Agent skill

Elixir OTP Concurrency

by georgeguimaraes in georgeguimaraes/elixir-agent-tools

Guides choices among GenServer, Supervisor, Task, Registry, ETS and Broadway when designing or debugging Elixir concurrency, state and fault recovery.

Apache-2.0Auto-check passedBackend & APIs

Install Elixir OTP Concurrency

skills CLI

$ npx skills add georgeguimaraes/elixir-agent-tools --skill otp -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install georgeguimaraes/elixir-agent-tools otp --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/georgeguimaraes/elixir-agent-tools.git skills-src && mkdir -p .claude/skills && cp -r skills-src/plugins/elixir-dev/skills/otp .claude/skills/otp && rm -rf skills-src

Use ~/.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/

Paste into Claude Code

Install the "otp" agent skill from https://github.com/georgeguimaraes/elixir-agent-tools/tree/main/plugins/elixir-dev/skills/otp into .claude/skills/otp/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "otp", 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

$skill-installer install https://github.com/georgeguimaraes/elixir-agent-tools/tree/main/plugins/elixir-dev/skills/otp

Type 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.

skills CLI

$ npx skills add georgeguimaraes/elixir-agent-tools --skill otp -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install georgeguimaraes/elixir-agent-tools otp --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/georgeguimaraes/elixir-agent-tools.git skills-src && mkdir -p .agents/skills && cp -r skills-src/plugins/elixir-dev/skills/otp .agents/skills/otp && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "otp" agent skill from https://github.com/georgeguimaraes/elixir-agent-tools/tree/main/plugins/elixir-dev/skills/otp into .agents/skills/otp/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "otp", 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.

skills CLI

$ npx skills add georgeguimaraes/elixir-agent-tools --skill otp -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install georgeguimaraes/elixir-agent-tools otp --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/georgeguimaraes/elixir-agent-tools.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/plugins/elixir-dev/skills/otp .cursor/skills/otp && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "otp" agent skill from https://github.com/georgeguimaraes/elixir-agent-tools/tree/main/plugins/elixir-dev/skills/otp into .cursor/skills/otp/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "otp", 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

$ gemini skills install https://github.com/georgeguimaraes/elixir-agent-tools.git --path plugins/elixir-dev/skills/otp

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add georgeguimaraes/elixir-agent-tools --skill otp -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install georgeguimaraes/elixir-agent-tools otp --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/georgeguimaraes/elixir-agent-tools.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/plugins/elixir-dev/skills/otp .gemini/skills/otp && rm -rf skills-src

Use ~/.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/

Paste into Gemini CLI

Install the "otp" agent skill from https://github.com/georgeguimaraes/elixir-agent-tools/tree/main/plugins/elixir-dev/skills/otp into .gemini/skills/otp/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "otp", 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.

GitHub CLI

$ gh skill install georgeguimaraes/elixir-agent-tools otp

Installs 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).

skills CLI

$ npx skills add georgeguimaraes/elixir-agent-tools --skill otp -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/georgeguimaraes/elixir-agent-tools.git skills-src && mkdir -p .github/skills && cp -r skills-src/plugins/elixir-dev/skills/otp .github/skills/otp && rm -rf skills-src

Use ~/.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/

Paste into GitHub Copilot

Install the "otp" agent skill from https://github.com/georgeguimaraes/elixir-agent-tools/tree/main/plugins/elixir-dev/skills/otp into .github/skills/otp/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "otp", 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.

skills CLI

$ npx skills add georgeguimaraes/elixir-agent-tools --skill otp -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install georgeguimaraes/elixir-agent-tools otp --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/georgeguimaraes/elixir-agent-tools.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/plugins/elixir-dev/skills/otp .opencode/skills/otp && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "otp" agent skill from https://github.com/georgeguimaraes/elixir-agent-tools/tree/main/plugins/elixir-dev/skills/otp into .opencode/skills/otp/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "otp", 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: otp
GitHub stars: 184
Token cost: ~1.2k tokens
SKILL.md length: 455 words
Files: 1
Skills in repo: 5
Repo updated: Sep 20, 2026
First seen: Oct 7, 2026
Licence: Apache-2.0

At a glance

Guides choices among GenServer, Supervisor, Task, Registry, ETS and Broadway when designing or debugging Elixir concurrency, state and fault recovery.

