diff --git a/AGENTS.md b/AGENTS.md
index 4e6e039..a0797e4 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -139,7 +139,17 @@ What the suite covers:
   through `json.load`
 - **install.sh** — places the binary; seeds `~/.config/git-trees/AGENTS.md` from
   the template under a redirected `HOME`; does not overwrite an existing config
-  file
+  file; honours `TREES_DEST`, with a positional argument still winning over it
+- **install.sh — no-repo bootstrap** — the `curl | bash` path, with
+  `TREES_BASE_URL` pointed at a `file://` fixture so the real download branch
+  runs without touching the network: piped on stdin from a directory with no
+  `git-trees` in it (piped bash has neither `BASH_SOURCE` nor `$1`, and `set -u`
+  makes a bare reference to either fatal), the `wget` fallback on a `PATH` built
+  without `curl`, a clear error when neither downloader exists, a **zero-byte
+  body** rejected (the transfer succeeds, so only the non-empty check catches
+  it), a missing script failing loudly and installing nothing, a missing
+  template warning while the binary still installs, no-clobber on rerun, and the
+  temp download directory cleaned up by its trap
 - **rm** — dry run vs `--apply`, worktree removal by branch and by path (a
   slugged directory whose name is not a branch name, so the path arm is the one
   that runs), `-d` escalating to `-D` so an unmerged branch is still deleted
diff --git a/README.md b/README.md
index e5588cf..df3b20c 100644
--- a/README.md
+++ b/README.md
@@ -119,22 +119,25 @@ cd git-trees && ./install.sh              # → ~/.local/bin
 ./install.sh /usr/local/bin               # or anywhere else
 ```
 
-**Convenience — curl.** Fetches the script and the agents template (skips the
-template if that path is already occupied, including a broken symlink):
+**Convenience — one-line curl.** Same installer, downloaded and run in place.
+It fetches the script *and* the agents template (skipping the template if that
+path is already occupied, including a broken symlink):
 
 ```bash
-mkdir -p ~/.local/bin ~/.config/git-trees
-tmp=$(mktemp) && curl -fsSL -o "$tmp" \
-  https://raw.githubusercontent.com/brightdigit/git-trees/main/git-trees \
-  && mv "$tmp" ~/.local/bin/git-trees
-chmod +x ~/.local/bin/git-trees
-if [ ! -e ~/.config/git-trees/AGENTS.md ] && [ ! -L ~/.config/git-trees/AGENTS.md ]; then
-  tmp=$(mktemp) && curl -fsSL -o "$tmp" \
-    https://raw.githubusercontent.com/brightdigit/git-trees/main/AGENTS.md.template \
-    && mv "$tmp" ~/.config/git-trees/AGENTS.md
-fi
+curl -fsSL https://raw.githubusercontent.com/brightdigit/git-trees/main/install.sh | bash
 ```
 
+A piped script receives no positional arguments, so set `TREES_DEST` to install
+somewhere other than `~/.local/bin`:
+
+```bash
+TREES_DEST=/usr/local/bin curl -fsSL \
+  https://raw.githubusercontent.com/brightdigit/git-trees/main/install.sh | bash
+```
+
+The installer uses `curl` or `wget`, whichever it finds, and verifies each
+download is complete and non-empty before installing anything.
+
 `main` is the stable release. A re-install from these URLs picks up the current
 stable script and template.
 
@@ -145,12 +148,13 @@ case ":$PATH:" in *":$HOME/.local/bin:"*) ;; *)
   echo 'export PATH="$HOME/.local/bin:$PATH"' >> ~/.zshrc ;; esac
 ```
 
-`install.sh` warns if it isn't; the curl path cannot. Anything on `PATH` named
-`git-trees` becomes `git trees`.
+`install.sh` warns if it isn't — either way you run it. Anything on `PATH`
+named `git-trees` becomes `git trees`.
