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+# Shared relative-time display helper (spec)
+
+> Brainstorm scratch artifact. On approval, copy to
+> `docs/superpowers/specs/2026-05-16-timeago-shared-display-design.md`
+> and commit (per `AGENTS.md` planning-artifact convention).
+
+## Context
+
+`left4me`'s web UI renders datetimes inconsistently. Three styles coexist:
+
+1. **Raw Python `datetime` repr** in admin/blueprint/job tables
+   (`admin_users.html`, `blueprints.html`, `_job_table.html`,
+   `job_detail.html`) — unfriendly for users.
+2. **Bespoke inline math** in `templates/_live_state.html` — three
+   expressions of the form `((now - x).total_seconds() // 60) | int }}m ago`
+   with their own vocabulary (`12s ago`, `0m ago` inside the first minute,
+   no singular handling).
+3. **Centralised but Python-side** `humanize_delta` (in
+   `l4d2web/l4d2web/services/timeago.py`) called from `page_routes.py` for
+   `latest_job_when` and `latest_build_when`. Correct output but only
+   reachable by route-side precomputation, so adoption is friction-heavy.
+
+The existing `humanize_delta` also has three design gaps that make it
+unsuitable as the single source of truth:
+
+- No sub-minute precision (under 45s it returns `just now`, hiding the
+  detail `_live_state.html` cares about).
+- Future timestamps are clamped to `just now` (latent bug).
+- Falls back to a bare ISO date (`2025-04-21`) after 7 days, which
+  reads awkwardly next to relative siblings.
+
+This spec unifies the three styles behind one Jinja filter, fixes the
+ladder, and leaves a known follow-up.
+
+## Goal
+
+Every user-facing datetime in `l4d2web` templates flows through one
+filter, `{{ ts | timeago }}`, producing a self-describing HTML `<time>`
+element that combines a friendly relative label with a precise tooltip.
+
+## Contract
+
+A single Jinja filter `timeago` returns a `markupsafe.Markup` wrapping
+an HTML `<time>` element:
+
+```html
+<time datetime="2026-05-16T14:32:11+00:00"
+      title="2026-05-16 14:32:11 UTC">5 minutes ago</time>
+```
+
+- `datetime=` carries the ISO 8601 form with explicit timezone offset.
+- `title=` is the hover tooltip — human-readable UTC string.
+- The text node is the relative label produced by the ladder below.
+
+### Ladder (long form, symmetric for past and future)
+
+| `abs(delta)` | Past label | Future label |
+|---|---|---|
+| `0` (sub-second) | `now` | `now` |
+| `< 60s` | `1 second ago` / `N seconds ago` | `in 1 second` / `in N seconds` |
+| `< 60m` | `1 minute ago` / `N minutes ago` | `in 1 minute` / `in N minutes` |
+| `< 24h` | `1 hour ago` / `N hours ago` | `in 1 hour` / `in N hours` |
+| `< 7d` | `1 day ago` / `N days ago` | `in 1 day` / `in N days` |
+| `≥ 7d`, same year as `now` | `16 Feb` | `30 May` |
+| `≥ 7d`, different year | `16 May 2025` | `16 May 2027` |
+
+- Singular form when the leading number is exactly `1`.
+- Day-first English month abbreviation (`16 Feb`, not `Feb 16`).
+- Year suppressed only when `then.year == now.year`.
+- `then.day` rendered without leading zero (use `then.day` directly,
+  not `%d`, for portability).
+
+### Defensive input handling
+
+- `then.tzinfo is None` → assume UTC (preserves current behaviour and
+  works against today's naive-UTC SQLite columns; becomes a harmless
+  no-op once the follow-up cleanup lands).
+- `now` defaults to `datetime.now(UTC)` and is similarly normalised.
+- `None` is **not** accepted — callers guard nullable columns with
+  `{% if x %}{{ x | timeago }}{% else %}-{% endif %}`.
+
+## Module shape
+
+File: `l4d2web/l4d2web/services/timeago.py` (existing).
+
+Two callables, one source of truth for the ladder:
+
+- `humanize_delta(then: datetime, now: datetime | None = None) -> str`
+  — pure text; ladder above. Kept for non-HTML callers (e.g. log lines,
+  emails) and for unit-testing the label logic in isolation.
+- `format_time_html(then: datetime, now: datetime | None = None) -> Markup`
+  — wraps `humanize_delta` in the `<time>` element. UTC-normalises
+  `then` for the `datetime=` and `title=` attributes. Escapes the
+  title via `markupsafe.escape` (defensive — ISO strings carry no
+  HTML-special characters, but the explicit call is free and keeps the
+  helper trustworthy if its inputs ever grow).
+
+Register `format_time_html` as Jinja filter `timeago` in the Flask app
+factory.
+
+## Files to modify
+
+### Helper + registration
+
+- `l4d2web/l4d2web/services/timeago.py` — rewrite `humanize_delta` to
+  the symmetric ladder with sub-minute precision and future support;
+  add `format_time_html`.
+- Flask app factory (locate during implementation; likely
+  `l4d2web/l4d2web/app.py` or `__init__.py`) — register
+  `format_time_html` as filter `timeago`:
+  `app.add_template_filter(format_time_html, "timeago")`.
