x402

name	x402
version	2.20.2
description	Monetize any user project/service with the x402 payment protocol on platform networks (Base + Monad + Robinhood; Starchild platform billing: pay_per_use / lifetime / weekly / monthly / quarterly / yearly / prepaid, plus multi-plan services), and pay other agents' x402 services. Use when the user wants to charge for an API/service, accept USDC from other agents, or call a paid x402 endpoint.
author	starchild
tags	["x402","payments","base","monad","robinhood","usdc","usdg","monetization","api","subscription","metered","agent-commerce"]
delivery	script
metadata	{"starchild":{"emoji":"💸","skillKey":"x402","requires":{"bins":["python3"]}}}

💸 x402 Monetization Skill

Turn any local HTTP service into a paid service on platform networks (Base + Monad + Robinhood; x402 V2 protocol, exact scheme, USDC/USDG via EIP-3009 — buyer pays zero gas), and act as a buyer paying other agents' x402 services with the user's Privy wallet.

Architecture: reverse-proxy sidecar. The gateway (gateway/app.py) sits in front of the user's untouched service. One unified gateway, three billing modes as config presets — the error contract is identical across all modes.

buyer agent ──402/PAYMENT-SIGNATURE──> gateway :840x ──plain HTTP──> user service :port
                     │
               facilitator (verify + settle on Base/Monad/Robinhood) ──USDC/USDG──> user's Privy wallet

Reference files (MUST read before the matching task)

Detailed material lives in skills/x402/references/ — it is part of this skill. Do NOT guess or improvise what these files cover:

Before you…	MUST first read_file
deploy ANY selling mode beyond basic pay_per_use (full commands, prepaid & multi-plan contracts, admin tokens, templates, gateway lifecycle, always-on/update-mode)	skills/x402/references/selling.md
debug ANY error (facilitator verify errors, error contract, security model, port ownership, proxy)	skills/x402/references/troubleshooting.md
use the session EOA signer, fund a buyer wallet, or pay on a non-Base-USDC chain/token	skills/x402/references/buying-advanced.md

Sell — monetize a service (quick start)

FAC=https://starchild-x402-facilitator.fly.dev
# pay_per_use: verify -> settle on EVERY request (simplest mode)
# --networks defaults to "all" (Base + Monad + Robinhood mainnet); the 402 challenge
# returns a multi-accepts list — the buyer picks one chain per payment.
python3 skills/x402/scripts/monetize.py --name my-api --upstream-port 5173 \
    --mode pay_per_use --price 0.01 --facilitator $FAC

# lock to a single chain (custom)
python3 skills/x402/scripts/monetize.py --name my-api --upstream-port 5173 \
    --mode pay_per_use --price 0.01 --networks eip155:8453 --facilitator $FAC

Platform modes follow the community-gateway billing contract: 402 JSON body with accepts as a list (multi-accepts, one entry per network — the buyer picks one chain per payment), accepts[].pricingModel, facilitator is the single source of truth for "already paid", every settle auto-callbacks community-gateway for records.

Billing mode decision table

Mode	Tier	Buyer UX	When
pay_per_use	platform	X-PAYMENT each request, settled every call	simple data endpoints, agent-to-agent one-shots
lifetime	platform	pay once, permanent access (facilitator-verified)	one-time unlock, buyout pricing
monthly	platform	pay once per natural month	SaaS-style subscriptions
weekly / quarterly / yearly	platform	fixed-length pass: 7 / 90 / 365 days from newest payment	short trials, annual discounts
prepaid	platform	one on-chain deposit → off-chain debit per call	high-frequency / sub-cent / usage-metered APIs
payperuse	legacy	SDK V2 headers, pay per request	pre-2.0 deployments
subscription	extended	x402 top-up → API key + N credits, 1 credit/call	prepaid credits, avoids per-call payment latency
metered	extended	like subscription, route-weighted units	mixed cheap/expensive endpoints (LLM calls etc.)
timepass	extended	x402 payment → N-day pass on an API key	fixed-duration passes (non-natural-month)

⚠️ lifetime/monthly/weekly/quarterly/yearly REQUIRE --facilitator-admin-token (fail-closed at startup). Multi-plan: --plan MODE=PRICE (repeatable). → MUST read references/selling.md BEFORE deploying any of these modes — it has the exact commands, contract details, and template list.

Output includes gateway_port. Expose the GATEWAY port, not the upstream (via preview or community-publish). pay_to defaults to the user's Privy EVM wallet — revenue lands there directly. Registry: /data/workspace/.x402/services.json; per-service config/log/state: /data/workspace/.x402/<name>/.

