Dorothy J Aubrey

Posted on Jan 24 • Originally published at github.com

Mother CLAUDE: Automating Everything with Hooks

#ai #automation #productivity #devrel

TL;DR: We built three hooks that automate the Mother CLAUDE workflow: (1) auto-generate session handoffs on context compaction, (2) load previous handoffs at session start, and (3) auto-approve safe operations. Manual discipline becomes invisible infrastructure.

Who this is for: Anyone who wants AI memory that doesn't depend on human discipline. Anyone tired of clicking "yes" to approve safe operations.

Part 3 of the Designing AI Teammates series. Part 1 covered documentation structure. Part 2 covered why session handoffs matter. This one covers automating the workflow with hooks. Part 4 will cover quality checkpoints.

The Problem

Session handoffs work. We covered that in Part 2. The template captures:

What was accomplished
Key decisions made
Files modified
Next steps
Open questions

The problem? Humans forget to create them.

You finish a productive session, you're in the flow, you close the terminal... and the handoff doesn't get written. The next session starts cold. All that context—gone.

We needed handoffs to happen automatically, without relying on human discipline at the end of a long session.

The Solution: Claude Code Hooks

Claude Code has a hooks system that runs scripts at specific events. Two events matter for us:

Hook	When It Fires	Why It Matters
PreCompact	Before context compression	Captures everything before detail is lost
SessionEnd	When you close the session	Captures final state

The hook receives the full conversation transcript. We can parse it, send it to Claude Haiku for summarization, and save a structured handoff document—all automatically.

The Architecture

┌─────────────────────────────────────────────────────┐
│                  Claude Code Session                 │
│                                                     │
│  [Working...]  [Working...]  [Context getting full] │
│                                                     │
│                         │                           │
│                         ▼                           │
│              ┌──────────────────┐                   │
│              │  PreCompact Hook │                   │
│              └────────┬─────────┘                   │
│                       │                             │
└───────────────────────┼─────────────────────────────┘
                        │
                        ▼
              ┌──────────────────┐
              │ session_handoff  │
              │     .py          │
              │                  │
              │ 1. Read transcript
              │ 2. Parse conversation
              │ 3. Call Claude Haiku
              │ 4. Save handoff.md
              └────────┬─────────┘
                       │
                       ▼
         ┌─────────────────────────────┐
         │  docs/session_handoffs/      │
         │  20260121-1145-hooks-setup.md│
         └─────────────────────────────┘

The Implementation

Step 1: The Hook Script

A Python script that:

Receives hook input via stdin (includes transcript path)
Parses the JSONL transcript into readable conversation
Sends it to Claude Haiku with a structured prompt
Extracts a descriptive title for the filename
Saves to the project's session_handoffs/ directory

#!/usr/bin/env python3
"""
Mother CLAUDE Session Handoff Generator

Runs on PreCompact (auto) and SessionEnd events to automatically
generate session handoff documents using Claude Haiku.
"""

import json
import os
import sys
from datetime import datetime
from pathlib import Path
import anthropic

def parse_transcript(transcript_path: str) -> str:
    """Parse JSONL transcript into readable conversation."""
    messages = []
    with open(transcript_path, 'r', encoding='utf-8') as f:
        for line in f:
            entry = json.loads(line)
            if entry.get("type") == "human":
                content = extract_text(entry)
                messages.append(f"USER: {content[:3000]}")
            elif entry.get("type") == "assistant":
                content = extract_text(entry)
                messages.append(f"ASSISTANT: {content[:3000]}")

    # Return last 80 messages for context
    return "\n\n---\n\n".join(messages[-80:])

def generate_handoff(conversation: str, cwd: str, api_key: str):
    """Use Claude Haiku to generate a session handoff."""
    client = anthropic.Anthropic(api_key=api_key)

    response = client.messages.create(
        model="claude-3-haiku-20240307",
        max_tokens=4000,
        messages=[{
            "role": "user",
            "content": HANDOFF_PROMPT.format(
                conversation=conversation,
                project=Path(cwd).name,
                date=datetime.now().strftime("%Y-%m-%d")
            )
        }]
    )

    return response.content[0].text

Step 2: The Prompt Template

The prompt asks for a comprehensive handoff matching our template:

HANDOFF_TEMPLATE = """
Generate a session handoff document with these sections:

SHORT_TITLE: [2-4 words, hyphenated, for filename]

# Session Handoff - [Descriptive Title]

**Date**: {date}
**Focus**: [Main focus of this session]
**Status**: [Current state of the work]

## Quick Context
**What's Working:** [Specific things that are functional]
**What Needs Attention:** [Issues, blockers, pending decisions]

