feat: add GitHub Copilot CLI backend (#42)

Author: Cannon07

.gitignore

@@ -7,5 +7,8 @@
 # OpenCode local plugins (installed by :CodePreviewInstallOpenCodeHooks)
 .opencode/
 
+# Copilot CLI local hooks (installed by :CodePreviewInstallCopilotCliHooks)
+.github/hooks/code-preview.json
+
 # Test dependencies (plenary.nvim, installed by tests/run_lua.sh)
 deps/

README.md

@@ -2,17 +2,20 @@
 
 A Neovim plugin that shows a **diff preview before your AI coding agent applies any file change** — letting you review exactly what's changing before accepting.
 
-Supports [Claude Code](https://docs.anthropic.com/en/docs/claude-code) and [OpenCode](https://opencode.ai) as backends.
+Supports [Claude Code](https://docs.anthropic.com/en/docs/claude-code), [OpenCode](https://opencode.ai), and [GitHub Copilot CLI](https://github.com/github/copilot-cli) as backends.
 
 ---
 
 ## Demo
 
 ### Claude Code
-![Claude Code demo](docs/claude-preview-demo.gif)
+![Claude Code demo](docs/code-preview-claudecode.gif)
 
 ### OpenCode
-![OpenCode demo](docs/claude-preview-opencode.gif)
+![OpenCode demo](docs/code-preview-opencode.gif)
+
+### GitHub Copilot CLI
+![GitHub Copilot CLI demo](docs/code-preview-copilot.gif)
 
 ---
 
@@ -24,6 +27,7 @@ Supports [Claude Code](https://docs.anthropic.com/en/docs/claude-code) and [Open
 - [Quick Start](#quick-start)
   - [Claude Code](#claude-code)
   - [OpenCode](#opencode)
+  - [GitHub Copilot CLI](#github-copilot-cli)
 - [How it works](#how-it-works)
 - [Configuration](#configuration)
 - [Commands](#commands)
@@ -55,6 +59,10 @@ Supports [Claude Code](https://docs.anthropic.com/en/docs/claude-code) and [Open
 **For OpenCode backend:**
 - [OpenCode](https://opencode.ai) >= 1.3.0
 
+**For GitHub Copilot CLI backend:**
+- [GitHub Copilot CLI](https://github.com/github/copilot-cli) (generally available since Feb 2026)
+- [jq](https://jqlang.github.io/jq/) — for hook payload translation
+
 ---
 
 ## Installation
@@ -110,6 +118,18 @@ require("code-preview").setup()
 7. Accept/reject in OpenCode; the diff closes automatically on accept
 8. If rejected, press `<leader>dq` to close the diff manually
 
+### GitHub Copilot CLI
+
+1. Install the plugin and call `setup()`
+2. Open a project in Neovim
+3. Run `:CodePreviewInstallCopilotCliHooks` — writes `.github/hooks/code-preview.json`
+4. Start Copilot CLI in the project directory
+5. Ask Copilot to edit a file — a diff opens automatically in Neovim
+6. Accept/reject in the CLI; the diff closes automatically on accept
+7. If rejected, press `<leader>dq` to close the diff manually
+
+> **Note:** Copilot CLI does not fire post-tool hooks on rejection, so rejected diffs remain open until you dismiss them (same as Claude Code).
+
 ---
 
 ## How it works
@@ -132,7 +152,9 @@ AI Agent (terminal)                              Neovim
 
 **OpenCode** uses a TypeScript plugin (`tool.execute.before`/`tool.execute.after`) loaded from `.opencode/plugins/`.
 
-Both backends communicate with Neovim via RPC (`nvim --server <socket> --remote-send`).
+**GitHub Copilot CLI** uses shell-based hooks (`preToolUse`/`postToolUse`) configured in `.github/hooks/code-preview.json`. The adapter translates Copilot's tool vocabulary (`apply_patch`, `edit`, `create`, `bash`) into the same normalized format used by the other backends.
+
+All backends communicate with Neovim via RPC (`nvim --server <socket> --remote-send`).
 
