# simulateTransactionsAtSlot > For the complete documentation index, see [llms.txt](/docs/llms.txt). POST https://solana-mainnet.g.alchemy.com/v2/{apiKey} Simulates one or more transactions against the archived account state at a historical slot, using the real Solana runtime. It is a separate method from `simulateTransaction` and from Jito's `simulateBundle`, combining `simulateTransaction`'s "what would this do" question with `simulateBundle`'s multi-transaction sequencing, and extending both to any slot in the [Account Archive](/docs/solana/account-archive)'s coverage. Up to 5 transactions execute in order over a single shared, mutable overlay: each successful transaction's writable-account changes are written back before the next entry runs, even across a slot change. The first failure aborts the rest of the sequence, which are marked `skipped`. `stateOverrides` lets you patch specific accounts (or the Clock sysvar) before each entry runs; everything you do not override keeps its archived value. Response invariants: - `simulationResults` is always an array, in request order, even for a single-entry request. - `status` is authoritative; filter on it rather than on `err`, because `skipped` entries also carry `err: null`. - A `failed` entry still ran, so it reports `feeLamports` and an empty (not `null`) `changedWritableAccounts`. - A failed transaction returns a successful JSON-RPC response with the entry's `err` populated. Bad input (unknown fields, more than 5 simulations, decreasing slots, a vote-program transaction, an unparseable transaction) is a `-32602` JSON-RPC error, detected before anything executes. - Each entry's `postExecutionAccounts` is filtered to only the accounts the simulation actually touched (its `stateOverrides` plus the transaction's writes); accounts named in `postExecutionAccountsConfigs` that the simulation did not touch are omitted from that entry (expect `[]` on a `success` whose transaction touched none of them). Caps enforced before execution (each triggers `-32602` if exceeded): at most 5 simulations per request; 100 accounts per accounts config; 100 `stateOverrides` entries per simulation (10 MiB per `data` override); 128 unique transaction-referenced accounts per entry (static keys plus lookup-table entries); 25 MiB combined byte budget across the rendered result. Notes on behavior worth knowing before you build: - Durable-nonce transactions (an `AdvanceNonceAccount` instruction at index 0) validate against the archived nonce account's real state at that slot, not against a blockhash. - Vote-program transactions are rejected outright with `-32602` because vote accounts are not in the archive. - `sigVerify: true` requires `replaceRecentBlockhash: false`, since replacing the blockhash would invalidate signatures; sending both as `true` is refused with `-32602`. - The simulator pins a single Agave/SVM release, so very old slots fall outside what the current build can reproduce faithfully. The usable window is recent history and grows over time as the backfill pipeline extends further back. Reference: https://www.alchemy.com/docs/chains/solana/solana-api-endpoints/simulate-transactions-at-slot ## Parameters | Name | Type | Required | Description | |------|------|----------|-------------| | Simulation request | object | Yes | A single object containing the ordered simulations, optional pre- and post-execution account captures, and the execution flags (`innerInstructions`, `sigVerify`, `replaceRecentBlockhash`). | ## Result **Simulation results** (object): A context slot plus the per-simulation execution results. `simulationResults` is always present and in request order, even for a single-entry request. ## Example ### Request ```json { "jsonrpc": "2.0", "method": "simulateTransactionsAtSlot", "params": [ { "simulations": [ { "slot": 400000000, "encodedTransaction": "AVshRNwSzqLB+PQb2vsbiK/ZUNZuyrcWvArv9sv9/AQieAx9gXlF0MApk8AZpYh6ESEbchfb8BBg7VYJrKJdeQ4BAAEDiojj3XQJ8ZX9UtstPLpdcspnCb8dlBIb83SIAbQPb1yBOXcOqH0XX1ajVGbDTH7My42KkbTuN6Jd9g9bj8mzlAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA4zLa+S+r7Oi2P/ekQAXl/f2a+hWHVrYcWpX5BLO40IEBAgIAAQwCAAAAQEIPAAAAAAA=" } ], "postExecutionAccountsConfigs": { "accounts": [ "9hSR6S7WPtxmTojgo6GG3k4yDPecgJY292j7xrsUGWBu" ], "encoding": "base64" }, "innerInstructions": false, "sigVerify": false, "replaceRecentBlockhash": true } ], "id": 1 } ``` ### Response ```json { "jsonrpc": "2.0", "result": { "context": { "apiVersion": "2.3.3", "slot": 400000000 }, "value": { "preExecutionAccounts": null, "simulationResults": [ { "slot": 400000000, "status": "success", "err": null, "replacementBlockhash": "FwRYtTPRk5N4wUeP87rTw9kQVSwigB6kbikGzzeCMrW5", "logs": [ "Program 11111111111111111111111111111111 invoke [1]", "Program 11111111111111111111111111111111 success" ], "unitsConsumed": 150, "feeLamports": 5000, "changedWritableAccounts": [ "AKnL4NNf3DGWZJS6cPknBuEGnVsV4A4m5tgebLHaRSZ9", "9hSR6S7WPtxmTojgo6GG3k4yDPecgJY292j7xrsUGWBu" ], "postExecutionAccounts": [ { "address": "9hSR6S7WPtxmTojgo6GG3k4yDPecgJY292j7xrsUGWBu", "account": { "lamports": 1001000000, "owner": "11111111111111111111111111111111", "executable": false, "rentEpoch": 18446744073709552000, "data": [ "", "base64" ], "space": 0 } } ], "innerInstructions": null, "returnData": null, "loadedAccountsDataSize": 0, "loadedAddresses": null } ] } }, "id": 1 } ``` ## Code Examples ### cURL ```bash curl --request POST \ --url https://solana-mainnet.g.alchemy.com/v2/docs-demo \ --header 'Content-Type: application/json' \ --data '{ "jsonrpc": "2.0", "id": 1, "method": "simulateTransactionsAtSlot", "params": [ { "simulations": [ { "slot": 400000000, "encodedTransaction": "AVshRNwSzqLB+PQb2vsbiK/ZUNZuyrcWvArv9sv9/AQieAx9gXlF0MApk8AZpYh6ESEbchfb8BBg7VYJrKJdeQ4BAAEDiojj3XQJ8ZX9UtstPLpdcspnCb8dlBIb83SIAbQPb1yBOXcOqH0XX1ajVGbDTH7My42KkbTuN6Jd9g9bj8mzlAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA4zLa+S+r7Oi2P/ekQAXl/f2a+hWHVrYcWpX5BLO40IEBAgIAAQwCAAAAQEIPAAAAAAA=" } ], "postExecutionAccountsConfigs": { "accounts": [ "9hSR6S7WPtxmTojgo6GG3k4yDPecgJY292j7xrsUGWBu" ], "encoding": "base64" }, "innerInstructions": false, "sigVerify": false, "replaceRecentBlockhash": true } ] }' ``` ### JavaScript ```javascript const options = { method: 'POST', headers: {'Content-Type': 'application/json'}, body: JSON.stringify({ jsonrpc: '2.0', id: 1, method: 'simulateTransactionsAtSlot', params: [ { simulations: [ { slot: 400000000, encodedTransaction: 'AVshRNwSzqLB+PQb2vsbiK/ZUNZuyrcWvArv9sv9/AQieAx9gXlF0MApk8AZpYh6ESEbchfb8BBg7VYJrKJdeQ4BAAEDiojj3XQJ8ZX9UtstPLpdcspnCb8dlBIb83SIAbQPb1yBOXcOqH0XX1ajVGbDTH7My42KkbTuN6Jd9g9bj8mzlAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA4zLa+S+r7Oi2P/ekQAXl/f2a+hWHVrYcWpX5BLO40IEBAgIAAQwCAAAAQEIPAAAAAAA=' } ], postExecutionAccountsConfigs: {accounts: ['9hSR6S7WPtxmTojgo6GG3k4yDPecgJY292j7xrsUGWBu'], encoding: 'base64'}, innerInstructions: false, sigVerify: false, replaceRecentBlockhash: true } ] }) }; fetch('https://solana-mainnet.g.alchemy.com/v2/docs-demo', options) .then(res => res.json()) .then(res => console.log(res)) .catch(err => console.error(err)); ``` ### Python ```python import requests url = "https://solana-mainnet.g.alchemy.com/v2/docs-demo" payload = { "jsonrpc": "2.0", "id": 1, "method": "simulateTransactionsAtSlot", "params": [ { "simulations": [ { "slot": 400000000, "encodedTransaction": "AVshRNwSzqLB+PQb2vsbiK/ZUNZuyrcWvArv9sv9/AQieAx9gXlF0MApk8AZpYh6ESEbchfb8BBg7VYJrKJdeQ4BAAEDiojj3XQJ8ZX9UtstPLpdcspnCb8dlBIb83SIAbQPb1yBOXcOqH0XX1ajVGbDTH7My42KkbTuN6Jd9g9bj8mzlAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA4zLa+S+r7Oi2P/ekQAXl/f2a+hWHVrYcWpX5BLO40IEBAgIAAQwCAAAAQEIPAAAAAAA=" } ], "postExecutionAccountsConfigs": { "accounts": ["9hSR6S7WPtxmTojgo6GG3k4yDPecgJY292j7xrsUGWBu"], "encoding": "base64" }, "innerInstructions": False, "sigVerify": False, "replaceRecentBlockhash": True } ] } headers = {"Content-Type": "application/json"} response = requests.post(url, json=payload, headers=headers) print(response.text) ``` ### Go ```go package main import ( "fmt" "strings" "net/http" "io" ) func main() { url := "https://solana-mainnet.g.alchemy.com/v2/docs-demo" payload := strings.NewReader("{\n \"jsonrpc\": \"2.0\",\n \"id\": 1,\n \"method\": \"simulateTransactionsAtSlot\",\n \"params\": [\n {\n \"simulations\": [\n {\n \"slot\": 400000000,\n \"encodedTransaction\": \"AVshRNwSzqLB+PQb2vsbiK/ZUNZuyrcWvArv9sv9/AQieAx9gXlF0MApk8AZpYh6ESEbchfb8BBg7VYJrKJdeQ4BAAEDiojj3XQJ8ZX9UtstPLpdcspnCb8dlBIb83SIAbQPb1yBOXcOqH0XX1ajVGbDTH7My42KkbTuN6Jd9g9bj8mzlAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA4zLa+S+r7Oi2P/ekQAXl/f2a+hWHVrYcWpX5BLO40IEBAgIAAQwCAAAAQEIPAAAAAAA=\"\n }\n ],\n \"postExecutionAccountsConfigs\": {\n \"accounts\": [\n \"9hSR6S7WPtxmTojgo6GG3k4yDPecgJY292j7xrsUGWBu\"\n ],\n \"encoding\": \"base64\"\n },\n \"innerInstructions\": false,\n \"sigVerify\": false,\n \"replaceRecentBlockhash\": true\n }\n ]\n}") req, _ := http.NewRequest("POST", url, payload) req.Header.Add("Content-Type", "application/json") res, _ := http.DefaultClient.Do(req) defer res.Body.Close() body, _ := io.ReadAll(res.Body) fmt.Println(string(body)) } ``` ### Java ```java HttpResponse response = Unirest.post("https://solana-mainnet.g.alchemy.com/v2/docs-demo") .header("Content-Type", "application/json") .body("{\n \"jsonrpc\": \"2.0\",\n \"id\": 1,\n \"method\": \"simulateTransactionsAtSlot\",\n \"params\": [\n {\n \"simulations\": [\n {\n \"slot\": 400000000,\n \"encodedTransaction\": \"AVshRNwSzqLB+PQb2vsbiK/ZUNZuyrcWvArv9sv9/AQieAx9gXlF0MApk8AZpYh6ESEbchfb8BBg7VYJrKJdeQ4BAAEDiojj3XQJ8ZX9UtstPLpdcspnCb8dlBIb83SIAbQPb1yBOXcOqH0XX1ajVGbDTH7My42KkbTuN6Jd9g9bj8mzlAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA4zLa+S+r7Oi2P/ekQAXl/f2a+hWHVrYcWpX5BLO40IEBAgIAAQwCAAAAQEIPAAAAAAA=\"\n }\n ],\n \"postExecutionAccountsConfigs\": {\n \"accounts\": [\n \"9hSR6S7WPtxmTojgo6GG3k4yDPecgJY292j7xrsUGWBu\"\n ],\n \"encoding\": \"base64\"\n },\n \"innerInstructions\": false,\n \"sigVerify\": false,\n \"replaceRecentBlockhash\": true\n }\n ]\n}") .asString(); ``` ### C# ```csharp using RestSharp; var options = new RestClientOptions("https://solana-mainnet.g.alchemy.com/v2/docs-demo"); var client = new RestClient(options); var request = new RestRequest(""); request.AddJsonBody("{\n \"jsonrpc\": \"2.0\",\n \"id\": 1,\n \"method\": \"simulateTransactionsAtSlot\",\n \"params\": [\n {\n \"simulations\": [\n {\n \"slot\": 400000000,\n \"encodedTransaction\": \"AVshRNwSzqLB+PQb2vsbiK/ZUNZuyrcWvArv9sv9/AQieAx9gXlF0MApk8AZpYh6ESEbchfb8BBg7VYJrKJdeQ4BAAEDiojj3XQJ8ZX9UtstPLpdcspnCb8dlBIb83SIAbQPb1yBOXcOqH0XX1ajVGbDTH7My42KkbTuN6Jd9g9bj8mzlAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA4zLa+S+r7Oi2P/ekQAXl/f2a+hWHVrYcWpX5BLO40IEBAgIAAQwCAAAAQEIPAAAAAAA=\"\n }\n ],\n \"postExecutionAccountsConfigs\": {\n \"accounts\": [\n \"9hSR6S7WPtxmTojgo6GG3k4yDPecgJY292j7xrsUGWBu\"\n ],\n \"encoding\": \"base64\"\n },\n \"innerInstructions\": false,\n \"sigVerify\": false,\n \"replaceRecentBlockhash\": true\n }\n ]\n}", false); var response = await client.PostAsync(request); Console.WriteLine("{0}", response.Content); ``` ## OpenRPC Method Specification ```yaml name: simulateTransactionsAtSlot summary: Simulates one or more transactions against archived Solana account state at a historical slot. description: |- Simulates one or more transactions against the archived account state at a historical slot, using the real Solana runtime. It is a separate method from `simulateTransaction` and from Jito's `simulateBundle`, combining `simulateTransaction`'s "what would this do" question with `simulateBundle`'s multi-transaction sequencing, and extending both to any slot in the [Account Archive](/docs/solana/account-archive)'s coverage. Up to 5 transactions execute in order over a single shared, mutable overlay: each successful transaction's writable-account changes are written back before the next entry runs, even across a slot change. The first failure aborts the rest of the sequence, which are marked `skipped`. `stateOverrides` lets you patch specific accounts (or the Clock sysvar) before each entry runs; everything you do not override keeps its archived value. Response invariants: - `simulationResults` is always an array, in request order, even for a single-entry request. - `status` is authoritative; filter on it rather than on `err`, because `skipped` entries also carry `err: null`. - A `failed` entry still ran, so it reports `feeLamports` and an empty (not `null`) `changedWritableAccounts`. - A failed transaction returns a successful JSON-RPC response with the entry's `err` populated. Bad input (unknown fields, more than 5 simulations, decreasing slots, a vote-program transaction, an unparseable transaction) is a `-32602` JSON-RPC error, detected before anything executes. - Each entry's `postExecutionAccounts` is filtered to only the accounts the