Undominated.ai

Model comparison · accepted catalogue facts 2026-09-23

Claude Sonnet 5 vs Gemini 3.8 Flash

A quality score or a computable price is missing. This pair has no better-and-cheaper verdict.

Editorial comparison: Cross-provider application shortlist: inspect modality, output and cache differences at the same stated workload. Inclusion does not recommend either model.

Claude Sonnet 5

LMArena general · Elo · higher is better

Scale starts at 1040 Elo

1442.2

Balanced effective USD / 1M tokens · lower is better

$4.00/M

Gemini 3.8 Flash

LMArena general · Elo · higher is better

Scale starts at 1040 Elo

1494.7

Balanced effective USD / 1M tokens · lower is better

Unknown

Compare · model decision

Choose two or three models

Inspect the differences, estimate your workload and keep the evidence. All standard catalogue models are available, including unrated ones.

Catalogue facts
2026-09-23

2 / 3 selected · 0 requirements
Open public comparison link
Public workload and requirements

These settings are included in the share link. The fixed-request scenario and private evaluation data below are excluded.

A ↔ B

A quality score or a computable price is missing. This pair has no better-and-cheaper verdict.

Estimated blend: 75% input, 25% output; 0% cached input. Base context tier. Prompt length selects the billing tier. An unlisted cache-read rate uses that tier’s full input rate in this blend; missing required input or output rates prevent an estimate. The fixed-request estimate below validates actual context and output limits and requires a published cache-read rate when cache hits are assumed.

What changes between these models

Quality first, then estimated price. LMArena scores are human-preference measurements, not a benchmark of your application. A missing score is unrated.

  • Claude Sonnet 5 · Meets the stated model requirements
  • Gemini 3.8 Flash · Meets the stated model requirements
Material differences and unknown evidence. Deltas compare each model with model A. Unknown facts remain visible.
Measured factA Claude Sonnet 5B Gemini 3.8 Flash
LMArena general score (Elo)1,442.21,494.7Δ vs A: +52.5 Elo
Score interval half-width (± Elo)4.588.53Δ vs A: +3.95 Elo
LMArena document score (Elo)1,466.1Unknown
Estimated effective USD / 1M tokens$4Unknown
Base input USD / 1M tokens$2$0.75Δ vs A: -1.25 USD/M
Base output USD / 1M tokens$10$3.75Δ vs A: -6.25 USD/M
Base cached-input USD / 1M tokens$0.2$0.075Δ vs A: -0.125 USD/M
Context window (tokens)1,000,0001,048,576Δ vs A: +48,576 tokens
Output limit (tokens)128,00065,536Δ vs A: -62,464 tokens
Input modalitiestext, image, filetext, image, video, file, audio
Open weightsNot supportedUnknown
Recorded licenceproprietaryUnknown
Model providerAnthropicGoogle
Distinct sellers in the catalogue51Δ vs A: -4
Recorded retirement dateUnknownUnknown
5 shared measured facts
Shared measured facts. Deltas compare each model with model A. Unknown facts remain visible.
Measured factA Claude Sonnet 5B Gemini 3.8 Flash
Benchmark reasoning efforthighhigh
Tool useSupportedSupportedΔ vs A: 0
ReasoningSupportedSupportedΔ vs A: 0
Serving precision differs across offersNot supportedNot supportedΔ vs A: 0
Retirement evidenceNone announced; not a guaranteeNone announced; not a guarantee

Provider counts and precision flags describe catalogue offers. They do not establish the precision, availability, region, tool behaviour or limits of your chosen endpoint. Open each model’s provider table before switching.

Complete price ladders and billing conditions

Claude Sonnet 5

Rates below are USD per 1M tokens. A threshold selects that whole input/output rate pair.

Input-token thresholdInputOutputCached input
Base, up to and including first threshold$2$10$0.2

Gemini 3.8 Flash

Estimate unavailable: Separately billed reasoning tokens are not part of this token blend.

