diff --git a/apisix/plugins/ai-providers/base.lua b/apisix/plugins/ai-providers/base.lua
index 3021b89cdd4b..33403329b853 100644
--- a/apisix/plugins/ai-providers/base.lua
+++ b/apisix/plugins/ai-providers/base.lua
@@ -201,8 +201,20 @@ function _M.build_request(self, ctx, conf, request_body, opts)
         ctx.ai_converter.convert_headers(headers)
     end
 
+    -- For the passthrough protocol the gateway acts as a catch-all proxy, so
+    -- forward the client's HTTP method and original query string unchanged.
+    -- Other protocols always issue a POST with provider-specific query args.
+    local method = "POST"
+    if ctx.ai_target_protocol == "passthrough" then
+        method = core.request.get_method()
+        local client_args = ctx.var.args and core.string.decode_args(ctx.var.args)
+        if type(client_args) == "table" then
+            core.table.merge(query_params, client_args)
+        end
+    end
+
     local params = {
-        method = "POST",
+        method = method,
         scheme = scheme,
         headers = headers,
         ssl_verify = conf.ssl_verify,
diff --git a/t/plugin/ai-proxy-passthrough.t b/t/plugin/ai-proxy-passthrough.t
index b01e7a513c90..d4b7ad6889ac 100644
--- a/t/plugin/ai-proxy-passthrough.t
+++ b/t/plugin/ai-proxy-passthrough.t
@@ -278,3 +278,156 @@ images: passthrough
 empty: nil
 --- no_error_log
 no matching AI protocol
+
+
+
+=== TEST 10: set route for passthrough query/method forwarding
+--- config
+    location /t {
+        content_by_lua_block {
+            local t = require("lib.test_admin").test
+            local code, body = t('/apisix/admin/routes/1',
+                 ngx.HTTP_PUT,
+                 [[{
+                    "uri": "/plugin_proxy_rewrite_args",
+                    "plugins": {
+                        "ai-proxy": {
+                            "provider": "openai",
+                            "auth": {
+                                "header": {
+                                    "Authorization": "Bearer token"
+                                }
+                            },
+                            "override": {
+                                "endpoint": "http://127.0.0.1:1980"
+                            },
+                            "ssl_verify": false
+                        }
+                    }
+                }]]
+            )
+
+            if code >= 300 then
+                ngx.status = code
+            end
+            ngx.say(body)
+        }
+    }
+--- response_body
+passed
+
+
+
+=== TEST 11: passthrough forwards the client query string to the upstream
+--- request
+POST /plugin_proxy_rewrite_args?name=foo
+{"prompt":"x"}
+--- more_headers
+Content-Type: application/json
+--- response_body eval
+qr/name: foo/
+--- no_error_log
+no matching AI protocol
+
+
+
+=== TEST 12: set route for passthrough method forwarding
+--- config
+    location /t {
+        content_by_lua_block {
+            local t = require("lib.test_admin").test
+            local code, body = t('/apisix/admin/routes/1',
+                 ngx.HTTP_PUT,
+                 [[{
+                    "uri": "/plugin_proxy_rewrite",
+                    "plugins": {
+                        "ai-proxy": {
+                            "provider": "openai",
+                            "auth": {
+                                "header": {
+                                    "Authorization": "Bearer token"
+                                }
+                            },
+                            "override": {
+                                "endpoint": "http://127.0.0.1:1980"
+                            },
+                            "ssl_verify": false
+                        }
+                    }
+                }]]
+            )
+
+            if code >= 300 then
+                ngx.status = code
+            end
+            ngx.say(body)
+        }
+    }
+--- response_body
+passed
+
+
+
+=== TEST 13: passthrough forwards the client HTTP method to the upstream
+--- request
+PUT /plugin_proxy_rewrite
+{"prompt":"x"}
+--- more_headers
+Content-Type: application/json
+--- error_log
+plugin_proxy_rewrite get method: PUT
+--- no_error_log
+no matching AI protocol
+
+
+
+=== TEST 14: set route whose override.endpoint carries its own query args
+--- config
+    location /t {
+        content_by_lua_block {
+            local t = require("lib.test_admin").test
+            local code, body = t('/apisix/admin/routes/1',
+                 ngx.HTTP_PUT,
+                 [[{
+                    "uri": "/plugin_proxy_rewrite_args",
+                    "plugins": {
+                        "ai-proxy": {
+                            "provider": "openai",
+                            "auth": {
+                                "header": {
+                                    "Authorization": "Bearer token"
+                                }
+                            },
+                            "override": {
+                                "endpoint": "http://127.0.0.1:1980/plugin_proxy_rewrite_args?name=fromendpoint&ekey=eval"
+                            },
+                            "ssl_verify": false
+                        }
+                    }
+                }]]
+            )
+
+            if code >= 300 then
+                ngx.status = code
+            end
+            ngx.say(body)
+        }
+    }
+--- response_body
+passed
+
+
+
+=== TEST 15: client query overrides the endpoint query on conflicting keys
+--- request
+POST /plugin_proxy_rewrite_args?name=fromclient&ckey=cval
+{"prompt":"x"}
+--- more_headers
+Content-Type: application/json
+--- response_body
+uri: /plugin_proxy_rewrite_args
+ckey: cval
+ekey: eval
+name: fromclient
+--- no_error_log
+no matching AI protocol