diff --git a/README.md b/README.md
index cb2d382..4a14a49 100644
--- a/README.md
+++ b/README.md
@@ -553,8 +553,12 @@ POST /api/v1/projects
   que esta API, y se le pasa el de quien llama (en el panel, el de su sesión). Un token de máquina (`pmt_…`)
   allí no significa nada, así que esas peticiones usan `TASKSTREAM_TOKEN`; sin
   él, no pueden pedir tablero.
-- Solo al crear: en una edición los dos campos se ignoran, y un proyecto
-  duplicado no hereda el tablero del original.
+- **Después**: un proyecto que se creó sin tablero puede tenerlo luego, con
+  «Crear en TaskStream» en su ficha o `taskstream: true` en un `PATCH` (si
+  TaskStream lo rechaza, la edición tampoco se guarda). Uno que ya tiene tablero
+  lo conserva, y `taskstream_key` sin la casilla se ignora, así que un cliente
+  puede devolver tal cual lo que leyó. Un proyecto duplicado no hereda el
+  tablero del original.
 
 ```dotenv
 TASKSTREAM_API_URL=https://api.taskstream.pireon.dev   # por defecto
diff --git a/app/Actions/Projects/OpenInTaskStream.php b/app/Actions/Projects/OpenInTaskStream.php
index c8eb396..c2e7fcd 100644
--- a/app/Actions/Projects/OpenInTaskStream.php
+++ b/app/Actions/Projects/OpenInTaskStream.php
@@ -13,11 +13,11 @@ use Illuminate\Validation\ValidationException;
 use Symfony\Component\HttpKernel\Exception\HttpException;
 
 /**
- * Opens a board in TaskStream for a project that is about to be created
- * here, and points the project at it.
+ * Opens a board in TaskStream for a project, new or one without a board
+ * yet, and points the project at it.
  *
  * It runs before the project is saved: if TaskStream says no, nothing is
- * created here either, and the caller gets the reason to fix and retry.
+ * saved here either, and the caller gets the reason to fix and retry.
  * The board is public, like the project it tracks is meant to be.
  */
 class OpenInTaskStream
diff --git a/app/Filament/Resources/Projects/Pages/EditProject.php b/app/Filament/Resources/Projects/Pages/EditProject.php
index f0cddeb..d5f0ed0 100644
--- a/app/Filament/Resources/Projects/Pages/EditProject.php
+++ b/app/Filament/Resources/Projects/Pages/EditProject.php
@@ -4,15 +4,22 @@ declare(strict_types=1);
 
 namespace App\Filament\Resources\Projects\Pages;
 
+use App\Actions\Projects\OpenInTaskStream;
 use App\Filament\Concerns\WarnsOfConcurrentEditing;
 use App\Filament\Resources\Projects\ProjectResource;
 use App\Filament\Support\DuplicateAction;
 use App\Filament\Support\PreviewAction;
 use App\Filament\Support\TranslateAction;
+use App\Services\Pireon\TokenStore;
 use App\Services\TaskStream\TaskStreamClient;
 use Filament\Actions\Action;
 use Filament\Actions\DeleteAction;
+use Filament\Forms\Components\TextInput;
+use Filament\Notifications\Notification;
 use Filament\Resources\Pages\EditRecord;
+use Illuminate\Support\Facades\Auth;
+use Illuminate\Validation\ValidationException;
+use Symfony\Component\HttpKernel\Exception\HttpException;
 
 class EditProject extends EditRecord
 {
@@ -32,9 +39,72 @@ class EditProject extends EditRecord
                 ->url(fn () => app(TaskStreamClient::class)->projectUrl((string) $this->record->taskstream_key))
                 ->openUrlInNewTab()
                 ->visible(fn () => filled($this->record->taskstream_key)),
+            $this->createInTaskStream(),
             DuplicateAction::make(),
             TranslateAction::make(),
             DeleteAction::make(),
         ];
     }
+
+    /**
+     * For a project made without a board: opens one now, as the person
+     * signed in, and saves only the link (whatever is being edited in the
+     * form stays as it is, unsaved).
+     */
+    protected function createInTaskStream(): Action
+    {
+        return Action::make('createInTaskStream')
+            ->label(__('panel.projects.taskstream.create'))
+            ->icon('heroicon-o-plus')
+            ->color('gray')
+            ->visible(fn () => blank($this->record->taskstream_key))
+            ->authorize('update')
+            ->modalHeading(__('panel.projects.taskstream.create_heading'))
+            ->modalDescription(__('panel.projects.taskstream.section_hint'))
+            ->modalSubmitActionLabel(__('panel.projects.taskstream.create'))
+            ->schema([
+                TextInput::make('key')
+                    ->label(__('panel.projects.taskstream.key'))
+                    ->helperText(__('panel.projects.taskstream.key_hint'))
+                    ->placeholder(fn () => app(OpenInTaskStream::class)
+                        ->keyFrom((string) $this->record->getTranslation('slug', (string) config('locales.default'), false)))
+                    ->maxLength(10)
+                    ->regex('/^[A-Za-z][A-Za-z0-9]{1,9}$/'),
+            ])
+            ->action(function (array $data, Action $action): void {
+                $project = $this->record;
+
+                try {
+                    app(OpenInTaskStream::class)->handle(
+                        $project,
+                        Auth::user(),
+                        app(TokenStore::class)->accessToken(),
+                        filled($data['key'] ?? null) ? $data['key'] : null,
+                    );
+                } catch (ValidationException|HttpException $e) {
+                    // The modal stays open, to change the key and try again.