+
+### Templates (replace raw datetimes / bespoke math)
+
+- `l4d2web/l4d2web/templates/admin_users.html:25-26`
+- `l4d2web/l4d2web/templates/blueprints.html:17-18`
+- `l4d2web/l4d2web/templates/_job_table.html:22-23`
+- `l4d2web/l4d2web/templates/job_detail.html:24-26`
+- `l4d2web/l4d2web/templates/_live_state.html:10, 31, 55`
+
+For nullable columns (`finished_at`, `started_at`,
+`last_downloaded_at`), preserve the current `-` placeholder:
+
+```jinja
+{% if job.finished_at %}{{ job.finished_at | timeago }}{% else %}-{% endif %}
+```
+
+### Routes
+
+- `l4d2web/l4d2web/routes/page_routes.py:240, 294, 443, 475` — drop
+  the inline `humanize_delta` imports and `latest_job_when` /
+  `latest_build_when` precomputation. Pass the raw `datetime` into the
+  template context (rename keys to `latest_job_at` / `latest_build_at`
+  for type-honesty) and let the templates call `| timeago`.
+
+### `_live_state.html` `now` parameter
+
+After the rewrite, check whether the `now` context variable is still
+referenced anywhere in `_live_state.html`. If not, remove it from the
+template render call (likely in `page_routes.py` and `server_routes.py`)
+and from whichever helper builds the live-state context. Dead-code
+cleanup, not behaviour change.
+
+## Files to read for context during implementation
+
+- `l4d2web/l4d2web/services/timeago.py:1-29` — current ladder, the
+  function we're extending.
+- `l4d2web/l4d2web/models.py:22-23` — `now_utc()` factory.
+- `l4d2web/l4d2web/routes/profile_routes.py:86-88` — documented
+  workaround comment that explains why naive datetimes exist
+  (informs the defensive `tzinfo is None` line).
+- `l4d2web/l4d2web/routes/page_routes.py:240-294, 443-475` — the
+  existing precomputation pattern being removed.
+
+## Testing
+
+### Unit tests (`l4d2web/tests/test_timeago.py`, new file)
+
+Parameterised boundary coverage for `humanize_delta`:
+
+| Input delta | Expected |
+|---|---|
+| `0` | `now` |
+| `+1s` past | `1 second ago` |
+| `+2s` past | `2 seconds ago` |
+| `+59s` past | `59 seconds ago` |
+| `+60s` past | `1 minute ago` |
+| `+1m` past | `1 minute ago` |
+| `+59m past` | `59 minutes ago` |
+| `+60m past` | `1 hour ago` |
+| `+23h past` | `23 hours ago` |
+| `+24h past` | `1 day ago` |
+| `+6d past` | `6 days ago` |
+| `+7d past`, same year | date form (e.g. `now=2026-02-23` → `16 Feb`) |
+| `+1y past`, different year | date form with year (e.g. `now=2026-05-16` → `16 May 2025`) |
+| `-1s` future | `in 1 second` |
+| `-59s` future | `in 59 seconds` |
+| `-60s` future | `in 1 minute` |
+| `-1d` future | `in 1 day` |
+| `-7d` future, same year | date form |
+| `-1y` future, different year | date form |
+
+Plus:
+
+- Naive input → treated as UTC; no `TypeError`.
+- Same-year vs different-year branch.
+- Year-boundary edge: `then = 2025-12-30`, `now = 2026-01-02` →
+  `16 May 2025`-style with year (because years differ).
+
+### `format_time_html` tests
+
+- Returns `markupsafe.Markup`.
+- Contains `<time datetime="..." title="...">...</time>`.
+- `datetime=` attribute is ISO 8601 with `+00:00` offset.
+- `title=` matches `YYYY-MM-DD HH:MM:SS UTC`.
+- Label inside element equals `humanize_delta(then, now)`.
+
+### Smoke test (Flask test client)
+
+Render a minimal template `{{ ts | timeago }}` via the test client and
+assert:
+
+- Response contains `<time` (filter is registered).
+- No literal `&lt;time&gt;` (no double-escaping).
+
+## Verification
+
+End-to-end checks before declaring done:
+
+1. `pytest l4d2web/tests -q` — full suite green, including the new
+   `test_timeago.py`.
+2. Manual UI walk in a logged-in session:
+   - `/admin/users` — `Created` / `Updated` columns show "N minutes
+     ago" / date form.
+   - `/blueprints` — same.
+   - `/jobs` (and a single job detail) — `Created` / `Started` /
+     `Finished` use the filter; null `Finished` still shows `-`.
+   - A server with live state — `polled N seconds ago`,
+     `joined N minutes ago`, `last seen N minutes ago`.
+3. Hover one of the new `<time>` elements — browser-native tooltip
+   shows the UTC string.
+4. Check page source — no double-escaped tags; `<time>` element
+   present with both attributes.
+
+## Out of scope
+
+- Switching `models.py` DateTime columns to `timezone=True` and
+  removing the ~6 `replace(tzinfo=None)` workarounds. Worth doing,
+  but mechanical and separable. See follow-up below.
+- Client-side ticker JS to keep visible labels fresh on long-open
+  tabs. The tooltip carries the precise UTC value; HTMX-polled pages
+  refresh anyway.
+- Duration formatting (`running for 12 minutes`). The helper renders
+  points in time, not intervals.
+- Localisation. English month names everywhere, matching the rest of
+  the app's strings.
+
+## Follow-up spec (file separately after this lands)
+
+`docs/superpowers/specs/YYYY-MM-DD-naive-datetime-cleanup-design.md` —
+switch `models.py` `DateTime` columns to `DateTime(timezone=True)`,
+remove the `.replace(tzinfo=None)` workarounds in
+`profile_routes.py:88`, `server_routes.py:210/234/273`,
+`page_routes.py:174`, `live_state_poller.py:37`, and confirm auth
+markers, staleness comparisons, and session helpers still work.
+Mechanical refactor, no behaviour change visible to users. The
+`timeago` helper's defensive `tzinfo is None` line becomes a no-op
+afterwards — leave it as a safety net.