# Ingest Codebase > Guide the creation of a high-quality mental model for a codebase. Use when starting a new mental model, when the model feels incomplete or unclear, or when onboarding to understand a system's architecture. Produces domains, capabilities, aspects, and architectural decisions. - Skill: `michaelliv/ingest-codebase` (Agent Skill) - Install (CLI): `npx skillmds@latest add michaelliv/ingest-codebase` - Raw SKILL.md: https://api.skillmd.com/api/skills/michaelliv/ingest-codebase/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: AI & ML - Author: michaelliv (https://skillmd.com/u/michaelliv) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/michaelliv/ingest-codebase --- # Ingest Codebase - Mental Model Creation Create a comprehensive mental model that captures how a system *actually works* - not just what files exist, but the conceptual boundaries, responsibilities, decisions, and **connections** that shape it. ## When to Use - Starting a new mental model for a codebase - The existing model feels incomplete or shallow - Onboarding to understand a system's architecture - After major changes to verify the model is still accurate ## Philosophy A good domain model answers: - "What are the core *things* this system deals with?" → **Domains** - "What can this system *do*?" → **Capabilities** (with `--operates-on` connections!) - "What concerns cut *across* multiple parts?" → **Aspects** (with `--applies-to` connections!) - "Why was it built *this way*?" → **Decisions** **CRITICAL**: Every capability MUST have `--operates-on` linking it to domains. Every aspect MUST have `--applies-to`. Orphan entities indicate incomplete modeling. --- ## Phase 1: Rapid Codebase Survey (Launch 5-10 Agents in Parallel) Before modeling, understand the codebase structure. **Launch parallel agents** to explore different aspects simultaneously: ``` Agent 1: "Read README.md, package.json, and entry points. What problem does this solve? Who are the users?" Agent 2: "List all top-level directories. What's in each? (src/, lib/, apps/, packages/, etc.)" Agent 3: "Find configuration files (*.config.*, .env*, etc.). What can be configured?" Agent 4: "Search for 'export class' or 'export function' in key directories. What are the main abstractions?" Agent 5: "Look for test directories. What's being tested? This reveals important functionality." Agent 6: "Search for API routes, CLI commands, or event handlers. What are the entry points?" Agent 7: "Look for database models, schemas, or types. What data does this system manage?" Agent 8: "Search for external integrations (HTTP clients, SDKs, third-party services)." ``` **Output**: A map of the codebase with preliminary domain candidates. --- ## Phase 2: Deep Domain Exploration (Launch 10-20 Agents in Parallel) For each potential domain area discovered in Phase 1, **launch a dedicated agent**: ``` For EACH major directory or subsystem, launch an agent with this prompt: "Thoroughly explore [DIRECTORY] in [REPO_PATH]. Answer: 1. What domain concepts exist here? (nouns - things with identity) 2. What capabilities does it provide? (verbs - actions that can be performed) 3. What does this area depend on? (imports, calls to other modules) 4. What depends on this area? (who imports/uses this) 5. What architectural decisions are visible? (patterns, trade-offs) 6. List key files and their purposes. Be comprehensive - read the actual code, don't just list files." ``` **Example for a large codebase with 15 directories:** ``` Launch 15 agents in parallel, one for each: - src/auth/ - src/users/ - src/payments/ - src/notifications/ - src/api/ - src/database/ - apps/web/ - apps/mobile/ - packages/shared/ - packages/ui/ - src/infrastructure/ - src/integrations/ - src/jobs/ - scripts/ - etc. ``` **Each agent should return:** - 2-5 domain candidates with descriptions - 3-10 capability candidates with what domains they operate on - 1-3 aspect candidates (cross-cutting concerns) - 2-5 notable architectural decisions --- ## Phase 3: Build the Mental Model Based on agent findings, create entities using the `mental` CLI: ### Domains (Nouns - Core Business Concepts) ```bash mental add domain \ --desc "What it represents, its lifecycle, key attributes" \ --files "path/to/key/files.ts,another/file.ts" ``` **Good domains:** - Have clear boundaries ("this is a User, that is a Session") - Are spoken about by stakeholders (ubiquitous language) - Would exist even if you rewrote the code - Typically 8-15 domains for a medium/large codebase **Anti-patterns to avoid:** - "Utils", "Helpers", "Services" - code organization, not domains - "Data", "Info" - too generic - Implementation details ("RedisCache", "PostgresStore") ### Capabilities (Verbs - What the System Does) ```bash mental add capability \ --desc "What it does, when it's triggered" \ --files "path/to/implementation.ts" \ --operates-on "Domain1,Domain2,Domain3" ``` **CRITICAL**: Always include `--operates-on` to connect capabilities to domains! After adding, verify with: ```bash mental update capability --operates-on "Domain1,Domain2" ``` **Good capabilities:** - Describe behavior, not structure (e.g., "AuthenticateUser" not "AuthService") - Have clear inputs and outputs - Typically 15-30 capabilities for a medium/large codebase ### Aspects (Cross-Cutting Concerns) ```bash