archdb

LLM architectures and pretraining recipes, with sources.

Mistral-Small-4-119B-2603

Mistral AI · reasoning checkpoint

No base checkpoint is public; facts describe the released post-trained checkpoint.

Open in the comparison table Hugging Face ↗ Paper ↗

KV calculations use one sequence at 131,072 tokens and 16-bit cache elements. They include bounded sliding-window caches. This is retained cache payload, not peak prefill memory. The comparison table also offers sourced mixed-precision layouts, including quantization scales.

Release

Released

2026-03-16

Source: blog · Introducing Mistral Small 4; header
Introducing Mistral Small 4 March 16, 2026

Same post: "Mistral Small 4 is released under the Apache 2.0 license".

Date the weights (or, if earlier, the technical report) were first made public, YYYY-MM-DD, as dated by the publisher. A Hugging Face repository creation date is used only when no dated publisher page exists, with a note.

License

apache-2.0

Source: model-card · README.md; YAML front matter
license: apache-2.0

License of the released weights as declared by the publisher (model card metadata or license file), e.g. apache-2.0, mit, or the name of a custom license.

Input modalities

text + image

Source: model-card · README.md; Key Features
Multimodal input: Accepts both text and image input, with text output.

Input modalities of the released checkpoint as the publisher states them, from: text, image, video, audio, joined with ' + ' in that order ("text", "text + image + video").

Parameters

Total params

119B parameters

Source: model-card · README.md; Key Features
119B parameters, with 6.5B activated per token.

Total parameter count as reported by the publisher. See params.note for whether embeddings, MTP heads or vision towers are included.

Active params

6.5B parameters

Source: model-card · README.md; Key Features
119B parameters, with 6.5B activated per token.

The blog says 6B active (8B including embedding and output layers); the card title says A6B.

Parameters used per token in the forward pass, as reported by the publisher.

Active non-embedding (stated)

6B parameters

Source: blog · Key architectural details
119B total parameters, with 6B active parameters per token (8B including embedding and output layers).

Active parameters excluding the input embedding and the output head (unembedding). Stated by the publisher, or computed from params.active by subtracting vocab × d_model for each of the embedding and output head that params.active is stated to include (basis inferred, note with the arithmetic). Not disclosed when the scope of params.active is not stated.

Counted total params

119B parameters

Calculated: embedding + output head + all experts + other weights, mistralai/Mistral-Small-4-119B-2603@a11f36b safetensors headers; reproduces stated total (backbone) and active (with embedding and output head)

Parameters of the text backbone counted from the released checkpoint's safetensors headers (embedding, output head, all experts and other weights; excluding MTP modules, vision/audio towers and n-gram lookup tables). Shown only when the counts reproduce the publisher's stated total and active parameters within 5% under some scope.

Counted embedding + head

1.074B parameters

Calculated: input embedding + output head, mistralai/Mistral-Small-4-119B-2603@a11f36b safetensors headers

Input embedding plus output head (once if tied), counted from the checkpoint.

Non-emb. params (counted)

117.9B parameters

Calculated: dense + routed backbone weights; excludes input embedding, output head, lookup tables, MTP and other modalities, mistralai/Mistral-Small-4-119B-2603@a11f36b safetensors headers; reproduces stated total (backbone) and active (with embedding and output head)

Language backbone weights excluding input embeddings, output head, lookup/Engram tables, MTP modules and vision/audio towers. Equals params.counted_total minus params.counted_embedding. Same validation as params.counted_total.

Largest layer (counted)

3.275B parameters

Calculated: max(sum of dense and routed weights sharing a full layers.<index> tensor path), all experts included, mistralai/Mistral-Small-4-119B-2603@a11f36b safetensors headers

Largest group of language-backbone weights sharing a full layers.<index> tensor path, including every routed expert. Excludes lookup/Engram tables, embeddings, output head, MTP and other modalities. Hybrid checkpoints may store mixers and FFNs as separate layers. All-gather volume also depends on wrapping, sharding and dtype.

Active non-emb. (counted)

5.559B parameters

Calculated: non-expert weights + routed experts × 4/128, excluding embedding and output head, mistralai/Mistral-Small-4-119B-2603@a11f36b safetensors headers; reproduces stated total (backbone) and active (with embedding and output head)

Active parameters per token excluding the input embedding and output head, counted from the checkpoint as all non-expert weights plus routed-expert weights × top_k / experts. Same validation as params.counted_total.

