PATCH /config hot-reload w/ selective cache invalidation (#14) - #4285

Implements runtime configuration updates through a PATCH /config endpoint with optional hot-reload capability controlled by OPENCODE_CONFIG_HOT_RELOAD environment variable.

Changes

Features

• PATCH /config endpoint for updating project or global configuration at runtime
• File locking mechanism with 30s timeout to prevent concurrent write conflicts
• Automatic backup and restore on configuration update failures
• Config invalidation system that triggers targeted cache invalidation and event publishing
• Event bus integration for config.updated notifications across project instances
• Deep merge support for partial configuration updates with JSONC comment preservation

Infrastructure

• New config write module with atomic file operations and validation
• Lock file management for concurrent access control
• Configuration diffing to detect actual changes before triggering invalidations
• State-based hot reload that respects feature flag for backward compatibility
• Integration with agent, provider, server, mcp, lsp and plugin systems for config subscription

Testing

• Hot-reload test suite covering GET/PATCH workflows
• Lock file management tests
• Config write and persistence tests

Documentation

• Complete PATCH /config specification with examples
• Feature flag documentation for OPENCODE_CONFIG_HOT_RELOAD
• Client integration guide with curl examples

Breaking Changes

None. Hot-reload is opt-in via environment variable. Default behavior maintains existing cache semantics.

Configuration

Set OPENCODE_CONFIG_HOT_RELOAD=true before starting server to enable runtime config updates without restart. Without this flag, disk writes persist but in-memory cache remains until process restart.