fix(agents): skip compaction API call when session has no real messages (#36451)

Merged via squash.

Prepared head SHA: 52dd631789
Co-authored-by: Sid-Qin <201593046+Sid-Qin@users.noreply.github.com>
Co-authored-by: jalehman <550978+jalehman@users.noreply.github.com>
Reviewed-by: @jalehman

CHANGELOG.md

@@ -26,6 +26,7 @@ Docs: https://docs.openclaw.ai
 
 ### Fixes
 
+- Agents/compaction safeguard pre-check: skip embedded compaction before entering the Pi SDK when a session has no real conversation messages, avoiding unnecessary LLM API calls on idle sessions. (#36451) thanks @Sid-Qin.
 - iMessage/cron completion announces: strip leaked inline reply tags (for example `[[reply_to:6100]]`) from user-visible completion text so announcement deliveries do not expose threading metadata. (#24600) Thanks @vincentkoc.
 - Feishu/group slash command detection: normalize group mention wrappers before command-authorization probing so mention-prefixed commands (for example `@Bot/model` and `@Bot /reset`) are recognized as gateway commands instead of being forwarded to the agent. (#35994) Thanks @liuxiaopai-ai.
 - Agents/context pruning: guard assistant thinking/text char estimation against malformed blocks (missing `thinking`/`text` strings or null entries) so pruning no longer crashes with malformed provider content. (openclaw#35146) thanks @Sid-Qin.

src/agents/pi-embedded-runner/compact.ts

@@ -132,6 +132,10 @@ type CompactionMessageMetrics = {
   contributors: Array<{ role: string; chars: number; tool?: string }>;
 };
 
+function hasRealConversationContent(msg: AgentMessage): boolean {
+  return msg.role === "user" || msg.role === "assistant" || msg.role === "toolResult";
+}
+
 function createCompactionDiagId(): string {
   return `cmp-${Date.now().toString(36)}-${generateSecureToken(4)}`;
 }
@@ -663,6 +667,17 @@ export async function compactEmbeddedPiSessionDirect(
           );
         }
 
+        if (!session.messages.some(hasRealConversationContent)) {
+          log.info(
+            `[compaction] skipping — no real conversation messages (sessionKey=${params.sessionKey ?? params.sessionId})`,
+          );
+          return {
+            ok: true,
+            compacted: false,
+            reason: "no real conversation messages",
+          };
+        }
+
         const compactStartedAt = Date.now();
         const result = await compactWithSafetyTimeout(() =>
           session.compact(params.customInstructions),