Networks & facilitators

The platform supports multiple chains. By default a service follows the platform mainnet full set (--networks all, the default) — currently Base + Monad + Robinhood. The 402 challenge returns a multi-accepts list (one entry per chain); the buyer picks one chain per payment. Lock to specific chains with --networks eip155:8453,eip155:143,eip155:4663 (custom).

Network	CAIP-2	Stablecoin	EIP-712 name	Gas
Base mainnet	eip155:8453	USDC 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913	USD Coin	ETH (platform-paid)
Base Sepolia (testnet)	eip155:84532	USDC 0x036CbD53842c5426634e7929541eC2318f3dCF7e	USDC	ETH (platform-paid)
Monad mainnet	eip155:143	USDC 0x754704bc059f8c67012fed69bc8a327a5aafb603	USDC	MON (platform-paid)
Monad testnet	eip155:10143	USDC 0x534b2f3A21130d7a60830c2Df862319e593943A3	USDC	MON (platform-paid)
Robinhood mainnet	eip155:4663	USDG 0x5fc5360D0400a0Fd4f2af552ADD042D716F1d168	Global Dollar	ETH (platform-paid)
Robinhood testnet	eip155:46630	USDG 0x7E955252E15c84f5768B83c41a71F9eba181802F	Global Dollar	ETH (platform-paid)

Facilitator	Networks	When
platform (https://starchild-x402-facilitator.fly.dev, the default for mainnet; override via X402_FACILITATOR_URL or --facilitator)	Base + Monad + Robinhood mainnet	production — platform settler pays gas on every chain
https://x402.org/facilitator (default for testnet)	Base Sepolia + Monad + Robinhood testnet	testing only — REJECTED for mainnet (startup guard)

The platform facilitator handles /verify + /settle on every supported chain; its settler key only pays gas — fund flow is fixed by the buyer's signature and can never touch user funds. Gas is paid by the platform on every chain (ETH on Base, MON on Monad, ETH on Robinhood) — never passed to the service provider. Safety: mandatory eth_call simulation before spending gas, per-payer rate limiting, authorization-nonce idempotency. Testnet USDC (Base Sepolia): 0x036CbD53842c5426634e7929541eC2318f3dCF7e, faucet at faucet.circle.com. Prices auto-convert: $0.01 → 10000 atomic USDC units.

Multi-chain config (networks_mode)

Config	Behavior
--networks all (default) or networks_mode: all	402 accepts = platform mainnet full set (Base + Monad + Robinhood); testnet full set when facilitator is x402.org
--networks eip155:8453 or networks_mode: custom + networks: [...]	402 accepts = exactly the listed chains (custom lock)
(no networks field)	same as all

Extending the platform with a new chain only requires updating ASSETS + MAINNET_NETWORKS in platform_modes.py (and the facilitator's KNOWN_ASSETS) — every all-configured service picks up the new chain on its next 402, with zero business-table updates.

⚠️ Robinhood USDG note: the USDG contract uses a Diamond proxy with a non-standard EIP-712 domain. The facilitator reads DOMAIN_SEPARATOR() from chain for verification. Buyer-side raw-digest signing is a TODO (see client.py _CHAIN_DOMAIN_SEP_CHAIN_IDS); standard typed-data signing is used for now and works if the on-chain domain matches the metadata.

Historical Base-only configs are migrated once (SQL/config sweep to networks_mode: all); resolve_networks does NOT guess "bare Base means all".

Keepalive (register once per machine)

One watchdog guards ALL x402 gateways (cloudflare-skill pattern: idempotent, prints only on state change → silent scheduled task when healthy):

1. Boot: append to /data/workspace/setup.sh: bash /data/workspace/skills/x402/scripts/keepalive.sh || true
2. Watchdog: scheduled_task(action="schedule", schedule="every 10 minutes", command="bash skills/x402/scripts/keepalive.sh", deliver="origin") — empty output = silent. ⚠️ Use the RELATIVE path (skills/x402/...), never /data/workspace/skills/... — the scheduler's path sanitizer strips workspace/ from absolute commands, mangling them into a nonexistent /data/skills/... and the task fails every run. After registering, verify with get_log that the first execution succeeds.

Gateway down → restarted from its config. Upstream down → reported but NOT restarted (upstream has its own supervisor via previews — don't fight it).

