diff --git a/gateway/config_loader.py b/gateway/config_loader.py
index fd276eb431..491685da5b 100644
--- a/gateway/config_loader.py
+++ b/gateway/config_loader.py
@@ -313,7 +313,15 @@ def bridge_core_env_settings(yaml_cfg: dict, platforms_data: dict) -> None:
     Top-level ``require_mention`` → Telegram when the ``telegram:`` section has none: users write it
     alongside ``group_sessions_per_user`` expecting it to work, and the telegram plugin's hook only
     runs when a telegram block exists. Signal ``require_mention`` → ``SIGNAL_REQUIRE_MENTION`` (env wins).
+
+    Both values are ALWAYS seeded into the owning platform's ``extra`` (the adapters read extra first);
+    the process-env write is skipped while a multiplexed secondary profile's scope is active — the
+    loader runs inside ``_profile_runtime_scope`` for every secondary, and a first-writer-wins write
+    there would make the secondary's mention policy the DEFAULT profile's (#80099 class).
     """
+    from gateway.platforms._shared import profile_scoped
+
+    skip_env_bridge = profile_scoped()
     tl_require_mention = yaml_cfg.get("require_mention")
     if tl_require_mention is not None and "require_mention" not in (yaml_cfg.get("telegram") or {}):
         tg_plat = platforms_data.setdefault(Platform.TELEGRAM.value, {})
@@ -323,7 +331,7 @@ def bridge_core_env_settings(yaml_cfg: dict, platforms_data: dict) -> None:
         # require_mention (not a telegram: block), so the telegram plugin's apply_yaml_config_fn hook —
         # which only runs when a telegram config block exists — can't cover the no-telegram-block case
         # (#3979).
-        if not os.getenv("TELEGRAM_REQUIRE_MENTION"):
+        if not skip_env_bridge and not os.getenv("TELEGRAM_REQUIRE_MENTION"):
             os.environ["TELEGRAM_REQUIRE_MENTION"] = str(tl_require_mention).lower()
 
     # Telegram settings → env vars / extra: migrated to the telegram plugin's apply_yaml_config_fn hook
@@ -331,8 +339,11 @@ def bridge_core_env_settings(yaml_cfg: dict, platforms_data: dict) -> None:
     # WhatsApp settings → env vars: migrated to the whatsapp plugin's apply_yaml_config_fn hook
     # (plugins/platforms/whatsapp/adapter.py). #41112 / #3823.
     signal_cfg = yaml_cfg.get("signal", {})
-    if isinstance(signal_cfg, dict) and "require_mention" in signal_cfg and not os.getenv("SIGNAL_REQUIRE_MENTION"):
-        os.environ["SIGNAL_REQUIRE_MENTION"] = str(signal_cfg["require_mention"]).lower()
+    if isinstance(signal_cfg, dict) and "require_mention" in signal_cfg:
+        sig_plat = platforms_data.setdefault(Platform.SIGNAL.value, {})
+        sig_plat.setdefault("extra", {}).setdefault("require_mention", signal_cfg["require_mention"])
+        if not skip_env_bridge and not os.getenv("SIGNAL_REQUIRE_MENTION"):
+            os.environ["SIGNAL_REQUIRE_MENTION"] = str(signal_cfg["require_mention"]).lower()
 
 
 def read_yaml_layers(home: Path) -> dict:
diff --git a/gateway/platforms/_shared.py b/gateway/platforms/_shared.py
index 3edb326d32..202cc3e3ec 100644
--- a/gateway/platforms/_shared.py
+++ b/gateway/platforms/_shared.py
@@ -7,7 +7,7 @@ import it at module top level without cycles.
 from __future__ import annotations
 
 import os
-from typing import Any
+from typing import Any, Callable
 
 # Profile-scoped secret reader for multiplexing support (PR #50094)
 from agent.secret_scope import UnscopedSecretError as _UnscopedSecretError
@@ -48,6 +48,25 @@ def profile_scoped() -> bool:
         return False
 
 
+def yaml_env_setter() -> Callable[[str, Any], None]:
+    """``set_env(name, value)`` for ``apply_yaml_config_fn`` hooks: writes ``os.environ[name]`` only
+    when the var is unset (explicit env wins over YAML) and NEVER while a multiplexed secondary
+    profile's scope is active — the gateway loads every secondary's config inside
+    ``_profile_runtime_scope``, so a write there would pin that profile's policy process-wide and the
+    default profile's adapters would read it as their own (first-writer-wins poisoning, #80099).
+    Hooks seed the same values into the returned ``extra`` so each profile's adapter reads its own.
+    Lists are comma-joined; ``None`` is skipped.
+    """
+    skip = profile_scoped()
+
+    def set_env(name: str, value: Any) -> None:
+        if value is None or skip or os.getenv(name):
+            return
+        os.environ[name] = ",".join(str(v) for v in value) if isinstance(value, list) else str(value)
+
+    return set_env
+
+
 def coerce_port(value: Any, default: int) -> int:
     """``int(value)`` or ``default`` when unparseable."""
     try:
diff --git a/gateway/platforms/signal.py b/gateway/platforms/signal.py
index 4fce8d22cb..1772f349d0 100644
--- a/gateway/platforms/signal.py
+++ b/gateway/platforms/signal.py
@@ -192,7 +192,7 @@ class SignalAdapter(BasePlatformAdapter):
         self.group_allow_from = set(_parse_comma_list(_sig_secret("SIGNAL_GROUP_ALLOWED_USERS", "")))
         _rm_cfg = extra.get("require_mention")
         self.require_mention = (bool(_rm_cfg) if _rm_cfg is not None
-                                else os.getenv("SIGNAL_REQUIRE_MENTION", "false").lower() in TRUTHY_STRINGS)
+                                else (_sig_secret("SIGNAL_REQUIRE_MENTION", "false") or "false").lower() in TRUTHY_STRINGS)
         self.dm_allow_from = set(_parse_comma_list(_sig_secret("SIGNAL_ALLOWED_USERS", "*")))
         self.client: Optional[httpx.AsyncClient] = None
         self._sse_task: Optional[asyncio.Task] = None
diff --git a/plugins/platforms/dingtalk/adapter.py b/plugins/platforms/dingtalk/adapter.py
index 1d73eae067..215296773e 100644
--- a/plugins/platforms/dingtalk/adapter.py
+++ b/plugins/platforms/dingtalk/adapter.py
@@ -50,7 +50,7 @@ from gateway.config import Platform, PlatformConfig
 from gateway.platforms.helpers import MessageDeduplicator, compile_mention_patterns
 from gateway.platforms.base import BasePlatformAdapter, SendResult
 from gateway.platforms.event import MessageEvent
-from gateway.platforms._shared import get_scoped_secret as _get_scoped_secret
+from gateway.platforms._shared import get_scoped_secret as _get_scoped_secret, yaml_env_setter as _yaml_env_setter
 from plugins.platforms.dingtalk.inbound import collect_download_codes, extract_media, extract_text
 
