diff --git a/CHANGELOG.md b/CHANGELOG.md
index b90fd6b..4e55da8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com), and this
 
 ### Fixed
 
+- `.gtrconfig` trust works on systems that have `sha256sum` but not `shasum`, such as Alpine and Fedora/RHEL with only `git-core`. Hashing falls back to `sha256sum`, so `git gtr trust` no longer fails and the generated `gtr cd` helpers recognize trusted hooks. The shell-integration cache schema is now `init=7`, so caches generated by older versions are refreshed; update the `init=6` check in your shell rc to `init=7`.
 - The integration test helper now canonicalizes its temporary repository path. On macOS `mktemp -d` returns a `/var` path while git records the resolved `/private/var` one, so `cmd_clean --merged uses nested registered worktree path` compared two spellings of the same directory and failed locally while passing in CI.
 
 ## [2.11.1] - 2026-09-14
diff --git a/README.md b/README.md
index c7b88f8..77f6019 100644
--- a/README.md
+++ b/README.md
@@ -272,17 +272,17 @@ cd "$(git gtr go 1)"             # Navigate to main repo
 ```bash
 # Bash (add to ~/.bashrc)
 _gtr_init="${XDG_CACHE_HOME:-$HOME/.cache}/gtr/init-gtr.bash"
-[[ -f "$_gtr_init" ]] && head -n 1 "$_gtr_init" | grep -q ' init=6 ' || eval "$(git gtr init bash)" || true
+[[ -f "$_gtr_init" ]] && head -n 1 "$_gtr_init" | grep -q ' init=7 ' || eval "$(git gtr init bash)" || true
 source "$_gtr_init" 2>/dev/null || true; unset _gtr_init
 
 # Zsh (add to ~/.zshrc)
 _gtr_init="${XDG_CACHE_HOME:-$HOME/.cache}/gtr/init-gtr.zsh"
-[[ -f "$_gtr_init" ]] && head -n 1 "$_gtr_init" | grep -q ' init=6 ' || eval "$(git gtr init zsh)" || true
+[[ -f "$_gtr_init" ]] && head -n 1 "$_gtr_init" | grep -q ' init=7 ' || eval "$(git gtr init zsh)" || true
 source "$_gtr_init" 2>/dev/null || true; unset _gtr_init
 
 # Fish (add to ~/.config/fish/config.fish)
 set -l _gtr_init (test -n "$XDG_CACHE_HOME" && echo $XDG_CACHE_HOME || echo $HOME/.cache)/gtr/init-gtr.fish
-test -f "$_gtr_init"; and head -n 1 "$_gtr_init" | string match -q '* init=6 *'; or git gtr init fish >/dev/null 2>&1
+test -f "$_gtr_init"; and head -n 1 "$_gtr_init" | string match -q '* init=7 *'; or git gtr init fish >/dev/null 2>&1
 source "$_gtr_init" 2>/dev/null
 
 # Then navigate with:
diff --git a/lib/commands/help.sh b/lib/commands/help.sh
index ed0bab1..34f4f24 100644
--- a/lib/commands/help.sh
+++ b/lib/commands/help.sh
@@ -427,17 +427,17 @@ Options:
 Setup (sources cached output directly for fast startup):
   # Bash (add to ~/.bashrc)
   _gtr_init="${XDG_CACHE_HOME:-$HOME/.cache}/gtr/init-gtr.bash"
-  [[ -f "$_gtr_init" ]] && head -n 1 "$_gtr_init" | grep -q ' init=6 ' || eval "$(git gtr init bash)" || true
