Gemini 3.8 Live Extended Thinking is ahead on reliability, success rate, data accuracy and response time, and GPT Realtime 2.1 Mini on agent responses, stalled calls and interruption.
Last updated Methodology by Dileep Chagam
Pick Gemini 3.8 Live Extended Thinking for reliability across repeated calls (2.4 points higher), calls that pass every check (14.6 points higher), saving the caller's data correctly (19.9 points higher) and fast replies (0.01s sooner). Pick GPT Realtime 2.1 Mini for getting the agent's replies right (4.9 points higher), fewer stalled calls (2.8 points lower) and handling interruptions (0.04 higher).
Scenarios that passed on all three runs.
Gemini 3.8 Live Thinking, 2.4 points higher
Calls that passed every check.
Gemini 3.8 Live Thinking, 14.6 points higher
Calls where the agent's replies reached the expected outcome.
Realtime 2.1 Mini, 4.9 points higher
Calls where everything the agent saved matched exactly.
Gemini 3.8 Live Thinking, 19.9 points higher
Calls where the agent went silent for 10 seconds or more.
Realtime 2.1 Mini, 2.8 points lower
How well it handled being talked over, 0 to 5.
Realtime 2.1 Mini, 0.04 higher
Median time to start replying after the caller finishes.
Gemini 3.8 Live Thinking, 0.01s sooner
One minute of call at the vendor's published rates.
Not comparable
The small figure is the place among ranked models. The cascade is not ranked.
Gemini 3.8 Live Thinking 2.07s, Realtime 2.1 Mini 2.08s at the median.
Both providers, every model: Google vs OpenAI
Gemini 3.8 Live Extended Thinking is more reliable, by 2.4 points. Gemini 3.8 Live Extended Thinking passed 43 of 82 scenarios on all three runs, and GPT Realtime 2.1 Mini passed 41. A scenario only counts when every run of it passed.
For a phone agent, Gemini 3.8 Live Extended Thinking, since it gets more scenarios right on every run. Gemini 3.8 Live Extended Thinking is ahead on reliability, success rate, data accuracy and response time, and GPT Realtime 2.1 Mini on agent responses, stalled calls and interruption.
Gemini 3.8 Live Extended Thinking, by 19.9 points. Gemini 3.8 Live Extended Thinking saved everything exactly right on 84.4% of the calls that save data, and GPT Realtime 2.1 Mini on 64.5%. On Appointments, 88.9% against 88.8%. On Medicare, 72.7% against 0.0%. A call counts only when nothing is missing, wrong, extra or saved twice.
Yes. Gemini 3.8 Live Extended Thinking starts replying 0.01s sooner at the median. Gemini 3.8 Live Extended Thinking takes 2.07s at the median and 2.74s at p90; GPT Realtime 2.1 Mini takes 2.08s and 2.75s. Both are measured on the call audio, from the caller finishing to the agent starting to reply.
GPT Realtime 2.1 Mini, by 0.04 on a 0 to 5 scale. Gemini 3.8 Live Extended Thinking scores 4.95 and GPT Realtime 2.1 Mini 4.99 for how well the agent handled being talked over.
GPT Realtime 2.1 Mini, by 2.8 points. The agent went silent for 10 seconds or more on 5.3% of Gemini 3.8 Live Extended Thinking calls and 2.5% of GPT Realtime 2.1 Mini calls.
There is no verified per-minute rate for Gemini 3.8 Live Extended Thinking, so cost cannot be compared yet.
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.
