What is the cheapest AI API for a coding assistant right now?

DeepSeek V4.1 Flash, at $0.045 per 1M input tokens and $0.5 per 1M output tokens. For a workload of 200M input and 40M output tokens a month, that works out to $29/mo, the lowest of all 35 tracked models.

Is the cheapest model always the best choice for coding?

Not necessarily. This data covers price only, not code quality or accuracy. Budget models like DeepSeek V4.1 Flash, GPT-6 Luna, Claude Haiku 5.5, Qwen3.8 Flash, and GLM 5.3 Flash are all under $55/mo for this workload and have large 1M context windows, but you should still test any model against your real codebase and tasks before standardizing on it.

Does context window size affect which model is cheapest?

Context window and price are separate. Several of the cheapest models — DeepSeek V4.1 Flash, GPT-6 Luna, Claude Haiku 5.5, Qwen3.8 Flash, GLM 5.3 Flash — offer a 1M token context window, while GPT-4o mini, also a budget option at $54/mo, is limited to 128K. If your coding assistant needs to hold a lot of codebase context at once, check the context window alongside the price.

USE CASE · VERIFIED 1 NOV 2026

What's the cheapest AI API for a coding assistant?

For a coding workload of 200M input and 40M output tokens a month, DeepSeek V4.1 Flash is the cheapest at $29/mo, followed by GPT-6 Luna and Claude Haiku 5.5, both $40/mo. Qwen3.8 Flash comes next at $49/mo, then GLM 5.3 Flash at $50/mo, so there are five budget models under $55/mo for this workload.

Worked example: 200M input, 40M output tokens/month

A coding assistant with moderate codebase context reused across many requests. The six cheapest of the 35 models we track, plus two flagships for scale. Open-weight models are priced at the original provider's own list price.

DeepSeek V4.1 Flash$29/mo

GPT-6 Luna$40/mo

Claude Haiku 5.5$40/mo

Qwen3.8 Flash$49/mo

GLM 5.3 Flash$50/mo

GPT-4o mini$54/mo

Grok 4.7$640/mo

Gemini 3.1 Pro$880/mo

Why coding workloads favor cheap input pricing

Coding assistants typically send a lot of context — open files, surrounding code, project structure — on every request, but generate relatively short completions in comparison. That means the input price per 1M tokens matters more than the output price for most of these workloads, and it's why models like DeepSeek V4.1 Flash ($0.045/$0.5) and GPT-6 Luna ($0.1/$0.5) come out ahead of models with flashier output but pricier input. If your assistant generates longer responses — full file rewrites, long diffs, verbose explanations — the output price starts to matter more, and something like DeepSeek V3 ($0.27/$0.41) with its unusually low output cost relative to input can look more attractive despite a higher input rate.

Budget, mid, and flagship: what you give up by going cheap

The budget tier (DeepSeek V4.1 Flash, GPT-6 Luna, Claude Haiku 5.5, Qwen3.8 Flash, GLM 5.3 Flash, GPT-4o mini, MiniMax M3.1 Flash, DeepSeek V3, MiniMax M3, MiMo V2.6 Pro, Gemini 2.5 Flash, Claude Haiku 4.5) covers this workload for $29–$400/mo. Mid-tier models like Gemini 3 Flash, DeepSeek V4 Pro, Claude Sonnet 5/5.5, and GPT-6.1 Sol run $220–$900/mo, and flagship models like Claude Opus 5, GPT-5.5, and GPT-6 Astra run up to $4,000/mo for the identical token volume. Cheaper models aren't automatically worse for coding — several budget options here have 1M context windows, same as many flagships — but this data only tracks price, not output quality, so you still need to test a model against your actual codebase and task mix before committing.

Context window, caching, and batching change the real cost

Context window size matters separately from price: GPT-4o mini and GPT-4o are capped at 128K, Claude Haiku 4.5 is capped at 200K, while most other models here — including several of the cheapest ones — offer 1M or more (Gemini 3.1 Pro reaches 2M), which matters if your assistant needs to hold a large codebase or long conversation history in context. Beyond the headline per-token price, two things can lower your real bill further: prompt caching, which many providers offer for repeated or reused context (common in coding assistants that resend similar codebase context across requests) and often cuts the effective cost of that reused input by around half or more, and batching, which can reduce cost for non-interactive or async requests. Neither is reflected in the numbers above, so your actual monthly cost may be lower than the flat-rate figures shown here if your provider supports caching and you're reusing context heavily.

How we'd actually decide

Situation: You want the absolute lowest cost and don't need huge context — DeepSeek V4.1 Flash — cheapest overall at $29/mo with a 1M context window.
Situation: You want a budget model but prefer an established provider ecosystem — GPT-4o mini — $54/mo, OpenAI's budget tier, though limited to 128K context.
Situation: Your assistant generates long outputs (full rewrites, long explanations) rather than short diffs — DeepSeek V3 — $0.41 per 1M output is the lowest output price among budget models, giving you $70/mo even with a higher input rate.
Situation: You need a large context window plus very low cost, no tradeoff — GPT-6 Luna or Claude Haiku 5.5 — both offer 1M context at $40/mo, just above DeepSeek V4.1 Flash.

Worked example uses standard (non-batch, non-cached) list pricing verified 1 November 2026. Prices change; use the calculator for today's numbers with your own volume. DeepSeek figures use DeepSeek's own weekday list price. On the weekends of 3–4 and 10–11 October we saw DeepSeek charge half of that, so if your jobs run on weekends the DeepSeek numbers can come in lower.