fix(google): handle content blocking and generation failures

.changeset/google-generation-failures.md

@@ -0,0 +1,5 @@
+---
+'@livekit/agents-plugin-google': patch
+---
+
+fix(google): surface Gemini content blocking and empty generation failures

plugins/google/src/llm.ts

@@ -2,7 +2,12 @@
 //
 // SPDX-License-Identifier: Apache-2.0
 import type * as types from '@google/genai';
-import { FunctionCallingConfigMode, type GenerateContentConfig, GoogleGenAI } from '@google/genai';
+import {
+  FinishReason,
+  FunctionCallingConfigMode,
+  type GenerateContentConfig,
+  GoogleGenAI,
+} from '@google/genai';
 import type { APIConnectOptions } from '@livekit/agents';
 import {
   APIConnectionError,
@@ -296,13 +301,13 @@ export class LLM extends llm.LLM {
   }
 }
 
-const BLOCKED_REASONS = [
-  'SAFETY',
-  'SPII',
-  'PROHIBITED_CONTENT',
-  'BLOCKLIST',
-  'LANGUAGE',
-  'RECITATION',
+const BLOCKED_REASONS: types.FinishReason[] = [
+  FinishReason.SAFETY,
+  FinishReason.SPII,
+  FinishReason.PROHIBITED_CONTENT,
+  FinishReason.BLOCKLIST,
+  FinishReason.LANGUAGE,
+  FinishReason.RECITATION,
 ];
 
 export class LLMStream extends llm.LLMStream {
@@ -391,35 +396,17 @@ export class LLMStream extends llm.LLMStream {
           });
         }
 
-        // Check for blocked reasons first — safety-blocked responses often lack content.parts,
-        // so this must run before the no-content guard to avoid wasting retries.
-        if (
-          chunk.candidates?.[0]?.finishReason &&
-          BLOCKED_REASONS.includes(chunk.candidates[0].finishReason)
-        ) {
+        if (!chunk.candidates || !chunk.candidates[0]?.content?.parts) {
+          this.logger.warn(`No content in the response: ${JSON.stringify(chunk)}`);
           throw new APIStatusError({
-            message: `Google LLM: generation blocked - ${chunk.candidates[0].finishReason}`,
+            message: 'Google LLM: no content in the response',
             options: {
-              retryable: false,
+              retryable,
               requestId,
             },
           });
         }
 
-        if (!chunk.candidates || !chunk.candidates[0]?.content?.parts) {
-          this.logger.warn(`No content in the response: ${JSON.stringify(chunk)}`);
-          if (retryable) {
-            throw new APIStatusError({
-              message: 'Google LLM: no content in the response',
-              options: {
-                retryable: true,
-                requestId,
-              },
-            });
-          }
-          continue;
-        }
-
         if (chunk.candidates.length > 1) {
           this.logger.warn(
             'Google LLM: there are multiple candidates in the response, returning response from the first one.',
@@ -429,8 +416,28 @@ export class LLMStream extends llm.LLMStream {
         const candidate = chunk.candidates[0];
         const finishReason = candidate.finishReason;
 
+        if (finishReason && BLOCKED_REASONS.includes(finishReason)) {
+          throw new APIStatusError({
+            message: `Google LLM: generation blocked by Gemini: ${finishReason}`,
+            options: {
+              retryable: false,
+              requestId,
+            },
+          });
+        }
+
+        if (!candidate.content?.parts) {
+          throw new APIStatusError({
+            message: 'Google LLM: no content in the response',
+            options: {
+              retryable,
+              requestId,
+            },
+          });
+        }
+
         let chunksYielded = false;
-        for (const part of candidate.content!.parts!) {
+        for (const part of candidate.content.parts) {
           const chatChunk = this.#parsePart(requestId, part);
           if (chatChunk) {
             chunksYielded = true;
@@ -439,7 +446,7 @@ export class LLMStream extends llm.LLMStream {
           }
         }
 
-        if (finishReason === 'STOP' && !chunksYielded && retryable) {
+        if (finishReason === FinishReason.STOP && !chunksYielded) {
           throw new APIStatusError({
             message: 'Google LLM: no response generated',
             options: {