diff --git a/gateway/platforms/discord.py b/gateway/platforms/discord.py
index c5b12e09c1..ae107cdfb2 100644
--- a/gateway/platforms/discord.py
+++ b/gateway/platforms/discord.py
@@ -477,6 +477,34 @@ class VoiceReceiver:
                 pass
 
 
+def _read_dm_role_auth_guild() -> Optional[int]:
+    """Return the guild ID opted-in for DM role-based auth, or None.
+
+    Reads ``discord.dm_role_auth_guild`` from config.yaml. This is
+    deliberately a config.yaml-only setting (not an env var): per repo
+    policy, ``~/.hermes/.env`` is for secrets only, and this is a
+    behavioral setting. Guild IDs aren't secrets.
+
+    Accepts ints or numeric strings in the config. Anything else
+    (empty, malformed, None) returns None, which keeps the secure
+    default (DM role-auth disabled).
+    """
+    try:
+        from hermes_cli.config import read_raw_config
+        cfg = read_raw_config() or {}
+        discord_cfg = cfg.get("discord", {}) or {}
+        raw = discord_cfg.get("dm_role_auth_guild")
+    except Exception:
+        return None
+    if raw is None or raw == "":
+        return None
+    try:
+        guild_id = int(raw)
+    except (TypeError, ValueError):
+        return None
+    return guild_id if guild_id > 0 else None
+
+
 class DiscordAdapter(BasePlatformAdapter):
     """
     Discord bot adapter.
@@ -2140,11 +2168,11 @@ class DiscordAdapter(BasePlatformAdapter):
 
         Role checks are **scoped to the guild the message originated from**.
         For DMs (no guild context), role-based auth is disabled by default and
-        only user-ID allowlist applies. Set ``DISCORD_DM_ROLE_AUTH_GUILD``
-        to a specific guild ID to opt-in: role membership in that one guild
-        will authorize DMs. This prevents cross-guild privilege escalation
-        where a user with the configured role in any shared public server
-        could DM the bot and pass the allowlist.
+        only user-ID allowlist applies. Set ``discord.dm_role_auth_guild``
+        in config.yaml to a specific guild ID to opt-in: role membership in
+        that one guild will authorize DMs. This prevents cross-guild
+        privilege escalation where a user with the configured role in any
+        shared public server could DM the bot and pass the allowlist.
 
         Args:
             user_id: Author ID as a string.
@@ -2168,14 +2196,14 @@ class DiscordAdapter(BasePlatformAdapter):
         if not has_roles:
             return False
 
-        # DM path: roles require explicit opt-in via DISCORD_DM_ROLE_AUTH_GUILD.
-        # Without this, a user with the configured role in ANY mutual guild
-        # could DM the bot and bypass the allowlist (cross-guild leakage).
+        # DM path: roles require explicit opt-in via
+        # ``discord.dm_role_auth_guild`` in config.yaml. Without this, a
+        # user with the configured role in ANY mutual guild could DM the
+        # bot and bypass the allowlist (cross-guild leakage).
         if is_dm or guild is None:
-            dm_guild_env = os.getenv("DISCORD_DM_ROLE_AUTH_GUILD", "").strip()
-            if not dm_guild_env.isdigit():
+            dm_guild_id = _read_dm_role_auth_guild()
+            if dm_guild_id is None:
                 return False
-            dm_guild_id = int(dm_guild_env)
             if self._client is None:
                 return False
             dm_guild = self._client.get_guild(dm_guild_id)
diff --git a/hermes_cli/config.py b/hermes_cli/config.py
index 6753ae3de0..9db661a27e 100644
--- a/hermes_cli/config.py
+++ b/hermes_cli/config.py
@@ -1108,6 +1108,12 @@ DEFAULT_CONFIG = {
         "auto_thread": True,           # Auto-create threads on @mention in channels (like Slack)
         "reactions": True,             # Add 👀/✅/❌ reactions to messages during processing
         "channel_prompts": {},         # Per-channel ephemeral system prompts (forum parents apply to child threads)
+        # Opt-in DM role-based auth (#12136). By default, DISCORD_ALLOWED_ROLES
+        # authorizes only guild messages in the role's own guild — DMs require
+        # DISCORD_ALLOWED_USERS. Set dm_role_auth_guild to a guild ID to also
+        # authorize DMs from members of that one trusted guild holding the
+        # allowed role. Unset / empty / 0 = secure default (DM role-auth off).
+        "dm_role_auth_guild": "",
         # discord / discord_admin tools: restrict which actions the agent may call.
         # Default (empty) = all actions allowed (subject to bot privileged intents).
         # Accepts comma-separated string ("list_guilds,list_channels,fetch_messages")
diff --git a/tests/gateway/test_discord_roles_dm_scope.py b/tests/gateway/test_discord_roles_dm_scope.py
index 604b4e0aab..0f10ba79ae 100644
--- a/tests/gateway/test_discord_roles_dm_scope.py
+++ b/tests/gateway/test_discord_roles_dm_scope.py
@@ -11,8 +11,8 @@ allowed a cross-guild DM bypass:
    in public server A, and authorizes the DM.
 
