diff --git a/docs/installation.md b/docs/installation.md
index a8a13ac82c..7f12b7ea63 100644
--- a/docs/installation.md
+++ b/docs/installation.md
@@ -179,6 +179,8 @@ as well, so it is broader than this Claude-only migration.
 history under `CLAUDE_CONFIG_DIR`. Setup follows the same
 variable: it writes the registration to `$CLAUDE_CONFIG_DIR/.claude.json` and
 the skill to `$CLAUDE_CONFIG_DIR/skills`.
+For REA setup, an empty `CLAUDE_CONFIG_DIR` is treated as unset: registration
+goes to `~/.claude.json` and the skill goes to `~/.claude/skills`.
 
 ```bash
 CLAUDE_CONFIG_DIR=~/.claude-rea npx rea-agents setup --client claude_code
diff --git a/src/application/SupportedClients.ts b/src/application/SupportedClients.ts
index c4da675e70..a45599578a 100644
--- a/src/application/SupportedClients.ts
+++ b/src/application/SupportedClients.ts
@@ -159,10 +159,10 @@ const claudeDesktopLocation = (
 };
 
 const claudeCodeConfigDirectory = ({ home, env }: ClientPathContext): string =>
-  env.CLAUDE_CONFIG_DIR ?? home;
+  env.CLAUDE_CONFIG_DIR || home;
 
 const claudeCodeMarkerDirectory = ({ home, env }: ClientPathContext): string =>
-  env.CLAUDE_CONFIG_DIR ?? join(home, ".claude");
+  env.CLAUDE_CONFIG_DIR || join(home, ".claude");
 
 const codexDirectory = ({ home, env }: ClientPathContext): string =>
   env.CODEX_HOME || join(home, ".codex");
@@ -486,8 +486,8 @@ export const SUPPORTED_CLIENT_DEFINITIONS = [
   {
     name: "claude_code",
     displayName: "Claude Code",
-    skillPath: ({ home, env }: ClientPathContext) =>
-      join(env.CLAUDE_CONFIG_DIR ?? join(home, ".claude"), "skills"),
+    skillPath: (context: ClientPathContext) =>
+      join(claudeCodeMarkerDirectory(context), "skills"),
     configPath: (context: ClientPathContext) =>
       join(claudeCodeConfigDirectory(context), ".claude.json"),
     markerPath: claudeCodeMarkerDirectory,
diff --git a/tests/boundary/cli/clientProfiles.test.ts b/tests/boundary/cli/clientProfiles.test.ts
index 092ce65d0c..700001753f 100644
--- a/tests/boundary/cli/clientProfiles.test.ts
+++ b/tests/boundary/cli/clientProfiles.test.ts
@@ -6,6 +6,128 @@ import { PRODUCT_IDENTITY } from "../../../src/identity.js";
 import { createTestTempDirectory } from "../../fixtures/temporaryDirectory.js";
 import { cliTest } from "../../support/cli/cliFixture.js";
 
+cliTest(
+  "Claude Code routes an empty config directory to its home registration",
+  async ({ cli }) => {
+    const root = await createTestTempDirectory("rea-claude-empty-config-dir-");
+    const home = join(root, "home");
+    const cwd = join(root, "work");
+    const config = join(home, ".claude.json");
+    const backup = `${config}.rea.backup`;
+    const skill = join(home, ".claude", "skills", PRODUCT_IDENTITY.skillName);
+    const cwdSkill = join(cwd, "skills", PRODUCT_IDENTITY.skillName);
+    const original = JSON.stringify({
+      theme: "dark",
+      mcpServers: { other: { command: "other" } },
+    });
+    await mkdir(home, { recursive: true });
+    await mkdir(cwd, { recursive: true });
+    await writeFile(config, original);
+    const run = (arguments_: readonly string[]) =>
+      cli.run({
+        arguments: arguments_,
+        cwd,
+        environment: {
+          HOME: home,
+          USERPROFILE: home,
+          CLAUDE_CONFIG_DIR: "",
+        },
+        timeoutMs: 20_000,
+      });
