Claude Opus 5.5 (Reasoning)

anthropic/claude-opus-5.5

Claude Opus 5.5 (Reasoning)

via OpenRouter

Release Date

Sep 21st, 2026

Context Size

Reasoning

Yes

Benchmark Cost

$33.81

Speed

72.2 tok/s

Subcategories

Bad Writing Habits

Detects common prose quality anti-patterns in AI-generated creative writing, including passive voice, past progressive overuse, weak dialogue tags, filter words, purple prose, cliches, AI-ism words/adverbs/names, and more.

Scenario	#1	#2	#3	#4	#5	Total
Detailed Writing Rules
Fantasy: entering an ancient ruin Creative Writing Hallucination	93	93	92	91	90	92%
Horror: alone in an eerie place at night Creative Writing Hallucination	96	94	93	93	90	93%
Literary fiction: old friends reunite Creative Writing Hallucination	90	89	89	88	86	88%
Mystery: examining a crime scene Creative Writing Hallucination	94	94	93	91	90	92%
Romance: separated couple reunites Creative Writing Hallucination	92	91	90	89	89	90%
Thriller: chase through city streets Creative Writing Hallucination	94	93	93	92	89	92%
Detailed Writing Rules						91.35%
genre
Fantasy: entering an ancient ruin Creative Writing Hallucination	90	87	87	86	85	87%
Horror: alone in an eerie place at night Creative Writing Hallucination	87	86	85	85	82	85%
Literary fiction: old friends reunite Creative Writing Hallucination	88	87	86	81	81	85%
Mystery: examining a crime scene Creative Writing Hallucination	93	91	91	90	90	91%
Romance: separated couple reunites Creative Writing Hallucination	88	88	86	85	81	86%
Thriller: chase through city streets Creative Writing Hallucination	94	91	90	89	88	90%
genre						87.17%
Novelcrafter Default Prompt
Fantasy: entering an ancient ruin Creative Writing Hallucination	91	90	86	85	84	87%
Horror: alone in an eerie place at night Creative Writing Hallucination	97	96	96	94	93	95%
Literary fiction: old friends reunite Creative Writing Hallucination	87	87	86	86	83	86%
Mystery: examining a crime scene Creative Writing Hallucination	95	93	93	92	92	93%
Romance: separated couple reunites Creative Writing Hallucination	87	87	86	86	83	86%
Thriller: chase through city streets Creative Writing Hallucination	93	92	90	88	88	90%
Novelcrafter Default Prompt						89.56%
89.36%

Codex Extraction

Evaluates a model's ability to extract structured codex entries (characters, locations, objects, lore) from prose passages and return them as well-formed XML.

Scenario	#1	#2	#3	#4	#5	Total
Long: The Spire of Echoes (Dense) Tooling Reasoning	99	98	98	98	98	99%
Medium: The Hollow (Inferred) Tooling Reasoning	100	100	99	99	99	99%
Medium: Through the Thornveil (Scattered) Tooling Reasoning	99	99	99	98	98	99%
Short: The Rusty Lantern (Explicit) Tooling Reasoning	99	99	99	99	99	99%
98.77%

Codex Red Herring (False Positive Detection)

Tests whether models correctly report "no violations" when a codex is fully consistent with the prose passage. Models that hallucinate false violations (false positives) fail. Uses a 2×2 matrix of text length × codex size, with bare and detailed-entry variants.

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
basic entries
Long text (~1594 words), big codex (51 entries) Hallucination	100	100	100	100	100	100	100	100	100	100	100%
Long text (~1594 words), small codex (11 entries) Hallucination	100	100	100	100	100	100	100	100	100	100	100%
Short text (~524 words), big codex (51 entries) Hallucination	100	100	100	100	100	100	100	100	100	100	100%
Short text (~524 words), small codex (11 entries) Hallucination	100	100	100	100	100	100	100	100	100	100	100%
basic entries											100.00%
detailed entries
Long text (~1594 words), big codex (51 detailed entries) Hallucination	100	100	100	100	100	100	100	100	100	100	100%
Long text (~1594 words), small codex (11 detailed entries) Hallucination	100	100	100	100	100	100	100	100	100	100	100%
Short text (~524 words), big codex (51 detailed entries) Hallucination	100	100	100	100	100	100	100	100	100	25	93%
Short text (~524 words), small codex (11 detailed entries) Hallucination	100	100	100	100	100	100	25	25	25	25	70%
detailed entries											90.63%
95.31%

Codex Violation Detection

Detects factual inconsistencies between a story bible and prose passages. The model must output structured XML identifying each violation with paragraph number and substring.

