diff --git a/configs/airootfs/usr/local/bin/omarchy-install-dashboard b/configs/airootfs/usr/local/bin/omarchy-install-dashboard
index 0048b4c..91e960b 100755
--- a/configs/airootfs/usr/local/bin/omarchy-install-dashboard
+++ b/configs/airootfs/usr/local/bin/omarchy-install-dashboard
@@ -571,10 +571,13 @@ truncate_for_width() {
 }
 
 render_failure_log_tail() {
-  local rows lines width line tail_log label
+  # The caller passes the rows it spent above this point that the constant below
+  # does not know about, so the tail gives way rather than pushing the top of
+  # the screen off a short console.
+  local reserved="${1:-0}" rows lines width line tail_log label
   rows=$(term_size)
   rows=${rows%% *}
-  lines=$((rows - LOGO_HEIGHT - 18))
+  lines=$((rows - LOGO_HEIGHT - 18 - reserved))
   (( lines < 6 )) && lines=6
   (( lines > 14 )) && lines=14
   width=$((CONTENT_WIDTH - 4))
@@ -643,8 +646,52 @@ view_failure_log() {
   fi
 }
 
+# A failure the medium explains is worth saying before the log tail, because
+# the tail is where "invalid or corrupted package" already scrolled past
+# without ever naming the USB stick it came off.
+diagnose_media() {
+  local logs=("$LOG_FILE")
+
+  [[ -f /mnt/var/log/omarchy-install.log ]] && logs+=(/mnt/var/log/omarchy-install.log)
+  [[ -n ${OMARCHY_FAILURE_TAIL_LOG:-} ]] && logs+=("$OMARCHY_FAILURE_TAIL_LOG")
+
+  omarchy-install-diagnose-media "${logs[@]}" 2>/dev/null
+}
+
+# Rows the diagnosis occupies, its leading blank included.
+media_diagnosis_rows() {
+  local diagnosis="$1"
+
+  if [[ -z $diagnosis ]]; then
+    printf '0\n'
+  else
+    printf '%s\n' "$(( $(grep -c '' <<<"$diagnosis") + 1 ))"
+  fi
+}
+
+render_media_diagnosis() {
+  local diagnosis="$1" line first=1
+
+  [[ -n $diagnosis ]] || return 0
+  blank_line
+  while IFS= read -r line; do
+    # A blank line inside the diagnosis is deliberate: it separates what
+    # happened from what to do about it, so it is drawn rather than skipped.
+    if [[ -z $line ]]; then
+      blank_line
+      continue
+    fi
+    if (( first )); then
+      center "${RED}$(truncate_for_width "$line" "$CONTENT_WIDTH")${RESET}" "$CONTENT_WIDTH"
+      first=0
+    else
+      center "$(truncate_for_width "$line" "$CONTENT_WIDTH")" "$CONTENT_WIDTH"
+    fi
+  done <<<"$diagnosis"
+}
+
 render_failure() {
-  local status="$1" state_summary="${2:-}" line
+  local status="$1" state_summary="${2:-}" media_diagnosis="${3:-}" line
   printf '%s%s' "$SHOW_CURSOR" "$CLEAR"
   blank_line
   render_logo
@@ -652,6 +699,8 @@ render_failure() {
   center "${RED}Omarchy installation stopped${RESET}" "$CONTENT_WIDTH"
   center "Installer exited with status $status" "$CONTENT_WIDTH"
 
+  render_media_diagnosis "$media_diagnosis"
+
   if [[ -n $state_summary ]]; then
     blank_line
     while IFS= read -r line; do
@@ -661,7 +710,7 @@ render_failure() {
   fi
 
   blank_line
-  render_failure_log_tail
+  render_failure_log_tail "$(media_diagnosis_rows "$media_diagnosis")"
   blank_line
   center "${DIM}Get help at https://omarchy.org/discord${RESET}" "$CONTENT_WIDTH"
   blank_line
@@ -702,11 +751,11 @@ failure_menu() {
     case "$choice" in
       "Upload log for support")
         upload_failure_log
-        render_failure "${failure_status:-1}" "${failure_summary:-}" >"$TTY_PATH" 2>/dev/null || true
+        render_failure "${failure_status:-1}" "${failure_summary:-}" "${failure_media_diagnosis:-}" >"$TTY_PATH" 2>/dev/null || true
         ;;
       "View full log")
         view_failure_log
-        render_failure "${failure_status:-1}" "${failure_summary:-}" >"$TTY_PATH" 2>/dev/null || true
+        render_failure "${failure_status:-1}" "${failure_summary:-}" "${failure_media_diagnosis:-}" >"$TTY_PATH" 2>/dev/null || true
         ;;
       "Reboot")
         reboot 2>/dev/null || systemctl reboot 2>/dev/null || true
@@ -792,7 +841,15 @@ if (( status != 0 )); then
       done <<<"$failure_summary"
     fi
   fi
-  render_failure "$failure_status" "$failure_summary" >"$TTY_PATH" 2>/dev/null || true
+  failure_media_diagnosis="$(diagnose_media || true)"
+  render_failure "$failure_status" "$failure_summary" "$failure_media_diagnosis" >"$TTY_PATH" 2>/dev/null || true
+  # Recorded after the screen is drawn, not before: the log tail on that screen
+  # reads this same file, and the diagnosis printed twice reads as two findings.
