diff --git a/src/shared/opencode-command-dirs.ts b/src/shared/opencode-command-dirs.ts
index 34f2ecce1..4066fe640 100644
--- a/src/shared/opencode-command-dirs.ts
+++ b/src/shared/opencode-command-dirs.ts
@@ -1,5 +1,5 @@
 import { basename, dirname, join } from "node:path"
-import { getOpenCodeConfigDir } from "./opencode-config-dir"
+import { getOpenCodeConfigDirs } from "./opencode-config-dir"
 import type { OpenCodeConfigDirOptions } from "./opencode-config-dir-types"
 
 function getParentOpencodeConfigDir(configDir: string): string | null {
@@ -12,25 +12,33 @@ function getParentOpencodeConfigDir(configDir: string): string | null {
 }
 
 export function getOpenCodeCommandDirs(options: OpenCodeConfigDirOptions): string[] {
-  const configDir = getOpenCodeConfigDir(options)
-  const parentConfigDir = getParentOpencodeConfigDir(configDir)
+  const configDirs = getOpenCodeConfigDirs(options)
   return Array.from(
     new Set([
-      join(configDir, "commands"),
-      join(configDir, "command"),
-      ...(parentConfigDir ? [join(parentConfigDir, "commands"), join(parentConfigDir, "command")] : []),
+      ...configDirs.flatMap((configDir) => {
+        const parentConfigDir = getParentOpencodeConfigDir(configDir)
+        return [
+          join(configDir, "commands"),
+          join(configDir, "command"),
+          ...(parentConfigDir ? [join(parentConfigDir, "commands"), join(parentConfigDir, "command")] : []),
+        ]
+      }),
     ])
   )
 }
 
 export function getOpenCodeSkillDirs(options: OpenCodeConfigDirOptions): string[] {
-  const configDir = getOpenCodeConfigDir(options)
-  const parentConfigDir = getParentOpencodeConfigDir(configDir)
+  const configDirs = getOpenCodeConfigDirs(options)
   return Array.from(
     new Set([
-      join(configDir, "skills"),
-      join(configDir, "skill"),
-      ...(parentConfigDir ? [join(parentConfigDir, "skills"), join(parentConfigDir, "skill")] : []),
+      ...configDirs.flatMap((configDir) => {
+        const parentConfigDir = getParentOpencodeConfigDir(configDir)
+        return [
+          join(configDir, "skills"),
+          join(configDir, "skill"),
+          ...(parentConfigDir ? [join(parentConfigDir, "skills"), join(parentConfigDir, "skill")] : []),
+        ]
+      }),
     ])
   )
 }
diff --git a/src/shared/opencode-config-dir.test.ts b/src/shared/opencode-config-dir.test.ts
index 7ddf8e009..275f988c5 100644
--- a/src/shared/opencode-config-dir.test.ts
+++ b/src/shared/opencode-config-dir.test.ts
@@ -3,6 +3,7 @@ import { homedir } from "node:os"
 import { join, resolve, win32 } from "node:path"
 import {
   getOpenCodeConfigDir,
+  getOpenCodeConfigDirs,
   getOpenCodeConfigPaths,
   isDevBuild,
   detectExistingConfigDir,
@@ -45,7 +46,7 @@ describe("opencode-config-dir", () => {
       const result = getOpenCodeConfigDir({ binary: "opencode", version: "1.0.200" })
 
       // then returns the custom path
-      expect(result).toBe("/custom/opencode/path")
+      expect(result).toBe(resolve("/custom/opencode/path"))
     })
 
     test("falls back to default when env var is not set", () => {
@@ -109,7 +110,23 @@ describe("opencode-config-dir", () => {
       const result = getOpenCodeConfigDir({ binary: "opencode", version: "1.0.200" })
 
       // then OPENCODE_CONFIG_DIR takes priority
-      expect(result).toBe("/custom/opencode/path")
+      expect(result).toBe(resolve("/custom/opencode/path"))
+    })
+
+    test("returns both custom and default config directories for additive discovery", () => {
+      // given both OPENCODE_CONFIG_DIR and XDG_CONFIG_HOME are set
+      process.env.OPENCODE_CONFIG_DIR = "/custom/opencode/path"
+      process.env.XDG_CONFIG_HOME = "/xdg/config"
+      Object.defineProperty(process, "platform", { value: "linux" })
+
+      // when getOpenCodeConfigDirs is called
+      const result = getOpenCodeConfigDirs({ binary: "opencode", version: "1.0.200" })
+
+      // then the custom path stays first, but the default global path remains visible
+      expect(result).toEqual([
+        resolve("/custom/opencode/path"),
+        resolve("/xdg/config/opencode"),
+      ])
     })
   })
 
@@ -163,7 +180,7 @@ describe("opencode-config-dir", () => {
         const result = getOpenCodeConfigDir({ binary: "opencode", version: "1.0.200" })
 
