diff --git a/packages/adapter-utils/src/server-utils.test.ts b/packages/adapter-utils/src/server-utils.test.ts
index 81ec8458b5..1bfea41d35 100644
--- a/packages/adapter-utils/src/server-utils.test.ts
+++ b/packages/adapter-utils/src/server-utils.test.ts
@@ -10,6 +10,7 @@ import {
   buildPersistentSkillSnapshot,
   buildRuntimeMountedSkillSnapshot,
   buildInvocationEnvForLogs,
+  buildPaperclipEnv,
   DEFAULT_PAPERCLIP_AGENT_PROMPT_TEMPLATE,
   materializePaperclipSkillCopy,
   refreshPaperclipWorkspaceEnvForExecution,
@@ -2581,3 +2582,58 @@ describe("appendWithByteCap", () => {
     expect(Buffer.byteLength(output, "utf8")).toBeLessThanOrEqual(7);
   });
 });
+
+describe("buildPaperclipEnv", () => {
+  const ENV_KEYS = [
+    "PAPERCLIP_API_URL",
+    "PAPERCLIP_RUNTIME_API_URL",
+    "PAPERCLIP_LISTEN_HOST",
+    "PAPERCLIP_LISTEN_PORT",
+    "HOST",
+    "PORT",
+  ] as const;
+
+  function withEnv(overrides: Record<string, string>, fn: () => void) {
+    const saved = new Map<string, string | undefined>();
+    for (const key of ENV_KEYS) saved.set(key, process.env[key]);
+    try {
+      for (const key of ENV_KEYS) delete process.env[key];
+      for (const [key, value] of Object.entries(overrides)) process.env[key] = value;
+      fn();
+    } finally {
+      for (const [key, value] of saved) {
+        if (value === undefined) delete process.env[key];
+        else process.env[key] = value;
+      }
+    }
+  }
+
+  it("prefers an explicit PAPERCLIP_API_URL override over the derived runtime URL", () => {
+    withEnv(
+      {
+        PAPERCLIP_API_URL: "http://localhost:3100",
+        PAPERCLIP_RUNTIME_API_URL: "http://203.0.113.7:3100",
+      },
+      () => {
+        const env = buildPaperclipEnv({ id: "agent-1", companyId: "company-1" });
+        expect(env.PAPERCLIP_API_URL).toBe("http://localhost:3100");
+        expect(env.PAPERCLIP_AGENT_ID).toBe("agent-1");
+        expect(env.PAPERCLIP_COMPANY_ID).toBe("company-1");
+      },
+    );
+  });
+
+  it("falls back to the derived runtime URL when no explicit override is set", () => {
+    withEnv({ PAPERCLIP_RUNTIME_API_URL: "http://203.0.113.7:3100" }, () => {
+      const env = buildPaperclipEnv({ id: "agent-1", companyId: "company-1" });
+      expect(env.PAPERCLIP_API_URL).toBe("http://203.0.113.7:3100");
+    });
+  });
+
+  it("derives a listen-host URL when neither override is set", () => {
+    withEnv({ PAPERCLIP_LISTEN_HOST: "0.0.0.0", PAPERCLIP_LISTEN_PORT: "3200" }, () => {
+      const env = buildPaperclipEnv({ id: "agent-1", companyId: "company-1" });
+      expect(env.PAPERCLIP_API_URL).toBe("http://localhost:3200");
+    });
+  });
+});
diff --git a/packages/adapter-utils/src/server-utils.ts b/packages/adapter-utils/src/server-utils.ts
index 7f4cf5cd70..80b9909b23 100644
--- a/packages/adapter-utils/src/server-utils.ts
+++ b/packages/adapter-utils/src/server-utils.ts
@@ -1993,9 +1993,12 @@ export function buildPaperclipEnv(agent: { id: string; companyId: string }): Rec
     process.env.PAPERCLIP_LISTEN_HOST ?? process.env.HOST ?? "localhost",
   );
   const runtimePort = process.env.PAPERCLIP_LISTEN_PORT ?? process.env.PORT ?? "3100";
+  // An explicit PAPERCLIP_API_URL override must win over the URL derived from
+  // authPublicBaseUrl: the derived URL can be unreachable from inside the
+  // runtime container (e.g. when the public base URL is VPN/tailnet-only).
   const apiUrl =
-    process.env.PAPERCLIP_RUNTIME_API_URL ??
     process.env.PAPERCLIP_API_URL ??
+    process.env.PAPERCLIP_RUNTIME_API_URL ??
     `http://${runtimeHost}:${runtimePort}`;
   vars.PAPERCLIP_API_URL = apiUrl;
   return vars;
diff --git a/server/src/__tests__/paperclip-env.test.ts b/server/src/__tests__/paperclip-env.test.ts
index e397f08242..e48c32fdc6 100644
--- a/server/src/__tests__/paperclip-env.test.ts
+++ b/server/src/__tests__/paperclip-env.test.ts
@@ -29,7 +29,7 @@ afterEach(() => {
 });
 
 describe("buildPaperclipEnv", () => {
-  it("prefers an explicit PAPERCLIP_RUNTIME_API_URL", () => {
+  it("prefers an explicit PAPERCLIP_API_URL override over the derived runtime URL", () => {
     process.env.PAPERCLIP_RUNTIME_API_URL = "http://203.0.113.42:3102";
     process.env.PAPERCLIP_API_URL = "http://localhost:4100";
     process.env.PAPERCLIP_LISTEN_HOST = "127.0.0.1";
@@ -37,6 +37,17 @@ describe("buildPaperclipEnv", () => {
 
     const env = buildPaperclipEnv({ id: "agent-1", companyId: "company-1" });
 
+    expect(env.PAPERCLIP_API_URL).toBe("http://localhost:4100");
+  });
+
+  it("falls back to PAPERCLIP_RUNTIME_API_URL when no explicit override is set", () => {
+    process.env.PAPERCLIP_RUNTIME_API_URL = "http://203.0.113.42:3102";
+    delete process.env.PAPERCLIP_API_URL;
+    process.env.PAPERCLIP_LISTEN_HOST = "127.0.0.1";
+    process.env.PAPERCLIP_LISTEN_PORT = "3101";
+
+    const env = buildPaperclipEnv({ id: "agent-1", companyId: "company-1" });
+
     expect(env.PAPERCLIP_API_URL).toBe("http://203.0.113.42:3102");
   });