diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 05f7e39de..e5f53cdf7 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -282,6 +282,7 @@ jobs:
           rpm_depends: "openssl"
           config_dir: ".release/linux/package/"
           preinstall: ".release/linux/preinst"
+          postinstall: ".release/linux/postinst"
           postremove: ".release/linux/postrm"
       - name: Add Linux Package names to env
         run: |
diff --git a/.release/docker/README_docker_io.md b/.release/docker/README_docker_io.md
index 5eab76624..4a58fb989 100644
--- a/.release/docker/README_docker_io.md
+++ b/.release/docker/README_docker_io.md
@@ -25,6 +25,16 @@ and is not suitable for actual deployment.
 Please see the comments within the file for more information;
 full configuration details can be found on Threshold's documentation site.
 
+#### Upgrading from the HashiCorp Boundary image
+
+The configuration directory moved from `/boundary` to `/threshold`. For
+compatibility, `/boundary` is a symlink to `/threshold` inside the image, a
+`-config /boundary/config.hcl` argument (or a config mounted at
+`/boundary/config.hcl`) is still honored with a deprecation warning, `boundary`
+is accepted as a command name, and `BOUNDARY_*` environment variables are
+mirrored to `THRESHOLD_*`. Please migrate your mounts and arguments to the
+`/threshold` and `THRESHOLD_*` names.
+
 ### Postgres
 
 The usage instructions in this README assume you have an external postgres database (version 12 or greater) to run threshold server with.
diff --git a/.release/docker/docker-entrypoint.sh b/.release/docker/docker-entrypoint.sh
index f9b4b6293..8c12c0583 100755
--- a/.release/docker/docker-entrypoint.sh
+++ b/.release/docker/docker-entrypoint.sh
@@ -22,6 +22,54 @@ for legacy_name in $(env | sed -n 's/^\(BOUNDARY_[A-Za-z0-9_]*\)=.*/\1/p'); do
     fi
 done
 
+# Backwards compatibility: the legacy HashiCorp Boundary image kept its config
+# in /boundary/config.hcl and ran the "boundary" binary. Accept both.
+# (The *_TEST_* overrides exist only for .release/docker/test-entrypoint.sh.)
+NEW_CONFIG_PATH=${THRESHOLD_ENTRYPOINT_TEST_NEW:-/threshold/config.hcl}
+LEGACY_CONFIG_PATH=${THRESHOLD_ENTRYPOINT_TEST_LEGACY:-/boundary/config.hcl}
+STOCK_CONFIG_COPY=${THRESHOLD_ENTRYPOINT_TEST_STOCK:-/usr/share/threshold/config.hcl.default}
+
+legacy_warn() {
+    >&2 echo "WARNING: $1 (deprecated Boundary-era path); please move to /threshold/config.hcl"
+}
+
+# Prints the config path that should actually be used for a requested -config
+# path. Prefers /threshold/config.hcl, falling back to /boundary/config.hcl.
+resolve_config_path() {
+    case "$1" in
+    "$NEW_CONFIG_PATH")
+        # The image ships a stock demo config at /threshold/config.hcl. If it is
+        # still the stock one and the user supplied their own legacy config
+        # (for example by mounting it at /boundary/config.hcl on an image
+        # where /boundary is a real directory), use theirs.
+        if [ -f "$LEGACY_CONFIG_PATH" ] && ! [ "$LEGACY_CONFIG_PATH" -ef "$NEW_CONFIG_PATH" ] \
+            && [ -f "$STOCK_CONFIG_COPY" ] && cmp -s "$NEW_CONFIG_PATH" "$STOCK_CONFIG_COPY"; then
+            legacy_warn "using $LEGACY_CONFIG_PATH"
+            echo "$LEGACY_CONFIG_PATH"
+            return
+        fi
+        ;;
+    "$LEGACY_CONFIG_PATH")
+        if [ -f "$LEGACY_CONFIG_PATH" ]; then
+            legacy_warn "using $LEGACY_CONFIG_PATH"
+        elif [ -f "$NEW_CONFIG_PATH" ]; then
+            legacy_warn "$LEGACY_CONFIG_PATH not found, falling back to $NEW_CONFIG_PATH"
+            echo "$NEW_CONFIG_PATH"
+            return
+        fi
+        ;;
+    esac
+    echo "$1"
+}
+
+# Accept the legacy command name: "docker run <image> boundary ..." (or an
+# entrypoint/command override that invokes boundary) runs threshold.
+if [ "$1" = 'boundary' ]; then
+    >&2 echo "WARNING: the 'boundary' command is deprecated; use 'threshold' (running threshold)"
+    shift
+    set -- threshold "$@"
+fi
+
 # If the user is trying to run Threshold directly with some arguments, then
 # pass them to Threshold.
 if [ "${1:0:1}" = '-' ]; then
@@ -38,6 +86,26 @@ elif threshold --help "$1" 2>&1 | grep -q "threshold $1"; then
     set -- threshold "$@"
 fi
 