+                    Notification::make()
+                        ->danger()
+                        ->title($e instanceof ValidationException ? collect($e->errors())->flatten()->first() : $e->getMessage())
+                        ->send();
+
+                    $action->halt();
+                }
+
+                $project->save();
+
+                $url = app(TaskStreamClient::class)->projectUrl((string) $project->taskstream_key);
+
+                Notification::make()
+                    ->success()
+                    ->title(__('panel.projects.taskstream.created', ['url' => $url]))
+                    ->actions([
+                        Action::make('taskstream')
+                            ->label(__('panel.projects.taskstream.open'))
+                            ->url($url, shouldOpenInNewTab: true),
+                    ])
+                    ->persistent()
+                    ->send();
+            });
+    }
 }
diff --git a/app/Http/Controllers/Api/V1/ProjectController.php b/app/Http/Controllers/Api/V1/ProjectController.php
index 365551f..f7515ce 100644
--- a/app/Http/Controllers/Api/V1/ProjectController.php
+++ b/app/Http/Controllers/Api/V1/ProjectController.php
@@ -72,11 +72,22 @@ class ProjectController extends Controller
         return ProjectResource::make($project->load(self::WITH));
     }
 
-    public function update(ProjectRequest $request, Project $project): ProjectResource
+    /**
+     * `taskstream: true` opens a board for a project that has none yet, as on
+     * creation (and nothing is saved if that fails); one that has a board
+     * keeps it.
+     */
+    public function update(ProjectRequest $request, Project $project, OpenInTaskStream $openInTaskStream): ProjectResource
     {
         $this->authorize('update', $project);
 
-        return ProjectResource::make($this->persist($this->fill($project, $request), $request));
+        $project = $this->fill($project, $request);
+
+        if ($request->boolean('taskstream') && $project->taskstream_project_id === null) {
+            $openInTaskStream->handle($project, $request->user(), $request->bearerToken(), $request->validated('taskstream_key'));
+        }
+
+        return ProjectResource::make($this->persist($project, $request));
     }
 
     public function destroy(Project $project): JsonResponse
diff --git a/app/Http/Requests/Api/V1/ProjectRequest.php b/app/Http/Requests/Api/V1/ProjectRequest.php
index ff53595..a836ff7 100644
--- a/app/Http/Requests/Api/V1/ProjectRequest.php
+++ b/app/Http/Requests/Api/V1/ProjectRequest.php
@@ -20,8 +20,9 @@ use Illuminate\Validation\Validator;
  * Relations travel as ids and are replaced whole when sent: `technology_ids`,
  * `service_ids`, and `members` with each one's role on the project.
  *
- * `taskstream` (on creation only) opens a public board in TaskStream for the
- * project, keyed `taskstream_key` or one derived from the slug.
+ * `taskstream` opens a public board in TaskStream for the project, keyed
+ * `taskstream_key` or one derived from the slug; on an update, only when the
+ * project has none yet.
  */
 class ProjectRequest extends FormRequest
 {
@@ -78,10 +79,10 @@ class ProjectRequest extends FormRequest
             'members.*.id' => ['required', 'integer', 'distinct', Rule::exists('members', 'id')->whereNull('deleted_at')],
             'members.*.role' => ['nullable', 'string', 'max:120'],
 
-            // Only when creating; a client PATCHing back what it read sends
-            // the key it got, which is ignored rather than refused.
-            'taskstream' => [$creating ? 'sometimes' : 'exclude', 'boolean'],
-            'taskstream_key' => [$creating ? 'sometimes' : 'exclude', 'nullable', 'string', 'regex:/^[A-Za-z][A-Za-z0-9]{1,9}$/'],
+            // The key is only read along with `taskstream`: a client PATCHing
+            // back what it read sends the key it got, which changes nothing.
