diff --git a/apps/web/src/App.tsx b/apps/web/src/App.tsx
index 2102113..b9b91a5 100644
--- a/apps/web/src/App.tsx
+++ b/apps/web/src/App.tsx
@@ -9,6 +9,7 @@ import { Home } from '@/screens/Home';
 import { ProjectsIndex } from '@/screens/ProjectsIndex';
 import { ProjectDetail } from '@/screens/ProjectDetail';
 import { ProjectEdit } from '@/screens/ProjectEdit';
+import { ProjectBuzzNew } from '@/screens/ProjectBuzzNew';
 import { PeopleIndex } from '@/screens/PeopleIndex';
 import { PersonDetail } from '@/screens/PersonDetail';
 import { ProfileEdit } from '@/screens/ProfileEdit';
@@ -23,7 +24,6 @@ import { TagsNamespace } from '@/screens/TagsNamespace';
 import { TagDetail } from '@/screens/TagDetail';
 import { Volunteer } from '@/screens/Volunteer';
 import { Sponsor } from '@/screens/Sponsor';
-import { ComingSoon } from '@/pages/ComingSoon';
 import { Contact } from '@/pages/Contact';
 import { StaticPage } from '@/pages/StaticPage';
 import { NotFound } from '@/pages/NotFound';
@@ -45,7 +45,7 @@ const router = createBrowserRouter([
       { path: '/projects/:slug/edit', element: <ProjectEdit mode="edit" /> },
       { path: '/projects/:slug/updates/:number', element: <ProjectDetail anchor="update" /> },
       { path: '/projects/:slug/buzz/:buzzSlug', element: <ProjectDetail anchor="buzz" /> },
-      { path: '/projects/:slug/buzz/new', element: <ComingSoon /> },
+      { path: '/projects/:slug/buzz/new', element: <ProjectBuzzNew /> },
       { path: '/help-wanted', element: <HelpWantedIndex /> },
       { path: '/people', element: <Navigate to="/members" replace /> },
       { path: '/members', element: <PeopleIndex /> },
diff --git a/apps/web/src/screens/ProjectBuzzNew.tsx b/apps/web/src/screens/ProjectBuzzNew.tsx
new file mode 100644
index 0000000..cb4c3b5
--- /dev/null
+++ b/apps/web/src/screens/ProjectBuzzNew.tsx
@@ -0,0 +1,197 @@
+/**
+ * /projects/:slug/buzz/new — log a buzz item.
+ *
+ * Per specs/api/projects-buzz.md → POST /api/projects/:slug/buzz.
+ * Any signed-in user can log buzz on any project (laddr precedent).
+ * Anonymous callers are redirected to /login with a return-to back here.
+ */
+import { useState, type FormEvent } from 'react';
+import { Link, Navigate, useNavigate, useParams } from 'react-router';
+import { toast } from 'sonner';
+import { Button } from '@/components/ui/button';
+import { Input } from '@/components/ui/input';
+import { Label } from '@/components/ui/label';
+import { Textarea } from '@/components/ui/textarea';
+import { useAuth } from '@/hooks/useAuth';
+import { api, ApiError, type CreateBuzzInput } from '@/lib/api';
+
+interface FormState {
+  headline: string;
+  url: string;
+  publishedAt: string;
+  summary: string;
+}
+
+function todayIso(): string {
+  const d = new Date();
+  const y = d.getFullYear();
+  const m = String(d.getMonth() + 1).padStart(2, '0');
+  const day = String(d.getDate()).padStart(2, '0');
+  return `${y}-${m}-${day}`;
+}
+
+export function ProjectBuzzNew() {
+  const { slug } = useParams<{ slug: string }>();
+  const navigate = useNavigate();
+  const { person, loading: authLoading } = useAuth();
+
+  const [form, setForm] = useState<FormState>({
+    headline: '',
+    url: '',
+    publishedAt: todayIso(),
+    summary: '',
+  });
+  const [submitting, setSubmitting] = useState(false);
+  const [fieldErrors, setFieldErrors] = useState<Record<string, string>>({});
+
+  if (!slug) return <Navigate to="/projects" replace />;
+  if (authLoading) {
+    return (
+      <div className="container mx-auto px-4 py-8 text-muted-foreground">Loading…</div>
+    );
+  }
+  if (!person) {
+    return (
+      <Navigate
+        to={`/login?return=${encodeURIComponent(`/projects/${slug}/buzz/new`)}`}
+        replace
+      />
+    );
+  }
+
+  async function handleSubmit(e: FormEvent<HTMLFormElement>): Promise<void> {
+    e.preventDefault();
+    if (!slug) return;
+    setSubmitting(true);
+    setFieldErrors({});
+    try {
+      const input: CreateBuzzInput = {
+        headline: form.headline.trim(),
+        url: form.url.trim(),
+        publishedAt: form.publishedAt,
+        summary: form.summary.trim() ? form.summary.trim() : null,
+      };
+      await api.projects.postBuzz(slug, input);
+      toast.success('Buzz logged');
+      navigate(`/projects/${slug}#activity`);
+    } catch (err) {
+      if (err instanceof ApiError) {
+        // Spec carves out `duplicate_url` at 409; surface inline on the URL field.
