agentmods.dev

fun-with-flags

A feature-flag setup for switching application features on or off while the app is running. Feature flags are runtime switches that can also limit a feature to selected users or teams.

In plain words
What is it for?
Use it for staged rollouts, user- or team-specific access, and emergency kill switches. It includes database storage, cache updates, wrapper modules, and an administration page.
Why use it?
It lets you release changes gradually or disable a faulty feature without redeploying the application.

Skill for Claude CodeCodex

2 2mo ago A scan 54 tokens original MIT
View the source file fullstack-phoenix/saas_kit
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/fullstack-phoenix/saas_kit/fun-with-flags
Any agent
npx skills add fullstack-phoenix/saas_kit --skill fun-with-flags
Clone the repo
git clone --depth 1 https://github.com/fullstack-phoenix/saas_kit

Made for: Claude Code, Codex.

Per session 54 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,301 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00054 $0.01301
Opus 5 $0.00027 $0.00651
Sonnet 5 $0.00011 $0.00260
Haiku 4.5 $0.00005 $0.00130

Measured yesterday against content hash 009f09133322, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

fun-with-flags scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/fun-with-flags/SKILL.md · 141 lines

How it starts

The opening of the file, as written. The whole thing — 141 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Feature flags with FunWithFlags

Wires FunWithFlags into the app with the Ecto persistence adapter and Phoenix PubSub cache notifications, so flags toggle at runtime without a deploy. Adds two app-owned wrapper modules — MyApp.Feature for application code and MyAppWeb.FeatureFlags for conns/sockets/assigns — plus a web admin UI for managing flags. When authentication or teams are installed, it generates the FunWithFlags.Actor implementations needed to gate flags per user and per team.

When to use

  • The app needs to turn features on/off at runtime without a deploy or restart.
  • You want gradual rollouts (enable a flag for specific users or teams first).
  • You need an emergency kill switch for a misbehaving feature.
  • Don't reach for this for static, compile-time config — use config/*.exs instead. Flags add a DB table and runtime lookups.

Dependencies

  • Requires: None.
  • Recommended: None. Install authentication first if you want per-user gating, and teams for per-team gating — the actor implementations are generated only when those features are present.

Install

mix saaskit.feature.install fun_with_flags

No install decisions. Behavior adapts to what's already installed:

  • With admin: mounts the flag UI at /admin/feature-flags behind :require_authenticated_user + :require_admin_user, and adds a link on the admin developer page. Without admin: mounts an unguarded UI at /feature-flags.
  • With authentication: generates lib/my_app/feature_actor/user.ex.
  • With teams: generates lib/my_app/feature_actor/team.ex.

What it generates

  • lib/my_app/feature.ex — MyApp.Feature.enabled?/2, the domain-level API. Resolves a %{team:, user:} scope and OR's the team and user gates.
  • lib/my_app_web/feature_flags.ex — MyAppWeb.FeatureFlags.enabled?/2, accepts a conn, LiveView socket, or assigns map and forwards :current_scope.
  • lib/my_app/feature_actor/user.ex — FunWithFlags.Actor impl for User (only with authentication).
  • lib/my_app/feature_actor/team.ex — FunWithFlags.Actor impl for Team (only with teams).
  • Migration priv/repo/migrations/*_create_feature_flags_table.exs — creates the fun_with_flags_toggles table with the configured primary-key type.
  • Router scope mounting FunWithFlags.UI.Router.
  • Adds :fun_with_flags and :fun_with_flags_ui to mix.exs.

Read the full file on GitHub · 141 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 141 lines · 54 tokens per session scan A 009f09133322

Subscribe to this mod's changes

fun-with-flags is a skill published in the GitHub repository fullstack-phoenix/saas_kit (2 stars, last pushed 2mo ago), licensed MIT. It adds 54 tokens to every session and 1,301 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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