Add global config support (~/.config/claude-sandbox/config.json)

Config priority: defaults < global < local project config

This allows setting dockerImage globally without modifying code:
  mkdir -p ~/.config/claude-sandbox
  echo '{"dockerImage": "docker-devbox:latest"}' > ~/.config/claude-sandbox/config.json

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: jlaustill

src/config.ts

@@ -3,6 +3,14 @@ import path from "path";
 import os from "os";
 import { SandboxConfig } from "./types";
 
+// Global config location: ~/.config/claude-sandbox/config.json
+const GLOBAL_CONFIG_PATH = path.join(
+  os.homedir(),
+  ".config",
+  "claude-sandbox",
+  "config.json"
+);
+
 const DEFAULT_CONFIG: SandboxConfig = {
   dockerImage: "claude-code-sandbox:latest",
   autoPush: true,
@@ -17,27 +25,38 @@ const DEFAULT_CONFIG: SandboxConfig = {
   // bashTimeout: 600000, // 10 minutes
 };
 
-export async function loadConfig(configPath: string): Promise<SandboxConfig> {
+async function loadJsonFile(filePath: string): Promise<Partial<SandboxConfig> | null> {
   try {
-    const fullPath = path.resolve(configPath);
-    const configContent = await fs.readFile(fullPath, "utf-8");
-    const userConfig = JSON.parse(configContent);
-
-    // Merge with defaults
-    return {
-      ...DEFAULT_CONFIG,
-      ...userConfig,
-    };
-  } catch (error) {
-    // Config file not found or invalid, use defaults
-    return DEFAULT_CONFIG;
+    const content = await fs.readFile(filePath, "utf-8");
+    return JSON.parse(content);
+  } catch {
+    return null;
   }
 }
 
+export async function loadConfig(configPath: string): Promise<SandboxConfig> {
+  // Load global config first (if exists)
+  const globalConfig = await loadJsonFile(GLOBAL_CONFIG_PATH);
+
+  // Load local project config (if exists)
+  const localConfig = await loadJsonFile(path.resolve(configPath));
+
+  // Merge: defaults < global < local
+  return {
+    ...DEFAULT_CONFIG,
+    ...(globalConfig || {}),
+    ...(localConfig || {}),
+  };
+}
+
 export async function saveConfig(
   config: SandboxConfig,
   configPath: string,
 ): Promise<void> {
   const fullPath = path.resolve(configPath);
   await fs.writeFile(fullPath, JSON.stringify(config, null, 2));
 }
+
+export function getGlobalConfigPath(): string {
+  return GLOBAL_CONFIG_PATH;
+}

src/index.ts

@@ -212,7 +212,7 @@ export class ClaudeSandbox {
       credentials,
       workDir,
       repoName,
-      dockerImage: this.config.dockerImage || "claude-sandbox:latest",
+      dockerImage: this.config.dockerImage || "claude-code-sandbox:latest",
       prFetchRef,
       remoteFetchRef,
     };