 
 ## Configuration
 
-All three variables are optional. Add to `~/.zshrc` (or `~/.bashrc`):
+Every variable in [**Environment**](#environment) is optional. Add to
+`~/.zshrc` (or `~/.bashrc`):
 
 ```zsh
 export TREES_ORG=your-org
@@ -322,6 +326,7 @@ git worktree prune
 | `TREES_AGENTS_TEMPLATE` | `~/.config/git-trees/AGENTS.md` | Seeded at the container root by `init` (and `root --agents`) |
 | `TREES_NO_PUSH` | *(unset)* | Any non-empty value: `add`/`track` never create a branch on `origin` |
 | `TREES_RM_CMD` | *(unset)* | Custom command for worktree directory removal (defaults to `git worktree remove`). Bypasses git's uncommitted-work check — see [`git trees rm`](#git-trees-rm-branchpath---apply) |
+| `TREES_DEST` | `~/.local/bin` | Install destination for `install.sh`; the only way to choose one when piping the installer |
 
 ## Shell wrapper (optional)
 
diff --git a/install.sh b/install.sh
index 98363a4..740896e 100755
--- a/install.sh
+++ b/install.sh
@@ -3,22 +3,62 @@
 #
 #   ./install.sh                      install to ~/.local/bin
 #   ./install.sh /usr/local/bin       install elsewhere
+#
+# Also works with no repo around it, piped straight from the raw URL:
+#
+#   curl -fsSL .../install.sh | bash
+#   TREES_DEST=/usr/local/bin curl -fsSL .../install.sh | bash
+#
+# A piped script gets no positional arguments, so TREES_DEST is the only way to
+# choose a destination on that path.
 
 set -uo pipefail
 
-SRC="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+# Pinned to main: main is the stable release for this project.
+BASE_URL="${TREES_BASE_URL:-https://raw.githubusercontent.com/brightdigit/git-trees/main}"
+
+SRC="$(cd "$(dirname "${BASH_SOURCE[0]:-$0}")" 2>/dev/null && pwd)" || SRC=""
 CFG="$HOME/.config/git-trees"
 
-DEST="${1:-$HOME/.local/bin}"
+# Positional wins for the clone path; TREES_DEST is the piped path's only lever.
+DEST="${1:-${TREES_DEST:-$HOME/.local/bin}}"
 
-[ -f "$SRC/git-trees" ] || { echo "install.sh: git-trees not found in $SRC" >&2; exit 1; }
+# Fetch one file to a path. Verifies the transfer rather than trusting that a
+# file appeared: a truncated or 404 body installed onto PATH is the worst
+# outcome here, and `curl -o` leaves an empty file behind on failure.
+fetch() { # fetch <url> <out>
+  if command -v curl >/dev/null 2>&1; then
+    curl -fsSL -o "$2" "$1" || return 1
+  elif command -v wget >/dev/null 2>&1; then
+    wget -qO "$2" "$1" || return 1
+  else
+    echo "install.sh: need curl or wget to download $1" >&2
+    return 1
+  fi
+  [ -s "$2" ]
+}
+
+# No repo around the script — piped into bash, or copied off somewhere alone.
+if [ -z "$SRC" ] || [ ! -f "$SRC/git-trees" ]; then
+  SRC=$(mktemp -d "${TMPDIR:-/tmp}/git-trees-install.XXXXXX") || exit 1
+  trap 'rm -rf "$SRC"' EXIT
+
+  echo "downloading git-trees from $BASE_URL" >&2
+  fetch "$BASE_URL/git-trees" "$SRC/git-trees" || {
+    echo "install.sh: failed to download git-trees" >&2; exit 1; }
+  # The template is optional at install time; git-trees warns without it.
+  fetch "$BASE_URL/AGENTS.md.template" "$SRC/AGENTS.md.template" || {
+    echo "warning: failed to download AGENTS.md.template — skipping" >&2
+    rm -f "$SRC/AGENTS.md.template"
+  }
+fi
 
 mkdir -p "$DEST" || exit 1
 install -m 0755 "$SRC/git-trees" "$DEST/git-trees" || exit 1
 echo "installed $DEST/git-trees"
 
-# AGENTS.md template — README's curl path installs this too.
