# ADR-0004: Configuration Management Library

## Status
Accepted

## Context
The platform needs a configuration system that:
- Supports hierarchical configuration (defaults → files → env → secrets)
- Handles multiple formats (YAML, JSON, env vars)
- Provides type-safe access to configuration values
- Supports environment-specific overrides
- Can integrate with secret managers (future)

Options considered:
1. **spf13/viper** - Comprehensive configuration management
2. **envconfig** - Environment variable only
3. **koanf** - Lightweight configuration library
4. **Standard library + manual parsing** - No external dependency

## Decision
Use **spf13/viper** (v1.18.0+) with **spf13/cobra** (v1.8.0+) for configuration management.

**Rationale:**
- Industry standard for Go configuration management
- Supports multiple sources (files, env vars, flags)
- Hierarchical configuration with precedence rules
- Easy integration with Cobra for CLI commands
- Well-documented and widely used
- Supports future secret manager integration

## Consequences

### Positive
- Flexible configuration loading from multiple sources
- Easy to add new configuration sources
- Type-safe access methods
- Environment variable support via automatic env binding

### Negative
- Additional dependency
- Viper can be verbose for simple use cases
- Some learning curve for advanced features

### Implementation Notes
- Install: `go get github.com/spf13/viper@v1.18.0` and `github.com/spf13/cobra@v1.8.0`
- Create `pkg/config/config.go` interface to abstract Viper
- Implement `internal/config/viper_config.go` as concrete implementation
- Load order: `default.yaml` → `development.yaml`/`production.yaml` → env vars → secrets (future)
- Use typed getters (GetString, GetInt, GetBool) for type safety