# `Sigra.Install.MigrationTimestamps`
[🔗](https://github.com/sztheory/sigra/blob/v1.20.0/lib/sigra/install/migration_timestamps.ex#L1)

Deterministic slot-based timestamp allocator for installer
migrations (GEN-07).

Replaces the old `offset_timestamp/1` helper that lived in
`Mix.Tasks.Sigra.Install` before Phase 11, which based timestamps
on `:calendar.universal_time`, making re-runs
non-deterministic and cross-feature ordering implicit. The slot
allocator:

  1. Walks the canonical feature list in order.
  2. For each feature, iterates `migrations/1` slot entries in the
     order the feature returned them.
  3. Assigns `base_time + N seconds` where `N` is a globally
     incrementing counter across all features.

This means `Features.Core`'s `:primary` slot always gets an earlier
timestamp than `Features.Organizations`'s first slot, regardless
of wall-clock time. Cross-feature ordering is static, not timing-
dependent.

Idempotent re-run is handled by the walker layer: if a migration
file already exists on disk that matches `target_basename`, the
walker reuses its filename instead of allocating a new timestamp.

# `allocate`

```elixir
@spec allocate(features :: [module()], base_time :: DateTime.t()) :: %{
  required(module()) => %{required(atom()) => String.t()}
}
```

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*Consult [api-reference.md](api-reference.md) for complete listing*