Expire Stale Memories Without Losing Active Goals

Expire stale transient memories while preserving context needed for active goals.

Problem statement

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Implement TTLMemory(ttl_seconds, count_tokens, max_tokens). - add(role, content) appends a message with the current timestamp. - render() returns messages that: 1. Have not expired (age < ttl_seconds). 2. Fit within max_tokens (dropping oldest non-expired first). Always keep the first system message if present. - stats() returns {"total_added": int, "expired": int, "active": int}. - total_added: total messages ever added (excluding evicted). - expired: messages removed due to TTL. - active: messages currently in the internal store.

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solution.py

import time

class TTLMemory:
    def __init__(self, ttl_seconds: int, count_tokens, max_tokens):
        self.ttl_seconds = ttl_seconds
        self.count_tokens = count_tokens
        self.max_tokens = max_tokens
        self.messages: list[dict] = []
        self.total_added = 0
        self.expired_count = 0

    def add(self, role: str, content: str) -> None:
        self.messages.append({
            "role": role,
            "content": content,
            "timestamp": time.time()
        })
        self.total_added += 1

    def render(self) -> list[dict]:

Filter expired, apply budget, return active messages


    def stats(self) -> dict:
        active = len(self.messages)
        return {
            "total_added": self.total_added,
            "expired": self.expired_count,
            "active": active,
        }

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import time class TTLMemory: def __init__(self, ttl_seconds: int, count_tokens, max_tokens): self.ttl_seconds = ttl_seconds self.count_tokens = count_tokens self.max_tokens = max_tokens self.messages: list[dict] = [] self.total_added = 0 self.expired_count = 0 def add(self, role: str, content: str) -> None: self.messages.append({ "role": role, "content": content, "timestamp": time.time() }) self.total_added += 1 def render(self) -> list[dict]:

def stats(self) -> dict: active = len(self.messages) return { "total_added": self.total_added, "expired": self.expired_count, "active": active, }