diff --git a/src/domain/referenceSourceClassification.ts b/src/domain/referenceSourceClassification.ts
index 212bafb46c..95a796468c 100644
--- a/src/domain/referenceSourceClassification.ts
+++ b/src/domain/referenceSourceClassification.ts
@@ -285,7 +285,8 @@ const filenameIsTest = (filename: string): boolean => {
   if (lower.includes(".test.") || lower.includes(".spec.")) return true;
   if (lower.startsWith("test_") || lower.startsWith("spec_")) return true;
   if (lower.endsWith("_test") || lower.endsWith("_spec")) return true;
-  return false;
+  const stem = basenameParts(lower).base;
+  return stem.endsWith("_test") || stem.endsWith("_spec");
 };
 
 const filenameIsGenerated = (filename: string): boolean => {
diff --git a/src/domain/referenceSourceTestClassification.test.ts b/src/domain/referenceSourceTestClassification.test.ts
new file mode 100644
index 0000000000..cd7e45d560
--- /dev/null
+++ b/src/domain/referenceSourceTestClassification.test.ts
@@ -0,0 +1,60 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  classifyReferenceSourcePath,
+  detectReferenceSourceLanguage,
+} from "./referenceSourceClassification.js";
+
+describe("reference source test filenames", () => {
+  it.each([
+    ["main_test.go", ["source", "test"], "Go"],
+    ["main_test.py", ["source", "test"], "Python"],
+    ["parser_spec.rs", ["source", "test"], "Rust"],
+    ["widget_spec.cpp", ["source", "test"], "C++"],
+    ["Widget_TeSt.TS", ["source", "test"], "TypeScript"],
+    ["Widget_SpEc.PY", ["source", "test"], "Python"],
+    ["widget.v2_test.py", ["source", "test"], "Python"],
+    [".widget_spec.js", ["source", "test"], "JavaScript"],
+    ["widget_test.fixture", ["test"], null],
+    ["settings_spec.json", ["config", "test"], "JSON"],
+    ["notes_test.md", ["documentation", "test"], "Markdown"],
+    ["widget_test.map", ["generated", "test"], null],
+    ["dist/widget_spec.js", ["generated", "source", "test"], "JavaScript"],
+    ["vendor/widget_test.go", ["source", "test", "vendor"], "Go"],
+  ])("recognizes the final basename suffix in %s", (path, tags, language) => {
+    expect(classifyReferenceSourcePath(path)).toEqual(tags);
+    expect(detectReferenceSourceLanguage(path)).toBe(language);
+  });
+
+  it.each([
+    ["test_main.py", ["source", "test"]],
+    ["SPEC_main.rs", ["source", "test"]],
+    ["main.test.js", ["source", "test"]],
+    ["main.SPEC.ts", ["source", "test"]],
+    ["main_test", ["test"]],
+    ["main_SPEC", ["test"]],
+    ["main.py_test", ["test"]],
+    ["main.rs_spec", ["test"]],
+    ["tests/main.go", ["source", "test"]],
+  ])("preserves existing test classification for %s", (path, tags) => {
+    expect(classifyReferenceSourcePath(path)).toEqual(tags);
+  });
+
+  it.each([
+    ["main.go", ["source"]],
+    ["main.py", ["source"]],
+    ["main_test_helper.go", ["source"]],
+    ["main_tests.go", ["source"]],
+    ["main_testing.py", ["source"]],
+    ["main_tester.py", ["source"]],
+    ["main_spec_helper.rs", ["source"]],
+    ["main_specs.rs", ["source"]],
+    ["main_specimen.rs", ["source"]],
+    ["main_test.py.bak", ["unknown"]],
+    ["main_spec.ts.bak", ["unknown"]],
+    ["main_test_helpers", ["unknown"]],
+    ["main_spec_helpers", ["unknown"]],
+  ])("does not infer a test from a near-name in %s", (path, tags) => {
+    expect(classifyReferenceSourcePath(path)).toEqual(tags);
+  });
+});
diff --git a/tests/boundary/filesystem/referenceSourceTestFilenames.test.ts b/tests/boundary/filesystem/referenceSourceTestFilenames.test.ts
new file mode 100644
index 0000000000..a1cbaaf281
--- /dev/null
+++ b/tests/boundary/filesystem/referenceSourceTestFilenames.test.ts
@@ -0,0 +1,105 @@
