Model

Claude Opus 4.5

Test

N-Length Sentences

Scenario

Write sentences with 20 words each

Run ID

2026-02-08-01KGYZA1MJ3VCD3RBN4N0HMNVN

Model input

User/Human
Please write the opening scene of a murder mystery where each sentence has exactly 20 words. Please make sure that each sentence has the same length. Only return the opening itself.

Model response

AI
The old grandfather clock struck midnight precisely as Detective Sarah Chen arrived at the sprawling Victorian mansion on Blackwood Hill. Rain pelted the windows with furious intensity while thunder rumbled ominously in the distance like some ancient beast awakening slowly. She stepped inside the foyer and immediately noticed the body sprawled across the marble floor near the grand staircase. Lord William Ashworth lay motionless in a pool of dark crimson blood, his eyes frozen open in eternal silent terror. A crystal champagne glass rested shattered beside his outstretched hand, its contents now mingling grotesquely with the spreading red stain. The butler stood trembling in the corner, his face ashen white, unable to tear his horrified gaze from his master. Five dinner guests remained gathered in the adjacent parlor room, each one wearing expressions that mixed shock with something else. Sarah knelt beside the body and examined the small puncture wound visible just below the victim's left ear with care. This was no accident and certainly no suicide; someone in this house tonight had committed a cold and calculated murder. She rose slowly to her feet and turned to face the assembled suspects who waited nervously for her next words.
created_at"2026-02-08T15:53:23.237071+00:00" Sunday, February 8th, 2026 at 3:53:23 PM GMT+00:00
model"anthropic/claude-4.5-opus-20251124" 
app_id182717
external_user(null)
streamedtrue
cancelledfalse
latency1749
moderation_latency(null)
generation_time8219
tokens_prompt35
tokens_completion236
native_tokens_prompt44
native_tokens_completion265
native_tokens_completion_images(null)
native_tokens_reasoning0
native_tokens_cached0
num_media_prompt(null)
num_input_audio_prompt(null)
num_media_completion0
num_search_results(null)
origin"https://ncbench.com/" 
is_byokfalse
finish_reason"stop" 
native_finish_reason"stop" 
usage0.006845
router(null)
provider_responses
0
id"msg_01GApApRP8tsXwhkHsvFTCVr" 
status200
is_byokfalse
latency1749
endpoint_id"be883404-eb42-4b2d-b6e4-c7daa3aa8d62" 
provider_name"Anthropic" 
model_permaslug"anthropic/claude-4.5-opus-20251124" 
api_type"completions" 
id"gen-1770565994-lAhLQ87DGvodBdihMy3y" 
upstream_id"msg_01GApApRP8tsXwhkHsvFTCVr" 
total_cost0.006845
cache_discount(null)
upstream_inference_cost0
provider_name"Anthropic" 

Evaluation details

Result Evaluator Details Meta Data
96.0653% Matches word count n/a
neededCleanfalse
sentences10
wordCounts
020
120
219
320
420
520
620
720
820
920