import { spawn, type ChildProcessWithoutNullStreams } from "node:child_process";import process from "node:process";import readline from "node:readline"; type JsonPrimitive = null | boolean | number | string;type JsonValue = JsonPrimitive | JsonValue[] | { [key: string]: JsonValue }; type JsonRpcId = number | string; type JsonRpcMessage = { jsonrpc?: string; id?: JsonRpcId; method?: string; params?: JsonValue; result?: JsonValue; error?: JsonValue; headers?: JsonValue;}; type SelectLeafOption = { value: string; label?: string; name?: string;}; type SelectGroupOption = { label?: string; name?: string; options: SelectLeafOption[];}; type SessionConfigOption = { id: string; name?: string; category?: string; type?: string; options?: Array<SelectLeafOption | SelectGroupOption>;}; type SessionNewResult = { sessionId: string; configOptions?: SessionConfigOption[];}; type SetConfigResult = { configOptions?: SessionConfigOption[];}; type PendingRequest = { method: string; resolve: (value: JsonValue | undefined) => void; reject: (error: Error) => void;}; const targetCwd = process.argv[2] ?? process.cwd();const targetModel = process.argv[3] ?? "gpt-5.4";const promptText = process.argv[4] ?? "helo";const targetReasoning = process.env.CURSOR_REASONING ?? "";const targetContext = process.env.CURSOR_CONTEXT ?? "";const targetFast = process.env.CURSOR_FAST ?? "";const agentBin = process.env.CURSOR_AGENT_BIN ?? "agent";const promptWaitMs = Number(process.env.CURSOR_PROMPT_WAIT_MS ?? "4000");const requestTimeoutMs = Number(process.env.CURSOR_REQUEST_TIMEOUT_MS ?? "20000"); function logSection(title: string, value: unknown) { process.stdout.write(`\n=== ${title} ===\n`); process.stdout.write(`${JSON.stringify(value, null, 2)}\n`);} function fail(message: string): never { throw new Error(message);} function asString(value: JsonValue | undefined): string | null { return typeof value === "string" ? value : null;} function flattenSelectValues(option: SessionConfigOption | undefined): string[] { if (!option || option.type !== "select" || !Array.isArray(option.options)) { return []; } const values: string[] = []; for (const entry of option.options) { if (!entry || typeof entry !== "object") { continue; } if ("value" in entry && typeof entry.value === "string") { values.push(entry.value); continue; } if ("options" in entry && Array.isArray(entry.options)) { for (const nested of entry.options) { if (nested && typeof nested === "object" && typeof nested.value === "string") { values.push(nested.value); } } } } return values;} function findConfigOption( configOptions: SessionConfigOption[], predicate: (option: SessionConfigOption) => boolean,): SessionConfigOption | undefined { return configOptions.find(predicate);} function matchesKeyword(option: SessionConfigOption, keyword: string): boolean { const haystack = `${option.id} ${option.name ?? ""}`.toLowerCase(); return haystack.includes(keyword.toLowerCase());} function sleep(ms: number) { return new Promise<void>((resolve) => { setTimeout(resolve, ms); });} class JsonRpcChild { readonly child: ChildProcessWithoutNullStreams; readonly pending = new Map<JsonRpcId, PendingRequest>(); nextId = 1; closed = false; constructor(bin: string, args: string[], cwd: string) { this.child = spawn(bin, args, { cwd, shell: process.platform === "win32", stdio: ["pipe", "pipe", "pipe"], env: process.env, }); this.child.on("exit", (code, signal) => { this.closed = true; const detail = `ACP process exited (code=${String(code)}, signal=${String(signal)})`; for (const pending of this.pending.values()) { pending.reject(new Error(`${detail} while waiting for ${pending.method}`)); } this.pending.clear(); }); this.child.on("error", (error) => { this.closed = true; for (const pending of this.pending.values()) { pending.reject(error); } this.pending.clear(); }); const stdout = readline.createInterface({ input: this.child.stdout }); stdout.on("line", (line) => { void this.handleStdoutLine(line); }); const