Cost per coding-agent request

Is Gemini 3.5 Flash or GPT-5.5 cheaper for coding agents?

For coding agents, GPT-5.5 costs 4.3x as much as Gemini 3.5 Flash per request ($0.21 vs $0.049 on our measured traffic), because GPT-5.5 lists at $5 input, $0.50 cached input and $30 output per million tokens against $1.50, $0.15 and $9 for Gemini 3.5 Flash, and GPT-5.5 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

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Cost per coding-agent request, side by side

Cost at list price	Gemini 3.5 Flash	GPT-5.5
Prompt under 100K tokens50% of requests, 87% of input cached	$0.024	$0.081
Prompt of 100K to 272K39% of requests, 88% of input cached	$0.060	$0.20
Prompt over 272K tokens11% of requests, 86% of input cached	$0.13	$0.86
Average request	$0.049	$0.21
100 requests	$4.93	$20.99
Median session16 requests; a session ends after 10 idle minutes	$0.67	$2.30
A month of regular usemedian of 20 users active on 5+ days	$75.17	$296

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-5.5
Intelligence Index10 evaluations, 0 to 100	33	38
Terminal-Bench 4.0agentic coding in a terminal	6.6%	14.6%
Output speedmedian	197 tokens/s	105 tokens/s
Time to first answer tokenincludes thinking time	17 s	71 s

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

The gap widens on long prompts: under 100K tokens GPT-5.5 costs 3.3x as much per request, over 272K 6.6x. Gemini 3.5 Flash is superseded: Gemini 3.8 Flash costs $0.048 per request. GPT-5.5 is superseded: GPT-6.1 Sol costs $0.067 per request.

FAQ

Is Gemini 3.5 Flash cheaper than GPT-5.5 for coding agents?

Yes, at the listed prices. 100 average coding-agent requests cost $4.93 on Gemini 3.5 Flash and $20.99 on GPT-5.5. A median 16-request session costs $0.67 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 Gemini 3.5 Flash cost?

For the median regular user in our data (1,478 requests in 30 days), about $296 on GPT-5.5 and $75.17 on Gemini 3.5 Flash at list price. Heavier users pay proportionally more.

Gemini 3.5 Flash vs GPT-5.5: which is better for agents?

GPT-5.5 scores higher on output quality (7.6/10 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-5.5 is best for existing GPT-5.5 setups on an API key until they move to GPT-6.1 Sol. Live community votes on this page show what people actually prefer.

Can I switch between Gemini 3.5 Flash and GPT-5.5 in the same agent?

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