diff --git a/AIStudyApp/AIStudyAppTests/ReadingPositionAdapterTests.swift b/AIStudyApp/AIStudyAppTests/ReadingPositionAdapterTests.swift
new file mode 100644
index 0000000..09594e2
--- /dev/null
+++ b/AIStudyApp/AIStudyAppTests/ReadingPositionAdapterTests.swift
@@ -0,0 +1,202 @@
+import XCTest
+@testable import AIStudyApp
+
+final class ReadingPositionAdapterTests: XCTestCase {
+
+    // MARK: - fromValue: Markdown
+
+    func test_fromValue_markdown_with_blockId() {
+        let v = ReadingPositionValue(type: "Markdown", blockId: "b1", lineNumber: nil,
+            pageNumber: nil, chapterId: nil, scrollProgress: 0.5, pageProgress: nil,
+            overallProgress: nil, zoomScale: nil, offsetX: nil, offsetY: nil, chapterProgress: nil)
+        let pos = ReadingPositionAdapter.fromValue(v)
+        guard case let .markdown(blockId, scrollProgress) = pos else {
+            return XCTFail("Expected .markdown, got \(String(describing: pos))")
+        }
+        XCTAssertEqual(blockId, "b1")
+        XCTAssertEqual(scrollProgress, 0.5)
+    }
+
+    func test_fromValue_markdown_nil_blockId_returns_nil() {
+        let v = ReadingPositionValue(type: "Markdown", blockId: nil, lineNumber: nil,
+            pageNumber: nil, chapterId: nil, scrollProgress: nil, pageProgress: nil,
+            overallProgress: nil, zoomScale: nil, offsetX: nil, offsetY: nil, chapterProgress: nil)
+        XCTAssertNil(ReadingPositionAdapter.fromValue(v))
+    }
+
+    // MARK: - fromValue: Text
+
+    func test_fromValue_text_with_optional_fields() {
+        let v = ReadingPositionValue(type: "Text", blockId: nil, lineNumber: 42,
+            pageNumber: nil, chapterId: nil, scrollProgress: 0.8, pageProgress: nil,
+            overallProgress: nil, zoomScale: nil, offsetX: nil, offsetY: nil, chapterProgress: nil)
+        guard case let .text(lineNumber, scrollProgress) = ReadingPositionAdapter.fromValue(v) else {
+            return XCTFail("Expected .text")
+        }
+        XCTAssertEqual(lineNumber, 42)
+        XCTAssertEqual(scrollProgress, 0.8)
+    }
+
+    func test_fromValue_text_defaults_lineNumber_to_1() {
+        let v = ReadingPositionValue(type: "Text", blockId: nil, lineNumber: nil,
+            pageNumber: nil, chapterId: nil, scrollProgress: nil, pageProgress: nil,
+            overallProgress: nil, zoomScale: nil, offsetX: nil, offsetY: nil, chapterProgress: nil)
+        guard case let .text(lineNumber, _) = ReadingPositionAdapter.fromValue(v) else {
+            return XCTFail("Expected .text")
+        }
+        XCTAssertEqual(lineNumber, 1)
+    }
+
+    // MARK: - fromValue: Pdf
+
+    func test_fromValue_pdf_with_all_fields() {
+        let v = ReadingPositionValue(type: "Pdf", blockId: nil, lineNumber: nil,
+            pageNumber: 5, chapterId: nil, scrollProgress: nil, pageProgress: 0.3,
+            overallProgress: 0.15, zoomScale: nil, offsetX: nil, offsetY: nil, chapterProgress: nil)
+        guard case let .pdf(pageNumber, pageProgress, overallProgress) = ReadingPositionAdapter.fromValue(v) else {
+            return XCTFail("Expected .pdf")
+        }
+        XCTAssertEqual(pageNumber, 5)
+        XCTAssertEqual(pageProgress, 0.3)
+        XCTAssertEqual(overallProgress, 0.15)
+    }
+
+    func test_fromValue_pdf_defaults_to_page_1() {
+        let v = ReadingPositionValue(type: "Pdf", blockId: nil, lineNumber: nil,
+            pageNumber: nil, chapterId: nil, scrollProgress: nil, pageProgress: nil,
+            overallProgress: nil, zoomScale: nil, offsetX: nil, offsetY: nil, chapterProgress: nil)
+        guard case let .pdf(pageNumber, _, _) = ReadingPositionAdapter.fromValue(v) else {
+            return XCTFail("Expected .pdf")
+        }
+        XCTAssertEqual(pageNumber, 1)
+    }
+
+    // MARK: - fromValue: Image
+
+    func test_fromValue_image_with_zoom_and_offset() {
+        let v = ReadingPositionValue(type: "Image", blockId: nil, lineNumber: nil,
+            pageNumber: nil, chapterId: nil, scrollProgress: nil, pageProgress: nil,
+            overallProgress: nil, zoomScale: 2.0, offsetX: 100, offsetY: 200, chapterProgress: nil)
+        guard case let .image(zoomScale, offsetX, offsetY) = ReadingPositionAdapter.fromValue(v) else {
+            return XCTFail("Expected .image")
+        }
+        XCTAssertEqual(zoomScale, 2.0)
+        XCTAssertEqual(offsetX, 100)
+        XCTAssertEqual(offsetY, 200)
+    }
+
+    func test_fromValue_image_defaults_zoom_to_1() {
+        let v = ReadingPositionValue(type: "Image", blockId: nil, lineNumber: nil,
+            pageNumber: nil, chapterId: nil, scrollProgress: nil, pageProgress: nil,
+            overallProgress: nil, zoomScale: nil, offsetX: nil, offsetY: nil, chapterProgress: nil)
+        guard case let .image(zoomScale, _, _) = ReadingPositionAdapter.fromValue(v) else {
+            return XCTFail("Expected .image")