 ---
 
@@ -184,6 +206,8 @@ require("code-preview").setup({
 | `:CodePreviewUninstallClaudeCodeHooks` | Remove Claude Code hooks (leaves other hooks intact) |
 | `:CodePreviewInstallOpenCodeHooks` | Install OpenCode plugin to `.opencode/plugins/` |
 | `:CodePreviewUninstallOpenCodeHooks` | Remove OpenCode plugin |
+| `:CodePreviewInstallCopilotCliHooks` | Install Copilot CLI hooks to `.github/hooks/code-preview.json` |
+| `:CodePreviewUninstallCopilotCliHooks` | Remove Copilot CLI hooks |
 | `:CodePreviewCloseDiff` | Manually close the diff (use after rejecting a change) |
 | `:CodePreviewStatus` | Show socket path, hook status, and dependency check |
 | `:CodePreviewToggleVisibleOnly` | Toggle visible_only — show diffs only for open buffers |
@@ -230,7 +254,7 @@ require("code-preview").setup({
 
 If you use [neo-tree.nvim](https://github.com/nvim-neo-tree/neo-tree.nvim), code-preview will automatically decorate your file tree with visual indicators when changes are proposed. No extra configuration is required — it works out of the box.
 
-![neo-tree integration demo](docs/claude-preview-neotree-integration.gif)
+![neo-tree integration demo](docs/code-preview-neotree-integration.gif)
 
