# Configuration Internals

This document describes the maintainer-facing configuration boundary in
**internal/core/config**. The [Configuration](../config.md) reference owns the
file format, fields, defaults, precedence contract, and selectable keys. The
[CLI reference](../cli.md) owns command syntax; this document does not redefine
either interface.

## Boundary

The configuration package turns a selected YAML file and supported environment
values into a validated, independently owned configuration. It then resolves a
requested pipeline against a module catalog before the framework prepares or
runs anything.

| Boundary | Inputs | Outputs | Does not own |
| --- | --- | --- | --- |
| Loading | Selected file path and environment lookup | Parsed file model and a populated **Config** | Choosing the file path or reporting a command result. |
| Validation | **Config** | Structural configuration errors with pipeline, lane, or binding context | Module availability, capabilities, or construction. |
| Resolution | Valid **Config**, selected pipeline and lanes, runtime reference changes, LLM override, and module catalog | **EffectiveConfig** with a **ResolvedPipeline** | Materializing reference bytes, preparing modules, execution, or filesystem state. |
| Summary | **Config** or **EffectiveConfig** | Detached redacted payload suitable for debug summaries | Redacting arbitrary process state or provider traffic. |

The CLI discovers a configuration file, invokes this package, and supplies the
result to the framework. Configuration never reads an input file, constructs a
module, or creates output, cache, or debug paths. Those responsibilities remain
at their respective [CLI](cli.md), [pipeline](pipeline.md), and
[run-state](state.md) boundaries.

## Loading And Validation

The CLI loads configuration in this order:

1. parse the selected YAML file strictly into the file model;
2. start from **Default**;
3. apply the file model; and
4. apply the supported environment overrides.

This establishes the public precedence order without giving environment input a
second file schema. Loading and application reject malformed YAML, unsupported
file versions, unknown fields, invalid values, and identifiers that are empty
or collide after whitespace normalization. The file application also makes the
effective extraction-worker default follow the effective LLM limit. A present
PromptKit local-backend object requires and trims its endpoint, defaults its
omitted concurrency limit to zero, and is copied so the parsed file model
cannot alias the populated **Config**. A pipeline `llm_profile` is
presence-aware: omission remains empty, while a present blank value is
rejected and a non-empty file value is trimmed before it reaches **Config**.

**Config.Validate** checks configuration-only invariants before resolution. It
rejects incompatible profile sources, invalid state-surface values, unsupported
concurrency settings, malformed bindings and references, invalid retries, and
invalid pipeline, step, or lane structure. PromptKit local-backend validation
accepts only an absolute HTTP or HTTPS endpoint with a host and no user
information, query, or fragment, and rejects a negative local concurrency
limit. Its errors retain the closest known pipeline, lane, and binding context.
It deliberately does not require modules to be registered: that requires a
catalog and belongs to resolution.

The exact user-selectable values and validation rules are defined in
[Configuration](../config.md). Keep additions to the file model, an
environment override, its validation, and that reference in the same change.

## Effective Resolution

**Config.Resolve** first recomputes derived concurrency defaults and validates
the configuration. It normalizes the requested pipeline ID, copies the selected
profile, and passes the non-empty command-level LLM profile override, requested
lane selection, and reference changes to the framework resolver.

After module and validator selection, the resolver applies the effective
profile policy to LLM-backed bindings only: command override, binding profile,
pipeline profile, then the prompt default. Deterministic bindings remain
profile-free, and no second inheritance decision occurs during execution. The
public field definitions and precedence are owned by
[Configuration](../config.md#pipelines).

The framework resolver supplies defaults, selects lanes, resolves validator
chains, checks registered module and artifact compatibility, validates module
options, and returns the fixed ordered pipeline shape. The resulting
**EffectiveConfig** retains the selected ID, requested selection and reference
changes, a clone of the input configuration, and the resolved pipeline.
Callers may therefore retain or modify their input slices and maps without
changing the resolved result, and later consumers cannot mutate the original
configuration through the effective value. This ownership includes the nested
PromptKit local-backend value.

Resolution failures stop before module construction and source parsing. They
include an error path for an unconfigured pipeline, missing module, missing
capability, incompatible artifact variant, invalid option, invalid reference,
or invalid lane selection. CLI code maps these valid-invocation failures to the
runtime error class described in the [CLI reference](../cli.md#output-streams-and-exit-statuses).

## Resolved Identity And Redaction

The framework assigns the resolved pipeline a deterministic SHA-256 digest
after defaults, lane selection, module bindings, reference bindings, validator
chains, effective LLM profiles, and artifact schema identity have been
resolved. The digest excludes
its own stored value. It identifies resolved composition rather than raw YAML
bytes, a debug payload, or all runtime state. The CLI records it as invocation
provenance before execution; cache and checkpoint identity have additional
owners in [Run State Internals](state.md).

Configuration summaries must use **Redacted**, **RedactedSummaryPayload**, or
**RedactedResolvedPipelinePayload**, never a direct configuration marshal.
Those methods copy every binding and nested option container, replace values
whose key is credential-shaped with **[REDACTED]**, and omit materialized
reference content while retaining safe binding and reference provenance. The
payload must not alias the source configuration or resolved pipeline.
PromptKit's local endpoint and concurrency limit are preserved as non-secret
configuration metadata in the independently owned summary; the object contains
no credential value. This redaction is deliberately narrow: it protects
configuration summaries and does not authorize recording arbitrary environment
values or provider requests.

## Invariants To Preserve

- Defaults, YAML values, and environment values are applied in one direction;
  later sources may override only their supported operational settings.
- A configuration is structurally valid before it is resolved, and a resolved
  pipeline is compatible with the supplied catalog before preparation begins.
- Whitespace-normalized identifiers are unique wherever they identify a
  pipeline, step, lane, worker, or reference slot.
- Resolution and summary generation return detached data. Redaction must cover
  every configured and resolved binding, including nested validator bindings.
- The resolved digest changes when resolved composition changes and never
  includes itself.

## Focused Tests

- **internal/core/config/file_config_contract_test.go** covers strict file
  parsing, normalization, file application, and structural rejection.
- **internal/core/config/env_contract_test.go** covers supported operational
  overrides and their precedence.
- **internal/core/config/validation_contract_test.go** covers configuration
  invariants and contextual failures.
- **internal/core/config/effective_config_contract_test.go** covers defaults,
  selections, overrides, resolution context, digest changes, and ownership.
- **internal/core/config/redaction_test.go** covers recursive credential
  redaction, reference-content exclusion, and non-aliasing payloads.

Run **go test ./internal/core/config** after changing this boundary. Changes to
the handoff or resolved-composition semantics also need the focused framework
pipeline tests.
