Cost per coding-agent request

Is GPT-5.3-Codex or GPT-5.6 Luna cheaper for coding agents?

For coding agents, GPT-5.3-Codex costs 7.7x as much as GPT-5.6 Luna per request ($0.055 vs $0.0072 on our measured traffic), because Codex lists at $1.75/$14 against Luna's $0.20/$1.20.

List prices: OpenAI API pricing, checked 2026-10-13. Request costs: Standard Compute gateway data, 79,301 coding-agent requests from 75 users, Sep 13 to Oct 12, 2026. How we compute this

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Cost per coding-agent request, side by side

Cost at list price	GPT-5.6 Luna	GPT-5.3-Codex
Prompt under 100K tokens50% of requests, 87% of input cached	$0.0032	$0.030
Prompt of 100K to 272K39% of requests, 88% of input cached	$0.0080	$0.073
Prompt over 272K tokens11% of requests, 86% of input cached	$0.030	$0.13
Average request	$0.0072	$0.055
100 requests	$0.72	$5.55
Median session16 requests; a session ends after 10 idle minutes	$0.082	$0.74
A month of regular usemedian of 20 users active on 5+ days	$11.66	$84.36

Each logged request priced at the vendor’s list rates for its own token counts, including cache reads and any higher rate for long prompts. Average output: 698 tokens per request. Both models are priced on the requests up to 400K tokens that fit in both context windows; band shares above describe all requests.

Benchmarks, speed and latency, side by side

Artificial Analysis	GPT-5.6 Luna	GPT-5.3-Codex
Intelligence Index10 evaluations, 0 to 100	37	33 (estimate)
Terminal-Bench 4.0agentic coding in a terminal	11.6%	n/a
Output speedmedian	123 tokens/s	113 tokens/s
Time to first answer tokenincludes thinking time	117 s	72 s

Source: Artificial Analysis (artificialanalysis.ai). Measured variants: GPT-5.6 Luna (Max), speed on OpenAI; GPT-5.3 Codex (Xhigh), speed on OpenAI. Fetched October 13, 2026. Artificial Analysis runs Terminal-Bench 4.0 in its own setup, so its scores differ from the tbench.ai leaderboard.

What to watch for

Codex is tuned for long coding sessions and Luna is a small model, so Luna may need more steps for the same task. GPT-5.3 Codex's 400K window cannot take 3% of requests; the comparison uses requests both can take. GPT-6 Luna now replaces GPT-5.6 Luna at half the price.

FAQ

Is GPT-5.6 Luna cheaper than GPT-5.3-Codex for coding agents?

Yes, at list prices. 100 average coding-agent requests cost $0.72 on GPT-5.6 Luna and $5.55 on GPT-5.3-Codex. A median 16-request session costs $0.082 vs $0.74. Measured on 79,301 real coding-agent requests (Sep 13 to Oct 12, 2026), counting only the requests up to 400K tokens that both can take.

How much does a month of GPT-5.3-Codex vs GPT-5.6 Luna cost?

For the median regular user in our data (1,478 requests in 30 days), about $84.36 on GPT-5.3-Codex and $11.66 on GPT-5.6 Luna at list price. Heavier users pay proportionally more.

GPT-5.3-Codex vs GPT-5.6 Luna: which is better for agents?

GPT-5.6 Luna scores higher on output quality (7.4/10 vs 6.8/10), while GPT-5.6 Luna is the cheaper option. GPT-5.3-Codex is best for existing Codex setups on an API key that still pin GPT-5.3-Codex; GPT-5.6 Luna is best for cheap subtasks in existing GPT-5.6 setups. Live community votes on this page show what people actually prefer.

Can I switch between GPT-5.3-Codex and GPT-5.6 Luna in the same agent?

Yes. Model-agnostic agents (Cline, Aider, OpenClaw, Hermes Agent, Kilo Code, OpenCode) let you swap models per task. Many people route hard tasks to the stronger model and routine work to the cheaper one.

Community vote

Pick a winner in each dimension. You can change your vote any time. 31 votes cast so far.

Output Quality

Correctness and depth of what it produces

41%17 votes59%

Agentic Ability

Tool calls, instruction-following, and multi-step tasks

17%6 votes83%

Speed

Tokens per second and time-to-first-token

60%5 votes40%

Value for Money

How much capability you get per dollar

0%2 votes100%

Reliability

Consistent results: fewer refusals, loops and format breaks

100%1 vote0%

Current Claude, GPT, Gemini and open models are included with Standard Compute

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