diff --git a/src/api/routes/config.ts b/src/api/routes/config.ts
index fab4f1a..d3633d1 100644
--- a/src/api/routes/config.ts
+++ b/src/api/routes/config.ts
@@ -47,17 +47,19 @@ export function configRouter(config: Config) {
       return res.badRequest(c, "minUploadRateBytesPerSec must be ≤ maxUploadRateBytesPerSec");
     }
 
-    // Apply patch to the live config object (affects all new seeders)
-    Object.assign(config, patch);
-
-    // Persist to disk so the next container start picks it up
+    // Persist to disk first — only apply to live config if write succeeds
+    const merged = { ...config, ...patch };
     try {
       mkdirSync(dirname(CONFIG_PATH), { recursive: true });
-      writeFileSync(CONFIG_PATH, dump(config), "utf8");
+      writeFileSync(CONFIG_PATH, dump(merged), "utf8");
     } catch (err) {
       console.warn("Could not persist config to disk:", err);
+      return res.unprocessable(c, "Failed to persist config to disk");
     }
 
+    // Apply patch to the live config object (affects all new seeders)
+    Object.assign(config, patch);
+
     return c.json(config);
   });
 
diff --git a/src/api/routes/status.ts b/src/api/routes/status.ts
index e3c4b7a..46464b0 100644
--- a/src/api/routes/status.ts
+++ b/src/api/routes/status.ts
@@ -2,8 +2,12 @@ import { Hono } from "hono";
 import { streamSSE } from "hono/streaming";
 import type { SeederRegistry } from "../SeederRegistry.js";
 
+/** Maximum number of concurrent SSE connections */
+const MAX_SSE_CONNECTIONS = 50;
+
 export function statusRouter(registry: SeederRegistry) {
   const app = new Hono();
+  let activeConnections = 0;
 
   /** Global stats snapshot */
   app.get("/", (c) => {
@@ -17,9 +21,25 @@ export function statusRouter(registry: SeederRegistry) {
    * Events:
    *   - "stats" with global stats (every change)
    *   - "torrent" with per-torrent state (on each seeder stateChange)
+   *   - "torrents" with full list on initial connection
+   *   - "ping" keep-alive every 30s
    */
   app.get("/stream", (c) => {
+    if (activeConnections >= MAX_SSE_CONNECTIONS) {
+      return c.text("Too many SSE connections", 429);
+    }
+    activeConnections++;
+
     return streamSSE(c, async (stream) => {
+      let cleaned = false;
+      function cleanup() {
+        if (cleaned) return;
+        cleaned = true;
+        activeConnections--;
+        clearInterval(keepAlive);
+        unsubscribe();
+      }
+
       // Send initial snapshot
       await stream.writeSSE({
         event: "stats",
@@ -43,27 +63,23 @@ export function statusRouter(registry: SeederRegistry) {
             data: JSON.stringify(registry.globalStats()),
           });
         } catch {
-          // client disconnected
+          cleanup();
         }
       });
 
-      // Keep alive with a comment every 30s
+      // Keep alive with a ping every 30s
       const keepAlive = setInterval(async () => {
         try {
           await stream.writeSSE({ event: "ping", data: "" });
         } catch {
-          clearInterval(keepAlive);
-          unsubscribe();
+          cleanup();
         }
       }, 30_000);
 
       // Clean up when client disconnects
-      stream.onAbort(() => {
-        clearInterval(keepAlive);
-        unsubscribe();
-      });
+      stream.onAbort(() => cleanup());
 
-      // Hold the connection open
+      // Hold the connection open until abort
       await new Promise<void>((resolve) => {
         stream.onAbort(() => resolve());
       });
diff --git a/src/api/routes/torrents.ts b/src/api/routes/torrents.ts
index 338626a..afc2551 100644
--- a/src/api/routes/torrents.ts
+++ b/src/api/routes/torrents.ts
@@ -2,6 +2,16 @@ import { Hono } from "hono";
 import { res } from "../response.js";
 import type { SeederRegistry } from "../SeederRegistry.js";
 
+/** Maximum upload size for .torrent files (10 MB) */
+const MAX_TORRENT_SIZE = 10 * 1024 * 1024;
+
+/** Validates that a hash parameter is a 40-char hex string (SHA-1) */
+const HASH_RE = /^[a-f0-9]{40}$/i;
+
+function validateHash(hash: string): boolean {
+  return HASH_RE.test(hash);
+}
+
 export function torrentsRouter(registry: SeederRegistry) {
   const app = new Hono();
 
