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Analyze Phoenix context boundaries and module coupling via mix xref.
Install Phx Boundaries
$ npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-boundaries -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install oliver-kriska/claude-elixir-phoenix phx-boundaries --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/oliver-kriska/claude-elixir-phoenix.git skills-src && mkdir -p .claude/skills && cp -r skills-src/targets/pi/skills/phx-boundaries .claude/skills/phx-boundaries && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "phx-boundaries" agent skill from https://github.com/oliver-kriska/claude-elixir-phoenix/tree/main/targets/pi/skills/phx-boundaries into .claude/skills/phx-boundaries/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "phx-boundaries", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/oliver-kriska/claude-elixir-phoenix/tree/main/targets/pi/skills/phx-boundariesType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-boundaries -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install oliver-kriska/claude-elixir-phoenix phx-boundaries --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/oliver-kriska/claude-elixir-phoenix.git skills-src && mkdir -p .agents/skills && cp -r skills-src/targets/pi/skills/phx-boundaries .agents/skills/phx-boundaries && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "phx-boundaries" agent skill from https://github.com/oliver-kriska/claude-elixir-phoenix/tree/main/targets/pi/skills/phx-boundaries into .agents/skills/phx-boundaries/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "phx-boundaries", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-boundaries -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install oliver-kriska/claude-elixir-phoenix phx-boundaries --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/oliver-kriska/claude-elixir-phoenix.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/targets/pi/skills/phx-boundaries .cursor/skills/phx-boundaries && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "phx-boundaries" agent skill from https://github.com/oliver-kriska/claude-elixir-phoenix/tree/main/targets/pi/skills/phx-boundaries into .cursor/skills/phx-boundaries/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "phx-boundaries", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/oliver-kriska/claude-elixir-phoenix.git --path targets/pi/skills/phx-boundaries--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-boundaries -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install oliver-kriska/claude-elixir-phoenix phx-boundaries --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/oliver-kriska/claude-elixir-phoenix.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/targets/pi/skills/phx-boundaries .gemini/skills/phx-boundaries && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "phx-boundaries" agent skill from https://github.com/oliver-kriska/claude-elixir-phoenix/tree/main/targets/pi/skills/phx-boundaries into .gemini/skills/phx-boundaries/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "phx-boundaries", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install oliver-kriska/claude-elixir-phoenix phx-boundariesInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-boundaries -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/oliver-kriska/claude-elixir-phoenix.git skills-src && mkdir -p .github/skills && cp -r skills-src/targets/pi/skills/phx-boundaries .github/skills/phx-boundaries && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "phx-boundaries" agent skill from https://github.com/oliver-kriska/claude-elixir-phoenix/tree/main/targets/pi/skills/phx-boundaries into .github/skills/phx-boundaries/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "phx-boundaries", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-boundaries -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install oliver-kriska/claude-elixir-phoenix phx-boundaries --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/oliver-kriska/claude-elixir-phoenix.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/targets/pi/skills/phx-boundaries .opencode/skills/phx-boundaries && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "phx-boundaries" agent skill from https://github.com/oliver-kriska/claude-elixir-phoenix/tree/main/targets/pi/skills/phx-boundaries into .opencode/skills/phx-boundaries/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "phx-boundaries", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
phx-boundaries- GitHub stars
- 565
- Token cost
- ~1.1k tokens
- SKILL.md length
- 403 words
- Files
- 3 (incl. references)
- Skills in repo
- 109
- Repo updated
- First seen
- Licence
- MIT
At a glance
Analyze Phoenix context boundaries and module coupling via mix xref.
- Works in 5 steps: Controllers call only contexts - No… → Schemas are pure data - No side effects,… → Contexts own their schemas - Don't… → …
- Checking cross-context calls
- SKILL.md covers Usage, --assess Mode: Context Health…, Iron Laws - Never Violate These and Dependency Rules, plus 5 more sections
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
What it does
Phx Boundaries is an agent skill from oliver-kriska/claude-elixir-phoenix. Analyze Phoenix context boundaries and module coupling via mix xref. Use when checking cross-context calls, validating dependencies, before splitting modules, or reviewing architecture.
Its SKILL.md is about 1.1k tokens, which your agent loads only when the skill is triggered. The skill folder holds 3 other files, including reference files (for example `references/context-design.md` and `references/refactoring-boundaries.md`).
It sits in AI & LLM Engineering, covering LLM observability. The repository describes itself as: Claude Code plugin for Elixir/Phoenix/LiveView — 26 specialist agents, Iron Laws enforcement, and Tidewave MCP integration. Plan features with parallel research agents, execute… The licence is MIT.
