nvim/.github/copilot-instructions.md

# Neovim Config - AI Agent Instructions

## Project Overview
Modern Lua-first Neovim configuration using lazy.nvim, currently in active migration from legacy Vimscript. Target: minimal, fast, tab-per-context workflow with Neo-tree, Telescope, LSP, and Copilot.

**Critical**: Read `AGENTS.md` first—it defines all coding rules, migration strategy, and what NOT to reintroduce.

## Architecture & Files

```
~/.config/nvim/
├── init.lua              # Entry point: loads settings/keymaps/autocmds, bootstraps lazy.nvim
├── lua/
│   ├── settings.lua      # Non-plugin vim options (exrc, secure, spelllang, listchars)
│   ├── keymaps.lua       # Non-plugin keymaps
│   ├── autocmds.lua      # Non-plugin autocommands
│   ├── abbreviations.lua # Insert-mode abbreviations (typo corrections)
│   ├── netrw-config.lua  # Netrw configuration
│   └── plugins/          # One file per plugin/domain (lazy.nvim specs)
│       ├── lsp.lua       # LSP via vim.lsp.config + vim.lsp.enable (Neovim 0.11+)
│       ├── cmp.lua       # Completion: nvim-cmp + LuaSnip
│       └── mason*.lua    # LSP server installation
├── AGENTS.md             # PRIMARY: All rules, migration plan, do-not-reintroduce list
├── MIGRATION_PLAN.md     # Phase-by-phase checklist (source of truth for progress)
├── README.md             # Decision log and design rationale
└── legacy/               # Archived Vimscript (do not edit; reference only)
```

## Critical Patterns

### 1. LSP Configuration (Phase 3 Complete)
**Modern API (Neovim 0.11+)**: Uses `vim.lsp.config()` + `vim.lsp.enable()`, NOT `require('lspconfig')[server].setup()`.

**CRITICAL (2025-12-07)**: Neovim 0.11+ does NOT support `on_new_config` callback. Use `LspAttach` autocmd instead.

```lua
-- lua/plugins/lsp.lua pattern:
-- Define config
vim.lsp.config(server_name, {
  capabilities = capabilities,
  -- NO on_attach here, NO on_new_config here
})

-- Enable server
vim.lsp.enable({ "lua_ls", "intelephense", ... })

-- Load project settings via LspAttach autocmd
vim.api.nvim_create_autocmd('LspAttach', {
  callback = function(args)
    local client = vim.lsp.get_client_by_id(args.data.client_id)
    -- Load .nvim.lua from client.root_dir
    -- Merge into client.settings
    -- Send workspace/didChangeConfiguration notification
  end,
})
```

**Key decisions**:
- No neoconf (incompatible with Neovim 0.11+, issue #116)
- Native `exrc` + `secure` for project config (see settings.lua)
- Project settings loaded via `LspAttach` autocmd (NOT `on_new_config` which is deprecated)
- `workspace/didChangeConfiguration` sent after merging settings into `client.settings`

### 2. Project-Local Configuration
**Format**: `.nvim.lua` at project root, returns:
```lua
return {
  lsp = {
    intelephense = {
      settings = {
        intelephense = {
          environment = {
            includePaths = { "/absolute/path/to/external/lib" }
          }
        }
      }
    }
  }
}
```

**Security**: `vim.opt.secure = true` prompts user before loading (one-time per file hash). Trusted files stored in `~/.local/state/nvim/trust`.

