初始化提交

backend/app/skills/context_budget.py

@@ -0,0 +1,47 @@
+"""上下文预算守卫：历史过长时折叠中间消息，保护 prompt 预算。"""
+
+from app.ai_provider.types.messages import BaseMessage
+from app.application.agent.extensions import (
+    AgentContext,
+    AgentRunContext,
+    ExtensionRegistry,
+)
+from app.application.agent.python_skills import PythonSkillDefinition
+
+# messages 总字符数软上限；超出则保留首条与末尾 _TAIL_KEEP 条，中间折叠。
+_MAX_CONTEXT_CHARS = 12000
+_TAIL_KEEP = 8
+
+
+async def _trim_history(context: AgentContext, _run: AgentRunContext) -> AgentContext:
+    messages = context.messages
+    total = sum(len(message.content) for message in messages)
+    if total <= _MAX_CONTEXT_CHARS or len(messages) <= _TAIL_KEEP + 1:
+        return context
+    first = messages[0]
+    tail = messages[-_TAIL_KEEP:]
+    dropped = len(messages) - 1 - _TAIL_KEEP
+    # 在首条追加折叠提示（新建对象避免污染原 message）；不在历史中间插入新消息，
+    # 以免破坏 provider 对 system 位置或多轮 tool 消息配对的预期。
+    folded = BaseMessage(
+        content=f"{first.content}\n\n[已省略 {dropped} 条较早历史]",
+        role=first.role,
+    )
+    return AgentContext(
+        messages=(folded, *tail),
+        tools=context.tools,
+        model_hint=context.model_hint,
+    )
+
+
+def _setup(registry: ExtensionRegistry) -> None:
+    registry.add_context_transformer(_trim_history)
+
+
+SKILL = PythonSkillDefinition(
+    name="context_budget",
+    description="对话历史过长时折叠中间消息，控制 prompt 预算。",
+    triggers=("长对话", "context", "历史"),
+    instructions="历史较长时优先依赖近期消息，不必回溯很早的内容。",
+    setup=_setup,
+)