You've felt it. The first twenty minutes with Claude Code, Cursor, or whatever agent you live in are magic. It nails the refactor, remembers your conventions, one-shots the test.
Then, an hour in, it turns into an intern who skipped lunch. It forgets a function you defined ten messages ago. It re-suggests a fix you already rejected. It loops. You start a sentence with "as I said earlier..." and feel slightly insane.
Everyone has a theory. "The model got nerfed." "It's MCP." "They're throttling me." I believed all three at various points.
The boring truth is none of them. It's your context window quietly filling up with garbage — and I can show you exactly where the garbage comes from.
The model didn't get dumber. The signal did.