 
@@ -273,7 +273,7 @@ class DingTalkAdapter(BasePlatformAdapter):
     def _compile_mention_patterns(self) -> List[re.Pattern]:
         """Compile optional regex wake-word patterns (config list, or env as JSON / lines / CSV)."""
         patterns = self._extra_get("mention_patterns")
-        if patterns is None and (raw := os.getenv("DINGTALK_MENTION_PATTERNS", "").strip()):
+        if patterns is None and (raw := str(_get_scoped_secret("DINGTALK_MENTION_PATTERNS", "") or "").strip()):
             try:
                 patterns = json.loads(raw)
             except Exception:
@@ -690,12 +690,6 @@ def _manual_credential_entry(prompt, save_env_value, print_success) -> None:
     print_success("DingTalk credentials saved")
 
 
-def _bridge_list_env(env_name: str, value) -> None:
-    """Export a YAML list/scalar as a comma-joined env var unless the env var is already set."""
-    if value is not None and not os.getenv(env_name):
-        os.environ[env_name] = ",".join(str(v) for v in value) if isinstance(value, list) else str(value)
-
-
 def _nested_allowed_users(yaml_cfg: dict, dingtalk_cfg: dict):
     """Allowlist from ``extra.allowed_users``: this block's own extra first, then ``gateway.platforms.dingtalk.extra`` and ``platforms.dingtalk.extra``."""
     _gw = yaml_cfg.get("gateway")
@@ -708,21 +702,28 @@ def _nested_allowed_users(yaml_cfg: dict, dingtalk_cfg: dict):
 
 
 def _apply_yaml_config(yaml_cfg: dict, dingtalk_cfg: dict) -> dict | None:
-    """Translate config.yaml dingtalk: keys into DINGTALK_* env vars (apply_yaml_config_fn); env wins, returns None. The docs put the allowlist at
-    ``gateway.platforms.dingtalk.extra.allowed_users`` but gateway authz only consults DINGTALK_ALLOWED_USERS, so nested-only allowlists are bridged too.
+    """Translate config.yaml dingtalk: keys into DINGTALK_* env vars + ``PlatformConfig.extra`` (apply_yaml_config_fn);
+    env wins. The docs put the allowlist at ``gateway.platforms.dingtalk.extra.allowed_users`` but gateway authz only
+    consults DINGTALK_ALLOWED_USERS, so nested-only allowlists are bridged too.
 
     Implements the apply_yaml_config_fn contract (#24849). Mirrors the legacy dingtalk_cfg block from
-    gateway/config.py::load_gateway_config(). Env vars take precedence over YAML (each assignment guarded by
-    not os.getenv(...)). Returns None — everything flows through env.
+    gateway/config.py::load_gateway_config(). The env write is skipped under a multiplexed secondary profile's
+    scope; the adapter's ``_extra_get`` readers consume the seeded extra.
     """
+    _set_env = _yaml_env_setter()
+    seeded: dict = {}
     for key, env, encode in (("require_mention", "DINGTALK_REQUIRE_MENTION", lambda v: str(v).lower()), ("mention_patterns", "DINGTALK_MENTION_PATTERNS", json.dumps)):
-        if key in dingtalk_cfg and not os.getenv(env):
-            os.environ[env] = encode(dingtalk_cfg[key])
+        if key in dingtalk_cfg:
+            seeded[key] = dingtalk_cfg[key]
+            _set_env(env, encode(dingtalk_cfg[key]))
     allowed = dingtalk_cfg.get("allowed_users")
-    for env, value in (("DINGTALK_FREE_RESPONSE_CHATS", dingtalk_cfg.get("free_response_chats")), ("DINGTALK_ALLOWED_CHATS", dingtalk_cfg.get("allowed_chats")),
-                       ("DINGTALK_ALLOWED_USERS", _nested_allowed_users(yaml_cfg, dingtalk_cfg) if allowed is None else allowed)):
-        _bridge_list_env(env, value)
-    return None
+    for key, env, value in (("free_response_chats", "DINGTALK_FREE_RESPONSE_CHATS", dingtalk_cfg.get("free_response_chats")),
+                            ("allowed_chats", "DINGTALK_ALLOWED_CHATS", dingtalk_cfg.get("allowed_chats")),
+                            ("allowed_users", "DINGTALK_ALLOWED_USERS", _nested_allowed_users(yaml_cfg, dingtalk_cfg) if allowed is None else allowed)):
+        if value is not None:
+            seeded[key] = value
+            _set_env(env, value)
+    return seeded or None
 
 
 def _is_connected(config) -> bool:
diff --git a/plugins/platforms/discord/adapter.py b/plugins/platforms/discord/adapter.py
index 0489c16656..88a18180b8 100644
--- a/plugins/platforms/discord/adapter.py
+++ b/plugins/platforms/discord/adapter.py
@@ -268,7 +268,7 @@ from gateway.platforms.base import (
 )
 from gateway.platforms.event import MessageEvent, MessageType, ProcessingOutcome
 from tools.url_safety import is_safe_url
-from gateway.platforms._shared import profile_scoped as _profile_scoped_config_load
+from gateway.platforms._shared import yaml_env_setter as _yaml_env_setter
 
 
 async def _read_url_image_with_redirect_guard(
@@ -602,11 +602,12 @@ def check_discord_requirements() -> bool:
     return True
 
 
-def _build_allowed_mentions():
+def _build_allowed_mentions(extra: Optional[dict] = None):
     """Build Discord ``AllowedMentions`` denying @everyone/@here/roles by default (any LLM output
     with ``@everyone`` would otherwise ping the server); user / replied-user pings stay on.
 
