fix(cron): reuse existing sessionId for webhook/cron sessions

When a webhook or cron job provides a stable sessionKey, the session
should maintain conversation history across invocations. Previously,
resolveCronSession always generated a new sessionId and hardcoded
isNewSession: true, preventing any conversation continuity.

Changes:
- Check if existing entry has a valid sessionId
- Evaluate freshness using configured reset policy
- Reuse sessionId and set isNewSession: false when fresh
- Add forceNew parameter to override reuse behavior
- Spread existing entry to preserve conversation context

This enables persistent, stateful conversations for webhook-driven
agent endpoints when allowRequestSessionKey is configured.

Fixes #18027

src/cron/isolated-agent/session.ts

@@ -1,12 +1,19 @@
 import crypto from "node:crypto";
 import type { OpenClawConfig } from "../../config/config.js";
-import { loadSessionStore, resolveStorePath, type SessionEntry } from "../../config/sessions.js";
+import {
+  evaluateSessionFreshness,
+  loadSessionStore,
+  resolveSessionResetPolicy,
+  resolveStorePath,
+  type SessionEntry,
+} from "../../config/sessions.js";
 
 export function resolveCronSession(params: {
   cfg: OpenClawConfig;
   sessionKey: string;
   nowMs: number;
   agentId: string;
+  forceNew?: boolean;
 }) {
   const sessionCfg = params.cfg.session;
   const storePath = resolveStorePath(sessionCfg?.store, {
@@ -14,12 +21,50 @@ export function resolveCronSession(params: {
   });
   const store = loadSessionStore(storePath);
   const entry = store[params.sessionKey];
-  const sessionId = crypto.randomUUID();
-  const systemSent = false;
+
+  // Check if we can reuse an existing session
+  let sessionId: string;
+  let isNewSession: boolean;
+  let systemSent: boolean;
+
+  if (!params.forceNew && entry?.sessionId) {
+    // Evaluate freshness using the configured reset policy
+    // Cron/webhook sessions use "direct" reset type (1:1 conversation style)
+    const resetPolicy = resolveSessionResetPolicy({
+      sessionCfg,
+      resetType: "direct",
+    });
+    const freshness = evaluateSessionFreshness({
+      updatedAt: entry.updatedAt,
+      now: params.nowMs,
+      policy: resetPolicy,
+    });
+
+    if (freshness.fresh) {
+      // Reuse existing session
+      sessionId = entry.sessionId;
+      isNewSession = false;
+      systemSent = entry.systemSent ?? false;
+    } else {
+      // Session expired, create new
+      sessionId = crypto.randomUUID();
+      isNewSession = true;
+      systemSent = false;
+    }
+  } else {
+    // No existing session or forced new
+    sessionId = crypto.randomUUID();
+    isNewSession = true;
+    systemSent = false;
+  }
+
   const sessionEntry: SessionEntry = {
+    // Spread existing entry to preserve conversation context when reusing
+    ...(isNewSession ? undefined : entry),
     sessionId,
     updatedAt: params.nowMs,
     systemSent,
+    // Preserve user preferences from existing entry
     thinkingLevel: entry?.thinkingLevel,
     verboseLevel: entry?.verboseLevel,
     model: entry?.model,
@@ -34,5 +79,5 @@ export function resolveCronSession(params: {
     displayName: entry?.displayName,
     skillsSnapshot: entry?.skillsSnapshot,
   };
-  return { storePath, store, sessionEntry, systemSent, isNewSession: true };
+  return { storePath, store, sessionEntry, systemSent, isNewSession };
 }