Slack: support Block Kit blocks in sendMessage actions

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

@@ -137,9 +137,76 @@ describe("handleSlackAction", () => {
     expect(sendSlackMessage).toHaveBeenCalledWith("channel:C123", "Hello thread", {
       mediaUrl: undefined,
       threadTs: "1234567890.123456",
+      blocks: undefined,
     });
   });
 
+  it("accepts blocks JSON and allows empty content", async () => {
+    const cfg = { channels: { slack: { botToken: "tok" } } } as OpenClawConfig;
+    sendSlackMessage.mockClear();
+    await handleSlackAction(
+      {
+        action: "sendMessage",
+        to: "channel:C123",
+        blocks: JSON.stringify([
+          { type: "section", text: { type: "mrkdwn", text: "*Deploy* status" } },
+        ]),
+      },
+      cfg,
+    );
+    expect(sendSlackMessage).toHaveBeenCalledWith("channel:C123", "", {
+      mediaUrl: undefined,
+      threadTs: undefined,
+      blocks: [{ type: "section", text: { type: "mrkdwn", text: "*Deploy* status" } }],
+    });
+  });
+
+  it("accepts blocks arrays directly", async () => {
+    const cfg = { channels: { slack: { botToken: "tok" } } } as OpenClawConfig;
+    sendSlackMessage.mockClear();
+    await handleSlackAction(
+      {
+        action: "sendMessage",
+        to: "channel:C123",
+        blocks: [{ type: "divider" }],
+      },
+      cfg,
+    );
+    expect(sendSlackMessage).toHaveBeenCalledWith("channel:C123", "", {
+      mediaUrl: undefined,
+      threadTs: undefined,
+      blocks: [{ type: "divider" }],
+    });
+  });
+
+  it("rejects invalid blocks JSON", async () => {
+    const cfg = { channels: { slack: { botToken: "tok" } } } as OpenClawConfig;
+    await expect(
+      handleSlackAction(
+        {
+          action: "sendMessage",
+          to: "channel:C123",
+          blocks: "{bad-json",
+        },
+        cfg,
+      ),
+    ).rejects.toThrow(/blocks must be valid JSON/i);
+  });
+
+  it("requires at least one of content, blocks, or mediaUrl", async () => {
+    const cfg = { channels: { slack: { botToken: "tok" } } } as OpenClawConfig;
+    await expect(
+      handleSlackAction(
+        {
+          action: "sendMessage",
+          to: "channel:C123",
+          content: "",
+        },
+        cfg,
+      ),
+    ).rejects.toThrow(/requires content, blocks, or mediaUrl/i);
+  });
+
   it("auto-injects threadTs from context when replyToMode=all", async () => {
     const cfg = { channels: { slack: { botToken: "tok" } } } as OpenClawConfig;
     sendSlackMessage.mockClear();
@@ -159,6 +226,7 @@ describe("handleSlackAction", () => {
     expect(sendSlackMessage).toHaveBeenCalledWith("channel:C123", "Auto-threaded", {
       mediaUrl: undefined,
       threadTs: "1111111111.111111",
+      blocks: undefined,
     });
   });
 
@@ -182,6 +250,7 @@ describe("handleSlackAction", () => {
     expect(sendSlackMessage).toHaveBeenLastCalledWith("channel:C123", "First", {
       mediaUrl: undefined,
       threadTs: "1111111111.111111",
+      blocks: undefined,
     });
     expect(hasRepliedRef.value).toBe(true);
 
@@ -194,6 +263,7 @@ describe("handleSlackAction", () => {
     expect(sendSlackMessage).toHaveBeenLastCalledWith("channel:C123", "Second", {
       mediaUrl: undefined,
       threadTs: undefined,
+      blocks: undefined,
     });
   });
 
@@ -221,6 +291,7 @@ describe("handleSlackAction", () => {
     expect(sendSlackMessage).toHaveBeenLastCalledWith("channel:C123", "Explicit", {
       mediaUrl: undefined,
       threadTs: "2222222222.222222",
+      blocks: undefined,
     });
     expect(hasRepliedRef.value).toBe(true);
 
@@ -232,6 +303,7 @@ describe("handleSlackAction", () => {
     expect(sendSlackMessage).toHaveBeenLastCalledWith("channel:C123", "Second", {
       mediaUrl: undefined,
       threadTs: undefined,
+      blocks: undefined,
     });
   });
 
@@ -247,6 +319,7 @@ describe("handleSlackAction", () => {
     expect(sendSlackMessage).toHaveBeenCalledWith("channel:C123", "No ref", {
       mediaUrl: undefined,
       threadTs: undefined,
+      blocks: undefined,
     });
   });
 
@@ -269,6 +342,7 @@ describe("handleSlackAction", () => {
     expect(sendSlackMessage).toHaveBeenCalledWith("channel:C123", "Off mode", {
       mediaUrl: undefined,
       threadTs: undefined,
+      blocks: undefined,
     });
   });
 
@@ -291,6 +365,7 @@ describe("handleSlackAction", () => {
     expect(sendSlackMessage).toHaveBeenCalledWith("channel:C999", "Different channel", {
       mediaUrl: undefined,
       threadTs: undefined,
+      blocks: undefined,
     });
   });
 
@@ -314,6 +389,7 @@ describe("handleSlackAction", () => {
     expect(sendSlackMessage).toHaveBeenCalledWith("channel:C123", "Explicit thread", {
       mediaUrl: undefined,
       threadTs: "2222222222.222222",
+      blocks: undefined,
     });
   });
 
