diff --git a/CHANGELOG.md b/CHANGELOG.md
index 562ab413..e586578c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3,6 +3,12 @@
 
 ## [Unreleased]
 
+## [v0.51.528] — 2026-06-20 — Release SM (isolated HERMES_HOME single-profile mode)
+
+### Added
+
+- **Pin the WebUI to a single profile by pointing `HERMES_HOME` at a profile directory (#2698).** When `HERMES_HOME` resolves to `~/.hermes/profiles/<name>` at startup, the WebUI now runs in isolated single-profile mode: it lists only that profile, rejects cross-profile switch/create/delete (403), scopes the WebUI state directory to `<HERMES_HOME>/webui` (so even a profile literally named `default` gets its own sessions/state rather than sharing the root profile's), forces `?all_profiles=1` aggregate reads off (no cross-profile session/project leak), and hides the multi-profile UI affordances (New-profile button, profile dropdown, Manage link). A normal install — `HERMES_HOME` unset or pointing at the base `~/.hermes` — is unaffected: isolation stays off and the state directory and multi-profile behavior are unchanged. Thanks @rodboev (state-dir contract folded in from @tomtong2015's #4449).
+
 ## [v0.51.527] — 2026-06-19 — Release SL (completion notifications survive a backgrounded tab)
 
 ### Fixed
diff --git a/README.md b/README.md
index 8cfcf82b..e5348d96 100644
--- a/README.md
+++ b/README.md
@@ -337,7 +337,7 @@ Full list of environment variables:
 | `HERMES_WEBUI_PYTHON` | auto-discovered | Python executable |
 | `HERMES_WEBUI_HOST` | `127.0.0.1` | Bind address (`0.0.0.0` for all IPv4, `::` for all IPv6, `::1` for IPv6 loopback) |
 | `HERMES_WEBUI_PORT` | `8787` | Port |
-| `HERMES_WEBUI_STATE_DIR` | `$HERMES_HOME/webui` (Windows default `%LOCALAPPDATA%\hermes\webui`, POSIX default `~/.hermes/webui`) | Where sessions and state are stored |
+| `HERMES_WEBUI_STATE_DIR` | `$HERMES_HOME/webui` (Windows default `%LOCALAPPDATA%\hermes\webui`, POSIX default `~/.hermes/webui`) | Where sessions and state are stored. **Note (upgrade):** the default now follows `HERMES_HOME` — if you previously relocated `HERMES_HOME` to a non-default base **without** setting `HERMES_WEBUI_STATE_DIR`, your WebUI state now resolves to `$HERMES_HOME/webui` instead of the old platform-default `~/.hermes/webui`. To keep using the old location, set `HERMES_WEBUI_STATE_DIR` to it (or move the directory). Installs with `HERMES_HOME` unset or at the default base are unaffected. |
 | `HERMES_WEBUI_DEFAULT_WORKSPACE` | `~/workspace` | Default workspace |
 | `HERMES_WEBUI_DEFAULT_MODEL` | *(provider default)* | Optional model override; leave unset to use the active Hermes provider default |
 | `HERMES_WEBUI_PASSWORD` | *(unset)* | Set to enable password authentication |
@@ -348,6 +348,7 @@ Full list of environment variables:
 | `HERMES_WEBUI_EXTENSION_STYLESHEET_URLS` | *(unset)* | Optional comma-separated same-origin stylesheet URLs to inject; see [WebUI Extensions](docs/EXTENSIONS.md) |
 | `HERMES_HOME` | Windows: `%LOCALAPPDATA%\hermes`; POSIX: `~/.hermes` | Base directory for Hermes state (affects all paths) |
 | `HERMES_CONFIG_PATH` | `$HERMES_HOME/config.yaml` | Path to Hermes config file |
+| `HERMES_WEBUI_SERVER_CWD` | *(unset)* | Working directory for the server process. Defaults to the agent dir; point it at a writable workspace when the agent dir is read-only so fallback relative writes land somewhere writable |
 | `HERMES_WEBUI_AGENT_CACHE_MAX` | `25` | Max live agent instances kept warm in the in-memory LRU. Each pins a full conversation transcript, so this is the dominant lever on resident memory — lower it on installs with many long sessions to cap RAM (at the cost of more cold reloads) |
 | `HERMES_WEBUI_SESSIONS_MAX` | `100` | Max compact `Session` objects held in the in-memory LRU. Lighter than the agent cache; lower it on installs with hundreds of sessions |
 
diff --git a/api/config.py b/api/config.py
index ba469670..46860e5e 100644
--- a/api/config.py
+++ b/api/config.py
@@ -70,9 +70,10 @@ TLS_ENABLED = TLS_CERT is not None and TLS_KEY is not None
 
 # ── State directory (env-overridable, never inside repo) ──────────────────────
 _DEFAULT_HERMES_HOME = _platform_default_hermes_home()
+_DEFAULT_STATE_HOME = Path(os.getenv("HERMES_HOME") or _DEFAULT_HERMES_HOME).expanduser()
 
 STATE_DIR = (
-    Path(os.getenv("HERMES_WEBUI_STATE_DIR", str(_DEFAULT_HERMES_HOME / "webui")))
+    Path(os.getenv("HERMES_WEBUI_STATE_DIR", str(_DEFAULT_STATE_HOME / "webui")))
     .expanduser()
     .resolve()
 )
diff --git a/api/profiles.py b/api/profiles.py
index 53965ec2..cc8481b4 100644
--- a/api/profiles.py
+++ b/api/profiles.py
@@ -33,6 +33,15 @@ _PROFILE_DIRS = [
 ]
 _CLONE_CONFIG_FILES = ['config.yaml', '.env', 'SOUL.md']
 
+# ── Snapshot initial HERMES_HOME before init_profile_state() mutates it ──────
+# _is_isolated_profile_mode() needs to detect whether HERMES_HOME *at startup*
+# points to a profile subdirectory (e.g., ~/.hermes/profiles/user1), not the
+# base home (~/.hermes). But init_profile_state() overwrites HERMES_HOME to the
+# base home, which would disable isolation detection. Snapshot it here at import
+# time (before init_profile_state runs) and use the snapshot in the detector.
+_INITIAL_HERMES_HOME = os.getenv('HERMES_HOME', '').strip()
+_ISOLATED_SYMLINK_WARNING_EMITTED = False
+
 # ── Module state ────────────────────────────────────────────────────────────
 _active_profile = 'default'
 _profile_lock = threading.Lock()
@@ -116,6 +125,52 @@ def _unwrap_profile_home_to_base(home: Path) -> Path:
     return home
 
 
+def _is_isolated_profile_mode() -> bool:
+    """Detect isolated single-profile mode from HERMES_HOME env var.
+
+    Returns True when HERMES_HOME points at a concrete profile subdirectory
+    (e.g., ~/.hermes/profiles/user1) rather than the base home (~/.hermes).
+    This indicates a single-profile deployment where the WebUI should pin to
+    that profile and reject cross-profile operations.
+
+    Isolation is derived only from the literal ``*/profiles/<name>`` shape of
+    HERMES_HOME at startup. A normal multi-profile deployment points
+    HERMES_HOME at the base home (``~/.hermes``), which does not match the
+    shape, so isolation stays off. We deliberately do not key this off
+    HERMES_BASE_HOME: that variable normally points at the base home already,
+    so using it as an opt-out silently disables legitimate isolated-profile
+    deployments.
+
+    Uses _INITIAL_HERMES_HOME (snapshotted at import time) to detect isolation,
+    not the current os.environ value. init_profile_state() overwrites HERMES_HOME
+    at startup, which would disable isolation detection if we read it here.
+    """
+    hermes_home = _INITIAL_HERMES_HOME
+    if not hermes_home:
+        return False
+
+    p = Path(hermes_home).expanduser()
+    # Check if this path looks like ~/.hermes/profiles/<name>
+    # i.e., parent dir is named 'profiles' and grandparent exists
+    if p.parent.name == 'profiles' and p.parent.parent.exists():
+        return True
+    if p.is_symlink():
+        global _ISOLATED_SYMLINK_WARNING_EMITTED
+        if not _ISOLATED_SYMLINK_WARNING_EMITTED:
+            logger.warning(
+                "HERMES_HOME symlink %s does not literally match */profiles/<name>; "
+                "isolated profile mode is disabled unless the literal profile path is used.",
+                p,
+            )
+            _ISOLATED_SYMLINK_WARNING_EMITTED = True
+    return False
+
+
+def _isolated_profile_name() -> str:
+    """Return the profile directory name from _INITIAL_HERMES_HOME."""
+    return Path(_INITIAL_HERMES_HOME).expanduser().name
+
+
 def _resolve_base_hermes_home() -> Path:
     """Return the BASE ~/.hermes directory — the root that contains profiles/.
 
@@ -281,9 +336,12 @@ def get_active_profile_name() -> str:
     """Return the currently active profile name.
 