+# Rewrite -config arguments (see resolve_config_path).
+if [ "$1" = 'threshold' ]; then
+    _n=$#
+    _prev=""
+    while [ "$_n" -gt 0 ]; do
+        _a=$1
+        shift
+        _n=$((_n - 1))
+        case "$_prev" in
+        -config | --config) _new=$(resolve_config_path "$_a") ;;
+        *) _new=$_a ;;
+        esac
+        case "$_a" in
+        -config=* | --config=*) _new="${_a%%=*}=$(resolve_config_path "${_a#*=}")" ;;
+        esac
+        _prev=$_a
+        set -- "$@" "$_new"
+    done
+fi
+
 # If we are running Threshold, make sure it executes as the proper user.
 if [ "$1" = 'threshold' ]; then
 	is_root=0
@@ -51,6 +119,10 @@ if [ "$1" = 'threshold' ]; then
             if [ "$(stat -c %u /threshold)" != "$(id -u threshold)" ]; then
                 chown -R threshold:threshold /threshold || echo "Could not chown /threshold (may not have appropriate permissions)"
             fi
+            # Legacy config dir, when it is a real directory (not the symlink to /threshold)
+            if [ -d /boundary ] && [ ! -L /boundary ] && [ "$(stat -c %u /boundary)" != "$(id -u threshold)" ]; then
+                chown -R threshold:threshold /boundary || echo "Could not chown /boundary (may not have appropriate permissions)"
+            fi
         else
             >&2 echo "SKIP_CHOWN not set but running non-root; skipping chown /threshold"
         fi
diff --git a/.release/docker/test-entrypoint.sh b/.release/docker/test-entrypoint.sh
new file mode 100755
index 000000000..fefd19f6c
--- /dev/null
+++ b/.release/docker/test-entrypoint.sh
@@ -0,0 +1,107 @@
+#!/bin/bash
+# Self-contained test for the legacy-path handling in docker-entrypoint.sh.
+#
+# Runs the real entrypoint with a fake "threshold" binary and temporary
+# config paths (via the THRESHOLD_ENTRYPOINT_TEST_* overrides). No Docker or
+# root needed. The entrypoint is written for busybox/ash; bash is used here
+# because it accepts the same ${var:off:len} syntax.
+#
+# Usage: .release/docker/test-entrypoint.sh
+
+set -u
+
+HERE=$(cd "$(dirname "$0")" && pwd)
+ENTRY="$HERE/docker-entrypoint.sh"
+WORK=$(mktemp -d)
+trap 'rm -rf "$WORK"' EXIT
+
+FAILS=0
+PASSES=0
+check() { # check DESC EXPECTED ACTUAL
+	if [ "$2" = "$3" ]; then
+		PASSES=$((PASSES + 1))
+	else
+		FAILS=$((FAILS + 1))
+		echo "FAIL: $1" >&2
+		echo "  expected: $2" >&2
+		echo "  actual:   $3" >&2
+	fi
+}
+
+mkdir -p "$WORK/bin" "$WORK/new" "$WORK/legacy"
+# Fake threshold: print the argument vector on one line, "|"-separated.
+cat >"$WORK/bin/threshold" <<'EOF'
+#!/bin/sh
+case "$1" in --help) [ "$2" = threshold ] || echo "threshold $2"; exit 0 ;; esac
+IFS='|'
+echo "ARGS:$*"
+EOF
+cat >"$WORK/bin/su-exec" <<'EOF'
+#!/bin/sh
+shift
+exec "$@"
+EOF
+chmod 755 "$WORK/bin/threshold" "$WORK/bin/su-exec"
+
+NEWCFG="$WORK/new/config.hcl"
+LEGCFG="$WORK/legacy/config.hcl"
+STOCK="$WORK/stock.hcl"
+
+run() { # run ARGS... ; prints "<stdout-args> || <stderr>"
+	PATH="$WORK/bin:$PATH" SKIP_CHOWN=1 SKIP_SETCAP=1 \
+		THRESHOLD_ENTRYPOINT_TEST_NEW="$NEWCFG" \
+		THRESHOLD_ENTRYPOINT_TEST_LEGACY="$LEGCFG" \
+		THRESHOLD_ENTRYPOINT_TEST_STOCK="$STOCK" \
+		bash "$ENTRY" "$@" 2>"$WORK/err" | grep '^ARGS:'
+}
+stderr() { cat "$WORK/err"; }
+
+echo "stock demo config" >"$STOCK"
+cp "$STOCK" "$NEWCFG"
+
+# 1. default invocation, stock config, no legacy file -> unchanged, no warning
+out=$(run server -config "$NEWCFG")
+check "default path kept" "ARGS:server|-config|$NEWCFG" "$out"
+check "no warning by default" "" "$(stderr | grep -c deprecated | grep -v '^0$')"
+
+# 2. user's own /threshold config (differs from stock) wins over a legacy file
+echo "user threshold config" >"$NEWCFG"
+echo "user legacy config" >"$LEGCFG"
+out=$(run server -config "$NEWCFG")
+check "custom threshold config preferred" "ARGS:server|-config|$NEWCFG" "$out"
+
+# 3. stock /threshold config + user legacy config -> legacy used with warning
+cp "$STOCK" "$NEWCFG"
+out=$(run server -config "$NEWCFG")
+check "legacy config used when threshold is stock" "ARGS:server|-config|$LEGCFG" "$out"
+check "deprecation warning printed" "1" "$(stderr | grep -c 'WARNING.*Boundary-era')"
+
+# 4. explicit legacy path that exists -> used with warning
+out=$(run server -config "$LEGCFG")
+check "explicit legacy path kept" "ARGS:server|-config|$LEGCFG" "$out"
+check "explicit legacy warns" "1" "$(stderr | grep -c 'WARNING')"
+
+# 5. explicit legacy path that does not exist -> fall back to threshold path
+rm -f "$LEGCFG"
+out=$(run server -config "$LEGCFG")
+check "missing legacy falls back to threshold" "ARGS:server|-config|$NEWCFG" "$out"
+
+# 6. -config=PATH form
+echo "user legacy config" >"$LEGCFG"
+out=$(run server -config="$LEGCFG")
+check "-config=path form" "ARGS:server|-config=$LEGCFG" "$out"
+rm -f "$LEGCFG"
+out=$(run server -config="$LEGCFG")
+check "-config=path fallback" "ARGS:server|-config=$NEWCFG" "$out"
+
+# 7. legacy command name
+out=$(run boundary version)
+check "boundary command accepted" "ARGS:version" "$out"
+check "boundary command warns" "1" "$(stderr | grep -c "'boundary' command is deprecated")"
+
+# 8. unrelated args untouched
+out=$(run database init -config "$NEWCFG" -skip-auth-method-creation)
+check "other args preserved" "ARGS:database|init|-config|$NEWCFG|-skip-auth-method-creation" "$out"
+
+echo "passed: $PASSES, failed: $FAILS"
+[ "$FAILS" -eq 0 ]
diff --git a/.release/linux/package/usr/lib/systemd/system/threshold.service b/.release/linux/package/usr/lib/systemd/system/threshold.service
index 1c2926ba3..5529a5b68 100644
--- a/.release/linux/package/usr/lib/systemd/system/threshold.service
+++ b/.release/linux/package/usr/lib/systemd/system/threshold.service
@@ -5,6 +5,9 @@ StartLimitIntervalSec=60
 StartLimitBurst=3
 