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
matrix
Large codex (40 entries), long passage (1,019 words) Tooling Reasoning	99	99	98	98	98	98	98	98	97	96	98%
Large codex (40 entries), short passage (165 words) Tooling Reasoning	100	100	100	100	100	100	98	98	97	97	99%
Small codex (7 entries), long passage (734 words) Tooling Reasoning	100	100	100	100	100	100	100	100	100	92	99%
Small codex (7 entries), short passage (165 words) Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
matrix											99.06%
tiers
5 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
10 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
20 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	100	97	100%
40 codex entries Tooling Reasoning	100	100	100	100	100	100	100	100	100	100	100%
tiers											99.92%
99.49%

Data extraction

Extract key details from a given block of text.

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
All valid emails Utility	100	100	100	100	100	100	100	100	100	100	100%
Contextual pronoun Utility	100	100	100	100	100	100	100	100	100	100	100%
Fruits excluding citrus Utility	100	100	100	100	100	100	100	100	100	100	100%
Future event time Reasoning	50	50	50	50	50	50	50	50	50	50	50%
Guess the pet Reasoning	100	100	100	100	100	100	100	100	100	100	100%
Highest-rated movie Reasoning	100	100	100	100	100	100	100	100	100	100	100%
Indirect birth year Reasoning	100	100	100	100	100	100	100	100	100	100	100%
What instrument does Lucy play? Reasoning	100	100	100	100	100	100	100	100	100	100	100%
What's the color of the car? Utility	100	100	100	100	100	100	100	100	100	100	100%
Who's the sister? Reasoning	100	100	100	100	100	100	100	100	100	100	100%
Who's the tallest? Reasoning	100	100	100	100	100	100	100	100	100	100	100%
95.45%

Dialogue tags

Various tasks related to dialogue tags in text.

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
dialogue-200
Write 200 words with 10% dialogue Rule Following Utility	100	100	100	100	100	100	100	100	96	90	99%
Write 200 words with 50% dialogue Rule Following Utility	100	100	100	100	100	100	100	100	100	95	99%
Write 200 words with 90% dialogue Rule Following Utility	100	100	100	99	98	96	95	94	92	87	96%
dialogue-200											98.01%
dialogue-500
Write 500 words with 30% dialogue Rule Following Utility	100	99	99	98	97	80	80	68	40	39	80%
Write 500 words with 50% dialogue Rule Following Utility	93	73	62	58	56	54	52	51	49	22	57%
Write 500 words with 70% dialogue Rule Following Utility	89	83	77	59	50	47	43	28	21	0	50%
dialogue-500											62.28%
Ungrouped
Write unattributed dialogue Rule Following	100	100	100	100	100	100	100	100	100	100	100%
82.98%

Language Comprehension

Does the model understand more than just English?

Scenario	#1	#2	#3	#4	#5	Total
Asking for directions (Dutch) Language	100	100	100	100	100	100%
Asking for directions (German) Language	100	100	100	100	100	100%
Friend got new kittens (German) Language	100	100	100	100	100	100%
Friend got new kittens (Tagalog) Language	100	100	100	100	100	100%
100.00%

Language Writing

Can the model generate text in different languages?

Scenario	#1	#2	#3	#4	#5	Total
Character dialogue (French) in a story Language	100	100	100	100	100	100%
Character dialogue (German) in a story Language	100	100	100	98	97	99%
Character dialogue (Hindi) in a story Language	100	100	100	100	100	100%
Character dialogue (Italian) in a story Language	100	100	100	100	97	99%
Character dialogue (Spanish) in a story Language	100	100	100	100	97	99%
99.53%

N-Length Sentences

Write sentences with exactly N words

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
Write sentences with 5 words each Utility	100	100	100	100	96	95	95	95	91	91	96%
Write sentences with 10 words each Utility	100	100	100	100	100	100	100	100	100	94	99%
Write sentences with 20 words each Utility	100	100	100	100	100	100	100	100	100	100	100%
98.55%

Novel outline

Handle questions about the outline of a novel in various formats

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
outline-count
Count acts Utility	100	100	100	100	100	100	100	100	100	100	100%
Count chapters Utility	100	100	100	100	100	100	100	100	100	100	100%
Count scenes Utility	100	100	100	100	100	100	100	100	100	100	100%
outline-count											100.00%
pov-count
Count point of views for Jack and Olivia Utility	100	100	100	100	100	100	100	100	100	100	100%
Count point of views for Jack Harper Utility	100	100	100	100	100	100	100	100	100	100	100%
Count point of views for Olivia Utility	100	100	100	100	100	100	100	100	100	100	100%
pov-count											100.00%
100.00%

Relationship tree

Extracts a deterministic XML family and relationship tree from cumulative literary prose.

