diff --git a/src/domain/javascript/javascriptSourceMapPaths.ts b/src/domain/javascript/javascriptSourceMapPaths.ts
new file mode 100644
index 0000000000..8b46c4363e
--- /dev/null
+++ b/src/domain/javascript/javascriptSourceMapPaths.ts
@@ -0,0 +1,69 @@
+import { posix } from "node:path";
+import { fileURLToPath, pathToFileURL } from "node:url";
+
+interface SourceMapPath {
+  readonly value: string;
+  readonly scope: "artifact-relative" | "suffix";
+}
+
+/** Resolve a source-map URL reference without changing its recorded identity. */
+export const resolveJavaScriptSourceMapPath = (
+  source: string,
+  mapPath?: string,
+): SourceMapPath | null => {
+  const portable = source.replaceAll("\\", "/");
+  const windowsPath = /^[a-z]:\//iu.test(portable) || source.startsWith("\\\\");
+  // Preserve parent traversal rather than letting URL resolution clamp at '/'.
+  const anchor = `/${"source/".repeat(portable.split("/").length + 1)}`;
+  const directory = posix.join(
+    anchor,
+    posix.dirname(mapPath?.replaceAll("\\", "/") ?? "."),
+  );
+  const base = pathToFileURL(`${directory}/`, { windows: false });
+  const absolute = windowsPath ? windowsFileUrl(source) : URL.parse(source);
+  const resolved = windowsPath ? absolute : URL.parse(source, base);
+  if (
+    resolved === null ||
+    !resolved.pathname.startsWith("/") ||
+    resolved.pathname.endsWith("/")
+  )
+    return null;
+  const relative =
+    absolute === null
+      ? !portable.startsWith("/")
+      : absolute.href !== resolved.href;
+  const path = decodedUrlPath(resolved);
+  if (path === null) return null;
+  const value = relative
+    ? posix.relative(anchor, path)
+    : path.replace(/^\/+/, "");
+  if (value === "" || value === ".." || value.startsWith("../")) return null;
+  return {
+    value,
+    scope: relative && mapPath !== undefined ? "artifact-relative" : "suffix",
+  };
+};
+
+const windowsFileUrl = (path: string): URL | null => {
+  try {
+    return pathToFileURL(path, { windows: true });
+  } catch (cause: unknown) {
+    if (cause instanceof TypeError) return null;
+    throw cause;
+  }
+};
+
+const decodedUrlPath = (url: URL): string | null => {
+  // Encoded separators must not manufacture a different filesystem hierarchy.
+  if (/%(?:2f|5c)/iu.test(url.pathname)) return null;
+  try {
+    if (url.protocol === "file:")
+      return fileURLToPath(url, {
+        windows: url.hostname !== "" && url.hostname !== "localhost",
+      }).replaceAll("\\", "/");
+    return `${url.host}${decodeURIComponent(url.pathname)}`;
+  } catch (cause: unknown) {
+    if (cause instanceof URIError || cause instanceof TypeError) return null;
+    throw cause;
+  }
+};
diff --git a/src/domain/javascript/sourceToBundleComparison.test.ts b/src/domain/javascript/sourceToBundleComparison.test.ts
index 0610da1da3..6bc764a1e1 100644
--- a/src/domain/javascript/sourceToBundleComparison.test.ts
+++ b/src/domain/javascript/sourceToBundleComparison.test.ts
@@ -5,6 +5,7 @@ import {
   createJavaScriptApplicationNode,
 } from "./javascriptApplicationGraph.js";
 import { createHistoricalSourceGraph } from "../referenceSourceGraph.js";
+import { compareCodePoints } from "../canonicalOrdering.js";
 import { compareSourceToBundle } from "./sourceToBundleComparison.js";
 import {
   SOURCE_TO_BUNDLE_SIGNAL_WEIGHTS,
@@ -187,44 +188,47 @@ describe("source to bundle digest changes", () => {
 });
 
 describe("source to bundle path syntax", () => {
-  it.each(["src/modified#part.ts", "src/modified?part.ts"])(
-    "preserves literal filesystem punctuation in %s",
-    (path) => {
-      const node = moduleNode("punctuated", { path });
-      const graph = createJavaScriptApplicationGraph({
-        schema: "JavaScriptApplicationGraph",
-        root_node_ids: [node.node_id],
-        nodes: [node],
-        edges: [],
-        coverage: {
-          status: "complete",
-          truncated: false,
-          omitted_count: 0,
-          limits: [],
-        },
-        limitations: [],
-      });
-      const result = compareSourceToBundle({
-        reference: historicalGraph("complete", [path]),