When your agent uses it
- Checking cross-context calls
- Validating dependencies
- Before splitting modules
- Reviewing architecture
Example prompts
- “/phx-boundaries”
Workflow steps
5 steps, taken from the first numbered list in SKILL.md.
- Controllers call only contexts - No direct Repo access from web layer
- Schemas are pure data - No side effects, no Repo calls in schema modules
- Contexts own their schemas - Don't import schemas from other contexts
- Explicit dependencies only - Cross-context calls must be intentional
- DO NOT refactor context boundaries without running mix xref first — Refactoring without dependency data creates new violations; always map…
What it can do on your machine
Read from SKILL.md and the folder at commit 9767a82. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md (its code samples are markdown).
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Phx Boundaries loads about 1.1k tokens when it runs, and up to ~3.5k if it reads all its reference files. Until then it costs about 50 tokens; SKILL.md has 403 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from oliver-kriska/claude-elixir-phoenix at commit 9767a82, republished under its MIT licence (© oliver-kriska). 403 words, ~1,144 tokens.
Download SKILL.mdSave it as
.claude/skills/phx-boundaries/SKILL.md (or your agent's skills folder). This skill also uses 2 other files; get the full folder from GitHub.- name
- phx-boundaries
- description
- Analyze Phoenix context boundaries and module coupling via mix xref. Use when checking cross-context calls, validating dependencies, before splitting modules, or reviewing architecture.
Phoenix Context Boundary Validation
Analyze module dependencies to ensure clean context separation and proper architectural boundaries.
Usage
/skill:phx-boundaries # Check for violations
/skill:phx-boundaries --assess # Score context health (0-100)
/skill:phx-boundaries --fix # Suggest fixes for violations--assess Mode: Context Health Score
Evaluate overall boundary health with a quantified score.
Metrics Calculated
| Metric | Healthy Range | Red Flag | Weight |
|---|---|---|---|
| Modules per context | 3-15 | >20 or <2 | 20% |
| Public API surface | 5-30 funcs | >40 funcs | 15% |
| Fan-out (contexts called) | 1-4 | >6 | 20% |
| Fan-in (called by contexts) | 1-6 | >10 | 15% |
| Circular dependencies | 0 | >0 | 15% |
| Boundary violations | 0 | >0 | 15% |
Commands for Assessment
Use Glob to count .ex files per context directory under lib/my_app/*/.
Use Grep to count public function definitions per context file under lib/my_app/*.ex.
Run mix xref graph --format stats for dependency analysis.
Run mix xref graph --format cycles --label compile for compile-time circular dependencies.
Output Format
## Context Health Assessment
### Overall Score: 82/100 (Good)
| Context | Modules | API | Fan-Out | Fan-In | Score |
|---------|---------|-----|---------|--------|-------|
| Accounts | 5 | 12 | 2 | 4 | 95 |
| Orders | 18 | 45 | 8 | 3 | 62 |
| Shared | 2 | 8 | 0 | 12 | 78 |
### Issues Found
1. **Orders** - Too large (18 modules, 45 funcs)
- Consider: Extract Fulfillment, Invoicing sub-contexts
2. **Orders** - High fan-out (8 contexts)
- Consider: Review if all dependencies necessary
### Recommendations
- Split Orders into Orders + Fulfillment
- Review Accounts ← Billing dependencyIron Laws - Never Violate These
- Controllers call only contexts - No direct Repo access from web layer
- Schemas are pure data - No side effects, no Repo calls in schema modules
- Contexts own their schemas - Don't import schemas from other contexts
- Explicit dependencies only - Cross-context calls must be intentional
- DO NOT refactor context boundaries without running
mix xreffirst — Refactoring without dependency data creates new violations; always map the dependency graph before moving modules
Dependency Rules
| Layer | Can Call | Cannot Call |
|---|---|---|
| Controllers | Contexts, Plug, Conn | Repo, Schemas directly |
| LiveViews | Contexts, Components, PubSub | Repo, Schemas directly |
| Contexts | Own schemas, Repo, other contexts | Web layer modules |
| Schemas | Ecto types, validations | Contexts, Repo |
Analysis Commands
Show full SKILL.md (162 more words)Show less
Check Compile Dependencies
Run mix xref graph --label compile-connected.
Find What Depends on a Context
Run mix xref graph --sink MyApp.Accounts --label compile.
Find What a Module Calls
Run mix xref callers MyApp.Accounts.get_user!/1.
Check for Circular Dependencies
Run mix xref graph --format cycles --label compile.
