diff --git a/config/max-lines-baseline.txt b/config/max-lines-baseline.txt
index d92d91ebc04..fa89d01bfad 100644
--- a/config/max-lines-baseline.txt
+++ b/config/max-lines-baseline.txt
@@ -511,13 +511,13 @@ src/agents/model-selection.test.ts
 src/agents/models.profiles.live.test.ts
 src/agents/openai-completions-transport.ts
 src/agents/openai-responses-transport.ts
-src/agents/openai-transport-stream.base.test-utils.ts
-src/agents/openai-transport-stream.deepseek-and-shaping.test-utils.ts
-src/agents/openai-transport-stream.inline-reasoning-and-tool-calls.test-utils.ts
-src/agents/openai-transport-stream.reasoning-and-cache.test-utils.ts
-src/agents/openai-transport-stream.replay-and-tools.test-utils.ts
-src/agents/openai-transport-stream.streaming.test-utils.ts
-src/agents/openai-transport-stream.usage-and-calls.test-utils.ts
+src/agents/openai-transport-stream.base.test.ts
+src/agents/openai-transport-stream.deepseek-and-shaping.test.ts
+src/agents/openai-transport-stream.inline-reasoning-and-tool-calls.test.ts
+src/agents/openai-transport-stream.reasoning-and-cache.test.ts
+src/agents/openai-transport-stream.replay-and-tools.test.ts
+src/agents/openai-transport-stream.streaming.test.ts
+src/agents/openai-transport-stream.usage-and-calls.test.ts
 src/agents/openclaw-tools.media-factory-plan.test.ts
 src/agents/openclaw-tools.session-status.test.ts
 src/agents/openclaw-tools.sessions.test.ts
diff --git a/scripts/test-projects.test-support.mjs b/scripts/test-projects.test-support.mjs
index bdd6ce43499..800ff1c7336 100644
--- a/scripts/test-projects.test-support.mjs
+++ b/scripts/test-projects.test-support.mjs
@@ -2700,7 +2700,8 @@ function isPathLikeTargetArg(arg, cwd) {
     isGlobTarget(arg) ||
     isFileLikeTarget(arg) ||
     isVitestConfigPathLikeTarget(relative) ||
-    isExistingPathTarget(arg, cwd)
+    isExistingPathTarget(arg, cwd) ||
+    Boolean(resolveExplicitTestPrefixTargets(arg, cwd)?.length)
   );
 }
 
@@ -2767,6 +2768,26 @@ function listExplicitTestTargetFilesForCwd(cwd) {
   return cachedExplicitTestTargetFiles;
 }
 
+function resolveExplicitTestPrefixTargets(targetArg, cwd) {
+  if (isExistingPathTarget(targetArg, cwd) || isGlobTarget(targetArg)) {
+    return null;
+  }
+  const relative = toRepoRelativeTarget(targetArg, cwd).replace(/\/+$/u, "");
+  if (!relative || isLikelyFileTarget(relative)) {
+    return null;
+  }
+  const directory = path.posix.dirname(relative);
+  const prefix = `${relative}.`;
+  const targets = listExplicitTestTargetFilesForCwd(cwd).filter(
+    (file) =>
+      fs.existsSync(path.join(cwd, file)) &&
+      path.posix.dirname(file) === directory &&
+      file.startsWith(prefix) &&
+      isTestFileTarget(file),
+  );
+  return targets.length > 0 ? targets.toSorted((left, right) => left.localeCompare(right)) : null;
+}
+
 function includePatternMatchesAnyFile(pattern, files) {
   return files.some((file) => file === pattern || path.matchesGlob(file, pattern));
 }
@@ -2810,6 +2831,10 @@ function expandExplicitSourceTestTargets(targetArgs, cwd) {
   const forceFullImportGraph = sourceTargetCount > EXPLICIT_SOURCE_FULL_IMPORT_GRAPH_THRESHOLD;
   return targetArgs.flatMap((targetArg) => {
     const relative = toRepoRelativeTarget(targetArg, cwd);
+    const prefixTargets = resolveExplicitTestPrefixTargets(targetArg, cwd);
+    if (prefixTargets) {
+      return prefixTargets;
+    }
     if (relative === "src/commands" && isExistingDirectoryTarget(targetArg, cwd)) {
       return [COMMANDS_LIGHT_VITEST_CONFIG, COMMANDS_VITEST_CONFIG];
     }
@@ -2928,6 +2953,9 @@ export function findUnmatchedExplicitTestTargets(args, cwd = process.cwd()) {
 
     const absolute = path.resolve(cwd, targetArg);
     if (!fs.existsSync(absolute)) {
+      if (resolveExplicitTestPrefixTargets(targetArg, cwd)) {
+        continue;
+      }
       unmatched.push({
         target: targetArg,
         reason: "path-does-not-exist",
diff --git a/src/agents/openai-transport-stream.base.test-utils.ts b/src/agents/openai-transport-stream.base.test.ts
similarity index 99%
rename from src/agents/openai-transport-stream.base.test-utils.ts
rename to src/agents/openai-transport-stream.base.test.ts
index aad7561f1a8..83cabb8660f 100644
--- a/src/agents/openai-transport-stream.base.test-utils.ts
+++ b/src/agents/openai-transport-stream.base.test.ts
@@ -1,4 +1,3 @@
-// Imported by openai-transport-stream.test.ts to keep its mocked suite in one Vitest module graph.