-        application: {
-          evidenceId: EVIDENCE_ID,
-          rootArtifactSha256: HASH.artifact,
-          graph,
-        },
-      });
-      expect(item(result, path)).toMatchObject({
-        status: "unknown",
-        current_node_ids: [node.node_id],
-        candidates: [
-          expect.objectContaining({
-            signals: expect.arrayContaining([
-              expect.objectContaining({ kind: "current-path-exact" }),
-            ]),
-          }),
-        ],
-      });
-    },
-  );
+  it.each([
+    "src/modified#part.ts",
+    "src/modified?part.ts",
+    "pkg:app/src/modified#part.ts",
+    "pkg:app/src/modified?part.ts",
+    "data:/src/modified.ts",
+  ])("preserves literal filesystem punctuation in %s", (path) => {
+    const node = moduleNode("punctuated", { path });
+    const graph = createJavaScriptApplicationGraph({
+      schema: "JavaScriptApplicationGraph",
+      root_node_ids: [node.node_id],
+      nodes: [node],
+      edges: [],
+      coverage: {
+        status: "complete",
+        truncated: false,
+        omitted_count: 0,
+        limits: [],
+      },
+      limitations: [],
+    });
+    const result = compareSourceToBundle({
+      reference: historicalGraph("complete", [path]),
+      application: {
+        evidenceId: EVIDENCE_ID,
+        rootArtifactSha256: HASH.artifact,
+        graph,
+      },
+    });
+    expect(item(result, path)).toMatchObject({
+      status: "unknown",
+      current_node_ids: [node.node_id],
+      candidates: [
+        expect.objectContaining({
+          signals: expect.arrayContaining([
+            expect.objectContaining({ kind: "current-path-exact" }),
+          ]),
+        }),
+      ],
+    });
+  });
 
   it.each([
     "https://example.test/src/modified.ts?revision=2#section",
@@ -347,7 +351,7 @@ const historicalGraph = (
         content_state: "hashed" as const,
         limitations: [],
       })),
-    ],
+    ].sort((left, right) => compareCodePoints(left.path, right.path)),
     relationships: [],
     parse_failures: [],
     exclusions: [],
diff --git a/src/domain/javascript/sourceToBundleSignals.ts b/src/domain/javascript/sourceToBundleSignals.ts
index 096307d2e0..b72a0d1bf3 100644
--- a/src/domain/javascript/sourceToBundleSignals.ts
+++ b/src/domain/javascript/sourceToBundleSignals.ts
@@ -9,6 +9,7 @@ import {
   type SourceToBundleSignal,
 } from "./sourceToBundleComparisonSchemas.js";
 import { isDigest } from "../digests.js";
+import { resolveJavaScriptSourceMapPath } from "./javascriptSourceMapPaths.js";
 
 type SourceFile = Extract<
   HistoricalSourceGraph["entries"][number],
@@ -23,6 +24,8 @@ type CurrentPathKind =
 interface CurrentPath {
   readonly kind: CurrentPathKind;
   readonly value: string;
+  /** Artifact-relative map resolution identifies one path, not its suffixes. */
+  readonly allowSuffix: boolean;
 }
 
 interface CurrentProjection {
@@ -93,7 +96,9 @@ export const buildSourceToBundleCandidateIndex = (
     for (const digest of projection.digests)
       addIndexValue(byDigest, digest, projection.node.node_id);
     for (const path of projection.paths) {
-      for (const suffix of pathSuffixes(path.value))
+      for (const suffix of path.allowSuffix
+        ? pathSuffixes(path.value)
+        : [path.value])
         addIndexValue(byPathSuffix, suffix, projection.node.node_id);
       addIndexValue(
         byBasename,
@@ -169,7 +174,22 @@ const projectCurrentNode = (node: ApplicationNode): CurrentProjection => {
   if (node.identity.strategy === "source-map-original") {
     if (node.identity.source_sha256 !== null)
       digests.add(node.identity.source_sha256);
-    addPath(paths, "source-map-original", node.identity.original_source);
+    const mapLocations = node.observations.flatMap(({ evidence }) =>
+      evidence.extractor.operation === "parse-local-source-map" &&
+      evidence.location.available &&
+      evidence.location.value.kind === "artifact-path"
+        ? [evidence.location.value.path]
+        : [],
+    );
+    if (mapLocations.length === 0)
+      addPath(paths, "source-map-original", node.identity.original_source);