-if [ -f "$SRC/AGENTS.md.template" ] && [ ! -f "$CFG/AGENTS.md" ]; then
+# AGENTS.md template — the curl path installs this too.
+if [ -f "$SRC/AGENTS.md.template" ] && [ ! -e "$CFG/AGENTS.md" ] && [ ! -L "$CFG/AGENTS.md" ]; then
   mkdir -p "$CFG"
   cp "$SRC/AGENTS.md.template" "$CFG/AGENTS.md"
   echo "installed $CFG/AGENTS.md (template; used by init or root --agents to seed the container root)"
diff --git a/tests/smoke.sh b/tests/smoke.sh
index 63d4f59..2361b6e 100755
--- a/tests/smoke.sh
+++ b/tests/smoke.sh
@@ -487,6 +487,180 @@ assert_eq "install.sh rerun exits 0" "$rc" "0"
 assert_eq "install.sh does not overwrite an existing template" \
   "$(cat "$IHOME/.config/git-trees/AGENTS.md")" "CUSTOM"
 
+# TREES_DEST is the piped path's only way to choose a destination, but it must
+# work from a clone too, and the positional must still win over it.
+EDEST="$TMP/install-envdest"
+out=$(HOME="$IHOME" TREES_DEST="$EDEST" bash "$REPO/install.sh" 2>&1)
+rc=$?
+assert_eq "install.sh TREES_DEST exits 0" "$rc" "0"
+assert_ok "install.sh honours TREES_DEST" test -x "$EDEST/git-trees"
+PDEST="$TMP/install-posdest"
+HOME="$IHOME" TREES_DEST="$EDEST" bash "$REPO/install.sh" "$PDEST" >/dev/null 2>&1
+assert_ok "install.sh positional beats TREES_DEST" test -x "$PDEST/git-trees"
+
+# --- install.sh — no-repo bootstrap (the `curl | bash` path) -----------------
+#
+# The script is copied somewhere with no git-trees beside it, so it takes the
+# download branch. TREES_BASE_URL points at a file:// fixture: the real fetch
+# code runs, no network is touched, and the test cannot silently no-op offline.
+
+section "install.sh — no-repo bootstrap"
+SERVE="$TMP/serve"
+mkdir -p "$SERVE"
+cp "$REPO/git-trees" "$SERVE/git-trees"
+cp "$REPO/AGENTS.md.template" "$SERVE/AGENTS.md.template"
+BOOT="$TMP/boot"
+mkdir -p "$BOOT"
+cp "$REPO/install.sh" "$BOOT/install.sh"
+
+BHOME="$TMP/boot-home"
+BDEST="$TMP/boot-bin"
+mkdir -p "$BHOME"
+out=$(HOME="$BHOME" TREES_DEST="$BDEST" TREES_BASE_URL="file://$SERVE" \
+  bash "$BOOT/install.sh" 2>&1)
+rc=$?
+assert_eq "bootstrap exits 0" "$rc" "0"
+assert_contains "bootstrap announces the download" "$out" "downloading git-trees"
+assert_ok "bootstrap placed the binary" test -x "$BDEST/git-trees"
+assert_eq "bootstrap binary matches the source" \
+  "$(cat "$BDEST/git-trees")" "$(cat "$REPO/git-trees")"
+assert_ok "bootstrap binary runs" bash "$BDEST/git-trees" help
+assert_ok "bootstrap seeded the agents template" \
+  test -f "$BHOME/.config/git-trees/AGENTS.md"
+assert_eq "bootstrap template matches AGENTS.md.template" \
+  "$(cat "$BHOME/.config/git-trees/AGENTS.md")" "$(cat "$REPO/AGENTS.md.template")"
+
+# A rerun must not clobber a template the user has edited.
