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+---
+epic: 11
+story: 11.1
+title: "Single Expression Evaluation"
+status: draft
+---
+
+## Epic 11 — CLI Tool
+**Goal:** Command-line tool for scripting and automation, same Rust engine.
+
+### Story 11.1: Single Expression Evaluation
+
+As a developer or power user,
+I want to evaluate a single CalcPad expression from the command line,
+So that I can quickly compute values without opening an editor.
+
+**Acceptance Criteria:**
+
+**Given** the user has `calcpad` installed
+**When** they run `calcpad "5kg in lbs"`
+**Then** the output is `11.023 lbs` (or equivalent precision) printed to stdout
+**And** the process exits with code 0
+
+**Given** the user passes an invalid expression
+**When** they run `calcpad "5kg in ???"`
+**Then** an error message is printed to stderr describing the issue
+**And** the process exits with code 1
+
+**Given** the user passes a plain arithmetic expression
+**When** they run `calcpad "2 + 3 * 4"`
+**Then** the output is `14` printed to stdout
+**And** the process exits with code 0