diff --git a/libraries/overleaf-editor-core/lib/operation/index.js b/libraries/overleaf-editor-core/lib/operation/index.js
index ae7f2bcf01..47b08c37a6 100644
--- a/libraries/overleaf-editor-core/lib/operation/index.js
+++ b/libraries/overleaf-editor-core/lib/operation/index.js
@@ -35,7 +35,8 @@ class Operation {
     if (
       'textOperation' in raw ||
       'commentId' in raw ||
-      'deleteComment' in raw
+      'deleteComment' in raw ||
+      'noOp' in raw
     ) {
       return EditFileOperation.fromRaw(raw)
     }
diff --git a/libraries/overleaf-editor-core/test/unit/edit_file_operation.test.js b/libraries/overleaf-editor-core/test/unit/edit_file_operation.test.js
index 1ed1ab4a71..3538c68c79 100644
--- a/libraries/overleaf-editor-core/test/unit/edit_file_operation.test.js
+++ b/libraries/overleaf-editor-core/test/unit/edit_file_operation.test.js
@@ -78,4 +78,18 @@ describe('EditFileOperation', function () {
       expect(editFileOperation1).to.deep.equal(edit('foo.tex', ['x']))
     })
   })
+
+  describe('fromRaw / toRaw', function () {
+    it('round-trips an edit no-op', function () {
+      const editFileOperation = Operation.editFile(
+        'foo.tex',
+        EditOperationBuilder.fromJSON({ noOp: true })
+      )
+      const raw = editFileOperation.toRaw()
+      expect(raw).to.eql({ pathname: 'foo.tex', noOp: true })
+
+      const roundTripped = Operation.fromRaw(raw)
+      expect(roundTripped).to.deep.equal(editFileOperation)
+    })
+  })
 })
diff --git a/libraries/validation-tools/package.json b/libraries/validation-tools/package.json
index f951940ce5..0d0c41ee73 100644
--- a/libraries/validation-tools/package.json
+++ b/libraries/validation-tools/package.json
@@ -24,6 +24,7 @@
     "zod-validation-error": "^4.0.1"
   },
   "devDependencies": {
+    "@overleaf/logger": "workspace:*",
     "@types/express": "4.17.23",
     "@types/node": "^24.5.2",
     "eslint": "^10.4.0",
diff --git a/libraries/validation-tools/parseReq.js b/libraries/validation-tools/parseReq.js
index 7781866c10..9a313980d8 100644
--- a/libraries/validation-tools/parseReq.js
+++ b/libraries/validation-tools/parseReq.js
@@ -179,7 +179,12 @@ function sanitizeIssues(issues, depth = 0) {
       path: issue.path.map(seg => String(seg).slice(0, 64)).join('.'),
       message: String(issue.message).slice(0, 200),
     }
-    if (issue.code === 'invalid_union' && depth < 2) {
+    // Bounded by schema shape, not user input: each level corresponds to one
+    // more union nested inside a union member (e.g. rawOperation -> rawFile
+    // -> rawFileMetadata -> the linked-file provider discriminatedUnion), so
+    // raising this cannot be exploited to grow log volume from adversarial
+    // input the way an unbounded path/array traversal could.
+    if (issue.code === 'invalid_union' && depth < 5) {
       sanitized.errors = issue.errors.map(nested =>
         sanitizeIssues(nested, depth + 1)
       )
@@ -222,7 +227,7 @@ function logSchemaFailure(req, schema, kind, issues) {
     .join('\n')
 
   logger.warn(
-    { location, kind, issues: sanitizedIssues, caller },
+    { location, kind, issues: sanitizedIssues, caller, req },
     'req-validation: request failed schema in log-only rollout'
   )
 }
diff --git a/libraries/validation-tools/test/unit/src/parseReqLogOnlyRollout.test.ts b/libraries/validation-tools/test/unit/src/parseReqLogOnlyRollout.test.ts
index 5cb95c9e30..fb9a241d41 100644
--- a/libraries/validation-tools/test/unit/src/parseReqLogOnlyRollout.test.ts
+++ b/libraries/validation-tools/test/unit/src/parseReqLogOnlyRollout.test.ts
@@ -8,6 +8,7 @@ import {
   resetReqValidationLoggingForTests,
 } from '../../../parseReq'
 import { zz } from '../../../zodHelpers'
+import serializers from '@overleaf/logger/serializers'
 
 const RAW_BODY = Symbol.for('overleaf.lockdown.rawBody')
 const RAW_QUERY = Symbol.for('overleaf.lockdown.rawQuery')
@@ -56,6 +57,28 @@ function lockedRequest({
 
 type WarnCall = [Record<string, any>, string]
 
