dap-backtest-loop

dap-backtest-loop is a skill for Claude Code, Codex from svnscha/dap-dbgeng. It costs 62 tokens per session (966 once invoked), scanned A, original, MIT.

A workflow for testing debugger features against real targets through scripted VS Code sessions. It records DAP traces, fixes problems found in those traces, and turns successful cases into replay tests.

In plain words
What is it for?
Use it to run debugger scenarios, record and inspect session traces, apply fixes, and create replay fixtures and tests after a live scenario succeeds.
Why use it?
It catches issues that may not appear in isolated tests and preserves working real-world scenarios for later checks.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/svnscha/dap-dbgeng/dap-backtest-loop
Any agent
npx skills add svnscha/dap-dbgeng --skill dap-backtest-loop
Clone the repo
git clone --depth 1 https://github.com/svnscha/dap-dbgeng

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for dap-backtest-loop

README.md
[![agentmods](https://agentmods.dev/badge/skills/svnscha/dap-dbgeng/dap-backtest-loop.svg)](https://agentmods.dev/skills/svnscha/dap-dbgeng/dap-backtest-loop)
Your own site
<a href="https://agentmods.dev/skills/svnscha/dap-dbgeng/dap-backtest-loop"><img src="https://agentmods.dev/badge/skills/svnscha/dap-dbgeng/dap-backtest-loop.svg" alt="Measured on agentmods" height="20"></a>
Per session 62 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 966 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00062 $0.00966
Opus 5 $0.00031 $0.00483
Sonnet 5 $0.00012 $0.00193
Haiku 4.5 $0.00006 $0.00097

Measured 5d ago against content hash 579ff49a93f3, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

dap-backtest-loop 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.

.claude/skills/dap-backtest-loop/SKILL.md · 96 lines

How it starts

The opening of the file, as written. The whole thing — 96 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Back-testing features against real targets

The loop is: script a scenario -> run it -> read the trace -> fix what it exposes -> keep the trace as a fixture. A feature is back-tested when a recorded session proves it works against a real target and a replay test locks that behavior in.

The harness is C:\Users\svnscha\Code\dap-dbgeng-rc (uv run dap-dbgeng-rc run <scenario>). Scenarios live in src/dapdbgeng_rc/scenarios/.

What can and cannot run in parallel

Live scenarios cannot run in parallel, and no amount of fanning out changes it:

  • one desktop: two windows fight over focus, and the Remote Control extension binds one port,
  • one kernel target: KDNET accepts a single debugger,
  • one service per machine: starting it twice is the same service.

Run live scenarios one at a time. What does parallelize is everything after the trace exists: reading traces, cross-checking the request matrix, drafting fixtures and tests. Fan out there.

Running a scenario

The launch configuration must set trace (a path under recordings/), or the run produces nothing to analyze:

"trace": "${workspaceFolder}/recordings/kernel.session.json"

The trace is written when the adapter exits cleanly, from the recorder's destructor. A killed adapter leaves no trace - which is itself a finding, not a harness glitch. Copy the file to a scenario-specific name straight after the run; the next run overwrites it.

Reading the trace, not the screen

A scenario that sleeps through a failed session looks exactly like one that worked: steps print, the window looks plausible, nothing fails. Judge a run by its trace, never by the step log.

pwsh scripts/Format-DapSessionFlow.ps1 -Path recordings/<scenario>.session.json

Check: every request the scenario is about is present and status=ok; the stops match what the scenario asked for; the session ends with exited/terminated and a disconnect response. Screenshots are for what the viewer sees; the trace is for what the adapter did. Both lie in different directions, so use each for its own question.

Read the full file on GitHub · 96 lines

Changes

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.

  1. 5d ago First seen · 96 lines · 62 tokens per session scan A 579ff49a93f3

Subscribe to this mod's changes

dap-backtest-loop is a skill published in the GitHub repository svnscha/dap-dbgeng (10 stars, last pushed 4d ago), licensed MIT. It adds 62 tokens to every session and 966 once invoked, about $0.0003 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 2026-08-31.

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