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.
npx skills add BuilderCed/agent-skills --skill offline-first-developmentgit clone --depth 1 https://github.com/BuilderCed/agent-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/builderced/agent-skills/offline-first-development)<a href="https://agentmods.dev/skills/builderced/agent-skills/offline-first-development"><img src="https://agentmods.dev/badge/skills/builderced/agent-skills/offline-first-development/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/builderced/agent-skills/offline-first-development"><img src="https://agentmods.dev/badge/skills/builderced/agent-skills/offline-first-development.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00024 | $0.00974 |
| Opus 5.5 | $0.00010 | $0.00390 |
| Sonnet 5.5 | $0.00005 | $0.00195 |
| Haiku 4.5 | $0.00002 | $0.00097 |
Grade A, and why
offline-first-development 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 1mo ago.
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.
How it starts
The opening of the file, as written. The whole thing — 137 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Offline-First Development
When to Use
- Building apps for low-connectivity environments (rural, Africa, transit)
- Building PWAs that must work without internet
- Designing sync strategies for mobile apps
- Implementing local-first architectures
- Building for environments with unreliable connections
Core Principles
- Local-first: Data lives on the device. Server is backup, not source of truth.
- Sync on reconnect: Queue changes offline, sync when connection returns.
- Conflict resolution: Define merge strategy before building.
- Progressive enhancement: App works offline; online adds features.
Storage Options
| Storage | Size Limit | Persistence | Best For |
|---|---|---|---|
| IndexedDB | ~50% of disk | Persistent | Structured data, large datasets |
| Cache API | ~50% of disk | Persistent | HTTP responses, assets |
| localStorage | 5-10 MB | Persistent | Small key-value config |
| OPFS | ~50% of disk | Persistent | File-like access (new) |
Recommendation: IndexedDB for data, Cache API for assets, OPFS for files.
Service Worker Pattern
Install → Cache essential assets (app shell, fonts, icons)
Activate → Clean old caches
Fetch → Cache-first for assets, network-first for API data
Sync → Background sync for queued mutations
Caching Strategies
| Strategy | When | How |
|---|---|---|
| Cache-first | Static assets (CSS, JS, images) | Serve from cache, update in background |
| Network-first | API data | Try network, fall back to cache |
| Stale-while-revalidate | Semi-static (user profile) | Serve cache, update from network |
| Network-only | Real-time data (chat, payments) | No caching |
Sync Patterns
Optimistic Updates
- Apply change locally immediately
- Queue mutation for sync
- On reconnect: send queued mutations
- On conflict: apply resolution strategy
Conflict Resolution Strategies
| Strategy | When | How |
|---|---|---|
| Last-write-wins | Simple data, single user | Timestamp comparison |
| Server-wins | Authoritative server | Discard local on conflict |
| Client-wins | User autonomy priority | Overwrite server |
| Merge | Collaborative editing | Field-level merge |
| Manual | Critical data | Show conflict to user |
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.
- 1mo ago First seen · 137 lines · 24 tokens per session scan A a89e3e7bb61a
offline-first-development is a skill published in the GitHub repository BuilderCed/agent-skills (2 stars, last pushed 6mo ago), licensed MIT. It adds 24 tokens to every session and 974 once invoked, about $0.0001 per session on Opus 5.5. 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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