diff --git a/gitnexus/src/core/embeddings/ast-utils.ts b/gitnexus/src/core/embeddings/ast-utils.ts
index 8a2448ea0..a0a15d7ae 100644
--- a/gitnexus/src/core/embeddings/ast-utils.ts
+++ b/gitnexus/src/core/embeddings/ast-utils.ts
@@ -11,7 +11,7 @@ import {
 } from '../tree-sitter/parser-loader.js';
 import { parseSourceSafe } from '../tree-sitter/safe-parse.js';
 import { getLanguageForFileContent, getProvider } from '../ingestion/languages/index.js';
-import { extractNotebookPython } from '../ingestion/ipynb-extractor.js';
+import { extractNotebookPython, isNotebookPath } from '../ingestion/ipynb-extractor.js';
 
 const parserCache = new Map<string, any>();
 
@@ -42,13 +42,12 @@ export const ensureAndParse = async (content: string, filePath: string): Promise
   // offsets still index `content` except for `.ipynb`, which is replaced by
   // concatenated code-cell Python (same as the parse worker).
   let parseContent = getProvider(language).preprocessSource?.(content, filePath) ?? content;
-  if (filePath.replace(/\\/g, '/').toLowerCase().endsWith('.ipynb')) {
+  if (isNotebookPath(filePath)) {
     const extracted = extractNotebookPython(content);
-    if (extracted) {
-      parseContent =
-        getProvider(language).preprocessSource?.(extracted.pythonSource, filePath) ??
-        extracted.pythonSource;
-    }
+    if (!extracted) return null;
+    parseContent =
+      getProvider(language).preprocessSource?.(extracted.pythonSource, filePath) ??
+      extracted.pythonSource;
   }
 
   return parseSourceSafe(parserInstance, parseContent);
diff --git a/gitnexus/src/core/ingestion/ipynb-extractor.ts b/gitnexus/src/core/ingestion/ipynb-extractor.ts
index 327187741..075b664e6 100644
--- a/gitnexus/src/core/ingestion/ipynb-extractor.ts
+++ b/gitnexus/src/core/ingestion/ipynb-extractor.ts
@@ -2,7 +2,8 @@
  * Jupyter notebook (.ipynb) Python extractor.
  *
  * Pulls code-cell source from nbformat JSON so the Python tree-sitter
- * grammar can parse it. Pure — no I/O, no tree-sitter, worker-safe.
+ * grammar can parse it. Extraction helpers are I/O-free and worker-safe.
+ * `extractNotebookPythonCached` is an optional process-local LRU for FTS.
  *
  * Graph coordinates stay 0-based lines in the on-disk JSON file. Extract
  * buffer lines map through {@link mapExtractLine}.
@@ -22,6 +23,10 @@ export interface NotebookPythonExtraction {
 
 const PYTHON_FAMILY = new Set(['python', 'python2', 'python3', 'ipython']);
 
+export function isNotebookPath(filePath: string): boolean {
+  return filePath.replace(/\\/g, '/').toLowerCase().endsWith('.ipynb');
+}
+
 export function isPythonFamilyLanguage(name: string | undefined | null): boolean {
   if (name === undefined || name === null) return false;
   const n = name.trim().toLowerCase();
@@ -29,13 +34,29 @@ export function isPythonFamilyLanguage(name: string | undefined | null): boolean
   return /^python\d/.test(n);
 }
 
-function indexToLine(content: string, index: number): number {
-  let line = 0;
-  const end = Math.max(0, Math.min(index, content.length));
-  for (let i = 0; i < end; i++) {
-    if (content.charCodeAt(i) === 10) line++;
+function buildLineStarts(content: string): number[] {
+  const starts = [0];
+  for (let i = 0; i < content.length; i++) {
+    if (content.charCodeAt(i) === 10) starts.push(i + 1);
   }
-  return line;
+  return starts;
+}
+
+function indexToLine(lineStarts: readonly number[], index: number): number {
+  if (index <= 0) return 0;
+  let lo = 0;
+  let hi = lineStarts.length - 1;
+  let ans = 0;
+  while (lo <= hi) {
+    const mid = (lo + hi) >> 1;
+    if (lineStarts[mid] <= index) {
+      ans = mid;
+      lo = mid + 1;
+    } else {
+      hi = mid - 1;
+    }
+  }
+  return ans;
 }
 
 function skipWs(content: string, i: number): number {
@@ -144,26 +165,88 @@ function findDepth1Key(content: string, objStart: number, objEnd: number, key: s
   return -1;
 }
 