+  if [[ -n $failure_media_diagnosis ]]; then
+    while IFS= read -r line; do
+      [[ -n $line ]] && dashboard_log "$line"
+    done <<<"$failure_media_diagnosis"
+  fi
   failure_menu
   exit "$failure_status"
 fi
diff --git a/configs/airootfs/usr/local/bin/omarchy-install-diagnose-media b/configs/airootfs/usr/local/bin/omarchy-install-diagnose-media
new file mode 100755
index 0000000..9ce5dfd
--- /dev/null
+++ b/configs/airootfs/usr/local/bin/omarchy-install-diagnose-media
@@ -0,0 +1,124 @@
+#!/bin/bash
+#
+# Say whether an install failure was the install medium, and say it in words
+# that name the fix.
+#
+# The ISO's offline mirror is bind-mounted onto the target's package cache for
+# the duration of pacstrap (see _mount_offline_package_cache), so a package
+# pacman calls corrupt under that path is a byte that came off the medium --
+# nothing else ever writes there. That much is certain, and it is the part
+# worth saying out loud, because the failure screen otherwise ends at "get help
+# at discord" with the word USB nowhere on it.
+#
+# What is not certain is which way the medium failed. Bytes written wrong and
+# bytes read wrong produce the same checksum mismatch, and pacstrap runs with
+# --noconfirm, which answers yes to pacman's "delete it?" and unlinks the
+# package through the bind mount before anything here can weigh it. So the
+# usual verdict names the medium and gives both remedies in the order worth
+# trying. When the package does survive, its checksum in the mirror's database
+# tells the two apart, and then this says which.
+#
+# Prints the diagnosis on stdout, one line per line, headline first. Exits 1
+# with no output when there is nothing here to diagnose, so the caller can ask
+# unconditionally.
+
+set -uo pipefail
+
+TARGET_PACKAGE_CACHE="${OMARCHY_TARGET_PACKAGE_CACHE:-/mnt/var/cache/pacman/pkg}"
+OFFLINE_MIRROR="${OMARCHY_OFFLINE_MIRROR:-/var/cache/omarchy/mirror/offline}"
+
+if (( $# == 0 )); then
+  echo "Usage: omarchy-install-diagnose-media <log-file>..." >&2
+  exit 2
+fi
+
+# Only packages under the target cache count. A corrupt package anywhere else
+# was not read off this ISO, and guessing wrong here sends someone to buy a USB
+# stick they did not need.
+corrupt_package() {
+  local log match package=""
+
+  for log in "$@"; do
+    [[ -f $log ]] || continue
+    match=$(sed -n "s|.*${TARGET_PACKAGE_CACHE}/\([^ ]*\) is corrupted.*|\1|p" "$log" | tail -n 1)
+    [[ -n $match ]] && package="$match"
+  done
+
+  printf '%s' "$package"
+}
+
+expected_checksum() {
+  local package="$1" reader
+
+  [[ -f $OFFLINE_MIRROR/offline.db ]] || return 1
+
+  if command -v bsdtar >/dev/null 2>&1; then
+    reader=(bsdtar -xOf "$OFFLINE_MIRROR/offline.db")
+  else
+    reader=(tar -xOzf "$OFFLINE_MIRROR/offline.db")
+  fi
+
+  # repo-add writes %FILENAME% before %SHA256SUM% in every desc record, so the
+  # name in hand when a checksum arrives is the name it belongs to. The wanted
+  # name comes through the environment rather than -v, which would read a
+  # backslash in a package version as an escape sequence.