@@ -12,6 +22,12 @@ export function torrentsRouter(registry: SeederRegistry) {
 
   /** Add a torrent — accepts multipart/form-data with a 'torrent' file field */
   app.post("/", async (c) => {
+    // Reject oversized uploads early
+    const contentLength = Number(c.req.header("content-length") ?? 0);
+    if (contentLength > MAX_TORRENT_SIZE) {
+      return res.badRequest(c, `File too large (max ${MAX_TORRENT_SIZE / 1024 / 1024} MB)`);
+    }
+
     const body = await c.req.parseBody();
     const file = body.torrent;
 
@@ -21,6 +37,10 @@ export function torrentsRouter(registry: SeederRegistry) {
 
     const buf = Buffer.from(await (file as File).arrayBuffer());
 
+    if (buf.length > MAX_TORRENT_SIZE) {
+      return res.badRequest(c, `File too large (max ${MAX_TORRENT_SIZE / 1024 / 1024} MB)`);
+    }
+
     try {
       const state = await registry.addTorrent(buf);
       return res.created(c, state);
@@ -33,6 +53,8 @@ export function torrentsRouter(registry: SeederRegistry) {
   /** Get stats + announce history for a specific torrent */
   app.get("/:hash", (c) => {
     const { hash } = c.req.param();
+    if (!validateHash(hash)) return res.badRequest(c, "Invalid info hash format");
+
     const list = registry.listTorrents();
     const torrent = list.find((t) => t.infoHashHex === hash);
 
@@ -49,6 +71,7 @@ export function torrentsRouter(registry: SeederRegistry) {
   /** Pause a torrent — sends 'stopped' to trackers and halts the announce loop */
   app.post("/:hash/pause", async (c) => {
     const { hash } = c.req.param();
+    if (!validateHash(hash)) return res.badRequest(c, "Invalid info hash format");
     const ok = await registry.pauseTorrent(hash);
     if (!ok) return res.notFound(c);
     return c.json({ ok: true });
@@ -57,6 +80,7 @@ export function torrentsRouter(registry: SeederRegistry) {
   /** Resume a paused torrent — re-announces as 'started' and restarts the loop */
   app.post("/:hash/resume", async (c) => {
     const { hash } = c.req.param();
+    if (!validateHash(hash)) return res.badRequest(c, "Invalid info hash format");
     const ok = await registry.resumeTorrent(hash);
     if (!ok) return res.notFound(c);
     return c.json({ ok: true });
@@ -65,6 +89,7 @@ export function torrentsRouter(registry: SeederRegistry) {
   /** Remove a torrent — sends 'stopped' to trackers then removes it */
   app.delete("/:hash", async (c) => {
     const { hash } = c.req.param();
+    if (!validateHash(hash)) return res.badRequest(c, "Invalid info hash format");
     const removed = await registry.removeTorrent(hash);
 
     if (!removed) {
diff --git a/src/core/bencode/decoder.ts b/src/core/bencode/decoder.ts
index e00da1a..8d5713d 100644
--- a/src/core/bencode/decoder.ts
+++ b/src/core/bencode/decoder.ts
@@ -29,6 +29,10 @@ export function decode(data: Buffer | Uint8Array): BencodeValue {
 }
 
 export function decodeAt(buf: Buffer, offset: number): DecodeResult {
+  if (offset >= buf.length) {
+    throw new Error(`Unexpected end of data at offset ${offset}`);
+  }
+
   const byte = buf[offset];
 
