feat(checks): add duplicate-name rule

README.md

@@ -98,6 +98,7 @@ Exit codes:
 | `name-drift` | warn | Frontmatter `name:` doesn't match the filename or directory |
 | `description-collision` | warn | Two skills' descriptions have Jaccard ≥ 0.6 |
 | `tools-overloaded` | warn | `tools:` lists 10 or more entries; narrow the list to what this skill actually needs |
+| `duplicate-name` | warn | Two or more skills share the same `name:` value; resolution is ambiguous |
 | `parse` | error | The file doesn't have valid frontmatter / YAML |
 
 The MCP and built-in tool checks read `~/.claude/settings.json` and

src/checks.ts

@@ -36,6 +36,7 @@ export function runChecks(
   }
 
   diagnostics.push(...checkCollisions(validated));
+  diagnostics.push(...checkDuplicateNames(validated));
   return diagnostics;
 }
 
@@ -206,3 +207,30 @@ function checkCollisions(skills: ValidatedSkill[]): Diagnostic[] {
   }
   return out;
 }
+
+function checkDuplicateNames(skills: ValidatedSkill[]): Diagnostic[] {
+  const byName = new Map<string, ValidatedSkill[]>();
+  for (const s of skills) {
+    const key = s.name.toLowerCase();
+    const group = byName.get(key) ?? [];
+    group.push(s);
+    byName.set(key, group);
+  }
+  const out: Diagnostic[] = [];
+  for (const group of byName.values()) {
+    if (group.length < 2) continue;
+    for (const s of group) {
+      const others = group
+        .filter((g) => g.file !== s.file)
+        .map((g) => `'${g.file}'`)
+        .join(", ");
+      out.push({
+        severity: "warn",
+        rule: "duplicate-name",
+        message: `skill name '${s.name}' is also declared in ${others}`,
+        file: s.file,
+      });
+    }
+  }
+  return out;
+}

test/checks.test.ts

@@ -234,4 +234,34 @@ describe("runChecks", () => {
     const ds = runChecks([s], config);
     expect(ds.find((d) => d.rule === "empty-body")).toBeUndefined();
   });
+
+  it("flags duplicate skill names", () => {
+    const a = mkSkill("/test/a/deploy.md", { name: "deploy", description: "deploy the app" });
+    const b = mkSkill("/test/b/deploy.md", { name: "deploy", description: "deploy to staging" });
+    const ds = runChecks([a, b], config);
+    expect(ds.filter((d) => d.rule === "duplicate-name").length).toBe(2);
+  });
+
+  it("does not flag duplicate-name for unique names", () => {
+    const a = mkSkill("/test/a/deploy.md", { name: "deploy", description: "deploy the app" });
+    const b = mkSkill("/test/b/release.md", { name: "release", description: "cut a release" });
+    const ds = runChecks([a, b], config);
+    expect(ds.find((d) => d.rule === "duplicate-name")).toBeUndefined();
+  });
+
+  it("flags all skills in a three-way duplicate-name group", () => {
+    const a = mkSkill("/test/a/foo.md", { name: "foo", description: "do foo one way" });
+    const b = mkSkill("/test/b/foo.md", { name: "foo", description: "do foo another way" });
+    const c = mkSkill("/test/c/foo.md", { name: "foo", description: "do foo a third way" });
+    const ds = runChecks([a, b, c], config);
+    expect(ds.filter((d) => d.rule === "duplicate-name").length).toBe(3);
+  });
+
+  it("duplicate-name message names the conflicting file", () => {
+    const a = mkSkill("/test/a/deploy.md", { name: "deploy", description: "deploy the app" });
+    const b = mkSkill("/test/b/deploy.md", { name: "deploy", description: "deploy to staging" });
+    const ds = runChecks([a, b], config);
+    const diagA = ds.find((d) => d.rule === "duplicate-name" && d.file === "/test/a/deploy.md");
+    expect(diagA?.message).toContain("/test/b/deploy.md");
+  });
 });