diff --git a/DOCS-runnability.md b/DOCS-runnability.md
index 8daa0d51..953a1ed1 100644
--- a/DOCS-runnability.md
+++ b/DOCS-runnability.md
@@ -47,12 +47,12 @@ run cannot clobber the local column.
 | `Programming/E-PSYOPS` | runnable | - | opens in the Unity editor |
 | `Programming/ERSMS-project` | runnable | - | docker compose up |
 | `Programming/NLP` | runnable | - | python3 the entry script |
-| `Programming/PBAD` | blocked | - | jupyter is on PATH but broken (bad interpreter) |
+| `Programming/PBAD` | blocked | - | jupyter is on PATH but does not run (dead shim) |
 | `Programming/PORR` | runnable | - | python3 /home/kuhy/WUT_Computer_Science/Programming/PORR/code/main.py |
 | `Programming/PSD` | runnable | - | starts the Kafka/Flink stack (installs packages with sudo) |
 | `Programming/psd_project` | runnable | - | mvn package |
 | `Programming/TRAK` | runnable | - | python3 /home/kuhy/WUT_Computer_Science/Programming/TRAK/main.py |
-| `Programming/twm_4` | blocked | - | jupyter is on PATH but broken (bad interpreter) |
+| `Programming/twm_4` | blocked | - | jupyter is on PATH but does not run (dead shim) |
 | `Programming/USD` | no-code | - | README describes a MetaDrive RL assignment; no implementation was submitted |
 | `Programming/WDWR` | runnable | - | python3 the entry script |
 | `Programming/ZPOB` | runnable | - | builds the report with latexmk |
diff --git a/gates/runnability-local.tsv b/gates/runnability-local.tsv
index ffec41ae..ac5b9be1 100644
--- a/gates/runnability-local.tsv
+++ b/gates/runnability-local.tsv
@@ -33,12 +33,12 @@ Programming/EPFU	runnable	make
 Programming/E-PSYOPS	runnable	opens in the Unity editor
 Programming/ERSMS-project	runnable	docker compose up
 Programming/NLP	runnable	python3 the entry script
-Programming/PBAD	blocked	jupyter is on PATH but broken (bad interpreter)
+Programming/PBAD	blocked	jupyter is on PATH but does not run (dead shim)
 Programming/PORR	runnable	python3 /home/kuhy/WUT_Computer_Science/Programming/PORR/code/main.py
 Programming/PSD	runnable	starts the Kafka/Flink stack (installs packages with sudo)
 Programming/psd_project	runnable	mvn package
 Programming/TRAK	runnable	python3 /home/kuhy/WUT_Computer_Science/Programming/TRAK/main.py
-Programming/twm_4	blocked	jupyter is on PATH but broken (bad interpreter)
+Programming/twm_4	blocked	jupyter is on PATH but does not run (dead shim)
 Programming/USD	no-code	README describes a MetaDrive RL assignment; no implementation was submitted
 Programming/WDWR	runnable	python3 the entry script
 Programming/ZPOB	runnable	builds the report with latexmk
diff --git a/scripts/course_lib.sh b/scripts/course_lib.sh
index 955dc65c..c995c433 100644
--- a/scripts/course_lib.sh
+++ b/scripts/course_lib.sh
@@ -39,6 +39,15 @@ _have() { command -v "$1" > /dev/null 2>&1; }
 # _works only for tools that answer --version; _have is right for the rest.
 _works() { _have "$1" && timeout 5 "$1" --version > /dev/null 2>&1; }
 
+# Blocked-with-a-reason for a tool that has to actually run. "needs jupyter"
+# and "jupyter is on PATH but does not run" send you to different fixes, and
+# the status table is only worth keeping if it says which.
+_require_working() {
+    local tool="$1"
+    _have "$tool" || _blocked "needs $tool"
+    _works "$tool" || _blocked "$tool is on PATH but does not run (dead shim)"
+}
+
 # Report "blocked" with the reason, which is the whole point of the status
 # table: "needs X" is useful, "failed" is not.
 _blocked() {
diff --git a/scripts/course_probe.sh b/scripts/course_probe.sh
index 5dc43347..9e045cf9 100644
--- a/scripts/course_probe.sh
+++ b/scripts/course_probe.sh
@@ -52,7 +52,7 @@ _probe() {
             _runnable "compiles each standalone .cpp"
             ;;
         notebook)
-            _works jupyter || _blocked "needs jupyter"
+            _require_working jupyter
             # Being on PATH is not the same as working: this machine has a
             # jupyter shim whose pipx venv interpreter is gone, so it fails
             # with "bad interpreter". Probe by actually invoking it.
diff --git a/scripts/course_run.sh b/scripts/course_run.sh
index 4e135f00..0c5042fc 100644
--- a/scripts/course_run.sh
+++ b/scripts/course_run.sh
@@ -181,7 +181,7 @@ _run() {
             printf 'binaries in %s/build\n' "$COURSE_ROOT" 
             ;;
         notebook)
-            _works jupyter || _blocked "needs jupyter"
+            _require_working jupyter
             # NOT --inplace: all four notebooks in this repo are tracked WITH
             # their outputs, so executing in place rewrites a deliverable.
             # --output-dir sends the executed copy to a temp dir instead.