Count only a non-empty streamed reply as finished, so an empty one is refunded

Author: Programcode

supabase/functions/ai/provider.ts

@@ -218,8 +218,9 @@ export interface GenerationStream {
   /** The request moved to a step that writes nothing yet. */
   phase: (name: GenerationPhase) => void;
   /**
-   * The model ended its answer (any finish_reason but "length", which is
-   * retried). Arrives before the usage trailer, which a disconnect can lose.
+   * The model ended a non-empty answer (any finish_reason but "length",
+   * which is retried, or [DONE]). Arrives before the usage trailer, which a
+   * disconnect can lose.
    */
   finished?: () => void;
 }
@@ -484,8 +485,9 @@ export async function readOpenRouterStream(
     const data = trimmed.slice("data:".length).trim();
     if (data === "[DONE]") {
       done = true;
-      // A stream that ends without a finish_reason still finished its answer.
-      if (!finishReason) stream.finished?.();
+      // A stream that ends without a finish_reason still finished its answer,
+      // if it wrote one: an empty reply is a failure, not an answer.
+      if (!finishReason && text) stream.finished?.();
       return;
     }
     let chunk: OpenRouterStreamChunk;
@@ -510,7 +512,7 @@ export async function readOpenRouterStream(
       stream.delta(content);
     }
     if (typeof choice?.finish_reason === "string" && choice.finish_reason) {
-      if (!finishReason && choice.finish_reason !== "length") stream.finished?.();
+      if (!finishReason && choice.finish_reason !== "length" && text) stream.finished?.();
       finishReason = choice.finish_reason;
     }
   };

supabase/functions/ai/quota-sessions_test.ts

@@ -333,6 +333,21 @@ Deno.test("a finished answer stays charged when the provider connection drops be
   }
 });
 
+Deno.test("an empty streamed reply is refunded even though the model said it finished", async () => {
+  const originalError = console.error;
+  console.error = () => undefined;
+  install();
+  try {
+    reset({ content: "" });
+    const text = await (await send({ feature: "ask", input: { message: "A question", mode: "general", webSearch: false }, stream: true })).text();
+    assertEquals(rpcNames(), ["consume_ai_quota", "refund_daily_quota"]);
+    assertEquals(text.includes('"charged":false'), true);
+  } finally {
+    globalThis.fetch = originalFetch;
+    console.error = originalError;
+  }
+});
+
 Deno.test("a quota check reports a round's cost and what is left without reserving", async () => {
   install();
   try {