Add buy_exact_sol_in and buy_exact_quote_in instruction support

- Add BUY_EXACT_SOL_IN_DISCRIMINATOR for PumpFun
- Add BUY_EXACT_QUOTE_IN_DISCRIMINATOR for PumpSwap
- Add use_exact_in_instruction field to SwapParams
- When enabled, uses exact input instructions that spend exactly the
  specified SOL/quote amount with slippage applied to output tokens
- Defaults to false for backwards compatibility

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/instruction/pumpfun.rs

@@ -9,7 +9,7 @@ use crate::{
 use crate::{
     instruction::utils::pumpfun::{
         accounts, get_bonding_curve_pda, get_creator, get_user_volume_accumulator_pda,
-        global_constants::{self},
+        global_constants::{self}, BUY_DISCRIMINATOR, BUY_EXACT_SOL_IN_DISCRIMINATOR,
     },
     utils::calc::{
         common::{calculate_with_slippage_buy, calculate_with_slippage_sell},
@@ -118,9 +118,23 @@ impl InstructionBuilder for PumpFunInstructionBuilder {
         }
 
         let mut buy_data = [0u8; 24];
-        buy_data[..8].copy_from_slice(&[102, 6, 61, 18, 1, 218, 235, 234]); // Method ID
-        buy_data[8..16].copy_from_slice(&buy_token_amount.to_le_bytes());
-        buy_data[16..24].copy_from_slice(&max_sol_cost.to_le_bytes());
+        if params.use_exact_in_instruction {
+            // buy_exact_sol_in(spendable_sol_in: u64, min_tokens_out: u64)
+            // Spend exactly the input SOL amount, get at least min_tokens_out
+            let min_tokens_out = calculate_with_slippage_sell(
+                buy_token_amount,
+                params.slippage_basis_points.unwrap_or(DEFAULT_SLIPPAGE),
+            );
+            buy_data[..8].copy_from_slice(&BUY_EXACT_SOL_IN_DISCRIMINATOR);
+            buy_data[8..16].copy_from_slice(&params.input_amount.unwrap_or(0).to_le_bytes());
+            buy_data[16..24].copy_from_slice(&min_tokens_out.to_le_bytes());
+        } else {
+            // buy(token_amount: u64, max_sol_cost: u64)
+            // Buy exactly token_amount tokens, pay up to max_sol_cost
+            buy_data[..8].copy_from_slice(&BUY_DISCRIMINATOR);
+            buy_data[8..16].copy_from_slice(&buy_token_amount.to_le_bytes());
+            buy_data[16..24].copy_from_slice(&max_sol_cost.to_le_bytes());
+        }
 
         // Determine fee recipient based on mayhem mode
         let fee_recipient_meta = if is_mayhem_mode {