-    Override via env (or ``discord.allow_mentions.*`` in config.yaml):
+    Override via ``discord.allow_mentions.*`` in config.yaml (``extra["allow_mentions"]``, per profile)
+    or env — a secondary multiplex profile never sees the default profile's env (#72348):
 
         DISCORD_ALLOW_MENTION_EVERYONE      default false  — @everyone + @here
         DISCORD_ALLOW_MENTION_ROLES         default false  — @role pings
@@ -615,12 +616,19 @@ def _build_allowed_mentions():
     """
     if not DISCORD_AVAILABLE:
         return None
-    _b = _env_bool
+    configured = (extra or {}).get("allow_mentions")
+    configured = configured if isinstance(configured, dict) else {}
+
+    def _b(name: str, key: str, default: bool) -> bool:
+        if (raw := configured.get(key)) is not None:
+            return str(raw).strip().lower() in {"true", "1", "yes", "on"}
+        return _env_bool(name, default)
+
     return discord.AllowedMentions(
-        everyone=_b("DISCORD_ALLOW_MENTION_EVERYONE", False),
-        roles=_b("DISCORD_ALLOW_MENTION_ROLES", False),
-        users=_b("DISCORD_ALLOW_MENTION_USERS", True),
-        replied_user=_b("DISCORD_ALLOW_MENTION_REPLIED_USER", True),
+        everyone=_b("DISCORD_ALLOW_MENTION_EVERYONE", "everyone", False),
+        roles=_b("DISCORD_ALLOW_MENTION_ROLES", "roles", False),
+        users=_b("DISCORD_ALLOW_MENTION_USERS", "users", True),
+        replied_user=_b("DISCORD_ALLOW_MENTION_REPLIED_USER", "replied_user", True),
     )
 
 
@@ -1218,7 +1226,7 @@ class DiscordAdapter(DiscordMediaMixin, BasePlatformAdapter):
             self._client = commands.Bot(
                 command_prefix="!",  # Not really used, we handle raw messages
                 intents=intents,
-                allowed_mentions=_build_allowed_mentions(),
+                allowed_mentions=_build_allowed_mentions(getattr(self.config, "extra", None)),
                 **proxy_kwargs_for_bot(proxy_url),
             )
             adapter_self = self  # capture for closure
@@ -2745,8 +2753,8 @@ class DiscordAdapter(DiscordMediaMixin, BasePlatformAdapter):
             return False
 
     def _reactions_enabled(self) -> bool:
-        """Check if message reactions are enabled via config/env."""
-        return os.getenv("DISCORD_REACTIONS", "true").lower() not in {"false", "0", "no"}
+        """Reactions enabled via ``extra.reactions`` (YAML, per profile) or ``DISCORD_REACTIONS``."""
+        return self._extra_or_env_flag("reactions", "DISCORD_REACTIONS", "true", truthy=False)
 
     async def on_processing_start(self, event: MessageEvent) -> None:
         """Add an in-progress reaction and record durable handling state."""
@@ -4555,7 +4563,8 @@ class DiscordAdapter(DiscordMediaMixin, BasePlatformAdapter):
         """Boolean from ``config.extra[key]`` (str parsed permissively) else ``env_key``.
         ``truthy=True`` env values must be in {true,1,yes,on}; ``truthy=False`` env values are on
         unless in {false,0,no,off} — matching each flag's historical default shape."""
-        configured = self.config.extra.get(key)
+        extra = getattr(self.config, "extra", None)
+        configured = extra.get(key) if isinstance(extra, dict) else None
         if configured is not None:
             if isinstance(configured, str):
                 return configured.lower() not in {"false", "0", "no", "off"}
@@ -4774,10 +4783,7 @@ class DiscordAdapter(DiscordMediaMixin, BasePlatformAdapter):
 
     def _discord_history_backfill(self) -> bool:
         """Return whether history backfill is enabled for shared sessions."""
-        configured = self.config.extra.get("history_backfill")
-        if configured is not None:
-            return self._extra_or_env_flag("history_backfill", "DISCORD_HISTORY_BACKFILL", "true", truthy=True)
-        return os.getenv("DISCORD_HISTORY_BACKFILL", "true").lower() in {"true", "1", "yes"}
+        return self._extra_or_env_flag("history_backfill", "DISCORD_HISTORY_BACKFILL", "true", truthy=True)
 
     def _discord_history_backfill_limit(self) -> int:
         """Max messages scanned backwards; a safety cap since scans usually stop at the bot's last message."""
@@ -5203,7 +5209,7 @@ class DiscordAdapter(DiscordMediaMixin, BasePlatformAdapter):
     def _approval_mention_content(self) -> Optional[str]:
         """User mentions for approval prompts, gated on ``discord.approval_mentions``
         (``DISCORD_APPROVAL_MENTIONS``). Only numeric allowlist entries; default off."""
-        if not _env_bool("DISCORD_APPROVAL_MENTIONS", False):
+        if not self._extra_or_env_flag("approval_mentions", "DISCORD_APPROVAL_MENTIONS", "false", truthy=True):
             return None
         user_ids = sorted(uid for uid in self._allowed_user_ids if str(uid).isdigit())
         if not user_ids:
@@ -5727,7 +5733,7 @@ class DiscordAdapter(DiscordMediaMixin, BasePlatformAdapter):
         if not is_thread and not isinstance(message.channel, discord.DMChannel):
             no_thread_channels = self._get_no_thread_channels()
             skip_thread = bool(channel_keys & no_thread_channels) or is_free_channel
-            auto_thread = os.getenv("DISCORD_AUTO_THREAD", "true").lower() in {"true", "1", "yes"}
+            auto_thread = self._extra_or_env_flag("auto_thread", "DISCORD_AUTO_THREAD", "true", truthy=True)
             is_reply_message = getattr(message, "type", None) == discord.MessageType.reply
             if auto_thread and not skip_thread and not is_voice_linked_channel and not is_reply_message:
                 thread = await self._auto_create_thread(message)
@@ -6955,16 +6961,18 @@ def _apply_yaml_config(yaml_cfg: dict, discord_cfg: dict) -> dict | None:
     Implements the ``apply_yaml_config_fn`` contract (#24836). Mirrors the legacy ``discord_cfg`` block that
     used to live in ``gateway/config.py::load_gateway_config()`` before this migration.
     """
-    def _env_default(env_key: str, value) -> None:
-        # First-writer-wins: an explicit env var always beats the YAML value.
-        if not os.getenv(env_key):
-            os.environ[env_key] = value
+    # Every env write is first-writer-wins (an explicit env var beats YAML) and is skipped for a
+    # profile-scoped multiplex load: a secondary profile's settings must never land in process-global
+    # env where they'd become another profile's policy (#72348). Everything is seeded into extra too.
+    _env_default = _yaml_env_setter()
 
     def _csv(value) -> str:
         return ",".join(str(v) for v in value) if isinstance(value, list) else str(value)
 
