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+---
+epic: 8
+story: 8.2
+title: "Engine Integration (Direct Linking)"
+status: draft
+---
+
+## Epic 8 — Windows App (Rust + iced)
+**Goal:** Fast, lightweight native Windows app -- single .exe, no runtime dependencies.
+
+### Story 8.2: Engine Integration (Direct Linking)
+
+As a **Windows developer** building CalcPad,
+I want the iced app to directly link the Rust CalcPad engine with zero serialization overhead,
+So that the app is as fast as possible with no FFI boundary costs.
+
+**Acceptance Criteria:**
+
+**Given** the iced app's `Cargo.toml` includes `calcpad_engine` as a dependency
+**When** the app is compiled
+**Then** the engine is statically linked into the single `.exe` binary
+
+**Given** the app calls `SheetContext::new()` and `context.evaluate_line("2 + 2")`
+**When** the engine processes the call
+**Then** the result is returned as a native Rust type (no JSON/string serialization boundary)
+
+**Given** the app evaluates a full sheet
+**When** `context.evaluate_sheet(text)` is called
+**Then** all lines are evaluated with full dependency resolution and results are returned as a `Vec<LineResult>`
+
+**Given** the engine is used directly via `use calcpad_engine::SheetContext;`
+**When** the app binary is built in release mode
+**Then** the engine code is inlined and optimized by the Rust compiler as if it were part of the app itself