Works in 3 steps: Do I actually need serialized access? → Will this become a throughput bottleneck? → Can reads bypass the GenServer via ETS?
Deciding whether a piece of state needs a GenServer at all
SKILL.md covers The Iron Law, GenServer Patterns, Task.Supervisor, Not Task.async and DynamicSupervisor + Registry =…, plus 8 more sections
Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

The central rule is that a GenServer is a bottleneck by design, since it handles one message at a time. Before creating one, ask whether serialized access is really needed, whether it will limit throughput and whether reads can skip it through ETS. The suggested pattern has the GenServer own the ETS table, send writes through itself and let reads bypass it with read concurrency. Stateless functions should not be wrapped in a GenServer. Prefer `call` for back-pressure with sensible timeouts, and use `handle_continue` for post-init work.

Further guidance covers Task.Supervisor over Task.async, because linked tasks take the caller down while `async_nolink` lets it survive. DynamicSupervisor supports only one-for-one strategy and should pair with Registry for names, never dynamically created atoms, with PartitionSupervisor for scale. Registry serves a single node and `:pg` a cluster, and Horde adds a distributed supervisor and registry. Broadway suits external queues such as SQS, Kafka or RabbitMQ, while Oban handles durable database-backed background jobs.

When your agent uses it

Deciding whether a piece of state needs a GenServer at all
Fixing a process bottleneck in an Elixir application
Choosing between Task.async and Task.Supervisor for background work
Designing dynamic named processes with Registry and DynamicSupervisor

Example prompts

“Review this GenServer cache and move the reads to ETS.”
“Replace Task.async in our importer with something that survives task crashes.”
“Design a supervised process per chat room using Registry and DynamicSupervisor.”
“Should this SQS consumer use Broadway or Oban?”

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

Do I actually need serialized access?
Will this become a throughput bottleneck?
Can reads bypass the GenServer via ETS?

What it can do on your machine

Read from SKILL.md and the folder at commit ac3a5a1. 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 elixir).
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

Elixir OTP Concurrency loads about 1.2k tokens when it runs. Until then it costs about 60 tokens; SKILL.md has 455 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~60
When it runs · the whole SKILL.md, loaded when a task matches: ~1.2k

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 georgeguimaraes/elixir-agent-tools at commit ac3a5a1, republished under its Apache-2.0 licence (© georgeguimaraes). 455 words, ~1,242 tokens.

Download SKILL.mdSave it as .claude/skills/otp/SKILL.md (or your agent's skills folder).

name: otp
description: Design and debug Elixir runtime concurrency, process state, and supervision. Use for GenServer, Supervisor, Task, Registry, ETS, process bottlenecks, and Broadway pipelines. Use oban for durable background jobs, retries, and scheduling.

OTP

Choose processes, supervision strategies, and storage for runtime concurrency and fault recovery.

The Iron Law

GENSERVER IS A BOTTLENECK BY DESIGN

A GenServer processes ONE message at a time. Before creating one, ask:

Do I actually need serialized access?
Will this become a throughput bottleneck?
Can reads bypass the GenServer via ETS?

The ETS pattern: GenServer owns ETS table, writes serialize through GenServer, reads bypass it entirely with :read_concurrency.

No exceptions: Don't wrap stateless functions in GenServer. Don't create GenServer "for organization".

GenServer Patterns

Function	Use For
`call/3`	Synchronous requests expecting replies
`cast/2`	Fire-and-forget messages

When in doubt, use call to ensure back-pressure. Set appropriate timeouts for call/3.

Use handle_continue/2 for post-init work—keeps init/1 fast and non-blocking.

Task.Supervisor, Not Task.async

Task.async spawns a linked process—if task crashes, caller crashes too.

