CekuraBench
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GoogleOpenAI

Gemini 3.1 Flash Live Preview vs GPT Realtime 2.1

GPT Realtime 2.1 is ahead on reliability, success rate, agent responses, data accuracy and response time, and Gemini 3.1 Flash Live Preview on cost. The two tie on stalled calls and interruption.

Last updated Methodology by Dileep Chagam

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Success rate by suite

Higher is better
Appointments59 scenariosMedicare23 scenarios
  • GPT Realtime 2.1OpenAI
    92%
    81%
  • Gemini 3.1 Flash LiveGoogle
    93%
    32%
Each model's share of calls that passed every check, on each suite.
Verdict

Which to pick

Pick Gemini 3.1 Flash Live Preview for lower cost ($0.015 cheaper). Pick GPT Realtime 2.1 for reliability across repeated calls (17.1 points higher), calls that pass every check (13.0 points higher), getting the agent's replies right (3.3 points higher), saving the caller's data correctly (12.7 points higher) and fast replies (0.94s sooner). They are level on fewer stalled calls and handling interruptions.

Every metric, side by side

Reliability

Scenarios that passed on all three runs.

Gemini 3.1 Flash Live
62.2%6th
GPT Realtime 2.1
79.3%1st

GPT Realtime 2.1, 17.1 points higher

Success rate

Calls that passed every check.

Gemini 3.1 Flash Live
76.0%5th
GPT Realtime 2.1
89.0%1st

GPT Realtime 2.1, 13.0 points higher

Agent responses

Calls where the agent's replies reached the expected outcome.

Gemini 3.1 Flash Live
95.9%6th
GPT Realtime 2.1
99.2%2nd

GPT Realtime 2.1, 3.3 points higher

Data accuracy

Calls where everything the agent saved matched exactly.

Gemini 3.1 Flash Live
79.2%5th
GPT Realtime 2.1
92.0%1st

GPT Realtime 2.1, 12.7 points higher

Stalled calls

Calls where the agent went silent for 10 seconds or more.

Gemini 3.1 Flash Live
3.3%6th
GPT Realtime 2.1
3.3%5th

Level

Interruption

How well it handled being talked over, 0 to 5.

Gemini 3.1 Flash Live
4.985th
GPT Realtime 2.1
4.984th

Level

Response time

Median time to start replying after the caller finishes.

Gemini 3.1 Flash Live
2.88s11th
GPT Realtime 2.1
1.94s5th

GPT Realtime 2.1, 0.94s sooner

Cost / min

One minute of call at the vendor's published rates.

Gemini 3.1 Flash Live
$0.0703rd
GPT Realtime 2.1
$0.0856th

Gemini 3.1 Flash Live, $0.015 cheaper

The small figure is the place among ranked models. The cascade is not ranked.

GPT Realtime 2.1 answers first

GPT Realtime 2.1 1.94s, Gemini 3.1 Flash Live 2.88s at the median.

Response time, median to p90

Lower is betterMedianTo p90
Medianp90
  • GPT Realtime 2.1OpenAI
    GPT Realtime 2.1: median 1.94s, p90 2.46s
    1.94s2.46s
  • Gemini 3.1 Flash LiveGoogle
    Gemini 3.1 Flash Live: median 2.88s, p90 4.00s
    2.88s4.00s
2.0s3.0s4.0s
Seconds from the caller finishing to the agent starting to reply, per model.

What we saw on the calls

Gemini 3.1 Flash Live Preview

  • Reliable on bookings.
All 3 notes on Gemini 3.1 Flash Live
Model
models/gemini-3.1-flash-live-preview
Setting
Thinking level high
Voice
Charon
Turn taking
Shared local turn detection
Audio
16 kHz
Cost
Averaged over the calls with a usage record.

GPT Realtime 2.1

  • Almost never fails, and rarely twice in a row.
All 4 notes on GPT Realtime 2.1
Model
gpt-realtime-2.1
Setting
Reasoning high
Voice
marin
Turn taking
Service turn detection
Audio
24 kHz
Cost
Excludes caller transcription, which the service does not meter per call.
See the full leaderboardReference agent

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Frequently asked questions

Is Gemini 3.1 Flash Live Preview or GPT Realtime 2.1 more reliable?

GPT Realtime 2.1 is more reliable, by 17.1 points. Gemini 3.1 Flash Live Preview passed 51 of 82 scenarios on all three runs, and GPT Realtime 2.1 passed 65. A scenario only counts when every run of it passed.

Which should I pick, Gemini 3.1 Flash Live Preview or GPT Realtime 2.1?

For a phone agent, GPT Realtime 2.1, since it gets more scenarios right on every run. GPT Realtime 2.1 is ahead on reliability, success rate, agent responses, data accuracy and response time, and Gemini 3.1 Flash Live Preview on cost. The two tie on stalled calls and interruption.

Which saves caller data more accurately, Gemini 3.1 Flash Live Preview or GPT Realtime 2.1?

GPT Realtime 2.1, by 12.7 points. Gemini 3.1 Flash Live Preview saved everything exactly right on 79.2% of the calls that save data, and GPT Realtime 2.1 on 92.0%. On Appointments, 96.5% against 95.9%. On Medicare, 34.8% against 81.8%. A call counts only when nothing is missing, wrong, extra or saved twice.

Is Gemini 3.1 Flash Live Preview faster than GPT Realtime 2.1?

No. GPT Realtime 2.1 starts replying 0.94s sooner at the median. Gemini 3.1 Flash Live Preview takes 2.88s at the median and 4.00s at p90; GPT Realtime 2.1 takes 1.94s and 2.46s. Both are measured on the call audio, from the caller finishing to the agent starting to reply.

Which handles interruptions better, Gemini 3.1 Flash Live Preview or GPT Realtime 2.1?

They score the same. Gemini 3.1 Flash Live Preview scores 4.98 and GPT Realtime 2.1 4.98 for how well the agent handled being talked over.

Which goes silent on callers less often, Gemini 3.1 Flash Live Preview or GPT Realtime 2.1?

They stall on the same share of calls. The agent went silent for 10 seconds or more on 3.3% of Gemini 3.1 Flash Live Preview calls and 3.3% of GPT Realtime 2.1 calls.

Which is cheaper, Gemini 3.1 Flash Live Preview or GPT Realtime 2.1?

Gemini 3.1 Flash Live Preview is $0.015 cheaper a minute. Gemini 3.1 Flash Live Preview costs $0.070 a minute of call and GPT Realtime 2.1 $0.085, at each vendor's published rates.

Where does the Gemini 3.1 Flash Live Preview vs GPT Realtime 2.1 data come from?

Cekura ran both as the whole agent in the same open-source Pipecat pipeline, with the same prompt, tools and connection. A simulated caller worked through all 82 scenarios on live calls, three times each, 2,952 calls across the benchmark. A call passes only when the agent said the right things and saved the right data.