+echo BOOTCUSTOM > "$BHOME/.config/git-trees/AGENTS.md"
+HOME="$BHOME" TREES_DEST="$BDEST" TREES_BASE_URL="file://$SERVE" \
+  bash "$BOOT/install.sh" >/dev/null 2>&1
+rc=$?
+assert_eq "bootstrap rerun exits 0" "$rc" "0"
+assert_eq "bootstrap rerun does not overwrite the template" \
+  "$(cat "$BHOME/.config/git-trees/AGENTS.md")" "BOOTCUSTOM"
+
+# The temp download directory is trapped away on exit. A private TMPDIR makes
+# that observable: mktemp -d lands inside it, so anything left is a leak.
+SCRATCH="$TMP/boot-tmpdir"
+mkdir -p "$SCRATCH"
+HOME="$BHOME" TMPDIR="$SCRATCH" TREES_DEST="$BDEST" TREES_BASE_URL="file://$SERVE" \
+  bash "$BOOT/install.sh" >/dev/null 2>&1
+assert_eq "bootstrap cleans up its temp dir" \
+  "$(find "$SCRATCH" -mindepth 1 -maxdepth 1 | wc -l | tr -d ' ')" "0"
+
+# A missing git-trees at the base URL must fail loudly, not install nothing
+# quietly. `curl -fsSL` fails on HTTP errors; file:// fails on a missing path.
+EMPTY="$TMP/serve-empty"
+mkdir -p "$EMPTY"
+FHOME="$TMP/boot-fail-home"
+FDEST="$TMP/boot-fail-bin"
+mkdir -p "$FHOME"
+out=$(HOME="$FHOME" TREES_DEST="$FDEST" TREES_BASE_URL="file://$EMPTY" \
+  bash "$BOOT/install.sh" 2>&1)
+rc=$?
+assert_eq "bootstrap fails when git-trees is missing" "$rc" "1"
+assert_contains "bootstrap says why it failed" "$out" "failed to download git-trees"
+assert_fail "bootstrap installed nothing on failure" test -e "$FDEST/git-trees"
+
+# The actual `curl ... | bash` shape: piped on stdin, from a directory with no
+# git-trees in it. Piped bash has no BASH_SOURCE and no $1, and `set -u` makes a
+# bare reference to either fatal — a copied-file test cannot catch that.
+PHOME="$TMP/boot-piped-home"
+PPDEST="$TMP/boot-piped-bin"
+mkdir -p "$PHOME" "$TMP/boot-piped-cwd"
+out=$(in_dir "$TMP/boot-piped-cwd" env HOME="$PHOME" TREES_DEST="$PPDEST" \
+  TREES_BASE_URL="file://$SERVE" bash < "$BOOT/install.sh" 2>&1)
+rc=$?
+assert_eq "piped bootstrap exits 0" "$rc" "0"
+assert_not_contains "piped bootstrap has no unbound-variable error" \
+  "$out" "unbound variable"
+assert_ok "piped bootstrap placed the binary" test -x "$PPDEST/git-trees"
+assert_ok "piped bootstrap seeded the template" \
+  test -f "$PHOME/.config/git-trees/AGENTS.md"
+
+# The wget fallback and the neither-downloader error, on a PATH built to contain
+# exactly what each case needs. macOS ships /usr/bin/curl, so proving the
+# fallback runs at all means excluding the real curl from PATH.
+STUBBIN="$TMP/stub-bin"
+mkdir -p "$STUBBIN"
+for c in bash mkdir install cp mktemp rm cat dirname pwd sed find chmod wc tr; do
+  cbin=$(command -v "$c") && ln -sf "$cbin" "$STUBBIN/$c"
+done
+
+WHOME="$TMP/boot-wget-home"
+WDEST="$TMP/boot-wget-bin"
+mkdir -p "$WHOME"
+out=$(env -i HOME="$WHOME" PATH="$STUBBIN" TREES_DEST="$WDEST" \
+  TREES_BASE_URL="file://$SERVE" "$STUBBIN/bash" "$BOOT/install.sh" 2>&1)
+rc=$?
