> ## Documentation Index
> Fetch the complete documentation index at: https://docs.orbitflare.com/llms.txt
> Use this file to discover all available pages before exploring further.

# simulateTransaction

> Simulates sending a transaction

## Parameters

<ResponseField name="transaction" type="string" required>
  Transaction to simulate, as a base-64 encoded string
</ResponseField>

<ResponseField name="config" type="object" optional>
  Configuration object containing:

  <ResponseField name="sigVerify" type="boolean" optional>
    If true, verify transaction signatures
  </ResponseField>

  <ResponseField name="commitment" type="string" optional>
    Commitment level (processed, confirmed, finalized)
  </ResponseField>

  <ResponseField name="encoding" type="string" optional>
    Encoding format for the transaction (base58, base64, json)
  </ResponseField>

  <ResponseField name="replaceRecentBlockhash" type="boolean" optional>
    If true, replace the transaction's recent blockhash with the most recent blockhash
  </ResponseField>

  <ResponseField name="accounts" type="object" optional>
    Accounts configuration object containing:

    <ResponseField name="encoding" type="string" optional>
      Encoding format for account data (base58, base64, json)
    </ResponseField>

    <ResponseField name="addresses" type="array" optional>
      Array of account addresses to return data for
    </ResponseField>
  </ResponseField>

  <ResponseField name="minContextSlot" type="number" optional>
    The minimum slot that the request can be evaluated at
  </ResponseField>
</ResponseField>

## Response

<ResponseField name="result" type="object">
  Object containing:

  <ResponseField name="err" type="string | null">
    Error if transaction simulation failed, null if simulation succeeded
  </ResponseField>

  <ResponseField name="logs" type="array">
    Array of log messages the transaction instructions output during execution
  </ResponseField>

  <ResponseField name="accounts" type="array" optional>
    Array of accounts with their data (if requested)
  </ResponseField>

  <ResponseField name="unitsConsumed" type="number" optional>
    Number of compute units consumed by the transaction
  </ResponseField>

  <ResponseField name="returnData" type="object" optional>
    Program return data from the simulation
  </ResponseField>
</ResponseField>

## Code Examples

### Basic Request

```bash theme={null}
curl https://fra.rpc.orbitflare.com?api_key=YOUR-API-KEY -X POST -H "Content-Type: application/json" -d '{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "simulateTransaction",
  "params": [
    "4hXTCkRzt9WyecNzV1XPgCDfGAZzQKNxLXgynz5QDuWWPSAZBZSHptvWRL3BjCvzUXRdKvHL2b7yGrRQcWyaqsaBCncVG7BFggS8w9snUts67BSh3EqKpXLUm5UMHfD7ZBe9GhARjbNQMLJ1QD3Spr6oMTFNhyKNMr3WNFCrXgDS7uV7u",
    {
      "sigVerify": false,
      "commitment": "confirmed",
      "encoding": "base64"
    }
  ]
}'
```

### Using web3.js

```typescript theme={null}
import { Connection, Transaction, PublicKey, SystemProgram } from '@solana/web3.js';

const connection = new Connection('https://fra.rpc.orbitflare.com?api_key=YOUR-API-KEY');

// Create and simulate transaction
const transaction = new Transaction().add(
  SystemProgram.transfer({
    fromPubkey: new PublicKey('83astBRguLMdt2h5U1Tpdq5tjFoJ6noeGwaY3mDLVcri'),
    toPubkey: new PublicKey('J7rBdM6AecPDEZp8aPq5tPmsPzPhQG4HD6YtAcQBDfJj'),
    lamports: 1000000000
  })
);

const simulation = await connection.simulateTransaction(transaction);
console.log('Simulation result:', simulation);

// Simulate transaction with analysis
async function simulateTransactionWithAnalysis(
  transaction: Transaction,
  config: { 
    sigVerify?: boolean;
    commitment?: string;
    replaceRecentBlockhash?: boolean;
  }
) {
  const simulation = await connection.simulateTransaction(transaction, config);
  
  return {
    simulation: {
      success: !simulation.value.err,
      error: simulation.value.err,
      logs: simulation.value.logs,
      unitsConsumed: simulation.value.unitsConsumed
    },
    transaction: {
      recentBlockhash: transaction.recentBlockhash,
      feePayer: transaction.feePayer?.toBase58(),
      instructions: transaction.instructions.length
    },
    metadata: {
      timestamp: Date.now(),
      commitment: config.commitment
    }
  };
}
```

## Notes

1. Simulates sending a transaction without actually sending it
2. The response includes execution logs and errors
3. The simulation is performed on the current state
4. No state changes are persisted
5. Useful for testing and debugging transactions

