From a51ad98182ee50323296c2ec287a4362e6838329 Mon Sep 17 00:00:00 2001
From: YeonGyu-Kim <code.yeon.gyu@gmail.com>
Date: Fri, 2 Jan 2026 16:07:33 +0900
Subject: [PATCH] fix(skill-mcp): always inherit process.env for MCP servers
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- Always merge parent process.env when spawning MCP child processes
- Overlay config.env on top if present (for skill-specific overrides)
- Fixes issue where skills without explicit env: block started with zero environment variables
- Adds 2 tests for env inheritance behavior

🤖 Generated with assistance of OhMyOpenCode (https://github.com/code-yeongyu/oh-my-opencode)
---
 .../skill-mcp-manager/manager.test.ts         | 50 +++++++++++++++++++
 src/features/skill-mcp-manager/manager.ts     | 10 ++--
 2 files changed, 56 insertions(+), 4 deletions(-)

diff --git a/src/features/skill-mcp-manager/manager.test.ts b/src/features/skill-mcp-manager/manager.test.ts
index ab77f04..2313e22 100644
--- a/src/features/skill-mcp-manager/manager.test.ts
+++ b/src/features/skill-mcp-manager/manager.test.ts
@@ -106,4 +106,54 @@ describe("SkillMcpManager", () => {
       expect(manager.getConnectedServers()).toEqual([])
     })
   })
+
+  describe("environment variable handling", () => {
+    it("always inherits process.env even when config.env is undefined", async () => {
+      // #given
+      const info: SkillMcpClientInfo = {
+        serverName: "test-server",
+        skillName: "test-skill",
+        sessionID: "session-1",
+      }
+      const configWithoutEnv: ClaudeCodeMcpServer = {
+        command: "node",
+        args: ["-e", "process.exit(0)"],
+      }
+
+      // #when - attempt connection (will fail but exercises env merging code path)
+      // #then - should not throw "undefined" related errors for env
+      try {
+        await manager.getOrCreateClient(info, configWithoutEnv)
+      } catch (error) {
+        const message = error instanceof Error ? error.message : String(error)
+        expect(message).not.toContain("env")
+        expect(message).not.toContain("undefined")
+      }
+    })
+
+    it("overlays config.env on top of inherited process.env", async () => {
+      // #given
+      const info: SkillMcpClientInfo = {
+        serverName: "test-server",
+        skillName: "test-skill",
+        sessionID: "session-2",
+      }
+      const configWithEnv: ClaudeCodeMcpServer = {
+        command: "node",
+        args: ["-e", "process.exit(0)"],
+        env: {
+          CUSTOM_VAR: "custom_value",
+        },
+      }
+
+      // #when - attempt connection
+      // #then - should not throw, env merging should work
+      try {
+        await manager.getOrCreateClient(info, configWithEnv)
+      } catch (error) {
+        const message = error instanceof Error ? error.message : String(error)
+        expect(message).toContain("Failed to connect")
+      }
+    })
+  })
 })
diff --git a/src/features/skill-mcp-manager/manager.ts b/src/features/skill-mcp-manager/manager.ts
index 967f06a..027edaf 100644
--- a/src/features/skill-mcp-manager/manager.ts
+++ b/src/features/skill-mcp-manager/manager.ts
@@ -55,18 +55,20 @@ export class SkillMcpManager {
     const command = config.command
     const args = config.args || []
 
+    // Always inherit parent process environment
     const mergedEnv: Record<string, string> = {}
+    for (const [key, value] of Object.entries(process.env)) {
+      if (value !== undefined) mergedEnv[key] = value
+    }
+    // Overlay with skill-specific env vars if present
     if (config.env) {
-      for (const [key, value] of Object.entries(process.env)) {
-        if (value !== undefined) mergedEnv[key] = value
-      }
       Object.assign(mergedEnv, config.env)
     }
 
     const transport = new StdioClientTransport({
       command,
       args,
-      env: config.env ? mergedEnv : undefined,
+      env: mergedEnv,
     })
 
     const client = new Client(