Session Brain

Session Brain

Persistent per-repo working memory stored under .claude/voyager/.

State Files

How It Works

Session Brain updates automatically via hooks:

• SessionStart: Injects current brain context + repo snapshot
• PreCompact/SessionEnd: Persists changes to brain.json and creates episode

You don't need to manually update the brain—just work normally and it tracks context.

Reading brain.json

When exploring brain.json, use jq to query specific sections instead of reading the whole file:

# Current context (goal, plan, questions)
jq '.working_set' .claude/voyager/brain.json

# Decision history
jq '.decisions' .claude/voyager/brain.json

# Recent progress
jq '.progress' .claude/voyager/brain.json

# Project overview
jq '.project' .claude/voyager/brain.json

For a quick human-readable summary, read .claude/voyager/brain.md instead.

Answering User Questions

When users ask about context, read and interpret the brain files:

"Resume" / "What were we doing?"

1. Read .claude/voyager/brain.md for quick context
2. Check brain.json → working_set.current_goal and working_set.current_plan
3. Summarize: current goal, plan progress, any open questions

"What's next?"

1. Read brain.json → working_set.current_plan
2. Check progress.recent_changes to see what's done
3. Suggest the next uncompleted step from the plan

"Why did we decide X?" / "What was the rationale?"

1. Read brain.json → decisions array
2. Find matching decision by keyword
3. Return the rationale and implications

"What are the open questions?"

1. Read brain.json → working_set.open_questions
2. Also check working_set.risks for blockers

Recording Decisions

When the user says "remember this decision: ..." or explicitly wants to record a decision:

1. Read current .claude/voyager/brain.json
2. Append to the decisions array:

   {
     "when": "<ISO timestamp>",
     "decision": "<what was decided>",
     "rationale": "<why>",
     "implications": ["<what this affects>"]
   }
   

3. Write updated brain.json

Note: brain.md will be re-rendered automatically on the next session end or compaction.

Brain Schema Overview

See schemas/brain.schema.json for full schema. Key sections:

• project: Stable project understanding (summary, stack, key commands)
• working_set: Current context (goal, plan, open questions, risks)
• decisions: Append-only decision log with rationale
• progress: Recent changes and completed milestones
• signals: Metadata (last session ID, timestamp)

Technical Details

See reference.md for:

• Full file structure
• Update flow details
• Manual operations (reset, view history)
• Graceful degradation behavior