diff --git a/CHANGELOG.md b/CHANGELOG.md
index 1493b0331..4f56e1cb2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,7 +10,7 @@
 - **Quota preflight**: `up` adds the size's vCPUs to the project's running VMs and refuses before the create request when that exceeds the known ceiling (`UBI_QUOTA_VCPUS`, or the maximum the last API refusal printed, remembered in the state root); `UBI_QUOTA_WAIT=<seconds>` polls for room instead of refusing. The per-owner `usage` table is printed either way.
 - **Watchdog and heartbeat**: `run`, `verify` and `ssh NAME COMMAND` stream the remote output (both streams kept in the VM's state dir) through a watchdog: a heartbeat every `UBI_HEARTBEAT` seconds (300), and a command silent for `UBI_IDLE_TIMEOUT` seconds (1800) or older than `UBI_RUN_TIMEOUT` (0, unlimited) is killed in its own session with exit 124 and its last 40 lines on stderr. `run` also prints the VM's TTL and its `down` recovery command as soon as the VM is ready.
 - **`verify`**: runs the repository's committed `.gstack/ubicloud.json` (setup, command, size, location, storage, image, env, pass, pull; flags and a trailing `-- COMMAND` override it) and refuses without the file or a command, so every lane runs one definition instead of its own wrapper. The file is repository content and gets no reach beyond the checkout: `setup` and each `pull` destination must be relative paths that resolve inside `--src` (absolute, `~` and `..` paths are refused before any API call), and a name under `pass` is forwarded only when the command line grants it (`--pass NAME`, or every listed name with `--trust-config`). `--pass` never forwards `UBICLOUD_*`, from the file or the command line.
-- **Watched commands keep their stdin and exit codes**: `ssh NAME COMMAND` hands the caller's stdin to the remote command (`printf payload | gstack-ubi ssh NAME 'cat > file'` wrote an empty file once the watchdog backgrounded the client), a command that finished while the watchdog read the clock is never reported as a timeout, a hung setup script exits 124 like a hung command instead of 1, Ctrl-C on a watched command takes the ssh session down with it, and when the watchdog fires the runner also ends the command's session on the VM (`setsid` there, leader pid in `~/.ubirun-<phase>.sid`, `pkill -s` bounded to 20 s), since killing the local client alone leaves a silent remote command running until it next writes.
+- **Watched commands keep their stdin and exit codes**: `ssh NAME COMMAND` hands the caller's stdin to the remote command (`printf payload | gstack-ubi ssh NAME 'cat > file'` wrote an empty file once the watchdog backgrounded the client), a command that finished while the watchdog read the clock is never reported as a timeout, a hung setup script exits 124 like a hung command instead of 1, Ctrl-C on a watched command takes the ssh session down with it, and when the watchdog fires the runner also ends the command's session on the VM (`setsid` there, leader pid in `~/.ubirun-<phase>-<runner pid>.sid`, `pkill -s` bounded to 20 s), since killing the local client alone leaves a silent remote command running until it next writes.
 - **Quota ceiling and reaper outcomes**: the maximum a refusal cached is trusted for a day, then the API's own answer decides again; the refusal line says where the ceiling came from and names `UBI_QUOTA_VCPUS`, and its `vCPU quota exhausted` wording is the one `pregate-remote.sh` retries once on. `reap` returns 1 when the list fails (nothing destroyed) or an expired VM could not be destroyed, instead of 0 either way; a TTL suffix is read in base 10 (`UBI_TTL_HOURS` takes 0 to 999 with no leading zero).
 
 ### Tests
diff --git a/scripts/ubicloud/ubi-runner.sh b/scripts/ubicloud/ubi-runner.sh
index a9e861b01..25e71360c 100755
--- a/scripts/ubicloud/ubi-runner.sh
+++ b/scripts/ubicloud/ubi-runner.sh
@@ -182,13 +182,13 @@ mtime() { stat -c %Y "$1" 2>/dev/null || stat -f %m "$1"; }
 # sq STRING: STRING as one single-quoted shell word.
 sq() { printf "'%s'" "$(printf %s "$1" | sed "s/'/'\\\\''/g")"; }
 
-# remote_cancel NAME PHASE: end the session a watched PHASE started on the VM
-# (its leader pid is in ~/.ubirun-PHASE.sid there), bounded to 20 seconds.
-# Killing the local ssh client alone leaves a silent remote command running
-# until it next writes to the closed channel.
+# remote_cancel NAME SIDFILE: end the session a watched command started on the
+# VM (its leader pid is in SIDFILE there), bounded to 20 seconds. Killing the
+# local ssh client alone leaves a silent remote command running until it next
+# writes to the closed channel.
 remote_cancel() {
-  local name=$1 phase=$2 cpid i=0
-  remote "$name" "sid=\$(cat ~/.ubirun-$phase.sid 2>/dev/null); [ -z \"\$sid\" ] || { pkill -TERM -s \"\$sid\"; sleep 2; pkill -KILL -s \"\$sid\"; }; true" >/dev/null 2>&1 </dev/null &
+  local name=$1 sidf=$2 cpid i=0
+  remote "$name" "sid=\$(cat $sidf 2>/dev/null); [ -z \"\$sid\" ] || { pkill -TERM -s \"\$sid\"; sleep 2; pkill -KILL -s \"\$sid\"; }; true" >/dev/null 2>&1 </dev/null &
   cpid=$!
   while kill -0 "$cpid" 2>/dev/null && [ "$i" -lt 20 ]; do sleep 1; i=$(( i + 1 )); done
   kill "$cpid" 2>/dev/null || true
@@ -201,14 +201,17 @@ remote_cancel() {
 # RUN_TIMEOUT seconds in total: exit 124, reason and the last 40 lines on
 # stderr. The ssh runs in its own session (python3's setsid) so the watchdog
 # kills it and anything it started, not just the shell that launched it; on
-# the VM the command runs in its own session too, whose leader pid is written
-# to ~/.ubirun-PHASE.sid so remote_cancel can end it when the client is killed.