     Priority:
-      1. Thread-local (set per-request from hermes_profile cookie) — issue #798
-      2. Process-level default (_active_profile)
+      1. Isolated-profile deployment name from the configured HERMES_HOME path
+      2. Thread-local (set per-request from hermes_profile cookie) — issue #798
+      3. Process-level default (_active_profile)
     """
+    if _is_isolated_profile_mode():
+        return _isolated_profile_name()
     tls_name = getattr(_tls, 'profile', None)
     if tls_name is not None:
         return tls_name
@@ -318,6 +376,17 @@ def _resolve_profile_home_for_name(name: str) -> Path:
     names fall back to the base home so traversal-shaped cookie values cannot
     influence filesystem paths.
     """
+    # In isolated mode, every logical profile lookup clamps to the configured
+    # startup HERMES_HOME so callers cannot resolve a foreign profile path.
+    if _is_isolated_profile_mode():
+        isolated_name = _isolated_profile_name()
+        isolated_home = Path(_INITIAL_HERMES_HOME).expanduser()
+        if name and not _profiles_match(name, isolated_name):
+            logger.warning(
+                "Ignoring profile lookup %r in isolated profile mode; using pinned profile %r",
+                name, isolated_name,
+            )
+        return isolated_home
     if not name or _is_root_profile(name):
         return _DEFAULT_HERMES_HOME
     if not _PROFILE_ID_RE.fullmatch(name):
@@ -331,6 +400,8 @@ def get_active_hermes_home() -> Path:
     Uses get_active_profile_name() so per-request TLS context (issue #798)
     is respected, not just the process-level global.
     """
+    if _is_isolated_profile_mode():
+        return Path(_INITIAL_HERMES_HOME).expanduser()
     return _resolve_profile_home_for_name(get_active_profile_name())
 
 
@@ -378,6 +449,14 @@ def _home_for_scheduled_cron_job(job: dict) -> Path:
     fall back to the server default rather than crashing every scheduler tick.
     """
     raw = str((job or {}).get('profile') or '').strip()
+    if _is_isolated_profile_mode():
+        active = _isolated_profile_name()
+        if raw and not _profiles_match(raw, active):
+            logger.warning(
+                "Cron job %s references profile %r outside isolated profile %r; falling back to isolated home",
+                (job or {}).get('id', '?'), raw, active,
+            )
+        return get_active_hermes_home()
     if not raw:
         return get_active_hermes_home()
     if _is_root_profile(raw):
@@ -428,6 +507,8 @@ def install_cron_scheduler_profile_isolation() -> None:
                 return original(job, *args, **kwargs)
         finally:
             event_profile = str((job or {}).get("profile") or "").strip() or None
+            if _is_isolated_profile_mode():
+                event_profile = _isolated_profile_name()
             try:
                 publish_session_list_changed("cron_complete", profile=event_profile)
             except TypeError:
@@ -965,8 +1046,12 @@ def init_profile_state() -> None:
     module-level cached paths.  Called once from config.py after imports.
     """
     global _active_profile
-    _active_profile = _read_active_profile_file()
-    home = get_active_hermes_home()
+    if _is_isolated_profile_mode():
+        _active_profile = _isolated_profile_name()
+        home = Path(_INITIAL_HERMES_HOME).expanduser()
+    else:
+        _active_profile = _read_active_profile_file()
+        home = get_active_hermes_home()
     _set_hermes_home(home)
     install_cron_scheduler_profile_isolation()
     _reload_dotenv(home)
@@ -978,6 +1063,9 @@ def switch_profile(name: str, *, process_wide: bool = True) -> dict:
     Validates the profile exists, updates process state, patches module caches,
     reloads .env, and reloads config.yaml.
 
+    In isolated profile mode, switching to a different profile is rejected (403).
+    Switching to the isolated profile itself is allowed (idempotent).
+
     Args:
         name: Profile name to switch to.
         process_wide: If True (default), updates the process-global
@@ -985,10 +1073,20 @@ def switch_profile(name: str, *, process_wide: bool = True) -> dict:
             WebUI where the profile is managed via cookie + thread-local (#798).
 
     Returns: {'profiles': [...], 'active': name}
-    Raises ValueError if profile doesn't exist or agent is busy.
+    Raises ValueError when profile doesn't exist, RuntimeError when agent is running,
+    PermissionError in isolated mode for cross-profile switches.
     """
     global _active_profile
 
+    # In isolated profile mode, reject switching to other profiles
+    if _is_isolated_profile_mode():
+        active = _isolated_profile_name()
+        if name != active:
+            raise PermissionError(
+                f"Profile switching is not allowed in isolated profile mode. "
+                f"Currently pinned to profile '{active}'."
+            )
+
     # Import here to avoid circular import at module load
     from api.config import STREAMS, STREAMS_LOCK, reload_config
 
@@ -1006,7 +1104,9 @@ def switch_profile(name: str, *, process_wide: bool = True) -> dict:
                 )
 
     # Resolve profile directory
-    if _is_root_profile(name):
+    if _is_isolated_profile_mode():
+        home = Path(_INITIAL_HERMES_HOME).expanduser()
+    elif _is_root_profile(name):
         home = _DEFAULT_HERMES_HOME
     else:
         home = _resolve_named_profile_home(name)
@@ -1281,6 +1381,9 @@ def _build_profile_rows_fast() -> list | None:
 def list_profiles_api() -> list:
     """List all profiles with metadata, serialized for JSON response.
 
+    In isolated profile mode (HERMES_HOME points to ~/.hermes/profiles/<name>),
+    returns only that single profile and skips other profiles entirely.
+
     Fast path: build the rows from upstream's cheap per-profile helpers and skip
     ``find_alias_for_profile`` (whose result the WebUI discards) — see
     ``_build_profile_rows_fast``. Results are cached for a short TTL so rapid
@@ -1292,6 +1395,56 @@ def list_profiles_api() -> list:
     global _LIST_PROFILES_CACHE
     now = time.time()
 
+    # In isolated profile mode, return only the active (isolated) profile
+    if _is_isolated_profile_mode():
+        active = _isolated_profile_name()
+        hermes_home = Path(_INITIAL_HERMES_HOME).expanduser()
+        try:
+            from hermes_cli.profiles import list_profiles
+            infos = list_profiles()
+            # When the isolated profile is literally named "default", upstream
+            # can surface the base-home row first. Only trust a row whose path
+            # resolves to the same directory as the isolated startup home.
+            for p in infos:
+                try:
+                    same_home = Path(p.path).expanduser().resolve() == hermes_home.resolve()
+                except OSError:
+                    same_home = False
+                if p.name == active and same_home:
+                    enabled_count, total_count = _get_profile_skills_stats(p.path)
+                    return [{
+                        'name': p.name,
+                        'path': str(p.path),
+                        'is_default': p.is_default,
+                        'is_active': True,  # Always true in isolated mode
+                        'gateway_running': p.gateway_running,
+                        'model': p.model,
+                        'provider': p.provider,
+                        'has_env': p.has_env,
+                        'visible': _profile_visible_from_meta(p.path),
+                        'skill_count': enabled_count,
+                        'enabled_skills': enabled_count,
+                        'total_skills': total_count,
+                    }]
+        except (ImportError, OSError, PermissionError):
+            pass
+        # Fallback: construct profile dict with actual active name and hermes_home path
+        enabled_count, total_count = _get_profile_skills_stats(hermes_home)
+        return [{
+            'name': active,
+            'path': str(hermes_home),
+            'is_default': active == 'default',
+            'is_active': True,
+            'gateway_running': False,
+            'model': None,
+            'provider': None,
+            'has_env': (hermes_home / '.env').exists(),
+            'visible': _profile_visible_from_meta(hermes_home),
+            'skill_count': enabled_count,
+            'enabled_skills': enabled_count,
+            'total_skills': total_count,
+        }]
+
     with _LIST_PROFILES_CACHE_LOCK:
         cached = _LIST_PROFILES_CACHE
     if cached is not None and now - cached[1] < _LIST_PROFILES_CACHE_TTL:
@@ -1709,7 +1862,12 @@ def create_profile_api(name: str, clone_from: str = None,
                        api_key: str = None,
                        default_model: str = None,
                        model_provider: str = None) -> dict:
-    """Create a new profile. Returns the new profile info dict."""
+    """Create a new profile. Returns the new profile info dict.
+
+    In isolated profile mode, profile creation is rejected (403).
+    """
+    if _is_isolated_profile_mode():
+        raise PermissionError("Profile creation is not allowed in isolated profile mode.")
     _validate_profile_name(name)
     # Defense-in-depth: validate clone_from here too, even though routes.py
     # also validates it. Any caller that bypasses the HTTP layer gets protection.
@@ -1808,7 +1966,12 @@ def create_profile_api(name: str, clone_from: str = None,
 
 
 def delete_profile_api(name: str) -> dict:
-    """Delete a profile. Switches to default first if it's the active one."""
+    """Delete a profile. Switches to default first if it's the active one.
+
+    In isolated profile mode, profile deletion is rejected (403).
+    """
+    if _is_isolated_profile_mode():
+        raise PermissionError("Profile deletion is not allowed in isolated profile mode.")
     if _is_root_profile(name):
         raise ValueError("Cannot delete the default profile.")
     _validate_profile_name(name)
diff --git a/api/routes.py b/api/routes.py
index 94c431bd..fb93e965 100644
--- a/api/routes.py
+++ b/api/routes.py
@@ -429,6 +429,7 @@ def _visible_pinned_lineage_ids(session_rows) -> set[str]:
 # module keep resolving without per-call-site refactors.
 from api.profiles import (  # noqa: F401, E402  (re-export)
     _profiles_match,
+    _is_isolated_profile_mode,
     get_active_profile_name,
     get_active_profile_name as _get_active_profile_name,
 )
@@ -445,6 +446,11 @@ def _all_profiles_query_flag(parsed_url) -> bool:
     return raw in ('1', 'true', 'yes', 'on')
 
