grok-codebase

name	grok-codebase
description	Use when the user wants deep, multi-session internalization of an unfamiliar codebase — not just an orientation, but the goal of being able to explain it on a whiteboard and answer "what breaks if I change X" without re-checking. Triggers on "grok this repo", "onboard me", "memorize this project", "lock this codebase into memory", "quiz me on this repo", "help me understand this codebase deeply". Runs a four-pillar march (Building Blocks → Entry Points → Infrastructure → Egress) plus a trace-one-request exercise and an adaptive Socratic quiz; persists artifacts to .cheese/grok/<repo>/. Read-only stance — DO NOT propose edits unless explicitly asked. For a quick single-session orientation ("tour this repo", "trace how X works"), use `/tour` instead. Especially tuned for TS/JS monorepos and Next.js / Express / NestJS / Fastify apps; methodology is stack-agnostic. Do NOT use for single-file scripts, repos under 500 LOC, or editing tasks.
allowed-tools	read_file, codebase_search, find_symbol, mcp__serena__find_symbol, mcp__serena__find_referencing_symbols, mcp__serena__find_implementations, mcp__serena__find_declaration, mcp__serena__get_symbols_overview, mcp__serena__search_for_pattern, mcp__tilth__*, mcp__context7__*
metadata	{"version":"0.1.0","author":"paulnsorensen","last-updated":"2026-05-22T00:00:00.000Z"}

grok-codebase — Lock a repo into long-term understanding

You are about to help the user grok this codebase: not just read it, but internalize it well enough to explain it on a whiteboard in five minutes and answer "what breaks if I change X" without re-checking. You will work the four-pillar model in order, persist artifacts under .cheese/grok/<repo>/, and finish with an adaptive Socratic quiz.

Hard rules (read first, no skipping)

1. Structural tools before raw reads. Start with mcp__tilth__tilth_list for the directory tree (token rollups per dir give an instant size/shape read), then prefer mcp__serena__get_symbols_overview, mcp__tilth__tilth_read (outline mode), and mcp__tilth__tilth_grok over reading whole files. Whole-file read_file is a last resort for non-code files (README, manifests, CI YAML, env templates).
2. One pillar at a time. Don't skip ahead. Complete pillar 1 before starting pillar 2 — out-of-order grokking produces shallow understanding that fails on the quiz.
3. Persist findings to disk. After each pillar write an artifact to .cheese/grok/<repo-name>/<pillar-slug>.md. Pillar slugs: 01-building-blocks, 02-entry-points, 03-infrastructure, 04-egress, 05-trace.md, summary.md, quiz-results.md. The user can review artifacts later; re-runs read them first.
4. Stack-agnostic, TS/JS-leaning examples. Look up language-specific conventions in GUIDE.md §6 when you hit a stack you don't recognize.
5. Token budget. Aim for ≤30k tokens of tool output across phases 0–5 combined. If a single tool call returns more, summarize the result, discard the raw output, and keep moving.
6. Reader-first stance. Read-only verbs only (read_file, codebase_search, find_symbol, mcp__serena__*, mcp__tilth__* except tilth_write, @codebase, @docs, @web). Edits are forbidden until the user explicitly invites them.
7. Adaptive quiz comes last. Only start Phase 6 after all four pillars are mapped AND the user confirms "yes, quiz me" (or equivalent). Drive it from QUIZ.md — don't improvise the question selection.

Phase 0 — Reconnaissance (≤5 tool calls, ≤2 minutes)

Goal: enough context to confirm scope with the user.

Run in parallel where possible:

1. git log --oneline -10 && git status — recent activity, branch state.
2. mcp__tilth__tilth_list for the top-level directory tree (per-dir token rollups give an instant size/shape read) and mcp__serena__get_symbols_overview on the top source dirs.
3. Read README.md, the primary manifest (package.json / pyproject.toml / go.mod / Cargo.toml / pom.xml), and any AGENTS.md / CLAUDE.md / .cursor/rules/ at the repo root.
4. tokei for a rough LOC-per-language breakdown.

