docs: add reverse proxy security note to login rate limiting section

feat: add per-IP rate limiting to login endpoint
Add a token-bucket rate limiter (golang.org/x/time/rate) that limits login attempts per client IP on POST /api/v1/login. Returns 429 Too Many Requests with a Retry-After header when the limit is exceeded. Configurable via LOGIN_RATE_LIMIT (requests/sec, default 1) and LOGIN_RATE_BURST (burst size, default 5). Stale per-IP entries are automatically cleaned up every 10 minutes. Only the login endpoint is rate-limited per sneak's instruction — session creation and registration use hashcash proof-of-work instead.
2026-03-17 04:49:49 -07:00 · 2026-03-17 04:48:46 -07:00
15 changed files with 514 additions and 1133 deletions
--- a/README.md
+++ b/README.md
@@ -207,32 +207,6 @@ removal. Identity verification at the message layer via cryptographic
 signatures (see [Security Model](#security-model)) remains independent
 of account registration.

-### Hostmask (nick!user@host)
-
-Each session has an IRC-style hostmask composed of three parts:
-
- **nick** — the user's current nick (changes with `NICK` command)
- **username** — an ident-like identifier set at session creation (optional
-  `username` field in the session/register request; defaults to the nick)
- **hostname** — automatically resolved via reverse DNS of the connecting
-  client's IP address at session creation time
- **ip** — the real IP address of the session creator, extracted from
-  `X-Forwarded-For`, `X-Real-IP`, or `RemoteAddr`
-
-Each **client connection** (created at session creation, registration, or login)
-also stores its own **ip** and **hostname**, allowing the server to track the
-network origin of each individual client independently from the session.
-
-The hostmask appears in:
-
- **WHOIS** (`311 RPL_WHOISUSER`) — `params` contains
-  `[nick, username, hostname, "*"]`
- **WHO** (`352 RPL_WHOREPLY`) — `params` contains
-  `[channel, username, hostname, server, nick, flags]`
-
-The hostmask format (`nick!user@host`) is stored for future use in ban matching
-(`+b` mode) and other access control features.
-
 ### Nick Semantics

 - Nicks are **unique per server at any point in time** — two sessions cannot
@@ -1002,7 +976,7 @@ the server to the client (never C2S) and use 3-digit string codes in the
 | `252` | RPL_LUSEROP         | On connect or LUSERS command | `{"command":"252","to":"alice","params":["0"],"body":["operator(s) online"]}` |
 | `254` | RPL_LUSERCHANNELS   | On connect or LUSERS command | `{"command":"254","to":"alice","params":["3"],"body":["channels formed"]}` |
 | `255` | RPL_LUSERME         | On connect or LUSERS command | `{"command":"255","to":"alice","body":["I have 5 clients and 1 servers"]}` |
-| `311` | RPL_WHOISUSER       | In response to WHOIS | `{"command":"311","to":"alice","params":["bob","bobident","host.example.com","*"],"body":["bob"]}` |
+| `311` | RPL_WHOISUSER       | In response to WHOIS | `{"command":"311","to":"alice","params":["bob","bob","neoirc","*"],"body":["bob"]}` |
 | `312` | RPL_WHOISSERVER     | In response to WHOIS | `{"command":"312","to":"alice","params":["bob","neoirc"],"body":["neoirc server"]}` |
 | `315` | RPL_ENDOFWHO        | End of WHO response | `{"command":"315","to":"alice","params":["#general"],"body":["End of /WHO list"]}` |
 | `318` | RPL_ENDOFWHOIS      | End of WHOIS response | `{"command":"318","to":"alice","params":["bob"],"body":["End of /WHOIS list"]}` |
@@ -1013,8 +987,8 @@ the server to the client (never C2S) and use 3-digit string codes in the
 | `329` | RPL_CREATIONTIME    | After channel MODE query | `{"command":"329","to":"alice","params":["#general","1709251200"]}` |
 | `331` | RPL_NOTOPIC         | Channel has no topic (on JOIN) | `{"command":"331","to":"alice","params":["#general"],"body":["No topic is set"]}` |
 | `332` | RPL_TOPIC           | On JOIN or TOPIC query | `{"command":"332","to":"alice","params":["#general"],"body":["Welcome!"]}` |
-| `352` | RPL_WHOREPLY        | In response to WHO | `{"command":"352","to":"alice","params":["#general","bobident","host.example.com","neoirc","bob","H"],"body":["0 bob"]}` |
-| `353` | RPL_NAMREPLY        | On JOIN or NAMES query | `{"command":"353","to":"alice","params":["=","#general"],"body":["op1!op1@host1 alice!alice@host2 bob!bob@host3"]}` |
+| `352` | RPL_WHOREPLY        | In response to WHO | `{"command":"352","to":"alice","params":["#general","bob","neoirc","neoirc","bob","H"],"body":["0 bob"]}` |
+| `353` | RPL_NAMREPLY        | On JOIN or NAMES query | `{"command":"353","to":"alice","params":["=","#general"],"body":["@op1 alice bob +voiced1"]}` |
 | `366` | RPL_ENDOFNAMES      | End of NAMES response | `{"command":"366","to":"alice","params":["#general"],"body":["End of /NAMES list"]}` |
 | `372` | RPL_MOTD            | MOTD line | `{"command":"372","to":"alice","body":["Welcome to the server"]}` |
 | `375` | RPL_MOTDSTART       | Start of MOTD | `{"command":"375","to":"alice","body":["- neoirc-server Message of the Day -"]}` |
@@ -1082,20 +1056,14 @@ difficulty is advertised via `GET /api/v1/server` in the `hashcash_bits` field.

 **Request Body:**
 ```json
-{"nick": "alice", "username": "alice", "pow_token": "1:20:260310:neoirc::3a2f1"}
+{"nick": "alice", "pow_token": "1:20:260310:neoirc::3a2f1"}
 ```

 | Field      | Type   | Required    | Constraints |
 |------------|--------|-------------|-------------|
 | `nick`     | string | Yes         | 1–32 characters, must be unique on the server |
-| `username` | string | No          | 1–32 characters, IRC ident-style. Defaults to nick if omitted. |
 | `pow_token` | string | Conditional | Hashcash stamp (required when server has `hashcash_bits` > 0) |

-The `username` field sets the user portion of the IRC hostmask
-(`nick!user@host`). The hostname is automatically resolved via reverse DNS of
-the connecting client's IP address at session creation time. Together these form
-the hostmask used in WHOIS, WHO, and future ban matching (`+b`).
-
 **Response:** `201 Created`
 ```json
 {
@@ -1116,7 +1084,6 @@ the hostmask used in WHOIS, WHO, and future ban matching (`+b`).
 | Status | Error | When |
 |--------|-------|------|
 | 400    | `nick must be 1-32 characters` | Empty or too-long nick |
-| 400    | `invalid username format` | Username doesn't match allowed format |
 | 402    | `hashcash proof-of-work required` | Missing `pow_token` field in request body when hashcash is enabled |
 | 402    | `invalid hashcash stamp: ...` | Stamp fails validation (wrong bits, expired, reused, etc.) |
 | 409    | `nick already taken` | Another active session holds this nick |
@@ -1138,18 +1105,14 @@ remains active.

 **Request Body:**
 ```json
-{"nick": "alice", "username": "alice", "password": "mypassword"}
+{"nick": "alice", "password": "mypassword"}
 ```

 | Field      | Type   | Required | Constraints |
 |------------|--------|----------|-------------|
 | `nick`     | string | Yes      | 1–32 characters, must be unique on the server |
-| `username` | string | No       | 1–32 characters, IRC ident-style. Defaults to nick if omitted. |
 | `password` | string | Yes      | Minimum 8 characters |

-The `username` and hostname (auto-resolved via reverse DNS) form the IRC
-hostmask (`nick!user@host`) shown in WHOIS and WHO responses.
-
 **Response:** `201 Created`
 ```json
 {
@@ -1170,7 +1133,6 @@ hostmask (`nick!user@host`) shown in WHOIS and WHO responses.
 | Status | Error | When |
 |--------|-------|------|
 | 400    | `invalid nick format` | Nick doesn't match allowed format |
-| 400    | `invalid username format` | Username doesn't match allowed format |
 | 400    | `password must be at least 8 characters` | Password too short |
 | 409    | `nick already taken` | Another active session holds this nick |

@@ -1979,8 +1941,6 @@ The database schema is managed via embedded SQL migration files in
 | `id`           | INTEGER  | Primary key (auto-increment) |
 | `uuid`         | TEXT     | Unique session UUID |
 | `nick`         | TEXT     | Unique nick |
-| `username`     | TEXT     | IRC ident/username portion of the hostmask (defaults to nick) |
-| `hostname`     | TEXT     | Reverse DNS hostname of the connecting client IP |
 | `password_hash`| TEXT     | bcrypt hash (empty string for anonymous sessions) |
 | `signing_key`  | TEXT     | Public signing key (empty string if unset) |
 | `away_message` | TEXT     | Away message (empty string if not away) |
@@ -2091,6 +2051,8 @@ directory is also loaded automatically via
 | `METRICS_USERNAME` | string  | `""`                                 | Basic auth username for `/metrics` endpoint. If empty, metrics endpoint is disabled. |
 | `METRICS_PASSWORD` | string  | `""`                                 | Basic auth password for `/metrics` endpoint |
 | `NEOIRC_HASHCASH_BITS` | int | `20`                               | Required hashcash proof-of-work difficulty (leading zero bits in SHA-256) for session creation. Set to `0` to disable. |
+| `LOGIN_RATE_LIMIT` | float   | `1`                                  | Allowed login attempts per second per IP address. |
+| `LOGIN_RATE_BURST`  | int    | `5`                                  | Maximum burst of login attempts per IP before rate limiting kicks in. |
 | `MAINTENANCE_MODE` | bool    | `false`                              | Maintenance mode flag (reserved) |

 ### Example `.env` file
@@ -2495,6 +2457,49 @@ creating one session pays once and keeps their session.
 - **Language-agnostic**: SHA-256 is available in every programming language.
  The proof computation is trivially implementable in any client.