+// Mirrors what a real bunyan logger does to each field before writing a log
+// line -- warnMock only records the raw ctx, so assertions on the logged
+// output must run it through the same serializers to see what would actually
+// reach the log (e.g. the req serializer drops req.body).
+function serializedLogOutput(calls: WarnCall[]) {
+  return JSON.stringify(
+    calls.map(([ctx, msg]) => [
+      Object.fromEntries(
+        Object.entries(ctx).map(([key, value]) => [
+          key,
+          key in serializers
+            ? (serializers as Record<string, (v: unknown) => unknown>)[key](
+                value
+              )
+            : value,
+        ])
+      ),
+      msg,
+    ])
+  )
+}
+
 describe('parseReq log-only rollout', () => {
   // This block intentionally runs before anything else in the file calls
   // setLogger(), so the module-level logger is still unset here.
@@ -296,7 +319,7 @@ describe('parseReq log-only rollout', () => {
 
           parseReq(req, schema, { logOnly: true })
 
-          expect(JSON.stringify(warnMock.mock.calls)).not.toContain(
+          expect(serializedLogOutput(warnMock.mock.calls)).not.toContain(
             'SECRET_VALUE_123'
           )
         })
@@ -311,7 +334,7 @@ describe('parseReq log-only rollout', () => {
 
           parseReq(req, schema, { logOnly: true })
 
-          const logged = JSON.stringify(warnMock.mock.calls)
+          const logged = serializedLogOutput(warnMock.mock.calls)
           expect(logged).toContain('extraSecretField')
           expect(logged).not.toContain('TOP_SECRET_VALUE')
         })
@@ -325,7 +348,7 @@ describe('parseReq log-only rollout', () => {
 
           parseReq(req, schema, { logOnly: true })
 
-          const logged = JSON.stringify(warnMock.mock.calls)
+          const logged = serializedLogOutput(warnMock.mock.calls)
           expect(logged).toContain(longKey.slice(0, 64))
           expect(logged).not.toContain(longKey)
         })
@@ -367,10 +390,50 @@ describe('parseReq log-only rollout', () => {
           expect(Array.isArray(unionIssue.errors)).toBe(true)
           expect(unionIssue.errors.length).toBeGreaterThan(0)
 
-          expect(JSON.stringify(warnMock.mock.calls)).not.toContain(
+          expect(serializedLogOutput(warnMock.mock.calls)).not.toContain(
             'UNION_SECRET_VALUE'
           )
         })
+
+        it('expands a union nested 3 levels deep inside other unions', () => {
+          // Mirrors overleaf-editor-core's rawOperation -> rawFile ->
+          // rawFileMetadata shape: a union of objects, one of whose fields is
+          // itself a union of objects, one of whose fields is itself a union.
+          const level3 = z.union([
+            z.strictObject({ a: z.literal('a') }),
+            z.strictObject({ b: z.literal('b') }),
+          ])
+          const level2 = z.union([
+            z.strictObject({ inner: level3 }),
+            z.strictObject({ other: z.string() }),
+          ])
+          const level1 = z.union([
+            z.strictObject({ mid: level2 }),
+            z.strictObject({ different: z.string() }),
+          ])
+          const req = {
+            body: { value: { mid: { inner: { c: 'nope' } } } },
+          } as Request
+          const schema = z.object({ body: z.object({ value: level1 }) })
+
+          parseReq(req, schema, { logOnly: true })
+
+          const [ctx] = warnMock.mock.calls[0] as WarnCall
+          // Walk down: top union (value) -> level1 branch (mid) -> level2
+          // union (inner) -> level3 union, whose own branch errors (unknown
+          // keys "a"/"b" not satisfied by "c") must have survived.
+          const top = ctx.issues.find((i: any) => i.code === 'invalid_union')
+          const level1Errors = top.errors[0] // the "mid" branch
+          const level2Issue = level1Errors.find(
+            (i: any) => i.code === 'invalid_union'
+          )
+          const level2Errors = level2Issue.errors[0] // the "inner" branch
+          const level3Issue = level2Errors.find(
+            (i: any) => i.code === 'invalid_union'
+          )
+          expect(level3Issue.errors).toBeDefined()
+          expect(level3Issue.errors.length).toBeGreaterThan(0)
+        })
       })
     })
 
