diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index a96ce3e..c87ff42 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -30,6 +30,13 @@ jobs:
             cs50/cli:amd64
             cs50/cli:canary-amd64
 
+      - name: Check out tests
+        uses: actions/checkout@v7
+
+      - name: Smoke-test linux/amd64 build
+        run: |
+          bash tests/smoke.sh cs50/cli:canary-amd64
+
       - name: Push linux/amd64 build to Docker Hub
         if: ${{ github.ref == 'refs/heads/main' }}
         run: |
@@ -68,6 +75,13 @@ jobs:
             cs50/cli:arm64
             cs50/cli:canary-arm64
 
+      - name: Check out tests
+        uses: actions/checkout@v7
+
+      - name: Smoke-test linux/arm64 build
+        run: |
+          bash tests/smoke.sh cs50/cli:canary-arm64
+
       - name: Push linux/arm64 build to Docker Hub
         if: ${{ github.ref == 'refs/heads/main' }}
         run: |
diff --git a/Dockerfile b/Dockerfile
index c7e01e6..3ff4866 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -188,6 +188,7 @@ RUN apt update && \
     apt install --no-install-recommends --no-install-suggests --yes \
         astyle \
         bash-completion \
+        bsdextrautils `# For col, for help50` \
         build-essential `# dpkg-dev, libc, gcc, g++, make, etc.` \
         ca-certificates \
         clang \
diff --git a/Makefile b/Makefile
index 2d9b392..f000d0e 100644
--- a/Makefile
+++ b/Makefile
@@ -13,7 +13,10 @@ rebuild:
 	docker build --build-arg VCS_REF=$(shell git rev-parse HEAD) --no-cache --tag $(IMAGE) .
 
 run:
-	docker run --env LANG=$(LANG) --env LOCAL_WORKSPACE_FOLDER="$(PWD)" --env WORKDIR=/mnt --interactive --publish-all --rm --security-opt seccomp=unconfined --tty --volume "$(PWD)":/mnt --volume /var/run/docker.sock:/var/run/docker-host.sock --workdir /mnt cs50/cli bash --login || true
+	docker run --env LANG=$(LANG) --env LOCAL_WORKSPACE_FOLDER="$(PWD)" --env WORKDIR=/mnt --interactive --publish-all --rm --security-opt seccomp=unconfined --tty --volume "$(PWD)":/mnt --volume /var/run/docker.sock:/var/run/docker-host.sock --workdir /mnt $(IMAGE) bash --login || true
+
+smoke:
+	bash tests/smoke.sh $(IMAGE)
 
 squash: depends
 	docker-squash --tag $(IMAGE) $(IMAGE)
diff --git a/etc/profile.d/cli.sh b/etc/profile.d/cli.sh
index 6a8dd61..d4efd2b 100644
--- a/etc/profile.d/cli.sh
+++ b/etc/profile.d/cli.sh
@@ -62,8 +62,8 @@ if [ `id -u` -ne 0 ]; then
     # Valgrind
     export VALGRIND_OPTS="--memcheck:leak-check=full --memcheck:show-leak-kinds=all --memcheck:track-origins=yes"
 
-    # Start help50 if enabled
-    if help50 is-enabled > /dev/null; then
+    # Start help50 if enabled (only for interactive shells with a terminal, else `script` would hang, e.g., in `bash --login -c`)
+    if [[ $- == *i* && -t 0 ]] && help50 is-enabled > /dev/null; then
         help50 start
     fi
 fi
diff --git a/etc/profile.d/help50.sh b/etc/profile.d/help50.sh
index 04dca38..05cddd4 100644
--- a/etc/profile.d/help50.sh
+++ b/etc/profile.d/help50.sh
@@ -90,7 +90,9 @@ function _help50() {
         if [[ -n "$help" ]]; then # If helpful
             _helpful "$help"
         elif [[ $status -ne 0 ]]; then # If helpless
-            _helpless "$typescript"
+
+            # Cap what's relayed downstream (e.g., ddb50 rejects > 10,000 characters), keeping the end, where errors tend to be
+            _helpless "$(echo "$typescript" | tail -c 8192)"
         fi
     else
         _helped
@@ -113,7 +115,7 @@ if ! type _helpful >/dev/null 2>&1; then
 
         # Intercept accidental invocation of `yes` and `n`, which are actual programs
         for name in n no y yes; do
-            alias $name=_rhetocial
+            alias $name=_rhetorical
         done
 
         # Output help
diff --git a/opt/cs50/bin/valgrind b/opt/cs50/bin/valgrind
index dd19aa8..f318aab 100755
--- a/opt/cs50/bin/valgrind
+++ b/opt/cs50/bin/valgrind
@@ -1,8 +1,10 @@
 #!/bin/bash
 
