Modeltell

Computational linguistics analysis of AI-generated text.

Modeltell systematically measures the lexical and syntactic fingerprints of large language models. Unlike word-level "AI detector" lists, this project analyzes grammatical constructions - the sentence structures, rhetorical patterns, and compositional habits that define each model's linguistic identity.

What Makes This Different

Everyone knows LLMs overuse "delve" and "leverage." That's table stakes. Modeltell goes deeper:

• Syntactic pattern detection: Tricolon frequency, hedging constructions, pseudo-inclusive openers ("Whether you're X or Y"), em-dash dramatic pivots, power verb stacking density
• Structural analysis: Opener/closer classification, bullet-to-prose ratios, formatting density, sentence length variance
• Cross-model fingerprinting: Radar profiles that reveal each model's unique combination of linguistic habits
• Evolution tracking: How do these patterns shift across model versions? Are models converging or diverging?

Architecture

prompts/catalog.json       30 standardized content generation prompts
patterns/definitions.json  15 syntactic patterns + lexical watchlists
src/runner/                Multi-provider API runner (3 runs per prompt per model)
src/analysis/              Lexical (cross-model TF-IDF, Burrows's Delta) + Syntactic (regex patterns)
src/publish/               Transforms analysis → community JSON (published/)
src/cli/                   Zero-dependency content linter (npm run check)
scripts/mock-run.ts        Synthetic dataset generator (no API keys needed)
data/{run-id}/             Raw outputs + analysis results per run
published/                 Versioned community dataset (the static JSON API)
frontend/                  Scrollytelling visualization (React + Vite + D3)

Tracked Models

Tier	Models
Frontier	Claude Opus 4.8 / 4.7 / 4.6, GPT-5.5, Gemini 3.1 Pro
Mid	Claude Sonnet 4.6, GPT-5.4 Mini, Gemini 3.5 Flash
Open Source	Llama 4 Maverick, DeepSeek V4 Pro / V3.2, Mistral Large (2512), Qwen3.7 Max

The current registry lives in src/runner/models.ts (13 models, with family/version for drift). Adding a model = one entry there.

Detected Patterns

Pattern	What It Detects	Severity
Tricolon	"innovative, scalable, and transformative"	High
Whether-You're	"Whether you're a startup or enterprise..."	Critical
Hedging Opener	"It's worth noting that..."	High
Not-Just-But	"not just a tool, but a partner"	High
In-Today's-Landscape	"In today's fast-paced digital landscape..."	Critical
Em-Dash Pivot	"one platform - endless possibilities"	Medium
Power Verb Stacking	"drive, boost, and accelerate"	High
Future-Forward Closing	"As we move forward..."	High
... and 7 more	See patterns/definitions.json

Quick Start

# Install
npm install

# Configure keys: copy and edit .env (auto-loaded by the runner)
cp .env.example .env

Keys: set OPENROUTER_API_KEY. The default registry routes all 13 models through OpenRouter's single OpenAI-compatible API, so that one key is all you need. Open models are provider-pinned (and the serving backend is recorded in each result) for reproducibility.

The runner also ships direct-provider adapters (callAnthropic, callOpenAI, …), but they're only used if you change a model's provider in src/runner/models.ts away from "openrouter". With the default registry the direct keys (ANTHROPIC_API_KEY, …) are not consulted.

# Run generation (all models you have keys for)
npm run run:all

# Fast smoke run: a few models, 1 generation per prompt
RUNS_PER_PROMPT=1 ONLY_MODELS=claude-sonnet-4.6,gpt-5.5 npm run run:all

# German corpus instead of English (prompts, patterns, stopwords)
LOCALE=de npm run run:all

# Convenience model groups (just preset ONLY_MODELS filters - everything
# still runs through OpenRouter, these don't hit providers directly)
npm run run:anthropic   # the Claude models   (run:openai, run:google, run:opensource too)

# Analyze results (set LOCALE=de for German lexical stopwords)
npm run analyze:lexical -- data/<run-id>
npm run analyze:syntactic -- data/<run-id>

# Publish the community dataset → published/<locale>/
npm run publish:data -- data/<run-id>

No API keys? Use the mock generator

For developing the analysis, publisher, or frontend without spending anything, generate a full synthetic dataset (model-specific pattern density, no API calls):

npx tsx scripts/mock-run.ts
RUN=$(ls -td data/*_mock | head -1)
npx tsx src/analysis/lexical.ts "$RUN" && npx tsx src/analysis/syntactic.ts "$RUN" && npx tsx src/publish/publish.ts "$RUN"

CLI Linter

A zero-dependency, bilingual (EN/DE) linter that flags AI patterns in any text. The language is auto-detected; override with --locale en|de. Exits non-zero on grade C or below, so it drops straight into CI:

npm run check -- "In today's fast-paced landscape, whether you're a pro or a beginner..."
npx modeltell check --locale de "In der heutigen schnelllebigen Welt optimieren wir nahtlos."
npx modeltell check --file landing-page.md --json
echo "some text" | npx modeltell check -

It embeds its own patterns/words per language (no external files), so it runs standalone after npm run build:cli (output: dist/cli/check.js).