+    seeded_extra = {}
     for key, env_key in _YAML_BOOL_ENV_KEYS:
         if key in discord_cfg:
+            seeded_extra[key] = discord_cfg[key]  # original type: the shared-key loop seeds bools as bools
             _env_default(env_key, str(discord_cfg[key]).lower())
     platforms_cfg = yaml_cfg.get("platforms")
     platform_extra_cfg = {}
@@ -6974,13 +6982,6 @@ def _apply_yaml_config(yaml_cfg: dict, discord_cfg: dict) -> dict | None:
             candidate_extra = discord_platform_cfg.get("extra")
             if isinstance(candidate_extra, dict):
                 platform_extra_cfg = candidate_extra
-    seeded_extra = {}
-    # Gate keys are ALWAYS seeded into PlatformConfig.extra (per-profile lists); the os.environ writes
-    # below are first-writer-wins for legacy consumers and skipped for profile-scoped multiplex loads.
-    # The os.environ writes below remain first-writer-wins for legacy env-only consumers, but are skipped
-    # for profile-scoped loads under multiplex — a secondary profile's gates must never land in
-    # process-global env where they'd become another profile's policy. See #72348.
-    _skip_env_bridge = _profile_scoped_config_load()
 
     def _gate(key: str, env_key: str, *, from_platform_extra: bool, lower: bool = False) -> None:
         value = discord_cfg[key] if key in discord_cfg else (platform_extra_cfg.get(key) if from_platform_extra else None)
@@ -6988,8 +6989,7 @@ def _apply_yaml_config(yaml_cfg: dict, discord_cfg: dict) -> dict | None:
             return
         text = str(value).lower() if lower else _csv(value)
         seeded_extra[key] = text
-        if not _skip_env_bridge:
-            _env_default(env_key, text)
+        _env_default(env_key, text)
 
     _gate("allow_from", "DISCORD_ALLOWED_USERS", from_platform_extra=True)
     _gate("allowed_roles", "DISCORD_ALLOWED_ROLES", from_platform_extra=True)
@@ -7000,10 +7000,12 @@ def _apply_yaml_config(yaml_cfg: dict, discord_cfg: dict) -> dict | None:
         else platform_extra_cfg.get("approval_mentions")
     )
     if approval_mentions_cfg is not None:
+        seeded_extra["approval_mentions"] = approval_mentions_cfg
         _env_default("DISCORD_APPROVAL_MENTIONS", str(approval_mentions_cfg).lower())
     _gate("free_response_channels", "DISCORD_FREE_RESPONSE_CHANNELS", from_platform_extra=False)
     for key, env_key in (("auto_thread", "DISCORD_AUTO_THREAD"), ("reactions", "DISCORD_REACTIONS")):
         if key in discord_cfg:
+            seeded_extra[key] = discord_cfg[key]
             _env_default(env_key, str(discord_cfg[key]).lower())
     backfill_cfg = discord_cfg.get("missed_message_backfill")
     if isinstance(backfill_cfg, dict):
@@ -7013,13 +7015,16 @@ def _apply_yaml_config(yaml_cfg: dict, discord_cfg: dict) -> dict | None:
     _gate("no_thread_channels", "DISCORD_NO_THREAD_CHANNELS", from_platform_extra=False)
     # history_backfill: recover mention-gated channel messages between bot turns.
     if "history_backfill" in discord_cfg:
+        seeded_extra["history_backfill"] = discord_cfg["history_backfill"]
         _env_default("DISCORD_HISTORY_BACKFILL", str(discord_cfg["history_backfill"]).lower())
     hbl = discord_cfg.get("history_backfill_limit")
     if hbl is not None:
+        seeded_extra["history_backfill_limit"] = hbl
         _env_default("DISCORD_HISTORY_BACKFILL_LIMIT", str(hbl))
     # allow_mentions: safe defaults live in the adapter; these keys only override when set.
     allow_mentions_cfg = discord_cfg.get("allow_mentions")
     if isinstance(allow_mentions_cfg, dict):
+        seeded_extra["allow_mentions"] = dict(allow_mentions_cfg)
         for yaml_key in ("everyone", "roles", "users", "replied_user"):
             if yaml_key in allow_mentions_cfg:
                 _env_default(f"DISCORD_ALLOW_MENTION_{yaml_key.upper()}", str(allow_mentions_cfg[yaml_key]).lower())
@@ -7037,8 +7042,8 @@ def _apply_yaml_config(yaml_cfg: dict, discord_cfg: dict) -> dict | None:
             value = _websocket_liveness_cfg.get(legacy_key)
         if value is not None:
             seeded_extra[primary_key] = value
-            if env_key and not os.getenv(env_key):
-                os.environ[env_key] = str(value)
+            if env_key:
+                _env_default(env_key, str(value))
     return seeded_extra or None
 
 
diff --git a/plugins/platforms/feishu/adapter.py b/plugins/platforms/feishu/adapter.py
index 584eb17b7c..a3be3a6efb 100644
--- a/plugins/platforms/feishu/adapter.py
+++ b/plugins/platforms/feishu/adapter.py
@@ -92,7 +92,7 @@ from gateway.status import acquire_scoped_lock, release_scoped_lock
 from hermes_constants import get_hermes_home
 from utils import atomic_json_write, env_float, env_int
 
-from gateway.platforms._shared import get_scoped_secret as _get_scoped_secret
+from gateway.platforms._shared import get_scoped_secret as _get_scoped_secret, yaml_env_setter as _yaml_env_setter
 
 
 logger = logging.getLogger(__name__)
@@ -1283,11 +1283,10 @@ class FeishuAdapter(BasePlatformAdapter):
                     require_mention=_to_boolean(rule_cfg["require_mention"]) if "require_mention" in rule_cfg else None,
                 )
 
-        # Env-only so adapter and gateway auth bypass share one source (yaml feishu.allow_bots
-        # is bridged to the env var at config load). Scoped read: under multiplex a secondary
-        # profile's .env must govern its own adapter.
+        # Scoped read: under multiplex a secondary profile's .env must govern its own adapter; yaml
+        # feishu.allow_bots reaches it via ``extra`` (the env bridge is skipped under its scope).
         # See #86905.
-        allow_bots = _get_scoped_secret("FEISHU_ALLOW_BOTS", "none").strip().lower()
+        allow_bots = str(_get_scoped_secret("FEISHU_ALLOW_BOTS", "") or extra.get("allow_bots") or "none").strip().lower()
         if allow_bots not in {"none", "mentions", "all"}:
             logger.warning(
                 "[Feishu] Unknown allow_bots=%r, falling back to 'none'. Valid: none, mentions, all.",
@@ -4295,14 +4294,17 @@ def interactive_setup() -> None:
 
 
 def _apply_yaml_config(yaml_cfg: dict, feishu_cfg: dict) -> dict | None:
-    """apply_yaml_config_fn: bridge config.yaml feishu.allow_bots to FEISHU_ALLOW_BOTS (env wins); returns None.
+    """apply_yaml_config_fn: bridge config.yaml feishu.allow_bots to FEISHU_ALLOW_BOTS (env wins) and seed
+    ``extra.allow_bots`` so a multiplexed secondary profile's adapter reads its own value.
 