   if (byte === 0x69) {
@@ -68,11 +72,17 @@ function decodeInteger(buf: Buffer, offset: number): DecodeResult {
 function decodeString(buf: Buffer, offset: number): DecodeResult {
   const colonIdx = buf.indexOf(0x3a, offset); // ':'
   if (colonIdx === -1) throw new Error(`Malformed string at offset ${offset}`);
-  const len = Number(buf.subarray(offset, colonIdx).toString("ascii"));
-  if (!Number.isInteger(len) || len < 0) {
-    throw new Error(`Invalid string length at offset ${offset}`);
+  const lenStr = buf.subarray(offset, colonIdx).toString("ascii");
+  const len = Number.parseInt(lenStr, 10);
+  if (!Number.isInteger(len) || len < 0 || lenStr !== String(len)) {
+    throw new Error(`Invalid string length "${lenStr}" at offset ${offset}`);
   }
   const start = colonIdx + 1;
+  if (start + len > buf.length) {
+    throw new Error(
+      `String at offset ${offset} claims length ${len} but only ${buf.length - start} bytes remain`
+    );
+  }
   const value = Buffer.from(buf.subarray(start, start + len));
   return { value, end: start + len };
 }
diff --git a/src/core/seeder/FakeSeeder.ts b/src/core/seeder/FakeSeeder.ts
index 37f1bfc..b119d8e 100644
--- a/src/core/seeder/FakeSeeder.ts
+++ b/src/core/seeder/FakeSeeder.ts
@@ -42,7 +42,7 @@ export class FakeSeeder extends EventEmitter {
   on(event: "stopped", listener: () => void): this;
   on(event: "stateChange", listener: (state: SeederState) => void): this;
   on(event: string, listener: (...args: unknown[]) => void): this {
-    return super.on(event, listener);
+    return super.on(event, listener) as this;
   }
   private readonly torrent: TorrentFileInfo;
   private readonly profile: ClientProfile;
@@ -104,14 +104,7 @@ export class FakeSeeder extends EventEmitter {
     this.setStatus("running");
 
     // Start speed tick
-    this.lastTickTime = Date.now();
-    this.tickTimer = setInterval(() => {
-      const now = Date.now();
-      const delta = now - this.lastTickTime;
-      this.lastTickTime = now;
-      this.uploaded += this.speedSim.tick(delta);
-      this.emit("stateChange", this.getState());
-    }, 5_000);
+    this.startTickTimer();
 
     // First announce: started
     await this.doAnnounce("started");
@@ -154,14 +147,7 @@ export class FakeSeeder extends EventEmitter {
     this.setStatus("running");
 
     // Restart speed tick
-    this.lastTickTime = Date.now();
-    this.tickTimer = setInterval(() => {
-      const now = Date.now();
-      const delta = now - this.lastTickTime;
-      this.lastTickTime = now;
-      this.uploaded += this.speedSim.tick(delta);
-      this.emit("stateChange", this.getState());
-    }, 5_000);
+    this.startTickTimer();
 
     // Re-announce as started then resume loop
     await this.doAnnounce("started");
@@ -170,7 +156,7 @@ export class FakeSeeder extends EventEmitter {
 
   async stop(): Promise<void> {
     if (this.status === "stopped" || this.status === "stopping") return;
-    const waspaused = this.status === "paused";
+    const wasPaused = this.status === "paused";
     this.setStatus("stopping");
 
     if (this.announceTimer) {
@@ -183,7 +169,7 @@ export class FakeSeeder extends EventEmitter {
     }
 
     // If already paused, trackers were already notified — skip the stopped announce
-    if (!waspaused) {
+    if (!wasPaused) {
       await Promise.allSettled(
         this.trackers.map((t) =>
           t.stop({
@@ -204,6 +190,22 @@ export class FakeSeeder extends EventEmitter {
     this.emit("stopped");
   }
 
+  /** Starts the 5-second speed simulation tick timer */
+  private startTickTimer(): void {
+    this.lastTickTime = Date.now();
+    this.tickTimer = setInterval(() => {
+      try {
+        const now = Date.now();
+        const delta = now - this.lastTickTime;
+        this.lastTickTime = now;
+        this.uploaded += this.speedSim.tick(delta);
+        this.emit("stateChange", this.getState());
+      } catch (err) {
+        console.error("[seeder] Tick error:", err);
+      }
+    }, 5_000);
+  }
+
   private scheduleNextAnnounce(): void {
     const intervalMs = this.lastInterval * 1000;
     this.announceTimer = setTimeout(async () => {
@@ -258,19 +260,21 @@ export class FakeSeeder extends EventEmitter {
         };
         this.emit("announce", record);
       } else {
-        this.error = (result.reason as Error).message;
+        this.error = result.reason instanceof Error ? result.reason.message : String(result.reason);
         // Fallback: scrape to at least get current seeder/leecher counts
-        if (tracker.scrape) {
+        if (tracker.scrape && this.status === "running") {
           tracker
             .scrape(this.torrent.infoHash)
             .then((stats) => {
-              if (stats) {
+              if (stats && this.status === "running") {
                 this.lastSeeder = stats.seeders;
                 this.lastLeecher = stats.leechers;
                 this.emit("stateChange", this.getState());
               }
             })
-            .catch(() => {});
+            .catch((err) => {
+              console.warn(`[seeder] Scrape fallback failed for ${tracker.url}:`, err);
+            });
         }
       }
     }
@@ -285,10 +289,43 @@ export class FakeSeeder extends EventEmitter {
   }
 }
 
