fix(mentor): restore Add Project on mentoring rounds + gate mentor assignment

Three related bugs around the mentoring-round Projects tab:

1. Add Project to Round was unreachable on MENTORING rounds — the table swap
   in the prior commit lost the button. Export AddProjectDialog from
   project-states-table and render it inside MentoringProjectsTable with an
   "Add" button in the filter row and a CTA in the empty state.
2. The "Assign Projects" quick action on the round overview linked to the
   global pool with an opaque filter; on MENTORING rounds it now switches
   to the Projects tab where the new Add Project button + auto-fill +
   per-team picker all live. Non-mentoring rounds keep the old behavior.
3. mentor.assign and mentor.bulkAssign now refuse projects that aren't
   enrolled in any MENTORING round (any status). The single-assign throws
   BAD_REQUEST with a guidance message; the bulk path filters them out and
   reports ineligibleProjectCount in the result so the UI can warn the
   admin instead of silently skipping.

Tests: the multi-mentor-assignment suite now sets up a MENTORING round +
ProjectRoundState for each project it tests against, matching the new gate.

src/app/(admin)/admin/rounds/[roundId]/page.tsx

@@ -1265,17 +1265,32 @@ export default function RoundDetailPage() {
                 <div>
                   <p className="text-[11px] font-semibold uppercase tracking-wider text-muted-foreground mb-2">Project Management</p>
                   <div className="grid gap-3 sm:grid-cols-2 lg:grid-cols-3">
-                    <Link href={poolLink}>
+                    {isMentoring ? (
-                      <button className="flex items-start gap-3 p-4 rounded-lg border hover:-translate-y-0.5 hover:shadow-md transition-all text-left w-full">
+                      <button
+                        onClick={() => setActiveTab('projects')}
+                        className="flex items-start gap-3 p-4 rounded-lg border hover:-translate-y-0.5 hover:shadow-md transition-all text-left w-full"
+                      >
                         <Layers className="h-5 w-5 text-[#557f8c] mt-0.5 shrink-0" />
                         <div>
                           <p className="text-sm font-medium">Assign Projects</p>
                           <p className="text-xs text-muted-foreground mt-0.5">
-                            Add projects from the pool to this round
+                            Open the Projects tab to add or auto-fill teams in this round
                           </p>
                         </div>
                       </button>
-                    </Link>
+                    ) : (
+                      <Link href={poolLink}>
+                        <button className="flex items-start gap-3 p-4 rounded-lg border hover:-translate-y-0.5 hover:shadow-md transition-all text-left w-full">
+                          <Layers className="h-5 w-5 text-[#557f8c] mt-0.5 shrink-0" />
+                          <div>
+                            <p className="text-sm font-medium">Assign Projects</p>
+                            <p className="text-xs text-muted-foreground mt-0.5">
+                              Add projects from the pool to this round
+                            </p>
+                          </div>
+                        </button>
+                      </Link>
+                    )}
 
                     <button
                       onClick={() => setActiveTab('projects')}
@@ -1595,7 +1610,12 @@ export default function RoundDetailPage() {
           {isMentoring && (
             <>
               <MentoringBulkAssignToolbar roundId={roundId} configJson={config} />
-              <MentoringProjectsTable roundId={roundId} />
+              <MentoringProjectsTable
+                roundId={roundId}
+                competitionId={competitionId}
+                competitionRounds={competition?.rounds}
+                currentSortOrder={round?.sortOrder}
+              />
             </>
           )}
           {!isMentoring && (

src/components/admin/round/mentoring-projects-table.tsx

@@ -33,12 +33,32 @@ import {
   Loader2,
   Download,
   X,
+  Plus,
 } from 'lucide-react'
 import { CountryDisplay } from '@/components/shared/country-display'
+import { AddProjectDialog } from '@/components/admin/round/project-states-table'
 
 type Filter = 'all' | 'unassigned' | 'assigned' | 'wants_only'
 