+  [[ -f "$_gtr_init" ]] && head -n 1 "$_gtr_init" | grep -q ' init=7 ' || eval "$(git gtr init bash)" || true
   source "$_gtr_init" 2>/dev/null || true; unset _gtr_init
 
   # Zsh (add to ~/.zshrc)
   _gtr_init="${XDG_CACHE_HOME:-$HOME/.cache}/gtr/init-gtr.zsh"
-  [[ -f "$_gtr_init" ]] && head -n 1 "$_gtr_init" | grep -q ' init=6 ' || eval "$(git gtr init zsh)" || true
+  [[ -f "$_gtr_init" ]] && head -n 1 "$_gtr_init" | grep -q ' init=7 ' || eval "$(git gtr init zsh)" || true
   source "$_gtr_init" 2>/dev/null || true; unset _gtr_init
 
   # Fish (add to ~/.config/fish/config.fish)
   set -l _gtr_init (test -n "$XDG_CACHE_HOME" && echo $XDG_CACHE_HOME || echo $HOME/.cache)/gtr/init-gtr.fish
-  test -f "$_gtr_init"; and head -n 1 "$_gtr_init" | string match -q '* init=6 *'; or git gtr init fish >/dev/null 2>&1
+  test -f "$_gtr_init"; and head -n 1 "$_gtr_init" | string match -q '* init=7 *'; or git gtr init fish >/dev/null 2>&1
   source "$_gtr_init" 2>/dev/null
 
   # Custom function name (avoids conflict with coreutils gtr)
diff --git a/lib/commands/init.sh b/lib/commands/init.sh
index e526744..1db18ec 100644
--- a/lib/commands/init.sh
+++ b/lib/commands/init.sh
@@ -68,7 +68,7 @@ cmd_init() {
   # Generate output (cached to ~/.cache/gtr/, auto-invalidates on shell integration changes)
   local cache_dir="${XDG_CACHE_HOME:-$HOME/.cache}/gtr"
   local cache_file="$cache_dir/init-${func_name}.${shell}"
-  local cache_schema="${GTR_INIT_CACHE_VERSION:-6}"
+  local cache_schema="${GTR_INIT_CACHE_VERSION:-7}"
   local cache_stamp="# gtr-cache: version=${GTR_VERSION:-unknown} init=${cache_schema} func=$func_name shell=$shell"
 
   # Return cached output if version matches
@@ -95,6 +95,17 @@ _init_emit_posix_trust_helpers() {
   local template
 
   template=$(cat <<'EOF'
+__FUNC___sha256() {
+__SHELL_PRELUDE__
+  if command -v shasum >/dev/null 2>&1; then
+    shasum -a 256 | cut -d' ' -f1
+  elif command -v sha256sum >/dev/null 2>&1; then
+    sha256sum | cut -d' ' -f1
+  else
+    return 1
+  fi
+}
+
 __FUNC___gtrconfig_path() {
 __SHELL_PRELUDE__
   local _gtr_git_common_dir _gtr_repo_root
@@ -114,7 +125,7 @@ __SHELL_PRELUDE__
   local _gtr_config_file="$1"
   local _gtr_hook_defs
   _gtr_hook_defs="$(git config -f "$_gtr_config_file" --get-regexp '^hooks\.|^defaults\.editor$|^defaults\.ai$' 2>/dev/null)" || return 1
-  printf '%s\n' "$_gtr_hook_defs" | shasum -a 256 | cut -d' ' -f1
+  printf '%s\n' "$_gtr_hook_defs" | __FUNC___sha256
 }
 
 __FUNC___hooks_repo_root() {
@@ -137,7 +148,7 @@ __SHELL_PRELUDE__
   local _gtr_hook_hash _gtr_repo_root
   _gtr_hook_hash="$(__FUNC___hooks_current_content_hash "$_gtr_config_file" 2>/dev/null)" || return 1
