diff --git a/cmd/mbf/internal/pkgserver/ui/jstest/jstest.ts b/cmd/mbf/internal/pkgserver/ui/jstest/jstest.ts
new file mode 100644
index 00000000..79c47d2a
--- /dev/null
+++ b/cmd/mbf/internal/pkgserver/ui/jstest/jstest.ts
@@ -0,0 +1,136 @@
+export interface TestResult {
+    success: boolean;
+    logs: string[];
+}
+
+// =============================================================================
+// Reporting
+
+export interface Reporter {
+    // While we could simply call a function with a tree representing all
+    // results, which would indeed greatly simplify implementation of reporters,
+    // simply registering a path and allowing the reporter to—either implicitly
+    // or explicitly—construct a tree themselves allows for results to be
+    // *incrementally reported*, instead of a great deal of silence until all
+    // tests finish.
+    update(path: string[], result: TestResult): void;
+    // With just update(), the reporter never knows when all tests have
+    // completed. The simplest possible use for this is to notify the user, but
+    // its intent is actually more tailored to the StreamReporter scenario:
+    // while destructively updated report rendering (as with a tree of DOM nodes
+    // which are mutated) always displays the results in a structured manner
+    // matching that of the tests, “rerendering” or otherwise destructively
+    // updating the rendered output might be infeasible in some paradigms, such
+    // as command-line applications—all existing implementations of such
+    // rendering both mess up the scrollback position and necessarily crop out
+    // some of the data at the bottom (since the top of the tree is forced to be
+    // at the top of the screen, as one cannot unscroll portably). Explicitly
+    // signaling to the reporter that no more results will be received permits
+    // it to simply display live test progress linearly, while building up
+    // a tree and displaying it once it's known the tree is complete.
+    finalize(): void;
+}
+
+export interface Stream {
+    writeln(s: string): void;
+}
+
+const SEP = " ❯ ";
+
+// A simple reporter that outputs to some stream; suitable for CLIs.
+export class StreamReporter implements Reporter {
+    stream: Stream;
+    verbose: boolean;
+    #failures: ({ path: string[] } & TestResult)[];
+    counts: { successes: number, failures: number };
+
+    constructor(stream: Stream, verbose: boolean = false) {
+        this.stream = stream;
+        this.verbose = verbose;
+        this.#failures = [];
+        this.counts = { successes: 0, failures: 0 };
+    }
+
+    update(path: string[], result: TestResult) {
+        if (path.length === 0) throw new RangeError("path is empty");
+        const pathStr = path.join(SEP);
+        if (result.success) {
+            this.counts.successes++;
+            // NOTE: emojis are used instead of colored Unicode symbols as
+            // coloring isn't possible through all streams, which would make
+            // this terminal-specific, and even in terminals and emulators
+            // thereof, it's very tedious to correctly detect whether one should
+            // use colors (https://no-color.org, https://bixense.com/clicolors,
+            // https://force-color.org), ensure reasonable contrast is retained
+            // on every possible theme (using reverse video is often the only
+            // way), and be immediately noticeable. Emojis have an upper hand in
+            // that they're more common than obscure Unicode characters—which
+            // also means you're more likely to have an emoji font but not
+            // a font with those symbols—and that they're double-width.
+            if (this.verbose) this.stream.writeln(`✅️ ${pathStr}`);
+        } else {
+            this.counts.failures++;
+            this.stream.writeln(`⚠️ ${pathStr}`);
+            this.#failures.push({ path, ...result });
+        }
+    }
+
+    finalize() {
+        // Transform [{ path: ["a", "b", "c"] }, { path: ["a", "b", "d"] }] into
+        // { "a ❯ b": ["c", "d"] }. NOTE: intermediate nodes are collapsed as
+        // excessive nesting is difficult to convey clearly in a text-only
+        // environment.
+        let pathMap = new Map<string, ({ name: string } & TestResult)[]>();
+        for (const f of this.#failures) {
+            if (f.path.length === 0) throw new RangeError("path is empty");
+            const key = f.path.slice(0, -1).join(SEP);
+            if (!pathMap.has(key)) pathMap.set(key, []);
+            pathMap.get(key)!.push({ name: f.path.at(-1)!, ...f });
+        }
+
+        this.stream.writeln("");
+        this.stream.writeln("FAILURES");
+        this.stream.writeln("========");
+
+        for (const [path, tests] of pathMap) {
+            if (tests.length === 1) {
+                this.#writeOutput(tests[0], path ? `${path}${SEP}` : "", false);
+            } else {
+                this.stream.writeln(path);
+                for (const t of tests) this.#writeOutput(t, "  - ", true);
+            }
+        }
+
+        this.stream.writeln("");
+        const { successes, failures } = this.counts;
+        this.stream.writeln(`${successes} succeeded, ${failures} failed`);
+    }
+
+    #writeOutput(test: { name: string } & TestResult, prefix: string, nested: boolean) {
+        let output = "";
+        if (test.logs.length) {
+            // Individual logs might span multiple lines, so join them together
+            // then split it again.
+            const logStr = test.logs.join("\n");
+            const lines = logStr.split("\n");
+            if (lines.length <= 1) {
+                output = `: ${logStr}`;
+            } else {
+                const padding = nested ? "      " : "  ";
+                output = ":\n" + lines.map((line) => padding + line).join("\n");
+            }
+        }
+        this.stream.writeln(`${prefix}${test.name}${output}`);
+    }
+}
+
+const r = new StreamReporter({ writeln: console.log }, true);
+r.update(["alien", "can walk"], { success: false, logs: ["assertion failed"] });
+r.update(["alien", "can speak"], { success: false, logs: ["Uncaught ReferenceError: larynx is not defined"] });
+r.update(["alien", "sleep"], { success: true, logs: [] });
+r.update(["Tetromino", "generate", "tessellates"], { success: false, logs: ["assertion failed: 1 != 2"] });
+r.update(["Tetromino", "solve", "works"], { success: true, logs: [] });
+r.update(["discombobulate", "english"], { success: false, logs: ["hippopotomonstrosesquipedaliophobia\npneumonoultramicroscopicsilicovolcanoconiosis", "supercalifragilisticexpialidocious"] });
+r.update(["discombobulate", "geography"], { success: false, logs: ["Taumatawhakatangihangakoauauotamateaturipukakapikimaungahoronukupokaiwhenuakitanatahu"] });
+r.update(["recombobulate"], { success: true, logs: [] });
+r.finalize();
diff --git a/cmd/mbf/internal/pkgserver/ui/test_ui.go b/cmd/mbf/internal/pkgserver/ui/test_ui.go
new file mode 100644
index 00000000..aeb14b12
--- /dev/null
+++ b/cmd/mbf/internal/pkgserver/ui/test_ui.go
@@ -0,0 +1,11 @@
+//go:build frontend && frontend_test
+
+package ui
+
+import "embed"
+
+//go:generate tsc -p tsconfig.test.json
+//go:generate cp index.html style.css favicon.ico static
+//go:embed static
+var _static embed.FS
+var static = staticFS(_static)
diff --git a/cmd/mbf/internal/pkgserver/ui/tsconfig.json b/cmd/mbf/internal/pkgserver/ui/tsconfig.json
index 24df4936..a157aab9 100644
--- a/cmd/mbf/internal/pkgserver/ui/tsconfig.json
+++ b/cmd/mbf/internal/pkgserver/ui/tsconfig.json
@@ -1,8 +1,11 @@
+// This file defines the common options for all TypeScript here. This shouldn't
+// be directly used as the project file in builds; see tsconfig.*.json instead,
+// which inherit from this file and essentially define specific build targets.
 {
   "compilerOptions": {
     "target": "ES2024",
     "strict": true,
     "alwaysStrict": true,
-    "outDir": "static"
-  }
-}
\ No newline at end of file
+    "outDir": "static",
+  },
+}
diff --git a/cmd/mbf/internal/pkgserver/ui/tsconfig.test.json b/cmd/mbf/internal/pkgserver/ui/tsconfig.test.json
new file mode 100644
index 00000000..0e38d7a4
--- /dev/null
+++ b/cmd/mbf/internal/pkgserver/ui/tsconfig.test.json
@@ -0,0 +1,5 @@
+// Project file for building pkgserver alongside its tests. test_ui.go uses this
+// as its project file.
+{
+  "extends": "./tsconfig.json",
+}
diff --git a/cmd/mbf/internal/pkgserver/ui/tsconfig.ui.json b/cmd/mbf/internal/pkgserver/ui/tsconfig.ui.json
new file mode 100644
index 00000000..a2c8979f
--- /dev/null
+++ b/cmd/mbf/internal/pkgserver/ui/tsconfig.ui.json
@@ -0,0 +1,6 @@
+// Project file for building just the pkgserver UI, with none of the testing
+// stuff attached. ui_full.go uses this as its project file.
+{
+  "extends": "./tsconfig.json",
+  "exclude": ["jstest"],
+}
diff --git a/cmd/mbf/internal/pkgserver/ui/ui.go b/cmd/mbf/internal/pkgserver/ui/ui.go
index 3fc0d89c..352a3f8f 100644
--- a/cmd/mbf/internal/pkgserver/ui/ui.go
+++ b/cmd/mbf/internal/pkgserver/ui/ui.go
@@ -1,7 +1,19 @@
 // Package ui holds the static web UI.
 package ui
 
