File formats

File formats

Bouncer saves three kinds of file so you can share and reuse your setup: a configuration file (.bcn), a model file (.bml), and a project file (.bproj). Each one is plain JSON, so you can read it, diff it, and keep it in version control.

The three file types

File	Icon	Name	What it holds
.bcn		Bouncer Configuration	Settings, chat presets, and the mode.
.bml		Bouncer Model	A model manifest: where to get the model, and its load and sampling settings.
.bproj		Bouncer Project	A coding project: its name, folder, instructions file, and mode.

None of these files ever contains your Hugging Face token. Bouncer ignores unknown fields when it reads or writes a file, so a token cannot be stored in one by accident.

Open a file

Double-click a .bcn, .bml, or .bproj file, or use Open with on your system to choose Bouncer. You can also pick the file from Bouncer's open dialog. Bouncer reads the file and then does one of three things.

File	What happens
.bproj	The project folder opens in the IDE right away. If you last used Bouncer Code, it opens there instead.
.bml	An Open model dialog shows the model, its repo and file, and its load settings. It also says whether the model is already in your library. Click Load if it is, or Open in Marketplace to find and download it.
.bcn	An Import settings dialog lists what the file holds: settings, presets, and mode. Tick the parts you want, then click Import.

If Bouncer cannot read a file, the Couldn't open this file dialog says why. For example, a damaged file reports where the JSON is broken, with its line and column.

Export a file

• Configuration (.bcn): open Settings > Experience and click Export settings…. You can also run Export settings from the command palette.
• Model (.bml): in Models > Library, use the Export action on a model you downloaded from Hugging Face. Models you imported from a local file have no repo, so they cannot be exported.
• Project (.bproj): run Export project file from the command palette while a project is open. The file is saved in the project folder by default.

Bouncer Configuration (.bcn)

A .bcn file carries the settings you choose to share between machines. It leaves out machine-specific values, such as the onboarding state and your list of recent folders.

Fields:

Field	Type	Notes
format	"bouncer.config"	Required. Identifies the file.
version	integer	Required. The format version, currently 1.
settings	object	Optional. Any of the settings below. Each one may be left out.
settings.theme	system, dark, light, obsidian	The app theme. dark is the Graphite theme.
settings.accent	auto, signal, slate, mono, ember, glacier, ultraviolet, lime	The accent color.
settings.highContrast	boolean	Stronger text and borders.
settings.surface	chat, code, ide, rebound, studio, models	The screen Bouncer opens to.
settings.uiMode	standard, developer	Standard or developer mode.
settings.guardrails	off, relaxed, strict	How Bouncer treats models that won't fit.
settings.enabledGpus	array of GPU indexes, or null	Which GPUs the engine may use. null means all.
settings.editorFontSize	integer, 9 to 32	Editor font size.
settings.editorTabSize	integer, 1 to 8	Editor tab width.
settings.editorWordWrap	boolean	Wrap long lines in the editor.
settings.editorMinimap	boolean	Show the editor minimap.
presets	array, up to 200	Chat presets. Each has a name (1 to 80 characters), a systemPrompt (up to 20,000 characters), and optional sampling. Built-in presets are not exported.
agent	object	Optional. agent.mode is one of plan, manual, accept-edits, autopilot.
exportedAt	ISO 8601 date and time	When the file was written.
app.version	string	The Bouncer version that wrote the file.

A sampling object may contain any of these optional fields: temperature (0 to 5), topP (0 to 1), topK (integer, 0 to 1000), minP (0 to 1), repeatPenalty (0.5 to 3), and maxTokens (integer, 0 to 1,048,576).