+  "${reader[@]}" 2>/dev/null | want="$package" awk '
+    BEGIN { want = ENVIRON["want"] }
+    $0 == "%FILENAME%" { getline name; next }
+    $0 == "%SHA256SUM%" { getline sha; if (name == want) { print sha; exit } }
+  '
+}
+
+actual_checksum() {
+  local package="$1" sum
+
+  [[ -f $OFFLINE_MIRROR/$package ]] || return 1
+  sum=$(sha256sum "$OFFLINE_MIRROR/$package" 2>/dev/null) || return 1
+  printf '%s' "${sum%% *}"
+}
+
+package=$(corrupt_package "$@")
+if [[ -z $package ]]; then
+  exit 1
+fi
+
+# The name reaches a terminal, and a package version may legally hold a
+# backslash that the renderer would read as an escape. Strip anything a package
+# filename has no business containing before printing it.
+display_package="${package//[^A-Za-z0-9._+:@%-]/}"
+
+expected=$(expected_checksum "$package")
+actual=$(actual_checksum "$package")
+
+# The package name goes on a line of its own throughout. Names run past fifty
+# characters and the screen is only as wide as the logo, so a name sharing a
+# line with the sentence that explains it truncates the explanation away. The
+# blank line after it separates what happened from what to do about it.
+if [[ -n $expected && -n $actual ]]; then
+  if [[ $expected == "$actual" ]]; then
+    # Intact now, so the bytes were misread rather than written wrong, and
+    # re-downloading fixes neither of the things that could have done it.
+    echo "The install medium was misread"
+    echo "This package is intact on this ISO, so the download and the write were fine:"
+    echo "$display_package"
+    echo
+    echo "Try another USB port or another stick, and test this machine's memory"
+  else
+    echo "The install medium is damaged"
+    echo "This package no longer matches the checksum it was built with:"
+    echo "$display_package"
+    echo
+    echo "Re-download the ISO, verify it with sha256sum, and write the USB again"
+    echo "If a verified ISO fails here too, the USB stick itself is the problem"
+  fi
+  exit 0
+fi
+
+# The usual case: pacman deleted the package it rejected, so the medium is the
+# answer but the manner of its failure is not recoverable from here.
+echo "The install medium is damaged or misread"
+echo "pacman rejected this package, read straight off this ISO:"
+echo "$display_package"
+echo
+echo "Verify your download with sha256sum, then write the USB again"
+echo "If the download verifies, the stick or this machine's memory is at fault"
diff --git a/configs/profiledef.sh b/configs/profiledef.sh
index 268a3ce..d7d483c 100644
--- a/configs/profiledef.sh
+++ b/configs/profiledef.sh
@@ -39,6 +39,7 @@ file_permissions=(
   ["/usr/local/bin/omarchy-cidata-load"]="0:0:755"
   ["/usr/local/bin/omarchy-iso-cleanup-disk"]="0:0:755"
   ["/usr/local/bin/omarchy-install-dashboard"]="0:0:755"
+  ["/usr/local/bin/omarchy-install-diagnose-media"]="0:0:755"
   ["/usr/local/bin/omarchy-iso-install"]="0:0:755"
   ["/usr/local/bin/omarchy-upload-log"]="0:0:755"
   ["/var/cache/omarchy/mirror/offline/"]="0:0:775"
diff --git a/test/unit/install-media-diagnosis-test.sh b/test/unit/install-media-diagnosis-test.sh
new file mode 100755
index 0000000..cbad41d
--- /dev/null
+++ b/test/unit/install-media-diagnosis-test.sh
@@ -0,0 +1,452 @@
+#!/bin/bash
+#
+# Unit tests for omarchy-install-diagnose-media and the failure screen that
+# renders it. Every case builds a throwaway offline mirror -- a package file
+# and a real repo-add-shaped offline.db naming its sha256 -- so the three
+# verdicts are told apart by the same evidence the live ISO has.
