Agent Documentation Guide

Overview: .erk/docs/agent/ contains agent-focused documentation with:

• YAML frontmatter for routing and discovery
• Hierarchical category organization (categories listed in index below)
• Index files for category navigation
• Routing tables in AGENTS.md

Document Registry (Auto-Generated)

@.erk/docs/agent/index.md

Frontmatter Requirements

Every markdown file (except index.md) MUST have:

---
title: Document Title
read_when:
  - "first condition"
  - "second condition"
---

Required Fields

Field	Type	Purpose
title	string	Human-readable title for index tables
read_when	list[string]	Conditions when agent should read this doc

Writing Effective read_when Values

• Use gerund phrases: "creating a plan", "styling CLI output"
• Be specific: "fixing merge conflicts in tests" not "tests"
• Include 2-4 conditions covering primary use cases
• Think: "An agent should read this when they are..."

Good:

read_when:
  - "creating or closing plans"
  - "understanding plan states"
  - "working with .impl/ folders"

Bad:

read_when:
  - "plans" # Too vague
  - "the user asks" # Not descriptive

Documentation Structure

Read the master index for current categories and documents:

.erk/docs/agent/index.md

The index contains:

• All category paths and descriptions
• Root-level documents
• Document listings with "Read when..." conditions

Category Placement Guidelines

1. Match by topic - Does the doc clearly fit one category? (see index above for categories)
2. Match by related docs - Are similar docs already in a category?
3. When unclear - Place at root level; categorize later when patterns emerge
4. Create new category - When 3+ related docs exist at root level

Distinguishing cli/ vs architecture/

This is the most common confusion:

• cli/: Patterns for building CLI commands - how users interact with the tool

  • Fast-path patterns (skipping expensive ops)
  • Output formatting and styling
  • Script mode behavior
  • Command organization

• architecture/: Internal implementation patterns - how the code works

  • Gateway ABCs and dependency injection
  • Dry-run via wrapper classes
  • Shell integration constraints
  • Protocol vs ABC decisions

Document Structure Template

---
title: [Clear Document Title]
read_when:
  - "[first condition]"
  - "[second condition]"
---

# [Title Matching Frontmatter]

[1-2 sentence overview]

## [Main Content Sections]

[Organized content with clear headers]

## Related Topics

- [Link to related docs](../category/doc.md) - Brief description

Index File Template

Each category has an index.md following this pattern:

---
title: [Category] Documentation
read_when:
  - "[when to browse this category]"
---

# [Category] Documentation

[Brief category description]

## Quick Navigation

| When you need to... | Read this        |
| ------------------- | ---------------- |
| [specific task]     | [doc.md](doc.md) |

## Documents in This Category

### [Document Title]

**File:** [doc.md](doc.md)

[1-2 sentence description]

## Related Topics

- [Other Category](../other/) - Brief relevance

Code in Documentation

Critical rule: NEVER embed Python functions that process erk data or encode business logic.

Why This Matters

Embedded Python code in documentation:

• Is NOT under test - it silently goes stale
• Causes bugs when agents copy outdated patterns
• Encodes business assumptions (field names, conventions) that can change
• Creates maintenance burden requiring docs-code sync

PR #2681 demonstrated this: an agent copied incorrect scratch directory paths from documentation because the docs hadn't been updated when the implementation changed.

The "Simple Function" Trap

Even "simple" functions are dangerous. A one-liner like:

# DANGEROUS - encodes `agent-` prefix convention
files = [f for f in dir.glob("*.jsonl") if not f.name.startswith("agent-")]

Embeds a naming convention that could change. When it does, the docs become a source of bugs.

What to REMOVE (Aggressive Stance)

Remove ALL Python def functions that:

• Process session logs, JSONL, or erk data
• Encode path patterns or naming conventions
• Filter, parse, or transform erk-specific data
• Implement algorithms that exist (or could exist) in production
• Show "how to" implementation patterns for erk internals

Even if the function doesn't exist in production today, it could be added later, creating divergence.

