File size: 3,508 Bytes
fc93158 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 | #!/usr/bin/env node
import { spawn } from "node:child_process";
import { createInterface } from "node:readline";
function splitCommandLine(value) {
const parts = [];
let current = "";
let quote = null;
let escaping = false;
for (const ch of value) {
if (escaping) {
current += ch;
escaping = false;
continue;
}
if (ch === "\\" && quote !== "'") {
escaping = true;
continue;
}
if (quote) {
if (ch === quote) {
quote = null;
} else {
current += ch;
}
continue;
}
if (ch === "'" || ch === '"') {
quote = ch;
continue;
}
if (/\s/.test(ch)) {
if (current.length > 0) {
parts.push(current);
current = "";
}
continue;
}
current += ch;
}
if (escaping) {
current += "\\";
}
if (quote) {
throw new Error("Invalid agent command: unterminated quote");
}
if (current.length > 0) {
parts.push(current);
}
if (parts.length === 0) {
throw new Error("Invalid agent command: empty command");
}
return {
command: parts[0],
args: parts.slice(1),
};
}
function decodePayload(argv) {
const payloadIndex = argv.indexOf("--payload");
if (payloadIndex < 0) {
throw new Error("Missing --payload");
}
const encoded = argv[payloadIndex + 1];
if (!encoded) {
throw new Error("Missing MCP proxy payload value");
}
const parsed = JSON.parse(Buffer.from(encoded, "base64url").toString("utf8"));
if (!parsed || typeof parsed !== "object" || Array.isArray(parsed)) {
throw new Error("Invalid MCP proxy payload");
}
if (typeof parsed.targetCommand !== "string" || parsed.targetCommand.trim() === "") {
throw new Error("MCP proxy payload missing targetCommand");
}
const mcpServers = Array.isArray(parsed.mcpServers) ? parsed.mcpServers : [];
return {
targetCommand: parsed.targetCommand,
mcpServers,
};
}
function shouldInject(method) {
return method === "session/new" || method === "session/load" || method === "session/fork";
}
function rewriteLine(line, mcpServers) {
if (!line.trim()) {
return line;
}
try {
const parsed = JSON.parse(line);
if (
!parsed ||
typeof parsed !== "object" ||
Array.isArray(parsed) ||
!shouldInject(parsed.method) ||
!parsed.params ||
typeof parsed.params !== "object" ||
Array.isArray(parsed.params)
) {
return line;
}
const next = {
...parsed,
params: {
...parsed.params,
mcpServers,
},
};
return JSON.stringify(next);
} catch {
return line;
}
}
const { targetCommand, mcpServers } = decodePayload(process.argv.slice(2));
const target = splitCommandLine(targetCommand);
const child = spawn(target.command, target.args, {
stdio: ["pipe", "pipe", "inherit"],
env: process.env,
});
if (!child.stdin || !child.stdout) {
throw new Error("Failed to create MCP proxy stdio pipes");
}
const input = createInterface({ input: process.stdin });
input.on("line", (line) => {
child.stdin.write(`${rewriteLine(line, mcpServers)}\n`);
});
input.on("close", () => {
child.stdin.end();
});
child.stdout.pipe(process.stdout);
child.on("error", (error) => {
process.stderr.write(`${error instanceof Error ? error.message : String(error)}\n`);
process.exit(1);
});
child.on("close", (code, signal) => {
if (signal) {
process.kill(process.pid, signal);
return;
}
process.exit(code ?? 0);
});
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