MiniMax M3.1 Flash Preview confirmed in code – benchmarks, pricing and parameters still open

Research date: September 27, 2026. MiniMax M3.1 is no longer just a rumored successor name. The official MiniMax Code repository now contains concrete MiniMax-M3.1 model fixtures and configuration tests, while users are reporting a “M3.1 Flash Preview” inside MiniMax Code today. The missing pieces matter just as much: at the time of review, MiniMax has not published a public M3.1 model card, an official M3.1 benchmark table, or a verified M3.1 API price sheet. [S7][S8][S21][S23]

M3.1 Flash Preview appears to be a real preview deployment, but there is not enough verified evidence for a clean quality ranking yet. The strongest evidence covers the model identifier, context/output fixtures and reasoning controls in MiniMax’s own code. Early performance reports are anecdotal. Space Bunny Alpha is an intriguing candidate signal, but its scores must not be relabeled as confirmed M3.1 benchmarks. [S7][S10][S24][S26]

What is confirmed about MiniMax M3.1?

MiniMax founder Yan Junjie was reported on August 26 as saying that M3.1, M3 Pro and H3.1 were close to completion. The same report characterized M3.1 as an effort to improve stability, output quality, inference efficiency and agent generalization. A follow-up report described it as a continuation of the M3 base with more post-training and a focus on coding, tool use and agent workloads. These are reports from the earnings-call context, not an M3.1 technical model card. [S15][S16]

The more concrete evidence is now in MiniMax’s own code. An official MiniMax Code test fixture names MiniMax-M3.1 and includes a 512,000-token catalog context, a 1,000,000-token selectable context option and a 128,000-token output cap. Other fixtures persist M3.1 selections with 1M context and reasoning settings. This is strong evidence of product integration, but a test fixture is not the same thing as a public API guarantee. [S7][S9][S10]

What does “Flash Preview” tell us?

Same-day reports on September 27 show the label MiniMax-M3.1-Flash-Preview in MiniMax Code. A TRAE community thread records the name while also noting that the standard MiniMax website did not yet provide useful details. A same-day Linux DO report describes the preview in active use. That is useful field evidence, not a controlled benchmark. MiniMax’s own code artifacts separately show multi-level reasoning configuration for M3.1. [S7][S21][S22]

For now, “Flash” should be treated as a preview/product label, not as proof of a smaller parameter count, a new architecture or a particular price tier.

Confirmed, observed and unknown

Item	Status on Sep. 27, 2026	Evidence
MiniMax-M3.1 model identifier	Confirmed	official MiniMax Code artifacts [S7][S8]
“M3.1 Flash Preview” label	Observed, not yet documented in a public model card	same-day field reports [S21][S23]
Context	512K/1M in official code tests	[S7][S10]
Max output	128K in official code tests	[S7]
Reasoning effort	multi-level evidence in official code artifacts	[S7][S9]
Image/video input	confirmed for M3; not yet publicly specified for M3.1 Preview	M3 card [S2]
Parameter count	Unknown	no public M3.1 card found
Architecture	Unknown	no public M3.1 card found
API pricing	Unknown	no verified M3.1 price sheet found
Open weights	Not confirmed	no M3.1 weights found
Official M3.1 benchmark table	Not found	research through Sep. 27

Do not automatically copy M3’s 428B/23B specification to M3.1

The official M3 card describes roughly 428B total parameters and ~23B activated parameters, one-million-token context and native text/image/video input. NVIDIA independently lists 428B total and roughly 22B active for M3. Until MiniMax publishes M3.1 specifications, those numbers remain M3 specifications, not M3.1 facts. [S2][S34]

Are there real M3.1 benchmarks yet?

Not benchmarks that can be cleanly labeled as verified M3.1 results.

MiniMax has not published an M3.1 benchmark table at the time of review. Artificial Analysis currently tracks M3 rather than a verified M3.1 entry. Its current M3 page reports an Intelligence Index score of 29 in the current index version, around 179 output tokens/s, a 1M context window and a listed M3 API price of $0.30/$1.20 per million input/output tokens. These are useful M3 baseline measurements, not M3.1 scores. [S30]

Benchmark versioning matters. Artificial Analysis scored M3 at 55 in its June 8 launch-era index. That does not mean the model suddenly lost half its capability; the index, benchmark composition and comparison set changed. Any M3.1 claim should therefore include benchmark version, date and methodology. [S31]

Is Space Bunny Alpha actually M3.1?

