curl -s -o /dev/null --max-time 3 \
  "https://pancakeswap.ai/api/ping?skill=pcs-api-integration&version=1.0.0&agent=AGENT_NAME&ts=$(date -u +%Y-%m-%dT%H:%M:%SZ)&os=$(uname -s)&arch=$(uname -m)" \
  2>/dev/null &

idle
 └─[user selects tokens + enters amount]──→ dirty
     └─[debounce 500ms fires]──────────────→ fetching
         ├─[/quote success]────────────────→ quoted
         │    └─[15-30s timer expires]─────→ stale
         │         └─[auto-requote]─────────→ fetching
         ├─[/quote error: ASM-5002]─────────→ idle (no route)
         └─[/quote error: other]────────────→ idle (error)

quoted
 └─[ERC-20 src token]──────────────────────→ needs_approval (if allowance < amountIn)
     └─[user approves]────────────────────→ quoted (re-check allowance)
 └─[user confirms]───────────────────────→ executing
     ├─[/calldata success]────────────────→ handoff_ready
     │    └─[wallet signs]───────────────→ confirmed / failed
     └─[/calldata error]──────────────────→ idle (error, no fallback to web link)

{
  "address": "0x2170Ed0880ac9A755fd29B2688956BD959F933F8",
  "decimals": 18,
  "symbol": "ETH",
  "name": "Ethereum Token",
  "chainId": 56
}

{
  "chainId": 56,
  "src": "0x2170Ed0880ac9A755fd29B2688956BD959F933F8",
  "dst": "0x55d398326f99059fF775485246999027B3197955",
  "amountIn": "1000000000000000000",
  "gasPrice": "5000000000",
  "maxHops": "2",
  "maxSplits": "2"
}

{
  "srcToken": {
    "address": "0x2170Ed0880ac9A755fd29B2688956BD959F933F8",
    "decimals": 18,
    "symbol": "ETH",
    "name": "Ethereum Token"
  },
  "dstToken": {
    "address": "0x55d398326f99059fF775485246999027B3197955",
    "decimals": 18,
    "symbol": "USDT",
    "name": "Tether USD"
  },
  "fromAmount": "1000000000000000000",
  "dstAmount": "3192936412525193112600",
  "protocols": [
    {
      "percent": 55,
      "path": [
        { "address": "0x2170...", "symbol": "ETH", "decimals": 18, "chainId": 56 },
        { "address": "0x7130...", "symbol": "BTCB", "decimals": 18, "chainId": 56 },
        { "address": "0x55d3...", "symbol": "USDT", "decimals": 18, "chainId": 56 }
      ],
      "pools": [
        { "type": 1, "liquidityProvider": "PCS", "address": "0xCEc3...", "fee": 100 },
        { "type": 1, "liquidityProvider": "PCS", "address": "0x247f...", "fee": 100 }
      ],
      "inputAmount": "550000000000000000",
      "outputAmount": "1755948085078420231919"
    },
    {
      "percent": 45,
      "path": [
        { "address": "0x2170...", "symbol": "ETH", "decimals": 18, "chainId": 56 },
        { "address": "0x55d3...", "symbol": "USDT", "decimals": 18, "chainId": 56 }
      ],
      "pools": [{ "type": 1, "liquidityProvider": "PCS", "address": "0x9F59...", "fee": 100 }],
      "inputAmount": "450000000000000000",
      "outputAmount": "1436988327446772880681"
    }
  ],
  "gas": 306000
}

undefined

If the returned value (as uint256) is less than `amountIn`, the user must approve before executing.

{
  "srcToken": { ... },
  "dstToken": { ... },
  "fromAmount": "280000000000000000",
  "dstAmount": "131178293243871584359",
  "protocols": [ ... ],
  "gas": 248000,
  "recipient": "0x9D24d495F7380BA80dC114D8C2cF1a54a68e25A4",
  "slippageTolerance": 0.05
}

{
  "value": "0x00",
  "calldata": "0x9aa90356..."
}

ethereum:0x5efc784D444126ECc05f22c49FF3FBD7D9F4868a@56?value={hex_value}&data={calldata_hex}

https://link.trustwallet.com/send?asset=c20000714&address=0x5efc784D444126ECc05f22c49FF3FBD7D9F4868a&amount={decimal_bnb}&data={calldata_hex}

Integration Summary
───────────────────
Mode:              Full execution handoff
Channel:           Mobile app (external wallet — Trust Wallet)
Chain:             BNB Smart Chain (BSC, chainId: 56)
Wallet environment: External — Trust Wallet send link
Token scope:       All BSC tokens (PancakeSwap token list + manual address entry)
User flow:         Token picker → Amount input → Quote preview → Approve (if needed) → Sign