+
+set -euo pipefail
+
+ROOT=$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/../.." && pwd)
+DIAGNOSE="$ROOT/configs/airootfs/usr/local/bin/omarchy-install-diagnose-media"
+DASHBOARD="$ROOT/configs/airootfs/usr/local/bin/omarchy-install-dashboard"
+PACKAGE="npth-1.8-1-x86_64.pkg.tar.zst"
+TARGET_CACHE="/mnt/var/cache/pacman/pkg"
+
+pass() {
+  printf 'ok - %s\n' "$1"
+}
+
+fail() {
+  local description="$1"
+  local detail="${2:-}"
+
+  [[ -n $detail ]] && printf '%s\n' "$detail" >&2
+  printf 'not ok - %s\n' "$description" >&2
+  exit 1
+}
+
+work=$(mktemp -d)
+trap 'rm -rf "$work"' EXIT
+
+mirror="$work/mirror"
+mkdir -p "$mirror"
+
+# repo-add writes one desc record per package, %FILENAME% before %SHA256SUM%.
+# Building a real gzipped tar of that shape keeps the parser honest.
+write_mirror_db() {
+  local checksum="$1" filename="${2:-$PACKAGE}" staging="$work/db"
+
+  rm -rf "$staging"
+  mkdir -p "$staging/npth-1.8-1"
+  {
+    printf '%%FILENAME%%\n%s\n\n' "$filename"
+    printf '%%NAME%%\nnpth\n\n'
+    printf '%%VERSION%%\n1.8-1\n\n'
+    printf '%%SHA256SUM%%\n%s\n\n' "$checksum"
+  } >"$staging/npth-1.8-1/desc"
+
+  # A second package proves the lookup matches on name rather than on order.
+  mkdir -p "$staging/zlib-1.3-1"
+  {
+    printf '%%FILENAME%%\nzlib-1.3-1-x86_64.pkg.tar.zst\n\n'
+    printf '%%NAME%%\nzlib\n\n'
+    printf '%%SHA256SUM%%\n%s\n\n' "$(printf 'f%.0s' {1..64})"
+  } >"$staging/zlib-1.3-1/desc"
+
+  tar -czf "$mirror/offline.db" -C "$staging" npth-1.8-1 zlib-1.3-1
+}
+
+write_log() {
+  local log="$1" path="${2:-$TARGET_CACHE/$PACKAGE}"
+
+  {
+    echo "[dashboard] checking package integrity..."
+    echo "[dashboard] :: File $path is corrupted (invalid or corrupted package)."
+    echo "[dashboard] error: failed to commit transaction (invalid or corrupted package)"
+    echo "[dashboard] ==> ERROR: Failed to install packages to new root"
+  } >"$log"
+}
+
+diagnose() {
+  OMARCHY_OFFLINE_MIRROR="$mirror" OMARCHY_TARGET_PACKAGE_CACHE="$TARGET_CACHE" \
+    "$DIAGNOSE" "$@"
+}
+
+log="$work/install.log"
+write_log "$log"
+
+# The medium was written wrong: the package on the ISO no longer hashes to what
+# the build recorded for it.
+printf 'a package, but damaged\n' >"$mirror/$PACKAGE"
+write_mirror_db "$(printf '0%.0s' {1..64})"
+
+set +e
+output=$(diagnose "$log")
+status=$?
+set -e
+
+(( status == 0 )) || fail "a checksum mismatch is diagnosed" "exit status $status"
+[[ $(head -n 1 <<<"$output") == "The install medium is damaged" ]] ||
+  fail "a checksum mismatch is diagnosed" "$output"
+grep -qF "$PACKAGE" <<<"$output" ||
+  fail "the diagnosis names the package" "$output"
+grep -qF "no longer matches the checksum" <<<"$output" ||
+  fail "the diagnosis says the checksum disagrees" "$output"
+grep -qF "sha256sum" <<<"$output" ||
+  fail "the diagnosis says how to verify a fresh download" "$output"
+pass "a checksum mismatch says the medium is damaged and names the package"
+
+# The medium reads clean now, so the bytes were misread rather than written
+# wrong. Re-downloading fixes nothing, and the advice has to say so.
+write_mirror_db "$(sha256sum "$mirror/$PACKAGE" | cut -d " " -f 1)"
+
+set +e
+output=$(diagnose "$log")
+status=$?
