diff --git a/scripts/run-vitest.mjs b/scripts/run-vitest.mjs
index 46eb11805671..4346d62acf8b 100644
--- a/scripts/run-vitest.mjs
+++ b/scripts/run-vitest.mjs
@@ -1,6 +1,7 @@
 import { spawn } from "node:child_process";
 import { createRequire } from "node:module";
 import path from "node:path";
+import { isUnitUiTestTarget } from "../test/vitest/vitest.ui-paths.mjs";
 import { resolveLocalVitestEnv } from "./lib/vitest-local-scheduling.mjs";
 import { spawnPnpmRunner } from "./pnpm-runner.mjs";
 import {
@@ -13,6 +14,7 @@ const TRUTHY_ENV_VALUES = new Set(["1", "true", "yes", "on"]);
 const ANSI_CSI_PREFIX = `${String.fromCharCode(27)}[`;
 const ANSI_CSI_SUFFIX_RE = /^[0-?]*[ -/]*[@-~]/u;
 const SUPPRESSED_VITEST_STDERR_PATTERNS = ["[PLUGIN_TIMINGS]"];
+const UNIT_UI_VITEST_CONFIG = "test/vitest/vitest.unit-ui.config.ts";
 const require = createRequire(import.meta.url);
 
 function isTruthyEnvValue(value) {
@@ -92,6 +94,31 @@ export function resolveDirectNodeVitestArgs(pnpmArgs) {
   return pnpmArgs[0] === "exec" && pnpmArgs[1] === "node" ? pnpmArgs.slice(2) : null;
 }
 
+function hasExplicitVitestConfigArg(argv) {
+  return argv.some((arg) => arg === "--config" || arg === "-c" || arg.startsWith("--config="));
+}
+
+function toRepoRelativeArg(arg, cwd) {
+  const normalized = path.isAbsolute(arg) ? path.relative(cwd, arg) : arg;
+  return normalized.replaceAll(path.sep, "/").replace(/^\.\//u, "");
+}
+
+export function resolveImplicitVitestArgs(argv, cwd = process.cwd()) {
+  if (hasExplicitVitestConfigArg(argv)) {
+    return argv;
+  }
+  const testTargets = argv
+    .filter((arg) => !arg.startsWith("-") && arg.endsWith(".test.ts"))
+    .map((arg) => toRepoRelativeArg(arg, cwd));
+  if (testTargets.length === 0 || !testTargets.every(isUnitUiTestTarget)) {
+    return argv;
+  }
+  if (argv[0] === "run") {
+    return ["run", "--config", UNIT_UI_VITEST_CONFIG, ...argv.slice(1)];
+  }
+  return ["--config", UNIT_UI_VITEST_CONFIG, ...argv];
+}
+
 function spawnVitestProcess({ pnpmArgs, spawnParams }) {
   const directNodeArgs = resolveDirectNodeVitestArgs(pnpmArgs);
   if (directNodeArgs) {
@@ -271,11 +298,18 @@ function main(argv = process.argv.slice(2), env = process.env) {
     process.exit(1);
   }
 
+  const vitestArgs = resolveImplicitVitestArgs(argv);
   const { child, teardown } = spawnWatchedVitestProcess({
-    pnpmArgs: ["exec", "node", ...resolveVitestNodeArgs(env), resolveVitestCliEntry(), ...argv],
+    pnpmArgs: [
+      "exec",
+      "node",
+      ...resolveVitestNodeArgs(env),
+      resolveVitestCliEntry(),
+      ...vitestArgs,
+    ],
     spawnParams: resolveVitestSpawnParams(env),
     env,
-    label: argv.join(" "),
+    label: vitestArgs.join(" "),
   });
 
   child.on("exit", (code, signal) => {
diff --git a/scripts/test-projects.test-support.mjs b/scripts/test-projects.test-support.mjs
index e8c6206b5de3..b140146369eb 100644
--- a/scripts/test-projects.test-support.mjs
+++ b/scripts/test-projects.test-support.mjs
@@ -34,6 +34,7 @@ import {
   resolvePluginSdkLightIncludePattern,
 } from "../test/vitest/vitest.plugin-sdk-paths.mjs";
 import { fullSuiteVitestShards } from "../test/vitest/vitest.test-shards.mjs";
+import { isUnitUiTestTarget } from "../test/vitest/vitest.ui-paths.mjs";
 import { resolveUnitFastTestIncludePattern } from "../test/vitest/vitest.unit-fast-paths.mjs";
 import {
   isBoundaryTestFile,
@@ -1126,23 +1127,6 @@ function isVitestConfigTargetForKind(kind, targetArg, cwd) {
   return resolveVitestConfigTargetKind(toRepoRelativeTarget(targetArg, cwd)) === kind;
 }
 
-function isUnitUiTestTarget(relative) {
-  if (!relative.endsWith(".test.ts")) {
-    return false;
-  }
-  return (
-    relative === "ui/src/ui/app-chat.test.ts" ||
-    relative.startsWith("ui/src/ui/chat/") ||
-    relative === "ui/src/ui/views/agents-utils.test.ts" ||
-    relative === "ui/src/ui/views/channels.test.ts" ||
-    relative === "ui/src/ui/views/chat.test.ts" ||
-    relative === "ui/src/ui/views/dreaming.test.ts" ||
-    relative === "ui/src/ui/views/usage-render-details.test.ts" ||
-    relative === "ui/src/ui/controllers/agents.test.ts" ||
-    relative === "ui/src/ui/controllers/chat.test.ts"
-  );
-}
-
 function isControlUiE2eTarget(relative) {
   return (
     relative === "ui/src/test-helpers/control-ui-e2e.ts" ||
diff --git a/test/scripts/run-vitest.test.ts b/test/scripts/run-vitest.test.ts
index faf3e0b08fed..d53c363e862a 100644
--- a/test/scripts/run-vitest.test.ts
+++ b/test/scripts/run-vitest.test.ts
@@ -3,6 +3,7 @@ import { describe, expect, it, vi } from "vitest";
 import {
   installVitestNoOutputWatchdog,
   resolveDirectNodeVitestArgs,
+  resolveImplicitVitestArgs,
   resolveVitestNodeArgs,
   resolveVitestNoOutputTimeoutMs,
   resolveVitestSpawnParams,
@@ -26,6 +27,40 @@ describe("scripts/run-vitest", () => {
     expect(resolveDirectNodeVitestArgs(["exec", "vitest", "run"])).toBeNull();
   });
 