 ### What you get
 
@@ -301,10 +325,13 @@ code-preview.nvim/
 │   ├── claudecode/                  Claude Code adapter
 │   │   ├── code-preview-diff.sh     PreToolUse hook entry point
 │   │   └── code-close-diff.sh       PostToolUse hook entry point
-│   └── opencode/                    OpenCode adapter
-│       ├── index.ts                 tool.execute.before/after hooks
-│       ├── package.json
-│       └── tsconfig.json
+│   ├── opencode/                    OpenCode adapter
+│   │   ├── index.ts                 tool.execute.before/after hooks
+│   │   ├── package.json
+│   │   └── tsconfig.json
+│   └── copilot/                     GitHub Copilot CLI adapter
+│       ├── code-preview-diff.sh     preToolUse hook — translates Copilot JSON → core
+│       └── code-close-diff.sh       postToolUse hook — same for close
 ```
 
 ---
@@ -357,6 +384,12 @@ vim.api.nvim_create_autocmd({ "FocusGained", "BufEnter", "CursorHold" }, {
 - Ensure `"permission": { "edit": "ask" }` is set in `~/.config/opencode/opencode.json`
 - Restart OpenCode
 
+**Copilot CLI hooks not firing**
+- Run `:CodePreviewInstallCopilotCliHooks` in the project root
+- Verify `.github/hooks/code-preview.json` exists
+- Ensure `jq` is in PATH
+- Restart Copilot CLI (hooks are loaded at session start)
+
 **Diff doesn't close after rejecting**
 - Press `<leader>dq` or run `:CodePreviewCloseDiff` — the post hook only fires on accept
 

backends/copilot/code-close-diff.sh

@@ -0,0 +1,85 @@
+#!/usr/bin/env bash
+# code-close-diff.sh — PostToolUse hook adapter for GitHub Copilot CLI.
+#
+# Mirrors the translation in code-preview-diff.sh and delegates to
+# bin/core-post-tool.sh. Only the fields core-post-tool.sh reads are
+# populated (tool_name, cwd, file_path or patch_text).
+
+set -uo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+BIN_DIR="$SCRIPT_DIR/../../bin"
+export CODE_PREVIEW_BACKEND="copilot"
+
+INPUT="$(cat)"
+
+TOOL="$(printf '%s' "$INPUT" | jq -r '.toolName // ""')"
+CWD="$(printf '%s' "$INPUT" | jq -r '.cwd // ""')"
+
+case "$TOOL" in
+  ""|view|glob|grep|ls|report_intent) exit 0 ;;
+esac
+
+# Logging — gated on `debug = true` in setup().
+log() { :; }
+# shellcheck source=/dev/null
+source "$BIN_DIR/nvim-socket.sh" "$CWD" 2>/dev/null || true
+# shellcheck source=/dev/null
+source "$BIN_DIR/nvim-send.sh" 2>/dev/null || true
+if [[ -n "${NVIM_SOCKET:-}" ]]; then
+  _CTX=$(nvim --server "$NVIM_SOCKET" --remote-expr "luaeval(\"vim.json.encode({debug=require('code-preview.log').is_enabled(),log_file=require('code-preview.log').get_log_path() or ''})\")" 2>/dev/null || echo '{}')
+  _DBG=$(echo "$_CTX" | jq -r '.debug // false' 2>/dev/null)
+  _LOG=$(echo "$_CTX" | jq -r '.log_file // ""' 2>/dev/null)
+  if [[ "$_DBG" == "true" && -n "$_LOG" ]]; then
+    log() { printf '[%s] [INFO] copilot/post: %s\n' "$(date '+%Y-%m-%d %H:%M:%S')" "$*" >> "$_LOG"; }
+  fi
+fi
+
+log "tool=$TOOL"
+
+RAW_ARGS="$(printf '%s' "$INPUT" | jq -r '.toolArgs // "" | if type == "string" then . else tojson end')"
+
+# Bind the key as data via --arg, not interpolated into the jq program.
+# Supports single-key lookup only (no dotted paths) — all current callers
+# pass a single field like `.path`, `.command`, etc.
+arg() { printf '%s' "$RAW_ARGS" | jq -r --arg k "${1#.}" '.[$k] // ""'; }
+
+resolve_path() {
+  local p="$1"
+  if [[ -z "$p" ]]; then printf ''; return; fi
+  if [[ "$p" != /* ]]; then printf '%s/%s' "$CWD" "$p"; else printf '%s' "$p"; fi
+}
+
+case "$TOOL" in
+  apply_patch)
+    NORMALIZED="$(jq -n --arg cwd "$CWD" --arg patch "$RAW_ARGS" \
+      '{tool_name:"ApplyPatch", cwd:$cwd, tool_input:{patch_text:$patch}}')"
+    ;;
+
+  edit|str_replace)
+    FP="$(resolve_path "$(arg .path)")"
+    NORMALIZED="$(jq -n --arg cwd "$CWD" --arg fp "$FP" \
+      '{tool_name:"Edit", cwd:$cwd, tool_input:{file_path:$fp}}')"