     Implements the apply_yaml_config_fn contract (#24849). Mirrors the legacy feishu_cfg block from
     gateway/config.py::load_gateway_config() (allow_bots). Env vars take precedence over YAML.
     """
-    if "allow_bots" in feishu_cfg and not os.getenv("FEISHU_ALLOW_BOTS"):
-        os.environ["FEISHU_ALLOW_BOTS"] = str(feishu_cfg["allow_bots"]).lower()
-    return None
+    if "allow_bots" not in feishu_cfg:
+        return None
+    _set_env = _yaml_env_setter()
+    _set_env("FEISHU_ALLOW_BOTS", str(feishu_cfg["allow_bots"]).lower())
+    return {"allow_bots": str(feishu_cfg["allow_bots"]).lower()}
 
 
 def _is_connected(config) -> bool:
diff --git a/plugins/platforms/matrix/adapter.py b/plugins/platforms/matrix/adapter.py
index 02e3d8e0af..55ba3c0dad 100644
--- a/plugins/platforms/matrix/adapter.py
+++ b/plugins/platforms/matrix/adapter.py
@@ -38,6 +38,7 @@ from pathlib import Path
 from typing import Any, Dict, Optional, Set
 
 from agent.secret_scope import UnscopedSecretError, get_secret
+from gateway.platforms._shared import yaml_env_setter as _yaml_env_setter
 
 try:
     from mautrix.types import (
@@ -853,12 +854,14 @@ class MatrixAdapter(BasePlatformAdapter):
         # If non-empty, bot ONLY responds in these rooms (whitelist); DMs exempt.
         self._allowed_rooms: Set[str] = _extra_csv_set(config, "allowed_rooms", "MATRIX_ALLOWED_ROOMS")
         self._allow_room_mentions: bool = _env_truthy("MATRIX_ALLOW_ROOM_MENTIONS", "false")
-        self._auto_thread: bool = _env_truthy("MATRIX_AUTO_THREAD", "true")
+        # Extra-first: the YAML bridge seeds these into extra and skips the env write under a
+        # multiplexed secondary scope, where os.environ holds the DEFAULT profile's flags.
+        self._auto_thread: bool = self._extra_truthy(config, "auto_thread", "MATRIX_AUTO_THREAD", "true")
         self._dm_auto_thread: bool = _env_truthy("MATRIX_DM_AUTO_THREAD", "false")
-        self._dm_mention_threads: bool = _env_truthy("MATRIX_DM_MENTION_THREADS", "false")
-        raw_session_scope = os.getenv("MATRIX_SESSION_SCOPE", "auto").strip().lower()
+        self._dm_mention_threads: bool = self._extra_truthy(config, "dm_mention_threads", "MATRIX_DM_MENTION_THREADS", "false")
+        raw_session_scope = str(config.extra.get("session_scope") or os.getenv("MATRIX_SESSION_SCOPE", "auto")).strip().lower()
         self._matrix_session_scope = raw_session_scope if raw_session_scope in {"auto", "room", "thread"} else "auto"
-        self._process_notices: bool = _env_truthy("MATRIX_PROCESS_NOTICES", "false")
+        self._process_notices: bool = self._extra_truthy(config, "process_notices", "MATRIX_PROCESS_NOTICES", "false")
         self._reactions_enabled: bool = os.getenv("MATRIX_REACTIONS", "true").lower() not in {"false", "0", "no"}
         self._pending_reactions: dict[tuple[str, str], str] = {}
         # Let the final message land before redacting reactions ("missing event" in some
@@ -906,6 +909,14 @@ class MatrixAdapter(BasePlatformAdapter):
         self._processed_events_set.add(event_id)
         return False
 
+    @staticmethod
+    def _extra_truthy(config, key: str, env_name: str, default: str) -> bool:
+        """``config.extra[key]`` (YAML-bridged, per profile) else the env var, true/1/yes semantics."""
+        configured = config.extra.get(key)
+        if configured is None:
+            return _env_truthy(env_name, default)
+        return configured if isinstance(configured, bool) else str(configured).lower() in ("true", "1", "yes")
+
     @staticmethod
     def _configured_bool(config, key: str) -> Optional[bool]:
         """Parse a YAML bool / "true"/"off"-style string from config.extra; None if unset."""
@@ -3033,25 +3044,28 @@ _YAML_LIST_KEYS = (
 
 
 def _apply_yaml_config(yaml_cfg: dict, matrix_cfg: dict) -> dict | None:
-    """apply_yaml_config_fn: config.yaml matrix: keys → MATRIX_* env (env wins). Returns None. Lowercased
-    flags apply whenever the key is present (None still writes "none"); list-valued keys skip None.
+    """apply_yaml_config_fn: config.yaml matrix: keys → MATRIX_* env (env wins) + ``PlatformConfig.extra``.
+    Lowercased flags apply whenever the key is present (None still writes "none"); list-valued keys skip None.
 
     Implements the apply_yaml_config_fn contract (#24849). Mirrors the legacy matrix_cfg block from
-    gateway/config.py::load_gateway_config(). Env vars take precedence over YAML. Returns None — everything
-    flows through env.
+    gateway/config.py::load_gateway_config(). The env write is skipped under a multiplexed secondary
+    profile's scope; the seeded ``extra`` is what its adapter reads (extra-first readers).
     """
+    _set_env = _yaml_env_setter()
+    seeded: dict = {}
     for key, env_name in _YAML_LOWER_KEYS:
-        if key in matrix_cfg and not os.getenv(env_name):
-            os.environ[env_name] = str(matrix_cfg[key]).lower()
+        if key in matrix_cfg:
+            seeded[key] = matrix_cfg[key]
+            _set_env(env_name, str(matrix_cfg[key]).lower())
     for key, env_name in _YAML_LIST_KEYS:
         value = matrix_cfg.get(key)
-        if value is not None and not os.getenv(env_name):
-            if isinstance(value, list):
-                value = ",".join(str(v) for v in value)
-            os.environ[env_name] = str(value)
-    if "max_message_length" in matrix_cfg and not os.getenv("MATRIX_MAX_MESSAGE_LENGTH"):
-        os.environ["MATRIX_MAX_MESSAGE_LENGTH"] = str(matrix_cfg["max_message_length"])
-    return None
+        if value is not None:
+            seeded[key] = value
+            _set_env(env_name, value)
+    if "max_message_length" in matrix_cfg:
+        seeded["max_message_length"] = matrix_cfg["max_message_length"]
+        _set_env("MATRIX_MAX_MESSAGE_LENGTH", str(matrix_cfg["max_message_length"]))
+    return seeded or None
 