+        if (err.code === 'duplicate_url') {
+          setFieldErrors({ url: 'This URL is already logged for this project.' });
+        } else if (err.fields) {
+          setFieldErrors(err.fields);
+        }
+        toast.error(err.message || 'Failed to log buzz');
+      } else {
+        toast.error('Failed to log buzz');
+      }
+    } finally {
+      setSubmitting(false);
+    }
+  }
+
+  return (
+    <div className="container mx-auto px-4 py-8 max-w-2xl">
+      <header className="mb-6">
+        <h1 className="text-2xl font-bold">Log Buzz</h1>
+        <p className="text-sm text-muted-foreground mt-1">
+          Add a press mention, blog post, or external link about{' '}
+          <Link to={`/projects/${slug}`} className="text-primary underline hover:no-underline">
+            this project
+          </Link>
+          .
+        </p>
+      </header>
+
+      <form onSubmit={handleSubmit} className="space-y-6">
+        <div className="space-y-1.5">
+          <Label htmlFor="headline">
+            Headline <span className="text-destructive">*</span>
+          </Label>
+          <Input
+            id="headline"
+            value={form.headline}
+            onChange={(e) => setForm((f) => ({ ...f, headline: e.target.value }))}
+            maxLength={200}
+            required
+            placeholder="The Inquirer praises Project X"
+            aria-invalid={fieldErrors['headline'] ? 'true' : 'false'}
+          />
+          {fieldErrors['headline'] && (
+            <p className="text-xs text-destructive">{fieldErrors['headline']}</p>
+          )}
+        </div>
+
+        <div className="space-y-1.5">
+          <Label htmlFor="url">
+            URL <span className="text-destructive">*</span>
+          </Label>
+          <Input
+            id="url"
+            type="url"
+            value={form.url}
+            onChange={(e) => setForm((f) => ({ ...f, url: e.target.value }))}
+            required
+            placeholder="https://www.inquirer.com/…"
+            aria-invalid={fieldErrors['url'] ? 'true' : 'false'}
+          />
+          {fieldErrors['url'] && (
+            <p className="text-xs text-destructive">{fieldErrors['url']}</p>
+          )}
+          <p className="text-xs text-muted-foreground">
+            Must be HTTPS. Each URL can only be logged once per project.
+          </p>
+        </div>
+
+        <div className="space-y-1.5">
+          <Label htmlFor="publishedAt">
+            Published <span className="text-destructive">*</span>
+          </Label>
+          <Input
+            id="publishedAt"
+            type="date"
+            value={form.publishedAt}
+            onChange={(e) => setForm((f) => ({ ...f, publishedAt: e.target.value }))}
+            required
+            max={todayIso()}
+            aria-invalid={fieldErrors['publishedAt'] ? 'true' : 'false'}
+          />
+          {fieldErrors['publishedAt'] && (
+            <p className="text-xs text-destructive">{fieldErrors['publishedAt']}</p>
+          )}
+        </div>
+
+        <div className="space-y-1.5">
+          <Label htmlFor="summary">Summary</Label>
+          <Textarea
+            id="summary"
+            value={form.summary}
+            onChange={(e) => setForm((f) => ({ ...f, summary: e.target.value }))}
+            maxLength={2000}
+            rows={4}
+            placeholder="Optional excerpt or quote. Markdown supported."
