From 39ee5ef96e7bfe24049ea903b1c080779b77f372 Mon Sep 17 00:00:00 2001
From: Xin Wang <your-email@example.com>
Date: Fri, 7 Aug 2026 11:30:58 +0800
Subject: [PATCH] refactor(backend): change prompt field type from
 varchar(8192) to text

Update the 'prompt' field in the Assistant model to use a Text type for improved flexibility. This change is accompanied by a migration script to alter the database schema accordingly.
---
 backend/db/models.py                          |  2 +-
 .../20260807_0014_assistant_prompt_to_text.py | 40 +++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)
 create mode 100644 backend/migrations/versions/20260807_0014_assistant_prompt_to_text.py

diff --git a/backend/db/models.py b/backend/db/models.py
index 02c385f..6933fe2 100644
--- a/backend/db/models.py
+++ b/backend/db/models.py
@@ -171,7 +171,7 @@ class Assistant(Base):
     )
 
     # ---- 瘦类型专属字段(真列,稀疏:按 type 用其中几列) ----
-    prompt: Mapped[str] = mapped_column(String(8192), default="")    # prompt / opencode
+    prompt: Mapped[str] = mapped_column(Text, default="")    # prompt / opencode
     dynamic_variable_definitions: Mapped[dict] = mapped_column(JSON, default=dict)
     analysis_config: Mapped[dict] = mapped_column(JSONB, default=dict)
     api_url: Mapped[str] = mapped_column(String(512), default="")    # dify / fastgpt / opencode
diff --git a/backend/migrations/versions/20260807_0014_assistant_prompt_to_text.py b/backend/migrations/versions/20260807_0014_assistant_prompt_to_text.py
new file mode 100644
index 0000000..d9650b4
--- /dev/null
+++ b/backend/migrations/versions/20260807_0014_assistant_prompt_to_text.py
@@ -0,0 +1,40 @@
+"""change assistants.prompt from varchar(8192) to text
+
+Revision ID: 20260807_0014
+Revises: 20260807_0013
+"""
+
+from __future__ import annotations
+
+from collections.abc import Sequence
+
+from alembic import op
+import sqlalchemy as sa
+
+
+revision: str = "20260807_0014"
+down_revision: str | Sequence[str] | None = "20260807_0013"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def upgrade() -> None:
+    op.alter_column(
+        "assistants",
+        "prompt",
+        existing_type=sa.String(length=8192),
+        type_=sa.Text(),
+        existing_nullable=False,
+        existing_server_default=sa.text("''"),
+    )
+
+
+def downgrade() -> None:
+    op.alter_column(
+        "assistants",
+        "prompt",
+        existing_type=sa.Text(),
+        type_=sa.String(length=8192),
+        existing_nullable=False,
+        existing_server_default=sa.text("''"),
+    )