diff --git a/__tests__/installer-targets.test.ts b/__tests__/installer-targets.test.ts
index ffa708197..a40a37ba3 100644
--- a/__tests__/installer-targets.test.ts
+++ b/__tests__/installer-targets.test.ts
@@ -38,12 +38,16 @@ function setHome(dir: string): { restore: () => void } {
     APPDATA: process.env.APPDATA,
     XDG_CONFIG_HOME: process.env.XDG_CONFIG_HOME,
     HERMES_HOME: process.env.HERMES_HOME,
+    CLAUDE_CONFIG_DIR: process.env.CLAUDE_CONFIG_DIR,
   };
   process.env.HOME = dir;
   process.env.USERPROFILE = dir;
   process.env.APPDATA = path.join(dir, '.config');
   process.env.XDG_CONFIG_HOME = path.join(dir, '.config');
   delete process.env.HERMES_HOME;
+  // Clear CLAUDE_CONFIG_DIR so a custom profile in the real environment
+  // doesn't leak into tests that assume the default ~/.claude profile.
+  delete process.env.CLAUDE_CONFIG_DIR;
   return {
     restore() {
       if (prev.HOME === undefined) delete process.env.HOME; else process.env.HOME = prev.HOME;
@@ -51,6 +55,7 @@ function setHome(dir: string): { restore: () => void } {
       if (prev.APPDATA === undefined) delete process.env.APPDATA; else process.env.APPDATA = prev.APPDATA;
       if (prev.XDG_CONFIG_HOME === undefined) delete process.env.XDG_CONFIG_HOME; else process.env.XDG_CONFIG_HOME = prev.XDG_CONFIG_HOME;
       if (prev.HERMES_HOME === undefined) delete process.env.HERMES_HOME; else process.env.HERMES_HOME = prev.HERMES_HOME;
+      if (prev.CLAUDE_CONFIG_DIR === undefined) delete process.env.CLAUDE_CONFIG_DIR; else process.env.CLAUDE_CONFIG_DIR = prev.CLAUDE_CONFIG_DIR;
     },
   };
 }
@@ -921,6 +926,31 @@ describe('Installer targets — partial-state idempotency', () => {
     expect(cfg.mcpServers.codegraph).toBeDefined();
   });
 
+  it('claude: global install honors CLAUDE_CONFIG_DIR, leaving ~/.claude untouched', () => {
+    const claude = getTarget('claude')!;
+    const profile = path.join(tmpHome, '.claude-gc');
+    const prev = process.env.CLAUDE_CONFIG_DIR;
+    process.env.CLAUDE_CONFIG_DIR = profile;
+    try {
+      claude.install('global', { autoAllow: true });
+
+      // MCP entry, settings.json, and CLAUDE.md all land in the custom
+      // profile dir — Claude Code keeps .claude.json *inside* it when the
+      // env var is set.
+      const mcp = JSON.parse(fs.readFileSync(path.join(profile, '.claude.json'), 'utf-8'));
+      expect(mcp.mcpServers.codegraph).toBeDefined();
+      expect(fs.existsSync(path.join(profile, 'settings.json'))).toBe(true);
+      expect(fs.existsSync(path.join(profile, 'CLAUDE.md'))).toBe(true);
+
+      // The default profile must be left alone.
+      expect(fs.existsSync(path.join(tmpHome, '.claude.json'))).toBe(false);
+      expect(fs.existsSync(path.join(tmpHome, '.claude'))).toBe(false);
+    } finally {
+      if (prev === undefined) delete process.env.CLAUDE_CONFIG_DIR;
+      else process.env.CLAUDE_CONFIG_DIR = prev;
+    }
+  });
+
   it('claude: local install migrates a legacy ./.claude.json codegraph entry into ./.mcp.json', () => {
     const claude = getTarget('claude')!;
     const legacy = path.join(tmpCwd, '.claude.json');
diff --git a/src/installer/targets/claude.ts b/src/installer/targets/claude.ts
index bdfe6e6fb..0446a0fde 100644
--- a/src/installer/targets/claude.ts
+++ b/src/installer/targets/claude.ts
@@ -41,18 +41,36 @@ import {
   CODEGRAPH_SECTION_START,
 } from '../instructions-template';
 
+/**
+ * Root of the global Claude Code profile. Honors CLAUDE_CONFIG_DIR so
+ * non-default profiles (e.g. `~/.claude-gc`) get configured instead of
+ * `~/.claude` — Claude Code reads settings.json, CLAUDE.md, and (when
+ * the env var is set) .claude.json from this directory. Only affects the
+ * global location; project-local files are unaffected by the env var.
+ */
+function globalConfigDir(): string {
+  const cfg = process.env.CLAUDE_CONFIG_DIR;
+  return cfg && cfg.trim().length > 0
+    ? path.resolve(cfg)
+    : path.join(os.homedir(), '.claude');
+}
 function configDir(loc: Location): string {
   return loc === 'global'
-    ? path.join(os.homedir(), '.claude')
+    ? globalConfigDir()
     : path.join(process.cwd(), '.claude');
 }
 function mcpJsonPath(loc: Location): string {
-  // global → ~/.claude.json (user scope: visible in every project).
+  // global → $CLAUDE_CONFIG_DIR/.claude.json when that env var is set
+  //   (Claude Code keeps .claude.json inside a custom profile dir), else
+  //   ~/.claude.json in HOME (the default profile keeps it beside, not
+  //   inside, ~/.claude). User scope: visible in every project.
   // local  → ./.mcp.json (project scope: the ONLY project-level MCP
-  // file Claude Code reads — NOT ./.claude.json, which it ignores).
-  return loc === 'global'
-    ? path.join(os.homedir(), '.claude.json')
-    : path.join(process.cwd(), '.mcp.json');
+  //   file Claude Code reads — NOT ./.claude.json, which it ignores).
+  if (loc !== 'global') return path.join(process.cwd(), '.mcp.json');
+  const cfg = process.env.CLAUDE_CONFIG_DIR;
+  return cfg && cfg.trim().length > 0
+    ? path.join(path.resolve(cfg), '.claude.json')
+    : path.join(os.homedir(), '.claude.json');
 }
 /**
  * Where pre-#207 installers wrote the local MCP entry. Claude Code