Sewist StudioRunway Hackathon · The Masonic, SF · Sept 30, 2026
Runway Hackathon · Sept 30, 2026
Sewist Studio
See the dress before you cut the fabric.
A digital sewing room I built and run, rebuilt today on Runway so it shows you the finished garment, on the person you're sewing for, before the scissors touch the fabric.
Sabrina Dowling · solo builder · sewist.studio
Use → or Space for the next slide, ← to go back, or just scroll.
My daughter, in a dress I haven't sewn yet.
Hi, I'm Sabrina
I taught myself to sew from TikTok. Then I built the sewing room I needed.
I sew for my daughter. I have no teacher, a stash of fabric I love and a pile of vintage patterns. Sewist Studio is the web app I built for that. It's live at sewist.studio, and I built it solo.
I learned from TikTok
A video teaches a stitch, not my pattern. When I'm stuck at 10pm, there's no one to ask.
→ Wren, a live coach
Vintage instructions are confusing
"Understitch the facing," one tiny drawing, no explanation.
→ Wren explains each step
I can't picture it
I won't cut $30-a-yard fabric for a dress I can't see.
→ See it, move it, wear it
I want to mix and match
This bodice, that skirt. Would it actually work?
→ Pattern Mashup
I saw it online
A dress I love, but in fabric I already own.
→ Recreate This Look
My stash is everywhere
Patterns, fabric, thread and notions in drawers and bins.
→ Stash and projects
It's a live web app. Today I rebuilt all of its AI features on Runway and created 5 new ones, so it can show me the garment and talk me through it.
Why sewing, why now
Millions of people sew. AI hasn't shown up for them yet.
AI can write, draw and drive. It still can't sew, and the tools sewists use haven't changed: a paper envelope, tissue pattern pieces, and videos you can't ask a question. A new generation is learning online, and the biggest fabric chain, with its in-person classes, closed last year.
30M
sewists in the U.S., many of them teens and tweens
725M+
views on #SewingTikTok, back in 2021
~800
Joann fabric stores closed in 2025, and their classes with them
$5.3B
U.S. fabric, craft and sewing supply store sales, 2025
Sewists are learning from TikTok, YouTube and Reddit, with no one to ask when they're stuck. I looked for a tool that shows my pattern, in my fabric, on my kid, and answers my questions while I sew. I couldn't find one, so I built it.
Cutting into fabric doesn't undo. And my old AI preview drew the wrong dress.
You can preview a haircut or a paint color before you commit. Sewing has never had that: you cut, then you find out. Sewist Studio already had an AI preview, and it was confident, generic and wrong in the details a sewist checks first.
$18–40
per yard, gone if the cut is wrong
0
undo buttons at the cutting table
3
photos it takes: pattern, fabric, the person you sew for
Before
Input
Pattern and fabric photos
→
Text model
Turns them into one generic sentence
→
Image model
Draws the sentence and invents the rest
On Runway
Input
Same photos, labeled pattern, fabric, wearer
→
Runway API, reference-first
Draws from the photos. Words only pick the view.
My pattern and fabricOld preview: a stranger's dressRunway: my pattern, my fabric
Real inputs, photographed this morning
Four real envelopes. One real fabric.
These are the patterns I'm actually choosing between and the star-quilt cotton already in my stash. Pattern and fabric photos are already in every Sewist Studio account.
Simplicity 7460
Butterick 6494
Butterick 6714
Simplicity 9273
My fabric
What I built on Runway today
Four steps, from first look to last stitch.
Steps 1 to 3 follow one dress, Simplicity 9273 in my star cotton. Step 4 is the coach I talk to while I sew. Each step is a real feature in the app, on a different Runway model.
Step 1See it
My pattern, my fabric, on her.
Her, from a beach snapshot
Simplicity 9273, the puff-sleeve dress
My star-quilt cotton
→
Puffed sleeves, round neck, gathered skirt from the envelope. The star print from my fabric. Gemini 3 Pro Image via the Runway API
Same three photos, same prompt, on Runway's own gen4_image. It nails the dress in 36 seconds but loses her likeness, so for "on her" the app uses Gemini through Runway, with Gen-4 Image Turbo as its fast mode.
"Three photos I already had. Runway puts them together: her, in that pattern, in that fabric."
Step 1Does it work on any pattern?
Three of my envelopes, the same star fabric.
Each card is one pattern. On the left, what the old preview drew. On the right, what Runway drew from my photos. The old preview made up a different dress each time. Runway kept each pattern's shape and my fabric's print.
Simplicity 7460
Old: from words
New: from photos
Ruffle-collar smock. The star print scales correctly across the yoke.
Butterick 6494
Old: from words
New: from photos
Pinafore with a patch pocket, read straight from the envelope line art.
Simplicity 9273
Old: from words
New: from photos
Dress, view A. Same print, a completely different silhouette.
Step 1Print detail
A closer look at the print.
