Merge pull request #64 from BrunoMarc/fix/empty-response-retry

fix: add retry mechanism for empty API responses

src/cloudcode/sse-streamer.js

@@ -7,6 +7,7 @@
 
 import crypto from 'crypto';
 import { MIN_SIGNATURE_LENGTH, getModelFamily } from '../constants.js';
+import { EmptyResponseError } from '../errors.js';
 import { cacheSignature, cacheThinkingSignature } from '../format/signature-cache.js';
 import { logger } from '../utils/logger.js';
 
@@ -226,39 +227,10 @@ export async function* streamSSEResponse(response, originalModel) {
         }
     }
 
-    // Handle no content received
+    // Handle no content received - throw error to trigger retry in streaming-handler
     if (!hasEmittedStart) {
-        logger.warn('[CloudCode] No content parts received, emitting empty message');
-        yield {
-            type: 'message_start',
-            message: {
-                id: messageId,
-                type: 'message',
-                role: 'assistant',
-                content: [],
-                model: originalModel,
-                stop_reason: null,
-                stop_sequence: null,
-                usage: {
-                    input_tokens: inputTokens - cacheReadTokens,
-                    output_tokens: 0,
-                    cache_read_input_tokens: cacheReadTokens,
-                    cache_creation_input_tokens: 0
-                }
-            }
-        };
-
-        yield {
-            type: 'content_block_start',
-            index: 0,
-            content_block: { type: 'text', text: '' }
-        };
-        yield {
-            type: 'content_block_delta',
-            index: 0,
-            delta: { type: 'text_delta', text: '[No response received from API]' }
-        };
-        yield { type: 'content_block_stop', index: 0 };
+        logger.warn('[CloudCode] No content parts received, throwing for retry');
+        throw new EmptyResponseError('No content parts received from API');
     } else {
         // Close any open block
         if (currentBlockType !== null) {

src/cloudcode/streaming-handler.js

@@ -8,16 +8,17 @@
 import {
     ANTIGRAVITY_ENDPOINT_FALLBACKS,
     MAX_RETRIES,
+    MAX_EMPTY_RESPONSE_RETRIES,
     MAX_WAIT_BEFORE_ERROR_MS
 } from '../constants.js';
-import { isRateLimitError, isAuthError } from '../errors.js';
+import { isRateLimitError, isAuthError, isEmptyResponseError } from '../errors.js';
 import { formatDuration, sleep, isNetworkError } from '../utils/helpers.js';
 import { logger } from '../utils/logger.js';
 import { parseResetTime } from './rate-limit-parser.js';
 import { buildCloudCodeRequest, buildHeaders } from './request-builder.js';
 import { streamSSEResponse } from './sse-streamer.js';
 import { getFallbackModel } from '../fallback-config.js';
-
+import crypto from 'crypto';
 
 /**
  * Send a streaming request to Cloud Code with multi-account support
@@ -143,16 +144,90 @@ export async function* sendMessageStream(anthropicRequest, accountManager, fallb
                         continue;
                     }
 
-                    // Stream the response - yield events as they arrive
-                    yield* streamSSEResponse(response, anthropicRequest.model);
+                    // Stream the response with retry logic for empty responses
+                    // Uses a for-loop for clearer retry semantics
+                    let currentResponse = response;
 
-                    logger.debug('[CloudCode] Stream completed');
-                    return;
+                    for (let emptyRetries = 0; emptyRetries <= MAX_EMPTY_RESPONSE_RETRIES; emptyRetries++) {
+                        try {
+                            yield* streamSSEResponse(currentResponse, anthropicRequest.model);
+                            logger.debug('[CloudCode] Stream completed');
+                            return;
+                        } catch (streamError) {
+                            // Only retry on EmptyResponseError
+                            if (!isEmptyResponseError(streamError)) {
+                                throw streamError;
+                            }
+
+                            // Check if we have retries left
+                            if (emptyRetries >= MAX_EMPTY_RESPONSE_RETRIES) {
+                                logger.error(`[CloudCode] Empty response after ${MAX_EMPTY_RESPONSE_RETRIES} retries`);
+                                yield* emitEmptyResponseFallback(anthropicRequest.model);
+                                return;
+                            }
+
+                            // Exponential backoff: 500ms, 1000ms, 2000ms
+                            const backoffMs = 500 * Math.pow(2, emptyRetries);
+                            logger.warn(`[CloudCode] Empty response, retry ${emptyRetries + 1}/${MAX_EMPTY_RESPONSE_RETRIES} after ${backoffMs}ms...`);
+                            await sleep(backoffMs);
+
+                            // Refetch the response
+                            currentResponse = await fetch(url, {
+                                method: 'POST',
+                                headers: buildHeaders(token, model, 'text/event-stream'),
+                                body: JSON.stringify(payload)
+                            });
+
+                            // Handle specific error codes on retry
+                            if (!currentResponse.ok) {
+                                const retryErrorText = await currentResponse.text();
+
+                                // Rate limit error - mark account and throw to trigger account switch
+                                if (currentResponse.status === 429) {
+                                    const resetMs = parseResetTime(currentResponse, retryErrorText);
+                                    accountManager.markRateLimited(account.email, resetMs, model);
+                                    throw new Error(`429 RESOURCE_EXHAUSTED during retry: ${retryErrorText}`);
+                                }
+
+                                // Auth error - clear caches and throw with recognizable message
+                                if (currentResponse.status === 401) {
+                                    accountManager.clearTokenCache(account.email);
+                                    accountManager.clearProjectCache(account.email);
+                                    throw new Error(`401 AUTH_INVALID during retry: ${retryErrorText}`);
+                                }
+
+                                // For 5xx errors, don't pass to streamer - just continue to next retry
+                                if (currentResponse.status >= 500) {
+                                    logger.warn(`[CloudCode] Retry got ${currentResponse.status}, will retry...`);
+                                    // Don't continue here - let the loop increment and refetch
+                                    // Set currentResponse to null to force refetch at loop start
+                                    emptyRetries--; // Compensate for loop increment since we didn't actually try
+                                    await sleep(1000);
+                                    // Refetch immediately for 5xx
+                                    currentResponse = await fetch(url, {
+                                        method: 'POST',
+                                        headers: buildHeaders(token, model, 'text/event-stream'),
+                                        body: JSON.stringify(payload)
+                                    });
+                                    if (currentResponse.ok) {
+                                        continue; // Try streaming with new response
+                                    }
+                                    // If still failing, let it fall through to throw
+                                }
+
+                                throw new Error(`Empty response retry failed: ${currentResponse.status} - ${retryErrorText}`);
+                            }
+                            // Response is OK, loop will continue to try streamSSEResponse
+                        }
+                    }
 
