Rabbithole

Example: CGPA — Cat Girl Program Analysis

forum technical dark theme Live at: cgpa.isarabbithole.com

1. Overview & Concept #

CGPA (Cat Girl Program Analysis) is one of the most-cited Rabbithole demo sites, and arguably the most successful illustration of what happens when you give the generator a deeply strange, hyper-specific intersection of subcultures. The site presents itself as a long-running phpBB forum — circa 2006 in aesthetic — populated entirely by cat girls who are also serious researchers in static program analysis, type theory, abstract interpretation, and formal verification.

The concept was born from a simple observation: niche intersection prompts produce coherent, richly-detailed sites. A generic “programming forum” prompt yields a generic site. A “dark phpBB forum where anthropomorphic cat girls debate the relative merits of the Cousot & Cousot '77 fixpoint framework vs. later refinements” prompt forces the model to commit hard to a personality, a visual style, and a domain of expertise — and the result is far more interesting to read.

The site is not satirical toward the CS content. The program analysis discussions are technically substantive. The absurdity is purely in the juxtaposition: the forum members write with the earnestness of academic researchers, but their usernames are things like abstract_paws and their post signatures contain ASCII art of cats.

2. The Forum Aesthetic #

The visual design of CGPA is a faithful reproduction of a mid-2000s phpBB installation with a custom dark skin. The key CSS parameters baked into the seed prompt are:

The overall effect is that familiar late-noughties darkness — the kind of forum skin that was genuinely considered sophisticated circa 2007 — combined with the structural chrome of phpBB: board index with subforum descriptions, post counts, “Last post by” metadata, sticky threads marked with a push-pin icon (rendered as a Unicode character), and pagination at the bottom of thread views.

Here is a rendered preview of the CGPA board index as it appears when generated by Rabbithole:

3. Recurring Users & Rank Structure #

The seed prompt establishes four primary personas who appear throughout the generated site. Because each page is generated in isolation, the personas need to be embedded in every page prompt — but having them defined once in the seed means the initial index page sets up a strong enough template that linked pages inherit their character through prompt chaining.

The rank system also includes several implied titles visible in user profiles on generated member pages: Galois Connection Groupie (100+ posts), Monotone Function Fancier (500+ posts), Abstract Domain Goddess (admin-only), and Verified by Coq (a special flair awarded for contributing a formally verified result to the community repo).

4. Subforum Structure #

The seed prompt defines eight subforums across three categories:

5. The Seed Prompt #

The seed prompt for CGPA is longer than average — approximately 420 words — because it needs to establish both visual style and domain expertise simultaneously. Here is the full prompt as used:

A dark phpBB-style internet forum circa 2006 called "CGPA — Cat Girl Program Analysis"
(cgpa.isarabbithole.com). The forum is populated entirely by cat girls who are serious
researchers in static program analysis, type theory, abstract interpretation, and formal
verification. The tone is earnest and technical — not satirical. The CS content is real
and accurate.

VISUAL DESIGN: Dark phpBB skin. Background #0d0d0d, post background #111111, text #cccccc,
links #7ab8f5, borders #222/#333. Usernames in pink (#ff9eb5) for members, red-orange
(#ff6b6b) for admins, blue (#7ecbff) for moderators. Rank titles in muted lavender
(#b39ddb). Font: Verdana, Tahoma. No JavaScript. Render as a board index page showing
all subforums with post counts and last-post metadata.

SUBFORUMS (3 categories):
General: "Introductions & Off-Topic", "Resources & Paper Drops"
Abstract Interpretation: "Foundations & Classical Papers", "Widening & Narrowing",
  "Numeric Domains"
Type Theory & Verification: "Coq & Proof Assistants", "Dependent Types",
  "Certified Static Analyzers"

USERS (embed in the page as last-post attributions):
- Nyanko_Fixpoint (admin) — rank: "Abstract Domain Goddess" — cold, precise, authoritative
- Felis_Monad (mod) — rank: "Fixed-Point Fanatic" — pedantic, thorough, pro-polyhedra
- mittentype (member) — rank: "Kleene Chain Climber" — type theory obsessive
- abstract_paws (member) — rank: "Lattice Kitten" — thoughtful beginner

STICKY THREADS visible in board index (show in "Foundations" subforum):
- "[STICKY] Welcome to CGPA — READ BEFORE POSTING" by Nyanko_Fixpoint
- "[STICKY] Cousot & Cousot '77 reading group megathread" by Nyanko_Fixpoint

Board tagline: "Where the lattice meets the litter box"
Show forum statistics: 47 members, 14,823 posts, 1,102 topics.
Include a "Who is online" section at the bottom.
Generate at least 10 local links to individual thread pages, member profiles,
subforum index pages.

6. Notable Generated Threads #

The following threads were generated as linked pages from the board index and have become reference examples of Rabbithole's ability to produce technically dense, contextually consistent content.

6.1 Cousot & Cousot '77 Reading Group Megathread

The single most impressive generated page on CGPA. The thread spans a simulated 12-session reading group working through the landmark 1977 paper “Abstract interpretation: a unified lattice model for static analysis of programs by construction or approximation of fixpoints.” Each session is a separate post, attributed to different users.