 [Service]
+# Legacy HashiCorp Boundary environment file (BOUNDARY_* variables are still
+# honored). Read first so that threshold.env takes precedence.
+EnvironmentFile=-/etc/boundary.d/boundary.env
 EnvironmentFile=-/etc/threshold.d/threshold.env
 User=threshold
 Group=threshold
diff --git a/.release/linux/postinst b/.release/linux/postinst
new file mode 100755
index 000000000..f80cfb519
--- /dev/null
+++ b/.release/linux/postinst
@@ -0,0 +1,163 @@
+#!/bin/sh
+# Threshold package post-install script (deb "postinst" / rpm "%post").
+#
+# Completes an in-place upgrade from a HashiCorp Boundary install. Safe to run
+# repeatedly; never deletes user configuration or data:
+#
+#   1. If the legacy "boundary" user exists and there is no "threshold" user,
+#      run the service as "boundary" through a systemd drop-in, so existing
+#      data/log directory ownership keeps working.
+#   2. Provide a "boundary" command: /usr/bin/boundary -> threshold, only if
+#      /usr/bin/boundary does not exist.
+#   3. If the legacy boundary.service is enabled/active: stop it, carry its
+#      enablement over to threshold.service, and start threshold.service if the
+#      old service was running (rolling back to boundary.service if that fails).
+#   4. Make "systemctl <verb> boundary" address threshold.service by adding a
+#      boundary.service alias symlink, unless something already exists there.
+#
+# THRESHOLD_PKG_ROOT exists only so the logic can be exercised by
+# .release/linux/test/test-package-scripts.sh without root; it is empty in
+# normal use.
+
+set -eu
+
+ROOT="${THRESHOLD_PKG_ROOT:-}"
+NEW_USER="threshold"
+LEGACY_USER="boundary"
+UNIT="threshold.service"
+LEGACY_UNIT="boundary.service"
+SYSTEMD_ETC="$ROOT/etc/systemd/system"
+DROPIN_DIR="$SYSTEMD_ETC/threshold.service.d"
+DROPIN="$DROPIN_DIR/10-legacy-boundary-user.conf"
+DROPIN_MARK="# Managed by the Threshold package (legacy boundary user reuse)"
+
+say() {
+	echo "threshold postinst: $*" >&2
+}
+
+user_exists() {
+	id -u "$1" >/dev/null 2>&1
+}
+
+have_systemd() {
+	command -v systemctl >/dev/null 2>&1 && [ -d "$ROOT/run/systemd/system" ]
+}
+
+# Print the Id= systemd resolves a unit name to (follows aliases).
+unit_id() {
+	systemctl show -p Id "$1" 2>/dev/null | sed -n 's/^Id=//p'
+}
+
+unit_load_state() {
+	systemctl show -p LoadState "$1" 2>/dev/null | sed -n 's/^LoadState=//p'
+}
+
+# Where the packaged threshold.service lives (merged-usr or not).
+packaged_unit_path() {
+	for _p in "$ROOT/usr/lib/systemd/system/$UNIT" "$ROOT/lib/systemd/system/$UNIT"; do
+		if [ -f "$_p" ]; then
+			echo "${_p#"$ROOT"}"
+			return 0
+		fi
+	done
+	return 1
+}
+
+# --- 1. legacy service user -------------------------------------------------
+if user_exists "$LEGACY_USER" && ! user_exists "$NEW_USER"; then
+	_group=$(id -gn "$LEGACY_USER" 2>/dev/null || echo "$LEGACY_USER")
+	_content="$DROPIN_MARK
+[Service]
+User=$LEGACY_USER
+Group=$_group"
+	if [ -e "$DROPIN" ] && ! grep -qF "$DROPIN_MARK" "$DROPIN"; then
+		say "leaving existing $DROPIN untouched (not managed by this package)"
+	else
+		mkdir -p "$DROPIN_DIR"
+		_tmp="$DROPIN.tmp.$$"
+		printf '%s\n' "$_content" >"$_tmp"
+		mv -f "$_tmp" "$DROPIN"
+		say "service will run as existing user '$LEGACY_USER' ($DROPIN)"
+	fi
+fi
+
+# --- 2. "boundary" command ----------------------------------------------------
+_bin="$ROOT/usr/bin/boundary"
+if [ ! -e "$_bin" ] && [ ! -L "$_bin" ]; then
+	if [ -e "$ROOT/usr/bin/threshold" ]; then
+		ln -s threshold "$_bin"
+	fi
+elif [ ! -L "$_bin" ]; then
+	say "/usr/bin/boundary is still the HashiCorp Boundary binary (old package installed); leaving it"
+	say "after removing the old package run: ln -s threshold /usr/bin/boundary"
+fi
+
+# --- 3 + 4. legacy systemd service ----------------------------------------------
+if have_systemd; then
+	_alias="$SYSTEMD_ETC/$LEGACY_UNIT"
+
+	if [ -L "$_alias" ]; then
+		# Already aliased (previous run): nothing to migrate.
+		:
+	elif [ -e "$_alias" ]; then
+		say "$_alias is a custom unit; not touching the legacy service."
+		say "move it away and re-run the package configuration to migrate."
+	else
+		_id=$(unit_id "$LEGACY_UNIT")
+		_load=$(unit_load_state "$LEGACY_UNIT")
+		_legacy_present=0
+		_was_enabled=0
+		_was_active=0
+		if [ "$_id" = "$LEGACY_UNIT" ] && [ "$_load" = "loaded" ]; then
+			_legacy_present=1
+			if systemctl is-enabled --quiet "$LEGACY_UNIT" 2>/dev/null; then
+				_was_enabled=1
+			fi
+			if systemctl is-active --quiet "$LEGACY_UNIT" 2>/dev/null; then
+				_was_active=1
+			fi
+		fi
+
+		# Only act on upgrades: a legacy unit or legacy config is present.
+		if [ "$_legacy_present" = 1 ] || [ -d "$ROOT/etc/boundary.d" ]; then
+			if [ "$_was_active" = 1 ]; then
+				say "stopping $LEGACY_UNIT"
+				systemctl stop "$LEGACY_UNIT" || say "could not stop $LEGACY_UNIT"
+			fi
+			if [ "$_was_enabled" = 1 ]; then
+				systemctl disable "$LEGACY_UNIT" >/dev/null 2>&1 || say "could not disable $LEGACY_UNIT"
+			fi
+
+			# Alias symlink so `systemctl restart boundary` reaches threshold.service.
+			if _unit_path=$(packaged_unit_path); then
+				mkdir -p "$SYSTEMD_ETC"
+				ln -s "$_unit_path" "$_alias"
+			fi
+			systemctl daemon-reload || true
+
+			if [ "$_was_enabled" = 1 ]; then
+				systemctl enable "$UNIT" >/dev/null 2>&1 || say "could not enable $UNIT"
+			fi
+			if [ "$_was_active" = 1 ]; then
+				if systemctl start "$UNIT"; then
+					say "$LEGACY_UNIT migrated to $UNIT (config: /etc/threshold.d)"
+				else
+					say "FAILED to start $UNIT; rolling back to $LEGACY_UNIT"
+					systemctl disable "$UNIT" >/dev/null 2>&1 || true
+					rm -f "$_alias"
+					systemctl daemon-reload || true
+					if [ "$_was_enabled" = 1 ]; then
+						systemctl enable "$LEGACY_UNIT" >/dev/null 2>&1 || true
+					fi
+					systemctl start "$LEGACY_UNIT" || say "could not restart $LEGACY_UNIT"
+				fi
+			elif [ "$_was_enabled" = 1 ]; then
+				say "$LEGACY_UNIT enablement carried over to $UNIT (not started: it was stopped)"
+			fi
+		fi
+	fi
+	# Pick up a new/changed user drop-in even when no migration was needed.
+	systemctl daemon-reload || true
+fi
+
+exit 0
diff --git a/.release/linux/postrm b/.release/linux/postrm
old mode 100644
new mode 100755
index ecf8f5079..53e6f61d7
--- a/.release/linux/postrm
+++ b/.release/linux/postrm
@@ -1,8 +1,55 @@
-#!/bin/bash
+#!/bin/sh
+# Threshold package post-remove script (deb "postrm" / rpm "%postun").
+#
+# deb: $1 is remove|purge|upgrade|...    rpm: $1 is 0 (erase) or 1+ (upgrade)
+#
+# On final removal this removes only what the Threshold package scripts
+# themselves created: the managed systemd drop-in, the /usr/bin/boundary and
+# /etc/systemd/system/boundary.service symlinks (only if they point at
+# Threshold), and on purge the "threshold" user. User configuration, data and
+# the legacy "boundary" user are never touched.
+#
+# THRESHOLD_PKG_ROOT exists only so the logic can be exercised by
+# .release/linux/test/test-package-scripts.sh without root; it is empty in
+# normal use.
 
