Failure Oriented Instrumentation
ArabelaTso/Skills-4-SE
Selectively instruments code to capture runtime data for debugging failures and bugs.
Diagnose and fix standards-compatibility gaps in a browser engine across HTML, DOM, JavaScript bindings, events, CSSOM, forms, fetch, storage, and Web APIs.
Install Fix Web Platform Compat
$ npx skills add nordstjernen-web/northstar-browser --skill fix-web-platform-compat -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install nordstjernen-web/northstar-browser fix-web-platform-compat --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/nordstjernen-web/northstar-browser.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/fix-web-platform-compat .claude/skills/fix-web-platform-compat && rm -rf skills-srcUse ~/.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/
Install the "fix-web-platform-compat" agent skill from https://github.com/nordstjernen-web/northstar-browser/tree/main/.agents/skills/fix-web-platform-compat into .claude/skills/fix-web-platform-compat/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "fix-web-platform-compat", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/nordstjernen-web/northstar-browser/tree/main/.agents/skills/fix-web-platform-compatType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add nordstjernen-web/northstar-browser --skill fix-web-platform-compat -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install nordstjernen-web/northstar-browser fix-web-platform-compat --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/nordstjernen-web/northstar-browser.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.agents/skills/fix-web-platform-compat .agents/skills/fix-web-platform-compat && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "fix-web-platform-compat" agent skill from https://github.com/nordstjernen-web/northstar-browser/tree/main/.agents/skills/fix-web-platform-compat into .agents/skills/fix-web-platform-compat/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "fix-web-platform-compat", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add nordstjernen-web/northstar-browser --skill fix-web-platform-compat -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install nordstjernen-web/northstar-browser fix-web-platform-compat --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/nordstjernen-web/northstar-browser.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.agents/skills/fix-web-platform-compat .cursor/skills/fix-web-platform-compat && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "fix-web-platform-compat" agent skill from https://github.com/nordstjernen-web/northstar-browser/tree/main/.agents/skills/fix-web-platform-compat into .cursor/skills/fix-web-platform-compat/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "fix-web-platform-compat", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/nordstjernen-web/northstar-browser.git --path .agents/skills/fix-web-platform-compat--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add nordstjernen-web/northstar-browser --skill fix-web-platform-compat -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install nordstjernen-web/northstar-browser fix-web-platform-compat --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/nordstjernen-web/northstar-browser.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.agents/skills/fix-web-platform-compat .gemini/skills/fix-web-platform-compat && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "fix-web-platform-compat" agent skill from https://github.com/nordstjernen-web/northstar-browser/tree/main/.agents/skills/fix-web-platform-compat into .gemini/skills/fix-web-platform-compat/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "fix-web-platform-compat", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install nordstjernen-web/northstar-browser fix-web-platform-compatInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add nordstjernen-web/northstar-browser --skill fix-web-platform-compat -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/nordstjernen-web/northstar-browser.git skills-src && mkdir -p .github/skills && cp -r skills-src/.agents/skills/fix-web-platform-compat .github/skills/fix-web-platform-compat && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "fix-web-platform-compat" agent skill from https://github.com/nordstjernen-web/northstar-browser/tree/main/.agents/skills/fix-web-platform-compat into .github/skills/fix-web-platform-compat/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "fix-web-platform-compat", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add nordstjernen-web/northstar-browser --skill fix-web-platform-compat -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install nordstjernen-web/northstar-browser fix-web-platform-compat --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/nordstjernen-web/northstar-browser.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.agents/skills/fix-web-platform-compat .opencode/skills/fix-web-platform-compat && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "fix-web-platform-compat" agent skill from https://github.com/nordstjernen-web/northstar-browser/tree/main/.agents/skills/fix-web-platform-compat into .opencode/skills/fix-web-platform-compat/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "fix-web-platform-compat", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
fix-web-platform-compat- GitHub stars
- 127
- Token cost
- ~1.1k tokens
- SKILL.md length
- 545 words
- Files
- 2
- Skills in repo
- 5
- Repo updated
- First seen
- Licence
- GPL-3.0
At a glance
Diagnose and fix standards-compatibility gaps in a browser engine across HTML, DOM, JavaScript bindings, events, CSSOM, forms, fetch, storage, and Web APIs.
- Works in 4 steps: Reduce the problem to a minimal page or… → Read the authoritative WHATWG, W3C,… → Write down the observable contract:… → …
- Web Platform Test failures
- SKILL.md covers Define the contract, Find the owning layer, Apply the fix and Verify the result, plus 1 more section
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
What it does
Fix Web Platform Compat is an agent skill from nordstjernen-web/northstar-browser. Diagnose and fix standards-compatibility gaps in a browser engine across HTML, DOM, JavaScript bindings, events, CSSOM, forms, fetch, storage, and Web APIs. Use for Web Platform Test failures, missing or incorrect APIs, lifecycle differences, or standards behavior that breaks ordinary sites.
