Files and schemas

Application data directory

~/Library/Application Support/molt/

File	Purpose	Format	Created when
config.toml	Interpreter and application settings	TOML	First configuration load when missing, or Settings save
notebooks.json	Saved cell source for all four tabs	Compact JSON	First persistable notebook change after load

The code falls back to a relative working-directory path only if the operating system configuration directory cannot be resolved.

Notebook schema version 1

A representative file is:

notebooks.json

{
  "version": 1,
  "tabs": [
    {
      "tabIndex": 0,
      "cells": [
        {
          "id": "0f4a9e9a-72de-4b04-a180-56e0c44fbf05",
          "type": "code",
          "source": "value = 21\nvalue * 2"
        }
      ]
    },
    {
      "tabIndex": 1,
      "cells": [
        {
          "id": "1ec4e25e-81e4-4b44-8429-07ff095e8052",
          "type": "code",
          "source": ""
        }
      ]
    },
    {
      "tabIndex": 2,
      "cells": [
        {
          "id": "97f8ef11-6248-4cd8-bc4f-e1386ec69cc0",
          "type": "code",
          "source": ""
        }
      ]
    },
    {
      "tabIndex": 3,
      "cells": [
        {
          "id": "9b87faef-1524-4f13-b64d-8a0cf4701303",
          "type": "code",
          "source": ""
        }
      ]
    }
  ]
}

Field reference

Field	Type	Meaning	Validation on load
version	Number	Persistence format marker; writer emits 1	Must equal 1
tabs	Array	Persisted tab entries	Must be an array
tabIndex	Number	Identifies Tab 1 through Tab 4 as indices 0 through 3	Unique integer from 0 through 3
cells	Array	Ordered cell records	Empty array is replaced with one fresh code cell
id	String	Stable cell identity, normally a browser-generated UUID	Nonempty and unique across all tabs
type	code or markdown	Reserved cell kind	Restored, but UI still renders a Python editor
source	String	Raw Python source	Restored verbatim

Fields not stored

The writer strips:

• executionCount
• outputs
• state
• Notebook kernelState
• Notebook executionCounter
• Global activeTab
• Focus and command-mode state

Load behavior

1. Molt reads the file, or treats a missing file as a first launch.
2. It validates the version, tabs, indices, cells, IDs, types, and sources.
3. Valid matching tabs restore their ordered cell sources.
4. Outputs, execution labels, and Python state begin fresh.
5. The loaded snapshot is not immediately rewritten when nothing has changed.

If reading or validation fails, Molt shows a warning and disables autosave so the existing file is not overwritten with defaults.

Write behavior

• The JSON is serialized without presentation whitespace.
• Writes occur after a 1.5-second debounce.
• Identical persistable snapshots are skipped.
• Saves are serialized so older writes cannot finish after newer ones.
• Molt creates the directory if necessary and atomically replaces the file through a temporary file.
• A pending write is attempted when the app closes, but native Quit does not wait for it.

There is no cross-process file lock, backup rotation, or built-in history. Avoid concurrent manual edits.