-export function MentoringProjectsTable({ roundId }: { roundId: string }) {
+type CompetitionRound = {
+  id: string
+  name: string
+  sortOrder: number
+  _count: { projectRoundStates: number }
+}
+
+export function MentoringProjectsTable({
+  roundId,
+  competitionId,
+  competitionRounds,
+  currentSortOrder,
+}: {
+  roundId: string
+  competitionId: string
+  competitionRounds?: CompetitionRound[]
+  currentSortOrder?: number
+}) {
+  const [addProjectOpen, setAddProjectOpen] = useState(false)
   const [search, setSearch] = useState('')
   const [filter, setFilter] = useState<Filter>('all')
   const [selected, setSelected] = useState<Set<string>>(new Set())
@@ -67,6 +87,10 @@ export function MentoringProjectsTable({ roundId }: { roundId: string }) {
         toast.info(
           `No new assignments — every selected mentor is already on every selected project (${result.totalSkipped} pair${result.totalSkipped === 1 ? '' : 's'} skipped).`,
         )
+      } else if (result.totalAssigned === 0 && result.ineligibleProjectCount > 0) {
+        toast.warning(
+          `${result.ineligibleProjectCount} project${result.ineligibleProjectCount === 1 ? '' : 's'} aren't in a mentoring round and were skipped.`,
+        )
       } else {
         const mentorCount = result.perMentor.filter((m) => m.assigned > 0).length
         toast.success(
@@ -197,18 +221,32 @@ export function MentoringProjectsTable({ roundId }: { roundId: string }) {
     return (
       <div className="space-y-3">
         {importBanner}
-        <div className="rounded-md border bg-muted/30 px-4 py-12 text-center text-sm text-muted-foreground">
+        <div className="flex items-center justify-end">
-          No projects in this mentoring round yet.
+          <Button size="sm" onClick={() => setAddProjectOpen(true)}>
-          {!importBanner && (
+            <Plus className="mr-1.5 h-4 w-4" />
-            <>
+            Add Project to Round
-              {' '}Use{' '}
+          </Button>
-              <span className="font-medium text-foreground">
-                Add Project to Round
-              </span>{' '}
-              to populate it.
-            </>
-          )}
         </div>
+        <div className="rounded-md border bg-muted/30 px-4 py-12 text-center text-sm text-muted-foreground">
+          No projects in this mentoring round yet. Click{' '}
+          <span className="font-medium text-foreground">Add Project to Round</span>{' '}
+          above to populate it.
+        </div>
+
+        <AddProjectDialog
+          open={addProjectOpen}
+          onOpenChange={setAddProjectOpen}
+          roundId={roundId}
+          competitionId={competitionId}
+          competitionRounds={competitionRounds}
+          currentSortOrder={currentSortOrder}
+          onAssigned={() => {
+            utils.round.listMentoringProjects.invalidate({ roundId })
+            utils.round.getProjectsNeedingMentor.invalidate({ roundId })
+            utils.round.getMentoringImportCandidates.invalidate({ roundId })
+            utils.mentor.getRoundStats.invalidate({ roundId })
+          }}
+        />
       </div>
     )
   }
@@ -246,14 +284,24 @@ export function MentoringProjectsTable({ roundId }: { roundId: string }) {
           <Pill value="assigned" label="Has mentor" count={totals.assigned} />
           <Pill value="wants_only" label="Wants mentorship" count={totals.wants} />
         </div>
-        <div className="relative w-full sm:max-w-xs">
+        <div className="flex items-center gap-2">
-          <Search className="absolute left-2.5 top-1/2 h-3.5 w-3.5 -translate-y-1/2 text-muted-foreground" />
+          <div className="relative w-full sm:w-72">
-          <Input
+            <Search className="absolute left-2.5 top-1/2 h-3.5 w-3.5 -translate-y-1/2 text-muted-foreground" />
-            value={search}
+            <Input
-            onChange={(e) => setSearch(e.target.value)}
+              value={search}
-            placeholder="Search projects, teams, or mentors…"
+              onChange={(e) => setSearch(e.target.value)}
-            className="pl-8"
+              placeholder="Search projects, teams, or mentors…"
-          />
+              className="pl-8"
+            />
+          </div>
+          <Button
+            size="sm"
+            onClick={() => setAddProjectOpen(true)}
+            className="shrink-0"
+          >
+            <Plus className="mr-1 h-4 w-4" />
+            Add
+          </Button>
         </div>
       </div>
 
