Docs: clarify plugin-owned message discovery

docs/help/testing.md

@@ -52,6 +52,17 @@ Think of the suites as “increasing realism” (and increasing flakiness/cost):
   - Runs in CI
   - No real keys required
   - Should be fast and stable
+- Embedded runner note:
+  - When you change message-tool discovery inputs or compaction runtime context,
+    keep both levels of coverage.
+  - Add focused helper regressions for pure routing/normalization seams.
+  - Also keep the embedded runner integration suites healthy:
+    `src/agents/pi-embedded-runner/compact.hooks.test.ts`,
+    `src/agents/pi-embedded-runner/run.overflow-compaction.test.ts`, and
+    `src/agents/pi-embedded-runner/run.overflow-compaction.loop.test.ts`.
+  - Those suites verify that scoped ids and compaction behavior still flow
+    through the real `run.ts` / `compact.ts` paths; helper-only tests are not a
+    sufficient substitute for those seams.
 - Pool note:
   - OpenClaw uses Vitest `vmForks` on Node 22, 23, and 24 for faster unit shards.
   - On Node 25+, OpenClaw automatically falls back to regular `forks` until the repo is re-validated there.

docs/tools/plugin.md

@@ -188,6 +188,46 @@ The important design boundary:
 That split lets OpenClaw validate config, explain missing/disabled plugins, and
 build UI/schema hints before the full runtime is active.
 
+### Channel plugins and the shared message tool
+
+Channel plugins do not need to register a separate send/edit/react tool for
+normal chat actions. OpenClaw keeps one shared `message` tool in core, and
+channel plugins own the channel-specific discovery and execution behind it.
+
+The current boundary is:
+
+- core owns the shared `message` tool host, prompt wiring, session/thread
+  bookkeeping, and execution dispatch
+- channel plugins own scoped action discovery, capability discovery, and any
+  channel-specific schema fragments
+- channel plugins execute the final action through their action adapter
+
+For channel plugins, the preferred SDK surface is
+`ChannelMessageActionAdapter.describeMessageTool(...)`. That unified discovery
+call lets a plugin return its visible actions, capabilities, and schema
+contributions together so those pieces do not drift apart.
+
+Core passes runtime scope into that discovery step. Important fields include:
+
+- `accountId`
+- `currentChannelId`
+- `currentThreadTs`
+- `currentMessageId`
+- `sessionKey`
+- `sessionId`
+- `agentId`
+- trusted inbound `requesterSenderId`
+
+That matters for context-sensitive plugins. A channel can hide or expose
+message actions based on the active account, current room/thread/message, or
+trusted requester identity without hardcoding channel-specific branches in the
+core `message` tool.
+
+This is why embedded-runner routing changes are still plugin work: the runner is
+responsible for forwarding the current chat/session identity into the plugin
+discovery boundary so the shared `message` tool exposes the right channel-owned
+surface for the current turn.
+
 ## Capability ownership model
 
 OpenClaw treats a native plugin as the ownership boundary for a **company** or a