debugging

A guide to investigating failures and IDE problems in IntelliJ-based development. IntelliJ is a development environment, and its idea.log file records diagnostic messages that can help explain errors and freezes.

In plain words
What is it for?
Use it to investigate exceptions, freezes, unexpected IDE behavior, and log messages by tracing execution and searching idea.log for the relevant class or log level.
Why use it?
It gives a consistent way to follow a problem from the user-facing entry point through the code that actually handles it. This helps reveal layers that transform, ignore, or hide the original failure.

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/jetbrains/mps/debugging
Any agent
npx skills add JetBrains/MPS --skill debugging
Clone the repo
git clone --depth 1 https://github.com/JetBrains/MPS

Made for: Claude Code, Codex.

Per session 22 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 451 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 $0.00022 $0.00451
Opus 5 $0.00011 $0.00226
Sonnet 5 $0.00004 $0.00090
Haiku 4.5 $0.00002 $0.00045

Measured yesterday against content hash 5e55cb1cdd62, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

debugging 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.

.agents/skills/debugging/SKILL.md · 47 lines

What it actually says

Debugging

Documentation

Searching idea.log

When debugging IntelliJ code, search idea.log using these patterns:

Log Levels:

  • FINE = debug level (from LOG.debug { })
  • INFO = info level (from LOG.info())

Category Format: #<abbreviated.package.path>.<ClassName>

Example: com.intellij.openapi.wm.impl.status.IdeStatusBarImpl#c.i.o.w.i.s.IdeStatusBarImpl

Search Examples:

# Debug logs from IdeStatusBarImpl
grep "FINE - #c.i.o.w.i.s.IdeStatusBarImpl" idea.log

# Info logs from IdeStatusBarImpl
grep "INFO - #c.i.o.w.i.s.IdeStatusBarImpl" idea.log

# All logs from a class
grep "#c.i.o.w.i.s.IdeStatusBarImpl" idea.log

End-to-End Behavior

When fixing issues where a user-facing entry point (script, command, API) doesn't behave as expected:

  1. Trace the full execution chain from entry point to actual executor before making changes
  2. Identify all layers that handle the relevant behavior - each layer may swallow, transform, or ignore it
  3. Verify the fix at the entry point the user actually invokes, not just at the layer you modified
  4. Add debugging output if still unsure - add to all layers to trace the issue
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 · 47 lines · 22 tokens per session scan A 5e55cb1cdd62

Subscribe to this mod's changes

debugging is a skill published in the GitHub repository JetBrains/MPS (1,656 stars, last pushed 2d ago), licensed Apache-2.0. It adds 22 tokens to every session and 451 once invoked, about $0.0001 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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