diff --git a/src/middleware/ip-blocklist.ts b/src/middleware/ip-blocklist.ts
index ba84876..ea421d7 100644
--- a/src/middleware/ip-blocklist.ts
+++ b/src/middleware/ip-blocklist.ts
@@ -19,10 +19,10 @@ const logger = createLogger("api:ip-blocklist");
  */
 
 const PROXY_DEPTH = (() => {
-  const parsed = Number(process.env.TRUSTED_PROXY_DEPTH ?? 1);
+  const parsed = Number(process.env.TRUSTED_PROXY_DEPTH ?? 0);
   if (!Number.isFinite(parsed) || !Number.isInteger(parsed) || parsed < 0) {
     logger.warn("Invalid TRUSTED_PROXY_DEPTH, falling back to default", { value: process.env.TRUSTED_PROXY_DEPTH });
-    return 1;
+    return 0;
   }
   return parsed;
 })();
diff --git a/src/middleware/rate-limit.ts b/src/middleware/rate-limit.ts
index 7042042..e0b7584 100644
--- a/src/middleware/rate-limit.ts
+++ b/src/middleware/rate-limit.ts
@@ -29,10 +29,10 @@ setInterval(() => {
  * no trusted proxy is configured.
  */
 const PROXY_DEPTH = (() => {
-  const parsed = Number(process.env.TRUSTED_PROXY_DEPTH ?? 1);
+  const parsed = Number(process.env.TRUSTED_PROXY_DEPTH ?? 0);
   if (!Number.isFinite(parsed) || !Number.isInteger(parsed) || parsed < 0) {
     logger.warn("Invalid TRUSTED_PROXY_DEPTH, falling back to default", { value: process.env.TRUSTED_PROXY_DEPTH });
-    return 1;
+    return 0;
   }
   return parsed;
 })();
diff --git a/src/routes/ws.ts b/src/routes/ws.ts
index b2ee32e..25b0d77 100644
--- a/src/routes/ws.ts
+++ b/src/routes/ws.ts
@@ -262,10 +262,10 @@ setInterval(() => {
  * See rate-limit.ts for full documentation.
  */
 const WS_PROXY_DEPTH = (() => {
-  const parsed = Number(process.env.TRUSTED_PROXY_DEPTH ?? 1);
+  const parsed = Number(process.env.TRUSTED_PROXY_DEPTH ?? 0);
   if (!Number.isFinite(parsed) || !Number.isInteger(parsed) || parsed < 0) {
     logger.warn("Invalid TRUSTED_PROXY_DEPTH, falling back to default", { value: process.env.TRUSTED_PROXY_DEPTH });
-    return 1;
+    return 0;
   }
   return parsed;
 })();
diff --git a/tests/middleware/proxy-depth-default.test.ts b/tests/middleware/proxy-depth-default.test.ts
new file mode 100644
index 0000000..2f8e34f
--- /dev/null
+++ b/tests/middleware/proxy-depth-default.test.ts
@@ -0,0 +1,123 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
+import { Hono } from "hono";
+
+vi.mock("@percolator/shared", () => ({
+  createLogger: vi.fn(() => ({
+    info: vi.fn(),
+    warn: vi.fn(),
+    error: vi.fn(),
+    debug: vi.fn(),
+  })),
+}));
+
+describe("TRUSTED_PROXY_DEPTH secure default behavior", () => {
+  const oldDepth = process.env.TRUSTED_PROXY_DEPTH;
+  const oldBlocklist = process.env.IP_BLOCKLIST;
+
+  beforeEach(() => {
+    vi.resetModules();
+    vi.doUnmock("@hono/node-server/conninfo");
+    delete process.env.TRUSTED_PROXY_DEPTH;
+    delete process.env.IP_BLOCKLIST;
+  });
+
+  afterEach(() => {
+    if (oldDepth === undefined) delete process.env.TRUSTED_PROXY_DEPTH;
+    else process.env.TRUSTED_PROXY_DEPTH = oldDepth;
+
+    if (oldBlocklist === undefined) delete process.env.IP_BLOCKLIST;
+    else process.env.IP_BLOCKLIST = oldBlocklist;
+
+    vi.doUnmock("@hono/node-server/conninfo");
+    vi.resetModules();
+  });
+
+  function mockSocketIp(ip: string) {
+    vi.doMock("@hono/node-server/conninfo", () => ({
+      getConnInfo: vi.fn(() => ({
+        remote: {
+          address: ip,
+        },
+      })),
+    }));
+  }
+
+  it("Regression: unset TRUSTED_PROXY_DEPTH ignores spoofed X-Forwarded-For and rate-limits by socket IP", async () => {
+    mockSocketIp("10.0.0.1");
+
+    const { readRateLimit } = await import("../../src/middleware/rate-limit.js");
+    const { resetSharedStore, InMemoryStore } = await import("../../src/middleware/shared-store.js");
+
+    resetSharedStore(new InMemoryStore());
+
+    const app = new Hono();
+    app.get("/test", readRateLimit(), (c) => c.json({ ok: true }));
+
+    // Even though X-Forwarded-For rotates, the secure default must ignore it.
