fix: prevent deepMerge from corrupting arrays by treating them as leaf values

cursoragent · cursoragent · commit 2388e7d43fc8 · 2026-03-26T00:07:31.000Z
P.isObject returns true for arrays, causing deepMerge to spread arrays
into plain objects with numeric keys and recursively merge entries.
This corrupted customModels arrays in ServerSettings whenever
updateSettings was called.

Add Array.isArray guards at both the top-level check and the per-key
recursive branch so arrays are replaced wholesale instead of merged.
diff --git a/packages/shared/src/Struct.ts b/packages/shared/src/Struct.ts
@@ -1,7 +1,12 @@
 import * as P from "effect/Predicate";
 
 export function deepMerge<T>(current: T, patch: unknown): T {
-  if (!P.isObject(current) || !P.isObject(patch)) {
+  if (
+    !P.isObject(current) ||
+    !P.isObject(patch) ||
+    Array.isArray(current) ||
+    Array.isArray(patch)
+  ) {
     return patch as T;
   }
 
@@ -10,7 +15,10 @@ export function deepMerge<T>(current: T, patch: unknown): T {
     if (value === undefined) continue;
 
     const existing = next[key];
-    next[key] = P.isObject(existing) && P.isObject(value) ? deepMerge(existing, value) : value;
+    next[key] =
+      P.isObject(existing) && P.isObject(value) && !Array.isArray(existing) && !Array.isArray(value)
+        ? deepMerge(existing, value)
+        : value;
   }
 
   return next as T;
