fix(discord): apply effective maxLinesPerMessage in live replies (#40133)

Merged via squash.

Prepared head SHA: 031d032
Co-authored-by: rbutera <6047293+rbutera@users.noreply.github.com>
Co-authored-by: altaywtf <9790196+altaywtf@users.noreply.github.com>
Reviewed-by: @altaywtf

Author: rbutera

CHANGELOG.md

@@ -36,6 +36,7 @@ Docs: https://docs.openclaw.ai
 - ACP/follow-up hardening: make session restore and prompt completion degrade gracefully on transcript/update failures, enforce bounded tool-location traversal, and skip non-image ACPX turns the runtime cannot serialize. (#41464) Thanks @mbelinky.
 - Agents/fallback observability: add structured, sanitized model-fallback decision and auth-profile failure-state events with correlated run IDs so cooldown probes and failover paths are easier to trace in logs. (#41337) thanks @altaywtf.
 - Protocol/Swift model sync: regenerate pending node work Swift bindings after the landed `node.pending.*` schema additions so generated protocol artifacts are consistent again. (#41477) Thanks @mbelinky.
+- Discord/reply chunking: resolve the effective `maxLinesPerMessage` config across live reply paths and preserve `chunkMode` in the fast send path so long Discord replies no longer split unexpectedly at the default 17-line limit. (#40133) thanks @rbutera.
 
 ## 2026.3.8
 

src/discord/accounts.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from "vitest";
-import { resolveDiscordAccount } from "./accounts.js";
+import { resolveDiscordAccount, resolveDiscordMaxLinesPerMessage } from "./accounts.js";
 
 describe("resolveDiscordAccount allowFrom precedence", () => {
   it("prefers accounts.default.allowFrom over top-level for default account", () => {
@@ -56,3 +56,62 @@ describe("resolveDiscordAccount allowFrom precedence", () => {
     expect(resolved.config.allowFrom).toBeUndefined();
   });
 });
+
+describe("resolveDiscordMaxLinesPerMessage", () => {
+  it("falls back to merged root discord maxLinesPerMessage when runtime config omits it", () => {
+    const resolved = resolveDiscordMaxLinesPerMessage({
+      cfg: {
+        channels: {
+          discord: {
+            maxLinesPerMessage: 120,
+            accounts: {
+              default: { token: "token-default" },
+            },
+          },
+        },
+      },
+      discordConfig: {},
+      accountId: "default",
+    });
+
+    expect(resolved).toBe(120);
+  });
+
+  it("prefers explicit runtime discord maxLinesPerMessage over merged config", () => {
+    const resolved = resolveDiscordMaxLinesPerMessage({
+      cfg: {
+        channels: {
+          discord: {
+            maxLinesPerMessage: 120,
+            accounts: {
+              default: { token: "token-default", maxLinesPerMessage: 80 },
+            },
+          },
+        },
+      },
+      discordConfig: { maxLinesPerMessage: 55 },
+      accountId: "default",
+    });
+
+    expect(resolved).toBe(55);
+  });
+
+  it("uses per-account discord maxLinesPerMessage over the root value when runtime config omits it", () => {
+    const resolved = resolveDiscordMaxLinesPerMessage({
+      cfg: {
+        channels: {
+          discord: {
+            maxLinesPerMessage: 120,
+            accounts: {
+              work: { token: "token-work", maxLinesPerMessage: 80 },
+            },
+          },
+        },
+      },
+      discordConfig: {},
+      accountId: "work",
+    });
+
+    expect(resolved).toBe(80);
+  });
+});

src/discord/accounts.ts

@@ -68,6 +68,20 @@ export function resolveDiscordAccount(params: {
   };
 }
 
+export function resolveDiscordMaxLinesPerMessage(params: {
+  cfg: OpenClawConfig;
+  discordConfig?: DiscordAccountConfig | null;
+  accountId?: string | null;
+}): number | undefined {
+  if (typeof params.discordConfig?.maxLinesPerMessage === "number") {
+    return params.discordConfig.maxLinesPerMessage;
+  }
+  return resolveDiscordAccount({
+    cfg: params.cfg,
+    accountId: params.accountId,
+  }).config.maxLinesPerMessage;
+}
+
 export function listEnabledDiscordAccounts(cfg: OpenClawConfig): ResolvedDiscordAccount[] {
   return listDiscordAccountIds(cfg)
     .map((accountId) => resolveDiscordAccount({ cfg, accountId }))

