Default .understandignore File Content in Understand Anything

The default .understandignore file contains a descriptive header explaining gitignore-style syntax, followed by commented-out suggestions for test-file patterns like *.test.* and *.snap.

When Understand Anything scans a project for the first time, it automatically creates a starter .understandignore file in the project root. This file controls which paths are excluded from AI analysis using familiar glob syntax inherited from .gitignore.

Core Structure of the Default File

The starter file is constructed by generateStarterIgnoreFile() in packages/core/src/ignore-generator.ts. Every generated file contains two mandatory sections: the built-in header and generic test-file suggestions.

The Built-in Header

The file always opens with a static header block that documents the syntax rules and lists the hard-coded exclusions. According to the Understand Anything source code, this header is defined as the HEADER constant:

const HEADER = `# .understandignore — patterns for files/dirs to exclude from analysis

# Syntax: same as .gitignore (globs, # comments, ! negation, trailing / for dirs)

# Lines below are suggestions — uncomment to activate.

# Use ! prefix to force-include something excluded by defaults.

#

# Built-in defaults (always excluded unless negated):

#   node_modules/, .git/, dist/, build/, obj/, *.lock, *.min.js, etc.

#
`;

These built-in defaults are always active during scanning unless explicitly negated with !.

Generic Test-File Patterns

Below the header, the generator appends a standard section containing commented patterns for common test files. This section is always present regardless of project structure:

# --- Test file patterns (uncomment to exclude) ---

# *.test.*

# *.spec.*

# *.snap

Users must remove the # characters to activate these exclusions.

Optional Dynamic Sections

If the project contains specific files or directories, ignore-generator.ts appends additional commented suggestions above the generic test patterns.

.gitignore Pattern Inheritance

When a .gitignore file exists in the project root, the generator parses it and appends any patterns not already covered by the hard-coded defaults. These inherited patterns are inserted as suggestions that users can uncomment to align analysis exclusions with Git exclusions.

Auto-Detected Directories

The scanner checks for common development directories such as __tests__/, test/, docs/, and similar folders. When detected, these paths are added as commented suggestions, allowing users to quickly exclude entire directory trees from analysis.

Minimum Default Content

If a project has no .gitignore file and none of the detectable directories exist, the minimum generated content includes only the header and test-file suggestions:

# .understandignore — patterns for files/dirs to exclude from analysis

# Syntax: same as .gitignore (globs, # comments, ! negation, trailing / for dirs)

# Lines below are suggestions — uncomment to activate.

# Use ! prefix to force-include something excluded by defaults.

#

# Built-in defaults (always excluded unless negated):

#   node_modules/, .git/, dist/, build/, obj/, *.lock, *.min.js, etc.

#

# --- Test file patterns (uncomment to exclude) ---

# *.test.*

# *.spec.*

# *.snap

Source Code Implementation

The generation logic resides in packages/core/src/ignore-generator.ts. The primary export generateStarterIgnoreFile accepts a project root path, analyzes the directory structure, and assembles the content:

import { generateStarterIgnoreFile } from "./ignore-generator.js";

const projectRoot = "/path/to/your/project";
const starterContent = generateStarterIgnoreFile(projectRoot);
console.log(starterContent);

During the scanning workflow, skills/understand/scan-project.mjs invokes this generator if no .understandignore file exists. After the file is created, packages/core/src/ignore-filter.ts handles the actual exclusion logic by merging user-defined patterns with the built-in defaults.

Summary

• The default .understandignore file begins with a built-in header explaining gitignore-style syntax and documenting hard-coded exclusions.
• Hard-coded defaults include node_modules/, .git/, dist/, build/, obj/, *.lock, and *.min.js.
• Commented test-file patterns (*.test.*, *.spec.*, *.snap) are always included for optional activation.
• Dynamic sections may append patterns from existing .gitignore files and auto-detected directories like __tests__/ or docs/.
• The generation is handled by generateStarterIgnoreFile() in packages/core/src/ignore-generator.ts.

Frequently Asked Questions

What syntax does .understandignore use?

The file uses standard .gitignore glob syntax. You can use * for wildcards, ? for single characters, / to mark directories, # for comments, and ! for negation to force-include otherwise excluded paths.

Can I override the built-in exclusions?

Yes. While hard-coded exclusions like node_modules/ are active by default, you can negate them by adding a line with the ! prefix, such as !node_modules/, to your .understandignore file.

Where is the default content defined?

The header template and suggestion patterns are defined as constants in packages/core/src/ignore-generator.ts, specifically within the HEADER constant and the hard-coded test-pattern strings.

Does Understand Anything update the file automatically after creation?

No. After the initial creation during the first scan, the file becomes user-maintained. Future scans will respect your modifications but will not overwrite the file automatically, even if new directories are detected.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}