 
+def _all_profiles_enabled(parsed_url) -> bool:
+    """Enable aggregate profile reads only when the request asks and mode allows it."""
+    return _all_profiles_query_flag(parsed_url) and not _is_isolated_profile_mode()
+
+
 def _session_visible_to_active_profile(session_profile, handler=None) -> bool:
     """Return whether a detail-load session belongs to the active profile.
 
@@ -1927,7 +1933,7 @@ def _build_session_list_cache_payload(
         other_profile_count = 0
     else:
         scoped = [s for s in merged if _profiles_match(s.get("profile"), active_profile)]
-        other_profile_count = len(merged) - len(scoped)
+        other_profile_count = 0 if _is_isolated_profile_mode() else len(merged) - len(scoped)
     diag_stage("messaging_dedupe")
     scoped = _keep_latest_messaging_session_per_source(
         scoped,
@@ -8175,7 +8181,7 @@ def handle_get(handler, parsed) -> bool:
             show_cron_sessions = bool(settings.get("show_cron_sessions"))
             agent_session_source_filter = settings.get("agent_session_source_filter")
             active_profile = get_active_profile_name()
-            all_profiles = _all_profiles_query_flag(parsed)
+            all_profiles = _all_profiles_enabled(parsed)
             key = _session_list_cache_key(
                 active_profile=active_profile,
                 all_profiles=all_profiles,
@@ -8213,17 +8219,20 @@ def handle_get(handler, parsed) -> bool:
         from api.profiles import get_active_profile_name
         active_profile = get_active_profile_name()
         all_projects = load_projects()
-        all_profiles = _all_profiles_query_flag(parsed)
+        isolated_profile_mode = _is_isolated_profile_mode()
+        all_profiles = _all_profiles_enabled(parsed)
         if all_profiles:
             scoped = all_projects
+            other_profile_count = 0
         else:
             scoped = [p for p in all_projects
                       if _profiles_match(p.get("profile"), active_profile)]
+            other_profile_count = 0 if isolated_profile_mode else len(all_projects) - len(scoped)
         return j(handler, {
             "projects": scoped,
             "all_profiles": all_profiles,
             "active_profile": active_profile,
-            "other_profile_count": len(all_projects) - len(scoped),
+            "other_profile_count": other_profile_count,
         })
 
     if parsed.path == "/api/prompts":
@@ -8586,11 +8595,15 @@ def handle_get(handler, parsed) -> bool:
 
     # ── Profile API (GET) ──
     if parsed.path == "/api/profiles":
-        from api.profiles import list_profiles_api, get_active_profile_name
+        from api.profiles import list_profiles_api
 
         return j(
             handler,
-            {"profiles": list_profiles_api(), "active": get_active_profile_name()},
+            {
+                "profiles": list_profiles_api(),
+                "active": get_active_profile_name(),
+                "single_profile_mode": _is_isolated_profile_mode(),
+            },
         )
 
     if parsed.path == "/api/profile/active":
@@ -10064,6 +10077,8 @@ def handle_post(handler, parsed) -> bool:
             return j(handler, result, extra_headers={
                 'Set-Cookie': build_profile_cookie(name, handler),
             })
+        except PermissionError as e:
+            return bad(handler, _sanitize_error(e), 403)
         except (ValueError, FileNotFoundError) as e:
             return bad(handler, _sanitize_error(e), 404)
         except RuntimeError as e:
@@ -10104,6 +10119,8 @@ def handle_post(handler, parsed) -> bool:
                 model_provider=model_provider,
             )
             return j(handler, {"ok": True, "profile": result})
+        except PermissionError as e:
+            return bad(handler, _sanitize_error(e), 403)
         except (ValueError, FileExistsError, RuntimeError) as e:
             return bad(handler, str(e))
 
@@ -10117,6 +10134,8 @@ def handle_post(handler, parsed) -> bool:
             _validate_profile_name(name)
             result = delete_profile_api(name)
             return j(handler, result)
+        except PermissionError as e:
+            return bad(handler, _sanitize_error(e), 403)
         except (ValueError, FileNotFoundError) as e:
             return bad(handler, _sanitize_error(e))
         except RuntimeError as e:
@@ -11177,7 +11196,7 @@ def _handle_sessions_search(handler, parsed):
     content_search = qs.get("content", ["1"])[0] == "1"
     from api.profiles import get_active_profile_name
     active_profile = get_active_profile_name()
-    all_profiles = _all_profiles_query_flag(parsed)
+    all_profiles = _all_profiles_enabled(parsed)
     sessions = all_sessions()
     if not all_profiles:
         sessions = [
@@ -18065,6 +18084,8 @@ def _handle_session_import_cli(handler, body):
     if requested_profile == "":
         return bad(handler, "invalid profile", 400)
     allow_all_profiles = _request_wants_all_profiles_import(body)
+    if allow_all_profiles and _is_isolated_profile_mode():
+        return bad(handler, "all_profiles import is not allowed in isolated profile mode", 403)
     if allow_all_profiles and not requested_profile:
         return bad(handler, "profile is required for all_profiles import", 400)
 
diff --git a/bootstrap.py b/bootstrap.py
index 9bccf09e..f8f0ced2 100755
--- a/bootstrap.py
+++ b/bootstrap.py
@@ -494,7 +494,8 @@ def main() -> int:
 
     python_exe = ensure_python_has_webui_deps(discover_launcher_python(agent_dir), agent_dir)
     state_dir = Path(
-        os.getenv("HERMES_WEBUI_STATE_DIR", str(Path.home() / ".hermes" / "webui"))
+        os.getenv("HERMES_WEBUI_STATE_DIR")
+        or Path(os.getenv("HERMES_HOME") or (Path.home() / ".hermes")) / "webui"
     ).expanduser()
     state_dir.mkdir(parents=True, exist_ok=True)
 
@@ -505,7 +506,8 @@ def main() -> int:
     if agent_dir:
         os.environ["HERMES_WEBUI_AGENT_DIR"] = str(agent_dir)
 
