diff --git a/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/.oxfmtrc.json b/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/.oxfmtrc.json
new file mode 100644
index 0000000000..fd496a820e
--- /dev/null
+++ b/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/.oxfmtrc.json
@@ -0,0 +1,4 @@
+{
+  "singleQuote": true,
+  "semi": false
+}
diff --git a/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/package.json b/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/package.json
new file mode 100644
index 0000000000..cdaf891df3
--- /dev/null
+++ b/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/package.json
@@ -0,0 +1,9 @@
+{
+  "name": "migration-existing-oxc-configs",
+  "private": true,
+  "type": "module",
+  "packageManager": "pnpm@12.3.4",
+  "devDependencies": {
+    "vite-plus": "latest"
+  }
+}
diff --git a/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/snapshots.toml b/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/snapshots.toml
new file mode 100644
index 0000000000..eb4e7224f9
--- /dev/null
+++ b/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/snapshots.toml
@@ -0,0 +1,32 @@
+[[case]]
+name = "migration_existing_oxc_configs"
+vp = "global"
+steps = [
+  { argv = ["vp", "migrate", "--no-interactive", "--no-hooks", "--no-agent", "--no-editor"], comment = "finish a leftover Oxfmt config even when Vite+ is already installed" },
+  ["vpt", "print-file", "vite.config.ts"],
+  ["vpt", "stat-file", ".oxfmtrc.json", "--assert-not", "file"],
+  { argv = ["vp", "fmt", "src/index.ts"], comment = "the migrated options must affect formatting" },
+  ["vpt", "print-file", "src/index.ts"],
+  { argv = ["vp", "migrate", "--no-interactive", "--no-hooks", "--no-agent", "--no-editor"], comment = "a completed migration should be a no-op on retry" },
+  ["vpt", "print-file", "vite.config.ts"],
+  ["vpt", "stat-file", "AGENTS.md", "--assert-not", "file"],
+  ["vpt", "stat-file", ".vite-hooks", "--assert-not", "dir"],
+  ["vpt", "stat-file", ".vscode", "--assert-not", "dir"],
+]
+
+[[case]]
+name = "migration_existing_oxc_configs_inline_fmt"
+vp = "global"
+steps = [
+  { argv = ["vpt", "write-file", "vite.config.ts", "export default { fmt: { singleQuote: false, semi: false } };\n"], snapshot = false },
+  { argv = ["vp", "fmt", "src/index.ts"], comment = "the existing inline fmt config takes precedence over the standalone config" },
+  ["vpt", "print-file", "src/index.ts"],
+  { argv = ["vpt", "write-file", "src/index.ts", "export const message = \"preserved\";\n"], snapshot = false },
+  { argv = ["vp", "migrate", "--no-interactive", "--no-hooks", "--no-agent", "--no-editor"], comment = "remove the leftover standalone config without changing the existing fmt config" },
+  ["vpt", "print-file", "vite.config.ts"],
+  ["vpt", "stat-file", ".oxfmtrc.json", "--assert-not", "file"],
+  { argv = ["vp", "fmt", "src/index.ts"], comment = "formatting must still use the existing inline options after migration" },
+  ["vpt", "print-file", "src/index.ts"],
+  { argv = ["vp", "migrate", "--no-interactive", "--no-hooks", "--no-agent", "--no-editor"], comment = "retrying the completed migration should be a no-op" },
+  ["vpt", "print-file", "vite.config.ts"],
+]
diff --git a/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/snapshots/migration_existing_oxc_configs.md b/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/snapshots/migration_existing_oxc_configs.md
new file mode 100644
index 0000000000..d124881fe9
--- /dev/null
+++ b/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/snapshots/migration_existing_oxc_configs.md
@@ -0,0 +1,91 @@
+# migration_existing_oxc_configs
+
+## `vp migrate --no-interactive --no-hooks --no-agent --no-editor`
+
+finish a leftover Oxfmt config even when Vite+ is already installed
+
+```
+VITE+ - The Unified Toolchain for the Web
+
+◇ Updated . to Vite+ <version>
+• Node <version>  pnpm <version>
+• Dependencies:
+    vite-plus  latest → <version>
+    vite              → <version>
+• 1 config update applied
+• Package manager settings configured
+```
+
+## `vpt print-file vite.config.ts`
+
+```
+export default {
+  fmt: {
+    "singleQuote": true,
+    "semi": false
+  },
+
+}
+```
+
+## `vpt stat-file .oxfmtrc.json --assert-not file`
+
+```
+.oxfmtrc.json: missing
+```
+
+## `vp fmt src/index.ts`
+
+the migrated options must affect formatting
+
+```
+VITE+ - The Unified Toolchain for the Web
+
+Finished in <duration> on 1 files using <n> threads.
