Pre-flight API

Ask before you sign.

One POST tells an agent whether the transaction it is about to sign breaks its published spec.

The watchdog judges transactions after they land. Pre-flight moves the same rules in front of the signature. Haltr reads the agent's spec and halt state from the registry, checks the token's mint and a Jupiter sell-back, and simulates the transaction on mainnet when you send it. Every check served is logged on this page.

Checks served11from 3 client labels

Cleared to sign10ok was true

Stopped1ok was false

Average latency2001msmeasured at Haltr

Endpoint

JSON in, JSON out. CORS is open, so an agent can call it from anywhere. Limits: 30 checks a minute per agent and 240 per IP, a transaction of up to 2,400 base64 characters, and 4s for each external read. A read that times out marks its check as warn. It never passes silently.

POSThttps://haltr.xyz/api/preflight

Request

Field	Type	Required	Meaning
agent	string	Required	Registry id, such as haltr-demo-agent, or the agent's wallet address.
client	string	Optional	Label shown in the public log below. Trimmed to 60 characters.
intent.dex	string	Required	Venue the trade routes through: Raydium, ClawPump, Jupiter, Orca, Meteora or PumpSwap. Any other name is evaluated as Other. When the sent programs call a different known venue, that venue is evaluated instead.
intent.side	"buy" \| "sell"	Required	Direction of the trade.
intent.assetMint	string	Required	Mint of the token bought or sold. Use So11111111111111111111111111111111111111112 for SOL. SOL, USDC and USDT are named by their mint. Any other mint that calls itself one of those is named by its short address, so it cannot pass an asset allowlist.
intent.sizeSol	number	Required	SOL notional of the trade. At least one lamport, 0.000000001.
intent.slippageBps	number	Required	Slippage tolerance the agent will sign with, 0 to 10000.
intent.programIds	string[]	Optional	Top-level programs the transaction calls. Ignored when a transaction is sent. Without either, Haltr infers the venue's usual programs and only warns about them.
intent.transaction	string	Optional	Base64 transaction, legacy or v0, up to 2,400 characters. Send it unsigned. Signatures are not needed because Haltr simulates with signature checks off. The agent wallet must be one of its signers. Haltr reads its programs and simulates it on mainnet.
intent.projectedPnlSol	number	Optional	Expected PnL in SOL, negative for a loss. Feeds the drawdown rule. Defaults to 0.

Response

Field	Type	Meaning
ok	boolean	True only when the agent is armed, no spec rule breaks, the honeypot check does not fail and the simulation does not fail. Sign only on true.
agentId	string	Registry id the request resolved to.
agentStatus	"active" \| "halted" \| "flattened"	Registry status at the time of the check.
specVersion	number	The published spec version that was applied.
certified	boolean	True when that spec version is certified with a $ANSEM burn.
violations	Violation[]	Broken rules, most severe first. Each has rule, severity, title, detail, observed and limit.
checks	object	Seven named checks, each { status, detail }. Status is pass, warn, fail or skipped.
evaluatedMs	number	Wall time Haltr spent on the check, in milliseconds.
checkId	number \| null	Row id in the public log.
docs	string	Link to this page.
resolved	object	How the intent was read: dex, asset, programIds, programSource and roundTripPct.

Checks

ok is false when the agent is not armed, any spec rule breaks, or the honeypot or simulation check fails. Warnings are for the agent's own judgment and never flip ok on their own.