 
 def _is_connected(config) -> bool:
diff --git a/plugins/platforms/slack/adapter.py b/plugins/platforms/slack/adapter.py
index b6eecc4537..6d55a9922c 100644
--- a/plugins/platforms/slack/adapter.py
+++ b/plugins/platforms/slack/adapter.py
@@ -35,7 +35,7 @@ sys.path.insert(0, str(_Path(__file__).resolve().parents[3]))
 from agent.secret_scope import UnscopedSecretError, get_secret
 from gateway.config import Platform, PlatformConfig
 from gateway.platforms.helpers import MessageDeduplicator
-from gateway.platforms._shared import get_scoped_secret as _get_scoped_secret
+from gateway.platforms._shared import get_scoped_secret as _get_scoped_secret, yaml_env_setter as _yaml_env_setter
 from gateway.platforms.base import (
     gateway_trust_env, BasePlatformAdapter,
     SendResult, SUPPORTED_DOCUMENT_TYPES, SUPPORTED_VIDEO_TYPES, _TEXT_INJECT_EXTENSIONS,
@@ -2938,8 +2938,11 @@ class SlackAdapter(BasePlatformAdapter):
         return await self._react(channel, timestamp, emoji, team_id, remove=True)
 
     def _reactions_enabled(self) -> bool:
-        """Whether message reactions are enabled (``SLACK_REACTIONS`` env)."""
-        return os.getenv("SLACK_REACTIONS", "true").lower() not in {"false", "0", "no"}
+        """Whether message reactions are enabled (``extra.reactions`` / ``SLACK_REACTIONS``)."""
+        configured = self.config.extra.get("reactions")
+        if configured is None:
+            configured = os.getenv("SLACK_REACTIONS", "true")
+        return str(configured).lower() not in {"false", "0", "no"}
 
     def _reacting_target(self, event: MessageEvent) -> Optional[Tuple[str, str, Any]]:
         """``(ts, team_id, marker)`` when reactions are on and ``event`` is being tracked."""
@@ -6452,22 +6455,27 @@ _YAML_LIST_KEYS = (
 
 
 def _apply_yaml_config(yaml_cfg: dict, slack_cfg: dict) -> dict | None:
-    """``apply_yaml_config_fn`` hook: ``slack:`` YAML keys → ``SLACK_*`` env vars (the adapter reads
-    ``os.getenv()``; explicit env wins). Returns None: nothing is seeded into ``extra``.
+    """``apply_yaml_config_fn`` hook: ``slack:`` YAML keys → ``SLACK_*`` env vars (explicit env wins) and
+    ``PlatformConfig.extra`` (extra-first readers; the env write is skipped under a multiplexed
+    secondary profile's scope so its policy never becomes the default profile's).
 
     Implements the ``apply_yaml_config_fn`` contract (#24849). Mirrors the legacy ``slack_cfg`` block that
     used to live in ``gateway/config.py::load_gateway_config()`` before this migration.
     """
+    _set_env = _yaml_env_setter()
+    seeded: dict = {}
     for key, env in _YAML_BOOL_KEYS:
-        if key in slack_cfg and not os.getenv(env):
-            os.environ[env] = str(slack_cfg[key]).lower()
+        if key in slack_cfg:
+            seeded[key] = slack_cfg[key]  # original type: the shared-key loop already seeded bools as bools
+            _set_env(env, str(slack_cfg[key]).lower())
     for key, env, list_types in _YAML_LIST_KEYS:
         val = slack_cfg.get(key)
-        if val is not None and not os.getenv(env):
+        if val is not None:
+            seeded[key] = val
             if list_types and isinstance(val, list_types):
                 val = ",".join(str(v) for v in val)
-            os.environ[env] = str(val)
-    return None
+            _set_env(env, str(val))
+    return seeded or None
 
 
 def _is_connected(config) -> bool:
diff --git a/plugins/platforms/telegram/adapter.py b/plugins/platforms/telegram/adapter.py
index 986465ea57..0085982926 100644
--- a/plugins/platforms/telegram/adapter.py
+++ b/plugins/platforms/telegram/adapter.py
@@ -5027,7 +5027,7 @@ class TelegramAdapter(BasePlatformAdapter):
             if isinstance(configured, str):
                 return configured.lower() in {"true", "1", "yes", "on"}
             return bool(configured)
-        return os.getenv(env_name, default).lower() in {"true", "1", "yes", "on"}
+        return _scoped_gate_env(env_name, default).lower() in {"true", "1", "yes", "on"}
 
     def _extra_str_set(self, key: str, env_name: str) -> set[str]:
         """Comma/list allowlist from ``config.extra[key]``, else the profile-scoped env var."""
@@ -5122,7 +5122,7 @@ class TelegramAdapter(BasePlatformAdapter):
         """Compile optional regex wake-word patterns for group triggers."""
         patterns = self.config.extra.get("mention_patterns")
         if patterns is None:
-            raw = os.getenv("TELEGRAM_MENTION_PATTERNS", "").strip()
+            raw = _scoped_gate_env("TELEGRAM_MENTION_PATTERNS", "").strip()
             if raw:
                 try:
                     loaded = json.loads(raw)
@@ -6354,8 +6354,11 @@ class TelegramAdapter(BasePlatformAdapter):
     # -- Message reactions (processing lifecycle) --
 
     def _reactions_enabled(self) -> bool:
-        """Reactions enabled via TELEGRAM_REACTIONS env/config."""
-        return os.getenv("TELEGRAM_REACTIONS", "false").lower() not in {"false", "0", "no"}
+        """Reactions enabled via ``extra.reactions`` (YAML, per profile) or TELEGRAM_REACTIONS."""
+        configured = self.config.extra.get("reactions")
+        if configured is None:
+            configured = _scoped_gate_env("TELEGRAM_REACTIONS", "false")
+        return str(configured).lower() not in {"false", "0", "no"}
 
     async def _set_reaction(self, chat_id: str, message_id: str, emoji: Optional[str]) -> bool:
         """Set a single emoji reaction (``None`` clears all bot-set reactions, the documented Bot API way)."""
@@ -6478,34 +6481,25 @@ def _apply_yaml_config(yaml_cfg: dict, telegram_cfg: dict) -> dict | None:
     gateway/config.py::load_gateway_config().
     """
     import json as _json
+    from gateway.platforms._shared import yaml_env_setter
     extras: dict = {}
-    # Under multiplex a secondary profile's authorization gates must NOT hit the process-global env
-    # (first-writer-wins would pin them for every profile); they flow via extra/secret scope.
-    try:
-        # See #72348.
-        from agent.secret_scope import current_secret_scope, is_multiplex_active
-        _skip_env_bridge = bool(is_multiplex_active() and current_secret_scope() is not None)
-    except Exception:
-        _skip_env_bridge = False
-
-    def _set_env(env: str, value: str) -> None:
-        if not os.getenv(env):
-            os.environ[env] = value
+    # Under multiplex a secondary profile's settings must NOT hit the process-global env (first-writer-wins
+    # would pin them for every profile, #72348); yaml_env_setter skips the write under its scope and the
+    # values flow via extra/secret scope instead.
+    _set_env = yaml_env_setter()
 