+set -e
+
+(( status == 0 )) || fail "an intact package is still diagnosed" "exit status $status"
+[[ $(head -n 1 <<<"$output") == "The install medium was misread" ]] ||
+  fail "an intact package is diagnosed as a misread" "$output"
+grep -qF "another USB port" <<<"$output" ||
+  fail "a misread points at the hardware" "$output"
+if grep -qF "Re-download" <<<"$output"; then
+  fail "a misread does not send anyone to re-download" "$output"
+fi
+pass "an intact package on the medium is diagnosed as a misread, not a bad download"
+
+# The usual case. pacstrap runs with --noconfirm, which answers yes to pacman's
+# "delete it?" and unlinks the package through the bind mount, so by the time
+# anything here looks there is nothing left to weigh. The verdict must name the
+# medium without claiming a comparison it never made, and must offer both
+# remedies: a bad write and a bad read leave identical evidence.
+rm "$mirror/$PACKAGE"
+
+set +e
+output=$(diagnose "$log")
+status=$?
+set -e
+
+(( status == 0 )) || fail "a deleted package is still diagnosed" "exit status $status"
+[[ $(head -n 1 <<<"$output") == "The install medium is damaged or misread" ]] ||
+  fail "a deleted package is diagnosed without over-claiming" "$output"
+grep -qF "read straight off this ISO" <<<"$output" ||
+  fail "a deleted package still names the medium" "$output"
+grep -qF "sha256sum" <<<"$output" ||
+  fail "a deleted package offers the download remedy" "$output"
+grep -qF "memory is at fault" <<<"$output" ||
+  fail "a deleted package offers the hardware remedy too" "$output"
+if grep -qF "no longer matches the checksum" <<<"$output"; then
+  fail "a deleted package claims no comparison" "$output"
+fi
+pass "a deleted package names the medium without claiming which way it failed"
+
+# A record with no %SHA256SUM% must not borrow the next record's, which would
+# compare a real file against another package's checksum.
+printf 'a package, but damaged\n' >"$mirror/$PACKAGE"
+staging="$work/db"
+rm -rf "$staging"
+mkdir -p "$staging/npth-1.8-1" "$staging/zlib-1.3-1"
+printf '%%FILENAME%%\n%s\n\n%%NAME%%\nnpth\n\n' "$PACKAGE" >"$staging/npth-1.8-1/desc"
+{
+  printf '%%FILENAME%%\nzlib-1.3-1-x86_64.pkg.tar.zst\n\n'
+  printf '%%SHA256SUM%%\n%s\n\n' "$(sha256sum "$mirror/$PACKAGE" | cut -d " " -f 1)"
+} >"$staging/zlib-1.3-1/desc"
+tar -czf "$mirror/offline.db" -C "$staging" npth-1.8-1 zlib-1.3-1
+
+set +e
+output=$(diagnose "$log")
+set -e
+
+[[ $(head -n 1 <<<"$output") == "The install medium is damaged or misread" ]] ||
+  fail "a record without a checksum borrows nobody else's" "$output"
+pass "a record without a checksum borrows nobody else's"
+
+# A package version may legally hold a backslash. It must not reach a terminal
+# as an escape sequence, and awk must look it up literally rather than as one.
+escaped='demo-1\033[2J-1-x86_64.pkg.tar.zst'
+write_log "$work/escaped.log" "$TARGET_CACHE/$escaped"
+printf 'a package, but damaged\n' >"$mirror/$escaped"
+write_mirror_db "$(printf '0%.0s' {1..64})" "$escaped"
+
+set +e
+output=$(diagnose "$work/escaped.log")
+set -e
+
+# The dashboard renders these lines through printf %b, which turns a surviving
+# backslash into whatever escape it spells. None may reach it.
+if grep -qF '\' <<<"$output"; then
+  fail "a backslash in a package name never reaches the renderer" "$(cat -v <<<"$output")"
+fi
+grep -qF "demo-1033" <<<"$output" ||
+  fail "the sanitized name still identifies the package" "$output"
+# The database record is found despite the backslash, so the verdict is the
+# mismatch rather than the one that means no comparison could be made.
