feat(chat): Solana wallets — connect, sign in, and pay

[VickyXAI]

Lets a Phantom / Solflare / Backpack user do everything a Base user can: connect, sign in, see their USDC balance, and pay for generations, media, tools and phone numbers.

Two commits: the first is @spacemandev-git's connect/SIWS/balance work, cherry-picked from his fork. The second adds payments.

The premise that blocked this was wrong

The original design note concluded Solana payments were blocked upstream, because a probe of blockrun.ai returned a 402 with a single eip155:8453 entry. But sol.blockrun.ai is a separate deployment hardcoded to its own chain, and it has been serving a Solana paywall the whole time — with extra.feePayer already set, so the user needs no SOL for gas.

Routing: the host is the chain

Neither gateway switches chains on a header or query param (?network=solana, x-payment-network, x-blockrun-chain, accept-payment were all tried against blockrun.ai; every one still returned Base), and neither ever offers both chains in one accepts array. So /api/blockrun now picks its upstream per request from x-blockrun-chain, set client-side from the connected wallet and consumed by the proxy rather than forwarded. Anything unrecognised — including a missing header from a cached older bundle — falls back to Base, so existing clients behave exactly as before.

Two things that needed care:

• Media jobs pin their chain. Submit-then-poll runs for up to five minutes across many renders; a wallet switch mid-flight must not send a poll to a gateway that never saw the job.
• Price labels follow the signature. Both the "$0.0013" label and the signer now read the offer selected by network, instead of one reading accepts[0] while the other selected properly.

Paying

src/lib/solana-x402.ts builds the SPL transfer the facilitator expects, ported from createSolanaPaymentPayload() in blockrun-llm-ts/src/x402.ts — same instruction order, same envelope. Keep the two in step. Two deliberate differences:

• The blockhash comes from the 402, not an RPC round trip. BlockRun stamps a finalized one in for exactly this reason; a confirmed hash races the facilitator's own RPC pool and settles as BlockhashNotFound.
• The fee-nonce guard is kept. Two same-priced payments on one blockhash compile to byte-identical messages, ed25519 is deterministic, and Solana rejects the second as already-processed. Two same-priced calls in a row is an ordinary chat pattern.

A new same-origin RPC proxy

BlockRun's Solana RPC is free and keyless but serves no CORS, and a JSON-RPC POST is always preflighted — so the browser could not read a balance at all. /api/solana/rpc forwards to it.

It is its own route rather than an entry in the /api/blockrun path allowlist on purpose: that proxy defaults to the Base host, where /v1/solana/rpc is a paid endpoint ($0.0005/call). Billing someone for looking at their own balance should not be one config change away.

Verified

• npm run typecheck, npx eslint src, npm run build all clean.
• Proxy chain selection, incl. fallback on an unknown header value.
• Free-model anonymous path unchanged; /chat renders with no console errors.
• Network chooser and both connect branches driven in a real browser.
• Payment envelope against production, using a throwaway keypair: the facilitator parsed the envelope, decoded the transaction and extracted the payer, failing only on insufficient_funds. Format accepted end to end.

Still needs a human

• A real payment from Phantom with USDC and zero SOL, proving the facilitator pays gas.
• Base regression — this refactors seven wagmi call sites behind useWallet(), which is where a regression would hide.
• Cross-chain history isolation: sign in on Base, save a chat, switch to Phantom, confirm the history is empty and comes back on switching return.

Notes

• Pricing differs by a flat $0.001/call in Solana's favour: Base adds TRANSACTION_FEE_USD = 0.001, Solana zeroed its service fee ("PayAI is the fee payer"). Same catalog underneath.
• Declares @solana/wallet-standard-chains and @solana/wallet-standard-features, which were imported directly but only resolved transitively.
• Drops the research .mcp.json and rewrites the design note around what is actually true.
• Left alone deliberately: use-phone-call.ts's paidPost still doesn't call onSpend, so $5 number purchases stay missing from the usage ledger (pre-existing). npm run lint reports ~1584 errors from the stale .worktrees/ copy, which is gitignored but not eslint-ignored (also pre-existing) — npx eslint src is clean.

franklin.run is on Cloud Run, so merging does not deploy. npm run deploy after.