# Custom GitHub Actions Runners

## Available Runners

| Runner Label               | Architecture | Size   | Ephemeral | Notes                                                      |
| -------------------------- | ------------ | ------ | --------- | ---------------------------------------------------------- |
| `runner-small`             | x86_64       | Small  | No        | Light tasks: linting, formatting, validation               |
| `runner-medium`            | x86_64       | Medium | No        | Standard CI: tests, builds                                 |
| `runner-medium-arm64`      | arm64        | Medium | No        | ARM64 builds and tests                                     |
| `runner-large`             | x86_64       | Large  | No        | Heavy workloads: benchmarks, coverage, release builds      |
| `runner-large-spot`        | x86_64       | Large  | Yes       | Cost-optimized large jobs where interruption is acceptable |
| `runner-medium-arm64-spot` | arm64        | Medium | Yes       | Cost-optimized ARM64 jobs where interruption is acceptable |

## Spot Runners

Spot runners (`*-spot`) use ephemeral cloud instances provisioned on a best-effort basis. They are significantly cheaper but can be preempted at any time if the cloud provider reclaims capacity.

**Use spot runners for:**

- Jobs that can be retried without consequence (test suites, linting)
- Non-time-critical workloads
- PR validation where re-runs are acceptable

**Do not use spot runners for:**

- Benchmarks (preemption and noisy-neighbor effects skew results)
- Release builds and publishing
- Jobs requiring consistent, reproducible timing

## Choosing a Runner

| Workload                        | Recommended Runner         |
| ------------------------------- | -------------------------- |
| Linting, formatting, validation | `runner-small`             |
| Unit tests, standard builds     | `runner-medium`            |
| ARM64 cross-compilation / tests | `runner-medium-arm64`      |
| Benchmarks, coverage reports    | `runner-large`             |
| Non-critical large builds       | `runner-large-spot`        |
| Non-critical ARM64 builds       | `runner-medium-arm64-spot` |