+[[ $(head -n 1 <<<"$output") == "The install medium is damaged" ]] ||
+  fail "a backslash in a package name is looked up literally" "$output"
+pass "a backslash in a package name is looked up literally and never rendered as an escape"
+rm "$mirror/$escaped"
+
+# The live ISO has bsdtar through pacman's libarchive, but the tar fallback is
+# the one that runs if that ever stops being true.
+printf 'a package, but damaged\n' >"$mirror/$PACKAGE"
+write_mirror_db "$(sha256sum "$mirror/$PACKAGE" | cut -d " " -f 1)"
+no_bsdtar="$work/no-bsdtar"
+mkdir -p "$no_bsdtar"
+for tool in sed awk tar gzip sha256sum cat grep head tail cut printf; do
+  command -v "$tool" >/dev/null && ln -sf "$(command -v "$tool")" "$no_bsdtar/$tool"
+done
+
+set +e
+output=$(PATH="$no_bsdtar" diagnose "$log")
+set -e
+
+[[ $(head -n 1 <<<"$output") == "The install medium was misread" ]] ||
+  fail "the tar fallback reads the database when bsdtar is absent" "$output"
+pass "the tar fallback reads the database when bsdtar is absent"
+
+printf 'a package, but damaged\n' >"$mirror/$PACKAGE"
+write_mirror_db "$(printf '0%.0s' {1..64})"
+
+# A corrupt package that was never read off this ISO is somebody else's
+# problem. Guessing here sends people to buy a USB stick they did not need.
+write_log "$work/elsewhere.log" "/var/tmp/build/$PACKAGE"
+
+set +e
+output=$(diagnose "$work/elsewhere.log")
+status=$?
+set -e
+
+(( status == 1 )) || fail "corruption outside the target cache is not diagnosed" "exit $status: $output"
+[[ -z $output ]] || fail "corruption outside the target cache prints nothing" "$output"
+pass "corruption outside the target cache is not blamed on the medium"
+
+# An ordinary failure has no media diagnosis, and the caller asks
+# unconditionally, so silence has to be the answer.
+printf 'error: something else went wrong entirely\n' >"$work/other.log"
+
+set +e
+output=$(diagnose "$work/other.log")
+status=$?
+set -e
+
+(( status == 1 )) || fail "an unrelated failure is not diagnosed" "exit $status: $output"
+[[ -z $output ]] || fail "an unrelated failure prints nothing" "$output"
+pass "an unrelated failure produces no diagnosis"
+
+set +e
+output=$(diagnose "$work/does-not-exist.log")
+status=$?
+set -e
+
+(( status == 1 )) || fail "a missing log is not diagnosed" "exit $status: $output"
+pass "a missing log produces no diagnosis"
+
+# End to end: the dashboard runs a failing installer and the diagnosis has to
+# reach both the screen and the support log, above the tail it explains.
+#
+# The screen goes through a real pty rather than a file. The dashboard's exit
+# handler reopens its TTY with a truncating redirect, which does nothing to a
+# character device and empties a regular file, so a file would capture nothing.
+stubs="$work/stubs"
+mkdir -p "$stubs"
+{
+  echo '#!/bin/bash'
+  echo "OMARCHY_OFFLINE_MIRROR='$mirror' OMARCHY_TARGET_PACKAGE_CACHE='$TARGET_CACHE' exec '$DIAGNOSE' \"\$@\""
+} >"$stubs/omarchy-install-diagnose-media"
+chmod +x "$stubs/omarchy-install-diagnose-media"
+
+state_file="$work/state.json"
+screen="$work/screen"
+
+# A ten-line logo, the height of the real one. Without it the dashboard falls
+# back to a single centred word and the screen can never be tall enough to
+# overflow, which is exactly the case worth testing.
+omarchy_share="$work/share"
+mkdir -p "$omarchy_share"
+# 81 columns wide, like the real logo: the dashboard takes its content width
+# from the logo, and a narrow one would truncate every line under test.
+{
+  printf 'LOGO TOP ROW%*s\n' 69 ''
+  for n in 2 3 4 5 6 7 8 9; do printf 'logo row %s%*s\n' "$n" 71 ''; done
+  printf 'logo bottom row%*s\n' 66 ''
+} >"$omarchy_share/logo.txt"
+
+run_dashboard() {
+  local install_log="$1"
+
+  # A real failure carries the failed phase as well as the current one, and
+  # that second summary line is another row the screen has to find space for.