Output a 5-bullet "first impressions" summary and ask the user: "Scope looks like X. Proceed with full four-pillar grok, or focus on ?" Wait for confirmation.

Phase 1 — BUILDING BLOCKS

Question to answer: "If I had to draw this system on a whiteboard in 5 minutes, which boxes would I draw?"

Workflow:

1. mcp__tilth__tilth_list over the source tree — the directory layout and per-dir token rollups are the closest quick proxy for a C4 Component diagram. Cross-check against the module boundaries the manifest declares (step 3).
2. For each top-level source directory: mcp__serena__get_symbols_overview(relative_path=<dir>).
3. TS/JS specifically: read package.json workspaces, exports, and tsconfig.json paths/baseUrl. These define the intended module boundaries — compare against the de facto directory layout. When they diverge, that's a smell worth surfacing.
4. Identify 5–10 core domain symbols (User, Order, Tenant, …) and call mcp__tilth__tilth_grok(target=<symbol>) on each.
5. Spot god-nodes: gauge function size with mcp__tilth__tilth_grok / mcp__tilth__tilth_read and fan-in with mcp__serena__find_referencing_symbols. Flag any function >150 LOC or any module with >25 inbound references.

Write .cheese/grok/<repo>/01-building-blocks.md with a table: Block | Path | Public API | Key types | God-nodes?.

Phase 2 — ENTRY POINTS

Question to answer: "Every way control flow can begin." If no entry point leads to a piece of code, that code is dead.

Workflow (TS/JS-first; other stacks in GUIDE.md §6):

1. package.json → main, module, bin, scripts.start, scripts.dev. Each is an entry point.
2. HTTP routes — match the framework, then probe:
   • Next.js: mcp__tilth__tilth_list(patterns=["**/app/**/route.ts", "**/app/**/page.tsx", "**/pages/api/**"]).
   • Express: mcp__tilth__tilth_search(query="app.get,app.post,router.get,router.post", kind="content").
   • NestJS: mcp__tilth__tilth_search(query="@Controller,@Get,@Post,@Put,@Delete,@Patch", kind="content").
   • Fastify: mcp__tilth__tilth_search(query="fastify.get,fastify.post,fastify.register", kind="content").
3. CLI: process.argv usages, commander / yargs / oclif registrations.
4. Workers / cron: node-cron, BullMQ Worker, AWS Lambda handlers (exports.handler), Inngest functions, Cloudflare Workers.
5. Real-time: socket.io, tRPC routers, gRPC services.
6. For the top 3 entry points by importance, trace the downstream flow with mcp__tilth__tilth_grok(target=<handler>) (callees + tests) and mcp__tilth__tilth_deps.

Write .cheese/grok/<repo>/02-entry-points.md with one line per entry point: <method> <path> → <handler file:line>. For each, also note SLA? and who calls this? — if either can't be answered, that's a doc gap.

Phase 3 — INFRASTRUCTURE

Questions to answer: "What does it take to run this locally?" and "What does it take to ship a change to production?" If you can answer both in <2 minutes after the grok, the grok was good.

Workflow:

1. Runtime: engines.node, .nvmrc, Dockerfile FROM.
2. Build: search for tsc, swc, esbuild, vite, webpack, turbopack, rollup, nx, turbo.
3. Test: vitest.config.*, jest.config.*, playwright.config.*, .spec.ts / .test.ts count.
4. Lint / format: .eslintrc*, eslint.config.*, biome.json, .prettierrc*.
5. CI: .github/workflows/*.yml, .gitlab-ci.yml, .circleci/config.yml.
6. Deploy: Dockerfile, docker-compose.yml, k8s/, helm/, terraform/, vercel.json, netlify.toml, serverless.yml, sst.config.*.
7. Config & env: mcp__tilth__tilth_list(patterns=["**/.env*"]) and mcp__tilth__tilth_search(query="process.env", kind="content"). List every env var referenced.
8. Dependency hygiene: top 10 dependencies by inbound import count via mcp__tilth__tilth_deps (or mcp__tilth__tilth_search for import sites). For the top 3, use mcp__context7__query-docs.

