# Phase 2: Plugin System - Context

**Gathered:** 2026-02-04
**Status:** Ready for planning

<domain>
## Phase Boundary

Establish the plugin architecture that all other features build upon. This includes plugin discovery, manifest parsing, lifecycle management (register, boot, shutdown), dependency resolution, and a type-safe extension API for plugins to extend each other. Components, themes, auth, admin, content, and core plugins all depend on this foundation.

</domain>

<decisions>
## Implementation Decisions

### Manifest Format
- **Hybrid approach:** YAML for metadata, Scala trait for code contracts
- YAML contains: vendor, name, version, description, author, homepage, license, tags, min Scala version, dependencies
- Scala trait contains: lifecycle hooks only (register, boot, shutdown)
- **Dependencies:** Semver ranges (e.g., `golem15.blog:^1.2.0`)
- **Soft dependencies:** Supported via `optionalDeps` — loads after if present, ignored if not
- **Vendor namespace:** Explicitly declared in YAML (`vendor: golem15, name: blog`)
- **Versioning:** Standard semver — MAJOR.MINOR.PATCH, major bump = breaking change
- **No conflict declarations** — handle incompatibilities via dependency constraints

### Lifecycle Hooks
- **Three phases:** register, boot, shutdown (like WinterCMS)
- **Execution model:** Hybrid — register is sync (pure data), boot/shutdown are async (ZIO effects)
- **Boot failures:** Graceful degradation — failed plugin disabled, dependents disabled, rest of app runs
- **Boot ordering:** Sequential by dependency order, then by numeric priority (higher boots first among peers)
- **Circular dependencies:** Error at discovery time (fail early)
- **Enabled flag:** Plugins can be disabled via config without removing from directory
- **Migrations:** Separate CLI command only, not during boot
- **Hot reload:** Supported in dev mode — file changes trigger plugin reload
- **Logging:** Minimal by default (errors/warnings only)
- **Plugin context:** Both PluginContext (simple access) and ZIO environment (advanced DI)
- **Health checks:** Optional health trait plugins can implement for /health endpoint
- **State tracking:** Full state machine (registered, booting, running, failed, disabled)
- **Enable/disable control:** Admin API only, plugins cannot control each other

### Extension Mechanics
- **Multi-pattern approach** (like WinterCMS):
  - Events for loose coupling (pub/sub)
  - Traits for type-safe contracts
  - Registration system for UI extensions (forms, navigation)
- **Form/list extensions:** Hybrid — simple extensions in YAML, complex logic in code
- **Type safety:** Compile-time where possible using Scala's type system
- **Admin navigation:** Both YAML for standard items, code for dynamic/conditional items
- **Model extensions:** Full API — plugins can add columns and relations to other plugins' models
- **Route/controller interception:** Middleware-style wrapping (before/after logic)
- **Multiple extensions merge:** Additive (like WinterCMS) — Plugin A and B can both extend Plugin C, extensions accumulate
- **Extension conflicts:** Actual conflicts (same field name) error, otherwise merge
- **Granularity:** Plugin-level only — disable plugin = disable all its extensions

### Developer Experience
- **Dependency errors:** Console message with suggested fix (e.g., "try: install golem15.blog ^1.2.0")
- **Plugin doctor:** Full diagnostic command — manifests, dependencies, conflicts, health
- **Dev mode debugging:** Full tracing — verbose logs, timing, dependency graph visualization, event flow tracing
- **API documentation:** Auto-generated from traits, events, extension points

### Claude's Discretion
- Shutdown timeout policy
- Event listener priority ordering
- Runtime error handling patterns (isolated vs propagated)
- Asset injection targeting (global vs page-specific)

</decisions>

<specifics>
## Specific Ideas

- "Make it similar to WinterCMS" — multiple plugins extending the same target, extensions merge additively
- Events, traits, AND registration system — all three patterns available like WinterCMS
- Plugin B can extend Plugin A's backend forms and navigation
- Example: Golem15.Golem extending Blog with AI image generation AND Golem15.SEO extending Blog with SEO fields — both work simultaneously

</specifics>

<deferred>
## Deferred Ideas

None — discussion stayed within phase scope

</deferred>

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*Phase: 02-plugin-system*
*Context gathered: 2026-02-04*
