From 7cc2f7cab2a360e944e616607a2809683a09b2a8 Mon Sep 17 00:00:00 2001
From: hugo <hugoms@me.com>
Date: Mon, 23 Feb 2026 21:38:12 +0100
Subject: [PATCH] feat: added syntax check

---
 .../components/ScriptsView/ScriptsView.css    |   6 +
 .../components/ScriptsView/ScriptsView.tsx    | 130 +++++++++++++++++-
 src/renderer/i18n/locales/de.json             |   5 +
 src/renderer/i18n/locales/en.json             |   5 +
 src/renderer/i18n/locales/es.json             |   5 +
 src/renderer/i18n/locales/fr.json             |   5 +
 src/renderer/i18n/locales/it.json             |   5 +
 src/renderer/python/PythonRuntimeManager.ts   |  54 +++++++-
 src/renderer/python/pythonRuntime.worker.ts   |  39 ++++++
 src/renderer/python/pythonSyntaxCheck.ts      |  73 ++++++++++
 src/renderer/python/runtimeProtocol.ts        |  15 ++
 .../renderer/components/ScriptsView.test.tsx  |  91 +++++++++++-
 .../python/PythonRuntimeManager.test.ts       |  41 ++++++
 .../pythonSyntaxCheck.integration.test.ts     |  43 ++++++
 14 files changed, 507 insertions(+), 10 deletions(-)
 create mode 100644 src/renderer/python/pythonSyntaxCheck.ts
 create mode 100644 tests/renderer/python/pythonSyntaxCheck.integration.test.ts

diff --git a/src/renderer/components/ScriptsView/ScriptsView.css b/src/renderer/components/ScriptsView/ScriptsView.css
index 5f89456..d50808c 100644
--- a/src/renderer/components/ScriptsView/ScriptsView.css
+++ b/src/renderer/components/ScriptsView/ScriptsView.css
@@ -52,3 +52,9 @@
   font-size: 12px;
   border-radius: 4px;
 }
+
+.scripts-check-button {
+  padding: 4px 12px;
+  font-size: 12px;
+  border-radius: 4px;
+}
diff --git a/src/renderer/components/ScriptsView/ScriptsView.tsx b/src/renderer/components/ScriptsView/ScriptsView.tsx
index 3d58642..c0e0a01 100644
--- a/src/renderer/components/ScriptsView/ScriptsView.tsx
+++ b/src/renderer/components/ScriptsView/ScriptsView.tsx
@@ -1,5 +1,5 @@
-import React, { useEffect, useState } from 'react';
-import MonacoEditor from '@monaco-editor/react';
+import React, { useCallback, useEffect, useRef, useState } from 'react';
+import MonacoEditor, { type Monaco } from '@monaco-editor/react';
 import type { ScriptData } from '../../../main/shared/electronApi';
 import { useAppStore } from '../../store';
 import { BDS_EVENT_SCRIPTS_CHANGED, dispatchWindowEvent } from '../../utils';
@@ -8,6 +8,28 @@ import { useI18n } from '../../i18n';
 import { showToast } from '../Toast';
 import './ScriptsView.css';
 
+type ScriptMonacoEditor = {
+  getModel: () => unknown;
+};
+
+type ScriptMonacoRuntime = {
+  editor: {
+    setModelMarkers: (model: unknown, owner: string, markers: Array<{
+      startLineNumber: number;
+      startColumn: number;
+      endLineNumber: number;
+      endColumn: number;
+      message: string;
+      severity: number;
+    }>) => void;
+  };
+  MarkerSeverity: {
+    Error: number;
+  };
+};
+
+const SCRIPT_SYNTAX_MARKER_OWNER = 'scripts-python-syntax';
+
 const UI_DATE_LOCALE: Record<string, string> = {
   en: 'en-US',
   de: 'de-DE',
@@ -35,6 +57,9 @@ export const ScriptsView: React.FC<ScriptsViewProps> = ({ scriptId }) => {
   const [isSlugManuallyEdited, setIsSlugManuallyEdited] = useState(false);
   const [isRunning, setIsRunning] = useState(false);
   const [isSaving, setIsSaving] = useState(false);
+  const [isCheckingSyntax, setIsCheckingSyntax] = useState(false);
+  const editorRef = useRef<ScriptMonacoEditor | null>(null);
+  const monacoRef = useRef<ScriptMonacoRuntime | null>(null);
 
   const buildCacheKey = (scriptMeta: Pick<ScriptData, 'id' | 'version'>, content: string): string => {
     let hash = 0;
@@ -57,6 +82,87 @@ export const ScriptsView: React.FC<ScriptsViewProps> = ({ scriptId }) => {
     return normalized || 'script';
   };
 
