Context and Problem Statement

As Spec Kitty grows in complexity, we need a systematic way to document significant architectural decisions. Team members (both human and AI agents) need to understand:

  • Why certain approaches were chosen
  • What alternatives were considered
  • What tradeoffs were accepted
  • What consequences resulted from decisions

Without structured decision documentation, we face:

  • Loss of architectural context over time
  • Repeated debates about settled decisions
  • Difficulty onboarding new contributors
  • Unclear rationale for existing patterns

Decision Drivers

  • Need to preserve architectural knowledge as project evolves
  • Multiple AI agents need clear decision context
  • Want to avoid "tribal knowledge" that exists only in conversation history
  • Need accountability for architectural choices
  • Want to learn from both successful and unsuccessful decisions

Considered Options

  • Option 1: No formal decision documentation (status quo)
  • Option 2: Architecture Decision Records (ADRs)
  • Option 3: Design documents in wiki
  • Option 4: Comprehensive architecture specification document

Decision Outcome

Chosen option: "Option 2: Architecture Decision Records (ADRs)", because:

  • Lightweight and low-ceremony (fits agile development)
  • One decision per document (focused and digestible)
  • Immutable once accepted (provides historical record)
  • Widely adopted standard with excellent tooling
  • Works well with version control (git)
  • AI agents can easily read and reference ADRs

Consequences

Positive

  • Architectural decisions are documented and discoverable
  • New team members can understand decision history
  • AI agents have clear context for development work
  • Prevents revisiting settled decisions repeatedly
  • Creates knowledge base of tradeoffs and lessons learned
  • Supports code reviews with architectural validation

Negative

  • Requires discipline to create ADRs consistently
  • Additional documentation overhead
  • Risk of ADRs becoming stale if not maintained

Neutral

  • ADRs are stored in architecture/1.x/adr/ and architecture/2.x/adr/ directory
  • Use sequential numbering (0001, 0002, etc.)
  • Follow standardized template format

Confirmation

We'll know this decision is successful if:

  • ADRs are consistently created for significant decisions
  • Team references ADRs during code reviews and planning
  • New contributors find ADRs helpful for understanding codebase
  • Decision rationale is clear 6+ months after decisions are made

Pros and Cons of the Options

Option 1: No Formal Decision Documentation

Pros:

  • No overhead or process burden
  • Maximum flexibility

Cons:

  • Architectural knowledge lost over time
  • Decisions must be reverse-engineered from code
  • Repeated debates about settled issues
  • Difficult onboarding for new contributors

Option 2: Architecture Decision Records (ADRs)

Pros:

  • Lightweight and focused (one decision per document)
  • Immutable historical record
  • Widely adopted industry standard
  • Works well with version control
  • Easy for AI agents to read and reference
  • Template-driven for consistency

Cons:

  • Requires discipline to maintain
  • Documentation overhead for each decision
  • Can become stale if not kept in sync

Option 3: Design Documents in Wiki

Pros:

  • Easy to update and edit
  • Can include diagrams and rich media
  • Searchable and cross-linked

Cons:

  • Separate from code repository
  • Encourages editing rather than superseding
  • No clear versioning or history
  • Can become monolithic and hard to navigate

Option 4: Comprehensive Architecture Specification

Pros:

  • Single comprehensive reference
  • Covers entire system architecture

Cons:

  • Becomes outdated quickly
  • Too large to read or maintain
  • Doesn't capture decision history or alternatives
  • Difficult to determine when decisions were made

More Information

Template and Guidelines

  • See architecture/adr-template.md for the standard ADR template
  • See architecture/README.md for naming conventions and process

External References

This decision follows the approach documented in:

  • All subsequent ADRs follow the format established here
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