diff --git a/hooks/pre-push b/hooks/pre-push
index 780b78b..04d4477 100755
--- a/hooks/pre-push
+++ b/hooks/pre-push
@@ -14,23 +14,55 @@ if [[ -z "$expected_sha" || ! "$expected_sha" =~ ^[0-9a-f]{40}$ ]]; then
   exit 2
 fi
 
+# Git exports GIT_DIR (and friends) into hook processes. In a linked worktree
+# that value is an ABSOLUTE path, so a plain `git -C "$shared_dir" ...` still
+# resolves against the pushing repository and reports ITS HEAD, origin and
+# status instead of the pinned policy checkout's — the hook then refuses a
+# perfectly good checkout ("Vana scanner checkout is at <repo HEAD>"). In a
+# normal checkout GIT_DIR is the relative ".git", which happens to resolve
+# correctly under -C, which is why this only bites worktrees. Scrub the
+# inherited repository environment for commands that must target the checkout;
+# commands that scan the pushing repository keep it.
+# The scrub list comes from git itself (`--local-env-vars` covers GIT_DIR,
+# GIT_WORK_TREE, GIT_INDEX_FILE, the object-directory pair, and crucially
+# GIT_CONFIG_PARAMETERS / GIT_CONFIG_COUNT, which `git -c foo=bar push` exports
+# into hooks and which would otherwise let the caller's environment satisfy the
+# origin check below instead of the checkout's real config). The GIT_CONFIG_*
+# file overrides are not in that list, so they are added explicitly, and a
+# hardcoded fallback covers a git too old to answer.
+_shared_git_scrub=()
+while IFS= read -r _v; do
+  [[ -n "$_v" ]] && _shared_git_scrub+=(-u "$_v")
+done < <(git rev-parse --local-env-vars 2>/dev/null || printf '%s\n' \
+  GIT_DIR GIT_WORK_TREE GIT_INDEX_FILE GIT_OBJECT_DIRECTORY \
+  GIT_ALTERNATE_OBJECT_DIRECTORIES GIT_COMMON_DIR \
+  GIT_CONFIG GIT_CONFIG_PARAMETERS GIT_CONFIG_COUNT)
+for _v in GIT_CONFIG_GLOBAL GIT_CONFIG_SYSTEM GIT_CONFIG_NOSYSTEM; do
+  _shared_git_scrub+=(-u "$_v")
+done
+unset _v
+
+shared_git() {
+  env "${_shared_git_scrub[@]}" git "$@"
+}
+
 scanner="$shared_dir/scripts/scan-commit-range.sh"
 verifier="$shared_dir/scripts/verify-gitleaks.sh"
 [[ -x "$scanner" && -x "$verifier" ]] || {
   printf 'VANA_SECRET_SCAN_HOME is not a valid shared scanner checkout.\n' >&2
   exit 2
 }
-actual_sha=$(git -C "$shared_dir" rev-parse HEAD)
+actual_sha=$(shared_git -C "$shared_dir" rev-parse HEAD)
 if [[ "$actual_sha" != "$expected_sha" ]]; then
   printf 'Vana scanner checkout is at %s, expected %s.\n' "$actual_sha" "$expected_sha" >&2
   exit 2
 fi
-origin_url=$(git -C "$shared_dir" config --get remote.origin.url || true)
+origin_url=$(shared_git -C "$shared_dir" config --get remote.origin.url || true)
 case "$origin_url" in
   git@github.com:vana-com/.github|git@github.com:vana-com/.github.git|https://github.com/vana-com/.github|https://github.com/vana-com/.github.git) ;;
   *) printf 'Vana scanner checkout origin is not vana-com/.github: %s\n' "${origin_url:-<unset>}" >&2; exit 2 ;;
 esac
-git -C "$shared_dir" diff --quiet -- . && git -C "$shared_dir" diff --cached --quiet -- . || {
+shared_git -C "$shared_dir" diff --quiet -- . && shared_git -C "$shared_dir" diff --cached --quiet -- . || {
   printf 'Vana scanner checkout has local changes: %s\n' "$shared_dir" >&2
   exit 2
 }
diff --git a/scripts/install-gitleaks.sh b/scripts/install-gitleaks.sh
index 04a2017..cf53b33 100755
--- a/scripts/install-gitleaks.sh
+++ b/scripts/install-gitleaks.sh
@@ -62,10 +62,17 @@ trap 'rm -rf "$workdir"' EXIT
 archive="$workdir/$asset"
 curl --fail --silent --show-error --location --proto '=https' --tlsv1.2 \
   "$RELEASE_BASE/$asset" --output "$archive"
-if command -v sha256sum >/dev/null 2>&1; then
-  printf '%s  %s\n' "$sha256" "$archive" | sha256sum --check --status
-else
+# macOS ships its own /sbin/sha256sum ("sha256sum (Darwin) 1.0") which does NOT
+# accept the GNU long options below, so `command -v sha256sum` succeeds there
+# and this verification fails for every download regardless of authenticity —
+# the shasum fallback was never reachable on the platform that needed it.