### 3. Plugin Management
- **lazy.nvim**: All plugins in `lua/plugins/` as individual files returning spec tables
- **Mason**: Installs LSP servers only; custom lspconfig setup retained
- **Plugin specs**: Use `opts = {}` for defaults, `config = function(_, opts)` for setup
- **Approval policy**: Do not install unlisted plugins without explicit user confirmation

### 4. Tab-Per-Context Workflow (Future Phase 4)
- Each tab maintains own Neo-tree root
- Splits stay within tabs
- Neo-tree: sidebar toggle + floating view + preview (no buffer pollution)
- Heavy PHP/HTML/JS/Markdown usage (WordPress plugin dev)

## Conventions

### Code Style
- **Lua APIs only**: `vim.opt`, `vim.keymap.set`, `vim.api.nvim_create_autocmd`
- **No Vimscript**: Avoid `vim.cmd` blocks unless strictly necessary
- **Keymaps**: `{ silent = true, noremap = true }` by default
- **Autocommands**: Group via `vim.api.nvim_create_augroup`, narrow scope

### File Organization
- One plugin = one file in `lua/plugins/`
- Keep plugin config self-contained in its spec
- Settings/keymaps/autocmds: only non-plugin logic in respective files
- No global state; return tables from modules

### Migration Process
1. Check `MIGRATION_PLAN.md` for current phase and priorities
2. **Before large changes**: Update plan via CLI `update_plan` tool (if available)
3. **After any change**: Immediately update `MIGRATION_PLAN.md` (check off items, add notes)
4. **After decisions**: Update `README.md` decisions log
5. Execute phases via subphases (N.x); one bullet = one implement-and-test step
6. Archive legacy files to `legacy/` instead of deleting

## Do NOT Reintroduce (from AGENTS.md)
- Custom Vimscript tabline/statusline/foldtext
- Legacy autocommands (cursorline/column per window)
- CoC or CoC-specific config
- netrw settings (Neo-tree replaces it)
- Providers for ruby/perl/node (disabled unless required)
- Auto-reload vimrc-on-write templates
- `cursorcolumn` and old folding logic (UFO will handle folding)
- neoconf plugin (incompatible with Neovim 0.11+)

## Developer Workflows

### Testing Changes
```bash
# Quick syntax check
nvim --headless -c 'lua print("Config loads")' -c 'quitall'

# Check LSP status in test workspace
cd ~/.config/nvim/WORKSPACE_TEST
nvim site/external.php  # Then :LspInfo

# Validate goto-definition for external libs
# In external.php, cursor on Util::greetExternal, press gd
```

### Validation Workspaces
- `WORKSPACE_TEST/`: PHP project with `.nvim.lua` and `.git`
- `EXTERNAL_TEST/`: External library referenced via includePaths
- Test that `gd` resolves symbols in EXTERNAL_TEST from WORKSPACE_TEST

### Current Migration Status (as of 2025-12-07)
- ✅ Phase 1-2: Archive legacy, bootstrap lazy.nvim
- ✅ Phase 3: Core editing & LSP complete
  - Settings, completion, LSP servers, Mason installed
  - Native exrc + vim.lsp.config migration done
  - Project-local `.nvim.lua` working
- ⏸️ Phase 4+: Navigation (Neo-tree, Telescope), Treesitter, UX plugins pending

## Integration Points

### External Dependencies
- **Neovim 0.11+**: Required for `vim.lsp.config` API
- **LSP Servers** (via Mason): lua_ls, ts_ls, html, cssls, jsonls, bashls, marksman, intelephense
- **PHP**: intelephense with `single_file_support = false`, uses `environment.includePaths` for external libs

### Cross-Component Communication
- LSP settings flow: `.nvim.lua` → `on_new_config` → `new_config.settings` → `workspace/didChangeConfiguration`
- Completion: cmp-nvim-lsp provides capabilities → lspconfig → LSP servers

## Common Issues

### lua_ls Won't Start
Mason-installed lua_ls may fail with missing `libbfd-2.38-system.so`. Install via system package manager instead.

### LSP Root Detection
If parent repo picked as root, create empty `.git` or `.nvimroot` marker in intended workspace root.

### Duplicate gd Results (Fixed)
Was caused by settings loading at wrong time; fixed by using `on_new_config` with actual `root_dir`.

## When Stuck
1. Check `MIGRATION_PLAN.md` for known issues and current phase
2. Review `AGENTS.md` for rules about what to avoid
3. Read `README.md` decisions log for context on past choices
4. Validate with test workspaces before modifying production config