+  const applySyntaxMarkers = useCallback((errors: Array<{
+    line: number;
+    column: number;
+    endLine: number;
+    endColumn: number;
+    message: string;
+  }>) => {
+    const model = editorRef.current?.getModel?.();
+    const monacoRuntime = monacoRef.current;
+
+    if (!model || !monacoRuntime) {
+      return;
+    }
+
+    const markers = errors.map((error) => {
+      const startLineNumber = Math.max(1, Math.floor(error.line || 1));
+      const startColumn = Math.max(1, Math.floor(error.column || 1));
+      const endLineNumber = Math.max(startLineNumber, Math.floor(error.endLine || startLineNumber));
+      const fallbackEndColumn = startColumn + 1;
+      const endColumn = Math.max(startColumn, Math.floor(error.endColumn || fallbackEndColumn));
+
+      return {
+        startLineNumber,
+        startColumn,
+        endLineNumber,
+        endColumn,
+        message: error.message,
+        severity: monacoRuntime.MarkerSeverity.Error,
+      };
+    });
+
+    monacoRuntime.editor.setModelMarkers(model, SCRIPT_SYNTAX_MARKER_OWNER, markers);
+  }, []);
+
+  const handleEditorDidMount = useCallback((editor: unknown, monaco: Monaco) => {
+    editorRef.current = editor as ScriptMonacoEditor;
+    monacoRef.current = monaco as unknown as ScriptMonacoRuntime;
+  }, []);
+
+  const handleCheckSyntax = useCallback(async (options: { notify: boolean } = { notify: true }): Promise<boolean> => {
+    if (!script || isCheckingSyntax) {
+      return false;
+    }
+
+    setIsCheckingSyntax(true);
+    try {
+      const runtimeManager = getPythonRuntimeManager();
+      const syntax = await runtimeManager.syntaxCheck(scriptContent, {
+        cacheKey: buildCacheKey(script, scriptContent),
+      });
+
+      applySyntaxMarkers(syntax.errors);
+
+      if (syntax.errors.length > 0) {
+        if (options.notify) {
+          showToast.error(t('scripts.syntax.invalid', { count: syntax.errors.length }));
+        }
+        return false;
+      }
+
+      if (options.notify) {
+        showToast.success(t('scripts.syntax.valid'));
+      }
+      return true;
+    } catch (error) {
+      const message = error instanceof Error ? error.message : String(error);
+      appendPanelOutputEntry({
+        id: `output-${Date.now()}-syntax-error`,
+        message,
+        createdAt: new Date().toISOString(),
+        kind: 'error',
+      });
+      if (options.notify) {
+        showToast.error(t('scripts.syntax.checkFailed'));
+      }
+      return false;
+    } finally {
+      setIsCheckingSyntax(false);
+    }
+  }, [appendPanelOutputEntry, applySyntaxMarkers, isCheckingSyntax, script, scriptContent, t]);
+
   useEffect(() => {
     let cancelled = false;
 
@@ -162,6 +268,11 @@ export const ScriptsView: React.FC<ScriptsViewProps> = ({ scriptId }) => {
 
