We spent a year teaching coding agents to remember things. Remembering turned out to be the easy part. The hard part is knowing which of those memories are still true .

Here's the failure that finally got me.

A guess, promoted to a fact

I told Cursor my project had switched from npm to bun . Later, over in Claude Code, the agent confidently ran npm install and spent a while debugging a build that was never going to work. The "we use npm" belief had outlived the truth — and nothing flagged it, because to the agent it looked exactly like every other fact in memory.

Same shape as the classic one: "we use Jest" survives a migration to Vitest, and three sessions later an agent is cheerfully writing Jest tests for a repo that doesn't have Jest anymore.

Neither of these is a forgetting problem. The agent remembered fine.…