This is the most interesting unresolved lead.

OpenRouter has listed Space Bunny Alpha since September 23 as an anonymous stealth model with 1M context, text/image/video input, adjustable reasoning and a free preview. OpenRouter explicitly says the provider is anonymous and that OpenRouter is not the model’s developer or owner. [S24]

Independent tokenizer probes point strongly toward the MiniMax model family. YFarmX reports an exact MiniMax-family token-count match across a broader probe set. Other independent identity reviews reach the same limitation: the tokenizer evidence supports MiniMax-family lineage, but does not reliably distinguish older and newer M generations. It therefore cannot prove “M3.1.” [S26][S27][S28]

The appearance of an actual M3.1 Flash Preview in MiniMax Code only days later makes the hypothesis more plausible. It still does not make it proven. Until MiniMax or the stealth provider confirms the identity, Space Bunny results should be labeled candidate data. [S21][S24][S26][S27][S28]

Space Bunny candidate data — not confirmed M3.1 results

An independent Space Bunny benchmark page reports:

Evaluation	Result	Caveat
AI BENCHY, high	7.0/10	12/22 tasks fully passed; custom suite
GPQA Diamond	82.0%	60-question subset
MMLU-Pro	75%	independent run, not MiniMax official
Humanity’s Last Exam	46.1%	300-question subset; not directly comparable with full-set scores

These numbers describe Space Bunny Alpha. They become M3.1 evidence only if the identity is independently established. [S25]

The M3 baseline is still useful

MiniMax’s M3 launch report listed 59.0% on SWE-Bench Pro, 66.0% on Terminal-Bench 2.1, 34.8% on SWE-fficiency, 28.8% on KernelBench Hard and 74.2% on MCP Atlas. These are vendor-reported M3 results under MiniMax’s documented evaluation setups. They are useful as a baseline for any future M3.1 delta, but should not be presented as M3.1 performance. [S1][S36]

M3 also introduced MiniMax Sparse Attention. The MSA paper documents block-sparse attention and large long-context compute/runtime improvements in its experimental setup, and M3 is the publicly released production model built around that attention line. [S5]

Early hands-on reports are encouraging, but weak evidence

A Linux DO report on September 27 describes ongoing hands-on use of the preview. Same-day community observations are useful signals, but they lack standardized prompts, controlled routing, repeated trials and blind scoring. They should be separated from reproducible benchmarks. [S22]

How to evaluate M3.1 Flash Preview now

For agentic coding, a small reproducible harness is more valuable than a leaderboard guess:

1. 10 previously solved real bugs, each pinned to the same repository commit.
2. Tool-use tasks covering files, shell, search and at least one deliberately failing tool call.
3. Long-context checks at 128K, 512K and 1M, where the preview actually permits them.
4. Reasoning-effort A/B runs at low, high and max, recording success rate, output tokens and wall time.
5. Cost per successful task once M3.1 pricing is published, rather than price per million tokens alone.

That dataset would create a stronger reason to revisit an article than simply repeating vendor benchmark tables.

Bottom line: M3.1 Flash Preview is real, but undocumented

MiniMax M3.1 Flash Preview is real enough to investigate, but not documented enough to rank responsibly yet. The strongest public technical evidence is MiniMax’s own repository, which already contains MiniMax-M3.1, 512K/1M context options, a 128K output fixture and reasoning configuration. Early community reports indicate the preview is usable, while Space Bunny Alpha remains a plausible candidate for the same model family rather than a confirmed identity. [S7][S10][S22][S26]

The next meaningful update should happen when MiniMax publishes an official M3.1 model card, price sheet, benchmark table or public API specification.

Methodology and source note

Research carried out on September 27, 2026. The model identifier, the context and output caps and the reasoning configuration were checked against MiniMax’s official code repository. The early preview observations come from community sources and are explicitly labeled as field observations. Space Bunny Alpha candidate values are not presented as M3.1 benchmarks. Vendor-reported M3 numbers are labeled as such and used only as a baseline. The full research log with every opened source ships with the source package.