---
license: cc-by-4.0
pretty_name: Bonsai 2 drafter evaluation corpora
language:
  - en
task_categories:
  - text-generation
tags:
  - speculative-decoding
  - drafter
  - bonsai
  - dflash2
  - evaluation
size_categories:
  - n<1K
configs:
  - config_name: general
    default: true
    data_files:
      - split: eval
        path: general.jsonl
  - config_name: code
    data_files:
      - split: train_and_eval
        path: code.jsonl
---

# Bonsai 2 drafter evaluation corpora

Prompts and greedy responses from PrismML's
[Ternary-Bonsai-2-27B](https://huggingface.co/prism-ml/Ternary-Bonsai-2-27B-mlx-2bit), recorded
as token ids together with the per-round accepted lengths of the speculative decoding loop that
produced them. The data exists to evaluate and train DFlash 2 drafters against this one target.

| | |
| --- | --- |
| **Target** | `prism-ml/Ternary-Bonsai-2-27B-mlx-2bit` (MLX pack), greedy, temperature 0 |
| **Loop** | mlx-dspark 0.18.0 DFlash 2 loop, stock drafter `z-lab/Qwen3.8-27B-DFlash2`, draft cap 7, 8-bit KV cache |
| **`general`** | 40 locally written prompts, all `eval`: eight categories of five, 20 with thinking on and 20 off |
| **`code`** | 300 CodeAlpaca-20k prompts: 260 `train`, 40 `eval`; thinking on for 200 of 300 |
| **Tokenizer** | the Bonsai 2 pack's, which is Qwen3.8-27B's (248,077 tokens) |
| **Licence** | CC BY 4.0; see [Licence and attribution](#licence-and-attribution) |

## What it is for

- **Evaluating drafters.** The `eval` rows of both files are the frozen inputs of the published
  benchmark protocol, `BENCHMARK.md` in
  [github.com/alexschiltmans/bonsai2-drafter](https://github.com/alexschiltmans/bonsai2-drafter).
  `general` is the deciding suite there. `code` is reported alongside it but never decides,
  for the reason given under [Limits](#limits).
- **Reproducing the published acceptance numbers.** That repository's served-acceptance runner
  (`bench/drafter/served_accept.py`) feeds each `eval` row's `prompt_ids` to the served loop
  and writes a per-prompt report. The stdlib-only analyser
  (`bench/analysis/analyse_served_accept.py`) then computes paired acceptance from two such
  reports under the contract `budgeted-prefix-identity/v2`. It needs no model or GPU. Check the
  files against the sha256 values below before a run; the protocol identifies its inputs by them.
- **Training drafters.** `code.jsonl`'s `train` rows are the exact training corpus of
  [`Schiltmans/Ternary-Bonsai-2-27B-DFlash2-ft5`](https://huggingface.co/Schiltmans/Ternary-Bonsai-2-27B-DFlash2-ft5).
  Because decoding was greedy, every response is the target's own argmax path. `round_lengths`
  records where the served loop placed its anchors, which is what served-geometry training
  and served-anchored proxies need.

## Files

| File | Rows | sha256 |
| --- | --- | --- |
| `general.jsonl` | 40 | `3dcc1327c0d254e2191322503f6cc4fe0cc464389ef0799093778ca55996c50b` |
| `code.jsonl` | 300 | `4252b5bc10babf0605a8afb454bc1296befceb87e1e8042d6a65e0478841654d` |
| `general_chat.json` | 40 | `86ffdea752b2e24c51ba07a75bcd83afae9f53541e2a86c785cf8a104752e4c2` |

`general_chat.json` is a JSON array of the 40 prompts behind `general.jsonl`, in the same order.
Each entry has `instruction`, `category` and `thinking`. It is not one of the viewer's configs.

The JSONL files are byte-identical to the protocol's inputs. Nothing has been reformatted,
re-sorted or cleaned since.

## Loading

The Hub cannot split one file into several splits by a column, so the `code` config exposes all
300 rows as a single split named `train_and_eval`. Filter on the `split` field yourself:

```python
from datasets import load_dataset

general = load_dataset("Schiltmans/bonsai2-drafter-eval", "general", split="eval")
code = load_dataset("Schiltmans/bonsai2-drafter-eval", "code", split="train_and_eval")
code_train = code.filter(lambda r: r["split"] == "train")  # 260 rows
code_eval = code.filter(lambda r: r["split"] == "eval")    # 40 rows
```

Decoding the token ids:

```python
import json
from transformers import AutoTokenizer

tok = AutoTokenizer.from_pretrained("prism-ml/Ternary-Bonsai-2-27B-mlx-2bit")

with open("general.jsonl") as f:
    row = json.loads(next(f))

print(tok.decode(row["prompt_ids"]))    # the chat-templated prompt the target saw
print(tok.decode(row["response_ids"]))  # the target's response; ends in <|im_end|> when finish == "stop"
```

Notes on the tokenizer:

- A Qwen3.8-27B tokenizer decodes every row identically. This was checked on all 340 rows.
- Use the recorded `prompt_ids` as they are. Re-applying the pack's chat template with its
  tokenizer, as in the snippet, reproduces all 340 of them. With thinking on, the template also
  inserts its default system message about reasoning effort. With thinking off, it closes an
  empty `<think></think>` block inside the prompt.
- Recent `transformers` releases may warn on load about the tokenizer's regex pattern and
  suggest `fix_mistral_regex=True`. Do not pass that flag here. It changes the tokenization of
  28 of the 340 prompts, so they no longer match `prompt_ids`. Decoding is unaffected either way.

