api-inspect-state

name	api-inspect-state
description	Read state from a live nanoTracker session through the Local API. Pick the cheapest query for the question, never load full patterns when a slice would do, resolve patternId via getPatternList before any pattern op.

Inspect a live nanoTracker session

When to use

Use this any time you need to know what's in the project — what patterns exist, what cells they hold, what samples are loaded, what the song tempo is — before suggesting or making a change.

Cheap before expensive

Call queries in this order. Stop as soon as you have what you need.

1. nanotracker_health — confirm the page is connected.
2. nanotracker_read { op: "getProjectSummary" } — bpm, speed, channels, pattern count, sample count.
3. nanotracker_read { op: "getPatternList" } — every pattern's id, name, row count, filled-cell count, order-list positions.
4. nanotracker_read { op: "getRange", patternId, rowStart, rowEnd, channels? } — slice of cells. Prefer this over getPattern for surveys.
5. nanotracker_read { op: "getPattern", patternId } — only when you really need every cell of a pattern.

patternId, not order-list index

Pattern ids are persistent. Order-list positions are not. The order list maps positions → pattern ids; multiple positions can reference the same pattern. Always resolve via getPatternList first.

// WRONG — assumes order list position 0 is pattern id 0
nanotracker_read { "op": "getPattern", "patternId": 0 }

// RIGHT — discover, then read
const list  = nanotracker_read { "op": "getPatternList" }
const first = list.data[0].id
nanotracker_read { "op": "getPattern", "patternId": first }

Cell shape

{
  note:        number   // 0 empty, 1-96 = C-0..B-7, 97 = note-off
  instrument:  number   // 0 empty, 1-31 = sample slot
  volume:      number   // 0xFF = use default, 0x00-0x40 = override
  effect:      number
  effectParam: number
}

volume === 0xFF means "use the sample's stored default", not 255 dB. Don't render it as 255 in user-facing output.

Channels are 0-indexed

channels[0] is the leftmost track. project.channels is the count (1..32).

Empty cells are common and not a problem

Most cells in a fresh pattern have note: 0, instrument: 0, volume: 0xFF, effect: 0, effectParam: 0. Treat that as "empty" — don't report it as data.

Skip subscribe; poll cheap reads

External callers can't subscribe to mutations. To detect changes, poll getProjectSummary (returns instantly) and compare. The page ALSO exposes subscribe to in-page code, but the relay doesn't forward those events.

Schema is always available

nanotracker_read { "op": "getSchema" }

returns the structured list of every command, query, and field. Useful when you need to know whether an op exists or what fields it takes.