diff --git a/services/web/app/src/Features/Compile/CompileController.mjs b/services/web/app/src/Features/Compile/CompileController.mjs
index 9b3debb2d3..7a2000b745 100644
--- a/services/web/app/src/Features/Compile/CompileController.mjs
+++ b/services/web/app/src/Features/Compile/CompileController.mjs
@@ -583,7 +583,7 @@ const _CompileController = {
 
   async proxySyncCode(req, res) {
     const { file, line, column } = req.query
-    if (file == null) {
+    if (!file) {
       throw new Error('missing file parameter')
     }
     // Check that we are dealing with a simple file path (this is not
diff --git a/services/web/frontend/extracted-translations.json b/services/web/frontend/extracted-translations.json
index 83fac34879..660829b326 100644
--- a/services/web/frontend/extracted-translations.json
+++ b/services/web/frontend/extracted-translations.json
@@ -2066,6 +2066,7 @@
   "syncing": "",
   "synctex_error_recompile_and_try_again": "",
   "synctex_failed": "",
+  "synctex_switch_files_and_try_again": "",
   "syntax_checks": "",
   "syntax_validation": "",
   "tab_connecting": "",
diff --git a/services/web/frontend/js/features/pdf-preview/components/synctex-toasts.tsx b/services/web/frontend/js/features/pdf-preview/components/synctex-toasts.tsx
index ad0a7f53b9..c37ffe76d3 100644
--- a/services/web/frontend/js/features/pdf-preview/components/synctex-toasts.tsx
+++ b/services/web/frontend/js/features/pdf-preview/components/synctex-toasts.tsx
@@ -28,6 +28,12 @@ export const SynctexRequestErrorToast = () => {
   return <span>{t('synctex_error_recompile_and_try_again')}</span>
 }
 
+export const SynctexNoFileToast = () => {
+  const { t } = useTranslation()
+
+  return <span>{t('synctex_switch_files_and_try_again')}</span>
+}
+
 const generators: GlobalToastGeneratorEntry[] = [
   {
     key: 'synctex:file-error',
@@ -49,6 +55,16 @@ const generators: GlobalToastGeneratorEntry[] = [
       isDismissible: true,
     }),
   },
+  {
+    key: 'synctex:no-file-error',
+    generator: () => ({
+      content: <SynctexNoFileToast />,
+      type: 'warning',
+      autoHide: true,
+      delay: 4000,
+      isDismissible: true,
+    }),
+  },
 ]
 
 export default generators
@@ -72,3 +88,13 @@ export const showSynctexRequestErrorToast = () => {
     })
   )
 }
+
+export const showSynctexNoFileToast = () => {
+  window.dispatchEvent(
+    new CustomEvent('ide:show-toast', {
+      detail: {
+        key: 'synctex:no-file-error',
+      },
+    })
+  )
+}
diff --git a/services/web/frontend/js/features/pdf-preview/hooks/use-synctex.ts b/services/web/frontend/js/features/pdf-preview/hooks/use-synctex.ts
index 5ef488fc8d..38ceabb0e4 100644
--- a/services/web/frontend/js/features/pdf-preview/hooks/use-synctex.ts
+++ b/services/web/frontend/js/features/pdf-preview/hooks/use-synctex.ts
@@ -18,11 +18,12 @@ import { isValidTeXFile } from '@/main/is-valid-tex-file'
 import { PdfScrollPosition } from '@/shared/hooks/use-pdf-scroll-position'
 import {
   showFileErrorToast,
+  showSynctexNoFileToast,
   showSynctexRequestErrorToast,
 } from '@/features/pdf-preview/components/synctex-toasts'
 
 export default function useSynctex(): {
-  syncToPdf: () => void
+  syncToPdf: () => boolean
   syncToCode: ({ visualOffset }: { visualOffset?: number }) => void
   syncToPdfInFlight: boolean
   syncToCodeInFlight: boolean
@@ -150,18 +151,25 @@ export default function useSynctex(): {
 