+function findLastDepth1Key(content: string, objStart: number, objEnd: number, key: string): number {
+  let depth = 0;
+  let inStr = false;
+  let j = objStart;
+  let found = -1;
+  while (j < objEnd) {
+    const ch = content[j];
+    if (inStr) {
+      if (ch === '\\') j += 2;
+      else {
+        if (ch === '"') inStr = false;
+        j++;
+      }
+      continue;
+    }
+    if (ch === '"') {
+      if (depth === 1 && content.startsWith(key, j)) found = j;
+      inStr = true;
+      j++;
+      continue;
+    }
+    if (ch === '{' || ch === '[') depth++;
+    else if (ch === '}' || ch === ']') depth--;
+    j++;
+  }
+  return found;
+}
+
 function findCellsArraySpan(content: string): { start: number; end: number } | null {
   const root = jsonBraceSpan(content, 0, '{', '}');
   if (!root) return null;
-  const cellsKey = findDepth1Key(content, root.start, root.end, '"cells"');
+  const cellsKey = findLastDepth1Key(content, root.start, root.end, '"cells"');
   if (cellsKey < 0) return null;
   const colon = content.indexOf(':', cellsKey + 7);
   if (colon < 0 || colon >= root.end) return null;
   return jsonBraceSpan(content, colon + 1, '[', ']');
 }
 
+function nextUnquotedChar(content: string, from: number, until: number, needle: '{' | '"'): number {
+  let inStr = false;
+  let j = from;
+  while (j < until) {
+    const ch = content[j];
+    if (inStr) {
+      if (ch === '\\') j += 2;
+      else {
+        if (ch === '"') inStr = false;
+        j++;
+      }
+      continue;
+    }
+    if (ch === '"') {
+      if (needle === '"') return j;
+      inStr = true;
+      j++;
+      continue;
+    }
+    if (ch === needle) return j;
+    j++;
+  }
+  return -1;
+}
+
+function firstQuoteInValue(content: string, span: { start: number; end: number }): number {
+  const i = skipWs(content, span.start);
+  if (i < span.end && content[i] === '"') return i;
+  if (i < span.end && content[i] === '[') {
+    const q = nextUnquotedChar(content, i + 1, span.end, '"');
+    if (q >= 0) return q;
+  }
+  return span.start;
+}
+
 function findNextCodeCellSourceSpan(
   content: string,
   from: number,
-): { span: { start: number; end: number }; nextFrom: number } | null {
-  const cells = findCellsArraySpan(content);
-  if (!cells) return null;
+  cells: { start: number; end: number },
+): { span: { start: number; end: number } | null; nextFrom: number } | null {
   let search = Math.max(from, cells.start + 1);
   while (search < cells.end) {
-    const brace = content.indexOf('{', search);
-    if (brace < 0 || brace >= cells.end) return null;
+    const brace = nextUnquotedChar(content, search, cells.end, '{');
+    if (brace < 0) return null;
     const obj = jsonBraceSpan(content, brace, '{', '}');
     if (!obj || obj.end > cells.end) {
       search = brace + 1;
@@ -186,18 +269,15 @@ function findNextCodeCellSourceSpan(
     }
     const sourceKey = findDepth1Key(content, obj.start, obj.end, '"source"');
     if (sourceKey < 0) {
-      search = obj.end;
-      continue;
+      return { span: null, nextFrom: obj.end };
     }
     const srcColon = content.indexOf(':', sourceKey + 8);
     if (srcColon < 0 || srcColon >= obj.end) {
-      search = obj.end;
-      continue;
+      return { span: null, nextFrom: obj.end };
     }
     const span = jsonValueSpan(content, srcColon + 1);
     if (!span) {
-      search = obj.end;
-      continue;
+      return { span: null, nextFrom: obj.end };
     }
     return { span, nextFrom: obj.end };
   }
@@ -287,6 +367,10 @@ export function extractNotebookPython(content: string): NotebookPythonExtraction
   if (!Array.isArray(nb.cells)) return null;
   if (kernelShouldSkip(nb)) return null;
 
