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VS Code Extension Automation

Automate VS Code Insiders with the Copilot Chat extension using @playwright/cli. VS Code is built on Electron/Chromium and exposes a Chrome DevTools Protocol (CDP) port that @playwright/cli can attach to, enabling the same snapshot-interact workflow used for web pages.

Prerequisites

• @playwright/cli is available via devDependencies. Run npm install at the repo root, then use npx @playwright/cli to invoke commands. Alternatively, install globally with npm install -g @playwright/cli.
• code-insiders is required. This extension uses 58 proposed VS Code APIs and targets vscode ^1.110.0-20260223. VS Code Stable will not activate it — you must use VS Code Insiders.
• The extension must be compiled first. Use npm run compile for a one-shot build, or npm run watch for iterative development.
• CSS selectors are internal implementation details. Selectors like .interactive-input-part, .monaco-editor, and .view-line are VS Code internals that may change across versions. If automation breaks after a VS Code update, re-snapshot and check for selector changes.

Core Workflow

1. Build the extension
2. Launch VS Code Insiders with the extension and remote debugging enabled
3. Attach npx @playwright/cli to the CDP port
4. Snapshot to discover interactive elements
5. Interact using element refs
6. Re-snapshot after navigation or state changes

📸 Take screenshots for a paper trail. Use npx @playwright/cli screenshot --filename=<path> at key moments — after launch, before/after interactions, and when something goes wrong. Screenshots provide visual proof of what the UI looked like and are invaluable for debugging failures or documenting what was accomplished.

Save screenshots inside .vscode-ext-debug/screenshots/ (gitignored) using a timestamped subfolder so each run is isolated and nothing gets overwritten:

# Create a timestamped folder for this run's screenshots
SCREENSHOT_DIR=".vscode-ext-debug/screenshots/$(date +%Y-%m-%dT%H-%M-%S)"
mkdir -p "$SCREENSHOT_DIR"
 
# Windows (PowerShell):
# $screenshotDir = ".vscode-ext-debug\screenshots\$(Get-Date -Format 'yyyy-MM-ddTHH-mm-ss')"
# New-Item -ItemType Directory -Force -Path $screenshotDir
 
# Save a screenshot
npx @playwright/cli screenshot --filename="$SCREENSHOT_DIR/after-launch.png"

# Build and launch with the extension
npm run compile
# Use a PERSISTENT user-data-dir so auth state is preserved across sessions.
# .vscode-ext-debug is relative to the project root — works in worktrees and is gitignored.
code-insiders --extensionDevelopmentPath="$PWD" --remote-debugging-port=9223 --user-data-dir="$PWD/.vscode-ext-debug"
# On Windows (PowerShell):
# code-insiders --extensionDevelopmentPath="$PWD" --remote-debugging-port=9223 --user-data-dir="$PWD\.vscode-ext-debug"
 
# Wait for VS Code to start, retry until attached
for i in 1 2 3 4 5; do npx @playwright/cli attach --cdp=http://127.0.0.1:9223 2>/dev/null && break || sleep 3; done
 
# Verify you're connected to the right target (not about:blank)
# If `tab-list` shows the wrong target, run `npx @playwright/cli close` and reattach
npx @playwright/cli tab-list
npx @playwright/cli snapshot

Attaching

# Attach to a specific CDP port
npx @playwright/cli attach --cdp=http://127.0.0.1:9223

After attach, all subsequent commands target the connected app without needing to reattach.

Tab Management

VS Code uses multiple webviews internally. Use tab commands to list and switch between them:

# List all available targets (windows, webviews, etc.)
npx @playwright/cli tab-list
 
# Switch to a specific tab by index
npx @playwright/cli tab-select 2

Launching VS Code Extensions for Debugging

To debug a VS Code extension via npx @playwright/cli, launch VS Code Insiders with --extensionDevelopmentPath pointing to your extension source and --remote-debugging-port for CDP. Use --user-data-dir to avoid conflicting with an already-running VS Code instance.

