ?? "-";
@@ -149,6 +173,71 @@ export function App() {
     }
   }
 
+  function applyJsonFromEditor() {
+    const parsed = actionsApi.applyJsonText(jsonEditorText);
+    if (!parsed.ok) {
+      actionsApi.failCompile("apply-json", parsed.error);
+      return;
+    }
+    actionsApi.completeCompile("apply-json");
+  }
+
+  async function validateJsonEditor() {
+    const parsed = actionsApi.applyJsonText(jsonEditorText);
+    if (!parsed.ok) {
+      actionsApi.failCompile("validate-json", parsed.error);
+      return;
+    }
+
+    const modelCandidate = store.getState().model;
+    if (!modelCandidate) {
+      actionsApi.failCompile("validate-json", "No model loaded");
+      return;
+    }
+
+    actionsApi.beginCompile("validate-json");
+    try {
+      const analyzed = await analyze(modelCandidate);
+      actionsApi.setCompileResult(toCompileFromAnalyze(analyzed));
+      actionsApi.completeCompile("validate-json");
+    } catch (error) {
+      actionsApi.failCompile("validate-json", error);
+    }
+  }
+
+  function formatJsonEditor() {
+    const parsed = actionsApi.applyJsonText(jsonEditorText);
+    if (!parsed.ok) {
+      actionsApi.failCompile("format-json", parsed.error);
+      return;
+    }
+    const next = store.getState().model;
+    if (next) {
+      setJsonEditorText(JSON.stringify(next, null, 2));
+    }
+    actionsApi.completeCompile("format-json");
+  }
+
+  function sortJsonEditorKeys() {
+    try {
+      const parsed = JSON.parse(jsonEditorText);
+      const sorted = sortKeysDeep(parsed);
+      setJsonEditorText(JSON.stringify(sorted, null, 2));
+      actionsApi.completeCompile("sort-json");
+    } catch (error) {
+      actionsApi.failCompile("sort-json", error);
+    }
+  }
+
+  async function copyReproJson() {
+    try {
+      await navigator.clipboard.writeText(jsonEditorText);
+      actionsApi.completeCompile("copy-repro");
+    } catch {
+      actionsApi.failCompile("copy-repro", "Clipboard write failed");
+    }
+  }
+
   return (
     <div className="app-shell">
       <TopBar
@@ -185,7 +274,23 @@ export function App() {
           }
         />
         <CanvasArea store={store} />
-        <RightInspector model={model} selection={selection} compileResult={compileResult} />
+        <RightInspector
+          model={model}
+          selection={selection}
+          compileResult={compileResult}
+          jsonText={jsonEditorText}
+          jsonError={jsonError}
+          onJsonTextChange={setJsonEditorText}
+          onApplyJson={applyJsonFromEditor}
+          onValidateJson={() => {
+            void validateJsonEditor();
+          }}
+          onFormatJson={formatJsonEditor}
+          onSortJson={sortJsonEditorKeys}
+          onCopyRepro={() => {
+            void copyReproJson();
+          }}
+        />
       </div>
     </div>
   );
diff --git a/frontend-react/src/components/RightInspector.tsx b/frontend-react/src/components/RightInspector.tsx
index 878c3fc..e31b13d 100644
--- a/frontend-react/src/components/RightInspector.tsx
+++ b/frontend-react/src/components/RightInspector.tsx
@@ -4,6 +4,14 @@ type RightInspectorProps = {
   model: SchemetaModel | null;
   selection: SelectionSlice;
   compileResult: unknown | null;
+  jsonText: string;
+  jsonError: string | null;
+  onJsonTextChange: (value: string) => void;
+  onApplyJson: () => void;
+  onValidateJson: () => void;
+  onFormatJson: () => void;
+  onSortJson: () => void;
+  onCopyRepro: () => void;
 };
 
 function asRecord(value: unknown): Record<string, unknown> | null {
@@ -33,7 +41,19 @@ function toSnippet(value: unknown, fallback: string): string {
   }
 }
 
-export function RightInspector({ model, selection, compileResult }: RightInspectorProps) {
+export function RightInspector({
+  model,
+  selection,
+  compileResult,
+  jsonText,
+  jsonError,
+  onJsonTextChange,
+  onApplyJson,
+  onValidateJson,
+  onFormatJson,
+  onSortJson,
+  onCopyRepro
+}: RightInspectorProps) {
   const selectedRef = selection.selectedRefs[0] ?? null;
   const selectedInstance = selectedRef ? (model?.instances ?? []).find((instance) => instance.ref === selectedRef) : null;
 
@@ -66,6 +86,35 @@ export function RightInspector({ model, selection, compileResult }: RightInspect
 
       <h2 className="panel__title">Layout Metrics</h2>
       <pre>{toSnippet(layoutMetrics, "No layout metrics available yet.")}</pre>
+
+      <h2 className="panel__title">JSON Editor</h2>
+      <div className="json-tools">
+        <button type="button" onClick={onValidateJson}>
+          Validate
+        </button>
+        <button type="button" onClick={onFormatJson}>
+          Format
+        </button>
+        <button type="button" onClick={onSortJson}>
+          Sort Keys
+        </button>
+        <button type="button" onClick={onCopyRepro}>
+          Copy Repro
+        </button>
+        <button type="button" onClick={onApplyJson}>
+          Apply JSON
+        </button>
+      </div>
+      <textarea
+        className="json-editor"
+        value={jsonText}
+        onChange={(event) => onJsonTextChange(event.target.value)}
+        spellCheck={false}
+        aria-label="Schematic JSON editor"
+      />
+      <p className={`panel__body ${jsonError ? "json-status--error" : "json-status--ok"}`}>
+        {jsonError ? `JSON error: ${jsonError}` : "JSON ready"}
+      </p>
     </aside>
   );
 }
diff --git a/frontend-react/src/styles.css b/frontend-react/src/styles.css
index 2130de4..b2e561b 100644
--- a/frontend-react/src/styles.css
+++ b/frontend-react/src/styles.css
@@ -190,6 +190,49 @@ body {
   font-size: 0.76rem;
 }
 
+.json-tools {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 0.35rem;
+  margin-bottom: 0.5rem;
+}
+
+.json-tools button {
+  padding: 0.28rem 0.48rem;
+  border: 1px solid #b9c9d6;
+  border-radius: 6px;
+  background: #f8fbff;
+  color: #173247;
+  font: inherit;
+  cursor: pointer;
+}
+
+.json-tools button:hover {
+  background: #eaf2f8;
+}
+
+.json-editor {
+  width: 100%;
+  min-height: 220px;
+  border: 1px solid #c1d0dd;
+  border-radius: 8px;
+  padding: 0.5rem;
+  background: #fbfdff;
+  color: #173247;
+  font-family: "IBM Plex Mono", "Fira Code", monospace;
+  font-size: 0.78rem;
+  line-height: 1.35;
+  resize: vertical;
+}
+
+.json-status--ok {
+  color: #12633c;
+}
+
+.json-status--error {
+  color: #a31515;
+}
+
 .canvas {
   display: grid;
   grid-template-rows: auto 1fr;