-if [ "$1" = "purge" ]
-then
-  userdel threshold
+set -eu
+
+ROOT="${THRESHOLD_PKG_ROOT:-}"
+SYSTEMD_ETC="$ROOT/etc/systemd/system"
+DROPIN_DIR="$SYSTEMD_ETC/threshold.service.d"
+DROPIN="$DROPIN_DIR/10-legacy-boundary-user.conf"
+DROPIN_MARK="# Managed by the Threshold package (legacy boundary user reuse)"
+
+# rm a symlink only if its target's basename matches $2.
+rm_link_if() {
+	if [ -L "$1" ]; then
+		_t=$(readlink "$1" || true)
+		case "${_t##*/}" in
+		"$2") rm -f "$1" ;;
+		esac
+	fi
+}
+
+case "${1:-}" in
+remove | purge | 0)
+	rm_link_if "$ROOT/usr/bin/boundary" threshold
+	rm_link_if "$SYSTEMD_ETC/boundary.service" threshold.service
+	rm_link_if "$SYSTEMD_ETC/multi-user.target.wants/threshold.service" threshold.service
+	if [ -f "$DROPIN" ] && grep -qF "$DROPIN_MARK" "$DROPIN"; then
+		rm -f "$DROPIN"
+		rmdir "$DROPIN_DIR" 2>/dev/null || true
+	fi
+	if command -v systemctl >/dev/null 2>&1 && [ -d "$ROOT/run/systemd/system" ]; then
+		systemctl daemon-reload >/dev/null 2>&1 || true
+	fi
+	;;
+esac
+
+if [ "${1:-}" = "purge" ]; then
+	if id -u threshold >/dev/null 2>&1; then
+		userdel threshold || true
+	fi
 fi
 
-exit 0
\ No newline at end of file
+exit 0
diff --git a/.release/linux/preinst b/.release/linux/preinst
old mode 100644
new mode 100755
index 5f0fcaf9a..6f04424ce
--- a/.release/linux/preinst
+++ b/.release/linux/preinst
@@ -1,13 +1,98 @@
-#!/bin/bash
+#!/bin/sh
+# Threshold package pre-install script (deb "preinst" / rpm "%pre").
+#
+# Runs before the package files are unpacked. It is safe to run repeatedly and
+# never deletes or overwrites anything:
+#
+#   * Service user: if a HashiCorp Boundary "boundary" user already exists and
+#     there is no "threshold" user yet, no new user is created. The postinst
+#     script makes the service run as the existing "boundary" user so that its
+#     data/log directory ownership keeps working.
+#   * Configuration: files from /etc/boundary.d are COPIED to /etc/threshold.d
+#     (boundary.hcl -> threshold.hcl, boundary.env -> threshold.env, everything
+#     else keeps its name). An existing file in /etc/threshold.d is never
+#     replaced, and the originals in /etc/boundary.d are left untouched.
+#
+# THRESHOLD_PKG_ROOT exists only so the logic can be exercised by
+# .release/linux/test/test-package-scripts.sh without root; it is empty in
+# normal use.
 
 set -eu
 
-USER="threshold"
+ROOT="${THRESHOLD_PKG_ROOT:-}"
+NEW_USER="threshold"
+LEGACY_USER="boundary"
+LEGACY_DIR="$ROOT/etc/boundary.d"
+NEW_DIR="$ROOT/etc/threshold.d"
 
