diff --git a/apps/api/.env.example b/apps/api/.env.example
index 4cebb08..bf20945 100644
--- a/apps/api/.env.example
+++ b/apps/api/.env.example
@@ -21,9 +21,18 @@ PORT=3333
 API_URL="http://localhost:3333"
 NODE_ENV="development"
 FRONTEND_URL="http://localhost:3001"    # dashboard origin
-CHECKOUT_URL="http://localhost:3002"    # hosted checkout (apps/checkout)
+CHECKOUT_URL="http://localhost:3003"    # hosted checkout (apps/checkout, `next dev --port 3003`)
 TAVVIO_FEE_BPS=50                        # default platform fee = 0.5%
 
+# Base stamped onto every generated payment-link URL. It must point at the
+# checkout app's `/l` route — the API appends `/<shortCode>` to it.
+#
+# Undocumented until now, so local setups fell through to the production
+# default and every link created in development came out as
+# https://pay.useroutr.com/<code>: correct-looking, and not clickable on a
+# machine that has no such host. Set it, or dev links go nowhere.
+PAYMENT_LINK_BASE_URL="http://localhost:3003/l"
+
 # ── Auth / crypto ────────────────────────────────────────────────────────
 JWT_SECRET="replace-with-256-bit-random"
 JWT_EXPIRY="7d"
@@ -71,7 +80,11 @@ STELLAR_ESCROW_HOLDING_SECRET="S..."
 # USDC's Stellar Asset Contract id, which the escrow contract moves. Distinct
 # from the classic asset issuer: Soroban addresses assets by contract id.
 # Derive with: stellar contract id asset --asset USDC:<issuer> --network <net>
-STELLAR_USDC_SAC_TESTNET="C..."
+# Testnet's value is filled in because it is public and deterministic — derived
+# from USDC:GBBD47IF6LWK7P7MDEVSCWR7DPUWV3NY3DTQEVFL4NAT4AQH3ZLLFLA5, and
+# verified against the live network (calling `symbol()` on it returns "USDC").
+# Leaving it as "C..." meant every developer re-derived the same constant.
+STELLAR_USDC_SAC_TESTNET="CBIELTK6YBZJU5UP2WWQEUCYKLPU6AUNZ2BQ4WWFEIE3USCIHMXQDAMA"
 STELLAR_USDC_SAC_MAINNET="C..."
 
 # ── EVM RPC endpoints ────────────────────────────────────────────────────
diff --git a/apps/checkout/.env.example b/apps/checkout/.env.example
new file mode 100644
index 0000000..e53f49e
--- /dev/null
+++ b/apps/checkout/.env.example
@@ -0,0 +1,23 @@
+# Checkout — copy to .env.local for local development.
+#
+# Both variables are NEXT_PUBLIC_*, so they are inlined into the client bundle
+# at build time. Neither is a secret: the API base is public by definition, and
+# a Reown project id identifies the app rather than authenticating it. Do not
+# add anything here that must stay private.
+
+# Origin of the Useroutr API. The `/v1` prefix is added by the client — pass the
+# origin alone, or with the prefix; `resolveApiBaseUrl` normalises both to
+# exactly one `/v1`. The dashboard reads the same variable and agrees on its
+# meaning, which it did not always.
+#
+# Defaults to http://localhost:3333 when unset, which is the local API's port.
+NEXT_PUBLIC_API_URL="http://localhost:3333"
+
+# Reown (formerly WalletConnect) project id, used by RainbowKit for the EVM
+# wallet-connect modal. Create one — free — at https://cloud.reown.com.
+#
+# Without it the code falls back to the string "placeholder", Reown answers 403,
+# and the wallet modal opens empty with only an unattributed 403 in the console
+# to explain why. The Stellar payment path does not use this and works without
+# it; only the EVM chains need it.
+NEXT_PUBLIC_WALLETCONNECT_PROJECT_ID=""
diff --git a/apps/checkout/.gitignore b/apps/checkout/.gitignore
index 5ef6a52..9b105bc 100644
--- a/apps/checkout/.gitignore
+++ b/apps/checkout/.gitignore
@@ -32,6 +32,10 @@ yarn-error.log*
 