-    server_cwd = str(agent_dir or REPO_ROOT)
+    # Let operators move fallback relative writes out of a read-only agent dir.
+    server_cwd = os.environ.get("HERMES_WEBUI_SERVER_CWD", "").strip() or str(agent_dir or REPO_ROOT)
     server_path = str(REPO_ROOT / "server.py")
     # Scheme the server will advertise (HTTPS when TLS cert+key are configured).
     scheme = "https" if _tls_probe_enabled() else "http"
@@ -547,6 +549,8 @@ def main() -> int:
             # for SO_EXCLUSIVEADDRUSE.
             _CREATE_NEW_PROCESS_GROUP = getattr(subprocess, "CREATE_NEW_PROCESS_GROUP", 0)
             subprocess.Popen([python_exe, server_path],
+                             cwd=server_cwd,
+                             env=os.environ.copy(),
                              creationflags=_CREATE_NEW_PROCESS_GROUP)
             sys.exit(0)
         os.execv(python_exe, [python_exe, server_path])
diff --git a/static/panels.js b/static/panels.js
index 9aa3e35e..5c2a884f 100644
--- a/static/panels.js
+++ b/static/panels.js
@@ -5566,17 +5566,28 @@ async function loadProfilesPanel() {
     const data = await api('/api/profiles');
     _profilesCache = data;
     panel.innerHTML = '';
-    const explainer = document.createElement('div');
-    explainer.className = 'profile-card profile-help-card';
-    explainer.innerHTML = `
-      <div class="profile-card-header">
-        <div style="min-width:0;flex:1">
-          <div class="profile-card-name">Profiles vs workspaces</div>
-          <div class="profile-card-meta">Use profiles for how the agent works; use workspaces for what files it works on.</div>
-        </div>
-      </div>`;
-    explainer.onclick = () => _renderProfileConceptHelp(data.active || 'default');
-    panel.appendChild(explainer);
+
+    // Hide "New profile" button in single profile mode
+    const newProfileBtn = document.querySelector('[onclick="openProfileCreate()"]');
+    if (newProfileBtn) {
+      newProfileBtn.style.display = data.single_profile_mode ? 'none' : '';
+    }
+
+    // In single profile mode, don't show the explanatory card
+    if (!data.single_profile_mode) {
+      const explainer = document.createElement('div');
+      explainer.className = 'profile-card profile-help-card';
+      explainer.innerHTML = `
+        <div class="profile-card-header">
+          <div style="min-width:0;flex:1">
+            <div class="profile-card-name">Profiles vs workspaces</div>
+            <div class="profile-card-meta">Use profiles for how the agent works; use workspaces for what files it works on.</div>
+          </div>
+        </div>`;
+      explainer.onclick = () => _renderProfileConceptHelp(data.active || 'default');
+      panel.appendChild(explainer);
+    }
+
     if (!data.profiles || !data.profiles.length) {
       const emptyMsg = document.createElement('div');
       emptyMsg.style.cssText = 'padding:16px;color:var(--muted);font-size:12px';
@@ -5695,8 +5706,9 @@ function _setProfileHeaderButtons(mode, p, activeName){
   if (mode === 'read') {
     const isActive = p && p.name === activeName;
     const isDefault = !!(p && p.is_default);
-    if (isActive) hide(actBtn); else show(actBtn);
-    if (isDefault) hide(delBtn); else show(delBtn);
+    const singleProfileMode = !!(_profilesCache && _profilesCache.single_profile_mode);
+    if (isActive || singleProfileMode) hide(actBtn); else show(actBtn);
+    if (isDefault || singleProfileMode) hide(delBtn); else show(delBtn);
     hide(cancelBtn); hide(saveBtn);
   } else if (mode === 'create') {
     hide(actBtn); hide(delBtn); show(cancelBtn); show(saveBtn);
@@ -5774,12 +5786,14 @@ function renderProfileDropdown(data) {
     };
     dd.appendChild(opt);
   }
-  // Divider + Manage link
-  const div = document.createElement('div'); div.className = 'ws-divider'; dd.appendChild(div);
-  const mgmt = document.createElement('div'); mgmt.className = 'profile-opt ws-manage';
-  mgmt.innerHTML = `${li('settings',12)} ${esc(t('manage_profiles'))}`;
-  mgmt.onclick = () => { closeProfileDropdown(); mobileSwitchPanel('profiles'); };
-  dd.appendChild(mgmt);
+  // Divider + Manage link (hidden in single profile mode)
+  if (!data.single_profile_mode) {
+    const div = document.createElement('div'); div.className = 'ws-divider'; dd.appendChild(div);
+    const mgmt = document.createElement('div'); mgmt.className = 'profile-opt ws-manage';
+    mgmt.innerHTML = `${li('settings',12)} ${esc(t('manage_profiles'))}`;
+    mgmt.onclick = () => { closeProfileDropdown(); mobileSwitchPanel('profiles'); };
+    dd.appendChild(mgmt);
+  }
 }
 
 function toggleProfileDropdown() {
@@ -5789,6 +5803,11 @@ function toggleProfileDropdown() {
   closeWsDropdown(); // close workspace dropdown if open
   if(typeof closeModelDropdown==='function') closeModelDropdown();
   api('/api/profiles').then(data => {
+    // In single profile mode, don't show profile dropdown at all
+    if (data.single_profile_mode) {
+      closeProfileDropdown();
+      return;
+    }
     renderProfileDropdown(data);
     dd.classList.add('open');
     _positionProfileDropdown();
diff --git a/tests/test_bootstrap_foreground.py b/tests/test_bootstrap_foreground.py
index cb2169e7..4aa200ae 100644
--- a/tests/test_bootstrap_foreground.py
+++ b/tests/test_bootstrap_foreground.py
@@ -92,6 +92,9 @@ def clean_env(monkeypatch):
         "HERMES_WEBUI_HOST",
         "HERMES_WEBUI_PORT",
         "HERMES_WEBUI_AGENT_DIR",
+        "HERMES_WEBUI_STATE_DIR",
+        "HERMES_WEBUI_SERVER_CWD",
+        "HERMES_HOME",
     ):
         monkeypatch.delenv(name, raising=False)
 
@@ -346,6 +349,27 @@ class TestMainForegroundRouting:
             bs.main()
         assert len(execv_calls) == 1
 
+    def test_foreground_defaults_state_dir_to_hermes_home_webui(self, stub_main_dependencies, clean_env, monkeypatch, tmp_path):
+        bs = stub_main_dependencies
+        hermes_home = tmp_path / ".hermes" / "profiles" / "webui"
+        hermes_home.mkdir(parents=True, exist_ok=True)
+        monkeypatch.setenv("HERMES_HOME", str(hermes_home))
+        monkeypatch.delenv("HERMES_WEBUI_STATE_DIR", raising=False)
+        monkeypatch.setattr(sys, "argv", ["bootstrap.py", "--foreground"])
+        monkeypatch.setattr(sys, "platform", "linux")
+        monkeypatch.setattr(os, "chdir", lambda p: None)
+        monkeypatch.setattr(os, "access", lambda path, mode: True)
+
+        def fake_execv(*_args):
+            raise SystemExit(0)
+
+        monkeypatch.setattr(os, "execv", fake_execv)
+
+        with pytest.raises(SystemExit):
+            bs.main()
+
+        assert os.environ["HERMES_WEBUI_STATE_DIR"] == str(hermes_home / "webui")
+
 
 class TestForegroundEnvAndCwd:
     """The post-execv server.py inherits os.environ and cwd from us."""
@@ -384,6 +408,49 @@ class TestForegroundEnvAndCwd:
         assert len(chdir_calls) == 1
         assert chdir_calls[0] == str(agent_dir)
 
+    def test_foreground_chdirs_to_server_cwd_override_before_launch(self, setup, monkeypatch, clean_env, tmp_path):
+        bs, _agent_dir = setup
+        workspace = tmp_path / "workspace"
+        workspace.mkdir()
+        monkeypatch.setenv("HERMES_WEBUI_SERVER_CWD", str(workspace))
+        monkeypatch.setattr(sys, "argv", ["bootstrap.py", "--foreground"])
+        monkeypatch.setattr(sys, "platform", "linux")
+
+        chdir_calls = []
+        monkeypatch.setattr(os, "chdir", lambda p: chdir_calls.append(p))
+
+        def fake_execv(*_args):
+            raise SystemExit(0)
+
+        monkeypatch.setattr(os, "execv", fake_execv)
+
+        with pytest.raises(SystemExit):
+            bs.main()
+
+        assert chdir_calls == [str(workspace)]
+
+    def test_windows_foreground_popen_uses_server_cwd_override(self, setup, monkeypatch, clean_env, tmp_path):
+        bs, _agent_dir = setup
+        workspace = tmp_path / "workspace-win"
+        workspace.mkdir()
+        monkeypatch.setenv("HERMES_WEBUI_SERVER_CWD", str(workspace))
+        monkeypatch.setattr(sys, "argv", ["bootstrap.py", "--foreground"])
+        monkeypatch.setattr(sys, "platform", "win32")
+        monkeypatch.setattr(os, "chdir", lambda p: None)
+
+        popen_calls = []
+
+        def fake_popen(*args, **kwargs):
+            popen_calls.append((args, kwargs))
+            return None
+
+        monkeypatch.setattr(subprocess, "Popen", fake_popen)
+
+        with pytest.raises(SystemExit):
+            bs.main()
+
+        assert popen_calls[0][1]["cwd"] == str(workspace)
+
     def test_foreground_exports_resolved_env_vars(self, setup, monkeypatch, clean_env):
         bs, agent_dir = setup
         monkeypatch.setattr(sys, "argv", [
diff --git a/tests/test_issue1611_session_profile_filtering.py b/tests/test_issue1611_session_profile_filtering.py
index 0ca9cd03..3d68551d 100644
--- a/tests/test_issue1611_session_profile_filtering.py
+++ b/tests/test_issue1611_session_profile_filtering.py
@@ -106,6 +106,22 @@ def test_all_profiles_query_flag_false_values():
         assert _all_profiles_query_flag(u) is False, f"path {path!r} should be false"
 