A LISTED paid service must stay reachable 24/7 (idle suspend + auto-update restarts work against this) → read references/selling.md § Always-on availability BEFORE publishing for the update-mode check/flip flow.

Buy — pay other agents' x402 services

Quick Start — preset CLI scripts (use these FIRST, no custom code)

One process per step, ONE JSON object on stdout — no per-call LLM reasoning about balances/signatures/rail selection needed:

# 1. FREE probe: is it x402? which rails? (never pays)
python3 skills/x402/scripts/discover.py --url https://host/api/thing
python3 skills/x402/scripts/discover.py --query "weather api"   # catalog search

# 2. Preflight: signer + policy + live USDC per rail + recommended_rail
python3 skills/x402/scripts/preflight.py --usd 0.05

# 3. Pay — resolve → probe → pick final rail → preflight THAT rail's own
#    price+network → pay the SAME resolved URL (rail pinned; --max-usd is
#    only a spend ceiling). Exit 2 = blocked/over-cap/network-not-accepted,
#    nothing signed. --network not in accepts fails fast (no silent fallback).
python3 skills/x402/scripts/buy.py --url https://host/api/thing --max-usd 0.05
python3 skills/x402/scripts/buy.py --url https://host/x402/q \
    --json '{"q":"hello"}' --max-usd 0.10 --network eip155:8453

Raw client (advanced / custom flows):

python3 skills/x402/client.py GET https://host/api/thing
X402_MAX_ATOMIC=50000 python3 skills/x402/client.py POST https://host/x402/topup

Pre-flight FIRST (one round-trip, not serial walls)

Before asking the user to confirm any purchase, run client.payment_preflight(amount_atomic, networks=<the 402's accept networks>) and present ALL blockers together. It checks in one shot: ① signers reachable, ② wallet policy sanity — an ENABLED policy with EMPTY rules is deny-all and rejects every signature (new Privy wallets should be allow-all; if found, propose a policy card and get it signed BEFORE paying), ③ USDC balance per candidate rail (direct RPC). If no rail is funded, offer every option at once — pay from another funded chain, bridge, or fiat-onramp — never a bare "fund the wallet" that leads to the next wall. Never let the user fix funding, then discover a policy block, then a dependency error in three separate round-trips.

Dependencies: the buyer path needs web3>=7. If the machine pins an older web3 (trading bots often pin 6.x), NEVER upgrade it globally — run bash skills/x402/scripts/ensure_env.sh (zero-interaction, idempotent): it creates an isolated .venv-x402 immune to PIP_USER/PYTHONPATH/user-site interference (venv built --without-pip + PYTHONNOUSERSITE=1) and prints the interpreter to use on the last stdout line. payment_preflight detects the version conflict and points here. Do this at setup, not mid-purchase.

Multi-chain selection (buyer receives multiple accepts)

When a service returns 402 with accepts as a list (one entry per network, e.g. Base + Monad + Robinhood), the buyer Agent does NOT need to ask the user which chain to use — chain selection is fully automatic in both paid_request and bazaar_pay. The logic:

1. payment_preflight (run BEFORE confirming): checks USDC balance on every candidate rail and returns funded_rails[]. If multiple rails are funded, the automatic selector picks the best one. If NO rail is funded, present ALL funding options at once (bridge, on-ramp, pay from another chain) — never ask "which chain?" when the answer is "none of them".

2. Automatic rail ranking — balance-aware, Base default (shared by bazaar.probe_402 display and paid_request payment — so the chain shown at probe time IS the chain actually paid). Selection order:

   • ① Funded rails first: live USDC balance ≥ amount on that rail (direct RPC, cached ~60s). A signature-friendly chain with 0 USDC is never picked over a funded one, so settlement cannot fail for lack of balance on the selected rail.
   • ② Base (eip155:8453) is the default chain when funding ties (platform wallets hold USDC on Base).
   • ③ Static tiebreak (network_rank): Solana (ed25519) → Base → other EVM without EIP-7702 delegation (plain ECDSA, e.g. Monad) → EVM with delegation code (Kernel EIP-1271). signer_mode="eoa": Solana excluded, all EVM equal.
   • ④ Within the same rank, cheaper amount / first accept wins.
   • Balance check failure = unknown, NOT unfunded (fail-open to ranking).

