fix(nip05): add redirect prevention docs and zap field validation

Gap #5: Document NIP-05 spec requirement that /.well-known/nostr.json
MUST NOT return HTTP redirects. The extension already complies (always
returns direct responses), but reverse proxy deployments need awareness.

Gap #7: Log a warning when getLnurlPayInfo() response is missing
allowsNostr or nostrPubkey fields required by NIP-57 for zap support.
This surfaces misconfiguration early instead of silently breaking zaps.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/extensions/nip05/index.ts

@@ -189,6 +189,12 @@ export default class Nip05Extension implements Extension {
    *   "relays": { "<pubkey hex>": ["wss://..."] }
    * }
    */
+  /**
+   * NIP-05 spec: "The /.well-known/nostr.json endpoint MUST NOT return any
+   * HTTP redirects." This extension always returns direct 200/4xx/5xx responses.
+   * Deployment note: ensure reverse proxies do not add 3xx redirects on this path
+   * (e.g. HTTP→HTTPS or trailing-slash redirects).
+   */
   private async handleNostrJson(req: HttpRequest): Promise<HttpResponse> {
     try {
       // Get application ID from request context
@@ -272,6 +278,11 @@ export default class Nip05Extension implements Extension {
         description: `Pay to ${username}`
       })
 
+      // NIP-57: ensure zap support fields are present for wallet compatibility
+      if (!lnurlPayInfo.allowsNostr || !lnurlPayInfo.nostrPubkey) {
+        this.ctx.log('warn', `LNURL-pay response for ${username} missing zap fields (allowsNostr=${lnurlPayInfo.allowsNostr}, nostrPubkey=${!!lnurlPayInfo.nostrPubkey}). Zaps will not work.`)
+      }
+
       return {
         status: 200,
         body: lnurlPayInfo,

src/extensions/nip05/managers/nip05Manager.ts

@@ -55,10 +55,12 @@ function generateId(): string {
 }
 
 /**
- * Validate username format
+ * Validate username format per NIP-05 spec
- * - Lowercase alphanumeric and underscore only
+ * - Characters allowed: a-z, 0-9, hyphen (-), underscore (_), period (.)
  * - Must start with a letter
+ * - Must not end with a hyphen, underscore, or period
  * - Length within bounds
+ * - Special case: "_" alone is the root identifier (_@domain)
  */
 function validateUsername(username: string, config: Required<Nip05Config>): UsernameValidation {
   if (!username) {
@@ -67,6 +69,11 @@ function validateUsername(username: string, config: Required<Nip05Config>): User
 
   const normalized = username.toLowerCase().trim()
 
+  // Special case: root identifier "_" per NIP-05
+  if (normalized === '_') {
+    return { valid: true }
+  }
+
   if (normalized.length < config.min_username_length) {
     return { valid: false, error: `Username must be at least ${config.min_username_length} character(s)` }
   }
@@ -75,9 +82,10 @@ function validateUsername(username: string, config: Required<Nip05Config>): User
     return { valid: false, error: `Username must be at most ${config.max_username_length} characters` }
   }
 
-  // Only lowercase letters, numbers, and underscores
+  // NIP-05 spec: local-part MUST only use characters a-z0-9-_.
-  if (!/^[a-z][a-z0-9_]*$/.test(normalized)) {
+  // Must start with a letter, must not end with separator
-    return { valid: false, error: 'Username must start with a letter and contain only lowercase letters, numbers, and underscores' }
+  if (!/^[a-z][a-z0-9._-]*[a-z0-9]$/.test(normalized) && !/^[a-z]$/.test(normalized)) {
+    return { valid: false, error: 'Username must start with a letter, end with a letter or number, and contain only a-z, 0-9, hyphens, underscores, and periods' }
   }
 
   // Check reserved usernames

src/extensions/types.ts

@@ -191,6 +191,31 @@ export interface ExtensionContext {
   log(level: 'debug' | 'info' | 'warn' | 'error', message: string, ...args: any[]): void
 }
 
+/**
+ * HTTP route handler types
+ * Used by extensions that expose HTTP endpoints (e.g. LNURL, .well-known)
+ */
+export interface HttpRequest {
+  method: string
+  path: string
+  params: Record<string, string>
+  query: Record<string, string>
+  headers: Record<string, string>
+  body?: any
+}
+
+export interface HttpResponse {
+  status: number
+  body: any
+  headers?: Record<string, string>
+}
+
+export interface HttpRoute {
+  method: 'GET' | 'POST'
+  path: string
+  handler: (req: HttpRequest) => Promise<HttpResponse>
+}
+
 /**
  * Extension interface - what extensions must implement
  */
@@ -217,6 +242,12 @@ export interface Extension {
    * Return true if extension is healthy
    */
   healthCheck?(): Promise<boolean>
+
+  /**
+   * Get HTTP routes exposed by this extension
+   * The main HTTP server will mount these routes
+   */
+  getHttpRoutes?(): HttpRoute[]
 }
 
 /**