 import type { ChatCompletionChunk } from "openai/resources/chat/completions.js";
 import type { Api, Model } from "openclaw/plugin-sdk/llm";
 import { describe, expect, it, vi } from "vitest";
diff --git a/src/agents/openai-transport-stream.deepseek-and-shaping.test-utils.ts b/src/agents/openai-transport-stream.deepseek-and-shaping.test.ts
similarity index 99%
rename from src/agents/openai-transport-stream.deepseek-and-shaping.test-utils.ts
rename to src/agents/openai-transport-stream.deepseek-and-shaping.test.ts
index 525f763619e..4f004477616 100644
--- a/src/agents/openai-transport-stream.deepseek-and-shaping.test-utils.ts
+++ b/src/agents/openai-transport-stream.deepseek-and-shaping.test.ts
@@ -1,4 +1,3 @@
-// Imported by openai-transport-stream.test.ts to keep its mocked suite in one Vitest module graph.
 import { createServer } from "node:http";
 import { SYSTEM_PROMPT_CACHE_BOUNDARY } from "@openclaw/ai/internal/shared";
 import type { ChatCompletionChunk } from "openai/resources/chat/completions.js";
diff --git a/src/agents/openai-transport-stream.inline-reasoning-and-tool-calls.test-utils.ts b/src/agents/openai-transport-stream.inline-reasoning-and-tool-calls.test.ts
similarity index 99%
rename from src/agents/openai-transport-stream.inline-reasoning-and-tool-calls.test-utils.ts
rename to src/agents/openai-transport-stream.inline-reasoning-and-tool-calls.test.ts
index 183b7780ead..8e89477c8fd 100644
--- a/src/agents/openai-transport-stream.inline-reasoning-and-tool-calls.test-utils.ts
+++ b/src/agents/openai-transport-stream.inline-reasoning-and-tool-calls.test.ts
@@ -1,4 +1,3 @@
-// Imported by openai-transport-stream.test.ts to keep its mocked suite in one Vitest module graph.
 import { createServer } from "node:http";
 import { expectDefined } from "@openclaw/normalization-core";
 import { describe, expect, it } from "vitest";
diff --git a/src/agents/openai-transport-stream.reasoning-and-cache.test-utils.ts b/src/agents/openai-transport-stream.reasoning-and-cache.test.ts
similarity index 99%
rename from src/agents/openai-transport-stream.reasoning-and-cache.test-utils.ts
rename to src/agents/openai-transport-stream.reasoning-and-cache.test.ts
index 42f999f2b32..30b9a004146 100644
--- a/src/agents/openai-transport-stream.reasoning-and-cache.test-utils.ts
+++ b/src/agents/openai-transport-stream.reasoning-and-cache.test.ts
@@ -1,4 +1,3 @@
-// Imported by openai-transport-stream.test.ts to keep its mocked suite in one Vitest module graph.
 import { SYSTEM_PROMPT_CACHE_BOUNDARY } from "@openclaw/ai/internal/shared";
 import { expectDefined } from "@openclaw/normalization-core";
 import type { Model } from "openclaw/plugin-sdk/llm";
diff --git a/src/agents/openai-transport-stream.replay-and-tools.test-utils.ts b/src/agents/openai-transport-stream.replay-and-tools.test.ts
similarity index 99%
rename from src/agents/openai-transport-stream.replay-and-tools.test-utils.ts
rename to src/agents/openai-transport-stream.replay-and-tools.test.ts
index eb0a721d319..3a02dd15280 100644
--- a/src/agents/openai-transport-stream.replay-and-tools.test-utils.ts
+++ b/src/agents/openai-transport-stream.replay-and-tools.test.ts
@@ -1,4 +1,3 @@
-// Imported by openai-transport-stream.test.ts to keep its mocked suite in one Vitest module graph.
