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Agent skill

Codetrial Web

by sysprog21 in sysprog21/codetrial

The CodeTrial browser half and the boundary it talks across - why web/ has no build step, how a file reaches the browser embedded or from disk, the vendored checksum-pinned assets, the data-channel…

MITAuto-check passedDevelopment

Install Codetrial Web

skills CLI
$ npx skills add sysprog21/codetrial --skill codetrial-web -a claude-code

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

GitHub CLI
$ gh skill install sysprog21/codetrial codetrial-web --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/sysprog21/codetrial.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.claude/skills/codetrial-web .claude/skills/codetrial-web && 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
codetrial-web
GitHub stars
149
Token cost
~1.3k tokens
SKILL.md length
715 words
Files
1
Skills in repo
4
Repo updated
First seen
Licence
MIT

At a glance

The CodeTrial browser half and the boundary it talks across - why web/ has no build step, how a file reaches the browser embedded or from disk, the vendored checksum-pinned assets, the data-channel…

  • Works in 3 steps: Change the producer in web/lib.js. → Regenerate the fixtures and commit them… → Change the consumer the grep named,…
  • Editing anything under web/
  • SKILL.md covers How a file reaches the browser, Vendored assets, The data channel is two… and Generated pages, plus 1 more section
  • Calls node

What it does

Codetrial Web is an agent skill from sysprog21/codetrial. The CodeTrial browser half and the boundary it talks across - why web/ has no build step, how a file reaches the browser embedded or from disk, the vendored checksum-pinned assets, the data-channel topics implemented once in web/lib.js and once against the TOPIC constants in src/runtime.rs, in both directions, and the wire fixtures that keep the two agreeing. Use when editing anything under web/, adding or changing a data-channel message, touching src/web/, or wondering why a browser change passed every Rust test…

Its SKILL.md is about 1.3k 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: A live technical interview simulator. The licence is MIT.

When your agent uses it

  • Editing anything under web/
  • Changing a data-channel message
  • Touching src/web/
  • Wondering why a browser change passed every Rust test and still broke the interview

Example prompts

  • “/codetrial-web”

Workflow steps

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

  1. Change the producer in web/lib.js.
  2. Regenerate the fixtures and commit them with the change.
  3. Change the consumer the grep named, against the new fixture.

What it can do on your machine

Read from SKILL.md and the folder at commit a77b0db. 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

    Shell commands in SKILL.md call:

    • node

    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

Codetrial Web loads about 1.3k tokens when it runs. Until then it costs about 141 tokens; SKILL.md has 715 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~141
When it runs · the whole SKILL.md, loaded when a task matches
~1.3k

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 sysprog21/codetrial at commit a77b0db, republished under its MIT licence (© sysprog21). 715 words, ~1,292 tokens.

Download SKILL.mdSave it as .claude/skills/codetrial-web/SKILL.md (or your agent's skills folder).
name
codetrial-web
description
The CodeTrial browser half and the boundary it talks across - why web/ has no build step, how a file reaches the browser embedded or from disk, the vendored checksum-pinned assets, the data-channel topics implemented once in web/lib.js and once against the TOPIC_ constants in src/runtime.rs, in both directions, and the wire fixtures that keep the two agreeing. Use when editing anything under web/, adding or changing a data-channel message, touching src/web/, or wondering why a browser change passed every Rust test and still broke the interview.

The CodeTrial browser boundary

web/ is plain ES modules loaded by the page. There is no bundler, no transpile step and no framework, which is what makes an edit in the checkout visible on reload. Keep it that way: a build step here would turn every browser fix into a build artifact somebody has to remember to regenerate.

How a file reaches the browser

rust-embed compiles web/ into the binary, so a release build serves a complete application with no web/ directory beside it. The fallback is per file rather than wholesale: a file present on disk wins, and one that is missing is filled in from the embedded copy. That is why a partially populated tree serves rather than 404s, and why running the binary from a checkout picks up your edit with nothing set. --web-dir or CODETRIAL_WEB_DIR points that root somewhere else.

The consequence worth remembering: a debug build that reads from disk and a release build that serves embedded bytes can disagree, and only the second is what ships. scripts/test.sh covers this, and CI proves the binary serves with the web tree deleted.

Vendored assets

web/vendor/ holds third-party bytes, some committed and some fetched. The LiveKit client, avatar/three-vrm.js and MediaPipe JavaScript loaders are in git. FETCH manifests name the downloadable Pyodide, PDF.js and MediaPipe model/wasm payloads; only those files can be restored by scripts/fetch-vendor.sh. Both kinds are pinned by a SHA256SUMS beside them, and scripts/verify-vendor.sh checks them; both scripts are wired into the gate. Never edit a file under web/vendor/, never lint it, and never add a dependency by dropping a file there by hand: the checksum is the whole mechanism. The avatar model is not even vendored, the browser fetches it from a pinned upstream URL against a pinned hash, and the interview falls back to a voice-only panel when it is unreachable.

