[recipes] Add OB-Graph knowledge graph layer

[justfinethanku]

Summary

• Adds a new recipes/ob-graph recipe that brings graph database functionality to Open Brain using PostgreSQL nodes + edges
• Includes graph_nodes and graph_edges tables with RLS, indexes, and recursive CTE functions for traversal and shortest-path queries
• Deploys as a Supabase Edge Function MCP server with 10 tools: create/update/delete nodes and edges, search, get neighbors, traverse, and find paths

What's Included

File	Purpose
schema.sql	Tables, indexes, RLS policies, traverse_graph() and find_shortest_path() functions, GRANT statements
index.ts	MCP server (Hono + StreamableHTTPTransport) with 10 graph tools
deno.json	Deno import map matching existing extension patterns
metadata.json	Recipe metadata conforming to .github/metadata.schema.json
README.md	Setup guide with credential tracker, step badges, tool reference, troubleshooting
.env.example	Environment variable template

Design Decisions

• PostgreSQL recursive CTEs instead of a separate graph database — stays within Supabase free tier, no extra services
• Nodes + edges model with typed relationships and JSONB properties for flexibility
• Optional thought_id FK on nodes lets users link graph entities back to existing thoughts without modifying the core thoughts table
• Cycle prevention built into traversal via path array tracking
• Unique edge constraint prevents duplicate relationships of the same type between the same node pair

Test plan

• Run schema.sql in Supabase SQL Editor — verify tables and functions appear
• Deploy Edge Function via supabase functions deploy ob-graph-mcp --no-verify-jwt
• Create nodes and edges via MCP tools
• Test traverse_graph with multi-hop depth
• Test find_path between two connected nodes
• Verify RLS prevents cross-user data access
• Validate metadata.json against .github/metadata.schema.json

https://claude.ai/code/session_015Z8wCeokTMTdrVMthqzGKJ

[justfinethanku]

Thanks for the contribution here. There’s a lot to like in this one, and we’ll merge it as soon as these smaller fixes are in:

• add ✅ Done when checkpoints to Steps 2 and 3 in the README
• make the deployment flow explicit about generating and setting MCP_ACCESS_KEY and DEFAULT_USER_ID
• make find_shortest_path() return rows in explicit path order so the output is deterministic

If you want, enable maintainer edits and we can help patch the final details.

[mikedavis949-code]

Hey @justfinethanku,

I implemented the OB-Graph recipe and ran into high Supabase Edge Function invocation usage — the ob-graph-mcp function was quickly exceeding the free tier quota (I hit 847k/500k in a couple weeks).

Root cause: The McpServer + all 10 tool registrations were being recreated on every request (including the frequent GET discovery/polling requests from Claude Desktop).

Fix: I moved the server initialization and tool registration to module scope (outside the request handler), similar to how open-brain-mcp is structured.

ob-graph-index.ts.txt

I'm new to github, so appoligies if I'm sticking this feedback in the wrong place.
Thanks for the great recipe — the graph tools are really powerful.