feat: make packages/ai ESM-only (#265)

## Summary
- switch `packages/ai` tsup output to ESM-only
- remove CommonJS export conditions and `.cjs`/`.d.cts` references from
`packages/ai/package.json`
- keep explicit Node-only path/require handling in eval runtime
(`run-vitest.ts`, `context/manager.ts`) without global tsup shims

## Why
- avoids the Workers startup regression caused by global tsup ESM shims
initialization
- aligns package distribution with ESM-only direction

## Validation
- `pnpm --filter axiom build`
- verified `check-vitest-entrypoints` passes
- verified no `.cjs` or `.d.cts` artifacts are produced in
`packages/ai/dist`

## Breaking change
- `packages/ai` no longer supports CommonJS `require(...)` consumers;
users must import via ESM.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Medium risk because it removes CommonJS support (breaking for
`require` consumers) and changes package entry/export behavior; the new
Wrangler smoke test should catch runtime regressions in Workers startup.
> 
> **Overview**
> Switches `packages/ai` distribution to **ESM-only** by emitting only
`esm` from `tsup` and simplifying `package.json` (`main`/`exports`) to
remove all CommonJS (`.cjs`/`.d.cts`) conditions.
> 
> Updates Node-only eval runtime code to avoid reliance on tsup global
shims by resolving `require`/`__dirname` safely in both CJS and ESM
(`context/manager.ts`, `run-vitest.ts`).
> 
> Adds a CI `Wrangler Smoke` GitHub Action plus a Vitest smoke suite and
Workers fixture that packs the package, installs it into a minimal
Wrangler app, boots `wrangler dev --local`, and verifies a request can
call `axiom/ai` APIs; TS config excludes fixture/smoke files from normal
typechecking.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
e4c1fee. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Christopher Ehrlich <ehrlich.christopher@gmail.com>

Author: gabrielelpidio

.github/workflows/wrangler-smoke.yaml

@@ -0,0 +1,35 @@
+name: Wrangler Smoke
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - 'packages/ai/**'
+      - '.github/workflows/wrangler-smoke.yaml'
+  pull_request:
+    branches:
+      - main
+    paths:
+      - 'packages/ai/**'
+      - '.github/workflows/wrangler-smoke.yaml'
+
+env:
+  PNPM_VERSION: 10.16.1
+  NODE_VERSION: 22
+
+jobs:
+  wrangler-smoke:
+    name: Wrangler smoke test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: pnpm/action-setup@v4
+        with:
+          version: ${{ env.PNPM_VERSION }}
+      - uses: actions/setup-node@v4
+        with:
+          node-version: ${{ env.NODE_VERSION }}
+          cache: 'pnpm'
+      - run: pnpm install --frozen-lockfile --ignore-scripts
+      - run: pnpm -C packages/ai test:wrangler-smoke

packages/ai/package.json

@@ -18,84 +18,43 @@
     "typecheck": "tsc --noEmit",
     "test": "vitest run",
     "test:watch": "vitest --watch",
+    "test:wrangler-smoke": "pnpm build && vitest run --config vitest.smoke.config.ts",
     "publint": "npx publint"
   },
   "types": "./dist/index.d.ts",
-  "main": "./dist/index.cjs",
+  "main": "./dist/index.js",
   "module": "./dist/index.js",
   "bin": {
     "axiom": "./dist/bin.js"
   },
   "exports": {
     "./ai": {
-      "import": {
-        "types": "./dist/index.d.ts",
-        "default": "./dist/index.js"
-      },
-      "require": {
-        "types": "./dist/index.d.cts",
-        "default": "./dist/index.cjs"
-      }
+      "types": "./dist/index.d.ts",
+      "default": "./dist/index.js"
     },
     "./ai/evals": {
-      "import": {
-        "types": "./dist/evals.d.ts",
-        "default": "./dist/evals.js"
-      },
-      "require": {
-        "types": "./dist/evals.d.cts",
-        "default": "./dist/evals.cjs"
-      }
+      "types": "./dist/evals.d.ts",
+      "default": "./dist/evals.js"
     },
     "./ai/evals/aggregations": {
-      "import": {
-        "types": "./dist/evals/aggregations.d.ts",
-        "default": "./dist/evals/aggregations.js"
-      },
-      "require": {
-        "types": "./dist/evals/aggregations.d.cts",
-        "default": "./dist/evals/aggregations.cjs"
-      }
+      "types": "./dist/evals/aggregations.d.ts",
+      "default": "./dist/evals/aggregations.js"
     },
     "./ai/evals/scorers": {
-      "import": {
-        "types": "./dist/evals/scorers.d.ts",
-        "default": "./dist/evals/scorers.js"
-      },
-      "require": {
-        "types": "./dist/evals/scorers.d.cts",
-        "default": "./dist/evals/scorers.cjs"
-      }
+      "types": "./dist/evals/scorers.d.ts",
+      "default": "./dist/evals/scorers.js"
     },
     "./ai/evals/online": {
-      "import": {
-        "types": "./dist/evals/online.d.ts",
-        "default": "./dist/evals/online.js"
-      },
-      "require": {
-        "types": "./dist/evals/online.d.cts",
-        "default": "./dist/evals/online.cjs"
-      }
+      "types": "./dist/evals/online.d.ts",
+      "default": "./dist/evals/online.js"
     },
     "./ai/config": {
-      "import": {
-        "types": "./dist/config.d.ts",
-        "default": "./dist/config.js"
-      },
-      "require": {
-        "types": "./dist/config.d.cts",
-        "default": "./dist/config.cjs"
-      }
+      "types": "./dist/config.d.ts",
+      "default": "./dist/config.js"
     },
     "./ai/feedback": {
-      "import": {
-        "types": "./dist/feedback.d.ts",
-        "default": "./dist/feedback.js"
-      },
-      "require": {
-        "types": "./dist/feedback.d.cts",
-        "default": "./dist/feedback.cjs"
-      }
+      "types": "./dist/feedback.d.ts",
+      "default": "./dist/feedback.js"
     }
   },
   "keywords": [

