---
name: a-cold-pool-costs-2500-worktrees
description: "Disk on this box is spent by CONCURRENT POOLS, never by worktree count: 45 worktrees = 0.79 GB, 3 pools = 130.45 GB. Ceiling is TWO live pools against the 40 GB floor."
metadata: 
  node_type: memory
  type: reference
  originSessionId: 8530ee91-5742-4df0-a973-21a034d9db72
  modified: 2026-08-22T07:59:48.493Z
---

**Measured 2026-08-22 (todlando, HFENDULEAM), read-only, whole `.worktrees` tree:**

| | count | size |
|---|---|---|
| worktrees carrying a pool | 3 | **130.45 GB** (74.42 + 43.58 + 12.45) |
| worktrees carrying no pool | 42 | — |
| all 45 worktrees, non-pool bytes | 45 | **0.79 GB** (~18 MB each) |

**One cold pool is worth roughly 2,500 worktrees.** Worktrees are 0.6% of the project's footprint;
pools are 99.4%.

**Why this matters more than it sounds:** the obvious remedy for a full disk is "we have too many
worktrees, prune them". That is a day of fiddly `git worktree remove` work for under a gigabyte, it
risks removing a lane someone still wants, and it leaves the actual lever untouched. A register
entry keyed on worktree count would have made things worse while looking like diligence. doyle's
draft said exactly that and was retired on these numbers.

**The ceiling, as arithmetic rather than hygiene:** a cold pool on this workspace costs **45–75 GB**;
the gate floor refuses below **40 GB**. So the box supports **TWO live pools comfortably, THREE only
if one is small**. The 2026-08-22 floor event happened at FOUR (root, two lane pools, a gate rig)
plus the milestone head — that is the whole event and it needs no other cause.

**So the two existing rules are right and only needed a number attached:**
- **Reap a pool when its lane finishes** — 45–75 GB back, immediately. (Classify first:
  [[gate-worktree-target-disk]].)
- **Never two builds at once** — not only the contention argument, but 75–150 GB of *simultaneous*
  allocation against a 40 GB floor.

**A footprint is a property of an INSTANT.** Two totals taken hours apart are not a trend: a 252 GB
reading that counted since-reaped pools and a 130 GB reading of what stands are both true and must
not be stitched. Same reason free space read 134.61 GB and 115.42 GB twenty minutes apart — a gate
was allocating between them. Report each figure with its instant attached and derive no history.

Kin: [[disk-full-reds-as-lnk1318-pdb-error]] (what a near-full volume does to a build, and the rule
that free space goes in the FIRST line of a failure report), [[gate-worktree-target-disk]],
[[free-space-floor-blocks-golden]].