+  cat >"$state_file" <<'STATE'
+{"current_phase": "Installing Arch + Omarchy",
+ "phases": [{"name": "Installing Arch + Omarchy", "status": "failed",
+             "error": "Pacstrap failed. See /var/log/archinstall.log"}]}
+STATE
+  : >"$screen"
+  script -qefc "stty rows 40 cols 120; PATH='$stubs:$PATH' OMARCHY_PATH='$omarchy_share' OMARCHY_UI_INTERACTIVE=no OMARCHY_UI_FAILURE_ACTION=exit OMARCHY_FAILURE_TAIL_LOG='$install_log' '$DASHBOARD' '$install_log' '$state_file' -- bash -c 'exit 1'" \
+    "$screen" >/dev/null 2>&1
+}
+
+visible_screen() {
+  # Carriage returns as well as escapes: the pty ends every line with one, and
+  # a row that looks blank still carries it.
+  sed -E $'s/\x1b\\[[0-9;?]*[A-Za-z]//g; s/\r//g' "$screen"
+}
+
+dashboard_log="$work/dashboard.log"
+write_log "$dashboard_log"
+
+# A real install log is longer than the tail can show, so the tail actually
+# spends its whole budget. A short one hides an over-tall screen.
+{
+  for n in $(seq 1 20); do printf '[dashboard] installing package %s\n' "$n"; done
+  cat "$dashboard_log"
+} >"$dashboard_log.padded"
+mv "$dashboard_log.padded" "$dashboard_log"
+
+# State the case rather than inheriting whichever verdict the previous one left
+# behind: this is the shape a real install fails in, with pacman having deleted
+# the package it rejected.
+rm -f "$mirror/$PACKAGE"
+write_mirror_db "$(printf '0%.0s' {1..64})"
+
+set +e
+run_dashboard "$dashboard_log"
+dashboard_status=$?
+set -e
+
+(( dashboard_status == 1 )) ||
+  fail "the dashboard still exits with the installer's status" "exit $dashboard_status"
+visible_screen | grep -qF "The install medium is damaged" ||
+  fail "the failure screen shows the diagnosis" "$(visible_screen | tail -n 25)"
+visible_screen | grep -qF "$PACKAGE" ||
+  fail "the failure screen names the package" "$(visible_screen | tail -n 25)"
+grep -qF "[dashboard] The install medium is damaged" "$dashboard_log" ||
+  fail "the diagnosis is written to the support log" "$(tail -n 20 "$dashboard_log")"
+
+# Once on the screen. The log tail rendered underneath reads the same file the
+# diagnosis is recorded in, and the same finding printed twice reads as two.
+headline_count=$(visible_screen | grep -cF "The install medium is damaged or misread" || true)
+(( headline_count == 1 )) ||
+  fail "the diagnosis appears once on the screen" "found $headline_count times"
+
+# The renderer used to drop blank lines, so the break has to be checked where
+# it matters: on the screen, not only in the text the helper produced.
+package_row=$(visible_screen | grep -nF "$PACKAGE" | grep -v "dashboard" | head -n 1 | cut -d: -f1)
+[[ -n $package_row ]] ||
+  fail "the screen names the package on its own row" "$(visible_screen | tail -n 25)"
+next_row=$(visible_screen | sed -n "$((package_row + 1))p")
+[[ -z ${next_row// /} ]] ||
+  fail "the screen breaks after the package" "next row was: $next_row"
+pass "the dashboard renders the diagnosis once, with the break, and logs it"
+
+# The diagnosis costs rows the log tail's budget knew nothing about, so a
+# screen carrying one scrolled its own logo off the top of the console. The
+# tail gives those rows back now, which is visible as a shorter tail: count the
+# filler lines it reaches, with a diagnosis and without one.
+#
+# Asserting the logo is still on screen would be the direct test, and it cannot
+# be written here: this reads the output stream, which keeps every row ever
+# emitted whether or not it stayed visible. Only a terminal emulator could tell
+# the difference, so the mechanism is what gets checked.
+tail_filler_rows() {
+  visible_screen | grep -c "installing package" || true
+}
+
+with_diagnosis=$(tail_filler_rows)
+
+# The same log line for line, differing only in the one path that decides
+# whether there is a diagnosis at all. Two differently shaped logs would show
+# different amounts of filler for reasons that have nothing to do with the
+# budget, and the comparison would prove nothing.