+/**
+ * Reject tracker URLs that point to private/internal networks (SSRF protection).
+ * Checks the hostname against RFC 1918, loopback, link-local, and metadata ranges.
+ */
+function isPrivateHost(hostname: string): boolean {
+  // Strip IPv6 brackets
+  const host = hostname.replace(/^\[|\]$/g, "");
+
+  // Loopback
+  if (host === "localhost" || host === "::1" || host.startsWith("127.")) return true;
+
+  // Cloud metadata endpoints
+  if (host === "169.254.169.254" || host === "metadata.google.internal") return true;
+
+  // IPv4 private ranges
+  const ipv4 = host.match(/^(\d+)\.(\d+)\.\d+\.\d+$/);
+  if (ipv4) {
+    const [, a, b] = ipv4.map(Number);
+    if (a === 10) return true; // 10.0.0.0/8
+    if (a === 172 && b >= 16 && b <= 31) return true; // 172.16.0.0/12
+    if (a === 192 && b === 168) return true; // 192.168.0.0/16
+    if (a === 169 && b === 254) return true; // 169.254.0.0/16 link-local
+    if (a === 0) return true; // 0.0.0.0/8
+  }
+
+  return false;
+}
+
 function buildTrackers(urls: string[]): ITracker[] {
   return urls
-    .map((url) => {
+    .map((url): ITracker | null => {
       try {
+        const parsed = new URL(url);
+        if (isPrivateHost(parsed.hostname)) {
+          console.warn(`[tracker] Skipping private/internal URL: ${url}`);
+          return null;
+        }
         if (url.startsWith("http://") || url.startsWith("https://")) {
           return new HttpTracker(url);
         }
@@ -296,7 +333,7 @@ function buildTrackers(urls: string[]): ITracker[] {
           return new UdpTracker(url);
         }
       } catch {
-        // skip malformed URLs
+        console.warn(`[tracker] Skipping malformed URL: ${url}`);
       }
       return null;
     })
diff --git a/src/core/torrent/TorrentFile.ts b/src/core/torrent/TorrentFile.ts
index c3ff0fc..f03ecf8 100644
--- a/src/core/torrent/TorrentFile.ts
+++ b/src/core/torrent/TorrentFile.ts
@@ -28,7 +28,11 @@ export interface TorrentFileEntry {
 }
 
 export function parseTorrentBuffer(buf: Buffer): TorrentFileInfo {
-  const torrent = decode(buf) as BencodeDict;
+  const decoded = decode(buf);
+  if (!decoded || typeof decoded !== "object" || Array.isArray(decoded)) {
+    throw new Error("Invalid torrent file: expected a bencoded dictionary");
+  }
+  const torrent = decoded as BencodeDict;
 
   // --- info_hash: SHA-1 of raw bencoded info dict ---
   const infoRaw = rawSlice(buf, "info");
@@ -36,15 +40,24 @@ export function parseTorrentBuffer(buf: Buffer): TorrentFileInfo {
   const infoHashHex = createHash("sha1").update(infoRaw).digest("hex");
   const infoHash = Buffer.from(infoHashHex, "hex");
 
+  if (!torrent.info || typeof torrent.info !== "object" || Array.isArray(torrent.info)) {
+    throw new Error("Missing or invalid 'info' dict in torrent file");
+  }
   const info = torrent.info as BencodeDict;
-  if (!info) throw new Error("Missing 'info' dict");
 
-  const name = bufToStr(info.name as Buffer);
-  const pieceLength = info["piece length"] as number;
+  if (!info.name || !Buffer.isBuffer(info.name)) {
+    throw new Error("Missing or invalid 'info.name' in torrent file");
+  }
+  const name = info.name.toString("utf8");
+
+  if (typeof info["piece length"] !== "number") {
+    throw new Error("Missing or invalid 'info.piece length' in torrent file");
+  }
+  const pieceLength = info["piece length"];
 
