OpenErrata

OpenErrata highlighting an incorrect claim on Astral Codex Ten

OpenErrata is a browser extension that uses LLMs to pre-investigate posts from the sites you read, and underlines unambiguously incorrect claims, with sources available. It prioritizes an extremely low false-positive rate over coverage, and the prompts, details, and reasoning behind every investigation are inspectable by users.

How It Works

1. You browse normally. The extension detects supported posts and sends observed content to the API, which records views and returns any existing investigation results triggered by other users.
2. Posts get investigated. You or someone else clicks "Investigate Now", or has the "auto-investigate posts" setting checked, or the service pre-selects it using a very-likely-to-be-read heuristic.
3. The LLM investigates. The full post text (plus images) are sent to GPT-5.4-thinking, which uses native web search and browsing tools to verify claims. Only demonstrably incorrect claims are flagged — disputed, ambiguous, or unverifiable claims are left alone.
4. Incorrect claims are highlighted. For all extension users, every incorrect sentence gets a red underline in the post. Hover for a summary; click for full reasoning and sources.

Install

Chrome Web Store — Install directly from the store.

Firefox Add-ons (AMO) — Coming soon.

Manual install from GitHub Releases:

1. Download the latest browser-specific zip from the Releases page:
2. Chrome: openerrata-extension-chrome-*.zip
3. Firefox: openerrata-extension-firefox-*.zip
4. Unzip the file
5. Install by browser:
6. Chrome: open chrome://extensions, enable Developer mode, then click Load unpacked and select the unzipped folder.
7. Firefox: open about:debugging#/runtime/this-firefox, click Load Temporary Add-on..., then choose the extension manifest.json in the unzipped folder.
8. (Optional) Set your OpenAI API Key in the settings

Errata are first pulled from the public instance before being regenerated. If you do not have an OpenAI API key, you can receive the errata generated by other users, but they won't be generated on demand. Right now the public instance is configured to investigate the most popular posts every hour (though this may change as we hit spend thresholds).

To point the extension at a self-hosted instance, open the extension options page and change the API URL.

Supported Platforms

Public API

All complete investigations are publicly accessible via GraphQL at POST /graphql. No authentication required. Responses include trust signals (content provenance, corroboration count, server verification timestamps) so consumers can apply their own trust policy.

Design Principles

• When in doubt, don't flag. False positives erode trust and will be adversarially scrutinized. The system only flags claims with concrete, credible counter-evidence.
• Only flag sentences that would otherwise mislead readers. Don't flag e.g. clearly satirical or humorous posts.
• Transparency. The design, spec, code, and individual investigations are all publicly inspectable. Every investigation stores full audit artifacts (prompt, model metadata, tool traces, source snapshots).
• Lean on frontier models. The LLM uses provider-native web search and browsing rather than a custom search-and-scrape pipeline. We orchestrate; the model investigates.
• Single-pass investigation. The entire post is investigated in one agentic call, giving the model full context for understanding caveats, qualifications, and claim relationships.

Documentation

• SPEC.md — Full product spec covering design goals, architecture, data model, API surface, and implementation details. This is the source of truth for product behavior.

Repository Layout

src/
├── helm/openerrata/         # Helm chart (single artifact for on-prem + hosted)
└── typescript/
    ├── shared/              # @openerrata/shared — types, Zod schemas, normalization
    ├── api/                 # @openerrata/api — SvelteKit + tRPC backend, Prisma, job queue
    ├── extension/           # @openerrata/extension — WebExtension (Chrome + Firefox)
    └── pulumi/              # @openerrata/pulumi — deploys the Helm chart for hosted env

The monorepo uses pnpm workspaces. Dependencies flow: shared -> api and shared -> extension.

Tech Stack

Getting Started

Prerequisites

• Node.js (LTS)
• pnpm
• Docker (for local Postgres + MinIO)

Local Development

# Start Postgres (port 5433) and MinIO S3-compatible storage (ports 9000/9001)
docker compose up -d

# Install dependencies
cd src/typescript
pnpm install

# Apply database migrations
pnpm db:migrate

# Start the API dev server
pnpm dev:api

# Build the extension in watch mode (separate terminal)
pnpm dev:ext

# Start the job queue worker (separate terminal)
pnpm worker

Common Commands

pnpm check              # Typecheck all packages + lint
pnpm lint:fix            # ESLint with auto-fix
pnpm test               # Run unit + integration tests
pnpm selector            # Run investigation selector (cron equivalent)
pnpm db:migrate          # Create/apply Prisma migrations
pnpm db:migrate:deploy   # Apply SQL migrations (e.g. Postgres views)
pnpm db:generate         # Regenerate Prisma client

Loading the Extension

After pnpm dev:ext, load the built extension as an unpacked extension:

1. Chrome:
2. Navigate to chrome://extensions
3. Enable "Developer mode"
4. Click "Load unpacked" and select src/typescript/extension/dist
5. Firefox:
6. Navigate to about:debugging#/runtime/this-firefox
7. Click "Load Temporary Add-on..."
8. Select src/typescript/extension/dist/firefox/manifest.json

For signed Firefox releases, set FIREFOX_GECKO_ID=<your-addon-id> before building to control the generated browser_specific_settings.gecko.id.

Deployment

The Helm chart at src/helm/openerrata/ is the single deployment artifact for both on-prem and hosted environments. It does not bundle a database — it takes a DATABASE_URL as config.

On-prem:

helm install openerrata ./src/helm/openerrata \
  --set secrets.databaseUrl="postgresql://..." \
  --set secrets.openaiApiKey="sk-..."

Hosted: The official hosted deployment uses Pulumi (src/typescript/pulumi/) to deploy the same Helm chart with hosted-specific overrides (Supabase connection, domain, TLS, autoscaling). This guarantees identical workload definitions between on-prem and hosted — no deployment drift.

License

GNU Affero General Public License v3.0