# Default Generation Length Without Constraints (gpt-oss-120b)

> Without a length constraint, LLM outputs cluster around a 'natural' default length that varies by topic type and prompt framing.

Date: 2026-02-06



## Test

Establishes the model's unconstrained baseline output length, which the prior [word count](/scratchpads/llm-length-compliance) and [character count](/scratchpads/character-count-compliance) experiments can be compared against.

60 completions: 3 topics × 2 framings × 10 runs.

**Topics:** factual (solar panels), creative (lighthouse keeper story), argumentative (remote work)

**Framings:**
- Bare: "Write about the following topic: {topic}"
- Direct: "{topic}" (topic text only, no wrapper)

No word count, character count, or length instructions of any kind.

- Model: gpt-oss-120b via Cerebras API (free tier)
- Temperature: 1.0, top_p: 0.95, max_completion_tokens: 65000


## Result

**CONFIRMED**

Outputs cluster around topic-dependent default lengths. Topic matters; framing doesn't.

**By topic (n=20 each):**

| Topic | Mean words | Mean chars |
|-------|:-:|:-:|
| Factual | 1586 | 10,252 |
| Creative | 1399 | 7,881 |
| Argumentative | 1015 | 7,309 |

Factual prompts produce 56% more words than argumentative. The ordering is consistent across both framings.

**By framing (n=30 each):**

| Framing | Mean words |
|---------|:-:|
| Bare ("Write about...") | 1348 |
| Direct (topic only) | 1319 |

A 2.1% difference, well within the per-group standard deviations. The framing wrapper adds no meaningful length.

**Overall:** median 1359 words, range 770–2061. All 60 completions finished naturally (finish_reason=stop). Creative writing had the highest variability (SD=354 words with bare framing), argumentative the most consistent (SD=109 with direct framing).

Characters per word varied by topic: argumentative used longer words (7.20 chars/word) vs creative (5.64), reflecting formal vs conversational vocabulary.


## Next

1. Compare these baselines against the constrained experiments — the unconstrained argumentative mean (1015 words) is close to the "exactly 1000 words" constrained result (~988 words)
2. Test whether system prompts or role instructions shift the default length
3. Measure default length on other models for cross-model comparison