+# `shasum -a 256` accepts --check/--status on both macOS and Linux (and still
+# exits non-zero on a checksum mismatch), so prefer it, keeping sha256sum for
+# minimal images that ship coreutils but no perl.
+if command -v shasum >/dev/null 2>&1; then
   printf '%s  %s\n' "$sha256" "$archive" | shasum -a 256 --check --status
+else
+  printf '%s  %s\n' "$sha256" "$archive" | sha256sum --check --status
 fi
 tar -xzf "$archive" -C "$workdir" gitleaks
 install -m 0755 "$workdir/gitleaks" "$destination/gitleaks"
diff --git a/scripts/install-pre-push.sh b/scripts/install-pre-push.sh
index 84dac94..237a61c 100755
--- a/scripts/install-pre-push.sh
+++ b/scripts/install-pre-push.sh
@@ -45,7 +45,39 @@ esac
   exit 2
 }
 
-git -C "$shared_dir" rev-parse --is-inside-work-tree >/dev/null 2>&1 || {
+# Git exports GIT_DIR (and friends) into hook processes. In a linked worktree
+# that value is an ABSOLUTE path, so a plain `git -C "$shared_dir" ...` still
+# resolves against the pushing repository and reports ITS HEAD, origin and
+# status instead of the pinned policy checkout's — the hook then refuses a
+# perfectly good checkout ("Vana scanner checkout is at <repo HEAD>"). In a
+# normal checkout GIT_DIR is the relative ".git", which happens to resolve
+# correctly under -C, which is why this only bites worktrees. Scrub the
+# inherited repository environment for commands that must target the checkout;
+# commands that scan the pushing repository keep it.
+# The scrub list comes from git itself (`--local-env-vars` covers GIT_DIR,
+# GIT_WORK_TREE, GIT_INDEX_FILE, the object-directory pair, and crucially
+# GIT_CONFIG_PARAMETERS / GIT_CONFIG_COUNT, which `git -c foo=bar push` exports
+# into hooks and which would otherwise let the caller's environment satisfy the
+# origin check below instead of the checkout's real config). The GIT_CONFIG_*
+# file overrides are not in that list, so they are added explicitly, and a
+# hardcoded fallback covers a git too old to answer.