   _gtr_repo_root="$(__FUNC___hooks_repo_root "$_gtr_config_file" 2>/dev/null)" || return 1
-  printf '%s\n%s\n' "$_gtr_repo_root" "$_gtr_hook_hash" | shasum -a 256 | cut -d' ' -f1
+  printf '%s\n%s\n' "$_gtr_repo_root" "$_gtr_hook_hash" | __FUNC___sha256
 }
 
 __FUNC___hooks_marker_matches_config() {
@@ -167,6 +178,16 @@ EOF
 
 _init_emit_fish_trust_helpers() {
   cat <<'FISH'
+function __FUNC___sha256
+  if command -q shasum
+    shasum -a 256 | cut -d' ' -f1
+  else if command -q sha256sum
+    sha256sum | cut -d' ' -f1
+  else
+    return 1
+  end
+end
+
 function __FUNC___gtrconfig_path
   set -l _gtr_git_common_dir (git rev-parse --git-common-dir 2>/dev/null)
   test -n "$_gtr_git_common_dir"; or return 1
@@ -182,7 +203,7 @@ end
 
 function __FUNC___hooks_current_content_hash
   set -l _gtr_config_file "$argv[1]"
-  set -l _gtr_hook_defs (git config -f "$_gtr_config_file" --get-regexp '^hooks\.|^defaults\.editor$|^defaults\.ai$' 2>/dev/null | shasum -a 256 | cut -d' ' -f1)
+  set -l _gtr_hook_defs (git config -f "$_gtr_config_file" --get-regexp '^hooks\.|^defaults\.editor$|^defaults\.ai$' 2>/dev/null | __FUNC___sha256)
   test $pipestatus[1] -eq 0; or return 1
   test -n "$_gtr_hook_defs"; or return 1
   printf '%s\n' "$_gtr_hook_defs"
@@ -206,7 +227,7 @@ function __FUNC___hooks_current_trust_key
   test -n "$_gtr_hook_hash"; or return 1
   set -l _gtr_repo_root (__FUNC___hooks_repo_root "$_gtr_config_file" 2>/dev/null)
   test -n "$_gtr_repo_root"; or return 1
-  printf '%s\n%s\n' "$_gtr_repo_root" "$_gtr_hook_hash" | shasum -a 256 | cut -d' ' -f1
+  printf '%s\n%s\n' "$_gtr_repo_root" "$_gtr_hook_hash" | __FUNC___sha256
 end
 
 function __FUNC___hooks_marker_matches_config
diff --git a/lib/hooks.sh b/lib/hooks.sh
index 4622a1c..af7aa54 100644
--- a/lib/hooks.sh
+++ b/lib/hooks.sh
@@ -24,12 +24,26 @@ _hooks_read_definitions() {
   printf '%s\n' "$hook_content"
 }
 
+# Print the SHA-256 hex digest of stdin.
+# Falls back to sha256sum where Perl's shasum is not installed
+# (for example Alpine or minimal Fedora/RHEL images).
+# Usage: printf '%s' "$data" | _hooks_sha256
+_hooks_sha256() {
+  if command -v shasum >/dev/null 2>&1; then
+    shasum -a 256 | cut -d' ' -f1
+  elif command -v sha256sum >/dev/null 2>&1; then
+    sha256sum | cut -d' ' -f1
+  else
+    return 1
+  fi
+}
+
 # Compute a content hash for trusted command definitions.
 # Usage: _hooks_content_hash <hook_content>
 _hooks_content_hash() {
   local hook_content="$1"
   [ -n "$hook_content" ] || return 1
-  printf '%s\n' "$hook_content" | shasum -a 256 | cut -d' ' -f1
+  printf '%s\n' "$hook_content" | _hooks_sha256
 }
 