+elsewhere_log="$work/elsewhere-padded.log"
+write_log "$elsewhere_log" "/var/tmp/build/$PACKAGE"
+{
+  for n in $(seq 1 20); do printf '[dashboard] installing package %s\n' "$n"; done
+  cat "$elsewhere_log"
+} >"$elsewhere_log.padded"
+mv "$elsewhere_log.padded" "$elsewhere_log"
+
+set +e
+run_dashboard "$elsewhere_log"
+set -e
+without_diagnosis=$(tail_filler_rows)
+
+(( with_diagnosis < without_diagnosis )) ||
+  fail "the tail gives up rows to the diagnosis" \
+    "with: $with_diagnosis, without: $without_diagnosis"
+pass "the log tail gives up rows to the diagnosis so the screen still fits"
+
+# The screen is only as wide as the logo and the dashboard truncates to it with
+# an ellipsis. Every sentence has to survive that, whatever the package is
+# called, or the advice arrives with its second half cut off.
+long_package="linux-firmware-nvidia-tegra-20250917.0e800e46-1-any.pkg.tar.zst"
+long_log="$work/long.log"
+write_log "$long_log" "$TARGET_CACHE/$long_package"
+
+check_widths() {
+  local label="$1" line
+  while IFS= read -r line; do
+    (( ${#line} <= 81 )) ||
+      fail "no diagnosis line outruns the screen ($label)" "${#line} chars: $line"
+  done < <(diagnose "$long_log")
+}
+
+# The package line and the remedy that follows it are two different thoughts,
+# so a blank line separates them in every verdict.
+check_break() {
+  local label="$1" package="$2" out
+  out=$(diagnose "$long_log")
+  local -a lines
+  mapfile -t lines <<<"$out"
+
+  local i
+  for i in "${!lines[@]}"; do
+    [[ ${lines[i]} == "$package" ]] || continue
+    [[ -z ${lines[i + 1]-x} ]] ||
+      fail "a break follows the package ($label)" "$out"
+    [[ -n ${lines[i + 2]-} ]] ||
+      fail "the remedy follows the break ($label)" "$out"
+    return 0
+  done
+  fail "the package is on a line of its own ($label)" "$out"
+}
+
+# All three verdicts, since each writes its own sentences.
+rm -f "$mirror/$long_package"
+check_widths "deleted"
+check_break "deleted" "$long_package"
+printf 'these are not the bytes that were built\n' >"$mirror/$long_package"
+write_mirror_db "$(printf '0%.0s' {1..64})" "$long_package"
+check_widths "damaged"
+check_break "damaged" "$long_package"
+write_mirror_db "$(sha256sum "$mirror/$long_package" | cut -d " " -f 1)" "$long_package"
+check_widths "misread"
+check_break "misread" "$long_package"
+rm -f "$mirror/$long_package"
+pass "no diagnosis line outruns the screen, even with a long package name"
+pass "a break separates the package from the remedy in every verdict"
+
+# A failure with no media explanation must leave the screen as it was, rather
+# than gaining a banner or an empty gap where the diagnosis would go.
+printf 'error: something else went wrong entirely\n' >"$work/plain.log"
+
+set +e
+run_dashboard "$work/plain.log"
+set -e
+
+if visible_screen | grep -qF "install medium"; then
+  fail "an unrelated failure gets no media banner" "$(visible_screen | tail -n 25)"
+fi
+visible_screen | grep -qF "Omarchy installation stopped" ||
+  fail "an unrelated failure still renders the normal failure screen" "$(visible_screen | tail -n 25)"
+pass "an unrelated failure renders the failure screen unchanged"
+
+# The failure menu redraws the screen after uploading or viewing the log, and a
+# redraw that drops the diagnosis loses it exactly when someone went looking.
+# Those paths need gum and a person at the keyboard, so they are checked here.
+missing_redraw=$(grep -n 'render_failure "' "$DASHBOARD" | grep -v 'failure_media_diagnosis' || true)
+[[ -z $missing_redraw ]] ||
+  fail "every failure-screen redraw carries the diagnosis" "$missing_redraw"
+pass "every failure-screen redraw carries the diagnosis"