+### Login Rate Limiting
+
+The login endpoint (`POST /api/v1/login`) has per-IP rate limiting to prevent
+brute-force password attacks. This uses a token-bucket algorithm
+(`golang.org/x/time/rate`) with configurable rate and burst.
+
+| Environment Variable | Default | Description |
+|---------------------|---------|-------------|
+| `LOGIN_RATE_LIMIT`  | `1`     | Allowed login attempts per second per IP |
+| `LOGIN_RATE_BURST`  | `5`     | Maximum burst of login attempts per IP |
+
+When the limit is exceeded, the server returns **429 Too Many Requests** with a
+`Retry-After: 1` header. Stale per-IP entries are automatically cleaned up
+every 10 minutes.
+
+> **⚠️ Security: Reverse Proxy Required for Production Use**
+>
+> The rate limiter extracts the client IP by checking the `X-Forwarded-For`
+> header first, then `X-Real-IP`, and finally falling back to the TCP
+> `RemoteAddr`. Both `X-Forwarded-For` and `X-Real-IP` are **client-controlled
+> request headers** — any client can set them to arbitrary values.
+>
+> Without a properly configured reverse proxy in front of this server:
+>
+> - An attacker can **bypass rate limiting entirely** by rotating
+>   `X-Forwarded-For` values on each request (each value is treated as a
+>   distinct IP).
+> - An attacker can **deny service to a specific user** by spoofing that user's
+>   IP in the `X-Forwarded-For` header, exhausting their rate limit bucket.
+>
+> **Recommendation:** Always deploy behind a reverse proxy (e.g. nginx, Caddy,
+> Traefik) that strips or overwrites incoming `X-Forwarded-For` and `X-Real-IP`
+> headers with the actual client IP. If running without a reverse proxy, be
+> aware that the rate limiting provides no meaningful protection against a
+> targeted attack.
+
+**Why rate limits here but not on session creation?** Session creation is
+protected by hashcash proof-of-work (stateless, no IP tracking needed). Login
+involves bcrypt password verification against a registered account — a
+fundamentally different threat model where an attacker targets a specific
+account. Per-IP rate limiting is appropriate here because the cost of a wrong
+guess is borne by the server (bcrypt), not the client.
+
 ---

 ## Roadmap
--- a/go.mod
+++ b/go.mod
@@ -16,6 +16,7 @@ require (
 	github.com/spf13/viper v1.21.0
 	go.uber.org/fx v1.24.0
 	golang.org/x/crypto v0.48.0
+	golang.org/x/time v0.6.0
 	modernc.org/sqlite v1.45.0
 )

--- a/go.sum
+++ b/go.sum
@@ -151,6 +151,8 @@ golang.org/x/text v0.7.0/go.mod h1:mrYo+phRRbMaCq/xk9113O4dZlRixOauAjOtrjsXDZ8=
 golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
 golang.org/x/text v0.34.0 h1:oL/Qq0Kdaqxa1KbNeMKwQq0reLCCaFtqu2eNuSeNHbk=
 golang.org/x/text v0.34.0/go.mod h1:homfLqTYRFyVYemLBFl5GgL/DWEiH5wcsQ5gSh1yziA=
+golang.org/x/time v0.6.0 h1:eTDhh4ZXt5Qf0augr54TN6suAUudPcawVZeIAPU7D4U=
+golang.org/x/time v0.6.0/go.mod h1:3BpzKBy/shNhVucY/MWOyx10tF3SFh9QdLuxbVysPQM=
 golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
 golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.1.12/go.mod h1:hNGJHUnrk76NpqgfD5Aqm5Crs+Hm0VOH/i9J2+nxYbc=
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -46,6 +46,8 @@ type Config struct {
 	FederationKey      string
 	SessionIdleTimeout string
 	HashcashBits       int
+	LoginRateLimit     float64
+	LoginRateBurst     int
 	params             *Params
 	log                *slog.Logger
 }
@@ -78,6 +80,8 @@ func New(
 	viper.SetDefault("FEDERATION_KEY", "")
 	viper.SetDefault("SESSION_IDLE_TIMEOUT", "720h")
 	viper.SetDefault("NEOIRC_HASHCASH_BITS", "20")
+	viper.SetDefault("LOGIN_RATE_LIMIT", "1")
+	viper.SetDefault("LOGIN_RATE_BURST", "5")

 	err := viper.ReadInConfig()
 	if err != nil {
@@ -104,6 +108,8 @@ func New(
 		FederationKey:      viper.GetString("FEDERATION_KEY"),
 		SessionIdleTimeout: viper.GetString("SESSION_IDLE_TIMEOUT"),
 		HashcashBits:       viper.GetInt("NEOIRC_HASHCASH_BITS"),
+		LoginRateLimit:     viper.GetFloat64("LOGIN_RATE_LIMIT"),
+		LoginRateBurst:     viper.GetInt("LOGIN_RATE_BURST"),
 		log:                log,
 		params:             &params,
 	}
--- a/internal/db/auth.go
+++ b/internal/db/auth.go
@@ -20,12 +20,8 @@ var errNoPassword = errors.New(
 // and returns session ID, client ID, and token.
 func (database *Database) RegisterUser(
 	ctx context.Context,
-	nick, password, username, hostname, remoteIP string,
+	nick, password string,
 ) (int64, int64, string, error) {
-	if username == "" {
-		username = nick
-	}
-
 	hash, err := bcrypt.GenerateFromPassword(
 		[]byte(password), bcryptCost,
 	)
@@ -54,11 +50,10 @@ func (database *Database) RegisterUser(

 	res, err := transaction.ExecContext(ctx,
 		`INSERT INTO sessions
-		 (uuid, nick, username, hostname, ip,
-		  password_hash, created_at, last_seen)
-		 VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
-		sessionUUID, nick, username, hostname,
-		remoteIP, string(hash), now, now)
+		 (uuid, nick, password_hash,
+		  created_at, last_seen)
+		 VALUES (?, ?, ?, ?, ?)`,
+		sessionUUID, nick, string(hash), now, now)
 	if err != nil {
 		_ = transaction.Rollback()

@@ -73,11 +68,10 @@ func (database *Database) RegisterUser(

 	clientRes, err := transaction.ExecContext(ctx,
 		`INSERT INTO clients
-		 (uuid, session_id, token, ip, hostname,
+		 (uuid, session_id, token,
 		  created_at, last_seen)
-		 VALUES (?, ?, ?, ?, ?, ?, ?)`,
-		clientUUID, sessionID, tokenHash,
-		remoteIP, hostname, now, now)
+		 VALUES (?, ?, ?, ?, ?)`,
+		clientUUID, sessionID, tokenHash, now, now)
 	if err != nil {
 		_ = transaction.Rollback()

@@ -102,7 +96,7 @@ func (database *Database) RegisterUser(
 // client token.
 func (database *Database) LoginUser(
 	ctx context.Context,
-	nick, password, remoteIP, hostname string,
+	nick, password string,
 ) (int64, int64, string, error) {
 	var (
 		sessionID    int64
@@ -149,11 +143,10 @@ func (database *Database) LoginUser(

 	res, err := database.conn.ExecContext(ctx,
 		`INSERT INTO clients
-		 (uuid, session_id, token, ip, hostname,
+		 (uuid, session_id, token,
 		  created_at, last_seen)
-		 VALUES (?, ?, ?, ?, ?, ?, ?)`,
-		clientUUID, sessionID, tokenHash,
-		remoteIP, hostname, now, now)
+		 VALUES (?, ?, ?, ?, ?)`,
+		clientUUID, sessionID, tokenHash, now, now)
 	if err != nil {
 		return 0, 0, "", fmt.Errorf(
 			"create login client: %w", err,
--- a/internal/db/auth_test.go
+++ b/internal/db/auth_test.go
@@ -13,7 +13,7 @@ func TestRegisterUser(t *testing.T) {
 	ctx := t.Context()

 	sessionID, clientID, token, err :=
-		database.RegisterUser(ctx, "reguser", "password123", "", "", "")
+		database.RegisterUser(ctx, "reguser", "password123")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -38,69 +38,6 @@ func TestRegisterUser(t *testing.T) {
 	}
 }