-if ! id -u $USER > /dev/null 2>&1; then
-	useradd \
-		--system \
-		--user-group \
-		--shell /bin/false \
-		$USER
-fi
\ No newline at end of file
+say() {
+	echo "threshold preinst: $*" >&2
+}
+
+user_exists() {
+	id -u "$1" >/dev/null 2>&1
+}
+
+# Map a top-level legacy file name to its Threshold name.
+map_name() {
+	case "$1" in
+	boundary.hcl) echo "threshold.hcl" ;;
+	boundary.env) echo "threshold.env" ;;
+	*) echo "$1" ;;
+	esac
+}
+
+# copy_tree SRC_DIR DST_DIR TOPLEVEL(0/1)
+# Copies entries that do not exist yet in DST_DIR; never overwrites.
+copy_tree() {
+	_src=$1
+	_dst=$2
+	_top=$3
+	for _f in "$_src"/* "$_src"/.[!.]*; do
+		if [ ! -e "$_f" ] && [ ! -L "$_f" ]; then
+			continue
+		fi
+		_name=${_f##*/}
+		if [ "$_top" = 1 ]; then
+			_name=$(map_name "$_name")
+		fi
+		_target="$_dst/$_name"
+		if [ -d "$_f" ] && [ ! -L "$_f" ]; then
+			if [ -d "$_target" ]; then
+				copy_tree "$_f" "$_target" 0
+			elif [ -e "$_target" ] || [ -L "$_target" ]; then
+				say "not replacing existing $_target"
+			else
+				cp -pR "$_f" "$_target"
+				say "copied $_f -> $_target"
+			fi
+		elif [ -e "$_target" ] || [ -L "$_target" ]; then
+			# Already present (user's own file, or a previous run): keep it.
+			:
+		else
+			cp -pP "$_f" "$_target"
+			say "copied $_f -> $_target"
+		fi
+	done
+}
+
+# --- service user -----------------------------------------------------------
+if ! user_exists "$NEW_USER"; then
+	if user_exists "$LEGACY_USER"; then
+		say "existing '$LEGACY_USER' user found; reusing it instead of creating '$NEW_USER'"
+	else
+		useradd \
+			--system \
+			--user-group \
+			--shell /bin/false \
+			"$NEW_USER"
+	fi
+fi
+
+# --- configuration migration ------------------------------------------------
+if [ -d "$LEGACY_DIR" ]; then
+	mkdir -p "$NEW_DIR"
+	copy_tree "$LEGACY_DIR" "$NEW_DIR" 1
+fi
+
+exit 0
diff --git a/.release/linux/test/test-package-scripts.sh b/.release/linux/test/test-package-scripts.sh
new file mode 100755
index 000000000..f1261ec86
--- /dev/null
+++ b/.release/linux/test/test-package-scripts.sh
@@ -0,0 +1,267 @@
+#!/bin/sh
+# Self-contained test for the Linux package scripts (preinst/postinst/postrm).
+#
+# Simulates an old HashiCorp Boundary layout in a temporary directory (fake
+# /etc/boundary.d, a "boundary" user, a running boundary.service) using the
+# THRESHOLD_PKG_ROOT prefix and fake id/useradd/userdel/systemctl commands.
+# Needs neither root nor systemd.
+#
+# Usage: .release/linux/test/test-package-scripts.sh
+
+set -eu
+
+HERE=$(cd "$(dirname "$0")" && pwd)
+PKG_DIR=$(cd "$HERE/.." && pwd)
+PREINST="$PKG_DIR/preinst"
+POSTINST="$PKG_DIR/postinst"
+POSTRM="$PKG_DIR/postrm"
+SH=${TEST_SH:-sh}
+
+WORK=$(mktemp -d)
+trap 'rm -rf "$WORK"' EXIT INT TERM
+
+FAILS=0
+PASSES=0
+
+pass() { PASSES=$((PASSES + 1)); }
+fail() {
+	FAILS=$((FAILS + 1))
+	echo "FAIL: $*" >&2
+}
+assert() { # assert DESC cmd...
+	_d=$1
+	shift
+	if "$@"; then pass; else fail "$_d"; fi
+}
+refute() { # refute DESC cmd...
+	_d=$1
+	shift
+	if "$@"; then fail "$_d"; else pass; fi
+}
+file_has() { grep -qF -- "$2" "$1"; }
+file_eq() { [ "$(cat "$1")" = "$2" ]; }
+
+# --- fake commands ------------------------------------------------------------
+BIN="$WORK/bin"
+mkdir -p "$BIN"
+
+cat >"$BIN/id" <<'EOF'
+#!/bin/sh
+# fake id: id -u NAME | id -gn NAME ; users in $FAKE/users as name:group
+mode=$1
+name=$2
+line=$(grep "^$name:" "$FAKE/users" 2>/dev/null) || exit 1
+case "$mode" in
+-u) echo 1000 ;;
+-gn) echo "${line#*:}" ;;
+esac
+EOF
+cat >"$BIN/useradd" <<'EOF'
+#!/bin/sh
+for a in "$@"; do name=$a; done
+echo "$name:$name" >>"$FAKE/users"
+echo "useradd $name" >>"$FAKE/calls"
+EOF
+cat >"$BIN/userdel" <<'EOF'
+#!/bin/sh
+grep -v "^$1:" "$FAKE/users" >"$FAKE/users.new" || true
+mv "$FAKE/users.new" "$FAKE/users"
+echo "userdel $1" >>"$FAKE/calls"
+EOF
+cat >"$BIN/systemctl" <<'EOF'
+#!/bin/sh
+# fake systemctl backed by files in $FAKE (state) and $THRESHOLD_PKG_ROOT
+resolve() {
+	if [ -L "$THRESHOLD_PKG_ROOT/etc/systemd/system/$1" ]; then
+		_t=$(readlink "$THRESHOLD_PKG_ROOT/etc/systemd/system/$1")
+		echo "${_t##*/}"
+	else
+		echo "$1"
+	fi
+}
+echo "systemctl $*" >>"$FAKE/calls"
+case "$1" in
+show)
+	u=$(resolve "$4")
+	case "$3" in
+	Id) echo "Id=$u" ;;
+	LoadState)
+		if [ -f "$THRESHOLD_PKG_ROOT/usr/lib/systemd/system/$u" ]; then
+			echo "LoadState=loaded"
+		else
+			echo "LoadState=not-found"
+		fi
+		;;
+	esac
+	;;
+is-enabled) u=$(resolve "$3"); [ -e "$FAKE/enabled/$u" ] ;;
+is-active) u=$(resolve "$3"); [ -e "$FAKE/active/$u" ] ;;
+enable) u=$(resolve "$2"); : >"$FAKE/enabled/$u" ;;
+disable) u=$(resolve "$2"); rm -f "$FAKE/enabled/$u" ;;
+start)
+	u=$(resolve "$2")
+	[ -e "$FAKE/fail_start/$u" ] && exit 1
+	: >"$FAKE/active/$u"
+	;;
+stop) u=$(resolve "$2"); rm -f "$FAKE/active/$u" ;;
+daemon-reload) : ;;
+esac
+exit $?
+EOF
+chmod 755 "$BIN"/*
+
+# --- scenario helpers -----------------------------------------------------------
+new_root() { # new_root NAME -> sets ROOT and FAKE, creates skeleton
+	ROOT="$WORK/$1/root"
+	FAKE="$WORK/$1/fake"
+	mkdir -p "$ROOT/etc" "$ROOT/usr/bin" "$ROOT/usr/lib/systemd/system" \
+		"$ROOT/etc/systemd/system" "$ROOT/run/systemd/system" \
+		"$FAKE/enabled" "$FAKE/active" "$FAKE/fail_start"
+	: >"$FAKE/users"
+	: >"$FAKE/calls"
+	# What the package itself would have unpacked.
+	: >"$ROOT/usr/bin/threshold"
+	echo "[Service]" >"$ROOT/usr/lib/systemd/system/threshold.service"
+	export THRESHOLD_PKG_ROOT="$ROOT" FAKE
+}
+
+run_script() { # run_script SCRIPT [ARGS...]
+	_s=$1
+	shift
+	PATH="$BIN:$PATH" "$SH" "$_s" "$@" >"$WORK/out.log" 2>&1
+}
+
+add_legacy_layout() {
+	mkdir -p "$ROOT/etc/boundary.d/tls"
+	echo 'controller { name = "mine" }' >"$ROOT/etc/boundary.d/boundary.hcl"
+	echo 'BOUNDARY_POSTGRES_URL=secret' >"$ROOT/etc/boundary.d/boundary.env"
+	echo 'worker { name = "w" }' >"$ROOT/etc/boundary.d/worker.hcl"
+	echo 'KEY' >"$ROOT/etc/boundary.d/tls/server.key"
+	chmod 600 "$ROOT/etc/boundary.d/tls/server.key"
+	echo "boundary:boundary" >>"$FAKE/users"
+	echo "[Service]" >"$ROOT/usr/lib/systemd/system/boundary.service"
+}
+
+# ==============================================================================
+echo "== scenario 1: upgrade from Boundary (running + enabled), existing threshold.hcl"
+new_root s1
+add_legacy_layout
+: >"$FAKE/enabled/boundary.service"
+: >"$FAKE/active/boundary.service"
+mkdir -p "$ROOT/etc/threshold.d"
+echo 'USER-OWNED' >"$ROOT/etc/threshold.d/threshold.hcl"
+
+assert "preinst succeeds" run_script "$PREINST" install
+assert "threshold.hcl NOT clobbered" file_eq "$ROOT/etc/threshold.d/threshold.hcl" "USER-OWNED"
+assert "boundary.env migrated to threshold.env" file_has "$ROOT/etc/threshold.d/threshold.env" "BOUNDARY_POSTGRES_URL=secret"
+assert "worker.hcl copied under same name" file_has "$ROOT/etc/threshold.d/worker.hcl" 'name = "w"'
