diff --git a/__tests__/unit/node/markdown/plugins/include.test.ts b/__tests__/unit/node/markdown/plugins/include.test.ts
index 5a7813ee..b9567b26 100644
--- a/__tests__/unit/node/markdown/plugins/include.test.ts
+++ b/__tests__/unit/node/markdown/plugins/include.test.ts
@@ -571,9 +571,9 @@ describe('node/markdown/plugins/include', () => {
         '---\ntitle: x\n---\n\n# Guide\n\n<!-- @include: ./sub/part.md -->\n\npara [a](./a)\nand [b](./b)\n'
       )
       expect(locs).toEqual([
-        { file: path.join(root, 'sub/part.md'), line: 5, column: 1 },
-        { file: path.join(root, 'index.md'), line: 9, column: 6 },
-        { file: path.join(root, 'index.md'), line: 10, column: 5 }
+        { file: slash(path.join(root, 'sub/part.md')), line: 5, column: 1 },
+        { file: slash(path.join(root, 'index.md')), line: 9, column: 6 },
+        { file: slash(path.join(root, 'index.md')), line: 10, column: 5 }
       ])
     })
 
@@ -583,7 +583,7 @@ describe('node/markdown/plugins/include', () => {
 
       const { locs } = await renderLocs('<!-- @include: ./a/one.md -->\n')
       expect(locs).toEqual([
-        { file: path.join(root, 'b/two.md'), line: 1, column: 5 }
+        { file: slash(path.join(root, 'b/two.md')), line: 1, column: 5 }
       ])
     })
 
@@ -597,7 +597,7 @@ describe('node/markdown/plugins/include', () => {
         '<!-- @include: ./sub/part.md#sec -->\n'
       )
       expect(locs).toEqual([
-        { file: path.join(root, 'sub/part.md'), line: 6, column: 4 }
+        { file: slash(path.join(root, 'sub/part.md')), line: 6, column: 4 }
       ])
     })
 
@@ -608,7 +608,7 @@ describe('node/markdown/plugins/include', () => {
         '<!-- @include: ./sub/part.md{2,2} -->\n'
       )
       expect(locs).toEqual([
-        { file: path.join(root, 'sub/part.md'), line: 2, column: 5 }
+        { file: slash(path.join(root, 'sub/part.md')), line: 2, column: 5 }
       ])
     })
 
@@ -623,7 +623,7 @@ describe('node/markdown/plugins/include', () => {
       // location at all; the included file's own subsequent lines resolve
       // exactly
       expect(locs).toEqual([
-        { file: path.join(root, 'sub/part.md'), line: 2, column: 6 }
+        { file: slash(path.join(root, 'sub/part.md')), line: 2, column: 6 }
       ])
     })
 
@@ -656,7 +656,7 @@ describe('node/markdown/plugins/include', () => {
         include: { silent: true }
       })
       expect(env.lineMap!.resolve(0)).toEqual({
-        file: path.join(root, 'index.md'),
+        file: slash(path.join(root, 'index.md')),
         line: 0
       })
     })
@@ -666,14 +666,14 @@ describe('node/markdown/plugins/include', () => {
 
       const { locs } = await renderLocs('<!-- @include: ./sub/part.md -->\n')
       expect(locs).toEqual([
-        { file: path.join(root, 'sub/part.md'), line: 2, column: 8 }
+        { file: slash(path.join(root, 'sub/part.md')), line: 2, column: 8 }
       ])
     })
 
     test('pages without includes get an identity line map', async () => {
       const { env } = await render('# Hi\n\n[a](./a)\n')
       expect(env.lineMap!.resolve(2)).toEqual({
-        file: path.join(root, 'index.md'),
+        file: slash(path.join(root, 'index.md')),
         line: 2
       })
     })
diff --git a/__tests__/unit/node/markdownToVue.test.ts b/__tests__/unit/node/markdownToVue.test.ts
index add8a2d3..e14a9462 100644
--- a/__tests__/unit/node/markdownToVue.test.ts
+++ b/__tests__/unit/node/markdownToVue.test.ts
@@ -5,6 +5,7 @@ import path from 'node:path'
 import { resolveConfig } from 'node/config'
 import { disposeMdItInstance } from 'node/markdown/markdown'
 import { createMarkdownToVueRenderFn } from 'node/markdownToVue'
+import { slash } from 'node/shared'
 
 describe('node/markdownToVue', () => {
   let root: string | undefined
@@ -39,7 +40,7 @@ describe('node/markdownToVue', () => {
     expect(result.deadLinks).toContainEqual({
       url: './missing.md',
       resolved: '/missing',
-      file,
+      file: slash(file),
       line: 5,
       column: 1
     })
@@ -69,7 +70,7 @@ describe('node/markdownToVue', () => {
     expect(result.deadLinks).toContainEqual({
       url: './missing.md',
       resolved: '/missing',
-      file,
+      file: slash(file),
       line: 8,
       column: 1
     })
@@ -105,13 +106,13 @@ describe('node/markdownToVue', () => {
       {
         url: './nope',
         resolved: '/nope',
-        file: partial,
+        file: slash(partial),
         line: 5,
         column: 1,
-        via: file
+        via: slash(file)
       },
-      { url: './a', resolved: '/a', file, line: 9, column: 6 },
-      { url: './b', resolved: '/b', file, line: 10, column: 5 }
+      { url: './a', resolved: '/a', file: slash(file), line: 9, column: 6 },
+      { url: './b', resolved: '/b', file: slash(file), line: 10, column: 5 }
     ])
   })
 