 
+def test_all_profiles_enabled_in_normal_mode(monkeypatch):
+    """The aggregate toggle still works outside isolated-profile mode."""
+    import api.routes as routes
+
+    monkeypatch.setattr(routes, "_is_isolated_profile_mode", lambda: False)
+    assert routes._all_profiles_enabled(urlparse('/api/sessions?all_profiles=1')) is True
+
+
+def test_all_profiles_disabled_in_isolated_mode(monkeypatch):
+    """An isolated deployment must ignore all_profiles=1 aggregate requests."""
+    import api.routes as routes
+
+    monkeypatch.setattr(routes, "_is_isolated_profile_mode", lambda: True)
+    assert routes._all_profiles_enabled(urlparse('/api/sessions?all_profiles=1')) is False
+
+
 # ── No client-side CLI bypass ──────────────────────────────────────────────
 
 
diff --git a/tests/test_issue2698_isolated_hermes_home.py b/tests/test_issue2698_isolated_hermes_home.py
new file mode 100644
index 00000000..dae1026d
--- /dev/null
+++ b/tests/test_issue2698_isolated_hermes_home.py
@@ -0,0 +1,575 @@
+"""
+Tests for issue #2698: HERMES_HOME isolated profile mode.
+
+When HERMES_HOME points at a specific profile directory like ~/.hermes/profiles/user1,
+the WebUI should pin to that single profile: list only it, reject create/switch/delete
+of other profiles, and hide multi-profile UI affordances.
+"""
+
+import os
+import io
+import sys
+import tempfile
+import types
+from pathlib import Path
+from unittest import mock
+
+import pytest
+
+import api.profiles as _profiles_mod
+from api.profiles import (
+    _is_isolated_profile_mode,
+    clear_request_profile,
+    list_profiles_api,
+    create_profile_api,
+    delete_profile_api,
+    get_active_hermes_home,
+    get_active_profile_name,
+    init_profile_state,
+    set_request_profile,
+    switch_profile,
+)
+
+
+@pytest.fixture(autouse=True)
+def _clear_profile_cache():
+    """Clear the profile list cache before and after each test to prevent cross-test leakage."""
+    _profiles_mod._LIST_PROFILES_CACHE = None
+    yield
+    _profiles_mod._LIST_PROFILES_CACHE = None
+
+
+@pytest.fixture
+def temp_hermes_home():
+    """Create a temporary .hermes directory structure for testing."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        home = Path(tmpdir) / ".hermes"
+        home.mkdir()
+        profiles_root = home / "profiles"
+        profiles_root.mkdir()
+        yield home
+
+
+@pytest.fixture
+def temp_single_profile():
+    """Create a temporary .hermes/profiles/user1 structure for isolated mode."""
+    with tempfile.TemporaryDirectory() as tmpdir:
+        home = Path(tmpdir) / ".hermes"
+        home.mkdir()
+        profiles_root = home / "profiles"
+        profiles_root.mkdir()
+        user1 = profiles_root / "user1"
+        user1.mkdir()
+        # Create required subdirs
+        for subdir in ["memories", "sessions", "skills", "skins", "logs", "plans", "workspace", "cron"]:
+            (user1 / subdir).mkdir(exist_ok=True)
+        yield user1
+
+
+class TestIsolatedProfileModeDetection:
+    """Test _is_isolated_profile_mode() helper."""
+
+    def test_normal_mode_when_hermes_home_is_base(self, temp_hermes_home):
+        """Normal mode when HERMES_HOME points to base ~/.hermes."""
+        with mock.patch.dict(os.environ, {"HERMES_HOME": str(temp_hermes_home)}):
+            with mock.patch("api.profiles._DEFAULT_HERMES_HOME", temp_hermes_home):
+                with mock.patch("api.profiles._INITIAL_HERMES_HOME", str(temp_hermes_home)):
+                    isolated = _is_isolated_profile_mode()
+                    assert isolated is False
+
+    def test_isolated_mode_when_hermes_home_is_profile_subdir(self, temp_single_profile):
+        """Isolated mode when HERMES_HOME points to ~/.hermes/profiles/user1."""
+        # Ensure we're in the fixture context where temp_single_profile exists
+        assert temp_single_profile.exists(), f"Test fixture path doesn't exist: {temp_single_profile}"
+        assert temp_single_profile.parent.name == "profiles", f"Parent not named 'profiles': {temp_single_profile.parent}"
+
+        # _is_isolated_profile_mode() uses _INITIAL_HERMES_HOME (snapshotted at import time),
+        # not the current os.environ value. Patch both for this test.
+        with mock.patch.dict(os.environ, {"HERMES_HOME": str(temp_single_profile)}, clear=False):
+            with mock.patch.dict(os.environ, {"HERMES_BASE_HOME": ""}, clear=False):
+                with mock.patch("api.profiles._INITIAL_HERMES_HOME", str(temp_single_profile)):
+                    isolated = _is_isolated_profile_mode()
+                    assert isolated is True, f"Expected isolated mode for {temp_single_profile}"
+
+    def test_hermes_base_home_does_not_disable_isolation(self, temp_single_profile):
+        """HERMES_BASE_HOME must not disable isolation for a profiles/<name> path."""
+        base_home = temp_single_profile.parent.parent
+        with mock.patch.dict(
+            os.environ,
+            {
+                "HERMES_HOME": str(temp_single_profile),
+                "HERMES_BASE_HOME": str(base_home),
+            },
+        ):
+            with mock.patch("api.profiles._DEFAULT_HERMES_HOME", base_home):
+                with mock.patch("api.profiles._INITIAL_HERMES_HOME", str(temp_single_profile)):
+                    isolated = _is_isolated_profile_mode()
+                    assert isolated is True
+
+
+class TestListProfilesInIsolatedMode:
+    """Test list_profiles_api() returns only isolated profile when in isolated mode."""
+
+    def test_list_returns_all_profiles_in_normal_mode(self, temp_hermes_home):
+        """Normal mode lists all profiles."""
+        # Create a few test profiles
+        profiles_root = temp_hermes_home / "profiles"
+        (profiles_root / "user1").mkdir()
+        (profiles_root / "user2").mkdir()
+        (profiles_root / "user3").mkdir()
+
+        # Create required subdirs for each
+        for prof_dir in profiles_root.iterdir():
+            if prof_dir.is_dir():
+                for subdir in ["memories", "sessions", "skills", "skins", "logs", "plans", "workspace", "cron"]:
+                    (prof_dir / subdir).mkdir(exist_ok=True)
+
+        with mock.patch.dict(os.environ, {"HERMES_HOME": str(temp_hermes_home)}):
+            with mock.patch("api.profiles._DEFAULT_HERMES_HOME", temp_hermes_home):
+                with mock.patch("api.profiles._is_isolated_profile_mode", return_value=False):
+                    # Mock _get_profile_skills_stats to avoid importing agent.skill_utils
+                    with mock.patch("api.profiles._get_profile_skills_stats", return_value=(0, 0)):
+                        # Mock _build_profile_rows_fast to return the expected profiles
+                        def mock_build_profiles():
+                            return [
+                                {'name': 'default', 'path': str(temp_hermes_home), 'is_default': True,
+                                 'is_active': False, 'gateway_running': False, 'model': None, 'provider': None,
+                                 'has_env': False, 'visible': True, 'skill_count': 0, 'enabled_skills': 0, 'total_skills': 0},
+                                {'name': 'user1', 'path': str(profiles_root / 'user1'), 'is_default': False,
+                                 'is_active': False, 'gateway_running': False, 'model': None, 'provider': None,
+                                 'has_env': False, 'visible': True, 'skill_count': 0, 'enabled_skills': 0, 'total_skills': 0},
+                                {'name': 'user2', 'path': str(profiles_root / 'user2'), 'is_default': False,
+                                 'is_active': False, 'gateway_running': False, 'model': None, 'provider': None,
+                                 'has_env': False, 'visible': True, 'skill_count': 0, 'enabled_skills': 0, 'total_skills': 0},
+                                {'name': 'user3', 'path': str(profiles_root / 'user3'), 'is_default': False,
+                                 'is_active': False, 'gateway_running': False, 'model': None, 'provider': None,
+                                 'has_env': False, 'visible': True, 'skill_count': 0, 'enabled_skills': 0, 'total_skills': 0},
+                            ]
+                        with mock.patch("api.profiles._build_profile_rows_fast", side_effect=mock_build_profiles):
+                            profiles = list_profiles_api()
+                            # Should have at least 'default' plus the created profiles
+                            names = [p["name"] for p in profiles]
+                            assert "user1" in names
+                            assert "user2" in names
+                            assert "user3" in names
+
+    def test_list_returns_only_isolated_profile_in_isolated_mode(self, temp_single_profile):
+        """Isolated mode lists only the configured profile."""
+        base_home = temp_single_profile.parent.parent
+        # Create other profiles that should be hidden
+        other_profiles = base_home / "profiles"
+        (other_profiles / "user2").mkdir()
+        (other_profiles / "user3").mkdir()
+        for prof_dir in [other_profiles / "user2", other_profiles / "user3"]:
+            for subdir in ["memories", "sessions", "skills", "skins", "logs", "plans", "workspace", "cron"]:
+                (prof_dir / subdir).mkdir(exist_ok=True)
+
+        # Clear HERMES_BASE_HOME to allow isolated mode detection to fire
+        env_dict = {
+            "HERMES_HOME": str(temp_single_profile),
+            "HERMES_BASE_HOME": "",
+        }
+        with mock.patch.dict(os.environ, env_dict, clear=False):
+            with mock.patch("api.profiles._DEFAULT_HERMES_HOME", base_home):
+                with mock.patch("api.profiles._INITIAL_HERMES_HOME", str(temp_single_profile)):
+                    # Mock _get_profile_skills_stats to avoid importing agent.skill_utils
+                    with mock.patch("api.profiles._get_profile_skills_stats", return_value=(0, 0)):
+                        profiles = list_profiles_api()
+                        # Should only have user1
+                        assert len(profiles) == 1
+                        assert profiles[0]["name"] == "user1"
+
+    def test_list_includes_single_profile_mode_flag(self, temp_single_profile):
+        """Response includes single_profile_mode: true in isolated mode."""
+        base_home = temp_single_profile.parent.parent
