Forward Opt+Enter as ESC+CR to alt-screen programs on macOS

[altjx]

Summary

When a TUI like Claude, vim, or fish runs in alt-screen mode, pressing Option+Enter on macOS (without the "Option as Meta" setting enabled) was sending a bare \r to the PTY instead of the xterm-style \x1b\r. The TUI then treated it as a plain Enter and submitted, instead of inserting a newline.

Root cause

When alt-screen is active, focus is on TerminalView (via focus_terminal() → ctx.focus_self()), so the editor's alt-enter keybinding never fires. The keystroke reaches alt_screen_element.rs's KeyDown handler and calls KeystrokeWithDetails::to_escape_sequence(). In the legacy fallback chain inside meta_keystroke_to_escape_sequence (crates/warp_terminal/src/model/escape_sequences.rs):

if OperatingSystem::get().is_mac() {
    if !keystroke.meta {
        return None;            // ← exits here for Opt+Enter on Mac
    }
}

For default Mac config, Opt+Enter has keystroke.alt = true, keystroke.meta = false. The function returns None, the rest of the chain returns None too, and the alt_screen_element falls through to key_down(chars) which dispatches the raw \r to the PTY. The Mac meta-only gate is correct for letter keys (Option+E = é, etc., shouldn't become ESC+e) but Enter has no Option-modified glyph, so it's safe — and expected by xterm-style TUIs — to encode Opt+Enter as a meta keystroke.

A secondary bug: when users do have Option-as-Meta enabled (alt → meta upstream), map_special_key_to_bytes had no entry for "enter", so the fallback at the end of meta_keystroke_to_escape_sequence sent literal ESC + the bytes of the string "enter".

Changes

• crates/warp_terminal/src/model/escape_sequences.rs
  • Allow alt-enter through meta_keystroke_to_escape_sequence on Mac even when meta is unset.
  • Add "enter" => "\r" to map_special_key_to_bytes.
• crates/warp_terminal/src/model/escape_sequences_test.rs
  • Extend the existing meta keystroke test to cover Enter.
  • Add a Mac-only test asserting alt-enter produces ESC+CR when Option-as-Meta is off.

Test plan

• cargo test -p warp_terminal escape_sequences passes
• Built locally (./script/macos/bundle --selfsign --nouniversal) and verified Opt+Enter inserts a newline in Claude inside the alt-screen instead of submitting
• Verify behavior is unchanged with extra_meta_keys.left_alt = true (Option-as-Meta enabled)
• Verify behavior is unchanged when Kitty keyboard protocol is enabled (CSI u path takes precedence)
• Sanity-check that Opt+letter still produces special glyphs (é, ø, etc.) and isn't being intercepted as ESC+letter

Notes

Filed as a draft. Per CONTRIBUTING.md, bug fixes need a triaged issue first — happy to file one and link it back here once a maintainer confirms scope.

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