# v12 Chat SFT Quality Check

Date: 2026-06-29

## Goal

Turn the completed v12 1.05B base checkpoint into a usable chat-alpha model with
SFT, then judge whether it is stable enough to call a high-quality chat model.

Base checkpoint:

```text
/dashscope-tmp/wjh/xtrain_v12/xtrain_v12.ckpt
```

Architecture:

```text
dim=1664 layers=22 heads=52 kv_heads=13 head_dim=32 ffn=6656
total params=1.0506B
```

## Stage A: Synthetic SFT

Data:

```text
/dashscope-tmp/wjh/xtrain_sft_alpha_v2/chat_alpha_v2_sft.tsv
211,257 examples, about 14.96M SFT tokens
```

Run:

```text
/dashscope-tmp/wjh/xtrain_sft_v12_alpha_v2/chat_alpha_v12_v2.ckpt
```

Metrics:

```text
train loss: 3.5730 -> 0.0426
eval: step39 0.1078, step79 0.0582, step119 0.0466, step159 0.0423,
      step199 0.0403, step239 0.0390, step279 0.0389, step319 0.0378
best/final val loss: 0.0378
```

Export:

```text
/opt/wjh/projects/tiny-models/v12-chat-alpha-sft-v2
```

Quality notes:

- Learns the User/Assistant format and usually stops correctly.
- Too narrow and template-heavy.
- Fails basic math and code prompts in fixed greedy evaluation.

## Stage B: Anchor SFT

Data:

```text
/dashscope-tmp/wjh/xtrain_sft_alpha_v2_anchor/chat_alpha_v2_anchor.tsv
32,020 examples, about 1.73M SFT tokens
```

Run:

```text
/dashscope-tmp/wjh/xtrain_sft_v12_anchor/chat_alpha_v12_anchor.ckpt
```

Metrics:

```text
train loss: 1.7777 -> 0.1165
eval: step19 0.3447, step39 0.1449, step59 0.1217, step79 0.1158
best/final val loss: 0.1158
```

Export:

```text
/opt/wjh/projects/tiny-models/v12-chat-alpha-sft-v2-anchor
```

Generation artifacts:

```text
/dashscope-tmp/wjh/xtrain_sft_v12_anchor/generation/anchor_xserv_greedy.txt
/dashscope-tmp/wjh/xtrain_sft_v12_anchor/generation/anchor_diagnostic_greedy.txt
```

Quality notes:

- Better project-context answers and summaries than synthetic-only.
- Still unreliable on basic multiplication, yes/no facts, translation, and code.
- Overuses "cannot verify" style answers outside appropriate uncertainty cases.

## Stage C: Real-Mix Repair

Data:

```text
/dashscope-tmp/wjh/xtrain_sft_real_mix_v1/smol_smoltalk_real_mix.tsv
96,287 examples, about 25.3M SFT tokens
```

Run:

```text
/dashscope-tmp/wjh/xtrain_sft_v12_real_mix_repair/chat_alpha_v12_real_mix_repair.ckpt
```

Training setup:

```text
init=/dashscope-tmp/wjh/xtrain_sft_v12_anchor/chat_alpha_v12_anchor.ckpt
steps=200
seq=512
batch=32
accum=8
effective batch=256
lr=1e-6 -> 2e-7
```

Metrics:

```text
train loss: 2.7391 -> 2.0384
eval: step49 2.1964, step99 2.0383, step149 1.9801, step199 1.9570
best/final val loss: 1.9570
```

Export:

```text
/opt/wjh/projects/tiny-models/v12-chat-alpha-real-mix-repair
```

Generation artifacts:

```text
/dashscope-tmp/wjh/xtrain_sft_v12_real_mix_repair/generation/real_mix_repair_xserv_greedy.txt
/dashscope-tmp/wjh/xtrain_sft_v12_real_mix_repair/generation/real_mix_repair_diagnostic_greedy.txt
/dashscope-tmp/wjh/xtrain_sft_v12_real_mix_repair/generation/real_mix_repair_diagnostic_greedy_reppenalty1.txt
```

Quality notes:

- Loss improved cleanly and the model kept chat formatting.
- Fixed prompt math `17% of 240` improved in the standard suite.
- General diagnostic math still fails, e.g. `12 * 13`.
- Code generation remains unusable for simple Python function prompts.
- Some outputs contain corrupted or off-topic fragments.
- Reducing repeat penalty from 1.15 to 1.0 did not fix the failures.

## Verdict

The SFT pipeline works, and v12 can be turned into a chat-shaped model that follows
the prompt format and stops correctly. However, none of the three SFT variants is a
stable high-quality chat model yet.

The limiting issue is no longer infrastructure. It is data and objective quality:
the current synthetic/anchor data is too narrow, while the current real-mix data
adds breadth but also noisy or low-quality behavior. Validation loss alone is not a
sufficient selection signal for chat quality.

## Recommended Next Step

Build a smaller, higher-precision SFT curriculum before another large run:

1. Keep the anchor data, but reduce over-refusal templates.
2. Add verified small instruction sets for math, code, translation, summarization,
   and closed-book common facts.
3. Add an automatic fixed-prompt eval harness that scores exact-match math, simple
   code syntax, refusal appropriateness, stop-token behavior, and corruption.
4. Train a short curriculum from the v12 base or v12 anchor checkpoint, then pick
   by generation eval rather than SFT loss alone.
