Session Log – August 21, 2026 (Air Flow engine)

August 21, 2026 — Air Flow last-two engine, CFM↔L/s, ΔT °F↔°C

Path: · Site v1.1.9 · SW cache v106 · Help accuracy follow-up is local only (not on live until the next plan ships)

Need CFM and L/s as simultaneous live I/O (not a toggle that hides one unit).
Need ΔT °F and ΔT °C as the same difference (× 5/9, not absolute +32).
Electrical Power already uses last-two roles + aliases. Air Flow step 1 was a three-field role set; Pressure used two role groups plus a VP↔FPM bridge hop.

Grid: BTU/hr | CFM; ΔT (°F) | L/s; ΔT (°C) | (empty).
Last two typed of BTU, CFM, L/s, ΔT °F, ΔT °C are inputs. Others that are determined fill live.
CFM↔L/s and ΔT °F↔°C are aliases. Alias-only pairs do not invent the rest of the equation.
Removed the CFM/L/s toggle from this step.

One PressureStep engine. Deleted bridgeFromVp / bridgeFromFpm / two independent role groups.
VP↔FPM is an internal relation (FPM = 4005 × √|VP|). CFM↔L/s is an alias; L/s sits beside CFM.
Area already entered is kept when last-two are SP+TP so CFM/L/s can fill.
Removed the CFM/L/s toggle from this step. Fan Laws still has the toggle.

Reviewed help against the engine. Live v1.1.9 already has the first-pass help; these corrections stay on local main with the help commit.
Pressure: leftover FPM is not an extra input. Only Area (or CFM/L/s if Area is empty) is sticky. Last-two of only CFM + L/s does not reuse a previous FPM.
Sensible: five fields always visible; last-two of only the two ΔT boxes does not invent BTU or volume; Settings °F/°C does not relabel this step.
Temp Split: still absolute °F. ΔT °C is step 1 only (a difference, not a thermometer).
Fan Laws: CFM/L/s toggle is this step + Settings / RefCalc duct, not steps 1–2.
RefCalc units: duct volume can display CFM or L/s; FPM/area/tons stay imperial; Settings °F/°C is RefCalc, not Air Flow.
L/s factor in help: ≈ 0.472 (1 CFM = 0.4719 L/s).

js/airflow-engine.js (new, no DOM)
js/airflow-calc.js
app/tools/aircalc.htm
scripts/test-airflow-live.mjs
Help (v1.1.9): airflow-sensible.htm, airflow-pressure.htm, helpindex.htm
Help follow-up (local): airflow-sensible.htm, airflow-pressure.htm, airflow-fanlaws.htm, airflow-tempsplit.htm, refcalc-units.htm, gen-help-pages-paths.mjs

Service worker phvac-app-v106; precache airflow-engine.js; aircalc script ?v=12.
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