## Fields

| Field | Type | Meaning |
| --- | --- | --- |
| `prompt` | string | the user message, before the chat template |
| `prompt_ids` | list of int | the chat-templated prompt, generation prompt included, as fed to the target |
| `response_ids` | list of int | the target's response tokens (see [The `round_lengths` rule](#the-round_lengths-rule)) |
| `round_lengths` | list of int | tokens committed in each round of the speculative loop, each 1 to 8 |
| `finish` | string | `stop` (end-of-turn token emitted) or `length` (output budget reached) |
| `temperature` | float | always `0.0` |
| `thinking` | bool | whether the chat template was applied with thinking enabled |
| `split` | string | `train` or `eval`; every `general` row is `eval` |
| `category` | string | `general.jsonl` only: `explanation`, `planning`, `writing`, `summarization`, `reasoning`, `advice`, `critical_reading` or `language` |

## How it was generated

Everything was produced by the repository's `bench/drafter/gen_data.py`, in process, with
mlx-dspark's `dflash_generate`:

- **Target**: `prism-ml/Ternary-Bonsai-2-27B-mlx-2bit` at revision `3f926b41`, loaded through
  the repository's patched mlx-dspark 0.18.0 (MLX 0.32.2, mlx-lm 0.31.3) with an 8-bit KV cache.
- **Drafter**: the stock `z-lab/Qwen3.8-27B-DFlash2` (revision `50307d4c`), quantized to 4 bits
  at load, which is mlx-dspark's default. Its block is 8 positions: the anchor plus 7 drafted
  tokens. The draft cap is 7, so every round verifies the full block.
- **Decoding**: greedy (temperature 0). The loop verifies each drafted token against the
  target's argmax and keeps the longest matching prefix plus the target's own next token. The
  tokens are therefore the target's greedy output up to floating-point ties. The drafter
  changes how many rounds a response takes and never which tokens it contains. `top_p`, `top_k`
  and the seed are passed but have no effect at temperature 0.
- **Output budget**: `max_new_tokens` of 1024 with thinking on and 400 with thinking off. The
  loop tests the budget before each round, not during it, so a `length` finish can overshoot by
  up to 7 tokens. Observed maxima are 1031 and 407. One `code` row that ends in `stop` is also
  over budget, because its end-of-turn token arrived in the round that crossed the budget.
- **`code` prompts**: `random.Random(7).sample(rows, 300)` over `code_alpaca_20k.json` from
  [sahil2801/CodeAlpaca-20k](https://huggingface.co/datasets/sahil2801/CodeAlpaca-20k)
  (revision `152bb5e9`). Each prompt is the stripped `instruction`, followed by a blank line and
  the stripped `input` when there is one; an empty input or a `<noinput>` marker adds nothing.
  Rows are in sampled order. Row `i` (0-based) has thinking on unless `i % 3 == 2`, and rows 260
  to 299 are `eval`.
- **`general` prompts**: `general_chat.json` in file order, with each entry's own `thinking`
  and `category`. All 40 are `eval`.
- **Hardware**: one Apple M4 Pro with 48 GB of unified memory.

## The `round_lengths` rule

Anyone using these rows as served-geometry anchors needs this rule. It follows directly from
mlx-dspark 0.18.0's `dflash_generate`.

1. **`response_ids[0]` belongs to no round.** The loop seeds its output with the token the
   target picks from the prefill logits (`out_ids = [pending]`) before the first round runs.
2. **Round `r` is anchored at `response_ids[a_r]`, where `a_r = sum(round_lengths[:r])`.** The
   round feeds the anchor and 7 mask slots to the drafter, verifies the 7 proposals, and commits
   `round_lengths[r]` tokens: the accepted proposals plus the target's own next token. So
   `round_lengths[r]` equals accepted + 1, between 1 and 8. Those tokens are
   `response_ids[a_r + 1 : a_r + 1 + round_lengths[r]]`.
3. **The end-of-turn token is kept.** A `stop` row's last token is `<|im_end|>` (id 248046). The
   loop also stops on `<|endoftext|>` (248044), but no row ends with it. A `length` row contains
   neither.
4. **The final round can be truncated, but its recorded length is not.** When the end-of-turn
   token lands inside a round's committed block, the loop appends tokens up to and including it
   and discards the rest, while `round_lengths` still records the whole block. Only the last
   round can do this, because the loop ends there.

