Find the advisor additions array by shape, not a fixed alias list

DeepSeek keeps inventing its own key for the additions array — first
"creatures", then "addCreatures". Chasing named aliases is whack-a-mole, so
detect it structurally: a known synonym first, else any top-level array of
{name, …} objects that isn't the "remove" list. Any invented key now resolves
to "add".

Tests cover creatures/addCreatures/monsters/an invented key, and that a lone
"remove" list is not mistaken for additions.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/lib/assistant/prompts.test.ts

@@ -49,17 +49,29 @@ describe('balanceSuggestionSchema', () => {
     expect(r.success).toBe(true);
     if (r.success) expect(r.data.add[0]!.count).toBe(2);
   });
-  it('accepts the "creatures" alias some models use for the add array', () => {
-    // Exact shape DeepSeek returned in the wild — array keyed "creatures", not "add".
-    const r = balanceSuggestionSchema.safeParse({
-      creatures: [{ name: 'Berserker', count: 1 }],
-      reasoning: 'Adding one CR 2 Berserker makes this deadly for a lone level 1 paladin.',
-      targetDifficulty: 'deadly',
-    });
-    expect(r.success).toBe(true);
-    if (r.success) {
-      expect(r.data.add).toHaveLength(1);
-      expect(r.data.add[0]!.name).toBe('Berserker');
+  it('finds the add array whatever the model names it', () => {
+    // Exact shapes DeepSeek returned in the wild: "creatures", then "addCreatures".
+    for (const key of ['creatures', 'addCreatures', 'monsters', 'someInventedKey'] as const) {
+      const r = balanceSuggestionSchema.safeParse({
+        [key]: [{ name: 'Goblin', count: 2 }],
+        reasoning: 'Two goblins push this to Deadly for a lone level 1 paladin.',
+        targetDifficulty: 'Deadly',
+      });
+      expect(r.success, `key="${key}"`).toBe(true);
+      if (r.success) {
+        expect(r.data.add).toHaveLength(1);
+        expect(r.data.add[0]!.name).toBe('Goblin');
+        expect(r.data.add[0]!.count).toBe(2);
+      }
     }
   });
+  it('does not mistake the remove list for additions', () => {
+    const r = balanceSuggestionSchema.safeParse({
+      remove: [{ name: 'Ogre', count: 1 }],
+      reasoning: 'Drop the ogre to ease this fight.',
+      targetDifficulty: 'Medium',
+    });
+    // No additions array at all → add is required and absent → reject.
+    expect(r.success).toBe(false);
+  });
 });

src/lib/assistant/prompts.ts

@@ -7,18 +7,31 @@ import type { CampaignContext, CreatureCandidate } from './context';
 // over-eager suggestion is accepted rather than rejecting the whole response.
 const monsterCount = z.coerce.number().int().min(1).max(12);
 
+/** An array of at least one `{ name, … }` object — the shape of an additions list. */
+function looksLikeCreatureList(v: unknown): v is Record<string, unknown>[] {
+  return Array.isArray(v) && v.length > 0 &&
+    v.every((x) => !!x && typeof x === 'object' && typeof (x as { name?: unknown }).name === 'string');
+}
+
 /**
- * Models sometimes name the additions array "creatures"/"monsters" instead of the
- * expected "add" (DeepSeek does this). Normalize those synonyms before validation
- * so a correct suggestion isn't discarded over a key-name mismatch.
+ * Models keep inventing their own name for the additions array — DeepSeek has
+ * returned "creatures", "addCreatures", … instead of the expected "add". Rather
+ * than chase a fixed alias list, find the additions array structurally: a known
+ * synonym first, else any other top-level array of `{ name, … }` objects that
+ * isn't the "remove" list. Keeps a correct suggestion from being discarded over a
+ * key-name mismatch.
  */
 function normalizeBalanceShape(raw: unknown): unknown {
   if (!raw || typeof raw !== 'object' || Array.isArray(raw)) return raw;
   const o = { ...(raw as Record<string, unknown>) };
-  if (o.add === undefined) {
-    for (const alias of ['creatures', 'monsters', 'additions', 'addCreatures', 'add_creatures']) {
-      if (Array.isArray(o[alias])) { o.add = o[alias]; break; }
-    }
+  if (Array.isArray(o.add)) return o;
+
+  for (const alias of ['creatures', 'monsters', 'additions', 'addCreatures', 'add_creatures', 'toAdd']) {
+    if (looksLikeCreatureList(o[alias])) { o.add = o[alias]; return o; }
+  }
+  for (const [key, value] of Object.entries(o)) {
+    if (key === 'add' || key === 'remove') continue;
+    if (looksLikeCreatureList(value)) { o.add = value; return o; }
   }
   return o;
 }