diff --git a/lib/data.js b/lib/data.js
index c11873c7084264208c01abd66ee4a5c43e9e9aee..0858ce94961c27e880dbe6226b44a36e4553ed2f 100644
--- a/lib/data.js
+++ b/lib/data.js
@@ -49,6 +49,28 @@ const v8_to_istanbul_1 = __importDefault(require("v8-to-istanbul"));
 const convertSourceMap = __importStar(require("convert-source-map"));
 exports.attachmentName = '@bgotink/playwright-coverage';
 const fetch = import('node-fetch');
+async function tryReadLocalSourceMap(url) {
+    try {
+        const parsed = new url_1.URL(url);
+        const urlPath = parsed.pathname.replace(/^\//, '');
+        const candidates = [
+            (0, path_1.join)(process.cwd(), 'dist', urlPath),
+            (0, path_1.join)(process.cwd(), urlPath),
+        ];
+        for (const candidate of candidates) {
+            try {
+                return await fs_1.promises.readFile(candidate, 'utf8');
+            }
+            catch {
+                // try next candidate
+            }
+        }
+    }
+    catch {
+        // invalid URL
+    }
+    return null;
+}
 async function getSourceMap(url, source) {
     const inlineMap = convertSourceMap.fromSource(source);
     if (inlineMap != null) {
@@ -72,10 +94,19 @@ async function getSourceMap(url, source) {
                     return dataString;
                 }
                 default: {
-                    const response = await (await fetch).default(resolved.href, {
-                        method: 'GET',
-                    });
-                    return await response.text();
+                    try {
+                        const response = await (await fetch).default(resolved.href, {
+                            method: 'GET',
+                        });
+                        return await response.text();
+                    }
+                    catch {
+                        const local = await tryReadLocalSourceMap(resolved.href);
+                        if (local != null) {
+                            return local;
+                        }
+                        throw new Error(`Failed to fetch sourcemap: ${resolved.href}`);
+                    }
                 }
             }
         });
@@ -94,6 +125,15 @@ async function getSourceMap(url, source) {
         return (await response.json());
     }
     catch {
+        try {
+            const local = await tryReadLocalSourceMap(`${url}.map`);
+            if (local != null) {
+                return JSON.parse(local);
+            }
+        }
+        catch {
+            // ignore
+        }
         return undefined;
     }
 }
@@ -104,10 +144,40 @@ async function convertToIstanbulCoverage(v8Coverage, sources, sourceMaps, exclud
     const istanbulCoverage = (0, istanbul_lib_coverage_1.createCoverageMap)({});
     for (const script of v8Coverage.result) {
         const source = sources.get(script.url);
-        const sourceMap = sourceMaps.get(script.url);
+        let sourceMap = sourceMaps.get(script.url);
         if (source == null || !(sourceMap === null || sourceMap === void 0 ? void 0 : sourceMap.mappings)) {
             continue;
         }
+        // Rewrite sourcemap sources from build-output-relative paths to
+        // project-relative paths. Vite emits sources like "../../src/foo.ts"
+        // relative to dist/assets/. Resolve them against the script URL to
+        // get server-absolute paths, then strip the origin.
+        if (sourceMap.sources != null) {
+            const scriptUrl = script.url;
+            try {
+                const origin = new url_1.URL(scriptUrl).origin;
+                sourceMap = {
+                    ...sourceMap,
+                    sources: sourceMap.sources.map(s => {
+                        if (s == null)
+                            return s;
+                        try {
+                            const resolved = new url_1.URL(s, scriptUrl).href;
+                            if (resolved.startsWith(origin + '/')) {
+                                return resolved.slice(origin.length + 1);
+                            }
+                        }
+                        catch {
+                            // not a valid URL combo
+                        }
+                        return s;
+                    }),
+                };
+            }
+            catch {
+                // scriptUrl is not a valid URL — skip rewriting
+            }
+        }
         function sanitizePath(path) {
             let url;
             try {
diff --git a/src/data.ts b/src/data.ts
index 539a70e5bde5c2ab8644b0bfa3ff52625cf4490e..29bc26bf729cbf9496594d9b9e91745a095658c5 100644
--- a/src/data.ts
+++ b/src/data.ts
@@ -12,6 +12,33 @@ export const attachmentName = '@bgotink/playwright-coverage';
 
 const fetch = import('node-fetch');
 