+```
+
+## `vpt print-file src/index.ts`
+
+```
+export const message = 'preserved'
+```
+
+## `vp migrate --no-interactive --no-hooks --no-agent --no-editor`
+
+a completed migration should be a no-op on retry
+
+```
+VITE+ - The Unified Toolchain for the Web
+
+This project is already using Vite+! Happy coding!
+```
+
+## `vpt print-file vite.config.ts`
+
+```
+export default {
+  fmt: {
+    "singleQuote": true,
+    "semi": false
+  },
+
+}
+```
+
+## `vpt stat-file AGENTS.md --assert-not file`
+
+```
+AGENTS.md: missing
+```
+
+## `vpt stat-file .vite-hooks --assert-not dir`
+
+```
+.vite-hooks: missing
+```
+
+## `vpt stat-file .vscode --assert-not dir`
+
+```
+.vscode: missing
+```
diff --git a/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/snapshots/migration_existing_oxc_configs_inline_fmt.md b/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/snapshots/migration_existing_oxc_configs_inline_fmt.md
new file mode 100644
index 0000000000..5e5db5b33d
--- /dev/null
+++ b/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/snapshots/migration_existing_oxc_configs_inline_fmt.md
@@ -0,0 +1,84 @@
+# migration_existing_oxc_configs_inline_fmt
+
+## `vpt write-file vite.config.ts 'export default { fmt: { singleQuote: false, semi: false } };
+'`
+
+
+## `vp fmt src/index.ts`
+
+the existing inline fmt config takes precedence over the standalone config
+
+```
+VITE+ - The Unified Toolchain for the Web
+
+Finished in <duration> on 1 files using <n> threads.
+```
+
+## `vpt print-file src/index.ts`
+
+```
+export const message = "preserved"
+```
+
+## `vpt write-file src/index.ts 'export const message = "preserved";
+'`
+
+
+## `vp migrate --no-interactive --no-hooks --no-agent --no-editor`
+
+remove the leftover standalone config without changing the existing fmt config
+
+```
+VITE+ - The Unified Toolchain for the Web
+
+◇ Updated . to Vite+ <version>
+• Node <version>  pnpm <version>
+• Dependencies:
+    vite-plus  latest → <version>
+    vite              → <version>
+• Package manager settings configured
+```
+
+## `vpt print-file vite.config.ts`
+
+```
+export default { fmt: { singleQuote: false, semi: false } };
+```
+
+## `vpt stat-file .oxfmtrc.json --assert-not file`
+
+```
+.oxfmtrc.json: missing
+```
+
+## `vp fmt src/index.ts`
+
+formatting must still use the existing inline options after migration
+
+```
+VITE+ - The Unified Toolchain for the Web
+
+Finished in <duration> on 1 files using <n> threads.
+```
+
+## `vpt print-file src/index.ts`
+
+```
+export const message = "preserved"
+```
+
+## `vp migrate --no-interactive --no-hooks --no-agent --no-editor`
+
+retrying the completed migration should be a no-op
+
+```
+VITE+ - The Unified Toolchain for the Web
+
+This project is already using Vite+! Happy coding!