 The fix scopes role checks to the originating guild and disables role-based
-auth on DMs unless ``DISCORD_DM_ROLE_AUTH_GUILD`` explicitly opts into a
-single trusted guild.
+auth on DMs unless ``discord.dm_role_auth_guild`` in config.yaml explicitly
+opts into a single trusted guild.
 """
 
 from types import SimpleNamespace
@@ -23,6 +23,17 @@ import pytest
 from gateway.platforms.discord import DiscordAdapter
 
 
+def _set_dm_role_auth_guild(monkeypatch, guild_id=None):
+    """Stub ``hermes_cli.config.read_raw_config`` so ``_read_dm_role_auth_guild``
+    resolves to ``guild_id`` (or None for the opt-out default).
+    """
+    cfg = {"discord": {"dm_role_auth_guild": guild_id if guild_id is not None else ""}}
+    # Patch the attribute ``hermes_cli.config.read_raw_config`` — that's
+    # what ``_read_dm_role_auth_guild`` imports at call time.
+    import hermes_cli.config as _cfg_mod
+    monkeypatch.setattr(_cfg_mod, "read_raw_config", lambda: cfg, raising=True)
+
+
 def _make_adapter(allowed_users=None, allowed_roles=None, guilds=None):
     """Build a minimal DiscordAdapter without running __init__."""
     adapter = object.__new__(DiscordAdapter)
@@ -69,7 +80,7 @@ def test_dm_rejects_role_held_in_other_guild(monkeypatch):
     Regression guard for the cross-guild DM bypass in the initial
     DISCORD_ALLOWED_ROLES implementation.
     """
-    monkeypatch.delenv("DISCORD_DM_ROLE_AUTH_GUILD", raising=False)
+    _set_dm_role_auth_guild(monkeypatch)
 
     public_guild, _ = _guild_with_member(
         guild_id=111111,
@@ -91,7 +102,7 @@ def test_dm_rejects_role_held_in_other_guild(monkeypatch):
 
 
 def test_dm_role_auth_requires_explicit_guild_optin(monkeypatch):
-    """With DISCORD_DM_ROLE_AUTH_GUILD set, only that specific guild counts.
+    """With dm_role_auth_guild set, only that specific guild counts.
 
     The user has the role in the opted-in guild — allowed.
     """
@@ -106,7 +117,7 @@ def test_dm_role_auth_requires_explicit_guild_optin(monkeypatch):
         allowed_roles=[5555],
         guilds=[other_guild, trusted_guild],
     )
-    monkeypatch.setenv("DISCORD_DM_ROLE_AUTH_GUILD", "222222")
+    _set_dm_role_auth_guild(monkeypatch, 222222)
 
     assert (
         adapter._is_allowed_user("42", author=None, guild=None, is_dm=True)
@@ -115,7 +126,7 @@ def test_dm_role_auth_requires_explicit_guild_optin(monkeypatch):
 