+_shared_git_scrub=()
+while IFS= read -r _v; do
+  [[ -n "$_v" ]] && _shared_git_scrub+=(-u "$_v")
+done < <(git rev-parse --local-env-vars 2>/dev/null || printf '%s\n' \
+  GIT_DIR GIT_WORK_TREE GIT_INDEX_FILE GIT_OBJECT_DIRECTORY \
+  GIT_ALTERNATE_OBJECT_DIRECTORIES GIT_COMMON_DIR \
+  GIT_CONFIG GIT_CONFIG_PARAMETERS GIT_CONFIG_COUNT)
+for _v in GIT_CONFIG_GLOBAL GIT_CONFIG_SYSTEM GIT_CONFIG_NOSYSTEM; do
+  _shared_git_scrub+=(-u "$_v")
+done
+unset _v
+
+shared_git() {
+  env "${_shared_git_scrub[@]}" git "$@"
+}
+
+shared_git -C "$shared_dir" rev-parse --is-inside-work-tree >/dev/null 2>&1 || {
   printf 'Policy checkout is not a Git work tree: %s\n' "$shared_dir" >&2
   exit 2
 }
@@ -53,17 +85,17 @@ git -C "$shared_dir" rev-parse --is-inside-work-tree >/dev/null 2>&1 || {
 [[ -x "$shared_dir/scripts/install-gitleaks.sh" ]] || { printf 'No installer at: %s/scripts/install-gitleaks.sh\n' "$shared_dir" >&2; exit 2; }
 [[ -x "$shared_dir/scripts/verify-gitleaks.sh" ]] || { printf 'No verifier at: %s/scripts/verify-gitleaks.sh\n' "$shared_dir" >&2; exit 2; }
 shared_dir=$(cd "$shared_dir" && pwd -P)
-actual_sha=$(git -C "$shared_dir" rev-parse HEAD)
+actual_sha=$(shared_git -C "$shared_dir" rev-parse HEAD)
 [[ "$actual_sha" == "$expected_sha" ]] || {
   printf 'Policy checkout is at %s, expected %s.\n' "$actual_sha" "$expected_sha" >&2
   exit 2
 }
-origin_url=$(git -C "$shared_dir" config --get remote.origin.url || true)
+origin_url=$(shared_git -C "$shared_dir" config --get remote.origin.url || true)
 case "$origin_url" in
   git@github.com:vana-com/.github|git@github.com:vana-com/.github.git|https://github.com/vana-com/.github|https://github.com/vana-com/.github.git) ;;
   *) printf 'Policy checkout origin is not vana-com/.github: %s\n' "${origin_url:-<unset>}" >&2; exit 2 ;;
 esac
-if [[ -n "$(git -C "$shared_dir" status --porcelain --untracked-files=all -- ':!/.tools')" ]]; then
+if [[ -n "$(shared_git -C "$shared_dir" status --porcelain --untracked-files=all -- ':!/.tools')" ]]; then
   printf 'Policy checkout has local changes: %s\n' "$shared_dir" >&2
   exit 2
 fi
diff --git a/tests/run.sh b/tests/run.sh
index 0f652c1..846e1fb 100755
--- a/tests/run.sh
+++ b/tests/run.sh
@@ -153,6 +153,86 @@ if [[ -e "$test_root/external-tools/gitleaks/gitleaks" ]]; then
   exit 1
 fi
 
+# Git exports the repository environment into hook processes. A command that
+# must target the policy checkout has to ignore it: GIT_DIR is absolute in a
+# linked worktree, so a bare `git -C "$policy" ...` reads the PUSHING repo's
+# HEAD and origin instead, and GIT_CONFIG_PARAMETERS (exported by
+# `git -c foo=bar push`) lets the caller's environment answer the origin check.
+# Both are accepted inputs from an untrusted caller, so both are tested here.
+env_policy="$test_root/env-policy"
+git clone -q "$root" "$env_policy"
+git -C "$env_policy" remote set-url origin https://github.com/vana-com/.github.git
+git -C "$env_policy" checkout -q "$policy_sha"
+"$env_policy/scripts/install-pre-push.sh" prepare --shared-dir "$env_policy" --ref "$policy_sha"
+
+# A decoy repository standing in for the one being pushed: a different HEAD and
+# a non-Vana origin, so leaking into it fails the SHA and origin checks.
+decoy="$test_root/env-decoy"
+git init -q -b main "$decoy"
+git -C "$decoy" config user.name test
+git -C "$decoy" config user.email test@example.invalid
+git -C "$decoy" remote add origin https://example.invalid/pushing-repo.git
+git -C "$decoy" commit --allow-empty -q -m decoy
+decoy_git_dir=$(git -C "$decoy" rev-parse --absolute-git-dir)
+
+# `prepare` only inspects the policy checkout, so it isolates the scrub from
+# the target-repository resolution that legitimately reads the environment.