+    for (const mapPath of mapLocations)
+      addPath(
+        paths,
+        "source-map-original",
+        node.identity.original_source,
+        mapPath,
+      );
   }
   if (node.identity.strategy === "canonical-path")
     addPath(paths, "canonical-path", node.identity.path);
@@ -177,8 +197,18 @@ const projectCurrentNode = (node: ApplicationNode): CurrentProjection => {
     const sourceDigest = observation.properties.source_sha256;
     if (typeof sourceDigest === "string" && isDigest(sourceDigest))
       digests.add(sourceDigest);
-    for (const key of PATH_PROPERTIES)
-      addJsonPath(paths, observation.properties[key]);
+    for (const key of PATH_PROPERTIES) {
+      const location = observation.evidence.location;
+      const mapPath =
+        node.identity.strategy === "source-map-original" &&
+        observation.evidence.extractor.operation === "parse-local-source-map" &&
+        (key === "source" || key === "original_source") &&
+        location.available &&
+        location.value.kind === "artifact-path"
+          ? location.value.path
+          : undefined;
+      addJsonPath(paths, observation.properties[key], mapPath);
+    }
   }
   return {
     node,
@@ -212,7 +242,10 @@ const candidateSignals = (
     signals.push(signal("current-path-exact", source.path, exactPaths));
   const suffixPaths = otherPaths
     .filter(
-      ({ value }) => value !== source.path && value.endsWith(`/${source.path}`),
+      ({ value, allowSuffix }) =>
+        allowSuffix &&
+        value !== source.path &&
+        value.endsWith(`/${source.path}`),
     )
     .map(({ value }) => value);
   if (suffixPaths.length > 0)
@@ -259,45 +292,70 @@ const matchingPaths = (
 ): string[] =>
   currentPaths
     .filter(
-      ({ value }) => value === sourcePath || value.endsWith(`/${sourcePath}`),
+      ({ value, allowSuffix }) =>
+        value === sourcePath ||
+        (allowSuffix && value.endsWith(`/${sourcePath}`)),
     )
     .map(({ value }) => value);
 
-const addJsonPath = (paths: CurrentPath[], value: unknown): void => {
-  if (typeof value === "string") addPath(paths, "observation-path", value);
+const addJsonPath = (
+  paths: CurrentPath[],
+  value: unknown,
+  mapPath?: string,
+): void => {
+  if (typeof value === "string")
+    addPath(paths, "observation-path", value, mapPath);
 };
 
 const addPath = (
   paths: CurrentPath[],
   kind: CurrentPathKind,
   raw: string,
+  mapPath?: string,
 ): void => {
+  if (kind === "source-map-original" || mapPath !== undefined) {
+    const resolved = resolveJavaScriptSourceMapPath(raw, mapPath);
+    if (resolved !== null)
+      paths.push({
+        kind,
+        value: resolved.value,
+        allowSuffix: resolved.scope === "suffix",
+      });
+    return;
+  }
   const value = normalizeCurrentPath(raw);
-  if (value !== null) paths.push({ kind, value });
+  if (value !== null) paths.push({ kind, value, allowSuffix: true });
 };
 
-/** Matches a `scheme://...` URL prefix; bare filesystem paths keep `?`/`#`. */
 const SCHEME_URL = /^[a-z][a-z0-9+.-]*:\/\//iu;
-/** Matches a `scheme://...` URL prefix with any run of slashes, for stripping. */
 const SCHEME_URL_PREFIX = /^[a-z][a-z0-9+.-]*:\/\/+/iu;
 
 const normalizeCurrentPath = (raw: string): string | null => {
   const withoutQuery = SCHEME_URL.test(raw)
     ? (raw.split(/[?#]/u, 1)[0] ?? "")
     : raw;
-  const withoutScheme = withoutQuery.replace(SCHEME_URL_PREFIX, "");
-  const parts = withoutScheme
-    .replaceAll("\\", "/")
-    .split("/")
-    .filter((part) => part !== "" && part !== ".");
-  if (parts.length === 0 || parts.includes("..")) return null;
+  const portable = withoutQuery
+    .replace(SCHEME_URL_PREFIX, "")
+    .replaceAll("\\", "/");
+  const parts: string[] = [];
+  for (const part of portable.split("/")) {
+    if (part === "" || part === ".") continue;
+    if (part === "..") {
+      if (parts.length === 0) return null;
+      parts.pop();
+    } else parts.push(part);
+  }
+  if (parts.length === 0) return null;
   return parts.join("/");
 };
 
 const uniquePaths = (paths: readonly CurrentPath[]): CurrentPath[] =>
