custom-claude-skills/skills/distill-best-practices/SKILL.md

---
name: distill-best-practices
description: >
  Cross-project best practices distillation. Reads changed memory files from all tracked
  projects and proposes additions, updates, or removals to claude-foundations/best-practices/.
  Run from any project — always targets claude-foundations as output. Interactive — presents
  proposals for approval before making changes.
allowed-tools: Read, Edit, Write, Glob, Grep, Bash(git -C *), Bash(git rev-parse *), Bash(ls *), Bash(cat *), Bash(head *), Bash(date *)
---

# Distill Best Practices Skill

You are extracting generalisable best practices from project-specific memory files across all tracked projects.

## Pre-gathered context

### CLAUDE_PROJECT_ROOT
!`test -n "$CLAUDE_PROJECT_ROOT" && echo "$CLAUDE_PROJECT_ROOT" || echo "NOT_SET"`

### Distill state
!`cat $CLAUDE_PROJECT_ROOT/projects/claude-foundations/best-practices/.distill-state.json 2>/dev/null || echo "{}"`

### Settings
!`cat $CLAUDE_PROJECT_ROOT/projects/claude-foundations/settings.yaml 2>/dev/null || echo "Settings not found — CLAUDE_PROJECT_ROOT may not be set"`

### Current best-practices index
!`cat $CLAUDE_PROJECT_ROOT/projects/claude-foundations/BESTPRACTICES.md 2>/dev/null || echo "Index not found"`

### Available best-practices files
!`ls -1 $CLAUDE_PROJECT_ROOT/projects/claude-foundations/best-practices/ 2>/dev/null || echo "No best-practices directory"`

### Projects directory listing
!`ls -1d $CLAUDE_PROJECT_ROOT/projects/*/ 2>/dev/null || echo "No projects directory"`

## Instructions

### Step 0: Detect project root

Check the pre-gathered `CLAUDE_PROJECT_ROOT` value above. If it shows `NOT_SET` or the pre-gathered context is missing:

1. Walk up from the current working directory to find the **highest** parent directory containing a `CLAUDE.md` file — that is the project root.
2. Use that path as `PROJECT_ROOT` for all subsequent steps.

If `CLAUDE_PROJECT_ROOT` was set, use that value as `PROJECT_ROOT`.

The key paths derived from the root:
- **Settings**: `<PROJECT_ROOT>/projects/claude-foundations/settings.yaml`
- **Best practices dir**: `<PROJECT_ROOT>/projects/claude-foundations/best-practices/`
- **Best practices index**: `<PROJECT_ROOT>/projects/claude-foundations/BESTPRACTICES.md`
- **Distill state**: `<PROJECT_ROOT>/projects/claude-foundations/best-practices/.distill-state.json`

### Step 1: Discover changes per project

Read `settings.yaml` (pre-gathered above, or read it now if Step 0 detected the root manually).

For each project in `distill.projects`, get its path: `<PROJECT_ROOT>/<projects_dir>/<project_name>`.
Also process any `distill.extra_projects` entries — these have a `path` field relative to `PROJECT_ROOT`.

For each project (from both lists):

1. Get current HEAD: `git -C <path> rev-parse HEAD`
2. Look up `last_sha` from `.distill-state.json` for this project
3. If SHA matches → skip this project (no changes)
4. If `last_sha` exists → find changed files: `git -C <path> diff --name-only <last_sha>..HEAD -- memory/`
5. If `last_sha` is missing (first run) → list all memory files: `ls <path>/memory/*.md`

Filter to only `memory/*.md` files (exclude `memory/log/` — those are raw, unprocessed).

If no projects have changes, say so and stop.

### Step 2: Read changed memory files

For each changed memory file, read its full content using the Read tool.

Also identify which existing best-practices topic files cover the same domain. Use this mapping as a guide:
- `gotchas-k8s.md` → `kubernetes.md`
- `gotchas-cilium.md` → `kubernetes.md`
- `gotchas-helm.md` → `helm.md`
- `gotchas-ansible.md` → `ansible.md`
- `gotchas-sops.md` → `secrets-management.md`
- `process-lessons.md` → `validation.md`, `debugging.md`
- `decisions.md` → various (match by content)
- Other gotchas → match by topic or propose a new file

Read the matching best-practices files so you can compare.

### Step 3: Analyse and propose

For each potential change, classify it:

- **ADD**: A lesson that is project-agnostic and valuable across projects. When generalising:
  - Strip project-specific details (IPs, namespace names, service names, hostnames)
  - Replace specifics with generic descriptions (e.g., "10.111.0.5" → "the DNS server IP")
  - Keep the principle and the reasoning — lose the implementation detail
  - Only promote lessons that would apply to at least one other project type

- **UPDATE**: An existing best-practice entry that has new supporting evidence, needs refinement, or should be expanded with a new example.

- **REMOVE**: A best-practice that has been invalidated — version-specific bug fixed, tool changed, approach superseded. Cross-reference: if the source gotcha was removed from the project's memory, the best-practice may be stale.

### Step 4: Present proposals

**Do NOT make any changes yet.** Present a numbered list of proposals:

```
Proposals:

1. ADD to kubernetes.md: "<brief description of the new entry>"
   Source: cluster-bootstrap/memory/gotchas-k8s.md

2. UPDATE validation.md: "<what changes and why>"
   Source: cluster-bootstrap/memory/process-lessons.md

3. REMOVE helm.md: "<entry to remove and why it's stale>"
   Reason: Source gotcha removed in cluster-bootstrap commit abc1234
```

Wait for the user to approve, modify, or reject proposals. The user may say "all", give specific numbers, or ask for changes.

### Step 5: Apply approved changes

For each approved proposal:
- **ADD**: Append the new entry to the target file, matching the existing style (heading level, bullet format, explanation depth)
- **UPDATE**: Edit the existing entry in place
- **REMOVE**: Delete the entry from the file

If a new best-practices topic file is needed:
- Create it following the format of existing files (top-level heading, subheadings per entry, 2-6 lines per entry)
- Add it to `<PROJECT_ROOT>/projects/claude-foundations/BESTPRACTICES.md` with a one-line description

### Step 6: Update distill state

Write `<PROJECT_ROOT>/projects/claude-foundations/best-practices/.distill-state.json`:

```json
{
  "version": 1,
  "last_run": "<ISO-8601 timestamp>",
  "projects": {
    "<project_name>": {
      "path": "<absolute_path>",
      "last_sha": "<current HEAD sha>",
      "last_run": "<ISO-8601 timestamp>"
    }
  }
}
```

Preserve entries for projects that weren't processed this run (no changes).

### Step 7: Summary

Print:
- Projects scanned and number of changed memory files per project
- Number of proposals (add/update/remove)
- Number approved and applied
- Any new best-practices files created

## Quality checks

- Best practices must be **project-agnostic** — no hardcoded IPs, namespaces, or service names
- Each entry should include the **principle and reasoning**, not just the rule
- Entries must be **deduplicated** against existing best-practices content
- The **BESTPRACTICES.md** must stay accurate after any file additions
- Proposals are **always presented before applying** — never auto-apply