 # Compute a content hash of all current trusted command entries in a .gtrconfig file.
@@ -73,7 +87,7 @@ _hooks_reviewed_trust_key() {
   local hash repo_root
   hash=$(_hooks_content_hash "$hook_content") || return 1
   repo_root=$(_hooks_repo_root "$config_file") || return 1
-  printf '%s\n%s\n' "$repo_root" "$hash" | shasum -a 256 | cut -d' ' -f1
+  printf '%s\n%s\n' "$repo_root" "$hash" | _hooks_sha256
 }
 
 # Compute the repo-scoped trust key for the current trusted command content
diff --git a/tests/hooks.bats b/tests/hooks.bats
index a94543e..58fdcc0 100644
--- a/tests/hooks.bats
+++ b/tests/hooks.bats
@@ -10,7 +10,7 @@ setup() {
 }
 
 teardown() {
-  rm -rf "$XDG_CONFIG_HOME"
+  rm -rf "$XDG_CONFIG_HOME" "$BATS_TMPDIR/no-shasum-bin-$$"
   teardown_integration_repo
 }
 
@@ -69,6 +69,30 @@ EOF
   [ "$(_hooks_file_hash "$TEST_REPO/.gtrconfig")" = "$expected" ]
 }
 
+@test "trust markers work when shasum is not installed" {
+  cat > "$TEST_REPO/.gtrconfig" <<'EOF'
+[hooks]
+  postCd = echo hi
+EOF
+
+  local expected
+  expected="$(_hooks_file_hash "$TEST_REPO/.gtrconfig")"
+
+  local no_shasum_path
+  no_shasum_path="$(path_without_command "$BATS_TMPDIR/no-shasum-bin-$$" shasum)"
+
+  (
+    PATH="$no_shasum_path"
+    if command -v shasum >/dev/null 2>&1; then
+      exit 1
+    fi
+
+    [ "$(_hooks_file_hash "$TEST_REPO/.gtrconfig")" = "$expected" ]
+    _hooks_mark_trusted "$TEST_REPO/.gtrconfig"
+    _hooks_are_trusted "$TEST_REPO/.gtrconfig"
+  )
+}
+
 @test "_hooks_mark_trusted creates a marker recognized by _hooks_are_trusted" {
   cat > "$TEST_REPO/.gtrconfig" <<'EOF'
 [hooks]
diff --git a/tests/init.bats b/tests/init.bats
index 2d759fa..63b0efd 100644
--- a/tests/init.bats
+++ b/tests/init.bats
@@ -112,13 +112,15 @@ SCRIPT
 
 run_generated_fish_gtrconfig_post_cd_hooks() {
   local trust_state="$1"
-  local root repo wt xdg init_file
+  local without_shasum="${2:-0}"
+  local root repo wt xdg init_file fish_path
 
   root=$(mktemp -d)
   repo="$root/repo"
   wt="$root/wt"
   xdg="$root/xdg"
   init_file="$root/gtr.fish"
+  fish_path="$PATH"
 
   git init --quiet "$repo"
   git -C "$repo" config user.name "Test User"
@@ -145,7 +147,11 @@ CFG
     )
   fi
 
-  XDG_CONFIG_HOME="$xdg" fish -c '
+  if [ "$without_shasum" -eq 1 ]; then
+    fish_path=$(path_without_command "$root/bin" shasum)
+  fi
+
+  PATH="$fish_path" XDG_CONFIG_HOME="$xdg" fish -c '
     source "$argv[1]"
     set -l wt "$argv[2]"
     set -l root "$argv[3]"
@@ -336,6 +342,33 @@ require_runtime_shell() {
   [[ "$output" == *"git gtr list --porcelain"* ]]
 }
 
+@test "generated bash wrapper recognizes trust markers when shasum is not installed" {
+  local root repo xdg no_shasum_path
+  root=$(mktemp -d)
+  repo="$root/repo"
+  xdg="$root/xdg"
+
+  git init --quiet "$repo"
+  cat > "$repo/.gtrconfig" <<'CFG'
+[hooks]
+  postCd = echo hi
+CFG
+
+  (
+    export XDG_CONFIG_HOME="$xdg"
+    # shellcheck disable=SC1091
+    . "$PROJECT_ROOT/lib/hooks.sh"
+    _hooks_mark_trusted "$repo/.gtrconfig"
+  )
+
+  no_shasum_path=$(path_without_command "$root/bin" shasum)
