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Agent skill

Return Error Not Panic

by 0xMiden in 0xMiden/protocol

A skill your agent uses when writing a public Rust API, a deserialization path, or any code reachable from untrusted input — surface recoverable failures as a Result.

MITAuto-check passedDevelopment

Install Return Error Not Panic

skills CLI
$ npx skills add 0xMiden/protocol --skill return-error-not-panic -a claude-code

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

GitHub CLI
$ gh skill install 0xMiden/protocol return-error-not-panic --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/0xMiden/protocol.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.claude/skills/return-error-not-panic .claude/skills/return-error-not-panic && 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/

Facts

Skill name
return-error-not-panic
GitHub stars
133
Token cost
~671 tokens
SKILL.md length
215 words
Files
1
Skills in repo
34
Repo updated
First seen
Licence
MIT

At a glance

A skill your agent uses when writing a public Rust API, a deserialization path, or any code reachable from untrusted input — surface recoverable failures as a Result.

  • Writing a public Rust API
  • SKILL.md covers Rule, Why and Examples
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
  • A deserialization path

What it does

Return Error Not Panic is an agent skill from 0xMiden/protocol. Use when writing a public Rust API, a deserialization path, or any code reachable from untrusted input — surface recoverable failures as a Result.

Its SKILL.md is about 670 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Development. It works with Rust. The repository describes itself as: Core components of the Miden protocol. The licence is MIT.

When your agent uses it

  • Writing a public Rust API
  • A deserialization path
  • Any code reachable from untrusted input — surface recoverable failures as a Result

Example prompts

  • “/return-error-not-panic”

What it can do on your machine

Read from SKILL.md and the folder at commit 3a8215e. 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 rust).

    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

Return Error Not Panic loads about 671 tokens when it runs. Until then it costs about 43 tokens; SKILL.md has 215 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~43
When it runs · the whole SKILL.md, loaded when a task matches
~671

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 0xMiden/protocol at commit 3a8215e, republished under its MIT licence (© 0xMiden). 215 words, ~671 tokens.

Download SKILL.mdSave it as .claude/skills/return-error-not-panic/SKILL.md (or your agent's skills folder).
name
return-error-not-panic
description
Use when writing a public Rust API, a deserialization path, or any code reachable from untrusted input — surface recoverable failures as a `Result`.

Return Errors, Don't Panic on External Input

Rule

Functions that touch external input — public API entry points, Deserializable::read_from, RPC handlers, advice-provider readers, parsing of user data — must surface failures as Err, not panics:

  • No unwrap(), expect(), or panic! on values whose validity depends on external data.
  • No unwrap_or_default() to silently substitute a fallback for invalid input.
  • No Option<T> return type that hides the cause of failure when a real error is available.
  • Missing required input is itself an error — don't substitute zero/empty/default and continue.

Convert any internal panic on external-derived values into a typed error variant.

Two-tier API for the trusted case

When a no-check fast path is genuinely needed for callers operating on already-validated in-memory state, expose it as a separate constructor (e.g. new_unchecked, from_parts_unchecked) with a # Safety doc comment spelling out the caller's obligation. The default constructor stays fallible.

Why

A panic on untrusted input is a denial-of-service vector and a debugging black hole, and unwrap_or_default() is worse — it fabricates a valid-looking value the caller never sent. A named *_unchecked entry point keeps the default path strict while forcing opt-in callers to acknowledge what they skip.

