A set of instructions for automating LosslessCut, a video, audio, and subtitle trimming application.

It helps trim media, preserve separate streams, choose suitable cut points, and process multiple segments from saved cut data.

It explains how to cut media quickly without re-encoding when the cut matches a suitable video keyframe, and when a small re-encode is needed.

losslesscut — Skill for Claude Code by alivirgo

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.

Any agent

npx skills add alivirgo/Major-AI-Skills --skill losslesscut

Clone the repo

git clone --depth 1 https://github.com/alivirgo/Major-AI-Skills

Made for: Claude Code.

Or install mas-video-lab, the plugin that ships this one along with the rest of its 7 skills.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/alivirgo/major-ai-skills/losslesscut/github.svg)](https://agentmods.dev/skills/alivirgo/major-ai-skills/losslesscut)

Your own site

<a href="https://agentmods.dev/skills/alivirgo/major-ai-skills/losslesscut"><img src="https://agentmods.dev/badge/skills/alivirgo/major-ai-skills/losslesscut/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/alivirgo/major-ai-skills/losslesscut"><img src="https://agentmods.dev/badge/skills/alivirgo/major-ai-skills/losslesscut.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 28 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,872 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.

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.

Model	Per session	Once invoked
Fable 5.1	$0.00028	$0.01872
Opus 5	$0.00014	$0.00936
Sonnet 5	$0.00006	$0.00374
Haiku 4.5	$0.00003	$0.00187

Measured today against content hash 392e748cf37e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

losslesscut scanned grade A with 1 finding 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 today.

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.

Runs shell commandslowCapability

Expected in a hook, worth knowing in a rule or an instructions file.

res = subprocess.run(cmd, capture_output=True, text=True)

plugins/mas-video-lab/skills/losslesscut/SKILL.md · 160 lines

How it starts

The opening of the file, as written. The whole thing — 160 lines — stays where its author put it; the contents beside it link to each section on GitHub.

LosslessCut Stream Editor AI Skill Guide (Claude)

Overview & Engine Architecture

LosslessCut is a fast, lossless video, audio, and subtitle trimming application powered by an Electron frontend and FFmpeg stream-copying (-c copy) engine. Claude operates as a Multimedia Streaming and Forensic Editing Specialist, specializing in GOP (Group of Pictures) keyframe alignment, Smart Cut boundary re-encoding, lossless multi-track stream muxing, and programmatic segment batch cutting (.llc JSON format).

Lossless Stream Copying & GOP Engine

┌─────────────────────────────────────────────────────────────┐
│                 LosslessCut Stream Processing               │
│                                                             │
│  GOP (Group of Pictures) Keyframe Architecture              │
│  [ I-Frame (IDR) ] ─── [ B-Frame ] ─── [ P-Frame ] ─── [ I-Frame ]│
│        ▲                                                     │
│        └── Safe Lossless Cut Point (No Re-encoding Needed)   │
│                                                             │
│  Cut Modes & Engine Mechanics                               │
│  ├── Keyframe Cut Mode (Fastest, snaps to nearest I-frame)  │
│  ├── Smart Cut Mode (Re-encodes strictly boundary GOPs)     │
│  └── Multi-Track Stream Preservation (Extract / Merge Audio)│
└─────────────────────────────────────────────────────────────┘

Operational Capabilities & Agent Directives

Keyframe Alignment & GOP Analysis: Diagnose video playback freezes and black frames caused by cutting on delta frames (P/B-frames) instead of Instantaneous Decoder Refresh (IDR) keyframes.
Smart Cut Configuration: Advise when to apply Smart Cut (re-encoding only the fractional GOP between the chosen frame and nearest I-frame) for frame-exact trimming without full video re-compression.
Lossless Segment Automation: Programmatically generate LosslessCut project files (<filename>-proj.llc) containing millisecond-accurate cut segment timestamps and labels.
Multi-Track Stream Extraction: Author CLI commands to split and remux secondary audio commentaries, embedded closed captions, and chapter metadata tracks without quality degradation.

Read the full file on GitHub · 160 lines

Files

What ships with it

2 files 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.

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.

today Changed · -14 tokens per session 392e748cf37e
12d ago First seen · 160 lines · 42 tokens per session scan A 009f4739650d

Subscribe to this mod's changes

losslesscut is a skill published in the GitHub repository alivirgo/Major-AI-Skills (1 stars, last pushed today), licensed MIT. It adds 28 tokens to every session and 1,872 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 1 finding (runs shell commands). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

Creative and media agent-skills agentic-skills ai-agent-skills ai-agents ai-coding claude cross-platform ffmpeg gop-alignment keyframe-cutting losslesscut stream-copy

losslesscut

Getting it into your agent

Wrote this? Show the measurements

What it costs to keep this loaded

Grade A, and why

Runs shell commandslowCapability

How it starts

LosslessCut Stream Editor AI Skill Guide (Claude)

Overview & Engine Architecture

Lossless Stream Copying & GOP Engine

Operational Capabilities & Agent Directives

What ships with it

What this file has done since we first saw it

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