src/discord/monitor/agent-components.ts

@@ -43,6 +43,7 @@ import {
   readStoreAllowFromForDmPolicy,
   resolvePinnedMainDmOwnerFromAllowlist,
 } from "../../security/dm-policy-shared.js";
+import { resolveDiscordMaxLinesPerMessage } from "../accounts.js";
 import { resolveDiscordComponentEntry, resolveDiscordModalEntry } from "../components-registry.js";
 import {
   createDiscordFormModal,
@@ -1017,7 +1018,11 @@ async function dispatchDiscordComponentEvent(params: {
           replyToId,
           replyToMode,
           textLimit,
-          maxLinesPerMessage: ctx.discordConfig?.maxLinesPerMessage,
+          maxLinesPerMessage: resolveDiscordMaxLinesPerMessage({
+            cfg: ctx.cfg,
+            discordConfig: ctx.discordConfig,
+            accountId,
+          }),
           tableMode,
           chunkMode: resolveChunkMode(ctx.cfg, "discord", accountId),
           mediaLocalRoots,

src/discord/monitor/message-handler.process.test.ts

@@ -502,6 +502,38 @@ describe("processDiscordMessage draft streaming", () => {
     expect(deliverDiscordReply).toHaveBeenCalledTimes(1);
   });
 
+  it("uses root discord maxLinesPerMessage for preview finalization when runtime config omits it", async () => {
+    const longReply = Array.from({ length: 20 }, (_value, index) => `Line ${index + 1}`).join("\n");
+    dispatchInboundMessage.mockImplementationOnce(async (params?: DispatchInboundParams) => {
+      await params?.dispatcher.sendFinalReply({ text: longReply });
+      return { queuedFinal: true, counts: { final: 1, tool: 0, block: 0 } };
+    });
+
+    const ctx = await createBaseContext({
+      cfg: {
+        messages: { ackReaction: "👀" },
+        session: { store: "/tmp/openclaw-discord-process-test-sessions.json" },
+        channels: {
+          discord: {
+            maxLinesPerMessage: 120,
+          },
+        },
+      },
+      discordConfig: { streamMode: "partial" },
+    });
+
+    // oxlint-disable-next-line typescript/no-explicit-any
+    await processDiscordMessage(ctx as any);
+
+    expect(editMessageDiscord).toHaveBeenCalledWith(
+      "c1",
+      "preview-1",
+      { content: longReply },
+      { rest: {} },
+    );
+    expect(deliverDiscordReply).not.toHaveBeenCalled();
+  });
+
   it("suppresses reasoning payload delivery to Discord", async () => {
     mockDispatchSingleBlockReply({ text: "thinking...", isReasoning: true });
     await processStreamOffDiscordMessage();

src/discord/monitor/message-handler.process.ts

@@ -32,6 +32,7 @@ import { buildAgentSessionKey } from "../../routing/resolve-route.js";
 import { resolveThreadSessionKeys } from "../../routing/session-key.js";
 import { stripReasoningTagsFromText } from "../../shared/text/reasoning-tags.js";
 import { truncateUtf16Safe } from "../../utils.js";
+import { resolveDiscordMaxLinesPerMessage } from "../accounts.js";
 import { chunkDiscordTextWithMode } from "../chunk.js";
 import { resolveDiscordDraftStreamingChunking } from "../draft-chunking.js";
 import { createDiscordDraftStream } from "../draft-stream.js";
@@ -426,6 +427,11 @@ export async function processDiscordMessage(ctx: DiscordMessagePreflightContext)
     channel: "discord",
     accountId,
   });
+  const maxLinesPerMessage = resolveDiscordMaxLinesPerMessage({
+    cfg,
+    discordConfig,
+    accountId,
+  });
   const chunkMode = resolveChunkMode(cfg, "discord", accountId);
 
   const typingCallbacks = createTypingCallbacks({
@@ -484,7 +490,7 @@ export async function processDiscordMessage(ctx: DiscordMessagePreflightContext)
     const formatted = convertMarkdownTables(text, tableMode);
     const chunks = chunkDiscordTextWithMode(formatted, {
       maxChars: draftMaxChars,
-      maxLines: discordConfig?.maxLinesPerMessage,
+      maxLines: maxLinesPerMessage,
       chunkMode,
     });
     if (!chunks.length && formatted) {
@@ -687,7 +693,7 @@ export async function processDiscordMessage(ctx: DiscordMessagePreflightContext)
           replyToId,
           replyToMode,
           textLimit,
-          maxLinesPerMessage: discordConfig?.maxLinesPerMessage,
+          maxLinesPerMessage,
           tableMode,
           chunkMode,
           sessionKey: ctxPayload.SessionKey,

