# Alchemist: Pipeline Permutations

Reference for the pipeline shapes a ticket can run through.

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The Alchemist agent pipeline is content-shape, not time-shape. Which planner is chosen, and which model fills each slot, depends on the ticket's tier and the phase being run.

This page is a reference companion to [Agent Pipeline Configuration](/docs/guides/alchemist-pipeline-configuration), which is where you actually change these settings.

## Tier and slot

- **Plan.** The default planner runs at the `high` rung. The `max` tier, or an explicit request, upgrades to the strongest available planning model. The `fast` tier drops to a quicker model, and `economy` (explicit only) drops further.
- **Implement.** The default is tuned for fix quality per dollar, which is where most of a ticket's cost lands. The `max` tier upgrades to a frontier model. Trivial changes fall through to a mid-tier model.
- **Review, security, reconcile, and merge resolution.** Frontier models throughout. These phases are the safety net, so they are not cost-optimized.
- **Docs.** A large-context mid-tier model, since the docs pass has to hold the documentation corpus and the diff at once.
- **Investigate.** A fast, cheap model unless the `max` tier is set, which upgrades to frontier.

The `cheap` tier forces the fastest model across the board and skips the docs pass entirely.

> **Note:** Specific model assignments change as the platform re-benchmarks. Treat the tiering logic above as stable and the individual model names as current-state. Check the in-product **Model preferences** panel for the live per-tier caps.

## Choosing a tier for AV work

- **Client-facing production apps.** Default or `max`. The review and security passes are the reason you can hand the result to a client.
- **Internal tools and prototypes.** `fast` is usually fine.
- **Bulk refactors and cleanup.** `cheap` works, but read the diff before you ship it, since the docs pass is skipped.

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