diff --git a/.github/workflows/install.yml b/.github/workflows/install.yml
index 003cb47..0aa0483 100644
--- a/.github/workflows/install.yml
+++ b/.github/workflows/install.yml
@@ -245,10 +245,15 @@ jobs:
 
     steps:
       - name: Bootstrap prerequisites (as root - mirrors a shared host)
+        # tmux is deliberately NOT pre-installed. It used to be, and that is
+        # exactly why the no-sudo gap stayed invisible across 15 cells: `has tmux`
+        # was always true, so the missing installer never mattered while the repo
+        # still shipped tmux config and cloned tmux plugins. The environment was
+        # supplying the thing under test. install.sh must provide it now.
         run: |
           export DEBIAN_FRONTEND=noninteractive
           apt-get -yq update
-          apt-get -yq install apt-utils git curl wget ca-certificates zsh tmux python3
+          apt-get -yq install apt-utils git curl wget ca-certificates zsh python3
 
       - name: Install sudo binary (forced + nonsudoer)
         if: matrix.variant == 'forced' || matrix.variant == 'nonsudoer'
@@ -345,7 +350,8 @@ jobs:
         # --allowerasing: EL9+ images ship curl-minimal, which conflicts with
         # the full curl package - allow dnf to swap it out.
         run: |
-          dnf -yq install --allowerasing git curl wget ca-certificates zsh tmux python3 \
+          # tmux deliberately absent here too - see the Ubuntu no-sudo job.
+          dnf -yq install --allowerasing git curl wget ca-certificates zsh python3 \
             tar gzip xz findutils shadow-utils glibc-langpack-en
 
       - name: Install sudo binary (forced + nonsudoer)
diff --git a/AGENTS.md b/AGENTS.md
index 994b6e1..e050231 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -52,6 +52,12 @@ fallback and the unapplied-pins path - 28 cells total.
   list with a per-package retry, keep an optional tool's apt steps non-fatal
   (`|| { log_warn ...; return; }`), and let the `_install_*` GitHub fallbacks
   cover whatever apt cannot supply.
+- **Never let a test environment supply the thing under test.** The no-sudo CI jobs
+  and `Dockerfile.nosudo` pre-installed tmux as a root prerequisite, so `has tmux`
+  was true before install.sh ran. A non-sudoer therefore got tmux CONFIG and tmux
+  PLUGINS but no tmux BINARY, and 15 green cells said nothing about it for months -
+  found on a real host, not in CI. When adding a prerequisite to a test image, ask
+  whether the install is supposed to provide it; if it is, leave it out.
 - Never construct GitHub release asset URLs manually - use `_gh_release_info` or
   `_gh_latest_release` from `lib/utils.sh`; asset names change between releases.
   Exception: `releases/latest/download/<name>` for an asset whose name carries no
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3b6543c..d4d09ee 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,14 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.12.0] - 2026-09-19
+
+### Added
+- tmux is now installed without sudo, as a static AppImage, with an extract fallback for hosts without FUSE. The repo shipped tmux config and cloned tmux plugins while a non-sudoer could end up with no tmux binary at all.
+
+### Changed
+- The no-sudo CI jobs and `Dockerfile.nosudo` no longer pre-install tmux. Doing so made `has tmux` true before install.sh ran, which is why the gap stayed invisible across 15 cells.
+
 ## [1.11.9] - 2026-09-18
 
 ### Fixed
diff --git a/Dockerfile.nosudo b/Dockerfile.nosudo
index 24313d3..183fb03 100644
--- a/Dockerfile.nosudo
+++ b/Dockerfile.nosudo
@@ -72,16 +72,20 @@ ARG NOSUDO_INSTALL=
 # RHEL family). The dnf list adds what Ubuntu images already carry: tar/gzip/xz
 # (binary extraction), findutils (_download_tar_bin uses find), shadow-utils
 # (useradd below), glibc-langpack-en (en_US.UTF-8 locale data).
+# tmux is deliberately NOT here. Pre-installing it made `has tmux` true before
+# install.sh ran, which is why a no-sudo host getting tmux CONFIG but no tmux
+# BINARY went unnoticed - the image supplied the thing under test. install.sh
+# must provide it (_install_tmux in modules/base.sh).
 RUN if command -v apt-get >/dev/null 2>&1; then \
         apt-get -yq update && \
         apt-get -yq install --no-install-recommends \
-            apt-utils git curl wget ca-certificates zsh tmux python3 && \
+            apt-utils git curl wget ca-certificates zsh python3 && \
         rm -rf /var/lib/apt/lists/*; \
     else \
         # --allowerasing: EL9+ images ship curl-minimal, which conflicts with
         # the full curl package - allow dnf to swap it out.
         dnf -yq install --allowerasing \
-            git curl wget ca-certificates zsh tmux python3 \
+            git curl wget ca-certificates zsh python3 \
             tar gzip xz findutils shadow-utils glibc-langpack-en && \
         dnf clean all; \
     fi
diff --git a/VERSION b/VERSION
index 361ffc5..0eed1a2 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.11.9
+1.12.0
diff --git a/modules/base.sh b/modules/base.sh
index ca11f0f..d6d6389 100755
--- a/modules/base.sh
+++ b/modules/base.sh
@@ -60,13 +60,17 @@ install_base() {
         else
             log_warn "No sudo - skipping system packages; fetching tools as local binaries"
         fi
+        # git, zsh and python3 have no practical single-binary fallback, so they
+        # stay a hint. tmux does (see _install_tmux), and this repo ships tmux
+        # config and clones tmux plugins, so it is fetched rather than mentioned.
         local _hint tool; _hint=$(_pkg_install_hint)
-        for tool in git zsh tmux python3; do
+        for tool in git zsh python3; do
             has "$tool" || log_warn "$tool not found - install it: ${_hint} $tool"
         done
         _install_ripgrep
         _install_fd
         _install_jq
+        _install_tmux
     fi
 
