diff --git a/src/lib/messaging/channels/discord/template-resolver.ts b/src/lib/messaging/channels/discord/template-resolver.ts
index e866a4e3b2..9569a3d1d3 100644
--- a/src/lib/messaging/channels/discord/template-resolver.ts
+++ b/src/lib/messaging/channels/discord/template-resolver.ts
@@ -8,12 +8,16 @@ import {
   nonEmptyArray,
   nonEmptyCsv,
   nonEmptyObject,
+  nonEmptyString,
   parseBoolean,
   parseList,
   resolvedRenderTemplateReference,
   stateValue,
 } from "../template-resolver-utils";
 
+const DEFAULT_PROXY_HOST = "10.200.0.1";
+const DEFAULT_PROXY_PORT = "3128";
+
 type DiscordGuildConfig = {
   readonly requireMention?: boolean;
   readonly users?: readonly string[];
@@ -23,7 +27,8 @@ export const resolveDiscordTemplateReference: BuiltInRenderTemplateResolver = (
   reference,
   context,
 ) => {
-  if (reference === "discordProxyUrl") return resolvedRenderTemplateReference(undefined);
+  if (reference === "discordProxyUrl")
+    return resolvedRenderTemplateReference(proxyUrl(context.env));
 
   switch (reference) {
     case "discord.guilds":
@@ -83,3 +88,9 @@ function discordRequireMention(context: RenderTemplateContext): boolean {
   }
   return true;
 }
+
+function proxyUrl(env: RenderTemplateContext["env"]): string {
+  const host = nonEmptyString(env?.NEMOCLAW_PROXY_HOST) ?? DEFAULT_PROXY_HOST;
+  const port = nonEmptyString(env?.NEMOCLAW_PROXY_PORT) ?? DEFAULT_PROXY_PORT;
+  return `http://${host}:${port}`;
+}
diff --git a/test/discord-template-resolver-proxy.test.ts b/test/discord-template-resolver-proxy.test.ts
new file mode 100644
index 0000000000..95f0e318e2
--- /dev/null
+++ b/test/discord-template-resolver-proxy.test.ts
@@ -0,0 +1,30 @@
+// SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+import { describe, expect, it } from "vitest";
+
+import { resolveDiscordTemplateReference } from "../dist/lib/messaging/channels/discord/template-resolver.js";
+
+// The Discord gateway client honors only the per-account proxy (it ignores the
+// managed env proxy), so channels.discord.accounts.default.proxy must resolve to
+// the sandbox proxy or the gateway WebSocket cannot egress the deny-by-default
+// network namespace. Telegram already resolves its proxy this way; #5075.
+const ctx = (env: Record<string, string | undefined>) => ({ inputs: [], env });
+
+describe("discord template-resolver: discordProxyUrl", () => {
+  it("resolves discordProxyUrl to the default sandbox proxy (was previously undefined, #5075)", () => {
+    expect(resolveDiscordTemplateReference("discordProxyUrl", ctx({}))).toEqual({
+      matched: true,
+      value: "http://10.200.0.1:3128",
+    });
+  });
+
+  it("honors NEMOCLAW_PROXY_HOST / NEMOCLAW_PROXY_PORT overrides", () => {
+    expect(
+      resolveDiscordTemplateReference(
+        "discordProxyUrl",
+        ctx({ NEMOCLAW_PROXY_HOST: "10.201.0.9", NEMOCLAW_PROXY_PORT: "43128" }),
+      ),
+    ).toEqual({ matched: true, value: "http://10.201.0.9:43128" });
+  });
+});
diff --git a/test/generate-openclaw-config.test.ts b/test/generate-openclaw-config.test.ts
index 02826f6f80..e5492b15e9 100644
--- a/test/generate-openclaw-config.test.ts
+++ b/test/generate-openclaw-config.test.ts
@@ -6,11 +6,11 @@
 // Runs the actual TypeScript script with controlled env vars and asserts on
 // the generated openclaw.json output.
 