Scenario	#1	#2	#3	#4	#5	Total
Core relationship tree Tooling Reasoning Hallucination	98	98	98	98	98	98%
Family relationship tree Tooling Reasoning Hallucination	94	94	94	93	93	93%
95.92%

Text Replacement

Tests deterministic text transformations: renaming characters/locations, expanding contractions, tense rewriting, POV shifts, gender swaps, combined transformations, and word avoidance. Scored by checking each expected change independently.

Scenario	#1	#2	#3	#4	#5	#6	#7	Total
Generic Prompt
Avoid said/asked/replied/answered Text Editing	100	100	100	100	100	100	100	100%
Character rename: Elena->Mirabel, Gregor->Aldric Text Editing	100	100	100	100	100	100	100	100%
Combined: 3rd person past → 1st person present Text Editing	98	98	98	98	98	98	98	98%
Expand all contractions Text Editing	100	100	100	100	100	100	100	100%
Location rename: market square, outer ring, bridge, northern mines Text Editing	100	100	100	100	100	100	100	100%
Multi-character gender swap: Priya(F)->Rohan(M), Mara unchanged Text Editing	97	97	97	97	97	97	96	97%
Passive voice → active voice Text Editing Hallucination	98	97	97	97	97	95	81	94%
POV shift: 3rd person to 1st person (Elena's perspective) Text Editing	100	100	99	99	99	99	99	99%
Tense rewriting: past to present Text Editing	99	99	99	99	98	98	98	99%
Generic Prompt								98.56%
Specific Prompt
Avoid said/asked/replied/answered Text Editing	100	100	100	100	100	100	100	100%
Character rename: Elena->Mirabel, Gregor->Aldric Text Editing	100	100	100	100	100	100	100	100%
Combined: 3rd person past → 1st person present Text Editing	99	99	99	99	99	99	99	99%
Expand all contractions Text Editing	100	100	100	100	100	100	100	100%
Location rename: market square, outer ring, bridge, northern mines Text Editing	100	100	100	100	100	100	100	100%
Multi-character gender swap: Priya(F)->Rohan(M), Mara unchanged Text Editing	100	100	100	100	100	100	100	100%
Passive voice → active voice Text Editing Hallucination	100	100	99	99	99	98	98	99%
POV shift: 3rd person to 1st person (Elena's perspective) Text Editing	100	100	100	100	100	100	100	100%
Tense rewriting: past to present Text Editing	100	100	100	100	100	100	100	100%
Specific Prompt								99.78%
99.17%

Tool usage within Novelcrafter

Output messages that are related to tool usage within Novelcrafter

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
Create alternate prose sections Tooling	100	100	100	100	100	100	100	100	100	100	100%
100.00%

Voice/dialogue sheets

Extract dialogue from given text as voice sheets.

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
Multiple speakers Rule Following	100	100	100	100	100	100	100	100	0	0	80%
Simple Rule Following	100	100	100	100	100	100	100	100	100	100	100%
Simple (1-shot) 1-shot Rule Following	100	100	100	100	100	100	100	100	100	100	100%
Simple (5-shot) Few-shot Rule Following	100	100	100	100	100	100	100	100	100	0	90%
Unattributed dialogue Rule Following	100	100	100	100	100	100	100	100	100	100	100%
94.00%

Write N of X

Write exactly N words/sentences/paragraphs...

Scenario	#1	#2	#3	#4	#5	#6	#7	#8	#9	#10	Total
paragraphs
1 paragraph summary Utility	100	100	100	100	100	100	100	100	100	100	100%
3 paragraph summary Utility	100	100	100	100	100	100	100	100	100	100	100%
5 paragraph summary Utility	100	100	100	100	100	100	100	100	100	100	100%
paragraphs											100.00%
sentences
1 sentence summary Utility	100	100	100	100	100	100	100	100	100	100	100%
3 sentence summary Utility	100	100	100	100	100	100	100	100	100	100	100%
10 sentence summary Utility	100	100	100	100	100	100	100	100	100	100	100%
20 sentence summary Utility	100	100	100	100	100	100	100	100	100	100	100%
50 sentence summary Utility	100	100	100	100	100	100	100	100	100	100	100%
sentences											100.00%
words
10 word summary Utility	100	100	100	100	100	100	100	100	100	100	100%
20 word summary Utility	100	100	100	100	100	100	100	100	100	100	100%
50 word summary Utility	100	100	100	100	100	100	100	100	100	100	100%
100 word summary Utility	100	100	100	100	100	100	100	100	100	100	100%
200 word summary Utility	100	100	100	100	100	100	100	100	100	100	100%
words											100.00%
100.00%