diff --git a/tools/cargo-mutants.sh b/tools/cargo-mutants.sh
index cc1d19a..f95d5c6 100644
--- a/tools/cargo-mutants.sh
+++ b/tools/cargo-mutants.sh
@@ -135,11 +135,13 @@ if [ "$1" = --host ]; then
   trap cleanup EXIT; trap 'exit 143' TERM INT HUP
   killed() { [ -n "${YGG_KILLED:-}" ] && [ -e "$YGG_KILLED" ]; }
   now() { date +%s; }
+  # The shared volume is CARGO_HOME itself so sibling containers share cargo's package-cache lock; a registry-only mount left
+  # the lock in each container's layer and concurrent unpacks removed each other's crate directories (2026-11-03).
   # Every container carries the job label (the stopgap's watchdog kills by it) and the same caps.
   common=(--label "$YGG_LABEL" "--cpus=${YGG_CPUS:-4}" "--memory=${YGG_MEM:-6g}"
     -v "$YGG_WORK:/seed:ro" -v "$D:/cm:ro" -v /etc/machine-id:/etc/machine-id:ro
-    -v eureka-cargo-registry:/usr/local/cargo/registry -v eureka-nuget:/root/.nuget/packages -v eureka-sccache:/sccache
-    -e BASH_ENV=/tmp/.ygg-bash-env
+    -v eureka-cargo-home:/cargo-home -v eureka-nuget:/root/.nuget/packages -v eureka-sccache:/sccache
+    -e BASH_ENV=/tmp/.ygg-bash-env -e CARGO_HOME=/cargo-home
     -e "WORKDIR=${WORKDIR:-.}" -e "BASE=$BASE" -e "TEST_ARGS=${TEST_ARGS:-}" -e "FILTERS=${FILTERS:-}" -e "CM_NAMES=${CM_NAMES:-}" -e "JOBS=$JOBS"
     -e "MIN_TEST_TIMEOUT=$MIN_TEST_TIMEOUT" -e "CONFIRM_TIMEOUT_MULT=$CONFIRM_TIMEOUT_MULT"
     -e GIT_CONFIG_COUNT=1 -e GIT_CONFIG_KEY_0=safe.directory -e 'GIT_CONFIG_VALUE_0=*')
@@ -208,7 +210,7 @@ if [ "$1" = --host ]; then
   container_error() {   # container_error <label> <out dir>
     local rc; rc=$(cat "$2/hostrc" 2>/dev/null)
     sum "ERROR $1 container exited ${rc:-?} (4 is a red baseline: the unmutated tests failed there)"
-    tail -n 5 "$2/stdout" 2>/dev/null | sed "s|^|$SUMTAG: ERROR   |"
+    tail -n 25 "$2/stdout" 2>/dev/null | sed "s|^|$SUMTAG: ERROR   |"
   }
 
   # ---- stage 1: files whose filter selects tests (the plan container derived each file's filter and counted its tests)
diff --git a/tools/stopgap/ygg-verify.sh b/tools/stopgap/ygg-verify.sh
index aed061b..c39d8f0 100644
--- a/tools/stopgap/ygg-verify.sh
+++ b/tools/stopgap/ygg-verify.sh
@@ -20,7 +20,7 @@
 #      the commit out detached. It is a real clone, not a worktree, because a
 #      worktree's .git file points at a host path the container cannot see.
 #   3. Runs <command> in <image> under a CPU and memory cap, niced. Each
-#      toolchain gets one shared registry cache. The build output directory
+#      toolchain gets one shared cargo home (registry and package-cache lock). The build output directory
 #      stays inside the work directory and is never shared between checkouts.
 #      CARGO_TARGET_DIR is deliberately NOT set: cargo's default (<workspace>/
 #      target) is already inside /src, and forcing it made cargo-mutants' --jobs
@@ -405,10 +405,12 @@ else
 # Priority is set inside the container: nice on the docker client does not reach a process
 # containerd starts. Jobs run at nice 10 and idle IO class, so the swarm's daemons and turns
 # on the same disk go first (2026-10-31: three verify jobs held IO pressure at ~75% full).
+# Cargo's package-cache lock lives in $CARGO_HOME, so the shared volume is CARGO_HOME itself: a registry-only mount left the
+# lock in each container's layer and sibling containers unpacking one crate removed each other's directories (2026-11-03).
 sudo docker run --rm --name "$cname" --label "$label" --cpus="$cpus" --memory="$mem" \
   -v "$work:/src" -v /etc/machine-id:/etc/machine-id:ro \
-  -v eureka-cargo-registry:/usr/local/cargo/registry -v eureka-nuget:/root/.nuget/packages \
-  -v eureka-sccache:/sccache \
+  -v eureka-cargo-home:/cargo-home -v eureka-nuget:/root/.nuget/packages \
+  -v eureka-sccache:/sccache -e CARGO_HOME=/cargo-home \
   -e BASH_ENV=/tmp/.ygg-bash-env ${nonce:+-e YGG_NONCE=$nonce} \
   -e GIT_CONFIG_COUNT=1 -e GIT_CONFIG_KEY_0=safe.directory -e GIT_CONFIG_VALUE_0='*' \
   $docker_args \