@@ -670,6 +718,21 @@ export function MentoringProjectsTable({ roundId }: { roundId: string }) {
           </DialogFooter>
         </DialogContent>
       </Dialog>
+
+      <AddProjectDialog
+        open={addProjectOpen}
+        onOpenChange={setAddProjectOpen}
+        roundId={roundId}
+        competitionId={competitionId}
+        competitionRounds={competitionRounds}
+        currentSortOrder={currentSortOrder}
+        onAssigned={() => {
+          utils.round.listMentoringProjects.invalidate({ roundId })
+          utils.round.getProjectsNeedingMentor.invalidate({ roundId })
+          utils.round.getMentoringImportCandidates.invalidate({ roundId })
+          utils.mentor.getRoundStats.invalidate({ roundId })
+        }}
+      />
     </div>
   )
 }

src/components/admin/round/project-states-table.tsx

@@ -785,7 +785,7 @@ function QuickAddDialog({
  * Create New: form to create a project and assign it directly to the round.
  * From Pool: search existing projects not yet in this round and assign them.
  */
-function AddProjectDialog({
+export function AddProjectDialog({
   open,
   onOpenChange,
   roundId,

src/server/routers/mentor.ts

@@ -370,6 +370,25 @@ export const mentorRouter = router({
         where: { id: input.projectId },
       })
 
+      // Gate: the project MUST be in a MENTORING round (any status, including
+      // DRAFT, ACTIVE, or CLOSED). We do not allow mentor assignment for
+      // projects that aren't part of a mentoring round — those should be
+      // added to a mentoring round first.
+      const inMentoringRound = await ctx.prisma.projectRoundState.findFirst({
+        where: {
+          projectId: input.projectId,
+          round: { roundType: 'MENTORING' },
+        },
+        select: { id: true },
+      })
+      if (!inMentoringRound) {
+        throw new TRPCError({
+          code: 'BAD_REQUEST',
+          message:
+            'This project is not in a mentoring round. Add it to a mentoring round first, then assign mentors.',
+        })
+      }
+
       // Verify mentor exists
       const mentor = await ctx.prisma.user.findUniqueOrThrow({
         where: { id: input.mentorId },
@@ -704,7 +723,13 @@ export const mentorRouter = router({
       }
 
       const projects = await ctx.prisma.project.findMany({
-        where: { id: { in: input.projectIds } },
+        where: {
+          id: { in: input.projectIds },
+          // Gate: only projects that are in some MENTORING round (any status)
+          projectRoundStates: {
+            some: { round: { roundType: 'MENTORING' } },
+          },
+        },
         select: {
           id: true,
           title: true,
@@ -718,6 +743,16 @@ export const mentorRouter = router({
         },
       })
 
+      if (projects.length === 0) {
+        throw new TRPCError({
+          code: 'BAD_REQUEST',
+          message:
+            'None of the selected projects are in a mentoring round. Add them to a mentoring round first.',
+        })
+      }
+
+      const ineligibleCount = input.projectIds.length - projects.length
+
       // Track per-mentor (for emails) and per-project (for team intros) state.
       const perMentor = new Map<
         string,
@@ -884,6 +919,7 @@ export const mentorRouter = router({
       return {
         totalAssigned,
         totalSkipped,
+        ineligibleProjectCount: ineligibleCount,
         touchedProjectCount: touchedProjectIds.size,
         perMentor: Array.from(perMentor.entries()).map(([id, b]) => ({
           mentorId: id,

