Summary

• Fix categories not being deep merged when combining user and project configs
• Add comprehensive tests for mergeConfigs() function

Problem

When merging user (~/.config/opencode/oh-my-opencode.json) and project (.opencode/oh-my-opencode.json) configs, categories were simply spread instead of deep merged. This caused user-level category model settings to be completely overwritten by project-level configs, even when the project config only specified partial overrides like temperature.

Example of broken behavior:

// User config
{ "categories": { "general": { "model": "openai/gpt-5.2", "temperature": 0.5 } } }

// Project config  
{ "categories": { "general": { "temperature": 0.3 } } }

// Result (WRONG - model was lost!)
{ "categories": { "general": { "temperature": 0.3 } } }

Solution

Add deepMerge for categories field in mergeConfigs(), consistent with how agents and claude_code are already handled.

After fix:

// Result (CORRECT - model preserved, temperature overridden)
{ "categories": { "general": { "model": "openai/gpt-5.2", "temperature": 0.3 } } }

Testing

• Added new test file src/plugin-config.test.ts with BDD-style tests
• All 5 tests pass
• bun run typecheck passes
• bun run build succeeds

Summary by cubic

Fix category deep merge in mergeConfigs to preserve user settings. Prevent project overrides from wiping user-defined model fields.

• Bug Fixes
  • Deep-merge categories (same as agents) to preserve existing fields and apply partial overrides.
  • Added mergeConfigs tests covering categories, agents, and disabled_hooks.

^{Written for commit 6d4cebd. Summary will update on new commits.}