A representative excerpt from session 3, posted by Felis_Monad:

6.2 “Widening operators — are we doing it wrong?”

A 47-post thread in the Widening & Narrowing subforum sparked by abstract_paws asking why her interval analysis was diverging. The thread correctly identifies the standard interval widening operator, explains why naive widening loses precision, introduces threshold widening as an alternative, and includes a worked example comparing the two on a simple loop. Nyanko_Fixpoint makes a single post near the end correcting a subtlety about the narrowing phase, and the thread resolves cleanly.

6.3 “Coq proof tips: when does auto actually work?”

A 31-post thread cataloguing practical Coq proof strategies. Notably accurate: the discussion of when auto vs. eauto vs. tauto should be used, the explanation of hint databases, and a worked proof of a monotonicity lemma for the sign abstract domain all appear to be correct. The generated code blocks compile (several users have reported testing them).

6.4 Other Notable Threads

• “Galois connections vs. Galois insertions — does the difference matter in practice?” — Initiated by abstract_paws, answered definitively by Nyanko_Fixpoint in a single 600-word post that has been quoted on at least one real program analysis reading list.
• “Is there a cat girl mascot for CompCert?” — Off-topic thread in Introductions that nonetheless spawned a technically accurate discussion of CompCert's verified compilation guarantees and the semantics preservation theorem.
• “Polyhedra domain: is Parma Polyhedra Library still the best option?” — A serious benchmarking discussion. Mentions ELINA, Apron, and PPL with accurate characterizations of their trade-offs.
• “What even IS a trace semantics?” — A beautifully clear explanation of collecting semantics via trace sets, written as a forum post addressed to a newcomer. Regularly cited as a “surprisingly good introduction” to the topic.

7. Technical Accuracy Without Web Tools #

CGPA deliberately runs without web search tools enabled — web_tools = false in its configuration. This was intentional: program analysis is a sufficiently well-represented field in LLM training data that the model produces accurate content from parametric knowledge alone, and disabling web tools makes every page generation significantly faster and cheaper.

The results have been mostly positive:

The one recurring failure mode is that the generated forum feels frozen in time — the latest papers discussed are typically from before the model's training cutoff, even though the forum's in-universe date stamps span 2006–2010. This is actually thematically appropriate for the era being simulated, but it means CGPA wouldn't work as well for a forum about, say, recent LLM architecture papers.

8. Lessons for Forum-Style Sites #

CGPA is the most-studied Rabbithole example for forum-style sites. Here are the key learnings:

8.1 Persona depth pays forward

The four named users were each given exactly three properties in the seed: role, rank title, and a one-sentence personality description. This minimal investment yields enormous returns — every generated page that includes these personas produces consistent, recognizable character voices. Felis_Monad is always pedantic. abstract_paws always asks sincere questions. Nyanko_Fixpoint always posts once, precisely, and ends the debate. The model interpolates convincingly from minimal input.

8.2 Subforum structure as navigation scaffold

Defining subforums explicitly in the seed prompt gives the URL mapper a natural hierarchy. The generated board index links to /subforum/abstract-interpretation/foundations.html, /thread/widening-operators-are-we-doing-it-wrong.html, etc. These in turn link deeper. The subforum structure means the site explores a consistent topic space rather than drifting off-topic with each hop.

8.3 Post counts as verisimilitude signal

Including realistic post counts, topic counts, and “last post by” metadata in the seed prompt instructs the model to generate these on every page. A forum with “4,518 posts” in a subforum feels inhabited; a forum with no counts feels hollow. This costs nothing in the prompt but dramatically affects the sense of a living community.

8.4 The tagline anchors the aesthetic

“Where the lattice meets the litter box” does more work than it appears to. It signals to the generator that both the mathematical content and the cat-girl aesthetic are load-bearing — neither is decorative. Without a tagline, generated pages sometimes drift toward pure technical content and lose the distinctive character.

8.5 Prompt the absurdity; don't prompt the jokes

The seed prompt never explicitly asks the model to be funny. It establishes the absurd premise and then asks for earnest technical content within it. The humor emerges naturally from the juxtaposition. Prompting for jokes directly typically produces labored, self-conscious humor. Prompting for sincerity within an absurd frame produces something much more charming.

8.6 Forum chrome is easy to template but hard to vary

The biggest limitation of CGPA is that most thread pages look structurally identical — same post card layout, same sidebar, same pagination. This is authentic to phpBB but can feel repetitive. Future work: add more variation to thread page layouts (sticky posts vs. normal posts, locked thread notices, quote nesting) by encoding these variants explicitly in thread-page prompts.

8.7 Link to member profiles early

Member profile pages are some of the most delightful generated content on CGPA. Because the profile page prompt includes the persona description plus all established site context, the generator produces detailed “about me” sections, post history excerpts, and even custom profile fields (favorite abstract domain, current Coq version, reading list). Don't forget to link to profiles from every post signature block.

9. Related Examples & Further Reading #

See also:

• All Examples — full gallery of Rabbithole demo sites
• Configuration Reference — web_tools, seed_prompt, cache_ttl
• Architecture — how page isolation works and why prompts must be self-contained
• Getting Started — build your own forum-style site

The CGPA source configuration is available in the Rabbithole GitHub repository under examples/cgpa/.