feat(slack): add configurable stream modes

src/config/schema.help.ts

@@ -329,6 +329,8 @@ export const FIELD_HELP: Record<string, string> = {
   "channels.slack.commands.native": 'Override native commands for Slack (bool or "auto").',
   "channels.slack.commands.nativeSkills":
     'Override native skill commands for Slack (bool or "auto").',
+  "channels.slack.streamMode":
+    "Live stream preview mode for Slack replies (replace | status_final | append).",
   "session.agentToAgent.maxPingPongTurns":
     "Max reply-back turns between requester and target (0–5).",
   "channels.telegram.customCommands":

src/config/schema.labels.ts

@@ -279,6 +279,7 @@ export const FIELD_LABELS: Record<string, string> = {
   "channels.slack.appToken": "Slack App Token",
   "channels.slack.userToken": "Slack User Token",
   "channels.slack.userTokenReadOnly": "Slack User Token Read Only",
+  "channels.slack.streamMode": "Slack Stream Mode",
   "channels.slack.thread.historyScope": "Slack Thread History Scope",
   "channels.slack.thread.inheritParent": "Slack Thread Parent Inheritance",
   "channels.slack.thread.initialHistoryLimit": "Slack Thread Initial History Limit",

src/config/types.slack.ts

@@ -45,6 +45,7 @@ export type SlackChannelConfig = {
 };
 
 export type SlackReactionNotificationMode = "off" | "own" | "all" | "allowlist";
+export type SlackStreamMode = "replace" | "status_final" | "append";
 
 export type SlackActionConfig = {
   reactions?: boolean;
@@ -124,6 +125,8 @@ export type SlackAccountConfig = {
   blockStreaming?: boolean;
   /** Merge streamed block replies before sending. */
   blockStreamingCoalesce?: BlockStreamingCoalesceConfig;
+  /** Slack stream preview mode (replace|status_final|append). Default: replace. */
+  streamMode?: SlackStreamMode;
   mediaMaxMb?: number;
   /** Reaction notification mode (off|own|all|allowlist). Default: own. */
   reactionNotifications?: SlackReactionNotificationMode;

src/config/zod-schema.providers-core.ts

@@ -460,6 +460,7 @@ export const GoogleChatAccountSchema = z
     chunkMode: z.enum(["length", "newline"]).optional(),
     blockStreaming: z.boolean().optional(),
     blockStreamingCoalesce: BlockStreamingCoalesceSchema.optional(),
+    streamMode: z.enum(["replace", "status_final", "append"]).optional().default("replace"),
     mediaMaxMb: z.number().positive().optional(),
     replyToMode: ReplyToModeSchema.optional(),
     actions: z

src/slack/monitor/message-handler/dispatch.ts

@@ -11,6 +11,11 @@ import { resolveStorePath, updateLastRoute } from "../../../config/sessions.js";
 import { danger, logVerbose, shouldLogVerbose } from "../../../globals.js";
 import { removeSlackReaction } from "../../actions.js";
 import { createSlackDraftStream } from "../../draft-stream.js";
+import {
+  applyAppendOnlyStreamUpdate,
+  buildStatusFinalPreviewText,
+  resolveSlackStreamMode,
+} from "../../stream-mode.js";
 import { resolveSlackThreadTargets } from "../../threading.js";
 import { createSlackReplyDeliveryPlan, deliverReplies } from "../replies.js";
 
@@ -112,6 +117,7 @@ export async function dispatchPreparedSlackMessage(prepared: PreparedSlackMessag
       const draftChannelId = draftStream?.channelId();
       const finalText = payload.text;
       const canFinalizeViaPreviewEdit =
+        streamMode !== "status_final" &&
         mediaCount === 0 &&
         !payload.isError &&
         typeof finalText === "string" &&
@@ -134,6 +140,21 @@ export async function dispatchPreparedSlackMessage(prepared: PreparedSlackMessag
             `slack: preview final edit failed; falling back to standard send (${String(err)})`,
           );
         }
+      } else if (streamMode === "status_final" && hasStreamedMessage) {
+        try {
+          const statusChannelId = draftStream?.channelId();
+          const statusMessageId = draftStream?.messageId();
+          if (statusChannelId && statusMessageId) {
+            await ctx.app.client.chat.update({
+              token: ctx.botToken,
+              channel: statusChannelId,
+              ts: statusMessageId,
+              text: "Status: complete. Final answer posted below.",
+            });
+          }
+        } catch (err) {
+          logVerbose(`slack: status_final completion update failed (${String(err)})`);
+        }
       } else if (mediaCount > 0) {
         await draftStream?.clear();
         hasStreamedMessage = false;
@@ -170,11 +191,42 @@ export async function dispatchPreparedSlackMessage(prepared: PreparedSlackMessag
     warn: logVerbose,
   });
   let hasStreamedMessage = false;
+  const streamMode = resolveSlackStreamMode(account.config.streamMode);
+  let appendRenderedText = "";
+  let appendSourceText = "";
+  let statusUpdateCount = 0;
   const updateDraftFromPartial = (text?: string) => {
     const trimmed = text?.trimEnd();
     if (!trimmed) {
       return;
     }
+
+    if (streamMode === "append") {
+      const next = applyAppendOnlyStreamUpdate({
+        incoming: trimmed,
+        rendered: appendRenderedText,
+        source: appendSourceText,
+      });
+      appendRenderedText = next.rendered;
+      appendSourceText = next.source;
+      if (!next.changed) {
+        return;
+      }
+      draftStream.update(next.rendered);
+      hasStreamedMessage = true;
+      return;
+    }
+
+    if (streamMode === "status_final") {
+      statusUpdateCount += 1;
+      if (statusUpdateCount > 1 && statusUpdateCount % 4 !== 0) {
+        return;
+      }
+      draftStream.update(buildStatusFinalPreviewText(statusUpdateCount));
+      hasStreamedMessage = true;
+      return;
+    }
+
     draftStream.update(trimmed);
     hasStreamedMessage = true;
   };
@@ -199,12 +251,18 @@ export async function dispatchPreparedSlackMessage(prepared: PreparedSlackMessag
         if (hasStreamedMessage) {
           draftStream.forceNewMessage();
           hasStreamedMessage = false;
+          appendRenderedText = "";
+          appendSourceText = "";
+          statusUpdateCount = 0;
         }
       },
       onReasoningEnd: async () => {
         if (hasStreamedMessage) {
           draftStream.forceNewMessage();
           hasStreamedMessage = false;
+          appendRenderedText = "";
+          appendSourceText = "";
+          statusUpdateCount = 0;
         }
       },
     },

