Use Synapse with ChatGPT

Add persistent memory to any Custom GPT using Synapse Actions. Your GPT will remember everything across conversations — no more starting from scratch every session.

Before you start: this requires a paid ChatGPT plan

Creating or editing a Custom GPT is limited to ChatGPT Plus, Pro, Team, or Enterprise. Free-tier ChatGPT does not show the GPT builder. If you're on the Free plan, upgrade first or use the Claude Desktop path instead, which works on Claude's free tier.

Faster path: let your agent do this

Point a coding agent at this page and tell it to configure the Custom GPT Action for you — it reads the schema URL and auth steps below on its own. (Still requires a paid ChatGPT plan to access the GPT builder — see above. On the free tier, use the Claude Desktop path instead, and your agent can set that up the same way.)

Step 1: Get a free API key

Sign up at synapse.by-kit.com/signup. Your key is shown once at creation — save it immediately.

Step 2: Create a Custom GPT

Go to chat.openai.com → Explore GPTs → Create. Give your GPT a name and description.

Step 3: Add a Synapse Action

  1. In the GPT editor, go to Configure → Add actions
  2. Click Import from URL and paste this schema URL — it loads everything automatically:
    https://synapse.by-kit.com/openapi.json

    Or download directly: openapi.json ↓

  3. In Authentication: select API Key, type Bearer, paste your Synapse API key
    ⚠️ Only paste your key into this Authentication field. Never paste it into the schema/JSON text box above — that box is just the API description, it does nothing with a real key pasted into it, and anything typed there is visible to anyone who later sees the schema. If you accidentally paste your key into the schema box, remove it and rotate your key immediately.
  4. Add these instructions to your GPT's system prompt:
    You have Synapse memory tools (synapse_remember, synapse_recall, synapse_recent). At the start of every conversation, call synapse_recall with query='recent context'. Save important facts immediately with synapse_remember.

Save and publish your GPT. It will now load your Synapse memory at the start of every conversation and save important facts automatically.

Works with Claude Code too

If you use Claude Code (the CLI), you can also install the Synapse MCP package via npm:

npm install -g synapse-memory-mcp

See the Claude Desktop guide for full setup instructions including the config file and system prompt.

Next steps