microsoft/playwright · error · ValidationError

${path}: channels are not expected in SocksSupport

Error message

${path}: channels are not expected in SocksSupport

What it means

Playwright's SocksInterceptor validates every SocksSupport protocol message/event against a generated schema. The tChannelForSocks validator hook is invoked when the schema encounters a 'channel' (live object reference) field, but SocksSupport messages deliberately never carry channels. Seeing this error means a SocksSupport message contained a channel-typed field that the schema did not expect, signalling a malformed or out-of-spec message. It is an internal protocol integrity check, not an end-user configuration error.

Source

Thrown at packages/playwright-core/src/server/socksInterceptor.ts:87

      this._ids.delete(message.id);
      return true;
    }
    if (message.method === '__create__' && message.params.type === 'SocksSupport') {
      this._socksSupportObjectGuid = message.params.guid;
      return false;
    }
    if (this._socksSupportObjectGuid && message.guid === this._socksSupportObjectGuid) {
      const validator = findValidator('SocksSupport', message.method, 'Event');
      const params = validator(message.params, '', { tChannelImpl: tChannelForSocks, binary: 'fromBase64', isUnderTest });
      this._channel.emit(message.method, params);
      return true;
    }
    return false;
  }
}

function tChannelForSocks(names: '*' | string[], arg: any, path: string, context: ValidatorContext) {
  throw new ValidationError(`${path}: channels are not expected in SocksSupport`);
}

View on GitHub (pinned to c8fc3bf8d3)

Solutions

1. If you modified protocol.yml or the SocksSupport channels, ensure no SocksSupport event/param carries a channel type, or extend tChannelForSocks to whitelist the specific channel.
2. If running a custom/local build, rebuild (npm run build) so generated channels.d.ts and validators match protocol.yml.
3. Confirm the client and server run the same Playwright version (mismatched builds emit incompatible message shapes).

// No caller-side guard: this validates internal protocol integrity.
// Ensure client and server share the same Playwright version before connecting:
const { version } = require('playwright-core/package.json');
if (version !== expectedVersion) throw new Error(`version skew: ${version} vs ${expectedVersion}`);

When it happens

Trigger: Triggered inside interceptMessage when findValidator('SocksSupport', method, 'Event') (or the 'Params' validator used for outgoing calls) walks the params and hits a channel-typed property. This can only happen if the remote browser process sends a SocksSupport event whose params include a 'channel'/'guid' object, or if the protocol.yml definition for SocksSupport was edited to add a channel field without updating tChannelForSocks.

Common situations: Version mismatch between a client and server build where protocol.yml was regenerated with a channel field on a SocksSupport event; an in-tree change to the SocksSupport protocol surface; a corrupted/intercepted websocket message. Not seen in normal proxy usage (SOCKS connections, browser launches through a proxy).

Related errors

• Object with guid ${arg.guid} was not bound in the connection
• ${path}: expected channel ${names.toString()}
• ${path}: dispatcher with guid ${arg._guid} has type ${arg._t
• ${path}: expected dispatcher ${names.toString()}
• ${path}: expected channel ${names.toString()}

AI-assisted analysis of microsoft/playwright@c8fc3bf8d3 (2026-08-12). Data as JSON: /api/errors/9c122dd1f83c11a2. Report an issue: GitHub.