Codex Context Engine trims token waste

This is less prompt hacking than building a local operating layer for Codex. The smartest part is not memory by itself, but selective retrieval plus policy: the engine decides what context matters before the model burns tokens on it.

• –The layered stack is unusually complete: planner, optimizer, failure memory, task memory, graph links, telemetry, and mods all attack the same context churn problem.
• –The savings story is still early and low-confidence; the article itself treats the telemetry window as short and the gains as directional.
• –Domain mods are the real leap because they turn repeated workflows like UX and frontend into reusable expertise instead of one-off prompts.
• –The MCP and local-file hooks make this feel like real infrastructure for agent workflows, but they also raise the maintenance burden and stale-context risk.