add OPENCODE_CONFIG_DIR to allow loading a custom config directory (#3504)

Co-authored-by: opencode-agent[bot] <opencode-agent[bot]@users.noreply.github.com>
Co-authored-by: rekram1-node <rekram1-node@users.noreply.github.com>

packages/opencode/src/config/config.ts

@@ -61,6 +61,11 @@ export namespace Config {
       )),
     ]
 
+    if (Flag.OPENCODE_CONFIG_DIR) {
+      directories.push(Flag.OPENCODE_CONFIG_DIR)
+      log.debug("loading config from OPENCODE_CONFIG_DIR", { path: Flag.OPENCODE_CONFIG_DIR })
+    }
+
     for (const dir of directories) {
       await assertValid(dir)
       installDependencies(dir)

packages/opencode/src/flag/flag.ts

@@ -1,6 +1,7 @@
 export namespace Flag {
   export const OPENCODE_AUTO_SHARE = truthy("OPENCODE_AUTO_SHARE")
   export const OPENCODE_CONFIG = process.env["OPENCODE_CONFIG"]
+  export const OPENCODE_CONFIG_DIR = process.env["OPENCODE_CONFIG_DIR"]
   export const OPENCODE_CONFIG_CONTENT = process.env["OPENCODE_CONFIG_CONTENT"]
   export const OPENCODE_DISABLE_AUTOUPDATE = truthy("OPENCODE_DISABLE_AUTOUPDATE")
   export const OPENCODE_DISABLE_PRUNE = truthy("OPENCODE_DISABLE_PRUNE")

packages/web/src/content/docs/config.mdx

@@ -61,6 +61,22 @@ opencode run "Hello world"
 
 ---
 
+### Custom directory
+
+You can specify a custom config directory using the `OPENCODE_CONFIG_DIR`
+environment variable. This directory will be searched for agents, commands,
+modes, and plugins just like the standard `.opencode` directory, and should
+follow the same structure.
+
+```bash
+export OPENCODE_CONFIG_DIR=/path/to/my/config-directory
+opencode run "Hello world"
+```
+
+Note: The custom directory is loaded after the global config and `.opencode` directories, so it can override their settings.
+
+---
+
 ## Schema
 
 The config file has a schema that's defined in [**`opencode.ai/config.json`**](https://opencode.ai/config.json).