Nous: Self-Improving Context System

Architecture

Nous operates through two Claude Code hooks and a statusline trigger:

• SessionStart hook: Injects recent learnings and knowledge into Claude's context at the beginning of every session. Reads from per-project .claude/nous/ storage and prepends relevant entries so Claude benefits from prior session insights.
• Stop hook: Monitors context window usage percentage (via statusline activity data). When thresholds are met, spawns extraction workers to analyze the session transcript and extract structured JSONL entries.
• Activity Logger (hooks/nous-logger.sh): A minimal script that reads status JSON from stdin, enriches it with timestamp and hostname, and silently appends to ~/.claude/statusline-activity.jsonl. Produces no stdout output -- it is designed to run in the background without interfering with any visual statusline.

Statusline Integration (Trigger Pattern)

Nous does not own or replace the user's statusline. Instead, /nous:setup appends a small trigger block to the bottom of the user's ~/.claude/statusline.sh:

~/.claude/statusline.sh (user-owned)
  ├── rendering logic (model, git, context bar, etc.)
  └── plugin trigger (appended at bottom)
        └── pipes $input to hooks/nous-logger.sh in background (&)

This means:

• The user's statusline is theirs. Nous adds a 3-line trigger at the bottom — it never touches the rendering.
• The logger and the visual renderer are fully decoupled. The logger (nous-logger.sh) never writes to stdout. The statusline rendering never writes to the activity log. The trigger is the only piece that connects them.
• Graceful degradation. If the nous plugin is uninstalled, the trigger silently no-ops (existence check fails, nothing executes).

Data Flow

~/.claude/statusline.sh (user-owned, set as statusLine.command)
  → reads stdin (status JSON from Claude Code) into $input
  → rendering logic outputs to stdout (visual statusline)
  → trigger block (appended at bottom):
      → pipes $input to hooks/nous-logger.sh in background
          → enriches with meta_ts, meta_host
          → appends to ~/.claude/statusline-activity.jsonl
  → Stop hook reads statusline-activity.jsonl
      → if context >10%, spawns `claude --print` extraction workers
      → workers read the session transcript
      → extract JSONL entries to inbox fragments (.claude/nous/{learnings,knowledge}/inbox.jsonl.*)
      → flush_inbox() consolidates fragments into engram.jsonl / cortex.jsonl
      → next SessionStart hook injects recent entries from engram.jsonl / cortex.jsonl

Lenses

Extraction uses two perspectives (lenses), each with its own prompt and output format:

• Learnings (behavioral): What future sessions should do differently. Captures workflow improvements, tool usage patterns, error avoidance strategies, and user preferences. Stored in learnings/engram.jsonl.
• Knowledge (factual): What exists in the project. Captures architecture decisions, file locations, API patterns, configuration details, and discovered facts. Stored in knowledge/cortex.jsonl.

Each lens runs as a separate claude --print worker process, reading the same transcript but extracting different types of information.

Per-Project Storage

Each project maintains its own nous state in .claude/nous/:

.claude/nous/
├── extraction_cursor.json          # Tracks last extracted timestamp to avoid re-processing
├── learnings/
│   ├── inbox.jsonl.*               # Raw extraction fragments (temporary, per-worker)
│   └── engram.jsonl                # Consolidated learnings (injected at session start)
└── knowledge/
    ├── inbox.jsonl.*               # Raw extraction fragments (temporary, per-worker)
    └── cortex.jsonl                # Consolidated knowledge (injected at session start)

The extraction_cursor.json file prevents duplicate extraction across sessions. Inbox fragments are named with unique suffixes per worker invocation and consolidated during the flush step.

Context Threshold Behavior

The Stop hook reads the current context window percentage and applies these rules:

Statusline Dependency

The activity logger is required for nous to function. It provides the context window percentage that drives all threshold decisions. Without it, the Stop hook cannot determine whether extraction should run.

The logger must be triggered from the statusline because that is how Claude Code exposes periodic status data. Run /nous:setup to append the trigger automatically. The setup never replaces your statusline — it only adds silent background logging alongside your rendering.