+# the VM the command runs in its own session too (setsid where the image has
+# it), whose leader pid is written to ~/.ubirun-PHASE-<runner pid>.sid so
+# remote_cancel can end it when the client is killed.
 watched() {
-  local name=$1 phase=$2 cmd=$3 out pid rc=0 start now last_beat idle elapsed why="" old_traps
+  local name=$1 phase=$2 cmd=$3 out pid rc=0 start now last_beat idle elapsed why="" old_traps inner sidf
+  sidf="~/.ubirun-$phase-$$.sid"
   load "$name"
   out="$(state_dir "$name")/$phase.log"
   : >"$out"
-  cmd="setsid -w bash -c $(sq "printf %s \$\$ >~/.ubirun-$phase.sid; $cmd")"
+  inner=$(sq "printf %s \$\$ >$sidf; $cmd")
+  cmd="if command -v setsid >/dev/null 2>&1; then setsid -w bash -c $inner; else bash -c $inner; fi; rc=\$?; rm -f $sidf; exit \$rc"
   # The caller's stdin is handed to the background ssh explicitly (a background
   # job in a non-interactive shell would otherwise read /dev/null), so piped
   # input reaches the remote command as it did before the watchdog.
@@ -244,7 +247,7 @@ watched() {
       kill -TERM -- "-$pid" 2>/dev/null || kill "$pid" 2>/dev/null || true
       wait "$pid" 2>/dev/null || true
       trap - INT TERM; eval "$old_traps"
-      remote_cancel "$name" "$phase"
+      remote_cancel "$name" "$sidf"
       return 124
     fi
     if [ "$HEARTBEAT" -gt 0 ] && [ $(( now - last_beat )) -ge "$HEARTBEAT" ]; then
diff --git a/test/ubicloud-runner.test.ts b/test/ubicloud-runner.test.ts
index d53f70eb0..2243b7fc2 100644
--- a/test/ubicloud-runner.test.ts
+++ b/test/ubicloud-runner.test.ts
@@ -252,7 +252,7 @@ esac
       expect(err).toMatch(/watchdog: ssh printed nothing for \d+s \(UBI_IDLE_TIMEOUT=2\); killing it. Last output:/);
       expect(err.indexOf('line one')).toBeGreaterThan(err.indexOf('Last output:'));
       expect(readFileSync(join(f.root, 'state/vm-a/ssh.log'), 'utf8')).toContain('line one');
-      expect(readFileSync(join(f.root, 'cancel.log'), 'utf8')).toMatch(/sid=\$\(cat ~\/\.ubirun-ssh\.sid .*pkill -TERM -s/);
+      expect(readFileSync(join(f.root, 'cancel.log'), 'utf8')).toMatch(/sid=\$\(cat ~\/\.ubirun-ssh-\d+\.sid .*pkill -TERM -s/);
       writeFileSync(ssh, '#!/usr/bin/env bash\nfor i in 1 2 3 4 5 6; do echo "tick $i"; sleep 0.5; done\n');
       const beating = Bun.spawnSync(['bash', join(DIR, 'ubi-runner.sh'), 'ssh', 'vm-a', 'true'], { env: { ...env, UBI_IDLE_TIMEOUT: '0', UBI_HEARTBEAT: '1' }, timeout: 60_000 });
       expect(beating.exitCode).toBe(0);
@@ -371,8 +371,8 @@ describe('ubi-runner run, verify and quota against a fake API and a fake ssh', (
       expect(err).toMatch(/watchdog: setup printed nothing for \d+s \(UBI_IDLE_TIMEOUT=2\)/);
       expect(err).toContain('setup failed (exit 124)');
       expect(f.ssh()).not.toContain('bash -lc');
-      expect(readFileSync(join(f.root, 'cancel.log'), 'utf8')).toContain('cat ~/.ubirun-setup.sid');
-      expect(f.ssh()).toMatch(/setsid -w bash -c 'printf %s \$\$ >~\/\.ubirun-setup\.sid; cd work\/[^ ]+ && \. ~\/\.ubirun-env && bash -l ~\/\.ubirun-setup\.sh'/);
+      expect(readFileSync(join(f.root, 'cancel.log'), 'utf8')).toMatch(/cat ~\/\.ubirun-setup-\d+\.sid/);
+      expect(f.ssh()).toMatch(/setsid -w bash -c 'printf %s \$\$ >~\/\.ubirun-setup-\d+\.sid; cd work\/[^ ]+ && \. ~\/\.ubirun-env && bash -l ~\/\.ubirun-setup\.sh'; else bash -c '[^']*'; fi; rc=\$\?; rm -f ~\/\.ubirun-setup-\d+\.sid; exit \$rc/);
       expect(f.calls()).toContain('destroy');
       expect(err).toMatch(/destroyed eu-central-h1\/ubirun-thrd1-\d{10}-[0-9a-f]{8}-t4/);
       expect(f.listed()).toBe('');