Upscaled 2x with Magnific so the star print reads clearly at the sleeve and yoke. An upscaler sharpens detail; it isn't proof of construction.
Plain resizeMagnific 2x
magnific_precision_upscaler_v2
Step 2Move it
It moves the way cotton moves.
The still, handed to Gen-4.5 for 5 seconds of motion, with an ElevenLabs sound effect of fabric in a breeze. In the app it's the Make it move button.
Top, Gen-4 Turbo: the skirt puffs out. Bottom, Gen-4.5: she sways and steps like a real kid, and the stars hold. gen4.5eleven_text_to_sound_v2
"I tested both models on every dress. Gen-4.5 moves like a child and keeps the print, so the app uses it."
Step 3Wear it
Her real twirl, in our real kitchen, in the dress I planned.
My phone videoAleph 2
It isn't a generated girl. It's my kid, my footage and my fabric. Aleph keeps every move and swaps in Simplicity 9273 in the star cotton.
Film a 5-second clip on a phone, in whatever she's wearing.
Dress the first frame. Gemini 3 Pro puts the planned dress on her in the clip's own first frame. Her face, pose and the room stay put.
Aleph 2 carries that frame through the whole clip, following her real motion.
Without step 2, Aleph copies the render's plain backdrop and the kitchen disappears. In the app: Cut Line Studio, Render photo, Try it on in motion. aleph2
Top, the phone video. Bottom, Aleph. Same frames, same kitchen.
Step 4Sew it
When you're sewing, your hands are busy. So the help talks.
Wren is a live Runway Character inside Sewist Studio. She has the project I pick open, searches my whole stash live, and can see my fabric when I turn the camera on. She answers about the dress on the table, not sewing in general.
Me, hands full of pins"What does step 7 mean by understitch?"
Wren"Press the seam allowances toward the lining. Then, from the right side, stitch through the lining and the allowances only, about 3 mm from the seam. That keeps the lining rolled to the inside so it won't peek out."
Wren's answer is written from her step-7 notes; the live call below is the real thing. Fictional coach, generated portrait. Runway Characters
Ask her: "My hands are full of pins. What does step seven mean by understitch?" Opens the real coach in a new tab. Pick the project, click Start a call with Wren, allow the mic (and the camera to show fabric), then close the tab to come back here.
Step 4Runway Characters
A coach with a face, a voice and your pattern's instructions.
Sewing help today is a TikTok you pause with a pin in your mouth, and it can't answer back. Wren is a real-time Runway Character: you talk, she looks at you and answers, about your project, while your hands stay on the fabric.
Hands-free
Live voice and video over WebRTC, with captions. Turn on the camera and she sees the fabric: "Is this the right side?"
Grounded
She opens the project I pick and has two live tools, get_project and search_stash: "Do I have enough of the star print?" She answers from my data, not sewing in general.
Careful
Her persona rules: one action at a time, two to four sentences, warn before cutting or clipping, and never invent a measurement.
Built fast
Portrait, persona, voice and knowledge created from Claude Code through the Runway Dev MCP. In the app on Runway's React SDK, with the session made server-side.
runway DevCharactersModel RoutersWorkflowsManageProject: Sewist Studio
Wren, Sewist Studio Coach Character · Ready
Character ID
2666d58f-10c8-4d81-ade5-4c732dda8917
Voice
Clara, soft (Runway live preset)
Image
Generated portrait of a fictional teacher, gemini_image3_pro
Personality
Thirty years teaching garment sewing, talking live to someone whose hands are full of fabric and pins.
Two to four spoken sentences, then stop
One physical action at a time, in the order the hands do it
Warn before anything irreversible: cutting, trimming, clipping
Never invent measurements; ask for them
Saved opening
"Hi, I'm Wren. I've got your Beach Day Sundress open. Where are you up to? Just tell me the step number, and keep your hands on the fabric."
Live opening
"Hi, I'm Wren. I've got your [project] open. Where are you up to? You can turn your camera on and show me." Sent by the app on every call, with the picked project, its pattern and fabric yardage folded into her personality
Live rules
Use get_project and search_stash, never guess yardage or what I own. If the camera is on, say what she sees first. Offer a one-line recap near the 5-minute limit.
Knowledge 1 document
Document
Current project: Beach Day Sundress
Holds
Fabrics from the stash, cutting notes, 13 steps, a glossary
Step 7
Understitch the lining, 3 mm from the seam, stopping 2 cm short of the square-neck corners
In the app /sewing-coach
Client
Runway React SDK, @runwayml/avatars-react: call, camera toggle, live captions, 5-minute countdown
Session
coach-session edge function calls /v1/realtime_sessions, folds the picked project into Wren's personality, keeps the Runway secret on the server
Tools
get_project, search_stash, answered by the browser with the signed-in user's own row-level-secured queries
Every AI feature rebuilt on Runway today, plus 5 new ones.
Each card shows what went in and what Runway made. Every one now starts from real photos: the pattern, the fabric and the person you're sewing for.
