microsoft/typescript-go · critical · Error

Invalid message type from child: ${this._msgType}

Error message

Invalid message type from child: ${this._msgType}

What it means

Thrown by the parent side of the synchronous MessagePack RPC channel (SyncChannel) when an incoming [type, name, payload] tuple parses correctly but its type byte is neither MSG_RESPONSE nor MSG_CALL. It means the child process is speaking a different revision of the wire protocol than the JavaScript host expects.

Source

Thrown at _packages/native-preview/src/api/syncChannel.ts:324

                    if (this.collectTiming) {
                        this.lastBytesReceived = this._msgPayload.length;
                    }
                    return this._msgPayload;
                }
                case MSG_ERROR: {
                    if (methodBuf.equals(this._msgName)) {
                        throw new Error(this._msgPayload.toString("utf-8"));
                    }
                    throw new Error(
                        `name mismatch for response: expected \`${method}\`, got \`${this._msgName.toString("utf-8")}\``,
                    );
                }
                case MSG_CALL: {
                    this.handleCall(this._msgName.toString("utf-8"), this._msgPayload);
                    break;
                }
                default:
                    throw new Error(`Invalid message type from child: ${this._msgType}`);
            }
        }
    }

    // ── Callback handling ───────────────────────────────────────────

    /**
     * Handle an incoming MSG_CALL from the child process.
     *
     * After sending the error response back to the child, this method
     * intentionally re-throws to abort the caller's request loop.
     * A failed callback is treated as unrecoverable to match the
     * behavior of the native libsyncrpc addon.
     */
    private handleCall(name: string, payload: Buffer): void {
        const cb = this.callbacks.get(name);
        if (!cb) {
            const errMsg = `unknown callback: \`${name}\`. Please make sure to register it on the JavaScript side before invoking it.`;

View on GitHub (pinned to 1bcfa18d79)

Solutions

1. Rebuild or re-download the native child binary so it matches the installed @typescript/native-preview version (the package's postinstall/download step)
2. Delete any stale cached tsgo binary and reinstall the package
3. Check that nothing else writes into the child's stdin/stdout
4. If developing the protocol, verify the MSG_* constants in syncChannel.ts and the Go child agree

Example fix

// before
const channel = new SyncChannel(oldCachedChildPath, args);

// after
// force re-download of the child matching the host package
await ensureValidCachedBinary(version); // reinstall/update @typescript/native-preview
const channel = new SyncChannel(cachedBinaryPathFor(version), args);

import { createRequire } from 'node:module';
const require = createRequire(import.meta.url);
const hostPkg = require('@typescript/native-preview/package.json').version;
// ensure the spawned child binary was produced for this host version
classert(childVersionTag === hostPkg.version, 'host/child version skew');

try { channel.call(/* ... */); } catch (e) { if (String(e.message).startsWith('Invalid message type from child')) { /* respawn child with matching version */ } throw e; }

When it happens

Trigger: Reading a response loop iteration after the framing decoded a tuple whose first element is an unknown message type constant — typically a Go child binary built from a newer/older commit than the @typescript/native-preview JS package driving it.

Common situations: Mixed versions: a locally built tsgo child paired with an npm-installed native-preview host (or vice versa); stale child binary cached on disk after upgrading the package; protocol constants changed in a refactor.

Related errors

• Expected fixed 3-element array (0x93), received: 0x${marker.
• Expected positive fixint or uint8 marker, received: 0x${tb.t
• name mismatch for response: expected `${method}`, got `${thi
• no callback named `${name}` found
• Expected binary data (0xc4-0xc6), received: 0x${marker.toStr

AI-assisted analysis of microsoft/typescript-go@1bcfa18d79 (2026-08-16). Data as JSON: /api/errors/aa35acb7e207fbc1. Report an issue: GitHub.