@@ -336,6 +412,7 @@ describe("handleSlackAction", () => {
     expect(sendSlackMessage).toHaveBeenCalledWith("C123", "No prefix", {
       mediaUrl: undefined,
       threadTs: "1111111111.111111",
+      blocks: undefined,
     });
   });
 

src/agents/tools/slack-actions.ts

@@ -1,4 +1,5 @@
 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 {
@@ -84,6 +85,27 @@ function resolveThreadTsFromContext(
   return undefined;
 }
 
+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)[];
+}
+
 export async function handleSlackAction(
   params: Record<string, unknown>,
   cfg: OpenClawConfig,
@@ -174,17 +196,22 @@ export async function handleSlackAction(
     switch (action) {
       case "sendMessage": {
         const to = readStringParam(params, "to", { required: true });
-        const content = readStringParam(params, "content", { required: true });
+        const content = readStringParam(params, "content", { allowEmpty: true });
         const mediaUrl = readStringParam(params, "mediaUrl");
+        const blocks = readSlackBlocksParam(params);
+        if (!content && !mediaUrl && !blocks) {
+          throw new Error("Slack sendMessage requires content, blocks, or mediaUrl.");
+        }
         const threadTs = resolveThreadTsFromContext(
           readStringParam(params, "threadTs"),
           to,
           context,
         );
-        const result = await sendSlackMessage(to, content, {
+        const result = await sendSlackMessage(to, content ?? "", {
           ...writeOpts,
           mediaUrl: mediaUrl ?? undefined,
           threadTs: threadTs ?? undefined,
+          blocks,
         });
 
         // Keep "first" mode consistent even when the agent explicitly provided

src/slack/actions.ts

@@ -1,4 +1,4 @@
-import type { WebClient } from "@slack/web-api";
+import type { Block, KnownBlock, WebClient } from "@slack/web-api";
 import { loadConfig } from "../config/config.js";
 import { logVerbose } from "../globals.js";
 import { resolveSlackAccount } from "./accounts.js";
@@ -147,7 +147,11 @@ export async function listSlackReactions(
 export async function sendSlackMessage(
   to: string,
   content: string,
-  opts: SlackActionClientOpts & { mediaUrl?: string; threadTs?: string } = {},
+  opts: SlackActionClientOpts & {
+    mediaUrl?: string;
+    threadTs?: string;
+    blocks?: (Block | KnownBlock)[];
+  } = {},
 ) {
   return await sendMessageSlack(to, content, {
     accountId: opts.accountId,
@@ -155,6 +159,7 @@ export async function sendSlackMessage(
     mediaUrl: opts.mediaUrl,
     client: opts.client,
     threadTs: opts.threadTs,
+    blocks: opts.blocks,
   });
 }
 

src/slack/send.ts

@@ -1,4 +1,9 @@
-import { type FilesUploadV2Arguments, type WebClient } from "@slack/web-api";
+import {
+  type Block,
+  type FilesUploadV2Arguments,
+  type KnownBlock,
+  type WebClient,
+} from "@slack/web-api";
 import type { SlackTokenSource } from "./accounts.js";
 import {
   chunkMarkdownTextWithMode,
@@ -41,6 +46,7 @@ type SlackSendOpts = {
   client?: WebClient;
   threadTs?: string;
   identity?: SlackSendIdentity;
+  blocks?: (Block | KnownBlock)[];
 };
 
 function hasCustomIdentity(identity?: SlackSendIdentity): boolean {
@@ -79,11 +85,13 @@ async function postSlackMessageBestEffort(params: {
   text: string;
   threadTs?: string;
   identity?: SlackSendIdentity;
+  blocks?: (Block | KnownBlock)[];
 }) {
   const basePayload = {
     channel: params.channelId,
     text: params.text,
     thread_ts: params.threadTs,
+    ...(params.blocks?.length ? { blocks: params.blocks } : {}),
   };
   try {
     // Slack Web API types model icon_url and icon_emoji as mutually exclusive.
@@ -214,8 +222,9 @@ export async function sendMessageSlack(
   opts: SlackSendOpts = {},
 ): Promise<SlackSendResult> {
   const trimmedMessage = message?.trim() ?? "";
-  if (!trimmedMessage && !opts.mediaUrl) {
+  const blocks = opts.blocks?.length ? opts.blocks : undefined;
-    throw new Error("Slack send requires text or media");
+  if (!trimmedMessage && !opts.mediaUrl && !blocks) {
+    throw new Error("Slack send requires text, blocks, or media");
   }
   const cfg = loadConfig();
   const account = resolveSlackAccount({
@@ -231,6 +240,23 @@ export async function sendMessageSlack(
   const client = opts.client ?? createSlackWebClient(token);
   const recipient = parseRecipient(to);
   const { channelId } = await resolveChannelId(client, recipient);
+  if (blocks) {
+    if (opts.mediaUrl) {
+      throw new Error("Slack send does not support blocks with mediaUrl");
+    }
+    const response = await postSlackMessageBestEffort({
+      client,
+      channelId,
+      text: trimmedMessage || " ",
+      threadTs: opts.threadTs,
+      identity: opts.identity,
+      blocks,
+    });
+    return {
+      messageId: response.ts ?? "unknown",
+      channelId,
+    };
+  }
   const textLimit = resolveTextChunkLimit(cfg, "slack", account.accountId);
   const chunkLimit = Math.min(textLimit, SLACK_TEXT_LIMIT);
   const tableMode = resolveMarkdownTableMode({