Flash V4.1 vs Sonnet 5
Close intelligence (AA data is for the 0731 build; V4.1 is current)
Official prices as of 2026-10-20, per 1M tokens: DeepSeek V4.1 Flash cache-miss input $0.15 off-peak / $0.3 peak, output $0.6 / $1.2; Claude Sonnet 5 input $2, output $10. On the Artificial Analysis Intelligence Index Sonnet 5 is slightly ahead (55 vs 52, measured on the Flash 0731 build); Flash's edge is speed and open weights. Both offer a 1M context window.
Updated 2026-10-20
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Highlights
AA Intelligence
Sonnet 5 Adaptive Max vs Flash 0731 Max (the 2026-07-31 build). Overlap territory, not a blowout.
AA cost / task
Independent blended cost. Flash cache hits are extremely cheap.
Output tok/s
Flash is the faster decoder. Sonnet TTFT on max thinking can look huge (AA ~191s) because thinking counts.
Weights
Flash 0731 ships MIT weights on HF; since 2026-09-10 requests to that id are answered by deepseek-v4.1-flash. Sonnet 5 is proprietary, default in Claude Code.
The matchup
As of 2026-10-20, DeepSeek prices split into peak and off-peak, and off-peak rates are half of the peak rates; Search & Fetch costs $0.75 per 1,000 calls, with billing starting 2026-10-31 at 16:00 UTC. On the Anthropic side, Claude Sonnet 5 is listed as Active (legacy): it still runs, but the docs suggest migrating to Sonnet 5.5, and retirement is not sooner than 2027-06-30. Companies ask if they can swap Sonnet 5 for Flash to cut bills. The honest answer is: for high-volume, well-specified coding/agent loops, often yes; if what you need is fidelity to Claude's own tools and the enterprise Claude stack, keep Sonnet.
What people argue
Community threads describe Sonnet 5 as a token guzzler while Flash cache hits cost almost nothing — consistent with the per-task gap Artificial Analysis measures ($0.06 vs $1.54). OpenCode's published volume charts also put Flash at the top of Go traffic.
Dates that matter
Sonnet 5 ships at intro $2/$10. On 2026-08-10 that rate was made standard; the step to $3/$15 planned for 2026-09-01 was cancelled.
2026-07-31 public beta of Flash 0731 (this build was retired on 2026-09-10).
2026-08-16 DeepSeek peak/off-peak pricing. Still far under Sonnet.
Read the table honestly
Use these numbers
AA compare page: 52 vs 55, $0.06 vs $1.54, 115 vs 69 tok/s, TTFT 1.43s vs 191.38s, both 1M context.
Conclusions this data does not support
That Flash “ranks the same as Sonnet 5 on everything.” DeepSWE anecdotes ≠ AA index. Official DeepSeek tables compare Flash to Opus-4.8 / GLM-5.2, not Sonnet 5.
When to pick whom
Pick Flash 0731 (historical)
Volume, local/open, OpenCode Go, budget agent loops.
Pick Sonnet 5
Claude Code default, Bedrock/enterprise, instruction-fidelity, adaptive thinking productized.
How to use both
Same 1M window. Different tokenizer and thinking bills. Sonnet is $2/$10 as the standard rate (confirmed 2026-08-10); the $3/$15 planned from 2026-09-01 will not happen.
On QCode
QCode bills per token, and each model's price is on /models. deepseek-v4.1-flash and claude-sonnet-5 are available through one key; whether the official build DeepSeek-V4.1-Flash-1017 is available is what /models shows. The vendor retired the legacy name deepseek-v4-flash on 2026-09-10; on the official API its requests are now served by DeepSeek-V4.1-Flash-1017 and billed at the Flash price (that is the official API's behavior; what each QCode id maps to is whatever /models shows), so the 0731 figures belong to an earlier generation.
FAQ
Who is more intelligent?
Sonnet 5, slightly, on AA 55 vs 52.
Who is cheaper?
Flash, by a wide margin, even after 8-16 peak rates.
Did DeepSeek raise Flash prices?
Official prices are split into peak and off-peak (this page's timeline dates that from 2026-08-16), not a single price. In the 2026-10-20 official price table, off-peak rates are half of the peak rates. Cache hit $0.003 off-peak and $0.006 peak, cache miss $0.15 off-peak and $0.3 peak, output $0.6 off-peak and $1.2 peak, all per 1M tokens. Peak hours are 01:00-04:00 and 06:00-10:00 UTC, Monday through Friday, excluding Chinese public holidays. The current build DeepSeek-V4.1-Flash-1017 was released on 2026-10-17.
Can Flash replace Claude Code?
It can be the model inside another harness (OpenCode, dsh). It is not the Claude Code product.
Does Sonnet go to $3/$15 after Sep 1?
No. $2/$10 was confirmed as the standard rate on 2026-08-10; the 2026-09-01 step to $3/$15 will not happen.
Same context?
Both advertise 1M. Output caps differ (Flash 384K vs Sonnet 128K, 300K batches beta).
Sources
artificialanalysis.ai Flash vs Sonnet 5; DeepSeek pricing page and release notes; Anthropic Sonnet 5 model page and price list; retrieved 2026-10-20.
Run both, route by job
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Related
Flash 0731 historical guide
Historical 0731 specs (retired 2026-09-10).
DeepSeek Search and Fetch: per-request billing from 2026-11-01
Checked 2026-10-26: DeepSeek Search and Fetch are billed per successful request from 2026-11-01 Beijing time, with prices from both doc versions, billing conditions and QPS.
Sonnet 5 on this site
Existing Claude Sonnet 5 cluster.
Crypto payment guide
Nine coins, 56 networks, zero platform fee for AI coding API credits.
Checked on 2026-10-20. Prices and status follow the official DeepSeek and Anthropic pages, and model availability is whatever /models lists. Not affiliated with DeepSeek or Anthropic.