BUG: Cmd/Ctrl+A does not select all in the chat input #115

Root cause

The chat input is a contenteditable div inside a sandboxed cross-origin iframe (sandbox="allow-scripts allow-forms allow-same-origin allow-popups allow-downloads") embedded in a VS Code WebviewPanel.

Confirmed by code audit: no app code calls preventDefault() or stopPropagation() on Cmd+A/C/Z when the target is the contenteditable. The command.tsx capture-phase handler explicitly returns early for clipboard chords on editable targets. CSS user-select is correctly set to text. The iframe sandbox and Permissions-Policy (clipboard-read; clipboard-write) are permissive.

Conclusion by elimination: the VS Code / Electron platform layer suppresses native browser actions for these shortcuts. Keydown events DO reach the iframe (typing works, Cmd+V's explicit handler works), but the associated DOM default action (selectAll, clipboard copy, undo) never fires. The Electron Edit-menu accelerators or VS Code's webview keyboard routing consumes the action at the platform level.

This is the same class of bug that affected paste (patch #11): native browser defaults cannot be relied on inside this sandboxed-iframe-in-a-webview architecture. The fix is the same pattern: explicit JS implementation, activated only in the framed context.

Affected shortcuts

Approach: Global editing fallback (extends patch #11)

Architecture

Extend installGlobalPasteFallback (or rename it to installGlobalEditingFallback) in packages/app/src/utils/global-clipboard.ts to cover all standard editing shortcuts. Single install point in entry.tsx.

Activation guard (same as paste fallback):

• window.parent !== window — only fires in the framed/VS Code context; plain browser keeps native behavior
• Target is an editable element (input, textarea, or [contenteditable])
• event.metaKey || event.ctrlKey (platform-appropriate modifier)

Implementation per shortcut

File changes

• packages/app/src/utils/global-clipboard.ts — extend installGlobalPasteFallback to handle a, z, y in addition to existing v, c, x (fix the existing broken Cmd+C/X path while here)
• packages/app/src/entry.tsx — no change needed (already installs the fallback)
• Zero extension-side changes, zero package.json keybinding contributions

Diagnostic confirmation (pre-implementation)

To record the exact Electron mechanism (for AMICODE-PATCHES.md's root-cause documentation):

// Paste into the iframe's devtools console:
document.addEventListener('keydown', e => {
  if (e.metaKey) console.log(`META+${e.key}`, 'defaultPrevented:', e.defaultPrevented, 'target:', e.target.tagName)
}, true)

If defaultPrevented: true for Cmd+A, the event arrives already cancelled by Electron. If false, the native action is cancelled AFTER JS dispatch (accelerator fires asynchronously). Either way, the fix is the same — explicit JS implementation.

Approaches considered

Acceptance criteria

• Cmd+A selects all text in the chat input (contenteditable)
• Cmd+C copies mouse-selected or Cmd+A-selected text to OS clipboard
• Cmd+X cuts selected text to OS clipboard
• Cmd+Z undoes the last edit in the chat input
• Cmd+Shift+Z (or Cmd+Y) redoes
• All of the above also work in other editables inside the iframe (API key fields, search inputs)
• Plain browser tab at http://127.0.0.1:{port} is unaffected (native behavior preserved)
• Existing Cmd+V paste behavior unchanged
• bun test passes, typecheck green

Constraints & invariants

• The framed-context guard (window.parent !== window) MUST remain — non-VS-Code contexts keep native behavior.
• global-clipboard.ts's existing Cmd+C bridge path must be FIXED, not duplicated — diagnose why writeClipboardViaBridge silently fails and repair it.
• execCommand('undo'/'redo') is deprecated but functional in all Chromium-based webviews. A proper undo manager is out of scope (separate issue if needed).

Prior art

• Patch Fix chat scroll jitter during streaming; respect reduced motion #11 (installGlobalPasteFallback) — the exact same pattern for paste
• Patch Fix chat scroll jitter during streaming; respect reduced motion #11 addendum (installGlobalPasteFallback generalized to all editables, not just the composer) — same architectural decision we're extending here
• Upstream: [FEATURE]: Select all current text anomalyco/opencode#8504 (open feature request), #25637 (closed not-planned, TUI input)

intake: ready
suggested_path: C
diagnostics: inline
upstream: anomalyco/opencode#8504 (open); #25637 closed not-planned (same symptom, TUI input)