Day 03: Recovery drill: diagnose a failed environment

Build the broken fixture and reproduce the failure (paste the whole block; it aborts before writing if setup fails or if a non-executing check finds helper already resolvable):

(
set -e
SBX_ROOT=$(mktemp -d "${TMPDIR:-/tmp}/d03env.XXXXXX")
[ -n "$SBX_ROOT" ]
[ -d "$SBX_ROOT" ]
[ -w "$SBX_ROOT" ]
[ -x "$SBX_ROOT" ]
probe_rc=0
python3 -c "import sys, importlib.util
try:
    spec = importlib.util.find_spec('helper')
except Exception:
    sys.exit(4)
sys.exit(3 if spec is not None else 0)" || probe_rc=$?
if [ "$probe_rc" -ne 0 ]; then
  if [ "$probe_rc" -eq 3 ]; then
    echo "abort: ambient Python config already resolves 'helper' - the intended failure cannot be demonstrated"
  else
    echo "abort: helper-resolvability probe failed (rc=$probe_rc) - cannot verify the precondition safely"
  fi
  exit 1
fi
mkdir "$SBX_ROOT/env-drill"
cd "$SBX_ROOT/env-drill"
mkdir tools
printf 'def greet():\n    return "ok"\n' > tools/helper.py
printf 'from helper import greet\nprint(greet())\n' > app.py
rc=0
python3 app.py 2>err.txt || rc=$?
cat err.txt
grep -q "ModuleNotFoundError: No module named 'helper'" err.txt
echo "expected failure observed (rc=$rc)"
printf 'export SBX_ROOT=%q\n' "$SBX_ROOT"
)

Predict the error before running. Paste the printed export SBX_ROOT= line, then gather evidence:

(
set -e
: "${SBX_ROOT:?run the setup block first, then paste its printed export line}"
[ -d "$SBX_ROOT/env-drill" ]
cd "$SBX_ROOT/env-drill"
python3 -c "import sys, os; print([os.path.abspath(p or '.') for p in sys.path])"
ls tools
)

Apply the smallest justified correction for this invocation only and recheck, comparing PYTHONPATH against the recorded original — the block prints an explicit set/unset marker plus the value, so unset, empty, and nonempty originals are all distinguishable unchanged evidence):

(
set -e
: "${SBX_ROOT:?run the setup block first, then paste its printed export line}"
[ -d "$SBX_ROOT/env-drill" ]
cd "$SBX_ROOT/env-drill"
pp_state() { if [ "${PYTHONPATH+x}" = x ]; then printf 'PYTHONPATH %s: set value=<%s>\n' "$1" "$PYTHONPATH"; else printf 'PYTHONPATH %s: unset\n' "$1"; fi }
pp_state before
PYTHONPATH=tools python3 app.py
pp_state after
printf 'rm -r -- %q\n' "$SBX_ROOT"
)

Record symptom, evidence, the fix, why it is minimal, and the recheck result.

Independent behavior check (write it yourself, save as check_clamp.py):

from calc import clamp
assert clamp(5, 0, 10) == 5
assert clamp(-3, 0, 10) == 0
assert clamp(99, 0, 10) == 10
try:
    clamp(2, 10, 0)
except ValueError:
    pass
else:
    raise AssertionError('clamp must reject lo > hi')
print('clamp checks passed')

Run python3 check_clamp.py against the produced code. If it fails, write precise feedback (which case, expected vs actual, suspected cause), request the correction, capture the diff (git diff or diff -u against a saved copy), and rerun the check. Record: failure output, your feedback, the diff, and the passing recheck. If it passes first try, record the passing output and a substantive evidence review (each assert traced, the lo > hi ValueError path verified, add and other files untouched); you may still practise the feedback loop on the labelled drill patch, recorded as drill evidence, never as agent output.

Run the whole block below in a fresh Bash shell (as one block), writing predictions before each wc, diff, and find. A failed setup aborts the subshell and writes nothing into your current directory. The block ends by printing a literal rm -r -- <private-root> cleanup command you may run when you want that directory removed:

(
set -e
SBX_ROOT=$(mktemp -d "${TMPDIR:-/tmp}/d03rpt.XXXXXX")
[ -n "$SBX_ROOT" ]
[ -d "$SBX_ROOT" ]
[ -w "$SBX_ROOT" ]
[ -x "$SBX_ROOT" ]
mkdir "$SBX_ROOT/report-sandbox"
cd "$SBX_ROOT/report-sandbox"
mkdir data archive
printf 'month,total\njan,10\nfeb,20\n' > data/sales-q1.csv
wc -l data/sales-q1.csv
cp data/sales-q1.csv archive/sales-q1.bak
diff data/sales-q1.csv archive/sales-q1.bak
printf 'draft note\n' > data/readme.txt
mv data/readme.txt archive/notes.txt
find . -type f | sort
printf 'rm -r -- %q\n' "$SBX_ROOT"
)

Artifact checks to satisfy: the backup is byte-identical to the original; data/readme.txt no longer exists after the move; the final find output lists exactly ./archive/notes.txt, ./archive/sales-q1.bak, and ./data/sales-q1.csv.

Produce a recovery plan covering at least four Days 01–03 concepts. For each row record: concept | evidence status | next unaided check | date | recovery action if missed. Then list every actionable evidence gap in your records (things you believe but have not verified); if none exist inside your declared scope, an explicit "none found within this declared scope" is acceptable only when it cites the actual current evidence and a dated fresh unaided recheck - existing gaps must still be disclosed, never hidden. Close the plan with a scheduled fresh check: a date on which you will predict a new mutation/identity snippet and verify it unaided.