Borrowing it
Nothing to install: this file belongs to TheDecipherist/claude-code-mastery-project-starter-kit. 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/TheDecipherist/claude-code-mastery-project-starter-kit/main/.claude/skills/dev-pitfalls/SKILL.mdgit clone --depth 1 https://github.com/TheDecipherist/claude-code-mastery-project-starter-kitWrote 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/thedecipherist/claude-code-mastery-project-starter-kit/dev-pitfalls)<a href="https://agentmods.dev/skills/thedecipherist/claude-code-mastery-project-starter-kit/dev-pitfalls"><img src="https://agentmods.dev/badge/skills/thedecipherist/claude-code-mastery-project-starter-kit/dev-pitfalls/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/thedecipherist/claude-code-mastery-project-starter-kit/dev-pitfalls"><img src="https://agentmods.dev/badge/skills/thedecipherist/claude-code-mastery-project-starter-kit/dev-pitfalls.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 5 findings, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high Tool Misuse · line 110 Tool calls are chained to bypass individual safety checks or escalate capabilities beyond what any single tool call would allow.Fix: Limit tool chaining depth and validate the output of each tool before passing it to the next. Require explicit user approval for multi-step chains.
- high Tool Misuse · line 110 Tool calls are chained to bypass individual safety checks or escalate capabilities beyond what any single tool call would allow.Fix: Limit tool chaining depth and validate the output of each tool before passing it to the next. Require explicit user approval for multi-step chains.
- medium Rogue Agent · line 24 Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
- medium MCP Rug Pull · line 73 npx commands without a version suffix (e.g. @1.0.0) create a rug-pull risk if the upstream server is compromised and publishes a malicious update.Fix: Pin the version: npx @scope/[email protected]
- medium Privilege Escalation · line 110 Commands invoke sudo or root privileges. Verify this elevated access is necessary and justified.Fix: Avoid sudo/root unless strictly required. Prefer least-privilege patterns. If elevation is needed, document the justification and scope.
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 | $0.00100 | $0.03170 |
| Opus 5.5 | $0.00040 | $0.01268 |
| Sonnet 5.5 | $0.00020 | $0.00634 |
| Haiku 4.5 | $0.00010 | $0.00317 |
Grade B, and why
dev-pitfalls scanned grade B with 1 finding 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 2mo 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.
Asks for rootmediumPrivilege escalation
A mod that escalates privileges can change anything on the machine, not only the project.
- **`ENOSPC: no space left on device`** from a dev server, `npm start`, Vite, nodemon, or VS Code is almost never disk space. It's the Linux inotify file-watcher limit (default ~8192), exhausted by a large project's file How it starts
The opening of the file, as written. The whole thing — 119 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Common Dev Pitfalls (check the layer before debugging it)
These cost hours because the symptom points at the wrong thing, and they're easy to "fix" by going in circles. When something matches below, check the cause here before debugging the code.
Check project state before acting
Claude's frequent miss is assuming project state instead of verifying it. Two checks, stated plainly to the user:
- Is it even a git repo? Before staging, committing, or diffing, confirm the repo exists (
git rev-parse --is-inside-work-tree). If it doesn't, say so directly, "this directory isn't a git repository yet, rungit initfirst", rather than running git commands that fail confusingly or silently acting on a parent repo. - Is
node_modulesignored? Before the first commit, confirm.gitignoreexists and listsnode_modules/. Create.gitignoreBEFOREnpm installso it is never tracked. If it isn't ignored yet, say so before anything gets committed.
.gitignore only ignores UNtracked files. If node_modules (or .env, or build output) was already committed, adding it to .gitignore changes nothing, git keeps tracking it, and this is a classic "my .gitignore isn't working" loop. Untrack it, then commit:
git rm -r --cached node_modules
git commit -m "Stop tracking node_modules"
Confirm a rule actually bites with git check-ignore -v node_modules. Committed node_modules bloats the repo and breaks CI, its platform-specific compiled binaries fail on Linux runners. Same fix for anything that "won't stop showing up" after you ignored it.
WSL: put the project on the Linux filesystem, not /mnt/c
The single biggest WSL pitfall, and Claude rarely thinks to check it. A project under /mnt/c (any Windows drive) is reached from Linux over a 9P bridge, so:
- file operations run 10-100x slower,
npm install,git status, and test runs crawl inotifyis flaky across the bridge, so file watchers fire intermittently, hot reload and test watchers "work randomly" then silently stop, which becomes a circular debugging session if you chase it as a config problem- Linux permission bits are only emulated,
chmod +xcan silently fail and ssh rejects keys as "bad permissions" - editor integration breaks: Claude often can't see your active selection or the code you've highlighted, so it's working blind on what you're pointing at
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.
- 2mo ago First seen · 119 lines · 100 tokens per session scan B ad2b6eec0a77
dev-pitfalls is a skill published in the GitHub repository TheDecipherist/claude-code-mastery-project-starter-kit (342 stars, last pushed 4mo ago), licensed MIT. It adds 100 tokens to every session and 3,170 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it B with 1 finding (asks for root). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
dev-pitfalls compared with skills from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| dev-pitfallsTheDecipherist/claude-code-mastery-project-starter-kit | Skill | 342 | 4mo ago | MIT | B | 100 | Claude Code |
| systematic-debuggingopen-metadata/OpenMetadata | Skill | 16k | yesterday | Apache-2.0 | A | 37 | Claude Code |
| log-error-digestzebbern/claude-code-guide | Skill | 4.7k | 3d ago | MIT | A | 71 | Claude Code, Codex |
| cwv-optimizeradobe/skills | Skill | 319 | yesterday | Apache-2.0 | A | 112 | Claude Code |
| ci-fixersipyourdrink-ltd/bernstein | Skill | 1.2k | yesterday | Apache-2.0 | A | 15 | Claude Code, Codex |
| incident-response-incident-responsermyndharis/antigravity-skills | Skill | 1.9k | 23d ago | MIT | A | 36 | Claude Code |
| triaging-web-analytics-supportPostHog/posthog | Skill | 41k | yesterday | none | A | 151 | Claude Code, Codex |