Authentication

Hosts

Synpath serves two hostnames.

• api.synpath.dev: cross-venue market and event matching (/match/*).
• api2.synpath.dev: tick-level historical order books and trades (/v1/*).

The same Synpath API key authenticates against both; there are no separate credentials.

Trading is self-hosted: orders go from your own machine straight to the venues, and need no Synpath API key.

Synpath API key

1. Sign in

synpath login opens Google sign-in in your browser and returns to the terminal. It saves a short-lived session for managing data API keys; signing in does not create a key.

synpath login

While Google sign-in is in testing, your Google account must be in the OAuth test-user audience.

2. Create a data API key

Give the key a label for the device or application that will use it. The CLI saves the latest key to ~/.config/synpath/credentials.json, readable only by you, and prints the secret once. Keep it private, or add --no-print-key to save it without showing it.

synpath keys create my-laptop

The Python client reads the saved key automatically. SYNPATH_API_KEY, or api_key= on a call, overrides it. For direct HTTP requests, send the key as Authorization: Bearer <key>. The library sends it to Synpath's services only, never to a venue.

synpath.match_market("kalshi:KXFEDDECISION-26OCT-C25")                   # uses the saved key
synpath.fetch_order_book_at("kalshi:KXQUANTUM-30", as_of_ms=1789509599000,
                            api_key="spk_...")                           # an explicit key wins

Manage your keys

synpath keys list
synpath keys revoke <key-id>
synpath logout

logout ends the key-management session. It does not revoke an issued API key. The CLI supports --help on each command for options, including synpath keys create --help.

Set up venue credentials

To trade, synpath uses your own API keys at each venue. They stay on your machine, in a file or in environment variables, and are never sent to Synpath. You only need keys for the venues you trade on; market data needs none.

1. Create your keys at each venue

Kalshi

1. Sign in at kalshi.com and open Profile Settings → API Keys.
2. Click Create New API Key. Copy the Key ID, and save the private key file it downloads, for example to ~/.kalshi/kalshi.pem. Kalshi shows the private key only once.
3. To practise first, create a key the same way on demo.kalshi.co and set KALSHI_ENV=demo.

Polymarket

1. Export the private key of the wallet you sign in with: on polymarket.com, Settings → Private Key → Start Export. If you sign in with a browser wallet such as MetaMask, export it from that wallet.
2. Copy your trading wallet address, shown under your profile menu on polymarket.com. This is the funder.
3. Set the signature type: 3 for accounts created since May 2026, 1 or 2 for older proxy or Safe wallets.

Polymarket US

1. Complete identity verification in the Polymarket US app.
2. Create an API key at polymarket.us/developer and copy the key ID and the secret.

2. Save them in a .env file

synpath reads your keys from a file named .env in the folder you run it from, so they stay on your machine and out of your code. The easiest way to create it:

synpath init        # asks for each venue's keys and writes .env, readable by you only

Or write it yourself, one setting per line, leaving out the venues you do not use:

KALSHI_KEY_ID=a1b2c3d4-...
KALSHI_PRIVATE_KEY_PATH=/Users/you/.kalshi/kalshi.pem
KALSHI_ENV=prod                    # or demo for Kalshi's practice exchange

POLYMARKET_PRIVATE_KEY=0x...
POLYMARKET_FUNDER=0x...            # your trading wallet address
POLYMARKET_SIGNATURE_TYPE=3

POLYMARKET_US_KEY_ID=...
POLYMARKET_US_SECRET_KEY=...

Access token

Your self-hosted server (synpath serve) only accepts trading calls that carry its access token.

• Same machine: nothing to do. The server saves its token on first start, and your scripts on the same machine use it automatically.
• Another machine, such as a VPS: copy the token the server printed when it started, and pass it as SYNPATH_ACCESS_TOKEN.

client = synpath.Client(server="http://127.0.0.1:8000")          # same machine
client = synpath.Client(server="https://trading.example.com")    # elsewhere: reads SYNPATH_ACCESS_TOKEN

Errors