Runtime data model

These TypeScript contracts describe in-memory state in v0.2.7. Persistence stores only a subset.

Cell state

export type CellState = "idle" | "running" | "error" | "success";

Value	Meaning
idle	The cell is not executing and has no current success/error transition.
running	The frontend has started an execution request and exposes the interrupt control.
success	The last request returned without an error field.
error	Kernel startup, invoke, transport, or Python execution produced an error.

Cell state is not persisted.

Kernel state

export type KernelState = "starting" | "idle" | "busy" | "stopped" | "error";

Value	Meaning
starting	Frontend is ensuring or restarting a process.
idle	Backend process is available.
busy	The frontend coordinator has reserved the tab for an execution sequence.
stopped	No usable process is available, or a stopped sentinel was installed.
error	Process or communication failure.

Cell output

export interface CellOutput {
  outputType: "stream" | "error" | "image/png";
  streamName?: "stdout" | "stderr";
  text?: string;
  imageData?: string;
}

• stream uses streamName to distinguish stdout and stderr.
• error uses text for the traceback or transport error.
• image/png and imageData are reserved. The current renderer returns null for this type, and the Python server never emits it.

Cell

export interface Cell {
  id: string;
  type: "code" | "markdown";
  source: string;
  executionCount: number | null;
  outputs: CellOutput[];
  state: CellState;
}

Field	Durable?	Notes
id	Yes	Generated with crypto.randomUUID() for new cells.
type	Yes	New cells are code; markdown is reserved.
source	Yes	Raw editor text.
executionCount	No	Assigned optimistically before invoking Rust.
outputs	No	Replaced on every run and cleared on restart.
state	No	Session-only UI state.

Notebook

export interface Notebook {
  tabIndex: number;
  cells: Cell[];
  kernelState: KernelState;
  executionCounter: number;
}

The store initializes notebook indices 0 through 3. Only cell identity, type, source, order, and the tab index are serialized.

Kernel response

export type KernelResponse = {
  id: string;
  type: string;
  stdout: string;
  stderr: string;
  error: string | null;
  output_type: string;
};

The response uses snake case for output_type because it mirrors the Python JSON protocol. The frontend currently ignores that field when creating output records and derives streams from stdout, stderr, and error.

Store-wide state

The Zustand store also holds:

Field	Type	Meaning
notebooks	Notebook[]	Four notebook states.
activeTab	number	Current zero-based tab index; begins at 0.
focusedCellId	string | null	Temporary request to focus a newly created or advanced-to cell.
isCommandMode	boolean	Intended command-mode flag set by Escape.

Neither active-tab nor focus state is persisted.