+        with mock.patch.dict(os.environ, {"HERMES_HOME": str(temp_single_profile)}):
+            with mock.patch("api.profiles._DEFAULT_HERMES_HOME", base_home):
+                with mock.patch("api.profiles._INITIAL_HERMES_HOME", str(temp_single_profile)):
+                    with mock.patch("api.profiles._is_isolated_profile_mode", return_value=True):
+                        with mock.patch("api.profiles._resolve_base_hermes_home", return_value=base_home):
+                            # Mock _get_profile_skills_stats to avoid importing agent.skill_utils
+                            with mock.patch("api.profiles._get_profile_skills_stats", return_value=(0, 0)):
+                                profiles = list_profiles_api()
+                                # Check for single_profile_mode flag in response structure
+                                # For now, profiles should be a list; the flag will be in routes.py response
+                                assert len(profiles) == 1
+
+
+class TestIsolatedRuntimePinning:
+    """Test that isolated mode pins both detection and active runtime home."""
+
+    def test_get_active_profile_name_ignores_tls_and_global_in_isolated_mode(self, temp_single_profile):
+        """Isolated mode must ignore request TLS and process-global active profile."""
+        base_home = temp_single_profile.parent.parent
+        env_dict = {
+            "HERMES_HOME": str(temp_single_profile),
+            "HERMES_BASE_HOME": "",
+        }
+        with mock.patch.dict(os.environ, env_dict, clear=False):
+            with mock.patch("api.profiles._DEFAULT_HERMES_HOME", base_home):
+                with mock.patch("api.profiles._INITIAL_HERMES_HOME", str(temp_single_profile)):
+                    with mock.patch("api.profiles._active_profile", "other_profile"):
+                        set_request_profile("tls_profile")
+                        try:
+                            assert get_active_profile_name() == "user1"
+                        finally:
+                            clear_request_profile()
+
+    @pytest.mark.parametrize("active_profile_contents", [None, "user2"])
+    def test_init_profile_state_pins_runtime_home_to_isolated_profile(
+        self,
+        temp_single_profile,
+        monkeypatch,
+        active_profile_contents,
+    ):
+        """init_profile_state must ignore the base active_profile file in isolated mode."""
+        base_home = temp_single_profile.parent.parent
+        other_profile = base_home / "profiles" / "user2"
+        other_profile.mkdir()
+        for subdir in ["memories", "sessions", "skills", "skins", "logs", "plans", "workspace", "cron"]:
+            (other_profile / subdir).mkdir(exist_ok=True)
+
+        active_profile_file = base_home / "active_profile"
+        if active_profile_contents is None:
+            active_profile_file.unlink(missing_ok=True)
+        else:
+            active_profile_file.write_text(active_profile_contents, encoding="utf-8")
+
+        monkeypatch.setenv("HERMES_HOME", str(temp_single_profile))
+        monkeypatch.setenv("HERMES_BASE_HOME", "")
+        monkeypatch.setattr(_profiles_mod, "_DEFAULT_HERMES_HOME", base_home)
+        monkeypatch.setattr(_profiles_mod, "_INITIAL_HERMES_HOME", str(temp_single_profile))
+        monkeypatch.setattr(_profiles_mod, "_active_profile", "default")
+        monkeypatch.setattr(_profiles_mod, "install_cron_scheduler_profile_isolation", lambda: None)
+
+        reloaded = []
+        real_reload_dotenv = _profiles_mod._reload_dotenv
+
+        def _record_reload(home):
+            reloaded.append(home)
+            return real_reload_dotenv(home)
+
+        monkeypatch.setattr(_profiles_mod, "_reload_dotenv", _record_reload)
+
+        init_profile_state()
+
+        assert _profiles_mod._active_profile == "user1"
+        assert get_active_profile_name() == "user1"
+        assert get_active_hermes_home() == temp_single_profile
+        assert Path(os.environ["HERMES_HOME"]) == temp_single_profile
+        assert reloaded == [temp_single_profile]
+
+    def test_get_active_hermes_home_keeps_profiles_default_pinned(self, temp_hermes_home, monkeypatch):
+        """An isolated profiles/default path must not collapse back to the base home."""
+        isolated_default = temp_hermes_home / "profiles" / "default"
+        isolated_default.mkdir()
+        for subdir in ["memories", "sessions", "skills", "skins", "logs", "plans", "workspace", "cron"]:
+            (isolated_default / subdir).mkdir(exist_ok=True)
+
+        monkeypatch.setenv("HERMES_HOME", str(isolated_default))
+        monkeypatch.setenv("HERMES_BASE_HOME", "")
+        monkeypatch.setattr(_profiles_mod, "_DEFAULT_HERMES_HOME", temp_hermes_home)
+        monkeypatch.setattr(_profiles_mod, "_INITIAL_HERMES_HOME", str(isolated_default))
+        monkeypatch.setattr(_profiles_mod, "_active_profile", "other_profile")
+
+        assert get_active_profile_name() == "default"
+        assert get_active_hermes_home() == isolated_default
+
+    def test_explicit_profile_resolution_for_isolated_default_uses_pinned_home(self, temp_hermes_home, monkeypatch):
+        """Explicit default-profile resolution must stay on the isolated home."""
+        from api.profiles import get_hermes_home_for_profile, _resolve_profile_home_for_name
+
+        isolated_default = temp_hermes_home / "profiles" / "default"
+        isolated_default.mkdir()
+        for subdir in ["memories", "sessions", "skills", "skins", "logs", "plans", "workspace", "cron"]:
+            (isolated_default / subdir).mkdir(exist_ok=True)
+
+        monkeypatch.setenv("HERMES_HOME", str(isolated_default))
+        monkeypatch.setattr(_profiles_mod, "_DEFAULT_HERMES_HOME", temp_hermes_home)
+        monkeypatch.setattr(_profiles_mod, "_INITIAL_HERMES_HOME", str(isolated_default))
+
+        assert _resolve_profile_home_for_name("default") == isolated_default
+        assert get_hermes_home_for_profile("default") == isolated_default
+        assert get_hermes_home_for_profile("default") != temp_hermes_home
+
+    def test_explicit_foreign_profile_resolution_stays_on_isolated_home(self, temp_single_profile, monkeypatch):
+        """Explicit profile lookups must not escape the isolated startup home."""
+        from api.profiles import get_hermes_home_for_profile, _resolve_profile_home_for_name
+
+        base_home = temp_single_profile.parent.parent
+        monkeypatch.setenv("HERMES_HOME", str(temp_single_profile))
+        monkeypatch.setenv("HERMES_BASE_HOME", "")
+        monkeypatch.setattr(_profiles_mod, "_DEFAULT_HERMES_HOME", base_home)
+        monkeypatch.setattr(_profiles_mod, "_INITIAL_HERMES_HOME", str(temp_single_profile))
+
+        assert _resolve_profile_home_for_name("other_profile") == temp_single_profile
+        assert get_hermes_home_for_profile("other_profile") == temp_single_profile
+
+    def test_list_profiles_prefers_matching_isolated_default_home(self, temp_hermes_home, monkeypatch):
+        """The isolated profiles/default row must not collapse to the base-home row."""
+        isolated_default = temp_hermes_home / "profiles" / "default"
+        isolated_default.mkdir(parents=True)
+        for subdir in ["memories", "sessions", "skills", "skins", "logs", "plans", "workspace", "cron"]:
+            (isolated_default / subdir).mkdir(exist_ok=True)
+
+        class _Info:
+            def __init__(self, name, path, is_default):
+                self.name = name
+                self.path = path
+                self.is_default = is_default
+                self.gateway_running = False
+                self.model = None
+                self.provider = None
+                self.has_env = False
+
+        monkeypatch.setenv("HERMES_HOME", str(isolated_default))
+        monkeypatch.setattr(_profiles_mod, "_DEFAULT_HERMES_HOME", temp_hermes_home)
+        monkeypatch.setattr(_profiles_mod, "_INITIAL_HERMES_HOME", str(isolated_default))
+        monkeypatch.setattr(_profiles_mod, "_get_profile_skills_stats", lambda _path: (0, 0))
+
+        # Inject a STUB hermes_cli.profiles into sys.modules rather than
+        # mock.patch("hermes_cli.profiles.list_profiles", ...): that string
+        # target forces a real import of hermes_cli, which is NOT installed in
+        # CI (the bundled agent isn't on the WebUI test path) -> ModuleNotFoundError.
+        # list_profiles_api() does `from hermes_cli.profiles import list_profiles`
+        # internally, so a stub module satisfies it at the WebUI boundary. (#4454 CI)
+        stub_profiles = types.ModuleType("hermes_cli.profiles")
+        stub_profiles.list_profiles = lambda: [
+            _Info("default", temp_hermes_home, True),
+            _Info("default", isolated_default, False),
+        ]
+        stub_pkg = sys.modules.get("hermes_cli") or types.ModuleType("hermes_cli")
+        monkeypatch.setitem(sys.modules, "hermes_cli", stub_pkg)
+        monkeypatch.setitem(sys.modules, "hermes_cli.profiles", stub_profiles)
+
+        rows = list_profiles_api()
+
+        assert len(rows) == 1
+        assert Path(rows[0]["path"]) == isolated_default
+
+    def test_list_profiles_isolated_fallback_does_not_reenter_root_profile_lookup(self, temp_single_profile, monkeypatch):
+        """The isolated fallback must not recurse back through _is_root_profile."""
+        base_home = temp_single_profile.parent.parent
+        monkeypatch.setenv("HERMES_HOME", str(temp_single_profile))
+        monkeypatch.setenv("HERMES_BASE_HOME", "")
+        monkeypatch.setattr(_profiles_mod, "_DEFAULT_HERMES_HOME", base_home)
+        monkeypatch.setattr(_profiles_mod, "_INITIAL_HERMES_HOME", str(temp_single_profile))
+        monkeypatch.setattr(_profiles_mod, "_get_profile_skills_stats", lambda _path: (0, 0))
+        monkeypatch.setattr(
+            _profiles_mod,
+            "_is_root_profile",
+            lambda _name: (_ for _ in ()).throw(AssertionError("_is_root_profile should not run in isolated fallback")),
+        )
+
+        with mock.patch.dict(sys.modules, {"hermes_cli": None, "hermes_cli.profiles": None}):
+            rows = list_profiles_api()
+
+        assert len(rows) == 1
+        assert rows[0]["name"] == "user1"
+        assert rows[0]["is_default"] is False
+
+
+class TestProfileMutationsInIsolatedMode:
+    """Test that create/delete/switch are rejected (403) in isolated mode."""
+
+    def test_create_profile_rejected_in_isolated_mode(self, temp_single_profile):