+assert_eq "bootstrap fails with neither curl nor wget" "$rc" "1"
+assert_contains "bootstrap names the missing tools" "$out" "need curl or wget"
+assert_fail "bootstrap installed nothing without a downloader" \
+  test -e "$WDEST/git-trees"
+
+# Minimal wget standing in for the real thing: only the -qO form install.sh
+# uses, over file://. Exits nonzero on a missing source, as wget does.
+cat > "$STUBBIN/wget" <<'WGET_STUB'
+#!/usr/bin/env bash
+out=""; url=""
+while [ $# -gt 0 ]; do
+  case "$1" in
+    -qO) out="$2"; shift 2 ;;
+    -q) shift ;;
+    *) url="$1"; shift ;;
+  esac
+done
+src="${url#file://}"
+[ -f "$src" ] || exit 8
+cat "$src" > "$out"
+WGET_STUB
+chmod +x "$STUBBIN/wget"
+
+out=$(env -i HOME="$WHOME" PATH="$STUBBIN" TREES_DEST="$WDEST" \
+  TREES_BASE_URL="file://$SERVE" "$STUBBIN/bash" "$BOOT/install.sh" 2>&1)
+rc=$?
+assert_eq "bootstrap via wget exits 0" "$rc" "0"
+assert_ok "bootstrap via wget placed the binary" test -x "$WDEST/git-trees"
+assert_eq "bootstrap via wget binary matches the source" \
+  "$(cat "$WDEST/git-trees")" "$(cat "$REPO/git-trees")"
+assert_ok "bootstrap via wget seeded the template" \
+  test -f "$WHOME/.config/git-trees/AGENTS.md"
+
+# A zero-byte body is the truncated-download case: curl succeeds (the transfer
+# completed), so only the non-empty check catches it. Installing an empty
+# git-trees onto PATH is the worst outcome here, hence its own fixture.
+TRUNC="$TMP/serve-truncated"
+mkdir -p "$TRUNC"
+: > "$TRUNC/git-trees"
+cp "$REPO/AGENTS.md.template" "$TRUNC/AGENTS.md.template"
+THOME="$TMP/boot-trunc-home"
+TDEST="$TMP/boot-trunc-bin"
+mkdir -p "$THOME"
+out=$(HOME="$THOME" TREES_DEST="$TDEST" TREES_BASE_URL="file://$TRUNC" \
+  bash "$BOOT/install.sh" 2>&1)
+rc=$?
+assert_eq "bootstrap rejects a zero-byte download" "$rc" "1"
+assert_contains "bootstrap says why the empty download failed" \
+  "$out" "failed to download git-trees"
+assert_fail "bootstrap installed nothing from a zero-byte download" \
+  test -e "$TDEST/git-trees"
+
+# A present script with a missing template warns and still installs the binary.
+ONLY="$TMP/serve-binary-only"
+mkdir -p "$ONLY"
+cp "$REPO/git-trees" "$ONLY/git-trees"
+NHOME="$TMP/boot-notmpl-home"
+NDEST="$TMP/boot-notmpl-bin"
+mkdir -p "$NHOME"
+out=$(HOME="$NHOME" TREES_DEST="$NDEST" TREES_BASE_URL="file://$ONLY" \
+  bash "$BOOT/install.sh" 2>&1)
+rc=$?
+assert_eq "bootstrap without a template exits 0" "$rc" "0"
+assert_ok "bootstrap without a template still installs" test -x "$NDEST/git-trees"
+assert_contains "bootstrap warns about the missing template" "$out" "AGENTS.md.template"
+assert_fail "bootstrap wrote no config template" \
+  test -e "$NHOME/.config/git-trees/AGENTS.md"
+
 # --- rm ----------------------------------------------------------------------
 
 section "rm"