 import { SYSTEM_PROMPT_CACHE_BOUNDARY } from "@openclaw/ai/internal/shared";
 import { expectDefined } from "@openclaw/normalization-core";
 import OpenAI from "openai";
diff --git a/src/agents/openai-transport-stream.replay-sanitization.test-utils.ts b/src/agents/openai-transport-stream.replay-sanitization.test.ts
similarity index 99%
rename from src/agents/openai-transport-stream.replay-sanitization.test-utils.ts
rename to src/agents/openai-transport-stream.replay-sanitization.test.ts
index bcfaf8e3a18..7e8d41a2394 100644
--- a/src/agents/openai-transport-stream.replay-sanitization.test-utils.ts
+++ b/src/agents/openai-transport-stream.replay-sanitization.test.ts
@@ -1,4 +1,3 @@
-// Imported by openai-transport-stream.test.ts to keep its mocked suite in one Vitest module graph.
 import type { Model } from "openclaw/plugin-sdk/llm";
 import { describe, expect, it } from "vitest";
 import { buildOpenAICompletionsParams } from "./openai-transport-stream.js";
diff --git a/src/agents/openai-transport-stream.streaming.test-utils.ts b/src/agents/openai-transport-stream.streaming.test.ts
similarity index 99%
rename from src/agents/openai-transport-stream.streaming.test-utils.ts
rename to src/agents/openai-transport-stream.streaming.test.ts
index d9d6d9fc396..476ce195590 100644
--- a/src/agents/openai-transport-stream.streaming.test-utils.ts
+++ b/src/agents/openai-transport-stream.streaming.test.ts
@@ -1,4 +1,3 @@
-// Imported by openai-transport-stream.test.ts to keep its mocked suite in one Vitest module graph.
 import { createServer } from "node:http";
 import type { Model } from "openclaw/plugin-sdk/llm";
 import { describe, expect, it, vi } from "vitest";
diff --git a/src/agents/openai-transport-stream.test.ts b/src/agents/openai-transport-stream.test.ts
deleted file mode 100644
index 5c35bceb870..00000000000
--- a/src/agents/openai-transport-stream.test.ts
+++ /dev/null
@@ -1,8 +0,0 @@
-import "./openai-transport-stream.base.test-utils.js";
-import "./openai-transport-stream.streaming.test-utils.js";
-import "./openai-transport-stream.deepseek-and-shaping.test-utils.js";
-import "./openai-transport-stream.replay-and-tools.test-utils.js";
-import "./openai-transport-stream.reasoning-and-cache.test-utils.js";
-import "./openai-transport-stream.usage-and-calls.test-utils.js";
-import "./openai-transport-stream.inline-reasoning-and-tool-calls.test-utils.js";
-import "./openai-transport-stream.replay-sanitization.test-utils.js";
diff --git a/src/agents/openai-transport-stream.usage-and-calls.test-utils.ts b/src/agents/openai-transport-stream.usage-and-calls.test.ts
similarity index 99%
rename from src/agents/openai-transport-stream.usage-and-calls.test-utils.ts
rename to src/agents/openai-transport-stream.usage-and-calls.test.ts
index 4a78ec01916..69bea852708 100644
--- a/src/agents/openai-transport-stream.usage-and-calls.test-utils.ts
+++ b/src/agents/openai-transport-stream.usage-and-calls.test.ts
@@ -1,4 +1,3 @@
-// Imported by openai-transport-stream.test.ts to keep its mocked suite in one Vitest module graph.
