diff --git a/openclaw.plugin.json b/openclaw.plugin.json
index 8218aa9..8fc44a2 100644
--- a/openclaw.plugin.json
+++ b/openclaw.plugin.json
@@ -20,6 +20,7 @@
       "fabric-canvas",
       "fabric-channel",
       "fabric-send-message",
+      "fabric-send-sys-msg",
       "fabric-channel-list",
       "fabric-message-history",
       "fabric-guild-list",
diff --git a/src/tools.ts b/src/tools.ts
index a1d2806..cf0c906 100644
--- a/src/tools.ts
+++ b/src/tools.ts
@@ -555,6 +555,89 @@ export function registerFabricTools(
     },
   }));
 
+  // ───────────────────────────────────────────────────────────────────
+  // fabric-send-sys-msg: post a system-authored message (author =
+  // sentinel UUID 0000…, not the calling agent) using the Guild's
+  // x-fabric-system-key path. Use for cross-agent broadcasts where you
+  // don't want the message tied to one agent's identity — Dialectic
+  // topic announcements / lifecycle events, host-system advisories,
+  // etc. Caller doesn't need to be a member of the channel (the
+  // backend isSystem branch skips assertParticipant), but must be a
+  // member of the guild (their session resolves the guild endpoint).
+  //
+  // Shared secret: reads channels.fabric.commandsSyncKey (same value
+  // as the guild's FABRIC_BACKEND_GUILD_COMMANDS_SYNC_KEY env). Empty
+  // config → tool returns ok:false with a clear error, no fall-through
+  // to regular agent posting.
+  // ───────────────────────────────────────────────────────────────────
+  api.registerTool((ctx: Ctx) => ({
+    name: 'fabric-send-sys-msg',
+    description:
+      'Send a SYSTEM-AUTHORED message into a Fabric channel (author = guild sentinel, not you). ' +
+      'Use for cross-agent broadcasts that should not be attributed to a single agent — ' +
+      'Dialectic announce-channel topic broadcasts, lifecycle events, system advisories. ' +
+      'Optionally precise-wake one recipient via wakeupUserId; otherwise the message lands ' +
+      'silently in history (no wake).',
+    parameters: {
+      type: 'object',
+      additionalProperties: false,
+      required: ['guildNodeId', 'channelId', 'content'],
+      properties: {
+        guildNodeId: { type: 'string' },
+        channelId: { type: 'string' },
+        content: { type: 'string', description: 'Message body (markdown supported by the renderer).' },
+        wakeupUserId: {
+          type: 'string',
+          description:
+            "Optional: a single Fabric userId to wake with this message (everyone else in the " +
+            'channel sees it but with wakeup=false). Omit for fully silent broadcast.',
+        },
+      },
+    },
+    execute: async (
+      _id: string,
+      p: { guildNodeId: string; channelId: string; content: string; wakeupUserId?: string },
+    ) => {
+      const agentId = ctx.agentId;
+      if (!agentId) return { ok: false, error: 'no agent context' };
+      const systemKey = resolveCommandsSyncKey(cfg);
+      if (!systemKey) {
+        return {
+          ok: false,
+          error:
+            'channels.fabric.commandsSyncKey is not configured — fabric-send-sys-msg needs it for ' +
+            'the x-fabric-system-key header. Configure via openclaw config.',
+        };
+      }
+      const { guild } = await ctxGuild(agentId, p.guildNodeId);
+      const url = `${guild.endpoint}/api/channels/${encodeURIComponent(p.channelId)}/messages`;
+      const wakeup = typeof p.wakeupUserId === 'string' && p.wakeupUserId.trim()
+        ? p.wakeupUserId.trim()
+        : null;
+      const res = await fetch(url, {
+        method: 'POST',
+        headers: {
+          'content-type': 'application/json',
+          'x-fabric-system-key': systemKey,
+        },
+        body: JSON.stringify({ content: p.content, wakeupUserId: wakeup }),
+      });
+      if (!res.ok) {
+        const text = await res.text().catch(() => '');
+        return { ok: false, error: `POST ${url} -> ${res.status} ${text}` };
+      }
+      const json = (await res.json().catch(() => null)) as
+        | { messageId?: string; seq?: number; authorUserId?: string }
+        | null;
+      return {
+        ok: true,
+        messageId: json?.messageId,
+        seq: json?.seq,
+        authorUserId: json?.authorUserId,
+      };
+    },
+  }));
+
   // -----------------------------------------------------------------
   // fabric-channel-list: enumerate channels the calling agent can see
   // in a given guild. Backend filters to public channels + channels the