cook

A tuner works like this: they take the factory file from your car (the stock file), change it, and flash the result (the tuned file). If you have both files, cook does the clever part — it compares them and writes down every single change in a small text file called a recipe (.remap).

Think of the recipe as the tuner's change list: "at this location, replace these bytes with those". Once you have it, you can:

read it — it is human-readable text, so you can see exactly what the tune changes,
share it — the recipe is portable, so someone else can review it,
apply it — later commands (tune, validate) use the recipe to patch another file of the same ECU.

cook only reads your two files. It never changes them.

When do I need it?

After you have a stock and a tuned file and want to capture the tune as a reusable recipe.
When you want to review what a tune actually changes before you trust it — open the recipe in any text editor.
Not when you only have one file: cook needs both the stock and the tuned version to know what changed.

Important

A plain cook recipe is for applying to the same kind of file. If the tune changed things that are different from car to car (like the VIN or the checksum stores), use cook-volatile instead — it makes the recipe car-portable by excluding those "volatile" bytes with recorded evidence.

Try it (2 minutes)

openremap cook stock.bin stage1.bin --output recipe.remap

You will see a short summary like this:

  ✅ Recipe built successfully

  ECU                    Bosch · EDC17
  Match Key              EDC17::08001505827522B
  Format Version         4.4
  Instructions           277
  Bytes Changed          43,577
  Original               stock.bin
  Modified               stage1.bin

  Recipe saved to recipe.remap

(Shortened — a warning line appears when some changes sit outside the calibration area; see the CLI page for what that means.)

Understanding the answer

The summary says…	In plain words
ECU	Which ECU the recipe was built from (must match the target you apply it to)
Match Key	The ECU's name tag — the recipe refuses to apply to a different ECU
Instructions	How many separate changes were found. Zero means the two files are identical — you may have swapped the order
Bytes Changed	How many bytes differ in total — a rough idea of how big the tune is

If the recipe says ECU: Unknown, the file's family is not supported yet. The recipe is still built (all changes captured), but it has no name tag, so it cannot be matched to a target later.

For developers

cook is one method of openremap.api — the same comparison, from code or over JSON-RPC:

Way of using it	Where to look	Example
Terminal (CLI)	cook — CLI	`openremap cook stock.bin stage1.bin --output recipe.remap`
Python code	cook — API	`api.call("cook", {"original_path": "stock.bin", "modified_path": "stage1.bin"})`
Any language (JSON-RPC)	cook — API	a request with `"method": "cook"`

Where to go next

You want to…	Go to
See every flag and how the diff works	cook — CLI
Call `cook` from your own code	cook — API
Make the recipe car-portable	`cook-volatile`
Apply the recipe to a file safely	`tune`
Understand the recipe file format	Recipe format