3. User-specified chain (prefer_network): when the user explicitly asks to pay on a specific chain (e.g. "pay on Base", "use Monad"), pass prefer_network="eip155:8453" (or "eip155:143" for Monad) to paid_request or bazaar_pay. This overrides the automatic ranking and selects the matching accept first (if present in the 402 challenge). Also available via env X402_PREFER_NETWORK. If the specified chain is not in the service's accepts, the automatic ranking takes over as fallback. Common CAIP-2 ids: Base eip155:8453, Monad eip155:143, Solana solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp.

   # User says "pay on Base"
   paid_request("GET", url, prefer_network="eip155:8453")
   # User says "pay on Monad"
   bazaar_pay(url, prefer_network="eip155:143")
   # Via env (CLI)
   X402_PREFER_NETWORK=eip155:8453 python3 skills/x402/client.py GET https://host/api
   

4. Prepaid deposit retry: if the first payment triggers a 402 insufficient_balance (prepaid top-up needed), the retry stays on the SAME chain the buyer already chose (prefer_network parameter in _pick_accept) — it never jumps to a different chain mid-flow.

5. Result verification: every paid_request result includes network (the chain actually used) and signer_type — always report these to the user so they know where the payment landed.

paid_request auto-detects BOTH 402 flavors: V2 header challenge (PAYMENT-REQUIRED → x402 SDK path) and the platform JSON-body challenge (accepts.pricingModel → manual EIP-3009 sign → retry with X-PAYMENT). For lifetime/monthly services, repeat calls within the paid period verify but do NOT settle — the result has paid: true with no new on-chain tx.

Buyer signer = Privy wallet by default (signer_mode="auto"); smart accounts are detected and signed via an ERC-1271-compatible path automatically. Multi-accept routing prefers rails where Privy signs a plain signature (max facilitator compatibility, no EOA funding needed): ① Solana (ed25519) → ② EVM chains where the payer has no EIP-7702 code (plain ECDSA, e.g. Monad) → ③ EVM chains with delegation code (Kernel EIP-1271, e.g. Base) as last resort — spec-correct but some seller facilitators reject it; for Base-only sellers that do, use signer_mode="eoa". Do NOT revoke the wallet's delegation (it powers gas sponsorship). auto is FAIL-CLOSED: if the Privy signer cannot be initialized, paid_request raises instead of paying from a different identity — allow the session-EOA fallback only explicitly via allow_fallback_eoa=True / env X402_FALLBACK_EOA=1 / signer_mode="eoa". Every result includes signer_type ("privy" | "session_eoa"); an opted-in fallback also sets signer_warning — check them to confirm which identity actually paid. ⚠️ The two signers are DIFFERENT payer identities: subscriptions/prepaid balances do NOT carry over between them. → EOA funding steps and signer internals: read references/buying-advanced.md BEFORE using the session EOA.

Spend guard: refuses to sign above X402_MAX_ATOMIC (default 1_000_000 = 1 USDC). ⚠️ Signing = spending real money once settled — confirm with the user before paying unfamiliar services or raising the cap. Paid response bodies are returned in FULL; unpaid/error bodies are capped at 2000 chars (env X402_BODY_MAX, 0 = unlimited). Result includes settlement.transaction (on-chain tx hash) — report it and verify per transaction-verification rules.

Payment ledger (every payment is recorded locally)

client.py appends every payment it signs to $WORKSPACE/.x402/payments.jsonl (override path: env X402_LEDGER). Each line is one JSON event: signed (authorization submitted — url, amount, payTo, payer, caller) and result (HTTP status, paid, settlement tx). The caller field identifies who spent the money (SC_CALLER_ID / JOB_ID / pid), so payments made from background sessions are attributable too.

To answer "where did this USDC go": read the ledger first, then reconcile against the wallet's on-chain USDC transfers — every outgoing transfer must match a ledger line. Ledger writes are best-effort and never block a payment.

Spending rules for automated sessions

• A background / scheduled / spawned session MUST NOT make x402 payments unless its task explicitly grants a budget; set X402_MAX_ATOMIC to that budget for the session.
• Every payment an automated session makes MUST appear in its final output (amount, url, settlement tx) — a payment only in the ledger is auditable but still counts as unreported work.
• On any 4xx payment rejection, do not retry with a fresh payment: each retry can spend again. Diagnose first.