+```
+
+## `vpt print-file vite.config.ts`
+
+```
+export default { fmt: { singleQuote: false, semi: false } };
+```
diff --git a/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/src/index.ts b/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/src/index.ts
new file mode 100644
index 0000000000..38b0fa8a2f
--- /dev/null
+++ b/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/src/index.ts
@@ -0,0 +1 @@
+export const message = "preserved";
diff --git a/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/vite.config.ts b/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/vite.config.ts
new file mode 100644
index 0000000000..ff8b4c5632
--- /dev/null
+++ b/crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/migration_existing_oxc_configs/vite.config.ts
@@ -0,0 +1 @@
+export default {};
diff --git a/packages/cli/src/migration/__tests__/migrator.spec.ts b/packages/cli/src/migration/__tests__/migrator.spec.ts
index c395b594db..026874eb0a 100644
--- a/packages/cli/src/migration/__tests__/migrator.spec.ts
+++ b/packages/cli/src/migration/__tests__/migrator.spec.ts
@@ -8796,6 +8796,7 @@ describe('existing Vite+ core migration finalization', () => {
       scripts: true,
       tsconfigTypes: true,
       imports: true,
+      oxcConfigs: false,
       tsdownConfig: false,
     });
 
@@ -8827,6 +8828,96 @@ describe('existing Vite+ core migration finalization', () => {
     });
   });
 
+  it.each(['.oxfmtrc.json', '.oxfmtrc.jsonc'])(
+    'finishes a leftover %s config and remains idempotent',
+    (configFile) => {
+      fs.writeFileSync(
+        path.join(tmpDir, 'package.json'),
+        JSON.stringify({ name: 'test', devDependencies: { 'vite-plus': 'latest' } }),
+      );
+      fs.writeFileSync(path.join(tmpDir, 'vite.config.ts'), 'export default {};\n');
+      fs.writeFileSync(path.join(tmpDir, configFile), '{"singleQuote":true,"semi":false}\n');
+      const workspaceInfo = makeWorkspaceInfo(tmpDir, PackageManager.npm);
+      const report = createMigrationReport();
+
+      expect(finalizeCoreMigrationForExistingVitePlus(workspaceInfo, true, report).oxcConfigs).toBe(
+        true,
+      );
+      const config = fs.readFileSync(path.join(tmpDir, 'vite.config.ts'), 'utf8');
+      expect(config).toContain('fmt:');
+      expect(config).toContain('"singleQuote":true');
+      expect(config).toContain('"semi":false');
+      expect(fs.existsSync(path.join(tmpDir, configFile))).toBe(false);
+      expect(report.mergedConfigCount).toBe(1);
+      expect(finalizeCoreMigrationForExistingVitePlus(workspaceInfo, true).oxcConfigs).toBe(false);
+      expect(fs.readFileSync(path.join(tmpDir, 'vite.config.ts'), 'utf8')).toBe(config);
+    },
+  );
+
+  it('finishes leftover lint and format configs in workspace packages', () => {
+    const appDir = path.join(tmpDir, 'packages', 'app');
+    fs.mkdirSync(appDir, { recursive: true });
+    fs.writeFileSync(
+      path.join(tmpDir, 'package.json'),
+      JSON.stringify({ name: 'root', devDependencies: { 'vite-plus': 'latest' } }),
+    );
+    fs.writeFileSync(path.join(appDir, 'package.json'), JSON.stringify({ name: 'app' }));
+    fs.writeFileSync(path.join(appDir, '.oxfmtrc.json'), '{"singleQuote":true}\n');
+    fs.writeFileSync(path.join(appDir, '.oxlintrc.json'), '{"rules":{"no-console":"error"}}\n');
+    const workspaceInfo = {
+      ...makeWorkspaceInfo(tmpDir, PackageManager.pnpm),
+      isMonorepo: true,
+      packages: [{ name: 'app', path: 'packages/app' }],
+    };
+
+    expect(finalizeCoreMigrationForExistingVitePlus(workspaceInfo, true).oxcConfigs).toBe(true);
+    const config = fs.readFileSync(path.join(appDir, 'vite.config.ts'), 'utf8');
+    expect(config).toContain('fmt:');
+    expect(config).toContain('lint:');
