fix(build): compare routed CLI bin collisions case-insensitively (AB4766)

Codex review on #419: a host-emitted `bin/MyPlugin.mjs` is the same file
as the generated `bin/myplugin.mjs` on macOS and Windows, so the collision
check folds case and names both paths in the diagnostic.

Author: ScriptedAlchemy

docs/diagnostics.md

@@ -402,7 +402,7 @@ that claims the same path. See “The routed CLI shell” in
 | Code | Severity | Trigger |
 | --- | --- | --- |
 | `AB4765` | warning | The project has a routed CLI but a selected target's adapter publishes no supported `cli` capability, so that artifact ships no `bin/<name>.mjs`. Skills, hooks, and scripts in that artifact cannot invoke the routed CLI. `inspect` lists the same omission as an `unsupported-capability` skip of the `cli` component. Publish the capability (with a `cliBin` artifact layout) on the adapter, or keep references to the bin out of that target's surfaces. |
-| `AB4766` | error (build) | A target plan already emits `bin/<name>.mjs` or `bin/<name>-flight.mjs` (for example a Claude `claude.bin` directory shipping a file of that name). The routed CLI owns those paths, so the build refuses instead of choosing. Rename or remove the host-emitted file, or set `bin: false` to keep it and drop the routed CLI executable. |
+| `AB4766` | error (build) | A target plan already emits `bin/<name>.mjs` or `bin/<name>-flight.mjs` (for example a Claude `claude.bin` directory shipping a file of that name), compared case-insensitively because those are one file on macOS and Windows. The routed CLI owns those paths, so the build refuses instead of choosing. Rename or remove the host-emitted file, or set `bin: false` to keep it and drop the routed CLI executable. |
 
 ## Config beside a route-generated MCP server (`AB4340`)
 

packages/agent-bundle/src/build/cli-bins.ts

@@ -203,22 +203,34 @@ export const compileCliBins = async (
  * AB4766: the routed CLI bin's artifact paths are framework-owned. A target
  * plan that already places a file there (for example a Claude `claude.bin`
  * directory shipping `<plugin-name>.mjs`) cannot be merged silently, so the
- * build refuses with the colliding paths named.
+ * build refuses with the colliding paths named. Paths are compared
+ * case-folded: on the case-insensitive filesystems most plugins are developed
+ * and installed on, `bin/MyPlugin.mjs` and `bin/myplugin.mjs` are one file,
+ * and a name that differs only by case is a hazard everywhere else.
  */
 export const cliBinCollisionDiagnostics = (
   model: NormalizedPlugin,
   target: string,
   entries: readonly TargetArtifactEntry[],
 ): readonly Diagnostic[] => {
-  const planned = new Set(entries.map((entry) => entry.relativePath));
+  const planned = new Map<string, string>();
+  for (const entry of entries) {
+    const folded = entry.relativePath.toLowerCase();
+    if (!planned.has(folded)) planned.set(folded, entry.relativePath);
+  }
   return Object.freeze(routedCliBins(model).flatMap((bin) => {
     const rendered = generatedCli(bin).commands.some((command) => command.rendered);
     return [cliBinArtifactPath(bin.name), ...(rendered ? [cliBinWorkerArtifactPath(bin.name)] : [])]
-      .filter((path) => planned.has(path))
-      .map((path): Diagnostic => ({
+      .flatMap((owned) => {
+        const emitted = planned.get(owned.toLowerCase());
+        return emitted === undefined ? [] : [{ emitted, owned }];
+      })
+      .map(({ emitted, owned }): Diagnostic => ({
         code: 'AB4766',
-        message: `Target ${JSON.stringify(target)} already emits ${JSON.stringify(path)}, which the routed CLI bin ${JSON.stringify(bin.name)} owns; the compiler never chooses silently.`,
-        recovery: `Rename or remove the host-emitted ${JSON.stringify(path)} (for example the file in the configured claude.bin directory), or set bin: false to keep the host file and drop the routed CLI executable.`,
+        message: emitted === owned
+          ? `Target ${JSON.stringify(target)} already emits ${JSON.stringify(emitted)}, which the routed CLI bin ${JSON.stringify(bin.name)} owns; the compiler never chooses silently.`
+          : `Target ${JSON.stringify(target)} already emits ${JSON.stringify(emitted)}, which differs only by case from ${JSON.stringify(owned)} owned by the routed CLI bin ${JSON.stringify(bin.name)}; on a case-insensitive filesystem they are one file, so the compiler never chooses silently.`,
+        recovery: `Rename or remove the host-emitted ${JSON.stringify(emitted)} (for example the file in the configured claude.bin directory), or set bin: false to keep the host file and drop the routed CLI executable.`,
         severity: 'error',
         sourcePath: bin.provenance.sourcePath,
         target,

packages/agent-bundle/tests/artifact-cli-bin.test.ts

@@ -290,6 +290,11 @@ it('refuses a host-emitted file that collides with the routed CLI bin (AB4766)',
   // CLI owns: the compiler never chooses between them silently.
   await writeProjectFile(root, `host-bin/${pluginName}.mjs`, "console.log('host bin');\n");
   await chmod(join(root, 'host-bin', `${pluginName}.mjs`), 0o755);
+  // A second entry differing only by case is the same file on macOS and
+  // Windows, so it is a collision too and is named beside the owned path.
+  const caseVariant = `${pluginName.toUpperCase()}-flight.mjs`;
+  await writeProjectFile(root, `host-bin/${caseVariant}`, "console.log('host worker');\n");
+  await chmod(join(root, 'host-bin', caseVariant), 0o755);
   await writeProjectFile(root, 'agent-bundle.config.ts', [
     "import { defineConfig } from 'agent-bundle/config';",
     'export default defineConfig({',
@@ -300,8 +305,12 @@ it('refuses a host-emitted file that collides with the routed CLI bin (AB4766)',
     '',
   ].join('\n'));
 
-  await expect(build({ output: 'artifact', root })).rejects.toThrow(
+  const failure = build({ output: 'artifact', root });
+  await expect(failure).rejects.toThrow(
     new RegExp(`\\[AB4766\\] Target "claude" already emits "bin/${pluginName}\\.mjs"`, 'u'),
   );
+  await expect(failure).rejects.toThrow(
+    new RegExp(`\\[AB4766\\] Target "claude" already emits "bin/${caseVariant}", which differs only by case from "bin/${pluginName}-flight\\.mjs"`, 'u'),
+  );
   await expect(stat(join(root, 'artifact'))).rejects.toMatchObject({ code: 'ENOENT' });
 });