   [
     ...new Map(
-      paths.map((path) => [`${path.kind}\0${path.value}`, path]),
+      paths.map((path) => [
+        `${path.kind}\0${path.value}\0${String(path.allowSuffix)}`,
+        path,
+      ]),
     ).values(),
   ].sort((left, right) =>
     compareCodePoints(
diff --git a/tests/boundary/filesystem/sourceToBundlePaths.test.ts b/tests/boundary/filesystem/sourceToBundlePaths.test.ts
index fffd7bf05f..17ee916c98 100644
--- a/tests/boundary/filesystem/sourceToBundlePaths.test.ts
+++ b/tests/boundary/filesystem/sourceToBundlePaths.test.ts
@@ -6,6 +6,7 @@ import { analyzeJavaScriptApplication } from "../../../src/application/javascrip
 import { parseApplicationGraphEvidence } from "../../../src/application/javascript/JavaScriptApplicationEvidenceGraph.js";
 import { importReferenceSource } from "../../../src/application/ReferenceSourceImport.js";
 import { compareSourceToBundle } from "../../../src/domain/javascript/sourceToBundleComparison.js";
+import { resolveSourceMapSource } from "../../../src/javascript/sourceMaps/DecodedSourceMap.js";
 import { createTestTempDirectory } from "../../fixtures/temporaryDirectory.js";
 
 it("keeps literal hash characters in historical/current filesystem paths", async () => {
@@ -17,25 +18,9 @@ it("keeps literal hash characters in historical/current filesystem paths", async
     writeFile(join(previous, "worker#main.js"), "export const value = 1;"),
     writeFile(join(current, "worker#main.js"), "export const value = 2;"),
   ]);
-  const reference = await importReferenceSource({
-    root: previous,
-    caller: "source-to-bundle-path-test",
-    policy: { secretPatterns: [] },
-  });
-  if (!reference.ok) throw new Error(reference.error.message);
-  const analyzed = await analyzeJavaScriptApplication({ input_path: current });
-  if (!analyzed.ok) throw analyzed.error;
-  const application = parseApplicationGraphEvidence(analyzed.value);
-  const comparison = compareSourceToBundle({
-    reference: reference.value,
-    application: {
-      evidenceId: application.evidence.evidence_id,
-      rootArtifactSha256: application.rootArtifactSha256,
-      graph: application.graph,
-    },
-  });
+  const { reference, comparison } = await compareTrees(previous, current);
 
-  expect(reference.value.entries).toContainEqual(
+  expect(reference.entries).toContainEqual(
     expect.objectContaining({
       kind: "file",
       path: "worker#main.js",
@@ -59,6 +44,507 @@ it("keeps literal hash characters in historical/current filesystem paths", async
   );
 });
 
+it("matches source-map originals named relative to the map", async () => {
+  const root = await createTestTempDirectory("rea-source-map-parent-");
+  const previous = join(root, "previous");
+  const current = join(root, "current");
+  await Promise.all([
+    mkdir(join(previous, "src"), { recursive: true }),
+    mkdir(join(current, "dist"), { recursive: true }),
+  ]);
+  await Promise.all([
+    writeFile(join(previous, "src", "a.js"), "export const value = 1;\n"),
+    writeFile(
+      join(current, "dist", "main.js"),
+      "var value = 2;\n//# sourceMappingURL=main.js.map\n",
+    ),
+    writeFile(
+      join(current, "dist", "main.js.map"),
+      JSON.stringify({
+        version: 3,
+        file: "main.js",
+        sources: ["../src/a.js"],
+        sourcesContent: ["export const value = 2;\n"],
+        names: [],
+        mappings: "AAAA",
+      }),
+    ),
+  ]);
+  const { comparison } = await compareTrees(previous, current);
+
+  expect(comparison.items).toContainEqual(
+    expect.objectContaining({
+      source_path: "src/a.js",
+      candidates: expect.arrayContaining([
+        expect.objectContaining({
+          current_node_kind: "source-module",
+          signals: expect.arrayContaining([
+            expect.objectContaining({
+              kind: "source-map-original-path",
+              current_values: ["src/a.js"],
+            }),
+          ]),
+        }),
+      ]),
+    }),
+  );
+});
+
+it.each([
+  {
+    mapPath: "pkg/dist/main.js.map",
+    source: "..\\src\\a.js",
+    expected: "pkg/src/a.js",