Red Flags to Detect
| Issue | Detection Command | Fix |
|---|---|---|
| Repo in web layer | grep -r "Repo\." lib/my_app_web/ | Move to context |
| Schema with queries | grep -r "import Ecto.Query" lib/my_app/**/schemas/ | Move queries to context |
| Cross-context schema import | grep -r "alias MyApp.Other.Schema" lib/my_app/ctx/ | Call context API |
| Business logic in LiveView | grep -r "Repo\.|Ecto\.Multi" lib/my_app_web/live/ | Extract to context |
Boundary Verification Process
- Run
mix xref graph --label compile-connectedfor overview - Check for context cross-contamination
- Verify no direct Repo calls from web layer
- Ensure schemas have no side effects
- Validate explicit cross-context dependencies
Next Steps
Always end with actionable follow-up — findings without a plan get lost:
- `/skill:phx-plan` — Create a plan to fix violations (recommended for 3+ issues)
- `/skill:phx-quick` — Fix a single boundary violation directly
- `/skill:phx-review` — Review specific modules for deeper issuesReferences
For detailed patterns, see:
references/context-design.md- Context design principlesreferences/refactoring-boundaries.md- Fixing boundary violations
© oliver-kriska, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
SKILL.md and 2 other files (references) in targets/pi/skills/phx-boundaries of oliver-kriska/claude-elixir-phoenix.
- SKILL.md
- references/context-design.md
- references/refactoring-boundaries.md
Open the folder on GitHubat commit 9767a82
Compare with similar skills
Phx Boundaries next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Phx Boundaries this skilloliver-kriska/claude-elixir-phoenix | 565 | — | ~1.1k | Automated safety check: Pass | MIT | |
| Langfuse Codebase Navigatorlangfuse/langfuse | 36k | — | ~1.4k | Automated safety check: Pass | Custom licence | |
| LLM Trace Review Interfaceai-evals-course/evals-skills | 1.5k | — | ~1.4k | Automated safety check: Pass | Apache-2.0 | |
| Langfuse Integration Pagelangfuse/langfuse-docs | 246 | — | ~3.7k | Automated safety check: Pass | MIT | |
| Langfuselangfuse/skills | 301 | — | ~2.1k | Automated safety check: Notes | MIT | |
| Livetablegurujada/live_table | 211 | — | ~1.9k | Automated safety check: Pass | MIT |
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Categories
Questions about Phx Boundaries
What does Phx Boundaries do?
Analyze Phoenix context boundaries and module coupling via mix xref. Phx Boundaries is an agent skill from oliver-kriska/claude-elixir-phoenix. Analyze Phoenix context boundaries and module coupling via mix xref.
When should I use Phx Boundaries?
Phx Boundaries fits situations like: checking cross-context calls; validating dependencies; before splitting modules; reviewing architecture.
How do I install Phx Boundaries in Claude Code?
Run `npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-boundaries -a claude-code`. Or copy the skill folder (targets/pi/skills/phx-boundaries in oliver-kriska/claude-elixir-phoenix) into .claude/skills/phx-boundaries in your project. Claude Code loads it when a task matches its description.
How do I install Phx Boundaries in Codex?
Run `npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-boundaries -a codex`. Or copy the skill folder (targets/pi/skills/phx-boundaries in oliver-kriska/claude-elixir-phoenix) into .agents/skills/phx-boundaries in your project. Codex loads it when a task matches its description.
Can I use Phx Boundaries in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add oliver-kriska/claude-elixir-phoenix --skill phx-boundaries -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/phx-boundaries, .gemini/skills/phx-boundaries, .github/skills/phx-boundaries and .opencode/skills/phx-boundaries in your project.
What does Phx Boundaries need to run?
SKILL.md names no scripts, command-line tools or credentials: Phx Boundaries is instructions for the agent only.
Does Phx Boundaries access the network?
SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.
Is Phx Boundaries safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Phx Boundaries use?
Phx Boundaries is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Phx Boundaries use?
About 1.1k tokens (SKILL.md is roughly 4.6k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full. Its references folder adds about 2.3k tokens, read only when the agent opens those files.
What are the alternatives to Phx Boundaries?
Skills that share tags, products or a category with Phx Boundaries: Langfuse Codebase Navigator (langfuse/langfuse, 36k stars), LLM Trace Review Interface (ai-evals-course/evals-skills, 1.5k stars), Langfuse Integration Page (langfuse/langfuse-docs, 246 stars) and Langfuse (langfuse/skills, 301 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Phx Boundaries?
oliver-kriska (a GitHub user) maintains it in oliver-kriska/claude-elixir-phoenix, which has 565 GitHub stars. The repository holds 109 skills in this directory. The repository was last updated on October 5, 2026.
Source: oliver-kriska/claude-elixir-phoenix on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.