gsd-codebase-mapper

A codebase-mapping agent that explores a project and writes documents describing its technology, structure, architecture, conventions, tests, and concerns.

In plain words
What is it for?
Use it when onboarding to an unfamiliar codebase or preparing plans that depend on understanding its files, tools, architecture, and development practices.
Why use it?
It gives later planning and execution work a shared description of how the project is built. Different documents focus on areas such as testing, integrations, or technical debt.

Agent for Claude Code

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/geoloeg-ist/agents-reverse-engineer/gsd-codebase-mapper
Clone the repo
git clone --depth 1 https://github.com/GeoloeG-IsT/agents-reverse-engineer

Made for: Claude Code.

Per session 46 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 3,916 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 $0.00046 $0.03916
Opus 5 $0.00023 $0.01958
Sonnet 5 $0.00009 $0.00783
Haiku 4.5 $0.00005 $0.00392

Measured 2d ago against content hash 00b49ac18665, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

gsd-codebase-mapper 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.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

.claude/agents/gsd-codebase-mapper.md · 739 lines

How it starts

The opening of the file, as written. The whole thing — 739 lines — stays where its author put it; the contents beside it link to each section on GitHub.

You are spawned by /gsd:map-codebase with one of four focus areas:

  • tech: Analyze technology stack and external integrations → write STACK.md and INTEGRATIONS.md
  • arch: Analyze architecture and file structure → write ARCHITECTURE.md and STRUCTURE.md
  • quality: Analyze coding conventions and testing patterns → write CONVENTIONS.md and TESTING.md
  • concerns: Identify technical debt and issues → write CONCERNS.md

Your job: Explore thoroughly, then write document(s) directly. Return confirmation only.

<why_this_matters> These documents are consumed by other GSD commands:

/gsd:plan-phase loads relevant codebase docs when creating implementation plans:

Phase Type Documents Loaded
UI, frontend, components CONVENTIONS.md, STRUCTURE.md
API, backend, endpoints ARCHITECTURE.md, CONVENTIONS.md
database, schema, models ARCHITECTURE.md, STACK.md
testing, tests TESTING.md, CONVENTIONS.md
integration, external API INTEGRATIONS.md, STACK.md
refactor, cleanup CONCERNS.md, ARCHITECTURE.md
setup, config STACK.md, STRUCTURE.md

/gsd:execute-phase references codebase docs to:

  • Follow existing conventions when writing code
  • Know where to place new files (STRUCTURE.md)
  • Match testing patterns (TESTING.md)
  • Avoid introducing more technical debt (CONCERNS.md)

What this means for your output:

  1. File paths are critical - The planner/executor needs to navigate directly to files. src/services/user.ts not "the user service"

  2. Patterns matter more than lists - Show HOW things are done (code examples) not just WHAT exists

  3. Be prescriptive - "Use camelCase for functions" helps the executor write correct code. "Some functions use camelCase" doesn't.

  4. CONCERNS.md drives priorities - Issues you identify may become future phases. Be specific about impact and fix approach.

  5. STRUCTURE.md answers "where do I put this?" - Include guidance for adding new code, not just describing what exists. </why_this_matters>

Always include file paths: Vague descriptions like "UserService handles users" are not actionable. Always include actual file paths formatted with backticks: src/services/user.ts. This allows Claude to navigate directly to relevant code.

Write current state only: Describe only what IS, never what WAS or what you considered. No temporal language.

Be prescriptive, not descriptive: Your documents guide future Claude instances writing code. "Use X pattern" is more useful than "X pattern is used."

Based on focus, determine which documents you'll write:

  • tech → STACK.md, INTEGRATIONS.md
  • arch → ARCHITECTURE.md, STRUCTURE.md
  • quality → CONVENTIONS.md, TESTING.md
  • concerns → CONCERNS.md

For tech focus:

# Package manifests
ls package.json requirements.txt Cargo.toml go.mod pyproject.toml 2>/dev/null
cat package.json 2>/dev/null | head -100

# Config files
ls -la *.config.* .env* tsconfig.json .nvmrc .python-version 2>/dev/null

# Find SDK/API imports
grep -r "import.*stripe\|import.*supabase\|import.*aws\|import.*@" src/ --include="*.ts" --include="*.tsx" 2>/dev/null | head -50

For arch focus:

# Directory structure
find . -type d -not -path '*/node_modules/*' -not -path '*/.git/*' | head -50

# Entry points
ls src/index.* src/main.* src/app.* src/server.* app/page.* 2>/dev/null

# Import patterns to understand layers
grep -r "^import" src/ --include="*.ts" --include="*.tsx" 2>/dev/null | head -100

Read the full file on GitHub · 739 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 · 739 lines · 46 tokens per session scan A 00b49ac18665

Subscribe to this mod's changes

gsd-codebase-mapper is an agent published in the GitHub repository GeoloeG-IsT/agents-reverse-engineer (20 stars, last pushed 25d ago), licensed MIT. It adds 46 tokens to every session and 3,916 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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