   const syncToPdf = useCallback(() => {
     const file = getCurrentFilePath()
+    if (!file) {
+      showSynctexNoFileToast()
+      return false
+    }
 
     if (cursorPositionRef.current) {
       const { row, column } = cursorPositionRef.current
 
       const params = new URLSearchParams({
-        file: file ?? '',
+        file,
         line: String(row + 1),
         column: String(column),
       }).toString()
 
       goToPdfLocation(params)
+      return true
     }
+
+    return false
   }, [getCurrentFilePath, goToPdfLocation])
 
   useEventListener(
diff --git a/services/web/frontend/js/features/source-editor/hooks/use-context-menu-items.tsx b/services/web/frontend/js/features/source-editor/hooks/use-context-menu-items.tsx
index 612f283965..12d6652aa7 100644
--- a/services/web/frontend/js/features/source-editor/hooks/use-context-menu-items.tsx
+++ b/services/web/frontend/js/features/source-editor/hooks/use-context-menu-items.tsx
@@ -221,10 +221,14 @@ export const useContextMenuItems = () => {
       method: 'editor-context-menu',
       direction: 'code-location-in-pdf',
     })
-    requestedPdfSyncRef.current = true
-    syncToPdf()
-    view.focus()
-  }, [syncToPdf, view, changeLayout, isEditorOnly])
+
+    if (syncToPdf()) {
+      requestedPdfSyncRef.current = true
+      view.focus()
+    } else {
+      closeMenu()
+    }
+  }, [syncToPdf, view, changeLayout, isEditorOnly, closeMenu])
 
   return {
     closeMenu,
diff --git a/services/web/locales/en.json b/services/web/locales/en.json
index a3587ad5a4..fdaab07611 100644
--- a/services/web/locales/en.json
+++ b/services/web/locales/en.json
@@ -2651,6 +2651,7 @@
   "syncing": "Syncing",
   "synctex_error_recompile_and_try_again": "That didn’t work. Recompile and try again.",
   "synctex_failed": "Couldn’t find the corresponding source file",
+  "synctex_switch_files_and_try_again": "That didn’t work. Try switching files and try again.",
   "syntax_checks": "Syntax checks",
   "syntax_validation": "Code check",
   "tab_connecting": "Connecting with the editor",
diff --git a/services/web/test/frontend/components/pdf-preview/pdf-synctex-controls.spec.tsx b/services/web/test/frontend/components/pdf-preview/pdf-synctex-controls.spec.tsx
index 279dc9b533..376a7bb3f2 100644
--- a/services/web/test/frontend/components/pdf-preview/pdf-synctex-controls.spec.tsx
+++ b/services/web/test/frontend/components/pdf-preview/pdf-synctex-controls.spec.tsx
@@ -1,4 +1,5 @@
 import PdfSynctexControls from '../../../../frontend/js/features/pdf-preview/components/pdf-synctex-controls'
+import { GlobalToasts } from '../../../../frontend/js/features/ide-react/components/global-toasts'
 import { cloneDeep } from 'lodash'
 import { useDetachCompileContext as useCompileContext } from '../../../../frontend/js/shared/context/detach-compile-context'
 import { useFileTreeData } from '../../../../frontend/js/shared/context/file-tree-data-context'
@@ -76,11 +77,11 @@ const WithSelectedEntities = ({
   return null
 }
 
-function mockProviders() {
+function mockProviders(currentDocumentId: string | null = '_root_doc_id') {
   return {
     EditorOpenDocProvider: makeEditorOpenDocProvider({
       openDocName: 'main.tex',
-      currentDocumentId: null,
+      currentDocumentId: currentDocumentId as any,
       currentDocument: {
         doc_id: 'test-doc',
         getSnapshot: () => 'some doc content',
@@ -162,6 +163,50 @@ describe('<PdfSynctexControls/>', function () {
     )
   })
 