     def _bridge_lower(key: str, env: str) -> None:
         if key in telegram_cfg:
+            extras.setdefault(key, telegram_cfg[key])
             _set_env(env, str(telegram_cfg[key]).lower())
 
     def _bridge_gate(key: str, env: str, value: Any, *, seed_extra: bool = False) -> None:
-        """CSV allowlist gate: list → comma-joined; skipped under multiplex secret scope."""
+        """CSV allowlist gate: list → comma-joined; env write skipped under multiplex secret scope."""
         if value is None:
             return
         if seed_extra:
             extras.setdefault(key, value)
-        if isinstance(value, list):
-            value = ",".join(str(v) for v in value)
-        if not _skip_env_bridge:
-            _set_env(env, str(value))
+        _set_env(env, value)
 
     if "disable_topic_auto_rename" in telegram_cfg:
         extras.setdefault("disable_topic_auto_rename", telegram_cfg["disable_topic_auto_rename"])
diff --git a/plugins/platforms/whatsapp/adapter.py b/plugins/platforms/whatsapp/adapter.py
index 7ce812384d..d001c0215f 100644
--- a/plugins/platforms/whatsapp/adapter.py
+++ b/plugins/platforms/whatsapp/adapter.py
@@ -13,7 +13,7 @@ from functools import wraps
 from pathlib import Path
 from typing import Dict, Optional, Any
 
-from gateway.platforms._shared import get_scoped_secret
+from gateway.platforms._shared import get_scoped_secret, yaml_env_setter
 from hermes_cli._subprocess_compat import windows_detach_popen_kwargs
 from hermes_constants import (find_node_executable, get_hermes_dir, with_hermes_node_path)
 
@@ -924,22 +924,29 @@ _YAML_LIST_KEYS = (("free_response_chats", "WHATSAPP_FREE_RESPONSE_CHATS"), ("al
 
 
 def _apply_yaml_config(yaml_cfg: dict, whatsapp_cfg: dict) -> dict | None:
-    """config.yaml whatsapp: keys → WHATSAPP_* env vars (apply_yaml_config_fn contract; returns None).
+    """config.yaml whatsapp: keys → WHATSAPP_* env vars + ``PlatformConfig.extra`` (apply_yaml_config_fn).
 
     Mirrors the legacy whatsapp_cfg block from gateway/config.py::load_gateway_config(). Env vars take
-    precedence over YAML. Returns None — everything flows through env. See #24849.
+    precedence over YAML. The env write is skipped under a multiplexed secondary profile's scope (#80099);
+    every field has an extra-first reader (``WhatsAppAdapter.__init__`` policies/allowlists,
+    ``whatsapp_common`` require_mention/free_response_chats/mention_patterns). See #24849.
     """
     import json as _json
+    _set_env = yaml_env_setter()
+    seeded: dict = {}
     for key, env in _YAML_LOWERCASE_KEYS:
-        if key in whatsapp_cfg and not os.getenv(env):
-            os.environ[env] = str(whatsapp_cfg[key]).lower()
-    if "mention_patterns" in whatsapp_cfg and not os.getenv("WHATSAPP_MENTION_PATTERNS"):
-        os.environ["WHATSAPP_MENTION_PATTERNS"] = _json.dumps(whatsapp_cfg["mention_patterns"])
+        if key in whatsapp_cfg:
+            seeded[key] = whatsapp_cfg[key]
+            _set_env(env, str(whatsapp_cfg[key]).lower())
+    if "mention_patterns" in whatsapp_cfg:
+        seeded["mention_patterns"] = whatsapp_cfg["mention_patterns"]
+        _set_env("WHATSAPP_MENTION_PATTERNS", _json.dumps(whatsapp_cfg["mention_patterns"]))
     for key, env in _YAML_LIST_KEYS:
         val = whatsapp_cfg.get(key)
-        if val is not None and not os.getenv(env):
-            os.environ[env] = ",".join(str(v) for v in val) if isinstance(val, list) else str(val)
-    return None
+        if val is not None:
+            seeded[key] = val
+            _set_env(env, val)
+    return seeded or None
 