stderr = readline.createInterface({ input: this.child.stderr }); stderr.on("line", (line) => { process.stdout.write(`[stderr] ${line}\n`); }); } write(message: JsonRpcMessage) { if (this.closed) { fail("ACP process is already closed."); } const payload = JSON.stringify({ jsonrpc: "2.0", headers: [], ...message, }); process.stdout.write(`>>> ${payload}\n`); this.child.stdin.write(`${payload}\n`); } async request(method: string, params: JsonValue, timeoutMs = requestTimeoutMs) { const id = this.nextId++; const responsePromise = new Promise<JsonValue | undefined>((resolve, reject) => { const timeout = setTimeout(() => { this.pending.delete(id); reject(new Error(`Timed out waiting for ${method} response after ${timeoutMs}ms.`)); }, timeoutMs); this.pending.set(id, { method, resolve: (value) => { clearTimeout(timeout); resolve(value); }, reject: (error) => { clearTimeout(timeout); reject(error); }, }); }); this.write({ id, method, params, }); return responsePromise; } notify(method: string, params: JsonValue) { this.write({ method, params, }); } respond(id: JsonRpcId, result: JsonValue) { this.write({ id, result, }); } respondError(id: JsonRpcId, code: number, message: string) { this.write({ id, error: { code, message, }, }); } async handleStdoutLine(line: string) { if (line.trim().length === 0) { return; } process.stdout.write(`<<< ${line}\n`); let message: JsonRpcMessage; try { message = JSON.parse(line) as JsonRpcMessage; } catch (error) { process.stdout.write(`[parse-error] ${(error as Error).message}\n`); return; } if (typeof message.id !== "undefined" && !message.method) { const pending = this.pending.get(message.id); if (!pending) { return; } this.pending.delete(message.id); if (typeof message.error !== "undefined") { pending.reject( new Error(`RPC ${pending.method} failed: ${JSON.stringify(message.error, null, 2)}`), ); return; } pending.resolve(message.result); return; } if (message.method === "session/request_permission" && typeof message.id !== "undefined") { this.respond(message.id, { outcome: { outcome: "selected", optionId: "allow", }, }); return; } if (typeof message.id !== "undefined" && message.id !== "") { this.respondError( message.id, -32601, `Unhandled server request: ${message.method ?? "unknown"}`, ); } } async close() { if (this.closed) { return; } this.child.kill("SIGTERM"); await sleep(250); if (!this.closed) { this.child.kill("SIGKILL"); } }} async function setSelectOptionIfAdvertised( rpc: JsonRpcChild, sessionId: string, configOptions: SessionConfigOption[], predicate: (option: SessionConfigOption) => boolean, value: string, label: string,) { if (value.length === 0) { return configOptions; } const option = findConfigOption(configOptions, predicate); const values = flattenSelectValues(option); if (!option || !values.includes(value)) { logSection(`SKIP_${label}`, { requestedValue: value, availableValues: values, }); return configOptions; } const response = (await rpc.request("session/set_config_option", { sessionId, configId: option.id, value, })) as SetConfigResult | null | undefined; logSection(`SET_${label}_RESPONSE`, response); return response?.configOptions ?? configOptions;} async function main() { const rpc = new JsonRpcChild(agentBin, ["acp"], targetCwd); try { const initializeResponse = await rpc.request("initialize", { protocolVersion: 1, clientCapabilities: { fs: { readTextFile: false, writeTextFile: false }, terminal: false, _meta: { parameterizedModelPicker: true, }, }, clientInfo: { name: "cursor-acp-model-mismatch-probe", version: "0.0.0", }, }); logSection("INITIALIZE_RESPONSE", initializeResponse); const authenticateResponse = await rpc.request("authenticate", { methodId: "cursor_login", }); logSection("AUTHENTICATE_RESPONSE", authenticateResponse); const sessionResponse = (await rpc.request("session/new", { cwd: targetCwd, mcpServers: [], })) as SessionNewResult; logSection("SESSION_NEW_RESPONSE", sessionResponse); const sessionId = asString(sessionResponse.sessionId); if (!sessionId) { fail("session/new did not return a sessionId."); } let configOptions = sessionResponse.configOptions ?? []; const modelConfig = findConfigOption(configOptions, (option) => option.category === "model"); const advertisedModels = flattenSelectValues(modelConfig); logSection("ADVERTISED_MODEL_VALUES", advertisedModels); if (!modelConfig || modelConfig.type !