+  it("routes explicit unit ui tests through the narrow unit ui config", () => {
+    expect(
+      resolveImplicitVitestArgs([
+        "ui/src/ui/controllers/chat.test.ts",
+        "-t",
+        "keeps optimistic user attachment previews",
+      ]),
+    ).toEqual([
+      "--config",
+      "test/vitest/vitest.unit-ui.config.ts",
+      "ui/src/ui/controllers/chat.test.ts",
+      "-t",
+      "keeps optimistic user attachment previews",
+    ]);
+  });
+
+  it("does not override explicit vitest configs", () => {
+    const argv = [
+      "--config",
+      "test/vitest/vitest.ui.config.ts",
+      "ui/src/ui/controllers/chat.test.ts",
+    ];
+    expect(resolveImplicitVitestArgs(argv)).toBe(argv);
+  });
+
+  it("keeps the run subcommand first when routing unit ui tests", () => {
+    expect(resolveImplicitVitestArgs(["run", "ui/src/ui/controllers/chat.test.ts"])).toEqual([
+      "run",
+      "--config",
+      "test/vitest/vitest.unit-ui.config.ts",
+      "ui/src/ui/controllers/chat.test.ts",
+    ]);
+  });
+
   it("allows opting back into Maglev explicitly", () => {
     expect(
       resolveVitestNodeArgs({
diff --git a/test/vitest/vitest.ui-paths.mjs b/test/vitest/vitest.ui-paths.mjs
new file mode 100644
index 000000000000..7c2576c107c5
--- /dev/null
+++ b/test/vitest/vitest.ui-paths.mjs
@@ -0,0 +1,28 @@
+export const unitUiIncludePatterns = [
+  "ui/src/ui/app-chat.test.ts",
+  "ui/src/ui/chat/**/*.test.ts",
+  "ui/src/ui/views/agents-utils.test.ts",
+  "ui/src/ui/views/channels.test.ts",
+  "ui/src/ui/views/chat.test.ts",
+  "ui/src/ui/views/dreaming.test.ts",
+  "ui/src/ui/views/usage-render-details.test.ts",
+  "ui/src/ui/controllers/agents.test.ts",
+  "ui/src/ui/controllers/chat.test.ts",
+];
+
+export function isUnitUiTestTarget(relative) {
+  if (!relative.endsWith(".test.ts")) {
+    return false;
+  }
+  return (
+    relative === "ui/src/ui/app-chat.test.ts" ||
+    relative.startsWith("ui/src/ui/chat/") ||
+    relative === "ui/src/ui/views/agents-utils.test.ts" ||
+    relative === "ui/src/ui/views/channels.test.ts" ||
+    relative === "ui/src/ui/views/chat.test.ts" ||
+    relative === "ui/src/ui/views/dreaming.test.ts" ||
+    relative === "ui/src/ui/views/usage-render-details.test.ts" ||
+    relative === "ui/src/ui/controllers/agents.test.ts" ||
+    relative === "ui/src/ui/controllers/chat.test.ts"
+  );
+}
diff --git a/test/vitest/vitest.ui.config.ts b/test/vitest/vitest.ui.config.ts
index a5d0fdeb2740..e10dcb031fdc 100644
--- a/test/vitest/vitest.ui.config.ts
+++ b/test/vitest/vitest.ui.config.ts
@@ -1,17 +1,6 @@
 import { createScopedVitestConfig } from "./vitest.scoped-config.ts";
 import { jsdomOptimizedDeps } from "./vitest.shared.config.ts";
-
-export const unitUiIncludePatterns = [
-  "ui/src/ui/app-chat.test.ts",
-  "ui/src/ui/chat/**/*.test.ts",
-  "ui/src/ui/views/agents-utils.test.ts",
-  "ui/src/ui/views/channels.test.ts",
-  "ui/src/ui/views/chat.test.ts",
-  "ui/src/ui/views/dreaming.test.ts",
-  "ui/src/ui/views/usage-render-details.test.ts",
-  "ui/src/ui/controllers/agents.test.ts",
-  "ui/src/ui/controllers/chat.test.ts",
-];
+import { unitUiIncludePatterns } from "./vitest.ui-paths.mjs";
 
 export function createUiVitestConfig(
   env?: Record<string, string | undefined>,
diff --git a/test/vitest/vitest.unit-ui.config.ts b/test/vitest/vitest.unit-ui.config.ts
index a06998e1fbff..61af2c16c018 100644
--- a/test/vitest/vitest.unit-ui.config.ts
+++ b/test/vitest/vitest.unit-ui.config.ts
@@ -1,4 +1,5 @@
-import { createUiVitestConfig, unitUiIncludePatterns } from "./vitest.ui.config.ts";
+import { unitUiIncludePatterns } from "./vitest.ui-paths.mjs";
+import { createUiVitestConfig } from "./vitest.ui.config.ts";
 
 export default createUiVitestConfig(process.env, {
   includePatterns: unitUiIncludePatterns,