diff --git a/CHANGELOG.md b/CHANGELOG.md
index d2c1316ae5c..0f6e38fc551 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -107,6 +107,7 @@ Docs: https://docs.openclaw.ai
 - Telegram/config schema: accept `channels.telegram.actions.editMessage` and `createForumTopic` in strict config validation so existing Telegram action toggles no longer fail as unrecognized keys. (#35498) Thanks @ingyukoh.
 - Agents/cooldowns: default cooldown windows with no recorded failure history to `unknown` instead of `rate_limit`, avoiding false API rate-limit warnings while preserving cooldown recovery probes. (#42911) Thanks @VibhorGautam.
 - Discord/config typing: expose channel-level `autoThread` on the canonical guild-channel config type so strict config loading matches the existing Discord schema and runtime behavior. (#35608) Thanks @ingyukoh.
+- Agents/error rendering: ignore stale assistant `errorMessage` fields on successful turns so background/tool-side failures no longer prepend synthetic billing errors over valid replies. (#40616) Thanks @ingyukoh.
 
 ## 2026.3.8
 
diff --git a/src/agents/pi-embedded-runner/run/payloads.errors.test.ts b/src/agents/pi-embedded-runner/run/payloads.errors.test.ts
index 4268e177dfc..a2e7873aedf 100644
--- a/src/agents/pi-embedded-runner/run/payloads.errors.test.ts
+++ b/src/agents/pi-embedded-runner/run/payloads.errors.test.ts
@@ -101,6 +101,18 @@ describe("buildEmbeddedRunPayloads", () => {
     expect(payloads[0]?.isError).toBe(true);
   });
 
+  it("does not emit a synthetic billing error for successful turns with stale errorMessage", () => {
+    const payloads = buildPayloads({
+      lastAssistant: makeAssistant({
+        stopReason: "stop",
+        errorMessage: "insufficient credits for embedding model",
+        content: [{ type: "text", text: "Handle payment required errors in your API." }],
+      }),
+    });
+
+    expectSinglePayloadText(payloads, "Handle payment required errors in your API.");
+  });
+
   it("suppresses raw error JSON even when errorMessage is missing", () => {
     const payloads = buildPayloads({
       assistantTexts: [errorJsonPretty],
diff --git a/src/agents/pi-embedded-runner/run/payloads.ts b/src/agents/pi-embedded-runner/run/payloads.ts
index 16a78ec2e97..c0e0ded136e 100644
--- a/src/agents/pi-embedded-runner/run/payloads.ts
+++ b/src/agents/pi-embedded-runner/run/payloads.ts
@@ -128,16 +128,17 @@ export function buildEmbeddedRunPayloads(params: {
   const useMarkdown = params.toolResultFormat === "markdown";
   const suppressAssistantArtifacts = params.didSendDeterministicApprovalPrompt === true;
   const lastAssistantErrored = params.lastAssistant?.stopReason === "error";
-  const errorText = params.lastAssistant
-    ? suppressAssistantArtifacts
-      ? undefined
-      : formatAssistantErrorText(params.lastAssistant, {
-          cfg: params.config,
-          sessionKey: params.sessionKey,
-          provider: params.provider,
-          model: params.model,
-        })
-    : undefined;
+  const errorText =
+    params.lastAssistant && lastAssistantErrored
+      ? suppressAssistantArtifacts
+        ? undefined
+        : formatAssistantErrorText(params.lastAssistant, {
+            cfg: params.config,
+            sessionKey: params.sessionKey,
+            provider: params.provider,
+            model: params.model,
+          })
+      : undefined;
   const rawErrorMessage = lastAssistantErrored
     ? params.lastAssistant?.errorMessage?.trim() || undefined
     : undefined;
diff --git a/src/agents/pi-embedded-utils.test.ts b/src/agents/pi-embedded-utils.test.ts
index 6a5ce710c85..ab84a375d94 100644
--- a/src/agents/pi-embedded-utils.test.ts
+++ b/src/agents/pi-embedded-utils.test.ts
@@ -134,6 +134,20 @@ describe("extractAssistantText", () => {
     );
   });
 
+  it("preserves response when errorMessage set from background failure (#13935)", () => {
+    const responseText = "Handle payment required errors in your API.";
+    const msg = makeAssistantMessage({
+      role: "assistant",
+      errorMessage: "insufficient credits for embedding model",
+      stopReason: "stop",
+      content: [{ type: "text", text: responseText }],
+      timestamp: Date.now(),
+    });
+
+    const result = extractAssistantText(msg);
+    expect(result).toBe(responseText);
+  });
+
   it("strips Minimax tool invocations with extra attributes", () => {
     const msg = makeAssistantMessage({
       role: "assistant",
diff --git a/src/agents/pi-embedded-utils.ts b/src/agents/pi-embedded-utils.ts
index da1dd7911b8..375df11654d 100644
--- a/src/agents/pi-embedded-utils.ts
+++ b/src/agents/pi-embedded-utils.ts
@@ -245,7 +245,9 @@ export function extractAssistantText(msg: AssistantMessage): string {
     }) ?? "";
   // Only apply keyword-based error rewrites when the assistant message is actually an error.
   // Otherwise normal prose that *mentions* errors (e.g. "context overflow") can get clobbered.
-  const errorContext = msg.stopReason === "error" || Boolean(msg.errorMessage?.trim());
+  // Gate on stopReason only — a non-error response with an errorMessage set (e.g. from a
+  // background tool failure) should not have its content rewritten (#13935).
+  const errorContext = msg.stopReason === "error";
   return sanitizeUserFacingText(extracted, { errorContext });
 }
 
diff --git a/src/agents/tools/sessions-helpers.ts b/src/agents/tools/sessions-helpers.ts
index 5b5f94699c6..e638438758c 100644
--- a/src/agents/tools/sessions-helpers.ts
+++ b/src/agents/tools/sessions-helpers.ts
@@ -166,9 +166,9 @@ export function extractAssistantText(message: unknown): string | undefined {
       normalizeText: (text) => text.trim(),
     }) ?? "";
   const stopReason = (message as { stopReason?: unknown }).stopReason;
-  const errorMessage = (message as { errorMessage?: unknown }).errorMessage;
-  const errorContext =
-    stopReason === "error" || (typeof errorMessage === "string" && Boolean(errorMessage.trim()));
+  // Gate on stopReason only — a non-error response with a stale/background errorMessage
+  // should not have its content rewritten with error templates (#13935).
+  const errorContext = stopReason === "error";
 
   return joined ? sanitizeUserFacingText(joined, { errorContext }) : undefined;
 }
diff --git a/src/agents/tools/sessions.test.ts b/src/agents/tools/sessions.test.ts
index aa831027f68..ce849e45d07 100644
--- a/src/agents/tools/sessions.test.ts
+++ b/src/agents/tools/sessions.test.ts
@@ -199,6 +199,16 @@ describe("extractAssistantText", () => {
       "Firebase downgraded us to the free Spark plan. Check whether billing should be re-enabled.",
     );
   });
+
+  it("preserves successful turns with stale background errorMessage", () => {
+    const message = {
+      role: "assistant",
+      stopReason: "end_turn",
+      errorMessage: "insufficient credits for embedding model",
+      content: [{ type: "text", text: "Handle payment required errors in your API." }],
+    };
+    expect(extractAssistantText(message)).toBe("Handle payment required errors in your API.");
+  });
 });
 
 describe("resolveAnnounceTarget", () => {