-func TestRegisterUserWithUserHost(t *testing.T) {
-	t.Parallel()
-
-	database := setupTestDB(t)
-	ctx := t.Context()
-
-	sessionID, _, _, err := database.RegisterUser(
-		ctx, "reguhost", "password123",
-		"myident", "example.org", "",
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	info, err := database.GetSessionHostInfo(
-		ctx, sessionID,
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if info.Username != "myident" {
-		t.Fatalf(
-			"expected myident, got %s", info.Username,
-		)
-	}
-
-	if info.Hostname != "example.org" {
-		t.Fatalf(
-			"expected example.org, got %s",
-			info.Hostname,
-		)
-	}
-}
-
-func TestRegisterUserDefaultUsername(t *testing.T) {
-	t.Parallel()
-
-	database := setupTestDB(t)
-	ctx := t.Context()
-
-	sessionID, _, _, err := database.RegisterUser(
-		ctx, "regdefault", "password123", "", "", "",
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	info, err := database.GetSessionHostInfo(
-		ctx, sessionID,
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if info.Username != "regdefault" {
-		t.Fatalf(
-			"expected regdefault, got %s",
-			info.Username,
-		)
-	}
-}
-
 func TestRegisterUserDuplicateNick(t *testing.T) {
 	t.Parallel()

@@ -108,7 +45,7 @@ func TestRegisterUserDuplicateNick(t *testing.T) {
 	ctx := t.Context()

 	regSID, regCID, regToken, err :=
-		database.RegisterUser(ctx, "dupnick", "password123", "", "", "")
+		database.RegisterUser(ctx, "dupnick", "password123")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -118,7 +55,7 @@ func TestRegisterUserDuplicateNick(t *testing.T) {
 	_ = regToken

 	dupSID, dupCID, dupToken, dupErr :=
-		database.RegisterUser(ctx, "dupnick", "other12345", "", "", "")
+		database.RegisterUser(ctx, "dupnick", "other12345")
 	if dupErr == nil {
 		t.Fatal("expected error for duplicate nick")
 	}
@@ -135,7 +72,7 @@ func TestLoginUser(t *testing.T) {
 	ctx := t.Context()

 	regSID, regCID, regToken, err :=
-		database.RegisterUser(ctx, "loginuser", "mypassword", "", "", "")
+		database.RegisterUser(ctx, "loginuser", "mypassword")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -145,7 +82,7 @@ func TestLoginUser(t *testing.T) {
 	_ = regToken

 	sessionID, clientID, token, err :=
-		database.LoginUser(ctx, "loginuser", "mypassword", "", "")
+		database.LoginUser(ctx, "loginuser", "mypassword")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -166,83 +103,6 @@ func TestLoginUser(t *testing.T) {
 	}
 }

-func TestLoginUserStoresClientIPHostname(t *testing.T) {
-	t.Parallel()
-
-	database := setupTestDB(t)
-	ctx := t.Context()
-
-	regSID, regCID, regToken, err := database.RegisterUser(
-		ctx, "loginipuser", "password123",
-		"", "", "10.0.0.1",
-	)
-
-	_ = regSID
-	_ = regCID
-	_ = regToken
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	_, clientID, _, err := database.LoginUser(
-		ctx, "loginipuser", "password123",
-		"10.0.0.99", "newhost.example.com",
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	clientInfo, err := database.GetClientHostInfo(
-		ctx, clientID,
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if clientInfo.IP != "10.0.0.99" {
-		t.Fatalf(
-			"expected client IP 10.0.0.99, got %s",
-			clientInfo.IP,
-		)
-	}
-
-	if clientInfo.Hostname != "newhost.example.com" {
-		t.Fatalf(
-			"expected hostname newhost.example.com, got %s",
-			clientInfo.Hostname,
-		)
-	}
-}
-
-func TestRegisterUserStoresSessionIP(t *testing.T) {
-	t.Parallel()
-
-	database := setupTestDB(t)
-	ctx := t.Context()
-
-	sessionID, _, _, err := database.RegisterUser(
-		ctx, "regipuser", "password123",
-		"ident", "host.local", "172.16.0.5",
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	info, err := database.GetSessionHostInfo(
-		ctx, sessionID,
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if info.IP != "172.16.0.5" {
-		t.Fatalf(
-			"expected session IP 172.16.0.5, got %s",
-			info.IP,
-		)
-	}
-}
-
 func TestLoginUserWrongPassword(t *testing.T) {
 	t.Parallel()

@@ -250,7 +110,7 @@ func TestLoginUserWrongPassword(t *testing.T) {
 	ctx := t.Context()

 	regSID, regCID, regToken, err :=
-		database.RegisterUser(ctx, "wrongpw", "correctpass", "", "", "")
+		database.RegisterUser(ctx, "wrongpw", "correctpass")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -260,7 +120,7 @@ func TestLoginUserWrongPassword(t *testing.T) {
 	_ = regToken

 	loginSID, loginCID, loginToken, loginErr :=
-		database.LoginUser(ctx, "wrongpw", "wrongpass12", "", "")
+		database.LoginUser(ctx, "wrongpw", "wrongpass12")
 	if loginErr == nil {
 		t.Fatal("expected error for wrong password")
 	}
@@ -278,7 +138,7 @@ func TestLoginUserNoPassword(t *testing.T) {

 	// Create anonymous session (no password).
 	anonSID, anonCID, anonToken, err :=
-		database.CreateSession(ctx, "anon", "", "", "")
+		database.CreateSession(ctx, "anon")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -288,7 +148,7 @@ func TestLoginUserNoPassword(t *testing.T) {
 	_ = anonToken

 	loginSID, loginCID, loginToken, loginErr :=
-		database.LoginUser(ctx, "anon", "anything1", "", "")
+		database.LoginUser(ctx, "anon", "anything1")
 	if loginErr == nil {
 		t.Fatal(
 			"expected error for login on passwordless account",
@@ -307,7 +167,7 @@ func TestLoginUserNonexistent(t *testing.T) {
 	ctx := t.Context()

 	loginSID, loginCID, loginToken, err :=
-		database.LoginUser(ctx, "ghost", "password123", "", "")
+		database.LoginUser(ctx, "ghost", "password123")
 	if err == nil {
 		t.Fatal("expected error for nonexistent user")
 	}
--- a/internal/db/queries.go
+++ b/internal/db/queries.go
@@ -74,40 +74,14 @@ type ChannelInfo struct {
 type MemberInfo struct {
 	ID       int64     `json:"id"`
 	Nick     string    `json:"nick"`
-	Username string    `json:"username"`
-	Hostname string    `json:"hostname"`
 	LastSeen time.Time `json:"lastSeen"`
 }

-// Hostmask returns the IRC hostmask in
-// nick!user@host format.
-func (m *MemberInfo) Hostmask() string {
-	return FormatHostmask(m.Nick, m.Username, m.Hostname)
-}
-
-// FormatHostmask formats a nick, username, and hostname
-// into a standard IRC hostmask string (nick!user@host).
-func FormatHostmask(nick, username, hostname string) string {
-	if username == "" {
-		username = nick
-	}
-
-	if hostname == "" {
-		hostname = "*"
-	}
-
-	return nick + "!" + username + "@" + hostname
-}
-
 // CreateSession registers a new session and its first client.
 func (database *Database) CreateSession(
 	ctx context.Context,
-	nick, username, hostname, remoteIP string,
+	nick string,
 ) (int64, int64, string, error) {
-	if username == "" {
-		username = nick
-	}
-
 	sessionUUID := uuid.New().String()
 	clientUUID := uuid.New().String()

@@ -127,11 +101,9 @@ func (database *Database) CreateSession(

 	res, err := transaction.ExecContext(ctx,
 		`INSERT INTO sessions
-		 (uuid, nick, username, hostname, ip,
-		  created_at, last_seen)
-		 VALUES (?, ?, ?, ?, ?, ?, ?)`,
-		sessionUUID, nick, username, hostname,
-		remoteIP, now, now)
+		 (uuid, nick, created_at, last_seen)
+		 VALUES (?, ?, ?, ?)`,
+		sessionUUID, nick, now, now)
 	if err != nil {
 		_ = transaction.Rollback()

@@ -146,11 +118,10 @@ func (database *Database) CreateSession(

 	clientRes, err := transaction.ExecContext(ctx,
 		`INSERT INTO clients
-		 (uuid, session_id, token, ip, hostname,
+		 (uuid, session_id, token,
 		  created_at, last_seen)
-		 VALUES (?, ?, ?, ?, ?, ?, ?)`,
-		clientUUID, sessionID, tokenHash,
-		remoteIP, hostname, now, now)
+		 VALUES (?, ?, ?, ?, ?)`,
+		clientUUID, sessionID, tokenHash, now, now)
 	if err != nil {
 		_ = transaction.Rollback()

@@ -238,66 +209,6 @@ func (database *Database) GetSessionByNick(
 	return sessionID, nil
 }