     setIsSaving(true);
     try {
+      const isSyntaxValid = await handleCheckSyntax({ notify: true });
+      if (!isSyntaxValid) {
+        return;
+      }
+
       const runtimeManager = getPythonRuntimeManager();
       const discoveredEntrypoints = await runtimeManager.inspectEntrypoints(scriptContent, {
         cacheKey: buildCacheKey(script, scriptContent),
@@ -279,10 +390,6 @@ export const ScriptsView: React.FC<ScriptsViewProps> = ({ scriptId }) => {
         kind: 'error',
       });
     } finally {
-      useAppStore.setState({
-        panelVisible: true,
-        panelActiveTab: 'output',
-      });
       setIsRunning(false);
     }
   };
@@ -312,6 +419,16 @@ export const ScriptsView: React.FC<ScriptsViewProps> = ({ scriptId }) => {
           >
             {t('scripts.run')}
           </button>
+          <button
+            type="button"
+            className="scripts-check-button"
+            onClick={() => {
+              void handleCheckSyntax({ notify: true });
+            }}
+            disabled={!script || isCheckingSyntax || isSaving}
+          >
+            {isCheckingSyntax ? t('scripts.syntax.checking') : t('scripts.syntax.check')}
+          </button>
           <button
             type="button"
             className="secondary danger"
@@ -408,6 +525,7 @@ export const ScriptsView: React.FC<ScriptsViewProps> = ({ scriptId }) => {
             theme="vs-dark"
             value={scriptContent}
             onChange={(value) => setScriptContent(value || '')}
+            onMount={handleEditorDidMount}
             options={{
               minimap: { enabled: false },
               wordWrap: 'on',
diff --git a/src/renderer/i18n/locales/de.json b/src/renderer/i18n/locales/de.json
index b067b84..576777d 100644
--- a/src/renderer/i18n/locales/de.json
+++ b/src/renderer/i18n/locales/de.json
@@ -434,6 +434,11 @@
   "scripts.entrypoint.main": "main",
   "scripts.entrypoint.none": "Keine Funktionen gefunden",
   "scripts.field.enabled": "Aktiviert",
+  "scripts.syntax.check": "Syntax prüfen",
+  "scripts.syntax.checking": "Prüfe...",
+  "scripts.syntax.valid": "Python-Syntax ist gültig",
+  "scripts.syntax.invalid": "Python-Syntaxfehler: {count}",
+  "scripts.syntax.checkFailed": "Python-Syntaxprüfung fehlgeschlagen",
   "scripts.kind.utility": "utility",
   "scripts.kind.macro": "macro",
   "scripts.kind.transform": "transform",
diff --git a/src/renderer/i18n/locales/en.json b/src/renderer/i18n/locales/en.json
index 04bf787..7520bbe 100644
--- a/src/renderer/i18n/locales/en.json
+++ b/src/renderer/i18n/locales/en.json
@@ -434,6 +434,11 @@
   "scripts.entrypoint.main": "main",
   "scripts.entrypoint.none": "No functions found",
   "scripts.field.enabled": "Enabled",
+  "scripts.syntax.check": "Check Syntax",
+  "scripts.syntax.checking": "Checking...",
+  "scripts.syntax.valid": "Python syntax is valid",
+  "scripts.syntax.invalid": "Python syntax errors: {count}",
+  "scripts.syntax.checkFailed": "Python syntax check failed",