Examples

rust
// Good
pub fn parse_account_id(bytes: &[u8]) -> Result<AccountId, AccountError> {
    if bytes.len() != ACCOUNT_ID_LEN {
        return Err(AccountError::InvalidLength { expected: ACCOUNT_ID_LEN, got: bytes.len() });
    }
    AccountId::try_from(bytes)
}

// Bad: panics on bad input
pub fn parse_account_id(bytes: &[u8]) -> AccountId {
    AccountId::try_from(bytes).unwrap()
}

// Bad: silently substitutes a default
pub fn parse_account_id(bytes: &[u8]) -> AccountId {
    AccountId::try_from(bytes).unwrap_or_default()
}

Two-tier API when a trusted fast path is justified:

rust
impl AccountId {
    /// Fallible default — validates the bytes.
    pub fn try_from_bytes(b: &[u8]) -> Result<Self, AccountError> { /* ... */ }

    /// # Safety
    /// Caller must guarantee `b` came from a previously validated source
    /// (e.g. a value already constructed via `try_from_bytes`).
    pub fn from_bytes_unchecked(b: &[u8]) -> Self { /* ... */ }
}

For the MASM analog (validating against a commitment, content-addressed advice keys, erroring on missing advice), see advice-provider-hygiene.

© 0xMiden, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in .claude/skills/return-error-not-panic of 0xMiden/protocol.

Open the folder on GitHubat commit 3a8215e

Compare with similar skills

Return Error Not Panic 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.

Return Error Not Panic compared with similar skills
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Return Error Not Panic this skill0xMiden/protocol133—~671Automated safety check: PassMIT
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Rust Best Practicesfarm-fe/farm5.6k3 repos~1.1kAutomated safety check: PassMIT
OpenLogi macOS Permissions TriageAprilNEA/OpenLogi23k—~2.5kAutomated safety check: NotesApache-2.0
RTK Rust Design Patternsrtk-ai/rtk83k—~1.9kAutomated safety check: PassApache-2.0
Release Skillsnexmoe/eve4213 repos~3.3kAutomated safety check: PassNone

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Works with

Categories

Questions about Return Error Not Panic

What does Return Error Not Panic do?

A skill your agent uses when writing a public Rust API, a deserialization path, or any code reachable from untrusted input — surface recoverable failures as a Result. Return Error Not Panic is an agent skill from 0xMiden/protocol. Use when writing a public Rust API, a deserialization path, or any code reachable from untrusted input — surface recoverable failures as a Result.

When should I use Return Error Not Panic?

Return Error Not Panic fits situations like: writing a public Rust API; A deserialization path; any code reachable from untrusted input — surface recoverable failures as a Result.

How do I install Return Error Not Panic in Claude Code?

Run `npx skills add 0xMiden/protocol --skill return-error-not-panic -a claude-code`. Or copy the skill folder (.claude/skills/return-error-not-panic in 0xMiden/protocol) into .claude/skills/return-error-not-panic in your project. Claude Code loads it when a task matches its description.

How do I install Return Error Not Panic in Codex?

Run `npx skills add 0xMiden/protocol --skill return-error-not-panic -a codex`. Or copy the skill folder (.claude/skills/return-error-not-panic in 0xMiden/protocol) into .agents/skills/return-error-not-panic in your project. Codex loads it when a task matches its description.

Can I use Return Error Not Panic 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 0xMiden/protocol --skill return-error-not-panic -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/return-error-not-panic, .gemini/skills/return-error-not-panic, .github/skills/return-error-not-panic and .opencode/skills/return-error-not-panic in your project.

What does Return Error Not Panic need to run?

SKILL.md names no scripts, command-line tools or credentials: Return Error Not Panic is instructions for the agent only.

Does Return Error Not Panic 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 Return Error Not Panic 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 Return Error Not Panic use?

Return Error Not Panic 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 Return Error Not Panic use?

About 671 tokens (SKILL.md is roughly 2.7k 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 Return Error Not Panic?

Skills that share tags, products or a category with Return Error Not Panic: Migrate Core Code to Submodules (tinyhumansai/openhuman, 41k stars), Rust Best Practices (farm-fe/farm, 5.6k stars), OpenLogi macOS Permissions Triage (AprilNEA/OpenLogi, 23k stars) and RTK Rust Design Patterns (rtk-ai/rtk, 83k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Return Error Not Panic?

0xMiden (a GitHub organization) maintains it in 0xMiden/protocol, which has 133 GitHub stars. The repository holds 34 skills in this directory. The repository was last updated on October 6, 2026.

Source: 0xMiden/protocol on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.