fix(remote): copies leave the agent's tmux; exact-text clipboard tool for agents

[bborn]

Fixes copy/paste to and from executor panes, especially on placed hosts (found in InfluenceKit task 5547).

What was wrong

1. The agent's tmux swallowed clipboard writes. fix(hosts): a task on another host behaves like a local one #758 set set-clipboard on on the outer (UI) server only. The server the agent runs on (the local agent server, or the placed host's tmux) kept tmux's default, external. Under that default an OSC 52 written by an application in the pane is dropped: Claude Code's copy, an editor yank, printf '\e]52;…'. It never reaches the view. I reproduced this with two nested tmux servers, and it is now a test.
2. Wrapped output gains hard newlines. When you select text in the terminal, you get a line break wherever the agent's UI wrapped it. Agents like Claude Code draw those breaks themselves, so no tmux option (copy-mode -J, capture-pane -J) can join them. The fix has to avoid the terminal altogether.

Changes

• tmuxctl.AgentClipboardArgs / PassthroughArgs, applied whenever a view opens, both locally (ensureViewSession) and on the placed host (the attach chain). They set:

  • set-clipboard on on the agent server.
  • terminal-features[90|91] = tmux*:clipboard, screen*:clipboard, so an older tmux on a host, or one whose feature query was lost over ssh, still knows ty's view can take OSC 52. These use fixed indices, so they overwrite rather than append each time a view opens.
  • allow-passthrough on scoped to the task's window, for programs that wrap OSC 52 in tmux passthrough.

  All of these are set before the client attaches, because tmux reads terminal features on connect. On the host, errors are discarded so an older tmux still attaches.

• New MCP tool taskyou_copy_to_clipboard(text) and a new internal/clipboard package. The tool runs where the task was scheduled; placed tasks reach it over the existing MCP relay. It delivers the text byte for byte:

  • to the system clipboard (pbcopy, wl-copy, xclip, xsel or clip.exe),
  • and, when a ty view is attached, as OSC 52 through it (load-buffer -b ty-clipboard -w), which covers a TUI reached over ssh.

  There are no terminal escapes from the agent and no secret written to a file on the host. The task log records only the byte count. The tool is auto-approved, and agents are told to use it in both the local guidance and the relayed-host guidance.

• Docs: docs/remote-execution.md and docs/mcp-tools-reference.md.

Tests

• internal/tmuxctl: a real two-server test. An app's OSC 52 inside the inner server reaches the outer server with AgentClipboardArgs, and a control test shows it is dropped without them. Also an idempotency test against real tmux.
• internal/executor: the attach chain sets every option, before the attach, scoped to the task's window, and silences errors. I also ran the generated chain by hand against an isolated tmux to check the quoting.
• internal/clipboard: choice of route per OS and session, fallback when a command fails, the OSC 52 route, the no-route error, and the size limits.
• internal/mcp: the tool is advertised, delivers the exact text, keeps the text out of the task log, and returns failures as tool errors.

TestEnsureTaskWindow_ExportedEnvVarsReachLiveShellPane fails on the host I ran this on (mona), with or without this change. It is environmental and unrelated.

Not in this PR

• Your local terminal still has to accept OSC 52. In iTerm2 that is "Applications in terminal may access clipboard".
• The web GUI doesn't receive clipboard pushes. The tool reaches the scheduling machine's system clipboard, which covers the desktop app on the same machine.

🤖 Generated with Claude Code