   // --- tracker URLs ---
-  const announce = torrent.announce ? bufToStr(torrent.announce as Buffer) : "";
-  const announceList = flattenAnnounceList(torrent["announce-list"] as BencodeList | undefined);
+  const announce = Buffer.isBuffer(torrent.announce) ? torrent.announce.toString("utf8") : "";
+  const announceList = flattenAnnounceList(torrent["announce-list"]);
   if (announce && !announceList.includes(announce)) {
     announceList.unshift(announce);
   }
@@ -55,20 +68,33 @@ export function parseTorrentBuffer(buf: Buffer): TorrentFileInfo {
   const isMultiFile = "files" in info;
 
   if (isMultiFile) {
-    const fileList = info.files as BencodeList;
-    files = fileList.map((f) => {
+    if (!Array.isArray(info.files)) {
+      throw new Error("Invalid 'info.files': expected a list");
+    }
+    files = (info.files as BencodeList).map((f, i) => {
+      if (!f || typeof f !== "object" || Array.isArray(f)) {
+        throw new Error(`Invalid file entry at index ${i}`);
+      }
       const fd = f as BencodeDict;
-      const pathParts = (fd.path as BencodeList).map((p) => bufToStr(p as Buffer));
+      if (!Array.isArray(fd.path)) {
+        throw new Error(`Missing or invalid 'path' in file entry ${i}`);
+      }
+      const pathParts = (fd.path as BencodeList).map((p) => bufToStr(p));
+      if (typeof fd.length !== "number") {
+        throw new Error(`Missing or invalid 'length' in file entry ${i}`);
+      }
       return {
         path: pathParts.join("/"),
-        size: fd.length as number,
+        size: fd.length,
       };
     });
     totalSize = files.reduce((sum, f) => sum + f.size, 0);
   } else {
-    const length = info.length as number;
-    files = [{ path: name, size: length }];
-    totalSize = length;
+    if (typeof info.length !== "number") {
+      throw new Error("Missing 'info.length' for single-file torrent");
+    }
+    files = [{ path: name, size: info.length }];
+    totalSize = info.length;
   }
 
   return {
@@ -84,17 +110,19 @@ export function parseTorrentBuffer(buf: Buffer): TorrentFileInfo {
   };
 }
 
-function bufToStr(buf: Buffer): string {
-  return Buffer.isBuffer(buf) ? buf.toString("utf8") : String(buf);
+function bufToStr(val: unknown): string {
+  if (Buffer.isBuffer(val)) return val.toString("utf8");
+  if (typeof val === "string") return val;
+  return String(val);
 }
 
-function flattenAnnounceList(announceList: BencodeList | undefined): string[] {
-  if (!announceList) return [];
+function flattenAnnounceList(raw: unknown): string[] {
+  if (!Array.isArray(raw)) return [];
   const urls: string[] = [];
-  for (const tier of announceList) {
+  for (const tier of raw) {
     if (Array.isArray(tier)) {
       for (const url of tier) {
-        const s = bufToStr(url as Buffer);
+        const s = bufToStr(url);
         if (s && !urls.includes(s)) urls.push(s);
       }
     }
diff --git a/src/core/tracker/HttpTracker.ts b/src/core/tracker/HttpTracker.ts
index 468ff22..ea5d7cb 100644
--- a/src/core/tracker/HttpTracker.ts
+++ b/src/core/tracker/HttpTracker.ts
@@ -2,6 +2,12 @@ import { type BencodeDict, type BencodeList, decode } from "../bencode/decoder.j
 import type { AnnounceParams, ITracker, ScrapeResult } from "./ITracker.js";
 import type { TrackerPeer, TrackerResponse } from "./TrackerResponse.js";
 