Its SKILL.md is about 1.1k tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files (for example `agents/openai.yaml`).
It sits in Testing & QA, covering Failing and flaky tests. It works with JavaScript. The repository describes itself as: Northstar web browser, Open Source License: GPL v3. Northstar web browser is a real web browser, not based on Firefox or Chrome. The licence is GPL-3.0.
When your agent uses it
- Web Platform Test failures
- Lifecycle differences
- Standards behavior that breaks ordinary sites
Example prompts
- “/fix-web-platform-compat”
Workflow steps
4 steps, taken from the first numbered list in SKILL.md.
- Reduce the problem to a minimal page or the narrowest relevant standards test.
- Read the authoritative WHATWG, W3C, TC39, Web IDL, or API specification. Use other browsers only as supporting evidence.
- Write down the observable contract: conversions, exceptions, property descriptors, identity, ordering, event timing, realm behavior…
- Record the current result before editing. Separate harness failures and timeouts from assertion failures.
What it can do on your machine
Read from SKILL.md and the folder at commit 98475ea. 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.
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
Fix Web Platform Compat loads about 1.1k tokens when it runs. Until then it costs about 79 tokens; SKILL.md has 545 words of instructions outside code blocks.
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 nordstjernen-web/northstar-browser at commit 98475ea, republished under its GPL-3.0 licence (© nordstjernen-web). 545 words, ~1,067 tokens.
Download SKILL.mdSave it as
.claude/skills/fix-web-platform-compat/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.- name
- fix-web-platform-compat
- description
- Diagnose and fix standards-compatibility gaps in a browser engine across HTML, DOM, JavaScript bindings, events, CSSOM, forms, fetch, storage, and Web APIs. Use for Web Platform Test failures, missing or incorrect APIs, lifecycle differences, or standards behavior that breaks ordinary sites.
Fix Web Platform Compatibility
Read the repository instructions, architecture notes, build guide, and current diff. Preserve unrelated changes.
Define the contract
- Reduce the problem to a minimal page or the narrowest relevant standards test.
- Read the authoritative WHATWG, W3C, TC39, Web IDL, or API specification. Use other browsers only as supporting evidence.
- Write down the observable contract: conversions, exceptions, property descriptors, identity, ordering, event timing, realm behavior, security checks, and side effects.
- Record the current result before editing. Separate harness failures and timeouts from assertion failures.
Find the owning layer
Route the first incorrect behavior to parsing, DOM state, language binding, CSS processing, networking, storage, or a dedicated API module. Follow data and lifetime across layer boundaries instead of adding a surface-level special case.
For native language bindings, match the engine's conventions for ownership, exceptions, prototypes, descriptors, realms, callbacks, and invalidated native handles. Prefer public dependency APIs and existing compatibility shims; do not patch fetched dependencies for browser-side behavior.
Apply the fix
Implement the smallest generic behavior required by the specification. Do not add site-specific workarounds, false feature-detection stubs, or no-op APIs that claim unsupported behavior. Keep deliberate product-scope exclusions intact.
Verify the result
Run the original case and the smallest targeted standards-test slice. Compare before and after counts, then run nearby tests that exercise the same primitive. Exercise the behavior through the real browser path, run deterministic smoke cases, and complete the documented build and launch gates.
Aggregate pass and fail totals hide compensating movement: a change can gain subtests in one file while losing them in another and still look flat. Diff the per-test results, not the totals, and account for every file that moved in either direction.
Build the baseline from the published head with your change alone applied. Comparing against a working tree that carries unrelated edits attributes their wins and losses to you; when a suite moves in an area your change cannot influence, rebuild the head plus only your diff before drawing any conclusion.
Show full SKILL.md (211 more words)Show less
Northstar routing
- Parsing and encoding:
src/html.c,src/html_lexbor.c,src/xml.c - DOM state and mutation:
src/dom.c,src/dom.h - QuickJS bindings and most Web APIs:
src/js.c,src/js_internal.h - CSS and CSSOM:
src/css_syntax.c,src/css.c,src/css_media.c,src/js.c - Fetch, URL, cache, and policy:
src/net.c,src/cache.c,src/csp.c - Dedicated APIs: the corresponding
src/*.cmodule - JavaScript fallbacks:
data/js/polyfills.js, only when native integration is unnecessary
Use scripts/wpt-fast.sh for scored WPT work: it serves the checkout, runs the headless --wpt harness in parallel, writes a wptreport.json, and prints per-standard scores. Point it at the checkout with --fast-root=DIR or NS_WPT_FAST_ROOT when it is not at ~/wpt-fast, and pass paths to limit the run to the subtrees you care about. scripts/wpt-run.sh covers a stock WPT checkout.
