diff --git a/src/auto-reply/chunk.test.ts b/src/auto-reply/chunk.test.ts
index eb08e9642..02f6d75cb 100644
--- a/src/auto-reply/chunk.test.ts
+++ b/src/auto-reply/chunk.test.ts
@@ -50,6 +50,7 @@ describe("resolveTextChunkLimit", () => {
   it("uses per-surface defaults", () => {
     expect(resolveTextChunkLimit(undefined, "whatsapp")).toBe(4000);
     expect(resolveTextChunkLimit(undefined, "telegram")).toBe(4000);
+    expect(resolveTextChunkLimit(undefined, "slack")).toBe(4000);
     expect(resolveTextChunkLimit(undefined, "signal")).toBe(4000);
     expect(resolveTextChunkLimit(undefined, "imessage")).toBe(4000);
     expect(resolveTextChunkLimit(undefined, "discord")).toBe(2000);
@@ -62,8 +63,9 @@ describe("resolveTextChunkLimit", () => {
   });
 
   it("uses the matching provider override", () => {
-    const cfg = { discord: { textChunkLimit: 111 } };
+    const cfg = { discord: { textChunkLimit: 111 }, slack: { textChunkLimit: 222 } };
     expect(resolveTextChunkLimit(cfg, "discord")).toBe(111);
+    expect(resolveTextChunkLimit(cfg, "slack")).toBe(222);
     expect(resolveTextChunkLimit(cfg, "telegram")).toBe(4000);
   });
 });
diff --git a/src/auto-reply/chunk.ts b/src/auto-reply/chunk.ts
index 9d8f1e35d..b924e67a3 100644
--- a/src/auto-reply/chunk.ts
+++ b/src/auto-reply/chunk.ts
@@ -8,6 +8,7 @@ export type TextChunkSurface =
   | "whatsapp"
   | "telegram"
   | "discord"
+  | "slack"
   | "signal"
   | "imessage"
   | "webchat";
@@ -16,6 +17,7 @@ const DEFAULT_CHUNK_LIMIT_BY_SURFACE: Record<TextChunkSurface, number> = {
   whatsapp: 4000,
   telegram: 4000,
   discord: 2000,
+  slack: 4000,
   signal: 4000,
   imessage: 4000,
   webchat: 4000,
@@ -30,6 +32,7 @@ export function resolveTextChunkLimit(
     if (surface === "whatsapp") return cfg?.whatsapp?.textChunkLimit;
     if (surface === "telegram") return cfg?.telegram?.textChunkLimit;
     if (surface === "discord") return cfg?.discord?.textChunkLimit;
+    if (surface === "slack") return cfg?.slack?.textChunkLimit;
     if (surface === "signal") return cfg?.signal?.textChunkLimit;
     if (surface === "imessage") return cfg?.imessage?.textChunkLimit;
     return undefined;