+    const setup = (flags: readonly string[] = []) =>
+      run(["setup", "--client", "claude_code", ...flags, "--json"]);
+
+    const planned = await setup(["--dry-run"]);
+    expect(planned.exitCode, planned.stderr).toBe(0);
+    expect(planned.json).toMatchObject({
+      status: "planned",
+      plannedActions: expect.arrayContaining([
+        expect.objectContaining({
+          id: "configure_client:claude_code",
+          target: config,
+          backupPath: backup,
+        }),
+        expect.objectContaining({
+          id: "install_skill:claude_code",
+          target: skill,
+        }),
+      ]),
+    });
+    expect(await readFile(config, "utf8")).toBe(original);
+    await expect(access(join(cwd, ".claude.json"))).rejects.toMatchObject({
+      code: "ENOENT",
+    });
+    await expect(access(join(skill, "SKILL.md"))).rejects.toMatchObject({
+      code: "ENOENT",
+    });
+    await expect(access(join(cwdSkill, "SKILL.md"))).rejects.toMatchObject({
+      code: "ENOENT",
+    });
+    await expect(access(backup)).rejects.toMatchObject({ code: "ENOENT" });
+
+    const applied = await setup(["--yes"]);
+    expect(applied.exitCode, applied.stderr).toBe(0);
+    expect(applied.json).toMatchObject({ status: "ready" });
+    expect(await readFile(backup, "utf8")).toBe(original);
+    expect(parse(await readFile(config, "utf8"))).toMatchObject({
+      theme: "dark",
+      mcpServers: {
+        other: { command: "other" },
+        rea: expect.any(Object),
+      },
+    });
+    await expect(access(join(skill, "SKILL.md"))).resolves.toBeUndefined();
+    await expect(access(join(cwd, ".claude.json"))).rejects.toMatchObject({
+      code: "ENOENT",
+    });
+    await expect(access(join(cwdSkill, "SKILL.md"))).rejects.toMatchObject({
+      code: "ENOENT",
+    });
+
+    const repeat = await setup(["--yes"]);
+    expect(repeat.exitCode, repeat.stderr).toBe(0);
+    expect(repeat.json).toMatchObject({
+      status: "ready",
+      appliedActions: [],
+    });
+    expect(await readFile(backup, "utf8")).toBe(original);
+    const doctor = await run([
+      "doctor",
+      "--client",
+      "claude_code",
+      "--skill",
+      "--json",
+    ]);
+    expect(doctor.exitCode, doctor.stderr).toBe(0);
+    expect(doctor.json).toMatchObject({
+      healthy: true,
+      identity: {
+        skill: { state: "aligned" },
+        registrations: expect.arrayContaining([
+          expect.objectContaining({ client: "claude_code", state: "aligned" }),
+        ]),
+      },
+    });
+
+    const uninstall = await run(["uninstall", "--json"]);
+    expect(uninstall.exitCode, uninstall.stderr).toBe(0);
+    expect(uninstall.json).toMatchObject({ status: "complete" });
+    expect(parse(await readFile(config, "utf8"))).toEqual({
+      theme: "dark",
+      mcpServers: { other: { command: "other" } },
+    });
+    await expect(access(join(skill, "SKILL.md"))).rejects.toMatchObject({
+      code: "ENOENT",
+    });
+    await expect(access(join(cwd, ".claude.json"))).rejects.toMatchObject({
+      code: "ENOENT",
+    });
+    await expect(access(join(cwdSkill, "SKILL.md"))).rejects.toMatchObject({
+      code: "ENOENT",
+    });
+  },
+);
+
 for (const policy of [{ excluded: ["rea"] }, { allowed: ["other"] }]) {
   cliTest(
     `Gemini refuses a registration blocked by ${Object.keys(policy)[0]}`,