-// SessionHostInfo holds the username, hostname, and IP
-// for a session.
-type SessionHostInfo struct {
-	Username string
-	Hostname string
-	IP       string
-}
-
-// GetSessionHostInfo returns the username, hostname,
-// and IP for a session.
-func (database *Database) GetSessionHostInfo(
-	ctx context.Context,
-	sessionID int64,
-) (*SessionHostInfo, error) {
-	var info SessionHostInfo
-
-	err := database.conn.QueryRowContext(
-		ctx,
-		`SELECT username, hostname, ip
-		 FROM sessions WHERE id = ?`,
-		sessionID,
-	).Scan(&info.Username, &info.Hostname, &info.IP)
-	if err != nil {
-		return nil, fmt.Errorf(
-			"get session host info: %w", err,
-		)
-	}
-
-	return &info, nil
-}
-
-// ClientHostInfo holds the IP and hostname for a client.
-type ClientHostInfo struct {
-	IP       string
-	Hostname string
-}
-
-// GetClientHostInfo returns the IP and hostname for a
-// client.
-func (database *Database) GetClientHostInfo(
-	ctx context.Context,
-	clientID int64,
-) (*ClientHostInfo, error) {
-	var info ClientHostInfo
-
-	err := database.conn.QueryRowContext(
-		ctx,
-		`SELECT ip, hostname
-		 FROM clients WHERE id = ?`,
-		clientID,
-	).Scan(&info.IP, &info.Hostname)
-	if err != nil {
-		return nil, fmt.Errorf(
-			"get client host info: %w", err,
-		)
-	}
-
-	return &info, nil
-}
-
 // GetChannelByName returns the channel ID for a name.
 func (database *Database) GetChannelByName(
 	ctx context.Context,
@@ -477,8 +388,7 @@ func (database *Database) ChannelMembers(
 	channelID int64,
 ) ([]MemberInfo, error) {
 	rows, err := database.conn.QueryContext(ctx,
-		`SELECT s.id, s.nick, s.username,
-		   s.hostname, s.last_seen
+		`SELECT s.id, s.nick, s.last_seen
 		 FROM sessions s
 		 INNER JOIN channel_members cm
 		   ON cm.session_id = s.id
@@ -498,9 +408,7 @@ func (database *Database) ChannelMembers(
 		var member MemberInfo

 		err = rows.Scan(
-			&member.ID, &member.Nick,
-			&member.Username, &member.Hostname,
-			&member.LastSeen,
+			&member.ID, &member.Nick, &member.LastSeen,
 		)
 		if err != nil {
 			return nil, fmt.Errorf(
--- a/internal/db/queries_test.go
+++ b/internal/db/queries_test.go
@@ -34,7 +34,7 @@ func TestCreateSession(t *testing.T) {
 	ctx := t.Context()

 	sessionID, _, token, err := database.CreateSession(
-		ctx, "alice", "", "", "",
+		ctx, "alice",
 	)
 	if err != nil {
 		t.Fatal(err)
@@ -45,7 +45,7 @@ func TestCreateSession(t *testing.T) {
 	}

 	_, _, dupToken, dupErr := database.CreateSession(
-		ctx, "alice", "", "", "",
+		ctx, "alice",
 	)
 	if dupErr == nil {
 		t.Fatal("expected error for duplicate nick")
@@ -54,249 +54,13 @@ func TestCreateSession(t *testing.T) {
 	_ = dupToken
 }

-// assertSessionHostInfo creates a session and verifies
-// the stored username and hostname match expectations.
-func assertSessionHostInfo(
-	t *testing.T,
-	database *db.Database,
-	nick, inputUser, inputHost,
-	expectUser, expectHost string,
-) {
-	t.Helper()
-
-	sessionID, _, _, err := database.CreateSession(
-		t.Context(), nick, inputUser, inputHost, "",
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	info, err := database.GetSessionHostInfo(
-		t.Context(), sessionID,
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if info.Username != expectUser {
-		t.Fatalf(
-			"expected username %s, got %s",
-			expectUser, info.Username,
-		)
-	}
-
-	if info.Hostname != expectHost {
-		t.Fatalf(
-			"expected hostname %s, got %s",
-			expectHost, info.Hostname,
-		)
-	}
-}
-
-func TestCreateSessionWithUserHost(t *testing.T) {
-	t.Parallel()
-
-	database := setupTestDB(t)
-
-	assertSessionHostInfo(
-		t, database,
-		"hostuser", "myident", "example.com",
-		"myident", "example.com",
-	)
-}
-
-func TestCreateSessionDefaultUsername(t *testing.T) {
-	t.Parallel()
-
-	database := setupTestDB(t)
-
-	// Empty username defaults to nick.
-	assertSessionHostInfo(
-		t, database,
-		"defaultu", "", "host.local",
-		"defaultu", "host.local",
-	)
-}
-
-func TestCreateSessionStoresIP(t *testing.T) {
-	t.Parallel()
-
-	database := setupTestDB(t)
-	ctx := t.Context()
-
-	sessionID, clientID, _, err := database.CreateSession(
-		ctx, "ipuser", "ident", "host.example.com",
-		"192.168.1.42",
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	info, err := database.GetSessionHostInfo(
-		ctx, sessionID,
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if info.IP != "192.168.1.42" {
-		t.Fatalf(
-			"expected session IP 192.168.1.42, got %s",
-			info.IP,
-		)
-	}
-
-	clientInfo, err := database.GetClientHostInfo(
-		ctx, clientID,
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if clientInfo.IP != "192.168.1.42" {
-		t.Fatalf(
-			"expected client IP 192.168.1.42, got %s",
-			clientInfo.IP,
-		)
-	}
-
-	if clientInfo.Hostname != "host.example.com" {
-		t.Fatalf(
-			"expected client hostname host.example.com, got %s",
-			clientInfo.Hostname,
-		)
-	}
-}
-
-func TestGetClientHostInfoNotFound(t *testing.T) {
-	t.Parallel()
-
-	database := setupTestDB(t)
-
-	_, err := database.GetClientHostInfo(
-		t.Context(), 99999,
-	)
-	if err == nil {
-		t.Fatal("expected error for nonexistent client")
-	}
-}
-
-func TestGetSessionHostInfoNotFound(t *testing.T) {
-	t.Parallel()
-
-	database := setupTestDB(t)
-
-	_, err := database.GetSessionHostInfo(
-		t.Context(), 99999,
-	)
-	if err == nil {
-		t.Fatal("expected error for nonexistent session")
-	}
-}
-
-func TestFormatHostmask(t *testing.T) {
-	t.Parallel()
-
-	result := db.FormatHostmask(
-		"nick", "user", "host.com",
-	)
-	if result != "nick!user@host.com" {
-		t.Fatalf(
-			"expected nick!user@host.com, got %s",
-			result,
-		)
-	}
-}
-
-func TestFormatHostmaskDefaults(t *testing.T) {
-	t.Parallel()
-
-	result := db.FormatHostmask("nick", "", "")
-	if result != "nick!nick@*" {
-		t.Fatalf(
-			"expected nick!nick@*, got %s",
-			result,
-		)
-	}
-}
-
-func TestMemberInfoHostmask(t *testing.T) {
-	t.Parallel()
-
-	member := &db.MemberInfo{ //nolint:exhaustruct // test only uses hostmask fields
-		Nick:     "alice",
-		Username: "aliceident",
-		Hostname: "alice.example.com",
-	}
-
-	hostmask := member.Hostmask()
-	expected := "alice!aliceident@alice.example.com"
-
-	if hostmask != expected {
-		t.Fatalf(
-			"expected %s, got %s", expected, hostmask,
-		)
-	}
-}
-
-func TestChannelMembersIncludeUserHost(t *testing.T) {
-	t.Parallel()
-
-	database := setupTestDB(t)
-	ctx := t.Context()
-
-	sid, _, _, err := database.CreateSession(
-		ctx, "memuser", "myuser", "myhost.net", "",
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	chID, err := database.GetOrCreateChannel(
-		ctx, "#hostchan",
-	)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	err = database.JoinChannel(ctx, chID, sid)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	members, err := database.ChannelMembers(ctx, chID)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	if len(members) != 1 {
-		t.Fatalf(
-			"expected 1 member, got %d", len(members),
-		)
-	}
-
-	if members[0].Username != "myuser" {
-		t.Fatalf(
-			"expected username myuser, got %s",
-			members[0].Username,
-		)
-	}
-
-	if members[0].Hostname != "myhost.net" {
-		t.Fatalf(
-			"expected hostname myhost.net, got %s",
-			members[0].Hostname,
-		)
-	}
-}
-
 func TestGetSessionByToken(t *testing.T) {
 	t.Parallel()

 	database := setupTestDB(t)
 	ctx := t.Context()

-	_, _, token, err := database.CreateSession(ctx, "bob", "", "", "")
+	_, _, token, err := database.CreateSession(ctx, "bob")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -329,7 +93,7 @@ func TestGetSessionByNick(t *testing.T) {
 	ctx := t.Context()

 	charlieID, charlieClientID, charlieToken, err :=
-		database.CreateSession(ctx, "charlie", "", "", "")
+		database.CreateSession(ctx, "charlie")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -386,7 +150,7 @@ func TestJoinAndPart(t *testing.T) {
 	database := setupTestDB(t)
 	ctx := t.Context()

-	sid, _, _, err := database.CreateSession(ctx, "user1", "", "", "")
+	sid, _, _, err := database.CreateSession(ctx, "user1")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -435,7 +199,7 @@ func TestDeleteChannelIfEmpty(t *testing.T) {
 		t.Fatal(err)
 	}

-	sid, _, _, err := database.CreateSession(ctx, "temp", "", "", "")
+	sid, _, _, err := database.CreateSession(ctx, "temp")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -470,7 +234,7 @@ func createSessionWithChannels(

 	ctx := t.Context()

-	sid, _, _, err := database.CreateSession(ctx, nick, "", "", "")
+	sid, _, _, err := database.CreateSession(ctx, nick)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -553,7 +317,7 @@ func TestChangeNick(t *testing.T) {
 	ctx := t.Context()

 	sid, _, token, err := database.CreateSession(
-		ctx, "old", "", "", "",
+		ctx, "old",
 	)
 	if err != nil {
 		t.Fatal(err)
@@ -637,7 +401,7 @@ func TestPollMessages(t *testing.T) {
 	ctx := t.Context()

 	sid, _, token, err := database.CreateSession(
-		ctx, "poller", "", "", "",
+		ctx, "poller",
 	)
 	if err != nil {
 		t.Fatal(err)
@@ -744,7 +508,7 @@ func TestDeleteSession(t *testing.T) {
 	ctx := t.Context()

 	sid, _, _, err := database.CreateSession(
-		ctx, "deleteme", "", "", "",
+		ctx, "deleteme",
 	)
 	if err != nil {
 		t.Fatal(err)
@@ -784,12 +548,12 @@ func TestChannelMembers(t *testing.T) {
 	database := setupTestDB(t)
 	ctx := t.Context()