src/instruction/pumpswap.rs

@@ -2,7 +2,7 @@ use crate::{
     constants::trade::trade::DEFAULT_SLIPPAGE,
     instruction::utils::pumpswap::{
         accounts, fee_recipient_ata, get_user_volume_accumulator_pda, BUY_DISCRIMINATOR,
-        SELL_DISCRIMINATOR,
+        BUY_EXACT_QUOTE_IN_DISCRIMINATOR, SELL_DISCRIMINATOR,
     },
     trading::{
         common::wsol_manager,
@@ -187,11 +187,27 @@ impl InstructionBuilder for PumpSwapInstructionBuilder {
         // Create instruction data
         let mut data = [0u8; 24];
         if quote_is_wsol_or_usdc {
-            data[..8].copy_from_slice(&BUY_DISCRIMINATOR);
-            // base_amount_out
-            data[8..16].copy_from_slice(&token_amount.to_le_bytes());
-            // max_quote_amount_in
-            data[16..24].copy_from_slice(&sol_amount.to_le_bytes());
+            if params.use_exact_in_instruction {
+                // buy_exact_quote_in(spendable_quote_in: u64, min_base_amount_out: u64)
+                // Spend exactly the input SOL/quote amount, get at least min_base_amount_out
+                let min_base_amount_out = crate::utils::calc::common::calculate_with_slippage_sell(
+                    token_amount,
+                    params.slippage_basis_points.unwrap_or(DEFAULT_SLIPPAGE),
+                );
+                data[..8].copy_from_slice(&BUY_EXACT_QUOTE_IN_DISCRIMINATOR);
+                // spendable_quote_in (exact SOL amount to spend)
+                data[8..16].copy_from_slice(&params.input_amount.unwrap_or(0).to_le_bytes());
+                // min_base_amount_out (minimum tokens to receive)
+                data[16..24].copy_from_slice(&min_base_amount_out.to_le_bytes());
+            } else {
+                // buy(base_amount_out: u64, max_quote_amount_in: u64)
+                // Buy exactly base_amount_out tokens, pay up to max_quote_amount_in
+                data[..8].copy_from_slice(&BUY_DISCRIMINATOR);
+                // base_amount_out
+                data[8..16].copy_from_slice(&token_amount.to_le_bytes());
+                // max_quote_amount_in
+                data[16..24].copy_from_slice(&sol_amount.to_le_bytes());
+            }
         } else {
             data[..8].copy_from_slice(&SELL_DISCRIMINATOR);
             // base_amount_in

src/instruction/utils/pumpfun.rs

@@ -154,6 +154,11 @@ pub mod accounts {
         };
 }
 
+/// Instruction discriminators for PumpFun program
+pub const BUY_DISCRIMINATOR: [u8; 8] = [102, 6, 61, 18, 1, 218, 235, 234];
+pub const BUY_EXACT_SOL_IN_DISCRIMINATOR: [u8; 8] = [56, 252, 116, 8, 158, 223, 205, 95];
+pub const SELL_DISCRIMINATOR: [u8; 8] = [51, 230, 133, 164, 1, 127, 131, 173];
+
 pub struct Symbol;
 
 impl Symbol {

src/instruction/utils/pumpswap.rs

@@ -136,6 +136,7 @@ pub mod accounts {
 }
 
 pub const BUY_DISCRIMINATOR: [u8; 8] = [102, 6, 61, 18, 1, 218, 235, 234];
+pub const BUY_EXACT_QUOTE_IN_DISCRIMINATOR: [u8; 8] = [198, 46, 21, 82, 180, 217, 232, 112];
 pub const SELL_DISCRIMINATOR: [u8; 8] = [51, 230, 133, 164, 1, 127, 131, 173];
 
 // Find a pool for a specific mint

src/lib.rs

@@ -508,6 +508,7 @@ impl TradingClient {
             fixed_output_amount: params.fixed_output_token_amount,
             gas_fee_strategy: params.gas_fee_strategy,
             simulate: params.simulate,
+            use_exact_in_instruction: false,
         };
 
         // Validate protocol params
@@ -617,6 +618,7 @@ impl TradingClient {
             fixed_output_amount: params.fixed_output_token_amount,
             gas_fee_strategy: params.gas_fee_strategy,
             simulate: params.simulate,
+            use_exact_in_instruction: false,
         };
 
         // Validate protocol params

src/trading/core/params.rs

@@ -67,6 +67,10 @@ pub struct SwapParams {
     pub fixed_output_amount: Option<u64>,
     pub gas_fee_strategy: GasFeeStrategy,
     pub simulate: bool,
+    /// Use exact input instructions (buy_exact_sol_in for PumpFun, buy_exact_quote_in for PumpSwap).
+    /// When true, the exact SOL/quote amount is spent and slippage is applied to output tokens.
+    /// When false (default), uses regular buy instruction where slippage is applied to SOL/quote input.
+    pub use_exact_in_instruction: bool,
 }
 
 impl std::fmt::Debug for SwapParams {