# Sema — When the Hash Is the Word

> Sema is a semantic commons that content-addresses meaning itself:
> the definition *is* the identifier. By deriving identifiers from the
> cryptographic hash of a pattern's canonicalized definition, any
> divergence in meaning produces a distinct hash — guaranteeing that
> misaligned agents halt rather than silently drift apart. This site is
> the interactive browser for the public Sema pattern library (~450
> cognitive patterns) and a home for the API and MCP server that agents
> use to resolve, search, and mint patterns.

Sema exists to solve a coordination problem: two agents that share a
word are not guaranteed to share its meaning. Prior content-addressing
systems (Git, IPFS, SDH) keep the hash in an infrastructure layer
separate from communication. Sema dissolves the hash into language
itself — agents write sentences where each anchored term is
simultaneously a word and a cryptographic proof. Any channel that
carries text carries verified meaning.

## How Sema is used

- **Humans.** Read or search the pattern library at https://semahash.org.
  Each pattern has a name, a stable hash, a mechanism description,
  invariants, worked examples, and a lineage.
- **AI agents (MCP).** Add the Sema MCP server with one command
  (`claude mcp add sema -- uvx --from semahash sema mcp` or similar for
  other clients). The agent can then call `sema_search`, `sema_resolve`,
  `sema_handshake`, and `sema_mint` during its reasoning.
- **Python API.** `pip install semahash` gives you the client library and
  the optional FastAPI server used to run the web UI locally.
- **HTTP API.** Live at https://semahash.org/api/* — documented below.

## Public HTTP API

All endpoints are GET, JSON, CORS-open. No auth required for reads.

- [/api/graph](https://semahash.org/api/graph): The full pattern graph — nodes (patterns) and edges (relationships) — as a single JSON object suitable for direct visualization.
- [/api/patterns](https://semahash.org/api/patterns): List of all patterns, paginated.
- [/api/patterns/{handle}](https://semahash.org/api/patterns/StateLock): Full record for a single pattern, keyed by handle or hash. Returns name, mechanism, invariants, lineage, and the content hash.
- [/api/patterns/{handle}/source](https://semahash.org/api/patterns/StateLock/source): Canonical definition source for a pattern — the bytes that hash to the pattern's identifier.
- [/api/search](https://semahash.org/api/search?q=coordination): Full-text search across the pattern library.
- [/api/patterns/by-category/{category}](https://semahash.org/api/patterns/by-category/coordination): Patterns grouped by category.
- [/api/patterns/by-layer/{layer}](https://semahash.org/api/patterns/by-layer/cognitive): Patterns grouped by architectural layer.
- [/api/docs](https://semahash.org/api/docs): List of documentation pages.
- [/api/docs/{slug}](https://semahash.org/api/docs/introduction): A single documentation page.
- [/api/paper](https://semahash.org/api/paper): Access to the Sema paper content.

## MCP discovery

- [/.well-known/mcp/server.json](https://semahash.org/.well-known/mcp/server.json): Model Context Protocol registry descriptor. AI agents that follow the 2026 MCP Registry convention can auto-discover the sema MCP server via this path.
- Registry entry: https://registry.modelcontextprotocol.io/servers/io.github.emergent-wisdom/semahash

## Pages

- [Home](https://semahash.org/): Introduction, quick search, entry point.
- [Graph](https://semahash.org/graph): Interactive 3D visualization of the entire pattern library. Each node is a pattern; edges are semantic relationships.
- [Docs](https://semahash.org/docs): Full documentation, onboarding, and conceptual background.

## Paper

- [Sema — When the Hash Is the Word (PDF)](https://emergentwisdom.org/papers/sema.pdf): The paper introducing content-addressed semantics. March 2026.
- [DOI: 10.5281/zenodo.19462703](https://doi.org/10.5281/zenodo.19462703)

## About

- GitHub: https://github.com/emergent-wisdom/sema
- PyPI: https://pypi.org/project/semahash/
- Authors: Henrik Westerberg (emergent-wisdom)
- License: code MIT, content (patterns + docs) CC-BY-4.0
- Companion site: https://emergentwisdom.org