The save file

Settings, scheduler state and history are one JSON file, profile.json.

Where it is

Settings > Data shows the exact path. Set the environment variable ABAX_DATA_DIR to use another directory on the desktop:

ABAX_DATA_DIR=~/abax-test abax     # a separate, throwaway profile

To move your progress to another computer, copy profile.json into the same place there while Abax is closed.

How it is written

Abax writes the whole document to profile.json.tmp, flushes it to disk (fsync), and renames it over profile.json. The rename is atomic: the file is either the old version or the new one.

If the file cannot be read (damaged, or written by a newer Abax), Abax copies it to profile.json.bak, starts a fresh profile and logs a warning.

Versioning

The document carries a version field. This build writes version 1 and reads versions up to 1; a missing or newer version is rejected. Two rules let the format grow:

• Unknown fields are ignored, so an older Abax can open a file a newer one wrote, as long as the version number did not change.
• Missing fields take their defaults, so a newer Abax can open an older file. The finish setting was added in 0.2.0; a 0.1.0 profile has no such field and loads as walnut. 0.3.0 added marked_known to each skill and builds_on_noted at the top level; a 0.2 profile loads with every skill unmarked and no notes shown. Both changes are additive, so the version stays 1 and 0.2.x can still open a 0.3.0 file (it ignores the two fields).

When the curriculum gains a skill, loading fills in a fresh state for it. When a change needs real conversion, the version number goes up and SaveFile::migrate in crates/abax-core/src/store.rs gets a step for it.

The schema, annotated

The file is written on one line. Formatted and commented, after one answered item, with one of the fifteen skill entries:

{
  "version": 1,                       // format version
  "settings": {
    "rod_count": 13,                  // 9, 13, 17, 21, 23 or 27
    "theme": "System",                // "System" | "Light" | "Dark"
    "finish": "Walnut",               // "Walnut" | "Ebony" | "Maple" (0.2.0)
    "sound": false,
    "volume": 0.6,                    // 0..1
    "left_handed": false,
    "show_numbers": true,
    "show_keypad": true,
    "input_mode": "Both",             // "Tap" | "Drag" | "Both"
    "reduce_motion": false,
    "large_text": false,
    "hint_delay_seconds": 4.0,
    "flash_digits": 1,                // free flash anzan defaults
    "flash_count": 5,
    "flash_ms": 1000
  },
  "scheduler": {
    "skills": {                       // one entry per skill, keyed by name
      "Setting": {                    // S0; others: AddSimple, SubSimple, AddFive,
                                      // SubFive, AddTen, SubTen, Combined, MultiAdd,
                                      // MultiMixed, Multiply, Divide, Anzan,
                                      // FlashOne, FlashMulti
        "p_known": 0.4,               // BKT probability the skill is known
        "acc_ewma": 0.6,              // accuracy average
        "log_t_ewma": 1.8007,         // average ln(seconds per operand)
        "theta": 0.1824,              // Elo ability on this skill
        "n": 1,                       // answers so far
        "level": 0,                   // current ladder step, 0-based
        "last_practised": 1760000060, // unix seconds; 0 = never
        "mastered_at": null,          // unix seconds, or null
        "review_interval_days": 1.0,
        "consecutive_errors": 0,      // on the current step
        "items_at_level": 1,          // since the last step change
        "budget_seconds": 0.0,        // time budget per operand on a timed step
        "marked_known": false         // "I know this already" (0.3.0)
      }
    }
  },
  "history": {
    "attempts": [                     // oldest first, at most 50,000 kept
      {
        "ts": 1760000060,             // unix seconds
        "skill": "Setting",
        "level": 0,                   // ladder step the item came from
        "kind": "Set",                // Set | Read | AddSub | Multiply | Divide |
                                      // Mixed | Sprint | Anzan | Flash | Lesson
        "correct": true,
        "seconds": 2.4                // time for the whole item
      }
    ]
  },
  "created": 1760000000,              // unix seconds the profile was created
  "updated": 1760000060,              // unix seconds of the last save
  "builds_on_noted": []               // lessons whose "builds on" note was
                                      // shown once, e.g. ["Divide"] (0.3.0)
}

The scheduler chapter explains every field under scheduler. Everything on the stats screen (momentum, mastery bars, accuracy and speed curves, the session log) is computed from history when it is shown; none of it is stored separately.