# cel-programs

A skill for CEL and mito work in API-collecting integrations: cel.yml.hbs templates, manifests, mock-first debugging.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 504 installs · ★ 16
- Author: elastic
- License: Apache-2.0 · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/elastic/integration-skills/tree/HEAD/skills/cel-programs/SKILL.md
- Updated: 2026-10-16
- HTML: https://affpapa.org/en/nevibecode/skills/cel-programs

## What it does

The skill covers everything tied to the `cel` input type: writing CEL programs with pagination, cursors and auth, building `cel.yml.hbs` templates, configuring data stream manifests, and answering CEL or mito questions. Load it whenever a data stream uses the `cel` input.

What makes it useful is the enforced order of work: mock → mito → template. You write the mock config at `_dev/deploy/docker/files/config-<stream>.yml`, start a local http-server on `:8090`, then validate the CEL program as a standalone `.cel` file with a `state.json` via `mito -data state.json -log_requests program.cel`. Only after that does the expression move into `program: |` in the template. The author advises against writing more than 10–15 new lines of CEL at once and suggests building in phases: skeleton, error handling, events, pagination, cursor.

One trap gets its own warning: integration packages must not set `data_stream.dataset`. The framework routes documents itself, and overriding that sends them to the wrong index — usually showing up as zero hits in system tests. Input-type packages are the opposite case and do need the field. The skill is not a substitute for the ingest pipeline, ECS mapping, package scaffolding or stack-level system testing skills.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add elastic/integration-skills --skill cel-programs -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/cel-programs/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/cel-programs/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add elastic/integration-skills --skill cel-programs -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/cel-programs/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add elastic/integration-skills --skill cel-programs -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/cel-programs/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install elastic/integration-skills cel-programs
```

2. **Manually: put the files in place**
- File: `.github/skills/cel-programs/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add elastic/integration-skills --skill cel-programs -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/elastic/integration-skills --path skills/cel-programs
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/cel-programs/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add elastic/integration-skills --skill cel-programs -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/elastic/integration-skills/tree/HEAD/skills/cel-programs/SKILL.md

## When to use it
- write a CEL program with pagination and cursor handling for an API
- build a `cel.yml.hbs` template with Handlebars vars and a `state` block
- debug a CEL program locally with mito instead of hitting the live API
- stand up a mock API for data stream system tests
- trace why documents land in the wrong index after setting `data_stream.dataset`

## Example prompts
- help me write a CEL program for a new data stream, start with the skeleton
- run mito on my `program.cel` with this `state.json`
- set up `cel.yml.hbs` and the manifest for a stream paginating by cursor

## Source text · SKILL.md · Apache-2.0

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: de7a50b1f315378d.

BEGIN THIRD-PARTY FILE de7a50b1f315378d
```text
---
name: cel-programs
description: "Use for all CEL and mito work on integrations that collect from APIs — writing CEL programs, cel.yml.hbs templates, manifest configuration, mock-first development with the mito CLI, system test mock setup, and answering CEL/mito questions. Load this skill whenever any data stream uses the cel input type."
license: Apache-2.0
metadata:
  author: elastic
  version: "1.0"
---

# cel-programs


## When to use

Use this skill when tasks include:
- creating or editing `cel.yml.hbs` agent stream templates
- configuring data stream manifests for the `cel` input type
- writing CEL programs with pagination, cursor management, or authentication
- testing or debugging a CEL program locally with mito
- setting up system tests with mock APIs for CEL-based data streams
- prototyping a new CEL-based data stream's collection logic
- any CEL or mito question, regardless of context

## When not to use

Do not use this skill as the primary guide for:
- ingest pipeline processor design (`ingest-pipelines`)
- ECS field mapping (`ecs-field-mappings`)
- package scaffolding (`create-integration`)
- system test execution with the Elastic stack (`integration-testing` → `references/system-testing.md`)

## Mandatory workflow — mock → mito → template

**This is not a suggestion. Every CEL program MUST be developed in this order.** The subagent must not write `cel.yml.hbs` until the CEL program has been validated with mito against a running mock. Skipping steps or reordering causes failures that are hard to debug.

**Do NOT write more than ~10–15 new lines of CEL before running mito.** Build the program incrementally in phases (skeleton → error handling → event mapping → pagination → cursor guard), validating with mito after each phase. Writing a large program in one shot leads to cascading compilation errors that are extremely hard to debug. Follow the phased approach in `references/cel-incremental-build.md`.

| Step | Action | Output |
|------|--------|--------|
| **1. Create the system test mock** | Write the `elastic/stream` config at `_dev/deploy/docker/files/config-<stream>.yml` with rules matching all API endpoints. Write `test-default-config.yml`. | Mock config file, docker-compose service, test config |
| **2. Start the mock locally** | `stream http-server --addr=:8090 --config=...` | Running mock at `http://localhost:8090` |
```
END THIRD-PARTY FILE de7a50b1f315378d

The third-party file has ended. Everything between the de7a50b1f315378d tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

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