+        }
+        XCTAssertEqual(zoomScale, 1.0)
+    }
+
+    // MARK: - fromValue: Epub
+
+    func test_fromValue_epub_with_chapterId() {
+        let v = ReadingPositionValue(type: "Epub", blockId: nil, lineNumber: nil,
+            pageNumber: nil, chapterId: "ch3", scrollProgress: nil, pageProgress: nil,
+            overallProgress: 0.6, zoomScale: nil, offsetX: nil, offsetY: nil, chapterProgress: 0.4)
+        guard case let .epub(chapterId, chapterProgress, overallProgress) = ReadingPositionAdapter.fromValue(v) else {
+            return XCTFail("Expected .epub")
+        }
+        XCTAssertEqual(chapterId, "ch3")
+        XCTAssertEqual(chapterProgress, 0.4)
+        XCTAssertEqual(overallProgress, 0.6)
+    }
+
+    func test_fromValue_epub_nil_chapterId_returns_nil() {
+        let v = ReadingPositionValue(type: "Epub", blockId: nil, lineNumber: nil,
+            pageNumber: nil, chapterId: nil, scrollProgress: nil, pageProgress: nil,
+            overallProgress: nil, zoomScale: nil, offsetX: nil, offsetY: nil, chapterProgress: nil)
+        XCTAssertNil(ReadingPositionAdapter.fromValue(v))
+    }
+
+    // MARK: - fromValue: Unknown / default
+
+    func test_fromValue_unknown_type_returns_unknown() {
+        let v = ReadingPositionValue(type: "UnknownType", blockId: nil, lineNumber: nil,
+            pageNumber: nil, chapterId: nil, scrollProgress: nil, pageProgress: nil,
+            overallProgress: nil, zoomScale: nil, offsetX: nil, offsetY: nil, chapterProgress: nil)
+        guard case .unknown = ReadingPositionAdapter.fromValue(v) else {
+            return XCTFail("Expected .unknown")
+        }
+    }
+
+    func test_fromValue_nil_type_returns_unknown() {
+        let v = ReadingPositionValue(type: nil, blockId: nil, lineNumber: nil,
+            pageNumber: nil, chapterId: nil, scrollProgress: nil, pageProgress: nil,
+            overallProgress: nil, zoomScale: nil, offsetX: nil, offsetY: nil, chapterProgress: nil)
+        guard case .unknown = ReadingPositionAdapter.fromValue(v) else {
+            return XCTFail("Expected .unknown")
+        }
+    }
+
+    // MARK: - Clamp behavior
+
+    func test_clamp_scrollProgress_above_1() {
+        let v = ReadingPositionValue(type: "Text", blockId: nil, lineNumber: nil,
+            pageNumber: nil, chapterId: nil, scrollProgress: 1.5, pageProgress: nil,
+            overallProgress: nil, zoomScale: nil, offsetX: nil, offsetY: nil, chapterProgress: nil)
+        guard case let .text(_, scrollProgress) = ReadingPositionAdapter.fromValue(v) else {
+            return XCTFail("Expected .text")
+        }
+        XCTAssertEqual(scrollProgress, 1.0)
+    }
+
+    func test_clamp_progress_negative() {
+        let v = ReadingPositionValue(type: "Text", blockId: nil, lineNumber: nil,
+            pageNumber: nil, chapterId: nil, scrollProgress: -0.5, pageProgress: nil,
+            overallProgress: nil, zoomScale: nil, offsetX: nil, offsetY: nil, chapterProgress: nil)
+        guard case let .text(_, scrollProgress) = ReadingPositionAdapter.fromValue(v) else {
+            return XCTFail("Expected .text")
+        }
+        XCTAssertEqual(scrollProgress, 0.0)
+    }
+
+    // MARK: - blockId extraction
+
+    func test_blockId_from_heading() {
+        let block = DocumentBlock.heading(id: "h1", level: 2, text: "Title")
+        XCTAssertEqual(ReadingPositionAdapter.blockId(from: block), "h1")
+    }
+
+    func test_blockId_from_paragraph() {
+        let block = DocumentBlock.paragraph(id: "p1", text: "Content")
+        XCTAssertEqual(ReadingPositionAdapter.blockId(from: block), "p1")
+    }
+
+    func test_blockId_from_list() {
+        let block = DocumentBlock.list(id: "l1", items: [], ordered: true)
+        XCTAssertEqual(ReadingPositionAdapter.blockId(from: block), "l1")
+    }
+
+    func test_blockId_from_codeBlock() {
+        let block = DocumentBlock.codeBlock(id: "c1", language: "swift", code: "print(\"hi\")")
+        XCTAssertEqual(ReadingPositionAdapter.blockId(from: block), "c1")
+    }
+
+    func test_blockId_from_quote() {
+        let block = DocumentBlock.quote(id: "q1", text: "quote")
+        XCTAssertEqual(ReadingPositionAdapter.blockId(from: block), "q1")
+    }
+
+    func test_blockId_from_table() {
+        let block = DocumentBlock.table(id: "t1", headers: [], rows: [])
+        XCTAssertEqual(ReadingPositionAdapter.blockId(from: block), "t1")
+    }
+
+    func test_blockId_from_imageBlock() {
+        let block = DocumentBlock.imageBlock(id: "img1", alt: "img", source: "file.png")
+        XCTAssertEqual(ReadingPositionAdapter.blockId(from: block), "img1")
+    }
+
+    func test_blockId_from_horizontalRule() {
+        let block = DocumentBlock.horizontalRule(id: "hr1")
+        XCTAssertEqual(ReadingPositionAdapter.blockId(from: block), "hr1")
+    }
+}