+    ;;
+
+  create|write)
+    FP="$(resolve_path "$(arg .path)")"
+    NORMALIZED="$(jq -n --arg cwd "$CWD" --arg fp "$FP" \
+      '{tool_name:"Write", cwd:$cwd, tool_input:{file_path:$fp}}')"
+    ;;
+
+  bash)
+    CMD="$(arg .command)"
+    NORMALIZED="$(jq -n --arg cwd "$CWD" --arg cmd "$CMD" \
+      '{tool_name:"Bash", cwd:$cwd, tool_input:{command:$cmd}}')"
+    ;;
+
+  *)
+    log "unhandled tool=$TOOL — exiting"
+    exit 0
+    ;;
+esac
+
+log "translated tool=$TOOL → closing"
+
+printf '%s' "$NORMALIZED" | "$BIN_DIR/core-post-tool.sh"

backends/copilot/code-preview-diff.sh

@@ -0,0 +1,129 @@
+#!/usr/bin/env bash
+# code-preview-diff.sh — PreToolUse hook adapter for GitHub Copilot CLI.
+#
+# Translates Copilot's hook payload (stdin JSON with toolName/toolArgs) into
+# the normalized {tool_name, cwd, tool_input} format consumed by
+# bin/core-pre-tool.sh, then delegates to it.
+#
+# Field mapping:
+#   apply_patch      → ApplyPatch  (toolArgs is raw patch text)
+#   edit/str_replace → Edit        ({path, old_str, new_str})
+#   create/write     → Write       ({path, file_text | content})
+#   bash             → Bash        ({command, description})
+#   view/glob/...    → ignored
+#
+# Note: toolArgs is a JSON-encoded string in preToolUse and an object in
+# postToolUse; we normalize both to a string so downstream parsing is uniform.
+
+set -uo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+BIN_DIR="$SCRIPT_DIR/../../bin"
+export CODE_PREVIEW_BACKEND="copilot"
+
+INPUT="$(cat)"
+
+TOOL="$(printf '%s' "$INPUT" | jq -r '.toolName // ""')"
+CWD="$(printf '%s' "$INPUT" | jq -r '.cwd // ""')"
+
+# Noise tools never produce a preview — bail out before the expensive
+# socket/log-setup RPC so the log stays clean.
+case "$TOOL" in
+  ""|view|glob|grep|ls|report_intent) exit 0 ;;
+esac
+
+# Logging — mirrors core-pre-tool.sh. Gated on `debug = true` in setup().
+log() { :; }
+# shellcheck source=/dev/null
+source "$BIN_DIR/nvim-socket.sh" "$CWD" 2>/dev/null || true
+# shellcheck source=/dev/null
+source "$BIN_DIR/nvim-send.sh" 2>/dev/null || true
+_NVIM_SERVERNAME=""
+_NVIM_CWD=""
+if [[ -n "${NVIM_SOCKET:-}" ]]; then
+  _CTX=$(nvim --server "$NVIM_SOCKET" --remote-expr "luaeval(\"vim.json.encode({debug=require('code-preview.log').is_enabled(),log_file=require('code-preview.log').get_log_path() or '',servername=vim.v.servername,cwd=vim.fn.getcwd()})\")" 2>/dev/null || echo '{}')
+  _DBG=$(echo "$_CTX" | jq -r '.debug // false' 2>/dev/null)
+  _LOG=$(echo "$_CTX" | jq -r '.log_file // ""' 2>/dev/null)
+  _NVIM_SERVERNAME=$(echo "$_CTX" | jq -r '.servername // ""' 2>/dev/null)
+  _NVIM_CWD=$(echo "$_CTX" | jq -r '.cwd // ""' 2>/dev/null)
+  if [[ "$_DBG" == "true" && -n "$_LOG" ]]; then
+    log() { printf '[%s] [INFO] copilot/pre: %s\n' "$(date '+%Y-%m-%d %H:%M:%S')" "$*" >> "$_LOG"; }
+  fi
+fi
+
+log "tool=$TOOL servername=${_NVIM_SERVERNAME:-<none>} nvim_cwd=${_NVIM_CWD:-<none>} hook_cwd=$CWD"
+
+# Normalize toolArgs to a raw string. For JSON-object tools this becomes the
+# stringified JSON; for apply_patch it's the raw patch text.
+RAW_ARGS="$(printf '%s' "$INPUT" | jq -r '.toolArgs // "" | if type == "string" then . else tojson end')"
+
+# Bind the key as data via --arg, not interpolated into the jq program.
+# Supports single-key lookup only (no dotted paths) — all current callers
+# pass a single field like `.path`, `.command`, etc.
+arg() { printf '%s' "$RAW_ARGS" | jq -r --arg k "${1#.}" '.[$k] // ""'; }
+
+resolve_path() {
+  local p="$1"
+  if [[ -z "$p" ]]; then printf ''; return; fi
+  if [[ "$p" != /* ]]; then printf '%s/%s' "$CWD" "$p"; else printf '%s' "$p"; fi
+}
+
+case "$TOOL" in
+  apply_patch)
+    NORMALIZED="$(jq -n --arg cwd "$CWD" --arg patch "$RAW_ARGS" \
+      '{tool_name:"ApplyPatch", cwd:$cwd, tool_input:{patch_text:$patch}}')"
