Product-owner decision, 2026-08-27: the analytical need is stable
cross-window identity (retention curves, longitudinal install
behaviour), which the rotating pseudonym destroyed by design. The
feature has not shipped - zero consented users, zero production
transmissions - so identity semantics can change without breaking any
promise made to a user; existing (dev-only) consent windows carry
forward unchanged.
Removed in full rather than weakened in place:
- shared_metrics_identity.py (salt generation/rotation, HMAC-SHA256
derivation, payload substitution) and its 19-test file.
- The sender's derivation step. _freeze_identity keeps its validation
role (unreadable/non-object/id-less payloads still reject rather than
block the queue) and now records the raw install_id in
sent_install_id; _body rewrites the payload's install_id from that
frozen column, keeping byte-identical resends anchored to one
recorded value.
Consent surface updated in the same change: the setup wizard now states
plainly that packages carry the stable profile-scoped install ID (a
random UUID, no personal information, reset by deleting the
shared-metrics directory). No consent was ever collected under the old
wording in any shipped build.
Docs A.2/A.3 rewritten as decision records rather than silently
edited: A.2 records what is transmitted now and states the
consequences plainly (indefinite cross-package correlation is the
designed behaviour); A.3 records why rotation existed and why its
removal was accepted. The main-body "must not reuse the persistent
local identifier by default" escape hatch is exercised, not deleted:
that paragraph required exactly this product decision, which has now
been made. A.6's deletion note updated: install_id is now itself the
lookup key, so a future delete-on-request needs only a service-side
API, not a mapping.
Tests: the two privacy assertions invert deliberately
(test_the_stable_install_id_is_transmitted_as_is and the e2e wire
variant); freezing/byte-identical-retry coverage unchanged. Staging
E2E script now asserts transmitted == install_id.
258 targeted tests pass; ruff + footguns clean; both staging E2E
harnesses green with the raw id observed on the wire (202s).
Ben Barclay
a69a9c351d