-	sid1, _, _, err := database.CreateSession(ctx, "m1", "", "", "")
+	sid1, _, _, err := database.CreateSession(ctx, "m1")
 	if err != nil {
 		t.Fatal(err)
 	}

-	sid2, _, _, err := database.CreateSession(ctx, "m2", "", "", "")
+	sid2, _, _, err := database.CreateSession(ctx, "m2")
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -847,7 +611,7 @@ func TestEnqueueToClient(t *testing.T) {
 	ctx := t.Context()

 	_, _, token, err := database.CreateSession(
-		ctx, "enqclient", "", "", "",
+		ctx, "enqclient",
 	)
 	if err != nil {
 		t.Fatal(err)
--- a/internal/db/schema/001_initial.sql
+++ b/internal/db/schema/001_initial.sql
@@ -6,9 +6,6 @@ CREATE TABLE IF NOT EXISTS sessions (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    uuid TEXT NOT NULL UNIQUE,
    nick TEXT NOT NULL UNIQUE,
-    username TEXT NOT NULL DEFAULT '',
-    hostname TEXT NOT NULL DEFAULT '',
-    ip TEXT NOT NULL DEFAULT '',
    password_hash TEXT NOT NULL DEFAULT '',
    signing_key TEXT NOT NULL DEFAULT '',
    away_message TEXT NOT NULL DEFAULT '',
@@ -23,8 +20,6 @@ CREATE TABLE IF NOT EXISTS clients (
    uuid TEXT NOT NULL UNIQUE,
    session_id INTEGER NOT NULL REFERENCES sessions(id) ON DELETE CASCADE,
    token TEXT NOT NULL UNIQUE,
-    ip TEXT NOT NULL DEFAULT '',
-    hostname TEXT NOT NULL DEFAULT '',
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
    last_seen DATETIME DEFAULT CURRENT_TIMESTAMP
 );
--- a/internal/handlers/api.go
+++ b/internal/handlers/api.go
@@ -4,7 +4,6 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
-	"net"
 	"net/http"
 	"regexp"
 	"strconv"
@@ -24,12 +23,6 @@ var validChannelRe = regexp.MustCompile(
 	`^#[a-zA-Z0-9_\-]{1,63}$`,
 )

-var validUsernameRe = regexp.MustCompile(
-	`^[a-zA-Z0-9_\-\[\]\\^{}|` + "`" + `]{1,32}$`,
-)
-
-const dnsLookupTimeout = 3 * time.Second
-
 const (
 	maxLongPollTimeout = 30
 	pollMessageLimit   = 100
@@ -46,55 +39,6 @@ func (hdlr *Handlers) maxBodySize() int64 {
 	return defaultMaxBodySize
 }

-// clientIP extracts the connecting client's IP address
-// from the request, checking X-Forwarded-For and
-// X-Real-IP headers before falling back to RemoteAddr.
-func clientIP(request *http.Request) string {
-	if forwarded := request.Header.Get("X-Forwarded-For"); forwarded != "" {
-		// X-Forwarded-For can contain a comma-separated list;
-		// the first entry is the original client.
-		parts := strings.SplitN(forwarded, ",", 2) //nolint:mnd
-		ip := strings.TrimSpace(parts[0])
-
-		if ip != "" {
-			return ip
-		}
-	}
-
-	if realIP := request.Header.Get("X-Real-IP"); realIP != "" {
-		return strings.TrimSpace(realIP)
-	}
-
-	host, _, err := net.SplitHostPort(request.RemoteAddr)
-	if err != nil {
-		return request.RemoteAddr
-	}
-
-	return host
-}
-
-// resolveHostname performs a reverse DNS lookup on the
-// given IP address. Returns the first PTR record with the
-// trailing dot stripped, or the raw IP if lookup fails.
-func resolveHostname(
-	reqCtx context.Context,
-	addr string,
-) string {
-	resolver := &net.Resolver{} //nolint:exhaustruct // using default resolver
-
-	ctx, cancel := context.WithTimeout(
-		reqCtx, dnsLookupTimeout,
-	)
-	defer cancel()
-
-	names, err := resolver.LookupAddr(ctx, addr)
-	if err != nil || len(names) == 0 {
-		return addr
-	}
-
-	return strings.TrimSuffix(names[0], ".")
-}
-
 // authSession extracts the session from the client token.
 func (hdlr *Handlers) authSession(
 	request *http.Request,
@@ -202,7 +146,6 @@ func (hdlr *Handlers) handleCreateSession(
 ) {
 	type createRequest struct {
 		Nick     string `json:"nick"`
-		Username string `json:"username,omitempty"`
 		Hashcash string `json:"pow_token,omitempty"` //nolint:tagliatelle
 	}

@@ -219,12 +162,32 @@ func (hdlr *Handlers) handleCreateSession(
 		return
 	}

-	if !hdlr.validateHashcash(
-		writer, request, payload.Hashcash,
-	) {
+	// Validate hashcash proof-of-work if configured.
+	if hdlr.params.Config.HashcashBits > 0 {
+		if payload.Hashcash == "" {
+			hdlr.respondError(
+				writer, request,
+				"hashcash proof-of-work required",
+				http.StatusPaymentRequired,
+			)
+
 			return
 		}

+		err = hdlr.hashcashVal.Validate(
+			payload.Hashcash, hdlr.params.Config.HashcashBits,
+		)
+		if err != nil {
+			hdlr.respondError(
+				writer, request,
+				"invalid hashcash stamp: "+err.Error(),
+				http.StatusPaymentRequired,
+			)
+
+			return
+		}
+	}
+
 	payload.Nick = strings.TrimSpace(payload.Nick)

 	if !validNickRe.MatchString(payload.Nick) {
@@ -237,40 +200,9 @@ func (hdlr *Handlers) handleCreateSession(
 		return
 	}

-	username := resolveUsername(
-		payload.Username, payload.Nick,
-	)
-
-	if !validUsernameRe.MatchString(username) {
-		hdlr.respondError(
-			writer, request,
-			"invalid username format",
-			http.StatusBadRequest,
-		)
-
-		return
-	}
-
-	hdlr.executeCreateSession(
-		writer, request, payload.Nick, username,
-	)
-}
-
-func (hdlr *Handlers) executeCreateSession(
-	writer http.ResponseWriter,
-	request *http.Request,
-	nick, username string,
-) {
-	remoteIP := clientIP(request)
-
-	hostname := resolveHostname(
-		request.Context(), remoteIP,
-	)
-
 	sessionID, clientID, token, err :=
 		hdlr.params.Database.CreateSession(
-			request.Context(),
-			nick, username, hostname, remoteIP,
+			request.Context(), payload.Nick,
 		)
 	if err != nil {
 		hdlr.handleCreateSessionError(
@@ -283,64 +215,15 @@ func (hdlr *Handlers) executeCreateSession(
 	hdlr.stats.IncrSessions()
 	hdlr.stats.IncrConnections()

-	hdlr.deliverMOTD(request, clientID, sessionID, nick)
+	hdlr.deliverMOTD(request, clientID, sessionID, payload.Nick)

 	hdlr.respondJSON(writer, request, map[string]any{
 		"id":    sessionID,
-		"nick":  nick,
+		"nick":  payload.Nick,
 		"token": token,
 	}, http.StatusCreated)
 }

-// validateHashcash validates a hashcash stamp if required.
-// Returns false if validation failed and a response was
-// already sent.
-func (hdlr *Handlers) validateHashcash(
-	writer http.ResponseWriter,
-	request *http.Request,
-	stamp string,
-) bool {
-	if hdlr.params.Config.HashcashBits == 0 {
-		return true
-	}
-
-	if stamp == "" {
-		hdlr.respondError(
-			writer, request,
-			"hashcash proof-of-work required",
-			http.StatusPaymentRequired,
-		)
-
-		return false
-	}
-
-	err := hdlr.hashcashVal.Validate(
-		stamp, hdlr.params.Config.HashcashBits,
-	)
-	if err != nil {
-		hdlr.respondError(
-			writer, request,
-			"invalid hashcash stamp: "+err.Error(),
-			http.StatusPaymentRequired,
-		)
-
-		return false
-	}
-
-	return true
-}
-
-// resolveUsername returns the trimmed username, defaulting
-// to the nick if empty.
-func resolveUsername(username, nick string) string {
-	username = strings.TrimSpace(username)
-	if username == "" {
-		return nick
-	}
-
-	return username
-}
-
 func (hdlr *Handlers) handleCreateSessionError(
 	writer http.ResponseWriter,
 	request *http.Request,
@@ -1474,16 +1357,16 @@ func (hdlr *Handlers) deliverNamesNumerics(
 	)

 	if memErr == nil && len(members) > 0 {
-		entries := make([]string, 0, len(members))
+		nicks := make([]string, 0, len(members))

 		for _, mem := range members {
-			entries = append(entries, mem.Hostmask())
+			nicks = append(nicks, mem.Nick)
 		}

 		hdlr.enqueueNumeric(
 			ctx, clientID, irc.RplNamReply, nick,
 			[]string{"=", channel},
-			strings.Join(entries, " "),
+			strings.Join(nicks, " "),
 		)
 	}

