First-class config providers (pydantic-settings / environment / TOML)

[lesnik512]

Migrated from ROADMAP.md's ## Under consideration section, which is being deleted — an unscheduled item belongs in the tracker, not in a third hand-maintained file. See #438.

Why it is open

Configuration is the dependency almost every graph has, and today it is wired
the same way as anything else — a Factory over a function the application
writes. A first-class provider for pydantic-settings, environment variables, or
TOML would remove that boilerplate.

What it must clear first

The conservative feature set
bar: a new provider type is added only when the existing primitives genuinely
cannot solve the task. A Factory wrapping Settings() already solves the
common case, so a proposal has to show what it cannot express. The
zero-dependency guarantee also rules out a hard dependency on
pydantic-settings or a TOML library in core.

Revisit trigger

A design that stays zero-dependency and expresses something Factory cannot.

[lesnik512]

This was generated by AI during triage.

Triage outcome: needs-info

Relabeling needs-triage → needs-info. This is not an un-evaluated item: #446 authored it with its reasoning, its bar, and a revisit trigger already in place. What it waits on is a design that does not exist yet, not a maintainer decision.

What is established:

• The zero-dependency bar is a fact, not an aspiration. pyproject.toml has no dependencies key at all, so a hard dependency on pydantic-settings or a TOML library is ruled out on its face.
• Factory already covers the common case, and the provider set is closed. Core ships four providers — Alias, ContextProvider, Factory, and the internal _ContainerProvider. ADR 0013 closed the set. A new provider type therefore has to clear the conservative-feature-set bar, not merely remove boilerplate.
• Nothing here is partially built. No pydantic, tomllib or os.environ reference exists anywhere in modern_di/.

What would move it:

• A concrete configuration shape that a Factory over a Settings() callable cannot express — not "it is boilerplate", but a case where the wiring is impossible or wrong, with the graph that shows it.
• For that case, how the provider stays inert when pydantic-settings or a TOML library is absent.

Until one of those lands this stays open and unscheduled by design: per CLAUDE.md, real work that is not scheduled lives as an issue, and this is that.