diff --git a/docs/ROADMAP.md b/docs/ROADMAP.md
index 1512892..274884b 100644
--- a/docs/ROADMAP.md
+++ b/docs/ROADMAP.md
@@ -77,7 +77,7 @@ Each PR description should reference the row(s) in `docs/SCRIPTS.md` it closes,
 - Richer disk metadata (Shipped).
 - Form-factor → laptop preset (Now, depends on Pillar 5).
 - `disko-golden.nix` variants for software-RAID and BTRFS-pool-as-root (Shipped).
-- Pre-flight resume polish (Next).
+- Pre-flight resume polish (Shipped).
 - "What's installed?" summary screen on boot of a freshly-installed system, sourced from `state.json` + `nomarchy-system-scripts` introspection.
 - Optional non-LUKS branch in the installer for users who explicitly opt out of FDE.
 
@@ -121,6 +121,7 @@ Each PR description should reference the row(s) in `docs/SCRIPTS.md` it closes,
 
 (Move items here when they land — keep them brief, link the commit/PR.)
 
+- _2026-05-18_ — Pillar 4: pre-flight resume polish. Fixed four resume-flow gaps in `installer/install.sh`: (1) `--resume` with a missing state file now errors loudly with a tmpfs explanation instead of silently falling through to a fresh prompt cycle (the most common operator confusion was "rebooted, forgot tmpfs eats /tmp/, watched the installer start over without realising"); (2) on resume, the saved target drive is validated as a block device before any disk-phase step runs — catches the live-ISO USB-unplugged / non-deterministic /dev/sdX class of mid-install failures; (3) `save_state` now stamps an ISO-8601 timestamp and `load_state` shows a `(saved Xm ago)` banner plus a `Target: /dev/X → user @ host` summary line, so the user can `Ctrl-C` if they're resuming onto the wrong host before any destructive prompt fires; (4) `--help` now documents the tmpfs limitation. `shellcheck --severity=error` passes.
 - _2026-05-18_ — Declarative-state defaults centralization. Made `lib/state-schema.nix` the single source of truth for every state-default that previously lived in three places (the schema itself, `core/system/options.nix` / `core/home/options.nix` `default = …` clauses, and `core/home/state.nix` `or …` fallbacks). Replaced ~25 hardcoded literals with `schema.<scope>.<key>` reads. Side-effect: fixed a lingering bug where `core/home/options.nix:theme` still defaulted to `"summer-night"` after the system-side was moved to `"nord"` — half the codebase's home option resolved to the wrong theme when state.json was missing/blank. `nix flake check --no-build` confirms zero semantic change for every other field. Doesn't touch the installer-written `state.json` (separate batch — needs schema → JSON generation).
 - _2026-05-18_ — Pillar 7 first step: Forgejo Actions CI (eval + lint). New `.forgejo/workflows/check.yml` runs on every push to `main` and every PR: (1) `nix flake check --no-build` to catch eval regressions, (2) `bash -n` + `shellcheck --severity=error` over every `nomarchy-*` bash script (whole-tree, not just changed files — gates branches that bypass the pre-commit hook), (3) `docs/SCRIPTS.md` drift check (fails loudly if a script change didn't regenerate the audit doc). All three checks pass locally on the current tree. Activation requires enabling Actions on the Forgejo repo and registering a `forgejo-runner`; the workflow itself is dormant until then. ISO build job is intentionally deferred — needs a binary cache (Cachix/Attic) to be tractable.
 - _2026-05-18_ — **Pillar 3 Phase B: complete.** Final batch (restart/sudo/theme/misc clusters) cleared the last 13 `unused?` rows. Deleted five truly dead scripts: `nomarchy-restart-{hyprctl,mako}` (theme switching calls `hyprctl reload`/`makoctl reload` directly now), `nomarchy-restart-tmux` (one-liner of marginal value), `nomarchy-battery-present` (battery monitor checks `/sys/class/power_supply/BAT*` inline), `nomarchy-sudo-keepalive` (intended-to-be-sourced building block with no users). Surfaced eight useful tools in `SKILL.md` so the audit catches them as `kept` and AI assistants can discover them: `nomarchy-restart-trackpad` (intel_quicki2c reload), `nomarchy-sudo-{passwordless-toggle,reset}`, `nomarchy-theme-{bg-install,refresh,remove}`, `nomarchy-refresh-fastfetch`, `nomarchy-windows-vm` (new Virtualization section). Final state: 159 scripts, all `kept`, `unused?` = 0, missing references = 0.
diff --git a/installer/install.sh b/installer/install.sh
index fc983b7..b5ced6c 100755
--- a/installer/install.sh
+++ b/installer/install.sh
@@ -74,6 +74,9 @@ Usage: install.sh [--dry-run] [--resume] [-h|--help]
               Doesn't touch the disk, doesn't run nixos-install.
   --resume    Reuse answers from a previous interrupted run
               (saved at $STATE_FILE — passwords excluded).
+              NOTE: the live ISO uses tmpfs, so the state file is lost
+              on reboot. --resume only works within the same live-ISO
+              session as the original interrupted run.
   -h, --help  Print this message.
 USAGE
 }
@@ -102,19 +105,74 @@ parse_args() {
 # will silently install a system with an empty password hash and lock the
 # user out. Keep the guard checking the hash.
 save_state() {
-    declare -p \
-        TARGET_DRIVE USERNAME HOSTNAME TIMEZONE \
-        KEYMAP_LAYOUT KEYMAP_VARIANT LOCALE FORM_FACTOR \
-        ENABLE_IMPERMANENCE HARDWARE_MODULES NOMARCHY_HW_OPTS \
-        SELECTED_PROFILES NOMARCHY_REV \
-        > "$STATE_FILE"
+    # The leading timestamp lets --resume surface "how old is this state?"
+    # and is parsed back via NOMARCHY_INSTALL_STATE_SAVED_AT.
+    {
+        echo "NOMARCHY_INSTALL_STATE_SAVED_AT=\"$(date -Iseconds)\""
+        declare -p \
+            TARGET_DRIVE USERNAME HOSTNAME TIMEZONE \
+            KEYMAP_LAYOUT KEYMAP_VARIANT LOCALE FORM_FACTOR \
+            ENABLE_IMPERMANENCE HARDWARE_MODULES NOMARCHY_HW_OPTS \
+            SELECTED_PROFILES NOMARCHY_REV
+    } > "$STATE_FILE"
+}
+
+# Pretty-print "X minutes/hours/days ago" from an ISO-8601 timestamp.
+# Falls back to the raw string if `date -d` can't parse it (defensive —
+# the timestamp is always produced by `date -Iseconds` above, but we
+# don't want a stale state file to crash --resume).
+format_age() {
+    local saved="$1" saved_epoch now_epoch diff
+    saved_epoch=$(date -d "$saved" +%s 2>/dev/null) || { echo "$saved"; return; }
+    now_epoch=$(date +%s)
+    diff=$(( now_epoch - saved_epoch ))
+    if   (( diff < 60 ));    then echo "${diff}s ago"
+    elif (( diff < 3600 ));  then echo "$((diff / 60))m ago"
+    elif (( diff < 86400 )); then echo "$((diff / 3600))h $((diff % 3600 / 60))m ago"
+    else                          echo "$((diff / 86400))d ago"
+    fi
 }
 