+  const cells = findCellsArraySpan(content);
+  if (!cells) return null;
+
+  const lineStarts = buildLineStarts(content);
   const chunks: string[] = [];
   const segments: NotebookLineSegment[] = [];
   let searchFrom = 0;
@@ -296,9 +380,10 @@ export function extractNotebookPython(content: string): NotebookPythonExtraction
     const cell = rawCell as Record<string, unknown>;
     if (cell.cell_type !== 'code') continue;
 
-    const located = findNextCodeCellSourceSpan(content, searchFrom);
+    const located = findNextCodeCellSourceSpan(content, searchFrom, cells);
     if (!located) return null;
     searchFrom = located.nextFrom;
+    if (!located.span) continue;
 
     const lang = cellLanguage(cell);
     if (lang !== undefined && !isPythonFamilyLanguage(lang)) {
@@ -306,8 +391,8 @@ export function extractNotebookPython(content: string): NotebookPythonExtraction
     }
 
     const { skipCell, lines } = processCellLines(flattenSource(cell.source));
-    const jsonStartLine = indexToLine(content, located.span.start);
-    const jsonEndLine = Math.max(jsonStartLine, indexToLine(content, located.span.end - 1));
+    const jsonStartLine = indexToLine(lineStarts, firstQuoteInValue(content, located.span));
+    const jsonEndLine = Math.max(jsonStartLine, indexToLine(lineStarts, located.span.end - 1));
 
     if (skipCell) {
       continue;
@@ -385,6 +470,7 @@ export function notebookPythonSnippetFromExtract(
   const pyLines = extracted.pythonSource.split('\n');
   const out: string[] = [];
   for (const seg of extracted.segments) {
+    if (seg.jsonEndLine < startLine || seg.jsonStartLine > endLine) continue;
     for (let extract = seg.extractStartLine; extract <= seg.extractEndLine; extract++) {
       const jsonLine = mapExtractLine(extract, extracted.segments);
       if (jsonLine >= startLine && jsonLine <= endLine) {
diff --git a/gitnexus/src/core/ingestion/language-provider.ts b/gitnexus/src/core/ingestion/language-provider.ts
index 6b5fb2d76..3ed0a1a09 100644
--- a/gitnexus/src/core/ingestion/language-provider.ts
+++ b/gitnexus/src/core/ingestion/language-provider.ts
@@ -828,6 +828,13 @@ interface LanguageProviderConfig {
      */
     sourceMeta?: {
       readonly sourceKind?: 'full-file' | 'pre-extracted-script';
+      /** Python `.ipynb` only: JSON line segments for the pre-extracted buffer. */
+      readonly notebookSegments?: readonly {
+        readonly extractStartLine: number;
+        readonly extractEndLine: number;
+        readonly jsonStartLine: number;
+        readonly jsonEndLine: number;
+      }[];
     },
   ) => readonly CaptureMatch[];
 