   "scripts.kind.utility": "utility",
   "scripts.kind.macro": "macro",
   "scripts.kind.transform": "transform",
diff --git a/src/renderer/i18n/locales/es.json b/src/renderer/i18n/locales/es.json
index 462db6c..9f94f98 100644
--- a/src/renderer/i18n/locales/es.json
+++ b/src/renderer/i18n/locales/es.json
@@ -434,6 +434,11 @@
   "scripts.entrypoint.main": "main",
   "scripts.entrypoint.none": "No se encontraron funciones",
   "scripts.field.enabled": "Habilitado",
+  "scripts.syntax.check": "Comprobar sintaxis",
+  "scripts.syntax.checking": "Comprobando...",
+  "scripts.syntax.valid": "La sintaxis de Python es válida",
+  "scripts.syntax.invalid": "Errores de sintaxis de Python: {count}",
+  "scripts.syntax.checkFailed": "La comprobación de sintaxis de Python falló",
   "scripts.kind.utility": "utility",
   "scripts.kind.macro": "macro",
   "scripts.kind.transform": "transform",
diff --git a/src/renderer/i18n/locales/fr.json b/src/renderer/i18n/locales/fr.json
index 04db7a4..a38f296 100644
--- a/src/renderer/i18n/locales/fr.json
+++ b/src/renderer/i18n/locales/fr.json
@@ -434,6 +434,11 @@
   "scripts.entrypoint.main": "main",
   "scripts.entrypoint.none": "Aucune fonction trouvée",
   "scripts.field.enabled": "Activé",
+  "scripts.syntax.check": "Vérifier la syntaxe",
+  "scripts.syntax.checking": "Vérification...",
+  "scripts.syntax.valid": "La syntaxe Python est valide",
+  "scripts.syntax.invalid": "Erreurs de syntaxe Python : {count}",
+  "scripts.syntax.checkFailed": "Échec de la vérification de la syntaxe Python",
   "scripts.kind.utility": "utility",
   "scripts.kind.macro": "macro",
   "scripts.kind.transform": "transform",
diff --git a/src/renderer/i18n/locales/it.json b/src/renderer/i18n/locales/it.json
index 50da265..c28101d 100644
--- a/src/renderer/i18n/locales/it.json
+++ b/src/renderer/i18n/locales/it.json
@@ -434,6 +434,11 @@
   "scripts.entrypoint.main": "main",
   "scripts.entrypoint.none": "Nessuna funzione trovata",
   "scripts.field.enabled": "Abilitato",
+  "scripts.syntax.check": "Controlla sintassi",
+  "scripts.syntax.checking": "Controllo...",
+  "scripts.syntax.valid": "La sintassi Python è valida",
+  "scripts.syntax.invalid": "Errori di sintassi Python: {count}",
+  "scripts.syntax.checkFailed": "Controllo della sintassi Python non riuscito",
   "scripts.kind.utility": "utility",
   "scripts.kind.macro": "macro",
   "scripts.kind.transform": "transform",
diff --git a/src/renderer/python/PythonRuntimeManager.ts b/src/renderer/python/PythonRuntimeManager.ts
index cb2a52f..a22e296 100644
--- a/src/renderer/python/PythonRuntimeManager.ts
+++ b/src/renderer/python/PythonRuntimeManager.ts
@@ -1,5 +1,6 @@
 import { createPythonRuntimeWorker } from './createPythonRuntimeWorker';
 import type { PythonWorkerMessage, PythonWorkerRequest } from './runtimeProtocol';
+import type { PythonSyntaxError } from './runtimeProtocol';
 import { parseMacroContextV1, parseMacroResultV1, type MacroContextV1, type MacroResultV1 } from './abiV1';
 
