fix: inherit process.env when spawning agent subprocess (agentclientprotocol#374)

In 0.20.0, the env option was introduced with an explicit object spread,
but without including process.env. This caused the subprocess to receive
an empty environment, stripping HOME, PATH and other inherited variables
when spawned from an external editor such as Zed.

Add ...process.env as the base so user-provided and gateway env vars
still override it, while preserving the parent process environment.

Add tests to verify HOME/PATH are inherited and that user-provided vars
are merged on top correctly.

Fixes agentclientprotocol#373

---------

Co-authored-by: Ben Brandt <benjamin.j.brandt@gmail.com>

Author: joseotaviorf

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## 0.20.1
+
+- fix: inherit process.env when spawning agent subprocess
+
 ## 0.20.0
 
 - Update to @anthropic-ai/claude-agent-sdk@0.2.63

package-lock.json

@@ -3,7 +3,7 @@
   "publishConfig": {
     "access": "public"
   },
-  "version": "0.20.0",
+  "version": "0.20.1",
   "description": "An ACP-compatible coding agent powered by the Claude Agent SDK (TypeScript)",
   "main": "dist/lib.js",
   "types": "dist/lib.d.ts",

package.json

@@ -1240,6 +1240,7 @@ export class ClaudeAcpAgent implements Agent {
       ...(maxThinkingTokens !== undefined && { maxThinkingTokens }),
       ...userProvidedOptions,
       env: {
+        ...process.env,
         ...userProvidedOptions?.env,
         ...createEnvForGateway(this.gatewayAuthMeta),
       },

src/acp-agent.ts

@@ -227,7 +227,7 @@ describe.skipIf(!process.env.RUN_INTEGRATION_TESTS)("ACP subprocess integration"
       sessionId: newSessionResponse.sessionId,
     });
 
-    expect(client.takeReceivedText()).toBe("");
+    expect(client.takeReceivedText()).toBe("Error: No messages to compact");
 
     // Send something
     await connection.prompt({

src/tests/acp-agent.test.ts

@@ -101,12 +101,12 @@ describe("authorization", () => {
     expect(mockQuery).toHaveBeenCalledWith(
       expect.objectContaining({
         options: expect.objectContaining({
-          env: {
+          env: expect.objectContaining({
             ANTHROPIC_AUTH_TOKEN: "",
             ANTHROPIC_BASE_URL: "https://gateway.example",
             ANTHROPIC_CUSTOM_HEADERS: "x-api-key: test",
             userEnv: "userEnv",
-          },
+          }),
         }),
       }),
     );

src/tests/authorization.test.ts

@@ -151,6 +151,54 @@ describe("createSession options merging", () => {
     expect(capturedOptions!.hooks?.PostToolUse).toHaveLength(2);
   });
 
+  it("inherits HOME and PATH from process.env when no env is provided", async () => {
+    await agent.newSession({
+      cwd: "/test",
+      mcpServers: [],
+    });
+
+    expect(capturedOptions?.env?.HOME).toBe(process.env.HOME);
+    expect(capturedOptions?.env?.PATH).toBe(process.env.PATH);
+  });
+
+  it("merges user-provided env vars on top of process.env", async () => {
+    await agent.newSession({
+      cwd: "/test",
+      mcpServers: [],
+      _meta: {
+        claudeCode: {
+          options: {
+            env: {
+              CUSTOM_VAR: "custom-value",
+            },
+          },
+        },
+      },
+    });
+
+    expect(capturedOptions?.env?.HOME).toBe(process.env.HOME);
+    expect(capturedOptions?.env?.PATH).toBe(process.env.PATH);
+    expect(capturedOptions?.env?.CUSTOM_VAR).toBe("custom-value");
+  });
+
+  it("allows user-provided env vars to override process.env entries", async () => {
+    await agent.newSession({
+      cwd: "/test",
+      mcpServers: [],
+      _meta: {
+        claudeCode: {
+          options: {
+            env: {
+              HOME: "/custom/home",
+            },
+          },
+        },
+      },
+    });
+
+    expect(capturedOptions?.env?.HOME).toBe("/custom/home");
+  });
+
   it("merges user-provided mcpServers with ACP mcpServers", async () => {
     await agent.newSession({
       cwd: "/test",