simulation actually touched (its `stateOverrides` plus the transaction's writes); accounts named in `postExecutionAccountsConfigs` that the simulation did not touch are omitted from that entry (expect `[]` on a `success` whose transaction touched none of them). Caps enforced before execution (each triggers `-32602` if exceeded): at most 5 simulations per request; 100 accounts per accounts config; 100 `stateOverrides` entries per simulation (10 MiB per `data` override); 128 unique transaction-referenced accounts per entry (static keys plus lookup-table entries); 25 MiB combined byte budget across the rendered result. Notes on behavior worth knowing before you build: - Durable-nonce transactions (an `AdvanceNonceAccount` instruction at index 0) validate against the archived nonce account's real state at that slot, not against a blockhash. - Vote-program transactions are rejected outright with `-32602` because vote accounts are not in the archive. - `sigVerify: true` requires `replaceRecentBlockhash: false`, since replacing the blockhash would invalidate signatures; sending both as `true` is refused with `-32602`. - The simulator pins a single Agave/SVM release, so very old slots fall outside what the current build can reproduce faithfully. The usable window is recent history and grows over time as the backfill pipeline extends further back. x-compute-units: 1500 params: - name: Simulation request required: true description: A single object containing the ordered simulations, optional pre- and post-execution account captures, and the execution flags (`innerInstructions`, `sigVerify`, `replaceRecentBlockhash`). schema: title: SimulateTransactionsAtSlot Request type: object description: 'The full request body for `simulateTransactionsAtSlot`. The caller passes this as a single positional parameter (`params: [{...}]`).' required: - simulations properties: simulations: type: array minItems: 1 maxItems: 5 description: 'Ordered list of 1-5 transactions to simulate. They execute in order over a single shared overlay: each successful transaction''s writable-account changes are written back before the next entry runs, even across a slot change. The first failure aborts the rest of the sequence, which are marked `skipped`.' items: title: SimulateTransactionsAtSlot Simulation Entry type: object required: - encodedTransaction properties: encodedTransaction: type: string description: The transaction to simulate, encoded as a base64 string. `base58` is not accepted. slot: type: integer minimum: 0 description: The finalized slot whose archived state this transaction executes against. If omitted, defaults to the previous entry's `slot` (the first entry defaults to the finalized tip). Slots across entries must be non-decreasing; a decreasing slot is refused with `-32602`. stateOverrides: type: object description: Optional map of account overrides applied to the archived state before this transaction runs. Up to 100 entries per simulation. Keys are base-58 pubkeys; values are either an account override or, for the Clock sysvar pubkey only, a Clock override. Mixing the two shapes on the Clock pubkey is refused. additionalProperties: oneOf: - title: SimulateTransactionsAtSlot Account Override type: object additionalProperties: false description: Partial override of a single account's state. Only the fields present are overridden; every other field keeps its archived value. The combined byte size of all overridden `data` payloads is capped at 10 MiB per `data` override. properties: lamports: type: integer minimum: 0 description: Replacement lamport balance. data: description: Replacement account data. Either a bare base64 string, or a `[data, "base64"]` tuple. Base58 is not accepted. oneOf: - type: string - type: array minItems: 2 maxItems: 2 items: type: string owner: title: Pubkey type: string description: Replacement owner program. executable: type: boolean description: Replacement `executable` flag. - title: SimulateTransactionsAtSlot Clock Sysvar Override type: object additionalProperties: false description: Shape accepted only for the Clock sysvar pubkey (`SysvarC1ock11111111111111111111111111111111`). It overrides the clock fields that the runtime surfaces to programs. Mixing this shape with the generic account-override shape on the same