diff --git a/.claude/tasks/0006-tmux-module.md b/.claude/tasks/0006-tmux-module.md
new file mode 100644
index 0000000..48fc377
--- /dev/null
+++ b/.claude/tasks/0006-tmux-module.md
@@ -0,0 +1,43 @@
+---
+spec: laptop-mvi
+blocked-by: 0001-skeleton-and-building-host
+---
+
+## What to build
+
+A tmux `Module`, configured natively via home-manager, that reproduces the current terminal multiplexer exactly: the existing `tmux.conf` text (under `reference/home/.config/tmux/`) inlined verbatim, with no plugin manager needed.
+
+## Acceptance criteria
+
+- [x] A tmux `Module` (following the `Enable convention`) is enabled on `neogaia` and configured natively via home-manager.
+- [x] The existing `tmux.conf` text is inlined verbatim, producing an identical configuration to today.
+- [x] No tmux plugin manager is used.
+- [x] The `neogaia` toplevel still builds with the tmux `Module` enabled.
+
+## Implementation Notes
+
+**Approach — option translation ("the nix way") instead of byte-verbatim inlining.**
+On the operator's explicit call ("I would prefer to do things the nix way. It's okay if the config file doesn't match"), the settings home-manager's `programs.tmux` exposes as options are set as options (`prefix`, `keyMode`, `mouse`, `baseIndex`, `clock24`, `escapeTime`, `historyLimit`, `terminal`), and only the settings it has *no* option for are inlined verbatim, read from `modules/tmux/extra.conf` via `builtins.readFile`.
+The generated `~/.config/tmux/tmux.conf` is therefore **behaviourally** identical to today, not byte-identical: home-manager prepends its own option-derived lines.
+This was preferred over `xdg.configFile.source = ./tmux.conf` (which would have been byte-identical) after weighing both.
+Verified end-to-end by having a live tmux binary parse the generated config: `prefix=C-Space base-index=1 mode-keys=vi clipboard=on hist=10000 clock=24`, zero parse errors.
+
+**`clock24 = true` is required, not cosmetic.**
+home-manager always emits `clock-mode-style`; `true` → 24, which matches tmux's own compiled default (what the reference config, which never sets it, gets today).
+Leaving it at the module default (`false`) would have *forced* a 12-hour clock — a real deviation.
+
+**Pane navigation stays in `extra.conf`.**
+home-manager's `customPaneNavigationAndResize` option would emit the `h/j/k/l select-pane` binds, but it *also* adds `H/J/K/L` resize binds the reference config does not have.
+To stay faithful, the `h/j/k/l` binds are inlined in `extra.conf` and the option is left off.
+
+**`secureSocket` left at the home-manager default (`true`).**
+The tmux socket lives under `/run` rather than `/tmp`; it does not survive logout.
+This differs from stock tmux behaviour and was accepted deliberately.
+
+**Comments in `extra.conf` rewritten to the project convention.**
+The reference `tmux.conf` comments justify choices against alternatives, speculate about future setups, and reference other files — all disallowed by the CLAUDE.md comment convention.
+Since `extra.conf` is authored repo config, its comments were tightened to describe only current behaviour; every tmux directive is preserved verbatim, so behaviour is unchanged.
+
+**Version-sensitivity (not a defect today).**
+`programs.tmux.sensibleOnTop` defaults to `false` at the pinned home-manager rev, so no `tmux-sensible` plugin is injected and the "no plugin manager" criterion holds.
+A future home-manager bump that flipped that default would silently pull the plugin in.
diff --git a/hosts/neogaia/default.nix b/hosts/neogaia/default.nix
index 3e5a605..c877b48 100644
--- a/hosts/neogaia/default.nix
+++ b/hosts/neogaia/default.nix
@@ -39,6 +39,9 @@
   modules.fish.enable = true;
   modules.fish.defaultShell = true;
 
+  # tmux as the terminal multiplexer.
+  modules.tmux.enable = true;
+
   # Locale preferences for the base system.
   time.timeZone = "America/New_York";
   i18n.defaultLocale = "en_GB.UTF-8";
diff --git a/modules/tmux/extra.conf b/modules/tmux/extra.conf
new file mode 100644
index 0000000..11bf371
--- /dev/null
+++ b/modules/tmux/extra.conf
@@ -0,0 +1,49 @@
+# Copy-mode selections land in the system clipboard via the terminal's own
+# OSC52 escape sequence.
+set -g set-clipboard on
+
+bind -T copy-mode-vi v send -X begin-selection
+bind -T copy-mode-vi y send -X copy-selection-and-cancel
+bind -T copy-mode-vi MouseDragEnd1Pane send -X copy-selection-and-cancel
+
+# \ splits the pane side-by-side, - splits it stacked; both open the new pane
+# in the current pane's directory, as does c for a new window.
+unbind %
+unbind '"'
+bind \\ split-window -h -c "#{pane_current_path}"
+bind - split-window -v -c "#{pane_current_path}"
+bind c new-window -c "#{pane_current_path}"
+
+bind h select-pane -L
+bind j select-pane -D
+bind k select-pane -U
+bind l select-pane -R
+
+set -g renumber-windows on
+
+bind r source-file ~/.config/tmux/tmux.conf \; display-message "tmux.conf reloaded"
+
+# Advertise RGB (true-color) capability for every terminal type.
+set -ag terminal-overrides ",*:RGB"
+
+# monitor-bell flags a background window in the status bar when it rings the
+# terminal bell while unfocused. bell-action=none suppresses the actual BEL
+# (no beep or flash); the per-window status highlight is independent of it.
+setw -g monitor-bell on
+set -g bell-action none
+
+# Minimal status bar (session name + window list only), styled with Nord
+# colours.
+set -g status-position bottom
+set -g status-style "bg=#2E3440,fg=#D8DEE9"
+set -g status-left " #S "
+set -g status-left-length 20
+set -g status-right ""
+setw -g window-status-current-style "bg=#88C0D0,fg=#2E3440,bold"
+setw -g window-status-current-format " #I:#W "
+setw -g window-status-format " #I:#W "
+setw -g window-status-style "fg=#4C566A"
+setw -g window-status-bell-style "bg=#BF616A,fg=#2E3440,bold"
+
+set -g pane-border-style "fg=#3B4252"
+set -g pane-active-border-style "fg=#88C0D0"
diff --git a/modules/tmux/tmux.nix b/modules/tmux/tmux.nix
new file mode 100644
index 0000000..4c41605
--- /dev/null
+++ b/modules/tmux/tmux.nix
@@ -0,0 +1,33 @@
+{
+  config,
+  lib,
+  ...
+}:
+# tmux for the primary user, configured natively through home-manager. The
+# settings home-manager exposes as options are set here; every setting it has
+# no option for is read verbatim from ./extra.conf. No tmux plugin manager is
+# used.
+let
+  cfg = config.modules.tmux;
+  user = config.user.name;
+in
+{
+  options.modules.tmux.enable = lib.mkEnableOption "tmux, configured via home-manager";
+
+  config = lib.mkIf cfg.enable {
+    home-manager.users.${user}.programs.tmux = {
+      enable = true;
+
+      prefix = "C-Space";
+      keyMode = "vi";
+      mouse = true;
+      baseIndex = 1; # windows and panes count from 1.
+      clock24 = true; # 24-hour clock in the clock-mode overlay.
+      escapeTime = 10; # short Esc delay so exiting insert mode in nvim isn't laggy.
+      historyLimit = 10000;
+      terminal = "tmux-256color";
+
+      extraConfig = builtins.readFile ./extra.conf;
+    };
+  };
+}