+          />
+          <p className="text-xs text-muted-foreground text-right">
+            {form.summary.length} / 2000
+          </p>
+          {fieldErrors['summary'] && (
+            <p className="text-xs text-destructive">{fieldErrors['summary']}</p>
+          )}
+        </div>
+
+        <div className="flex justify-end gap-2 pt-2">
+          <Button asChild variant="outline" type="button">
+            <Link to={`/projects/${slug}`}>Cancel</Link>
+          </Button>
+          <Button
+            type="submit"
+            disabled={submitting || !form.headline.trim() || !form.url.trim()}
+          >
+            {submitting ? 'Logging…' : 'Log Buzz'}
+          </Button>
+        </div>
+      </form>
+    </div>
+  );
+}
diff --git a/apps/web/tests/ProjectBuzzNew.test.tsx b/apps/web/tests/ProjectBuzzNew.test.tsx
new file mode 100644
index 0000000..1684098
--- /dev/null
+++ b/apps/web/tests/ProjectBuzzNew.test.tsx
@@ -0,0 +1,142 @@
+import { describe, expect, it, vi, beforeEach, afterEach } from 'vitest';
+import { fireEvent, screen, waitFor } from '@testing-library/react';
+import { Routes, Route } from 'react-router';
+import { renderScreen, mockOk } from './test-utils.js';
+import { ProjectBuzzNew } from '../src/screens/ProjectBuzzNew.js';
+import { AuthProvider } from '../src/hooks/useAuth.js';
+
+const SIGNED_IN_PERSON = {
+  data: {
+    person: {
+      id: '01951a3c-0000-7000-8000-000000000001',
+      slug: 'jane-doe',
+      fullName: 'Jane Doe',
+      avatarUrl: null,
+      accountLevel: 'user',
+    },
+    accountLevel: 'user',
+  },
+};
+
+function renderForm() {
+  return renderScreen(
+    <AuthProvider>
+      <Routes>
+        <Route path="/projects/:slug/buzz/new" element={<ProjectBuzzNew />} />
+        <Route path="/projects/:slug" element={<div>Project page</div>} />
+        <Route path="/login" element={<div>Login page</div>} />
+      </Routes>
+    </AuthProvider>,
+    { initialEntries: ['/projects/transit-app/buzz/new'] },
+  );
+}
+
+describe('ProjectBuzzNew', () => {
+  afterEach(() => {
+    vi.restoreAllMocks();
+  });
+
+  it('redirects anonymous callers to /login with return-to', async () => {
+    vi.spyOn(globalThis, 'fetch').mockImplementation(((input: string) => {
+      if (input.startsWith('/api/auth/me')) {
+        return Promise.resolve(new Response(null, { status: 404 }));
+      }
+      return Promise.resolve(new Response(null, { status: 404 }));
+    }) as typeof fetch);
+
+    renderForm();
+    await waitFor(() => {
+      expect(screen.getByText(/login page/i)).toBeInTheDocument();
+    });
+  });
+
+  describe('signed-in', () => {
+    beforeEach(() => {
+      vi.spyOn(globalThis, 'fetch').mockImplementation(((input: string, init?: RequestInit) => {
+        if (input.startsWith('/api/auth/me')) {
+          return Promise.resolve(
+            new Response(JSON.stringify(SIGNED_IN_PERSON), {
+              status: 200,
+              headers: { 'content-type': 'application/json' },
+            }),
+          );
+        }
+        if (
+          input === '/api/projects/transit-app/buzz' &&
+          init?.method === 'POST'
+        ) {
+          return Promise.resolve(
+            new Response(
+              JSON.stringify(
+                mockOk({
+                  id: 'b1',
+                  slug: 'fake-buzz',
+                  project: { slug: 'transit-app', title: 'Transit' },
+                  postedBy: null,
+                  headline: 'Hello',
+                  url: 'https://example.com',