 type WorkerFactory = () => Worker;
@@ -10,9 +11,9 @@ interface InitializeDeferred {
 }
 
 interface PendingRun {
-  kind: 'run' | 'macro-v1' | 'inspect-entrypoints';
+  kind: 'run' | 'macro-v1' | 'inspect-entrypoints' | 'syntax-check';
   stdout: string;
-  resolve: (value: PythonRunResult | PythonMacroV1Result | string[]) => void;
+  resolve: (value: PythonRunResult | PythonMacroV1Result | string[] | PythonSyntaxCheckResult) => void;
   reject: (error: Error) => void;
   timeoutId: ReturnType<typeof setTimeout> | null;
 }
@@ -43,6 +44,10 @@ export interface PythonMacroV1Result {
   stdout: string;
 }
 
+export interface PythonSyntaxCheckResult {
+  errors: PythonSyntaxError[];
+}
+
 export class PythonRuntimeManager {
   private worker: Worker | null = null;
   private initializingPromise: Promise<void> | null = null;
@@ -197,6 +202,42 @@ export class PythonRuntimeManager {
     });
   }
 
+  async syntaxCheck(code: string, options?: PythonExecuteOptions): Promise<PythonSyntaxCheckResult> {
+    await this.initialize();
+
+    if (!this.worker || !this.ready) {
+      throw new Error('Python runtime is not ready');
+    }
+
+    const requestId = this.nextRequestId();
+    const timeoutMs = options?.timeoutMs ?? 5000;
+
+    return new Promise<PythonSyntaxCheckResult>((resolve, reject) => {
+      const timeoutId = setTimeout(() => {
+        this.pendingRuns.delete(requestId);
+        this.resetRuntime(`Python script execution timed out after ${timeoutMs}ms`);
+        reject(new Error(`Python script execution timed out after ${timeoutMs}ms`));
+      }, timeoutMs);
+
+      this.pendingRuns.set(requestId, {
+        kind: 'syntax-check',
+        stdout: '',
+        resolve: (value) => resolve(value as PythonSyntaxCheckResult),
+        reject,
+        timeoutId,
+      });
+
+      const message: PythonWorkerRequest = {
+        type: 'syntaxCheck',
+        requestId,
+        code,
+        cacheKey: options?.cacheKey,
+      };
+
+      this.worker!.postMessage(message);
+    });
+  }
+
   isReady(): boolean {
     return this.ready;
   }
@@ -252,6 +293,15 @@ export class PythonRuntimeManager {
       return;
     }
 
+    if (payload.type === 'syntaxResult') {
+      if (pendingRun.kind !== 'syntax-check') {
+        pendingRun.reject(new Error('Invalid response type for pending syntax check request'));
+        return;
+      }
+      pendingRun.resolve({ errors: payload.errors });
+      return;
+    }
+
     if (payload.type === 'macroResult') {
       if (pendingRun.kind !== 'macro-v1') {
         pendingRun.reject(new Error('Invalid response type for pending run request'));
diff --git a/src/renderer/python/pythonRuntime.worker.ts b/src/renderer/python/pythonRuntime.worker.ts
index d27bf54..1a30478 100644
--- a/src/renderer/python/pythonRuntime.worker.ts
+++ b/src/renderer/python/pythonRuntime.worker.ts
@@ -2,6 +2,7 @@ import { loadPyodide, type PyodideInterface } from 'pyodide';
 import type { PythonWorkerMessage, PythonWorkerRequest } from './runtimeProtocol';
 import { parseMacroContextV1, parseMacroResultV1 } from './abiV1';
 import { resolvePyodideIndexURL } from './pyodideAssetUrl';
+import { runPythonSyntaxCheck } from './pythonSyntaxCheck';
 
 let runtime: PyodideInterface | null = null;
 let activeRequestId: string | null = null;
@@ -181,6 +182,39 @@ json.dumps(__bds_entrypoints)
   }
 }
 
+async function syntaxCheck(request: PythonWorkerRequest): Promise<void> {
+  if (request.type !== 'syntaxCheck') {
+    return;
+  }
+
+  if (!runtime) {
+    postRuntimeMessage({ type: 'runError', requestId: request.requestId, error: 'Python runtime is not ready' });
+    return;
+  }
+
+  if (activeRequestId) {
+    postRuntimeMessage({ type: 'runError', requestId: request.requestId, error: 'Python runtime is busy' });
+    return;
+  }
+
+  activeRequestId = request.requestId;
+
+  try {
+    const errors = await runPythonSyntaxCheck(runtime, request.code);
+
+    postRuntimeMessage({
+      type: 'syntaxResult',
+      requestId: request.requestId,
+      errors,
+    });
+  } catch (error) {
+    const message = error instanceof Error ? error.message : String(error);
+    postRuntimeMessage({ type: 'runError', requestId: request.requestId, error: message });
+  } finally {
+    activeRequestId = null;
+  }
+}
+
 async function bootstrapRuntime(): Promise<void> {
   try {
     const indexURL = resolvePyodideIndexURL(import.meta.url);
@@ -217,6 +251,11 @@ self.onmessage = (event: MessageEvent<PythonWorkerRequest>) => {
 
   if (request.type === 'inspectEntrypoints') {
     void inspectEntrypoints(request);
+    return;
+  }
+
+  if (request.type === 'syntaxCheck') {
+    void syntaxCheck(request);
   }
 };
 
