fix(failover): classify Gemini MALFORMED_RESPONSE as retryable timeout (#42292)

Merged via squash.

Prepared head SHA: 68f106ff49fc7a28a806601bc8ca1e5e77c6e8c6
Co-authored-by: jnMetaCode <12096460+jnMetaCode@users.noreply.github.com>
Co-authored-by: altaywtf <9790196+altaywtf@users.noreply.github.com>
Reviewed-by: @altaywtf

CHANGELOG.md

@@ -68,6 +68,7 @@ Docs: https://docs.openclaw.ai
 - Agents/fallback: recognize Poe `402 You've used up your points!` billing errors so configured model fallbacks trigger instead of surfacing the raw provider error. (#42278) Thanks @CryUshio.
 - Telegram/outbound HTML sends: chunk long HTML-mode messages, preserve plain-text fallback and silent-delivery params across retries, and cut over to plain text when HTML chunk planning cannot safely preserve the full message. (#42240) thanks @obviyus.
 - Agents/embedded overload logs: include the failing model and provider in error-path console output, with lifecycle regression coverage for the rendered and sanitized `consoleMessage`. (#41236) thanks @jiarung.
+- Agents/failover: treat Gemini `MALFORMED_RESPONSE` stop reasons as retryable timeouts so preview-model enum drift falls back cleanly instead of crashing the run, without also reclassifying malformed function-call errors. (#42292) Thanks @jnMetaCode.
 
 ## 2026.3.8
 

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

@@ -501,6 +501,26 @@ describe("isFailoverErrorMessage", () => {
       expect(isFailoverErrorMessage(sample)).toBe(true);
     }
   });
+
+  it("matches Gemini MALFORMED_RESPONSE stop reason as timeout (#42149)", () => {
+    const samples = [
+      "Unhandled stop reason: MALFORMED_RESPONSE",
+      "Unhandled stop reason: malformed_response",
+      "stop reason: MALFORMED_RESPONSE",
+    ];
+    for (const sample of samples) {
+      expect(isTimeoutErrorMessage(sample)).toBe(true);
+      expect(classifyFailoverReason(sample)).toBe("timeout");
+      expect(isFailoverErrorMessage(sample)).toBe(true);
+    }
+  });
+
+  it("does not classify MALFORMED_FUNCTION_CALL as timeout", () => {
+    const sample = "Unhandled stop reason: MALFORMED_FUNCTION_CALL";
+    expect(isTimeoutErrorMessage(sample)).toBe(false);
+    expect(classifyFailoverReason(sample)).toBe(null);
+    expect(isFailoverErrorMessage(sample)).toBe(false);
+  });
 });
 
 describe("parseImageSizeError", () => {

src/agents/pi-embedded-helpers/failover-matches.ts

@@ -40,9 +40,9 @@ const ERROR_PATTERNS = {
     /\benotfound\b/i,
     /\beai_again\b/i,
     /without sending (?:any )?chunks?/i,
-    /\bstop reason:\s*(?:abort|error)\b/i,
-    /\breason:\s*(?:abort|error)\b/i,
-    /\bunhandled stop reason:\s*(?:abort|error)\b/i,
+    /\bstop reason:\s*(?:abort|error|malformed_response)\b/i,
+    /\breason:\s*(?:abort|error|malformed_response)\b/i,
+    /\bunhandled stop reason:\s*(?:abort|error|malformed_response)\b/i,
   ],
   billing: [
     /["']?(?:status|code)["']?\s*[:=]\s*402\b|\bhttp\s*402\b|\berror(?:\s+code)?\s*[:=]?\s*402\b|\b(?:got|returned|received)\s+(?:a\s+)?402\b|^\s*402\s+payment/i,