Public paid URL (Cloudflare Monetization Gateway parity)

Make any local service a PUBLIC paid API (charge any caller for any resource, no accounts / API keys needed — same capability set as Cloudflare's Monetization Gateway, running on your own machine):

1. python3 skills/x402/scripts/make_public.py --name my-api --upstream-port <port> --mode payperuse --route 'GET /api/*=$0.01' --pay-to <wallet> — scaffolds output/my-api/start.py + config (defaults to --networks all: Base + Monad + Robinhood)
2. preview(action='serve', dir='output/my-api', command='python3 start.py', port=<gateway_port>) — note: start the upstream in the same command if it isn't already running
3. community-publish skill → publish_preview(preview_id, slug='my-api') → public URL
4. Price discovery is built in: GET <public-url>/.well-known/x402 returns machine-readable routes/prices/payTo/networks (Bazaar-compatible shape; accepts is a multi-chain list).

A public URL is NOT a marketplace listing. Steps 1–4 only make the service reachable — the Service Marketplace will show nothing (or "free") until you complete the LIST chain (community-publish skill):

5. create_paid_service(name=..., service_type=..., api_endpoint=<public paid route>, provider_wallet=..., pricing_model=..., price=..., pricing_options=[...] for multi-plan) → service record.
6. publish_service(service_id) → live paid listing. Review is ADVISORY: optionally run submit_for_review(service_id) + get_review_status() for a 5-check self-report (402 reachable, price consistency, x402 validity, response match, doc completeness) — show it to the owner; it never blocks publishing.

⚠️ The LIST chain MUST go through the community-publish skill functions — NEVER hand-build a gateway payload. create_paid_service() makes every paid field a required argument; a hand-built payload with missing fields is rejected by the gateway (and on older gateways silently created a FREE service that later fails review with a misleading 400).

Skipping 5–6 is the #1 cause of "why does my paid service show as free / not appear in the marketplace".

Paid Project: two forms

A paid project is a Starchild project that charges for access. There are two forms — the platform supports both, and they share the same service_type="paid_project" + project_slug listing structure:

Form 1: Entire page behind paywall (user implements access control)

The page itself requires payment to access. The user (service provider) implements their own access control — a login-like component that checks a payment credential before serving content.

Platform responsibility: publish the project + list the paid API endpoint on the marketplace. The x402 gateway handles the payment protocol (402 challenge → settle → credential).

User responsibility: implement the access control interceptor in their own app:

• A paywall/login component on the frontend (credential input → localStorage)
• A backend endpoint that validates the credential and returns content
• The credential is issued by the user's own API after a successful x402 payment — the user's API returns the credential to the buyer

Flow:

1. Visitor opens the page → sees a paywall (user's frontend code)
2. Visitor pays via x402 (Agent or direct) → user's API returns a credential
3. Visitor enters the credential → user's backend validates it → serves content
4. Credential cached in localStorage → subsequent visits skip the paywall

What the platform provides:

• x402 gateway: handles the 402 payment challenge + on-chain settlement
• /x402/topup endpoint: buyer pays, gets an API key (timepass/subscription modes) or the x402 signature IS the credential (platform modes)
• /x402/balance endpoint: the user's app CAN use this to check if an API key is valid (optional — the user can also implement their own validation)

What the user implements (their own code, their own logic):

• Frontend: paywall UI, credential input, localStorage caching
• Backend: credential validation (can call gateway /x402/balance, or implement their own validation logic, or use the x402 signature directly)
• The "how to pay" documentation on the paywall page

"How to pay with Agent" documentation

The user's paywall page should include a "How to pay" section explaining how buyers can obtain an access credential via x402 payment. The Agent should generate this documentation based on the service's actual pricing, duration, and URL — do NOT copy a fixed template. The documentation should cover:

• The price and payment networks (e.g. "$2.99 USDC/USDG on Base, Monad, or Robinhood — buyer picks one chain per payment")
• How to pay via Agent (x402 client call to /x402/topup)
• How to pay directly (any x402-compatible client with X-PAYMENT header)
• What the buyer receives after payment (an api_key credential)

Form 2: Free page + paid API (Flow D)

The page is free to browse (intro/docs/landing page), but API calls cost money. This is Flow D — see the community-publish skill for details. The upstream app serves the free intro page at / and the paid API at /api/*.

Summary: paid project = free project + paid API (same pattern)

Both forms use service_type="paid_project" + project_slug. The difference is only in what the user implements:

Form	Page access	API access	User implements
Entire page paid	Paywall (user's access control)	Paid via x402	Paywall UI + credential validation
Free page + paid API	Free (intro/docs page)	Paid via x402	Nothing extra (gateway handles it)

The platform (x402 gateway + community-gateway) handles the payment protocol and marketplace listing in both cases. The user only needs to implement the access control interceptor for Form 1.

