fix(setup): preserve configuration directory requirements

src/application/ClientConfigPath.ts

@@ -74,10 +74,17 @@ const canonicalRegularConfigPath = async (
 ): Promise<string | undefined> => {
   if (fileSystem.realpath === undefined) return requestedPath;
   let ancestor = absoluteCallerPath(requestedPath);
+  const directoryRequired =
+    process.platform !== "win32" && ancestor.endsWith("/");
   const missing: string[] = [];
   while (true) {
     try {
-      return join(await fileSystem.realpath(ancestor), ...missing);
+      const canonical = join(await fileSystem.realpath(ancestor), ...missing);
+      // Reconstructing missing children must retain the caller's directory
+      // requirement; otherwise a missing `config.json/` becomes a writable file.
+      return directoryRequired && !canonical.endsWith("/")
+        ? `${canonical}/`
+        : canonical;
     } catch (cause: unknown) {
       if (!isAbsentPath(cause) || dirname(ancestor) === ancestor)
         return requestedPath;

src/application/ClientConfigurationPublication.ts

@@ -84,7 +84,10 @@ export class ClientConfigurationPublication {
     selection?: ClientConfigurationSelection,
   ): Promise<ClientConfigurationPublication> {
     const parent = await realpath(dirname(path));
-    const destination = join(parent, basename(path));
+    // Retain the transaction owner's directory requirement through final-file
+    // publication rather than allowing basename/join to select a regular file.
+    const destination =
+      join(parent, basename(path)) + (path.endsWith(sep) ? sep : "");
     const input = await selectedConfiguration(destination, previous);
     if (selection !== undefined) {
       await assertRequestedConfigurationPath(path, selection.requestedPath);

tests/acceptance/setup/hermesClientSetup.test.ts

@@ -40,7 +40,7 @@ for (const [version, keyStyle] of [
         "timestamp: 2026-10-14T00:00:00.123456+08:00\n";
       const original =
         settings +
-        "mcp_servers:\n  rea:\n    command: rea-old\n    args: [mcp]\n    env:\n" +
+        "mcp_servers:\n  rea:\n    command: rea\n    args: [mcp]\n    env:\n" +
         Object.entries(environment)
           .map(
             ([key, value]) =>
@@ -114,7 +114,7 @@ cliTest(
       "# Caller configuration",
       "mcp_servers:",
       "  rea:",
-      "    command: rea-old",
+      "    command: rea",
       "    args: [mcp]",
       "    env:",
       "      CALLER_SETTING: keep exactly",
@@ -173,7 +173,7 @@ cliTest(
       },
     });
     expect(parse(configured)).not.toMatchObject({
-      mcp_servers: { rea: { command: "rea-old" } },
+      mcp_servers: { rea: { command: "rea" } },
     });
     expect(configured).toContain("# Curated for this client.");
     expect(await readFile(`${config}.rea.backup`, "utf8")).toBe(original);

tests/boundary/filesystem/setupConfig.test.ts

@@ -7,7 +7,7 @@ import {
   symlink,
   writeFile,
 } from "node:fs/promises";
-import { join } from "node:path";
+import { join, relative } from "node:path";
 import { describe, expect, it } from "vitest";
 import { parse as parseToml } from "smol-toml";
 
@@ -25,6 +25,7 @@ import { supportedClients } from "../../../src/application/SupportedClients.js";
 import { readClientRegistrationStatuses } from "../../../src/application/ClientRegistrationStatus.js";
 import { failedConfigurationMessage } from "../../../src/application/SetupClients.js";
 import { PRODUCT_IDENTITY } from "../../../src/identity.js";
+import { CURRENT_ENTRYPOINT_PATH } from "../../../src/process/CurrentEntrypointPath.js";
 
 const pinnedPackage = PRODUCT_IDENTITY.registrationPackageSpecifier;
 
@@ -34,9 +35,9 @@ it.skipIf(process.platform === "win32")(
     const home = await createTestTempDirectory(
       "rea-config-equivalent-launcher-",
     );
-    const real = join(home, "rea-current");
+    const real = CURRENT_ENTRYPOINT_PATH;
+    if (real === undefined) throw new Error("missing current entrypoint");
     const alias = join(home, "rea-alias");
-    await writeFile(real, "current launcher\n");
     await symlink(real, alias);
     await mkdir(join(home, ".cursor"));
     const configPath = join(home, ".cursor", "mcp.json");
@@ -76,9 +77,9 @@ it.skipIf(process.platform === "win32")(
     const home = await createTestTempDirectory(
       "rea-config-timeout-launcher-alias-",
     );
-    const real = join(home, "rea-current");
+    const real = CURRENT_ENTRYPOINT_PATH;
+    if (real === undefined) throw new Error("missing current entrypoint");
     const alias = join(home, "rea-alias");
-    await writeFile(real, "current launcher\n");
     await symlink(real, alias);
     await mkdir(join(home, ".codex"));
     const configPath = join(home, ".codex", "config.toml");
@@ -157,6 +158,37 @@ it.skipIf(process.platform === "win32").each([false, true])(
   },
 );
 
+it
+  .skipIf(process.platform === "win32")
+  .each(
+    ["/", "/."].flatMap((suffix) =>
+      [false, true].map((relativePath) => ({ suffix, relativePath })),
+    ),
+  )(
+  "rejects a missing configuration with directory suffix $suffix and relative=$relativePath",
+  async ({ suffix, relativePath }) => {
+    const root = await createTestTempDirectory("rea-config-directory-suffix-");
+    const path = join(root, "config.json");
+    const requested = `${relativePath ? relative(process.cwd(), path) : path}${suffix}`;
+    expect(await resolveClientConfigTransactionPath(requested)).toBe(
+      `${path}/`,
+    );
+    expect(
+      await configureClientConfiguration({
+        name: "cursor",
+        format: "json",
+        configPath: requested,
+      }),
+    ).toMatchObject({ status: "failed" });
+    const selected = await lstat(path).catch((cause: unknown) => {
+      if (cause instanceof Error && "code" in cause && cause.code === "ENOENT")
+        return undefined;
+      throw cause;
+    });
+    expect(selected?.isFile() ?? false).toBe(false);
+  },
+);
+
 describe("JSON client configuration transaction: writing configuration through safe paths", () => {
   it.skipIf(typeof process.getuid !== "function")(
     "rejects a symlink target not owned by the current user",