+    expect(config).toMatch(/"no-console":\s*"error"/);
+    expect(fs.existsSync(path.join(appDir, '.oxfmtrc.json'))).toBe(false);
+    expect(fs.existsSync(path.join(appDir, '.oxlintrc.json'))).toBe(false);
+    expect(finalizeCoreMigrationForExistingVitePlus(workspaceInfo, true).oxcConfigs).toBe(false);
+  });
+
+  it('preserves existing inline config when removing a redundant standalone config', () => {
+    fs.writeFileSync(
+      path.join(tmpDir, 'package.json'),
+      JSON.stringify({ name: 'test', devDependencies: { 'vite-plus': 'latest' } }),
+    );
+    const config = 'export default { fmt: { singleQuote: false } };\n';
+    fs.writeFileSync(path.join(tmpDir, 'vite.config.ts'), config);
+    fs.writeFileSync(path.join(tmpDir, '.oxfmtrc.json'), '{"singleQuote":true}\n');
+    const workspaceInfo = makeWorkspaceInfo(tmpDir, PackageManager.npm);
+
+    expect(finalizeCoreMigrationForExistingVitePlus(workspaceInfo, true).oxcConfigs).toBe(true);
+    expect(fs.readFileSync(path.join(tmpDir, 'vite.config.ts'), 'utf8')).toBe(config);
+    expect(fs.existsSync(path.join(tmpDir, '.oxfmtrc.json'))).toBe(false);
+    expect(finalizeCoreMigrationForExistingVitePlus(workspaceInfo, true).oxcConfigs).toBe(false);
+  });
+
+  it('keeps an unmergeable config and reports the incomplete migration', () => {
+    fs.writeFileSync(
+      path.join(tmpDir, 'package.json'),
+      JSON.stringify({ name: 'test', devDependencies: { 'vite-plus': 'latest' } }),
+    );
+    fs.writeFileSync(
+      path.join(tmpDir, 'vite.config.ts'),
+      'const config = {}; export default config;\n',
+    );
+    fs.writeFileSync(path.join(tmpDir, '.oxfmtrc.json'), '{"singleQuote":true}\n');
+    const report = createMigrationReport();
+
+    const result = finalizeCoreMigrationForExistingVitePlus(
+      makeWorkspaceInfo(tmpDir, PackageManager.npm),
+      true,
+      report,
+    );
+    expect(result.oxcConfigs).toBe(false);
+    expect(fs.existsSync(path.join(tmpDir, '.oxfmtrc.json'))).toBe(true);
+    expect(report.warnings.some((warning) => warning.includes('Failed to merge'))).toBe(true);
+  });
+
   it('detects package-level legacy signals in workspaces', () => {
     const appDir = path.join(tmpDir, 'packages', 'app');
     fs.mkdirSync(appDir, { recursive: true });
@@ -8852,6 +8943,40 @@ describe('existing Vite+ core migration finalization', () => {
     expect(appPkg.scripts.dev).toBe('vp dev');
   });
 
+  it('finishes leftover Oxc and tsdown configs together and remains idempotent', () => {
+    fs.writeFileSync(
+      path.join(tmpDir, 'package.json'),
+      JSON.stringify({ name: 'test', devDependencies: { 'vite-plus': 'latest' } }),
+    );
+    fs.writeFileSync(path.join(tmpDir, 'vite.config.ts'), 'export default {};\n');
+    fs.writeFileSync(path.join(tmpDir, '.oxfmtrc.json'), '{"singleQuote":true,"semi":false}\n');
+    fs.writeFileSync(
+      path.join(tmpDir, 'tsdown.config.ts'),
+      "import { defineConfig } from 'tsdown'; export default defineConfig({ entry: 'src/index.ts' });\n",
+    );
+    const workspaceInfo = makeWorkspaceInfo(tmpDir, PackageManager.pnpm);
+
+    const result = finalizeCoreMigrationForExistingVitePlus(workspaceInfo, true);
+    expect(result.oxcConfigs).toBe(true);
+    expect(result.tsdownConfig).toBe(true);
+    const config = fs.readFileSync(path.join(tmpDir, 'vite.config.ts'), 'utf8');
+    expect(config).toContain('pack: tsdownConfig');
+    expect(config).toContain('"singleQuote":true');
+    expect(config).toContain('"semi":false');
+    expect(fs.existsSync(path.join(tmpDir, '.oxfmtrc.json'))).toBe(false);
+    expect(fs.readFileSync(path.join(tmpDir, 'tsdown.config.ts'), 'utf8')).toContain(
+      "from 'vite-plus/pack'",
+    );
+    expect(finalizeCoreMigrationForExistingVitePlus(workspaceInfo, true)).toEqual({