+  it('shows an error toast and does not sync when there is no resolvable file path', function () {
+    cy.interceptCompile()
+
+    const scope = mockScope()
+    const providers = mockProviders(null)
+
+    cy.intercept(
+      { pathname: '/project/*/sync/code' },
+      cy.spy().as('syncCodeRequest')
+    )
+
+    cy.mount(
+      <EditorProviders scope={scope} providers={providers}>
+        <WithPosition mockPosition={mockPosition} />
+        <WithSelectedEntities mockSelectedEntities={mockSelectedEntities} />
+        <PdfSynctexControls />
+        <GlobalToasts />
+      </EditorProviders>
+    )
+
+    cy.waitForCompile()
+
+    // mock editor cursor position update
+    cy.window().then(win => {
+      win.dispatchEvent(
+        new CustomEvent('cursor:editor:update', {
+          detail: { row: 100, column: 10 },
+        })
+      )
+    })
+
+    cy.findByRole('button', { name: 'Go to code location in PDF' }).click()
+
+    cy.findByText(
+      'That didn’t work. Try switching files and try again.'
+    ).should('exist')
+
+    cy.findByRole('button', { name: 'Go to code location in PDF' }).should(
+      'not.be.disabled'
+    )
+
+    cy.get('@syncCodeRequest').should('not.have.been.called')
+  })
+
   it('disables button when multiple entities are selected', function () {
     cy.interceptCompile()
 
diff --git a/services/web/test/frontend/features/source-editor/components/codemirror-editor-context-menu.spec.tsx b/services/web/test/frontend/features/source-editor/components/codemirror-editor-context-menu.spec.tsx
index 16e5afc79f..9edb2d39ab 100644
--- a/services/web/test/frontend/features/source-editor/components/codemirror-editor-context-menu.spec.tsx
+++ b/services/web/test/frontend/features/source-editor/components/codemirror-editor-context-menu.spec.tsx
@@ -65,6 +65,34 @@ const MockFileTreeDataProvider: FC<React.PropsWithChildren> = ({
     value={
       {
         selectedEntities: [{ type: 'doc', id: '_root_doc_id' } as any],
+        fileTreeData: {
+          _id: 'root-folder-id',
+          name: 'rootFolder',
+          docs: [{ _id: docId, name: 'test.tex' }],
+          folders: [],
+          fileRefs: [],
+        },
+      } as any
+    }
+  >
+    {children}
+  </FileTreeDataContext.Provider>
+)
+
+const MockEmptyFileTreeDataProvider: FC<React.PropsWithChildren> = ({
+  children,
+}) => (
+  <FileTreeDataContext.Provider
+    value={
+      {
+        selectedEntities: [{ type: 'doc', id: '_root_doc_id' } as any],
+        fileTreeData: {
+          _id: 'root-folder-id',
+          name: 'rootFolder',
+          docs: [],
+          folders: [],
+          fileRefs: [],
+        },
       } as any
     }
   >
@@ -1008,6 +1036,46 @@ describe('editor context menu', { scrollBehavior: false }, function () {
       })
     })
 
+    it('should close the menu and show an error toast when there is no resolvable file path', function () {
+      const scope = mockScope()
+
+      cy.intercept(
+        'GET',
+        '/project/*/sync/code*',
+        cy.spy().as('syncToPdfRequest')
+      )
+
+      cy.mount(
+        <TestContainer>
+          <EditorProviders
+            scope={scope}
+            providers={{
+              DetachCompileProvider: MockDetachCompileProvider,
+              FileTreeDataProvider: MockEmptyFileTreeDataProvider,
+            }}
+          >
+            <GlobalToasts />
+            <CodeMirrorEditor />
+          </EditorProviders>
+        </TestContainer>
+      )
+
+      cy.get('.cm-line').eq(10).rightclick()
+
+      cy.findByRole('menu').within(() => {
+        cy.findByRole('menuitem', { name: /jump to location in pdf/i }).click()
+      })
+
+      cy.findByRole('menu').should('not.exist')
+
+      cy.get('.global-toasts').should(
+        'contain.text',
+        'That didn’t work. Try switching files and try again.'
+      )
+
+      cy.get('@syncToPdfRequest').should('not.have.been.called')
+    })
+
     it('should hide button when visual preview is enabled', function () {
       window.metaAttributesCache.set('ol-splitTestVariants', {
         'editor-context-menu': 'enabled',
diff --git a/yarn.lock b/yarn.lock
index 6f44ae6fec..c5e3a68c5e 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -7870,6 +7870,7 @@ __metadata:
   version: 0.0.0-use.local
   resolution: "@overleaf/validation-tools@workspace:libraries/validation-tools"
   dependencies:
+    "@overleaf/logger": "workspace:*"
     "@overleaf/o-error": "workspace:*"
     "@types/express": "npm:4.17.23"
     "@types/node": "npm:^24.5.2"