diff --git a/plugins/platforms/discord/adapter.py b/plugins/platforms/discord/adapter.py
index 563ab5fa931..8b697275bdd 100644
--- a/plugins/platforms/discord/adapter.py
+++ b/plugins/platforms/discord/adapter.py
@@ -4811,14 +4811,17 @@ class DiscordAdapter(BasePlatformAdapter):
         # to keep the partition rule clean.
         _channel_context = None
         _is_dm = isinstance(message.channel, discord.DMChannel)
-        if not _is_dm:
-            _needed_mention = (
-                require_mention
-                and not is_free_channel
-                and not in_bot_thread
-            )
-            _backfill_enabled = self._discord_history_backfill()
-            if _backfill_enabled and (_needed_mention or is_thread):
+        if not _is_dm and self._discord_history_backfill():
+            # Run backfill when there's a real gap to fill:
+            #   - mention-gated channels with no free-response override
+            #     (messages between bot turns aren't in the transcript)
+            #   - any thread (in_bot_thread bypasses the mention check, but
+            #     processing-window gaps and post-restart context still need
+            #     recovery)
+            # DMs skip entirely because every DM message triggers the bot,
+            # so the session transcript already has everything.
+            _has_mention_gap = require_mention and not is_free_channel and not in_bot_thread
+            if _has_mention_gap or is_thread:
                 _backfill_text = await self._fetch_channel_context(
                     message.channel, before=message,
                 )