# Build the extension first (from the repo root)
npm run compile
 
# Launch VS Code Insiders with the extension and CDP
# IMPORTANT: Use a persistent directory (not /tmp) so auth state is preserved.
# .vscode-ext-debug is relative to the project root — works in worktrees and is gitignored.
code-insiders \
  --extensionDevelopmentPath="$PWD" \
  --remote-debugging-port=9223 \
  --user-data-dir="$PWD/.vscode-ext-debug"
 
# Wait for VS Code to start, retry until attached
for i in 1 2 3 4 5; do npx @playwright/cli attach --cdp=http://127.0.0.1:9223 2>/dev/null && break || sleep 3; done
 
# Verify you're connected to the right target (not about:blank)
# If `tab-list` shows the wrong target, run `npx @playwright/cli close` and reattach
npx @playwright/cli tab-list
npx @playwright/cli snapshot

Key flags:

• --extensionDevelopmentPath=<path> — loads your extension from source (must be compiled first). Use $PWD when running from the repo root.
• --remote-debugging-port=9223 — enables CDP (use 9223 to avoid conflicts with other apps on 9222)
• --user-data-dir=<path> — uses a separate profile so it starts a new process instead of sending to an existing VS Code instance. Always use a persistent path (e.g., $PWD/.vscode-ext-debug) rather than /tmp/... so authentication, settings, and extension state survive across sessions.

Without --user-data-dir, VS Code detects the running instance, forwards the args to it, and exits immediately — you'll see "Sent env to running instance. Terminating..." and CDP never starts.

⚠️ Authentication is required. The Copilot Chat extension needs an authenticated GitHub session to function. Using a temp directory (e.g., /tmp/...) creates a fresh profile with no auth — the agent will hit a "Sign in to use Copilot" wall and model resolution will fail with "Language model unavailable."

Always use a persistent --user-data-dir like $PWD/.vscode-ext-debug. On first use, launch once and sign in manually. Subsequent launches will reuse the auth session.

Restarting After Code Changes

After making changes to the extension source code, you must restart VS Code to pick up the new build. The extension host loads the compiled bundle at startup — changes are not hot-reloaded.

Restart Workflow

1. Recompile the extension
2. Kill the running VS Code instance (the one using your debug user-data-dir)
3. Relaunch VS Code with the same flags

# 1. Recompile
npm run compile
 
# 2. Kill the VS Code instance tied to this project's debug profile, then relaunch
# macOS / Linux:
kill $(ps ax -ww -o pid,command | grep "$PWD/.vscode-ext-debug" | grep -v grep | awk '{print $1}' | head -1)
 
# Windows (PowerShell):
# Get-CimInstance Win32_Process | Where-Object { $_.CommandLine -like "*$PWD\.vscode-ext-debug*" } | ForEach-Object { Stop-Process -Id $_.ProcessId }
 
# 3. Relaunch
code-insiders \
  --extensionDevelopmentPath="$PWD" \
  --remote-debugging-port=9223 \
  --user-data-dir="$PWD/.vscode-ext-debug"
 
# 4. Reattach npx @playwright/cli
for i in 1 2 3 4 5; do npx @playwright/cli attach --cdp=http://127.0.0.1:9223 2>/dev/null && break || sleep 3; done
npx @playwright/cli snapshot

Tip: If you're iterating frequently, run npm run watch in a separate terminal so compilation happens automatically. You still need to kill and relaunch VS Code to load the new bundle.

Interacting with Monaco Editor (Chat Input, Code Editors)

VS Code uses Monaco Editor for all text inputs including the Copilot Chat input. Monaco editors appear as textboxes in the accessibility snapshot but require specific npx @playwright/cli commands to interact with.

What Works

fill <ref> — The Best Approach

The fill command with a snapshot ref handles focus and input in one step:

# Snapshot to find the chat input ref
npx @playwright/cli snapshot
# Look for: textbox "The editor is not accessible..." [ref=e51]
 
# Fill directly using the ref — handles focus automatically
npx @playwright/cli fill e51 "Hello from George!"
 
# Send the message
npx @playwright/cli press Enter
 
# Wait for the response to complete before re-snapshotting.
# Poll until the "Stop generating" button disappears:
for i in $(seq 1 30); do
  npx @playwright/cli snapshot 2>/dev/null | grep -q "Stop generating" || break
  sleep 1
done
npx @playwright/cli snapshot

This is the simplest and most reliable method. It works for both the main editor chat input and the sidebar chat panel.