Automated Runs

A GitHub Action runs the full pipeline monthly and commits results. See .github/workflows/monthly-run.yml.

Frontend

A scroll-driven data story built with React, Vite, Framer Motion, and custom SVG/D3 visualizations. It reads the published/ dataset - no runtime API. See frontend/README.md for details.

cd frontend && npm install && npm run dev   # auto-syncs published/ first

Sections, in scroll order:

1. Hook - an annotated AI sentence, every "tell" highlighted inline
2. The Word Cloud - frequent AI-associated vocabulary, sized by frequency
3. Model Fingerprints - a radar chart per model across 8 syntactic dimensions
4. Head to Head - overlay any two models + a similarity score
5. Version Drift - one model family across its own versions (e.g. Opus 4.6→4.8)
6. Pattern Deep-Dive - each construction with a real example, CI whiskers, significance markers, the fix
7. Tier Analysis - Frontier vs Mid vs Open Source averages
8. Similarity Heatmap - every pair, scored (radar similarity ⇄ Burrows's Delta)
9. The Watchlist - full pattern list + CLI call-to-action

A language switcher (EN/DE) flips both the UI and the underlying corpus.

Data API

The pipeline publishes a versioned, self-contained JSON dataset under published/<locale>/, served as a static API via GitHub Pages (.github/workflows/pages.yml). Each corpus language gets its own namespace:

published/locales.json                            discovery: which languages exist
published/<locale>/index.json                     entry point  (locale = en | de | …)
published/<locale>/models/{model-id}.json         per-model fingerprint (self-contained)
published/<locale>/watchlist/words.json           frequent AI-associated words
published/<locale>/watchlist/constructions.json   syntactic constructions
published/<locale>/comparisons/tier-summary.json  frontier/mid/opensource averages
published/<locale>/comparisons/similarity-matrix.json   radar similarity matrix
published/<locale>/comparisons/delta-matrix.json        Burrows's Delta matrix
published/<locale>/validation/regex-precision.json      manual precision audit (optional)

validation/regex-precision.json is optional and currently English-only - a locale's index.json lists files.regex_precision only when that audit exists, so always read it from the index rather than assuming the path.

Start at locales.json, then published/en/index.json (or …/de/index.json). On GitHub Pages that's e.g. https://<owner>.github.io/modeltell/en/index.json.

Data Format

Raw outputs: data/{run-id}/{model-id}.json Lexical analysis: data/{run-id}/_lexical_analysis.json Syntactic analysis: data/{run-id}/_syntactic_analysis.json

All data is committed to the repo for full transparency and reproducibility.

Scope, accuracy & limitations

We try to be precise about what these numbers do and don't support. The full methodology & limitations page (in the frontend, route #/methodology) is the canonical reference. In short:

• Not an AI detector. This describes tendencies of model output in aggregate, not the provenance of any single text. Published AI detectors are unreliable and biased; don't use this to judge whether a person wrote something.
• No human baseline (yet). The lexical scores measure cross-model distinctiveness (TF-IDF vs the aggregate of all models), not "overuse vs humans." A matched human corpus is future work.
• Heuristic detection, partially validated. Patterns are regular expressions. A manual precision audit (validation/regex-precision.json) measured ~71% micro-precision with a wide spread - clean for some patterns (not-just-but, power verbs), but ~0% for parenthetical_aside and ~0.75 for tricolon/em_dash_pivot (they over-count in long lists). Recall is not yet measured, and the audit is single-annotator.
• Significance is pattern-level. Each frequency carries a 95% bootstrap CI and an FDR-corrected permutation test (model vs. field); full pairwise tests are not yet done.
• Task/prompt bias. One domain (business/marketing copy), one system prompt, default decoding - "model style" is entangled with "task style."

Contributing

PRs welcome - see CONTRIBUTING.md. In short: add patterns to patterns/definitions.json, models to src/runner/models.ts, prompts to prompts/catalog.json. Keep the pipeline zero-dependency and tsc --noEmit clean. (Pattern regexes are JavaScript - no Python-style (?i) inline flags.)

License

MIT

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Built by Third Shift Lab as an open research project.