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Open-weight model · Image and text to text

Mephisto-1.5-4B

by Model Merge JP ModelMerge-JP/Mephisto-1.5-4B

Mephisto-1.5-4B is an open-weight model for image and text to text from Model Merge JP. It has 4.2B parameters and a 262,144-token context. At 16-bit it needs about 10.1 GB of GPU memory, which fits on 1x MI300X from $1.85 an hour, at the lowest prices in the SAVRN Index.

Mephisto-1.5-4B is a 4B-parameter agentic language model constructed via multi-stage model merging using mergekit.

Parameters4.2B
Context262,144
Weights12.9 GB
License—
AccessOpen weights
Monthly Downloads—

Runs On

What it takes to serve Mephisto-1.5-4B (4.2B parameters): the memory its weights need at each precision, and the cheapest way to rent enough data-center GPUs to hold them.

PrecisionWeightsMemory neededCheapest setupPer hourAlso fits
16-bit 8.4 GB 10.1 GB 1x MI300X (192 GB)
Vultr
$1.85 1x H100 $1.99 · 1x MI325X $2.00
8-bit 4.2 GB 5.1 GB 1x MI300X (192 GB)
Vultr
$1.85 1x H100 $1.99 · 1x MI325X $2.00
4-bit 2.1 GB 2.5 GB 1x MI300X (192 GB)
Vultr
$1.85 1x H100 $1.99 · 1x MI325X $2.00

Memory is the weights at that precision plus 20% for the runtime and a short context; a long context needs more. Prices are the lowest on-demand hourly rates in the SAVRN Index, read Oct 16, 2026.

Mephisto-1.5-4B on every accelerator the SAVRN Index prices, at every precision

Model Card

Mephisto-1.5-4B is a 4B-parameter agentic language model constructed via multi-stage model merging using mergekit. The model integrates reasoning, coding, and agentic capabilities into a single 4B checkpoint based on the Qwen3.5-4B architecture, targeting performance exceeding Mephisto-4B-v2 on Japanese and agentic benchmarks while maintaining deployment feasibility on consumer hardware (RTX 3060 12GB). The model is constructed through a three-stage merging pipeline: Normalized spherical linear interpolation (NuSLERP) on task vectors derived from a common base model (Qwen3.5-4B). This stage fuses a reasoning-distilled model (Opus-reasoning distillation) with a code-specialized model.…

Excerpt from the card by Model Merge JP.

Configuration

Architecture
Qwen3_5ForConditionalGeneration
Context length (tokens)
262,144
Layers
32
Hidden size
2,560
Feed-forward size
9,216
Attention heads
16
Key/value heads
4
Head dimension
256
Vocabulary size
248,320
Model type
qwen3_5

Identity and Version

Repository
ModelMerge-JP/Mephisto-1.5-4B
Publisher
Model Merge JP
Task
Image and text to text
Modality
Image and text
Library
transformers
Parameters
4.2B parameters
Languages
Not stated by the source
Revision
fbeb48045c842cda2e7f806a8e14373f466e4b8d
First published
2026-10-10
Last updated
2026-10-10

Files and Weights

20 files, 12.9 GB in total. The weights are 10 files totalling 12.9 GB in gguf, safetensors.

Weights10 files · 12.9 GB
Configuration4 files · 45.9 KB
Tokenizer3 files · 16.2 MB
Documentation1 file · 6.4 KB
Other1 file · 7.8 KB
Repository1 file · 1.6 KB
Every file
FileTypeSizeSHA-256
GGUF/Mephisto-4B-v2.1_q8_0.ggufWeights4.5 GB 068b95b471ce
model-00001-of-00009.safetensorsWeights1.3 GB 6fa689629df8
model-00002-of-00009.safetensorsWeights976.8 MB 41217ca94655
model-00003-of-00009.safetensorsWeights986.9 MB e4ca03dfcb43
model-00004-of-00009.safetensorsWeights982.1 MB f6dade3236a5
model-00005-of-00009.safetensorsWeights981.6 MB 41fdf380e044
model-00006-of-00009.safetensorsWeights987.3 MB 2d5a15696d76
model-00007-of-00009.safetensorsWeights965.5 MB 79edf1798547
model-00008-of-00009.safetensorsWeights986.9 MB be7981524759
model-00009-of-00009.safetensorsWeights299.3 MB 4fc89658bee3
config.jsonConfiguration2.8 KB —
mergekit_config.ymlConfiguration438 B —
model.safetensors.index.jsonConfiguration42.3 KB —
video_preprocessor_config.jsonConfiguration385 B —
README.mdDocumentation6.4 KB —
chat_template.jinjaOther7.8 KB —
.gitattributesRepository1.6 KB —
merges.txtTokenizer3.4 MB —
tokenizer.jsonTokenizer12.8 MB 5f9e4d4901a9
tokenizer_config.jsonTokenizer16.7 KB —

License and Download

License
Not stated by the source
Access
Open weights, no gate
Download size
12.9 GB
Download from Model Merge JP

Released by Model Merge JP through its official repository on Hugging Face.

Built From

  • Derived from BAAI/AREX-Turbo
  • Derived from InternScience/Agents-A1-4B
  • Derived from Jackrong/Qwen3.5-4B-Claude-4.6-Opus-Reasoning-Distilled-v2
  • Derived from Jackrong/Qwopus3.5-4B-Coder
  • Derived from Jackrong/Qwopus3.5-4B-v3
  • Merged from BAAI/AREX-Turbo
  • Merged from InternScience/Agents-A1-4B
  • Merged from Jackrong/Qwen3.5-4B-Claude-4.6-Opus-Reasoning-Distilled-v2
  • Merged from Jackrong/Qwopus3.5-4B-Coder
  • Merged from Jackrong/Qwopus3.5-4B-v3

Memory Requirements

PrecisionWeights in memory
As published12.9 GB
16-bit8.4 GB
8-bit4.2 GB
4-bit2.1 GB

Weights only, from the published parameter count; the key-value cache and runtime add to this.

Questions About Mephisto-1.5-4B

How much GPU memory does Mephisto-1.5-4B need?

About 10.1 GB at 16-bit and 2.5 GB at 4-bit: the weights (4.2B parameters) plus a working margin. A long context needs more.

What is the cheapest GPU to run Mephisto-1.5-4B on?

At 16-bit, 1x MI300X from $1.85 an hour; at 4-bit, 1x MI300X from $1.85 an hour, at the lowest on-demand prices the SAVRN Index lists.

What is Mephisto-1.5-4B's context length?

262,144 tokens, from the maximum position embeddings in its published configuration.

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