Position Merge Event

Outcome tokens merged back into collateral on Polymarket.

Emitted when outcome tokens (YES + NO shares) are merged back into collateral (USDC) via the Conditional Tokens Framework mergePositions function. The inverse of a position split.

Merges are much rarer than splits (~20x less frequent). They happen when a trader holds both YES and NO tokens for a condition and redeems them back to USDC.

{
  "data": {
    "amount": 1414.0,
    "block_number": 84090704,
    "collateral_token": "0x3a3bd7bb9528e159577f7c2e685cc81a765002e2",
    "condition_id": "0xd1747284d6048b2a3dcfbee489db405f36de18f9590197dd0e5c9f0c246bf050",
    "event_title": "Republican Presidential Nominee 2028",
    "event_type": "position_merge",
    "log_index": 1004,
    "market_image": "https://polymarket-upload.s3.us-east-2.amazonaws.com/Byron_Donalds.png",
    "market_slug": "will-byron-donalds-win-the-2028-republican-presidential-nomination",
    "market_title": "Will Byron Donalds win the 2028 Republican presidential nomination?",
    "neg_risk": true,
    "stakeholder": "0xd91e80cf2e7be2e162c6513ced06f1dd0da35296",
    "taker_base_fee": 0.0,
    "tick_size": 0.001,
    "timestamp": 1773301441000,
    "tokens": {
      "311624663652221737215322113380496984764966764039692273354641152455298576851": "Yes",
      "43292374563904271719486871569114922516560719431752184778538513591321835161630": "No"
    },
    "tx_hash": "0x92fa6de980f6cad9eae9ef28e908d19faa10838a07f01352b0cae63b5f8299fb"
  },
  "timestamp": 1773301441000,
  "type": "position_merge"
}

Fields

type · string · required

Always "position_merge".

timestamp · number · required

Block timestamp in Unix milliseconds.

data · object · required

Show data fields

tx_hash · string · required

Transaction hash.

block_number · number · required

Block number.

log_index · number · required

Log index within the transaction.

timestamp · number · required

Block timestamp in Unix milliseconds.

stakeholder · string · required

Address that triggered the merge.

collateral_token · string · required

Collateral token address. USDC.e (0x2791bca1f2de4661ed88a30c99a7a9449aa84174) for standard markets, wrapped collateral (0x3a3bd7bb...) for neg_risk markets.

condition_id · string · required

Market condition ID — identifies which market’s outcome tokens were burned.

amount · number · required

USDC amount received from merging outcome tokens (6 decimal precision).

market_title · string

Human-readable market question. Populated when metadata is available.

market_slug · string

URL slug for the market.

market_image · string

Market image URL. Enriched from metadata.

event_title · string

Parent event title. Enriched from metadata.

neg_risk · boolean

Whether this market uses the negRisk contract type. Enriched from metadata.

tick_size · number

Minimum price increment (e.g. 0.01 or 0.001). Enriched from metadata.

taker_base_fee · number

Taker fee rate in basis points. 200 = 2%, 1000 = 10%, null = no fee. Short-term crypto markets (5-minute ETH/BTC) typically have 1000 (10%), while standard markets have 200 (2%). Enriched from Polymarket metadata.

tokens · object

Map of token ID → outcome name for all outcomes in this market. Enriched from metadata.

Use cases

• Position unwinding — detect when traders are closing positions by merging outcome tokens
• Liquidity withdrawal tracking — merges reduce the total supply of outcome tokens in a market
• Arbitrage detection — merges after buying both outcomes at favorable prices signal arbitrage

Not included in global firehose (full data stream) by default. Subscribe explicitly with event_types: ["position_merge"] or use the wallets/markets subscription types which include it automatically.