POST to /v2/batches with a 'shipments' array; each element must include from_address, to_address, parcel, carrier, service, and a single-element carrier_accounts array
The batch is created in 'creation_queued' state; poll GET /v2/batches/{id} or use a webhook to detect when state transitions to 'created' before issuing the buy call
POST to /v2/batches/{id}/buy to enqueue asynchronous label purchase; monitor the batch state via webhook or polling until it reaches 'purchased'
Once purchased, POST to /v2/batches/{id}/label with 'file_format': 'PDF' (or 'ZPLII') to generate a merged label file; poll until the label_url is populated
Keep each batch under 1,000 shipments; for larger volumes, split into multiple batches and process concurrently
Known gotchas
Batch operations are fully asynchronous; do not assume a buy call completes synchronously — always wait for the 'purchased' state before requesting the label file
An April 2026 EasyPost fix resolved an intermittent batch live-lock issue; upgrade to the latest SDK or API version if you encounter batches stuck in 'purchasing' indefinitely
All shipments in a batch must specify the same carrier_account; mixing carrier accounts within a single batch is not supported
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