== "select") { fail("Cursor ACP did not expose a select-type model config option."); } if (!advertisedModels.includes(targetModel)) { fail( `Cursor ACP did not advertise model ${JSON.stringify(targetModel)}. Advertised values: ${advertisedModels.join(", ")}`, ); } const setModelResponse = (await rpc.request("session/set_config_option", { sessionId, configId: modelConfig.id, value: targetModel, })) as SetConfigResult | null | undefined; logSection("SET_MODEL_RESPONSE", setModelResponse); configOptions = setModelResponse?.configOptions ?? configOptions; configOptions = await setSelectOptionIfAdvertised( rpc, sessionId, configOptions, (option) => option.category === "thought_level", targetReasoning, "REASONING", ); configOptions = await setSelectOptionIfAdvertised( rpc, sessionId, configOptions, (option) => option.category === "model_config" && matchesKeyword(option, "context"), targetContext, "CONTEXT", ); configOptions = await setSelectOptionIfAdvertised( rpc, sessionId, configOptions, (option) => option.category === "model_config" && matchesKeyword(option, "fast"), targetFast, "FAST", ); const promptResponse = await rpc.request("session/prompt", { sessionId, prompt: [ { type: "text", text: promptText, }, ], }); logSection("PROMPT_RESPONSE", promptResponse); await sleep(promptWaitMs); rpc.notify("session/cancel", { sessionId }); } finally { await rpc.close(); }} void main().catch((error: unknown) => { process.stderr.write( `${error instanceof Error ? (error.stack ?? error.message) : String(error)}\n`, ); process.exitCode = 1;});
import { spawn, type ChildProcessWithoutNullStreams } from "node:child_process";
import process from "node:process";
import readline from "node:readline";
type JsonPrimitive = null | boolean | number | string;
type JsonValue = JsonPrimitive | JsonValue[] | { [key: string]: JsonValue };
type JsonRpcId = number | string;
type JsonRpcMessage = {
jsonrpc?: string;
id?: JsonRpcId;
method?: string;
params?: JsonValue;
result?: JsonValue;
error?: JsonValue;
headers?: JsonValue;
};
type SelectLeafOption = {
value: string;
label?: string;
name?: string;
};
type SelectGroupOption = {
label?: string;
name?: string;
options: SelectLeafOption[];
};
type SessionConfigOption = {
id: string;
name?: string;
category?: string;
type?: string;
options?: Array<SelectLeafOption | SelectGroupOption>;
};
type SessionNewResult = {
sessionId: string;
configOptions?: SessionConfigOption[];
};
type SetConfigResult = {
configOptions?: SessionConfigOption[];
};
type PendingRequest = {
method: string;
resolve: (value: JsonValue | undefined) => void;
reject: (error: Error) => void;
};
const targetCwd = process.argv[2] ?? process.cwd();
const targetModel = process.argv[3] ?? "gpt-5.4";
const promptText = process.argv[4] ?? "helo";
const targetReasoning = process.env.CURSOR_REASONING ?? "";
const targetContext = process.env.CURSOR_CONTEXT ?? "";
const targetFast = process.env.CURSOR_FAST ?? "";
const agentBin = process.env.CURSOR_AGENT_BIN ?? "agent";
const promptWaitMs = Number(process.env.CURSOR_PROMPT_WAIT_MS ?? "4000");
const requestTimeoutMs = Number(process.env.CURSOR_REQUEST_TIMEOUT_MS ?? "20000");
function logSection(title: string, value: unknown) {
process.stdout.write(`\n=== ${title} ===\n`);
process.stdout.write(`${JSON.stringify(value, null, 2)}\n`);
}
function fail(message: string): never {
throw new Error(message);
}
function asString(value: JsonValue | undefined): string | null {
return typeof value === "string" ? value : null;
}
function flattenSelectValues(option: SessionConfigOption | undefined): string[] {
