microsoft/win-dev-skills is a collection of AI-agent instructions and tools for creating native Windows applications with WinUI 3 and the Windows App SDK. Windows developers use it to guide agents through app development tasks from scaffolding and design to testing, packaging, and release. The catalogue entries are its agents, skills, and plugin components.
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 microsoft/win-dev-skills --skill windbg-user-heap-corruption-investigationgit clone --depth 1 https://github.com/microsoft/win-dev-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/microsoft/win-dev-skills/windbg-user-heap-corruption-investigation)<a href="https://agentmods.dev/skills/microsoft/win-dev-skills/windbg-user-heap-corruption-investigation"><img src="https://agentmods.dev/badge/skills/microsoft/win-dev-skills/windbg-user-heap-corruption-investigation/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/microsoft/win-dev-skills/windbg-user-heap-corruption-investigation"><img src="https://agentmods.dev/badge/skills/microsoft/win-dev-skills/windbg-user-heap-corruption-investigation.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00046 | $0.01133 |
| Opus 5.5 | $0.00018 | $0.00453 |
| Sonnet 5.5 | $0.00009 | $0.00227 |
| Haiku 4.5 | $0.00005 | $0.00113 |
Grade A, and why
windbg-user-heap-corruption-investigation 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 8d 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 — 125 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Heap Corruption Investigation
Load windbg-diagnostic-method first if it is not already loaded in this
conversation, and apply it throughout for evidence ranking, hypothesis testing,
confidence calibration, independent review, and report validation. This skill
adds the bug-family-specific commands and evidence requirements.
Detection and limits
Look for STATUS_HEAP_CORRUPTION (0xC0000374), Application Verifier stops,
or failures in heap allocate/free/reallocate paths in an application, service,
or user-mode driver host such as an UMDF host process. A crash inside the allocator
may be the first detection of an earlier bad write, not the faulty operation.
Distinguish corruption from allocation failure; for the latter use
windbg-user-virtual-memory-exhaustion.
Allocation/free history depends on how the process was instrumented and which pages were captured. A missing history is a limitation, not proof of a leak or use-after-free.
Workflow
1. Decode the stop
.exr -1
.ecxr
!analyze -v
k
Record the stop reason, corrupted block, corruption address, and the operation
that detected the damage. If a verifier stop frame has parameter/local symbols,
select it with .frame /r <frame> and inspect dv; otherwise use the captured
stop output and the documented stop definition. Do not assume one fixed
parameter layout or a stop code shared by all verifier versions.
2. Recover available block history
!heap -p -a <address>
!avrf -hp -a <address>
The first command inspects a Page Heap allocation; the second searches available
Application Verifier heap-operation history. Use !heap -? and !avrf -? to
confirm support in the installed extension. On an uninstrumented dump these
commands may not recover the history needed to identify the writer.
Capture allocation and free stacks when present. Check the address is inside the user allocation rather than a header or neighboring block.
3. Test competing explanations
| Hypothesis | Evidence to seek |
|---|---|
| Use-after-free | Confirmed free before a later access through a retained reference |
| Double-free | Two ownership/completion paths freeing the same allocation |
| Overrun/underrun | A write outside the allocated user bounds |
| Wild write | Corrupted header or payload and a writer with an invalid target |
| Allocation/free contract mismatch | Different allocator/deallocator or incorrect owning heap |
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.
- 8d ago First seen · 125 lines · 46 tokens per session scan A 074409848cd4
windbg-user-heap-corruption-investigation is a skill published in the GitHub repository microsoft/win-dev-skills (472 stars, last pushed 2d ago), licensed MIT. It adds 46 tokens to every session and 1,133 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-10-08.
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