src/discord/monitor/native-command.commands-allowfrom.test.ts

@@ -3,6 +3,7 @@ import { beforeEach, describe, expect, it, vi } from "vitest";
 import type { NativeCommandSpec } from "../../auto-reply/commands-registry.js";
 import * as dispatcherModule from "../../auto-reply/reply/provider-dispatcher.js";
 import type { OpenClawConfig } from "../../config/config.js";
+import type { DiscordAccountConfig } from "../../config/types.discord.js";
 import * as pluginCommandsModule from "../../plugins/commands.js";
 import { createDiscordNativeCommand } from "./native-command.js";
 import {
@@ -49,7 +50,7 @@ function createConfig(): OpenClawConfig {
   } as OpenClawConfig;
 }
 
-function createCommand(cfg: OpenClawConfig) {
+function createCommand(cfg: OpenClawConfig, discordConfig?: DiscordAccountConfig) {
   const commandSpec: NativeCommandSpec = {
     name: "status",
     description: "Status",
@@ -58,7 +59,7 @@ function createCommand(cfg: OpenClawConfig) {
   return createDiscordNativeCommand({
     command: commandSpec,
     cfg,
-    discordConfig: cfg.channels?.discord ?? {},
+    discordConfig: discordConfig ?? cfg.channels?.discord ?? {},
     accountId: "default",
     sessionPrefix: "discord:slash",
     ephemeralDefault: true,
@@ -79,10 +80,11 @@ function createDispatchSpy() {
 async function runGuildSlashCommand(params?: {
   userId?: string;
   mutateConfig?: (cfg: OpenClawConfig) => void;
+  runtimeDiscordConfig?: DiscordAccountConfig;
 }) {
   const cfg = createConfig();
   params?.mutateConfig?.(cfg);
-  const command = createCommand(cfg);
+  const command = createCommand(cfg, params?.runtimeDiscordConfig);
   const interaction = createInteraction({ userId: params?.userId });
   vi.spyOn(pluginCommandsModule, "matchPluginCommand").mockReturnValue(null);
   const dispatchSpy = createDispatchSpy();
@@ -164,4 +166,41 @@ describe("Discord native slash commands with commands.allowFrom", () => {
     expect(dispatchSpy).not.toHaveBeenCalled();
     expectUnauthorizedReply(interaction);
   });
+
+  it("uses the root discord maxLinesPerMessage when runtime discordConfig omits it", async () => {
+    const longReply = Array.from({ length: 20 }, (_value, index) => `Line ${index + 1}`).join("\n");
+    const { interaction } = await runGuildSlashCommand({
+      mutateConfig: (cfg) => {
+        cfg.channels = {
+          ...cfg.channels,
+          discord: {
+            ...cfg.channels?.discord,
+            maxLinesPerMessage: 120,
+          },
+        };
+      },
+      runtimeDiscordConfig: {
+        groupPolicy: "allowlist",
+        guilds: {
+          "345678901234567890": {
+            channels: {
+              "234567890123456789": {
+                allow: true,
+                requireMention: false,
+              },
+            },
+          },
+        },
+      },
+    });
+
+    const dispatchCall = vi.mocked(dispatcherModule.dispatchReplyWithDispatcher).mock
+      .calls[0]?.[0] as
+      | Parameters<typeof dispatcherModule.dispatchReplyWithDispatcher>[0]
+      | undefined;
+    await dispatchCall?.dispatcherOptions.deliver({ text: longReply }, { kind: "final" });
+
+    expect(interaction.reply).toHaveBeenCalledWith(expect.objectContaining({ content: longReply }));
+    expect(interaction.followUp).not.toHaveBeenCalled();
+  });
 });