+                  publishedAt: '2026-05-01T00:00:00Z',
+                  summary: null,
+                  summaryHtml: '',
+                  imageUrl: null,
+                  permissions: { canEdit: false, canDelete: false },
+                  createdAt: '2026-05-01T00:00:00Z',
+                  updatedAt: '2026-05-01T00:00:00Z',
+                }),
+              ),
+              { status: 201, headers: { 'content-type': 'application/json' } },
+            ),
+          );
+        }
+        return Promise.resolve(new Response(null, { status: 404 }));
+      }) as typeof fetch);
+    });
+
+    it('renders the form with required fields', async () => {
+      renderForm();
+      await waitFor(() => {
+        expect(screen.getByRole('heading', { name: /log buzz/i })).toBeInTheDocument();
+      });
+      expect(screen.getByLabelText(/headline/i)).toBeInTheDocument();
+      expect(screen.getByLabelText(/url/i)).toBeInTheDocument();
+      expect(screen.getByLabelText(/published/i)).toBeInTheDocument();
+      expect(screen.getByLabelText(/summary/i)).toBeInTheDocument();
+    });
+
+    it('disables submit while required fields are empty', async () => {
+      renderForm();
+      await waitFor(() => {
+        expect(screen.getByRole('button', { name: /log buzz/i })).toBeInTheDocument();
+      });
+      const submit = screen.getByRole('button', { name: /log buzz/i });
+      expect(submit).toBeDisabled();
+    });
+
+    it('enables submit once headline + url are filled', async () => {
+      renderForm();
+      await waitFor(() => {
+        expect(screen.getByLabelText(/headline/i)).toBeInTheDocument();
+      });
+      fireEvent.change(screen.getByLabelText(/headline/i), { target: { value: 'Hello' } });
+      fireEvent.change(screen.getByLabelText(/url/i), {
+        target: { value: 'https://example.com' },
+      });
+      expect(screen.getByRole('button', { name: /log buzz/i })).not.toBeDisabled();
+    });
+
+    it('navigates to the project page on successful submit', async () => {
+      renderForm();
+      await waitFor(() => {
+        expect(screen.getByLabelText(/headline/i)).toBeInTheDocument();
+      });
+      fireEvent.change(screen.getByLabelText(/headline/i), { target: { value: 'Hello' } });
+      fireEvent.change(screen.getByLabelText(/url/i), {
+        target: { value: 'https://example.com' },
+      });
+      fireEvent.click(screen.getByRole('button', { name: /log buzz/i }));
+      await waitFor(() => {
+        expect(screen.getByText(/project page/i)).toBeInTheDocument();
+      });
+    });
+  });
+});
diff --git a/plans/screen-gaps-phase4.md b/plans/screen-gaps-phase4.md
new file mode 100644
index 0000000..1e90e3e
--- /dev/null
+++ b/plans/screen-gaps-phase4.md
@@ -0,0 +1,94 @@
+---
+status: done
+depends: [screen-gaps-phase3]
+specs:
+  - specs/api/projects-buzz.md
+  - specs/screens/project-detail.md
+issues: [83]
+pr: 105
+---
+
+# Plan: screen-gaps phase 4 — `/projects/:slug/buzz/new` create form
+
+## Scope
+
+Last open piece of [#83](https://github.com/CodeForPhilly/codeforphilly-ng/issues/83). The route was a `<ComingSoon />` placeholder; the API endpoint (`POST /api/projects/:slug/buzz`) is fully implemented + tested. This plan ships the SPA form that closes the loop.
+
+After this lands, `#83`'s engineering work is done — only the legacy-content port stays as a follow-up content PR.
+
+## Implements
+
+- [api/projects-buzz.md](../specs/api/projects-buzz.md) — request shape, validation, the `duplicate_url` 409.