+        """create_profile_api should reject creation in isolated mode."""
+        base_home = temp_single_profile.parent.parent
+        # Clear HERMES_BASE_HOME to allow isolated mode detection to fire
+        env_dict = {
+            "HERMES_HOME": str(temp_single_profile),
+            "HERMES_BASE_HOME": "",
+        }
+        with mock.patch.dict(os.environ, env_dict, clear=False):
+            with mock.patch("api.profiles._DEFAULT_HERMES_HOME", base_home):
+                with mock.patch("api.profiles._INITIAL_HERMES_HOME", str(temp_single_profile)):
+                    with pytest.raises(PermissionError, match=".*isolated.*|.*single.*"):
+                        create_profile_api("newprofile")
+
+    def test_delete_profile_rejected_in_isolated_mode(self, temp_single_profile):
+        """delete_profile_api should reject deletion in isolated mode."""
+        base_home = temp_single_profile.parent.parent
+        # Clear HERMES_BASE_HOME to allow isolated mode detection to fire
+        env_dict = {
+            "HERMES_HOME": str(temp_single_profile),
+            "HERMES_BASE_HOME": "",
+        }
+        with mock.patch.dict(os.environ, env_dict, clear=False):
+            with mock.patch("api.profiles._DEFAULT_HERMES_HOME", base_home):
+                with mock.patch("api.profiles._INITIAL_HERMES_HOME", str(temp_single_profile)):
+                    with pytest.raises(PermissionError, match=".*isolated.*|.*single.*"):
+                        delete_profile_api("user1")
+
+    def test_switch_to_different_profile_rejected(self, temp_single_profile):
+        """switch_profile should reject switching to another profile in isolated mode."""
+        base_home = temp_single_profile.parent.parent
+        env_dict = {
+            "HERMES_HOME": str(temp_single_profile),
+            "HERMES_BASE_HOME": "",
+        }
+        with mock.patch.dict(os.environ, env_dict, clear=False):
+            with mock.patch("api.profiles._DEFAULT_HERMES_HOME", base_home):
+                with mock.patch("api.profiles._INITIAL_HERMES_HOME", str(temp_single_profile)):
+                    with pytest.raises(PermissionError, match=".*isolated.*|.*pinned.*"):
+                        switch_profile("other_user")
+
+    def test_switch_to_same_profile_idempotent(self, temp_single_profile):
+        """switch_profile to the isolated profile itself should pass through."""
+        base_home = temp_single_profile.parent.parent
+        env_dict = {
+            "HERMES_HOME": str(temp_single_profile),
+            "HERMES_BASE_HOME": "",
+        }
+        with mock.patch.dict(os.environ, env_dict, clear=False):
+            with mock.patch("api.profiles._DEFAULT_HERMES_HOME", base_home):
+                with mock.patch("api.profiles._INITIAL_HERMES_HOME", str(temp_single_profile)):
+                    # Should not raise PermissionError; may fail downstream
+                    # for other reasons (missing hermes_cli), but the isolation
+                    # guard must pass for the same-name case.
+                    try:
+                        switch_profile("user1")
+                    except PermissionError:
+                        pytest.fail("switch_profile should allow switching to the isolated profile itself")
+                    except (ImportError, ValueError, RuntimeError):
+                        pass  # expected in test env without hermes_cli
+
+    def test_switch_to_same_default_profile_keeps_pinned_home(self, temp_hermes_home, monkeypatch, tmp_path):
+        """A same-name switch for isolated profiles/default must keep using the pinned home."""
+        isolated_default = temp_hermes_home / "profiles" / "default"
+        isolated_default.mkdir(parents=True)
+        (isolated_default / "workspace").mkdir()
+        base_workspace = tmp_path / "base-workspace"
+        isolated_workspace = tmp_path / "isolated-workspace"
+        base_workspace.mkdir()
+        isolated_workspace.mkdir()
+        (temp_hermes_home / "config.yaml").write_text(f"workspace: {base_workspace}\n", encoding="utf-8")
+        (isolated_default / "config.yaml").write_text(f"workspace: {isolated_workspace}\n", encoding="utf-8")
+
+        monkeypatch.setenv("HERMES_HOME", str(isolated_default))
+        monkeypatch.setenv("HERMES_BASE_HOME", "")
+        monkeypatch.setattr(_profiles_mod, "_DEFAULT_HERMES_HOME", temp_hermes_home)
+        monkeypatch.setattr(_profiles_mod, "_INITIAL_HERMES_HOME", str(isolated_default))
+        monkeypatch.setattr(_profiles_mod, "list_profiles_api", lambda: [])
+
+        result = switch_profile("default", process_wide=False)
+
+        assert result["default_workspace"] == str(isolated_workspace.resolve())
+
+    def test_scheduled_cron_jobs_stay_pinned_to_isolated_home(self, temp_single_profile, monkeypatch):
+        """Scheduler jobs must not resolve foreign profile homes in isolated mode."""
+        base_home = temp_single_profile.parent.parent
+        monkeypatch.setenv("HERMES_HOME", str(temp_single_profile))
+        monkeypatch.setenv("HERMES_BASE_HOME", "")
+        monkeypatch.setattr(_profiles_mod, "_DEFAULT_HERMES_HOME", base_home)
+        monkeypatch.setattr(_profiles_mod, "_INITIAL_HERMES_HOME", str(temp_single_profile))
+
+        assert _profiles_mod._home_for_scheduled_cron_job({"id": "job2698", "profile": "other"}) == temp_single_profile
+
+    def test_cli_import_all_profiles_is_rejected_in_isolated_mode(self, monkeypatch):
+        """Direct all_profiles CLI imports must not bypass isolated-profile boundaries."""
+        import api.routes as routes
+
+        captured = {}
+
+        class _Handler:
+            def __init__(self):
+                self.wfile = io.BytesIO()
+
+            def send_response(self, status):
+                self.status = status
+
+            def send_header(self, key, value):
+                pass
+
+            def end_headers(self):
+                pass
+
+        monkeypatch.setattr(routes, "_is_isolated_profile_mode", lambda: True)
+        monkeypatch.setattr(
+            routes,
+            "bad",
+            lambda h, m, c=400: (captured.__setitem__("bad", (m, c)), True)[1],
+        )
+
+        routes._handle_session_import_cli(
+            _Handler(),
+            {"session_id": "foreign-cli-2698", "all_profiles": 1, "profile": "other"},
+        )
+
+        assert captured["bad"] == (
+            "all_profiles import is not allowed in isolated profile mode",
+            403,
+        )
+
+    def test_scheduler_publishes_isolated_profile_after_foreign_job_profile(self, temp_single_profile, monkeypatch):
+        """Scheduled cron completion must publish the isolated profile identity."""
+        events = []
+        base_home = temp_single_profile.parent.parent
+
+        cron_pkg = types.ModuleType("cron")
+        cron_pkg.__path__ = []
+        cron_scheduler = types.ModuleType("cron.scheduler")
+        cron_scheduler.run_job = lambda job: events.append(("run", job["id"])) or "ok"
+
+        class _Ctx:
+            def __init__(self, home):
+                self.home = str(home)
+
+            def __enter__(self):
+                events.append(("enter", self.home))
+                return self
+
+            def __exit__(self, exc_type, exc, tb):
+                events.append(("exit", self.home))
+                return False
+
+        monkeypatch.setitem(sys.modules, "cron", cron_pkg)
+        monkeypatch.setitem(sys.modules, "cron.scheduler", cron_scheduler)
+        monkeypatch.setenv("HERMES_HOME", str(temp_single_profile))
+        monkeypatch.setenv("HERMES_BASE_HOME", "")
+        monkeypatch.setattr(_profiles_mod, "_DEFAULT_HERMES_HOME", base_home)
+        monkeypatch.setattr(_profiles_mod, "_INITIAL_HERMES_HOME", str(temp_single_profile))
+        monkeypatch.setattr(_profiles_mod, "cron_profile_context_for_home", _Ctx)
+        monkeypatch.setattr(
+            _profiles_mod,
+            "publish_session_list_changed",
+            lambda reason, profile=None: events.append(("publish", reason, profile)),
+        )
+
+        _profiles_mod.install_cron_scheduler_profile_isolation()
+
+        assert cron_scheduler.run_job({"id": "job2698", "profile": "other"}) == "ok"
+        assert events[-1] == ("publish", "cron_complete", "user1")
+
+
+class TestNormalModePreservation:
+    """Test that normal mode behavior is completely unchanged."""
+
+    def test_normal_mode_profile_operations_work(self, temp_hermes_home):
+        """Normal mode allows profile creation and deletion."""
+        with mock.patch.dict(os.environ, {"HERMES_HOME": str(temp_hermes_home)}):
+            with mock.patch("api.profiles._DEFAULT_HERMES_HOME", temp_hermes_home):
+                with mock.patch("api.profiles._is_isolated_profile_mode", return_value=False):
+                    # Normal mode should not raise errors for create/delete operations
+                    # (though they may fail for other reasons in this test environment)
+                    try:
+                        # Just verify the isolation guard doesn't trigger
+                        from api.profiles import create_profile_api
+                        # The actual call might fail due to missing hermes_cli,
+                        # but should NOT fail with an "isolated mode" error
+                        try:
+                            create_profile_api("testprof1")
+                        except ValueError as e:
+                            # Should be a different error, not about isolation
+                            assert "isolated" not in str(e).lower()
+                            assert "single" not in str(e).lower()
+                    except ImportError:
+                        # hermes_cli not available, skip
+                        pass
+
+
+def test_profiles_panel_hides_delete_controls_in_single_profile_mode():
+    panels_js = (Path(__file__).resolve().parents[1] / "static" / "panels.js").read_text(encoding="utf-8")
+
+    assert "const singleProfileMode = !!(_profilesCache && _profilesCache.single_profile_mode);" in panels_js
+    assert "if (isDefault || singleProfileMode) hide(delBtn); else show(delBtn);" in panels_js
diff --git a/tests/test_issue3623_profile_visibility.py b/tests/test_issue3623_profile_visibility.py
index fbe2884f..7a86bbe9 100644
--- a/tests/test_issue3623_profile_visibility.py
+++ b/tests/test_issue3623_profile_visibility.py
@@ -5,6 +5,8 @@ import types
 from pathlib import Path
 from types import SimpleNamespace
 
