diff --git a/src/features/opencode-skill-loader/project-skill-discovery.test.ts b/src/features/opencode-skill-loader/project-skill-discovery.test.ts
new file mode 100644
index 000000000..0d34da8ea
--- /dev/null
+++ b/src/features/opencode-skill-loader/project-skill-discovery.test.ts
@@ -0,0 +1,86 @@
+import { execFileSync } from "node:child_process"
+import { afterEach, beforeEach, describe, expect, it } from "bun:test"
+import { mkdtempSync, mkdirSync, rmSync, writeFileSync } from "node:fs"
+import { tmpdir } from "node:os"
+import { join } from "node:path"
+import {
+  discoverOpencodeProjectSkills,
+  discoverProjectAgentsSkills,
+  discoverProjectClaudeSkills,
+} from "./loader"
+
+function writeSkill(directory: string, name: string, description: string): void {
+  mkdirSync(directory, { recursive: true })
+  writeFileSync(
+    join(directory, "SKILL.md"),
+    `---\nname: ${name}\ndescription: ${description}\n---\nBody\n`,
+  )
+}
+
+describe("project skill discovery", () => {
+  let tempDir = ""
+
+  beforeEach(() => {
+    tempDir = mkdtempSync(join(tmpdir(), "omo-project-skill-discovery-"))
+  })
+
+  afterEach(() => {
+    rmSync(tempDir, { recursive: true, force: true })
+  })
+
+  it("discovers ancestor project skill directories up to the worktree root", async () => {
+    // given
+    const repositoryDir = join(tempDir, "repo")
+    const nestedDirectory = join(repositoryDir, "packages", "app", "src")
+
+    mkdirSync(nestedDirectory, { recursive: true })
+    execFileSync("git", ["init"], {
+      cwd: repositoryDir,
+      stdio: ["ignore", "ignore", "ignore"],
+    })
+
+    writeSkill(
+      join(repositoryDir, ".claude", "skills", "repo-claude"),
+      "repo-claude",
+      "Discovered from the repository root",
+    )
+    writeSkill(
+      join(repositoryDir, ".agents", "skills", "repo-agents"),
+      "repo-agents",
+      "Discovered from the repository root",
+    )
+    writeSkill(
+      join(repositoryDir, ".opencode", "skill", "repo-opencode"),
+      "repo-opencode",
+      "Discovered from the repository root",
+    )
+
+    writeSkill(
+      join(tempDir, ".claude", "skills", "outside-claude"),
+      "outside-claude",
+      "Should stay outside the worktree",
+    )
+    writeSkill(
+      join(tempDir, ".agents", "skills", "outside-agents"),
+      "outside-agents",
+      "Should stay outside the worktree",
+    )
+    writeSkill(
+      join(tempDir, ".opencode", "skills", "outside-opencode"),
+      "outside-opencode",
+      "Should stay outside the worktree",
+    )
+
+    // when
+    const [claudeSkills, agentSkills, opencodeSkills] = await Promise.all([
+      discoverProjectClaudeSkills(nestedDirectory),
+      discoverProjectAgentsSkills(nestedDirectory),
+      discoverOpencodeProjectSkills(nestedDirectory),
+    ])
+
+    // then
+    expect(claudeSkills.map(skill => skill.name)).toEqual(["repo-claude"])
+    expect(agentSkills.map(skill => skill.name)).toEqual(["repo-agents"])
+    expect(opencodeSkills.map(skill => skill.name)).toEqual(["repo-opencode"])
+  })
+})