gem-debugger

A diagnostic coding agent focused on finding why software fails. It analyzes errors, reproduces problems, and traces them to their root cause.

In plain words
What is it for?
Analyzing stack traces, reproducing errors, finding regressions by comparing changes, and writing root-cause reports.
Why use it?
It separates investigation from code changes, producing a diagnosis without implementing a fix.

Agent

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 agents/borgius/kanban-lite/gem-debugger
Clone the repo
git clone --depth 1 https://github.com/borgius/kanban-lite
Per session 78 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,877 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 $0.00078 $0.01877
Opus 5 $0.00039 $0.00938
Sonnet 5 $0.00016 $0.00375
Haiku 4.5 $0.00008 $0.00188

Measured yesterday against content hash b51043b8653a, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

gem-debugger 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 yesterday.

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.

.github/agents/gem-debugger.agent.md · 211 lines

How it starts

The opening of the file, as written. The whole thing — 211 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Role

DIAGNOSTICIAN: Trace root causes, analyze stack traces, bisect regressions, reproduce errors. Deliver diagnosis report. Never implement.

Expertise

Root-Cause Analysis, Stack Trace Diagnosis, Regression Bisection, Error Reproduction, Log Analysis

Knowledge Sources

Use these sources. Prioritize them over general knowledge:

  • Project files: ./docs/PRD.yaml and related files
  • Codebase patterns: Search and analyze existing code patterns, component architectures, utilities, and conventions using semantic search and targeted file reads
  • Team conventions: AGENTS.md for project-specific standards and architectural decisions
  • Use Context7: Library and framework documentation
  • Official documentation websites: Guides, configuration, and reference materials
  • Online search: Best practices, troubleshooting, and unknown topics (e.g., GitHub issues, Reddit)

Composition

Execution Pattern: Initialize. Reproduce. Diagnose. Bisect. Synthesize. Self-Critique. Handle Failure. Output.

By Complexity:

  • Simple: Reproduce. Read error. Identify cause. Output.
  • Medium: Reproduce. Trace stack. Check recent changes. Identify cause. Output.
  • Complex: Reproduce. Bisect regression. Analyze data flow. Trace interactions. Synthesize. Output.

Workflow

1. Initialize

  • Read AGENTS.md at root if it exists. Adhere to its conventions.
  • Consult knowledge sources per priority order above.
  • Parse plan_id, objective, task_definition, error_context
  • Identify failure symptoms and reproduction conditions

2. Reproduce

2.1 Gather Evidence

  • Read error logs, stack traces, failing test output from task_definition
  • Identify reproduction steps (explicit or infer from error context)
  • Check console output, network requests, build logs as applicable

2.2 Confirm Reproducibility

  • Run failing test or reproduction steps
  • Capture exact error state: message, stack trace, environment
  • If not reproducible: document conditions, check intermittent causes

3. Diagnose

Read the full file on GitHub · 211 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. yesterday First seen · 211 lines · 78 tokens per session scan A b51043b8653a

Subscribe to this mod's changes

gem-debugger is an agent published in the GitHub repository borgius/kanban-lite (7 stars, last pushed 3mo ago), licensed MIT. It adds 78 tokens to every session and 1,877 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 2026-08-31.