diff --git a/apisix/plugins/ai-prompt-decorator.lua b/apisix/plugins/ai-prompt-decorator.lua
index 587b15c35b67..10b36e82cd1d 100644
--- a/apisix/plugins/ai-prompt-decorator.lua
+++ b/apisix/plugins/ai-prompt-decorator.lua
@@ -114,5 +114,4 @@ function _M.rewrite(conf, ctx)
 end
 
 
-_M.__decorate = decorate -- for ai-rag plugin
 return _M
diff --git a/apisix/plugins/ai-rag.lua b/apisix/plugins/ai-rag.lua
index d2591eac1643..ab4b80ce832c 100644
--- a/apisix/plugins/ai-rag.lua
+++ b/apisix/plugins/ai-rag.lua
@@ -20,13 +20,12 @@ local ngx_req = ngx.req
 
 local http     = require("resty.http")
 local core     = require("apisix.core")
-local decorate = require("apisix.plugins.ai-prompt-decorator").__decorate
 
 local azure_openai_embeddings = require("apisix.plugins.ai-rag.embeddings.azure_openai").schema
 local azure_ai_search_schema = require("apisix.plugins.ai-rag.vector-search.azure_ai_search").schema
 
-local INTERNAL_SERVER_ERROR = ngx.HTTP_INTERNAL_SERVER_ERROR
-local BAD_REQUEST = ngx.HTTP_BAD_REQUEST
+local HTTP_INTERNAL_SERVER_ERROR = ngx.HTTP_INTERNAL_SERVER_ERROR
+local HTTP_BAD_REQUEST = ngx.HTTP_BAD_REQUEST
 
 local schema = {
     type = "object",
@@ -70,7 +69,7 @@ local request_schema = {
 
 local _M = {
     version = 0.1,
-    priority = 1060, -- TODO check with other ai plugins
+    priority = 1060,
     name = "ai-rag",
     schema = schema,
 }
@@ -85,11 +84,11 @@ function _M.access(conf, ctx)
     local httpc = http.new()
     local body_tab, err = core.request.get_json_request_body_table()
     if not body_tab then
-        return BAD_REQUEST, err
+        return HTTP_BAD_REQUEST, err
     end
     if not body_tab["ai_rag"] then
         core.log.error("request body must have \"ai-rag\" field")
-        return BAD_REQUEST
+        return HTTP_BAD_REQUEST
     end
 
     local embeddings_provider = next(conf.embeddings_provider)
@@ -110,7 +109,7 @@ function _M.access(conf, ctx)
     local ok, err = core.schema.check(request_schema, body_tab)
     if not ok then
         core.log.error("request body fails schema check: ", err)
-        return BAD_REQUEST
+        return HTTP_BAD_REQUEST
     end
 
     local embeddings, status, err = embeddings_driver.get_embeddings(embeddings_provider_conf,
@@ -133,22 +132,19 @@ function _M.access(conf, ctx)
     -- also, these values will cause failure when proxying requests to LLM.
     body_tab["ai_rag"] = nil
 
-    local prepend = {
-        {
-            role = "user",
-            content = res
-        }
-    }
-    local decorator_conf = {
-        prepend = prepend
-    }
     if not body_tab.messages then
         body_tab.messages = {}
     end
-    decorate(decorator_conf, body_tab)
+
+    local augment = {
+        role = "user",
+        content = res
+    }
+    core.table.insert_tail(body_tab.messages, augment)
+
     local req_body_json, err = core.json.encode(body_tab)
     if not req_body_json then
-        return INTERNAL_SERVER_ERROR, err
+        return HTTP_INTERNAL_SERVER_ERROR, err
     end
 
     ngx_req.set_body_data(req_body_json)
diff --git a/apisix/plugins/ai-rag/embeddings/azure_openai.lua b/apisix/plugins/ai-rag/embeddings/azure_openai.lua
index 64c46d16aa6a..d261471b4529 100644
--- a/apisix/plugins/ai-rag/embeddings/azure_openai.lua
+++ b/apisix/plugins/ai-rag/embeddings/azure_openai.lua
@@ -15,7 +15,7 @@
 -- limitations under the License.
 --
 local core = require("apisix.core")
-local INTERNAL_SERVER_ERROR = ngx.HTTP_INTERNAL_SERVER_ERROR
+local HTTP_INTERNAL_SERVER_ERROR = ngx.HTTP_INTERNAL_SERVER_ERROR
 local type = type
 
 local _M = {}
@@ -36,7 +36,7 @@ _M.schema = {
 function _M.get_embeddings(conf, body, httpc)
     local body_tab, err = core.json.encode(body)
     if not body_tab then
-        return nil, INTERNAL_SERVER_ERROR, err
+        return nil, HTTP_INTERNAL_SERVER_ERROR, err
     end
 
     local res, err = httpc:request_uri(conf.endpoint, {
@@ -49,7 +49,7 @@ function _M.get_embeddings(conf, body, httpc)
     })
 
     if not res or not res.body then
-        return nil, INTERNAL_SERVER_ERROR, err
+        return nil, HTTP_INTERNAL_SERVER_ERROR, err
     end
 
     if res.status ~= 200 then
@@ -58,16 +58,16 @@ function _M.get_embeddings(conf, body, httpc)
 
     local res_tab, err = core.json.decode(res.body)
     if not res_tab then
-        return nil, INTERNAL_SERVER_ERROR, err
+        return nil, HTTP_INTERNAL_SERVER_ERROR, err
     end
 
     if type(res_tab.data) ~= "table" or core.table.isempty(res_tab.data) then
-        return nil, INTERNAL_SERVER_ERROR, res.body
+        return nil, HTTP_INTERNAL_SERVER_ERROR, res.body
     end
 
     local embeddings, err = core.json.encode(res_tab.data[1].embedding)
     if not embeddings then
-        return nil, INTERNAL_SERVER_ERROR, err
+        return nil, HTTP_INTERNAL_SERVER_ERROR, err
     end
 
     return res_tab.data[1].embedding
diff --git a/apisix/plugins/ai-rag/vector-search/azure_ai_search.lua b/apisix/plugins/ai-rag/vector-search/azure_ai_search.lua
index a605be82d5bf..dd78c9ebc1ab 100644
--- a/apisix/plugins/ai-rag/vector-search/azure_ai_search.lua
+++ b/apisix/plugins/ai-rag/vector-search/azure_ai_search.lua
@@ -15,7 +15,7 @@
 -- limitations under the License.
 --
 local core = require("apisix.core")
-local INTERNAL_SERVER_ERROR = ngx.HTTP_INTERNAL_SERVER_ERROR
+local HTTP_INTERNAL_SERVER_ERROR = ngx.HTTP_INTERNAL_SERVER_ERROR
 
 local _M = {}
 
@@ -44,7 +44,7 @@ function _M.search(conf, search_body, httpc)
     }
     local final_body, err = core.json.encode(body)
     if not final_body then
-        return nil, INTERNAL_SERVER_ERROR, err
+        return nil, HTTP_INTERNAL_SERVER_ERROR, err
     end
 
     local res, err = httpc:request_uri(conf.endpoint, {
@@ -57,7 +57,7 @@ function _M.search(conf, search_body, httpc)
     })
 
     if not res or not res.body then
-        return nil, INTERNAL_SERVER_ERROR, err
+        return nil, HTTP_INTERNAL_SERVER_ERROR, err
     end
 
     if res.status ~= 200 then