## Completed This Session
### [Feature/Task Name]
**Files Created/Modified:**
- `path/to/file.ext` - [What was done]

**Details:** [Technical specifics]

## Technical Discoveries
- **[Topic]**: [What was learned]

## Files Changed This Session
### New Files
### Modified Files

## Next Steps
1. [ ] [Actionable task]

## Open Questions
- [Unresolved decisions]
"""

Step 3: Hook Configuration

In ~/.claude/settings.json:

{
  "hooks": {
    "PreCompact": [
      {
        "matcher": "auto",
        "hooks": [
          {
            "type": "command",
            "command": "python ~/.claude/hooks/session_handoff.py",
            "timeout": 120
          }
        ]
      }
    ],
    "SessionEnd": [
      {
        "hooks": [
          {
            "type": "command",
            "command": "python ~/.claude/hooks/session_handoff.py",
            "timeout": 120
          }
        ]
      }
    ]
  }
}

Step 4: API Key Setup

Store your Anthropic API key as an environment variable:

# Linux/Mac
export ANTHROPIC_API_KEY_HOOKS="sk-ant-..."

# Windows PowerShell
[System.Environment]::SetEnvironmentVariable(
    "ANTHROPIC_API_KEY_HOOKS",
    "sk-ant-...",
    "User"
)

Using a separate key (ANTHROPIC_API_KEY_HOOKS) lets you track usage for automated handoffs separately from your main Claude Code usage.

The Result

Before: Manual Handoffs

End of session:
- Forget to create handoff (60% of the time)
- Create hasty handoff (30% of the time)
- Create thorough handoff (10% of the time)

Next session:
- Spend 10-15 minutes re-establishing context
- Miss important details from previous session
- Repeat work already done

After: Automatic Handoffs

End of session:
- Hook fires automatically
- Handoff created in ~30 seconds
- Saved to docs/session_handoffs/

Next session:
- Read most recent handoff
- Productive in 2-3 minutes
- Full context preserved

Example Output

Here's an actual auto-generated handoff:

# Session Handoff - Implementing Automated Session Handoffs

**Date**: 2026-01-21
**Focus**: Integrating Claude hooks to automatically generate session handoffs
**Status**: Feature complete, ready for testing

---

## Quick Context

**What's Working:**
- Claude hook script written in Python to summarize sessions
- Hooks configured to trigger on auto-compact and session end
- Handoff files being generated in the expected location

**What Needs Attention:**
- API key needs to be regenerated (was exposed during testing)
- Template may need refinement based on real-world usage

---

## Completed This Session

### Implement Hook-Driven Session Handoffs
**Files Created/Modified:**
- `~/.claude/hooks/session_handoff.py` - Python script to generate handoffs
- `~/.claude/settings.json` - Hook configuration

**Details:**
- Wrote a Python script using the Anthropic API to summarize transcripts
- Configured two hook triggers: PreCompact (auto) and SessionEnd
- Script auto-detects working directory to determine project context
- Handoff files saved to project's `docs/session_handoffs/`

---

## Technical Discoveries

- **Environment Variables**: Using separate API key for hooks allows
  tracking automated usage separately from interactive sessions
- **Hook Timing**: PreCompact fires BEFORE compression, so full context
  is still available for summarization

---

## Files Changed This Session

### New Files
- `~/.claude/hooks/session_handoff.py` - Handoff generation script

### Modified Files
- `~/.claude/settings.json` - Added hook configuration

---

## Next Steps

1. [ ] Regenerate API key (current one exposed in conversation)
2. [ ] Test on different projects to verify directory detection
3. [ ] Consider adding git commit info to handoffs

---

## Open Questions

- Should handoffs include actual code snippets from the session?
- How to handle very long sessions that exceed Haiku's context window?

The Meta Moment: Using Claude to Summarize Claude

There's something delightfully recursive about this setup:

You work with Claude Code (Claude Opus/Sonnet)
Session ends or context fills
Hook sends transcript to Claude Haiku
Haiku summarizes what Opus/Sonnet did
Summary helps the next Opus/Sonnet session

Claude is documenting its own work for its future self.

This isn't just automation—it's AI infrastructure supporting AI collaboration.

Why Two Triggers? (And the Bug We Found)

Our first implementation used two triggers:

Trigger	When	Why
PreCompact	Context about to compress	Capture everything before detail is lost
SessionEnd	Session closes	Ensure final state is captured

Simple, right? Both triggers run the same script. What could go wrong?

The Problem We Discovered

A reader (okay, it was us during testing) noticed a flaw:

PreCompact fires → Rich, detailed handoff saved
Context compresses → Detail lost
SessionEnd fires → Second handoff saved (thinner, post-compression)
Next session starts → SessionStart loads the most recent handoff
Oops → You loaded the thin SessionEnd handoff, not the rich PreCompact one

The good handoff got buried by the thin one.

