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+---
+epic: 8
+story: 8.9
+title: "Portable Mode"
+status: draft
+---
+
+## Epic 8 — Windows App (Rust + iced)
+**Goal:** Fast, lightweight native Windows app -- single .exe, no runtime dependencies.
+
+### Story 8.9: Portable Mode
+
+As a **Windows user** who uses a USB drive,
+I want CalcPad to run in portable mode when a marker file is present,
+So that I can carry my calculator and all its data on a USB stick without installing anything on the host machine.
+
+**Acceptance Criteria:**
+
+**Given** a file named `portable.marker` exists in the same directory as `calcpad.exe`
+**When** the app launches
+**Then** all data (sheets, settings, configuration) is stored in a `data/` subdirectory alongside the `.exe` instead of in `%APPDATA%`
+
+**Given** `portable.marker` does NOT exist alongside the `.exe`
+**When** the app launches
+**Then** the app uses the standard `%APPDATA%\CalcPad\` directory for storage (normal installed mode)
+
+**Given** the app is in portable mode
+**When** the user creates sheets and changes settings
+**Then** all changes are written to the local `data/` directory
+**And** no files are written to the system `%APPDATA%` or registry
+
+**Given** the user copies the CalcPad folder (exe + portable.marker + data/) to a USB drive
+**When** the user runs calcpad.exe from the USB on a different Windows machine
+**Then** all sheets and settings from the original machine are available
+
+**Given** the app is in portable mode
+**When** the auto-update feature checks for updates
+**Then** auto-update is disabled (or updates are downloaded to the portable directory) to avoid modifying the host system