+- [screens/project-detail.md](../specs/screens/project-detail.md) — the "Log Buzz" affordance points here.
+
+## Approach
+
+### 1. Form component
+
+`apps/web/src/screens/ProjectBuzzNew.tsx`:
+
+- Route at `/projects/:slug/buzz/new` (replace `<ComingSoon />` in App.tsx).
+- Fields per spec: headline (1-200 chars, required), url (HTTPS, required), publishedAt (date, required, defaults to today, max=today), summary (≤2000 chars markdown, optional).
+- Submit calls existing `api.projects.postBuzz(slug, input)` helper.
+- Success → `navigate(`/projects/${slug}#activity`)` so the new buzz appears in the project's activity feed.
+- Failure surfaces inline field errors via `ApiError.fields`; the spec'd `duplicate_url` 409 maps to a field-level error on the URL input.
+- Anonymous callers redirect to `/login?return=…` so the post-login flow drops them back on the form.
+
+### 2. Tests
+
+`apps/web/tests/ProjectBuzzNew.test.tsx`:
+
+- Anonymous → login redirect carries return-to query
+- Signed-in: form renders all required fields
+- Submit disabled until headline + url filled
+- Submit enabled once both are filled
+- Successful submit navigates to project page
+
+## Validation
+
+- [x] `/projects/:slug/buzz/new` renders the form when signed in.
+- [x] Anonymous callers redirect to `/login?return=`.
+- [x] Successful POST navigates to `/projects/:slug`.
+- [x] `duplicate_url` 409 surfaces inline on the URL field via the `ApiError.code` check — unit test covers the success path, the error-path mapping is one-line and matches `ProjectEdit`'s established pattern.
+- [x] `npm run type-check && npm run lint && npm test` clean.
+
+## Risks / unknowns
+
+- **Image upload deferred.** Spec's request shape allows an optional `imageUpload.key` from a prior upload endpoint. That upload surface doesn't exist for general media in v1 (per the spec note). Out of scope here — surfaces in the form would just be dead UI.
+- **No anchor scroll on `#activity`.** The project-detail screen doesn't have an `#activity` element today. The navigate target stays as-is so the new buzz appears at the top of the activity feed (which is the default scroll position anyway). If a follow-up wants smooth scroll-to-anchor, the existing `anchor="update"` pattern works.
+
+## Notes
+
+Two commits: plan-open, impl + tests.
+
+Surprises:
+
+- **`useAuth` exposes `loading`, not `isLoading`.** Caught on first
+  type-check — a small TanStack-Query convention mismatch with the
+  project's own auth hook. Renamed at the destructure site.
+- **The lingering `ComingSoon` import.** Removing the last
+  `<ComingSoon />` usage at `/projects/:slug/buzz/new` left the
+  import unused. ESLint caught it in the local sweep this time (lesson
+  from PR #103's CI surprise). Bundled into this commit since it's
+  the same logical change.
+- **Submit-enabled gating.** Using a derived `disabled` (rather than
+  separate validation state) keeps the affordance honest — the button
+  literally can't be clicked until headline + url are non-empty. Native
+  `required` + `type="url"` handles deeper validation at submit time.
+
+## Follow-ups
+
+- **#83 is now fully closed engineering-wise.** Four phased PRs:
+  - phase 1 — ProjectDetail Share/stage-modal/Edit-on-GitHub + /contact (PR #102)
+  - phase 2 — PersonDetail slackHandle + email (PR #103)
+  - phase 3 — /pages/:slug bundled markdown (PR #104)
+  - phase 4 — this PR (#105)
+- **Legacy-content port** is the only remaining open thread under #83
+  — port the real Mission/Leadership/CoC/Hackathons copy from
+  `codeforphilly.org/site-root/pages/`. *Tracked as* — content task,
+  no engineering blocker. Will file an issue when the content owner
+  is identified.
+- **Image upload for buzz** — spec allows an optional `imageUpload.key`
+  attached to the POST. Needs a general-media upload endpoint that
+  doesn't exist for v1 (per `specs/api/projects-buzz.md`). *None* —
+  out of v1 scope.