fix(compaction): preserve assistant messages before surviving users in rotated transcript

OpenClaw Agent · OpenClaw Agent · commit 02e903152e0f · 2026-05-03T22:31:50.000+08:00
When compaction rotation creates a new session file via buildSuccessorEntries, all messages before firstKeptEntryId are marked for removal. This causes assistant replies to be dropped while user messages survive, resulting in consecutive user messages with no intermediate reply in the rotated transcript. When the agent reads the rotated transcript, it sees unanswered user messages and treats multiple turns as a single combined input, causing replies to 'disappear' from the Control UI/webchat and subsequent messages to be bundled together in a single LLM call. The fix preserves the last assistant message directly preceding each surviving user message, maintaining conversational turn structure (user → assistant → user → assistant) in the rotated transcript. Fixes #76729
diff --git a/src/agents/pi-embedded-runner/compaction-successor-transcript.ts b/src/agents/pi-embedded-runner/compaction-successor-transcript.ts
@@ -151,6 +151,11 @@ function buildSuccessorEntries(params: {
       removedIds.add(entry.id);
     }
   }
+  // Preserve assistant messages that precede surviving user messages.
+  // Otherwise the rotated transcript may show consecutive user messages
+  // with no intermediate reply, causing the agent to treat multiple turns
+  // as one combined input.
+  preserveLastAssistantBeforeSurvivingUser(allEntries, removedIds);
 
   const entryById = new Map(allEntries.map((entry) => [entry.id, entry]));
   const activeBranchIds = new Set(branch.map((entry) => entry.id));
@@ -178,6 +183,52 @@ function buildSuccessorEntries(params: {
   });
 }
 
+/**
+ * Preserve assistant messages that directly precede surviving user messages.
+ * Without this, the rotated transcript may contain consecutive user messages
+ * with no intermediate replies, causing the agent to treat multiple turns
+ * as a single combined input (since it sees unanswered user messages).
+ */
+function preserveLastAssistantBeforeSurvivingUser(
+  allEntries: SessionEntry[],
+  removedIds: Set<string>,
+): void {
+  // Collect surviving user message ids
+  const survivingUserIds = new Set<string>();
+  for (const entry of allEntries) {
+    if (
+      entry.type === "message" &&
+      typeof entry.message === "object" &&
+      entry.message !== null &&
+      (entry.message as { role?: string }).role === "user" &&
+      !removedIds.has(entry.id)
+    ) {
+      survivingUserIds.add(entry.id);
+    }
+  }
+
+  if (survivingUserIds.size === 0) return;
+
+  // Scan for removed assistant messages; if the next surviving user
+  // message directly follows (no intervening surviving user), keep it.
+  let pendingAssistantId: string | undefined;
+  for (const entry of allEntries) {
+    if (entry.type === "message" && typeof entry.message === "object" && entry.message !== null) {
+      const role = (entry.message as { role?: string }).role;
+      if (role === "assistant" && removedIds.has(entry.id)) {
+        pendingAssistantId = entry.id;
+      } else if (role === "user") {
+        if (survivingUserIds.has(entry.id) && pendingAssistantId) {
+          removedIds.delete(pendingAssistantId);
+        }
+        pendingAssistantId = undefined;
+      } else if (role !== "toolResult") {
+        pendingAssistantId = undefined;
+      }
+    }
+  }
+}
+
 function collectLatestStateEntryIds(entries: SessionEntry[]): Set<string> {
   const latestByType = new Map<string, SessionEntry>();
   for (const entry of entries) {
diff --git a/src/auto-reply/reply/reply-run-registry.compaction-regression.test.ts b/src/auto-reply/reply/reply-run-registry.compaction-regression.test.ts
@@ -3,10 +3,8 @@ import {
   __testing,
   createReplyOperation,
   forceClearReplyRunBySessionId,
-  isReplyRunActiveForSessionId,
   queueReplyRunMessage,
   replyRunRegistry,
-  waitForReplyRunEndBySessionId,
 } from "./reply-run-registry.js";
 
 describe("reply run registry – preflight compaction regression", () => {
