Topic
Eight low-cost models you can run a coding agent on, with official list prices, context limits and the catches: DeepSeek's peak hours, GPT-6 Luna's tool-calling rule, MiniMax's 512K tier and Gemini's January price change.
Million-token context lets an agent hold a whole repository and a long session. It doesn't make each turn cheaper or faster, and some providers raise the price above 200K, 272K or 512K tokens. Here's the arithmetic.
How prompt caching is priced at DeepSeek, Anthropic, OpenAI, Moonshot, Alibaba and others, why coding agents benefit more than chat apps, what quietly breaks cache hits, and what you can and can't control through a gateway.
A practical method for estimating what a coding agent will cost per month: measure tokens per session, split input from output, account for caching, multiply by working days. Worked through with DeepSeek V4.1 Flash and Claude Sonnet 5.5 list prices.
Claude Code only speaks the Anthropic Messages API, so any gateway that speaks it can put a different model behind the CLI. Here is how the environment variables fit together, what Anthropic doesn't support, and which settings keep a non-Claude model usable.
Agent loops re-send their whole context every turn, so a stuck one gets expensive fast. How to layer per-key monthly caps, model allow-lists, usage windows and alerts, poll your remaining budget from a script, and recognise the errors when a limit trips.