diff --git a/gitnexus/src/core/ingestion/languages/python/captures.ts b/gitnexus/src/core/ingestion/languages/python/captures.ts
index e1395df11..131ae7591 100644
--- a/gitnexus/src/core/ingestion/languages/python/captures.ts
+++ b/gitnexus/src/core/ingestion/languages/python/captures.ts
@@ -26,6 +26,7 @@ import { splitImportStatement } from './import-decomposer.js';
 import { getPythonParser, getPythonScopeQuery } from './query.js';
 import {
   extractNotebookPython,
+  isNotebookPath,
   mapExtractLine,
   type NotebookLineSegment,
 } from '../../ipynb-extractor.js';
@@ -64,20 +65,27 @@ export function emitPythonScopeCaptures(
   sourceText: string,
   filePath: string,
   cachedTree?: unknown,
-  sourceMeta?: { sourceKind?: 'full-file' | 'pre-extracted-script' },
+  sourceMeta?: {
+    sourceKind?: 'full-file' | 'pre-extracted-script';
+    notebookSegments?: readonly NotebookLineSegment[];
+  },
 ): readonly CaptureMatch[] {
   let parseText = sourceText;
   let tree = cachedTree as ReturnType<ReturnType<typeof getPythonParser>['parse']> | undefined;
   let notebookSegments: readonly NotebookLineSegment[] | undefined;
-  if (filePath.replace(/\\/g, '/').toLowerCase().endsWith('.ipynb')) {
-    const extracted = extractNotebookPython(sourceText);
-    if (extracted === null) {
-      if (sourceMeta?.sourceKind !== 'pre-extracted-script') return [];
+  if (isNotebookPath(filePath)) {
+    if (sourceMeta?.notebookSegments) {
+      notebookSegments = sourceMeta.notebookSegments;
     } else {
-      parseText = extracted.pythonSource;
-      notebookSegments = extracted.segments;
-      if (sourceMeta?.sourceKind !== 'pre-extracted-script') {
-        tree = undefined;
+      const extracted = extractNotebookPython(sourceText);
+      if (extracted === null) {
+        if (sourceMeta?.sourceKind !== 'pre-extracted-script') return [];
+      } else {
+        parseText = extracted.pythonSource;
+        notebookSegments = extracted.segments;
+        if (sourceMeta?.sourceKind !== 'pre-extracted-script') {
+          tree = undefined;
+        }
       }
     }
   }
diff --git a/gitnexus/src/core/ingestion/scope-extractor-bridge.ts b/gitnexus/src/core/ingestion/scope-extractor-bridge.ts
index 17f639941..9999cec03 100644
--- a/gitnexus/src/core/ingestion/scope-extractor-bridge.ts
+++ b/gitnexus/src/core/ingestion/scope-extractor-bridge.ts
@@ -45,6 +45,12 @@ export function extractParsedFile(
   onWarn?: ScopeBridgeWarn,
   cachedTree?: unknown,
   sourceKind: ScopeCaptureSourceKind = 'full-file',
+  notebookSegments?: readonly {
+    readonly extractStartLine: number;
+    readonly extractEndLine: number;
+    readonly jsonStartLine: number;
+    readonly jsonEndLine: number;
+  }[],
 ): ParsedFile | undefined {
   if (provider.emitScopeCaptures === undefined) return undefined;
   if (sourceText.trim().length === 0) return undefined;
@@ -58,7 +64,10 @@ export function extractParsedFile(
       cachedTree === undefined
         ? (provider.preprocessSource?.(sourceText, filePath) ?? sourceText)
         : sourceText;
-    const captures = provider.emitScopeCaptures(parseText, filePath, cachedTree, { sourceKind });
+    const captures = provider.emitScopeCaptures(parseText, filePath, cachedTree, {
+      sourceKind,
+      ...(notebookSegments ? { notebookSegments } : {}),
+    });
     return extractScope(captures, filePath, provider);
   } catch (err) {
     const message = `scope extraction failed for ${filePath}: ${
diff --git a/gitnexus/src/core/ingestion/workers/parse-worker.ts b/gitnexus/src/core/ingestion/workers/parse-worker.ts
index 4f9dbab36..2c397b5d8 100644
--- a/gitnexus/src/core/ingestion/workers/parse-worker.ts
+++ b/gitnexus/src/core/ingestion/workers/parse-worker.ts
@@ -137,6 +137,7 @@ import {
 } from '../vue-sfc-extractor.js';
 import {
   extractNotebookPython,
+  isNotebookPath,
   mapExtractLine,
   type NotebookLineSegment,
 } from '../ipynb-extractor.js';
@@ -1612,10 +1613,7 @@ const processFileGroup = (
       scopeSourceKind = 'pre-extracted-script';
       lineOffset = extracted.lineOffset;
       isVueSetup = extracted.isSetup;
-    } else if (
-      language === SupportedLanguages.Python &&
-      file.path.replace(/\\/g, '/').toLowerCase().endsWith('.ipynb')
-    ) {
+    } else if (language === SupportedLanguages.Python && isNotebookPath(file.path)) {
       const extracted = extractNotebookPython(file.content);
       if (!extracted) continue;
       parseContent = extracted.pythonSource;
@@ -1685,14 +1683,15 @@ const processFileGroup = (
     let scopeExtractionFailed = false;
     const parsedFile = extractParsedFile(
       provider,
-      notebookSegments ? file.content : parseContent,
+      parseContent,
       file.path,
       (message) => {
         scopeExtractionFailed = true;
         reportWarning(message);
       },
       tree,
-      notebookSegments ? 'full-file' : scopeSourceKind,
+      scopeSourceKind,
+      notebookSegments,
     );
     if (scopeExtractionFailed) (result.scopeExtractionFailures ??= []).push(file.path);
     if (parsedFile !== undefined) {
@@ -1931,7 +1930,7 @@ const processFileGroup = (
             filePath: file.path,
             httpMethod,
             decoratorName,
-            lineNumber: decoratorNode.startPosition.row + lineOffset,
+            lineNumber: mapRow(decoratorNode.startPosition.row),
             ...(decoratorReceiver ? { decoratorReceiver } : {}),
             ...(handlerName ? { handlerName } : {}),
           };
diff --git a/gitnexus/src/core/lbug/csv-generator.ts b/gitnexus/src/core/lbug/csv-generator.ts
index 99d9bb483..1a1ab4513 100644
--- a/gitnexus/src/core/lbug/csv-generator.ts
+++ b/gitnexus/src/core/lbug/csv-generator.ts
@@ -24,8 +24,9 @@ import { parseTruthyEnv } from '../ingestion/utils/env.js';
 import { SYMBOL_NODE_LABELS } from '../ingestion/utils/symbol-labels.js';
 import { applyCjkSegmentationIfEnabled } from '../search/cjk-segmentation.js';
 import {
-  notebookPythonSnippetFromExtract,
   extractNotebookPythonCached,
+  isNotebookPath,
+  notebookPythonSnippetFromExtract,
 } from '../ingestion/ipynb-extractor.js';
 