+/** Maximum response body size from trackers (1 MB) */
+const MAX_RESPONSE_SIZE = 1024 * 1024;
+
+/** Tracker HTTP request timeout (15 seconds) */
+const REQUEST_TIMEOUT_MS = 15_000;
+
 /**
  * HTTP/HTTPS tracker client.
  *
@@ -29,25 +35,37 @@ export class HttpTracker implements ITracker {
         "User-Agent": params.userAgent,
         "Accept-Encoding": "gzip",
       },
-      signal: AbortSignal.timeout(15_000),
+      signal: AbortSignal.timeout(REQUEST_TIMEOUT_MS),
     });
 
     if (!res.ok) {
       throw new Error(`HTTP tracker returned ${res.status} for ${this.url}`);
     }
 
-    const body = Buffer.from(await res.arrayBuffer());
-    const decoded = decode(body) as BencodeDict;
-
-    if (decoded["failure reason"]) {
-      throw new Error(`Tracker failure: ${(decoded["failure reason"] as Buffer).toString("utf8")}`);
+    const arrayBuf = await res.arrayBuffer();
+    if (arrayBuf.byteLength > MAX_RESPONSE_SIZE) {
+      throw new Error(`Tracker response too large (${arrayBuf.byteLength} bytes)`);
     }
 
-    if (decoded["tracker id"]) {
-      this.trackerId = (decoded["tracker id"] as Buffer).toString("utf8");
+    const body = Buffer.from(arrayBuf);
+    const decoded = decode(body);
+    if (!decoded || typeof decoded !== "object" || Array.isArray(decoded)) {
+      throw new Error("Tracker returned invalid bencode (expected dictionary)");
+    }
+    const dict = decoded as BencodeDict;
+
+    if (dict["failure reason"]) {
+      const raw = dict["failure reason"];
+      const reason = Buffer.isBuffer(raw) ? raw.toString("utf8") : String(raw);
+      throw new Error(`Tracker failure: ${reason}`);
     }
 
-    return parseResponse(decoded);
+    if (dict["tracker id"]) {
+      const raw = dict["tracker id"];
+      this.trackerId = Buffer.isBuffer(raw) ? raw.toString("utf8") : String(raw);
+    }
+
+    return parseResponse(dict);
   }
 
   async stop(params: Omit<AnnounceParams, "event">): Promise<void> {
@@ -73,22 +91,30 @@ export class HttpTracker implements ITracker {
       const fullUrl = `${scrapeUrl}${scrapeQSep}info_hash=${percentEncode(infoHash)}`;
       const res = await fetch(fullUrl, {
         headers: { "User-Agent": this.userAgent || "Mozilla/5.0" },
-        signal: AbortSignal.timeout(15_000),
+        signal: AbortSignal.timeout(REQUEST_TIMEOUT_MS),
       });
       if (!res.ok) return null;
 
       const body = Buffer.from(await res.arrayBuffer());
-      const decoded = decode(body) as BencodeDict;
-      if (!decoded.files) return null;
+      const decoded = decode(body);
+      if (!decoded || typeof decoded !== "object" || Array.isArray(decoded)) return null;
+      const dict = decoded as BencodeDict;
+      if (!dict.files || typeof dict.files !== "object") return null;
 
-      const entries = Object.values(decoded.files as BencodeDict);
+      const entries = Object.values(dict.files as BencodeDict);
       if (entries.length === 0) return null;
 
-      const entry = entries[0] as BencodeDict;
+      const entry = entries[0];
+      if (!entry || typeof entry !== "object" || Array.isArray(entry)) return null;
+      const e = entry as BencodeDict;
+
+      const complete = e.complete;
+      const incomplete = e.incomplete;
+      const downloaded = e.downloaded;
       return {
-        seeders: (entry.complete as number) ?? 0,
-        leechers: (entry.incomplete as number) ?? 0,
-        completed: (entry.downloaded as number) ?? 0,
+        seeders: typeof complete === "number" ? complete : 0,
+        leechers: typeof incomplete === "number" ? incomplete : 0,
+        completed: typeof downloaded === "number" ? downloaded : 0,
       };
     } catch {
       return null;
@@ -155,16 +181,18 @@ function percentEncode(buf: Buffer): string {
 }
 