Example:

{
  "format": "bouncer.config",
  "version": 1,
  "settings": {
    "theme": "dark",
    "accent": "signal",
    "editorFontSize": 13,
    "editorTabSize": 2
  },
  "presets": [
    {
      "name": "Careful writer",
      "systemPrompt": "You are a careful editor. Keep the author's voice and flag anything unclear.",
      "sampling": { "temperature": 0.4, "topP": 0.9 }
    }
  ],
  "agent": { "mode": "plan" },
  "exportedAt": "2026-10-16T09:00:00.000Z",
  "app": { "version": "0.0.0" }
}

Bouncer Model (.bml)

A .bml file is a manifest. It tells Bouncer which Hugging Face file to download and how to load it. It does not contain the model weights.

Fields:

Field	Type	Notes
format	"bouncer.model"	Required.
version	integer	Required. Currently 1.
repo	string	Required. A Hugging Face repo in the form owner/name.
file	string	Required. The .gguf file name, with no folders.
quant	string, up to 40 characters	Optional. The quantization, such as Q4_K_M.
sha256	64 hex characters	Optional. The expected SHA-256 hash of the file.
sizeBytes	integer	Optional. The expected file size in bytes.
label	string, up to 120 characters	Optional. The name shown in Bouncer.
load	object	Optional. Load settings, described below.
sampling	object	Optional. Sampling settings, the same as in .bcn presets.

Load settings, each optional:

Field	Values
ctxSize	integer from 512 to 1,048,576, or null for the model's default
gpuLayers	auto, all (the max setting), or an integer from 0 to 1000
flashAttn	auto, on, off
cacheTypeK, cacheTypeV	f16, q8_0, q4_0
threads	integer from 1 to 512, or null
batchSize	integer from 16 to 16,384, or null
mmap	boolean
kvOffload	boolean

Example:

{
  "format": "bouncer.model",
  "version": 1,
  "repo": "unsloth/Qwen3-8B-GGUF",
  "file": "Qwen3-8B-Q4_K_M.gguf",
  "quant": "Q4_K_M",
  "label": "Qwen3 8B (Q4_K_M)",
  "load": {
    "ctxSize": 8192,
    "gpuLayers": "all",
    "flashAttn": "auto"
  },
  "sampling": {
    "temperature": 0.6,
    "topP": 0.95,
    "topK": 20,
    "minP": 0
  }
}

Opening this file in Bouncer shows the model and its settings. If the model is not in your library, click Open in Marketplace to download it. The sha256 and sizeBytes fields are optional. They describe the file you expect, so you can share a manifest without the weights.

Bouncer Project (.bproj)

A .bproj file points Bouncer at a project folder and sets how Bouncer Code works in it.

Fields:

Field	Type	Notes
format	"bouncer.project"	Required.
version	integer	Required. Currently 1.
name	string, 1 to 200 characters	Required. The project name.
root	string	Required. The project folder. An absolute path, or a path relative to the folder that holds the .bproj file. "." means the same folder.
instructions	string	Optional. The instructions file for Bouncer Code, default BOUNCER.md.
agent	object	Optional. agent.mode, as in .bcn.

Example:

{
  "format": "bouncer.project",
  "version": 1,
  "name": "Example project",
  "root": ".",
  "instructions": "BOUNCER.md",
  "agent": { "mode": "accept-edits" }
}

Keep the .bproj file in the project folder and use a relative root (such as "."), so the project still opens if you move or share the folder.

Modes

The agent.mode field takes one of four values. They appear in Bouncer as:

Value	Label	What it does
plan	plan	Reads files and replies with a plan. Makes no changes.
manual	manual	Asks before every edit and command.
accept-edits	accept edits	Applies edits, and asks before running commands.
autopilot	autopilot	Runs everything in the project folder without asking.

Versions

Every file carries a version number. The current version of all three formats is 1.

• If a file's version is newer than your copy of Bouncer, Bouncer refuses to open it and says Made by a newer Bouncer (version N); update to open it. Update Bouncer, then open the file again.
• The version number lets a future Bouncer change the format and still read files written today.
• Bouncer rejects files larger than 5 MB.

Related

• Settings: the settings a .bcn file can carry.
• Models: downloading models and managing your library.
• Code: working with projects and Bouncer Code.
• Privacy: what stays on your machine.