key is refused. properties: unixTimestamp: type: integer description: Replacement UNIX timestamp (seconds). slot: type: integer minimum: 0 description: Replacement clock slot. epoch: type: integer minimum: 0 description: Replacement clock epoch. preExecutionAccountsConfigs: description: Accounts to capture once, from the archived state at the first simulation's slot, before any transaction runs. Omit to skip the pre-execution capture (`preExecutionAccounts` will be `null`). title: SimulateTransactionsAtSlot Accounts Config type: object required: - accounts properties: accounts: type: array maxItems: 100 description: Base-58 pubkeys to capture (up to 100). items: title: Pubkey type: string description: Base-58 encoded public key. encoding: type: string enum: - base64 - jsonParsed default: base64 description: Encoding for the returned account data. Only `base64` (default) and `jsonParsed` are supported here (not `base58` or `base64+zstd`). dataSlice: type: array description: Per-account byte slice to return instead of the full `data`. Supply one entry per `accounts` entry (use `null` for accounts you do not want sliced), or omit the field entirely. items: oneOf: - title: Data Slice type: object properties: length: type: integer description: Number of bytes to return. offset: type: integer description: Byte offset from which to start reading. - type: 'null' postExecutionAccountsConfigs: description: Accounts to capture after every simulation, applied once per simulation entry. Only the subset of these accounts that the simulation actually touched (via its own `stateOverrides` or the transaction's writes) is returned on each entry; untouched requested accounts are omitted from that entry's `postExecutionAccounts`. Omit the config entirely to skip the post-execution capture (each entry's `postExecutionAccounts` will be `null`). title: SimulateTransactionsAtSlot Accounts Config type: object required: - accounts properties: accounts: type: array maxItems: 100 description: Base-58 pubkeys to capture (up to 100). items: title: Pubkey type: string description: Base-58 encoded public key. encoding: type: string enum: - base64 - jsonParsed default: base64 description: Encoding for the returned account data. Only `base64` (default) and `jsonParsed` are supported here (not `base58` or `base64+zstd`). dataSlice: type: array description: Per-account byte slice to return instead of the full `data`. Supply one entry per `accounts` entry (use `null` for accounts you do not want sliced), or omit the field entirely. items: oneOf: - title: Data Slice type: object properties: length: type: integer description: Number of bytes to return. offset: type: integer description: Byte offset from which to start reading. - type: 'null' innerInstructions: type: boolean default: false description: If `true`, each entry's `innerInstructions` field is populated. Defaults to `false`, in which case `innerInstructions` is `null`. sigVerify: type: boolean default: false description: 'If `true`, the transaction signatures are verified. Requires `replaceRecentBlockhash: false` (sending both as `true` is refused with `-32602`, since replacing the blockhash would invalidate the signatures).' replaceRecentBlockhash: type: boolean default: true description: If `true` (the default), the simulator replaces the transaction's recent blockhash before execution so that archived or stale transactions still run. examples: - name: simulateTransactionsAtSlot example params: - name: Simulation request value: simulations: - slot: 400000000 encodedTransaction: AVshRNwSzqLB+PQb2vsbiK/ZUNZuyrcWvArv9sv9/AQieAx9gXlF0MApk8AZpYh6ESEbchfb8BBg7VYJrKJdeQ4BAAEDiojj3XQJ8ZX9UtstPLpdcspnCb8dlBIb83SIAbQPb1yBOXcOqH0XX1ajVGbDTH7My42KkbTuN6Jd9g9bj8mzlAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA4zLa+S+r7Oi2P/ekQAXl/f2a+hWHVrYcWpX5BLO40IEBAgIAAQwCAAAAQEIPAAAAAAA= postExecutionAccountsConfigs: accounts: - 9hSR6S7WPtxmTojgo6GG3k4yDPecgJY292j7xrsUGWBu encoding: base64 innerInstructions: false sigVerify: false replaceRecentBlockhash: true result: name: Simulation results value: context: apiVersion: 2.3.3 slot: 400000000 value: preExecutionAccounts: null simulationResults: - slot: 400000000 status: success err: null replacementBlockhash: FwRYtTPRk5N4wUeP87rTw9kQVSwigB6kbikGzzeCMrW5 logs: - Program 11111111111111111111111111111111 invoke [1] - Program 11111111111111111111111111111111 success unitsConsumed: 150 feeLamports: 5000 changedWritableAccounts: - AKnL4NNf3DGWZJS6cPknBuEGnVsV4A4m5tgebLHaRSZ9 - 9hSR6S7WPtxmTojgo6GG3k4yDPecgJY292j7xrsUGWBu postExecutionAccounts: - address: 9hSR6S7WPtxmTojgo6GG3k4yDPecgJY292j7xrsUGWBu account: lamports: 1001000000 owner: '11111111111111111111111111111111' executable: false rentEpoch: 18446744073709552000 data: - '' - base64 space: 0 innerInstructions: null returnData: null loadedAccountsDataSize: 0 loadedAddresses: null result: name: Simulation results description: A context slot plus the per-simulation execution results. `simulationResults` is always present and in request order, even for a single-entry request. schema: title: SimulateTransactionsAtSlot Result type: object description: The RPC response envelope. `context.slot` echoes the first simulation's slot; the per-entry `slot` in each result is the per-entry truth for a sequence spanning multiple slots. properties: context: type: object properties: apiVersion: type: string slot: type: integer description: The first simulation's slot. For multi-slot sequences, read each entry's own `slot` instead. value: type: object properties: preExecutionAccounts: type: array nullable: true description: Snapshot of the accounts named in `preExecutionAccountsConfigs`, taken from archived state at the first simulation's slot. `null` if the config was omitted. items: title: SimulateTransactionsAtSlot Captured Account type: object description: A `{address, account}` pair for a captured account. properties: address: title: Pubkey type: string description: Base-58 encoded public key. account: nullable: true description: Account state at the capture point, in the requested encoding, or `null` if the account did not exist. title: Account Information type: object properties: lamports: type: integer description: Number of lamports assigned to this account. owner: title: Pubkey type: string description: Program owner of this account. data: title: Account Data type: array description: Account data in the specified encoding format. items: type: string executable: type: boolean description: Indicates if the account contains a program. rentEpoch: type: integer description: The epoch at which this account will next owe rent. size: type: integer description: The data size of the account. simulationResults: type: array description: One entry per simulation, in request order. Always present as an array, even for a single-entry request. items: title: SimulateTransactionsAtSlot Simulation Result type: object description: 'Execution outcome for one simulation. Filter on `status` rather than `err`: a `skipped` entry also carries `err: null`.' properties: slot: type: integer description: The slot this entry executed against. status: type: string enum: - success - failed - skipped description: Authoritative outcome. `success` executed cleanly; `failed` executed but the transaction reverted; `skipped` was aborted because an earlier entry failed. err: nullable: true description: The `TransactionError` for a `failed` entry, otherwise `null`. Note that a `skipped` entry also carries `null`. replacementBlockhash: type: string nullable: true description: The blockhash the simulator substituted when `replaceRecentBlockhash` was `true`, as a bare base-58 string (not an object). `null` when the caller kept its own blockhash, when the transaction is durable-nonce, or when the entry was `skipped`. logs: type: array nullable: true description: Program log messages produced during execution. items: type: string unitsConsumed: type: integer nullable: true description: Compute units consumed by this transaction. `null` for a `skipped` entry. feeLamports: type: integer nullable: true description: Fee charged to the payer. `null` only before fee assessment runs (for example, an unpayable fee payer); a `failed` entry still debits the payer and reports its fee. changedWritableAccounts: type: array description: Accounts the transaction actually mutated. Empty (`[]`, not `null`) for a `failed` entry that ran; `null` only for `skipped`. nullable: true items: title: Pubkey type: string description: Base-58 encoded public key. postExecutionAccounts: type: array nullable: true