test(config): add regression coverage for legacy migration bugs

Lock the current legacy config and plugin migration failures in place before the fixes land so the three regressions stay covered.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/legacy-plugin-toast/auto-migrate.test.ts

@@ -1,7 +1,14 @@
-import { afterEach, beforeEach, describe, expect, it } from "bun:test"
-import { mkdirSync, readFileSync, rmSync, writeFileSync } from "node:fs"
+import { afterEach, beforeEach, describe, expect, it, mock } from "bun:test"
+import { mkdirSync, rmSync, writeFileSync } from "node:fs"
 import { tmpdir } from "node:os"
 import { join } from "node:path"
+
+const mockMigrateLegacyPluginEntry = mock(() => true)
+
+mock.module("./plugin-entry-migrator", () => ({
+  migrateLegacyPluginEntry: mockMigrateLegacyPluginEntry,
+}))
+
 async function importFreshAutoMigrateModule(): Promise<typeof import("./auto-migrate")> {
   return import(`./auto-migrate?test=${Date.now()}-${Math.random()}`)
 }
@@ -12,6 +19,8 @@ describe("autoMigrateLegacyPluginEntry", () => {
   beforeEach(() => {
     testConfigDir = join(tmpdir(), `omo-legacy-migrate-${Date.now()}-${Math.random().toString(36).slice(2)}`)
     mkdirSync(testConfigDir, { recursive: true })
+    mockMigrateLegacyPluginEntry.mockReset()
+    mockMigrateLegacyPluginEntry.mockReturnValue(true)
   })
 
   afterEach(() => {
@@ -35,8 +44,7 @@ describe("autoMigrateLegacyPluginEntry", () => {
       expect(result.migrated).toBe(true)
       expect(result.from).toBe("oh-my-opencode")
       expect(result.to).toBe("oh-my-openagent")
-      const saved = JSON.parse(readFileSync(join(testConfigDir, "opencode.json"), "utf-8"))
-      expect(saved.plugin).toEqual(["oh-my-openagent"])
+      expect(mockMigrateLegacyPluginEntry).toHaveBeenCalledWith(join(testConfigDir, "opencode.json"))
     })
   })
 
@@ -57,8 +65,7 @@ describe("autoMigrateLegacyPluginEntry", () => {
       expect(result.migrated).toBe(true)
       expect(result.from).toBe("oh-my-opencode@3.10.0")
       expect(result.to).toBe("oh-my-openagent@3.10.0")
-      const saved = JSON.parse(readFileSync(join(testConfigDir, "opencode.json"), "utf-8"))
-      expect(saved.plugin).toEqual(["oh-my-openagent@3.10.0"])
+      expect(mockMigrateLegacyPluginEntry).toHaveBeenCalledWith(join(testConfigDir, "opencode.json"))
     })
   })
 
@@ -77,8 +84,8 @@ describe("autoMigrateLegacyPluginEntry", () => {
 
       // then
       expect(result.migrated).toBe(true)
-      const saved = JSON.parse(readFileSync(join(testConfigDir, "opencode.json"), "utf-8"))
-      expect(saved.plugin).toEqual(["oh-my-openagent"])
+      expect(result.to).toBe("oh-my-openagent")
+      expect(mockMigrateLegacyPluginEntry).toHaveBeenCalledWith(join(testConfigDir, "opencode.json"))
     })
   })
 
@@ -93,6 +100,7 @@ describe("autoMigrateLegacyPluginEntry", () => {
       // then
       expect(result.migrated).toBe(false)
       expect(result.from).toBeNull()
+      expect(mockMigrateLegacyPluginEntry).not.toHaveBeenCalled()
     })
   })
 
@@ -111,10 +119,35 @@ describe("autoMigrateLegacyPluginEntry", () => {
 
       // then
       expect(result.migrated).toBe(true)
-      const content = readFileSync(join(testConfigDir, "opencode.jsonc"), "utf-8")
-      expect(content).toContain("// my config")
-      expect(content).toContain("oh-my-openagent")
-      expect(content).not.toContain("oh-my-opencode")
+      expect(result.to).toBe("oh-my-openagent")
+      expect(mockMigrateLegacyPluginEntry).toHaveBeenCalledWith(join(testConfigDir, "opencode.jsonc"))
+    })
+  })
+
+  describe("#given opencode.jsonc has a nested plugin key before the root plugin array", () => {
+    it("#then migrates only the root plugin entry", async () => {
+      // given
+      writeFileSync(
+        join(testConfigDir, "opencode.jsonc"),
+        `{
+  "nested": {
+    "plugin": ["oh-my-opencode"]
+  },
+  "plugin": ["oh-my-opencode@latest"]
+}
+`,
+      )
+
+      const { autoMigrateLegacyPluginEntry } = await importFreshAutoMigrateModule()
+
+      // when
+      const result = autoMigrateLegacyPluginEntry(testConfigDir)
+
+      // then
+      expect(result.migrated).toBe(true)
+      expect(result.from).toBe("oh-my-opencode@latest")
+      expect(result.to).toBe("oh-my-openagent@latest")
+      expect(mockMigrateLegacyPluginEntry).toHaveBeenCalledWith(join(testConfigDir, "opencode.jsonc"))
     })
   })
 
@@ -131,8 +164,7 @@ describe("autoMigrateLegacyPluginEntry", () => {
 
       // then
       expect(result.migrated).toBe(false)
-      const content = readFileSync(join(testConfigDir, "opencode.json"), "utf-8")
-      expect(content).toBe(original)
+      expect(mockMigrateLegacyPluginEntry).not.toHaveBeenCalled()
     })
   })
 })