The Fix: Smart Deduplication

We updated the script to track state:

# PreCompact: save marker with transcript size
save_handoff_state(session_id, transcript_size)

# SessionEnd: check if PreCompact already ran
if should_skip_handoff(session_id, current_size, trigger):
    cleanup_state(session_id)
    sys.exit(0)  # Skip - no new work since PreCompact

The logic:

PreCompact always generates a handoff and saves the transcript size
SessionEnd checks: did PreCompact already run? Did the transcript grow significantly (>10%)?
- If no significant new work → skip
- If new work happened after compact → generate new handoff

This handles all scenarios:

Compact then close immediately → SessionEnd skips (PreCompact got it)
Compact, more work, then close → SessionEnd generates (new work to capture)
Short session, just close → SessionEnd generates (only trigger)

The lesson: test your hooks end-to-end. The obvious solution (two triggers, same script) had a subtle interaction problem.

Handling Large Sessions

Haiku has a smaller context window than Opus. For very long sessions:

The script takes the last 80 messages of the conversation
Each message is truncated to 3,000 characters
This keeps the most recent (and usually most relevant) context

For most sessions, this captures everything that matters. The early parts of very long sessions (initial exploration, early false starts) are often less valuable than the recent work anyway.

Cost Considerations

Claude Haiku is cheap. A typical handoff:

Input: ~50,000 tokens (conversation)
Output: ~1,500 tokens (handoff)
Cost: ~$0.02-0.03 per handoff

Even with multiple sessions per day, the monthly cost is negligible compared to the value of preserved context.

Pro tip: Create a separate API key for hooks. The Anthropic console shows usage per key, so you can track exactly how much your automated handoffs cost.

Choosing a Model

As of this writing, we use Claude Haiku (claude-3-haiku-20240307) for handoff generation. It's cheap, fast, and good enough for structured summarization.

Model	Cost per Handoff	Speed	When to Use
Haiku	~$0.02	Fast	Default choice - summarization doesn't need genius
Sonnet	~$0.15	Medium	If you want richer, more nuanced summaries
Opus	~$1+	Slower	Overkill for handoffs - save it for real work

To change models, edit session_handoff.py:

# Default
model="claude-3-haiku-20240307"

# For richer summaries (costs more)
model="claude-sonnet-4-20250514"

Anthropic releases new models regularly. Check docs.anthropic.com for the latest model IDs. The hook script in our repo uses Haiku, but swap in whatever model suits your needs and budget.

Extending the System

Add Git Info

import subprocess

def get_recent_commits():
    result = subprocess.run(
        ["git", "log", "--oneline", "-5"],
        capture_output=True, text=True
    )
    return result.stdout

Add to Multiple Projects

The script auto-detects the project from cwd and finds the right session_handoffs/ directory. It works across all your projects without configuration.

Customize Per Project

If you need project-specific handoff formats, add a .claude/handoff-config.json to any project:

{
  "template": "custom",
  "include_git": true,
  "extra_sections": ["Jira Tickets", "API Changes"]
}

Known Limitations

Can't Prevent Compaction

PreCompact hooks can run side effects but can't stop compaction. The handoff happens, then compaction proceeds. This is fine—we just want to capture context, not block the workflow.

Timeout

Hooks have a 60-second default timeout (we set 120). Very long transcripts might need more time. The script handles timeouts gracefully—a failed handoff is better than a blocked session.

API Dependency

Requires an Anthropic API key and internet connection. If the API is down, the hook fails silently. Consider adding local fallback summarization for offline work.

How This Works with Agents

If you're using Claude Code's Task tool to spawn subagents (Explore, Plan, etc.), here's what you need to know:

Event	Hook Fires?	Why
Main session starts	✅ SessionStart	Loads previous handoff
Subagent spawned	❌ None	Subagents are subprocesses, not new sessions
Subagent finishes	❌ None*	Results return to main session
Main session ends	✅ SessionEnd	Generates handoff including subagent work

This is actually the right behavior:

The main session is the orchestrator—it has context and makes decisions
Subagents are workers—they do specific tasks and report back
The main session's handoff captures everything, including what subagents accomplished

You don't need separate handoffs for subagents because their work flows back to the main session. When the main session's handoff gets generated, it includes the full picture.

*Claude Code does have a SubagentStop hook if you want to capture subagent completions separately, but for most workflows the main session handoff is sufficient.

Bonus Hook #1: Auto-Load Previous Handoffs

Writing handoffs is half the equation. The other half: making sure Claude reads them.

The SessionStart Hook

When you start a new Claude Code session, the SessionStart hook fires. We use it to automatically load the most recent handoff:

# session_start.py - outputs previous handoff to stdout
handoffs = sorted(glob("docs/session_handoffs/*.md"))
if handoffs:
    print(f"Previous handoff: {handoffs[-1].name}")
    print(open(handoffs[-1]).read())

Claude sees this output as context at the start of every session. No manual loading required.

