diff --git a/src/shared/jsonc-parser.memoization.test.ts b/src/shared/jsonc-parser.memoization.test.ts
new file mode 100644
index 000000000..c4cd1f5b8
--- /dev/null
+++ b/src/shared/jsonc-parser.memoization.test.ts
@@ -0,0 +1,54 @@
+import { afterEach, describe, expect, mock, spyOn, test } from "bun:test"
+import * as fs from "node:fs"
+import { join } from "node:path"
+
+describe("detectPluginConfigFile memoization", () => {
+  const testDir = join(__dirname, ".test-detect-plugin-memoization")
+
+  afterEach(() => {
+    mock.restore()
+  })
+
+  test("returns cached result on repeated calls for the same directory", async () => {
+    // given
+    const existsSync = spyOn(fs, "existsSync").mockImplementation((filePath: fs.PathLike) => {
+      return String(filePath).endsWith("oh-my-openagent.jsonc")
+    })
+    const readdirSync = spyOn(fs, "readdirSync").mockImplementation(() => [])
+    spyOn(fs, "readFileSync").mockImplementation(() => "")
+
+    const parserModule = await import(`./jsonc-parser?memoization=${Date.now()}-${Math.random()}`)
+
+    // when
+    const firstResult = parserModule.detectPluginConfigFile(testDir)
+    const callsAfterFirstResult = existsSync.mock.calls.length
+    const secondResult = parserModule.detectPluginConfigFile(testDir)
+
+    // then
+    expect(firstResult).toEqual(secondResult)
+    expect(existsSync.mock.calls.length).toBe(callsAfterFirstResult)
+    expect(readdirSync).toHaveBeenCalledTimes(0)
+  })
+
+  test("clears cached result when requested", async () => {
+    // given
+    const existsSync = spyOn(fs, "existsSync").mockImplementation((filePath: fs.PathLike) => {
+      return String(filePath).endsWith("oh-my-openagent.jsonc")
+    })
+    const readdirSync = spyOn(fs, "readdirSync").mockImplementation(() => [])
+    spyOn(fs, "readFileSync").mockImplementation(() => "")
+
+    const parserModule = await import(`./jsonc-parser?memoization=${Date.now()}-${Math.random()}`)
+
+    parserModule.detectPluginConfigFile(testDir)
+    parserModule.clearPluginConfigFileDetectionCache()
+    const callsAfterClear = existsSync.mock.calls.length
+
+    // when
+    parserModule.detectPluginConfigFile(testDir)
+
+    // then
+    expect(existsSync.mock.calls.length).toBeGreaterThan(callsAfterClear)
+    expect(readdirSync).toHaveBeenCalledTimes(0)
+  })
+})
diff --git a/src/shared/jsonc-parser.test.ts b/src/shared/jsonc-parser.test.ts
index 279db1fc5..c06e36353 100644
--- a/src/shared/jsonc-parser.test.ts
+++ b/src/shared/jsonc-parser.test.ts
@@ -1,5 +1,5 @@
-import { describe, expect, test } from "bun:test"
-import { detectConfigFile, detectPluginConfigFile, parseJsonc, parseJsoncSafe, readJsoncFile } from "./jsonc-parser"
+import { afterEach, beforeEach, describe, expect, test } from "bun:test"
+import { clearPluginConfigFileDetectionCache, detectConfigFile, detectPluginConfigFile, parseJsonc, parseJsoncSafe, readJsoncFile } from "./jsonc-parser"
 import { existsSync, mkdirSync, rmSync, writeFileSync } from "node:fs"
 import { join } from "node:path"
 
@@ -330,6 +330,14 @@ describe("detectConfigFile", () => {
 describe("detectPluginConfigFile", () => {
   const testDir = join(__dirname, ".test-detect-plugin")
 
+  beforeEach(() => {
+    clearPluginConfigFileDetectionCache()
+  })
+
+  afterEach(() => {
+    clearPluginConfigFileDetectionCache()
+  })
+
   test("prefers oh-my-openagent over oh-my-opencode when both jsonc files exist", () => {
     // given
     if (!existsSync(testDir)) mkdirSync(testDir, { recursive: true })