paymos — Python SDK

Non-custodial, headless control of a wallet vault: read balances, preview fee-transparent quotes, and move money with swap and withdraw — all over a co-signed 2-of-2 vault.

Your process holds one half of the signing key; the Paymos server holds the other. Neither side alone can move funds — every swap and withdrawal is co-signed, and your half never reaches the server.

• Non-custodial — a leaked API key can't sign; your co-signing share stays in your process.
• Fee-transparent — every quote is a dry preview with a full platform / network / route fee breakdown you see before signing anything.
• Human amounts, no floats — you pass decimal strings like "100" / "0.5"; responses come back as raw integer strings.
• No Rust toolchain — the native signing core ships compiled inside the wheel.
• Async-first — built on httpx.AsyncClient, fully typed (py.typed).

The SDK talks in plain asset terms (USDC@base, ETH@arb) and hides the routing and the 2-of-2 signing behind a small, safe surface.

Install

pip install paymos

Requires Python ≥ 3.11. The only runtime dependency is httpx (installed automatically).

Prebuilt wheels cover Windows, macOS (Intel + Apple Silicon), and Linux (x86-64 and ARM, glibc and musl). Each cp311-abi3 wheel serves CPython 3.11 / 3.12 / 3.13+, so a single wheel per platform is all you need — and there's no compiler step on install.

Get a vault secret

The SDK is driven by one vs_live_… vault secret, minted in the wallet Mini App → Settings → Vault API. There are two kinds:

Key	Can do	Carries
read	assets, balances, quote_swap, quote_withdraw, movement, movements	API key only
full	everything a read key does, plus swap and withdraw	API key + your co-signing share

The share is decrypted on your device and never leaves your process. There is no CLI provisioner — the secret is minted in the Mini App. Treat a full secret like a private key.

Point the SDK at it with an environment variable:

export PAYMOS_VAULT_SECRET="vs_live_…"
# optional — defaults to https://wallet.paymos.io
# export PAYMOS_BASE_URL="https://wallet.paymos.io"

Quickstart

import asyncio
from paymos import Wallet

async def main():
    async with Wallet.from_env() as w:              # reads PAYMOS_VAULT_SECRET
        # Balances: per-asset, raw amount strings + a nullable USD value.
        for b in await w.balances():
            print(b.asset, b.amount_raw, b.usd)

        # Preview a withdraw — a dry, money-safe quote. Headline is the fee breakdown.
        q = await w.quote_withdraw(asset="USDC@base", amount="25", to="0xRecipient…")
        print(q.fees.platform, q.fees.network, q.fees.total)

        # Move money (full key only). Amounts are human decimal strings.
        mv = await w.swap(send="USDC@base", receive="ETH@arb", amount="100")
        settled = await w.wait(mv.id)               # poll to a terminal status
        print(settled.status)

asyncio.run(main())

Wallet is an async context manager (aclose() releases the HTTP client). You can also build it directly — Wallet("vs_live_…") — or from the environment with Wallet.from_env().

Core concepts

Amounts: human in, raw out

Amounts you pass are human decimal strings ("100", "0.5") — the server owns each asset's decimals and scales them to raw. Amounts in responses (balances, quote legs, fees) come back as raw integer strings. Never a float, in either direction.

Assets

Assets use white-label SYMBOL@chain ids (USDC@base, ETH@arb). assets() returns the catalog (fetched once and cached per Wallet); the SDK uses each asset's decimals to validate the amounts you pass — an unknown asset or an over-precise amount raises PaymosError locally, before anything hits the wire.

Quotes and fees

quote_swap / quote_withdraw always return a dry Quote — a pure preview that persists nothing and works for read and full keys alike. The headline is quote.fees:

q = await w.quote_swap(send="USDC@base", receive="ETH@arb", amount="100")
print(q.fees.platform)   # raw string
print(q.fees.network)    # raw string
print(q.fees.route)      # RouteFee(amount, estimate) — or None when there's no route leg
print(q.fees.total)      # raw string
print(q.receive.amount)  # expected out
print(q.receive.min)     # guaranteed out (your slippage floor)

Moving money

swap and withdraw (full key only) create a real movement and drive the 2-of-2 co-sign, then return a Movement. Before any signature the SDK re-checks that the server's quote echoes exactly the assets and amount you approved — a decimals bug, contract drift, or a lying server raises and signs nothing.

# Swap, delivered back to your own vault.
mv = await w.swap(send="USDC@base", receive="ETH@arb", amount="100",
                  min_receive="0.03")               # optional slippage floor

# Withdraw to an external chain address.
mv = await w.withdraw(asset="USDC@base", amount="25", to="0xRecipient…")

Withdraw modes

• mode="exact_out" (default) — the recipient receives exactly amount; the vault debit (amount + fees) is server-computed.
• mode="total_in" — amount is the total debited from the vault; the recipient gets that minus fees.

Safety caps

• slippage_bps (swap / quote_swap, default 50 = 0.5%) — the slippage tolerance sent with the quote in basis points; the quote's guaranteed receive.min already reflects it.
• min_receive (swap) — a human decimal in the receive asset. If the quote's guaranteed receive is below it, raises SlippageExceeded and signs nothing.
• max_debit (swap / withdraw) — a human decimal ceiling on the total vault debit. Strongly recommended for unattended exact_out payouts, whose input side is server-computed. Exceeded → raises, signs nothing.