Counting scope

Card's 6.5B active has no stated scope; the blog gives 6B without and 8B with embedding and output layers.

Source: blog · Key architectural details
119B total parameters, with 6B active parameters per token (8B including embedding and output layers).

What the publisher's counts include or exclude (MTP modules, embeddings, vision encoder, n-gram tables).

Shape

Layers

36

Source: config · /text_config/num_hidden_layers

Number of transformer blocks in the main backbone (attention or token mixer plus FFN), excluding MTP modules.

d_model

4,096

Source: config · /text_config/hidden_size

Residual stream width.

Vocab

131,072

Source: config · /text_config/vocab_size

Embedding table rows (vocab_size in config, may include padding).

Tied embeddings

No

Source: config · /text_config/tie_word_embeddings

Input embedding and output head share weights.

d_model / layers

113.778

Calculated: d_model / layers

Width-to-depth ratio, d_model divided by the number of blocks.

Attention

Token mixers

MLA

Source: code · modeling_mistral4.py; Mistral4Attention docstring
Multi-headed Latent Attention (MLA) from Deepseek V2, with support for rope interleave.

Token-mixing layer types in the backbone, e.g. GQA, MLA, SWA, Gated DeltaNet, Mamba-2, DSA (DeepSeek sparse attention).

Global-attention layers

36

Source: config · /text_config/num_hidden_layers

Every block uses Mistral4Attention (MLA); /text_config/sliding_window is null.

Layers whose KV cache grows with full context (dense or sparse global attention, MLA). Excludes sliding-window and linear/recurrent layers.

Query heads

32

Source: config · /text_config/num_attention_heads

Query heads in the global-attention layers.

Heads × head dim

4,096

Calculated: heads × head_dim

attn.heads × attn.head_dim, the query projection width of global layers.

QK head dim

128

Source: config · /text_config/qk_nope_head_dim + /text_config/qk_rope_head_dim

configuration_mistral4.py recomputes head_dim and qk_head_dim (both 128 in config) as this sum.

Query/key dimension per head in global-attention layers (for MLA, nope + rope dims).

V head dim

128

Source: config · /text_config/v_head_dim

Value dimension per head in global layers (MLA v_head_dim; stated for MLA even when equal to the QK head dim).

MLA KV latent

256

Source: config · /text_config/kv_lora_rank

Width of the compressed KV latent that MLA caches per token per layer.

MLA Q latent

1,024

Source: config · /text_config/q_lora_rank

Width of the low-rank query projection in MLA; 0 when queries use a full-rank projection.

Decoupled RoPE dim

64

Source: config · /text_config/qk_rope_head_dim

Width of the shared positional key that MLA caches next to the latent.

Positional encoding

partial RoPE (MLA decoupled, interleaved, 64 of 128 QK dims)

Source: code · modeling_mistral4.py; Mistral4Attention.forward
q_rot, k_rot = apply_rotary_pos_emb_interleave(q_rot, k_rot, cos, sin)

Config /text_config/rope_interleave is true.

Positional scheme in global layers: RoPE, partial RoPE, NoPE, or mixed per layer type.

RoPE base

10,000

Source: config · /text_config/rope_parameters/rope_theta

RoPE base frequency of the global layers at release.

QK norm

No

Source: code · modeling_mistral4.py; Mistral4Attention.forward
q_states = self.q_b_proj(self.q_a_layernorm(self.q_a_proj(hidden_states)))

RMSNorm is applied only to the Q and KV latents; per-head Q/K are not normalized.

Queries and keys are normalized per head before the dot product.

Attention scaling

queries × (1 + 0.1·ln(1 + ⌊pos/8192⌋)) (Llama-4 style)

Source: code · modeling_mistral4.py; get_llama_4_attn_scale
scaling = 1 + beta * torch.log(1 + torch.floor(positions_ids / max_position_embeddings))

beta = /text_config/rope_parameters/llama_4_scaling_beta (0.1), length = original_max_position_embeddings (8192).

