Cost per coding-agent request

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

For coding agents, GPT-5.6 Terra costs 1.3x as much as GPT-5.3-Codex per request ($0.072 vs $0.055 on our measured traffic), because GPT-5.6 Terra lists at $2 input, $0.20 cached input and $12 output per million tokens against $1.75, $0.175 and $14 for GPT-5.3-Codex, and GPT-5.6 Terra charges more for prompts over 272K tokens.

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-5.3-Codex	GPT-5.6 Terra
Prompt under 100K tokens50% of requests, 87% of input cached	$0.030	$0.032
Prompt of 100K to 272K39% of requests, 88% of input cached	$0.073	$0.080
Prompt over 272K tokens11% of requests, 86% of input cached	$0.13	$0.30
Average request	$0.055	$0.072
100 requests	$5.55	$7.22
Median session16 requests; a session ends after 10 idle minutes	$0.74	$0.81
A month of regular usemedian of 20 users active on 5+ days	$84.36	$117

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-5.3-Codex	GPT-5.6 Terra
Intelligence Index10 evaluations, 0 to 100	33 (estimate)	42
Terminal-Bench 4.0agentic coding in a terminal	n/a	35.4%
Output speedmedian	113 tokens/s	135 tokens/s
Time to first answer tokenincludes thinking time	72 s	2.2 min

Source: Artificial Analysis (artificialanalysis.ai). Measured variants: GPT-5.3 Codex (Xhigh), speed on OpenAI; GPT-5.6 Terra (Max), 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

GPT-5.3-Codex's 400K window cannot take 3% of coding-agent requests, so the comparison uses only requests both can take. The gap widens on long prompts: under 100K tokens GPT-5.6 Terra costs 1.1x as much per request, over 272K 2.2x. GPT-5.6 Terra scores clearly higher on the benchmarks above, so it may finish hard tasks in fewer steps.

FAQ

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

Yes, at list prices. 100 average coding-agent requests cost $5.55 on GPT-5.3-Codex and $7.22 on GPT-5.6 Terra. A median 16-request session costs $0.74 vs $0.81. 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-5.6 Terra vs GPT-5.3-Codex cost?

For the median regular user in our data (1,478 requests in 30 days), about $117 on GPT-5.6 Terra and $84.36 on GPT-5.3-Codex at list price. Heavier users pay proportionally more.

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

GPT-5.6 Terra scores higher on output quality (8.0/10 vs 6.8/10), while GPT-5.6 Terra 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 Terra is best for fast mid-tier work 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 Terra 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.

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Output Quality

Correctness and depth of what it produces

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Agentic Ability

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

Speed

Tokens per second and time-to-first-token

Value for Money

How much capability you get per dollar

Reliability

Consistent results: fewer refusals, loops and format breaks

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