Do not open WPT tests over file://. They load /resources/testharness.js from the server root, which does not resolve, and the run reports a harness timeout that looks like an engine hang. Let the script serve the checkout, or serve it yourself before pointing the browser at http:// URLs.
Only testharness.js tests are scored; reftests and crashtests do not run under the headless harness. A visual difference therefore needs scripts/render-tests.sh or a layout dump, not a WPT score.
Use scripts/dev.sh smoke for deterministic baselines and the repository build workflow for final verification. Do not introduce a new test framework or tests/ directory.
© nordstjernen-web, GPL-3.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
SKILL.md and 1 other file in .agents/skills/fix-web-platform-compat of nordstjernen-web/northstar-browser.
- SKILL.md
- agents/openai.yaml
Open the folder on GitHubat commit 98475ea
Compare with similar skills
Fix Web Platform Compat 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.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Fix Web Platform Compat this skillnordstjernen-web/northstar-browser | 127 | — | ~1.1k | Automated safety check: Pass | GPL-3.0 | |
| Failure Oriented InstrumentationArabelaTso/Skills-4-SE | 253 | — | ~2.1k | Automated safety check: Pass | Apache-2.0 | |
| Fory Performance Optimizationapache/fory | 4.6k | — | ~2.2k | Automated safety check: Pass | Apache-2.0 | |
| Debug CIweb-infra-dev/rslint | 461 | — | ~2.8k | Automated safety check: Pass | MIT | |
| Replay Oriented InstrumentationArabelaTso/Skills-4-SE | 253 | — | ~2.5k | Automated safety check: Pass | Apache-2.0 | |
| Pester Failure AnalysisPowerShell/PowerShell | 56k | — | ~5.1k | Automated safety check: Pass | MIT |
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Related
Works with
Categories
Questions about Fix Web Platform Compat
What does Fix Web Platform Compat do?
Diagnose and fix standards-compatibility gaps in a browser engine across HTML, DOM, JavaScript bindings, events, CSSOM, forms, fetch, storage, and Web APIs. Fix Web Platform Compat is an agent skill from nordstjernen-web/northstar-browser. Diagnose and fix standards-compatibility gaps in a browser engine across HTML, DOM, JavaScript bindings, events, CSSOM, forms, fetch, storage, and Web APIs.
When should I use Fix Web Platform Compat?
Fix Web Platform Compat fits situations like: web Platform Test failures; lifecycle differences; standards behavior that breaks ordinary sites.
How do I install Fix Web Platform Compat in Claude Code?
Run `npx skills add nordstjernen-web/northstar-browser --skill fix-web-platform-compat -a claude-code`. Or copy the skill folder (.agents/skills/fix-web-platform-compat in nordstjernen-web/northstar-browser) into .claude/skills/fix-web-platform-compat in your project. Claude Code loads it when a task matches its description.
How do I install Fix Web Platform Compat in Codex?
Run `npx skills add nordstjernen-web/northstar-browser --skill fix-web-platform-compat -a codex`. Or copy the skill folder (.agents/skills/fix-web-platform-compat in nordstjernen-web/northstar-browser) into .agents/skills/fix-web-platform-compat in your project. Codex loads it when a task matches its description.
Can I use Fix Web Platform Compat 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 nordstjernen-web/northstar-browser --skill fix-web-platform-compat -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/fix-web-platform-compat, .gemini/skills/fix-web-platform-compat, .github/skills/fix-web-platform-compat and .opencode/skills/fix-web-platform-compat in your project.
What does Fix Web Platform Compat need to run?
SKILL.md names no scripts, command-line tools or credentials: Fix Web Platform Compat is instructions for the agent only.
Does Fix Web Platform Compat 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 Fix Web Platform Compat 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 Fix Web Platform Compat use?
Fix Web Platform Compat is published under the GPL-3.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Fix Web Platform Compat use?
About 1.1k tokens (SKILL.md is roughly 4.3k 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 Fix Web Platform Compat?
Skills that share tags, products or a category with Fix Web Platform Compat: Failure Oriented Instrumentation (ArabelaTso/Skills-4-SE, 253 stars), Fory Performance Optimization (apache/fory, 4.6k stars), Debug CI (web-infra-dev/rslint, 461 stars) and Replay Oriented Instrumentation (ArabelaTso/Skills-4-SE, 253 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Fix Web Platform Compat?
nordstjernen-web (a GitHub organization) maintains it in nordstjernen-web/northstar-browser, which has 127 GitHub stars. The repository holds 5 skills in this directory. The repository was last updated on October 10, 2026.
Source: nordstjernen-web/northstar-browser on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.