mental add aspect \ --desc "What cross-cutting concern it addresses" \ --files "path/to/implementation.ts" \ --applies-to "Capability1,Domain2,Capability3" ``` **CRITICAL**: Always include `--applies-to` to show what the aspect affects! **Good aspects:** - Affect behavior of multiple capabilities - Are "-ilities": security, reliability, observability, caching, logging - Typically 5-10 aspects for a medium/large codebase ### Decisions (The Why) ```bash mental add decision "" \ --why "Rationale, constraints, trade-offs" ``` Capture at least 5-10 significant architectural decisions. --- ## Phase 4: Verify Completeness (Launch 5-10 Verification Agents) After initial modeling, **launch verification agents** to find gaps: ``` Agent 1: "List all domains in the mental model. For each, what capabilities operate on it? Flag any domains with zero capabilities - these are orphans that need capabilities added." Agent 2: "List all capabilities. Do they all have operates-on connections? Flag any without connections and suggest which domains they should connect to." Agent 3: "List all aspects. Do they all have applies-to connections? Flag any without connections and suggest what they should apply to." Agent 4: "Compare the directory structure to the mental model. Are there major directories not covered by any domain? List gaps." Agent 5: "Review the decisions captured. Are there obvious architectural patterns (monorepo, microservices, event-driven, etc.) not documented? What's missing?" Agent 6: "For each domain, are there CRUD-like capabilities? (Create, Read, Update, Delete, List) Many domains should have management capabilities - flag domains that seem incomplete." ``` ### Quality Checklist Before considering the model complete: - [ ] **Coverage**: Every significant directory maps to at least one entity - [ ] **No orphan domains**: Every domain has at least one capability operating on it - [ ] **No orphan capabilities**: Every capability has `--operates-on` connections - [ ] **No orphan aspects**: Every aspect has `--applies-to` connections - [ ] **Decisions captured**: At least 5-10 architectural decisions documented - [ ] **Reasonable granularity**: 8-15 domains, 15-30 capabilities for medium codebase - [ ] **Grounded in code**: Entities map to real files, not theoretical concepts --- ## Phase 5: Fill Gaps (Iterate Until Complete) If gaps are found, **launch targeted agents** to fill them: ``` "Domain X has no capabilities. Explore the files for X and find what actions/operations can be performed on it. Look for: create, update, delete, list, validate, transform, etc." "Capability Y has no operates-on. Read the implementation and determine which domains it actually works with. What data does it read? What does it modify?" "Directory Z is not covered by the model. Explore it thoroughly and determine if it represents a new domain, capabilities for existing domains, or cross-cutting aspects." ``` Use `mental update` to fix connections: ```bash mental update capability --operates-on "Domain1,Domain2" mental update aspect --applies-to "Capability1,Domain2" ``` --- ## Scaling Guidelines | Codebase Size | Domains | Capabilities | Aspects | Decisions | Total Agents | |---------------|---------|--------------|---------|-----------|--------------| | Small (<50k LOC) | 4-8 | 10-20 | 3-5 | 3-5 | 10-15 | | Medium (50-200k) | 8-15 | 20-40 | 5-10 | 5-10 | 20-30 | | Large (200k+) | 12-20 | 30-60 | 8-15 | 10-20 | 30-50 | **Don't be afraid to launch many agents** - parallel exploration is much faster than sequential. --- ## Example: Ingesting a 300k+ LOC Codebase **Phase 1** (8 agents in parallel): Quick survey → identify ~20 potential areas **Phase 2** (20 agents in parallel): Deep dive each area → raw findings **Phase 3**: Synthesize into 15 domains, 35 capabilities, 8 aspects, 12 decisions **Phase 4** (6 agents in parallel): Verify completeness → find 8 gaps **Phase 5** (8 agents in parallel): Fill gaps → add missing connections **Total: ~42 agent launches, model complete in one session** --- ## Common Mistakes 1. **Not launching enough agents** - One agent can't thoroughly explore a large codebase 2. **Missing `--operates-on`** - Capabilities without domain connections are useless 3. **Missing `--applies-to`** - Aspects without targets don't show their impact 4. **Too shallow** - "Auth" as single capability vs. "Login, Logout, TokenRefresh, PasswordReset, SessionManagement" 5. **Modeling code structure** - Avoid "Controllers", "Services", "Repositories" as domains 6. **Skipping verification** - Always run verification agents to catch gaps 7. **Not iterating** - First pass is never complete; plan for 2-3 rounds --- ## mental CLI Quick Reference ```bash # Add entities mental add domain --desc "..." --files "..." mental add capability --desc "..." --files "..." --operates-on "Dom1,Dom2" mental add aspect --desc "..." --files "..." --applies-to "Cap1,Dom2" mental add decision "" --why "..." # Update connections (IMPORTANT!) mental update capability --operates-on "Dom1,Dom2,Dom3" mental update aspect --applies-to "Cap1,Cap2,Dom1" mental update domain --desc "new description" # View model mental show # Text output mental view # Interactive visualization in browser # Delete if needed mental delete domain mental delete capability mental delete aspect ```