AppState {
  tokenIn: TokenInfo | null
  tokenOut: TokenInfo | null
  amountIn: string          // human-readable
  amountInWei: string       // wei, derived
  quote: QuoteResponse | null
  quoteAge: number          // ms since quote received
  isQuoteStale: boolean     // quoteAge > 30000
  allowance: bigint | null  // null = not yet checked
  calldataResult: { value: string; calldata: string } | null
  txHash: string | null
  status: 'idle' | 'fetching' | 'quoted' | 'needs_approval' | 'executing' | 'confirmed' | 'failed'
  error: string | null
}

Partner App                    Hub API                  User Wallet
     │                            │                          │
     │──[POST /quote]────────────>│                          │
     │<──[QuoteResponse]──────────│                          │
     │                            │                          │
     │  (start 30s timer)         │                          │
     │                            │                          │
     │  [if ERC-20 src]           │                          │
     │──[eth_call allowance]──────────────────────────────>BSC RPC
     │<──[allowance value]──────────────────────────────────│
     │                            │                          │
     │  [if allowance < amountIn] │                          │
     │──────────────────────────────────[show Approve btn]──>│
     │<─────────────────────────────────[user approves]──────│
     │                            │                          │
     │──[POST /calldata]─────────>│                          │
     │<──[{ value, calldata }]────│                          │
     │                            │                          │
     │  [construct handoff URL]   │                          │
     │──────────────────────────────────[send to wallet]────>│
     │<─────────────────────────────────[tx hash]────────────│
     │                            │                          │
     │──[poll eth_getTransactionReceipt]──────────────────>BSC RPC
     │<──[receipt { status }]───────────────────────────────│
     │                            │                          │
     │  [show confirmed / failed] │                          │

Quote fetch
  ├─ HTTP 429 ──→ back off 60s, show countdown, retry
  ├─ ASM-5002  ──→ "No route found" + suggest alternatives
  ├─ ASM-5000  ──→ retry once → if still fails, use PancakeSwap deep link
  ├─ network error ──→ use PancakeSwap deep link
  └─ success   ──→ start 30s timer

Quote stale (>30s)
  └─ auto-requote ──→ block confirm until fresh

Allowance check
  ├─ sufficient ──→ proceed to /calldata
  └─ insufficient ──→ show Approve btn → wait for approval tx → re-check

Calldata fetch
  ├─ HTTP 429  ──→ back off 60s, retry
  ├─ any error ──→ show error, offer retry (do NOT fall back to web link)
  └─ success   ──→ construct handoff URL

Wallet handoff
  ├─ deep link opens ──→ user signs in wallet
  └─ link fails      ──→ show URL for manual copy-paste

Transaction polling
  ├─ status 0x1 ──→ success state + BSCScan link
  ├─ status 0x0 ──→ failed state + retry CTA
  └─ timeout (10min) ──→ "Transaction pending — check BSCScan"

undefined

In a web app, inject via server-side env at build time or through a backend proxy. **Never expose `PCS_HUB_TOKEN` in client-side JavaScript or bundle output.** Use a backend proxy endpoint that forwards Hub API requests with the token attached server-side.

**Rate limit handling:**

- Use a request queue with a 100 req/min budget (≈1.67 req/s).
- Debounce quote fetches to ~500 ms after user input stops.
- On HTTP 429: wait 60 s, show a user-visible cooldown indicator, then retry.

**Wei/decimal conversion utilities:**

```typescript
// Human-readable → wei
function toWei(amount: string, decimals: number): string {
  return BigInt(Math.round(parseFloat(amount) * 10 ** decimals)).toString()
}

// Wei → human-readable (6 significant decimal places)
function fromWei(amountWei: string, decimals: number): string {
  const val = Number(BigInt(amountWei)) / 10 ** decimals
  return val.toFixed(6).replace(/\.?0+$/, '')
}

// Hex value → decimal BNB (for Trust Wallet send link)
function hexToBnb(hexValue: string): string {
  const wei = BigInt(hexValue)
  if (wei === 0n) return '0'
  return (Number(wei) / 1e18).toFixed(18).replace(/\.?0+$/, '')
}

const TOKEN_LIST_URL = 'https://tokens.pancakeswap.finance/pancakeswap-extended.json'

async function loadTokenList(): Promise<Token[]> {
  const res = await fetch(TOKEN_LIST_URL)
  const data = await res.json()
  return data.tokens.filter((t: Token) => t.chainId === 56)
}