Slack: validate blocks input shape centrally

src/agents/tools/slack-actions.e2e.test.ts

@@ -193,6 +193,20 @@ describe("handleSlackAction", () => {
     ).rejects.toThrow(/blocks must be valid JSON/i);
   });
 
+  it("rejects empty blocks arrays", async () => {
+    const cfg = { channels: { slack: { botToken: "tok" } } } as OpenClawConfig;
+    await expect(
+      handleSlackAction(
+        {
+          action: "sendMessage",
+          to: "channel:C123",
+          blocks: "[]",
+        },
+        cfg,
+      ),
+    ).rejects.toThrow(/at least one block/i);
+  });
+
   it("requires at least one of content, blocks, or mediaUrl", async () => {
     const cfg = { channels: { slack: { botToken: "tok" } } } as OpenClawConfig;
     await expect(

src/agents/tools/slack-actions.ts

@@ -1,5 +1,4 @@
 import type { AgentToolResult } from "@mariozechner/pi-agent-core";
-import type { Block, KnownBlock } from "@slack/web-api";
 import type { OpenClawConfig } from "../../config/config.js";
 import { resolveSlackAccount } from "../../slack/accounts.js";
 import {
@@ -17,6 +16,7 @@ import {
   sendSlackMessage,
   unpinSlackMessage,
 } from "../../slack/actions.js";
+import { parseSlackBlocksInput } from "../../slack/blocks-input.js";
 import { parseSlackTarget, resolveSlackChannelId } from "../../slack/targets.js";
 import { withNormalizedTimestamp } from "../date-time.js";
 import {
@@ -86,24 +86,7 @@ function resolveThreadTsFromContext(
 }
 
 function readSlackBlocksParam(params: Record<string, unknown>) {
-  const raw = params.blocks;
-  if (raw == null) {
-    return undefined;
-  }
-  const parsed =
-    typeof raw === "string"
-      ? (() => {
-          try {
-            return JSON.parse(raw);
-          } catch {
-            throw new Error("blocks must be valid JSON");
-          }
-        })()
-      : raw;
-  if (!Array.isArray(parsed)) {
-    throw new Error("blocks must be an array");
-  }
-  return parsed as (Block | KnownBlock)[];
+  return parseSlackBlocksInput(params.blocks);
 }
 
 export async function handleSlackAction(