                 } catch (endpointError) {
                     if (isRateLimitError(endpointError)) {
                         throw endpointError; // Re-throw to trigger account switch
                     }
+                    if (isEmptyResponseError(endpointError)) {
+                        throw endpointError; // Re-throw empty response errors to outer handler
+                    }
                     logger.warn(`[CloudCode] Stream error at ${endpoint}:`, endpointError.message);
                     lastError = endpointError;
                 }
@@ -201,3 +276,49 @@ export async function* sendMessageStream(anthropicRequest, accountManager, fallb
 
     throw new Error('Max retries exceeded');
 }
+
+/**
+ * Emit a fallback message when all retry attempts fail with empty response
+ * @param {string} model - The model name
+ * @yields {Object} Anthropic-format SSE events for empty response fallback
+ */
+function* emitEmptyResponseFallback(model) {
+    // Use proper message ID format consistent with Anthropic API
+    const messageId = `msg_${crypto.randomBytes(16).toString('hex')}`;
+
+    yield {
+        type: 'message_start',
+        message: {
+            id: messageId,
+            type: 'message',
+            role: 'assistant',
+            content: [],
+            model: model,
+            stop_reason: null,
+            stop_sequence: null,
+            usage: { input_tokens: 0, output_tokens: 0 }
+        }
+    };
+
+    yield {
+        type: 'content_block_start',
+        index: 0,
+        content_block: { type: 'text', text: '' }
+    };
+
+    yield {
+        type: 'content_block_delta',
+        index: 0,
+        delta: { type: 'text_delta', text: '[No response after retries - please try again]' }
+    };
+
+    yield { type: 'content_block_stop', index: 0 };
+
+    yield {
+        type: 'message_delta',
+        delta: { stop_reason: 'end_turn', stop_sequence: null },
+        usage: { output_tokens: 0 }
+    };
+
+    yield { type: 'message_stop' };
+}

src/constants.js

@@ -76,6 +76,7 @@ export const ANTIGRAVITY_DB_PATH = getAntigravityDbPath();
 
 export const DEFAULT_COOLDOWN_MS = 10 * 1000; // 10 second default cooldown
 export const MAX_RETRIES = 5; // Max retry attempts across accounts
+export const MAX_EMPTY_RESPONSE_RETRIES = 2; // Max retries for empty API responses
 export const MAX_ACCOUNTS = 10; // Maximum number of accounts allowed
 
 // Rate limit wait thresholds
@@ -249,6 +250,7 @@ export default {
     ANTIGRAVITY_DB_PATH,
     DEFAULT_COOLDOWN_MS,
     MAX_RETRIES,
+    MAX_EMPTY_RESPONSE_RETRIES,
     MAX_ACCOUNTS,
     MAX_WAIT_BEFORE_ERROR_MS,
     MIN_SIGNATURE_LENGTH,

src/errors.js

@@ -135,6 +135,20 @@ export class NativeModuleError extends AntigravityError {
     }
 }
 
+/**
+ * Empty response error - thrown when API returns no content
+ * Used to trigger retry logic in streaming handler
+ */
+export class EmptyResponseError extends AntigravityError {
+    /**
+     * @param {string} message - Error message
+     */
+    constructor(message = 'No content received from API') {
+        super(message, 'EMPTY_RESPONSE', true, {});
+        this.name = 'EmptyResponseError';
+    }
+}
+
 /**
  * Check if an error is a rate limit error
  * Works with both custom error classes and legacy string-based errors
@@ -164,6 +178,16 @@ export function isAuthError(error) {
         msg.includes('TOKEN REFRESH FAILED');
 }
 
+/**
+ * Check if an error is an empty response error
+ * @param {Error} error - Error to check
+ * @returns {boolean}
+ */
+export function isEmptyResponseError(error) {
+    return error instanceof EmptyResponseError ||
+        error?.name === 'EmptyResponseError';
+}
+
 export default {
     AntigravityError,
     RateLimitError,
@@ -172,6 +196,8 @@ export default {
     MaxRetriesError,
     ApiError,
     NativeModuleError,
+    EmptyResponseError,
     isRateLimitError,
-    isAuthError
+    isAuthError,
+    isEmptyResponseError
 };