OpenRemap Docs

Tune Format (.orst)

⚠ DEPRECATED. The .orst saved-tune format is being phased out. New work should use the portable .remap recipe format (schema 4.4), which now covers the saved-tune use case with the calibration-map annotation layer. Existing .orst files remain readable, but the format will not receive new features.

The .orst (OpenRemap Saved Tune) format is the workspace-native file that stores a saved tune. It carries the same instruction shape as a .remap recipe but with minimal metadata — just enough for the editor to reopen, display history, and export as a portable recipe.

This format is consumed by openremap-studio. It is not exposed through the CLI or TUI.

Format Version

The current format version is 2.0, recorded in the orst field.

Version Changes
1.0 Initial .orst format (Rust-only, had description and author fields)
2.0 Schema defined in Python library. Dropped description and author. Added message, base_tune_id, archived_at, instructions[].status.

Parsers MUST ignore unknown fields.

Top-level Structure

{
  "orst": "2.0",
  "id": "orst_a1b2c3d4...",
  "name": "Stage 1",
  "message": "Increased idle timing by 2°",
  "source_binary": {
    "sha256": "3a7bd3e2360a...",
    "file_size": 524288,
    "path_hint": "stock.bin"
  },
  "base_tune_id": null,
  "created_at": "2026-06-02T12:00:00Z",
  "modified_at": "2026-06-02T14:30:00Z",
  "archived_at": null,
  "instructions": [ ]
}
Field Type Description
orst string Schema version — "2.0"
id string Stable tune ID (orst_<32hex>). Survives renames
name string Display name, user-editable
message string | null Commit message from Ctrl+S, max ~120 chars
source_binary object Identity of the stock binary this tune was cooked against
base_tune_id string | null The tune this one was forked from. null = derived from stock
created_at string ISO 8601 UTC — when the tune was first created
modified_at string ISO 8601 UTC — last Ctrl+S
archived_at string | null Set when this is an archive snapshot; null for the live version
instructions array Changed byte ranges — same shape as recipe instructions

source_binary

Field Type Description
sha256 string SHA-256 of the stock binary
file_size integer Size of the stock binary in bytes
path_hint string Last-known filename; not authoritative

instructions

Same field shape as .remap recipe instructions, with one additional field:

Extra field Type Description
status string "Normal" (default) or "Unresolved" (ob not found after binary rebase)

All other fields (offset, ob, mb, ctx, context_after, context_size, ctx_entropy, ctx_unique, ctx_expanded, description, flags) are identical to the recipe instruction format.

Relationship to .remap

Stock.bin + Modified buffer
        │
        ▼
  ECUDiffAnalyzer
        │
        ├── build_recipe()  →  .remap  (full: ecu, statistics, creator, ...)
        │
        └── build_orst()    →  .orst   (minimal: instructions + source + name)

Exporting a recipe from a tune is a direct field copy of instructions — the instruction shape is identical between formats. The .orst just omits the ECU identity, statistics, creator provenance, and compatibility metadata that are irrelevant to the editor workflow.

See also

PreviousConceptsNext Recipe Format
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