fix(responses): keep the empty-completion notice to one log record

src/server/responses/core.ts

@@ -371,6 +371,7 @@ import { responsesJsonToSseStream } from "../responses-json-events";
 import { guardTerminalEventStream } from "./terminal-guard";
 import {
   emptyCompletionRetryEnabled,
+  emptyCompletionNotice,
   observeEmptyCompletion,
   guardEmptyCompletionEventStream,
 } from "./empty-completion-guard";
@@ -5271,10 +5272,7 @@ async function handleResponsesInner(
         // result (#2472). Retrying by default would re-send a turn that may already have had
         // billable side effects, so the honest default is observability, not recovery.
         : observeEmptyCompletion(eventSource, () => {
-          console.warn(
-            `[opencodex] ${route.providerName}/${route.modelId} completed with no output text `
-            + "and no tool call. Set \"emptyCompletionRetry\": true to retry such turns once.",
-          );
+          console.warn(emptyCompletionNotice(route.providerName, route.modelId));
         });
       const sseStream = bridgeToResponsesSSE(
         guardedSource, parsed._responseModelId ?? parsed.modelId, toolNsMap, freeformToolNames, toolSearchToolNames,

src/server/responses/empty-completion-guard.ts

@@ -1,4 +1,5 @@
 import type { AdapterEvent, OcxConfig, OcxUsage } from "../../types";
+import { sanitizeLogMetadataString } from "../../lib/redact";
 
 /**
  * Empty-completion guard for Responses turns (port of codex-router's
@@ -21,6 +22,21 @@ import type { AdapterEvent, OcxConfig, OcxUsage } from "../../types";
  */
 export const EMPTY_COMPLETION_RETRY_ENV = "OCX_EMPTY_COMPLETION_RETRY";
 
+/**
+ * The observability notice for a turn that ended empty with the retry guard off.
+ *
+ * Both labels are caller-supplied: the request names its provider and model. Interpolated raw,
+ * a model name carrying newlines or terminal escapes writes additional lines into whatever
+ * reads this warning, so a caller could forge log records it never produced. Both are reduced
+ * to bounded single-line metadata first.
+ */
+export function emptyCompletionNotice(providerName: unknown, modelId: unknown): string {
+  const provider = sanitizeLogMetadataString(providerName) ?? "unknown";
+  const model = sanitizeLogMetadataString(modelId) ?? "unknown";
+  return `[opencodex] ${provider}/${model} completed with no output text and no tool call. `
+    + "Set \"emptyCompletionRetry\": true to retry such turns once.";
+}
+
 /** Retained pre-content events are bounded independently by count and encoded size. */
 export const EMPTY_COMPLETION_MAX_BUFFERED_EVENTS = 1_024;
 export const EMPTY_COMPLETION_MAX_BUFFERED_BYTES = 1_048_576;

tests/empty-completion-guard.test.ts

@@ -3,6 +3,7 @@ import {
   EMPTY_COMPLETION_RETRY_ENV,
   EMPTY_COMPLETION_RETRY_FAILED_CODE,
   emptyCompletionRetryEnabled,
+  emptyCompletionNotice,
   guardEmptyCompletionEventStream,
   isContentEvent,
   observeEmptyCompletion,
@@ -443,5 +444,28 @@ describe("#2472 an empty turn is observable even when the retry guard is off", (
     const { empties } = await drain([]);
     expect(empties).toBe(1);
   });
-});
 
+  test("the notice cannot be forged through the caller-supplied provider or model label", () => {
+    // Both labels come from the request. Interpolated raw, a model name carrying newlines or
+    // terminal escapes writes extra lines into whatever reads this warning, so a caller could
+    // fabricate log records it never produced.
+    const notice = emptyCompletionNotice(
+      "fixture",
+      "model\r\n[opencodex] forged: injected\u001b[31m",
+    );
+
+    expect(notice).not.toContain("\n");
+    expect(notice).not.toContain("\r");
+    expect(notice).not.toContain("\u001b");
+    expect(notice).toContain("completed with no output text and no tool call");
+    // The forged text may survive as inert characters; what must not survive is its ability to
+    // become a separate record, so the notice stays exactly one line.
+    expect(notice.split(/\r|\n|\u2028|\u2029/)).toHaveLength(1);
+  });
+
+  test("the notice still names an ordinary route and degrades to a stated placeholder", () => {
+    expect(emptyCompletionNotice("fixture", "gpt-5.4")).toContain("fixture/gpt-5.4");
+    // An unusable label must not silently vanish into an empty slot in the sentence.
+    expect(emptyCompletionNotice(undefined, "")).toContain("unknown/unknown");
+  });
+});