phase: 04_llm_chart_readability

**Phase 04 final verification pass — all tasks already in `complete/`; verified + fixed 3 defects found in verification.**

- Verified `/llm` live (both engines, gufo-only instance on :8099, `llm_monitor` on :8095) in a real browser; dev server left running/healthy.
- Completed task-04's truncated layout fix: `#engines` now carries `.items-start` (the CSS rule existed but nothing used it) — gufo 544 px vs vLLM 715 px, no blank card; pinned by `test_llm_engine_panels_are_not_stretched_to_their_tallest_sibling`.
- Fixed: event rows said the subject twice ("gufo gufo is answering again"), and `/ups` mangled mid-message names ("sent to apc: OK" → "sent to  OK") → shared `Dash.eventText()` (strips `UpstreamError: ` + a *leading* name only, mirroring `alerts._clean_error`) used by `/system`, `/llm`, `/ups`; new test.
- Fixed: count sparklines autoscaled rollup averages (queue max 0.1379) into full-height spikes → `sparkline({minSpan})`, `minSpan: 1` on sessions/queued (spike 30 px → 4 px); assertions added.
- Tests: `bash .agents/validate.sh` → **EXIT=0** (`uv run pytest --cov --cov-fail-under=94`: **485 passed, 7 skipped**, coverage **96.87%**; `ruff check src tests agent`: All checks passed; `pyright`: 0 errors; `node --check` all static JS clean; repo hygiene clean; `uv pip list --outdated` empty). `uv run pytest -m live --live` → **7 passed**.
- Completion criteria: heroes largest per engine ✔ (38.4 px vs 16.8 px row values); sparkline per cell + selected window ✔ (5/5 gufo, 7/7 vLLM; 6 h chip moved KV max 53 %→58 %); mean+p95 without hover ✔ (243 / 48.8 / 285 ms feet); provenance tag ✔ (`Δ10.0s`/`Δ8.0s` + `title`=exact source); single-engine ✔ (1 panel, totals hidden, zero red); screenshots ✔ `data/logs/llm-verify-{both-engines,charts-and-slots,single-engine,monitor-reference}.png` + `NOTES-chart-set.md`; pytest/cov/ruff/pyright ✔; earlier phases unchanged-behaviour ✔ (all 01–03 tests pass).
- Deviation (documented, not code): throughput heroes stay **neutral ink** — `severity.py` has no throughput row and 0 tok/s idle is healthy; colour comes from rated cells (KV) + reachability. Kept per `NOTES-chart-set`.
- Deviation: could not append the task-04 written verdict to `NOTES-chart-set.md` (it lives in `todo/`, which I must not edit). Verdict: ours reads better than `:8095` — bigger throughput numbers, per-cell shape over the selected window, percentiles inline; `llm_monitor` only sparklines decode+KV and has no window control.
- Docs: AGENTS.md updated (485 test count, `sparkline` `minSpan` rule, `Dash.eventText` event-row rule, `/llm` panel `items-start`); README reviewed in full — commands, config table (all `config.py` vars present), architecture bullets, page descriptions verified accurate; no other inconsistencies found.
- Note for the harness: `.agents/phases/todo/03…/NOTES-verify.md` and `todo/04…/NOTES-chart-set.md` are untracked notes left behind by their phases (task files moved, notes did not).
- Next pending phase: `05_ups_hero_battery_glyph`.

tests/test_llm_source.py

@@ -231,6 +231,33 @@ def test_engine_result_charts_a_measured_rate_after_the_second_poll(metrics_text
     assert any(s.metric == "llm.decode_tokens_per_second" for s in result.samples)
 
 
+def test_vllm_stores_the_tpot_series_the_cell_sparkline_draws(metrics_text) -> None:
+    """Phase 04 added `llm.tpot_seconds` so the vLLM TPOT row has a shape, not a dead slot.
+
+    Hermetic twin of the live check: the captured exposition must resolve the histogram the
+    page charts, or `/llm` shows a permanent "no history" next to a real mean.
+    """
+    result = engine_result("vllm", "http://v:1", metrics_text("vllm"), RateEstimator(), now=1.0)
+    mean = result.payload["metrics"]["time_per_output_token_seconds__mean"]["value"]
+    assert mean is not None, "the vLLM capture lost its TPOT histogram — re-capture fixtures"
+    stored = {s.metric: s.value for s in result.samples}
+    assert stored["llm.tpot_seconds"] == pytest.approx(mean)
+    # gufo publishes no output-token histogram, so it stores no TPOT series (never a 0)
+    gufo = engine_result("gufo", "http://g:1", metrics_text("gufo"), RateEstimator(), now=1.0)
+    assert "llm.tpot_seconds" not in {s.metric for s in gufo.samples}
+
+
+def test_gufo_stores_the_spec_accept_series_the_cell_sparkline_draws(metrics_text) -> None:
+    """`llm.spec_accept_rate` is the gufo-only half of the phase-04 history addition."""
+    result = engine_result("gufo", "http://g:1", metrics_text("gufo"), RateEstimator(), now=1.0)
+    ratio = result.payload["metrics"]["spec_accept_rate"]["value"]
+    assert ratio is not None and 0.0 < ratio <= 1.0
+    stored = {s.metric: s.value for s in result.samples}
+    assert stored["llm.spec_accept_rate"] == pytest.approx(ratio)
+    vllm = engine_result("vllm", "http://v:1", metrics_text("vllm"), RateEstimator(), now=1.0)
+    assert "llm.spec_accept_rate" not in {s.metric for s in vllm.samples}
+
+
 def test_sessions_pass_through_slots_for_gufo() -> None:
     slots = [{"id": 0, "idle": False, "n_prompt": 12, "n_predict": 40}]
     result = engine_result("gufo", "http://g:1", "", RateEstimator(), slots=slots, now=1.0)