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fix(proxy): avoid replay after ambiguous transport errors #1269

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Merged
murdore merged 1 commit into from
Aug 4, 2026
Merged

fix(proxy): avoid replay after ambiguous transport errors #1269

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158 changes: 120 additions & 38 deletions src/lib/server/routes/claudeProxyRoutes.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@
import { access, readFile } from "node:fs/promises";
import { homedir } from "node:os";
import { join } from "node:path";
import { Agent } from "undici";
import {
buildStableClaudeCodeBillingHeader,
CLAUDE_CLI_USER_AGENT,
Expand Down Expand Up @@ -203,6 +204,26 @@ const AUTH_REFRESH_MAX_COOLDOWN_MS = 5 * 60 * 1000;
* thinking from Opus models (which can exceed 5 minutes for large contexts). */
const UPSTREAM_FETCH_TIMEOUT_MS = 15 * 60 * 1000; // 15 minutes

let anthropicUpstreamDispatcher: Agent | undefined;

function fetchAnthropicUpstream(
url: string,
init: RequestInit,
): Promise<Response> {
// Node's global fetch applies Undici's 300s default headers timeout before
// the route's 15-minute abort signal. Keep both transport deadlines aligned
// with the proxy contract and instantiate lazily so importing routes has no
// open transport handles.
anthropicUpstreamDispatcher ??= new Agent({
headersTimeout: UPSTREAM_FETCH_TIMEOUT_MS,
bodyTimeout: UPSTREAM_FETCH_TIMEOUT_MS,
});
return fetch(url, {
...init,
dispatcher: anthropicUpstreamDispatcher,
} as RequestInit);
}
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const accountRuntimeState = new Map<string, RuntimeAccountState>();

/** Shared across requests so a concurrent burst gets at most two retries for
Expand Down Expand Up @@ -2008,12 +2029,15 @@ async function handleClaudePassthroughRequest(args: {

let response: Response;
try {
response = await fetch("https://api.anthropic.com/v1/messages?beta=true", {
method: "POST",
headers: upstreamHeaders,
body: bodyStr,
signal: AbortSignal.timeout(UPSTREAM_FETCH_TIMEOUT_MS),
});
response = await fetchAnthropicUpstream(
"https://api.anthropic.com/v1/messages?beta=true",
{
method: "POST",
headers: upstreamHeaders,
body: bodyStr,
signal: AbortSignal.timeout(UPSTREAM_FETCH_TIMEOUT_MS),
},
);
} catch (fetchErr) {
const errMsg =
fetchErr instanceof Error ? fetchErr.message : String(fetchErr);
Expand Down Expand Up @@ -3717,12 +3741,13 @@ async function handleAnthropicStreamingSuccessResponse(args: {
const partialBody = Buffer.concat(
preflight.chunks.map((chunk) => Buffer.from(chunk)),
).toString("utf8");
// The POST has already returned a response. The upstream may have started
// processing it, so replaying it on another account could duplicate work.
logger.always(
`[proxy] stream failed before first chunk account=${account.label}: ${message}; trying next account`,
`[proxy] stream failed before first chunk account=${account.label}: ${message}; returning terminal error to avoid replaying an ambiguous request`,
);
recordAttemptError(account.label, account.type, 502);
logAttempt(502, "stream_error", message, { retryable: true });
tracer?.recordRetry(account.label, "stream_before_first_chunk");
logAttempt(502, "stream_error", message, { retryable: false });
upstreamSpan?.end();
logProxyBody({
phase: "upstream_response",
Expand All @@ -3738,8 +3763,16 @@ async function handleAnthropicStreamingSuccessResponse(args: {
metadata: { logicalStatus: 502, transportError: message },
});
return {
retryNextAccount: true,
failure: { message, rateLimit: false },
response: finalizeAnthropicTerminalTransportError({
account,
tracer,
requestStartTime,
attemptNumber,
logProxyBody,
logFinalRequest,
errorType: "stream_error",
message,
}),
};
}
if (preflight.kind === "empty") {
Expand Down Expand Up @@ -4744,7 +4777,7 @@ async function handleAnthropicAuthRetry(args: {
});