-import { describe, it, expect, beforeEach, afterEach } from "vitest";
+import { spawnSync } from "node:child_process";
 import fs from "node:fs";
 import os from "node:os";
 import path from "node:path";
-import { spawnSync } from "node:child_process";
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
 
 import { buildConfig, main } from "../scripts/generate-openclaw-config.mts";
 import {
@@ -613,10 +613,10 @@ describe("generate-openclaw-config.mts: config generation", () => {
       "openshell:resolve:env:DISCORD_BOT_TOKEN",
     );
     expect(config.channels.telegram.accounts.default.proxy).toBe("http://10.200.0.1:3128");
-    expect(config.channels.discord.accounts.default.proxy).toBeUndefined();
+    expect(config.channels.discord.accounts.default.proxy).toBe("http://10.200.0.1:3128");
   });
 
-  it("#3894: routes Discord gateway traffic through OpenClaw's managed proxy", () => {
+  it("#3894: routes Discord gateway traffic through the per-account proxy", () => {
     const channels = Buffer.from(JSON.stringify(["discord"])).toString("base64");
     const config = runConfigScript({
       NEMOCLAW_MESSAGING_CHANNELS_B64: channels,
@@ -633,10 +633,10 @@ describe("generate-openclaw-config.mts: config generation", () => {
       token: "openshell:resolve:env:DISCORD_BOT_TOKEN",
       enabled: true,
     });
-    expect(config.channels.discord.accounts.default.proxy).toBeUndefined();
+    expect(config.channels.discord.accounts.default.proxy).toBe("http://10.201.0.9:43128");
   });
 
-  it("does not write a Discord account proxy when the managed proxy is configured", () => {
+  it("writes the Discord account proxy alongside the managed proxy", () => {
     const channels = Buffer.from(JSON.stringify(["discord"])).toString("base64");
     const config = runConfigScript({
       NEMOCLAW_MESSAGING_CHANNELS_B64: channels,
@@ -644,7 +644,7 @@ describe("generate-openclaw-config.mts: config generation", () => {
     });
 
     expect(config.proxy.proxyUrl).toBe("http://10.200.0.1:43128");
-    expect(config.channels.discord.accounts.default.proxy).toBeUndefined();
+    expect(config.channels.discord.accounts.default.proxy).toBe("http://10.200.0.1:43128");
   });
 
   it("can defer OpenClaw managed proxy config for build-time doctor", () => {
@@ -655,7 +655,7 @@ describe("generate-openclaw-config.mts: config generation", () => {
     });
 
     expect(config.proxy).toBeUndefined();
-    expect(config.channels.discord.accounts.default.proxy).toBeUndefined();
+    expect(config.channels.discord.accounts.default.proxy).toBe("http://10.200.0.1:3128");
   });
 
   it("ignores the OpenShell loopback proxy env var when using OpenClaw managed proxy", () => {
@@ -667,10 +667,10 @@ describe("generate-openclaw-config.mts: config generation", () => {
     });
 
     expect(config.proxy.proxyUrl).toBe("http://10.200.0.1:3128");
-    expect(config.channels.discord.accounts.default.proxy).toBeUndefined();
+    expect(config.channels.discord.accounts.default.proxy).toBe("http://10.200.0.1:3128");
   });
 
-  it("keeps Telegram on the OpenShell proxy while Discord relies on the managed proxy", () => {
+  it("routes both Telegram and Discord through the per-account proxy", () => {
     const channels = Buffer.from(JSON.stringify(["telegram", "discord"])).toString("base64");
     const config = runConfigScript({
       NEMOCLAW_MESSAGING_CHANNELS_B64: channels,
@@ -680,7 +680,7 @@ describe("generate-openclaw-config.mts: config generation", () => {
 
     expect(config.proxy.proxyUrl).toBe("http://10.201.0.9:43128");
     expect(config.channels.telegram.accounts.default.proxy).toBe("http://10.201.0.9:43128");
-    expect(config.channels.discord.accounts.default.proxy).toBeUndefined();
+    expect(config.channels.discord.accounts.default.proxy).toBe("http://10.201.0.9:43128");
   });
 
   it("emits Bolt-shape placeholders for Slack so the SDK's prefix regex passes", () => {