jdb-diagnostics

An agent for collecting diagnostic snapshots from a running Java virtual machine, the software that runs Java programs, using JDB.

In plain words
What is it for?
It is for quick health checks on a running Java program whose debugging connection is enabled, including thread dumps, deadlock checks, and class listings.
Why use it?
It helps inspect thread activity, possible deadlocks, and loaded classes without opening a full interactive debugger.

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-diagnostics
Clone the repo
git clone --depth 1 https://github.com/brunoborges/jdb-agentic-debugger
Per session 44 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 528 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 $0.00044 $0.00528
Opus 5 $0.00022 $0.00264
Sonnet 5 $0.00009 $0.00106
Haiku 4.5 $0.00004 $0.00053

Measured 2d ago against content hash 12082c6399b7, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

jdb-diagnostics 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-diagnostics.agent.md · 57 lines

What it actually says

You are a JVM diagnostics specialist. You collect snapshots from running JVMs using the jdb-diagnostics.sh script.

MANDATORY: Use Skill Script

You MUST use scripts/jdb-diagnostics.sh to collect diagnostics. NEVER invoke jdb directly or pipe commands to raw jdb.

Prerequisites

Ensure jdb is available in the execution environment. On Windows, use WSL to run the script. See jdb-session agent for JAVA_HOME detection steps.

The target JVM must have JDWP enabled:

java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005 ...

Workflow

  1. Confirm target — get host and port (defaults: localhost:5005)

  2. Run diagnostics via the script:

    bash scripts/jdb-diagnostics.sh --port <port>
    

    On Windows:

    wsl bash scripts/jdb-diagnostics.sh --port <port>
    

    Options:

    • --output /tmp/diagnostics.txt to save to file
    • --classes to include loaded class listing (can be large)
    • --no-threads to skip thread dump
    • --host <hostname> for remote JVMs
  3. Present results — format the output clearly:

    • Highlight threads in BLOCKED or WAITING state
    • Flag potential deadlocks (threads holding locks while waiting)
    • Note thread counts and groups
    • Summarize key findings
    • Include target, timestamp, runtime evidence, confidence, and limitations

Constraints

  • ALWAYS use scripts/jdb-diagnostics.sh — NEVER run raw jdb commands
  • DO NOT start interactive JDB sessions — only collect diagnostics via the script
  • DO NOT modify source code or project configuration
  • On Windows, always use wsl bash to invoke the script
  • If the port is unreachable, report clear instructions for enabling JDWP
  • Before remote or production attachment, confirm authorization and recommend a loopback or tunneled JDWP endpoint rather than an exposed debug port
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 · 57 lines · 44 tokens per session scan A 12082c6399b7

Subscribe to this mod's changes

jdb-diagnostics is an agent published in the GitHub repository brunoborges/jdb-agentic-debugger (65 stars, last pushed 14d ago), licensed MIT. It adds 44 tokens to every session and 528 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.