webtmux v0.2.0

webtmux v0.2.0

The second tagged release of this fork, and the first whose binaries can be
re-derived from the tag they were built from.

Most of what is here came from asking what a feature already promises and then
finding the place it quietly does not keep that promise: a save button that could
only produce the smaller of a pane's two buffers, a scrollback limit you can raise
with no effect on the window in front of you, a copy that silently destroys the
last one, a highlight that outlives the text it named.

Copy buffers — copy several things, paste them one at a time

A system clipboard holds exactly one thing, so gathering three snippets out of a
scrollback meant three round trips, and every intermediate copy destroyed the last
one silently.

• A list of copy buffers with one FOCUSED entry, and one rule tying it to the
  machine's single clipboard: the focused buffer is the clipboard. Focusing a
  row writes it there, so this is not a second clipboard fighting the real one —
  it is a way to choose what the real one holds. Cmd/Ctrl+V keeps working
  everywhere, including in other applications.
• Whether a copy ADDS a buffer or REUSES one is decided by a single question: has
  the focused buffer been pasted yet? Copy before pasting and both are kept; copy
  after pasting and the spent slot is reused. So gathering grows the list and
  ordinary copy-paste never does — the panel stays one row for anyone who does not
  want the feature.
• Copying while the panel is shut floats it in for a couple of seconds so you can
  see where the copy landed: always floating (no terminal is resized), never taking
  the keyboard, and dismissed early by anything else you do. A panel you opened
  yourself is left alone — never auto-collapsed, because it was never auto-shown.
• Ctrl+Alt+= (tmux's own Prefix+=, choose-buffer), or the toolbar's NORMAL/COPY
  pill, which now opens the panel and carries a count. The copy/normal mode toggle
  moved inside it; Ctrl+Alt+[ still flips the mode directly.
• Buffers are per browser tab and survive a reload. They are deliberately not
  shared through the tmux server: text you copied is not UI arrangement.

Scrollback: see it, resize it, and get all of it out

• The ⤓ save now defaults to the ENTIRE buffer. Both destinations — the browser
  download and the file written on the machine tmux runs on — were built on the
  capture store that feeds the Exposé thumbnails, which holds only the VISIBLE
  SCREEN. The one thing a terminal is kept for, the output that has already
  scrolled past, was the part you could not get out, and nothing said so.
• Toolbar ⛁ answers the three things a fixed-capacity ring hides: how many lines
  a window can hold, how many it is holding (with a gauge that turns amber once
  tmux is already dropping the oldest), and the fact that changing history-limit
  does nothing to a pane that already exists.
• "Resize this window" is a rebuild, because tmux has no resize — a pane's
  buffer capacity is fixed when the pane is created. The window's panes are rebuilt
  in place at the new size, same name, index and shape, and the existing
  scrollback is carried across, colours included. It travels in a tmux buffer
  rather than a temp file, so it works when webtmux is a container that cannot see
  that filesystem.
• A pane tmux itself launched with a command (#{pane_start_command}) offers to
  start it again, naming the exact command. A program you started by typing at a
  prompt is one tmux never saw, so the confirmation stops offering rather than
  guessing.
• New windows sets history-limit for everything created from then on, and
  Also save it for future tmux servers writes the line into the tmux config
  file tmux actually loaded, naming the file it wrote.

Selection

• Shift-click moves the END of the selection you already have, keeping the
  anchor you dragged from — so an overshoot is one click to fix rather than a whole
  drag repeated, which matters in a pane that is still printing. It works over a
  mouse-grabbing program too, where xterm's own incremental-click path is disabled
  and therefore unusable.
• A highlight now ends when the window under it does. A selection names text,
  but xterm holds it as buffer coordinates and tmux repaints the viewport rather
  than scrolling it, so switching windows left a rectangle sitting over unrelated
  text. The decision comes from the layout, so switches this browser did not make
  are caught too — tmux's own prefix n, another client, a reconnect.

Reconnect and alerts

• A reload restores the connection; it does not answer your alerts. Opening a
  laptop to several tabs flashing, refreshing to get the connection back, and
  finding every flash gone was the page's death being indistinguishable from a full
  acknowledgement. The registry is now carried across the gap in per-tab storage,
  which has exactly the right lifetime.
• A reconnect puts the primary region back in the session it was in, instead of
  landing on whatever window the shared base session happened to be showing — a
  window nobody had opened, and which the recents strip correctly did not explain.

Reproducible builds

This is the first release whose assets can be checked against their source by
anyone. Four independent inputs used to leak into the binary, each invisible in
normal use and each fatal to an audit: a date-derived build stamp, no -trimpath
(-s -w does not strip file paths), a floating Go toolchain, and a docker context
that was the working tree rather than the commit.

make release-from-commit REF=v0.2.0   # the release build — no local Go needed
make verify-repro REF=v0.2.0          # proves it: same commit, two directories, same bytes

verify-repro deliberately varies the build directory, because building twice in
one place proves nothing about the leak that actually occurred.

v0.1.0's published assets were replaced with a reproducible rebuild after the fact,
but its tag does not name the commit they were built from. v0.2.0's do.

Install

Binaries are release assets, one per platform, named webtmux-<os>-<arch>. The
repository is public, so no token and no gh is needed:

curl -fsSL -o webtmux \
  https://github.com/sparant/webtmux/releases/download/v0.2.0/webtmux-linux-amd64
chmod +x webtmux
./webtmux -a 127.0.0.1 -w tmux new-session -A -s main

Bind loopback as above unless you mean otherwise: the default address is 0.0.0.0,
and authentication is HTTP basic auth over plain HTTP.

SHA256SUMS covers every binary in this release:

curl -fsSL -O https://github.com/sparant/webtmux/releases/download/v0.2.0/SHA256SUMS
sha256sum --check --ignore-missing SHA256SUMS

See the README's Installation section for a full fresh-machine walkthrough
(tmux prerequisite, ~/.local/bin, macOS quarantine xattr).

Upgrading from v0.1.0

• The toolbar's NORMAL/COPY pill no longer toggles copy mode — it opens the copy
  buffer panel, and the button that flips the mode is the first control inside it.
  Ctrl+Alt+[ is unchanged if you want the mode without the panel.
• The ⤓ save defaults to the whole scrollback, where it previously produced the
  visible screen. Pick "visible screen" in the dropdown for the old behaviour.
• If you pinned v0.1.0 with webtmux-launch --webtmux-version v0.1.0 and hit a
  sha256 mismatch, that is the pinned-version cache holding the sums from before
  v0.1.0's assets were rebuilt: rm -rf ~/.cache/webtmux-launch/v0.1.0. That check
  is the tamper detection, so it is not being loosened.

Notes

• Asset names are an interface. webtmux-launch builds its download URLs from
  them, so they will not be renamed. Adding platforms is safe.
• Read-only (-w absent) is a browser-facing authority boundary, not a sandbox —
  see v0.1.0's notes for what it does and does not cover. Bind loopback and tunnel
  over SSH.
• The browser UI still loads xterm.js and Tailwind from a CDN at runtime; removing
  that dependency is planned, not done.
• Built with CGO_ENABLED=0 by a pinned Go 1.23.12; the binaries are static and
  embed their assets.