         // then returns $XDG_CONFIG_HOME/opencode
-        expect(result).toBe("/custom/config/opencode")
+        expect(result).toBe(resolve("/custom/config/opencode"))
       })
 
       test("returns ~/.config/opencode on macOS", () => {
diff --git a/src/shared/opencode-config-dir.ts b/src/shared/opencode-config-dir.ts
index 691d0e2c4..de51fbdf1 100644
--- a/src/shared/opencode-config-dir.ts
+++ b/src/shared/opencode-config-dir.ts
@@ -55,16 +55,37 @@ function resolveConfigPath(pathValue: string): string {
   }
 }
 
-function getCliConfigDir(): string {
-  const envConfigDir = process.env.OPENCODE_CONFIG_DIR?.trim()
-  if (envConfigDir) {
-    return resolveConfigPath(envConfigDir)
-  }
-
+function getCliDefaultConfigDir(): string {
   const xdgConfig = process.env.XDG_CONFIG_HOME || join(homedir(), ".config")
   return resolveConfigPath(join(xdgConfig, "opencode"))
 }
 
+function getCliCustomConfigDir(): string | null {
+  const envConfigDir = process.env.OPENCODE_CONFIG_DIR?.trim()
+  if (!envConfigDir) {
+    return null
+  }
+
+  return resolveConfigPath(envConfigDir)
+}
+
+function getCliConfigDir(): string {
+  return getCliCustomConfigDir() ?? getCliDefaultConfigDir()
+}
+
+export function getOpenCodeConfigDirs(options: OpenCodeConfigDirOptions): string[] {
+  if (options.binary !== "opencode") {
+    return [getOpenCodeConfigDir(options)]
+  }
+
+  return Array.from(
+    new Set([
+      ...(getCliCustomConfigDir() ? [getCliCustomConfigDir()!] : []),
+      getCliDefaultConfigDir(),
+    ]),
+  )
+}
+
 export function getOpenCodeConfigDir(options: OpenCodeConfigDirOptions): string {
   const { binary, version, checkExisting = true } = options
 
diff --git a/src/tools/slashcommand/command-discovery.test.ts b/src/tools/slashcommand/command-discovery.test.ts
index fc193b61f..d45ef88b8 100644
--- a/src/tools/slashcommand/command-discovery.test.ts
+++ b/src/tools/slashcommand/command-discovery.test.ts
@@ -20,6 +20,7 @@ const ENV_KEYS = [
   "CLAUDE_PLUGINS_HOME",
   "CLAUDE_SETTINGS_PATH",
   "OPENCODE_CONFIG_DIR",
+  "XDG_CONFIG_HOME",
 ] as const
 
 type EnvKey = (typeof ENV_KEYS)[number]
@@ -119,6 +120,7 @@ describe("slashcommand command discovery plugin integration", () => {
       CLAUDE_PLUGINS_HOME: process.env.CLAUDE_PLUGINS_HOME,
       CLAUDE_SETTINGS_PATH: process.env.CLAUDE_SETTINGS_PATH,
       OPENCODE_CONFIG_DIR: process.env.OPENCODE_CONFIG_DIR,
+      XDG_CONFIG_HOME: process.env.XDG_CONFIG_HOME,
     }
     const setup = writePluginFixture(tempDir)
     projectDir = setup.projectDir
@@ -193,6 +195,40 @@ Use parent opencode commit command.
     expect(commitCommand?.content).toContain("Use parent opencode commit command.")
   })
 
+  it("discovers commands from both OPENCODE_CONFIG_DIR and the default global config directory", () => {
+    const defaultGlobalDir = join(tempDir, "xdg", "opencode", "commands")
+    const customGlobalDir = join(tempDir, "custom-opencode", "commands")
+
+    mkdirSync(defaultGlobalDir, { recursive: true })
+    mkdirSync(customGlobalDir, { recursive: true })
+
+    writeFileSync(
+      join(defaultGlobalDir, "global-default.md"),
+      `---
+description: Default global opencode command
+---
+Use default global command.
+`,
+    )
+    writeFileSync(
+      join(customGlobalDir, "global-custom.md"),
+      `---
+description: Custom global opencode command
+---
+Use custom global command.
+`,
+    )
+
+    process.env.XDG_CONFIG_HOME = join(tempDir, "xdg")
+    process.env.OPENCODE_CONFIG_DIR = join(tempDir, "custom-opencode")
+
+    const commands = discoverCommandsSync(projectDir)
+    const names = commands.map(command => command.name)
+
+    expect(names).toContain("global-default")
+    expect(names).toContain("global-custom")
+  })
+
   it("discovers ancestor project opencode commands from plural commands directory", () => {
     const projectRoot = join(projectDir, "workspace")
     const childDir = join(projectRoot, "apps", "cli")