+assert "subdirectory copied" file_has "$ROOT/etc/threshold.d/tls/server.key" "KEY"
+assert "originals kept: boundary.hcl" test -f "$ROOT/etc/boundary.d/boundary.hcl"
+assert "originals kept: boundary.env" test -f "$ROOT/etc/boundary.d/boundary.env"
+refute "no duplicate threshold user created" grep -q '^useradd' "$FAKE/calls"
+refute "no boundary.hcl name left in threshold.d" test -e "$ROOT/etc/threshold.d/boundary.hcl"
+
+assert "postinst succeeds" run_script "$POSTINST" configure
+assert "drop-in written" file_has "$ROOT/etc/systemd/system/threshold.service.d/10-legacy-boundary-user.conf" "User=boundary"
+assert "drop-in group" file_has "$ROOT/etc/systemd/system/threshold.service.d/10-legacy-boundary-user.conf" "Group=boundary"
+assert "boundary command symlink" test -L "$ROOT/usr/bin/boundary"
+assert "boundary symlink target is threshold" test "$(readlink "$ROOT/usr/bin/boundary")" = "threshold"
+assert "boundary.service alias symlink" test -L "$ROOT/etc/systemd/system/boundary.service"
+assert "legacy service stopped" test ! -e "$FAKE/active/boundary.service"
+assert "threshold enabled" test -e "$FAKE/enabled/threshold.service"
+assert "threshold started" test -e "$FAKE/active/threshold.service"
+refute "legacy unit not left enabled as itself" grep -q 'enable boundary.service' "$FAKE/calls"
+
+: >"$FAKE/calls"
+assert "postinst idempotent (2nd run)" run_script "$POSTINST" configure
+refute "2nd run does not stop/start anything" grep -qE 'systemctl (stop|start|enable|disable)' "$FAKE/calls"
+assert "preinst idempotent (2nd run)" run_script "$PREINST" upgrade
+assert "threshold.hcl still not clobbered" file_eq "$ROOT/etc/threshold.d/threshold.hcl" "USER-OWNED"
+
+echo "== scenario 1b: postrm remove/purge cleans only generated pieces"
+assert "postrm remove" run_script "$POSTRM" remove
+refute "boundary command symlink removed" test -L "$ROOT/usr/bin/boundary"
+refute "alias symlink removed" test -L "$ROOT/etc/systemd/system/boundary.service"
+refute "drop-in removed" test -e "$ROOT/etc/systemd/system/threshold.service.d/10-legacy-boundary-user.conf"
+assert "user config untouched after remove" test -f "$ROOT/etc/boundary.d/boundary.hcl"
+assert "migrated config untouched after remove" test -f "$ROOT/etc/threshold.d/threshold.env"
+assert "postrm purge (no threshold user: no userdel)" run_script "$POSTRM" purge
+refute "boundary user never deleted" grep -q 'userdel boundary' "$FAKE/calls"
+
+# ==============================================================================
+echo "== scenario 2: fresh install, no Boundary"
+new_root s2
+assert "preinst succeeds" run_script "$PREINST" install
+assert "threshold user created" grep -q '^useradd threshold' "$FAKE/calls"
+refute "no /etc/threshold.d created by migration" test -e "$ROOT/etc/threshold.d"
+assert "postinst succeeds" run_script "$POSTINST" configure
+refute "no drop-in" test -e "$ROOT/etc/systemd/system/threshold.service.d"
+refute "no boundary.service alias on fresh install" test -L "$ROOT/etc/systemd/system/boundary.service"
+assert "boundary command symlink still provided" test -L "$ROOT/usr/bin/boundary"
+refute "threshold not auto-enabled on fresh install" test -e "$FAKE/enabled/threshold.service"
+assert "postrm purge deletes threshold user" run_script "$POSTRM" purge
+assert "userdel threshold called" grep -q '^userdel threshold' "$FAKE/calls"
+
+# ==============================================================================
+echo "== scenario 3: boundary service enabled but threshold start fails -> rollback"
+new_root s3
+add_legacy_layout
+: >"$FAKE/enabled/boundary.service"
+: >"$FAKE/active/boundary.service"
+: >"$FAKE/fail_start/threshold.service"
+assert "preinst succeeds" run_script "$PREINST" install
+assert "postinst still exits 0" run_script "$POSTINST" configure
+assert "legacy service running again" test -e "$FAKE/active/boundary.service"
+assert "legacy service enabled again" test -e "$FAKE/enabled/boundary.service"
+refute "threshold left disabled" test -e "$FAKE/enabled/threshold.service"
+refute "alias removed on rollback" test -L "$ROOT/etc/systemd/system/boundary.service"
+assert "rollback explained" file_has "$WORK/out.log" "rolling back"
+
+# ==============================================================================
+echo "== scenario 4: enabled but stopped boundary service is only carried over"
+new_root s4
+add_legacy_layout
+: >"$FAKE/enabled/boundary.service"
+assert "preinst" run_script "$PREINST" install
+assert "postinst" run_script "$POSTINST" configure
+assert "threshold enabled" test -e "$FAKE/enabled/threshold.service"
+refute "threshold not started" test -e "$FAKE/active/threshold.service"
+
+# ==============================================================================
+echo "== scenario 5: custom regular-file /etc/systemd/system/boundary.service is left alone"
+new_root s5
+add_legacy_layout
+: >"$FAKE/enabled/boundary.service"
+: >"$FAKE/active/boundary.service"
+echo "CUSTOM" >"$ROOT/etc/systemd/system/boundary.service"
+assert "preinst" run_script "$PREINST" install
+assert "postinst" run_script "$POSTINST" configure
+assert "custom unit untouched" file_eq "$ROOT/etc/systemd/system/boundary.service" "CUSTOM"
+assert "legacy service still running" test -e "$FAKE/active/boundary.service"
+refute "threshold not started" test -e "$FAKE/active/threshold.service"
+
+# ==============================================================================
+echo "== scenario 6: old boundary package binary present is not replaced"
+new_root s6
+add_legacy_layout
+echo "OLDBIN" >"$ROOT/usr/bin/boundary"
+assert "preinst" run_script "$PREINST" install
+assert "postinst" run_script "$POSTINST" configure
+refute "boundary binary not turned into symlink" test -L "$ROOT/usr/bin/boundary"
+assert "boundary binary content kept" file_eq "$ROOT/usr/bin/boundary" "OLDBIN"
+assert "postrm remove does not delete the old binary" run_script "$POSTRM" remove
+assert "old binary still there" test -f "$ROOT/usr/bin/boundary"
+
+# ==============================================================================
+echo "== scenario 7: threshold user already exists alongside boundary -> no drop-in"
+new_root s7
+add_legacy_layout
+echo "threshold:threshold" >>"$FAKE/users"
+assert "preinst" run_script "$PREINST" install
+assert "postinst" run_script "$POSTINST" configure
+refute "no drop-in when threshold user exists" test -e "$ROOT/etc/systemd/system/threshold.service.d"
+
+# ==============================================================================
+echo
+echo "passed: $PASSES, failed: $FAILS"
+[ "$FAILS" -eq 0 ]
diff --git a/Dockerfile b/Dockerfile
index 726367bad..19bf03df7 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -29,6 +29,13 @@ ADD .release/docker/config.hcl /threshold/config.hcl
 RUN chown -R threshold:threshold /threshold/
 RUN chmod -R 640 /threshold/*
 