Old app
On Runway
Visualizer Rebuilt
BeforeWrote the pattern up as a sentence, then drew the sentence. A stranger's dress in fabric I don't own.
NowSends the envelope, the fabric and her photo to Runway. Photo, flat, or on her.
Runway API · gemini_image3_pro · gen4_image_turbo
Inspiration
On Runway
Recreate This Look Rebuilt
BeforeUsed the inspiration photo, through a general image model, with no fabric or wearer.
NowRebuilds the look from the photo in fabric I own, on her.
Runway API · gemini_image3_pro
Envelope in
On Runway
Pattern Mashup Rebuilt
BeforeDescribed each pattern piece in words, so the pieces came out invented.
NowSends the envelopes or clipped pattern pieces as the actual shapes.
Runway API · gemini_image3_pro
Still
On Runway
Make it move New
BeforeDidn't exist.
NowTurns any preview into a 5-second video of the dress moving.
Runway API · gen4.5
Phone video
On Runway
Try it on in motion New
BeforeDidn't exist.
NowPuts the planned dress on her in a real phone video, keeping her motion and the room.
Runway API · aleph2 · gemini_image3_pro
Cutting plan
On Runway
Cut Line Studio render New
BeforeDidn't exist.
NowPaints each panel of my cutting plan with the real fabric photo, then photographs the finished garment.
Runway API · gemini_image3_pro
My fabric
On Runway
Mood Board New
BeforeDidn't exist.
NowVibe boards from my fabric and pattern. A Runway Model Router picks the cheapest model that can do it: 1 credit a tile, vs 20 for a hero render.
Runway API · Model Router → muse_image
On Runway
Sewing Coach New
BeforeDidn't exist.
NowWren, a live coach who knows the project, searches your stash and sees your fabric on camera.
Runway API · Runway Characters + React SDK
Under the hood
One Runway project behind every feature.
One live Character, one Model Router, and nine API endpoints behind Sewist Studio's edge functions. One API gives me the right model for each job, from Aleph 2 and Gen-4.5 to Gemini 3 Pro Image.
runway DevCharactersModel RoutersWorkflowsManageProject: Sewist Studio
sewist-studio Model Router · v2
Optimize for
Cost
Models
muse_imageseedream5_liteallowlist only
Fallback
Switches model when one is at capacity
Mood Board
1 credit a tile, 4 for a board. A hero render is 20.
Async video edge functions
Why
Gen-4.5 and Aleph can outrun a Supabase edge function's time limit
How
Submit a Runway task, then poll /tasks/{id} every 5 seconds
API endpoints the app calls api.dev.runwayml.com/v1
Eight Runway models and products, each shipped as a feature.
Step
Runway build
Model
Where in the app
Credits
Time
See
Reference-first garment render
gemini_image3_pro
Look render, Visualizer, Recreate, Mashup
20
27–34s
See
Fast reference render
gen4_image_turbo
Visualizer, fast mode
2
17s
See
Print close-up
magnific_precision_upscaler_v2
Print detail
25
59s
Move
Garment in motion
gen4.5
Visualizer, Make it move
60
107s
Move
Fabric sound
eleven_text_to_sound_v2
Hero video
5
12s
Wear
Motion try-on, with first-frame dressing
aleph2 + gemini_image3_pro
Cut Line Studio, Try it on in motion
about 160
about 2 min
Sew
Live sewing coach
Runway Characters + React SDK
Sewing Coach page
per session
real time
Plan
Mood boards
Model Router → muse_image
Mood Board
about 1
38s
If a judge asks
Photos first, words second. Every sentence we send points at one of the photos. One stray sentence, "on a dress form", once out-voted "worn by her". It was a one-line fix, and it's why the rule exists.
Print scale. Each fabric reference carries its print type, bolt width and repeat, so the checks come out the right size on the body.
Models picked by testing. On an earlier gingham dress, Gen-4 Turbo lost the hem halfway through the clip and Gen-4.5 kept it. On the star dress both held the print, and Gen-4.5 moved more naturally.
Async video. Gen-4.5 and Aleph can outrun a Supabase edge function's time limit, so both submit a Runway task and the app polls every 5 seconds.
Cut Line render, found by testing. Plans drawn as flat color blocks got copied as fabric color: a star bodice came back solid navy. Painting each panel with the real fabric photo fixed it, so I shipped that to the app today. The render on these slides used the app's look-render prompt from a script, because the star cotton isn't in my stash yet.
Limits. Aleph outputs 612x1088, so fine prints soften; the bold star print holds up well. Aleph invents the back view, because the still only shows the front, so the demo clip is the first 5 seconds while she faces the camera.
Close
No scissors until you're sure.
See it before you cut. See it move. See it on her, in her real life. Then get talked through the sewing.
Every AI feature in Sewist Studio rebuilt on Runway today, plus 5 new ones. All from photos sewists already take.
