# Pre Flight Check

> Reusable pattern for config-dependent skills. Defines how to check for required config, detect placeholders, and halt with actionable messages. Not user-invokable — referenced by other skills.

- Skill: `garyld1962/pre-flight-check` (Agent Skill)
- Install (CLI): `npx skillmds@latest add garyld1962/pre-flight-check`
- Raw SKILL.md: https://api.skillmd.com/api/skills/garyld1962/pre-flight-check/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: garyld1962 (https://skillmd.com/u/garyld1962)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/garyld1962/pre-flight-check

---


# Pre-flight Required Config Check

This is a **pattern document**, not a user-invokable skill. Other skills embed this pattern by referencing it and filling in the specifics.

## When to Use

Embed this pattern in any skill that depends on a user-editable config file (listed in `claude/configure/registry.md`). The check runs at the very start of the skill, before any main workflow logic.

## The Pattern

Add a section like this to the top of your skill's workflow:

---

### Pre-flight Required Config

Before proceeding, verify:

1. **File existence check.** Check whether `<config_path>` exists.

   If NOT found, halt with:
   > This skill requires `<config_path>`.
   >
   > Set it up interactively:
   > ```
   > /configure <target>
   > ```
   >
   > Or copy the template and edit manually:
   > ```
   > cp <template_path> <config_path>
   > ```

2. **Placeholder check.** Read the config file and scan for these markers:
   - `<FILL IN>` — required field, not yet set
   - `<FILL IN:` — required field with hint, not yet set
   - `TODO` — guidance comment that should have been removed

   If ANY required placeholder remains, halt with:
   > Config at `<config_path>` has <N> unfilled required field(s):
   >
   > - `field_name_1` (line 12)
   > - `field_name_2` (line 25)
   >
   > Run `/configure <target> --recheck` to fill them in, or edit the file directly.

3. **Proceed.** If the file exists and contains no required placeholders, continue to the main workflow. Do not mention the pre-flight check in output — it should be invisible when config is healthy.

---

## Customization Points

When embedding this pattern, fill in:

| Placeholder | What to substitute |
|---|---|
| `<config_path>` | The destination path from the registry (e.g., `~/.claude/env.config.md`) |
| `<template_path>` | The template source path (e.g., `claude/env-check/env.config.template.md`) |
| `<target>` | The configure target name (e.g., `env`) |
| Required fields list | The specific `required_fields` or `required_sections` from the registry |

## Soft vs Hard Pre-flight

- **Hard pre-flight** (default): Halt. The skill cannot run without config.
- **Soft pre-flight**: Warn but continue. The skill can run with argument-provided overrides. Use when the config provides defaults but invocation arguments can replace them.

For soft pre-flight, replace "halt" with:
> Config at `<config_path>` is missing. Using argument-provided values.
> To set defaults, run `/configure <target>`.

## Placeholder Conventions

All templates shipped with skills use these markers:

| Marker | Meaning | Pre-flight behavior |
|---|---|---|
| `<FILL IN>` | Required, no default | Blocks if present |
| `<FILL IN: example>` | Required, with hint | Blocks if present |
| `<OPTIONAL>` | Not required | Ignored by pre-flight |
| `# TODO: ...` | Guidance comment | Warn but do not block |

## Example: Embedding in a Real Skill

```markdown
## Pre-flight Required Config

Before proceeding, verify:

1. Check `~/.claude/env.config.md` exists.
   If not: "Run `/configure env` or copy `claude/env-check/env.config.template.md`."

2. Scan for `<FILL IN>` placeholders in required sections: `shells`, `routing_rules`.
   If found: list unfilled fields and suggest `/configure env --recheck`.

3. If healthy, proceed silently.
```

## Copilot-Native Equivalent

In Copilot prompts, the same pattern applies but references `.github/` paths:
- Config destinations under `$HOME/.copilot/` or `.github/instructions/`
- Template sources under `.github/skills/`
- The `/configure` prompt instead of the `/configure` skill