fix(dashboard): verify assistant-health saves with read-back

docs/plans/state.json

@@ -5683,6 +5683,17 @@
         "docs/plans/state.json"
       ],
       "test_status": "pnpm typecheck passing"
+    },
+    "dashboard-assistant-health-readback-verification": {
+      "status": "completed",
+      "date": "2026-02-19",
+      "updated": "2026-02-19",
+      "summary": "Added read-after-write verification to Assistant Health saves. After `config.patch`, dashboard now performs `config.get` and confirms each patched key/value actually stuck; mismatches are surfaced as explicit errors instead of false green success.",
+      "files_modified": [
+        "src/gateway/ui/pages/dashboard.js",
+        "docs/plans/state.json"
+      ],
+      "test_status": "pnpm typecheck passing"
     }
   },
   "overall_progress": {

src/gateway/ui/pages/dashboard.js

@@ -123,6 +123,30 @@ function buildRollbackPatchesFromSnapshot(snapshot) {
   };
 }
 
+function getByPath(obj, dottedPath) {
+  if (!obj || typeof obj !== 'object') {return undefined;}
+  const parts = dottedPath.split('.');
+  let cursor = obj;
+  for (const part of parts) {
+    if (!cursor || typeof cursor !== 'object' || !(part in cursor)) {
+      return undefined;
+    }
+    cursor = cursor[part];
+  }
+  return cursor;
+}
+
+function valuesMatch(expected, actual) {
+  if (Array.isArray(expected) && Array.isArray(actual)) {
+    if (expected.length !== actual.length) {return false;}
+    for (let i = 0; i < expected.length; i++) {
+      if (expected[i] !== actual[i]) {return false;}
+    }
+    return true;
+  }
+  return expected === actual;
+}
+
 function setAssistantSaveState(message, tone = 'neutral') {
   _assistantSaveState = {
     message,
@@ -550,8 +574,28 @@ async function applyAssistantPatch(patches, statusEl) {
         message = `Runtime-only save (${applied.length} updated, file persistence unavailable)`;
         tone = 'warning';
       } else {
-        message = `Saved to runtime + config file (${applied.length} updated)`;
-        tone = 'success';
+        // Verify read-after-write so UI cannot claim persistence when value did not stick.
+        try {
+          const fresh = await _dashboardClient.call('config.get');
+          const mismatches = [];
+          for (const [key, value] of Object.entries(patches)) {
+            const actual = getByPath(fresh, key);
+            if (!valuesMatch(value, actual)) {
+              mismatches.push(`${key} expected=${JSON.stringify(value)} actual=${JSON.stringify(actual)}`);
+            }
+          }
+
+          if (mismatches.length > 0) {
+            message = `Saved response received but read-back mismatch: ${mismatches.join('; ')}`;
+            tone = 'error';
+          } else {
+            message = `Saved to runtime + config file (${applied.length} updated)`;
+            tone = 'success';
+          }
+        } catch (verifyError) {
+          message = `Saved response received, but verification failed: ${verifyError instanceof Error ? verifyError.message : String(verifyError)}`;
+          tone = 'warning';
+        }
       }
       setAssistantSaveState(message, tone);
       statusEl.textContent = message;