packages/ai/src/evals/context/manager.ts

@@ -1,4 +1,5 @@
 import { createRequire } from 'node:module';
+import { join } from 'node:path';
 
 interface ContextManager<T = any> {
   getStore(): T | undefined;
@@ -17,6 +18,15 @@ function setGlobalContextManager(manager: ContextManager): void {
 
 const isNodeJS = typeof process !== 'undefined' && !!process.versions?.node;
 
+function getNodeRequire(): NodeJS.Require {
+  if (typeof require === 'function') {
+    return require;
+  }
+
+  // We only require Node builtins, so any absolute path is valid as a createRequire base.
+  return createRequire(join(process.cwd(), '__axiom_require__.js'));
+}
+
 function getContextManager(): ContextManager {
   // Check global Symbol registry cache first (shared across VM contexts)
   const existing = getGlobalContextManager();
@@ -29,8 +39,8 @@ function getContextManager(): ContextManager {
       // Resolve AsyncLocalStorage in both ESM and CJS Node contexts without bundler interference
       let AsyncLocalStorage: any;
 
-      // Use createRequire to obtain a require in ESM
-      const req = createRequire(import.meta.url);
+      // Obtain require in both CJS and ESM Node runtimes without relying on tsup shims.
+      const req = getNodeRequire();
       try {
         AsyncLocalStorage = req('node:async_hooks').AsyncLocalStorage;
       } catch {

packages/ai/src/evals/run-vitest.ts

@@ -2,6 +2,7 @@ import c from 'tinyrainbow';
 import { resolve, join } from 'node:path';
 import { mkdirSync, writeFileSync, unlinkSync, existsSync, readFileSync } from 'node:fs';
 import { tmpdir } from 'node:os';
+import { fileURLToPath } from 'node:url';
 import path from 'node:path';
 import tsconfigPaths from 'vite-tsconfig-paths';
 
@@ -12,6 +13,16 @@ import { flush, initInstrumentation } from './instrument';
 import { setAxiomConfig } from './context/storage';
 import type { ResolvedAxiomConfig } from '../config/index';
 
+const getCurrentDir = (): string => {
+  if (typeof __dirname !== 'undefined') {
+    return __dirname;
+  }
+
+  return path.dirname(fileURLToPath(import.meta.url));
+};
+
+const evalsRunnerPath = resolve(getCurrentDir(), 'evals', 'custom-runner.js');
+
 const printCollectedEvals = (result: TestRunResult, rootDir: string) => {
   if (!result.testModules || result.testModules.length === 0) {
     console.log(c.yellow('\nNo evaluations found\n'));
@@ -117,7 +128,7 @@ export const runVitest = async (
       disableConsoleIntercept: true,
       testTimeout: opts.config?.eval?.timeoutMs || 60_000,
       globals: true,
-      runner: resolve(__dirname, 'evals', 'custom-runner.js'),
+      runner: evalsRunnerPath,
       provide: {
         baseline: opts.baseline,
         debug: opts.debug,

packages/ai/test/build/fixtures/wrangler-smoke/package.json

@@ -0,0 +1,5 @@
+{
+  "name": "axiom-wrangler-smoke",
+  "private": true,
+  "type": "module"
+}

packages/ai/test/build/fixtures/wrangler-smoke/src/index.ts

@@ -0,0 +1,15 @@
+import { withSpan, axiomAIMiddleware } from 'axiom/ai';
+
+export default {
+  async fetch() {
+    const result = await withSpan({ capability: 'chat', step: 'generate' }, async () => 'ok');
+    return new Response(
+      JSON.stringify({
+        withSpanType: typeof withSpan,
+        middlewareType: typeof axiomAIMiddleware,
+        result,
+      }),
+      { headers: { 'content-type': 'application/json' } },
+    );
+  },
+};

packages/ai/test/build/fixtures/wrangler-smoke/wrangler.toml

@@ -0,0 +1,4 @@
+name = "axiom-wrangler-smoke"
+main = "src/index.ts"
+compatibility_date = "2025-01-01"
+compatibility_flags = ["nodejs_compat"]