Pattern	On task crash
`Task.async/1`	Caller crashes (linked, unsupervised)
`Task.Supervisor.async/2`	Caller crashes (linked, supervised)
`Task.Supervisor.async_nolink/2`	Caller survives, can handle error

Use Task.Supervisor for: Production code, graceful shutdown, observability, async_nolink. Use Task.async for: Quick experiments, scripts, when crash-together is acceptable.

DynamicSupervisor + Registry = Named Dynamic Processes

DynamicSupervisor only supports :one_for_one (dynamic children have no ordering). Use Registry for names—never create atoms dynamically:

elixir

defp via_tuple(id), do: {:via, Registry, {MyApp.Registry, id}}

PartitionSupervisor scales DynamicSupervisor for millions of children.

:pg for Distributed, Registry for Local

Tool	Scope	Use Case
Registry	Single node	Named dynamic processes
:pg	Cluster-wide	Process groups, pub/sub

:pg replaced deprecated :pg2. Horde provides distributed supervisor/registry with CRDTs.

Broadway vs Oban: Different Problems

Tool	Use For
Broadway	External queues (SQS, Kafka, RabbitMQ) — data ingestion with batching
Oban	Background jobs with database persistence

Broadway is NOT a job queue.

Show full SKILL.md (199 more words)Show less

Broadway Gotchas

Processors are for runtime, not code organization. Dispatch to modules in handle_message, don't add processors for different message types.

one_for_all is for Broadway bugs, not your code. Your handle_message errors are caught and result in failed messages, not supervisor restarts.

Handle expected failures in the producer (connection loss, rate limits). Reserve max_restarts for unexpected bugs.

Supervision Strategies Encode Dependencies

Strategy	Children Relationship
:one_for_one	Independent
:one_for_all	Interdependent (all restart)
:rest_for_one	Sequential dependency

Use :max_restarts and :max_seconds to prevent restart loops.

Think about failure cascades BEFORE coding.

Abstraction Decision Tree

Need state?
├── No → Plain function
└── Yes → Complex behavior?
    ├── No → Agent
    └── Yes → Supervision?
        ├── No → spawn_link
        └── Yes → Request/response?
            ├── No → Task.Supervisor
            └── Yes → Explicit states?
                ├── No → GenServer
                └── Yes → GenStateMachine

Storage Options

Need	Use
Memory cache	ETS (`:read_concurrency` for reads)
Static config	:persistent_term (faster than ETS)
Disk persistence	DETS (2GB limit)
Transactions/Distribution	Mnesia

:sys Debugs ANY OTP Process

elixir

:sys.get_state(pid)        # Current state
:sys.trace(pid, true)      # Trace events (TURN OFF when done!)

Telemetry Is Built Into Everything

Phoenix, Ecto, and most libraries emit telemetry events. Attach handlers:

elixir

:telemetry.attach("my-handler", [:phoenix, :endpoint, :stop], &handle/4, nil)

Use Telemetry.Metrics + reporters (StatsD, Prometheus, LiveDashboard).

Red Flags - STOP and Reconsider

GenServer wrapping stateless computation
Task.async in production when you need error handling
Creating atoms dynamically for process names
Single GenServer becoming throughput bottleneck
Using Broadway for background jobs (use Oban)
Using Oban for external queue consumption (use Broadway)
No supervision strategy reasoning

Any of these? Re-read The Iron Law and use the Abstraction Decision Tree.

Files

Just SKILL.md in plugins/elixir-dev/skills/otp of georgeguimaraes/elixir-agent-tools.

Open the folder on GitHubat commit ac3a5a1

Compare with similar skills

Elixir OTP Concurrency 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.