+  },
+  {
+    mapPath: "pkg/dist/main.js.map",
+    source: "../src/a.js",
+    expected: "pkg/src/a.js",
+  },
+  {
+    mapPath: "apps/pkg/dist/maps/main.js.map",
+    source: "../../src/a.js",
+    expected: "apps/pkg/src/a.js",
+  },
+  {
+    mapPath: "pkg/dist/main.js.map",
+    sourceRoot: "../src",
+    source: "a.js",
+    expected: "pkg/src/a.js",
+  },
+  {
+    mapPath: "pkg/maps/main.map",
+    sourceRoot: "../src",
+    source: "/vendor/a.js",
+    expected: "pkg/src/vendor/a.js",
+    decoy: "vendor/a.js",
+  },
+  {
+    mapPath: "pkg/maps/main.js.map",
+    source: "modules/a.js",
+    expected: "pkg/maps/modules/a.js",
+  },
+  {
+    mapPath: "pkg/maps/main.js.map",
+    source: "generated/../src/a.js",
+    expected: "pkg/maps/src/a.js",
+  },
+  {
+    mapPath: "pkg/maps/main.js.map",
+    sourceRoot: "generated/..",
+    source: "src/a.js",
+    expected: "pkg/maps/src/a.js",
+  },
+  {
+    mapPath: "pkg/maps/main.js.map",
+    source: "../actual/%2e%2e/src/a.js",
+    expected: "pkg/src/a.js",
+    decoy: "pkg/actual/%2e%2e/src/a.js",
+  },
+  {
+    mapPath: "pkg/maps/main.js.map",
+    sourceRoot: "../actual/.%2E",
+    source: "src/a.js",
+    expected: "pkg/src/a.js",
+    decoy: "pkg/actual/.%2E/src/a.js",
+  },
+  {
+    mapPath: "pkg#name?/maps/main.js.map",
+    source: "../src/a.js",
+    expected: "pkg#name?/src/a.js",
+  },
+  {
+    mapPath: "pkg/maps/main.js.map",
+    source: "modules/a%20b.js",
+    expected: "pkg/maps/modules/a b.js",
+  },
+  {
+    mapPath: "pkg/maps/main.js.map",
+    source: "modules/a%23b.js",
+    expected: "pkg/maps/modules/a#b.js",
+  },
+  {
+    mapPath: "pkg/maps/main.js.map",
+    source: "../actual/%252e%252e/src/a.js",
+    expected: "pkg/actual/%2e%2e/src/a.js",
+    decoy: "pkg/src/a.js",
+  },
+])(
+  "resolves $source against $mapPath without selecting a same-basename decoy",
+  async ({
+    mapPath,
+    source,
+    sourceRoot,
+    expected,
+    decoy: decoyPath = "src/a.js",
+  }) => {
+    if (sourceRoot !== undefined) {
+      const resolved = resolveSourceMapSource(
+        source,
+        sourceRoot,
+        `https://example.test/${mapPath}`,
+      );
+      expect(decodeURIComponent(new URL(resolved).pathname)).toBe(
+        `/${expected}`,
+      );
+    }
+    const root = await createTestTempDirectory("rea-nested-map-");
+    const previous = join(root, "previous");
+    const current = join(root, "current");
+    await Promise.all([
+      mkdir(join(previous, expected, ".."), { recursive: true }),
+      mkdir(join(previous, decoyPath, ".."), { recursive: true }),
+      mkdir(join(current, mapPath, ".."), { recursive: true }),
+    ]);
+    await Promise.all([
+      writeFile(join(previous, expected), "export const value = 1;"),
+      writeFile(join(previous, decoyPath), "export const decoy = 99;"),
+      writeFile(
+        join(current, mapPath),
+        JSON.stringify({
+          version: 3,
+          sources: [source],
+          ...(sourceRoot === undefined ? {} : { sourceRoot }),
+          sourcesContent: ["export const value = 2;"],
+          names: [],
+          mappings: "AAAA",
+        }),
+      ),
+    ]);
+    const { comparison } = await compareTrees(previous, current);
+    const correct = comparison.items.find(
+      ({ source_path }) => source_path === expected,
+    );
+    expect(correct?.current_node_ids).toHaveLength(1);
+    expect(correct?.candidates).toContainEqual(
+      expect.objectContaining({
+        confidence: "high",
+        signals: expect.arrayContaining([
+          expect.objectContaining({
+            kind: "source-map-original-path",
+            current_values: [expected],
+          }),
+        ]),
+      }),
+    );
+    const decoy = comparison.items.find(
+      ({ source_path }) => source_path === decoyPath,
+    );
+    expect(decoy?.current_node_ids).toEqual([]);
+    expect(
+      decoy?.candidates
+        .flatMap(({ signals }) => signals)
+        .some(({ kind }) => kind === "current-path-exact"),
+    ).toBe(false);
+    // A suffix alone must not claim a second map-relative original identity.
