# Diagnose

> Debug coding failures through reproduction, ranked hypotheses, narrow fixes, and verification. Use when a bug, regression, flaky test, performance failure, or inconsistent behavior is broken, slow, throwing, or hard to reproduce and the task needs disciplined diagnosis instead of guessed fixes.

- **Type:** Skill
- **Install:** `agentstack add skill-markoblogo-abvx-agent-skills-diagnose`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [markoblogo](https://agentstack.voostack.com/s/markoblogo)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [markoblogo](https://github.com/markoblogo)
- **Source:** https://github.com/markoblogo/abvx-agent-skills/tree/main/skills/diagnose
- **Website:** https://abvx.xyz/work/abvx-agent-skills

## Install

```sh
agentstack add skill-markoblogo-abvx-agent-skills-diagnose
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Diagnose

The core job is to build a reliable feedback loop. Without one, hypotheses are weak.

## Phase 1: Feedback Loop

Create the smallest useful pass/fail signal:

- failing test;
- CLI command with fixture;
- HTTP request against local server;
- browser script;
- replayed trace or payload;
- small harness around the relevant function;
- repeated flake trigger with counted failure rate.

If no loop can be built, state what was tried and ask for logs, traces, access, or permission to instrument.

## Phase 2: Reproduce

Confirm the loop matches the user's symptom, not a nearby failure. Capture exact error text, wrong output, timing, network failure, or UI state.

For nondeterministic issues, raise the reproduction rate with repetition, stress, seeded randomness, timing controls, and isolation.

## Phase 3: Hypothesize

Write 3-5 ranked hypotheses before editing. Each must include:

```text
Hypothesis:
Prediction:
Probe:
Result:
Status:
```

Test one variable at a time. Update rankings as evidence arrives.

## Phase 4: Instrument

- Prefer debugger, REPL, targeted logs, traces, or profiler over broad logging.
- Tag temporary instrumentation with a unique marker such as `[DEBUG-7b3c]`.
- Remove all temporary instrumentation before finalizing.
- For performance regressions, measure first and fix second.

## Phase 5: Fix And Regression Test

If a correct seam exists, turn the minimized repro into a failing regression check before the fix. If no correct seam exists, document that as an architecture gap.

Apply the smallest fix supported by evidence, then rerun:

- the regression check;
- the original feedback loop;
- relevant project checks.

## Final Report

Include root cause, winning hypothesis, files changed, verification, debug cleanup, and residual risk.

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [markoblogo](https://github.com/markoblogo)
- **Source:** [markoblogo/abvx-agent-skills](https://github.com/markoblogo/abvx-agent-skills)
- **License:** MIT
- **Homepage:** https://abvx.xyz/work/abvx-agent-skills

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-markoblogo-abvx-agent-skills-diagnose
- Seller: https://agentstack.voostack.com/s/markoblogo
- Browse the marketplace: https://agentstack.voostack.com/browse

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Listed on AgentStack — the marketplace for AI agent skills and MCP servers. Every listing is security-reviewed. Creators keep 70%.