@@ -173,8 +174,8 @@ describe('node/markdownToVue', () => {
     const result = await render(src, file)
 
     expect(calls).toEqual([
-      ['./skip.md', { file, line: 1, column: 1, url: '/skip' }],
-      ['./keep.md', { file, line: 2, column: 5, url: '/keep' }]
+      ['./skip.md', { file: slash(file), line: 1, column: 1, url: '/skip' }],
+      ['./keep.md', { file: slash(file), line: 2, column: 5, url: '/keep' }]
     ])
     expect(result.deadLinks.map((l) => l.url)).toEqual(['./keep.md'])
   })
diff --git a/src/node/markdown/plugins/include.ts b/src/node/markdown/plugins/include.ts
index e9cc4526..22706790 100644
--- a/src/node/markdown/plugins/include.ts
+++ b/src/node/markdown/plugins/include.ts
@@ -66,8 +66,11 @@ export function includePlugin(
   const renderAsync = md.renderAsync.bind(md)
   md.renderAsync = async (src, env?) => {
     const mdEnv = env as MarkdownEnv | undefined
-    const file = mdEnv?.realPath ?? mdEnv?.path
-    if (file == null) return renderAsync(src, env)
+    const rawFile = mdEnv?.realPath ?? mdEnv?.path
+    if (rawFile == null) return renderAsync(src, env)
+    // one separator style for everything stored, compared or reported -
+    // segment files, the ancestor chain and includePath are all posix
+    const file = slash(rawFile)
 
     mdEnv!.includes ??= []
     const expanded = await processIncludes(
@@ -365,7 +368,7 @@ function registerRebaseRules(md: MarkdownItAsync) {
       // the physical file the construct was authored in, resolved through
       // the line map — different from the page means it came from an include
       const sourceFile: string | undefined = token.meta?.vpLoc?.file
-      if (page && sourceFile && sourceFile !== origin) {
+      if (page && sourceFile && origin && sourceFile !== slash(origin)) {
         const attr = rule === 'image' ? 'src' : 'href'
         const url = token.attrGet(attr)
         // a destination resolved from `$frontmatter` belongs to the page the
diff --git a/src/node/markdown/plugins/sourcePositions.ts b/src/node/markdown/plugins/sourcePositions.ts
index 5c85c1d2..3ed1a831 100644
--- a/src/node/markdown/plugins/sourcePositions.ts
+++ b/src/node/markdown/plugins/sourcePositions.ts
@@ -3,7 +3,7 @@ import type MarkdownIt from 'markdown-it'
 import type StateCore from 'markdown-it/lib/rules_core/state_core.mjs'
 import type Token from 'markdown-it/lib/token.mjs'
 
-import type { MarkdownEnv, MarkdownSourceLoc } from '../../shared'
+import { slash, type MarkdownEnv, type MarkdownSourceLoc } from '../../shared'
 
 // consumed source range of an inline token, [start, end) offsets into the
 // inline parser's src. Symbols ride on the token objects themselves, so they
@@ -220,9 +220,13 @@ function sourceLocs(state: StateCore): void {
       // it would be wrong in whichever file it names, so it gets none
       if (resolved?.spliced) continue
 
+      const fallbackFile = env.realPath ?? env.path
       const loc: MarkdownSourceLoc = resolved
         ? { file: resolved.file, line: resolved.line + 1 }
-        : { file: env.realPath ?? env.path, line: line + 1 }
+        : {
+            file: fallbackFile == null ? undefined : slash(fallbackFile),
+            line: line + 1
+          }
 
       // block parsing only ever strips a prefix per line, so the inline line
       // is a suffix of the raw source line; re-align to get the true column
diff --git a/src/node/markdownToVue.ts b/src/node/markdownToVue.ts
index f12031e7..bb55d978 100644
--- a/src/node/markdownToVue.ts
+++ b/src/node/markdownToVue.ts
@@ -60,7 +60,7 @@ export interface DeadLink {
   url: string
   /** the site page path it resolved to, for internal links */
   resolved?: string
-  /** absolute path of the file the link was authored in */
+  /** absolute path of the file the link was authored in, posix-style */
   file: string
   /** 1-based position in `file`, when known */
   line?: number
@@ -204,6 +204,8 @@ export async function createMarkdownToVueRenderFn(
 
     // validate data.links
     const deadLinks: MarkdownCompileResult['deadLinks'] = []
+    // reported alongside line-map files, which are posix-style
+    const sourceFile = slash(fileOrig)
 
     function shouldIgnoreDeadLink(link: MarkdownLink, resolved: string) {
       if (!siteConfig?.ignoreDeadLinks) {
@@ -217,7 +219,7 @@ export async function createMarkdownToVueRenderFn(
       }
 
       const context: DeadLinkContext = {
-        file: link.loc?.file ?? fileOrig,
+        file: link.loc?.file ?? sourceFile,
         line: link.loc?.line,
         column: link.loc?.column,
         url: resolved
@@ -273,10 +275,11 @@ export async function createMarkdownToVueRenderFn(
           deadLinks.push({
             url: link.raw,
             ...(resolvedPath != null && { resolved: resolvedPath }),
-            file: loc?.file ?? fileOrig,
+            file: loc?.file ?? sourceFile,
             ...(loc != null && { line: loc.line }),
             ...(loc?.column != null && { column: loc.column }),
-            ...(loc?.file != null && loc.file !== fileOrig && { via: fileOrig })
+            ...(loc?.file != null &&
+              loc.file !== sourceFile && { via: sourceFile })
           })
         }
       }