 import type { Model } from "openclaw/plugin-sdk/llm";
 import { describe, expect, it } from "vitest";
 import { buildOpenAICompletionsParams } from "./openai-transport-stream.js";
diff --git a/src/scripts/test-projects.test.ts b/src/scripts/test-projects.test.ts
index 78ac48fbf2b..273b5ae0dd4 100644
--- a/src/scripts/test-projects.test.ts
+++ b/src/scripts/test-projects.test.ts
@@ -94,12 +94,12 @@ describe("test-projects args", () => {
     ]);
   });
 
-  it("keeps extracted test entries in their owner configs", () => {
-    expect(buildVitestRunPlans(["src/agents/openai-transport-stream.test.ts"])).toEqual([
+  it("keeps split test entries in their owner configs", () => {
+    expect(buildVitestRunPlans(["src/agents/openai-transport-stream.base.test.ts"])).toEqual([
       {
         config: "test/vitest/vitest.agents.config.ts",
         forwardedArgs: [],
-        includePatterns: ["src/agents/openai-transport-stream.test.ts"],
+        includePatterns: ["src/agents/openai-transport-stream.base.test.ts"],
         watchMode: false,
       },
     ]);
@@ -113,6 +113,26 @@ describe("test-projects args", () => {
     ]);
   });
 
+  it("expands a test filename prefix into standalone sibling suites", () => {
+    expect(buildVitestRunPlans(["src/agents/openai-transport-stream"])).toEqual([
+      {
+        config: "test/vitest/vitest.agents.config.ts",
+        forwardedArgs: [],
+        includePatterns: [
+          "src/agents/openai-transport-stream.base.test.ts",
+          "src/agents/openai-transport-stream.deepseek-and-shaping.test.ts",
+          "src/agents/openai-transport-stream.inline-reasoning-and-tool-calls.test.ts",
+          "src/agents/openai-transport-stream.reasoning-and-cache.test.ts",
+          "src/agents/openai-transport-stream.replay-and-tools.test.ts",
+          "src/agents/openai-transport-stream.replay-sanitization.test.ts",
+          "src/agents/openai-transport-stream.streaming.test.ts",
+          "src/agents/openai-transport-stream.usage-and-calls.test.ts",
+        ],
+        watchMode: false,
+      },
+    ]);
+  });
+
   it("routes top-level repo tests to the contracts config", () => {
     expect(buildVitestRunPlans(["test/appcast.test.ts"])).toEqual([
       {
diff --git a/test/vitest-unit-fast-config.test.ts b/test/vitest-unit-fast-config.test.ts
index aac46d013dd..6d0b5d97d78 100644
--- a/test/vitest-unit-fast-config.test.ts
+++ b/test/vitest-unit-fast-config.test.ts
@@ -197,7 +197,7 @@ describe("unit-fast vitest lane", () => {
 
   it("keeps obvious stateful files out of the unit-fast lane", () => {
     expect(isUnitFastTestFile("src/plugin-sdk/temp-path.test.ts")).toBe(false);
-    expect(isUnitFastTestFile("src/agents/openai-transport-stream.test.ts")).toBe(false);
+    expect(isUnitFastTestFile("src/agents/openai-transport-stream.base.test.ts")).toBe(false);
     expect(isUnitFastTestFile("src/auto-reply/reply/dispatch-from-config.test.ts")).toBe(false);
     expect(isUnitFastTestFile("src/agents/sandbox.resolveSandboxContext.test.ts")).toBe(false);
     expect(isUnitFastTestFile("src/acp/runtime/session-meta.test.ts")).toBe(false);
diff --git a/test/vitest/vitest.unit-fast-paths.mjs b/test/vitest/vitest.unit-fast-paths.mjs
index 59a93c0c4d1..0bf2613b37e 100644
--- a/test/vitest/vitest.unit-fast-paths.mjs
+++ b/test/vitest/vitest.unit-fast-paths.mjs
@@ -221,8 +221,8 @@ const broadUnitFastCandidateGlobs = [
   "packages/**/*.test.ts",
   "test/**/*.test.ts",
 ];
-const ownerRoutedUnitTestFiles = [
-  "src/agents/openai-transport-stream.test.ts",
+const ownerRoutedUnitTestPatterns = [
+  "src/agents/openai-transport-stream.*.test.ts",
   "src/auto-reply/reply/dispatch-from-config.test.ts",
 ];
 const broadUnitFastCandidateSkipGlobs = [
@@ -233,9 +233,8 @@ const broadUnitFastCandidateSkipGlobs = [
   // Explicit bundled ownership outranks content-based discovery. Otherwise extracting
   // a test body can silently move its entry to a config with the wrong mocked setup.
   ...bundledPluginDependentUnitTestFiles,
-  // These entries register tests from imported utility modules. Their tiny entry files
-  // cannot carry the stateful-content signals that keep them in their owner configs.
-  ...ownerRoutedUnitTestFiles,
+  // Keep these suites in owner configs even when content-based discovery changes.
+  ...ownerRoutedUnitTestPatterns,
   "src/agents/sandbox.resolveSandboxContext.test.ts",
   "src/acp/runtime/session-meta.test.ts",
   "src/channels/plugins/contracts/**/*.test.ts",