Idempotency

Pass your own idempotency_key (e.g. a durable payout id) so a retry after an ambiguous failure replays the same movement instead of paying twice; a retry that finds it already signed/relayed converges on it rather than double-signing. Omit it and a fresh key is generated per call.

mv = await w.withdraw(asset="USDC@base", amount="25", to="0xRecipient…",
                      idempotency_key="payout-8f21", max_debit="26")

Waiting and statuses

wait(id) polls a movement until it reaches a terminal status — completed | failed | refunded | expired | cancelled — and raises PaymosError on timeout.

mv = await w.wait(mv.id, timeout=120, poll=2.0)

API reference

All Wallet methods are async.

Method	Returns	Notes
Wallet(secret, base_url=…, *, timeout=None)	Wallet	secret is a vs_live_… string
Wallet.from_env(base_url=None, *, timeout=None)	Wallet	reads PAYMOS_VAULT_SECRET / PAYMOS_BASE_URL
assets()	list[Asset]	curated catalog, cached
balances()	list[Balance]	per-asset vault balances
quote_swap(send, receive, amount, slippage_bps=50)	Quote	dry preview
quote_withdraw(asset, amount, to, mode="exact_out")	Quote	dry preview
swap(send, receive, amount, slippage_bps=50, min_receive=None, *, max_debit=None, idempotency_key=None)	Movement	full key
withdraw(asset, amount, to, mode="exact_out", *, max_debit=None, idempotency_key=None)	Movement	full key
movement(id)	Movement	one movement, with fee breakdown
movements(limit=50, cursor=None)	tuple[list[Movement], str | None]	page + next cursor (newest first)
wait(id, timeout=120, poll=2.0)	Movement	poll to a terminal status
aclose()	—	release the underlying HTTP client

The default HTTP timeout is httpx.Timeout(60s, connect=10s) (the co-sign is multi-round); override it with Wallet(..., timeout=…).

Data models

Every amount field is a raw integer string. All models are frozen dataclasses.

• Asset — asset, symbol, chain, decimals: int
• Balance — asset, symbol, chain, decimals: int, amount_raw, usd: str | None
• Amount — amount, asset
• Receive — amount, min (guaranteed), asset
• RouteFee — amount, estimate: bool (True = rate-derived cross-asset, False = exact same-asset spread)
• Fees — asset, platform, network, route: RouteFee | None, total, usd: dict | None
• Quote — movement_id: str | None (None on a dry preview), mode, send: Amount, debit: Amount (full vault debit = send + fees), receive: Receive, fees: Fees, expires_at, sources: int | None
• Movement — id, type, status, send: Amount, receive: Receive, fees: Fees | None, dest_chain_tx_hash: str | None, dest_chain_explorer_url: str | None, created_at, completed_at: str | None

Timestamps stay raw ISO-8601 strings — the SDK does not parse them to datetime.

Errors

Every call raises a typed subclass of PaymosError, which carries message and status (the HTTP status, or None for a transport-level failure). Branch on the type instead of string-matching a message.

Exception	When
AuthError	401 — API key missing, malformed, or unrecognized
Forbidden	403 — the key is valid but lacks the scope this call needs
InsufficientFunds	400 — the vault balance can't cover the amount (plus fees)
QuoteExpired	400 — the referenced quote expired; fetch a fresh one
SlippageExceeded	400 or local — delivered / guaranteed amount fell below your floor
CrossAssetWithdrawNotAllowed	400 — a withdraw changed the asset (that's a swap)
RouteUnavailable	400 — no route could be quoted right now; retry shortly
RateLimited	429 — carries .retry_after (seconds, or None)
Conflict	409 — idempotency key reused with a different request
PaymosError	base — 404, any other 4xx/5xx, and transport errors (status=None)

import asyncio
from paymos import Wallet, InsufficientFunds, SlippageExceeded, RateLimited, PaymosError

try:
    mv = await w.swap(send="USDC@base", receive="ETH@arb", amount="100", min_receive="0.03")
except SlippageExceeded:
    ...                                   # guaranteed receive below your floor — nothing signed
except InsufficientFunds:
    ...                                   # not enough balance for amount + fees
except RateLimited as e:
    await asyncio.sleep(e.retry_after or 1)
except PaymosError as e:
    print(e.status, e.message)

Calling swap / withdraw with a read-only key raises PaymosError before any movement is created — a read key can never sign.

Security

• A leaked API key alone cannot move funds — no share, no signature (and the key can be revoked).
• A leaked share alone cannot move funds — no server co-sign.
• Both are required, on purpose. The SDK additionally verifies every message it co-signs, and that the server's quote matches exactly what you approved — so a compromised server can't redirect funds or inflate an amount past your caps.

Treat a full vs_live_… secret like a private key, and back up the share — losing it means losing your ability to co-sign.

Examples

The source repository's examples/ folder has a clickable local web demo (FastAPI, prod-pointed) that loads balances, shows the fee breakdown, and — behind a confirm box — runs a real swap, plus a minimal demo.py CLI.

License

Proprietary. All rights reserved. Use of this SDK is subject to your agreement with Paymos.