Consuming any x402 service from just a URL

Given ONLY a service URL (no docs, no guidance), onboard and verify it with this sequence — everything needed is self-describing in the protocol:

1. Discover (free): GET <url> with no payment headers. A 402 response IS the price sheet: accepts is a list (multi-accepts, one entry per network) — each entry has amount (atomic USDC), pricingModel, network, asset, payTo. Pick one chain to pay on. On multi-plan services a plans map carries every option's accepts. Optionally GET <base>/.well-known/x402 for a machine-readable index of all routes/prices/networks.
2. Probe plans (free, multi-plan only): repeat the unpaid GET with X-Pricing-Model: <plan> — each 402 quotes that plan's exact amount. An unknown plan returns HTTP 400 listing the valid ones.
3. Pay & call: client.paid_request("GET", url, max_amount_atomic=<cap>) handles the whole flow (402 → EIP-3009 sign → retry with X-PAYMENT). Select a plan with pricing_model="<plan>". Payer = the Privy wallet by default (signer_mode="auto"); it must hold USDC on the service's network. The session EOA needs funding ONLY if you pin signer_mode="eoa" or the result reports signer_type: "session_eoa" (see Buyer side above). cap = your spend guard. Confirm with the user before paying — this is real money. Check signer_type in the result: it tells you WHICH identity actually paid. If the Privy signer is unavailable, auto raises (fail-closed) rather than silently paying from the session EOA; a signer_warning appears only when the fallback was explicitly allowed.
4. Verify billing semantics (subscription modes): call again — the result must be 200 with NO new settlement (paid: true, no new tx). On multi-plan services, requesting a different plan while holding one must also NOT re-charge. settlement.transaction from step 3 is the on-chain proof — report it and verify per transaction-verification rules.

The same sequence doubles as a smoke test of any x402 deployment: steps 1–2 are free and validate the challenge contract; steps 3–4 validate settlement and access accounting end-to-end.

Discover & pay — marketplace first, then CDP

Buyer flow is marketplace-first. Do not collapse tracks; do not scrape third-party x402 directories.

Step	Rule
1. Find	Prefer discover_services(query) or community-publish.explore_marketplace. CDP (bazaar_search) is fallback when marketplace has no hit.
2. Resolve pay URL	Listed services → community.iamstarchild.com/proxy/{service_id} (+ path) or internal /{user}-{slug}/.... Never pay the raw list external URL when a proxy exists.
3. Pay	bazaar_pay(url) re-resolves to marketplace proxy, then probe_402 → paid_request. Community transparent-proxies and books on HTTP 200. Unlisted external URLs are refused — list the service on the marketplace first, then pay its proxy URL.

import sys; sys.path.insert(0, "/data/workspace/skills/x402")
from bazaar import discover_services, resolve_marketplace, probe_402, bazaar_pay

discover_services("weather", limit=5)          # marketplace first, CDP fallback
resolve_marketplace("https://example.com/api") # → pay_url via community when listed
bazaar_pay(url, max_usd=0.01)                  # proxy-first pay; refuse non-standard

probe_402 / bazaar_pay only pay standard-v2 exact on known native USDC rails (see bazaar.PAYABLE_USDC): Base, Polygon, Arbitrum, World Chain, Solana mainnet, Monad, Avalanche, Ethereum, Optimism, Linea, Celo, Unichain. Multi-accept → prefer Privy-native rails (Solana → no-code EVM → delegated EVM; see buyer signer section). The same selector (client.network_rank) drives bazaar's probe_402 ordering, so the rail shown at probe time is the rail auto actually pays. signer_mode="eoa" never registers the SVM signer and hard-filters Solana accepts — the pinned session-EOA payer identity is never substituted. Results and ledger lines carry the ACTUAL selected network/payer/signer_type (Solana settlements report the Privy Solana address as payer). Solana signs via Privy wallet_sol_sign (base64 raw message). Not yet: EURC/alt-stables, testnets. Other shapes (wrong-rail, tx-hash, non-standard, no-payment) refused before any signature. Buyer signs; seller facilitator settles.

Errors & diagnostics

Payment or gateway failing → MUST read references/troubleshooting.md (error contract, facilitator verify errors, security model, port ownership checks, proxy config). Quick e2e check anytime: python3 skills/x402/scripts/verify_setup.py (fund-free; --funded adds a real settlement test).

Setup

Python SDK is x402 v2.10+. Deps are NOT auto-installed: run bash skills/x402/setup.sh once per machine (also append it to /data/workspace/setup.sh so restarts reinstall).