Elixir OTP Concurrency compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
Elixir OTP Concurrency this skillgeorgeguimaraes/elixir-agent-tools	184	—	~1.2k	Automated safety check: Pass	Apache-2.0	21 days ago
Dotnet Backend Patternswshobson/agents	40k	8 repos	~6.6k	Automated safety check: Pass	MIT	6 days ago
Nodejsblencorp/claude-code-kit	106	—	~2.6k	Automated safety check: Pass	MIT	10 mo ago
C# and .NET DeveloperJeffallan/claude-skills	12k	—	~1.3k	Automated safety check: Pass	MIT	7 days ago
Python Prodiegosouzapw/awesome-omni-skills	159	—	~3.8k	Automated safety check: Pass	MIT	3 mo ago
FastAPI Project Templateswshobson/agents	40k	11 repos	~901	Automated safety check: Pass	MIT	6 days ago

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Questions about Elixir OTP Concurrency

What does Elixir OTP Concurrency do?

Guides choices among GenServer, Supervisor, Task, Registry, ETS and Broadway when designing or debugging Elixir concurrency, state and fault recovery. The central rule is that a GenServer is a bottleneck by design, since it handles one message at a time. Before creating one, ask whether serialized access is really needed, whether it will limit throughput and whether reads can skip it through ETS.

When should I use Elixir OTP Concurrency?

Elixir OTP Concurrency fits situations like: deciding whether a piece of state needs a GenServer at all; fixing a process bottleneck in an Elixir application; choosing between Task.async and Task.Supervisor for background work; designing dynamic named processes with Registry and DynamicSupervisor.

How do I install Elixir OTP Concurrency in Claude Code?

Run `npx skills add georgeguimaraes/elixir-agent-tools --skill otp -a claude-code`. Or copy the skill folder (plugins/elixir-dev/skills/otp in georgeguimaraes/elixir-agent-tools) into .claude/skills/otp in your project. Claude Code loads it when a task matches its description.

How do I install Elixir OTP Concurrency in Codex?

Run `npx skills add georgeguimaraes/elixir-agent-tools --skill otp -a codex`. Or copy the skill folder (plugins/elixir-dev/skills/otp in georgeguimaraes/elixir-agent-tools) into .agents/skills/otp in your project. Codex loads it when a task matches its description.

Can I use Elixir OTP Concurrency 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 georgeguimaraes/elixir-agent-tools --skill otp -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/otp, .gemini/skills/otp, .github/skills/otp and .opencode/skills/otp in your project.

What does Elixir OTP Concurrency need to run?

SKILL.md names no scripts, command-line tools or credentials: Elixir OTP Concurrency is instructions for the agent only.

Does Elixir OTP Concurrency 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 Elixir OTP Concurrency 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 Elixir OTP Concurrency use?

Elixir OTP Concurrency is published under the Apache-2.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Elixir OTP Concurrency use?

About 1.2k tokens (SKILL.md is roughly 5k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Elixir OTP Concurrency?

Skills that share tags, products or a category with Elixir OTP Concurrency: Dotnet Backend Patterns (wshobson/agents, 40k stars), Nodejs (blencorp/claude-code-kit, 106 stars), C# and .NET Developer (Jeffallan/claude-skills, 12k stars) and Python Pro (diegosouzapw/awesome-omni-skills, 159 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Elixir OTP Concurrency?

georgeguimaraes (a GitHub user) maintains it in georgeguimaraes/elixir-agent-tools, which has 184 GitHub stars. The repository holds 5 skills in this directory. The repository was last updated on September 20, 2026.

Source: georgeguimaraes/elixir-agent-tools on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install Elixir OTP Concurrency

Facts

At a glance

What it does

When your agent uses it

Example prompts

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

OTP

The Iron Law

GenServer Patterns

Task.Supervisor, Not Task.async

DynamicSupervisor + Registry = Named Dynamic Processes

:pg for Distributed, Registry for Local

Broadway vs Oban: Different Problems

Broadway Gotchas

Supervision Strategies Encode Dependencies

Abstraction Decision Tree

Storage Options

:sys Debugs ANY OTP Process

Telemetry Is Built Into Everything

Red Flags - STOP and Reconsider

Files

Compare with similar skills

Similar skills

More from georgeguimaraes/elixir-agent-tools

Related

Questions about Elixir OTP Concurrency