+if ! GIT_DIR="$decoy_git_dir" \
+    "$env_policy/scripts/install-pre-push.sh" prepare --shared-dir "$env_policy" --ref "$policy_sha" >/dev/null 2>&1; then
+  printf 'expected prepare to resolve the policy checkout with GIT_DIR inherited\n' >&2
+  exit 1
+fi
+
+# The pre-push hook performs the same checks, so it must scrub the same way.
+worktree_repo="$test_root/worktree-repo"
+git init -q -b main "$worktree_repo"
+git -C "$worktree_repo" config user.name test
+git -C "$worktree_repo" config user.email test@example.invalid
+git -C "$worktree_repo" commit --allow-empty -q -m base
+"$root/scripts/install-pre-push.sh" --shared-dir "$env_policy" --repo "$worktree_repo" --ref "$policy_sha" >/dev/null
+git -C "$worktree_repo" worktree add -q "$test_root/worktree-linked" -b linked
+linked_git_dir=$(git -C "$test_root/worktree-linked" rev-parse --absolute-git-dir)
+worktree_head=$(git -C "$test_root/worktree-linked" rev-parse HEAD)
+if ! (cd "$test_root/worktree-linked" &&
+    GIT_DIR="$linked_git_dir" printf 'refs/heads/linked %s refs/heads/linked %040d\n' "$worktree_head" 0 |
+    GIT_DIR="$linked_git_dir" "$worktree_repo/.git/hooks/pre-push" origin example.invalid) >/dev/null 2>&1; then
+  printf 'expected pre-push hook to run from a linked worktree\n' >&2
+  exit 1
+fi
+
+# The origin check must read the checkout's real config, not the caller's
+# environment. Point the checkout at an attacker origin and claim otherwise.
+git -C "$env_policy" remote set-url origin https://github.com/attacker/evil.git
+if GIT_CONFIG_COUNT=1 \
+    GIT_CONFIG_KEY_0=remote.origin.url \
+    GIT_CONFIG_VALUE_0=https://github.com/vana-com/.github.git \
+    "$env_policy/scripts/install-pre-push.sh" prepare --shared-dir "$env_policy" --ref "$policy_sha" >/dev/null 2>&1; then
+  printf 'expected prepare to refuse an origin spoofed through the environment\n' >&2
+  exit 1
+fi
+if GIT_CONFIG_PARAMETERS="'remote.origin.url=https://github.com/vana-com/.github.git'" \
+    "$env_policy/scripts/install-pre-push.sh" prepare --shared-dir "$env_policy" --ref "$policy_sha" >/dev/null 2>&1; then
+  printf 'expected prepare to refuse an origin spoofed through GIT_CONFIG_PARAMETERS\n' >&2
+  exit 1
+fi
+git -C "$env_policy" remote set-url origin https://github.com/vana-com/.github.git
+
+# The download checksum gate must reject a corrupted archive on this platform,
+# whichever of shasum/sha256sum install-gitleaks.sh selects.
+checksum_digest=$(printf 'gitleaks' | { command -v shasum >/dev/null 2>&1 && shasum -a 256 || sha256sum; } | cut -d' ' -f1)
+checksum_file="$test_root/checksum-probe"
+printf 'gitleaks' >"$checksum_file"
+if ! printf '%s  %s\n' "$checksum_digest" "$checksum_file" |
+    { command -v shasum >/dev/null 2>&1 && shasum -a 256 --check --status || sha256sum --check --status; }; then
+  printf 'expected the checksum tool to accept a matching digest\n' >&2
+  exit 1
+fi
+if printf '%s  %s\n' "$(printf '0%.0s' {1..64})" "$checksum_file" |
+    { command -v shasum >/dev/null 2>&1 && shasum -a 256 --check --status || sha256sum --check --status; } 2>/dev/null; then
+  printf 'expected the checksum tool to reject a mismatched digest\n' >&2
+  exit 1
+fi
+
 key='4f3c8b1a9e6d2c7f0b5e1d8a6c3f9b2e''7d4a1c8f5b0e6d3a9c2f7b4e1d8a6c3f'
 scan() { "$scanner" --repo "$repo" --range "$1" --config "$config" --gitleaks "$gitleaks"; }
 expect_scan_status() {