Project Status

Yaduha · LLM-RBMT for Owens Valley Paiute

Fine-tuning a 3B open model to produce schema-constrained structured output that outperforms gpt-4o-mini on the cheat-proof comparator metric — a proof-of-concept for endangered-language translation via small, deployable local models.

0 parse failures COMET_c 0.492 ~$0.40 & 1 GPU-hour Qwen2.5-3B-Instruct

Overview

Yaduha is a type-safe framework for structured language translation: the LLM emits a Pydantic-modelled grammar tree (subject, verb, object, nominalizer, tense, proximity, etc.), and a deterministic renderer converts it to surface form. The lead target language is Owens Valley Paiute (OVP), a no-resource language with ~40 documented nouns and ~37 verbs in the current dictionary.

The experimental pipeline evaluates a forward model (English → structured JSON) against a fixed strong model (gpt-4o-mini) serving as the decoder. Scoring is done on two arms:

• backwards — strong LLM sees the full structured JSON (including OOV English lemmas) and produces natural English.
• comparator — same, but OOV lemmas are masked to [NOUN]/[VERB]. Cheat-proof: the decoder can't just pass English through.

Methodology

Synthetic data generation

~$0.30 at gpt-4o-mini produces a ~4,400-pair SFT dataset covering the behaviours we want the small model to learn:

• Structure sampling — stratified across SV / SVO, nominalization, multi-clause (1–3 clauses per record), and deliberate OOV injection.
• Paraphrase menu — 8 transforms (add_adverbial, passivize, substitute_rare_vocab, etc.) applied to each canonical rendering to teach surface-form robustness.
• OOV substitution — positive pairs (chihuahua→dog) teach hypernym collapse; negative pairs (laptop) teach when to emit a placeholder.
• Proper nouns with coreference — single-mention ("Susan runs") and multi-clause coref ("Susan eats and she drinks") teach name-as-placeholder plus pronoun resolution on second reference.
• Decoder pairs — clean and OOV-masked backward-direction pairs so a separate backward adapter can learn to preserve [NOUN]/[VERB] verbatim.

Training

LoRA fine-tune of Qwen/Qwen2.5-3B-Instruct (r=16, α=32, all linear projections, bf16) via HF TRL + PEFT — no Unsloth or bitsandbytes (which pin against older torch), so the pipeline runs cleanly on torch 2.11 + CUDA 13. 1 epoch, effective batch 8, cosine schedule, completion-only loss. Runs in ~45–60 min on a single RTX 5000 Ada.

Structured output is preserved, not replaced

Training shifts the model's preferred-token distribution toward schema-valid outputs without changing the inference stack: the EnglishToSentencesTool still passes response_format to the Pydantic SentenceList schema. The fine-tune makes the schema constraint a guardrail (near-no-op) rather than a forcing function — 97% of the time the raw generation already parses.

Results

Evaluated on the full 150-sentence eval set (6 sentence types × 25 each). COMET scores are over the cheat-proof comparator arm (higher = better structural choices that preserve meaning without leaning on English passthrough).

Aggregate comparator scores (all sentence types)

Model	Parse errs	COMET_b	COMET_c	Params
llama3.2:1b	9	0.787	0.306	1B
qwen2.5:3b (base)	15	0.771	0.430	3B
llama3.2:3b	5	0.861	0.413	3B
qwen2.5:7b	3	0.834	0.430	7B
llama3.1:8b	9	0.821	0.389	8B
gpt-4o-mini	0	0.865	0.461	~? (API)
ft-qwen2.5:3b (this work)	0	0.792	0.492	3B + LoRA

Per-type comparator COMET vs gpt-4o-mini

Sentence type	gpt-4o-mini	ft-qwen2.5:3b	Δ
subject-verb	0.709	0.710	˜tie
subject-verb-object	0.344	0.441	+28%
two-verb	0.533	0.593	+11%
two-clause	0.365	0.398	+9%
complex	0.340	0.370	+9%
nominalization	0.474	0.442	−7%

Iteration arc

Each dataset revision targeted a specific failure class; each delivered:

Version	What was added	Errors / 150	COMET_c
v1	single-clause structures + OOV subs	6	0.494
v2	+ multi-clause records (fixed two-clause errs)	5	0.495
v3	+ proper-noun coreference pairs	0	0.492

Caveats & honesty

• The fine-tune runs through an HF bf16 pipeline; the base Qwen2.5:3b baseline was measured through Ollama Q4_K_M. Same underlying model, different quantisation. An apples-to-apples re-run is on the list.
• Absolute COMET_c of 0.492 sits about 0.06 above the unrelated-pair noise floor (˜0.43). The grammar schema caps how much semantic meaning can survive the structural bottleneck; we're nowhere near the ceiling, but the ceiling itself is bounded by the schema.
• Training loss converges to ˜0.02 in ~100 steps — narrow-schema convergence rather than broad generalization. Generalization probe on an unrelated Pydantic schema hasn't been run yet.
• The comparison beats gpt-4o-mini on the cheat-proof metric, but gpt-4o-mini still leads on backwards (0.865 vs 0.792). The fine-tune deliberately produces fewer English-lemma passthroughs (a feature, not a bug — but it's a trade-off).

Next steps

• Scale up — full N=2000 structures + 3 epochs (CLAUDE.md's original recipe); estimated $1.20 data + ~2 h training. Likely closes the nominalization gap.
• Bigger base — same pipeline on Qwen2.5-7B-Instruct or Llama-3.1-8B to quantify how much the gains scale with parameters.
• Apples-to-apples baseline — put base Qwen2.5-3B-Instruct through the same HF pipeline so the fine-tune's isolated effect is cleanly measured.
• Ollama export — merge LoRA → GGUF → ollama create, then rerun through the existing sweep. Confirms the result holds through the deployed inference stack.
• Generalization probe — measure the fine-tune on an unrelated Pydantic schema (e.g. Person(name, age, occupation)) vs. the base model. Tells us whether the adapter locked in OVP-specific priors or learned a general schema-adherence skill.
• Backward adapter — train a separate LoRA for the structured → English direction so the pipeline runs end-to-end without a proprietary decoder.

Reproduce

cd yaduha-ovp

# 1. Generate the training dataset (~$0.40 at gpt-4o-mini, ~10 min)
N_STRUCTURES=750 bash experiments/run_datagen.sh

# 2. Train the LoRA adapter (~45-60 min on a single RTX 5000 Ada)
uv run --project yaduha-ovp python experiments/finetune/scripts/train.py \
    --direction forward --epochs 1 --max-seq-length 2304

# 3. Evaluate on the 150-sentence held-out set (~8 min)
uv run --project yaduha-ovp python experiments/finetune/scripts/run_finetune_eval.py \
    --adapter experiments/finetune/adapters/qwen2.5-3b-instruct-forward \
    --tag ft-qwen2.5_3b__gpt-4o-mini

# 4. Score + regenerate plots
uv run --project yaduha-ovp python experiments/run_metrics.py \
    --input experiments/results/ft-qwen2.5_3b__gpt-4o-mini.jsonl
uv run --project yaduha-ovp python experiments/analyze.py

References

• kubishi/yaduha — core framework
• kubishi/yaduha-ovp — OVP language package (this work lives on the feature/weakmodels branch)
• Coleman et al. 2024, LLM-assisted Rule-Based Machine Translation for Low/No-Resource Languages — AmericasNLP
• Coleman et al. 2026, Five-Translator Comparison for No-Resource Machine Translation — LoResMT