Query-key scaling when it is not 1/sqrt(head_dim), e.g. query_pre_attn_scalar, length-dependent (SSMax-style) scaling, or value scaling.

QKV bias

No

Source: config · /text_config/attention_bias

Query/key/value projections have bias terms.

Feed-forward

Activation

SwiGLU

Source: code · modeling_mistral4.py; Mistral4Experts.forward
current_hidden_states = self.act_fn(gate) * up

Config /text_config/hidden_act is silu.

FFN activation (SwiGLU, GeGLU, ...).

FFN bias

No

Source: code · modeling_mistral4.py; Mistral4MLP.__init__
self.gate_proj = nn.Linear(self.hidden_size, self.intermediate_size, bias=False)

FFN projections have bias terms.

Mixture of experts

Routed experts

128

Source: config · /text_config/n_routed_experts

Routed experts per MoE layer.

Experts per token

4

Source: config · /text_config/num_experts_per_tok

Routed experts selected per token.

Shared experts

1

Source: config · /text_config/n_shared_experts

Always-on experts per MoE layer.

Expert dim

2,048

Source: config · /text_config/moe_intermediate_size

Intermediate width of one routed expert.

Shared expert dim

2,048

Inferred from the source; see the explanation below.

Source: code · modeling_mistral4.py; Mistral4MoE.__init__
config=config, intermediate_size=config.moe_intermediate_size * config.n_shared_experts

moe_intermediate_size 2048 × n_shared_experts 1.

Total intermediate width of the shared expert(s).

Leading dense layers

0

Source: config · /text_config/first_k_dense_replace

All 36 blocks are MoE; /text_config/intermediate_size (12288) is unused.

Number of initial blocks that use a dense FFN instead of MoE.

Router score

softmax

Source: code · modeling_mistral4.py; Mistral4TopkRouter.forward
scores = router_logits.softmax(-1)

Gating function over expert logits (softmax, sigmoid).

Load balancing

Not disclosed

Load-balancing method, with coefficients where disclosed.

Routed scaling factor

1

Source: config · /text_config/routed_scaling_factor

Multiplier applied to the combined routed-expert output (routed_scaling_factor).

Renormalize top-k

Yes

Source: config · /text_config/norm_topk_prob

Selected expert weights are renormalized to sum to 1.

Expert dim / d_model

0.5

Calculated: moe.expert_dim / d_model

moe.expert_dim divided by shape.d_model.

Sparsity (experts / top-k)

32

Calculated: experts / top_k

Routed experts divided by experts selected per token.

Active / total

0.0546218

Calculated: params.active / params.total

params.active divided by params.total.

Multi-token prediction

MTP depth

Not disclosed

Additional future tokens predicted during pretraining (0 when the model was trained without MTP).

Normalization and stability

Norm

RMSNorm

Source: code · modeling_mistral4.py; Mistral4DecoderLayer.__init__
self.input_layernorm = Mistral4RMSNorm(config.hidden_size, eps=config.rms_norm_eps)

Normalization layer type in the blocks.

Norm placement

pre

Source: code · modeling_mistral4.py; Mistral4DecoderLayer.forward
hidden_states = self.input_layernorm(hidden_states)

Pre-norm, post-norm, or sandwich (pre and post).

Norm epsilon

1e-06

Source: config · /text_config/rms_norm_eps

Epsilon of the block normalization layers.

Context length

Pretraining context

Not disclosed

Sequence length of the main pretraining stage.

Trained context

Not disclosed

Longest sequence length trained on after context extension.

Advertised context

262.1K tokens

Source: model-card · README.md; Key Features
256k context length

Config /text_config/max_position_embeddings is 1,048,576.

Longest context the publisher says the model supports, possibly beyond trained length via RoPE scaling.

Extension method

YaRN factor 128 over original 8,192 (release config)

Source: config · config.json; text_config.rope_parameters
"factor": 128.0, "llama_4_scaling_beta": 0.1, "mscale": 1.0, "mscale_all_dim": 1.0, "original_max_position_embeddings": 8192,

Training-time context stages are not disclosed. Same dict: rope_type/type yarn, beta_fast 32, beta_slow 1.

How context was extended (stages, RoPE base change, YaRN factor).

Pretraining recipe

Pretraining tokens

Not disclosed

Tokens seen in pretraining including annealing and context extension, as reported.

