Happier is an open-source, end-to-end encrypted client that lets people run AI coding-agent sessions on a computer and continue controlling them from a phone, browser, or desktop app. It is for developers who use agents such as Claude Code, Codex, Gemini, or OpenCode across multiple devices, with self-hosting available. The catalogue entries are add-ons for configuring or extending this client and its supported coding-agent workflows.
Borrowing it
Nothing to install: this file belongs to happier-dev/happier. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/happier-dev/happier/dev/.agents/skills/happier-compatibility/SKILL.mdgit clone --depth 1 https://github.com/happier-dev/happierWrote 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/happier-dev/happier/happier-compatibility)<a href="https://agentmods.dev/skills/happier-dev/happier/happier-compatibility"><img src="https://agentmods.dev/badge/skills/happier-dev/happier/happier-compatibility/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/happier-dev/happier/happier-compatibility"><img src="https://agentmods.dev/badge/skills/happier-dev/happier/happier-compatibility.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00076 | $0.01665 |
| Opus 5.5 | $0.00030 | $0.00666 |
| Sonnet 5.5 | $0.00015 | $0.00333 |
| Haiku 4.5 | $0.00008 | $0.00167 |
Grade A, and why
happier-compatibility 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 — 113 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Happier Compatibility
Preserve real released and prospective predecessor behavior at system seams without preserving undeployed internal architecture or creating speculative compatibility debt.
Read docs/compatibility.md before acting. Also read the owning package instructions and the domain document for the affected protocol, feature, encryption, provider, installer, or persistence surface.
1. Classify the surface
Name the observable contract and classify it as wire, semantic, persistence, operational/installer, or internal-only.
If the change is internal-only and leaves external readers, writers, artifacts, and rollout behavior unchanged, stop the compatibility workflow. Do not create a matrix, shim, migration, or compatibility test merely because code moved.
2. Establish evidence-backed baselines
- Resolve active stable and preview baselines independently for every affected component. Record immutable version tag, commit, and artifact/deploy evidence; do not use a rolling tag alone as the final basis.
- Include older versions only when explicitly supported.
- Exclude
devbuilds, undeployed internal paths, and abandoned intermediates from lasting obligations. - Apply any repository-specific predecessor rule in
docs/compatibility.md. When it requires a live sibling worktree, inspect committed, staged, and unstaged code without modifying it and label observed versus inferred behavior.
Do not proceed from a vague claim such as “the old client probably sends this.” Inspect the released/predecessor producer, reader, serializer, artifact, or pinned golden vector.
Before building against an external or another-program-owned contract, characterize its success, failure, cancellation, and recovery behavior as provenance-pinned RED fixtures or runtime observations. Freeze the exact contract basis for the implementation/review slice; do not repeatedly review line-level adapters against a moving producer.
3. Map the corridor and close split-brains
Inventory the canonical owner and all affected producers, consumers, readers, writers, parsers, serializers, registries, decisions, persistence shapes, tests, and adapters.
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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 Changed · +10 lines a069f5941526
- 1mo ago Changed 4b53a6953faf
- 1mo ago First seen · 103 lines · 76 tokens per session scan A bb46a769448f
happier-compatibility is a skill published in the GitHub repository happier-dev/happier (2,072 stars, last pushed yesterday), licensed MIT. It adds 76 tokens to every session and 1,665 once invoked, about $0.0003 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 2026-09-03.
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