 function parseResponse(dict: BencodeDict): TrackerResponse {
-  const interval = (dict.interval as number) ?? 1800;
-  const minInterval = dict["min interval"] as number | undefined;
-  const seeders = dict.complete as number | undefined;
-  const leechers = dict.incomplete as number | undefined;
-  const warning = dict["warning message"]
-    ? (dict["warning message"] as Buffer).toString("utf8")
-    : undefined;
-  const trackerId = dict["tracker id"]
-    ? (dict["tracker id"] as Buffer).toString("utf8")
-    : undefined;
+  const rawInterval = dict.interval;
+  const interval = typeof rawInterval === "number" ? rawInterval : 1800;
+  const rawMinInterval = dict["min interval"];
+  const minInterval = typeof rawMinInterval === "number" ? rawMinInterval : undefined;
+  const rawSeeders = dict.complete;
+  const seeders = typeof rawSeeders === "number" ? rawSeeders : undefined;
+  const rawLeechers = dict.incomplete;
+  const leechers = typeof rawLeechers === "number" ? rawLeechers : undefined;
+  const rawWarning = dict["warning message"];
+  const warning = Buffer.isBuffer(rawWarning) ? rawWarning.toString("utf8") : undefined;
+  const rawTrackerId = dict["tracker id"];
+  const trackerId = Buffer.isBuffer(rawTrackerId) ? rawTrackerId.toString("utf8") : undefined;
 
   const peers = parsePeers(dict.peers);
 
@@ -177,7 +205,7 @@ function parsePeers(raw: unknown): TrackerPeer[] {
   // Compact format: 6 bytes per peer (4 IP + 2 port)
   if (Buffer.isBuffer(raw)) {
     const peers: TrackerPeer[] = [];
-    for (let i = 0; i + 5 < raw.length; i += 6) {
+    for (let i = 0; i + 6 <= raw.length; i += 6) {
       const ip = `${raw[i]}.${raw[i + 1]}.${raw[i + 2]}.${raw[i + 3]}`;
       const port = raw.readUInt16BE(i + 4);
       peers.push({ ip, port });
@@ -187,13 +215,12 @@ function parsePeers(raw: unknown): TrackerPeer[] {
 
   // Dict format (older trackers)
   if (Array.isArray(raw)) {
-    return (raw as BencodeList).map((p) => {
-      const pd = p as BencodeDict;
-      return {
-        ip: (pd.ip as Buffer).toString("ascii"),
-        port: pd.port as number,
-      };
-    });
+    return (raw as BencodeList)
+      .filter((p): p is BencodeDict => !!p && typeof p === "object" && !Array.isArray(p))
+      .map((pd) => ({
+        ip: Buffer.isBuffer(pd.ip) ? pd.ip.toString("ascii") : String(pd.ip ?? "0.0.0.0"),
+        port: typeof pd.port === "number" ? pd.port : 0,
+      }));
   }
 
   return [];
diff --git a/src/index.ts b/src/index.ts
index 80f058f..9568393 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -22,12 +22,17 @@ if (config.autoLoad) {
           const state = await registry.addTorrent(buf);
           console.log(`  ✓ ${state.name} [${state.infoHashHex.slice(0, 8)}]`);
         } catch (err) {
-          console.warn(`  ✗ Failed to load ${file}: ${(err as Error).message}`);
+          console.warn(`  ✗ Failed to load ${file}: ${err instanceof Error ? err.message : err}`);
         }
       }
     }
-  } catch {
-    // torrentsDir doesn't exist yet — that's fine
+  } catch (err) {
+    const code = (err as NodeJS.ErrnoException).code;
+    if (code === "ENOENT") {
+      // torrentsDir doesn't exist yet — that's fine
+    } else {
+      console.error(`Failed to read torrents directory (${config.torrentsDir}):`, err);
+    }
   }
 }
 
diff --git a/ui/src/components/TorrentList.svelte b/ui/src/components/TorrentList.svelte
index b6b3211..d43472c 100644
--- a/ui/src/components/TorrentList.svelte
+++ b/ui/src/components/TorrentList.svelte
@@ -32,6 +32,10 @@
     }
   }
 
+  function trackerHostname(url: string): string {
+    try { return new URL(url).hostname; } catch { return url; }
+  }
+
   function statusColor(status: TorrentState["status"]): string {
     switch (status) {
       case "running":  return "#4ade80";
@@ -65,7 +69,7 @@
       {#each torrents as t (t.infoHashHex)}
         <tr>
           <td class="name" title={t.name}>{t.name}</td>
-          <td class="hash" title={t.trackerUrl}>{new URL(t.trackerUrl).hostname}</td>
+          <td class="hash" title={t.trackerUrl}>{trackerHostname(t.trackerUrl)}</td>
           <td class="hash" title={t.infoHashHex}>{t.infoHashHex.slice(0, 8)}…</td>
           <td>
             <span class="badge" style="color: {statusColor(t.status)}">{t.status}</span>
diff --git a/ui/src/lib/api.ts b/ui/src/lib/api.ts
index 8223534..e6aea06 100644
--- a/ui/src/lib/api.ts
+++ b/ui/src/lib/api.ts
@@ -25,8 +25,22 @@ export interface GlobalStats {
   startedAt: string;
 }
 