## Best Practices

1. Use simulation before sending real transactions
2. Check compute unit consumption
3. Analyze program logs for errors
4. Verify account states after simulation
5. Handle simulation errors appropriately

## Common Errors

| Code   | Message                       | Solution                                         |
| ------ | ----------------------------- | ------------------------------------------------ |
| -32601 | Method not found              | Verify you're connected to a Solana RPC node     |
| -32602 | Invalid params                | Check transaction format and encoding            |
| -32003 | Transaction simulation failed | Verify transaction validity and account balances |
| -32004 | Blockhash not found           | Use a more recent blockhash                      |
| -32005 | Node is behind                | Try a different RPC node                         |

## Use Cases

1. **Transaction Analysis**
   ```typescript theme={null}
   interface TransactionAnalysis {
     transaction: {
       instructions: number;
       signers: number;
       estimatedUnits: number;
     };
     simulation: {
       success: boolean;
       error: string | null;
       logs: string[];
       unitsConsumed: number;
     };
     analysis: {
       programInvocations: number;
       accountAccesses: number;
       errorAnalysis?: string;
     };
     metadata: {
       timestamp: number;
       commitment?: string;
     };
   }

   class TransactionAnalyzer {
     async analyzeTransaction(
       transaction: Transaction,
       config: { 
         sigVerify?: boolean;
         commitment?: string;
       }
     ): Promise<TransactionAnalysis> {
       const simulation = await connection.simulateTransaction(transaction, config);
       
       const logs = simulation.value.logs || [];
       const programInvocations = logs.filter(log => 
         log.includes('Program') && log.includes('invoke')
       ).length;
       
       const accountAccesses = logs.filter(log =>
         log.includes('Account') || log.includes('Token')
       ).length;
       
       let errorAnalysis;
       if (simulation.value.err) {
         errorAnalysis = this.analyzeError(simulation.value.err);
       }
       
       return {
         transaction: {
           instructions: transaction.instructions.length,
           signers: transaction.signatures.length,
           estimatedUnits: simulation.value.unitsConsumed || 0
         },
         simulation: {
           success: !simulation.value.err,
           error: simulation.value.err,
           logs,
           unitsConsumed: simulation.value.unitsConsumed || 0
         },
         analysis: {
           programInvocations,
           accountAccesses,
           errorAnalysis
         },
         metadata: {
           timestamp: Date.now(),
           commitment: config.commitment
         }
       };
     }
     
     private analyzeError(error: any): string {
       if (typeof error === 'string') {
         if (error.includes('insufficient funds')) {
           return 'Transaction failed due to insufficient funds';
         }
         if (error.includes('invalid account owner')) {
           return 'Transaction failed due to invalid account ownership';
         }
         if (error.includes('account not found')) {
           return 'Transaction failed due to missing account';
         }
       }
       return 'Unknown error occurred during simulation';
     }
   }
   ```

2. **Transaction Validation**
   ```typescript theme={null}
   interface TransactionValidation {
     transaction: {
       signature: string;
       blockhash: string;
       feePayer: string;
     };
     checks: Array<{
       name: string;
       passed: boolean;
       details?: string;
     }>;
     recommendations: Array<{
       type: 'fix' | 'warning' | 'info';
       message: string;
     }>;
     metadata: {
       timestamp: number;
     };
   }

   class TransactionValidator {
     private readonly maxUnits = 200000;
     private readonly minAccountRent = 890880;
     
     async validateTransaction(
       transaction: Transaction,
       config: { 
         sigVerify?: boolean;
         commitment?: string;
       }
     ): Promise<TransactionValidation> {
       const simulation = await connection.simulateTransaction(transaction, config);
       
       const checks: Array<{
         name: string;
         passed: boolean;
         details?: string;
       }> = [];
       
       const recommendations: Array<{
         type: 'fix' | 'warning' | 'info';
         message: string;
       }> = [];
       
       // Check compute units
       const unitsConsumed = simulation.value.unitsConsumed || 0;
       checks.push({
         name: 'Compute Units',
         passed: unitsConsumed <= this.maxUnits,
         details: `${unitsConsumed} units consumed`
       });
       
       if (unitsConsumed > this.maxUnits) {
         recommendations.push({
           type: 'fix',
           message: 'Transaction exceeds compute unit limit'
         });
       }
       
       // Check for errors
       checks.push({
         name: 'Simulation',
         passed: !simulation.value.err,
         details: simulation.value.err?.toString()
       });
       
       if (simulation.value.err) {
         recommendations.push({
           type: 'fix',
           message: `Fix simulation error: ${simulation.value.err}`
         });
       }
       
       // Analyze logs
       const logs = simulation.value.logs || [];
       checks.push({
         name: 'Program Execution',
         passed: logs.some(log => log.includes('Program log:')),
         details: 'Program execution logs present'
       });
       
       // Check account rent
       const rentWarnings = logs.filter(log => 
         log.includes('insufficient lamports for rent')
       );
       
       if (rentWarnings.length > 0) {
         checks.push({
           name: 'Account Rent',
           passed: false,
           details: 'Insufficient lamports for rent'
         });
         
         recommendations.push({
           type: 'fix',
           message: `Ensure accounts have minimum rent: ${this.minAccountRent} lamports`
         });
       }
       
       return {
         transaction: {
           signature: transaction.signatures[0]?.signature?.toString() || '',
           blockhash: transaction.recentBlockhash || '',
           feePayer: transaction.feePayer?.toBase58() || ''
         },
         checks,
         recommendations,
         metadata: {
           timestamp: Date.now()
         }
       };
     }
   }
   ```

