> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ironlabs.ai/llms.txt
> Use this file to discover all available pages before exploring further.
# Reasoning effort
> Instant, Low, Medium, High — the four levels of how hard reasoning models think.
Reasoning models can think for milliseconds or for many seconds. Foundry exposes that choice as a four-level dial in **Settings → Reasoning Effort**.
**Pro feature.** Reasoning Effort is available on Pro plans.
**Screenshot coming.** Effort dropdown.
## The four levels
| Level | When to use | What it buys you |
| ----------- | ------------------------------------------ | ------------------------------------------- |
| **Instant** | Quick lookups, casual replies | No reasoning. Fastest. Cheapest. |
| **Low** | Light synthesis, simple multi-step | Brief reasoning trace. Snappy. |
| **Medium** | Coding, analysis, comparisons | Balanced. The default for serious work. |
| **High** | Hard math, long planning, complex research | Deepest trace. Slowest. Highest token cost. |
The dial applies to **every routed reply** until you change it.
## What "instant" means
`Instant` turns reasoning **off**, even when the routed model is reasoning-capable. The reply behaves like a regular chat completion. The Reasoning block doesn't render.
## Picking a level
Most people pick **Medium** and leave it there. Move to **High** for one-off hard problems, **Low** when you want speed, **Instant** when you don't want any thinking.
The footer of every reply tells you which level was used so you can audit cost and latency.
## Limits
* Reasoning Effort only affects **reasoning-capable** models. If the router picks a non-reasoning model for your prompt, the level is ignored.
* High runs can take 30+ seconds on the hardest prompts. Pair with [browser notifications](/foundry/chat/notifications) so you don't sit and watch.
## Related
Watch the trace stream.
Concept overview.