What we know, how we know it, and what we refuse to guess.

The interface labels each layer at the point of display. HazeWatch does not assign official categories, does not issue official warnings, and does not convert a concentration into an API value.

When APIMS publishes a class label for the hour, HazeWatch displays that class. The numeric band is still computed and any mismatch is surfaced on the station page. We never substitute US AQI, PM2.5 concentration thresholds or another country's scale for Malaysia's API.

• Window: the latest 24 hours of hourly readings for a station.
• Comparison: the latest reading against the reading closest to six hours earlier, within a 90-minute tolerance.
• Threshold: a change of at least ±10 API points is a trend. Smaller changes are stable. No history near the six-hour mark means the direction is insufficient.
• Peak: the highest observed value in the same 24-hour window, with its timestamp.

These rules describe what already happened. They are not a statistical forecast, not a model, and not a prediction. A rise can reverse in the next hour, which is why every insight carries the observed timestamps.

• Observed at: the hour APIMS attributes to the reading. APIMS publishes Malaysia wall-clock values without an offset, so HazeWatch interprets that text as UTC+8 and stores a UTC instant.
• Retrieved at: when our collector received the row. This changes even when the observation does not.
• Forecast cycle: MyCMAQ cycle identifiers are stored and shown as published. Their LST labels are not silently converted into instants.
• Display: all interface times are Malaysia Time (UTC+8) unless explicitly marked otherwise.

APIMS also returns an epoch field that behaves as if the wall clock were UTC. HazeWatch deliberately ignores it as an observation instant rather than inventing an eight-hour shift.

ASMC hotspot and haze information is not ingested: its published terms restrict automated collection and reuse without permission. We link to official sources instead of copying them.

MetMalaysia's MyCMAQ portal currently exposes forecast products as rendered map images and manifests. HazeWatch records the published cycle, retrieves the manifest to count available frames, and links to the official viewer.

• Enabled: official map links, cycle identifiers, published pollutants and frame counts.
• Disabled: numeric forecast timelines, forecast peaks, station-level forecast values, and forecast-based alerts.
• Why: no verified machine-readable numeric feed is available. Reading pixels would be an estimate presented as data.

MyCMAQ's LST frame labels are shown verbatim. Their numerical offset is not independently confirmed, so HazeWatch does not compare them with observation timestamps.

• The server builds a facts object from stored observations and calculated trends. Gemini receives only those facts.
• The response is constrained to a JSON schema and validated. Every number in the output must already appear in the supplied facts; otherwise the text is rejected.
• If Gemini is unconfigured, unreachable or fails validation, a deterministic rule-based briefing is shown instead. The label always tells you which one you are reading.
• Gemini never assigns a category, never creates a forecast and never receives the service-role or Maps keys. Requests are sent with store: false.

The map uses MapLibre GL JS with OpenFreeMap tiles and the station coordinates published by APIMS. Markers show the current API value; selecting one opens the station name, state, observation time and a link to its detail page.

No map API key is required. OpenFreeMap, OpenMapTiles and OpenStreetMap attribution stays visible on the map. If tiles or WebGL are unavailable, the searchable station list and selection panel remain usable. A dash means no reading, not zero.

When Supabase is configured, observations are written with a uniqueness key of station, metric and observation time. Re-running collection updates the same row instead of duplicating it. Each source gets its own ingestion log with accepted and rejected counts, so one failing provider cannot hide another.

Public tables have row-level security with read-only policies. The service-role key is used only on the server. Without Supabase credentials the app runs in a clearly labelled live-preview mode: it reads APIMS for the current window and archives nothing.

A pinned station is stored in this browser's local storage. No account is created, no preference is sent to the server, and clearing site data removes it.

Required for storage: NEXT_PUBLIC_SUPABASE_URL, SUPABASE_SERVICE_ROLE_KEY and CRON_SECRET. Optional: GEMINI_API_KEY, GEMINI_MODEL. Maps work without credentials; provider settings live in lib/map.ts.

Apply supabase/migrations/0001_init.sql in the Supabase SQL editor, then schedule an authenticated request to /api/ingest every hour. The endpoint accepts GET or POST with Authorization: Bearer <CRON_SECRET>. The repository README covers Supabase Cron, Vercel Cron and map configuration.

Credentials are never committed. The app remains usable without Google or Gemini configured; those layers degrade visibly rather than silently.

• APIMS endpoints are publicly reachable but undocumented. Their schema, rate limits and retention can change without notice.
• Missing or zero readings are treated as unavailable, never as clean air. Sentinel semantics are not confirmed.
• Stored history begins when collection begins. Early charts may be short, and the interface says so.
• HazeWatch is not an official government service and does not issue warnings. Follow DOE, MetMalaysia and local authorities for decisions.