fix: an empty reply whose budget went to reasoning is retried with room to write

Any call with a small max_tokens could come back blank from a reasoning
model: finish_reason=length, content empty, the budget spent thinking.
The shared LiteLLM call now retries that one signature once, with at least
6000 tokens and low reasoning effort, so no caller has to guess a budget.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Dv6sqaY6Vq3ChZHMem3cnU

src/utils/ai.js

@@ -356,6 +356,15 @@ async function callBedrock(messages, model, temperature, maxTokens) {
 // ============================================================
 // CALL LITELLM (OpenAI-compatible proxy)
 // ============================================================
+// A reasoning model spends part of max_tokens thinking before it writes. When
+// the budget is small (a query rewrite at 80, a milestone note at 500) it can
+// hit the limit with the whole budget spent on reasoning and nothing written:
+// a 200, finish_reason=length, content ''. Every caller then saw an empty
+// reply — the take-home sheet was the one the user noticed. The retry gives
+// the same request room to finish and asks for low reasoning effort; it fires
+// only for that signature, never for a genuinely empty answer.
+var REASONING_RETRY_FLOOR = 6000;
+
 async function callLiteLLM(messages, model, temperature, maxTokens, generation) {
   if (!litellmClient) throw new Error('LiteLLM not configured. Set LITELLM_API_BASE in .env');
 
@@ -375,6 +384,13 @@ async function callLiteLLM(messages, model, temperature, maxTokens, generation)
     var reasoningChars = String(choice.message.reasoning_content || choice.message.reasoning || '').length;
     console.warn('[ai] empty reply from ' + model + ': finish_reason=' + (choice.finish_reason || '?') +
       ' completion_tokens=' + (completion.usage && completion.usage.completion_tokens) + ' reasoning_chars=' + reasoningChars);
+    var starved = choice.finish_reason === 'length' && reasoningChars > 0 && !(generation && generation.reasoningRetried);
+    if (starved) {
+      var retryBudget = Math.max(REASONING_RETRY_FLOOR, (maxTokens || 0) * 4);
+      console.warn('[ai] reasoning consumed the budget; retrying ' + model + ' with max_tokens=' + retryBudget);
+      return callLiteLLM(messages, model, temperature, retryBudget,
+        Object.assign({}, generation || {}, { reasoningEffort: 'low', reasoningRetried: true }));
+    }
   }
   return {
     success: true,