PaperExPolymarket

Adapter between paper_ex (generic paper trading) and polymarket_sdk (the Polymarket SDK). Translates Polymarket CLOB order books, market metadata, and trade activity into the normalized paper_ex domain so callers can simulate or live-mirror Polymarket trading with the generic paper engine.

This package is:

• An adapter / translation layer, not a trading bot.
• The only package that bridges paper_ex and polymarket_sdk.
• Free of strategy decisions, dashboards, persistence, scheduling, Telegram, and live trading.

How the packages relate

paper_ex                     # generic engine, no Polymarket dep
   ^
   | PaperEx.Adapter behaviour
   |
paper_ex_polymarket          # this package — adapter
   |
   v uses polymarket_sdk shapes (CLOB books, Gamma, Data, RTDS)
polymarket_sdk               # Polymarket SDK: CLOB, Gamma, Data, RTDS, CTF

A consumer wires up:

1. polymarket_sdk for the live API surface they care about (often just order-book fetches, plus Gamma discovery and Data-API account data).
2. paper_ex_polymarket to translate (1) into the structs paper_ex understands.
3. paper_ex to simulate orders, hold portfolio state, and record execution attempts.

Status — 0.3.0

Implemented:

• PaperExPolymarket.Adapter — implements every PaperEx.Adapter callback (required and optional).
• PaperExPolymarket.Market — token id ↔ PaperEx.Instrument.
• PaperExPolymarket.OrderBook — CLOB /book body ↔ PaperEx.MarketSnapshot.
• PaperExPolymarket.Execution — Polymarket-flavored fill simulator (FAK for market orders, GTC for limit orders), with budget-walking semantics for :market :amount and strict numeric/timestamp parsing.
• PaperExPolymarket.ActivityMapper — Data-API / RTDS trade event ↔ PaperEx.Fill.
• PaperExPolymarket.Fees — bps-based fee helper.
• PaperExPolymarket.LiveMirror — live-mirror flows: simulate_intent/4, mirror_actual_fill/4, record_pending/3, resolve_pending/4 (:filled / :cancelled).
• PaperExPolymarket.Snapshot — convenience that composes instrument resolution + book normalization, with an injectable fetcher (from_clob_book/3, fetch_order_book_snapshot/3).
• Hand-authored fixture set under test/fixtures/ plus PaperExPolymarket.Fixtures loader used by fixture-backed integration tests.
• Wiring for PaperEx.Engine's opt-in :pending_remainder policy on partial :limit fills.
• 148 tests total covering CLOB-book conversion against realistic multi-level payloads, market normalization, activity-event mapping, fill simulation across every combination of :market / :limit / :buy / :sell / partial / missed / limit-not-crossed paths, end-to-end PaperEx.Engine.apply_order/4 through the adapter, the full live-mirror pending → filled / cancelled lifecycle, pending-remainder integration through the adapter, amount-based short guard through the adapter, the Snapshot convenience layer (function + MFA fetchers, error pass-through, malformed inputs), and bounded reason-code mapping for malformed payloads.

Not implemented (deferred to future versions):

• A built-in price-history loader. Callers pass snapshots in.
• Auto-fetching CLOB market metadata via polymarket_sdk. Callers pass metadata in.
• Polymarket FAK partial-remainder lifecycle (:pending for the unfilled remainder of a market order).

Quick start — research-mode simulation

alias PaperEx.{Engine, Order, Portfolio}
alias PaperExPolymarket.Adapter

# 1. Resolve a Polymarket instrument from a CLOB market payload.
clob_market = %{
  "condition_id" => "0xabc",
  "question" => "Will X happen by Y?",
  "market_slug" => "x-y",
  "minimum_tick_size" => "0.01",
  "token_id" => "111",
  "tokens" => [
    %{"token_id" => "111", "outcome" => "Yes"},
    %{"token_id" => "222", "outcome" => "No"}
  ]
}

{:ok, instrument} = Adapter.normalize_instrument(clob_market)

# 2. Get a CLOB /book body (the shape polymarket_sdk's order-book
#    endpoint returns) and turn it into a normalized snapshot.
clob_book = %{
  "market" => "0xabc",
  "asset_id" => "111",
  "bids" => [%{"price" => "0.53", "size" => "100"}],
  "asks" => [%{"price" => "0.55", "size" => "100"}]
}

{:ok, snapshot} = Adapter.normalize_snapshot(clob_book, instrument)

# 3. Apply an order through the generic engine.
portfolio = Portfolio.new(starting_balance: 1_000.0)

order =
  Order.new(
    market_id: "111",
    side: :buy,
    order_type: :market,
    size: 10,
    id: "order-1"
  )

{portfolio, execution} =
  Engine.apply_order(portfolio, order, snapshot, adapter: Adapter)

execution.status        # => :filled
execution.fill_price    # => 0.55
hd(portfolio.positions) # => %PaperEx.Position{shares: 10, side: :buy, ...}

Live-mirror flows

PaperExPolymarket.LiveMirror exposes four functions covering the operationally interesting cases. Each preserves the execution attempt ledger so misses, skips, and pending lifecycle events are first-class — not absorbed into "no trade".

Mirror an intent against the current book

alias PaperExPolymarket.LiveMirror

{portfolio, ex} = LiveMirror.simulate_intent(portfolio, order, snapshot)
ex.metadata.mode  # => :live_mirror

Record an actual exchange fill on the mirror

trade_event = %{
  "asset" => "111",
  "side" => "BUY",
  "size" => "5",
  "price" => "0.55",
  "transactionHash" => "0xdead"
}

{portfolio, ex} =
  LiveMirror.mirror_actual_fill(portfolio, order, trade_event, instrument)

ex.status              # => :filled
ex.metadata.source     # => :actual_fill
ex.metadata.raw_event  # => trade_event

Track a resting GTC order across its lifecycle

# Step 1 — place an order (e.g., via polymarket_sdk) and immediately
#          record a :pending execution on the mirror.
{portfolio, pending} =
  LiveMirror.record_pending(portfolio, order, id: "pend-1")

# Step 2a — when an actual fill arrives, resolve the pending into a
#           :filled and update portfolio cash/positions.
{portfolio, filled} =
  LiveMirror.resolve_pending(portfolio, "pend-1", :filled,
    order: order,
    instrument: instrument,
    trade_event: trade_event
  )

# Step 2b — or, if the order is cancelled, resolve it into a
#           :cancelled execution. State otherwise unchanged.
{portfolio, cancelled} =
  LiveMirror.resolve_pending(portfolio, "pend-1", :cancelled,
    reason: :cancelled_by_exchange
  )

Both lifecycle paths preserve the original :pending ledger entry plus the new :filled or :cancelled entry — so a downstream analyst can reconstruct the whole story from the Portfolio.executions field alone.

Non-goals

• Not a bot. No Phoenix, no Ecto, no Oban, no Telegram, no LiveView.
• Not a strategy framework. No copy-trading, no surge logic, no BTC arb, no stink-bid stencils.
• Not a substitute for polymarket_sdk. Live signing, balance checks, and order placement stay in polymarket_sdk.
• Not a market-data fetcher. Callers pass snapshots and metadata in; this package never opens a socket.

Hex publishability

Until paper_ex and polymarket_sdk are published on Hex, this package declares path deps and mix hex.build will fail with an explanatory error. That is intentional. (Set HEX_BUILD=1 to switch the workspace path deps to Hex requirements once both are published.)

License

MIT.