Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add pproenca/dot-skills --skill nginx-c-module-debuggit clone --depth 1 https://github.com/pproenca/dot-skillsWrote 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/pproenca/dot-skills/nginx-c-module-debug)<a href="https://agentmods.dev/skills/pproenca/dot-skills/nginx-c-module-debug"><img src="https://agentmods.dev/badge/skills/pproenca/dot-skills/nginx-c-module-debug/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/pproenca/dot-skills/nginx-c-module-debug"><img src="https://agentmods.dev/badge/skills/pproenca/dot-skills/nginx-c-module-debug.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 | $0.00080 | $0.02014 |
| Opus 5 | $0.00040 | $0.01007 |
| Sonnet 5 | $0.00016 | $0.00403 |
| Haiku 4.5 | $0.00008 | $0.00201 |
Grade A, and why
nginx-c-module-debug 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 5d 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 — 119 lines — stays where its author put it; the contents beside it link to each section on GitHub.
nginx.org C Module Debugging Best Practices
Comprehensive debugging guide for nginx C modules, derived from the official nginx development documentation and production debugging experience. Contains 45 rules across 8 categories, prioritized by impact to guide systematic diagnosis of crashes, memory bugs, and behavioral issues in nginx modules.
Companion skills: This skill complements nginx-c-modules (correctness) and nginx-c-module-perf-reliability (performance). This skill covers debugging and diagnosis.
When to Apply
Reference these guidelines when:
- Diagnosing nginx worker crashes (segfaults, SIGABRT, SIGSEGV)
- Finding memory bugs (use-after-free, leaks, pool corruption, buffer overruns)
- Setting up GDB and core dump analysis for nginx
- Tracing request flow through phases, subrequests, and filter chains
- Instrumenting nginx modules with debug logging and dynamic tracing tools
Rule Categories by Priority
| Priority | Category | Impact | Prefix |
|---|---|---|---|
| 1 | Crash Diagnosis & Signals | CRITICAL | crash- |
| 2 | Memory Bug Detection | CRITICAL | memdbg- |
| 3 | GDB & Core Dump Analysis | HIGH | gdb- |
| 4 | Request Flow Tracing | HIGH | trace- |
| 5 | Debug Logging Patterns | MEDIUM-HIGH | dbglog- |
| 6 | State & Lifecycle Debugging | MEDIUM | state- |
| 7 | Dynamic Tracing Tools | MEDIUM | probe- |
| 8 | Build & Sanitizer Configuration | LOW-MEDIUM | build- |
Quick Reference
1. Crash Diagnosis & Signals (CRITICAL)
crash-segfault-signature- Identify Segfault Crash Signature from Signal and Addresscrash-null-deref-pattern- Recognize NULL Pointer Dereference Patterns in nginx Modulescrash-double-free-finalize- Diagnose Double Finalize Crashes from Request Reference Countcrash-stack-overflow- Detect Stack Overflow from Recursive Subrequest or Filter Chainscrash-worker-exit-log- Extract Crash Context from Worker Exit Log Messagescrash-error-page-redirect- Avoid Crashes from error_page Internal Redirect Context Invalidation
What ships with it
48 files 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.
- assets/templates/_template.md 750 B
- metadata.json 1.1 KB
- references/_sections.md 2.0 KB
- references/build-asan-configure.md 3.5 KB
- references/build-debug-flags.md 3.7 KB
- references/build-debug-palloc.md 5.0 KB
- references/build-single-process.md 3.6 KB
- references/build-valgrind-suppressions.md 4.3 KB
- references/crash-double-free-finalize.md 2.9 KB
- references/crash-error-page-redirect.md 3.7 KB
- references/crash-null-deref-pattern.md 2.5 KB
- references/crash-segfault-signature.md 3.4 KB
- references/crash-stack-overflow.md 2.9 KB
- references/crash-worker-exit-log.md 3.3 KB
- references/dbglog-debug-connection.md 2.9 KB
- references/dbglog-debug-mask.md 3.2 KB
- references/dbglog-format-ngx-str.md 3.6 KB
- references/dbglog-log-action-string.md 3.9 KB
- references/dbglog-memory-buffer.md 3.6 KB
- references/gdb-attach-worker.md 2.4 KB
- references/gdb-backtrace-read.md 3.6 KB
- references/gdb-coredump-setup.md 3.1 KB
- references/gdb-inspect-request.md 2.6 KB
- references/gdb-memory-buffer-extract.md 3.1 KB
- references/gdb-watchpoint-corruption.md 3.1 KB
- references/memdbg-buffer-overrun.md 2.6 KB
- references/memdbg-cleanup-handler-leak.md 3.2 KB
- references/memdbg-pool-leak-pattern.md 2.5 KB
- references/memdbg-slab-corruption.md 3.3 KB
- references/memdbg-temp-pool-misuse.md 3.7 KB
- references/memdbg-use-after-free.md 3.1 KB
- references/memdbg-valgrind-pool-trace.md 2.9 KB
- references/probe-dtrace-request.md 4.1 KB
- references/probe-ebpf-latency.md 4.4 KB
- references/probe-strace-fd-leak.md 4.8 KB
- references/probe-strace-syscall.md 3.6 KB
- references/probe-systemtap-pool.md 4.0 KB
- references/state-connection-lifecycle.md 3.8 KB
- references/state-event-flag-debug.md 4.4 KB
- references/state-request-count-track.md 3.6 KB
- references/state-timer-leak.md 4.2 KB
- references/state-upstream-state-machine.md 3.9 KB
- references/trace-config-inheritance.md 5.0 KB
- references/trace-event-handler-chain.md 4.9 KB
- references/trace-filter-chain-order.md 4.4 KB
- references/trace-phase-handler-flow.md 3.9 KB
- references/trace-subrequest-tree.md 4.8 KB
- references/trace-upstream-callback-seq.md 5.1 KB
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.
- 5d ago First seen · 119 lines · 80 tokens per session scan A 5893b46bc057
nginx-c-module-debug is a skill published in the GitHub repository pproenca/dot-skills (205 stars, last pushed 24d ago), licensed MIT. It adds 80 tokens to every session and 2,014 once invoked, about $0.0004 per session on Opus 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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