# ADR-0008: Shared `var/t1` / `var/t3` runtime paths; state out of Git

## Status

Accepted (2026-07-08)

## Context

Compose, the k3d fleet, and the ground offload job all need to read and write
the same data lake, so that "go live" in the prototype shows the data the
simulator just generated. Early on, Terraform state and the provider cache were
accidentally committed (~6 MB of `*.tfstate` and a vendored provider binary),
polluting history and risking stale/secret data in Git.

## Decision

Standardise two **gitignored** runtime directories at the repo root:

| Path | Tier | Contents |
| --- | --- | --- |
| `var/t1/` | T1 live lake | In-flight Parquet from Compose or the k3d fleet |
| `var/t3/` | T3 warehouse | Offloaded historical partitions |

They are created automatically and overridable via
`SWARM_T1_DIR` / `SWARM_WAREHOUSE_DATA` / `SWARM_SIM_DATA`. Treat `var/` as
**runtime-only** per the ecosystem canonical layout. `.gitignore` excludes
`*.tfstate`, `*.tfstate.backup`, and `.terraform/` while **keeping**
`.terraform.lock.hcl` (the lock is source, the state is not).

## Consequences

- One lake feeds every component; the live prototype reflects real generated
  data.
- Git history carries no machine state or large binaries; `terraform` treats
  its state as local/remote-backend concern, not versioned source.
- Ownership of these paths is fixed to uid 10001
  ([ADR-0007](ADR-0007-non-root-image.md)).
- Recovery from earlier state drift is documented in
  [`../../infra/terraform/README.md`](../../infra/terraform/README.md)
  (`terraform import`).