diff --git a/src/renderer/python/pythonSyntaxCheck.ts b/src/renderer/python/pythonSyntaxCheck.ts
new file mode 100644
index 0000000..18cd5bf
--- /dev/null
+++ b/src/renderer/python/pythonSyntaxCheck.ts
@@ -0,0 +1,73 @@
+import type { PyodideInterface } from 'pyodide';
+import type { PythonSyntaxError } from './runtimeProtocol';
+
+const SYNTAX_CHECK_SCRIPT = [
+  'import ast',
+  'import json',
+  '',
+  '__bds_syntax_errors = []',
+  'try:',
+  '    ast.parse(__bds_syntax_source)',
+  'except SyntaxError as exc:',
+  '    line = exc.lineno or 1',
+  '    column = exc.offset or 1',
+  '    end_line = getattr(exc, "end_lineno", None) or line',
+  '    end_column = getattr(exc, "end_offset", None) or (column + 1)',
+  '    __bds_syntax_errors.append({',
+  '        "line": line,',
+  '        "column": column,',
+  '        "endLine": end_line,',
+  '        "endColumn": end_column,',
+  '        "message": exc.msg or "invalid syntax",',
+  '    })',
+  '__bds_syntax_result_json = json.dumps({"errors": __bds_syntax_errors})',
+  '__bds_syntax_result_json',
+].join('\n');
+
+function toResultString(result: unknown): string {
+  if (typeof result === 'string') {
+    return result;
+  }
+
+  if (result === null || result === undefined) {
+    return '';
+  }
+
+  return String(result);
+}
+
+function parseSyntaxErrors(rawJsonResult: unknown): PythonSyntaxError[] {
+  const rawText = toResultString(rawJsonResult).trim();
+  if (rawText.length === 0) {
+    throw new Error('Python syntax check returned no JSON result');
+  }
+
+  const parsed = JSON.parse(rawText) as { errors?: unknown };
+  if (!Array.isArray(parsed.errors)) {
+    return [];
+  }
+
+  return parsed.errors
+    .filter((item): item is PythonSyntaxError => {
+      return item
+        && typeof item === 'object'
+        && Number.isFinite((item as { line?: number }).line)
+        && Number.isFinite((item as { column?: number }).column)
+        && Number.isFinite((item as { endLine?: number }).endLine)
+        && Number.isFinite((item as { endColumn?: number }).endColumn)
+        && typeof (item as { message?: unknown }).message === 'string';
+    })
+    .map((item) => ({
+      line: Math.max(1, Math.floor(item.line)),
+      column: Math.max(1, Math.floor(item.column)),
+      endLine: Math.max(1, Math.floor(item.endLine)),
+      endColumn: Math.max(1, Math.floor(item.endColumn)),
+      message: item.message,
+    }));
+}
+
+export async function runPythonSyntaxCheck(runtime: PyodideInterface, sourceCode: string): Promise<PythonSyntaxError[]> {
+  runtime.globals.set('__bds_syntax_source', sourceCode);
+  const rawJsonResult = await runtime.runPythonAsync(SYNTAX_CHECK_SCRIPT);
+  return parseSyntaxErrors(rawJsonResult);
+}
diff --git a/src/renderer/python/runtimeProtocol.ts b/src/renderer/python/runtimeProtocol.ts
index 020e427..4d46735 100644
--- a/src/renderer/python/runtimeProtocol.ts
+++ b/src/renderer/python/runtimeProtocol.ts
@@ -20,13 +20,28 @@ export type PythonWorkerRequest =
       requestId: string;
       code: string;
       cacheKey?: string;
+    }
+  | {
+      type: 'syntaxCheck';
+      requestId: string;
+      code: string;
+      cacheKey?: string;
     };
 
+export interface PythonSyntaxError {
+  line: number;
+  column: number;
+  endLine: number;
+  endColumn: number;
+  message: string;
+}
+
 export type PythonWorkerMessage =
   | { type: 'ready' }
   | { type: 'error'; error: string }
   | { type: 'stdout'; requestId: string; chunk: string }
   | { type: 'runResult'; requestId: string; result: string }
   | { type: 'entrypoints'; requestId: string; entrypoints: string[] }
+  | { type: 'syntaxResult'; requestId: string; errors: PythonSyntaxError[] }
   | { type: 'macroResult'; requestId: string; result: MacroResultV1 }
   | { type: 'runError'; requestId: string; error: string };
diff --git a/tests/renderer/components/ScriptsView.test.tsx b/tests/renderer/components/ScriptsView.test.tsx
index 149bfb7..100879d 100644
--- a/tests/renderer/components/ScriptsView.test.tsx
+++ b/tests/renderer/components/ScriptsView.test.tsx
@@ -6,15 +6,31 @@ import { useAppStore } from '../../../src/renderer/store';
 
