docs: clarify ext-plugin-post-resp limitations

PR_TRACKING.md

@@ -0,0 +1,6 @@
+# PR Tracking
+
+| Issue | Branch | PR | Status | Created (UTC) | Testing | Notes |
+| --- | --- | --- | --- | --- | --- | --- |
+| #10787 | `auto/issue-10787` | TBD | In progress | TBD | `git diff` reviewed; `grep -RInE 'grpc-transcode\|gRPC\|HTTP upstream\|HTTP 上游\|gRPC 转码' docs/en/latest/plugins/ext-plugin-post-resp.md docs/zh/latest/plugins/ext-plugin-post-resp.md` confirmed English and Chinese limitation text. Full docs lint not run yet (documentation-only minimal change; no docs lint environment discovered/run before PR creation). | Clarifies `ext-plugin-post-resp` only works with HTTP upstreams / HTTP response flow and should not be used with `grpc-transcode` or non-HTTP upstream response flows. |
+| N/A | `fix/issue-...` | https://github.com/apache/apisix/pull/13390 | Review required; PR lint success | 2026-05-19 11:52 | PR lint success | Existing open PR. Not pinged this round because it has been less than 24 hours since creation, and an explanatory comment was already added on 2026-05-20 03:08 UTC. |

docs/en/latest/plugins/ext-plugin-post-resp.md

@@ -33,7 +33,7 @@ The `ext-plugin-post-resp` Plugin is for running specific external Plugins in th
 
 The `ext-plugin-post-resp` plugin will be executed after the request gets a response from the upstream.
 
-This plugin uses [lua-resty-http](https://github.com/api7/lua-resty-http) library under the hood to send requests to the upstream, due to which the [proxy-control](./proxy-control.md), [proxy-mirror](./proxy-mirror.md), and [proxy-cache](./proxy-cache.md) plugins are not available to be used alongside this plugin. Also, [mTLS Between APISIX and Upstream](../mtls.md#mtls-between-apisix-and-upstream) is not yet supported.
+This plugin uses [lua-resty-http](https://github.com/api7/lua-resty-http) library under the hood to send HTTP requests to the upstream, due to which it only works with HTTP upstreams and the HTTP response flow. Do not use this plugin with gRPC transcoding or non-HTTP upstream response flows, such as when using the [grpc-transcode](./grpc-transcode.md) plugin. The [proxy-control](./proxy-control.md), [proxy-mirror](./proxy-mirror.md), and [proxy-cache](./proxy-cache.md) plugins are not available to be used alongside this plugin. Also, [mTLS Between APISIX and Upstream](../mtls.md#mtls-between-apisix-and-upstream) is not yet supported.
 
 See [External Plugin](../external-plugin.md) to learn more.
 

docs/zh/latest/plugins/ext-plugin-post-resp.md

@@ -35,6 +35,7 @@ description: 本文介绍了关于 Apache APISIX `ext-plugin-post-resp` 插件
 
 启用本插件之后，APISIX 将使用 [lua-resty-http](https://github.com/api7/lua-resty-http) 库向上游发起请求，这会导致：
 
+- 本插件仅适用于 HTTP 上游和 HTTP 响应流程，不要与 gRPC 转码或非 HTTP 上游响应链路一起使用，例如不要与 [grpc-transcode](./grpc-transcode.md) 插件配合使用
 - [proxy-control](./proxy-control.md) 插件不可用
 - [proxy-mirror](./proxy-mirror.md) 插件不可用
 - [proxy-cache](./proxy-cache.md) 插件不可用