Optimizer

Not disclosed

Optimizer used for the bulk of parameters.

Peak LR

Not disclosed

Peak learning rate of the main pretraining stage.

Final LR

Not disclosed

Learning rate at the end of the decay.

LR schedule

Not disclosed

Learning-rate schedule shape with phase boundaries.

Warmup

Not disclosed

Warmup length in steps or tokens.

Batch size

Not disclosed

Global batch size, including any batch-size ramp: sequences × sequence length (token total), or the token total alone when only that is stated.

Weight decay

Not disclosed

Decoupled weight decay coefficient.

Adam betas

Not disclosed

(beta1, beta2) of the Adam-family optimizer or its AdamW fallback.

Grad clip

Not disclosed

Global gradient-norm clipping threshold.

Training precision

Not disclosed

Matmul precision of pretraining (BF16, FP8 recipe, NVFP4 recipe) with the scaling granularity where disclosed. Never inferred from the released checkpoint dtype.

Data mix

multilingual text and images: Common Crawl and other public datasets, licensed and third-party datasets, synthetic data, user interaction data (subject to opt-out)

Source: paper · §2.1 Publicly available datasets
The datasets used to train the model include Common Crawl.

§1.3 ticks "More than 10 trillions tokens" for the text training data.

Pretraining data composition as disclosed (domain shares, synthetic fraction, repetition).

Data cutoff

July 2025

Source: paper · §1.3 Latest date of data acquisition/collection
The latest date of data collection was July 2025.

Pretraining data cutoff date.

KV cache

KV bytes / token

23,040 bytes

Calculated: kv.bytes_at_context / 131072 tokens; uniform BF16, payload only; quantization overhead excluded. Global KV: 36 × (320 × 16/8) B/entry

Retained KV cache divided by context length, including bounded SWA caches and indexer keys. Exports use uniform BF16 at 131,072 tokens. The website can select uniform payload precision (no quantization overhead) or sourced component formats (including scales and documented padding). This is cache payload, not peak prefill memory or persistent prefix storage.

Global KV bytes / token

23,040 bytes

Calculated: 23040 B / 1 tokens (Global KV); uniform BF16, payload only; quantization overhead excluded. Global KV: 36 × (320 × 16/8) B/entry

Long-context global KV bytes per token, including indexer keys; excludes bounded SWA caches. Compression rates and cross-layer cache reuse are included. Exports use uniform BF16; the website's storage selector also applies here. This is the field to compare with global-KV figures in reports, using the matching storage recipe.

KV bytes / token / B active

3,545 bytes

Calculated: kv.bytes_per_token (131072 tokens) / (params.active / 1e9); uniform BF16, payload only; quantization overhead excluded. Global KV: 36 × (320 × 16/8) B/entry

kv.bytes_per_token divided by active parameters in billions (131,072 tokens in exports).

KV at context / B active

464,599,828 bytes

Calculated: kv.bytes_at_context (131072 tokens) / (params.active / 1e9); uniform BF16, payload only; quantization overhead excluded. Global KV: 36 × (320 × 16/8) B/entry

kv.bytes_at_context divided by active parameters in billions (131,072 tokens in exports).

KV at context

3,019,898,880 bytes

Calculated: 23040 B × 131072 (Global KV); uniform BF16, payload only; quantization overhead excluded. Global KV: 36 × (320 × 16/8) B/entry

Retained KV cache for one sequence at the selected context, including SWA windows and indexer keys. Exports use uniform BF16 at 131,072 tokens. Excludes recurrent state, compressor tail state, draft/MTP caches, temporary prefill tensors, allocator metadata and persistent prefix snapshots. Does not estimate peak prefill or total serving memory.

Evaluations

AA Intelligence Index

11

Source: leaderboard · Artificial Analysis model page /models/mistral-small-4, Wayback snapshot 2026-10-19
Mistral Small 4 (Reasoning) scores 11 on the Artificial Analysis Intelligence Index

Variant: Mistral Small 4 (Reasoning). Index v4.3.2.

Artificial Analysis Intelligence Index v4.3.2 of the post-trained model, from a dated Wayback snapshot of its Artificial Analysis page. The note names the variant (reasoning setting).

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