+import { createHash } from "node:crypto";
+import { writeFile } from "node:fs/promises";
+import { join } from "node:path";
+
+import { expect, it } from "vitest";
+
+import { importReferenceSource } from "../../../src/application/ReferenceSourceImport.js";
+import { createTestTempDirectory } from "../../fixtures/temporaryDirectory.js";
+
+it("imports test-suffixed filenames with unchanged paths, hashes, and languages", async () => {
+  const root = await createTestTempDirectory("rea-reference-test-filenames-");
+  const files = [
+    ["main_test.go", "package main\n", ["source", "test"], "Go"],
+    ["main_test.py", "assert True\n", ["source", "test"], "Python"],
+    ["parser_spec.rs", "fn checks() {}\n", ["source", "test"], "Rust"],
+    ["Widget_SPEC.TS", "export {};\n", ["source", "test"], "TypeScript"],
+    ["main_test", "test fixture\n", ["test"], null],
+    ["main_spec", "spec fixture\n", ["test"], null],
+    ["test_helper.py", "assert True\n", ["source", "test"], "Python"],
+    ["main.test.js", "export {};\n", ["source", "test"], "JavaScript"],
+    ["main.go", "package main\n", ["source"], "Go"],
+    ["main_test_helper.py", "value = 1\n", ["source"], "Python"],
+    ["main_specimen.rs", "fn main() {}\n", ["source"], "Rust"],
+    ["main_test.py.bak", "backup\n", ["unknown"], null],
+  ] as const;
+  await Promise.all(
+    files.map(([path, content]) => writeFile(join(root, path), content)),
+  );
+
+  const result = await importReferenceSource({
+    root,
+    caller: "reference-test-filenames-test",
+    policy: { secretPatterns: [] },
+  });
+  expect(result.ok).toBe(true);
+  if (!result.ok) return;
+  expect(result.value.entries).toHaveLength(files.length);
+  for (const [path, content, classifications, language] of files) {
+    expect(result.value.entries).toContainEqual({
+      path,
+      kind: "file",
+      sha256: createHash("sha256").update(content).digest("hex"),
+      size: Buffer.byteLength(content),
+      language,
+      classifications,
+      content_state: "hashed",
+      limitations: [],
+    });
+  }
+  expect(result.value.parse_failures).toEqual([]);
+  expect(result.value.relationships).toEqual([]);
+  expect(result.value.exclusions).toEqual([]);
+  expect(result.value.languages).toEqual([
+    "Go",
+    "JavaScript",
+    "Python",
+    "Rust",
+    "TypeScript",
+  ]);
+});
+
+it("keeps parser failures and unknown dependencies visible for test filenames", async () => {
+  const root = await createTestTempDirectory("rea-reference-test-parsing-");
+  await Promise.all([
+    writeFile(
+      join(root, "loader_test.js"),
+      'throw new Error("must not execute"); import(moduleName);\n',
+    ),
+    writeFile(join(root, "broken_spec.ts"), "const = ;\n"),
+  ]);
+
+  const result = await importReferenceSource({
+    root,
+    caller: "reference-test-parsing-test",
+    policy: { secretPatterns: [] },
+  });
+  expect(result.ok).toBe(true);
+  if (!result.ok) return;
+  expect(result.value.inventory_state).toBe("partial");
+  expect(result.value.relationships).toEqual([
+    {
+      from_path: "loader_test.js",
+      to: "<dynamic-import>",
+      kind: "imports",
+      resolution: "unknown",
+      parse_state: "partial",
+    },
+  ]);
+  expect(result.value.parse_failures).toEqual([
+    {
+      path: "broken_spec.ts",
+      parser: "babel",
+      reason: expect.any(String),
+    },
+  ]);
+  expect(
+    result.value.entries.map(({ path, classifications }) => ({
+      path,
+      classifications,
+    })),
+  ).toEqual([
+    { path: "broken_spec.ts", classifications: ["source", "test"] },
+    { path: "loader_test.js", classifications: ["source", "test"] },
+  ]);
+});