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ersatztv/docs/decisions/records/process/shared-tree-readonly.md
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feat(610): split the decision corpus into one YAML-frontmatter file per record
168 records -> docs/decisions/records/<area>/<topic>.md (163 active, 23 dirs) and
docs/decisions/archive/<area>/<topic>.md (5 archived). The filename IS the key,
so one-active-record-per-key becomes a filesystem property rather than a
validator check, and supersession becomes a `git mv`.

WHY: the monolith was a concurrency problem before an aesthetic one. A
3,900-line append target made parallel sessions collide -- PR #605 and PR #614
both hit append-vs-append conflicts during routine rebases, and hand-resolving
those inside the corpus is exactly the operation the rationale-rewrite guard
exists to police.

HOW IT IS VERIFIED: a ~170-file diff cannot be meaningfully read, so correctness
does not rest on reading it. The parser was taught BOTH formats first, so the
body-diff guard parses the old form at the merge-base and the new form at head --
the migration validates itself, no bypass. The proof is a field-level equivalence
harness: 168 records before and after, zero lost, zero gained, zero field
mismatches, zero rationale bodies differing. Reviewers should scrutinise the
harness; it is the actual evidence.

What measuring caught that reading would not have:

- ~500 lines sit OUTSIDE any record -- decisions.md's lifecycle schema and each
  topic file's preamble, mostly the only copy. Source files are kept and
  stripped, never deleted. They also cannot be filed per-area: topic files hold
  several areas and 4 of 23 areas span several files.
- Archive discovery was a non-recursive glob; after the split it found ZERO
  archived records, surfacing as four bogus "supersedes points to unknown key"
  errors rather than an obvious failure.
- ~32 live docs point into the corpus BY DATE, which the split dangles. Each
  stripped file now ends with a generated "Records formerly in this file" index,
  which also rescues the identical breadcrumbs in old issue comments.
- decisions.md's "In this file:" list was 97 same-file anchor bullets that the
  split makes WRONG, not merely stale. Dropped; the generated index replaces
  them with links that resolve.

The equivalence harness now runs against a checked-in FIXTURE, not the live
corpus. The earlier version migrated the real tree, which made it a one-shot:
the moment the migration landed there was nothing left to move and the tests
failed for reasons unrelated to the code. A fixture keeps them testing the
SCRIPT rather than the repo's current state.

Keys preserved verbatim, warts included: `sched` (12) and `scheduling` (1) remain
two directories for one concept. Renaming a key is not a move -- it changes
identity, breaks the equivalence proof, and invalidates MemPalace's per-key
drawers. Taxonomy normalisation is separate work.

refs #610
2026-07-25 19:45:09 +02:00

2.2 KiB

key, title, status, since, supersedes, superseded-by, rule, signals, mechanics
key title status since supersedes superseded-by rule signals mechanics
process.shared-tree-readonly 2026-07-21 — The shared tree at /Users/timothy/ersatztv is read-only and tells you nothing about `main` (#542) active 2026-07-21 none none Never commit in `/Users/timothy/ersatztv` and never read its `git log`/`git status`/HEAD to infer anything about `main` — work in a worktree off `origin/main`, which is the only source of truth. shared checkout · "main checkout" · worktree discipline · stale HEAD · origin/main is truth · node_modules copy · paths: `/Users/timothy/ersatztv`, `.claude/worktrees/`, `.worktrees/` · issues: #542 `git worktree add -b <branch> <path> origin/main`; `git fetch origin main` and reference `origin/main` explicitly — the local `main` ref lags and nobody is obliged to update it. The one sanctioned use of the shared tree is read-only: copying `web/node_modules` out of it (keep that fresh — a stale copy broke typecheck in a #198 worktree).

There is no "main checkout". /Users/timothy/ersatztv is a shared mutable working tree whose HEAD is whatever the last session left there; its name lies. The rule holds even for a one-line docs fix — make a worktree.

This is a design flaw, not a discipline failure: do not "fix" it by telling sessions to check harder, because a check does not stay true. It broke for two different sessions on the same day, 2026-07-17, both doing the obvious thing. Session A assumed it was on main — correct when it pulled at 12:46, stale by 14:17 — and committed; the commit landed on the CI session's ci/604-lane-rebalance, 24 seconds after that session's own commit at 14:17:28. Two writers, one tree; nothing tangled, by luck. Session B ran git log there, read that same branch's HEAD, and concluded main was "4 behind origin" — a phantom. A session-start git status appears to confirm the false assumption, which makes it worse than a plainly wrong claim.

Cross-reference session.shared-checkout-refresh, which covers the complementary failure mode: any FILE (including a pasted kickoff prompt) read out of that tree may be stale, and the session-end refresh script that mitigates it. This record covers the git-state failure mode only.