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.

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Success rate by suite

Appointments59 scenariosMedicare23 scenarios
  • GPT Realtime 2.1OpenAI
    92%
    81%
  • GPT-Live 1 + Sol lowOpenAI
    97%
    49%
  • Gemini 3.8 Live ThinkingGoogle
    82%
    61%
  • Grok Think Fast 2.0xAI
    96%
    25%
  • Gemini 3.1 Flash LiveGoogle
    93%
    32%
  • Phonic v1Phonic
    97%
    14%
  • Realtime 2.1 MiniOpenAI
    84%
    4%
  • Nova 2 SonicAmazon
    80%
    6%
  • Cascade, GPT-4.1Not ranked
    97%
    83%
Each model's share of calls that passed every check, on each suite.

Every metric, side by side

Reliability

Scenarios that passed on all three runs.

Gemini 3.1 Flash Live
62.2%5th
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%4th
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%5th
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%4th
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%5th
GPT Realtime 2.1
3.3%4th

Level

Interruption

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

Gemini 3.1 Flash Live
4.984th
GPT Realtime 2.1
4.983rd

Level

Response time

Median time to start replying after the caller finishes.

Gemini 3.1 Flash Live
2.88s8th
GPT Realtime 2.1
1.94s3rd

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
$0.0855th

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

MedianTo p90
Medianp90
  • Phonic v1Phonic
    Phonic v1: median 1.59s, p90 1.86s
    1.59s1.86s
  • Grok Think Fast 2.0xAI
    Grok Think Fast 2.0: median 1.62s, p90 1.94s
    1.62s1.94s
  • GPT Realtime 2.1OpenAI
    GPT Realtime 2.1: median 1.94s, p90 2.46s
    1.94s2.46s
  • GPT-Live 1 + Sol lowOpenAI
    GPT-Live 1 + Sol low: median 2.02s, p90 2.42s
    2.02s2.42s
  • Realtime 2.1 MiniOpenAI
    Realtime 2.1 Mini: median 2.08s, p90 2.75s
    2.08s2.75s
  • Nova 2 SonicAmazon
    Nova 2 Sonic: median 2.18s, p90 2.76s
    2.18s2.76s
  • Gemini 3.8 Live ThinkingGoogle
    Gemini 3.8 Live Thinking: median 2.32s, p90 3.06s
    2.32s3.06s
  • Gemini 3.1 Flash LiveGoogle
    Gemini 3.1 Flash Live: median 2.88s, p90 4.00s
    2.88s4.00s
  • Cascade, GPT-4.1Not ranked
    Cascade, GPT-4.1: median 2.17s, p90 2.51s
    2.17s2.51s
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

  • Steady on the short form, though it repeats lookups it already made.
  • On the long form it hands the caller over with the wrong details.
  • Slowest to reply; after several tool calls its replies fall behind or go missing.
  • Sometimes says goodbye without hanging up.
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

  • Only a handful of scenarios ever fail, and rarely twice.
  • Best realtime model on the long form, level with the cascade.
  • Few data errors: a phone number or an earlier reference, wrong or left out.
  • Weakest on noisy lines.
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.
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Frequently asked questions

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

Gemini 3.1 Flash Live Preview passed 51 of 82 scenarios on all three runs, and GPT Realtime 2.1 passed 65. GPT Realtime 2.1 is ahead, by 17.1 points.

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

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.

Which responds faster, Gemini 3.1 Flash Live Preview or GPT Realtime 2.1?

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 costs less, Gemini 3.1 Flash Live Preview or GPT Realtime 2.1?

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. Gemini 3.1 Flash Live Preview is $0.015 cheaper a minute.

How were Gemini 3.1 Flash Live Preview and GPT Realtime 2.1 compared?

Both ran as the whole agent in the same open-source Pipecat pipeline, with the same prompt, tools and phone line. A simulated caller worked through all 82 scenarios on live calls, three times each, 2,214 calls across the benchmark. A call passes only when the agent said the right things and saved the right data.