Using SQLite Worktrees

Overview

Rails projects on SQLite (especially Rails 8 with Solid Queue/Cache/Cable) keep their development data in storage/*.sqlite3 files. When you create a new git worktree, that directory is empty — so bin/rails console, feature work, or spec runs against real data all fail until you re-migrate and re-seed. This skill copies the main working tree's SQLite files into the new worktree safely, handling WAL journal mode and Rails 8 multi-database layouts.

Core principle: Checkpoint before copy. Copy sidecars with the main file. Back up before overwrite.

Announce at start: "I'm using the using-sqlite-worktrees skill to copy SQLite development databases into the worktree."

When to Activate

Activate in two situations:

1. Delegated from using-git-worktrees — that skill detects a Rails+SQLite project after running bundle install and delegates here before running bin/rails db:test:prepare.
2. Invoked directly — user says something like "copy my SQLite data into the worktree" or "refresh the worktree with current dev data."

Do NOT activate for:

• Non-Rails projects (no config/database.yml)
• Rails projects using Postgres, MySQL, or other non-SQLite adapters
• Production or test databases (this skill targets RAILS_ENV=development by default)

Prerequisites Check

Before running the helper script, verify all four conditions. If any fail, stop and report — do not proceed with partial setup.

Invocation

From the main working directory (not the worktree), run the helper script:

ruby "${CLAUDE_PLUGIN_ROOT}/skills/using-sqlite-worktrees/scripts/create_sqlite_worktree.rb" <worktree-path>

The script will:

1. Parse config/database.yml and collect all .sqlite3 paths for RAILS_ENV (defaults to development)
2. Run PRAGMA wal_checkpoint(TRUNCATE) on each source database (flushes WAL into main file, safe to copy)
3. Back up any existing file in the target storage/ as <filename>.bak before overwriting
4. Copy each .sqlite3 file plus its -wal and -shm sidecars (if present) into <worktree-path>/storage/
5. Print a summary showing every file copied and every backup created

Exit codes:

• 0 — success, or a clean "nothing to do" (non-Rails / non-SQLite / no DB files yet)
• 1 — an actual error (missing CLI, invalid worktree path, database.yml parse failure, etc.)

Re-syncing a Stale Worktree

If the main branch's dev data has moved forward and you want to refresh a worktree's storage/:

# Same script, same command. Existing worktree files get backed up as .bak before overwrite.
ruby "${CLAUDE_PLUGIN_ROOT}/skills/using-sqlite-worktrees/scripts/create_sqlite_worktree.rb" <path-to-existing-worktree>

Warning: This overwrites the worktree's current dev DB. Any uncommitted data in the worktree's SQLite files is preserved as <filename>.bak but only one level of backup is kept — re-running again will overwrite .bak too. If the worktree has important local data, commit/export it first.

Failure Contract with using-git-worktrees

When invoked via using-git-worktrees delegation:

• Script exits 0 → using-git-worktrees continues normally to bin/rails db:test:prepare and the baseline test run.
• Script exits non-zero → using-git-worktrees MUST print the captured stderr, SKIP bin/rails db:test:prepare, SKIP baseline tests, and report the worktree as "created but DB setup incomplete — investigate output before continuing."

Never silently ignore a non-zero exit from this script.

Quick Reference

Red Flags

Never:

• Copy .sqlite3 files with a raw cp without checkpointing WAL first — the copy will be inconsistent
• Copy the main .sqlite3 file without also copying its -wal and -shm sidecars when they exist
• Overwrite a worktree's storage/ without first backing up existing files
• Proceed past a non-zero exit code from the helper script
• Run the script while a rails server or rails console is actively writing to the source DB — stop the writer first

Always:

• Run prerequisites check before invoking the script
• Verify the worktree path is a genuine git worktree, not just any directory
• Pass the absolute or explicit path to the worktree as the single script argument
• Report the full summary output to the user (backups, files copied, skipped reasons)

Common Mistakes

Invoking from inside the worktree instead of main

Problem: The script reads config/database.yml from the current working directory (the source). If run from inside the worktree, it reads the worktree's own database.yml and tries to copy its own DBs onto itself. Fix: Always cd to the main working directory before invoking.

Trusting naive cp for SQLite files

Problem: SQLite in WAL mode keeps pending writes in <db>-wal. A plain cp <db> gives you a stale snapshot; the app sees a corrupted-looking state. Fix: Use this skill's helper script, which runs PRAGMA wal_checkpoint(TRUNCATE) first and copies all three files.

Skipping the git-worktree validation

Problem: If the user typos the target path, the script would happily create a storage/ directory anywhere on disk. Fix: The script guards with git -C <path> rev-parse --is-inside-work-tree. Do not bypass this guard.

Integration

Called by:

• using-git-worktrees — REQUIRED delegation when Rails + SQLite detected, after bundle install, before bin/rails db:test:prepare

Pairs with:

• using-git-worktrees — owns worktree creation, gitignore checks, bundle install, test DB prep, baseline tests
• finishing-a-development-branch — cleanup workflow; does NOT need to touch SQLite files (worktree removal handles that)

Example Workflow

Agent: I'm using the using-git-worktrees skill to set up an isolated workspace.
[Creates .worktrees/feature-x/ with git worktree add -b feature/x]
[Verifies .worktrees/ is in .gitignore]
[Runs bundle install in the worktree]
[Detects config/database.yml with adapter: sqlite3]

Agent: I'm using the using-sqlite-worktrees skill to copy SQLite development databases into the worktree.
[Runs ruby ${CLAUDE_PLUGIN_ROOT}/skills/using-sqlite-worktrees/scripts/create_sqlite_worktree.rb .worktrees/feature-x]

Output:
  Checkpointed: storage/development.sqlite3
  Checkpointed: storage/development_cache.sqlite3
  Checkpointed: storage/development_queue.sqlite3
  Checkpointed: storage/development_cable.sqlite3
  Checkpointed: storage/development_errors.sqlite3

  Copied 5 SQLite3 database(s) to .worktrees/feature-x/storage/
    development.sqlite3
    development_cache.sqlite3
    development_queue.sqlite3
    development_cable.sqlite3
    development_errors.sqlite3

[Back to using-git-worktrees: runs bin/rails db:test:prepare]
[Runs bin/rails test — 124 passing]

Worktree ready at .worktrees/feature-x/
SQLite dev databases copied (5 DBs, 0 backups)
Tests passing (124 tests, 0 failures)
Ready to implement feature-x