 const executeMock = vi.fn();
 const inspectEntrypointsMock = vi.fn();
+const syntaxCheckMock = vi.fn();
 const monacoPropsSpy = vi.fn();
+const setModelMarkersMock = vi.fn();
 
 vi.mock('@monaco-editor/react', () => ({
   default: (props: {
     value?: string;
     onChange?: (value?: string) => void;
     language?: string;
+    onMount?: (editor: unknown, monaco: unknown) => void;
   }) => {
     monacoPropsSpy(props);
+    props.onMount?.(
+      {
+        getModel: () => ({ uri: 'inmemory://script.py' }),
+      },
+      {
+        editor: {
+          setModelMarkers: setModelMarkersMock,
+        },
+        MarkerSeverity: {
+          Error: 8,
+        },
+      },
+    );
     return (
       <textarea
         aria-label="Script Content"
@@ -29,6 +45,7 @@ vi.mock('../../../src/renderer/python/runtimeManagerInstance', () => ({
   getPythonRuntimeManager: () => ({
     execute: executeMock,
     inspectEntrypoints: inspectEntrypointsMock,
+    syntaxCheck: syntaxCheckMock,
   }),
 }));
 
@@ -38,6 +55,7 @@ describe('ScriptsView', () => {
 
     executeMock.mockResolvedValue({ result: '2', stdout: 'hello\n' });
     inspectEntrypointsMock.mockResolvedValue(['render', 'helper']);
+    syntaxCheckMock.mockResolvedValue({ errors: [] });
 
     (window as any).electronAPI = {
       ...(window as any).electronAPI,
@@ -232,12 +250,81 @@ describe('ScriptsView', () => {
     });
 
     const state = useAppStore.getState();
-    expect(state.panelVisible).toBe(true);
-    expect(state.panelActiveTab).toBe('output');
+    expect(state.panelVisible).toBe(false);
+    expect(state.panelActiveTab).toBe('tasks');
     expect(state.panelOutputEntries.length).toBeGreaterThan(0);
     expect(state.panelOutputEntries[state.panelOutputEntries.length - 1].message).toContain('hello');
   });
 
+  it('checks syntax manually and writes editor markers for syntax errors', async () => {
+    syntaxCheckMock.mockResolvedValueOnce({
+      errors: [
+        {
+          line: 3,
+          column: 5,
+          endLine: 3,
+          endColumn: 10,
+          message: 'invalid syntax',
+        },
+      ],
+    });
+
+    render(<ScriptsView scriptId="script-1" />);
+
+    await screen.findByLabelText('Script Content');
+    fireEvent.click(screen.getByRole('button', { name: 'Check Syntax' }));
+
+    await vi.waitFor(() => {
+      expect(syntaxCheckMock).toHaveBeenCalledWith('print("hello")', {
+        cacheKey: expect.stringMatching(/^script-1:1:/),
+      });
+      expect(setModelMarkersMock).toHaveBeenCalledWith(
+        expect.anything(),
+        'scripts-python-syntax',
+        [
+          expect.objectContaining({
+            startLineNumber: 3,
+            startColumn: 5,
+            endLineNumber: 3,
+            endColumn: 10,
+            message: 'invalid syntax',
+          }),
+        ],
+      );
+    });
+  });
+
+  it('runs syntax check automatically on save before updating script', async () => {
+    const updateMock = vi.fn().mockResolvedValue({
+      id: 'script-1',
+      projectId: 'default',
+      slug: 'hello_script',
+      title: 'Hello Script',
+      kind: 'utility',
+      entrypoint: 'render',
+      enabled: true,
+      version: 2,
+      filePath: '/tmp/hello-script.py',
+      content: 'print("hello")',
+      createdAt: '2026-02-22T00:00:00.000Z',
+      updatedAt: '2026-02-22T00:01:00.000Z',
+    });
+    (window as any).electronAPI.scripts.update = updateMock;
+
+    render(<ScriptsView scriptId="script-1" />);
+
+    const titleInput = await screen.findByLabelText('Title');
+    fireEvent.change(titleInput, { target: { value: 'Hello Script Updated' } });
+    fireEvent.click(screen.getByRole('button', { name: 'Save Script' }));
+
+    await vi.waitFor(() => {
+      expect(syntaxCheckMock).toHaveBeenCalledWith('print("hello")', {
+        cacheKey: expect.stringMatching(/^script-1:1:/),
+      });
+      expect(updateMock).toHaveBeenCalled();
+    });
+  });
+
   it('runs selected non-main entrypoint function', async () => {
     render(<ScriptsView scriptId="script-1" />);
 
