tui: clipboard copy silently fails inside tmux (OpenTUI wraps OSC 52 in DCS passthrough that tmux drops) #59134

Summary

Copying from the OpenCode TUI silently fails to reach the system clipboard when OpenCode runs inside tmux. The root cause is in OpenTUI (anomalyco/opentui, the TUI toolkit OpenCode's terminal UI is built on), not in tmux: OpenTUI wraps its OSC 52 clipboard write in a tmux DCS passthrough escape, which tmux (3.3+) silently drops unless allow-passthrough is enabled. A plain (unwrapped) OSC 52 works fine through tmux's set-clipboard on path, so wrapping the clipboard write appears to be counterproductive.

Environment

• opencode version: 2.1.4 (latest)
• OS: Linux x86_64 (7.2.9-x64v3-xanmod1)
• Terminal: WezTerm (OSC 52-capable) → tmux 3.4 (TERM=tmux-256color inside); tmux reports client_termfeatures includes clipboard
• Shell: /bin/bash
• Install/channel: npm (@opencode/cli), release
• Active plugins: @slkiser/opencode-quota@latest
• tmux config: set -g set-clipboard on; allow-passthrough left at its default (off)

Reproduction

1. Start tmux 3.4 with default options plus set -g set-clipboard on, inside an OSC 52-capable terminal.

2. Sanity-check the clipboard chain from a shell pane — this works:

   printf '\033]52;c;%s\033\\' "$(printf 'hello' | base64)"

   Pasting into a GUI app yields hello. ✔

3. In the OpenCode TUI, copy something: <leader>y (messages.copy, leader defaults to ctrl+x), or select text (copy-on-select is the default terminal.copy mode).

4. Paste into a GUI app → nothing is pasted. No tmux paste buffer is created either.

Reproducible consistently.

Expected Behavior

Copy (messages.copy, copy-on-select) puts the text on the system clipboard when running inside tmux with set-clipboard on and an OSC 52-capable outer terminal — the plain-OSC 52 test above proves the chain works.

Actual Behavior

The copy action completes without any error, but the clipboard is unchanged.

Root cause: when OpenTUI detects tmux, Terminal.writeClipboard() wraps the OSC 52 sequence in a tmux DCS passthrough (ESC Ptmux; <ESC-doubled OSC 52> ESC \) instead of emitting it plainly — see writeClipboard in opentui packages/core/src/zig/terminal.zig. tmux ≥ 3.3 silently discards passthrough sequences unless allow-passthrough is enabled, so the write never reaches the outer terminal.

Additional Context

• Setting set -s allow-passthrough on in ~/.tmux.conf fixes it (verified). But every tmux layer must opt in, and the failure mode is completely silent — clipboard.ts write() reports success when the terminal destination status is merely "attempted".
• Since a plain OSC 52 works through tmux's set-clipboard on (tmux forwards it to the outer terminal itself), consider not wrapping clipboard writes for tmux, or documenting the allow-passthrough requirement.
• The host-clipboard fallback (xclip/wl-copy) doesn't help in SSH panes without a display, which is where this bites most.
• Nested tmux (e.g. opencode inside tmux on a remote host inside local tmux): OpenTUI wraps only a single level, so each layer needs the right option even with the workaround.