feat(agent): put time-now header to the end of system prompt to increase the cache rate

agent/src/prompts/system.ts

@@ -37,8 +37,13 @@ export const system = ({
   soulContent,
   toolsContent,
 }: SystemParams) => {
-  const headers = {
+  // ── Static section (stable prefix for LLM prompt caching) ──────────
+  const staticHeaders = {
     'language': language,
+  }
+
+  // ── Dynamic section (appended at the end to preserve cache prefix) ─
+  const dynamicHeaders = {
     'available-channels': channels.join(','),
     'current-session-channel': currentChannel,
     'max-context-load-time': maxContextLoadTime.toString(),
@@ -47,7 +52,7 @@ export const system = ({
 
   return `
 ---
-${Bun.YAML.stringify(headers)}
+${Bun.YAML.stringify(staticHeaders)}
 ---
 You are an AI agent, and now you wake up.
 
@@ -84,13 +89,11 @@ Before anything else:
 ## Safety
 
 - Keep private data private
-- Don’t run destructive commands without asking
+- Don't run destructive commands without asking
 - When in doubt, ask
 
 ## Memory
 
-Your context is loaded from the recent of ${maxContextLoadTime} minutes (${(maxContextLoadTime / 60).toFixed(2)} hours).
-
 For memory more previous, please use ${quote('search_memory')} tool.
 
 ## Contacts
@@ -101,8 +104,6 @@ You have a contacts book to record them that you do not need to worry about who
 
 ## Channels
 
-The current session (and the latest user message) is from channel: ${quote(currentChannel)}. You may receive messages from other channels listed in available-channels; each user message may include a ${quote('channel')} header indicating its source.
-
 You are able to receive and send messages or files to different channels.
 
 When you need to resolve a user or group on a channel (e.g. turn an open_id, user_id, or chat_id into a display name or handle), use the ${quote('lookup_channel_user')} tool: pass ${quote('platform')} (e.g. feishu, telegram), ${quote('input')} (the platform-specific id), and optionally ${quote('kind')} (${quote('user')} or ${quote('group')}). It returns name, handle, and id for that entry.
@@ -149,5 +150,15 @@ ${toolsContent}
 
 ${enabledSkills.map(skill => skillPrompt(skill)).join('\n\n---\n\n')}
 
+## Session Context
+
+---
+${Bun.YAML.stringify(dynamicHeaders)}
+---
+
+Your context is loaded from the recent of ${maxContextLoadTime} minutes (${(maxContextLoadTime / 60).toFixed(2)} hours).
+
+The current session (and the latest user message) is from channel: ${quote(currentChannel)}. You may receive messages from other channels listed in available-channels; each user message may include a ${quote('channel')} header indicating its source.
+
   `.trim()
 }