+/**
+ * Try to read a sourcemap from the local filesystem by mapping a URL path
+ * (e.g. /assets/index-abc.js.map) to a local file (e.g. dist/assets/index-abc.js.map).
+ * Falls back to common build output directories.
+ */
+async function tryReadLocalSourceMap(url: string): Promise<string | null> {
+  try {
+    const parsed = new URL(url);
+    // Try mapping URL pathname to dist/ directory
+    const urlPath = parsed.pathname.replace(/^\//, '');
+    const candidates = [
+      join(process.cwd(), 'dist', urlPath),
+      join(process.cwd(), urlPath),
+    ];
+    for (const candidate of candidates) {
+      try {
+        return await fs.readFile(candidate, 'utf8');
+      } catch {
+        // try next candidate
+      }
+    }
+  } catch {
+    // invalid URL
+  }
+  return null;
+}
+
 export async function getSourceMap(
   url: string,
   source: string,
@@ -44,13 +71,23 @@ export async function getSourceMap(
             return dataString;
           }
           default: {
-            const response = await (
-              await fetch
-            ).default(resolved.href, {
-              method: 'GET',
-            });
+            // Try HTTP fetch first, fall back to reading from local filesystem
+            try {
+              const response = await (
+                await fetch
+              ).default(resolved.href, {
+                method: 'GET',
+              });
 
-            return await response.text();
+              return await response.text();
+            } catch {
+              // HTTP fetch failed — try reading from local dist/ directory
+              const local = await tryReadLocalSourceMap(resolved.href);
+              if (local != null) {
+                return local;
+              }
+              throw new Error(`Failed to fetch sourcemap: ${resolved.href}`);
+            }
           }
         }
       },
@@ -73,6 +110,15 @@ export async function getSourceMap(
 
     return (await response.json()) as EncodedSourceMap;
   } catch {
+    // HTTP fetch failed — try reading from local dist/ directory
+    try {
+      const local = await tryReadLocalSourceMap(`${url}.map`);
+      if (local != null) {
+        return JSON.parse(local) as EncodedSourceMap;
+      }
+    } catch {
+      // ignore
+    }
     return undefined;
   }
 }
@@ -102,12 +148,41 @@ export async function convertToIstanbulCoverage(
 
   for (const script of v8Coverage.result) {
     const source = sources.get(script.url);
-    const sourceMap = sourceMaps.get(script.url);
+    let sourceMap = sourceMaps.get(script.url);
 
     if (source == null || !sourceMap?.mappings) {
       continue;
     }
 
+    // Rewrite sourcemap sources from build-output-relative paths to
+    // project-relative paths. Vite emits sources like "../../src/foo.ts"
+    // relative to dist/assets/. Resolve them against the script URL to
+    // get server-absolute paths, then strip the origin to get
+    // project-relative paths (e.g. "src/foo.ts").
+    if (sourceMap.sources != null) {
+      const scriptUrl = script.url;
+      try {
+        const origin = new URL(scriptUrl).origin;
+        sourceMap = {
+          ...sourceMap,
+          sources: sourceMap.sources.map(s => {
+            if (s == null) return s;
+            try {
+              const resolved = new URL(s, scriptUrl).href;
+              if (resolved.startsWith(origin + '/')) {
+                return resolved.slice(origin.length + 1);
+              }
+            } catch {
+              // not a valid URL combo
+            }
+            return s;
+          }),
+        };
+      } catch {
+        // scriptUrl is not a valid URL — skip rewriting
+      }
+    }
+
     function sanitizePath(path: string) {
       let url;