diff --git a/src/gateway/chat-abort.test.ts b/src/gateway/chat-abort.test.ts
index 17d21b22a02..726a284ac58 100644
--- a/src/gateway/chat-abort.test.ts
+++ b/src/gateway/chat-abort.test.ts
@@ -2,6 +2,7 @@ import { afterEach, describe, expect, it, vi } from "vitest";
 import {
   abortChatRunById,
   abortChatRunsForProvider,
+  boundInFlightRunSnapshotForChatHistory,
   isChatStopCommandText,
   registerChatAbortController,
   resolveAgentRunExpiresAtMs,
@@ -544,4 +545,24 @@ describe("resolveInFlightRunSnapshot", () => {
       }),
     ).toEqual({ runId: "run-b", text: "b" });
   });
+
+  it("keeps in-flight text when it fits the chat history budget", () => {
+    expect(
+      boundInFlightRunSnapshotForChatHistory({
+        snapshot: { runId: "run-1", text: "partial" },
+        messages: [],
+        maxBytes: 1_000,
+      }),
+    ).toEqual({ runId: "run-1", text: "partial" });
+  });
+
+  it("drops oversized in-flight text but keeps the run id for adoption", () => {
+    expect(
+      boundInFlightRunSnapshotForChatHistory({
+        snapshot: { runId: "run-1", text: "x".repeat(1_000) },
+        messages: [],
+        maxBytes: 100,
+      }),
+    ).toEqual({ runId: "run-1", text: "" });
+  });
 });
diff --git a/src/gateway/chat-abort.ts b/src/gateway/chat-abort.ts
index 8dd1c1bbac6..aba6c7c06c4 100644
--- a/src/gateway/chat-abort.ts
+++ b/src/gateway/chat-abort.ts
@@ -7,6 +7,7 @@ import { resolveDefaultAgentId } from "../agents/agent-scope-config.js";
 import { isAbortRequestText } from "../auto-reply/reply/abort-primitives.js";
 import type { OpenClawConfig } from "../config/types.openclaw.js";
 import { emitAgentEvent } from "../infra/agent-events.js";
+import { jsonUtf8Bytes } from "../infra/json-utf8-bytes.js";
 
 const DEFAULT_CHAT_RUN_ABORT_GRACE_MS = 60_000;
 
@@ -237,6 +238,25 @@ export function resolveInFlightRunSnapshot(params: {
   return { runId: best.runId, text: params.chatRunBuffers?.get(best.runId) ?? "" };
 }
 
+export function boundInFlightRunSnapshotForChatHistory(params: {
+  snapshot: { runId: string; text: string } | undefined;
+  messages: unknown[];
+  maxBytes: number;
+}): { runId: string; text: string } | undefined {
+  if (!params.snapshot?.text) {
+    return params.snapshot;
+  }
+  const messagesBytes = jsonUtf8Bytes(params.messages);
+  const snapshotBytes = jsonUtf8Bytes(params.snapshot);
+  if (messagesBytes + snapshotBytes <= params.maxBytes) {
+    return params.snapshot;
+  }
+  // The run id is the recovery contract; buffered partial text is opportunistic.
+  // If it would break the history payload budget, keep adoption and wait for the
+  // next live delta/final instead of sending an oversized chat.history response.
+  return { runId: params.snapshot.runId, text: "" };
+}
+
 export type ChatAbortOps = {
   chatAbortControllers: Map<string, ChatAbortControllerEntry>;
   chatRunBuffers: Map<string, string>;
diff --git a/src/gateway/server-methods/chat.ts b/src/gateway/server-methods/chat.ts
index 1e3be318b42..190011ec7b0 100644
--- a/src/gateway/server-methods/chat.ts
+++ b/src/gateway/server-methods/chat.ts
@@ -99,6 +99,7 @@ import {
 } from "../../utils/message-channel.js";
 import {
   abortChatRunById,
+  boundInFlightRunSnapshotForChatHistory,
   type ChatAbortControllerEntry,
   type ChatAbortOps,
   isChatStopCommandText,
@@ -2556,6 +2557,11 @@ export const chatHandlers: GatewayRequestHandlers = {
       agentId: requestedAgentId,
       defaultAgentId: resolveDefaultAgentId(cfg),
     });
+    const boundedInFlightRun = boundInFlightRunSnapshotForChatHistory({
+      snapshot: inFlightRun,
+      messages: bounded.messages,
+      maxBytes: maxHistoryBytes,
+    });
     respond(true, {
       sessionKey,
       sessionId,
@@ -2565,7 +2571,7 @@ export const chatHandlers: GatewayRequestHandlers = {
       thinkingLevel,
       fastMode: entry?.fastMode,
       verboseLevel,
-      ...(inFlightRun ? { inFlightRun } : {}),
+      ...(boundedInFlightRun ? { inFlightRun: boundedInFlightRun } : {}),
     });
   },
   "chat.message.get": async ({ params, respond, context }) => {