Configuration:

Add to ~/.claude/settings.json:

"SessionStart": [
  {
    "hooks": [
      {
        "type": "command",
        "command": "python ~/.claude/hooks/session_start.py",
        "timeout": 10
      }
    ]
  }
]

Result: Every new session starts with context from the previous one. The handoffs we auto-generate get auto-loaded. The circle is complete.

Bonus Hook #2: Auto-Approve Safe Operations

If you've used Claude Code for more than an hour, you've clicked "yes" to approve git status approximately 47 times.

The Permission Fatigue Problem

Claude Code asks permission for potentially dangerous operations. This is good! But it also asks for:

git status
ls
npm test
Reading files
And dozens of other safe operations

The PermissionRequest Hook

This hook intercepts permission requests and auto-approves safe ones:

# auto_approve.py
always_safe = ["Read", "Glob", "Grep", "Write", "Edit"]

safe_bash = [
    r'^git\s+(status|log|diff|add|commit|push|pull)',
    r'^npm\s+(test|run|install)',
    r'^ls(\s|$)',
]

dangerous = [
    r'\bsudo\b',
    r'git\s+push\s+.*--force',
    r'git\s+reset\s+--hard',
]

What gets auto-approved:

All file operations (Read, Write, Edit)
Git operations (add, commit, push, pull)
Package management (npm install, pip install)
Build/test commands

What still requires approval:

sudo anything
git push --force
git reset --hard
Destructive operations

Configuration:

"PermissionRequest": [
  {
    "matcher": "*",
    "hooks": [
      {
        "type": "command",
        "command": "python ~/.claude/hooks/auto_approve.py",
        "timeout": 5
      }
    ]
  }
]

Result: Claude flows. No more clicking "yes" fifty times a session. Dangerous operations still get caught.

Project-Specific Configuration

Different projects might want different settings. Create .claude/project.json in any project root:

{
  "handoffs_path": "docs/session_handoffs",
  "handoffs_to_load": 2
}

Setting	Default	Description
`handoffs_path`	`docs/session_handoffs`	Where to read/write handoffs
`handoffs_to_load`	`1`	How many previous handoffs to load

Both the session_handoff.py and session_start.py scripts check for this config.

The Complete Hook Suite

Here's what we built:

Hook	Trigger	What It Does
session_handoff.py	PreCompact, SessionEnd	Auto-generates handoff documents
session_start.py	SessionStart	Loads previous handoff into context
auto_approve.py	PermissionRequest	Auto-approves safe operations

The full settings.json:

{
  "hooks": {
    "SessionStart": [{"hooks": [{"type": "command", "command": "python ~/.claude/hooks/session_start.py"}]}],
    "PreCompact": [{"matcher": "auto", "hooks": [{"type": "command", "command": "python ~/.claude/hooks/session_handoff.py"}]}],
    "SessionEnd": [{"hooks": [{"type": "command", "command": "python ~/.claude/hooks/session_handoff.py"}]}],
    "PermissionRequest": [{"matcher": "*", "hooks": [{"type": "command", "command": "python ~/.claude/hooks/auto_approve.py"}]}]
  }
}

The Setup Checklist

[ ] Install Python 3.8+ and the anthropic package (pip install anthropic)
[ ] Copy hook scripts to ~/.claude/hooks/
[ ] Configure hooks in ~/.claude/settings.json
[ ] Set API key as environment variable
[ ] Restart terminal (hooks load at session start)
[ ] Verify by starting a new session and checking for previous handoff

Prefer Node.js?

We've included a smoke-tested Node.js version (session_handoff.js) in the repo. If you prefer Node:

Install: npm install @anthropic-ai/sdk
Update settings.json to use node instead of python

The Python version is our primary, daily-driver implementation. Only the main handoff script has a Node version—the simpler scripts (session_start.py, auto_approve.py) are Python-only but straightforward to port.

Contributions welcome! If you create Node versions of the other scripts, find bugs, improve the templates, or have ideas—we'd love PRs. This is a community resource.

The Core Insight

The best documentation is documentation that writes itself.

Session handoffs are valuable. But relying on human discipline at the end of a long session is a recipe for forgotten context.

By automating handoffs:

Memory persists without effort
Every session is documented
Context survives across sessions, machines, and time

The goal isn't to replace human judgment. It's to ensure the conversation happens.

This system was built in a single afternoon over lunch—and documented by the very hook system it describes. The handoff you're reading about was generated by the hook that creates handoffs. That's the feedback loop working as intended.

This article was written collaboratively with Claude, using the automated handoff system it describes.