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Gemini 3.1 Flash Live Preview vs Gemini 3.8 Live Extended Thinking

Gemini 3.1 Flash Live Preview is ahead on reliability, agent responses, stalled calls and interruption, and Gemini 3.8 Live Extended Thinking on data accuracy and response time. The two tie on success rate.

Last updated Methodology by Dileep Chagam

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Success rate by suite

Higher is better
Appointments59 scenariosMedicare23 scenarios
  • Gemini 3.8 Live ThinkingGoogle
    79%
    70%
  • 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 reliability across repeated calls (9.8 points higher), getting the agent's replies right (7.3 points higher), fewer stalled calls (2.0 points lower) and handling interruptions (0.03 higher). Pick Gemini 3.8 Live Extended Thinking for saving the caller's data correctly (5.2 points higher) and fast replies (0.81s sooner). They are level on calls that pass every check.

Every metric, side by side

Reliability

Scenarios that passed on all three runs.

Gemini 3.1 Flash Live
62.2%6th
Gemini 3.8 Live Thinking
52.4%8th

Gemini 3.1 Flash Live, 9.8 points higher

Success rate

Calls that passed every check.

Gemini 3.1 Flash Live
76.0%5th
Gemini 3.8 Live Thinking
76.0%5th

Level

Agent responses

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

Gemini 3.1 Flash Live
95.9%6th
Gemini 3.8 Live Thinking
88.6%11th

Gemini 3.1 Flash Live, 7.3 points higher

Data accuracy

Calls where everything the agent saved matched exactly.

Gemini 3.1 Flash Live
79.2%5th
Gemini 3.8 Live Thinking
84.4%4th

Gemini 3.8 Live Thinking, 5.2 points higher

Stalled calls

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

Gemini 3.1 Flash Live
3.3%6th
Gemini 3.8 Live Thinking
5.3%9th

Gemini 3.1 Flash Live, 2.0 points lower

Interruption

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

Gemini 3.1 Flash Live
4.985th
Gemini 3.8 Live Thinking
4.958th

Gemini 3.1 Flash Live, 0.03 higher

Response time

Median time to start replying after the caller finishes.

Gemini 3.1 Flash Live
2.88s11th
Gemini 3.8 Live Thinking
2.07s7th

Gemini 3.8 Live Thinking, 0.81s sooner

Cost / min

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

Gemini 3.1 Flash Live
$0.0703rd
Gemini 3.8 Live Thinking
No verified rate

Not comparable

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

Gemini 3.8 Live Thinking answers first

Gemini 3.8 Live Thinking 2.07s, Gemini 3.1 Flash Live 2.88s at the median.

Response time, median to p90

Lower is betterMedianTo p90
Medianp90
  • Gemini 3.8 Live ThinkingGoogle
    Gemini 3.8 Live Thinking: median 2.07s, p90 2.74s
    2.07s2.74s
  • 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.

Gemini 3.8 Live Extended Thinking

  • One of the strongest realtime models on Medicare calls.
All 3 notes on Gemini 3.8 Live Thinking
Model
gemini-3.8-live-extended-thinking
Setting
Thinking level high
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.
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Related comparisons

Frequently asked questions

Is Gemini 3.1 Flash Live Preview or Gemini 3.8 Live Extended Thinking more reliable?

Gemini 3.1 Flash Live Preview is more reliable, by 9.8 points. Gemini 3.1 Flash Live Preview passed 51 of 82 scenarios on all three runs, and Gemini 3.8 Live Extended Thinking passed 43. A scenario only counts when every run of it passed.

Which should I pick, Gemini 3.1 Flash Live Preview or Gemini 3.8 Live Extended Thinking?

For a phone agent, Gemini 3.1 Flash Live Preview, since it gets more scenarios right on every run. Gemini 3.1 Flash Live Preview is ahead on reliability, agent responses, stalled calls and interruption, and Gemini 3.8 Live Extended Thinking on data accuracy and response time. The two tie on success rate.

Which saves caller data more accurately, Gemini 3.1 Flash Live Preview or Gemini 3.8 Live Extended Thinking?

Gemini 3.8 Live Extended Thinking, by 5.2 points. Gemini 3.1 Flash Live Preview saved everything exactly right on 79.2% of the calls that save data, and Gemini 3.8 Live Extended Thinking on 84.4%. On Appointments, 96.5% against 88.9%. On Medicare, 34.8% against 72.7%. A call counts only when nothing is missing, wrong, extra or saved twice.

Is Gemini 3.1 Flash Live Preview faster than Gemini 3.8 Live Extended Thinking?

No. Gemini 3.8 Live Extended Thinking starts replying 0.81s sooner at the median. Gemini 3.1 Flash Live Preview takes 2.88s at the median and 4.00s at p90; Gemini 3.8 Live Extended Thinking takes 2.07s and 2.74s. 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 Gemini 3.8 Live Extended Thinking?

Gemini 3.1 Flash Live Preview, by 0.03 on a 0 to 5 scale. Gemini 3.1 Flash Live Preview scores 4.98 and Gemini 3.8 Live Extended Thinking 4.95 for how well the agent handled being talked over.

Which goes silent on callers less often, Gemini 3.1 Flash Live Preview or Gemini 3.8 Live Extended Thinking?

Gemini 3.1 Flash Live Preview, by 2.0 points. The agent went silent for 10 seconds or more on 3.3% of Gemini 3.1 Flash Live Preview calls and 5.3% of Gemini 3.8 Live Extended Thinking calls.

Which is cheaper, Gemini 3.1 Flash Live Preview or Gemini 3.8 Live Extended Thinking?

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

Where does the Gemini 3.1 Flash Live Preview vs Gemini 3.8 Live Extended Thinking 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.