CekuraBench
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GoogleOpenAI

Gemini 3.8 Live vs GPT Realtime 2.1

GPT Realtime 2.1 is ahead on reliability, success rate, agent responses and data accuracy, and Gemini 3.8 Live on stalled calls and response time. The two tie on 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%
  • Phonic v1Phonic
    97%
    26%
  • Gemini 3.8 Live ThinkingGoogle
    79%
    70%
  • Grok Think Fast 2.0xAI
    96%
    25%
  • Gemini 3.1 Flash LiveGoogle
    93%
    32%
  • Gemini 3.8 LiveGoogle
    76%
    52%
  • 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 3.8 Live
41.5%9th
GPT Realtime 2.1
79.3%1st

GPT Realtime 2.1, 37.8 points higher

Success rate

Calls that passed every check.

Gemini 3.8 Live
69.1%7th
GPT Realtime 2.1
89.0%1st

GPT Realtime 2.1, 19.9 points higher

Agent responses

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

Gemini 3.8 Live
94.3%6th
GPT Realtime 2.1
99.2%2nd

GPT Realtime 2.1, 4.9 points higher

Data accuracy

Calls where everything the agent saved matched exactly.

Gemini 3.8 Live
70.5%7th
GPT Realtime 2.1
92.0%1st

GPT Realtime 2.1, 21.5 points higher

Stalled calls

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

Gemini 3.8 Live
2.0%3rd
GPT Realtime 2.1
3.3%5th

Gemini 3.8 Live, 1.2 points lower

Interruption

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

Gemini 3.8 Live
4.983rd
GPT Realtime 2.1
4.984th

Level

Response time

Median time to start replying after the caller finishes.

Gemini 3.8 Live
1.91s3rd
GPT Realtime 2.1
1.94s4th

Gemini 3.8 Live, 0.03s sooner

Cost / min

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

Gemini 3.8 Live
No verified rate
GPT Realtime 2.1
$0.0855th

Not comparable

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

Gemini 3.8 Live answers first

Gemini 3.8 Live 1.91s, GPT Realtime 2.1 1.94s at the median.

Response time, median to p90

MedianTo p90
Medianp90
  • Phonic v1Phonic
    Phonic v1: median 1.60s, p90 1.88s
    1.60s1.88s
  • Grok Think Fast 2.0xAI
    Grok Think Fast 2.0: median 1.62s, p90 1.94s
    1.62s1.94s
  • Gemini 3.8 LiveGoogle
    Gemini 3.8 Live: median 1.91s, p90 2.23s
    1.91s2.23s
  • 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
  • Gemini 3.8 Live ThinkingGoogle
    Gemini 3.8 Live Thinking: median 2.07s, p90 2.74s
    2.07s2.74s
  • 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 3.1 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 3.8 Live

  • Without extended thinking it replies sooner, and short-form calls reach the outcome more often.
  • On the long form the conversation still reaches the outcome, but the saved record is wrong far more often.
  • Weakest of the field when the caller corrects themselves.
  • Google's turn detection stalls it under background conversation: the caller finishes and no reply comes (AS50, AS52, AS14).
  • Least predictable of the field.
Model
gemini-3.8-live
Setting
No thinking level
Voice
Charon
Turn taking
Service turn detection
Audio
16 kHz
Cost
The export carries audio tokens but not text or cached input, so a per-call cost is not derived.

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 3.8 Live or GPT Realtime 2.1 more reliable?

Gemini 3.8 Live passed 34 of 82 scenarios on all three runs, and GPT Realtime 2.1 passed 65. GPT Realtime 2.1 is ahead, by 37.8 points.

Which saves caller data more accurately, Gemini 3.8 Live or GPT Realtime 2.1?

Gemini 3.8 Live saved everything exactly right on 70.5% of the calls that save data, and GPT Realtime 2.1 on 92.0%. On Appointments, 78.4% against 95.9%. On Medicare, 50.0% against 81.8%. A call counts only when nothing is missing, wrong, extra or saved twice.

Which responds faster, Gemini 3.8 Live or GPT Realtime 2.1?

Gemini 3.8 Live starts replying 0.03s sooner at the median. Gemini 3.8 Live takes 1.91s at the median and 2.23s 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 3.8 Live or GPT Realtime 2.1?

There is no verified per-minute rate for Gemini 3.8 Live, so cost cannot be compared yet.

How were Gemini 3.8 Live 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 connection. A simulated caller worked through all 82 scenarios on live calls, three times each, 2,460 calls across the benchmark. A call passes only when the agent said the right things and saved the right data.