The brief is evidence, not decoration
Most “AI video editor” demonstrations begin with a sentence and end with an MP4. The interesting work in between disappears. That is convenient for a novelty demo and uncomfortable for real editorial work. A request such as “turn these interviews into a two-minute launch story” contains decisions about audience, protected statements, pacing, audio continuity, aspect ratio and what the speaker must never be made to imply. Timeline Studio's Skill preserves the original request as the creative brief and separates what was stated, what can be inferred from the media, what was defaulted and what remains unresolved.
For automatic editing, the Skill first classifies the material and delivery goal. It inspects the named files rather than sweeping a folder, records source-time keep, remove, shorten and reorder decisions, and attaches reasons and confidence. That makes a rough cut reviewable before it becomes a mysterious sequence. If a decision would materially change the story, the Skill asks; if duration, dimensions, audio presence or scene changes can be measured, it measures them instead of asking the user to do clerical work.
Analysis is routed to the smallest useful tool
Video analysis is not one model call. Speech, OCR, camera motion, subject motion, depth, repeated shots and compression damage answer different editorial questions. The Skill inventories local and pinned capabilities, then chooses the smallest model chain that closes the current evidence gap. It does not download every model “just in case,” and it records the runtime, model revision and fallback used for a result.
For a professional automatic edit, representative frames and speech are only the start. Global optical flow can reveal a camera move; subject-region flow can distinguish that move from a person crossing a static frame. A reference-video remake needs repeated-shot detection, source reuse, speed curves, holds, transitions and audio timing—not merely similar colors. Stabilization comes before tracking or enhancement because motion estimates built on a shaking frame contaminate everything downstream. Remote generation is considered only when inspection shows that supplied or legitimately sourced footage cannot express a required shot, and paid or privacy-sensitive jobs require separate approval.
The timeline is the contract
The portable .timeline archive is a ZIP containing project.json and the project's media. That file is the durable handoff between the Agent, the editor and another machine. When an operation is supported by the command layer, the Skill does not hunt for a button or drag a handle. It inspects stable clip IDs, source offsets, track placement and the current revision, then describes the intended change as a schema-versioned operation.
Before writing, the structural validator catches malformed transport data and project.diff runs the same registry, revision checks and reducers used by the real write. A stale base revision fails instead of overwriting a newer edit. Reusing an applied operation ID becomes a no-op instead of moving a clip twice after a retry. If one operation in a batch fails, the batch writes no half-edited archive. This is less theatrical than a cursor moving by itself, but it is far closer to how dependable editing software should behave.
npm run agent -- project.inspect launch.timeline node skills/edit-timeline-studio/scripts/validate_edit_plan.mjs launch-plan.json npm run agent -- project.diff launch-plan.json npm run agent -- project.run launch-plan.json npm run agent -- project.inspect launch-v2.timeline
Narration sets the clock
The newest voiceover work changed a deceptively important assumption: picture timing should follow accepted speech, not force speech into a guessed runtime. Timeline Studio's Skill treats narration as an audio spine. Chinese and mixed Chinese-English narration can use the editor's owned Kokoro multi-lang browser bundle with stable built-in speakers. More importantly, the script is synthesized as short phrase-level clips from the outset.
A comma is a valid breathing boundary. So are semicolons, colons, sentence endings and intentional pauses, unless splitting would break a name, number, URL or bilingual phrase. Each segment is a physical archived audio asset linked to its matching caption. Adjacent phrases normally keep roughly half a second to eight-tenths of a second of timeline space. The Skill measures the accepted clips and adapts pictures and captions around them. It does not generate one long, metallic performance, chop it into ranges and accelerate the result to hit an arbitrary fifteen seconds.
Verification is equally concrete. The complete narration is heard at normal speed. Phrase stems are checked for loudness consistency, clipped releases and unnatural cadence. Stereo placement must delay every channel, not just the first. A visible caption must resolve to audible speech for its active interval, while existing source speech must not receive a duplicate voiceover.
Promotion needs cases, not feature confetti
When the request is promotional, the Skill does not default to kinetic typography over a feature checklist. It builds a problem-to-transformation-to-proof-to-action narrative and looks for several visually distinct, supportable cases. Each case needs a setup, a visible product action, an observable result and a reason it contributes to the final promise. Customer names, performance claims and outcomes cannot be invented merely to make the edit feel larger.
The same discipline applies to website walkthroughs. The Skill rehearses the authorized route, builds a page and flow coverage manifest, and does not describe gated behavior it could not inspect. Attention treatments are chosen deliberately: magnify dense evidence, underline exact text or frame a precise control. A callout waits until the camera move stops. The result should direct a viewer's eye, not fill every empty region with motion.
For highlights and remakes, accuracy alone is not enough. Candidate moments receive dramatic roles—setup, rise, pre-impact, peak and aftershock—so the cut has a dominant payoff. The decisive frame is protected rather than buried in a flat sequence of equally loud moments.
Browser and command line each keep their honest job
The command runner can inspect projects, tracks, clips and transcripts; import probed and hashed visual or audio media; apply transactional timing, caption, transition, property, track-state and ratio changes; and preserve portable media while writing a new archive. Its first local renderer covers the documented Visuals, Voiceover and Music subset and verifies the H.264/AAC MP4 with ffprobe.
It does not pretend to cover everything. AI generation, automatic captions, rich overlays, stickers, effects, separated source audio and advanced composition still use the editor when required. A project containing unsupported render features is rejected rather than flattened into an incomplete video. Browser operation is therefore a compatibility and perception layer, not a falsely deterministic public API. The Skill reads the actual local server URL, handles visible state carefully, exports a portable archive and verifies files on disk instead of assuming a timed-out download failed.
Done means reopened, decoded and heard
A JSON summary can prove that a caption begins at 4.2 seconds. It cannot prove that the first syllable is audible, that a transition flashes, or that the final frame communicates the intended payoff. The Skill verifies both structural and perceptual facts. It rereads track state, checks every boundary, plays the timeline continuously, verifies caption-to-speech links and distinguishes embedded video audio from explicit source-audio lanes.
For a completed editing request, the output contract is intentionally demanding: an absolute output directory, a portable .timeline archive and the rendered video when rendering was requested. The archive is reopened in Timeline Studio. The main Visuals track must appear, archived media must resolve and the first frame must render. The video is fully decoded and checked for container, dimensions, duration, visible overlays or captions and a real audio stream.
This is the difference between automation that reports success and editorial tooling that earns trust. The Skill does not make the Agent the final authority. It makes the Agent's work inspectable, repeatable and easy to continue.