 
 def test_dm_role_auth_optin_rejects_when_not_member(monkeypatch):
-    """DISCORD_DM_ROLE_AUTH_GUILD set but user isn't a member → reject."""
+    """dm_role_auth_guild set but user isn't a member → reject."""
     trusted_guild = SimpleNamespace(
         id=222222,
         get_member=lambda uid: None,  # user not in trusted guild
@@ -129,7 +140,7 @@ def test_dm_role_auth_optin_rejects_when_not_member(monkeypatch):
         allowed_roles=[5555],
         guilds=[public_guild, trusted_guild],
     )
-    monkeypatch.setenv("DISCORD_DM_ROLE_AUTH_GUILD", "222222")
+    _set_dm_role_auth_guild(monkeypatch, 222222)
 
     assert (
         adapter._is_allowed_user("42", author=None, guild=None, is_dm=True)
@@ -146,7 +157,7 @@ def test_guild_message_role_check_scoped_to_originating_guild(monkeypatch):
     """A user with the role in a DIFFERENT guild than the message origin
     must NOT be authorized, even when both guilds are mutual.
     """
-    monkeypatch.delenv("DISCORD_DM_ROLE_AUTH_GUILD", raising=False)
+    _set_dm_role_auth_guild(monkeypatch)
 
     public_guild, _ = _guild_with_member(
         guild_id=111111,
@@ -172,7 +183,7 @@ def test_guild_message_role_check_scoped_to_originating_guild(monkeypatch):
 
 def test_guild_message_role_check_allows_when_role_in_same_guild(monkeypatch):
     """Positive path: user has the role IN the message's guild → allowed."""
-    monkeypatch.delenv("DISCORD_DM_ROLE_AUTH_GUILD", raising=False)
+    _set_dm_role_auth_guild(monkeypatch)
 
     trusted_guild, _ = _guild_with_member(
         guild_id=222222,
@@ -197,7 +208,7 @@ def test_guild_message_rejects_author_roles_from_different_guild(monkeypatch):
     message, the cached .roles on it must NOT be trusted — rely on the
     current guild's Member lookup instead.
     """
-    monkeypatch.delenv("DISCORD_DM_ROLE_AUTH_GUILD", raising=False)
+    _set_dm_role_auth_guild(monkeypatch)
 
     # Author is a Member of a DIFFERENT guild with the allowed role
     foreign_guild = SimpleNamespace(id=999, get_member=lambda uid: None)
@@ -264,7 +275,7 @@ def test_slash_authorization_rejects_cross_guild_role_dm(monkeypatch):
     """Slash interaction in a DM must not be authorized by a role held in
     any mutual guild (parallel to the on_message cross-guild bypass)."""
     import discord as _discord  # type: ignore
-    monkeypatch.delenv("DISCORD_DM_ROLE_AUTH_GUILD", raising=False)
+    _set_dm_role_auth_guild(monkeypatch)
 
     public_guild, _ = _guild_with_member(
         guild_id=111111,
@@ -292,7 +303,7 @@ def test_slash_authorization_rejects_cross_guild_role_dm(monkeypatch):
 
 def test_slash_authorization_rejects_cross_guild_role_in_guild(monkeypatch):
     """Slash in guild B must not be authorized by a role held in guild A."""
-    monkeypatch.delenv("DISCORD_DM_ROLE_AUTH_GUILD", raising=False)
+    _set_dm_role_auth_guild(monkeypatch)
 
     public_guild, _ = _guild_with_member(
         guild_id=111111,
@@ -320,7 +331,7 @@ def test_slash_authorization_rejects_cross_guild_role_in_guild(monkeypatch):
 
 def test_slash_authorization_allows_in_scope_guild_role(monkeypatch):
     """Positive control: slash in guild B, user has role in guild B → allowed."""
-    monkeypatch.delenv("DISCORD_DM_ROLE_AUTH_GUILD", raising=False)
+    _set_dm_role_auth_guild(monkeypatch)
 
     trusted_guild, _ = _guild_with_member(
         guild_id=222222,