Improve environment variable handling for ACP agents

README.md

@@ -1267,6 +1267,13 @@ ACP providers are configured in the `acp_providers` section of your configuratio
 }
 ```
 
+### Environment Variables Handling
+
+When spawning an ACP agent, `avante.nvim` handles environment variables as follows:
+
+1.  **Inheritance**: The agent inherits all environment variables from the current Neovim process.
+2.  **Overrides**: Environment variables defined in the `env` table of the ACP provider configuration will override inherited values. Setting a variable to `vim.NIL` will remove it from the environment.
+
 ### Prerequisites
 
 Before using ACP agents, ensure you have the required tools installed:
@@ -1707,4 +1714,4 @@ avante.nvim is licensed under the Apache 2.0 License. For more details, please r
       <img alt="NebulaGraph Data Intelligence Suite(ngdi)" src="https://api.star-history.com/svg?repos=yetone/avante.nvim&type=Date">
     </picture>
   </a>
-</p>
+</p>

lua/avante/libs/acp_client.lua

@@ -355,20 +355,28 @@ function ACPClient:_create_stdio_transport()
     end
 
     local args = vim.deepcopy(self.config.args or {})
-    local env = self.config.env
 
-    -- Start with system environment and override with config env
-    local final_env = {}
-
-    local path = vim.fn.getenv("PATH")
-    if path then final_env[#final_env + 1] = "PATH=" .. path end
+    -- Build the final environment map, inheriting from the current process
+    -- and allowing overrides from the plugin configuration.
+    local inherited_env = vim.fn.environ()
+    local override_env = self.config.env
 
-    if env then
-      for k, v in pairs(env) do
-        final_env[#final_env + 1] = k .. "=" .. v
+    if override_env then
+      for k, v in pairs(override_env) do
+        if v == vim.NIL then
+          inherited_env[k] = nil
+        else
+          inherited_env[k] = v
+        end
       end
     end
 
+    -- Convert map to list of "KEY=VALUE" strings for uv.spawn
+    local final_env = {}
+    for k, v in pairs(inherited_env) do
+      final_env[#final_env + 1] = k .. "=" .. v
+    end
+
     ---@diagnostic disable-next-line: missing-fields
     local handle, pid = uv.spawn(self.config.command, {
       args = args,

tests/libs/acp_client_env_spec.lua

@@ -0,0 +1,174 @@
+local ACPClient = require("avante.libs.acp_client")
+local stub = require("luassert.stub")
+
+describe("ACPClient Environment Handling", function()
+  local schedule_stub
+  local environ_stub
+  local spawn_stub
+  local uv = vim.uv or vim.loop
+
+  before_each(function()
+    schedule_stub = stub(vim, "schedule")
+    schedule_stub.invokes(function(fn) fn() end)
+
+    environ_stub = stub(vim.fn, "environ")
+    spawn_stub = stub(uv, "spawn")
+  end)
+
+  after_each(function()
+    schedule_stub:revert()
+    environ_stub:revert()
+    spawn_stub:revert()
+  end)
+
+  it("should inherit all environment variables when no overrides are provided", function()
+    -- Mock environment
+    environ_stub.returns({
+      USER = "testuser",
+      HOME = "/home/testuser",
+      PATH = "/usr/bin:/bin"
+    })
+
+    -- Mock successful spawn
+    spawn_stub.returns({}, 1234)
+
+    local config = {
+      transport_type = "stdio",
+      command = "test-agent",
+      args = {},
+      env = nil -- No overrides
+    }
+
+    local client = ACPClient:new(config)
+    client:connect(function() end)
+
+    assert.stub(spawn_stub).was_called(1)
+    local call_args = spawn_stub.calls[1].refs
+    local options = call_args[2]
+    local env_list = options.env
+
+    -- Verify env list contains all inherited variables
+    local env_map = {}
+    for _, item in ipairs(env_list) do
+      local k, v = item:match("([^=]+)=(.*)")
+      env_map[k] = v
+    end
+
+    assert.equals("testuser", env_map["USER"])
+    assert.equals("/home/testuser", env_map["HOME"])
+    assert.equals("/usr/bin:/bin", env_map["PATH"])
+  end)
+
+  it("should override existing environment variables", function()
+    -- Mock environment
+    environ_stub.returns({
+      USER = "testuser",
+      HOME = "/home/testuser",
+      PATH = "/usr/bin:/bin"
+    })
+
+    -- Mock successful spawn
+    spawn_stub.returns({}, 1234)
+
+    local config = {
+      transport_type = "stdio",
+      command = "test-agent",
+      args = {},
+      env = {
+        HOME = "/home/override"
+      }
+    }
+
+    local client = ACPClient:new(config)
+    client:connect(function() end)
+
+    assert.stub(spawn_stub).was_called(1)
+    local call_args = spawn_stub.calls[1].refs
+    local options = call_args[2]
+    local env_list = options.env
+
+    local env_map = {}
+    for _, item in ipairs(env_list) do
+      local k, v = item:match("([^=]+)=(.*)")
+      env_map[k] = v
+    end
+
+    assert.equals("testuser", env_map["USER"]) -- Inherited
+    assert.equals("/home/override", env_map["HOME"]) -- Overridden
+    assert.equals("/usr/bin:/bin", env_map["PATH"]) -- Inherited
+  end)
+
+  it("should add new environment variables", function()
+    -- Mock environment
+    environ_stub.returns({
+      USER = "testuser",
+    })
+
+    -- Mock successful spawn
+    spawn_stub.returns({}, 1234)
+
+    local config = {
+      transport_type = "stdio",
+      command = "test-agent",
+      args = {},
+      env = {
+        NEW_VAR = "new_value"
+      }
+    }
+
+    local client = ACPClient:new(config)
+    client:connect(function() end)
+
+    assert.stub(spawn_stub).was_called(1)
+    local call_args = spawn_stub.calls[1].refs
+    local options = call_args[2]
+    local env_list = options.env
+
+    local env_map = {}
+    for _, item in ipairs(env_list) do
+      local k, v = item:match("([^=]+)=(.*)")
+      env_map[k] = v
+    end
+
+    assert.equals("testuser", env_map["USER"])
+    assert.equals("new_value", env_map["NEW_VAR"])
+  end)
+
+  it("should delete inherited environment variables when overridden with nil", function()
+    -- Mock environment
+    environ_stub.returns({
+      USER = "testuser",
+      HOME = "/home/testuser",
+      TO_BE_REMOVED = "remove_me"
+    })
+
+    -- Mock successful spawn
+    spawn_stub.returns({}, 1234)
+
+    local config = {
+      transport_type = "stdio",
+      command = "test-agent",
+      args = {},
+      env = {
+        TO_BE_REMOVED = vim.NIL
+      }
+    }
+
+    local client = ACPClient:new(config)
+    client:connect(function() end)
+
+    assert.stub(spawn_stub).was_called(1)
+    local call_args = spawn_stub.calls[1].refs
+    local options = call_args[2]
+    local env_list = options.env
+
+    local env_map = {}
+    for _, item in ipairs(env_list) do
+      local k, v = item:match("([^=]+)=(.*)")
+      env_map[k] = v
+    end
+
+    assert.equals("testuser", env_map["USER"])
+    assert.is_nil(env_map["TO_BE_REMOVED"])
+  end)
+end)