 /** Computed once — `RELATION_SCHEMA` is a static template literal. Exported so
@@ -329,10 +330,8 @@ const extractContent = async (
   const endLine = node.properties.endLine;
   if (startLine === undefined || endLine === undefined) return '';
 
-  const notebookPath = String(filePath ?? '')
-    .replace(/\\/g, '/')
-    .toLowerCase();
-  if (notebookPath.endsWith('.ipynb')) {
+  const notebookPath = String(filePath ?? '');
+  if (isNotebookPath(notebookPath)) {
     const extracted = extractNotebookPythonCached(notebookPath, content);
     const reconstructed = extracted
       ? notebookPythonSnippetFromExtract(extracted, startLine, endLine)
diff --git a/gitnexus/src/storage/parse-cache.ts b/gitnexus/src/storage/parse-cache.ts
index 2c95bfb69..73c5d123d 100644
--- a/gitnexus/src/storage/parse-cache.ts
+++ b/gitnexus/src/storage/parse-cache.ts
@@ -778,9 +778,6 @@ import { copyV8CacheIfPresent, tryLoadV8Cache, writeV8CacheFile } from './v8-sid
 // v104 (#3339 review): TS/JS pair-HOC queries now name object-pair
 // `mutation(withAuth(arrow))` handlers. Warm caches replay the pre-fix
 // capture set (anonymous arrows, no Function name), so both stores re-extract.
-// v104 (#3339 review): TS/JS pair-HOC queries now name object-pair
-// `mutation(withAuth(arrow))` handlers. Warm caches replay the pre-fix
-// capture set (anonymous arrows, no Function name), so both stores re-extract.
 // v105 (#3371): `.ipynb` code cells are extracted to Python before parse.
 // Warm caches keyed on raw JSON would replay empty/failed Python parses.
 const SCHEMA_BUMP = 105;
diff --git a/gitnexus/test/integration/resolvers/ipynb-python-pipeline.test.ts b/gitnexus/test/integration/resolvers/ipynb-python-pipeline.test.ts
index c0b0c12ce..c0a6fd3d7 100644
--- a/gitnexus/test/integration/resolvers/ipynb-python-pipeline.test.ts
+++ b/gitnexus/test/integration/resolvers/ipynb-python-pipeline.test.ts
@@ -12,6 +12,7 @@ import {
   runPipelineFromRepo,
   writeFixtureRepo,
 } from './helpers.js';
+import { extractNotebookPython } from '../../../src/core/ingestion/ipynb-extractor.js';
 