 
 def _is_connected(config) -> bool:
diff --git a/tests/gateway/test_multiplex_process_global_sinks.py b/tests/gateway/test_multiplex_process_global_sinks.py
new file mode 100644
index 0000000000..87a0127ab3
--- /dev/null
+++ b/tests/gateway/test_multiplex_process_global_sinks.py
@@ -0,0 +1,74 @@
+"""Per-profile isolation for the remaining process-global sinks under gateway.multiplex_profiles:
+Yuanbao auto-sethome env write, the config ``terminal.env_passthrough`` allowlist, and the runner-level
+Slack ignored-channel fail-safe (which only had the DEFAULT profile's GatewayConfig)."""
+from __future__ import annotations
+
+import os
+
+from agent.secret_scope import reset_secret_scope, set_multiplex_active, set_secret_scope
+from hermes_constants import reset_hermes_home_override, set_hermes_home_override
+
+
+def _under_secondary(home, fn):
+    set_multiplex_active(True)
+    home_token = set_hermes_home_override(str(home))
+    secret_token = set_secret_scope({})
+    try:
+        return fn()
+    finally:
+        reset_secret_scope(secret_token)
+        reset_hermes_home_override(home_token)
+        set_multiplex_active(False)
+
+
+def test_yuanbao_auto_sethome_from_secondary_stays_in_its_config(tmp_path, monkeypatch):
+    from gateway.platforms.yuanbao import AutoSetHomeMiddleware
+
+    monkeypatch.delenv("YUANBAO_HOME_CHANNEL", raising=False)
+    secondary = tmp_path / "profiles" / "b2"
+    secondary.mkdir(parents=True)
+    (secondary / "config.yaml").write_text("{}\n")
+
+    class Adapter:
+        name = "yuanbao-b2"
+
+    class Ctx:
+        chat_id = "dm:tenant-b2"
+        chat_name = "b2"
+
+    _under_secondary(secondary, lambda: AutoSetHomeMiddleware._persist_home(Adapter(), Ctx()))
+
+    assert "YUANBAO_HOME_CHANNEL" not in os.environ
+    assert "dm:tenant-b2" in (secondary / "config.yaml").read_text()
+
+
+def test_env_passthrough_allowlist_follows_the_active_profile(tmp_path, monkeypatch):
+    import tools.env_passthrough as ep
+
+    default_home = tmp_path / "hermes"
+    secondary = default_home / "profiles" / "b2"
+    secondary.mkdir(parents=True)
+    (default_home / "config.yaml").write_text("terminal:\n  env_passthrough: [FOO_DEFAULT]\n")
+    (secondary / "config.yaml").write_text("terminal:\n  env_passthrough: [FOO_B2]\n")
+    monkeypatch.setenv("HERMES_HOME", str(default_home))
+    ep._config_passthrough.clear()
+
+    assert ep._load_config_passthrough() == {"FOO_DEFAULT"}
+    assert _under_secondary(secondary, ep._load_config_passthrough) == {"FOO_B2"}
+    assert ep._load_config_passthrough() == {"FOO_DEFAULT"}
+
+
+def test_slack_ignored_channels_use_the_routed_adapters_list(monkeypatch):
+    from gateway.config import GatewayConfig, Platform, PlatformConfig
+    from gateway.run import _is_slack_ignored_channel
+
+    monkeypatch.delenv("SLACK_IGNORED_CHANNELS", raising=False)
+    default_cfg = GatewayConfig(platforms={Platform.SLACK: PlatformConfig(enabled=True, extra={"ignored_channels": ["C_DEFAULT"]})})
+
+    class SecondaryAdapter:
+        config = PlatformConfig(enabled=True, extra={"ignored_channels": ["C_B2"]})
+
+    assert _is_slack_ignored_channel(default_cfg, "C_B2", SecondaryAdapter())
+    assert not _is_slack_ignored_channel(default_cfg, "C_DEFAULT", SecondaryAdapter())
+    # No routed adapter (legacy callers): the process-level config still rules.
+    assert _is_slack_ignored_channel(default_cfg, "C_DEFAULT")
diff --git a/tests/gateway/test_multiplex_yaml_env_bridge_isolation.py b/tests/gateway/test_multiplex_yaml_env_bridge_isolation.py
new file mode 100644
index 0000000000..27dde12775
--- /dev/null
+++ b/tests/gateway/test_multiplex_yaml_env_bridge_isolation.py
@@ -0,0 +1,101 @@
+"""A multiplexed secondary profile's config.yaml must never be bridged into the process env.
+
+``_load_secondary_profile_config`` runs ``load_gateway_config()`` inside ``_profile_runtime_scope``;
+every ``apply_yaml_config_fn`` hook and ``bridge_core_env_settings`` used to write ``os.environ`` there
+(first-writer-wins), so the first secondary's mention/allowlist policy became the DEFAULT profile's
+(#80099, #72348). The values must instead reach that profile's ``PlatformConfig.extra``.
+"""
+from __future__ import annotations
+
+import os
+
+import pytest
+
+from agent.secret_scope import (
+    reset_secret_scope,
+    set_multiplex_active,
+    set_secret_scope,
+)
+from hermes_constants import reset_hermes_home_override, set_hermes_home_override
+
+_SECONDARY_YAML = """\
+require_mention: false
+telegram:
+  mention_patterns: ['^bot2']
+  reactions: false
+matrix:
+  require_mention: false
+  allowed_users: ['@b2:example.org']
+  session_scope: room
+whatsapp:
+  dm_policy: open
+  allow_from: ['+15550002']
+feishu:
+  allow_bots: all
+slack:
+  allow_bots: all
+  ignored_channels: [C_B2]
+dingtalk:
+  allowed_users: [b2user]
+discord:
+  auto_thread: false
+  reactions: false
+signal:
+  require_mention: false
+"""
+
+_BRIDGED_ENV = (
+    "TELEGRAM_REQUIRE_MENTION", "TELEGRAM_MENTION_PATTERNS", "TELEGRAM_REACTIONS",
+    "MATRIX_REQUIRE_MENTION", "MATRIX_ALLOWED_USERS", "MATRIX_SESSION_SCOPE",
+    "WHATSAPP_DM_POLICY", "WHATSAPP_ALLOWED_USERS", "FEISHU_ALLOW_BOTS",
+    "SLACK_ALLOW_BOTS", "SLACK_IGNORED_CHANNELS", "DINGTALK_ALLOWED_USERS",
+    "DISCORD_AUTO_THREAD", "DISCORD_REACTIONS", "SIGNAL_REQUIRE_MENTION",
+)
+
+_EXPECTED_EXTRA = (
+    ("telegram", "mention_patterns"), ("telegram", "reactions"), ("matrix", "session_scope"),
+    ("matrix", "allowed_users"), ("whatsapp", "dm_policy"), ("feishu", "allow_bots"),
+    ("slack", "allow_bots"), ("slack", "ignored_channels"), ("dingtalk", "allowed_users"),
+    ("discord", "auto_thread"), ("signal", "require_mention"),
+)
+
+
+@pytest.fixture
+def secondary_scope(tmp_path, monkeypatch):
+    default_home = tmp_path / "hermes"
+    secondary = default_home / "profiles" / "bot2"
+    secondary.mkdir(parents=True)
+    (default_home / "config.yaml").write_text("gateway:\n  multiplex_profiles: true\n")
+    (secondary / "config.yaml").write_text(_SECONDARY_YAML)
+    monkeypatch.setenv("HERMES_HOME", str(default_home))
+    for name in _BRIDGED_ENV:
+        monkeypatch.delenv(name, raising=False)
+    set_multiplex_active(True)
+    home_token = set_hermes_home_override(str(secondary))
+    secret_token = set_secret_scope({"TELEGRAM_BOT_TOKEN": "222:b2"})
+    try:
+        yield
+    finally:
+        reset_secret_scope(secret_token)
+        reset_hermes_home_override(home_token)
+        set_multiplex_active(False)
+
+
+def test_secondary_profile_yaml_reaches_its_extra_not_the_process_env(secondary_scope):
+    from hermes_cli.plugins import discover_plugins
+    from gateway.config import Platform, load_gateway_config
+
+    discover_plugins()
+    cfg = load_gateway_config()
+
+    poisoned = {name: os.environ[name] for name in _BRIDGED_ENV if name in os.environ}
+    assert poisoned == {}, f"secondary profile wrote into process env: {poisoned}"
+    missing = [
+        f"{plat}.{key}" for plat, key in _EXPECTED_EXTRA
+        if key not in ((cfg.platforms.get(Platform(plat)) or _Empty()).extra or {})
+    ]
+    assert missing == [], f"secondary profile's own YAML not seeded into extra: {missing}"
+
+
+class _Empty:
+    extra: dict = {}