fix: prevent malformed_streaming_fragment sentinel from leaking through TUI/raw formatter paths

src/agents/anthropic-transport-stream.ts

@@ -9,6 +9,7 @@ import {
   type SimpleStreamOptions,
   type ThinkingLevel,
 } from "@mariozechner/pi-ai";
+import { MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE } from "../shared/assistant-error-format.js";
 import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import {
   applyAnthropicPayloadPolicyToParams,
@@ -24,7 +25,6 @@ import {
   createWritableTransportEventStream,
   failTransportStream,
   finalizeTransportStream,
-  MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE,
   mergeTransportHeaders,
   sanitizeNonEmptyTransportPayloadText,
   sanitizeTransportPayloadText,

src/agents/pi-embedded-helpers.formatassistanterrortext.test.ts

@@ -1,5 +1,6 @@
 import type { AssistantMessage } from "@mariozechner/pi-ai";
 import { describe, expect, it } from "vitest";
+import { MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE } from "../shared/assistant-error-format.js";
 import {
   BILLING_ERROR_USER_MESSAGE,
   formatBillingErrorMessage,
@@ -10,7 +11,6 @@ import {
   sanitizeUserFacingText,
 } from "./pi-embedded-helpers.js";
 import { makeAssistantMessageFixture } from "./test-helpers/assistant-message-fixtures.js";
-import { MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE } from "./transport-stream-shared.js";
 
 describe("formatAssistantErrorText", () => {
   const makeAssistantError = (errorMessage: string): AssistantMessage =>

src/agents/pi-embedded-helpers/errors.test.ts

@@ -1,7 +1,7 @@
 import type { AssistantMessage } from "@mariozechner/pi-ai";
 import { describe, expect, it } from "vitest";
+import { MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE } from "../../shared/assistant-error-format.js";
 import { makeAssistantMessageFixture } from "../test-helpers/assistant-message-fixtures.js";
-import { MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE } from "../transport-stream-shared.js";
 import { formatAssistantErrorText } from "./errors.js";
 
 describe("formatAssistantErrorText streaming JSON parse classification", () => {

src/agents/pi-embedded-helpers/sanitize-user-facing-text.ts

@@ -3,6 +3,7 @@ import {
   extractLeadingHttpStatus,
   formatRawAssistantErrorForUi,
   isCloudflareOrHtmlErrorPage,
+  MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE,
   parseApiErrorInfo,
   parseApiErrorPayload,
 } from "../../shared/assistant-error-format.js";
@@ -14,7 +15,6 @@ import {
 import { formatExecDeniedUserMessage } from "../exec-approval-result.js";
 import { stripInternalRuntimeContext } from "../internal-runtime-context.js";
 import { stableStringify } from "../stable-stringify.js";
-import { MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE } from "../transport-stream-shared.js";
 import {
   isBillingErrorMessage,
   isOverloadedErrorMessage,

src/agents/transport-stream-shared.ts

@@ -20,10 +20,6 @@ type TransportOutputShape = {
 };
 
 export const EMPTY_TOOL_RESULT_TEXT = "(no output)";
-
-export const MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE =
-  "OpenClaw transport error: malformed_streaming_fragment";
-
 export function sanitizeTransportPayloadText(text: string): string {
   return text.replace(
     /[\uD800-\uDBFF](?![\uDC00-\uDFFF])|(?<![\uD800-\uDBFF])[\uDC00-\uDFFF]/g,

src/shared/assistant-error-format.ts

@@ -15,6 +15,11 @@ const CLOUDFLARE_HTML_ERROR_CODES = new Set([521, 522, 523, 524, 525, 526, 530])
 const STANDALONE_HTML_ERROR_HINT_RE =
   /\bcloudflare\b|cdn-cgi\/challenge-platform|challenge-error-text|enable javascript and cookies to continue|access denied|forbidden|service unavailable|bad gateway|web server is down|captcha|attention required/i;
 
+export const MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE =
+  "OpenClaw transport error: malformed_streaming_fragment";
+export const MALFORMED_STREAMING_FRAGMENT_USER_MESSAGE =
+  "LLM streaming response contained a malformed fragment. Please try again.";
+
 type ErrorPayload = Record<string, unknown>;
 
 export type ApiErrorInfo = {
@@ -188,6 +193,10 @@ export function formatRawAssistantErrorForUi(raw?: string): string {
     return "LLM request failed with an unknown error.";
   }
 
+  if (trimmed === MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE) {
+    return MALFORMED_STREAMING_FRAGMENT_USER_MESSAGE;
+  }
+
   const leadingStatus = extractLeadingHttpStatus(trimmed);
   const isHtmlChallenge = isCloudflareOrHtmlErrorPage(trimmed);
   if (leadingStatus && isHtmlChallenge) {

src/tui/tui-event-handlers.test.ts

@@ -1,4 +1,5 @@
 import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE } from "../shared/assistant-error-format.js";
 import { createEventHandlers } from "./tui-event-handlers.js";
 import type { AgentEvent, BtwEvent, ChatEvent, TuiStateAccess } from "./tui-types.js";
 
