8 · Glossary

Every piece of jargon used across these docs and the codebase, in plain English. Skim it once; come back when a term bites.

Trading & perpetual-futures terms

Perpetual future (perp). A derivative contract that tracks an underlying price (here SOL/USD) with no expiry date. Held open indefinitely; tethered to spot by funding payments.

CLOB (central-limit order book). The matching mechanism where makers post resting limit orders and takers cross the spread, matched by price-time priority. The opposite of an AMM (automated market maker), which prices trades off a bonding curve / liquidity pool instead.

Maker / taker. A maker posts a resting order that adds liquidity (and earns a rebate). A taker crosses the spread, removing liquidity (and pays a fee).

Bid / ask / spread. Bid = highest price a buyer will pay. Ask = lowest a seller will accept. Spread = ask − bid. Best bid/ask is the "top of book."

Limit order. Buy/sell at a chosen price or better; rests in the book until filled or cancelled.

Market order. Execute immediately at the best available price(s), crossing the spread.

Long / short. Long = you profit if price rises (positive size). Short = you profit if price falls (negative size).

Notional. Full value of a position = size × price. A 10-SOL position at $150 has $1,500 notional regardless of how much margin backs it.

Leverage. The multiple between your notional and your margin. 20× means $75 of margin controls $1,500 of notional. Amplifies gains and losses.

Margin. Collateral backing a position. Initial margin = notional / leverage (required to open). Maintenance margin = initial / 2 (fall below and you're liquidated).

Collateral. Funds backing your account/position. In Slipstream: free_collateral (unencumbered, withdrawable) vs Position.collateral (backing an open position).

Credit / committed / available. On a TradingCredit: credit = margin allocated to a market; committed = reserved by live orders; available = credit − committed (what new orders can still use).

PnL (profit and loss). Unrealized = mark-to-market gain/loss on an open position. Realized = locked in when you close or partially close.

Mark price. The reference price used for PnL/liquidation (here, the Pyth feed).

Funding / funding rate. Periodic payment between longs and shorts that tethers the perp price to spot. Accrues at most once per funding interval (8h for SOL-PERP). Tracked via a cumulative_funding_index; each position snapshots the index and owes/earns the delta.

TWAP (time-weighted average price). Average price over a window (30 min here), used to smooth funding/safety. Self-computed on-chain because no oracle offers it natively.

Liquidation. Forced closing of a position whose health factor drops below 1.0 (net margin ≤ maintenance margin), to protect the system from bad debt.

Health factor. net_margin / maintenance_margin (6-dp, 1_000_000 = 1.0). ≥ 1.0 safe; < 1.0 liquidatable.

Liquidation price. The mark price at which health hits 1.0 — i.e. where you'd get liquidated.

VWAP entry. Volume-weighted average entry price when adding to an existing position, so the blended entry is priced correctly.

Open interest (OI). Total size of all open longs / shorts in a market.

Insurance fund. A reserve that absorbs bad debt from liquidations that can't fully cover losses.

Tick size / lot size. Tick = smallest price increment (TICK_SIZE = 1000). Lot = smallest size increment (LOT_SIZE = 0.1 SOL).

bps (basis points). Hundredths of a percent. 1 bps = 0.01%. Used for fees (taker_fee_bps, maker_rebate_bps).

Solana terms

L1 (base layer / Layer 1). The main Solana chain. ~400 ms blocks, full validator security, real fees. Holds all of Slipstream's value-bearing state.

PDA (Program Derived Address). An account whose address is derived from seeds + program ID and has no private key, so only the owning program can sign for it. How programs own persistent state.

Account. Solana's unit of storage. A blob of bytes (up to 10 MB) owned by a program, kept alive by being rent-exempt (holding enough lamports).

Rent / rent-exempt. Accounts must hold a minimum lamport balance proportional to their size to persist. Slipstream pre-funds the OrderBook's full-size rent at creation even though bytes are added later.

CPI (cross-program invocation). One program calling another. Subject to limits like the account-growth cap.

MAX_PERMITTED_DATA_INCREASE (10,240 bytes). The max an account can grow per instruction/CPI. The reason the 612 KB book is built in ~61 chunks and can't be undelegated.

Lamport. The smallest unit of SOL (1 SOL = 1e9 lamports).

BPF / SBF. The bytecode Solana programs compile to. Runs in a sandbox with a ~4 KB stack frame and a compute-unit budget — why big arrays can't live on the stack and why zero-copy matters.

Discriminator. A leading byte (or bytes) identifying an account type or instruction. Slipstream uses a one-byte instruction discriminator (0x00–0x27) and per-account-type discriminators (DISC_ORDER_BOOK, DISC_FILL_LOG, …).

Signer. An account that authorized a transaction with its key. Distinct from owner (the program/pubkey that controls an account).