src/slack/stream-mode.test.ts

@@ -0,0 +1,78 @@
+import { describe, expect, it } from "vitest";
+import {
+  applyAppendOnlyStreamUpdate,
+  buildStatusFinalPreviewText,
+  resolveSlackStreamMode,
+} from "./stream-mode.js";
+
+describe("resolveSlackStreamMode", () => {
+  it("defaults to replace", () => {
+    expect(resolveSlackStreamMode(undefined)).toBe("replace");
+    expect(resolveSlackStreamMode("")).toBe("replace");
+    expect(resolveSlackStreamMode("unknown")).toBe("replace");
+  });
+
+  it("accepts valid modes", () => {
+    expect(resolveSlackStreamMode("replace")).toBe("replace");
+    expect(resolveSlackStreamMode("status_final")).toBe("status_final");
+    expect(resolveSlackStreamMode("append")).toBe("append");
+  });
+});
+
+describe("applyAppendOnlyStreamUpdate", () => {
+  it("starts with first incoming text", () => {
+    const next = applyAppendOnlyStreamUpdate({
+      incoming: "hello",
+      rendered: "",
+      source: "",
+    });
+    expect(next).toEqual({ rendered: "hello", source: "hello", changed: true });
+  });
+
+  it("uses cumulative incoming text when it extends prior source", () => {
+    const next = applyAppendOnlyStreamUpdate({
+      incoming: "hello world",
+      rendered: "hello",
+      source: "hello",
+    });
+    expect(next).toEqual({
+      rendered: "hello world",
+      source: "hello world",
+      changed: true,
+    });
+  });
+
+  it("ignores regressive shorter incoming text", () => {
+    const next = applyAppendOnlyStreamUpdate({
+      incoming: "hello",
+      rendered: "hello world",
+      source: "hello world",
+    });
+    expect(next).toEqual({
+      rendered: "hello world",
+      source: "hello world",
+      changed: false,
+    });
+  });
+
+  it("appends non-prefix incoming chunks", () => {
+    const next = applyAppendOnlyStreamUpdate({
+      incoming: "next chunk",
+      rendered: "hello world",
+      source: "hello world",
+    });
+    expect(next).toEqual({
+      rendered: "hello world\nnext chunk",
+      source: "next chunk",
+      changed: true,
+    });
+  });
+});
+
+describe("buildStatusFinalPreviewText", () => {
+  it("cycles status dots", () => {
+    expect(buildStatusFinalPreviewText(1)).toBe("Status: thinking..");
+    expect(buildStatusFinalPreviewText(2)).toBe("Status: thinking...");
+    expect(buildStatusFinalPreviewText(3)).toBe("Status: thinking.");
+  });
+});

src/slack/stream-mode.ts

@@ -0,0 +1,53 @@
+export type SlackStreamMode = "replace" | "status_final" | "append";
+
+const DEFAULT_STREAM_MODE: SlackStreamMode = "replace";
+
+export function resolveSlackStreamMode(raw: unknown): SlackStreamMode {
+  if (typeof raw !== "string") {
+    return DEFAULT_STREAM_MODE;
+  }
+  const normalized = raw.trim().toLowerCase();
+  if (normalized === "replace" || normalized === "status_final" || normalized === "append") {
+    return normalized;
+  }
+  return DEFAULT_STREAM_MODE;
+}
+
+export function applyAppendOnlyStreamUpdate(params: {
+  incoming: string;
+  rendered: string;
+  source: string;
+}): { rendered: string; source: string; changed: boolean } {
+  const incoming = params.incoming.trimEnd();
+  if (!incoming) {
+    return { rendered: params.rendered, source: params.source, changed: false };
+  }
+  if (!params.rendered) {
+    return { rendered: incoming, source: incoming, changed: true };
+  }
+  if (incoming === params.source) {
+    return { rendered: params.rendered, source: params.source, changed: false };
+  }
+
+  // Typical model partials are cumulative prefixes.
+  if (incoming.startsWith(params.source) || incoming.startsWith(params.rendered)) {
+    return { rendered: incoming, source: incoming, changed: incoming !== params.rendered };
+  }
+
+  // Ignore regressive shorter variants of the same stream.
+  if (params.source.startsWith(incoming)) {
+    return { rendered: params.rendered, source: params.source, changed: false };
+  }
+
+  const separator = params.rendered.endsWith("\n") ? "" : "\n";
+  return {
+    rendered: `${params.rendered}${separator}${incoming}`,
+    source: incoming,
+    changed: true,
+  };
+}
+
+export function buildStatusFinalPreviewText(updateCount: number): string {
+  const dots = ".".repeat((Math.max(1, updateCount) % 3) + 1);
+  return `Status: thinking${dots}`;
+}