+# Legacy HashiCorp Boundary compatibility: /boundary -> /threshold and a
+# "boundary" command alias (prints a deprecation notice on stderr).
+RUN mkdir -p /usr/share/threshold && \
+    cp /threshold/config.hcl /usr/share/threshold/config.hcl.default && \
+    ln -s /threshold /boundary && \
+    ln -s threshold /bin/boundary
+
 EXPOSE 9200 9201 9202
 VOLUME /threshold/
 
@@ -80,6 +87,13 @@ RUN setcap cap_ipc_lock=+ep /bin/$BIN_NAME
 RUN chown -R ${NAME}:${NAME} /threshold
 RUN chmod -R 640 /threshold/*
 
+# Legacy HashiCorp Boundary compatibility: /boundary -> /threshold and a
+# "boundary" command alias (prints a deprecation notice on stderr).
+RUN mkdir -p /usr/share/threshold && \
+    cp /threshold/config.hcl /usr/share/threshold/config.hcl.default && \
+    ln -s /threshold /boundary && \
+    ln -s ${BIN_NAME} /bin/boundary
+
 EXPOSE 9200 9201 9202
 VOLUME /threshold/
 
diff --git a/README.md b/README.md
index 573ef2ed6..44aeadcc8 100644
--- a/README.md
+++ b/README.md
@@ -68,6 +68,117 @@ Other fallbacks:
 
 Tokens are always written using the new names.
 