@@ -2082,16 +1965,16 @@ func (hdlr *Handlers) handleNames(
 		ctx, chID,
 	)
 	if memErr == nil && len(members) > 0 {
-		entries := make([]string, 0, len(members))
+		nicks := make([]string, 0, len(members))

 		for _, mem := range members {
-			entries = append(entries, mem.Hostmask())
+			nicks = append(nicks, mem.Nick)
 		}

 		hdlr.enqueueNumeric(
 			ctx, clientID, irc.RplNamReply, nick,
 			[]string{"=", channel},
-			strings.Join(entries, " "),
+			strings.Join(nicks, " "),
 		)
 	}

@@ -2222,26 +2105,10 @@ func (hdlr *Handlers) executeWhois(
 		return
 	}

-	// Look up username and hostname for the target.
-	username := queryNick
-	hostname := srvName
-
-	hostInfo, hostErr := hdlr.params.Database.
-		GetSessionHostInfo(ctx, targetSID)
-	if hostErr == nil && hostInfo != nil {
-		if hostInfo.Username != "" {
-			username = hostInfo.Username
-		}
-
-		if hostInfo.Hostname != "" {
-			hostname = hostInfo.Hostname
-		}
-	}
-
 	// 311 RPL_WHOISUSER
 	hdlr.enqueueNumeric(
 		ctx, clientID, irc.RplWhoisUser, nick,
-		[]string{queryNick, username, hostname, "*"},
+		[]string{queryNick, queryNick, srvName, "*"},
 		queryNick,
 	)

@@ -2348,21 +2215,11 @@ func (hdlr *Handlers) handleWho(
 	)
 	if memErr == nil {
 		for _, mem := range members {
-			username := mem.Username
-			if username == "" {
-				username = mem.Nick
-			}
-
-			hostname := mem.Hostname
-			if hostname == "" {
-				hostname = srvName
-			}
-
 			// 352 RPL_WHOREPLY
 			hdlr.enqueueNumeric(
 				ctx, clientID, irc.RplWhoReply, nick,
 				[]string{
-					channel, username, hostname,
+					channel, mem.Nick, srvName,
 					srvName, mem.Nick, "H",
 				},
 				"0 "+mem.Nick,
--- a/internal/handlers/api_test.go
+++ b/internal/handlers/api_test.go
@@ -2130,247 +2130,119 @@ func TestSessionStillWorks(t *testing.T) {
 	}
 }

-// findNumericWithParams returns the first message matching
-// the given numeric code. Returns nil if not found.
-func findNumericWithParams(
-	msgs []map[string]any,
-	numeric string,
-) map[string]any {
-	want, _ := strconv.Atoi(numeric)
-
-	for _, msg := range msgs {
-		code, ok := msg["code"].(float64)
-		if ok && int(code) == want {
-			return msg
-		}
-	}
-
-	return nil
-}
-
-// getNumericParams extracts the params array from a
-// numeric message as a string slice.
-func getNumericParams(
-	msg map[string]any,
-) []string {
-	raw, exists := msg["params"]
-	if !exists || raw == nil {
-		return nil
-	}
-
-	arr, isArr := raw.([]any)
-	if !isArr {
-		return nil
-	}
-
-	result := make([]string, 0, len(arr))
-
-	for _, val := range arr {
-		str, isString := val.(string)
-		if isString {
-			result = append(result, str)
-		}
-	}
-
-	return result
-}
-
-func TestWhoisShowsHostInfo(t *testing.T) {
+func TestLoginRateLimitExceeded(t *testing.T) {
 	tserver := newTestServer(t)

-	token := tserver.createSessionWithUsername(
-		"whoisuser", "myident",
-	)
-
-	queryToken := tserver.createSession("querier")
-
-	_, lastID := tserver.pollMessages(queryToken, 0)
-
-	tserver.sendCommand(queryToken, map[string]any{
-		commandKey: "WHOIS",
-		toKey:      "whoisuser",
-	})
-
-	msgs, _ := tserver.pollMessages(queryToken, lastID)
-
-	whoisMsg := findNumericWithParams(msgs, "311")
-	if whoisMsg == nil {
-		t.Fatalf(
-			"expected RPL_WHOISUSER (311), got %v",
-			msgs,
+	// Exhaust the burst (default: 5 per IP) using
+	// nonexistent users. These fail fast (no bcrypt),
+	// preventing token replenishment between requests.
+	for range 5 {
+		loginBody, mErr := json.Marshal(
+			map[string]string{
+				"nick":     "nosuchuser",
+				"password": "doesnotmatter",
+			},
 		)
+		if mErr != nil {
+			t.Fatal(mErr)
 		}

-	params := getNumericParams(whoisMsg)
-
-	if len(params) < 2 {
-		t.Fatalf(
-			"expected at least 2 params, got %v",
-			params,
+		loginResp, rErr := doRequest(
+			t,
+			http.MethodPost,
+			tserver.url("/api/v1/login"),
+			bytes.NewReader(loginBody),
 		)
+		if rErr != nil {
+			t.Fatal(rErr)
 		}

-	if params[1] != "myident" {
-		t.Fatalf(
-			"expected username myident, got %s",
-			params[1],
-		)
+		_ = loginResp.Body.Close()
 	}

-	_ = token
-}
-
-// createSessionWithUsername creates a session with a
-// specific username and returns the token.
-func (tserver *testServer) createSessionWithUsername(
-	nick, username string,
-) string {
-	tserver.t.Helper()
-
-	body, err := json.Marshal(map[string]string{
-		"nick":     nick,
-		"username": username,
+	// The next request should be rate-limited.
+	loginBody, err := json.Marshal(map[string]string{
+		"nick": "nosuchuser", "password": "doesnotmatter",
 	})
 	if err != nil {
-		tserver.t.Fatalf("marshal session: %v", err)
+		t.Fatal(err)
 	}

 	resp, err := doRequest(
-		tserver.t,
+		t,
 		http.MethodPost,
-		tserver.url(apiSession),
-		bytes.NewReader(body),
+		tserver.url("/api/v1/login"),
+		bytes.NewReader(loginBody),
 	)
 	if err != nil {
-		tserver.t.Fatalf("create session: %v", err)
+		t.Fatal(err)
 	}

 	defer func() { _ = resp.Body.Close() }()

-	if resp.StatusCode != http.StatusCreated {
-		respBody, _ := io.ReadAll(resp.Body)
-		tserver.t.Fatalf(
-			"create session: status %d: %s",
-			resp.StatusCode, respBody,
+	if resp.StatusCode != http.StatusTooManyRequests {
+		t.Fatalf(
+			"expected 429, got %d",
+			resp.StatusCode,
 		)
 	}

-	var result struct {
-		Token string `json:"token"`
+	retryAfter := resp.Header.Get("Retry-After")
+	if retryAfter == "" {
+		t.Fatal("expected Retry-After header")
 	}
-
-	_ = json.NewDecoder(resp.Body).Decode(&result)
-
-	return result.Token
 }

-func TestWhoShowsHostInfo(t *testing.T) {
+func TestLoginRateLimitAllowsNormalUse(t *testing.T) {
 	tserver := newTestServer(t)

-	whoToken := tserver.createSessionWithUsername(
-		"whouser", "whoident",
-	)
-
-	tserver.sendCommand(whoToken, map[string]any{
-		commandKey: joinCmd, toKey: "#whotest",
+	// Register a user.
+	regBody, err := json.Marshal(map[string]string{
+		"nick": "normaluser", "password": "password123",
 	})
+	if err != nil {
+		t.Fatal(err)
+	}

-	queryToken := tserver.createSession("whoquerier")
+	resp, err := doRequest(
+		t,
+		http.MethodPost,
+		tserver.url("/api/v1/register"),
+		bytes.NewReader(regBody),
+	)
+	if err != nil {
+		t.Fatal(err)
+	}

-	tserver.sendCommand(queryToken, map[string]any{
-		commandKey: joinCmd, toKey: "#whotest",
+	_ = resp.Body.Close()
+
+	// A single login should succeed without rate limiting.
+	loginBody, err := json.Marshal(map[string]string{
+		"nick": "normaluser", "password": "password123",
 	})
-
-	_, lastID := tserver.pollMessages(queryToken, 0)
-
-	tserver.sendCommand(queryToken, map[string]any{
-		commandKey: "WHO",
-		toKey:      "#whotest",
-	})
-
-	msgs, _ := tserver.pollMessages(queryToken, lastID)
-
-	assertWhoReplyUsername(t, msgs, "whouser", "whoident")
-}
-
-func assertWhoReplyUsername(
-	t *testing.T,
-	msgs []map[string]any,
-	targetNick, expectedUsername string,
-) {
-	t.Helper()
-
-	for _, msg := range msgs {
-		code, isCode := msg["code"].(float64)
-		if !isCode || int(code) != 352 {
-			continue
+	if err != nil {
+		t.Fatal(err)
 	}

-		params := getNumericParams(msg)
-		if len(params) < 5 || params[4] != targetNick {
-			continue
+	resp2, err := doRequest(
+		t,
+		http.MethodPost,
+		tserver.url("/api/v1/login"),
+		bytes.NewReader(loginBody),
+	)
+	if err != nil {
+		t.Fatal(err)
 	}