Separate reasoning: $3.75/1M tokens; reasoning-token counts are not modelled here. Rates below are USD per 1M tokens. A threshold selects that whole input/output rate pair.

Input-token thresholdInputOutputCached input
Base, up to and including first threshold$0.75$3.75$0.075
Migration preflight · compare each candidate with model A

Keeping Claude Sonnet 5 is a valid decision. No pairwise comparison certifies a drop-in replacement.

Claude Sonnet 5 → Gemini 3.8 Flash

Known loss or failed requirement

  • Output limit: 128,000 → 65,536 tokens.
  • Provider endpoint, serving precision, availability and task success need your own verification. Catalogue model capabilities do not certify an endpoint.
Check alternatives to Claude Sonnet 5

Estimate a fixed request shape

Private to this tab unless you save locally or explicitly export private details. These are estimates, not observed invoices. Cross-model token counts and task success are assumptions.

0.1 extra attempts means 10 extra full attempts per 100 requests. Cache writes, tool charges, taxes and unlisted charges are excluded.

  • Claude Sonnet 5Estimated total: $9 1,000 full attempts · base rates
  • Gemini 3.8 FlashEstimated total: unknown Separately billed reasoning tokens are not part of this request shape.
Prompt and output sensitivity · sampled scenarios

Every point recalculates the entire request shape. Tier-boundary samples include one token below, at and above each threshold. Ordering between samples is not guaranteed. Lowest known cost excludes unknown estimates and is not a replacement recommendation.

Vary input; hold output, requests, cache and retries fixed.
Input tokensClaude Sonnet 5Gemini 3.8 FlashCoverage
2,000$9Lowest knownunknownSeparately billed reasoning tokens are not part of this request shape.Incomplete
4,096$13.192Lowest knownunknownSeparately billed reasoning tokens are not part of this request shape.Incomplete
32,768$70.536Lowest knownunknownSeparately billed reasoning tokens are not part of this request shape.Incomplete
131,072$267.144Lowest knownunknownSeparately billed reasoning tokens are not part of this request shape.Incomplete
Vary output; hold input, requests, cache and retries fixed.
Output tokensClaude Sonnet 5Gemini 3.8 Flash
128$5.28unknownSeparately billed reasoning tokens are not part of this request shape.
2,048$24.48unknownSeparately billed reasoning tokens are not part of this request shape.
8,192$85.92unknownSeparately billed reasoning tokens are not part of this request shape.

Bring your observed evaluation results

JSON is parsed locally. Prompts, filenames, individual responses and extra fields are not retained. Import only aggregate measurements for selected models. Task/version labels do not establish that two evaluations used the same dataset.

Expected format
[{"model":"provider/exact-model-id","task":"support-answer","version":"rubric-1","attempts":100,"successes":84,"costUsd":2.4,"latencyMs":950}]

Use the exact catalogue ID. Replace the example values with observed measurements. Omit costUsd or latencyMs when they are unknown. No public score is inferred from these observations.

Keep the decision and its evidence

A portable record retains selected facts, complete tier ladders, public requirements and the publication manifest. It also embeds the full permitted public catalogue to verify the input artifact checksum. Files are larger for this reason (up to 2 MB); local storage is limited to 12 records. Team review is local to this browser; there is no hosted collaboration.

Saving is opt-in and includes private review fields. Shared comparison links never include them. Version 1 Check references remain separate and are not overwritten or guessed into this format.

Saved local decisions · 0

No version 2 decision records are stored in this browser.

Questions this page answers

Is Claude Sonnet 5 a better-and-cheaper replacement for Gemini 3.8 Flash?

A quality score or a computable price is missing. This pair has no better-and-cheaper verdict.

What is included in this comparison?

Accepted model capabilities, context and output limits, complete price-tier ladders, independent LMArena measurements and missing evidence. Provider endpoint precision and application success still need verification.

Can I compare a different workload or keep a decision record?

Yes. Change the public workload, prompt length and requirements in the comparison workspace. Fixed-request scenarios, aggregate evaluations and review notes stay local unless explicitly exported.

Evidence & Ask