+    ;;
+
+  edit|str_replace)
+    FP="$(resolve_path "$(arg .path)")"
+    NORMALIZED="$(jq -n \
+      --arg cwd "$CWD" \
+      --arg fp "$FP" \
+      --arg os "$(arg .old_str)" \
+      --arg ns "$(arg .new_str)" \
+      '{tool_name:"Edit", cwd:$cwd,
+        tool_input:{file_path:$fp, old_string:$os, new_string:$ns, replace_all:false}}')"
+    ;;
+
+  create|write)
+    FP="$(resolve_path "$(arg .path)")"
+    # Copilot's create uses file_text; fall back to content for other models.
+    CONTENT="$(printf '%s' "$RAW_ARGS" | jq -r '.file_text // .content // ""')"
+    NORMALIZED="$(jq -n --arg cwd "$CWD" --arg fp "$FP" --arg c "$CONTENT" \
+      '{tool_name:"Write", cwd:$cwd, tool_input:{file_path:$fp, content:$c}}')"
+    ;;
+
+  bash)
+    CMD="$(arg .command)"
+    NORMALIZED="$(jq -n --arg cwd "$CWD" --arg cmd "$CMD" \
+      '{tool_name:"Bash", cwd:$cwd, tool_input:{command:$cmd}}')"
+    ;;
+
+  *)
+    log "unhandled tool=$TOOL — exiting"
+    exit 0
+    ;;
+esac
+
+# Guard against malformed payloads (missing toolArgs fields). Sending an
+# empty path or command downstream produces a broken/empty diff; a clean
+# skip is preferable. apply_patch is already resilient — apply-patch.lua
+# parses zero files from an empty patch and exits cleanly.
+case "$TOOL" in
+  edit|str_replace|create|write)
+    if [[ -z "$FP" ]]; then
+      log "empty file path for tool=$TOOL — skipping"
+      exit 0
+    fi
+    ;;
+  bash)
+    if [[ -z "$CMD" ]]; then
+      log "empty command for bash — skipping"
+      exit 0
+    fi
+    ;;
+esac
+
+log "translated tool=$TOOL → $(printf '%s' "$NORMALIZED" | jq -c '{tool_name, file: .tool_input.file_path // "", has_patch: (.tool_input.patch_text != null)}' 2>/dev/null || echo 'parse-error')"
+
+printf '%s' "$NORMALIZED" | "$BIN_DIR/core-pre-tool.sh"

bin/apply-patch.lua

@@ -76,8 +76,18 @@ for line in (patch_text .. "\n"):gmatch("([^\n]*)\n") do
     table.insert(current_file.hunks, current_file.current_hunk)
   elseif line == "*** End Patch" or line == "*** Begin Patch" then
     current_file = nil
-  elseif current_file and current_file.current_hunk then
-    table.insert(current_file.current_hunk.lines, line)
+  elseif current_file then
+    -- `*** Add File:` in the GPT patch format has no `@@` marker — content
+    -- lines follow directly. Lazy-create a hunk on the first content line
+    -- so those lines aren't dropped, without leaving an empty leading hunk
+    -- when `@@` *is* present.
+    if not current_file.current_hunk and current_action == "add" then
+      current_file.current_hunk = { lines = {} }
+      table.insert(current_file.hunks, current_file.current_hunk)
+    end
+    if current_file.current_hunk then
+      table.insert(current_file.current_hunk.lines, line)
+    end
   end
 end
 

bin/core-post-tool.sh

@@ -9,7 +9,9 @@
 #     "tool_input": { "file_path": "...", ... } }
 #
 # Environment:
-#   CODE_PREVIEW_BACKEND  — "claudecode" or "opencode" (currently unused, reserved)
+#   CODE_PREVIEW_BACKEND  — "claudecode" | "opencode" | "copilot". Not read
+#                           by this script; kept set by adapters for symmetry
+#                           with core-pre-tool.sh, which does gate on it.
 
 SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
 
@@ -56,8 +58,8 @@ if [[ "$TOOL_NAME" == "ApplyPatch" ]]; then
         [[ "$fpath" == "/dev/null" ]] && continue
         echo "$fpath"
       done
-      echo "$1" | grep -E '^\*\*\* (Update|Add) File:' | while IFS= read -r line; do
-        echo "$line" | sed -E 's/^\*\*\* (Update|Add) File:[[:space:]]*//' | sed 's/[[:space:]]*$//'
+      echo "$1" | grep -E '^\*\*\* (Update|Add|Delete) File:' | while IFS= read -r line; do
+        echo "$line" | sed -E 's/^\*\*\* (Update|Add|Delete) File:[[:space:]]*//' | sed 's/[[:space:]]*$//'
       done
     }