 load_state() {
-    if [[ "$RESUME" == "true" ]] && [[ -f "$STATE_FILE" ]]; then
-        # shellcheck disable=SC1090
-        source "$STATE_FILE"
-        info "Resumed from $STATE_FILE"
+    if [[ "$RESUME" != "true" ]]; then
+        return
+    fi
+
+    # --resume with no state file is almost always operator error — the
+    # most common cause is "rebooted the live ISO and forgot tmpfs eats
+    # /tmp/". Fail loudly so the user doesn't sit through a fresh prompt
+    # cycle thinking it was resumed.
+    if [[ ! -f "$STATE_FILE" ]]; then
+        error "--resume was passed but no saved state exists at $STATE_FILE."
+        info  "The live ISO uses tmpfs — saved state doesn't survive a reboot."
+        info  "Re-run install.sh without --resume to start fresh."
+        exit 1
+    fi
+
+    # shellcheck disable=SC1090
+    source "$STATE_FILE"
+
+    # If the saved target drive isn't visible right now, every later
+    # disk-phase step will fail with cryptic errors. Catch it here.
+    # Live ISOs frequently get their non-boot USB sticks unplugged
+    # between sessions, and dev hosts sometimes have non-deterministic
+    # /dev/sdX numbering.
+    if [[ -n "${TARGET_DRIVE:-}" ]] && [[ ! -b "$TARGET_DRIVE" ]]; then
+        error "Saved target drive $TARGET_DRIVE is no longer a block device."
+        info  "The drive may have been unplugged or renamed since the saved run."
+        info  "Delete $STATE_FILE and re-run without --resume."
+        exit 1
+    fi
+
+    # Show what we're resuming into so the user can Ctrl-C if they're on
+    # the wrong host before any password / disk-wipe prompts fire.
+    local age="unknown age"
+    if [[ -n "${NOMARCHY_INSTALL_STATE_SAVED_AT:-}" ]]; then
+        age=$(format_age "$NOMARCHY_INSTALL_STATE_SAVED_AT")
+    fi
+    info "Resumed from $STATE_FILE (saved $age)"
+    if [[ -n "${USERNAME:-}" || -n "${HOSTNAME:-}" || -n "${TARGET_DRIVE:-}" ]]; then
+        info "  Target: ${TARGET_DRIVE:-?}  →  ${USERNAME:-?} @ ${HOSTNAME:-?}"
     fi
 }