---
license: apache-2.0
language:
- en
tags:
- time-series
- multimodal
- forecasting
- foundation-model
- chronicle
library_name: pytorch
pipeline_tag: time-series-forecasting
---

<p align="center">
  <a href="https://www.inertialai.com">
    <img src="https://www.inertialai.com/biglogo-v2.webp" alt="InertialAI" height="56">
  </a>
</p>

# Chronicle

**A multimodal foundation model for joint language and time series understanding.**

Chronicle is a compact **324M-parameter decoder-only transformer trained from scratch on
natural language and time series** within a single unified architecture. Text tokens and
time-series patches share the same transformer blocks, attention mechanism, and residual
stream — cross-modal capability emerges from shared parameters rather than from bolting a
time-series encoder onto a pretrained LLM.

- 📄 **Paper:** [Chronicle: A Multimodal Foundation Model for Joint Language and Time
  Series Understanding](https://arxiv.org/abs/2605.20268) (Quinlan, Levasseur, Li, Zhu)
- 💻 **Code & finetuning examples:** [github.com/InertialAI/Chronicle](https://github.com/InertialAI/Chronicle)
- ☁️ **Hosted API with self-serve finetuning *(coming soon)*:** [inertialai.com](https://www.inertialai.com/platform)

## Checkpoints in this repo

| Path | Stage | Description |
| --- | --- | --- |
| `stage-1/` | **Stage 1** | Unimodal-batch pretraining (~92% text / 8% time series) — cross-modal ability from shared parameters alone. `model.safetensors` + `config.json` |
| `stage-2/` | **Stage 2** | Stage 1 + a short alignment stage that interleaves the two modalities (best multimodal results); context extended to 4096. `model.safetensors` + `config.json` |
| `tokenizer/` | — | 131k-vocabulary BPE tokenizer (trained from scratch) |
| `model.py` · `tokenizer.py` | — | Minimal inference implementation (`Chronicle`, `ChronicleConfig`, `ChronicleTokenizer`) |
| `config.json` | — | Repo-level model metadata (mirrors the stage-2 architecture); the per-stage `config.json` files remain authoritative for loading |

## Architecture

| | |
| --- | --- |
| Parameters | 324M, 16-layer decoder-only transformer |
| Width / heads | d=1024, 8 attention heads (4 KV, GQA) |
| Context | 2048 tokens (stage 1) / 4096 (stage 2) — text tokens + 32-step series patches, one shared stream |
| Series head | 21-quantile next-patch forecasting with instance normalization |
| Objective | causal next-token / next-patch prediction |

## Usage

Weights ship as **safetensors**; `model.py` and `tokenizer.py` are a minimal,
dependency-light inference implementation (`torch`, `tiktoken`). Verified example (text generation,
CPU):

```python
import json
import sys

import torch
from huggingface_hub import snapshot_download
from safetensors.torch import load_file

repo = snapshot_download("InertialAI/Chronicle")
sys.path.insert(0, repo)

from model import Chronicle, ChronicleConfig
from tokenizer import ChronicleTokenizer

config = ChronicleConfig(**json.load(open(f"{repo}/stage-2/config.json")))
model = Chronicle(config)
state = load_file(f"{repo}/stage-2/model.safetensors")
state = {k: v.float() if v.dtype is torch.bfloat16 else v for k, v in state.items()}
model.load_state_dict(state, strict=True)
model = model.float().eval()
model.cos, model.sin = model.cos.float(), model.sin.float()  # fp32 rotary on CPU

tokenizer = ChronicleTokenizer.from_directory(f"{repo}/tokenizer")
ids = [tokenizer.get_bos_token_id()] + tokenizer.encode("Time series forecasting is")
with torch.no_grad():
    for _ in range(16):
        out = model(torch.tensor([ids]))
        logits = out[0] if isinstance(out, tuple) else out
        ids.append(int(logits[0, -1].argmax()))
print(tokenizer.decode(ids[1:]))
# -> "Time series forecasting is a technique used to forecast future values
#     of a time series based on historical data."
```

For the time-series pathway (quantile forecasting via `ts_patches`) and
`forecast()` / `embed()` conveniences, use the **transformers-native port (in
progress)** or the [hosted API](https://docs.inertialai.com) (coming soon), which
will serve these models. The finetuning recipes in the
[GitHub repo](https://github.com/InertialAI/Chronicle) show the downstream-task
protocols used in the paper.

## Results

One backbone, evaluated against dedicated unimodal foundation models in *both*
domains — the core claim is breadth: strong language understanding, state-of-the-art
frozen time-series embeddings, and best-in-class multimodal forecasting, all from the
same weights. Numbers below are from the paper.

**Language understanding** (19-task NLU average) — parity with text-only models of the
same scale, trained on ~40× fewer text tokens:

| | GPT-2 (124M) | Gemma-3 (270M) | **Chronicle-1 (324M)** | **Chronicle-2 (324M)** | LFM-2 (350M) |
| --- | --- | --- | --- | --- | --- |
| NLU avg | 0.324 | 0.406 | **0.411** | **0.406** | 0.449 |

**Time series classification** (24 UCR/UEA datasets, linear probe on frozen
embeddings) — a new bar among TS foundation models:

| Dataset | Chronos-2 | TimesFM | Moirai-2 | **Chronicle-1** |
| --- | --- | --- | --- | --- |
| GunPoint | 0.528 | 0.712 | 0.931 | **0.919** |
| FaceFour | 0.236 | 0.609 | 0.582 | **0.864** |
| Trace | 0.288 | 0.630 | 0.802 | **0.936** |
| ECG200 | 0.672 | 0.840 | 0.820 | **0.846** |

**Multimodal forecasting** (Time-MMD, 9 domains, MAE ↓) — beats every supervised
fusion baseline and every frozen FM-fusion pairing (baseline columns show the best
baseline per metric):

| | Best MM-TSFlib | Best FM Fusion | **Chronicle-2 (LP)** |
| --- | --- | --- | --- |
| Avg NMAE | 0.621 | 0.588 | **0.514** |
| Avg rank | 6.78 | 6.11 | **2.56** |

**Multimodal classification** (TimeCAP: weather, finance, healthcare) — Chronicle-2
LoRA reaches **0.613 F1 / 0.757 AUC**, ahead of every MM-TSFlib and FM-fusion baseline.

See the [paper](https://arxiv.org/abs/2605.20268) for full tables, protocols, and
baselines, and the [GitHub repo](https://github.com/InertialAI/Chronicle) for
reproduction scripts on public data.

## Citation

```bibtex
@article{quinlan2026chronicle,
  title={Chronicle: A Multimodal Foundation Model for Joint Language and Time Series Understanding},
  author={Quinlan, Paul and Levasseur, Jeremy and Li, Qingguo and Zhu, Xiaodan},
  journal={arXiv preprint arXiv:2605.20268},
  year={2026}
}
```

## License

Apache 2.0.