-import "net/http"
+import (
+	"io/fs"
+	"net/http"
+)
+
+// staticFS is an internal helper to wrap around go:embed's filesystem.
+func staticFS(static fs.FS) fs.FS {
+	if f, err := fs.Sub(static, "static"); err != nil {
+		panic(err)
+	} else {
+		return f
+	}
+}
 
 // Register arranges for mux to serve the embedded frontend.
 func Register(mux *http.ServeMux) {
diff --git a/cmd/mbf/internal/pkgserver/ui/ui_full.go b/cmd/mbf/internal/pkgserver/ui/ui_full.go
index e3fc9134..3b5fb24f 100644
--- a/cmd/mbf/internal/pkgserver/ui/ui_full.go
+++ b/cmd/mbf/internal/pkgserver/ui/ui_full.go
@@ -1,21 +1,11 @@
-//go:build frontend
+//go:build frontend && !frontend_test
 
 package ui
 
-import (
-	"embed"
-	"io/fs"
-)
+import "embed"
 
-//go:generate tsc
+//go:generate tsc -p tsconfig.ui.json
 //go:generate cp index.html style.css favicon.ico static
 //go:embed static
 var _static embed.FS
-
-var static = func() fs.FS {
-	if f, err := fs.Sub(_static, "static"); err != nil {
-		panic(err)
-	} else {
-		return f
-	}
-}()
+var static = staticFS(_static)