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fix(llm-proxy): avoid disturbing response body when JSON parse fails #1923

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Merged
chrarnoldus merged 1 commit into from
Apr 2, 2026
+11 −6
Merged

fix(llm-proxy): avoid disturbing response body when JSON parse fails #1923

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17 changes: 11 additions & 6 deletions src/lib/rewriteModelResponse.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -22,12 +22,15 @@ export async function rewriteFreeModelResponse_ChatCompletions(response: Respons
const headers = getOutputHeaders(response);

if (headers.get('content-type')?.includes('application/json')) {
// Read the body text once to avoid "Response body object should not be
// disturbed or locked" errors that occur when `.clone().json()` fails.
const text = await response.text();
let json: OpenAI.ChatCompletion;
try {
json = (await response.clone().json()) as OpenAI.ChatCompletion;
json = JSON.parse(text) as OpenAI.ChatCompletion;
} catch {
// Upstream returned invalid/empty JSON body — pass through as-is
return new NextResponse(response.body, {
return new NextResponse(text, {
status: response.status,
statusText: response.statusText,
headers,
Expand Down Expand Up @@ -142,14 +145,15 @@ export async function rewriteFreeModelResponse_Messages(response: Response, mode
const headers = getOutputHeaders(response);

if (headers.get('content-type')?.includes('application/json')) {
const text = await response.text();
let json: Anthropic.Messages.Message & { usage?: MessagesApiUsage };
try {
json = (await response.clone().json()) as Anthropic.Messages.Message & {
json = JSON.parse(text) as Anthropic.Messages.Message & {
usage?: MessagesApiUsage;
};
} catch {
// Upstream returned invalid/empty JSON body — pass through as-is
return new NextResponse(response.body, {
return new NextResponse(text, {
status: response.status,
statusText: response.statusText,
headers,
Expand Down Expand Up @@ -240,14 +244,15 @@ export async function rewriteFreeModelResponse_Responses(response: Response, mod
const headers = getOutputHeaders(response);

if (headers.get('content-type')?.includes('application/json')) {
const text = await response.text();
let json: OpenAI.Responses.Response & { usage?: OpenRouterUsage | null };
try {
json = (await response.clone().json()) as OpenAI.Responses.Response & {
json = JSON.parse(text) as OpenAI.Responses.Response & {
usage?: OpenRouterUsage | null;
};
} catch {
// Upstream returned invalid/empty JSON body — pass through as-is
return new NextResponse(response.body, {
return new NextResponse(text, {
status: response.status,
statusText: response.statusText,
headers,
Expand Down
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