if (!option || option.type !== "select" || !Array.isArray(option.options)) {
return [];
}
const values: string[] = [];
for (const entry of option.options) {
if (!entry || typeof entry !== "object") {
continue;
}
if ("value" in entry && typeof entry.value === "string") {
values.push(entry.value);
continue;
}
if ("options" in entry && Array.isArray(entry.options)) {
for (const nested of entry.options) {
if (nested && typeof nested === "object" && typeof nested.value === "string") {
values.push(nested.value);
}
}
}
}
return values;
}
function findConfigOption(
configOptions: SessionConfigOption[],
predicate: (option: SessionConfigOption) => boolean,
): SessionConfigOption | undefined {
return configOptions.find(predicate);
}
function matchesKeyword(option: SessionConfigOption, keyword: string): boolean {
const haystack = `${option.id} ${option.name ?? ""}`.toLowerCase();
return haystack.includes(keyword.toLowerCase());
}
function sleep(ms: number) {
return new Promise<void>((resolve) => {
setTimeout(resolve, ms);
});
}
class JsonRpcChild {
readonly child: ChildProcessWithoutNullStreams;
readonly pending = new Map<JsonRpcId, PendingRequest>();
nextId = 1;
closed = false;
constructor(bin: string, args: string[], cwd: string) {
this.child = spawn(bin, args, {
cwd,
shell: process.platform === "win32",
stdio: ["pipe", "pipe", "pipe"],
env: process.env,
});
this.child.on("exit", (code, signal) => {
this.closed = true;
const detail = `ACP process exited (code=${String(code)}, signal=${String(signal)})`;
for (const pending of this.pending.values()) {
pending.reject(new Error(`${detail} while waiting for ${pending.method}`));
}
this.pending.clear();
});
this.child.on("error", (error) => {
this.closed = true;
for (const pending of this.pending.values()) {
pending.reject(error);
}
this.pending.clear();
});
const stdout = readline.createInterface({ input: this.child.stdout });
stdout.on("line", (line) => {
void this.handleStdoutLine(line);
});
const stderr = readline.createInterface({ input: this.child.stderr });
stderr.on("line", (line) => {
process.stdout.write(`[stderr] ${line}\n`);
});
}
write(message: JsonRpcMessage) {
if (this.closed) {
fail("ACP process is already closed.");
}
const payload = JSON.stringify({
jsonrpc: "2.0",
headers: [],
...message,
});
process.stdout.write(`>>> ${payload}\n`);
this.child.stdin.write(`${payload}\n`);
}
async request(method: string, params: JsonValue, timeoutMs = requestTimeoutMs) {
const id = this.nextId++;
const responsePromise = new Promise<JsonValue | undefined>((resolve, reject) => {
const timeout = setTimeout(() => {
this.pending.delete(id);
reject(new Error(`Timed out waiting for ${method} response after ${timeoutMs}ms.`));
}, timeoutMs);
this.pending.set(id, {
method,
resolve: (value) => {
clearTimeout(timeout);
resolve(value);
},
reject: (error) => {
clearTimeout(timeout);
reject(error);
},
});
});
this.write({
id,
method,
params,
});
return responsePromise;
}
notify(method: string, params: JsonValue) {
this.write({
method,
params,
});
}
respond(id: JsonRpcId, result: JsonValue) {
this.write({
id,
result,
});
}
respondError(id: JsonRpcId, code: number, message: string) {
this.write({
id,
error: {
code,
message,
},
});
}
async handleStdoutLine(line: string) {
if (line.trim().length === 0) {
return;
}
process.stdout.write(`<<< ${line}\n`);
let message: JsonRpcMessage;
try {
message = JSON.parse(line) as JsonRpcMessage;
} catch (error) {
process.stdout.write(`[parse-error] ${(error as Error).message}\n`);
return;
}
if (typeof message.id !== "undefined" && !message.method) {
const pending = this.pending.get(message.id);
if (!pending) {
return;
}
this.pending.delete(message.id);
if (typeof message.error !== "undefined") {
pending.reject(
new Error(`RPC ${pending.method} failed: ${JSON.stringify(message.error, null, 2)}`),
);
return;
}
pending.resolve(message.result);
return;
}
if (message.method === "session/request_permission" && typeof message.id !== "undefined") {
