fix(core): recognize Ctrl+Backspace on Windows Terminal and WSL

[Info-Cado]

Summary

• Fix Ctrl+Backspace not triggering delete-word-backward on Windows Terminal and WSL

Problem

Windows Terminal and WSL terminals send different byte sequences for backspace:

• Regular Backspace: \x7f (ASCII 127, DEL)
• Ctrl+Backspace: \b (ASCII 8)

The current parser treats both as plain backspace without setting ctrl: true, so keybindings like ctrl+backspace → delete-word-backward never trigger.

Additional WSL Complexity

In WSL, process.platform returns 'linux', not 'win32', even though Windows Terminal sends Windows-style key sequences. This required detecting WSL via environment variables (WSL_DISTRO_NAME, WSL_INTEROP).

Solution

Added isWindowsTerminal() helper that detects:

1. Native Windows (process.platform === 'win32')
2. WSL (WSL_DISTRO_NAME or WSL_INTEROP environment variables)

Platform	\b Handling	Result
Windows/WSL	Ctrl+Backspace	{ name: "backspace", ctrl: true }
macOS/Linux	Ctrl+H (unchanged)	{ name: "h", ctrl: true }

Testing

• All 41 tests pass
• Tests use the same isWindowsTerminal() helper for platform-aware assertions
• Manually verified in WSL with Windows Terminal

Fixes anomalyco/opencode#6991

[pkg-pr-new]

@opentui/core

npm i https://pkg.pr.new/anomalyco/opentui/@opentui/core@555

@opentui/react

npm i https://pkg.pr.new/anomalyco/opentui/@opentui/react@555

@opentui/solid

npm i https://pkg.pr.new/anomalyco/opentui/@opentui/solid@555

@opentui/core-darwin-arm64

npm i https://pkg.pr.new/anomalyco/opentui/@opentui/core-darwin-arm64@555

@opentui/core-darwin-x64

npm i https://pkg.pr.new/anomalyco/opentui/@opentui/core-darwin-x64@555

@opentui/core-linux-arm64

npm i https://pkg.pr.new/anomalyco/opentui/@opentui/core-linux-arm64@555

@opentui/core-linux-x64

npm i https://pkg.pr.new/anomalyco/opentui/@opentui/core-linux-x64@555

@opentui/core-win32-arm64

npm i https://pkg.pr.new/anomalyco/opentui/@opentui/core-win32-arm64@555

@opentui/core-win32-x64

npm i https://pkg.pr.new/anomalyco/opentui/@opentui/core-win32-x64@555

commit: 91d10f2

[kommander]

I think that could make sense, it does not play well with existing expectations though it seems.

[Info-Cado]

Thanks for the feedback @kommander!

You're right - I investigated the CI failures and I see the issue. The change breaks existing expectations around how \b (ASCII 8) is interpreted:

Current behavior: \b → { name: "h", ctrl: true } (via the generic ctrl+letter handler)

• This then matches keybindings like { name: "h", ctrl: true, action: "backspace" } for single-char deletion

My change: \b → { name: "backspace", ctrl: true }

• This matches { name: "backspace", ctrl: true, action: "delete-word-backward" } and triggers word deletion

The root cause is terminal semantics divergence:

• Unix/macOS: \b = Ctrl+H (traditionally "h" with ctrl modifier)
• Windows Terminal: \b = Ctrl+Backspace (a distinct key combination)

Options I see:

1. Platform detection: Only interpret \b as Ctrl+Backspace on Windows (process.platform === 'win32'). This preserves existing behavior on macOS/Linux but enables the fix for Windows/WSL users.

2. Keep existing behavior: Revert this change and document that Ctrl+Backspace requires Kitty keyboard protocol or modifyOtherKeys mode to work. The trade-off is that Windows Terminal users in WSL won't get word-deletion with Ctrl+Backspace.

3. Add explicit keybinding: Keep \b as Ctrl+H, but add a default keybinding { name: "h", ctrl: true, action: "delete-word-backward" } to make Ctrl+H also delete words. This would be a behavior change but wouldn't affect key parsing.

What approach would you prefer? I'm happy to implement whichever makes most sense for the project.

BTW this comment was written by AI

[Info-Cado]

I've pushed a fix that uses platform detection (Option 1).

Changes:

• On Windows (process.platform === 'win32'): \b → { name: "backspace", ctrl: true } (enables Ctrl+Backspace word deletion)
• On macOS/Linux: \b → { name: "h", ctrl: true } (preserves existing Ctrl+H behavior)

This should:

1. Pass all existing tests on macOS CI (behavior unchanged)
2. Enable Ctrl+Backspace on Windows Terminal/WSL users

The tests now use platform detection to validate the expected behavior on each platform.

[Info-Cado]

I discovered an issue with the previous platform detection approach: WSL reports process.platform as 'linux', not 'win32', even though Windows Terminal sends Windows-style key sequences to WSL applications.

Updated the fix to also check for WSL environment variables:

• WSL_DISTRO_NAME - set by WSL to the distribution name
• WSL_INTEROP - set by WSL2 for Windows interop

This ensures Ctrl+Backspace works correctly for:

1. Native Windows (process.platform === 'win32')
2. WSL1/WSL2 (detected via environment variables)
3. macOS/Linux (unchanged behavior - \b → Ctrl+H)

Tests updated to use the same detection logic.

[kommander]

The tests should probably use the same method as parse.keypress if it's not mocking anything?