elixir-phoenix-init

name	elixir-phoenix-init
description	Install or update the plugin rules and AGENTS.md wiring in a Phoenix project.
metadata	{"short-description":"Set up Phoenix plugin rules"}

Plugin Initialization

Install the Elixir/Phoenix plugin's behavioral instructions into the project's AGENTS.md.

Usage

`elixir-phoenix-init`           # First-time installation
`elixir-phoenix-init` --update  # Update existing installation with latest rules

Iron Laws

1. NEVER overwrite content outside plugin markers — User-written AGENTS.md rules must be preserved verbatim
2. Always detect stack before generating — Never assume Phoenix/Ecto versions
3. Always validate after installation — Verify markers present and stack correct

Workflow

Step 1: Check Existing AGENTS.md

Check whether AGENTS.md exists, then search it for an existing ELIXIR-PHOENIX-PLUGIN:START marker.

Step 2: Detect Project Stack

Scan the project to customize the injected instructions:

Read mix.exs and extract:

• Phoenix version: search for phoenix.*"~> in mix.exs
• Ecto version: search for ecto.*"~> in mix.exs
• Oban: search for "oban" and "oban_pro" in mix.exs
• Frameworks: search for "ash", "surface" in mix.exs
• Tidewave: search for "tidewave" in mix.exs
• Project size: count lib/**/*.ex files

Step 3: Handle Installation Modes

Mode A: Fresh Install (no AGENTS.md or no markers)

1. Create/append to AGENTS.md
2. Insert full behavioral instructions between markers
3. Include only relevant sections based on detected stack

Mode B: Update (--update flag or markers exist)

1. Find content between <!-- ELIXIR-PHOENIX-PLUGIN:START --> and <!-- ELIXIR-PHOENIX-PLUGIN:END -->
2. Replace with latest behavioral instructions
3. Preserve everything outside the markers

CRITICAL: NEVER overwrite or delete existing AGENTS.md content outside the plugin markers — user-written rules, project conventions, and other plugin sections must be preserved verbatim

Step 4: Generate Content

Write the following structure to AGENTS.md:

<!-- ELIXIR-PHOENIX-PLUGIN:START -->
<!-- Last updated: {date} | Plugin version: 1.0 | Stack: Phoenix {version}, Ecto {version}, {optional: Oban, Tidewave} -->

# Elixir/Phoenix Plugin - Auto-Activation Rules

{Include all sections from the Content Template below, filtered by detected stack}

<!-- ELIXIR-PHOENIX-PLUGIN:END -->

Step 5: Output Summary

✅ Elixir/Phoenix plugin initialized

Detected stack:
- Phoenix {version}
- Ecto {version}
- {Oban standard | Oban Pro | not detected}
- {Tidewave ✓ | Tidewave not detected}
- {Ash Framework detected - Ecto patterns disabled | not detected}

Added to AGENTS.md:
- Auto-activation rules (complexity detection, interview mode)
- Agent trigger patterns ({n} agents available)
- Reference auto-loading ({n} reference docs)
- Iron Laws enforcement ({n} laws)
- Verification rules

Run `elixir-phoenix-init` --update after plugin updates.
Run `elixir-phoenix-audit` for a full project health check.

Content Template

The exact content to inject is in references/injectable-template.md.

Key structure:

1. 7-Step Mandatory Procedure — Codex MUST execute before every response
2. Iron Laws — STOP behavior on violations
3. Conditional Sections — Include based on detected stack:
   • {OBAN_SECTION} — If Oban detected (not Pro)
   • {OBAN_PRO_SECTION} — If Oban Pro detected
   • {ASH_SECTION} — If Ash Framework detected
   • {TIDEWAVE_SECTION} — If Tidewave detected
4. Verification — Mandatory after code changes
5. Quick Reference — Skill routing table

Placeholder substitution:

Placeholder	Source
{DATE}	Current date
{PHOENIX_VERSION}	From mix.exs
{ECTO_VERSION}	From mix.exs
{OPTIONAL_STACK}	Detected optional deps

See references/injectable-template.md for full template with all placeholders and conditional sections.

Validation

After running elixir-phoenix-init:

1. Check AGENTS.md contains markers
2. Verify detected stack matches actual project
3. New session should:
   • Auto-detect complexity when given tasks
   • Stop on Iron Law violations
   • Offer relevant workflows based on task

Error Handling

Scenario	Action
AGENTS.md read-only	Error: "Cannot modify AGENTS.md - check permissions"
Markers corrupted	Warn, offer to remove and reinstall
Unknown Phoenix version	Use conservative defaults (all features enabled)
Not an Elixir project	Error: "No mix.exs found - is this an Elixir project?"

Relationship to Other Commands

Command	When to Use
elixir-phoenix-init	First time, or after plugin updates
elixir-phoenix-audit	Periodic project health check
elixir-phoenix-verify	After code changes