GPT-6.1 Terra Invoice Reader: Image to Ledger in Python

OpenAI shipped GPT-6.1 Terra on October 26, and the pitch is unusually specific: a fast, cheap model for visual reasoning and computer use, aimed at high-volume work like reading invoices and entering the data into accounting software. The API ID is gpt-6.1-terra, it costs $1 per million input tokens, $0.05 cached, and $5 per million output, and OpenAI says it is over three times faster than GPT-6 Astra and GPT-6.1 Sol on agent tasks.

That pitch is also a dare. Cheap vision models read numbers wrong in quiet ways, and a ledger with one misread digit is worse than an empty ledger. So this guide builds the thing OpenAI is pointing at, with the safety net that makes it trustworthy: image in, validated structured data out, a cost and accuracy sweep across the new reasoning.effort levels, and an escalation ladder that spends more tokens only when an invoice's own arithmetic fails to add up.