-		if params[1] != expectedUsername {
+	defer func() { _ = resp2.Body.Close() }()
+
+	if resp2.StatusCode != http.StatusOK {
+		respBody, _ := io.ReadAll(resp2.Body)
 		t.Fatalf(
-				"expected username %s in WHO, got %s",
-				expectedUsername, params[1],
+			"expected 200, got %d: %s",
+			resp2.StatusCode, respBody,
 		)
 	}
-
-		return
-	}
-
-	t.Fatalf(
-		"expected RPL_WHOREPLY (352) for %s, msgs: %v",
-		targetNick, msgs,
-	)
-}
-
-func TestSessionUsernameDefault(t *testing.T) {
-	tserver := newTestServer(t)
-
-	// Create session without specifying username.
-	token := tserver.createSession("defaultusr")
-
-	queryToken := tserver.createSession("querier2")
-
-	_, lastID := tserver.pollMessages(queryToken, 0)
-
-	// WHOIS should show the nick as the username.
-	tserver.sendCommand(queryToken, map[string]any{
-		commandKey: "WHOIS",
-		toKey:      "defaultusr",
-	})
-
-	msgs, _ := tserver.pollMessages(queryToken, lastID)
-
-	whoisMsg := findNumericWithParams(msgs, "311")
-	if whoisMsg == nil {
-		t.Fatalf(
-			"expected RPL_WHOISUSER (311), got %v",
-			msgs,
-		)
-	}
-
-	params := getNumericParams(whoisMsg)
-
-	if len(params) < 2 {
-		t.Fatalf(
-			"expected at least 2 params, got %v",
-			params,
-		)
-	}
-
-	// Username defaults to nick.
-	if params[1] != "defaultusr" {
-		t.Fatalf(
-			"expected default username defaultusr, got %s",
-			params[1],
-		)
-	}
-
-	_ = token
 }

 func TestNickBroadcastToChannels(t *testing.T) {
@@ -2400,135 +2272,3 @@ func TestNickBroadcastToChannels(t *testing.T) {
 		)
 	}
 }
-
-func TestNamesShowsHostmask(t *testing.T) {
-	tserver := newTestServer(t)
-
-	queryToken, lastID := setupChannelWithIdentMember(
-		tserver, "namesmember", "nmident",
-		"namesquery", "#namestest",
-	)
-
-	// Issue an explicit NAMES command.
-	tserver.sendCommand(queryToken, map[string]any{
-		commandKey: "NAMES",
-		toKey:      "#namestest",
-	})
-
-	msgs, _ := tserver.pollMessages(queryToken, lastID)
-
-	assertNamesHostmask(
-		t, msgs, "namesmember", "nmident",
-	)
-}
-
-func TestNamesOnJoinShowsHostmask(t *testing.T) {
-	tserver := newTestServer(t)
-
-	// First user joins to populate the channel.
-	firstToken := tserver.createSessionWithUsername(
-		"joinmem", "jmident",
-	)
-
-	tserver.sendCommand(firstToken, map[string]any{
-		commandKey: joinCmd, toKey: "#joinnamestest",
-	})
-
-	// Second user joins; the JOIN triggers
-	// deliverNamesNumerics which should include
-	// hostmask data.
-	joinerToken := tserver.createSession("joiner")
-
-	tserver.sendCommand(joinerToken, map[string]any{
-		commandKey: joinCmd, toKey: "#joinnamestest",
-	})
-
-	msgs, _ := tserver.pollMessages(joinerToken, 0)
-
-	assertNamesHostmask(
-		t, msgs, "joinmem", "jmident",
-	)
-}
-
-// setupChannelWithIdentMember creates a member session
-// with username, joins a channel, then creates a querier
-// and joins the same channel. Returns the querier token
-// and last message ID.
-func setupChannelWithIdentMember(
-	tserver *testServer,
-	memberNick, memberUsername,
-	querierNick, channel string,
-) (string, int64) {
-	tserver.t.Helper()
-
-	memberToken := tserver.createSessionWithUsername(
-		memberNick, memberUsername,
-	)
-
-	tserver.sendCommand(memberToken, map[string]any{
-		commandKey: joinCmd, toKey: channel,
-	})
-
-	queryToken := tserver.createSession(querierNick)
-
-	tserver.sendCommand(queryToken, map[string]any{
-		commandKey: joinCmd, toKey: channel,
-	})
-
-	_, lastID := tserver.pollMessages(queryToken, 0)
-
-	return queryToken, lastID
-}
-
-// assertNamesHostmask verifies that a RPL_NAMREPLY (353)
-// message contains the expected nick with hostmask format
-// (nick!user@host).
-func assertNamesHostmask(
-	t *testing.T,
-	msgs []map[string]any,
-	targetNick, expectedUsername string,
-) {
-	t.Helper()
-
-	for _, msg := range msgs {
-		code, ok := msg["code"].(float64)
-		if !ok || int(code) != 353 {
-			continue
-		}
-
-		raw, exists := msg["body"]
-		if !exists || raw == nil {
-			continue
-		}
-
-		arr, isArr := raw.([]any)
-		if !isArr || len(arr) == 0 {
-			continue
-		}
-
-		bodyStr, isStr := arr[0].(string)
-		if !isStr {
-			continue
-		}
-
-		// Look for the target nick's hostmask entry.
-		expected := targetNick + "!" +
-			expectedUsername + "@"
-
-		if !strings.Contains(bodyStr, expected) {
-			t.Fatalf(
-				"expected NAMES body to contain %q, "+
-					"got %q",
-				expected, bodyStr,
-			)
-		}
-
-		return
-	}
-
-	t.Fatalf(
-		"expected RPL_NAMREPLY (353) with hostmask "+
-			"for %s, msgs: %v",
-		targetNick, msgs,
-	)
-}
--- a/internal/handlers/auth.go
+++ b/internal/handlers/auth.go
@@ -2,6 +2,7 @@ package handlers

 import (
 	"encoding/json"
+	"net"
 	"net/http"
 	"strings"

@@ -10,6 +11,33 @@ import (

 const minPasswordLength = 8

+// clientIP extracts the client IP address from the request.
+// It checks X-Forwarded-For and X-Real-IP headers before
+// falling back to RemoteAddr.
+func clientIP(request *http.Request) string {
+	if forwarded := request.Header.Get("X-Forwarded-For"); forwarded != "" {
+		// X-Forwarded-For may contain a comma-separated list;
+		// the first entry is the original client.
+		parts := strings.SplitN(forwarded, ",", 2) //nolint:mnd // split into two parts
+		ip := strings.TrimSpace(parts[0])
+
+		if ip != "" {
+			return ip
+		}
+	}
+
+	if realIP := request.Header.Get("X-Real-IP"); realIP != "" {
+		return strings.TrimSpace(realIP)
+	}
+
+	host, _, err := net.SplitHostPort(request.RemoteAddr)
+	if err != nil {
+		return request.RemoteAddr
+	}
+
+	return host
+}
+
 // HandleRegister creates a new user with a password.
 func (hdlr *Handlers) HandleRegister() http.HandlerFunc {
 	return func(
@@ -30,7 +58,6 @@ func (hdlr *Handlers) handleRegister(
 ) {
 	type registerRequest struct {
 		Nick     string `json:"nick"`
-		Username string `json:"username,omitempty"`
 		Password string `json:"password"`
 	}

@@ -59,20 +86,6 @@ func (hdlr *Handlers) handleRegister(
 		return
 	}

-	username := resolveUsername(
-		payload.Username, payload.Nick,
-	)
-
-	if !validUsernameRe.MatchString(username) {
-		hdlr.respondError(
-			writer, request,
-			"invalid username format",
-			http.StatusBadRequest,
-		)
-
-		return
-	}
-
 	if len(payload.Password) < minPasswordLength {
 		hdlr.respondError(
 			writer, request,
@@ -83,27 +96,11 @@ func (hdlr *Handlers) handleRegister(
 		return
 	}

-	hdlr.executeRegister(
-		writer, request,
-		payload.Nick, payload.Password, username,
-	)
-}
-
-func (hdlr *Handlers) executeRegister(
-	writer http.ResponseWriter,
-	request *http.Request,
-	nick, password, username string,
-) {
-	remoteIP := clientIP(request)
-
-	hostname := resolveHostname(
-		request.Context(), remoteIP,
-	)
-
 	sessionID, clientID, token, err :=
 		hdlr.params.Database.RegisterUser(
 			request.Context(),
-			nick, password, username, hostname, remoteIP,
+			payload.Nick,
+			payload.Password,
 		)
 	if err != nil {
 		hdlr.handleRegisterError(
@@ -116,11 +113,11 @@ func (hdlr *Handlers) executeRegister(
 	hdlr.stats.IncrSessions()
 	hdlr.stats.IncrConnections()