3. **Transaction Optimization**
   ```typescript theme={null}
   interface TransactionOptimization {
     original: {
       instructions: number;
       unitsConsumed: number;
     };
     optimized: {
       instructions: number;
       unitsConsumed: number;
       savings: number;
     };
     changes: Array<{
       type: 'merge' | 'remove' | 'reorder';
       description: string;
       impact: number;
     }>;
     metadata: {
       timestamp: number;
     };
   }

   class TransactionOptimizer {
     async optimizeTransaction(
       transaction: Transaction
     ): Promise<TransactionOptimization> {
       // Simulate original transaction
       const originalSimulation = await connection.simulateTransaction(transaction);
       const originalUnits = originalSimulation.value.unitsConsumed || 0;
       
       const changes: Array<{
         type: 'merge' | 'remove' | 'reorder';
         description: string;
         impact: number;
       }> = [];
       
       // Create optimized transaction
       const optimizedTransaction = new Transaction();
       const instructions = [...transaction.instructions];
       
       // Analyze and merge similar instructions
       const mergedInstructions = this.mergeInstructions(instructions);
       if (mergedInstructions.length < instructions.length) {
         changes.push({
           type: 'merge',
           description: `Merged ${instructions.length - mergedInstructions.length} similar instructions`,
           impact: 0 // Will be updated after simulation
         });
       }
       
       // Remove redundant instructions
       const cleanedInstructions = this.removeRedundantInstructions(mergedInstructions);
       if (cleanedInstructions.length < mergedInstructions.length) {
         changes.push({
           type: 'remove',
           description: `Removed ${mergedInstructions.length - cleanedInstructions.length} redundant instructions`,
           impact: 0
         });
       }
       
       // Reorder instructions for optimal execution
       const orderedInstructions = this.reorderInstructions(cleanedInstructions);
       changes.push({
         type: 'reorder',
         description: 'Reordered instructions for optimal execution',
         impact: 0
       });
       
       // Add optimized instructions
       orderedInstructions.forEach(instruction => {
         optimizedTransaction.add(instruction);
       });
       
       // Simulate optimized transaction
       const optimizedSimulation = await connection.simulateTransaction(optimizedTransaction);
       const optimizedUnits = optimizedSimulation.value.unitsConsumed || 0;
       
       // Calculate impacts
       const totalSavings = originalUnits - optimizedUnits;
       changes.forEach(change => {
         change.impact = Math.floor(totalSavings / changes.length);
       });
       
       return {
         original: {
           instructions: instructions.length,
           unitsConsumed: originalUnits
         },
         optimized: {
           instructions: orderedInstructions.length,
           unitsConsumed: optimizedUnits,
           savings: totalSavings
         },
         changes,
         metadata: {
           timestamp: Date.now()
         }
       };
     }
     
     private mergeInstructions(
       instructions: Array<any>
     ): Array<any> {
       // Implementation would analyze and merge similar instructions
       // This is a placeholder that returns the original instructions
       return instructions;
     }
     
     private removeRedundantInstructions(
       instructions: Array<any>
     ): Array<any> {
       // Implementation would identify and remove redundant instructions
       // This is a placeholder that returns the original instructions
       return instructions;
     }
     
     private reorderInstructions(
       instructions: Array<any>
     ): Array<any> {
       // Implementation would reorder instructions for optimal execution
       // This is a placeholder that returns the original instructions
       return instructions;
     }
   }
   ```