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fix(mcp): execute tool dies on Deno >= 2.9 (unix sockets moved behind net permission) #101

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Merged
Dithilli merged 1 commit into from
Jul 17, 2026
Merged

fix(mcp): execute tool dies on Deno >= 2.9 (unix sockets moved behind net permission) #101

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30 changes: 20 additions & 10 deletions packages/mcp-server/src/code-tool.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -159,14 +159,21 @@ const localDenoHandler = async ({
}
}

// Deno >= 2 gates unix sockets behind --allow-net=unix:<path>, while Deno 1.x panics on a
// `unix:` token in --allow-net — so the socket grant below must be gated on the major version.
let denoMajor = 2;
// Deno 2.9.0 moved unix sockets behind the net permission (--allow-net=unix:<path>), part of
// the 2.8.2–2.9.1 socket-hardening series (denoland/deno#34395, #35835). Older Denos must NOT
// receive the token: 2.0–2.8 reject it at startup ("invalid port") and 1.x panics — and their
// legacy read/write grant still works. So gate the grant on exactly >= 2.9.
let denoNeedsUnixNetGrant = true;
try {
const versionOutput = execSync(`"${denoPath}" --version`, { encoding: 'utf8' });
denoMajor = Number(/deno (\d+)\./.exec(versionOutput)?.[1] ?? denoMajor);
const versionMatch = /deno (\d+)\.(\d+)\./.exec(versionOutput);
if (versionMatch) {
const major = Number(versionMatch[1]);
const minor = Number(versionMatch[2]);
denoNeedsUnixNetGrant = major > 2 || (major === 2 && minor >= 9);
}
} catch {
// Version detection failed; assume a current (2.x) Deno.
// Version detection failed; assume a current Deno.
}

const allowReadPaths = [
Expand Down Expand Up @@ -201,11 +208,14 @@ const localDenoHandler = async ({
],
printOutput: true,
// deno-http-worker grants its internal unix socket via --allow-read/--allow-write (the
// Deno 1.x permission model), but Deno >= 2 requires --allow-net=unix:<path> or the worker
// dies on startup ("Deno exited before being ready"). The socket path is generated inside
// newDenoHTTPWorker, so pluck it out of the --allow-write flag the library injects and graft
// it onto the --allow-net scope (Deno rejects repeated --allow-net flags, hence the comma).
...(denoMajor >= 2 && {
// pre-2.9 permission model — unchanged upstream as of 2.0.3, so a version bump is not a fix),
// which on Deno >= 2.9 kills the worker at startup ("Deno exited before being ready").
// The socket path is generated inside newDenoHTTPWorker, so no flag can be scoped up front
// (Deno accepts only exact socket paths — no globs/prefixes — and rejects repeated
// --allow-net flags). Instead, intercept the spawn, pluck the socket path out of the
// --allow-write flag the library injects, and comma-merge unix:<sock> onto the existing
// --allow-net scope.
...(denoNeedsUnixNetGrant && {
spawnFunc: (
command: string,
spawnArgs: string[],
Expand Down
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