ASCII Diagram Validator

Validate and fix alignment issues in ASCII box-drawing diagrams commonly used in architecture documentation, README files, and code comments.

Overview

ASCII diagrams using box-drawing characters (─│┌┐└┘├┤┬┴┼ and double-line variants ═║╔╗╚╝╠╣╦╩╬) require precise column alignment. This skill provides:

1. Validation script - Detects misaligned characters with file:line:column locations
2. Actionable fixes - Specific suggestions for correcting each issue
3. Multi-file support - Validate individual files or entire directories

When to Use This Skill

Invoke when:

• Creating or editing ASCII architecture diagrams in markdown
• Reviewing documentation with box-drawing diagrams
• Fixing "diagram looks wrong" complaints
• Before committing docs/ARCHITECTURE.md or similar files
• When user mentions "ASCII alignment", "diagram alignment", or "box drawing"

Supported Characters

Single-Line Box Drawing

Corners: ┌ ┐ └ ┘
Lines:   ─ │
T-joins: ├ ┤ ┬ ┴
Cross:   ┼

Double-Line Box Drawing

Corners: ╔ ╗ ╚ ╝
Lines:   ═ ║
T-joins: ╠ ╣ ╦ ╩
Cross:   ╬

Mixed (Double-Single)

╞ ╟ ╤ ╧ ╪ ╫

Quick Start

Validate a Single File

/usr/bin/env bash << 'PREFLIGHT_EOF'
uv run ${CLAUDE_PLUGIN_ROOT}/skills/ascii-diagram-validator/scripts/check_ascii_alignment.py docs/ARCHITECTURE.md
PREFLIGHT_EOF

Validate Multiple Files

/usr/bin/env bash << 'PREFLIGHT_EOF_2'
uv run ${CLAUDE_PLUGIN_ROOT}/skills/ascii-diagram-validator/scripts/check_ascii_alignment.py docs/*.md
PREFLIGHT_EOF_2

Validate Directory

/usr/bin/env bash << 'PREFLIGHT_EOF_3'
uv run ${CLAUDE_PLUGIN_ROOT}/skills/ascii-diagram-validator/scripts/check_ascii_alignment.py docs/
PREFLIGHT_EOF_3

Output Format

The script outputs issues in a compiler-like format for easy navigation:

docs/ARCHITECTURE.md:45:12: error: vertical connector '│' at column 12 has no matching character above
  → Suggestion: Add '│', '├', '┤', '┬', or '┼' at line 44, column 12

docs/ARCHITECTURE.md:67:8: warning: horizontal line '─' at column 8 has no terminator
  → Suggestion: Add '┐', '┘', '┤', '┴', or '┼' to close the line

Severity Levels

Validation Rules

The script checks for:

1. Vertical Alignment - Vertical connectors (│║) must align with characters above/below
2. Corner Connections - Corners (┌┐└┘╔╗╚╝) must connect properly to adjacent lines
3. Junction Validity - T-joins and crosses must have correct incoming/outgoing connections
4. Line Continuity - Horizontal lines (─═) should terminate at valid endpoints
5. Box Closure - Boxes should be properly closed (no dangling edges)

Exit Codes

Integration with Claude Code

When Claude Code creates or edits ASCII diagrams:

1. Run the validator script on the file
2. Review any errors in the output
3. Apply suggested fixes
4. Re-run until clean

Example Workflow

/usr/bin/env bash << 'PREFLIGHT_EOF_4'
# After editing docs/ARCHITECTURE.md
uv run ${CLAUDE_PLUGIN_ROOT}/skills/ascii-diagram-validator/scripts/check_ascii_alignment.py docs/ARCHITECTURE.md

# If errors found, Claude Code can read the output and fix:
# docs/ARCHITECTURE.md:45:12: error: vertical connector '│' at column 12 has no matching character above
# → Edit line 44, column 12 to add the missing connector
PREFLIGHT_EOF_4

Limitations

• Detects structural alignment issues, not aesthetic spacing
• Requires consistent use of box-drawing characters (no mixed ASCII like +---+)
• Tab characters may cause false positives (convert to spaces first)
• Unicode normalization not performed (use pre-composed characters)

Bundled Scripts

scripts/check_ascii_alignment.py

Related

• ARCHITECTURE.md best practices
• Unicode Box Drawing block