+    expect(
+      decoy?.candidates
+        .flatMap(({ signals }) => signals)
+        .some(({ kind }) => kind === "source-map-original-path"),
+    ).toBe(false);
+  },
+);
+
+it("retains every map location when identical map artifacts merge", async () => {
+  const root = await createTestTempDirectory("rea-source-map-merged-");
+  const previous = join(root, "previous");
+  const current = join(root, "current");
+  const map = JSON.stringify({
+    version: 3,
+    sources: ["../src/x.js"],
+    sourcesContent: ["export const value = 2;"],
+    names: [],
+    mappings: "AAAA",
+  });
+  for (const prefix of ["a", "b"]) {
+    await Promise.all([
+      mkdir(join(previous, prefix, "src"), { recursive: true }),
+      mkdir(join(current, prefix, "maps"), { recursive: true }),
+    ]);
+    await Promise.all([
+      writeFile(join(previous, prefix, "src/x.js"), "export const value = 1;"),
+      writeFile(join(current, prefix, "maps/main.js.map"), map),
+    ]);
+  }
+  const { comparison } = await compareTrees(previous, current);
+  for (const prefix of ["a", "b"]) {
+    const path = `${prefix}/src/x.js`;
+    const item = comparison.items.find(
+      ({ source_path }) => source_path === path,
+    );
+    expect(item?.current_node_ids).toHaveLength(1);
+    expect(item?.candidates).toContainEqual(
+      expect.objectContaining({
+        confidence: "high",
+        signals: expect.arrayContaining([
+          expect.objectContaining({
+            kind: "source-map-original-path",
+            current_values: [path],
+          }),
+        ]),
+      }),
+    );
+  }
+});
+
+it.each([
+  { source: "file:/repo/src/a.js", hasPath: true },
+  { source: "file:C:/repo/src/a.js", hasPath: true },
+  { source: "file:C:\\repo\\src\\a.js", hasPath: true },
+  { source: "C:\\repo\\src\\a.js", hasPath: true },
+  { source: "file://server/share/src/a.js", hasPath: true },
+  { source: "file:/repo/src/a.js?version=2#original", hasPath: true },
+  { source: "webpack:///src/a.js", hasPath: true },
+  { source: "https://example.com/src/a.js#original", hasPath: true },
+  { source: "node:internal/src/a.js", hasPath: false },
+  { source: "data:text/javascript,virtual/src/a.js", hasPath: false },
+  { source: "data:text/javascript,virtual/../src/a.js", hasPath: false },
+  { source: "data:\\src\\a.js", hasPath: false },
+])(
+  "projects source references from $source only when they name a file",
+  async ({ source, hasPath }) => {
+    const root = await createTestTempDirectory("rea-source-map-uri-");
+    const previous = join(root, "previous");
+    const current = join(root, "current");
+    await Promise.all([
+      mkdir(join(previous, "src"), { recursive: true }),
+      mkdir(join(current, "maps"), { recursive: true }),
+    ]);
+    await Promise.all([
+      writeFile(join(previous, "src/a.js"), "export const value = 1;"),
+      writeFile(
+        join(current, "maps/main.js.map"),
+        JSON.stringify({
+          version: 3,
+          sources: [source],
+          sourcesContent: ["export const value = 2;"],
+          names: [],
+          mappings: "AAAA",
+        }),
+      ),
+    ]);
+    const { comparison, application } = await compareTrees(previous, current);
+    expect(application.graph.nodes).toContainEqual(
+      expect.objectContaining({
+        identity: expect.objectContaining({ original_source: source }),
+      }),
+    );
+    if (hasPath)
+      expect(comparison.items[0]?.candidates).toContainEqual(
+        expect.objectContaining({
+          confidence: "high",
+          signals: expect.arrayContaining([
+            expect.objectContaining({ kind: "source-map-original-path" }),
+          ]),
+        }),
+      );
+    else expect(comparison.items[0]?.candidates).toEqual([]);
+  },
+);
+
+it.each(["#original.js", "?version.js", "?version.js#original.js"])(
+  "uses the relative URL pathname rather than a literal %s filename",
+  async (suffix) => {
+    const root = await createTestTempDirectory("rea-source-map-suffix-");
+    const previous = join(root, "previous");
+    const current = join(root, "current");
+    await Promise.all([