What to KEEP (Narrow Exceptions)

• JSON/YAML format examples: Showing data structure, not processing code
• External library patterns: Click commands, pytest fixtures, Rich tables (teaching third-party APIs)
• Anti-pattern demonstrations: Code explicitly marked "WRONG" or "DON'T DO THIS"
• Shell/bash commands: ls, jq, grep for operational tasks
• Type definitions: Dataclass/TypedDict showing structure (not methods)

Decision Test

Before keeping a Python code block, ask:

1. Does it contain a def statement? → Probably REMOVE
2. Does it process erk-specific data? → REMOVE
3. Does it encode a convention (field name, path pattern, prefix)? → REMOVE
4. Is it teaching a third-party API (Click, pytest, Rich)? → KEEP
5. Is it showing data FORMAT (not processing)? → KEEP

Replacement Format

When removing code, replace with:

1. Prose description of what the operation does
2. Source pointer to canonical implementation
3. CLI command if one exists for agents to use

Before (BAD):

```python
def find_session_logs(project_dir: Path) -> list[Path]:
    """Find all main session logs (exclude agent logs)."""
    return [
        f for f in project_dir.glob("*.jsonl")
        if f.is_file() and not f.name.startswith("agent-")
    ]
```

After (GOOD):

Main session logs are `.jsonl` files that don't start with `agent-`. Agent
subprocess logs use the `agent-<id>.jsonl` naming convention.

To list sessions for a project, use:
erk kit exec erk list-sessions

See `preprocess_session.py` for the canonical implementation.

Source Pointer Rules

• Point to source file path: package/module.py
• NEVER include line numbers (they go stale)
• Use backticks for file paths
• Prefer CLI commands over source pointers when available

Reorganizing Documentation

When moving files between categories:

Step 1: Move Files with git mv

cd .erk/docs/agent
git mv old-location/doc.md new-category/doc.md

Step 2: Update Cross-References

Find all references to moved files:

grep -r "old-filename.md" .erk/docs/agent/

Update relative links:

• Same category: [doc.md](doc.md)
• Different category: [doc.md](../category/doc.md)
• To category index: [Category](../category/)

Step 3: Update Index Files

Update Quick Navigation tables in affected index files.

Step 4: Update AGENTS.md

If the doc was in the routing table, update the path.

Step 5: Validate

Run make fast-ci to catch broken links and formatting issues.

Updating Routing Tables

AGENTS.md contains the Quick Routing Table for agent navigation.

When to Add Entries

• New category additions
• High-frequency tasks
• Tasks where wrong approach is common

Entry Format

| [Task description] | → [Link or skill] |

Examples:

• | Understand project architecture | → [Architecture](.erk/docs/agent/architecture/) |
• | Write Python code | → Load \dignified-python` skill FIRST |`

Validation

Run before committing:

make fast-ci

This validates:

• YAML frontmatter syntax
• Required fields present
• Markdown formatting (prettier)

⚠️ Generated Files - Do Not Edit Directly

The following files are auto-generated from frontmatter metadata:

File	Source
.erk/docs/agent/index.md	Frontmatter from all docs
.erk/docs/agent/<category>/index.md	Frontmatter from category
.erk/docs/agent/tripwires.md	tripwires: field in docs

Never edit these files directly. Changes will be overwritten.

Workflow for Changes

1. Edit the source frontmatter in the relevant documentation file(s)
2. Run sync: erk docs sync
3. Verify changes in the generated files
4. Commit both the source and generated files

Adding a New Tripwire

To add a tripwire rule:

1. Add to the tripwires: field in the relevant doc's frontmatter:

   tripwires:
     - action: "doing something dangerous"
       warning: "Do this instead."
   

2. Run erk docs sync to regenerate tripwires.md

Quick Reference

• Full navigation: .erk/docs/agent/guide.md
• Category index: .erk/docs/agent/index.md
• Regenerate indexes: erk docs sync
• Run validation: make fast-ci