Meta Platforms Inc. has terminated its contract with a longtime vendor that provides hundreds of service workers at its Silicon Valley headquarters, a year after MarketWatch reported about that vendor’s handling of janitors’ holiday pay.

The change appeared to be a layoff by ABM Industries Inc. ABM in a state filing, but the union representing the janitors told MarketWatch on Wednesday that all the workers it represents are expected to keep their jobs. They will be directly employed by a different contractor, SBM Management…