diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2fb258e7959..3ccec3cfcf2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@ Docs: https://docs.openclaw.ai
 - Agents/schema cleaning: detect Venice + Grok model IDs as xAI-proxied targets so unsupported JSON Schema keywords are stripped before requests, preventing Venice/Grok `Invalid arguments` failures. (openclaw#35355) thanks @Sid-Qin.
 - Skills/native command deduplication: centralize skill command dedupe by canonical `skillName` in `listSkillCommandsForAgents` so duplicate suffixed variants (for example `_2`) are no longer surfaced across interfaces outside Discord. (#27521) thanks @shivama205.
 - Agents/xAI tool-call argument decoding: decode HTML-entity encoded xAI/Grok tool-call argument values (`&`, `"`, `<`, `>`, numeric entities) before tool execution so commands with shell operators and quotes no longer fail with parse errors. (#35276) Thanks @Sid-Qin.
+- Agents/thinking-tag promotion hardening: guard `promoteThinkingTagsToBlocks` against malformed assistant content entries (`null`/`undefined`) before `block.type` reads so malformed provider payloads no longer crash session processing while preserving pass-through behavior. (#35143) thanks @Sid-Qin.
 - Feishu/streaming card delivery synthesis: unify snapshot and delta streaming merge semantics, apply overlap-aware final merge, suppress duplicate final text delivery (including text+media final packets), prefer topic-thread `message.reply` routing when a reply target exists, and tune card print cadence to avoid duplicate incremental rendering. (from #33245, #32896, #33840) Thanks @rexl2018, @kcinzgg, and @aerelune.
 - Security/dependency audit: patch transitive Hono vulnerabilities by pinning `hono` to `4.12.5` and `@hono/node-server` to `1.19.10` in production resolution paths. Thanks @shakkernerd.
 - Security/dependency audit: bump `tar` to `7.5.10` (from `7.5.9`) to address the high-severity hardlink path traversal advisory (`GHSA-qffp-2rhf-9h96`). Thanks @shakkernerd.
diff --git a/src/agents/pi-embedded-utils.test.ts b/src/agents/pi-embedded-utils.test.ts
index 5e8a9f39b8e..6a5ce710c85 100644
--- a/src/agents/pi-embedded-utils.test.ts
+++ b/src/agents/pi-embedded-utils.test.ts
@@ -3,6 +3,7 @@ import { describe, expect, it } from "vitest";
 import {
   extractAssistantText,
   formatReasoningMessage,
+  promoteThinkingTagsToBlocks,
   stripDowngradedToolCallText,
 } from "./pi-embedded-utils.js";
 
@@ -549,6 +550,39 @@ describe("stripDowngradedToolCallText", () => {
   });
 });
 
+describe("promoteThinkingTagsToBlocks", () => {
+  it("does not crash on malformed null content entries", () => {
+    const msg = makeAssistantMessage({
+      role: "assistant",
+      content: [null as never, { type: "text", text: "<thinking>hello</thinking>ok" }],
+      timestamp: Date.now(),
+    });
+    expect(() => promoteThinkingTagsToBlocks(msg)).not.toThrow();
+    const types = msg.content.map((b: { type?: string }) => b?.type);
+    expect(types).toContain("thinking");
+    expect(types).toContain("text");
+  });
+
+  it("does not crash on undefined content entries", () => {
+    const msg = makeAssistantMessage({
+      role: "assistant",
+      content: [undefined as never, { type: "text", text: "no tags here" }],
+      timestamp: Date.now(),
+    });
+    expect(() => promoteThinkingTagsToBlocks(msg)).not.toThrow();
+  });
+
+  it("passes through well-formed content unchanged when no thinking tags", () => {
+    const msg = makeAssistantMessage({
+      role: "assistant",
+      content: [{ type: "text", text: "hello world" }],
+      timestamp: Date.now(),
+    });
+    promoteThinkingTagsToBlocks(msg);
+    expect(msg.content).toEqual([{ type: "text", text: "hello world" }]);
+  });
+});
+
 describe("empty input handling", () => {
   it("returns empty string", () => {
     const helpers = [formatReasoningMessage, stripDowngradedToolCallText];
diff --git a/src/agents/pi-embedded-utils.ts b/src/agents/pi-embedded-utils.ts
index 82ad3efc03d..21a4eb39fd5 100644
--- a/src/agents/pi-embedded-utils.ts
+++ b/src/agents/pi-embedded-utils.ts
@@ -333,7 +333,9 @@ export function promoteThinkingTagsToBlocks(message: AssistantMessage): void {
   if (!Array.isArray(message.content)) {
     return;
   }
-  const hasThinkingBlock = message.content.some((block) => block.type === "thinking");
+  const hasThinkingBlock = message.content.some(
+    (block) => block && typeof block === "object" && block.type === "thinking",
+  );
   if (hasThinkingBlock) {
     return;
   }
@@ -342,6 +344,10 @@ export function promoteThinkingTagsToBlocks(message: AssistantMessage): void {
   let changed = false;
 
   for (const block of message.content) {
+    if (!block || typeof block !== "object" || !("type" in block)) {
+      next.push(block);
+      continue;
+    }
     if (block.type !== "text") {
       next.push(block);
       continue;