+  run env PATH="$no_shasum_path" bash -c 'eval "$1" && gtr_hooks_are_trusted "$2" "$3"' \
+    _ "$(cmd_init bash)" "$repo/.gtrconfig" "$xdg/gtr/trusted"
+  rm -rf "$root"
+
+  [ "$status" -eq 0 ]
+}
+
 @test "zsh output validates trust marker contents" {
   run cmd_init zsh
   [ "$status" -eq 0 ]
@@ -420,6 +453,18 @@ require_runtime_shell() {
   [ "$hook_pwd_line" = "$wt_line" ]
 }
 
+@test "fish generated postCd trusts gtrconfig hooks when shasum is unavailable" {
+  require_runtime_shell fish
+  command -v sha256sum >/dev/null 2>&1 || skip "sha256sum is not installed"
+
+  run run_generated_fish_gtrconfig_post_cd_hooks trusted 1
+
+  [ "$status" -eq 0 ]
+  [[ "$output" == *"RC=0"* ]]
+  [[ "$output" == *"HOOK_ORDER=second"* ]]
+  [[ "$output" == *"STDERR="* ]]
+}
+
 # ── new/pr --cd wrapper support ─────────────────────────────────────────────
 
 @test "bash output intercepts new/pr --cd and strips flag before delegating" {
@@ -952,7 +997,7 @@ require_runtime_shell() {
 
 @test "cache invalidates old default shell integration schema" {
   mkdir -p "$XDG_CACHE_HOME/gtr"
-  printf '%s\n%s\n' '# gtr-cache: version=test init=5 func=gtr shell=bash' old-cache > "$XDG_CACHE_HOME/gtr/init-gtr.bash"
+  printf '%s\n%s\n' '# gtr-cache: version=test init=6 func=gtr shell=bash' old-cache > "$XDG_CACHE_HOME/gtr/init-gtr.bash"
 
   run cmd_init bash
 
@@ -960,19 +1005,19 @@ require_runtime_shell() {
   [ "$output" != "old-cache" ]
   local stamp
   stamp="$(head -1 "$XDG_CACHE_HOME/gtr/init-gtr.bash")"
-  [[ "$stamp" == *"init=6"* ]]
+  [[ "$stamp" == *"init=7"* ]]
 }
 
 @test "documented bash setup regenerates old schema cache" {
   mkdir -p "$XDG_CACHE_HOME/gtr"
   local _gtr_init="$XDG_CACHE_HOME/gtr/init-gtr.bash"
-  printf '%s\n%s\n' '# gtr-cache: version=test init=5 func=gtr shell=bash' old-cache > "$_gtr_init"
+  printf '%s\n%s\n' '# gtr-cache: version=test init=6 func=gtr shell=bash' old-cache > "$_gtr_init"
 
   cmd_init bash >/dev/null
 
   local stamp
   stamp="$(head -1 "$_gtr_init")"
-  [[ "$stamp" == *"init=6"* ]]
+  [[ "$stamp" == *"init=7"* ]]
 }
 
 @test "cache uses --as func name in cache key" {
diff --git a/tests/test_helper.bash b/tests/test_helper.bash
index 6e4ada1..84c61db 100644
--- a/tests/test_helper.bash
+++ b/tests/test_helper.bash
@@ -108,3 +108,23 @@ SCRIPT
   chmod +x "$MOCK_BIN_DIR/$name"
   export PATH="$MOCK_BIN_DIR:$PATH"
 }
+
+# Mirror every command on PATH into a new directory, leaving out one command,
+# so tests can simulate systems where that command is not installed.
+# Usage: path_without_command <bin_dir> <command>
+# Prints: the directory to use as PATH
+path_without_command() {
+  local bin_dir="$1" omitted="$2" dir entry name
+  mkdir -p "$bin_dir"
+  local IFS=:
+  for dir in $PATH; do
+    [ -d "$dir" ] || continue
+    for entry in "$dir"/*; do
+      [ -e "$entry" ] || continue
+      name="${entry##*/}"
+      [ "$name" = "$omitted" ] && continue
+      [ -e "$bin_dir/$name" ] || ln -s "$entry" "$bin_dir/$name"
+    done
+  done
+  printf "%s" "$bin_dir"
+}