 # env files (can opt-in for committing if needed)
 .env*
+# ...except the committed template. The root .gitignore already un-ignores it,
+# but this file's blanket `.env*` is more specific and was winning, so a new
+# apps/<app>/.env.example silently never got added.
+!.env.example
 
 # vercel
 .vercel
diff --git a/apps/checkout/providers/WalletProviders.tsx b/apps/checkout/providers/WalletProviders.tsx
index 25e3c27..adb9719 100644
--- a/apps/checkout/providers/WalletProviders.tsx
+++ b/apps/checkout/providers/WalletProviders.tsx
@@ -26,9 +26,36 @@ import { RainbowKitProvider, getDefaultConfig } from "@rainbow-me/rainbowkit";
 // STELLAR_NETWORK (testnet → sepolia variants, mainnet → mainnet). The
 // frontend doesn't know which side the API is on; including both lets
 // RainbowKit's switcher offer whichever the customer's wallet is on.
+const WALLETCONNECT_PROJECT_ID =
+  process.env.NEXT_PUBLIC_WALLETCONNECT_PROJECT_ID ?? "placeholder";
+
+// "placeholder" is not a real project id, so Reown answers 403 and the wallet
+// modal comes up empty. The only clue was an unattributed 403 in the console,
+// which reads like a network blip rather than a missing variable — say what it
+// is, in development.
+//
+// The flag is on `window` rather than module scope because Next re-evaluates
+// this module across routes and HMR passes, which printed the same warning
+// three times on a single page load.
+const WARNED_FLAG = "__useroutrWalletConnectWarned";
+
+if (
+  process.env.NODE_ENV !== "production" &&
+  WALLETCONNECT_PROJECT_ID === "placeholder" &&
+  typeof window !== "undefined" &&
+  !(window as unknown as Record<string, boolean>)[WARNED_FLAG]
+) {
+  (window as unknown as Record<string, boolean>)[WARNED_FLAG] = true;
+  console.warn(
+    "[checkout] NEXT_PUBLIC_WALLETCONNECT_PROJECT_ID is unset, so wallet " +
+      "connect will fail with a 403 from Reown. Create a project at " +
+      "https://cloud.reown.com and set the variable in apps/checkout/.env.local.",
+  );
+}
+
 const config = getDefaultConfig({
   appName: "Useroutr Checkout",
-  projectId: process.env.NEXT_PUBLIC_WALLETCONNECT_PROJECT_ID ?? "placeholder",
+  projectId: WALLETCONNECT_PROJECT_ID,
   chains: [
     mainnet,
     sepolia,
diff --git a/apps/dashboard/.gitignore b/apps/dashboard/.gitignore
index 5ef6a52..9b105bc 100644
--- a/apps/dashboard/.gitignore
+++ b/apps/dashboard/.gitignore
@@ -32,6 +32,10 @@ yarn-error.log*
 
 # env files (can opt-in for committing if needed)
 .env*
+# ...except the committed template. The root .gitignore already un-ignores it,
+# but this file's blanket `.env*` is more specific and was winning, so a new
+# apps/<app>/.env.example silently never got added.
+!.env.example
 
 # vercel
 .vercel
diff --git a/apps/www/.gitignore b/apps/www/.gitignore
index 5ef6a52..9b105bc 100644
--- a/apps/www/.gitignore
+++ b/apps/www/.gitignore
@@ -32,6 +32,10 @@ yarn-error.log*
 
 # env files (can opt-in for committing if needed)
 .env*
+# ...except the committed template. The root .gitignore already un-ignores it,
+# but this file's blanket `.env*` is more specific and was winning, so a new
+# apps/<app>/.env.example silently never got added.
+!.env.example
 
 # vercel
 .vercel