FableCut CLAUDE.md

Repository instructions for FableCut, a browser-based video editor that coding agents control by editing a project timeline or using its API and MCP tools.

In plain words
What is it for?
Starting the editor, reading or patching timeline JSON, using its REST or MCP interface, and making browser video edits.
Why use it?
They explain how the editor represents video projects and how agents can inspect, change, and preview edits without manually operating the interface.

Instructions file

Install

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.

agentmods
npx agentmods add instructions/ronak-create/fablecut/claude-md
Clone the repo
git clone --depth 1 https://github.com/ronak-create/FableCut
Per session 8,937 This file is loaded in full into every session.
When invoked 8,937 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.08937 $0.08937
Opus 5 $0.04469 $0.04469
Sonnet 5 $0.01787 $0.01787
Haiku 4.5 $0.00894 $0.00894

Measured 2d ago against content hash 6ad47c1febf4, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

FableCut CLAUDE.md 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 2d 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.

CLAUDE.md · 563 lines

How it starts

The opening of the file, as written. The whole thing — 563 lines — stays where its author put it; the contents beside it link to each section on GitHub.

FableCut — browser video editor, drivable by Claude Code

A production-style non-linear video editor (Premiere-style) that runs in the browser. An AI agent edits videos by editing project.json (or calling the REST API / MCP tools) — the open browser UI live-reloads within ~150 ms via SSE. No build step, no npm dependencies.

This file is the master manual. Any model pointed at this document (or at the fablecut_docs MCP tool, which returns it) has everything needed to fully drive the editor.

MCP connection (preferred — works from any session, any directory)

Register the MCP server (mcp-server.js) once at user scope as fablecut: claude mcp add -s user fablecut -- node "<path-to>/fablecut/mcp-server.js". Every Claude Code session then has these tools:

  • fablecut_status — auto-starts the editor server, returns URL + project summary. Call first.
  • fablecut_docs — returns this document (section: "…" returns only matching ## sections).
  • fablecut_get_project / fablecut_set_project — read / replace the timeline JSON. fablecut_get_project {compact:true} returns a one-line-per-clip summary instead.
  • fablecut_patch_project — apply targeted ops (add/update/remove clip/media, set project fields) without round-tripping the document. Prefer this for edits.
  • fablecut_import_media — copy a local file into ./media/ and register it.
  • fablecut_analyze_reference — turn a reference video into an edit blueprint (shots, beats, BPM, energy, drop) + extract its music. See "Remake a reference video".

Token-efficient editing (important for agents)

Editing via full get→modify→set costs thousands of tokens per change. Cheaper:

  1. Plan from fablecut_get_project {compact:true} (≈10× smaller than the JSON) and fablecut_status — fetch the full JSON only to inspect exact keyframes.
  2. Edit with fablecut_patch_project ops — send only what changes, e.g. {ops:[{op:"updateClip", id:"c_v2", set:{props:{filterPreset:"noir"}}}]}. It re-reads the latest document internally, so it is merge-safe by design (no CONFLICT dance) and never destroys concurrent UI tweaks.
  3. Docs: request fablecut_docs {section:"schema"} (or "Recipes", "Remake", …) instead of the whole manual; skip it entirely if the schema is already in context.
  4. Media questions (duration, fps, size): read them from the registered media entries — don't shell out to ffprobe; the browser probes and writes them back.
  5. Batch related changes into ONE patch call (ops apply in order, one revision bump).

Read the full file on GitHub · 563 lines

Changes

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.

  1. 2d ago First seen · 563 lines · 8,937 tokens per session scan A 6ad47c1febf4

Subscribe to this mod's changes

FableCut CLAUDE.md is an instructions file published in the GitHub repository ronak-create/FableCut (643 stars, last pushed 4d ago), licensed MIT. It adds 8,937 tokens to every session, about $0.0447 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.