Hidden cost of context drift
The signs your session is gradually losing accuracy — and the restart hygiene that compounds.
Why long sessions decay
A session that’s sharp at hour 1 isn’t the same session at hour 5. Working memory has accumulated intermediate context — drafts, dead ends, in-progress reasoning — that increasingly competes with the original task and constraints. The agent doesn’t notice the decay; the operator often doesn’t either, until shipped output reveals the drift after the fact.
The decay is structural, not motivational. No amount of operator discipline prevents the gradual loss of session-start context across hours of working memory. The fix isn’t to push harder — it’s to detect drift and restart cleanly before output suffers.
Restart is engineering hygiene, not failure. A 10-minute structured restart usually ships better output than the next 60 minutes of pushed-through work. The discipline is recognizing the moment.
Three drift signals
Watch for any of these. One signal is a soft restart trigger; two or more is hard.
| Signal | What it indicates | How to detect |
|---|---|---|
| Forgotten constraints | Session-start context has dropped from working memory | Agent proposes something you explicitly ruled out and doesn’t remember the rule |
| Compounding hallucinations | Working memory has accumulated wrong facts as established truth | Ground-truth check: agent can’t verify a recent claim against the actual code |
| Scope drift | Session has lost its anchor; conversation is wandering | Anchor check: agent can’t cleanly name the original task and how current work serves it |
The signals usually appear in order. Forgotten constraints come first (1-3 hours). Hallucinations next (3-5 hours). Scope drift last (5+ hours). Catching the early signals saves the session; catching the late ones means you’ve already shipped some compromised work.
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Hidden cost of agent context drift (and how to detect it)
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