Long coding-agent sessions blow past any window. Compaction compresses history so work can continue, but early instructions and style rules often die unless they live above the line (system prompt, CLAUDE.md, AGENTS.md).

A write gate decides what enters permanent memory. Checkpointing saves state between nodes; durable execution plus idempotency is what keeps side effects safe when a process dies mid-node. Treat memory as an attack surface: one poisoned write can persist across sessions.