diff --git a/docs/plugins/building-plugins.md b/docs/plugins/building-plugins.md
index 28d04f0a5b5..905c32c99c4 100644
--- a/docs/plugins/building-plugins.md
+++ b/docs/plugins/building-plugins.md
@@ -181,6 +181,10 @@ Hook guard semantics to keep in mind:
 
 The `/approve` command handles both exec and plugin approvals with bounded fallback: when an exec approval id is not found, OpenClaw retries the same id through plugin approvals. Plugin approval forwarding can be configured independently via `approvals.plugin` in config.
 
+If custom approval plumbing needs to detect that same bounded fallback case,
+prefer `isApprovalNotFoundError` from `openclaw/plugin-sdk/error-runtime`
+instead of matching approval-expiry strings manually.
+
 See [SDK Overview hook decision semantics](/plugins/sdk-overview#hook-decision-semantics) for details.
 
 ## Registering agent tools
diff --git a/docs/plugins/sdk-overview.md b/docs/plugins/sdk-overview.md
index b1d07172f5c..25416ea446d 100644
--- a/docs/plugins/sdk-overview.md
+++ b/docs/plugins/sdk-overview.md
@@ -210,7 +210,7 @@ explicitly promotes one as public.
     | `plugin-sdk/infra-runtime` | System event/heartbeat helpers |
     | `plugin-sdk/collection-runtime` | Small bounded cache helpers |
     | `plugin-sdk/diagnostic-runtime` | Diagnostic flag and event helpers |
-    | `plugin-sdk/error-runtime` | Error graph, formatting, and shared error classification helpers |
+    | `plugin-sdk/error-runtime` | Error graph, formatting, shared error classification helpers, `isApprovalNotFoundError` |
     | `plugin-sdk/fetch-runtime` | Wrapped fetch, proxy, and pinned lookup helpers |
     | `plugin-sdk/host-runtime` | Hostname and SCP host normalization helpers |
     | `plugin-sdk/retry-runtime` | Retry config and retry runner helpers |