 function pythonNotebook(cells: Array<{ source: string | string[]; language?: string }>): string {
   return JSON.stringify(
@@ -62,7 +63,10 @@ describe('Jupyter notebook Python pipeline', () => {
       expect(functions).toContain('helper');
       const train = getNodesByLabelFull(result, 'Function').find((n) => n.name === 'train');
       expect(train?.properties.filePath.replace(/\\/g, '/')).toMatch(/analysis\.ipynb$/);
-      expect(train?.properties.startLine).toBeGreaterThan(0);
+      const extracted = extractNotebookPython(
+        fs.readFileSync(path.join(root, 'analysis.ipynb'), 'utf8'),
+      )!;
+      expect(train?.properties.startLine).toBe(extracted.segments[1].jsonStartLine);
       const imports = getRelationships(result, 'IMPORTS');
       expect(
         imports.some(
diff --git a/gitnexus/test/unit/ast-utils.test.ts b/gitnexus/test/unit/ast-utils.test.ts
index e2895592c..5611325a1 100644
--- a/gitnexus/test/unit/ast-utils.test.ts
+++ b/gitnexus/test/unit/ast-utils.test.ts
@@ -123,4 +123,33 @@ describe('ensureAndParse', () => {
     expect(objcParse).toHaveBeenCalledTimes(2);
     expect(cppParse).toHaveBeenCalledTimes(1);
   });
+
+  it('parses extracted notebook Python and returns null when extraction fails', async () => {
+    parseSourceSafeSpy.mockClear();
+    const pyParse = vi.fn().mockReturnValue({ lang: 'py', rootNode: { type: 'module' } });
+    createParserForLanguage.mockImplementation(async (language: string) => {
+      if (language === 'python') return { parse: pyParse };
+      throw new Error(`unexpected language ${language}`);
+    });
+
+    const { ensureAndParse } = await import('../../src/core/embeddings/ast-utils.js');
+    const nb = JSON.stringify({
+      nbformat: 4,
+      nbformat_minor: 5,
+      metadata: { kernelspec: { language: 'python', name: 'python3', display_name: 'Python' } },
+      cells: [
+        { cell_type: 'code', metadata: {}, source: ['def train():\n', '    pass\n'], outputs: [] },
+      ],
+    });
+
+    await ensureAndParse(nb, 'analysis.ipynb');
+    expect(parseSourceSafeSpy).toHaveBeenCalled();
+    const parsedText = parseSourceSafeSpy.mock.calls.at(-1)?.[1] as string;
+    expect(parsedText).toContain('def train');
+    expect(parsedText).not.toContain('cell_type');
+
+    parseSourceSafeSpy.mockClear();
+    expect(await ensureAndParse('{not json', 'broken.ipynb')).toBeNull();
+    expect(parseSourceSafeSpy).not.toHaveBeenCalled();
+  });
 });
diff --git a/gitnexus/test/unit/ipynb-extractor.test.ts b/gitnexus/test/unit/ipynb-extractor.test.ts
index ad10e5c92..5befb06cf 100644
--- a/gitnexus/test/unit/ipynb-extractor.test.ts
+++ b/gitnexus/test/unit/ipynb-extractor.test.ts
@@ -75,6 +75,8 @@ describe('extractNotebookPython', () => {
     expect(result).not.toBeNull();
     expect(result!.pythonSource).toContain('def train():');
     expect(result!.segments).toHaveLength(1);
+    const defJsonLine = content.split('\n').findIndex((l) => l.includes('def train'));
+    expect(result!.segments[0].jsonStartLine).toBe(defJsonLine);
   });
 
