* perf(mothership): virtualize chat transcript and isolate input from stream re-renders Long chats rendered every message into the DOM with no windowing — a custom rAF "progressive list" only smeared the mount cost across frames without capping it. At ~1000 messages this was 52k DOM nodes and a 21s main-thread block on open, and the input toolbar re-rendered on every streamed token. - Virtualize the message list with @tanstack/react-virtual using dynamic measureElement, stable per-row keys, and a tuned size estimate. Only the visible window mounts, so load cost is now flat regardless of transcript length. Remove the now-redundant useProgressiveList hook. - Memoize UserInput and stabilize its callbacks (useCallback in MothershipChat and home) so streaming ticks no longer re-render the entire input toolbar. - Keep the existing useAutoScroll for streaming stick-to-bottom (it reads the virtualizer's real scrollHeight) and add a per-chat scrollToIndex for initial positioning before paint. Measured on a cloned 1032-message chat: time-to-rendered 26.3s -> 1.7s, main-thread blocked 21.4s -> 0.8s, DOM nodes 52k -> 1.4k, typing-while- streaming p-max 104ms -> 26ms. Adds scripts/perf/ harness used to validate. * address review: pending-chat scroll, flash on tail unmount, empty-row gap, per-role estimate - Pending-chat initial scroll (Cursor, high): seed the scrolled-chat guard with a unique sentinel so a not-yet-persisted chat (undefined chatId) with messages still scrolls to bottom instead of being treated as already-scrolled. - Streaming-row flash (review of virtualization): pin the last row in the rendered window via rangeExtractor so scrolling it out of the overscan window and back mid-stream can't unmount/remount it and re-fire the reveal fade. - Empty assistant row gap (Greptile): move the row gap from the virtual-item wrapper into the row content so a null-rendering (finalised, empty) assistant turn collapses to zero height instead of leaving a pb-6 blank slot. - Per-role row-height estimate instead of a single blended constant, so the scrollbar drifts less as off-screen rows resolve. - Drop the scripts/perf harness from the PR. * fix(mothership): preserve user-row top spacing in virtualized layout Restoring pt-3/pt-2 on the user row keeps the exact inter-row rhythm from the old space-y-6 layout: assistant→user gaps stay 24+12px and user→assistant stay 24px, instead of becoming uniform when the gap moved to per-row pb. * fix(mothership): don't re-scroll when a pending chat persists its id The per-chat initial-scroll guard treated undefined→persisted-id as a chat switch and scrolled to the bottom again, yanking the viewport down if the user had scrolled up mid-stream. Treat that transition as the same conversation: adopt the id without re-scrolling. Genuine chat switches (id→different id) still re-scroll.
The open-source AI workspace where teams build, deploy, and manage AI agents. Build conversationally, visually, or with code. Connect 1,000+ integrations and every major LLM to automate real work.
Build everything in Mothership
Your AI command center. Describe what you want in plain language. Mothership knows your entire workspace and takes action: building agents, running them, querying data, and more.
Create files and documents
Generate documents, reports, and presentations from a single prompt, grounded in your workspace data.
Ground agents in your knowledge
Upload documents to a knowledge base and let agents answer questions from your own content.
Structured data with Tables
A database, built in. Store, query, and wire structured data into agent runs.
Build visually with Workflows
Prefer a canvas? Design agents block by block in the visual builder, and let Copilot generate blocks, wire variables, and fix errors from natural language.
Quickstart
Cloud-hosted: sim.ai
Self-hosted: NPM Package
npx simstudio
Note
Docker must be installed and running on your machine.
Options
| Flag | Description |
|---|---|
-p, --port <port> |
Port to run Sim on (default 3000) |
--no-pull |
Skip pulling latest Docker images |
Self-hosted: Docker Compose
git clone https://github.com/simstudioai/sim.git && cd sim
docker compose -f docker-compose.prod.yml up -d
Sim also supports local models via Ollama and vLLM. See the Docker self-hosting docs for setup details.
Self-hosted: Manual Setup
Requirements: Bun, Node.js v20+, PostgreSQL 12+ with pgvector
- Clone and install:
git clone https://github.com/simstudioai/sim.git
cd sim
bun install
bun run prepare # Set up pre-commit hooks
- Set up PostgreSQL with pgvector:
docker run --name simstudio-db -e POSTGRES_PASSWORD=your_password -e POSTGRES_DB=simstudio -p 5432:5432 -d pgvector/pgvector:pg17
Or install manually via the pgvector guide.
- Configure environment:
cp apps/sim/.env.example apps/sim/.env
# Create your secrets
perl -i -pe "s/your_encryption_key/$(openssl rand -hex 32)/" apps/sim/.env
perl -i -pe "s/your_internal_api_secret/$(openssl rand -hex 32)/" apps/sim/.env
perl -i -pe "s/your_api_encryption_key/$(openssl rand -hex 32)/" apps/sim/.env
# DB configs for migration
cp packages/db/.env.example packages/db/.env
# Edit both .env files to set DATABASE_URL="postgresql://postgres:your_password@localhost:5432/simstudio"
- Run migrations:
cd packages/db && bun run db:migrate
- Start development servers:
bun run dev:full # Starts Next.js app and realtime socket server
Or run separately: bun run dev (Next.js) and cd apps/sim && bun run dev:sockets (realtime).
Copilot API Keys
Copilot is a Sim-managed service. To use Copilot on a self-hosted instance:
- Go to https://sim.ai → Settings → Copilot and generate a Copilot API key
- Set
COPILOT_API_KEYenvironment variable in your self-hosted apps/sim/.env file to that value
Environment Variables
See the environment variables reference for the full list, or apps/sim/.env.example for defaults.
Tech Stack
- Framework: Next.js (App Router)
- Runtime: Bun
- Database: PostgreSQL with Drizzle ORM
- Authentication: Better Auth
- Schema Validation: Zod
- UI: Shadcn, Tailwind CSS
- Streaming Markdown: Streamdown
- State Management: Zustand, TanStack Query
- Flow Editor: ReactFlow
- Docs: Fumadocs
- Monorepo: Turborepo
- Realtime: Socket.io
- Background Jobs: Trigger.dev
- Remote Code Execution: E2B
- Isolated Code Execution: isolated-vm
Contributing
We welcome contributions! Please see our Contributing Guide for details.
License
This project is licensed under the Apache License 2.0 - see the LICENSE file for details.
Made with ❤️ by the Sim Team