With `k` as the number of committed tokens discarded after the end-of-turn token:

    len(response_ids) == 1 + sum(round_lengths) - k

| Case | `k` | `len(response_ids) - sum(round_lengths)` | `general` | `code` |
| --- | --- | --- | --- | --- |
| `length` | 0: no end-of-turn token | 1 | 19 | 94 |
| `stop`, end-of-turn was the target's own token, last in the block | 0 | 1 | 8 | 52 |
| `stop`, end-of-turn was an accepted draft token | 1: the target's token after it | 0 | 13 | 154 |

In this data `k` is never above 1. In general the final round emitted
`len(response_ids) - 1 - sum(round_lengths[:-1])` tokens, which lies between 1 and
`round_lengths[-1]`. Every earlier round emitted its full recorded length. A round starts only
while fewer tokens than the budget have been emitted, so the round that reaches the budget is
always the last.

For training at the served anchors, take `a_r = sum(round_lengths[:r])` for each round `r`. The
drafter's 7 slots predict `response_ids[a_r + 1 : a_r + 8]`, cut off at the end of the array.
Those are the target's greedy tokens whether or not the stock drafter got them right. In a
truncated final round, the slots past the end-of-turn token have no recorded target token.

The analyser in the GitHub repository applies the same arithmetic to its reports: a report's
`tokens` is `len(response_ids)`, which includes the seed token, and its `rounds` is
`len(round_lengths)`.

## Intended uses

- Measuring a DFlash 2 drafter's acceptance on Ternary-Bonsai-2-27B, greedy, against the
  published protocol and its analyser.
- Training or fine-tuning a drafter for this target on `code.jsonl`'s `train` rows, with
  `round_lengths` locating the anchors the served loop drew.
- Checking that a runtime's greedy speculative loop is lossless. On the same runtime and
  settings, any drafter should reproduce these token paths within the budget.

## Limits

- **One target, one runtime configuration.** The responses belong to this pack of
  Ternary-Bonsai-2-27B at these settings, with an 8-bit KV cache. Another quantization, another
  KV precision or another runtime can take a different greedy path.
- **Greedy only.** There are no sampled responses. Acceptance under sampling, including the
  target's published sampling defaults, has to be measured separately.
- **The `round_lengths` belong to the stock drafter.** A different drafter commits the same
  tokens in different rounds.
- **Truncated responses are prefixes.** `length` rows stop mid-answer. Of the thinking rows that
  hit the budget, 5 of 9 in `general` and 32 of 45 in `code` never close their reasoning block.
  Do not treat them as complete answers.
- **The `code` eval rows are not an untouched test set.** They selected the training iteration
  of the ft5 drafter, so they are a regression screen. They are not an independent test of ft5
  or of anything tuned on them. `general.jsonl` was not used for that selection, which is why the
  protocol decides on it.
- **Small.** 40 `eval` prompts per suite, from one machine. The protocol reports paired
  bootstrap intervals for that reason.
- **Not a quality benchmark.** The responses have not been checked for correctness. They record
  what the target said, not what it should have said.

## Licence and attribution

This dataset is released under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/).

- **Code prompts**: sampled from
  [sahil2801/CodeAlpaca-20k](https://huggingface.co/datasets/sahil2801/CodeAlpaca-20k) by Sahil
  Chaudhary, CC BY 4.0. The prompts are reproduced verbatim apart from joining `instruction`
  and `input`.
- **General prompts**: `general_chat.json` was written for this project.
- **Responses**: generated by
  [Ternary-Bonsai-2-27B](https://huggingface.co/prism-ml/Ternary-Bonsai-2-27B-mlx-2bit)
  (Apache-2.0), Prism ML's ternary model derived from Qwen3.8-27B. Created using Bonsai by
  Prism ML.

This is an independent project and not an official Prism ML, Qwen or z-lab release.

## Links

- Benchmark protocol, generator, runner and analyser:
  [github.com/alexschiltmans/bonsai2-drafter](https://github.com/alexschiltmans/bonsai2-drafter)
- Drafter trained on `code.jsonl`'s `train` rows:
  [Schiltmans/Ternary-Bonsai-2-27B-DFlash2-ft5](https://huggingface.co/Schiltmans/Ternary-Bonsai-2-27B-DFlash2-ft5)
- Stock drafter used for generation:
  [z-lab/Qwen3.8-27B-DFlash2](https://huggingface.co/z-lab/Qwen3.8-27B-DFlash2)
- Target: [prism-ml/Ternary-Bonsai-2-27B-mlx-2bit](https://huggingface.co/prism-ml/Ternary-Bonsai-2-27B-mlx-2bit)

## Citation

If you use the code prompts, please also cite Code Alpaca:

```bibtex
@misc{codealpaca,
  author = {Sahil Chaudhary},
  title = {Code Alpaca: An Instruction-following LLaMA model for code generation},
  year = {2023},
  publisher = {GitHub},
  journal = {GitHub repository},
  howpublished = {\url{https://github.com/sahil280114/codealpaca}}
}
```