Gemini 3.8 Flash vs GPT-5.6 Terra
Gemini 3.8 Flash wins on Overall, Coding, Multimodal. Every numeric field is compared below, with a worked monthly-cost example and a pick rule for each use case.
Verdict at a glance
Choose Gemini 3.8 Flash if you…
- Best-coding Flash yet
- Native text/image/audio/video
- Very fast and low-priced
- Stronger agentic reasoning
- Best for: Fast tasks, Multimodal, Coding
Choose GPT-5.6 Terra if you…
- OpenAI quality
- Halved price
- Rich ecosystem
- Best for: Value, General tasks, OpenAI ecosystem
Head-to-head aggregate scores
Scores are 0–100, aggregated from public benchmark information and independently weighted across three leaderboards. Rank is out of 26 tracked models.
Aggregated from public sources and independently weighted; methodology on the Terms page. Scores within 3 points are treated as statistically tied.
Specs & pricing — every field side by side
List API prices in USD per 1M tokens. The highlighted cell is the stronger value/capability on that row.
| Dimension | Gemini 3.8 Flash | GPT-5.6 Terra | Verdict |
|---|---|---|---|
| Vendor | Google (US) | OpenAI (US) | Different vendors |
| Released | 2026.09 | 2026.07 | Gemini 3.8 Flash is newer |
| Overall (rank) | 73 · #12 | 62 · #25 | Gemini 3.8 Flash +11 |
| Coding | 73 · #13 | 70 · #16 | Gemini 3.8 Flash +3 |
| Multimodal | 88 · #9 | 69 · #23 | Gemini 3.8 Flash +19 |
| Context window | 1M | 1.05M | GPT-5.6 Terra larger |
| Max output | 64K | 128K | Gemini 3.8 Flash longer |
| Effective-context | 90 | 88 | Gemini 3.8 Flash more reliable |
| Input $/1M | $0.75 | $2.5 | Gemini 3.8 Flash cheaper |
| Output $/1M | $3.75 | $15 | Gemini 3.8 Flash cheaper |
| Cache discount | none | 50% off | GPT-5.6 Terra deeper |
| Speed | ~85 tok/s | ~60 tok/s | Gemini 3.8 Flash faster |
| TTFT | 0.3s | 0.5s | Gemini 3.8 Flash snappier |
| Function calling | 78 | 90 | GPT-5.6 Terra ahead |
| Refusal rate | ~10% | ~13% | Gemini 3.8 Flash less restrictive |
| English | 88 | 88 | Tie |
| Chinese | 74 | 72 | Gemini 3.8 Flash |
| Modalities | text, image, audio, video | text, image | different coverage |
| Open weights | No | No | Both closed |
| Fine-tuning | Yes | No | |
| Free tier | Gemini App free; API free tier; intro price through Dec 31, 2026 | No free API | |
| SOC2 / no-train | yes / yes | yes / yes | |
| Private deployment | No | No | Neither |
Fields drawn from vendor public documentation and the Modelspectra 26-model dataset; speed varies with network, concurrency and prompt length. Verify current pricing before purchase.
Dimension-by-dimension analysis
Reasoning & overall intelligence
Gemini 3.8 Flash leads the overall aggregate by 11 points (73 vs 62). That is a meaningful, not marginal, edge on hard, multi-step reasoning, while GPT-5.6 Terra remains a strong generalist that is not out of its depth on routine work.
Agentic coding
This is a modest gap: Gemini 3.8 Flash scores 73 against 70. On multi-file edits, SWE-style tickets and long-horizon agent loops Gemini 3.8 Flash needs fewer correction turns; GPT-5.6 Terra is still competent for scripts and assisted completion but trails as task complexity rises.
Multimodal
Gemini 3.8 Flash leads multimodal 88 vs 69. A concrete modality difference: Gemini 3.8 Flash additionally handles audio, video.
Speed & latency
Gemini 3.8 Flash is faster in interactive use: ~85 tok/s with 0.3s TTFT versus ~60 tok/s with 0.5s TTFT (about 1.4× the throughput). For conversational UIs where perceived responsiveness drives retention, that edge is a real product factor even when raw reasoning is lower.
Context: window vs usable recall
Nominal windows are 1M for Gemini 3.8 Flash and 1.05M for GPT-5.6 Terra. Crucially, the larger nominal window does not win on usable recall: GPT-5.6 Terra advertises 1.05M but Gemini 3.8 Flash scores higher on effective-context (90 vs 88), i.e. it actually retains more of what it was given.
Price & total cost
Gemini 3.8 Flash is the cheaper API at $0.75/$3.75 versus GPT-5.6 Terra at $2.5/$15 per 1M input/output tokens — list input is about 3.3× lower. Cache discounts (GPT-5.6 Terra 50%) shift the effective bill, worked out below.
Chinese vs English
English: Gemini 3.8 Flash 88 vs GPT-5.6 Terra 88. Chinese: 74 vs 72. Both are US-based models; for Chinese-first workloads also compare domestic models on the leaderboard.
Tool use & ecosystem
Function-calling score: Gemini 3.8 Flash 78 vs GPT-5.6 Terra 90, so GPT-5.6 Terra has the edge on structured tool use. Fine-tuning is available from Gemini 3.8 Flash. Factor in existing SDK/plugin familiarity — switching cost often outweighs a few-point tool-use gap.
Cost worked example — same workload, real token math
Assume a production workload of 100M input + 30M output tokens per month, with 90% of input tokens served from cache. Figures use public list prices.
| Scenario · per month | Gemini 3.8 Flash | GPT-5.6 Terra | Gap |
|---|---|---|---|
| List priceno cache applied | $188100M in × $0.75 + 30M out × $3.75 | $700100M in × $2.5 + 30M out × $15 | 3.72×gap |
| With caching90% of inputs cache-hit | $188no published cache discount | $58890M cached in × $1.25 + 10M in × $2.5 + 30M out × $15 | 3.13×gap |
Illustrative model; your input/output mix and cache-hit ratio change the result. Prices are list rates before any enterprise agreement.