tests/unit/multi-mentor-assignment.test.ts

@@ -42,6 +42,37 @@ async function createUserWithRoles(
   })
 }
 
+/**
+ * mentor.assign and mentor.bulkAssign now require the project to be enrolled
+ * in some MENTORING round. This helper sets up the minimum: one competition
+ * + one MENTORING round + one ProjectRoundState linking the project.
+ */
+async function attachToMentoringRound(programId: string, projectId: string) {
+  const compSlug = `comp-${uid()}`
+  const competition = await prisma.competition.create({
+    data: {
+      name: `Comp ${compSlug}`,
+      slug: compSlug,
+      programId,
+      status: 'ACTIVE',
+    },
+  })
+  const round = await prisma.round.create({
+    data: {
+      name: `Mentoring ${uid()}`,
+      slug: `mentoring-${uid()}`,
+      roundType: 'MENTORING',
+      sortOrder: 1,
+      status: 'ROUND_ACTIVE',
+      competitionId: competition.id,
+    },
+  })
+  await prisma.projectRoundState.create({
+    data: { roundId: round.id, projectId },
+  })
+  return { competitionId: competition.id, roundId: round.id }
+}
+
 describe('mentor.assign — stacking + per-team email idempotency', () => {
   const programIds: string[] = []
   const userIds: string[] = []
@@ -62,6 +93,7 @@ describe('mentor.assign — stacking + per-team email idempotency', () => {
     const program = await createTestProgram({ name: `assign-stack-${uid()}` })
     programIds.push(program.id)
     const project = await createTestProject(program.id, { title: 'Stacking Project' })
+    await attachToMentoringRound(program.id, project.id)
 
     const m1 = await createUserWithRoles('MENTOR', ['MENTOR'], { name: 'M1' })
     const m2 = await createUserWithRoles('MENTOR', ['MENTOR'], { name: 'M2' })
@@ -93,6 +125,7 @@ describe('mentor.assign — stacking + per-team email idempotency', () => {
     const program = await createTestProgram({ name: `assign-dup-${uid()}` })
     programIds.push(program.id)
     const project = await createTestProject(program.id, { title: 'Dup Project' })
+    await attachToMentoringRound(program.id, project.id)
     const mentor = await createUserWithRoles('MENTOR', ['MENTOR'])
     userIds.push(mentor.id)
 
@@ -114,7 +147,9 @@ describe('mentor.assign — stacking + per-team email idempotency', () => {
     const program = await createTestProgram({ name: `assign-email-${uid()}` })
     programIds.push(program.id)
     const project1 = await createTestProject(program.id, { title: 'Project Alpha' })
+    await attachToMentoringRound(program.id, project1.id)
     const project2 = await createTestProject(program.id, { title: 'Project Beta' })
+    await attachToMentoringRound(program.id, project2.id)
     const mentor = await createUserWithRoles('MENTOR', ['MENTOR'])
     userIds.push(mentor.id)
 
@@ -144,6 +179,7 @@ describe('mentor.assign — stacking + per-team email idempotency', () => {
     const program = await createTestProgram({ name: `assign-comentor-${uid()}` })
     programIds.push(program.id)
     const project = await createTestProject(program.id, { title: 'Co-mentor Project' })
+    await attachToMentoringRound(program.id, project.id)
     const m1 = await createUserWithRoles('MENTOR', ['MENTOR'], { name: 'Co-1' })
     const m2 = await createUserWithRoles('MENTOR', ['MENTOR'], { name: 'Co-2' })
     userIds.push(m1.id, m2.id)
@@ -169,6 +205,7 @@ describe('mentor.assign — stacking + per-team email idempotency', () => {
     const program = await createTestProgram({ name: `assign-redrop-${uid()}` })
     programIds.push(program.id)
     const project = await createTestProject(program.id, { title: 'Re-assign Project' })
+    await attachToMentoringRound(program.id, project.id)
     const mentor = await createUserWithRoles('MENTOR', ['MENTOR'])
     userIds.push(mentor.id)