diff --git a/tests/renderer/python/PythonRuntimeManager.test.ts b/tests/renderer/python/PythonRuntimeManager.test.ts
index 233557e..9484f23 100644
--- a/tests/renderer/python/PythonRuntimeManager.test.ts
+++ b/tests/renderer/python/PythonRuntimeManager.test.ts
@@ -134,6 +134,47 @@ describe('PythonRuntimeManager', () => {
     await expect(inspectPromise).resolves.toEqual(['render', 'helper']);
   });
 
+  it('checks syntax and returns structured syntax errors', async () => {
+    const worker = new MockWorker();
+    const manager = new PythonRuntimeManager(() => worker as unknown as Worker);
+
+    const initPromise = manager.initialize();
+    worker.emitMessage({ type: 'ready' });
+    await initPromise;
+
+    const syntaxPromise = manager.syntaxCheck('def broken(:\n  pass');
+    await Promise.resolve();
+
+    const request = worker.postedMessages[0] as { type: string; requestId: string; code: string };
+    expect(request.type).toBe('syntaxCheck');
+
+    worker.emitMessage({
+      type: 'syntaxResult',
+      requestId: request.requestId,
+      errors: [
+        {
+          line: 1,
+          column: 11,
+          endLine: 1,
+          endColumn: 12,
+          message: 'invalid syntax',
+        },
+      ],
+    });
+
+    await expect(syntaxPromise).resolves.toEqual({
+      errors: [
+        {
+          line: 1,
+          column: 11,
+          endLine: 1,
+          endColumn: 12,
+          message: 'invalid syntax',
+        },
+      ],
+    });
+  });
+
   it('rejects when runtime returns run error', async () => {
     const worker = new MockWorker();
     const manager = new PythonRuntimeManager(() => worker as unknown as Worker);
diff --git a/tests/renderer/python/pythonSyntaxCheck.integration.test.ts b/tests/renderer/python/pythonSyntaxCheck.integration.test.ts
new file mode 100644
index 0000000..b397e5e
--- /dev/null
+++ b/tests/renderer/python/pythonSyntaxCheck.integration.test.ts
@@ -0,0 +1,43 @@
+import { beforeAll, describe, expect, it } from 'vitest';
+import { loadPyodide, type PyodideInterface } from 'pyodide';
+import { runPythonSyntaxCheck } from '../../../src/renderer/python/pythonSyntaxCheck';
+
+describe('pythonSyntaxCheck integration (real pyodide)', () => {
+  let runtime: PyodideInterface;
+
+  beforeAll(async () => {
+    runtime = await loadPyodide();
+  }, 60000);
+
+  it('returns no errors for syntactically valid python', async () => {
+    const source = [
+      'def normalize_blogmark(post):',
+      '    title = (post.get("title") or "").strip()',
+      '    if title:',
+      '        post["title"] = title',
+      '    return post',
+      '',
+    ].join('\n');
+
+    const errors = await runPythonSyntaxCheck(runtime, source);
+
+    expect(errors).toEqual([]);
+  });
+
+  it('returns structured syntax diagnostics for invalid python', async () => {
+    const source = [
+      'def normalize_blogmark(post):',
+      '    if post.get("title")',
+      '        return post',
+      '',
+    ].join('\n');
+
+    const errors = await runPythonSyntaxCheck(runtime, source);
+
+    expect(errors.length).toBeGreaterThan(0);
+    expect(errors[0]).toEqual(expect.objectContaining({
+      line: 2,
+      message: expect.any(String),
+    }));
+  });
+});