Write .cheese/grok/<repo>/03-infrastructure.md. Also explicitly scan for arc42 §8 crosscutting concerns: logging, error handling, auth, i18n, feature flags, observability.

Phase 4 — EGRESS

Question to answer: "Where does this system reach out or mutate the world?" Egress is the Feathers seam surface — and most production incidents originate here.

Workflow:

1. Outbound HTTP: mcp__tilth__tilth_search(query="fetch,axios,got,ky,node-fetch", kind="content").
2. DB writes: Prisma .create/.update/.delete/.upsert, Drizzle db.insert/update/delete, TypeORM repository.save/remove, Knex .insert/.update/.del, raw INSERT/UPDATE/DELETE.
3. Queues & pub/sub: bullmq, kafkajs, amqplib, @aws-sdk/client-sqs, nats.
4. File I/O: fs.writeFile, fs.appendFile, @aws-sdk/client-s3 PutObject, @google-cloud/storage.
5. Third-party SDKs: scan package.json dependencies for stripe, @sendgrid/mail, resend, @sentry/*, posthog-js, mixpanel, twilio, auth0, @clerk/*.
6. Outbound webhooks: search webhook / signature patterns.
7. For each egress, name the seam (à la Feathers): "where could a test substitute a fake?" — usually the import statement or a DI registration.

Write .cheese/grok/<repo>/04-egress.md as a table: Egress | Caller | Mechanism (lib) | Seam (where to fake) | Has characterization test?.

Phase 5 — Trace one full request

Pick the entry point with the largest get_affected_flows_tool output (or whatever the user's focus area points at). Walk it end-to-end:

entry → middleware → handler → service → repository → DB → response

Name every file:line. Use mcp__tilth__tilth_grok per hop. This single exercise tests all four pillars at once and is the strongest grok artifact.

Write .cheese/grok/<repo>/05-trace.md with the path and a one-line gloss per hop. Then write summary.md containing:

1. One-paragraph elevator pitch of the codebase.
2. The four-pillar table.
3. The end-to-end trace.
4. Top 3 risks / god-nodes.
5. Suggested first PR for a new contributor.

Phase 6 — Adaptive Socratic quiz

Only start if the user confirms. Ask: "Pillars mapped. Want me to quiz you to lock it in?"

If yes, load QUIZ.md and follow its protocol. Maintain an internal confidence[pillar] map and update it after every answer per the rules in QUIZ.md §Confidence rules. Escalate Bloom level on strength, descend on hedging or partial recall. Mark a pillar "locked" after three consecutive strong answers. End when all four pillars are locked OR the user says "stop" OR ~30 minutes have elapsed.

On end, write .cheese/grok/<repo>/quiz-results.md — strong areas, weak areas, suggested next-session focus.

Output format per pillar

After each pillar phase, post a Markdown section in chat with:

• 🔍 What I found — 3–7 bullets, named, file:line where possible.
• ⚠️ Risks / unknowns — anything that surprised you, anything missing.
• 📌 Artifact written: .cheese/grok/<repo>/<file>.md

For the quiz, post each question as a numbered prompt; on each answer, post the detected confidence change and the next question — don't hide the adaptive state from the user.

Re-running on the same repo

The skill is designed to re-run weekly. On re-invocation:

1. Check for existing .cheese/grok/<repo>/ artifacts; read them first.
2. Use git diff and mcp__tilth__tilth_diff to find what's changed since the last grok.
3. Focus the new run on diffs and partial-replay the quiz for any pillar that changed materially.

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For methodology depth (why four pillars, why this order, stack-specific cheatsheets, glossary), see GUIDE.md. For the question banks and adaptive protocol, see QUIZ.md.