Cost per coding-agent request

Is Gemini 3.5 Flash or GPT-5.6 Terra cheaper for coding agents?

For coding agents, GPT-5.6 Terra costs 1.7x as much as Gemini 3.5 Flash per request ($0.084 vs $0.049 on our measured traffic), because GPT-5.6 Terra lists at $2 input, $0.20 cached input and $12 output per million tokens against $1.50, $0.15 and $9 for Gemini 3.5 Flash, and GPT-5.6 Terra charges more for prompts over 272K tokens.

List prices: OpenRouter listed price, 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

Run GPT-5.6 Terra and Gemini 3.8 Flash in your agent from $19/month

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Cost per coding-agent request, side by side

Cost at list price	Gemini 3.5 Flash	GPT-5.6 Terra
Prompt under 100K tokens50% of requests, 87% of input cached	$0.024	$0.032
Prompt of 100K to 272K39% of requests, 88% of input cached	$0.060	$0.080
Prompt over 272K tokens11% of requests, 86% of input cached	$0.13	$0.34
Average request	$0.049	$0.084
100 requests	$4.93	$8.40
Median session16 requests; a session ends after 10 idle minutes	$0.67	$0.92
A month of regular usemedian of 20 users active on 5+ days	$75.17	$118

Each logged request priced at the listed rates above 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	Gemini 3.5 Flash	GPT-5.6 Terra
Intelligence Index10 evaluations, 0 to 100	33	42
Terminal-Bench 4.0agentic coding in a terminal	6.6%	35.4%
Output speedmedian	197 tokens/s	135 tokens/s
Time to first answer tokenincludes thinking time	17 s	2.2 min

Source: Artificial Analysis (artificialanalysis.ai). Measured variants: Gemini 3.5 Flash (High), speed on Google; 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

The gap widens on long prompts: under 100K tokens GPT-5.6 Terra costs 1.3x as much per request, over 272K 2.6x. Gemini 3.5 Flash is superseded: Gemini 3.8 Flash costs $0.048 per request. The price is OpenRouter's listed rate on October 13, 2026, which can be a third-party host's; Google's own API may charge differently.

FAQ

Is Gemini 3.5 Flash cheaper than GPT-5.6 Terra for coding agents?

Yes, at the listed prices. 100 average coding-agent requests cost $4.93 on Gemini 3.5 Flash and $8.40 on GPT-5.6 Terra. A median 16-request session costs $0.67 vs $0.92. Measured on 79,301 real coding-agent requests (Sep 13 to Oct 12, 2026).

How much does a month of GPT-5.6 Terra vs Gemini 3.5 Flash cost?

For the median regular user in our data (1,478 requests in 30 days), about $118 on GPT-5.6 Terra and $75.17 on Gemini 3.5 Flash at list price. Heavier users pay proportionally more.

Gemini 3.5 Flash 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 Gemini 3.5 Flash is the cheaper option. Gemini 3.5 Flash is best for existing Gemini 3.5 Flash setups until they move to 3.8 Flash; 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 Gemini 3.5 Flash 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. 1 vote cast so far.

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

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.

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