+    // All requests should count against the mocked socket IP bucket.
+    for (let i = 0; i < 100; i++) {
+      const res = await app.request("/test", {
+        headers: {
+          "x-forwarded-for": `198.51.100.${i}`,
+        },
+      });
+
+      expect(res.status).toBe(200);
+    }
+
+    const blocked = await app.request("/test", {
+      headers: {
+        "x-forwarded-for": "198.51.100.250",
+      },
+    });
+
+    expect(blocked.status).toBe(429);
+  });
+
+  it("Regression: unset TRUSTED_PROXY_DEPTH uses socket IP for blocklist decision, not spoofed X-Forwarded-For", async () => {
+    process.env.IP_BLOCKLIST = "10.0.0.1";
+    mockSocketIp("10.0.0.1");
+
+    const { ipBlocklist } = await import("../../src/middleware/ip-blocklist.js");
+
+    const app = new Hono();
+    app.get("/test", ipBlocklist(), (c) => c.json({ ok: true }));
+
+    const res = await app.request("/test", {
+      headers: {
+        "x-forwarded-for": "198.51.100.77",
+      },
+    });
+
+    // X-Forwarded-For is not blocklisted, but the socket IP is.
+    // With the secure default, the request must be blocked.
+    expect(res.status).toBe(403);
+  });
+
+  it("Explicit proxy mode: TRUSTED_PROXY_DEPTH=1 can still use X-Forwarded-For when intentionally configured", async () => {
+    process.env.TRUSTED_PROXY_DEPTH = "1";
+    process.env.IP_BLOCKLIST = "203.0.113.10";
+    mockSocketIp("10.0.0.1");
+
+    const { ipBlocklist } = await import("../../src/middleware/ip-blocklist.js");
+
+    const app = new Hono();
+    app.get("/test", ipBlocklist(), (c) => c.json({ ok: true }));
+
+    const blockedViaTrustedProxyHeader = await app.request("/test", {
+      headers: {
+        "x-forwarded-for": "203.0.113.10",
+      },
+    });
+
+    expect(blockedViaTrustedProxyHeader.status).toBe(403);
+
+    const allowedViaTrustedProxyHeader = await app.request("/test", {
+      headers: {
+        "x-forwarded-for": "198.51.100.77",
+      },
+    });
+
+    expect(allowedViaTrustedProxyHeader.status).toBe(200);
+  });
+});
diff --git a/tests/middleware/rate-limit.test.ts b/tests/middleware/rate-limit.test.ts
index c7b9862..868af69 100644
--- a/tests/middleware/rate-limit.test.ts
+++ b/tests/middleware/rate-limit.test.ts
@@ -1,6 +1,20 @@
-import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
+import { describe, it, expect, beforeEach, afterEach, afterAll, vi } from "vitest";
 import { Hono } from "hono";
 
+// These existing rate-limit tests intentionally exercise trusted-proxy
+// X-Forwarded-For parsing. The secure fail-closed default is covered by
+// tests/middleware/proxy-depth-default.test.ts.
+const originalTrustedProxyDepth = vi.hoisted(() => process.env.TRUSTED_PROXY_DEPTH);
+
+vi.hoisted(() => {
+  process.env.TRUSTED_PROXY_DEPTH = "1";
+});
+
+afterAll(() => {
+  if (originalTrustedProxyDepth === undefined) delete process.env.TRUSTED_PROXY_DEPTH;
+  else process.env.TRUSTED_PROXY_DEPTH = originalTrustedProxyDepth;
+});
+
 vi.mock("@percolator/shared", () => ({
   createLogger: vi.fn(() => ({
     info: vi.fn(), warn: vi.fn(), error: vi.fn(), debug: vi.fn(),