create-adapter skill

---
name: create-evlog-adapter
description: Create a new built-in evlog adapter to send wide events to an external observability platform. Use when adding a new drain adapter (e.g., for Datadog, Sentry, Loki, Elasticsearch, etc.) to the evlog package. Covers source code, build config, package exports, tests, and all documentation.
---

# Create evlog Adapter

Add a new built-in adapter to evlog. Every adapter follows the same architecture. This skill walks through all 8 touchpoints. **Every single touchpoint is mandatory** -- do not skip any.

## PR Title

Recommended format for the pull request title:

```
feat: add {name} adapter
```

The exact wording may vary depending on the adapter (e.g., `feat: add OTLP adapter`, `feat: add Axiom drain adapter`), but it should always follow the `feat:` conventional commit prefix.

## Touchpoints Checklist

| # | File | Action |
|---|------|--------|
| 1 | `packages/evlog/src/adapters/{name}.ts` | Create adapter source |
| 2 | `packages/evlog/tsdown.config.ts` | Add build entry |
| 3 | `packages/evlog/package.json` | Add `exports` + `typesVersions` entries |
| 4 | `packages/evlog/test/adapters/{name}.test.ts` | Create tests |
| 5 | `apps/docs/content/3.adapters/{n}.{name}.md` | Create adapter doc page (before `custom.md`) |
| 6 | `apps/docs/content/3.adapters/1.overview.md` | Add adapter to overview (links, card, env vars) |
| 7 | `AGENTS.md` | Add adapter to the "Built-in Adapters" table |
| 8 | Renumber `custom.md` | Ensure `custom.md` stays last after the new adapter |

**Important**: Do NOT consider the task complete until all 8 touchpoints have been addressed.

## Naming Conventions

Use these placeholders consistently:

| Placeholder | Example (Datadog) | Usage |
|-------------|-------------------|-------|
| `{name}` | `datadog` | File names, import paths, env var suffix |
| `{Name}` | `Datadog` | PascalCase in function/interface names |
| `{NAME}` | `DATADOG` | SCREAMING_CASE in env var prefixes |

## Step 1: Adapter Source

Create `packages/evlog/src/adapters/{name}.ts`.

Read [references/adapter-template.md](references/adapter-template.md) for the full annotated template.

Key architecture rules:

1. **Config interface** -- service-specific fields (API key, endpoint, etc.) plus optional `timeout?: number`
2. **`getRuntimeConfig()`** -- import from `./_utils` (shared helper, do NOT redefine locally)
3. **Config priority** (highest to lowest):
   - Overrides passed to `create{Name}Drain()`
   - `runtimeConfig.evlog.{name}`
   - `runtimeConfig.{name}`
   - Environment variables: `NUXT_{NAME}_*` then `{NAME}_*`
4. **Factory function** -- `create{Name}Drain(overrides?: Partial<Config>)` returns `(ctx: DrainContext) => Promise<void>`
5. **Exported send functions** -- `sendTo{Name}(event, config)` and `sendBatchTo{Name}(events, config)` for direct use and testability
6. **Error handling** -- try/catch with `console.error('[evlog/{name}] ...')`, never throw from the drain
7. **Timeout** -- `AbortController` with 5000ms default, configurable via `config.timeout`
8. **Event transformation** -- if the service needs a specific format, export a `to{Name}Event()` converter

## Step 2: Build Config

Add a build entry in `packages/evlog/tsdown.config.ts` alongside the existing adapters:

```typescript
'adapters/{name}': 'src/adapters/{name}.ts',
```

Place it after the last adapter entry (currently `sentry` at line 22).

## Step 3: Package Exports

In `packages/evlog/package.json`, add two entries:

**In `exports`** (after the last adapter, currently `./posthog`):

```json
"./{name}": {
  "types": "./dist/adapters/{name}.d.mts",
  "import": "./dist/adapters/{name}.mjs"
}
```

**In `typesVersions["*"]`** (after the last adapter):

```json
"{name}": [
  "./dist/adapters/{name}.d.mts"
]
```

## Step 4: Tests

Create `packages/evlog/test/adapters/{name}.test.ts`.

Read [references/test-template.md](references/test-template.md) for the full annotated template.

Required test categories:

1. URL construction (default + custom endpoint)
2. Headers (auth, content-type, service-specific)
3. Request body format (JSON structure matches service API)
4. Error handling (non-OK responses throw with status)
5. Batch operations (`sendBatchTo{Name}`)
6. Timeout handling (default 5000ms + custom)

## Step 5: Adapter Documentation Page

Create `apps/docs/content/3.adapters/{n}.{name}.md` where `{n}` is the next number before `custom.md` (custom should always be last).

Use the existing Axiom adapter page (`apps/docs/content/3.adapters/2.axiom.md`) as a reference for frontmatter structure, tone, and sections. Key sections: intro, quick setup, configuration (env vars table + priority), advanced usage, querying in the target service, troubleshooting, direct API usage, next steps.

## Step 6: Update Adapters Overview Page

Edit `apps/docs/content/3.adapters/1.overview.md` to add the new adapter in **three** places (follow the pattern of existing adapters):

1. **Frontmatter `links` array** -- add a link entry with icon and path
2. **`::card-group` section** -- add a card block before the Custom card
3. **Zero-Config Setup `.env` example** -- add the adapter's env vars

## Step 7: Update AGENTS.md

In the root `AGENTS.md` file, "Log Draining & Adapters" section:

1. Add a row to the **"Built-in Adapters"** table
2. Add a **"Using {Name} Adapter"** usage example block with `create{Name}Drain()` and env vars

Follow the pattern of existing adapters in the file.

## Step 8: Renumber `custom.md`

If the new adapter's number conflicts with `custom.md`, renumber `custom.md` to be the last entry. For example, if the new adapter is `5.{name}.md`, rename `5.custom.md` to `6.custom.md`.

## Verification

After completing all steps, run:

```bash
cd packages/evlog
bun run build    # Verify build succeeds with new entry
bun run test     # Verify tests pass
```