The data channel is two implementations

Every topic on the LiveKit data channel is implemented twice, and a change that tests only its own side is exactly the shape that once let the integrity hash diverge and silently empty the evidence section of every camera interview while the gate stayed green.

The direction decides what keeps the two sides honest. web/lib.js defines the topic set in topics and src/runtime.rs defines the matching TOPIC_* constants; that pair is the authority, and grep -rn TOPIC_ src/ names every Rust publisher and consumer, several of them outside src/agent/. A browser-to-agent topic has a generated producer fixture, and the files map in scripts/gen-wire-fixtures.mjs is the list of them, because that script builds each fixture from the real producer. An agent-to-browser topic has none, which is why web/lib.js guards the report topic with isAgent(participant) by hand.

Show full SKILL.md (267 more words)Show less

tests/fixtures/*.json are the answer: generated by node scripts/gen-wire-fixtures.mjs from the real producer, consumed by the Rust tests, and held to --check in the gate. So when you change a message that map names:

  1. Change the producer in web/lib.js.
  2. Regenerate the fixtures and commit them with the change.
  3. Change the consumer the grep named, against the new fixture.

A topic with no entry in that map has no generated fixture to lean on, so pair the Rust producer with the browser consumer by hand and test both sides.

Never hand-edit a fixture. Everything in the generator is deterministic, timestamps included, because a fixture that changes on every run cannot be checked.

Generated pages

web/problems/, web/judges/ and the problem cards inside web/index.html are generated from problem-bank/. Edit the bank and rerun the generators; see codetrial-verify.

The lint gate

eslint.config.mjs is narrow on purpose: every rule in it fails only where the code cannot mean what it says, so the gate never becomes something people learn to argue with. no-undef is the reason it exists, since a typo'd identifier in web/interview.js reaches a candidate's browser while the same mistake in src/web/mod.rs never leaves the terminal. Three recommended rules are excluded with the reasoning written above them. Adding an eslint-disable is a stronger claim than it looks: the tree carries none, and the few #[allow]s on the Rust half each have their reason on the same line. Match that bar or do not suppress the rule.

Browser behavior also gets a test, in tests/browser/*.test.js or, where it needs a real browser, scripts/browser-check.sh; codetrial-verify has what each lane requires.

© sysprog21, 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/codetrial-web of sysprog21/codetrial.

Open the folder on GitHubat commit a77b0db

Compare with similar skills

Codetrial Web 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.

Codetrial Web compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Codetrial Web this skillsysprog21/codetrial149—~1.3kAutomated safety check: PassMIT
Migrate Core Code to Submodulestinyhumansai/openhuman42k—~2.6kAutomated safety check: PassGPL-3.0
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 Codetrial Web

What does Codetrial Web do?

The CodeTrial browser half and the boundary it talks across - why web/ has no build step, how a file reaches the browser embedded or from disk, the vendored checksum-pinned assets, the data-channel…. Codetrial Web is an agent skill from sysprog21/codetrial.rs, in both directions, and the wire fixtures that keep the two agreeing.

When should I use Codetrial Web?

Codetrial Web fits situations like: editing anything under web/; changing a data-channel message; touching src/web/; wondering why a browser change passed every Rust test and still broke the interview.

How do I install Codetrial Web in Claude Code?

Run `npx skills add sysprog21/codetrial --skill codetrial-web -a claude-code`. Or copy the skill folder (.claude/skills/codetrial-web in sysprog21/codetrial) into .claude/skills/codetrial-web in your project. Claude Code loads it when a task matches its description.

How do I install Codetrial Web in Codex?

Run `npx skills add sysprog21/codetrial --skill codetrial-web -a codex`. Or copy the skill folder (.claude/skills/codetrial-web in sysprog21/codetrial) into .agents/skills/codetrial-web in your project. Codex loads it when a task matches its description.

Can I use Codetrial Web 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 sysprog21/codetrial --skill codetrial-web -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/codetrial-web, .gemini/skills/codetrial-web, .github/skills/codetrial-web and .opencode/skills/codetrial-web in your project.

What does Codetrial Web need to run?

Going by SKILL.md and its folder, Codetrial Web needs the command-line tools its instructions call (node).

Does Codetrial Web 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 Codetrial Web 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 Codetrial Web use?

Codetrial Web 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 Codetrial Web use?

About 1.3k tokens (SKILL.md is roughly 5.2k 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 Codetrial Web?

Skills that share tags, products or a category with Codetrial Web: Migrate Core Code to Submodules (tinyhumansai/openhuman, 42k 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 Codetrial Web?

sysprog21 (a GitHub organization) maintains it in sysprog21/codetrial, which has 149 GitHub stars. The repository holds 4 skills in this directory. The repository was last updated on October 7, 2026.

Source: sysprog21/codetrial on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.