LFM2.5-230M-CPT

LFM2.5-230M-CPT is a Japanese text continuation model obtained by continued pretraining of LiquidAI/LFM2.5-230M-Base on speech transcripts. It models the wording and style of Japanese spoken language. Despite the transcript source, this checkpoint has no audio input or audio encoder and cannot transcribe speech by itself. It is a base model for further adaptation, not an instruction-tuned assistant.

Model Details

Item Value
Architecture Lfm2ForCausalLM, decoder-only LFM2 hybrid
Parameters 229,693,184 serialized parameters (about 230M)
Layers 14: 8 causal-convolution blocks and 6 grouped-query attention blocks
Hidden size 1,024
Feed-forward intermediate size 2,560
Attention heads / key-value heads 16 / 8
Model vocabulary capacity 65,536 token IDs
Tokenizer Original LFM2.5-230M-Base tokenizer, unchanged
Base-model advertised context length 32,768 tokens
Maximum sequence length used in continued pretraining 512 tokens, including the end-of-sequence token
Weight format BF16 Safetensors (model.safetensors, about 459 MB)
Framework Hugging Face Transformers

The configuration retains the base model's positional-embedding setting, but this continued-pretraining run used sequences of at most 512 tokens. Performance on longer contexts has not been evaluated for this checkpoint.

Training Data

The continued-pretraining corpus is the text field of KeisukeMiyamoto/audio-transcript, a Japanese text-only dataset assembled from NHK radio news, NHK Archives, and technology podcasts. The source transcripts include machine-generated text and corrections. No audio, prev_text, token-count columns, or other dataset fields were supplied to the model.

Split Role Transcript rows Dataset text_token total
train Continued pretraining 1,143,151 70,156,912
validation Checkpoint selection 63,260 3,897,592
test Not used in training or checkpoint selection 63,253 3,897,621

The dataset token totals exclude special tokens. Each transcript was tokenized with the base-model tokenizer and followed by one end-of-sequence token for training. Transcripts were packed into training sequences. Dataset splits are separated by row, not by recording, episode, or speaker; related segments may appear in different splits. See the dataset card for construction details and source-rights information.

Training Configuration

Item Value
Method Full-parameter causal language-model continued pretraining
Objective Next-token prediction on transcript text
Epochs completed 3
Optimizer Fused AdamW
Peak learning rate 5 ร— 10โปโต
Learning-rate schedule Cosine decay with 10% warmup
Per-device batch size 72 configured; automatic batch-size adjustment enabled
Gradient accumulation 2 steps
Precision during training BF16 mixed precision
Gradient checkpointing Enabled
Validation frequency Once per epoch
Optimizer steps completed 23,817
Published checkpoint Best validation checkpoint at step 15,878 (end of epoch 2)

The selected checkpoint was saved in BF16 for distribution. The published configuration enables generation caching (use_cache=true). The tokenizer and model architecture remain compatible with standard Transformers from_pretrained() loading.

Evaluation

Validation loss is token-weighted next-token cross-entropy on the validation split. Lower is better.

Epoch Step Validation loss
1 7,939 3.0819
2 15,878 2.9808
3 23,817 2.9848

The epoch-2 checkpoint was selected because it had the lowest validation loss. This is a text language-modeling measurement, not an ASR metric. No audio-to-text evaluation, word error rate, character error rate, or standardized language-model benchmark is reported for this checkpoint.

Usage

Tested with Transformers 5.17.0, PyTorch 2.14.0, and python-dotenv 1.2.3. Set HF_TOKEN in a local .env file. The example performs greedy continuation on a CUDA device:

import torch
from dotenv import dotenv_values
from transformers import AutoModelForCausalLM, AutoTokenizer

model_id = "KeisukeMiyamoto/lfm2.5-230m-cpt"
token = dotenv_values(".env")["HF_TOKEN"]
tokenizer = AutoTokenizer.from_pretrained(model_id, token=token)
model = AutoModelForCausalLM.from_pretrained(model_id, dtype=torch.bfloat16, token=token).to("cuda")
inputs = tokenizer("ไปŠๆ—ฅใฏๅคฉๆฐ—ใŒ่‰ฏใ„ใฎใงใ€", return_tensors="pt").to("cuda")

with torch.inference_mode():
    output = model.generate(**inputs, max_new_tokens=48, do_sample=False)

continuation = tokenizer.decode(
    output[0, inputs["input_ids"].shape[1] :], skip_special_tokens=True
)
print(continuation)

This model repository is private at the time of writing. Authorized users must authenticate with Hugging Face before loading it. The included chat template is inherited from the base model; the continued-pretraining data contained plain transcripts, not chat instruction/response pairs.

Example Outputs

These are illustrative greedy continuations from the published BF16 checkpoint with max_new_tokens=48; they are not benchmark results.

Prompt Generated continuation
ไปŠๆ—ฅใฏๅคฉๆฐ—ใŒ่‰ฏใ„ใฎใงใ€ ใกใ‚‡ใฃใจใŠไผ‘ใฟใ•ใ›ใฆใ„ใŸใ ใใพใ™ใ€‚
ใ“ใฎๅ•้กŒใซใคใ„ใฆใ€็งใฏ ใ“ใฎๅ•้กŒใ‚’่งฃๆฑบใ™ใ‚‹ใซใฏใฉใ†ใ—ใŸใ‚‰ใ„ใ„ใ‹ใจใ„ใ†ใ“ใจใ‚’่€ƒใˆใฆใ€

Limitations

  • No audio support: an audio encoder and paired audio-text training would be required for speech recognition.
  • The dataset concentrates on Japanese broadcast and podcast speech. It is not representative of all Japanese domains or writing styles.
  • Transcripts may contain recognition errors, omissions, unusual punctuation, and content or speaker biases inherited from the sources.
  • Text may end abruptly, repeat phrases, or produce plausible but unsupported continuations. The end-of-sequence token can cause short or empty outputs.
  • The model has not been instruction-tuned or safety-aligned. Do not assume chat behavior from the inherited chat template.
  • Related recordings can span dataset splits, so the reported validation loss should not be interpreted as a source-independent generalization score.

License and Source Rights

The model inherits the base model's LFM 1.0 license. The transcript dataset and its source collections have separate rights and use conditions. Consult their dataset cards and underlying content owners before reusing or redistributing the training text. This model card does not grant rights to the source recordings or transcripts.

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