Qwen3-4B ReST Fused — model card

base_model: Qwen/Qwen3-4B-Instruct-2507
language:
  - en
library_name: mlx
license: other
pipeline_tag: text-generation
tags:
  - posttrainllm
  - mlx
  - tool-calling
  - function-calling
  - agentic
  - rest
  - research-specialist

Qwen3-4B ReST Fused

Model description

A research specialist built by PostTrainLLM — a Mac-local LLM factory that post-trains small models for narrow agentic tasks. This model preserves the best measured Qwen3-4B agentic candidate produced by a teacher-free ReST (Reinforced Self-Training) loop. One ReST iteration recovered the out-of-domain breadth lost by narrow distillation while retaining the saturated file-operations gate.

It is a research specialist package, not the default Pace planner. The model speaks BFCL/OpenAI-style tool calls; Pace uses a different intent envelope and requires its own ship gate.

Base model: Qwen/Qwen3-4B-Instruct-2507
Precision: bf16
Format: fused HF/MLX safetensors directory (8 files, ~8 GB)
Architecture: Qwen3ForCausalLM
Compatibility: mlx_lm, posttrainllm serve --hf-dir

Eval results

The current numbers come from the fresh paired run on 2026-09-03. Source: qwen3-4b-rest-fused.json.

Suite	Stock 4B	ReST 4B	Delta	n
File-ops hard gate	0.75	1.00	+0.25	12
Qualified breadth	0.667	0.556	-0.111	45

The breadth ruler passed its frontier gate at 44/45. ReST reached 12/12 on file-ops, removed all eight stock side effects, and ran that slice 2.42x faster wall-clock. It also lost five net breadth cases versus stock. This confirms a routed file-ops win and rejects the candidate as a general successor.

Evidence quality caveat: raw traces remain local and gitignored, with their SHA-256 receipts preserved in evals/verified-wins/rest-requalification-result-v1.json. The legacy package report-card adapter cannot promote those run fields to a fully verified ship.

Training recipe summary

Target: same GorillaFileSystem file-ops depth anchor as the distilled specialist, plus breadth recovery across TradingBot, VehicleControlAPI, and TravelAPI backends.
Method: teacher-free ReST — one iteration over checker-passing interleaved trajectories. No paid model API was used (training cost: $0). The checker validated tool-call correctness; passing trajectories were folded back into the training set.
Depth anchor: file-ops gold depth was preserved as an anchor so ReST could not regress the saturated 100% hard gate while recovering breadth.
Student: Qwen3-4B-Instruct-2507 bf16, fused into a single HF/MLX safetensors directory.
Decision: retain only as a routed file-ops specialist; reject as a general successor and do not use as the Pace default planner.

Limitations

Breadth regression. The frontier-qualified candidate scored 25/45 versus stock 30/45. Do not market it as breadth recovery or a general replacement.
Raw predictions are not committed. Their hashes are preserved in the tracked result, but the files remain local and gitignored.
Training duration and normalized latency remain absent. Fresh eval wall time, tok/s, and peak RSS are recorded per suite in the tracked result.
Not a Pace planner. Pace requires a different intent envelope and product-specific ship gate. Re-distill and evaluate on Pace’s intent envelope before considering any downstream promotion.
Multi-GB artifact. Weights are ~8 GB and live on Hugging Face Hub, not in git.

How to use

# Metadata check (no weights loaded)
python mlx_load.py

# Load weights into MLX arrays
python mlx_load.py --load

Serve with the PostTrainLLM CLI:

posttrainllm serve --hf-dir ./qwen3-4b-rest-fused

Or load with mlx_lm:

from mlx_lm import load, generate
model, tokenizer = load("posttrainllm/qwen3-4b-rest-fused")

Upload command

This model is already published. To re-upload or update metadata:

# Stage the public metadata surface (no token needed)
python3 scripts/plan_hf_artifact_upload.py \
  specialists/qwen3-4b-rest-fused \
  --repo-id posttrainllm/qwen3-4b-rest-fused

# Upload to Hugging Face Hub (requires HF login)
huggingface-cli upload posttrainllm/qwen3-4b-rest-fused \
  dist/hf-artifacts/qwen3-4b-rest-fused \
  --repo-type model

Qwen3-4B ReST Fused — model card