+      mkdir(join(previous, "src"), { recursive: true }),
+      mkdir(join(current, "maps"), { recursive: true }),
+    ]);
+    const source = `../src/a.js${suffix}`;
+    await Promise.all([
+      writeFile(join(previous, "src/a.js"), "export const value = 1;"),
+      writeFile(join(previous, `src/a.js${suffix}`), "export const decoy = 3;"),
+      writeFile(
+        join(current, "maps/main.js.map"),
+        JSON.stringify({
+          version: 3,
+          sources: [source],
+          sourcesContent: ["export const value = 2;"],
+          names: [],
+          mappings: "AAAA",
+        }),
+      ),
+    ]);
+    const { comparison, application } = await compareTrees(previous, current);
+    const actual = comparison.items.find(
+      ({ source_path }) => source_path === "src/a.js",
+    );
+    expect(actual?.current_node_ids).toHaveLength(1);
+    expect(actual?.candidates).toContainEqual(
+      expect.objectContaining({
+        confidence: "high",
+        signals: expect.arrayContaining([
+          expect.objectContaining({
+            kind: "source-map-original-path",
+            current_values: ["src/a.js"],
+          }),
+        ]),
+      }),
+    );
+    const decoy = comparison.items.find(
+      ({ source_path }) => source_path === `src/a.js${suffix}`,
+    );
+    expect(decoy?.current_node_ids).toEqual([]);
+    expect(decoy?.candidates).toEqual([]);
+    expect(application.graph.nodes).toContainEqual(
+      expect.objectContaining({
+        identity: expect.objectContaining({ original_source: source }),
+      }),
+    );
+  },
+);
+
+it.each([
+  { filename: "a#b.js", decoyFilename: "a" },
+  { filename: "a?b.js", decoyFilename: "a" },
+  { filename: "a%23b.js", decoyFilename: "a#b.js" },
+])(
+  "preserves the literal UNC filesystem name $filename without selecting a URL decoy",
+  async ({ filename, decoyFilename }) => {
+    const root = await createTestTempDirectory("rea-source-map-unc-");
+    const previous = join(root, "previous");
+    const current = join(root, "current");
+    const source = `\\\\server\\share\\src\\${filename}`;
+    const expected = `src/${filename}`;
+    const decoy = `src/${decoyFilename}`;
+    await Promise.all([
+      mkdir(join(previous, "src"), { recursive: true }),
+      mkdir(join(current, "maps"), { recursive: true }),
+    ]);
+    await Promise.all([
+      writeFile(join(previous, expected), "export const value = 1;"),
+      writeFile(join(previous, decoy), "export const decoy = 3;"),
+      writeFile(
+        join(current, "maps/main.map"),
+        JSON.stringify({
+          version: 3,
+          sources: [source],
+          sourcesContent: ["export const value = 2;"],
+          names: [],
+          mappings: "AAAA",
+        }),
+      ),
+    ]);
+    const { comparison, application } = await compareTrees(previous, current);
+    const actual = comparison.items.find(
+      ({ source_path }) => source_path === expected,
+    );
+    expect(actual?.current_node_ids).toHaveLength(1);
+    expect(actual?.candidates).toContainEqual(
+      expect.objectContaining({
+        signals: expect.arrayContaining([
+          expect.objectContaining({ kind: "source-map-original-path" }),
+        ]),
+      }),
+    );
+    expect(
+      comparison.items.find(({ source_path }) => source_path === decoy)
+        ?.current_node_ids,
+    ).toEqual([]);
+    expect(application.graph.nodes).toContainEqual(
+      expect.objectContaining({
+        identity: expect.objectContaining({ original_source: source }),
+      }),
+    );
+  },
+);
+
+it.each([
+  { source: "", historicalPath: "maps.js" },
+  { source: ".", historicalPath: "maps.js" },
+  { source: "./", historicalPath: "maps.js" },
+  { source: "child/..", historicalPath: "maps.js" },
+  { source: "child.js/", historicalPath: "maps.js/child.js" },
+  { source: "#original.js", historicalPath: "maps.js" },
+  { source: "?version.js", historicalPath: "maps.js" },
+  { source: "./?version.js", historicalPath: "maps.js" },
+  { source: "%2e", historicalPath: "maps.js" },
+  { source: "%2e%2e", historicalPath: "maps.js" },
