diff --git a/apps/server/trpc/routers/project.test.ts b/apps/server/trpc/routers/project.test.ts
new file mode 100644
index 0000000..4e0beb7
--- /dev/null
+++ b/apps/server/trpc/routers/project.test.ts
@@ -0,0 +1,92 @@
+/**
+ * Tests for registerProject CONFLICT error disambiguation.
+ * Verifies that UNIQUE constraint failures on specific columns produce
+ * column-specific error messages.
+ */
+
+import { describe, it, expect, vi } from 'vitest';
+import { TRPCError } from '@trpc/server';
+import { router, publicProcedure, createCallerFactory } from '../trpc.js';
+import { projectProcedures } from './project.js';
+import type { TRPCContext } from '../context.js';
+import type { ProjectRepository } from '../../db/repositories/project-repository.js';
+
+const testRouter = router({
+  ...projectProcedures(publicProcedure),
+});
+
+const createCaller = createCallerFactory(testRouter);
+
+function makeCtx(mockCreate: () => Promise<never>): TRPCContext {
+  const projectRepository: ProjectRepository = {
+    create: mockCreate as unknown as ProjectRepository['create'],
+    findById: vi.fn().mockResolvedValue(null),
+    findByName: vi.fn().mockResolvedValue(null),
+    findAll: vi.fn().mockResolvedValue([]),
+    update: vi.fn(),
+    delete: vi.fn(),
+    addProjectToInitiative: vi.fn(),
+    removeProjectFromInitiative: vi.fn(),
+    findProjectsByInitiativeId: vi.fn().mockResolvedValue([]),
+    setInitiativeProjects: vi.fn(),
+  };
+
+  return {
+    eventBus: {} as TRPCContext['eventBus'],
+    serverStartedAt: null,
+    processCount: 0,
+    projectRepository,
+    // No workspaceRoot — prevents cloneProject from running
+  };
+}
+
+const INPUT = { name: 'my-project', url: 'https://github.com/example/repo' };
+
+describe('registerProject — CONFLICT error disambiguation', () => {
+  it('throws CONFLICT with name-specific message on projects.name UNIQUE violation', async () => {
+    const caller = createCaller(makeCtx(() => {
+      throw new Error('UNIQUE constraint failed: projects.name');
+    }));
+
+    const err = await caller.registerProject(INPUT).catch(e => e);
+    expect(err).toBeInstanceOf(TRPCError);
+    expect(err.code).toBe('CONFLICT');
+    expect(err.message).toBe('A project with this name already exists');
+  });
+
+  it('throws CONFLICT with url-specific message on projects.url UNIQUE violation', async () => {
+    const caller = createCaller(makeCtx(() => {
+      throw new Error('UNIQUE constraint failed: projects.url');
+    }));
+
+    const err = await caller.registerProject(INPUT).catch(e => e);
+    expect(err).toBeInstanceOf(TRPCError);
+    expect(err.code).toBe('CONFLICT');
+    expect(err.message).toBe('A project with this URL already exists');
+  });
+
+  it('throws CONFLICT with fallback message on unknown UNIQUE constraint violation', async () => {
+    const caller = createCaller(makeCtx(() => {
+      throw new Error('UNIQUE constraint failed: projects.unknown_col');
+    }));
+
+    const err = await caller.registerProject(INPUT).catch(e => e);
+    expect(err).toBeInstanceOf(TRPCError);
+    expect(err.code).toBe('CONFLICT');
+    expect(err.message).toBe('A project with this name or URL already exists');
+  });
+
+  it('rethrows non-UNIQUE errors without wrapping in a CONFLICT', async () => {
+    const originalError = new Error('SQLITE_BUSY');
+    const caller = createCaller(makeCtx(() => {
+      throw originalError;
+    }));
+
+    const err = await caller.registerProject(INPUT).catch(e => e);
+    expect(err).toBeDefined();
+    // Must not be surfaced as a CONFLICT — the catch block should re-throw as-is
+    expect(err).not.toMatchObject({ code: 'CONFLICT' });
+    // The original error message must be preserved somewhere
+    expect(err.message).toContain('SQLITE_BUSY');
+  });
+});
diff --git a/apps/server/trpc/routers/project.ts b/apps/server/trpc/routers/project.ts
index 5d79400..cb0188e 100644
--- a/apps/server/trpc/routers/project.ts
+++ b/apps/server/trpc/routers/project.ts
@@ -30,11 +30,24 @@ export function projectProcedures(publicProcedure: ProcedureBuilder) {
             ...(input.defaultBranch && { defaultBranch: input.defaultBranch }),
           });
         } catch (error) {
-          const msg = (error as Error).message;
+          const msg = (error as Error).message ?? '';
           if (msg.includes('UNIQUE') || msg.includes('unique')) {
+            if (msg.includes('projects.name') || (msg.includes('name') && !msg.includes('url'))) {
+              throw new TRPCError({
+                code: 'CONFLICT',
+                message: 'A project with this name already exists',
+              });
+            }
+            if (msg.includes('projects.url') || msg.includes('url')) {
+              throw new TRPCError({
+                code: 'CONFLICT',
+                message: 'A project with this URL already exists',
+              });
+            }
+            // fallback: neither column identifiable
             throw new TRPCError({
               code: 'CONFLICT',
-              message: `A project with that name or URL already exists`,
+              message: 'A project with this name or URL already exists',
             });
           }
           throw error;
diff --git a/apps/web/src/components/RegisterProjectDialog.tsx b/apps/web/src/components/RegisterProjectDialog.tsx
index e0b42b9..f3b2937 100644
--- a/apps/web/src/components/RegisterProjectDialog.tsx
+++ b/apps/web/src/components/RegisterProjectDialog.tsx
@@ -10,6 +10,7 @@ import {
 import { Button } from "@/components/ui/button";
 import { Input } from "@/components/ui/input";
 import { Label } from "@/components/ui/label";
+import { Loader2 } from "lucide-react";
 import { toast } from "sonner";
 import { trpc } from "@/lib/trpc";
 
@@ -27,13 +28,20 @@ export function RegisterProjectDialog({
   const [defaultBranch, setDefaultBranch] = useState("main");
   const [error, setError] = useState<string | null>(null);
 
+  const utils = trpc.useUtils();
+
   const registerMutation = trpc.registerProject.useMutation({
     onSuccess: () => {
       onOpenChange(false);
       toast.success("Project registered");
+      void utils.listProjects.invalidate();
     },
     onError: (err) => {
-      setError(err.message);
+      if (err.data?.code === "INTERNAL_SERVER_ERROR") {
+        setError("Failed to clone repository. Check the URL and try again.");
+      } else {
+        setError(err.message);
+      }
     },
   });
 
@@ -109,7 +117,14 @@ export function RegisterProjectDialog({
               Cancel
             </Button>
             <Button type="submit" disabled={!canSubmit}>
-              {registerMutation.isPending ? "Registering..." : "Register"}
+              {registerMutation.isPending ? (
+                <>
+                  <Loader2 className="animate-spin mr-2 h-4 w-4" />
+                  Cloning repository…
+                </>
+              ) : (
+                "Register"
+              )}
             </Button>
           </DialogFooter>
         </form>