+. /opt/cs50/lib/cli
+
 # If run on Python program
 if [[ "$1" == "python" || "$1" == *.py ]]; then
-    echo "$(_help "Afraid \`valgrind\` does not support Python programs!")"
+    _alert "$(_ansi "Afraid \`valgrind\` does not support Python programs!")"
     exit 1
 fi
 
diff --git a/opt/cs50/lib/cli b/opt/cs50/lib/cli
index 9db45f2..6df5353 100644
--- a/opt/cs50/lib/cli
+++ b/opt/cs50/lib/cli
@@ -4,8 +4,8 @@ function _alert() {
 
 function _ansi() {
 
-    # If command-line arguments
-    if [[ -t 0 ]]; then
+    # If command-line arguments (don't test -t 0, else arguments are ignored whenever stdin is redirected)
+    if [[ $# -gt 0 ]]; then
         input="$*"
 
     # If standard input
@@ -48,8 +48,8 @@ function _find() {
 
 function _fold() {
 
-    # If command-line arguments
-    if [[ -t 0 ]]; then
+    # If command-line arguments (don't test -t 0, else arguments are ignored whenever stdin is redirected)
+    if [[ $# -gt 0 ]]; then
         input="$*"
 
     # If standard input
@@ -57,8 +57,9 @@ function _fold() {
         input=$(cat)
     fi
 
-    # Wrap long lines
-    local cols=$(tput cols)
+    # Wrap long lines (default to 80 columns if no terminal, e.g., when piped)
+    local cols=$(tput cols 2> /dev/null)
+    [[ "$cols" =~ ^[0-9]+$ ]] || cols=80
     echo "$input" | fold --spaces --width=$cols
 }
 
diff --git a/opt/cs50/lib/help50/python b/opt/cs50/lib/help50/python
index 1d8b3fd..c47be5d 100755
--- a/opt/cs50/lib/help50/python
+++ b/opt/cs50/lib/help50/python
@@ -35,8 +35,8 @@ fi
 regex="python: can't open file '(.*\.py)': \[Errno 2\] No such file or directory"
 if [[ "$output" =~ $regex ]]; then
 
-    # Relative path from $PWD
-    path=$(realpath --relative-to=. "${BASH_REMATCH[1]}")
+    # Relative path from $PWD (file doesn't exist, so don't require it to)
+    path=$(realpath --canonicalize-missing --relative-to=. "${BASH_REMATCH[1]}")
 
     # If command was `python baz.py` (i.e., without a dirname)
     if [[ -n "$path" && "$path" == $(basename "$path") ]]; then
@@ -51,11 +51,12 @@ if [[ "$output" =~ $regex ]]; then
     fi
 
     # If command was `python bar/baz.py` (i.e., with a dirname)
-    if [[ -n "$path" && "$path" == $(basename "$path") ]]; then
-        dir=$(_find -type f "$path")
+    if [[ -n "$path" ]]; then
+        base=$(basename "$path")
+        dir=$(_find -type f "$base")
         echo -n "There isn't a file called \`$path\` in your current directory."
         if [[ ! -z "$dir" ]]; then
-            echo " Did you mean to \`cd $dir\` first?"
+            echo " Did you mean to run \`python $dir/$base\` instead?"
         else
             echo
         fi
diff --git a/tests/smoke.sh b/tests/smoke.sh
new file mode 100755
index 0000000..41ac041
--- /dev/null
+++ b/tests/smoke.sh
@@ -0,0 +1,28 @@
+#!/bin/bash
+# Smoke-tests a built cs50/cli image. Usage: tests/smoke.sh [IMAGE]
+# Each check has a timeout so that a regression that hangs the shell fails loudly.
+
+set -o errexit -o nounset -o pipefail
+
+IMAGE="${1:-cs50/cli}"
+run() { timeout 60 docker run --rm "$@"; }
+
+echo "Checking $IMAGE"
+
+echo "- non-interactive login shell exits (help50 must not start without a terminal)"
+run "$IMAGE" bash --login -c 'echo ok' | grep -qx ok
+echo true | run --interactive "$IMAGE" bash --login
+
+echo "- runtime dependencies of help50 are installed"
+run "$IMAGE" bash --login -c 'for c in ansi2txt col file script fold; do command -v "$c" > /dev/null || { echo "missing $c" >&2; exit 1; }; done'
+
+echo "- help50 controller is the Bash version, on PATH, and enabled by default"
+run "$IMAGE" bash --login -c 'test "$(type -P help50)" = /opt/cs50/bin/help50 && help50 is-enabled && test "$(help50 status)" = stopped' > /dev/null
+
+echo "- wrappers print their message even when stdin is redirected"
+run "$IMAGE" bash --login -c 'valgrind python x.py < /dev/null; test $? -eq 1' 2>&1 | grep -q 'does not support Python'
+
+echo "- _fold wraps without a terminal"
+run "$IMAGE" bash --login -c '. /opt/cs50/lib/cli; TERM= _fold "$(printf "a %.0s" {1..100})"' | head -n 1 | grep -qE '^.{1,80}$'
+
+echo "OK"