Tip: If fill silently drops text (the editor stays empty), the ref may be stale or the editor not yet ready. Re-snapshot to get a fresh ref and try again. You can verify text was entered using the snippet in "Verifying Text in Monaco" below.

type — After Focus

If focus is already on a Monaco editor, type works:

# Focus first (via fill with empty string, or JS mouse events)
npx @playwright/cli fill e51 ""
# Then type works for subsequent input
npx @playwright/cli type "More text here"

press — Individual Keystrokes

Always works when focus is on a Monaco editor. Useful for special keys, keyboard shortcuts, and as a universal fallback for typing text character by character:

# Type text character by character (works on all builds)
npx @playwright/cli press H
npx @playwright/cli press e
npx @playwright/cli press l
npx @playwright/cli press l
npx @playwright/cli press o
npx @playwright/cli press Space  # Use "Space" for spaces
 
# Select all
# macOS:
npx @playwright/cli press Meta+a
# Linux / Windows:
npx @playwright/cli press Control+a
 
npx @playwright/cli press Backspace    # Delete selection
npx @playwright/cli press Enter        # Send message / new line
 
# Send to new chat
# macOS:
npx @playwright/cli press Meta+Shift+Enter
# Linux / Windows:
npx @playwright/cli press Control+Shift+Enter

What Does NOT Work

Fallback: Focus via JavaScript Mouse Events

If fill doesn't work (e.g., ref is stale), you can focus the editor via JavaScript:

npx @playwright/cli eval '
(() => {
  const inputPart = document.querySelector(".interactive-input-part");
  const editor = inputPart.querySelector(".monaco-editor");
  const rect = editor.getBoundingClientRect();
  const x = rect.x + rect.width / 2;
  const y = rect.y + rect.height / 2;
  editor.dispatchEvent(new MouseEvent("mousedown", { bubbles: true, clientX: x, clientY: y }));
  editor.dispatchEvent(new MouseEvent("mouseup", { bubbles: true, clientX: x, clientY: y }));
  editor.dispatchEvent(new MouseEvent("click", { bubbles: true, clientX: x, clientY: y }));
  return "activeElement: " + document.activeElement?.className;
})()'
 
# After JS focus, type and press work
npx @playwright/cli type "Text after JS focus"

After JS mouse events, document.activeElement becomes a DIV with class native-edit-context — this is VS Code's native text editing surface.

Verifying Text in Monaco

Monaco renders text in .view-line elements, not the textarea:

npx @playwright/cli eval '
(() => {
  const inputPart = document.querySelector(".interactive-input-part");
  return Array.from(inputPart.querySelectorAll(".view-line")).map(vl => vl.textContent).join("|");
})()'

Clearing Monaco Input

# macOS:
npx @playwright/cli press Meta+a
# Linux / Windows:
npx @playwright/cli press Control+a
 
npx @playwright/cli press Backspace

Troubleshooting

"Connection refused" or "Cannot connect"

• Make sure VS Code Insiders was launched with --remote-debugging-port=9223
• If VS Code was already running, quit and relaunch with the flag
• Check that the port isn't in use by another process:
  • macOS / Linux: lsof -i :9223
  • Windows: netstat -ano | findstr 9223

Elements not appearing in snapshot

• VS Code uses multiple webviews. Use npx @playwright/cli tab-list to list targets and switch to the right one with npx @playwright/cli tab-select <index>

Cannot type in Monaco inputs

• Standard click doesn't work on Monaco editors — see the "Interacting with Monaco Editor" section above for the full compatibility matrix
• fill <ref> is the best approach; individual press commands work everywhere; type works after focus is established

Screenshots fail with "Permission denied" (macOS)

If npx @playwright/cli screenshot returns "Permission denied", your terminal needs Screen Recording permission. Grant it in System Settings → Privacy & Security → Screen Recording. As a fallback, use the eval verification snippet to confirm text was entered — this doesn't require screen permissions.

Cleanup

Always kill the debug VS Code instance when you're done. Leaving it running wastes resources and holds the CDP port.

# Disconnect npx @playwright/cli
npx @playwright/cli close
 
# Kill the debug VS Code instance
# macOS / Linux:
kill $(ps ax -ww -o pid,command | grep "$PWD/.vscode-ext-debug" | grep -v grep | awk '{print $1}' | head -1)
 
# Windows (PowerShell):
# Get-CimInstance Win32_Process | Where-Object { $_.CommandLine -like "*$PWD\.vscode-ext-debug*" } | ForEach-Object { Stop-Process -Id $_.ProcessId }