---
title: "Floor and ceiling"
description: "Theo Browne argues that a model's ordinary reliability matters more than its peak on long agent runs."
plain: "Theo says a model's ordinary reliability matters more than its best result when an agent works for hours."
group: concept
terms:
  - "floor and ceiling"
  - "model floor"
sources:
  - url: https://youtu.be/iBrAWpjXNxs?t=259
    title: "Please stop using stupid models - YouTube"
    publisher: "Theo Browne"
    note: "Reliability argument; used to distinguish the ordinary floor from peak performance."
    accessed: "2026-10-01"
  - url: https://youtu.be/iBrAWpjXNxs?t=1359
    title: "Please stop using stupid models - YouTube"
    publisher: "Theo Browne"
    note: "Failure-rate example; used for compounding errors over long agent runs."
    accessed: "2026-10-01"
---

# Floor and ceiling

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Theo distinguishes a model's best performance from its ordinary reliability, which he calls the floor. He calls best performance the ceiling. He says the floor matters more when an agent must work through a long task. [04:19](https://youtu.be/iBrAWpjXNxs?t=259) [05:31](https://youtu.be/iBrAWpjXNxs?t=331).

He illustrates how small failure rates across repeated time windows compound over a four-hour run. [22:39](https://youtu.be/iBrAWpjXNxs?t=1359) [23:19](https://youtu.be/iBrAWpjXNxs?t=1399).

See [Theo Browne: Please stop using stupid models](/lore/theo-please-stop-using-stupid-models).

## Sources

1. [Please stop using stupid models - YouTube](https://youtu.be/iBrAWpjXNxs?t=259)
   Theo Browne. Reliability argument; used to distinguish the ordinary floor from peak performance. Accessed 2026-10-01.

2. [Please stop using stupid models - YouTube](https://youtu.be/iBrAWpjXNxs?t=1359)
   Theo Browne. Failure-rate example; used for compounding errors over long agent runs. Accessed 2026-10-01.

## Linked from

- Agent guide → An Effect stack so pure (aspirational) Kit Langton will blush. → [Read page](https://ratstack.sh/llms.txt)

- Change log → What changed in the files served here, newest first. → [Read page](https://ratstack.sh/log)

- Full agent guide → An Effect stack so pure (aspirational) Kit Langton will blush. → [Read page](https://ratstack.sh/llms-full.txt)

- Rat Stack lore | rat-stack → Short, source-grounded notes on the ideas and decisions behind rat-stack. → [Read page](https://ratstack.sh/lore)

- Source change history (log.md) → The generated change log as Markdown. → [Read page](https://ratstack.sh/log.md)