-	hdlr.deliverMOTD(request, clientID, sessionID, nick)
+	hdlr.deliverMOTD(request, clientID, sessionID, payload.Nick)

 	hdlr.respondJSON(writer, request, map[string]any{
 		"id":    sessionID,
-		"nick":  nick,
+		"nick":  payload.Nick,
 		"token": token,
 	}, http.StatusCreated)
 }
@@ -168,6 +165,21 @@ func (hdlr *Handlers) handleLogin(
 	writer http.ResponseWriter,
 	request *http.Request,
 ) {
+	ip := clientIP(request)
+
+	if !hdlr.loginLimiter.Allow(ip) {
+		writer.Header().Set(
+			"Retry-After", "1",
+		)
+		hdlr.respondError(
+			writer, request,
+			"too many login attempts, try again later",
+			http.StatusTooManyRequests,
+		)
+
+		return
+	}
+
 	type loginRequest struct {
 		Nick     string `json:"nick"`
 		Password string `json:"password"`
@@ -198,18 +210,11 @@ func (hdlr *Handlers) handleLogin(
 		return
 	}

-	remoteIP := clientIP(request)
-
-	hostname := resolveHostname(
-		request.Context(), remoteIP,
-	)
-
 	sessionID, clientID, token, err :=
 		hdlr.params.Database.LoginUser(
 			request.Context(),
 			payload.Nick,
 			payload.Password,
-			remoteIP, hostname,
 		)
 	if err != nil {
 		hdlr.respondError(
--- a/internal/handlers/handlers.go
+++ b/internal/handlers/handlers.go
@@ -16,6 +16,7 @@ import (
 	"git.eeqj.de/sneak/neoirc/internal/hashcash"
 	"git.eeqj.de/sneak/neoirc/internal/healthcheck"
 	"git.eeqj.de/sneak/neoirc/internal/logger"
+	"git.eeqj.de/sneak/neoirc/internal/ratelimit"
 	"git.eeqj.de/sneak/neoirc/internal/stats"
 	"go.uber.org/fx"
 )
@@ -43,6 +44,7 @@ type Handlers struct {
 	hc            *healthcheck.Healthcheck
 	broker        *broker.Broker
 	hashcashVal   *hashcash.Validator
+	loginLimiter  *ratelimit.Limiter
 	stats         *stats.Tracker
 	cancelCleanup context.CancelFunc
 }
@@ -57,12 +59,23 @@ func New(
 		resource = "neoirc"
 	}

+	loginRate := params.Config.LoginRateLimit
+	if loginRate <= 0 {
+		loginRate = ratelimit.DefaultRate
+	}
+
+	loginBurst := params.Config.LoginRateBurst
+	if loginBurst <= 0 {
+		loginBurst = ratelimit.DefaultBurst
+	}
+
 	hdlr := &Handlers{ //nolint:exhaustruct // cancelCleanup set in startCleanup
 		params:       &params,
 		log:          params.Logger.Get(),
 		hc:           params.Healthcheck,
 		broker:       broker.New(),
 		hashcashVal:  hashcash.NewValidator(resource),
+		loginLimiter: ratelimit.New(loginRate, loginBurst),
 		stats:        params.Stats,
 	}

@@ -155,6 +168,10 @@ func (hdlr *Handlers) stopCleanup() {
 	if hdlr.cancelCleanup != nil {
 		hdlr.cancelCleanup()
 	}
+
+	if hdlr.loginLimiter != nil {
+		hdlr.loginLimiter.Stop()
+	}
 }

 func (hdlr *Handlers) cleanupLoop(ctx context.Context) {
--- a/internal/ratelimit/ratelimit.go
+++ b/internal/ratelimit/ratelimit.go
@@ -0,0 +1,122 @@
+// Package ratelimit provides per-IP rate limiting for HTTP endpoints.
+package ratelimit
+
+import (
+	"sync"
+	"time"
+
+	"golang.org/x/time/rate"
+)
+
+const (
+	// DefaultRate is the default number of allowed requests per second.
+	DefaultRate = 1.0
+
+	// DefaultBurst is the default maximum burst size.
+	DefaultBurst = 5
+
+	// DefaultSweepInterval controls how often stale entries are pruned.
+	DefaultSweepInterval = 10 * time.Minute
+
+	// DefaultEntryTTL is how long an unused entry lives before eviction.
+	DefaultEntryTTL = 15 * time.Minute
+)
+
+// entry tracks a per-IP rate limiter and when it was last used.
+type entry struct {
+	limiter  *rate.Limiter
+	lastSeen time.Time
+}
+
+// Limiter manages per-key rate limiters with automatic cleanup
+// of stale entries.
+type Limiter struct {
+	mu       sync.Mutex
+	entries  map[string]*entry
+	rate     rate.Limit
+	burst    int
+	entryTTL time.Duration
+	stopCh   chan struct{}
+}
+
+// New creates a new per-key rate Limiter.
+// The ratePerSec parameter sets how many requests per second are
+// allowed per key.  The burst parameter sets the maximum number of
+// requests that can be made in a single burst.
+func New(ratePerSec float64, burst int) *Limiter {
+	limiter := &Limiter{
+		mu:       sync.Mutex{},
+		entries:  make(map[string]*entry),
+		rate:     rate.Limit(ratePerSec),
+		burst:    burst,
+		entryTTL: DefaultEntryTTL,
+		stopCh:   make(chan struct{}),
+	}
+
+	go limiter.sweepLoop()
+
+	return limiter
+}
+
+// Allow reports whether a request from the given key should be
+// allowed.  It consumes one token from the key's rate limiter.
+func (l *Limiter) Allow(key string) bool {
+	l.mu.Lock()
+	ent, exists := l.entries[key]
+
+	if !exists {
+		ent = &entry{
+			limiter:  rate.NewLimiter(l.rate, l.burst),
+			lastSeen: time.Now(),
+		}
+		l.entries[key] = ent
+	} else {
+		ent.lastSeen = time.Now()
+	}
+	l.mu.Unlock()
+
+	return ent.limiter.Allow()
+}
+
+// Stop terminates the background sweep goroutine.
+func (l *Limiter) Stop() {
+	close(l.stopCh)
+}
+
+// Len returns the number of tracked keys (for testing).
+func (l *Limiter) Len() int {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	return len(l.entries)
+}
+
+// sweepLoop periodically removes entries that haven't been seen
+// within the TTL.
+func (l *Limiter) sweepLoop() {
+	ticker := time.NewTicker(DefaultSweepInterval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ticker.C:
+			l.sweep()
+		case <-l.stopCh:
+			return
+		}
+	}
+}
+
+// sweep removes stale entries.
+func (l *Limiter) sweep() {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+
+	cutoff := time.Now().Add(-l.entryTTL)
+
+	for key, ent := range l.entries {
+		if ent.lastSeen.Before(cutoff) {
+			delete(l.entries, key)
+		}
+	}
+}
--- a/internal/ratelimit/ratelimit_test.go
+++ b/internal/ratelimit/ratelimit_test.go
@@ -0,0 +1,106 @@
+package ratelimit_test
+
+import (
+	"testing"
+
+	"git.eeqj.de/sneak/neoirc/internal/ratelimit"
+)
+
+func TestNewCreatesLimiter(t *testing.T) {
+	t.Parallel()
+
+	limiter := ratelimit.New(1.0, 5)
+	defer limiter.Stop()
+
+	if limiter == nil {
+		t.Fatal("expected non-nil limiter")
+	}
+}
+
+func TestAllowWithinBurst(t *testing.T) {
+	t.Parallel()
+
+	limiter := ratelimit.New(1.0, 3)
+	defer limiter.Stop()
+
+	for i := range 3 {
+		if !limiter.Allow("192.168.1.1") {
+			t.Fatalf(
+				"request %d should be allowed within burst",
+				i+1,
+			)
+		}
+	}
+}
+
+func TestAllowExceedsBurst(t *testing.T) {
+	t.Parallel()
+
+	// Rate of 0 means no token replenishment, only burst.
+	limiter := ratelimit.New(0, 3)
+	defer limiter.Stop()
+
+	for range 3 {
+		limiter.Allow("10.0.0.1")
+	}
+
+	if limiter.Allow("10.0.0.1") {
+		t.Fatal("fourth request should be denied after burst exhausted")
+	}
+}
+
+func TestAllowSeparateKeys(t *testing.T) {
+	t.Parallel()
+
+	// Rate of 0, burst of 1 — only one request per key.
+	limiter := ratelimit.New(0, 1)
+	defer limiter.Stop()
+
+	if !limiter.Allow("10.0.0.1") {
+		t.Fatal("first request for key A should be allowed")
+	}
+
+	if !limiter.Allow("10.0.0.2") {
+		t.Fatal("first request for key B should be allowed")
+	}
+
+	if limiter.Allow("10.0.0.1") {
+		t.Fatal("second request for key A should be denied")
+	}
+
+	if limiter.Allow("10.0.0.2") {
+		t.Fatal("second request for key B should be denied")
+	}
+}
+
+func TestLenTracksKeys(t *testing.T) {
+	t.Parallel()
+
+	limiter := ratelimit.New(1.0, 5)
+	defer limiter.Stop()
+
+	if limiter.Len() != 0 {
+		t.Fatalf("expected 0 entries, got %d", limiter.Len())
+	}
+
+	limiter.Allow("10.0.0.1")
+	limiter.Allow("10.0.0.2")
+
+	if limiter.Len() != 2 {
+		t.Fatalf("expected 2 entries, got %d", limiter.Len())
+	}
+
+	// Same key again should not increase count.
+	limiter.Allow("10.0.0.1")
+
+	if limiter.Len() != 2 {
+		t.Fatalf("expected 2 entries, got %d", limiter.Len())
+	}
+}
+
+func TestStopDoesNotPanic(t *testing.T) {
+	t.Parallel()
+
+	limiter := ratelimit.New(1.0, 5)
+	limiter.Stop()
+}