description: Captured accounts after this entry, filtered to only those that the simulation actually touched (via its own `stateOverrides` or the transaction's writes). Accounts named in `postExecutionAccountsConfigs` that this entry did not touch are omitted here (expect `[]` for a `success` entry whose transaction did not touch any requested account). `null` if the config was omitted or if the entry was `skipped`. items: title: SimulateTransactionsAtSlot Captured Account type: object description: A `{address, account}` pair for a captured account. properties: address: title: Pubkey type: string description: Base-58 encoded public key. account: nullable: true description: Account state at the capture point, in the requested encoding, or `null` if the account did not exist. title: Account Information type: object properties: lamports: type: integer description: Number of lamports assigned to this account. owner: title: Pubkey type: string description: Program owner of this account. data: title: Account Data type: array description: Account data in the specified encoding format. items: type: string executable: type: boolean description: Indicates if the account contains a program. rentEpoch: type: integer description: The epoch at which this account will next owe rent. size: type: integer description: The data size of the account. innerInstructions: type: array nullable: true description: 'Inner instructions produced during execution. `null` unless `innerInstructions: true` was set on the request.' items: title: SimulateTransactionsAtSlot Inner Instruction Group type: object description: Inner instructions emitted by a single top-level instruction. properties: index: type: integer description: Index into the transaction's top-level instructions array that produced these inner instructions. instructions: type: array items: type: object properties: programId: title: Pubkey type: string description: Program invoked by this inner instruction. accounts: type: array description: Accounts passed to the inner instruction. items: title: Pubkey type: string description: Base-58 encoded public key. data: type: string description: Instruction data, base-58 encoded. stackHeight: type: integer description: CPI stack depth at which this instruction was invoked. program: type: string nullable: true description: Human-readable program name when a parser is available, otherwise `null`. parsed: type: object nullable: true description: Parsed form of the instruction when a parser is available, otherwise `null`. properties: type: type: string info: type: object returnData: nullable: true description: Program return data, if the transaction produced any, otherwise `null`. type: object properties: programId: title: Pubkey type: string description: Base-58 encoded public key. data: type: array minItems: 2 maxItems: 2 description: '`[base64Data, "base64"]` tuple.' items: type: string loadedAccountsDataSize: type: integer nullable: true description: Total loaded account data size for the transaction. `null` only before the loader ran. loadedAddresses: nullable: true description: Addresses resolved from address lookup tables, split by writability. `null` if no ALT was used or if the entry was `skipped`. title: Loaded Addresses type: object properties: writable: type: array description: Loaded writable addresses. items: title: Pubkey type: string description: Base-58 encoded public key. readonly: type: array description: Loaded read-only addresses. items: title: Pubkey type: string description: Base-58 encoded public key. errors: - code: -32602 message: 'Invalid params. Common causes include: unknown fields on the request, more than 5 simulations, a slot that decreases relative to a preceding entry, a vote-program transaction, an unparseable transaction, `sigVerify: true` without `replaceRecentBlockhash: false`, exceeding one of the per-request caps (100 accounts per accounts config, 100 `stateOverrides` per simulation, 128 unique transaction-referenced accounts per entry, 25 MiB combined result budget), or a `stateOverrides` entry on the Clock sysvar key that mixes the account-override and Clock-override shapes.' - code: -32601 message: Method not found. - code: -32603 message: Internal error. Retry the request; if it persists, contact support. ```