---
license: apache-2.0
base_model: Qwen/Qwen2.5-1.5B-Instruct
library_name: transformers
pipeline_tag: text-generation
tags:
  - openenv
  - reinforcement-learning
  - mechanism-design
  - auctions
  - llm-agents
  - grpo
  - trl
  - unsloth
  - peft
  - lora
  - qwen2.5
language:
  - en
model-index:
  - name: daedalus-designer-v2
    results:
      - task:
          type: reinforcement-learning
          name: Adversarial mechanism design (DAEDALUS)
        dataset:
          type: kabilesh-c/Daedalus-Env
          name: DAEDALUS OpenEnv
        metrics:
          - type: composite_reward
            value: 0.434
            name: Informed-greedy baseline (mean over 30 episodes)
          - type: composite_reward
            value: 0.326
            name: Uniform-random baseline (mean over 30 episodes)
---

# DAEDALUS Designer v2 — Adversarial Auction-Mechanism Design

> A 1.5 B-parameter LLM that **designs auction mechanisms** robust to a
> population of strategic adversaries (colluders, shaders, dropouts,
> exploiters). Trained with **GRPO** (TRL) on the
> [`kabilesh-c/Daedalus-Env`](https://huggingface.co/spaces/kabilesh-c/Daedalus-Env) OpenEnv environment using
> **Unsloth + 4-bit + LoRA**.

| | |
|---|---|
| **Live demo (interactive UI)** | [`kabilesh-c/Daedalus-Env`](https://huggingface.co/spaces/kabilesh-c/Daedalus-Env) |
| **Base model** | [`Qwen/Qwen2.5-1.5B-Instruct`](https://huggingface.co/Qwen/Qwen2.5-1.5B-Instruct) |
| **Training Space (image builder)** | [`kabilesh-c/daedalus-training-space`](https://huggingface.co/spaces/kabilesh-c/daedalus-training-space) |
| **Long-form blog** | served from the live Space at `/blog.md` |
| **Standalone script** | `inference.py` in the live Space repo |
| **Author** | Laksh Krish Kabilesh |

---

## 1. What this model does

Given a partial observation of an auction market — recent (welfare,
fairness, participation) outcomes, round number, episode length — the
model emits a **structured JSON mechanism**:

```json
{
  "auction_type": "second_price",
  "reserve_price": 0.18,
  "reveal_reserve": false,
  "reveal_competing_bids": false,
  "reveal_winner_identity": true,
  "reveal_clearing_price": true,
  "reveal_bid_distribution": false,
  "shill_penalty": 1.2,
  "withdrawal_penalty": 0.6,
  "collusion_penalty": 1.9,
  "coalition_policy": "penalize_suspected"
}
```

The mechanism is then *used* — the env runs 5 market rounds against an
adaptive adversarial population, and scores the result on the composite
reward `R = welfare_ratio · fairness_score · participation_rate · stability_score`.

This is the **inverse** of the usual RL setup: the model is the
*referee*, not the player.

---

## 2. Model details

| | |
|---|---|
| **Architecture** | Qwen2.5-1.5B-Instruct (decoder-only transformer, 28 layers) |
| **Total parameters** | 1,562,179,072 |
| **Trainable parameters (LoRA)** | 18,464,768 (**1.18 %**) |
| **PEFT method** | LoRA, r = 16, applied to all attention + MLP linear layers |
| **Quantisation (training)** | 4-bit NF4 via `bitsandbytes` + Unsloth |
| **Storage format** | merged 16-bit `bf16` (no separate adapter file required at inference) |
| **Context length** | 32,768 tokens (Qwen2.5 default) |
| **Output schema** | Pydantic `DaedalusAction` — see live Space for full type definition |
| **License** | Apache-2.0 (inherited from Qwen2.5-1.5B-Instruct) |

---

## 3. Training details

### Pipeline

```
Qwen2.5-1.5B-Instruct (4-bit, Unsloth)
        |
        | LoRA r=16 on attn + MLP
        v
   +--- SFT on synthetic (prompt, valid_mechanism) pairs
   |    (teaches JSON shape only; ~300 steps)
   v
   GRPO (TRL) on DAEDALUS env, 50 steps
   reward = format_reward + welfare + fairness + composite
        |
        | merge_and_unload + push_to_hub_merged
        v
kabilesh-c/daedalus-designer-v2 (this checkpoint)
```

### Hyperparameters

| | |
|---|---|
| **RL algorithm** | GRPO (Group-Relative PPO, no value head) |
| **Generations per state** | 4 |
| **Steps** | 50 |
| **Batch size** | 4 × 2 grad-accum × 1 GPU = 8 effective |
| **Learning rate** | 5e-6 (LoRA) |
| **Reward stack** | `format` (JSON parseability) → `welfare` → `fairness` → `composite` |
| **Hardware** | 1 × NVIDIA L4 (24 GB) on Hugging Face Jobs |
| **Wall-clock** | ~7 minutes per +50-step iteration |
| **Cost** | ~\$0.10 per iteration |

### Training signals (from `training_history.json`)

| Metric | Range | Mean | What it tells you |
|---|---|---|---|
| `grad_norm` | 0.46 – 0.84 | 0.71 | healthy gradient flow, no vanish/explode |
| `reward_std` (within-group) | 0.53 – 0.86 | 0.69 | GRPO advantage signal stays informative |
| `entropy` (policy) | 1.65 – 2.50 nats | 1.95 | narrowed by ~5.5 nats from uniform; still exploring |
| `completions/mean_length` | 140 tokens (pinned) | 140 | schema-locked output |

Plots and per-step CSV are served from the live Space at `/plots/`.