+import pytest
+
 
 REPO_ROOT = Path(__file__).resolve().parents[1]
 
@@ -21,6 +23,15 @@ def _profile_row(name: str, path: Path, *, is_default: bool = False):
     )
 
 
+@pytest.fixture(autouse=True)
+def _clear_profile_rows_cache():
+    import api.profiles as profiles
+
+    profiles._LIST_PROFILES_CACHE = None
+    yield
+    profiles._LIST_PROFILES_CACHE = None
+
+
 def _install_fake_hermes_profiles(monkeypatch, rows):
     hermes_cli = types.ModuleType("hermes_cli")
     profiles_mod = types.ModuleType("hermes_cli.profiles")
diff --git a/tests/test_issue4449_state_dir_contract.py b/tests/test_issue4449_state_dir_contract.py
new file mode 100644
index 00000000..82671698
--- /dev/null
+++ b/tests/test_issue4449_state_dir_contract.py
@@ -0,0 +1,94 @@
+"""Regression tests for the #4449 state-dir contract folded into #4454.
+
+`api.config.STATE_DIR` is a module-level global computed from the environment at
+import time. Exercising how it's derived requires importing config under a
+specific HERMES_HOME / HERMES_WEBUI_STATE_DIR. We do this in a SUBPROCESS rather
+than `importlib.reload(config)` in-process: reloading config inside the shared
+pytest process leaks recomputed globals (STATE_DIR/SESSION_DIR) and stale
+references into later tests (the cancel/stream/health/state-isolation suites),
+which is fragile no matter how carefully env is restored. A subprocess gives a
+truly isolated import and can't pollute the test process.
+"""
+
+from __future__ import annotations
+
+import os
+import subprocess
+import sys
+from pathlib import Path
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+
+_PROBE = (
+    "import api.config as c; "
+    "print(c.STATE_DIR)"
+)
+
+
+def _state_dir_for_env(**env_overrides) -> Path:
+    """Import api.config in a fresh subprocess under the given env and return
+    the resolved STATE_DIR it computes. None-valued overrides unset the var."""
+    env = dict(os.environ)
+    # Start from a clean slate for the two vars under test so the parent
+    # process's pytest values don't bleed in.
+    env.pop("HERMES_HOME", None)
+    env.pop("HERMES_WEBUI_STATE_DIR", None)
+    for key, value in env_overrides.items():
+        if value is None:
+            env.pop(key, None)
+        else:
+            env[key] = str(value)
+    out = subprocess.run(
+        [sys.executable, "-c", _PROBE],
+        cwd=str(REPO_ROOT),
+        env=env,
+        capture_output=True,
+        text=True,
+        timeout=60,
+    )
+    assert out.returncode == 0, f"probe failed: {out.stderr}"
+    return Path(out.stdout.strip()).resolve()
+
+
+def _platform_default_state_dir() -> Path:
+    """What STATE_DIR resolves to with HERMES_HOME + STATE_DIR both unset."""
+    return _state_dir_for_env()
+
+
+def test_config_state_dir_defaults_to_hermes_home_webui(tmp_path):
+    hermes_home = tmp_path / ".hermes" / "profiles" / "isolated"
+    hermes_home.mkdir(parents=True)
+
+    state_dir = _state_dir_for_env(HERMES_HOME=hermes_home)
+    assert state_dir == (hermes_home / "webui").resolve()
+
+
+def test_config_state_dir_unchanged_for_normal_install_hermes_home_unset():
+    """Backward-compat: with HERMES_HOME unset, STATE_DIR stays at the platform
+    default `<~/.hermes>/webui` — a normal install's state must NOT relocate
+    (the #4449/#4454 state-dir move only affects an explicitly-set HERMES_HOME).
+
+    Cross-check: the unset-HERMES_HOME result must NOT equal the result of
+    pointing HERMES_HOME at an arbitrary other base — i.e. the default is
+    genuinely the platform home, not whatever the test environment injected."""
+    default = _platform_default_state_dir()
+    assert default.name == "webui"
+    # Pointing HERMES_HOME elsewhere produces a DIFFERENT dir, proving the unset
+    # case resolves to the platform default rather than echoing an injected base.
+    elsewhere = _state_dir_for_env(HERMES_HOME="/tmp/hermes-4449-elsewhere-base")
+    assert elsewhere == Path("/tmp/hermes-4449-elsewhere-base/webui").resolve()
+    assert default != elsewhere
+
+
+def test_config_state_dir_explicit_override_takes_precedence(tmp_path):
+    """HERMES_WEBUI_STATE_DIR always wins over the HERMES_HOME-derived default,
+    so an operator who pinned a state dir keeps it even in isolated mode."""
+    hermes_home = tmp_path / ".hermes" / "profiles" / "isolated"
+    hermes_home.mkdir(parents=True)
+    explicit = tmp_path / "custom-state"
+
+    state_dir = _state_dir_for_env(
+        HERMES_HOME=hermes_home,
+        HERMES_WEBUI_STATE_DIR=explicit,
+    )
+    assert state_dir == explicit.resolve()