Check	What Haltr looks at	When it fails or warns
halted	Registry status of the agent.	Fails when the agent is halted or flattened. A halted agent must not trade.
spec	The same deterministic rules the watchdog applies to landed transactions: size, drawdown, venue, asset list, slippage, programs, rate and honeypot.	Fails on any violation.
honeypot	For buys, a Jupiter quote from SOL to the token, then back to SOL for exactly what the buy returns. For every mint, its Token-2022 extensions.	Fails with no sell route, a round trip under 50%, a non-transferable mint, a permanent delegate, a transfer fee over 10%, or an address that is not a token mint. Warns on a transfer hook, a fee over 1%, or a read that did not answer.
tokenAuthorities	Mint and freeze authority on the mint.	Warns only. USDC has both and never fails here.
programs	Top-level programs against the spec allowlist. Read from the transaction, else intent.programIds, else inferred from the venue.	Fails on a sent or declared program outside the allowlist. Inferred programs are a guess, so they only warn and never fail.
simulation	simulateTransaction on mainnet with signature checks off and a fresh blockhash. Inner programs are listed from the logs. The agent wallet must be one of the transaction's signers.	Fails when the transaction errors, when the RPC rejects it as malformed, or when the agent wallet does not sign it. Warns when the RPC cannot be reached. Skipped without a transaction.
rateLimit	Actions the watchdog observed from the wallet in the last 60 seconds, plus this one.	Fails above the spec's trades per minute.

Status codes

200	A PreflightResponse. Read ok.
400	Bad input. The error names the field.
404	No registered agent matches agent.
413	Body over 16,384 bytes, or a transaction over 2,400 base64 characters.
429	Over 30 checks a minute for one agent, or 240 from one IP. Wait for Retry-After.
500, 503	Haltr could not evaluate. Treat it as not ok.

Examples

curl

curl -s -X POST https://haltr.xyz/api/preflight \
  -H 'content-type: application/json' \
  -d '{"agent":"haltr-demo-agent","client":"my-bot/1.0","intent":{"dex":"Raydium","side":"buy","assetMint":"EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v","sizeSol":0.004,"slippageBps":50}}'

TypeScriptfetch

import type { VersionedTransaction } from "@solana/web3.js";

/** Ask Haltr before signing. Send tx unsigned; sign only on true. */
export async function preflight(tx: VersionedTransaction): Promise<boolean> {
  const res = await fetch("https://haltr.xyz/api/preflight", {
    method: "POST",
    headers: { "content-type": "application/json" },
    body: JSON.stringify({
      agent: "haltr-demo-agent",
      client: "my-bot/1.0",
      intent: {
        dex: "Raydium", side: "buy", sizeSol: 0.004, slippageBps: 50,
        assetMint: "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
        transaction: Buffer.from(tx.serialize()).toString("base64"),
      },
    }),
  });
  if (!res.ok) return false; // fail closed
  const verdict = await res.json();
  return verdict.ok === true;
}

Try it

This form calls the live API for Haltr's demo agent. Its spec v7 allows Raydium only, at most 0.005 SOL a trade. Change the DEX or the size to see the check stop it.

Response

No request sent yet. Edit the intent and send it. The answer from the live API appears here.

Recent checks

The ten newest checks served, read from the pre-flight log.

Pre-flight log · newest first11 served

Time	Agent	Verdict	Reasons	Latency	Client
2026-09-29 18:12:55 UTC	Haltr Reference Agent	Clear	None	1081ms	haltr-reference-agent/1
2026-09-29 17:57:49 UTC	Haltr Reference Agent	Clear	None	1090ms	haltr-reference-agent/1
2026-09-29 17:42:43 UTC	Haltr Reference Agent	Clear	None	1102ms	haltr-reference-agent/1
2026-09-29 17:27:36 UTC	Haltr Reference Agent	Clear	None	1093ms	haltr-reference-agent/1
2026-09-29 17:12:30 UTC	Haltr Reference Agent	Clear	None	1076ms	haltr-reference-agent/1
2026-09-29 17:09:23 UTC	Haltr Demo Agent	Clear	None	1086ms	haltr-docs
2026-09-29 16:57:24 UTC	Haltr Reference Agent	Clear	None	1090ms	haltr-reference-agent/1
2026-09-29 16:42:20 UTC	Haltr Reference Agent	Clear	None	1104ms	haltr-reference-agent/1
2026-09-29 03:02:27 UTC	Haltr Demo Agent	Stop	MAX_TRADE_SIZE, MAX_SLIPPAGE	4183ms	skill-test
2026-09-29 03:02:14 UTC	Haltr Demo Agent	Clear	None	4195ms	skill-test