diff --git a/backend/bot.py b/backend/bot.py
index a8711b2..8aa43d9 100644
--- a/backend/bot.py
+++ b/backend/bot.py
@@ -35,6 +35,7 @@
 from supabase_service import (
     ban_user,
     clear_all_staged,
+    clear_github_token,
     count_stats,
     get_all_users,
     get_pending_files,
@@ -1130,13 +1131,23 @@ async def commit_now_callback(update: Update, context: ContextTypes.DEFAULT_TYPE
         return WAITING_PROTECTED_BRANCH_NAME
 
     else:
-        error_msg = result.get('message', 'Unknown error')
-        await channel_logger.log_commit_failed(telegram_id, active_repo, error_msg)
-        await query.edit_message_text(
-            f"[X] *Commit failed.*\n\n"
-            f"Error: {error_msg}\n\n"
-            f"Your staged files are safe. Try /files again."
-        )
+        if result.get("error") == "invalid_token":
+            clear_github_token(telegram_id)
+            await channel_logger.log_commit_failed(telegram_id, active_repo, "invalid_token")
+            await query.edit_message_text(
+                "🔑 *Your GitHub token has expired or been revoked.*\n\n"
+                "Your staged files are safe — no changes were made.\n\n"
+                "Please run /auth to reconnect your GitHub account and try again.",
+                parse_mode=ParseMode.MARKDOWN
+            )
+        else:
+            error_msg = result.get('message', 'Unknown error')
+            await channel_logger.log_commit_failed(telegram_id, active_repo, error_msg)
+            await query.edit_message_text(
+                f"[X] *Commit failed.*\n\n"
+                f"Error: {error_msg}\n\n"
+                f"Your staged files are safe. Try /files again."
+            )
 
     context.user_data.clear()
     return ConversationHandler.END
@@ -1211,9 +1222,19 @@ async def commit_force_callback(update: Update, context: ContextTypes.DEFAULT_TY
             parse_mode=ParseMode.MARKDOWN
         )
     else:
-        error_msg = result.get('message', 'Unknown error')
-        await channel_logger.log_commit_failed(telegram_id, active_repo, error_msg)
-        await query.edit_message_text(f"[X] Force commit failed: {error_msg}")
+        if result.get("error") == "invalid_token":
+            clear_github_token(telegram_id)
+            await channel_logger.log_commit_failed(telegram_id, active_repo, "invalid_token")
+            await query.edit_message_text(
+                "🔑 *Your GitHub token has expired or been revoked.*\n\n"
+                "Your staged files are safe — no changes were made.\n\n"
+                "Please run /auth to reconnect your GitHub account and try again.",
+                parse_mode=ParseMode.MARKDOWN
+            )
+        else:
+            error_msg = result.get('message', 'Unknown error')
+            await channel_logger.log_commit_failed(telegram_id, active_repo, error_msg)
+            await query.edit_message_text(f"[X] Force commit failed: {error_msg}")
 
     context.user_data.clear()
     return ConversationHandler.END
diff --git a/backend/github_service.py b/backend/github_service.py
index 7458469..118c949 100644
--- a/backend/github_service.py
+++ b/backend/github_service.py
@@ -240,6 +240,8 @@ def commit_files(
             }
 
         except GithubException as e:
+            if e.status == 401:
+                return {"ok": False, "error": "invalid_token", "message": "GitHub token is invalid or expired. Please re-authenticate via /auth."}
             if e.status == 409:
                 return {"ok": False, "error": "conflict", "message": "SHA conflict on GitHub"}
             if e.status == 422:
diff --git a/backend/routes/staged_files.py b/backend/routes/staged_files.py
index 6baf0ea..0da9d0d 100644
--- a/backend/routes/staged_files.py
+++ b/backend/routes/staged_files.py
@@ -169,6 +169,11 @@ async def commit_direct(payload: DirectCommitPayload, telegram_id: str = Depends
                 status_code=409,
                 detail=f"Conflict in: {', '.join(conflict_files)}. Use /files in Telegram \u2192 Force Commit.",
             )
+        if result.get("error") == "invalid_token":
+            raise HTTPException(
+                status_code=401,
+                detail="GitHub token is invalid or expired. Please re-authenticate via /auth in Telegram.",
+            )
         raise HTTPException(
             status_code=500,
             detail=result.get("message", "GitHub commit failed."),
diff --git a/backend/supabase_service.py b/backend/supabase_service.py
index 9bd8256..290c31a 100644
--- a/backend/supabase_service.py
+++ b/backend/supabase_service.py
@@ -441,3 +441,43 @@ def update_github_token(telegram_id: str, token: str) -> bool:
         print(f"[supabase] update_github_token error: {e}")
         return False
 
+
+def clear_github_token(telegram_id: str) -> bool:
+    """Clear a stale or revoked GitHub token so the user is prompted to re-authenticate."""
+    try:
+        get_client().table("users") \
+            .update({"github_token": None}) \
+            .eq("telegram_id", telegram_id) \
+            .execute()
+        return True
+    except Exception as e:
+        print(f"[supabase] clear_github_token error: {e}")
+        return False
+
+
+def update_github_username(telegram_id: str, github_username: str) -> None:
+    """Persist the user's GitHub login so webhooks can map assignee -> telegram_id."""
+    if not github_username:
+        return
+    try:
+        get_client().table("users") \
+            .update({"github_username": github_username.lower()}) \
+            .eq("telegram_id", telegram_id) \
+            .execute()
+    except Exception as e:
+        print(f"[supabase] update_github_username error: {e}")
+
+
+def get_user_by_github_username(github_username: str) -> dict | None:
+    """Reverse lookup: GitHub login -> user row. Case-insensitive. None if unmapped."""
+    if not github_username:
+        return None
+    try:
+        result = get_client().table("users") \
+            .select("*") \
+            .ilike("github_username", github_username) \
+            .execute()
+        return result.data[0] if result.data else None
+    except Exception as e:
+        print(f"[supabase] get_user_by_github_username error: {e}")
+        return None