MagicBlock / Ephemeral Rollup terms

Ephemeral Rollup (ER). A temporary, high-speed (~10 ms) execution environment that runs the same Solana program against delegated accounts at sponsored cost, periodically folding results back to L1.

Delegation. Handing an L1 account's mutation authority to the ER. After delegation the ER (not L1) writes the account. In Slipstream: the OrderBook (forever) and each TradingCredit (per session).

Commit. The ER snapshots a delegated account's state back to L1; the account stays delegated. Triggered by a ScheduleCommit CPI to the magic program.

Undelegate. Returning authority from the ER to L1. Impossible for the 612 KB OrderBook (growth cap + unclean path + defeats the premise).

Sponsored-commit cap. The hard limit of 10 commits per delegated account on the public devnet node (verified live; funding an escrow doesn't lift it). Beaten by epoch rotation.

Epoch rotation. Because the commit cap is per-account, the FillLog is a PDA keyed by an epoch number; bumping the epoch mints a fresh account with a fresh budget of 10 → unbounded settlement.

Delegation program (DELeGGvXpWV2fqJUEqsQ…). MagicBlock program that records delegation and enforces scope + session timeout (not fraud proofs).

Magic program (Magic11111…). Target of ScheduleCommit / undelegate CPIs from inside the ER.

Slipstream-specific accounts & instructions

OrderBook. The ~612 KB delegated PDA holding order slots, sorted price levels, and the fill-event ring. One per market. (doc 2)

FillLog. The small (~8 KB) epoch-rotatable PDA that carries fills from ER to L1 for settlement, so the OrderBook never has to be committed. (doc 4)

Market. L1 account holding market params (leverage, fees, tick/lot, funding interval), oracle feeds, OI, the TWAP ring, the funding index, and the last_settled_sequence settlement cursor.

Position. L1 account: a user's open exposure in a market (size, entry_price, collateral, realized_pnl, funding snapshot).

UserAccount. L1 account holding free_collateral and long-lived user lifecycle state. Never delegated.

TradingCredit. Per-(user, market) account holding margin delegated to the ER during a session; carries the session key fields. (docs 5, 6)

OrderSlot / PriceLevel / FillEvent. The in-book structures: a resting order, a sorted price ladder entry, and a recorded match, respectively. (doc 2)

Session key. A scoped, expiring browser key (session_authority + session_expiry on TradingCredit) authorized once to sign orders for the owner. (doc 6)

mirror_fills / commit_fill_log / settle_from_log. The three-step settlement pipeline: copy book fills → FillLog (ER); snapshot FillLog → L1; write Positions from the committed log (L1). (doc 4)

grow_orderbook. Reallocs the OrderBook up to 10,240 bytes per call until it reaches full size; called ~61 times at deploy. (doc 2)

reconcile_credit. Rescans the book for an owner's active slots to repair a stale TradingCredit.committed after fills drained margin the maker couldn't see in real time. (doc 5)

crank_twap / compute_funding / liquidate_position. L1 keeper-driven instructions for the TWAP accumulator, periodic funding accrual, and liquidating unhealthy positions. (doc 5)

Stack / tooling terms

Pinocchio. A minimal, zero-dependency Rust SDK for Solana programs (no Anchor). Slipstream's on-chain program is written in it; it hand-rolls account parsing and uses zero-copy.

Zero-copy. Reading/writing an account by reinterpreting its raw bytes in place as typed structs (no deserialization/copy). Requires #[repr(C)] + Pod layouts.

bytemuck / Pod / Zeroable. Rust crate + traits enabling safe zero-copy casts between bytes and plain-old-data structs.

#[repr(C)]. A fixed, predictable struct memory layout (C ABI) so the bytes match across Rust and the TypeScript decoders.

Ring buffer. A fixed-size circular array with head/tail indices that wrap around. Used for the fill-event queue, the FillLog, and the TWAP buffer.

Free list. An intrusive linked list of unused slots enabling O(1) allocate/free without heap allocation or fragmentation (the order-slot pool).

Object pool. A pre-allocated, reused set of fixed slots managed by a free list — what the OrderBook uses instead of dynamic allocation.

Fixed-point. Representing fractional numbers as scaled integers (price ×1e6, size ×1e9) because floats aren't used on-chain. Mixing scales is the classic bug.

Keeper. An off-chain bot that periodically calls on-chain instructions that need a heartbeat (funding, liquidation, TWAP, settlement, market-making).

Pyth. The price oracle providing SOL/USD via a Receiver PriceUpdateV2 feed, with on-chain freshness checks.

Switchboard. A second oracle intended for dual-oracle divergence checks — dead on devnet (reads 0), hence the Pyth-only fallback.

SSE (server-sent events). The streaming protocol the frontend uses to pull real-time Pyth prices (a true push stream, not polling).