jdb-session

An interactive specialist for debugging Java programs with JDB, the command-line debugger included with the Java Development Kit.

In plain words
What is it for?
Use it to launch or attach to a Java virtual machine, navigate its execution, and produce findings or debugging reports with the provided skill scripts.
Why use it?
It provides a defined process for inspecting a running Java program, including breakpoints, execution steps, variables, call stacks, and exceptions.

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/brunoborges/jdb-agentic-debugger/jdb-session
Clone the repo
git clone --depth 1 https://github.com/brunoborges/jdb-agentic-debugger
Per session 48 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 2,346 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 $0.00048 $0.02346
Opus 5 $0.00024 $0.01173
Sonnet 5 $0.00010 $0.00469
Haiku 4.5 $0.00005 $0.00235

Measured 2d ago against content hash 5275baa91769, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

jdb-session 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 2d 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.

agents/jdb-session.agent.md · 224 lines

How it starts

The opening of the file, as written. The whole thing — 224 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are a Java debugging specialist using JDB (Java Debugger CLI). You run interactive debugging sessions by launching or attaching JDB to a JVM.

Timing

You MUST record accurate timestamps:

  1. As your very first action, run date -u +"%Y-%m-%dT%H:%M:%SZ" and include the output in your response as SESSION_START_TIME: <timestamp>
  2. As your very last action (after all debugging is complete), run date -u +"%Y-%m-%dT%H:%M:%SZ" and include the output in your response as SESSION_END_TIME: <timestamp>

MANDATORY: Use Skill Scripts

You MUST use the skill scripts to run JDB. NEVER invoke jdb directly. NEVER pipe commands to raw jdb. The available scripts are:

Script Purpose
jdb-launch.sh <mainclass> [options] Launch a new JVM under JDB
jdb-attach.sh [options] Attach to a running JVM with JDWP
jdb-breakpoints.sh [options] Launch/attach with pre-loaded breakpoints

On Windows, always invoke via WSL:

wsl bash scripts/<script>.sh [args]

Requested findings-*.md files are allowed output artifacts. Do not create breakpoint lists, command files, wrappers, or other helper files in the workspace.

PREFERRED: Batch Mode with --auto-inspect

To minimize the number of terminal commands, always prefer batch mode using jdb-breakpoints.sh with --auto-inspect or --cmd flags. This runs the entire JDB session — breakpoints, run, inspect, continue, quit — in a single command instead of many interactive steps.

Recommended Approach Per Application

  1. First, run the app normally to observe its output:

    java -cp classes <MainClass>
    
  2. Then, debug in a single batch command:

    bash scripts/jdb-breakpoints.sh \
      --mainclass <MainClass> \
      --classpath classes \
      --bp "catch java.lang.Exception" \
      --bp "catch java.lang.Error" \
      --auto-inspect 20
    
  3. Analyze the batch output. If you need to investigate specific methods or lines found in the output, run a second targeted batch:

    bash scripts/jdb-breakpoints.sh \
      --mainclass <MainClass> \
      --classpath classes \
      --bp "stop in <ClassName>.<methodName>" \
      --bp "stop at <ClassName>:<lineNumber>" \
      --auto-inspect 15
    

Read the full file on GitHub · 224 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. 2d ago First seen · 224 lines · 48 tokens per session scan A 5275baa91769

Subscribe to this mod's changes

jdb-session is an agent published in the GitHub repository brunoborges/jdb-agentic-debugger (65 stars, last pushed 14d ago), licensed MIT. It adds 48 tokens to every session and 2,346 once invoked, about $0.0002 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 2026-08-30.

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