try {
const retryResp = await fetch(url, {
const retryResp = await fetchAnthropicUpstream(url, {
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method: "POST",
headers,
body: retryBodyStr,
Expand Down Expand Up @@ -5017,11 +5050,37 @@ async function handleAnthropicAuthRetry(args: {
: String(retryFetchErr);
authRetryError = `network error on retry ${authRetry + 1}: ${message}`;
currentLastError = authRetryError;
const retryable = isRetryableNetworkError(retryFetchErr);
retryLogAttempt(502, "network_error", message, {
retryable: isRetryableNetworkError(retryFetchErr),
retryable,
errorCode: getErrorCode(retryFetchErr) ?? "unknown",
});
logger.debug(`[proxy] ${authRetryError}`);
if (!retryable) {
// Once a POST has left this process, a reset/timeout or unknown fetch
// failure is ambiguous: retrying it on another account can duplicate
// the request. Only connection-establishment failures are replay-safe.
currentUpstreamSpan?.end();
return {
response: finalizeAnthropicTerminalTransportError({
account,
tracer,
requestStartTime,
attemptNumber: retryAttemptNumber,
logProxyBody,
logFinalRequest,
errorType: "network_error",
message,
}),
continueLoop: false,
lastError: currentLastError,
authFailureMessage: currentAuthFailureMessage,
sawRateLimit: currentSawRateLimit,
sawTransientFailure: currentSawTransientFailure,
sawNetworkError: currentSawNetworkError,
upstreamSpan: undefined,
};
}
break;
}
}
Expand Down Expand Up @@ -5170,6 +5229,46 @@ function finalizeAnthropicTerminalFetchError(args: {
});
}

function finalizeAnthropicTerminalTransportError(args: {
account: ProxyPassthroughAccount;
tracer?: ProxyTracer;
requestStartTime: number;
attemptNumber: number;
logProxyBody: ProxyBodyCaptureLogger;
logFinalRequest: ClaudeFinalRequestLogger;
errorType: "network_error" | "stream_error";
message: string;
}): Response | unknown {
const {
account,
tracer,
requestStartTime,
attemptNumber,
logProxyBody,
logFinalRequest,
errorType,
message,
} = args;
tracer?.setError(errorType, message);
tracer?.end(502, Date.now() - requestStartTime);
logFinalRequest(502, account.label, account.type, errorType, message);
const clientError = buildClaudeError(502, message);
const clientErrorBody = JSON.stringify(clientError);
logProxyBody({
phase: "client_response",
headers: { "content-type": "application/json" },
body: clientErrorBody,
bodySize: Buffer.byteLength(clientErrorBody, "utf8"),
contentType: "application/json",
account: account.label,
accountType: account.type,
attempt: attemptNumber,
responseStatus: 502,
durationMs: Date.now() - requestStartTime,
});
return clientError;
}

async function handleAnthropicNonOkResponse(args: {
response: Response;
account: ProxyPassthroughAccount;
Expand Down Expand Up @@ -6024,7 +6123,7 @@ async function fetchAnthropicAccountResponse(args: {
let response: Response;

try {
response = await fetch(url, {
response = await fetchAnthropicUpstream(url, {
method: "POST",
headers,
body: finalBodyStr,
Expand Down Expand Up @@ -7264,43 +7363,25 @@ function describeTransportError(error: unknown): string {
}

/**
* Determine whether a thrown fetch error is a transient connectivity issue.
* Determine whether a POST can be retried without risking duplicate provider
* work. Only failures that prove connection establishment did not complete are
* safe; a reset, socket error, or response timeout can happen after dispatch.
*/
function isRetryableNetworkError(error: unknown): boolean {
const code = getErrorCode(error);

if (
code &&
return (
code !== undefined &&
[
"ECONNREFUSED",
"ECONNRESET",
"EADDRNOTAVAIL",
// The Anthropic host is fixed, so ENOTFOUND can be a transient resolver
// outage. Keep it inside the existing bounded same-account retry budget.
"ENOTFOUND",
"ETIMEDOUT",
"EHOSTUNREACH",
"UND_ERR_CONNECT_TIMEOUT",
"UND_ERR_CONNECT",
"UND_ERR_SOCKET",
"UND_ERR_HEADERS_TIMEOUT",
].includes(code)
) {
return true;
}

const message = error instanceof Error ? error.message : String(error);
const normalized = message.toLowerCase();

return (
normalized.includes("econnrefused") ||
normalized.includes("econnreset") ||
normalized.includes("enotfound") ||
normalized.includes("etimedout") ||
normalized.includes("timed out") ||
normalized.includes("connection error") ||
normalized.includes("connect error") ||
normalized.includes("fetch failed") ||
normalized.includes("socket hang up")
);
}

Expand Down Expand Up @@ -7473,6 +7554,7 @@ export const __testHooks = {
maybeResetPrimaryToHome,
planCooldownFor429,
reconcileCooldownFromQuota,
isRetryableNetworkError,
isPermanentRefreshFailure,
getStreamFailureDetails,
trackUpstreamReadableStream,
Expand Down
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