Lesson

/lesson — Session Learning Capture

Purpose

Extract actionable, project-specific learnings from friction encountered in the current session and append them to the configured learnings file (default: learnings.md, reads lessonFilePath from project config when set) with domain and severity tags.

Workflow

Step 1: Scan for Friction Patterns

Review the current conversation for these pattern types, ordered by priority:

Pattern	Signal	Example
Repeated failure	Same error/approach tried 2+ times	Forgot WITH(NOLOCK) again, same enum serialization bug
Troubleshooting spiral	3+ back-and-forth attempts to fix one issue	4 tries to fix login fixture timing before finding networkidle
Wrong assumption	Approach based on incorrect mental model	Assumed MustAsync runs in same pipeline as sync validators
User correction	User had to redirect or correct the agent	"No, use Dapper not EF" or "That's the wrong table"
Convention violation	Broke a project convention, had to redo	Missing audit columns, wrong SP naming, hardcoded hex colors
Tool/API surprise	Tool or API behaved unexpectedly	git add silently fails with bracket paths in zsh
Failed tool use	Tool invoked incorrectly, skipped, or retried unnecessarily	Used Edit before Read, used Bash grep instead of Grep tool, wrong sqlcmd flag syntax
Process shortcut	Skipped a required workflow step	Claimed completion without running tests, made design decision without AskUserQuestion, skipped EnterPlanMode for 3+ file change

Step 2: Extract Tagged + Severity-Labeled Learnings

Each learning gets:

• Date: YYYY-MM-DD
• Domain tag: [backend], [frontend], [db], [e2e], [workflow], [tooling], [shell], [process]
  • [process] — tool discipline violations, skipped workflow steps, wrong-sequence tool use
• Severity tag: [one-off], [recurring], [spiral]
  • [one-off] — happened once, but non-obvious enough to record
  • [recurring] — same mistake or pattern seen before (check existing entries in the configured learnings file)
  • [spiral] — required 3+ attempts or a long back-and-forth to resolve

Quality bar: project-specific, actionable, non-obvious, 1-2 sentences max.

For [recurring] entries: read the configured learnings file to check if a similar entry already exists. If so, append a count bump like (x3) to the new entry to track frequency.

Step 3: Append to the configured learnings file (default: learnings.md)

Silently append — no AskUserQuestion, no multi-file routing. Just append.

Entry format:

- **2026-02-23** [backend] [spiral] Login fixture timing — 4 attempts before finding networkidle fix
- **2026-02-23** [db] [recurring] (x3) Forgot WITH(NOLOCK) on SELECT query
- **2026-02-23** [tooling] [one-off] SP parameter order mismatch caused silent null
- **2026-02-23** [process] [recurring] (x2) Used Edit before Read — always Read the file first, even for "obvious" edits
- **2026-02-23** [process] [one-off] Skipped EnterPlanMode for 4-file change — caused rework; use plan mode for 3+ files

Mistake entries must include the correction — record not just what failed, but what to do instead next time.

Guardrails

• No invented learnings — only extract from actual friction observed in the conversation
• No general advice — "always test your code" is not a valid learning; "Moq.Dapper fails on scalar Guid — wrap in record IdResult" is
• Keep it concise — each learning should be 1-2 sentences max
• For [recurring] tagging — quickly scan existing entries in the configured learnings file (the only file read)
• [process] entries must include the correction — "Used Edit before Read" is incomplete; "Used Edit before Read — always Read first to confirm line content" is valid