Pump SDK Core — Instruction Building & On-Chain Interaction

Build, extend, and maintain the core Pump SDK — an offline-first TypeScript SDK that constructs Solana TransactionInstructions for token creation, buying, selling, migration, and creator fee collection across three on-chain programs (Pump, PumpAMM, PumpFees) plus the Mayhem program.

Context

The SDK is published as @pump-fun/pump-sdk (npm) and powers the Pump protocol — a Solana-based token launchpad with bonding curve pricing, automatic AMM migration after graduation, tiered fees, and creator fee sharing. The codebase uses Anchor for IDL-based instruction building and supports both Token (SPL) and Token-2022 token programs.

Key Files

• src/sdk.ts — PumpSdk class with all instruction builders and account decoders
• src/onlineSdk.ts — OnlinePumpSdk class extending offline SDK with live RPC fetches
• src/index.ts — barrel re-export module defining the public API surface
• src/state.ts — TypeScript interfaces for all on-chain account state
• src/pda.ts — Program Derived Address derivation for all programs
• src/idl/pump.ts, src/idl/pump_amm.ts, src/idl/pump_fees.ts — Anchor IDL definitions

Architecture

• Offline SDK (PumpSdk): Builds instructions without a live connection. Uses Anchor Program instances initialized with a dummy keypair and connection. Exported as a singleton PUMP_SDK.
• Online SDK (OnlinePumpSdk): Wraps PumpSdk with a real Connection for fetching account state via getMultipleAccountsInfo. Provides "BothPrograms" methods that aggregate data across bonding curve (Pump) and AMM (PumpAMM) programs.
• Three program IDs: PUMP_PROGRAM_ID, PUMP_AMM_PROGRAM_ID, PUMP_FEE_PROGRAM_ID, plus MAYHEM_PROGRAM_ID for mayhem-mode tokens.

Instruction Builder Pattern

Every instruction method returns TransactionInstruction[] (not transactions), allowing callers to compose them into transactions freely. Methods follow a naming convention:

• *Instruction — single instruction
• *Instructions — multiple instructions (e.g., ATA creation + buy)

Account Decoders

The SDK decodes raw AccountInfo into typed interfaces using the Anchor coder:

• decodeGlobal, decodeBondingCurve, decodeFeeConfig, decodeSharingConfig, etc.
• Nullable variants (e.g., decodeBondingCurveNullable) handle missing or undersized accounts gracefully.

Slippage Calculation

maxSolCost = solAmount + (solAmount × slippage × 10 / 1000)
minSolReceived = solAmount - (solAmount × slippage × 10 / 1000)

Patterns to Follow

• Always return TransactionInstruction[] from instruction builders, never full Transaction objects
• Use getMultipleAccountsInfo to batch RPC calls (2–3 accounts per call)
• Support both Token (SPL) and Token-2022 programs via tokenProgram parameter
• Handle account extension (extendAccountInstruction) for bonding curves that need more space
• Validate shareholder arrays: max 10 shareholders, shares must total 10,000 bps, no duplicates, no zero shares
• Use typed error classes from src/errors.ts for validation failures
• Keep the offline SDK connection-free; all RPC calls belong in OnlinePumpSdk

Common Pitfalls

• Circular dependency between sdk.ts and onlineSdk.ts
• Buy instruction passes { 0: true } as a flags argument — this is intentional, not a bug
• BONDING_CURVE_NEW_SIZE = 151 — accounts may need extension before certain operations
• BondingCurve.complete === true means the token has graduated to AMM — bonding curve operations will fail
• The createInstruction (v1) is deprecated in favor of createV2Instruction (Token-2022)