diff --git a/tools/posix/mkiso.sh b/tools/posix/mkiso.sh
index 52fefbd..a1663a6 100644
--- a/tools/posix/mkiso.sh
+++ b/tools/posix/mkiso.sh
@@ -49,8 +49,25 @@
 
 set -e
 
-BUILD=${BUILD:-build}
+# Run from anywhere: resolve the repo root from this script's own location
+# rather than trusting the caller's working directory. Everything below is
+# relative to it, and running from tools/posix/ used to fail with "missing
+# build/kernel/kernel -- run make first" on a tree that was perfectly built.
+script_dir=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)
+repo=$(CDPATH= cd -- "$script_dir/../.." && pwd)
+# An output path given on the command line means where the *caller* is, not
+# where the repo is, so it is made absolute before the cd below moves the goal
+# posts under it. Without an argument the disc lands at the repo root, which is
+# where `make iso` has always put it.
+invoked_from=$(pwd)
 OUT=${1:-schos.iso}
+case $OUT in
+    /*) ;;
+    *)  OUT=$invoked_from/$OUT ;;
+esac
+cd "$repo"
+
+BUILD=${BUILD:-build}
 STAGING="$BUILD/iso"
 SYSROOT=${SYSROOT:-sysroot}
 
diff --git a/tools/posix/mutate.sh b/tools/posix/mutate.sh
index 7f890d8..b17a198 100644
--- a/tools/posix/mutate.sh
+++ b/tools/posix/mutate.sh
@@ -8,7 +8,22 @@
 # say -- would otherwise look exactly like a passing mutation test, which is
 # the same failure this script exists to catch.
 set -e
-cd /mnt/d/DEV/SchOS
+
+# Run from anywhere. This used to `cd /mnt/d/DEV/SchOS` -- an absolute WSL path
+# from the Windows machine this was written on, which meant the script could not
+# run on any other checkout at all.
+script_dir=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)
+repo=$(CDPATH= cd -- "$script_dir/../.." && pwd)
+cd "$repo"
+
+
+# Where the host tools land. These moved to build/tools/ in the bt/ -> tools/
+# migration and this script kept the old names; make then answered "No rule to
+# make target", which the harness reported as "rejected at compile time". Every
+# mutation looked handled and not one of them ever reached a test.
+MKSCHFS=build/tools/mkschfs
+FSCK=build/tools/schfs_fsck
+OBJT=build/tools/schfs_objtest
 
 OBJ=kernel/fs/schfs/obj.c
 OBJW=kernel/fs/schfs/objw.c
@@ -29,6 +44,16 @@ trap restore EXIT
 
 FAILED=0
 
+# Quote the line that says why, falling back to the last thing the suite said.
+# Two mutations used to report a bare "caught:" with nothing after it -- the
+# suite had failed, but nothing in it matched the patterns below, so the
+# evidence was an exit status and an empty string.
+why() {
+    line=$(grep -aE 'FAIL|Only in|differ|loop|error|assert' "$1" | head -1)
+    [ -n "$line" ] || line=$(grep -av '^[[:space:]]*$' "$1" | tail -1)
+    printf '%s' "$line" | sed 's/^ *//'
+}
+
 # try <description> <file> <sed-expression> [suite]
 #
 # suite is "image" (the default: build an image and diff it against the source
@@ -50,29 +75,31 @@ try() {
     fi
 
     if [ "$suite" = obj ]; then
-        if ! make build/schfs_objtest > /tmp/mk.log 2>&1; then
+        if ! make "$OBJT" > /tmp/mk.log 2>&1; then
             echo "  rejected at compile time"
+            sed -n '$p' /tmp/mk.log | sed 's/^/    /'
             return
         fi
-        if ./build/schfs_objtest > /tmp/rt.log 2>&1; then
+        if "./$OBJT" > /tmp/rt.log 2>&1; then
             echo "  NOT CAUGHT -- the suite passed with this bug present"
             FAILED=1
         else
-            echo "  caught: $(grep -aE 'FAIL' /tmp/rt.log | head -1 | sed 's/^ *//')"
+            echo "  caught: $(why /tmp/rt.log)"
         fi
         return
     fi
 
-    if ! make build/mkschfs build/schfs_fsck > /tmp/mk.log 2>&1; then
+    if ! make "$MKSCHFS" "$FSCK" > /tmp/mk.log 2>&1; then
         echo "  rejected at compile time"
+        sed -n '$p' /tmp/mk.log | sed 's/^/    /'
         return
     fi
-    if sh tools/schfs_roundtrip.sh ./build/mkschfs ./build/schfs_fsck \
+    if sh tools/posix/schfs_roundtrip.sh "./$MKSCHFS" "./$FSCK" \
             > /tmp/rt.log 2>&1; then
         echo "  NOT CAUGHT -- the suite passed with this bug present"
         FAILED=1
     else
-        echo "  caught: $(grep -aE 'FAIL|Only in|differ|loop' /tmp/rt.log | head -1 | sed 's/^ *//')"
+        echo "  caught: $(why /tmp/rt.log)"
     fi
 }
 
diff --git a/tools/posix/schcom_test.sh b/tools/posix/schcom_test.sh
index c419b78..551fa48 100644
--- a/tools/posix/schcom_test.sh
+++ b/tools/posix/schcom_test.sh
@@ -10,6 +10,14 @@
 # captures whichever QEMU considers active, which need not be the one /dev/fb0
 # maps.
 set -e
+# Run from anywhere: resolve the repo root from this script's own location
+# rather than trusting the caller's working directory. Everything below is
+# relative to it, and running from tools/posix/ used to fail with "missing
+# build/kernel/kernel -- run make first" on a tree that was perfectly built.
+script_dir=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)
+repo=$(CDPATH= cd -- "$script_dir/../.." && pwd)
+cd "$repo"
+
 BUILD=${BUILD:-build}
 mkdir -p "$BUILD"