+  { source: "child%2fpart.js", historicalPath: "maps.js/child/part.js" },
+  { source: "child%5cpart.js", historicalPath: "maps.js/child/part.js" },
+  { source: "bad%zz.js", historicalPath: "maps.js/bad%zz.js" },
+  { source: "\\\\bad host\\share\\a.js", historicalPath: "share/a.js" },
+  { source: "../../outside/a.js", historicalPath: "outside/a.js" },
+])(
+  "declines source references without a trustworthy file path: $source",
+  async ({ source, historicalPath }) => {
+    const root = await createTestTempDirectory("rea-source-map-empty-");
+    const previous = join(root, "previous");
+    const current = join(root, "current");
+    await Promise.all([
+      mkdir(join(previous, historicalPath, ".."), { recursive: true }),
+      mkdir(join(current, "maps.js"), { recursive: true }),
+    ]);
+    await Promise.all([
+      writeFile(join(previous, historicalPath), "export const value = 1;"),
+      writeFile(
+        join(current, "maps.js/main.js.map"),
+        JSON.stringify({
+          version: 3,
+          sources: [source],
+          sourcesContent: ["export const value = 2;"],
+          names: [],
+          mappings: "AAAA",
+        }),
+      ),
+    ]);
+    const { comparison } = await compareTrees(previous, current);
+    expect(comparison.items[0]?.source_path).toBe(historicalPath);
+    expect(comparison.items[0]?.candidates).toEqual([]);
+  },
+);
+
+it("resolves parent segments against a nested source map's directory", async () => {
+  const root = await createTestTempDirectory("rea-source-map-nested-");
+  const previous = join(root, "previous");
+  const current = join(root, "current");
+  await Promise.all([
+    mkdir(join(previous, "web", "src"), { recursive: true }),
+    mkdir(join(current, "web", "maps"), { recursive: true }),
+  ]);
+  await Promise.all([
+    writeFile(
+      join(previous, "web", "src", "a.js"),
+      "export const value = 1;\n",
+    ),
+    writeFile(
+      join(current, "web", "main.js"),
+      "var value = 2;\n//# sourceMappingURL=maps/main.js.map\n",
+    ),
+    writeFile(
+      join(current, "web", "maps", "main.js.map"),
+      JSON.stringify({
+        version: 3,
+        file: "../main.js",
+        sources: ["../src/a.js"],
+        sourcesContent: ["export const value = 2;\n"],
+        names: [],
+        mappings: "AAAA",
+      }),
+    ),
+  ]);
+  const { comparison } = await compareTrees(previous, current);
+
+  expect(comparison.items).toContainEqual(
+    expect.objectContaining({
+      source_path: "web/src/a.js",
+      candidates: expect.arrayContaining([
+        expect.objectContaining({
+          current_node_kind: "source-module",
+          signals: expect.arrayContaining([
+            expect.objectContaining({
+              kind: "source-map-original-path",
+              current_values: ["web/src/a.js"],
+            }),
+          ]),
+        }),
+      ]),
+    }),
+  );
+});
+
 it("rejects static application Evidence whose subject path disagrees with its result", async () => {
   const root = await createTestTempDirectory("rea-application-subject-path-");
   const analyzed = await analyzeJavaScriptApplication({ input_path: root });
@@ -77,3 +563,24 @@ it("rejects static application Evidence whose subject path disagrees with its re
     "JavaScript application Evidence subject does not match its result",
   );
 });
+
+const compareTrees = async (previous: string, current: string) => {
+  const reference = await importReferenceSource({
+    root: previous,
+    caller: "source-to-bundle-path-test",
+    policy: { secretPatterns: [] },
+  });
+  if (!reference.ok) throw new Error(reference.error.message);
+  const analyzed = await analyzeJavaScriptApplication({ input_path: current });
+  if (!analyzed.ok) throw analyzed.error;
+  const application = parseApplicationGraphEvidence(analyzed.value);
+  const comparison = compareSourceToBundle({
+    reference: reference.value,
+    application: {
+      evidenceId: application.evidence.evidence_id,
+      rootArtifactSha256: application.rootArtifactSha256,
+      graph: application.graph,
+    },
+  });
+  return { reference: reference.value, comparison, application };
+};