@@ -753,6 +754,42 @@ describe("tui-event-handlers: handleAgentEvent", () => {
     expect(chatLog.dropAssistant).not.toHaveBeenCalledWith("run-error-envelope");
   });
 
+  it("renders malformed streaming fragment text when chat final only has event errorMessage", () => {
+    const { state, chatLog, handleChatEvent } = createHandlersHarness({
+      state: { activeChatRunId: null },
+    });
+
+    handleChatEvent({
+      runId: "run-malformed-final",
+      sessionKey: state.currentSessionKey,
+      state: "final",
+      message: { content: [] },
+      errorMessage: MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE,
+    });
+
+    expect(chatLog.finalizeAssistant).toHaveBeenCalledWith(
+      "LLM streaming response contained a malformed fragment. Please try again.",
+      "run-malformed-final",
+    );
+  });
+
+  it("renders malformed streaming fragment text for chat error events", () => {
+    const { state, chatLog, handleChatEvent } = createHandlersHarness({
+      state: { activeChatRunId: null },
+    });
+
+    handleChatEvent({
+      runId: "run-malformed-error",
+      sessionKey: state.currentSessionKey,
+      state: "error",
+      errorMessage: MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE,
+    });
+
+    expect(chatLog.addSystem).toHaveBeenCalledWith(
+      "run error: LLM streaming response contained a malformed fragment. Please try again.",
+    );
+  });
+
   it("shows a concise /auth hint for local auth failures", () => {
     const { chatLog, handleChatEvent } = createHandlersHarness({
       localMode: true,

src/tui/tui-event-handlers.ts

@@ -1,5 +1,6 @@
 import { isAuthErrorMessage } from "../agents/pi-embedded-helpers.js";
 import { parseAgentSessionKey } from "../sessions/session-key-utils.js";
+import { formatRawAssistantErrorForUi } from "../shared/assistant-error-format.js";
 import { normalizeLowercaseStringOrEmpty } from "../shared/string-coerce.js";
 import { asString, extractTextFromMessage, isCommandMessage } from "./tui-formatters.js";
 import { TuiStreamAssembler } from "./tui-stream-assembler.js";
@@ -450,7 +451,8 @@ export function createEventHandlers(context: EventHandlerContext) {
       forgetLocalBtwRunId?.(evt.runId);
       const wasActiveRun = state.activeChatRunId === evt.runId;
       const errorMessage = evt.errorMessage ?? "unknown";
-      chatLog.addSystem(resolveAuthErrorHint(errorMessage) ?? `run error: ${errorMessage}`);
+      const renderedError = formatRawAssistantErrorForUi(errorMessage);
+      chatLog.addSystem(resolveAuthErrorHint(errorMessage) ?? `run error: ${renderedError}`);
       terminateRun({ runId: evt.runId, wasActiveRun, status: "error" });
       maybeRefreshHistoryForRun(evt.runId);
     }

src/tui/tui-formatters.test.ts

@@ -1,4 +1,5 @@
 import { describe, expect, it } from "vitest";
+import { MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE } from "../shared/assistant-error-format.js";
 import {
   extractContentFromMessage,
   extractTextFromMessage,
@@ -42,6 +43,17 @@ describe("extractTextFromMessage", () => {
     expect(text).toContain("This request would exceed your account's rate limit.");
   });
 
+  it("renders malformed streaming fragment errors with friendly text", () => {
+    const text = extractTextFromMessage({
+      role: "assistant",
+      content: [],
+      stopReason: "error",
+      errorMessage: MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE,
+    });
+
+    expect(text).toBe("LLM streaming response contained a malformed fragment. Please try again.");
+  });
+
   it("falls back to a generic message when errorMessage is missing", () => {
     const text = extractTextFromMessage({
       role: "assistant",
@@ -275,6 +287,16 @@ describe("extractContentFromMessage", () => {
 
     expect(text).toContain("HTTP 429");
   });
+
+  it("formats malformed streaming fragment errors when content is not an array", () => {
+    const text = extractContentFromMessage({
+      role: "assistant",
+      stopReason: "error",
+      errorMessage: MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE,
+    });
+
+    expect(text).toBe("LLM streaming response contained a malformed fragment. Please try again.");
+  });
 });
 
 describe("isCommandMessage", () => {

src/tui/tui.test.ts

@@ -1,5 +1,6 @@
 import { describe, expect, it, vi } from "vitest";
 import type { OpenClawConfig } from "../config/config.js";
+import { MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE } from "../shared/assistant-error-format.js";
 import { getSlashCommands, parseCommand } from "./commands.js";
 import {
   createBackspaceDeduper,
@@ -40,6 +41,16 @@ describe("resolveFinalAssistantText", () => {
       }),
     ).toContain("HTTP 401");
   });
+
+  it("formats malformed streaming fragment errors when final and streamed text are empty", () => {
+    expect(
+      resolveFinalAssistantText({
+        finalText: "",
+        streamedText: "",
+        errorMessage: MALFORMED_STREAMING_FRAGMENT_ERROR_MESSAGE,
+      }),
+    ).toBe("LLM streaming response contained a malformed fragment. Please try again.");
+  });
 });
 
 describe("tui slash commands", () => {