+      scripts: false,
+      tsconfigTypes: false,
+      imports: false,
+      oxcConfigs: false,
+      tsdownConfig: false,
+    });
+    expect(fs.readFileSync(path.join(tmpDir, 'vite.config.ts'), 'utf8')).toBe(config);
+  });
+
   it('makes a leftover tsdown config discoverable in an existing Vite+ project', () => {
     fs.writeFileSync(
       path.join(tmpDir, 'package.json'),
@@ -8873,6 +8998,7 @@ export default defineConfig({
       tsconfigTypes: false,
       imports: true,
       tsdownConfig: true,
+      oxcConfigs: false,
     });
     expect(fs.readFileSync(path.join(tmpDir, 'vite.config.ts'), 'utf8')).toContain(
       "import tsdownConfig from './tsdown.config.js';",
@@ -8889,6 +9015,7 @@ export default defineConfig({
       tsconfigTypes: false,
       imports: false,
       tsdownConfig: false,
+      oxcConfigs: false,
     });
   });
 
@@ -8925,6 +9052,7 @@ export default defineConfig({ entry: 'src/index.ts' });
       tsconfigTypes: false,
       imports: true,
       tsdownConfig: false,
+      oxcConfigs: false,
     });
     expect(fs.readFileSync(path.join(tmpDir, 'vite.config.ts'), 'utf8')).toBe(originalViteConfig);
     expect(report.tsdownImportCount).toBe(0);
diff --git a/packages/cli/src/migration/bin.ts b/packages/cli/src/migration/bin.ts
index ceaaa61ce8..673df61615 100644
--- a/packages/cli/src/migration/bin.ts
+++ b/packages/cli/src/migration/bin.ts
@@ -1115,6 +1115,7 @@ async function main() {
       coreMigrationResult.scripts ||
       coreMigrationResult.tsconfigTypes ||
       coreMigrationResult.imports ||
+      coreMigrationResult.oxcConfigs ||
       coreMigrationResult.tsdownConfig
     ) {
       didMigrate = true;
diff --git a/packages/cli/src/migration/migrator/core-finalization.ts b/packages/cli/src/migration/migrator/core-finalization.ts
index 46b0d51d76..ea2467186e 100644
--- a/packages/cli/src/migration/migrator/core-finalization.ts
+++ b/packages/cli/src/migration/migrator/core-finalization.ts
@@ -5,9 +5,11 @@ import { rewriteScripts } from '../../../binding/index.js';
 import { type WorkspacePackage } from '../../types/index.ts';
 import { editJsonFile, readJsonFile } from '../../utils/json.ts';
 import { rulesDir } from '../../utils/path.ts';
+import { detectConfigs } from '../detector.ts';
 import {
   hasTsconfigTypesToRewrite,
   mergeTsdownConfigFile,
+  mergeViteConfigFiles,
   rewriteAllImports,
   rewriteTsconfigTypes,
 } from '../migrator.ts';
@@ -81,6 +83,7 @@ export type CoreMigrationFinalizationResult = {
   scripts: boolean;
   tsconfigTypes: boolean;
   imports: boolean;
+  oxcConfigs: boolean;
   tsdownConfig: boolean;
 };
 
@@ -146,6 +149,7 @@ export function finalizeCoreMigrationForExistingVitePlus(
     scripts: false,
     tsconfigTypes: false,
     imports: false,
+    oxcConfigs: false,
     tsdownConfig: false,
   };
 
@@ -171,5 +175,27 @@ export function finalizeCoreMigrationForExistingVitePlus(
     result.tsdownConfig = mergeTsdownConfigFile(projectPath, silent, report) || result.tsdownConfig;
   }
 
+  // A failed migration may have installed Vite+ before merging these files.
+  // Finish that core work without opting into unrelated first-time setup.
+  for (const projectPath of projectPaths) {
+    const configs = detectConfigs(projectPath);
+    const standaloneConfigs = [configs.oxlintConfig, configs.oxfmtConfig].filter(
+      (config) => config !== undefined,
+    );
+    if (standaloneConfigs.length === 0) {
+      continue;
+    }
+    mergeViteConfigFiles(
+      projectPath,
+      silent,
+      report,
+      workspaceInfo.packages,
+      workspaceInfo.rootDir,
+    );
+    if (standaloneConfigs.some((config) => !fs.existsSync(path.join(projectPath, config)))) {
+      result.oxcConfigs = true;
+    }
+  }
+
   return result;
 }