     _install_fzf
@@ -118,13 +122,17 @@ install_base_docker() {
         _install_jq
     else
         log_warn "No apt - skipping system packages; fetching tools as local binaries"
+        # git, zsh and python3 have no practical single-binary fallback, so they
+        # stay a hint. tmux does (see _install_tmux), and this repo ships tmux
+        # config and clones tmux plugins, so it is fetched rather than mentioned.
         local _hint tool; _hint=$(_pkg_install_hint)
-        for tool in git zsh tmux python3; do
+        for tool in git zsh python3; do
             has "$tool" || log_warn "$tool not found - install it: ${_hint} $tool"
         done
         _install_ripgrep
         _install_fd
         _install_jq
+        _install_tmux
     fi
 
     _install_fzf
@@ -453,6 +461,56 @@ _install_ripgrep() {
     fi
 }
 
+# tmux: only reachable here as a static AppImage.
+#
+# This repo ships .tmux.conf, .tmux.conf.local and clones tmux plugins, so a host
+# that gets the configs but no tmux is incoherent - and that is exactly what a
+# non-sudoer on a box without tmux got, measured 2026-09-19 on a fleet host.
+# Upstream tmux publishes SOURCE ONLY (checked: the latest release carries just
+# tmux-<ver>.tar.gz), and building it needs libevent and ncurses built locally
+# too, so a prebuilt static binary is the only one-command option.
+#
+# The build is THIRD PARTY (nelsonenzo/tmux-appimage), which is why this verifies
+# the binary runs before linking it and says plainly where it came from, rather
+# than installing it silently. apt is always preferred when it is available.
+_install_tmux() {
+    if has tmux; then
+        log_ok "tmux already installed - skipping"
+        return
+    fi
+    log_step "tmux (static AppImage - third-party build)"
+    local arch; arch=$(uname -m)
+    if [ "$arch" != x86_64 ]; then
+        log_warn "tmux: the AppImage is x86_64 only, this is $arch - install it with your package manager"
+        return
+    fi
+    local url="https://github.com/nelsonenzo/tmux-appimage/releases/latest/download/tmux.appimage"
+    local optdir="$HOME/.local/opt"
+    mkdir -p "$optdir" ~/.local/bin
+    log_info "tmux: fetching the static AppImage from nelsonenzo/tmux-appimage"
+    if has curl; then
+        curl -sfLo "$optdir/tmux.appimage" "$url" || { log_warn "tmux: download failed - skipping"; return; }
+    else
+        wget -qO "$optdir/tmux.appimage" "$url" || { log_warn "tmux: download failed - skipping"; return; }
+    fi
+    chmod +x "$optdir/tmux.appimage"
+
+    # An AppImage mounts itself through FUSE, which many containers and hardened
+    # hosts do not have - measured on a fleet host, where the direct run failed and
+    # this fallback is what actually installed it. --appimage-extract needs no FUSE.
+    if "$optdir/tmux.appimage" -V >/dev/null 2>&1; then
+        ln -sf "$optdir/tmux.appimage" ~/.local/bin/tmux
+        log_ok "tmux installed → ~/.local/bin/tmux ($("$optdir/tmux.appimage" -V 2>/dev/null)) [AppImage]"
+    elif ( cd "$optdir" && "$optdir/tmux.appimage" --appimage-extract >/dev/null 2>&1 ) \
+            && [ -x "$optdir/squashfs-root/usr/bin/tmux" ]; then
+        ln -sf "$optdir/squashfs-root/usr/bin/tmux" ~/.local/bin/tmux
+        log_ok "tmux installed → ~/.local/bin/tmux ($("$optdir/squashfs-root/usr/bin/tmux" -V 2>/dev/null)) [extracted, no FUSE]"
+    else
+        log_warn "tmux: the AppImage neither ran nor extracted - skipping"
+        return
+    fi
+}
+
 # fd: GitHub tarball - binary is 'fd'
 _install_fd() {
     if has fd || has fdfind; then