+## Upgrading from Boundary
+
+Threshold is designed as an in-place replacement for HashiCorp Boundary CE:
+the same database, the same configuration files, and a binary that can still be
+invoked as `boundary`.
+
+### Compatibility guarantees
+
+These are unchanged from upstream Boundary CE, so a mixed fleet of Boundary and
+Threshold controllers and workers interoperates, and you can upgrade (and roll
+back) one node at a time:
+
+- **Database schema**: the schema migrations are untouched and the
+  `boundary_schema_version` table keeps its name. Threshold runs against an
+  existing Boundary database as-is (`threshold database migrate` applies the
+  same migrations Boundary would).
+- **Wire protocol**: protobuf packages, gRPC service names and the `/v1` HTTP
+  API paths are unchanged (only Go import paths were renamed). Versions are
+  still reported to peers with the `Boundary v` prefix.
+- **Plugin protocol**: the plugin magic cookie
+  (`HASHICORP_BOUNDARY_PLUGIN` / `boundary-plugin`) is unchanged, so existing
+  `boundary-plugin-*` binaries keep working.
+- **Configuration file format** (HCL) is unchanged.
+
+Do not run `database migrate` from a newer Threshold than your other nodes
+understand; as with Boundary, upgrade controllers before workers and follow the
+usual rolling-upgrade guidance for schema migrations.
+
+### Linux packages (deb/rpm)
+
+1. Back up `/etc/boundary.d` and take a database backup.
+2. Install the Threshold package. Do not `purge` the old `boundary` package
+   (removal is fine); purging runs its scripts, which may delete the `boundary`
+   user that Threshold will reuse. Installing Threshold while the old package is
+   still installed is supported.
+3. The package scripts then, automatically:
+   - **copy** `/etc/boundary.d` to `/etc/threshold.d` (`boundary.hcl` becomes
+     `threshold.hcl`, `boundary.env` becomes `threshold.env`; subdirectories such
+     as TLS material are copied as-is). Existing files in `/etc/threshold.d` are
+     never overwritten and the originals are never modified or deleted;
+   - keep reading `/etc/boundary.d/boundary.env` as a fallback environment file
+     (`threshold.env` takes precedence), so `BOUNDARY_*` variables keep working;
+   - reuse the existing `boundary` service user and group instead of creating a
+     `threshold` user (through a managed systemd drop-in,
+     `/etc/systemd/system/threshold.service.d/10-legacy-boundary-user.conf`), so
+     ownership of your data, log and key directories keeps working;
+   - if `boundary.service` was enabled and/or running, stop and disable it,
+     enable `threshold.service`, and start it if the old service was running.
+     If `threshold.service` fails to start, the old service is restored;
+   - make `systemctl restart boundary` (and `status`, `stop`, ...) address
+     `threshold.service` via a `boundary.service` alias symlink in
+     `/etc/systemd/system`, and provide `/usr/bin/boundary` as a symlink to
+     `threshold` if no such file exists. The `boundary` command prints a
+     one-line deprecation notice to **stderr** only (silence it with
+     `THRESHOLD_NO_DEPRECATION_NOTICE=1`); stdout, flags and exit codes are
+     identical to `threshold`.
+4. Verify: `systemctl status threshold`, `threshold version`.
+
+What is **not** migrated automatically:
+
+- Paths *inside* your configuration files are not rewritten. A config that
+  refers to `/etc/boundary.d/...` or `/var/lib/boundary` keeps working because
+  those locations are left in place; update them at your own pace.
+- A custom `/etc/systemd/system/boundary.service` unit (a regular file) is left
+  alone and the legacy service is not touched; migrate it by hand.
+- If `/usr/bin/boundary` is still the old binary from the Boundary package, it is
+  left alone. After removing the old package: `ln -s threshold /usr/bin/boundary`.
+- Distribution-specific package-manager behavior such as `--force-confnew` (dpkg)
+  can replace `/etc/threshold.d` defaults; your originals remain in
+  `/etc/boundary.d`.
+- Data directories, the database, KMS keys and the client cache are not moved
+  (the client cache directory is covered by the table above).
+
+Rollback: stop `threshold.service`, remove the `boundary.service` alias
+symlink (`/etc/systemd/system/boundary.service`) and the drop-in, reinstall the
+old Boundary package, and `systemctl enable --now boundary`. Because the
+database schema is unchanged and `/etc/boundary.d` was never modified, nothing
+else needs to be restored. If you ran a Threshold release that applied schema
+migrations newer than your Boundary version, restore the database backup
+instead.
+
+### Container image
+
+The image's configuration directory moved from `/boundary` to `/threshold`
+(default command: `threshold server -config /threshold/config.hcl`). For
+compatibility the image:
+
+- contains `/boundary` as a symlink to `/threshold`, so existing
+  `-v "$(pwd)":/boundary/` mounts land in the right place;
+- falls back to `/boundary/config.hcl` (printing a deprecation warning) when
+  `-config /boundary/config.hcl` is requested, or when the stock demo config is
+  still in place and a config exists at `/boundary/config.hcl`;
+- accepts `boundary ...` as the command and `BOUNDARY_*` environment variables
+  (mirrored to `THRESHOLD_*`).
+
+Plan to switch your mounts, `-config` arguments and environment variables to
+the `/threshold` and `THRESHOLD_*` names; the compatibility paths print
+warnings and may be removed in a future major release.
+
+### Other installs (binary / zip)
+
+Replace the `boundary` binary with `threshold` (or keep the file name
+`boundary`, which behaves identically). Existing `BOUNDARY_*` variables,
+`~/.boundary` and stored credentials are picked up as described above.
+
+### Development mode
+
+`threshold dev` creates the `ssh.threshold.dev` and `postgres.threshold.dev`
+aliases and, for compatibility, the legacy `ssh.boundary.dev` and
+`postgres.boundary.dev` aliases pointing at the same targets.
+
 ## Building
 
 ```
diff --git a/cmd/threshold/main.go b/cmd/threshold/main.go
index 55fae1d5a..f6f6f8fd7 100644
--- a/cmd/threshold/main.go
+++ b/cmd/threshold/main.go
@@ -10,5 +10,13 @@ import (
 )
 
 func main() {
+	// When invoked through the legacy "boundary" name (a symlink shipped in
+	// packages/images), print a one-line deprecation notice to stderr. Behavior
+	// is otherwise identical and stdout is never touched.
+	if len(os.Args) > 0 {
+		if notice := cmd.LegacyNameNotice(os.Args[0], os.Getenv); notice != "" {
+			_, _ = os.Stderr.WriteString(notice)
+		}
+	}
 	os.Exit(cmd.Run(os.Args[1:]))
 }
diff --git a/internal/cmd/base/initial_resources.go b/internal/cmd/base/initial_resources.go
index 6612e320d..0796940a4 100644
--- a/internal/cmd/base/initial_resources.go
+++ b/internal/cmd/base/initial_resources.go
@@ -615,9 +615,11 @@ func (b *Server) CreateInitialTargetWithHostSources(ctx context.Context) (target
 }
 
 // Create targets that can be connected to using an alias. The three targets created are:
-//   - "postgres.boundary.dev": the Threshold dev postgres instance. Uses brokered credentials
+//   - "postgres.threshold.dev": the Threshold dev postgres instance. Uses brokered credentials
+//     (the legacy "postgres.boundary.dev" alias is also created)
 //   - "www.hashicorp.com": a web target
-//   - "ssh.boundary.dev": A localhost ssh target
+//   - "ssh.threshold.dev": A localhost ssh target (the legacy "ssh.boundary.dev"
+//     alias is also created)
 func (b *Server) CreateInitialTargetsWithAlias(ctx context.Context) error {
 	rw := db.New(b.Database)
 
@@ -679,14 +681,9 @@ func (b *Server) createSshAliasTarget(ctx context.Context, targetRepo *target.Re
 		return err
 	}
 
-	sshAlias := "ssh.boundary.dev"
-	a, err := aliastar.NewAlias(ctx, "global", sshAlias, aliastar.WithDestinationId(t.GetPublicId()))
-	if err != nil {
-		return fmt.Errorf("failed to create alias object %w", err)
-	}
-	_, err = aliasRepo.CreateAlias(ctx, a)
-	if err != nil {
-		return fmt.Errorf("failed to save alias to the db %w", err)
+	sshAlias := "ssh.threshold.dev"
+	if err := createDevAliases(ctx, aliasRepo, t.GetPublicId(), sshAlias, legacySshAlias); err != nil {
+		return err
 	}
 
 	b.InfoKeys = append(b.InfoKeys, "generated ssh target with alias")
@@ -694,6 +691,29 @@ func (b *Server) createSshAliasTarget(ctx context.Context, targetRepo *target.Re
 	return nil
 }
 
+// Legacy dev-mode alias names used by upstream HashiCorp Boundary. They are
+// still created, pointing at the same targets, so existing scripts and muscle
+// memory keep working.
+const (
+	legacySshAlias      = "ssh.boundary.dev"
+	legacyPostgresAlias = "postgres.boundary.dev"
+)
+
+// createDevAliases creates one alias per value, all pointing at the given
+// destination target.
+func createDevAliases(ctx context.Context, aliasRepo *aliastar.Repository, destinationId string, values ...string) error {
+	for _, v := range values {
+		a, err := aliastar.NewAlias(ctx, "global", v, aliastar.WithDestinationId(destinationId))
+		if err != nil {
+			return fmt.Errorf("failed to create alias object %w", err)
+		}
+		if _, err = aliasRepo.CreateAlias(ctx, a); err != nil {
+			return fmt.Errorf("failed to save alias to the db %w", err)
+		}
+	}
+	return nil
+}
+
 func (b *Server) createPostgresAliasTarget(ctx context.Context,
 	targetRepo *target.Repository,
 	aliasRepo *aliastar.Repository,
@@ -757,14 +777,9 @@ func (b *Server) createPostgresAliasTarget(ctx context.Context,
 		return fmt.Errorf("failed to associate cred to target: %w", err)
 	}
 
-	postgresAlias := "postgres.boundary.dev"
-	a, err := aliastar.NewAlias(ctx, "global", postgresAlias, aliastar.WithDestinationId(t.GetPublicId()))
-	if err != nil {
-		return fmt.Errorf("failed to create alias object %w", err)
-	}
-	_, err = aliasRepo.CreateAlias(ctx, a)
-	if err != nil {
-		return fmt.Errorf("failed to save alias to the db %w", err)
+	postgresAlias := "postgres.threshold.dev"
+	if err := createDevAliases(ctx, aliasRepo, t.GetPublicId(), postgresAlias, legacyPostgresAlias); err != nil {
+		return err
 	}
 
 	b.InfoKeys = append(b.InfoKeys, "generated postgres target with alias")
diff --git a/internal/cmd/legacy_alias.go b/internal/cmd/legacy_alias.go
new file mode 100644
index 000000000..88c38b28c
--- /dev/null
+++ b/internal/cmd/legacy_alias.go
@@ -0,0 +1,49 @@
+// Copyright IBM Corp. 2020, 2026
+// SPDX-License-Identifier: BUSL-1.1
+
+package cmd
+
+import (
+	"path/filepath"
+	"strings"
+)
+
+// legacyBinaryName is the name of the upstream HashiCorp Boundary binary. A
+// "boundary" symlink to the threshold binary is shipped in packages and
+// container images so existing scripts keep working.
+const legacyBinaryName = "boundary"
+
+// envNoLegacyNameNotice, when set to a non-empty value, silences the
+// deprecation notice printed when the binary is invoked as "boundary".
+const envNoLegacyNameNotice = "THRESHOLD_NO_DEPRECATION_NOTICE"
+
+// invokedAsLegacyName reports whether argv0 refers to the legacy "boundary"
+// binary name. Directory components and a Windows ".exe" suffix are ignored.
+func invokedAsLegacyName(argv0 string) bool {
+	// Normalize Windows separators too, since filepath.Base on unix does not
+	// treat backslash as a separator.
+	argv0 = strings.ReplaceAll(argv0, `\`, "/")
+	base := strings.ToLower(filepath.Base(argv0))
+	base = strings.TrimSuffix(base, ".exe")
+	return base == legacyBinaryName
+}
+
+// LegacyNameNotice returns the one-line deprecation notice (including a
+// trailing newline) to write to stderr when the binary was invoked as
+// "boundary", or an empty string when no notice should be shown. No notice is
+// shown for any other invocation name, when shell completion is running
+// (COMP_LINE is set, so that a notice never corrupts the user's prompt), or
+// when THRESHOLD_NO_DEPRECATION_NOTICE is set. The notice is only ever written
+// to stderr so that machine-readable stdout output is unaffected.
+//
+// getenv is typically os.Getenv.
+func LegacyNameNotice(argv0 string, getenv func(string) string) string {
+	if !invokedAsLegacyName(argv0) {
+		return ""
+	}
+	if getenv("COMP_LINE") != "" || getenv(envNoLegacyNameNotice) != "" {
+		return ""
+	}
+	return "Note: the 'boundary' command name is deprecated; use 'threshold' instead. " +
+		"(Set " + envNoLegacyNameNotice + "=1 to silence this notice.)\n"
+}
diff --git a/internal/cmd/legacy_alias_test.go b/internal/cmd/legacy_alias_test.go
new file mode 100644
index 000000000..0569c39b9
--- /dev/null
+++ b/internal/cmd/legacy_alias_test.go
@@ -0,0 +1,49 @@
+// Copyright IBM Corp. 2020, 2026
+// SPDX-License-Identifier: BUSL-1.1
+
+package cmd
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestInvokedAsLegacyName(t *testing.T) {
+	t.Parallel()
+	tests := []struct {
+		argv0 string
+		want  bool
+	}{
+		{"boundary", true},
+		{"/usr/bin/boundary", true},
+		{"./boundary", true},
+		{`C:\bin\boundary.exe`, true},
+		{"Boundary.EXE", true},
+		{"threshold", false},
+		{"/usr/bin/threshold", false},
+		{"boundary-worker", false},
+		{"", false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.argv0, func(t *testing.T) {
+			assert.Equal(t, tt.want, invokedAsLegacyName(tt.argv0))
+		})
+	}
+}
+
+func TestLegacyNameNotice(t *testing.T) {
+	t.Parallel()
+	env := func(m map[string]string) func(string) string {
+		return func(k string) string { return m[k] }
+	}
+	n := LegacyNameNotice("/usr/bin/boundary", env(nil))
+	assert.True(t, strings.HasSuffix(n, "\n"))
+	assert.Equal(t, 1, strings.Count(n, "\n"), "notice must be a single line")
+	assert.Contains(t, n, "threshold")
+
+	assert.Empty(t, LegacyNameNotice("/usr/bin/threshold", env(nil)))
+	assert.Empty(t, LegacyNameNotice("boundary", env(map[string]string{"COMP_LINE": "boundary auth"})))
+	assert.Empty(t, LegacyNameNotice("boundary", env(map[string]string{envNoLegacyNameNotice: "1"})))
+}