One node_modules, fifteen worktrees

Measured on this checkout, 2026-08-04. Numbers below are real, not projected.

Before

5,201 MB

15 worktrees, each with its own copy. A fresh worktree needed five separate npm installs before it could run anything, and two worktrees had no node_modules at all, so they could not run tsc.

After

2,062 MB

One installed tree in the main repository, symlinked into every worktree by Claude Code at creation time. 70 links written, 3,139 MB reclaimed, 0 installs.

Surface	Was	Now	Effect
New worktree setup	5 x npm install	5 symlinks	minutes to instant
Disk across worktrees	5,201 MB	2,062 MB	-60%
Config drift	ungated, file is gitignored	tracked list + CI test	fails closed
Dependency isolation	per worktree	shared with main repo	traded away

How many worktrees do you keep open? 15

duplicated: 3,139 MB → reclaimed by sharing: 3,139 MB

Assumes the 224 MB average per-worktree install measured here (root 68, hooks 151, mcp-server 67, docs/site 605, demos 891, weighted by which workspaces a branch actually touches).

bin/worktree-config.sh --apply     write .claude/settings.json from the tracked list
bin/worktree-config.sh --check     fail if the live config drifted
bin/worktree-reclaim.sh --dry-run  show which existing worktrees are still duplicating
bin/worktree-reclaim.sh --apply    backfill the layout onto them

The trade-off is real and is not hidden. Symlinked worktrees share one installed tree, so an npm install inside a worktree writes into the main repository. If a branch needs a genuinely different dependency graph, drop its entry rather than pretending the isolation is still there.