   it('keeps two code cells in order with two segments', () => {
@@ -237,3 +239,52 @@ describe('notebookPythonSnippet', () => {
     expect(snippet).not.toContain('cell_type');
   });
 });
+
+describe('extractNotebookPython edge cases', () => {
+  it('skips a code cell without source and keeps later Python', () => {
+    const content = notebook({
+      language: 'python',
+      cells: [
+        { cell_type: 'code', metadata: {}, source: ['def ok():\n', '    pass\n'], outputs: [] },
+        { cell_type: 'code', metadata: {}, outputs: [] },
+        { cell_type: 'code', metadata: {}, source: ['def train():\n', '    pass\n'], outputs: [] },
+      ],
+    });
+    const result = extractNotebookPython(content);
+    expect(result!.pythonSource).toContain('def ok');
+    expect(result!.pythonSource).toContain('def train');
+  });
+
+  it('returns null when language_info is julia without kernelspec', () => {
+    const content = notebook({
+      languageInfo: 'julia',
+      cells: [{ cell_type: 'code', metadata: {}, source: ['1 + 1\n'], outputs: [] }],
+    });
+    expect(extractNotebookPython(content)).toBeNull();
+  });
+
+  it('maps coordinates to the last cells array when the key is duplicated', () => {
+    const decoy = JSON.stringify(
+      [{ cell_type: 'code', metadata: {}, source: ['def decoy():\n', '    pass\n'], outputs: [] }],
+      null,
+      2,
+    );
+    const real = JSON.stringify(
+      [{ cell_type: 'code', metadata: {}, source: ['def real():\n', '    pass\n'], outputs: [] }],
+      null,
+      2,
+    );
+    const content = `{
+  "nbformat": 4,
+  "nbformat_minor": 5,
+  "metadata": { "kernelspec": { "language": "python", "name": "python3", "display_name": "Python" } },
+  "cells": ${decoy},
+  "cells": ${real}
+}`;
+    const result = extractNotebookPython(content);
+    expect(result!.pythonSource).toContain('def real');
+    expect(result!.pythonSource).not.toContain('decoy');
+    const realLine = content.split('\n').findIndex((l) => l.includes('def real'));
+    expect(result!.segments[0].jsonStartLine).toBe(realLine);
+  });
+});
diff --git a/gitnexus/test/unit/ipynb-python-captures.test.ts b/gitnexus/test/unit/ipynb-python-captures.test.ts
index f03a759ce..e6074a73c 100644
--- a/gitnexus/test/unit/ipynb-python-captures.test.ts
+++ b/gitnexus/test/unit/ipynb-python-captures.test.ts
@@ -2,6 +2,7 @@ import { describe, it, expect } from 'vitest';
 import { emitPythonScopeCaptures } from '../../src/core/ingestion/languages/python/captures.js';
 import { pythonProvider } from '../../src/core/ingestion/languages/python.js';
 import { extractParsedFile } from '../../src/core/ingestion/scope-extractor-bridge.js';
+import { extractNotebookPython, mapExtractLine } from '../../src/core/ingestion/ipynb-extractor.js';
 import { getLanguageFromFilename, SupportedLanguages } from 'gitnexus-shared';
 import { getProviderForFile } from '../../src/core/ingestion/languages/index.js';
 
@@ -39,7 +40,9 @@ describe('Python notebook scope captures', () => {
   it('extractParsedFile yields a Function for train', () => {
     const captured = emitPythonScopeCaptures(notebook, 'analysis.ipynb');
     const fnCapture = captured.find((m) => m['@scope.function'] !== undefined);
-    expect(fnCapture?.['@scope.function']?.range.startLine).toBeGreaterThan(1);
+    const extracted = extractNotebookPython(notebook)!;
+    const expectedJson = mapExtractLine(extracted.segments[0].extractStartLine, extracted.segments);
+    expect(fnCapture?.['@scope.function']?.range.startLine).toBe(expectedJson + 1);
     const parsed = extractParsedFile(pythonProvider, notebook, 'analysis.ipynb');
     expect(parsed).toBeDefined();
     expect(parsed!.localDefs.some((d) => d.qualifiedName === 'train' || d.name === 'train')).toBe(