this.respond(message.id, {
outcome: {
outcome: "selected",
optionId: "allow",
},
});
return;
}
if (typeof message.id !== "undefined" && message.id !== "") {
this.respondError(
message.id,
-32601,
`Unhandled server request: ${message.method ?? "unknown"}`,
);
}
}
async close() {
if (this.closed) {
return;
}
this.child.kill("SIGTERM");
await sleep(250);
if (!this.closed) {
this.child.kill("SIGKILL");
}
}
}
async function setSelectOptionIfAdvertised(
rpc: JsonRpcChild,
sessionId: string,
configOptions: SessionConfigOption[],
predicate: (option: SessionConfigOption) => boolean,
value: string,
label: string,
) {
if (value.length === 0) {
return configOptions;
}
const option = findConfigOption(configOptions, predicate);
const values = flattenSelectValues(option);
if (!option || !values.includes(value)) {
logSection(`SKIP_${label}`, {
requestedValue: value,
availableValues: values,
});
return configOptions;
}
const response = (await rpc.request("session/set_config_option", {
sessionId,
configId: option.id,
value,
})) as SetConfigResult | null | undefined;
logSection(`SET_${label}_RESPONSE`, response);
return response?.configOptions ?? configOptions;
}
async function main() {
const rpc = new JsonRpcChild(agentBin, ["acp"], targetCwd);
try {
const initializeResponse = await rpc.request("initialize", {
protocolVersion: 1,
clientCapabilities: {
fs: { readTextFile: false, writeTextFile: false },
terminal: false,
_meta: {
parameterizedModelPicker: true,
},
},
clientInfo: {
name: "cursor-acp-model-mismatch-probe",
version: "0.0.0",
},
});
logSection("INITIALIZE_RESPONSE", initializeResponse);
const authenticateResponse = await rpc.request("authenticate", {
methodId: "cursor_login",
});
logSection("AUTHENTICATE_RESPONSE", authenticateResponse);
const sessionResponse = (await rpc.request("session/new", {
cwd: targetCwd,
mcpServers: [],
})) as SessionNewResult;
logSection("SESSION_NEW_RESPONSE", sessionResponse);
const sessionId = asString(sessionResponse.sessionId);
if (!sessionId) {
fail("session/new did not return a sessionId.");
}
let configOptions = sessionResponse.configOptions ?? [];
const modelConfig = findConfigOption(configOptions, (option) => option.category === "model");
const advertisedModels = flattenSelectValues(modelConfig);
logSection("ADVERTISED_MODEL_VALUES", advertisedModels);
if (!modelConfig || modelConfig.type !== "select") {
fail("Cursor ACP did not expose a select-type model config option.");
}
if (!advertisedModels.includes(targetModel)) {
fail(
`Cursor ACP did not advertise model ${JSON.stringify(targetModel)}. Advertised values: ${advertisedModels.join(", ")}`,
);
}
const setModelResponse = (await rpc.request("session/set_config_option", {
sessionId,
configId: modelConfig.id,
value: targetModel,
})) as SetConfigResult | null | undefined;
logSection("SET_MODEL_RESPONSE", setModelResponse);
configOptions = setModelResponse?.configOptions ?? configOptions;
configOptions = await setSelectOptionIfAdvertised(
rpc,
sessionId,
configOptions,
(option) => option.category === "thought_level",
targetReasoning,
"REASONING",
);
configOptions = await setSelectOptionIfAdvertised(
rpc,
sessionId,
configOptions,
(option) => option.category === "model_config" && matchesKeyword(option, "context"),
targetContext,
"CONTEXT",
);
configOptions = await setSelectOptionIfAdvertised(
rpc,
sessionId,
configOptions,
(option) => option.category === "model_config" && matchesKeyword(option, "fast"),
targetFast,
"FAST",
);
const promptResponse = await rpc.request("session/prompt", {
sessionId,
prompt: [
{
type: "text",
text: promptText,
},
],
});
logSection("PROMPT_RESPONSE", promptResponse);
await sleep(promptWaitMs);
rpc.notify("session/cancel", { sessionId });
} finally {
await rpc.close();
}
}
void main().catch((error: unknown) => {
process.stderr.write(
`${error instanceof Error ? (error.stack ?? error.message) : String(error)}\n`,
);
process.exitCode = 1;
});