Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add frabcd/codex-ai-game-studio --skill vertical-slicegit clone --depth 1 https://github.com/frabcd/codex-ai-game-studioWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/frabcd/codex-ai-game-studio/vertical-slice)<a href="https://agentmods.dev/skills/frabcd/codex-ai-game-studio/vertical-slice"><img src="https://agentmods.dev/badge/skills/frabcd/codex-ai-game-studio/vertical-slice/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/frabcd/codex-ai-game-studio/vertical-slice"><img src="https://agentmods.dev/badge/skills/frabcd/codex-ai-game-studio/vertical-slice.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00066 | $0.03927 |
| Opus 5.5 | $0.00026 | $0.01571 |
| Sonnet 5.5 | $0.00013 | $0.00785 |
| Haiku 4.5 | $0.00007 | $0.00393 |
Grade A, and why
vertical-slice scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
This is a copy
92% identical to vertical-slice — 168 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 360 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Port provenance: adapted from the pinned upstream source at
984023ddac0d5e27624f2baacde6105e45de375funder MIT; see the repository parity ledger for the exact path and blob.
Purpose
The vertical slice answers a different question from the concept prototype: "Can we build this full game loop at production quality, on schedule?"
Default use — run late in Pre-Production, after GDDs, architecture, and UX specs are complete. It is a near-production-quality build demonstrating one complete [start → challenge → resolution] cycle.
Post-pivot? If a PIVOT verdict from an earlier vertical slice sent you back to revise GDDs and architecture, run this again after revisions to re-validate. It can be run as many times as needed until a PROCEED or KILL verdict is reached.
It validates:
- The pipeline (can the team actually produce this quality of content?)
- Execution feasibility (are the architecture decisions correct for this game?)
- Fun survival (does the fun from the concept prototype survive full design?)
- Velocity (how long did this take? That's your real production rate estimate.)
Earlier in the project? If you haven't written GDDs yet and want to validate
whether the core idea is worth designing, run $ai-game-studio:prototype (concept prototype) instead.
Phase 1: Resolve Review Mode and Load Context
Resolve the review mode:
- If
--review [full|lean|solo]was passed → use that - Else read
production/review-mode.txt→ use that value - Else → default to
lean
See the installed Codex role-gate protocol for the full check pattern.
Read the following files to understand the full design intent:
AGENTS.md— tech stack and enginedesign/gdd/game-concept.md— core fantasy and game pillarsdesign/gdd/systems-index.md— MVP systems and their prioritiesdocs/architecture/architecture.md— layer structuredocs/architecture/control-manifest.md— technical rules for implementation- Key GDDs for the systems being sliced
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 360 lines · 66 tokens per session scan A a63266ba6854
vertical-slice is a skill published in the GitHub repository frabcd/codex-ai-game-studio (17 stars, last pushed 4d ago), licensed MIT. It adds 66 tokens to every session and 3,927 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 92% identical to vertical-slice, differing in 168 lines, and is treated as a copy.
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