---

## 4. Evaluation

30-episode baseline boxplot on the env's true composite reward (no
training-time shaping):

| Policy | Mean R | IQR |
|---|---|---|
| Uniform-random mechanisms | **+0.326** | ≈ 0.27 |
| Informed-greedy (hand-engineered "robust") | **+0.434** | ≈ 0.21 |

The +0.108 gap (≈ +33 % relative) is the structural signal the model is
trained to find. The trained model's online behaviour can be inspected
directly in the live Space — every `/api/design` call hits this
checkpoint.

A typical stage-3 (mixed shaders + colluders) output:

```json
{
  "auction_type": "second_price",
  "reserve_price": 0.18,
  "reveal_competing_bids": false,
  "reveal_clearing_price": true,
  "reveal_winner_identity": true,
  "collusion_penalty": 1.9,
  "shill_penalty": 1.2,
  "withdrawal_penalty": 0.6,
  "coalition_policy": "penalize_suspected"
}
```

Three things to read off this:
1. Picks **second-price** (truthful in static, robust to non-VCG-aware bidders).
2. **Hides bid distribution but reveals clearing price** — gives honest bidders calibration signal while starving cartels of enforcement signal.
3. Penalty ranking: `collusion (1.9) > shill (1.2) > withdrawal (0.6)` matches the relative cost of each pathology in this population.

---

## 5. Inference

### 5.1 Hosted (no setup) — call the live Space

```python
import requests

BASE = "https://kabilesh-c-daedalus-env.hf.space"

# Reset and read the initial observation
r = requests.post(BASE + "/reset",
                  json={"session_id": "demo", "n_agents": 8, "episode_length": 10})
obs = r.json()["observation"]

# Ask the trained designer for a mechanism
r = requests.post(BASE + "/api/design", json={
    "round_number": obs["round_number"],
    "episode_length": obs["episode_length"],
    "market_outcomes": obs.get("market_outcomes", []),
})
print(r.json()["mechanism"])

# Apply it and observe the reward
r = requests.post(BASE + "/step",
                  json={"session_id": "demo", "action": r.json()["mechanism"]})
print("R =", r.json()["reward"])
```

### 5.2 Local — `transformers` + `huggingface_hub`

> **Important:** this repo was originally pushed via Unsloth's
> `save_pretrained_merged()`, which leaves a leftover `adapter_config.json`
> whose `base_model_name_or_path` points at `./sft-merged` (a path that
> only exists on the training filesystem). Plain `from_pretrained(repo_id)`
> will follow that pointer and crash with
> `HFValidationError: Repo id must use alphanumeric chars`. Use
> `snapshot_download` with `ignore_patterns` to skip the adapter file:

```python
from huggingface_hub import snapshot_download
from transformers import AutoModelForCausalLM, AutoTokenizer
import torch

local_dir = snapshot_download(
    repo_id="kabilesh-c/daedalus-designer-v2",
    ignore_patterns=["adapter_config.json", "adapter_model.safetensors"],
)

tok = AutoTokenizer.from_pretrained(local_dir)
model = AutoModelForCausalLM.from_pretrained(
    local_dir,
    torch_dtype=torch.bfloat16,   # fp16 if no bf16
    device_map="auto",
)

system = (
    "You are an auction mechanism designer. Given a market observation, "
    "output ONLY a JSON object matching the DaedalusAction schema."
)
user = (
    "round_number: 3 / 10\n"
    "recent_outcomes: [{welfare:0.7, fairness:0.4, participation:1.0}]\n"
    "Respond with the JSON only."
)
prompt = tok.apply_chat_template(
    [{"role": "system", "content": system},
     {"role": "user",   "content": user}],
    tokenize=False, add_generation_prompt=True,
)
ids = tok(prompt, return_tensors="pt").to(model.device)
out = model.generate(**ids, max_new_tokens=180, do_sample=False, temperature=0.0)
print(tok.decode(out[0, ids.input_ids.shape[1]:], skip_special_tokens=True))
```

### 5.3 Local — full env rollouts via `inference.py`

The repo at [`kabilesh-c/Daedalus-Env`](https://huggingface.co/spaces/kabilesh-c/Daedalus-Env) ships an
`inference.py` that reproduces the §4 baseline numbers:

```bash
# one-shot mechanism for a fresh env
python inference.py

# 30 episodes trained-vs-random (writes inference_results.json)
python inference.py --n-episodes 30 --baseline

# point at a different checkpoint
python inference.py --repo-id kabilesh-c/daedalus-designer-v2
```

---

## 6. Intended use & limitations

**Intended use:** demonstration / research on LLM-driven mechanism
design. The model is trained to output well-formed `DaedalusAction`
JSON for the DAEDALUS env; it has no production guarantees.

**Limitations:**
- Trained for only 50 GRPO steps — the +50 step lift over a randomly-
  initialised LoRA is real but small in absolute terms (composite-reward
  mean from −0.594 → −0.579).
- The "format reward" dominates early steps; malformed JSON is heavily
  penalised, so the model is **schema-locked but not strategically
  perfect**. On stage-4 (full-adversarial) populations it occasionally
  emits `coalition_policy: "allow"`, which craters the run.
- Reward is engineered for the DAEDALUS env's specific multiplicative
  composite. The model is **not** guaranteed to produce sensible
  mechanisms outside this rubric.
- Inherits any biases / failure modes from
  [`Qwen/Qwen2.5-1.5B-Instruct`](https://huggingface.co/Qwen/Qwen2.5-1.5B-Instruct).

---

## 7. Citation

```bibtex
@misc{kabilesh2026daedalus,
  title  = {DAEDALUS: Training an LLM to Design Auction Markets via Adversarial RL},
  author = {Laksh Krish Kabilesh},
  year   = {2026},
  url    = {https://huggingface.co/spaces/kabilesh-c/Daedalus-Env},
}
```

---

*Made by Laksh Krish Kabilesh.*