fix(hooks): reuse shared legacy plugin migration helper

Replace the legacy toast regex writer with the shared atomic helper and route legacy plugin call sites through small wrappers so existing mock.module tests stop leaking across the suite.

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-runner.ts

@@ -0,0 +1,2 @@
+export { autoMigrateLegacyPluginEntry } from "./auto-migrate"
+export type { MigrationResult } from "./auto-migrate"

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

@@ -1,9 +1,10 @@
-import { existsSync, readFileSync, writeFileSync } from "node:fs"
+import { existsSync, readFileSync } from "node:fs"
 import { join } from "node:path"
 
 import { parseJsoncSafe } from "../../shared/jsonc-parser"
 import { getOpenCodeConfigPaths } from "../../shared/opencode-config-dir"
 import { LEGACY_PLUGIN_NAME, PLUGIN_NAME } from "../../shared/plugin-identity"
+import { migrateLegacyPluginEntry } from "./plugin-entry-migrator"
 
 export interface MigrationResult {
   migrated: boolean
@@ -63,27 +64,15 @@ export function autoMigrateLegacyPluginEntry(overrideConfigDir?: string): Migrat
     const hasCanonical = plugins.some(isCanonicalEntry)
     const from = legacyEntries[0]
     const to = toLegacyCanonical(from)
+    const migrated = migrateLegacyPluginEntry(configPath)
+    if (!migrated) return { migrated: false, from: null, to: null, configPath }
 
-    const normalized = hasCanonical
-      ? plugins.filter((p) => !isLegacyEntry(p))
-      : plugins.map((p) => (isLegacyEntry(p) ? toLegacyCanonical(p) : p))
-
-    const isJsonc = configPath.endsWith(".jsonc")
-    if (isJsonc) {
-      const pluginArrayRegex = /((?:"plugin"|plugin)\s*:\s*)\[([\s\S]*?)\]/
-      const match = content.match(pluginArrayRegex)
-      if (match) {
-        const formattedPlugins = normalized.map((p) => `"${p}"`).join(",\n    ")
-        const newContent = content.replace(pluginArrayRegex, `$1[\n    ${formattedPlugins}\n  ]`)
-        writeFileSync(configPath, newContent)
-        return { migrated: true, from, to, configPath }
-      }
+    return {
+      migrated: true,
+      from,
+      to: hasCanonical ? PLUGIN_NAME : to,
+      configPath,
     }
-
-    const parsed = JSON.parse(content) as Record<string, unknown>
-    parsed.plugin = normalized
-    writeFileSync(configPath, JSON.stringify(parsed, null, 2) + "\n")
-    return { migrated: true, from, to, configPath }
   } catch {
     return { migrated: false, from: null, to: null, configPath }
   }

src/hooks/legacy-plugin-toast/hook.test.ts

@@ -1,5 +1,5 @@
 import { afterAll, beforeEach, describe, expect, it, mock } from "bun:test"
-import type { MigrationResult } from "./auto-migrate"
+import type { MigrationResult } from "./auto-migrate-runner"
 
 const mockCheckForLegacyPluginEntry = mock(() => ({
   hasLegacyEntry: false,
@@ -26,7 +26,7 @@ mock.module("../../shared/logger", () => ({
   log: mockLog,
 }))
 
-mock.module("./auto-migrate", () => ({
+mock.module("./auto-migrate-runner", () => ({
   autoMigrateLegacyPluginEntry: mockAutoMigrate,
 }))
 

src/hooks/legacy-plugin-toast/hook.ts

@@ -3,7 +3,7 @@ import type { PluginInput } from "@opencode-ai/plugin"
 import { checkForLegacyPluginEntry } from "../../shared/legacy-plugin-warning"
 import { log } from "../../shared/logger"
 import { LEGACY_PLUGIN_NAME, PLUGIN_NAME } from "../../shared/plugin-identity"
-import { autoMigrateLegacyPluginEntry } from "./auto-migrate"
+import { autoMigrateLegacyPluginEntry } from "./auto-migrate-runner"
 
 export function createLegacyPluginToastHook(ctx: PluginInput) {
   let fired = false

src/hooks/legacy-plugin-toast/plugin-entry-migrator.ts

@@ -0,0 +1 @@
+export { migrateLegacyPluginEntry } from "../../shared/migrate-legacy-plugin-entry"

src/shared/log-legacy-plugin-startup-warning.test.ts

@@ -26,7 +26,7 @@ mock.module("./logger", () => ({
   log: mockLog,
 }))
 
-mock.module("./migrate-legacy-plugin-entry", () => ({
+mock.module("./plugin-entry-migrator", () => ({
   migrateLegacyPluginEntry: mockMigrateLegacyPluginEntry,
 }))
 

src/shared/log-legacy-plugin-startup-warning.ts

@@ -1,6 +1,6 @@
 import { checkForLegacyPluginEntry } from "./legacy-plugin-warning"
 import { log } from "./logger"
-import { migrateLegacyPluginEntry } from "./migrate-legacy-plugin-entry"
+import { migrateLegacyPluginEntry } from "./plugin-entry-migrator"
 import { LEGACY_PLUGIN_NAME, PLUGIN_NAME } from "./plugin-identity"
 
 function toCanonicalEntry(entry: string): string {

src/shared/plugin-entry-migrator.ts

@@ -0,0 +1 @@
+export { migrateLegacyPluginEntry } from "./migrate-legacy-plugin-entry"