Built skill-tree to classify my own Claude sessions against Anthropic's AI Fluency Index — 11 observable behaviors measured across 9,830 conversations in their February 2026 study. The tool assigns an archetype card, picks a behavior I haven't tried, and surfaces it as a growth quest at the start of my next session.
The growth quest persistence required a SessionStart hook writing to disk. In Claude Code that's straightforward: ~/.skill-tree/ is durable across sessions, stable path, no surprises.
Cowork broke that assumption immediately. Its $HOME is ephemeral — gets wiped between sessions. Any state I wrote there was gone by the next morning. The fix was a second path: $CLAUDE_PLUGIN_ROOT/.user-state/, which Cowork preserves across sessions. So the plugin now checks which environment it's running in and writes state accordingly.
This is the kind of thing that doesn't show up in docs — you find it when your growth quest silently disappears and you dig into why.
The rest of the pipeline: session files → extract user messages → remote classifier (Claude Haiku on Fly.io) → archetype assignment → narrative synthesis → render → stable URL. Takes 30–60 seconds end-to-end. Seven archetypes rendered as tarot cards with museum art; live example at skill-tree-ai.fly.dev/fixture/illuminator.
Install in Claude Code:
claude plugin marketplace add robertnowell/ai-fluency-skill-cards
claude plugin install skill-tree-ai@ai-fluency-skill-cards
For Cowork: skill-tree-ai.zip in the plugin settings. Also available as an MCP server (npm: skill-tree-ai) for Cursor, VS Code, Windsurf.
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