Cost per coding-agent request

Is GPT-5.5 or GPT-5.6 Terra cheaper for coding agents?

For coding agents, GPT-5.5 costs 2.5x as much as GPT-5.6 Terra per request ($0.21 vs $0.084 on our measured traffic), because GPT-5.5 lists at $5 input, $0.50 cached input and $30 output per million tokens against $2, $0.20 and $12 for GPT-5.6 Terra, and both charge more for long prompts.

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 Terra	GPT-5.5
Prompt under 100K tokens50% of requests, 87% of input cached	$0.032	$0.081
Prompt of 100K to 272K39% of requests, 88% of input cached	$0.080	$0.20
Prompt over 272K tokens11% of requests, 86% of input cached	$0.34	$0.86
Average request	$0.084	$0.21
100 requests	$8.40	$20.99
Median session16 requests; a session ends after 10 idle minutes	$0.92	$2.30
A month of regular usemedian of 20 users active on 5+ days	$118	$296

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.

Benchmarks, speed and latency, side by side

Artificial Analysis	GPT-5.6 Terra	GPT-5.5
Intelligence Index10 evaluations, 0 to 100	42	38
Terminal-Bench 4.0agentic coding in a terminal	35.4%	14.6%
Output speedmedian	135 tokens/s	105 tokens/s
Time to first answer tokenincludes thinking time	2.2 min	71 s

Source: Artificial Analysis (artificialanalysis.ai). Measured variants: GPT-5.6 Terra (Max), speed on OpenAI; GPT-5.5 (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

GPT-5.5 is superseded: GPT-6.1 Sol costs $0.067 per request. GPT-5.6 Terra scores as well or better on the benchmarks above, so the cheaper request is not bought with much lower ability.

FAQ

Is GPT-5.6 Terra cheaper than GPT-5.5 for coding agents?

Yes, at list prices. 100 average coding-agent requests cost $8.40 on GPT-5.6 Terra and $20.99 on GPT-5.5. A median 16-request session costs $0.92 vs $2.30. Measured on 79,301 real coding-agent requests (Sep 13 to Oct 12, 2026).

How much does a month of GPT-5.5 vs GPT-5.6 Terra cost?

For the median regular user in our data (1,478 requests in 30 days), about $296 on GPT-5.5 and $118 on GPT-5.6 Terra at list price. Heavier users pay proportionally more.

GPT-5.5 vs GPT-5.6 Terra: which is better for agents?

GPT-5.6 Terra scores higher on output quality (8.0/10 vs 7.6/10), while GPT-5.6 Terra is the cheaper option. GPT-5.5 is best for existing GPT-5.5 setups on an API key until they move to GPT-6.1 Sol; 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-5.5 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.

Community vote

Pick a winner in each dimension. You can change your vote any time. 3 votes cast so far.

Output Quality

Correctness and depth of what it produces

100%2 votes0%

Agentic Ability

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

0%1 vote100%

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

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

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Current frontier models Claude Fable 5.1 · GPT-6 Astra

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Each step goes to the cheapest model that can do it, on providers we vet for price, uptime and speed, with automatic fallback when one fails.

Compliance: Keep a key, team or company on European or US providers
Privacy: We don’t train on your prompts or store them

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