Cost per coding-agent request

Is Gemini 3.1 Pro or Gemini 3.5 Flash cheaper for coding agents?

For coding agents, Gemini 3.1 Pro costs 1.9x as much as Gemini 3.5 Flash per request ($0.095 vs $0.049 on our measured traffic), because Gemini 3.1 Pro 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 Gemini 3.1 Pro charges more for prompts over 200K tokens.

List prices: Gemini API pricing, OpenRouter listed price, 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 Gemini 3.1 Pro and Gemini 3.8 Flash in your agent

Or let the router send each step to the cheapest model that can do it, on providers we vet for price, uptime and speed. Plans from $19 a month.

See plans

Cost per coding-agent request, side by side

Cost at list price	Gemini 3.5 Flash	Gemini 3.1 Pro
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	$0.11
Prompt over 272K tokens11% of requests, 86% of input cached	$0.13	$0.34
Average request	$0.049	$0.095
100 requests	$4.93	$9.48
Median session16 requests; a session ends after 10 idle minutes	$0.67	$0.93
A month of regular usemedian of 20 users active on 5+ days	$75.17	$135

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	Gemini 3.1 Pro
Intelligence Index10 evaluations, 0 to 100	33	30
Terminal-Bench 4.0agentic coding in a terminal	6.6%	4.0%
Output speedmedian	197 tokens/s	144 tokens/s
Time to first answer tokenincludes thinking time	17 s	23 s

Source: Artificial Analysis (artificialanalysis.ai). Measured variants: Gemini 3.5 Flash (High), speed on Google; Gemini 3.1 Pro Preview, speed on Google. 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 Gemini 3.1 Pro 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 Gemini 3.5 Flash is superseded: Gemini 3.8 Flash costs $0.048 per request.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 Gemini 3.1 Pro for coding agents?

Yes, at the listed prices. 100 average coding-agent requests cost $4.93 on Gemini 3.5 Flash and $9.48 on Gemini 3.1 Pro. A median 16-request session costs $0.67 vs $0.93. Measured on 79,301 real coding-agent requests (Sep 13 to Oct 12, 2026).

How much does a month of Gemini 3.1 Pro vs Gemini 3.5 Flash cost?

For the median regular user in our data (1,478 requests in 30 days), about $135 on Gemini 3.1 Pro and $75.17 on Gemini 3.5 Flash at list price. Heavier users pay proportionally more.

Gemini 3.1 Pro vs Gemini 3.5 Flash: which is better for agents?

Gemini 3.5 Flash scores higher on output quality (6.8/10 vs 6.4/10), while Gemini 3.5 Flash is the cheaper option. Gemini 3.1 Pro is best for long multimodal inputs and Gemini CLI setups that still pin 3.1 Pro; Gemini 3.5 Flash is best for existing Gemini 3.5 Flash setups until they move to 3.8 Flash. Live community votes on this page show what people actually prefer.

Can I switch between Gemini 3.1 Pro and Gemini 3.5 Flash 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.

Output Quality

Correctness and depth of what it produces

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 run on Standard Compute

Standard Compute

Current frontier models Claude Fable 5.1 · GPT-6 Astra

More intelligence
per dollar.

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: Opt-in rules keep a company, team or key on European or US providers
Privacy: We don’t train on your prompts or store them

Get your API key See how it works

Fixed monthly plans from $19 · cancel anytime

7-day fair refund Free trial, no card Billing by Stripe4,100+ agent users