src/discord/monitor/native-command.ts

@@ -56,6 +56,7 @@ import type { ResolvedAgentRoute } from "../../routing/resolve-route.js";
 import { chunkItems } from "../../utils/chunk-items.js";
 import { withTimeout } from "../../utils/with-timeout.js";
 import { loadWebMedia } from "../../web/media.js";
+import { resolveDiscordMaxLinesPerMessage } from "../accounts.js";
 import { chunkDiscordTextWithMode } from "../chunk.js";
 import {
   isDiscordGroupAllowedByPolicy,
@@ -1571,7 +1572,7 @@ async function dispatchDiscordCommandInteraction(params: {
       textLimit: resolveTextChunkLimit(cfg, "discord", accountId, {
         fallbackLimit: 2000,
       }),
-      maxLinesPerMessage: discordConfig?.maxLinesPerMessage,
+      maxLinesPerMessage: resolveDiscordMaxLinesPerMessage({ cfg, discordConfig, accountId }),
       preferFollowUp,
       chunkMode: resolveChunkMode(cfg, "discord", accountId),
     });
@@ -1706,7 +1707,7 @@ async function dispatchDiscordCommandInteraction(params: {
             textLimit: resolveTextChunkLimit(cfg, "discord", accountId, {
               fallbackLimit: 2000,
             }),
-            maxLinesPerMessage: discordConfig?.maxLinesPerMessage,
+            maxLinesPerMessage: resolveDiscordMaxLinesPerMessage({ cfg, discordConfig, accountId }),
             preferFollowUp: preferFollowUp || didReply,
             chunkMode: resolveChunkMode(cfg, "discord", accountId),
           });

src/discord/monitor/reply-delivery.test.ts

@@ -256,6 +256,29 @@ describe("deliverDiscordReply", () => {
     expect(sendDiscordTextMock.mock.calls[1]?.[1]).toBe("789");
   });
 
+  it("passes maxLinesPerMessage and chunkMode through the fast path", async () => {
+    const fakeRest = {} as import("@buape/carbon").RequestClient;
+
+    await deliverDiscordReply({
+      replies: [{ text: Array.from({ length: 18 }, (_, index) => `line ${index + 1}`).join("\n") }],
+      target: "channel:789",
+      token: "token",
+      rest: fakeRest,
+      runtime,
+      textLimit: 2000,
+      maxLinesPerMessage: 120,
+      chunkMode: "newline",
+    });
+
+    expect(sendMessageDiscordMock).not.toHaveBeenCalled();
+    expect(sendDiscordTextMock).toHaveBeenCalledTimes(1);
+    const firstSendDiscordTextCall = sendDiscordTextMock.mock.calls[0];
+    const [, , , , , maxLinesPerMessageArg, , , chunkModeArg] = firstSendDiscordTextCall ?? [];
+
+    expect(maxLinesPerMessageArg).toBe(120);
+    expect(chunkModeArg).toBe("newline");
+  });
+
   it("falls back to sendMessageDiscord when rest is not provided", async () => {
     await deliverDiscordReply({
       replies: [{ text: "single chunk" }],

src/discord/monitor/reply-delivery.ts

@@ -130,9 +130,11 @@ async function sendDiscordChunkWithFallback(params: {
   text: string;
   token: string;
   accountId?: string;
+  maxLinesPerMessage?: number;
   rest?: RequestClient;
   replyTo?: string;
   binding?: DiscordThreadBindingLookupRecord;
+  chunkMode?: ChunkMode;
   username?: string;
   avatarUrl?: string;
   /** Pre-resolved channel ID to bypass redundant resolution per chunk. */
@@ -169,7 +171,18 @@ async function sendDiscordChunkWithFallback(params: {
   if (params.channelId && params.request && params.rest) {
     const { channelId, request, rest } = params;
     await sendWithRetry(
-      () => sendDiscordText(rest, channelId, text, params.replyTo, request),
+      () =>
+        sendDiscordText(
+          rest,
+          channelId,
+          text,
+          params.replyTo,
+          request,
+          params.maxLinesPerMessage,
+          undefined,
+          undefined,
+          params.chunkMode,
+        ),
       params.retryConfig,
     );
     return;
@@ -294,8 +307,10 @@ export async function deliverDiscordReply(params: {
           token: params.token,
           rest: params.rest,
           accountId: params.accountId,
+          maxLinesPerMessage: params.maxLinesPerMessage,
           replyTo,
           binding,
+          chunkMode: params.chunkMode,
           username: persona.username,
           avatarUrl: persona.avatarUrl,
           channelId,
@@ -329,8 +344,10 @@ export async function deliverDiscordReply(params: {
         token: params.token,
         rest: params.rest,
         accountId: params.accountId,
+        maxLinesPerMessage: params.maxLinesPerMessage,
         replyTo: resolveReplyTo(),
         binding,
+        chunkMode: params.chunkMode,
         username: persona.username,
         avatarUrl: persona.avatarUrl,
         channelId,