+/** Extract a human-readable error message from a failed response */
+async function extractError(res: Response): Promise<string> {
+  try {
+    const body = await res.json();
+    if (body && typeof body === "object" && "error" in body) {
+      return typeof body.error === "string" ? body.error : JSON.stringify(body.error);
+    }
+  } catch {
+    // response wasn't JSON
+  }
+  return `Request failed (${res.status})`;
+}
+
 export async function listTorrents(): Promise<TorrentState[]> {
   const res = await fetch(`${BASE}/torrents`);
+  if (!res.ok) throw new Error(await extractError(res));
   return res.json();
 }
 
@@ -34,23 +48,23 @@ export async function addTorrent(file: File): Promise<TorrentState> {
   const form = new FormData();
   form.append("torrent", file);
   const res = await fetch(`${BASE}/torrents`, { method: "POST", body: form });
-  if (!res.ok) {
-    const err = await res.json() as { error: string };
-    throw new Error(err.error);
-  }
+  if (!res.ok) throw new Error(await extractError(res));
   return res.json();
 }
 
 export async function removeTorrent(hash: string): Promise<void> {
-  await fetch(`${BASE}/torrents/${hash}`, { method: "DELETE" });
+  const res = await fetch(`${BASE}/torrents/${hash}`, { method: "DELETE" });
+  if (!res.ok) throw new Error(await extractError(res));
 }
 
 export async function pauseTorrent(hash: string): Promise<void> {
-  await fetch(`${BASE}/torrents/${hash}/pause`, { method: "POST" });
+  const res = await fetch(`${BASE}/torrents/${hash}/pause`, { method: "POST" });
+  if (!res.ok) throw new Error(await extractError(res));
 }
 
 export async function resumeTorrent(hash: string): Promise<void> {
-  await fetch(`${BASE}/torrents/${hash}/resume`, { method: "POST" });
+  const res = await fetch(`${BASE}/torrents/${hash}/resume`, { method: "POST" });
+  if (!res.ok) throw new Error(await extractError(res));
 }
 
 export interface AppConfig {
@@ -65,6 +79,7 @@ export interface AppConfig {
 
 export async function getConfig(): Promise<AppConfig> {
   const res = await fetch(`${BASE}/config`);
+  if (!res.ok) throw new Error(await extractError(res));
   return res.json();
 }
 
@@ -74,15 +89,13 @@ export async function updateConfig(patch: Partial<Pick<AppConfig, "minUploadRate
     headers: { "Content-Type": "application/json" },
     body: JSON.stringify(patch),
   });
-  if (!res.ok) {
-    const err = await res.json() as { error: string };
-    throw new Error(typeof err.error === "string" ? err.error : JSON.stringify(err.error));
-  }
+  if (!res.ok) throw new Error(await extractError(res));
   return res.json();
 }
 
 export async function getStats(): Promise<GlobalStats> {
   const res = await fetch(`${BASE}/status`);
+  if (!res.ok) throw new Error(await extractError(res));
   return res.json();
 }
 
@@ -94,15 +107,15 @@ export function connectSSE(
   const es = new EventSource(`${BASE}/status/stream`);
 
   es.addEventListener("torrent", (e) => {
-    onTorrent(JSON.parse(e.data));
+    try { onTorrent(JSON.parse(e.data)); } catch { /* malformed SSE data */ }
   });
 
   es.addEventListener("stats", (e) => {
-    onStats(JSON.parse(e.data));
+    try { onStats(JSON.parse(e.data)); } catch { /* malformed SSE data */ }
   });
 
   es.addEventListener("torrents", (e) => {
-    onTorrents(JSON.parse(e.data));
+    try { onTorrents(JSON.parse(e.data)); } catch { /* malformed SSE data */ }
   });
 
   return es;