+            'taskstream' => ['sometimes', 'boolean'],
+            'taskstream_key' => ['sometimes', 'nullable', 'string', 'regex:/^[A-Za-z][A-Za-z0-9]{1,9}$/'],
         ];
     }
 
diff --git a/docs/manual-de-uso.html b/docs/manual-de-uso.html
index 7c6c73d..6fe560f 100644
--- a/docs/manual-de-uso.html
+++ b/docs/manual-de-uso.html
@@ -383,8 +383,9 @@ catalán     /ca/projectes/gestor-de-socis</code></pre>
   </p>
   <p>
     Si TaskStream no lo acepta (porque esa clave ya existe, por ejemplo), el proyecto
-    tampoco se guarda aquí: cambia la clave y vuelve a guardar. Solo se puede hacer al
-    crearlo.
+    tampoco se guarda aquí: cambia la clave y vuelve a guardar. Si lo creaste sin tablero,
+    el botón <strong>Crear en TaskStream</strong> de su ficha se lo abre después, con la
+    misma clave a elegir.
   </p>
 
   <h3>Decisiones y postmortem</h3>
diff --git a/docs/manual-de-uso.pdf b/docs/manual-de-uso.pdf
index 3565a50..3b14fcd 100644
Binary files a/docs/manual-de-uso.pdf and b/docs/manual-de-uso.pdf differ
diff --git a/lang/ca/panel.php b/lang/ca/panel.php
index cf689f4..8ebc12e 100644
--- a/lang/ca/panel.php
+++ b/lang/ca/panel.php
@@ -529,6 +529,8 @@ return [
             'key_hint' => 'De 2 a 10 lletres o xifres, començant per lletra. Si la deixes buida, es treu de l\'slug.',
             'created' => 'Tauler creat a TaskStream: :url',
             'open' => 'Obrir a TaskStream',
+            'create' => 'Crear a TaskStream',
+            'create_heading' => 'Obrir un tauler a TaskStream',
         ],
         'filters' => ['unpublished' => 'Sense publicar'],
         'actions' => ['publish' => 'Publica'],
diff --git a/lang/en/panel.php b/lang/en/panel.php
index 4f31def..ad7d92c 100644
--- a/lang/en/panel.php
+++ b/lang/en/panel.php
@@ -527,6 +527,8 @@ return [
             'key_hint' => '2 to 10 letters or digits, starting with a letter. Left empty, it is made from the slug.',
             'created' => 'Board created in TaskStream: :url',
             'open' => 'Open in TaskStream',
+            'create' => 'Create in TaskStream',
+            'create_heading' => 'Open a board in TaskStream',
         ],
         'filters' => ['unpublished' => 'Unpublished'],
         'actions' => ['publish' => 'Publish'],
diff --git a/lang/es/panel.php b/lang/es/panel.php
index a0048fd..30e63f3 100644
--- a/lang/es/panel.php
+++ b/lang/es/panel.php
@@ -529,6 +529,8 @@ return [
             'key_hint' => 'De 2 a 10 letras o cifras, empezando por letra. Si la dejas vacía, se saca del slug.',
             'created' => 'Tablero creado en TaskStream: :url',
             'open' => 'Abrir en TaskStream',
+            'create' => 'Crear en TaskStream',
+            'create_heading' => 'Abrir un tablero en TaskStream',
         ],
         'filters' => ['unpublished' => 'Sin publicar'],
         'actions' => ['publish' => 'Publicar'],
diff --git a/public/openapi.yaml b/public/openapi.yaml
index 375da4e..2605010 100644
--- a/public/openapi.yaml
+++ b/public/openapi.yaml
@@ -1621,7 +1621,14 @@ paths:
     patch:
       tags: [Projects]
       summary: Update a project
-      description: Partial update. Translatable fields merge into the existing map.
+      description: |
+        Partial update. Translatable fields merge into the existing map.
+
+        `taskstream: true` opens a TaskStream board for a project that has none
+        yet, as on creation (`taskstream_key`, or one made from the slug); if
+        TaskStream refuses, the update is not saved either. A project that
+        already has a board keeps it, and `taskstream_key` without the flag is
+        ignored, so a client can PATCH back what it read.
       requestBody:
         required: true
         content:
@@ -5574,12 +5581,12 @@ components:
         demo_url: { type: string, format: uri, nullable: true }
         taskstream:
           type: boolean
-          description: On creation only. Also open a public board for it in TaskStream; see `POST /v1/projects`.
+          description: Also open a public board for it in TaskStream, on creation or when it has none yet; see `POST /v1/projects`.
         taskstream_key:
           type: string
           nullable: true
           pattern: "^[A-Za-z][A-Za-z0-9]{1,9}$"
-          description: On creation only, with `taskstream`. The key in TaskStream; made from the slug when left out.
+          description: Only read with `taskstream`. The key in TaskStream; made from the slug when left out.
         cover_image: { type: string, nullable: true, description: A path from `POST /v1/media` with `for=projects`. }
         started_at: { type: string, format: date, nullable: true }
         ended_at: { type: string, format: date, nullable: true }
diff --git a/tests/Feature/Api/TaskStreamProjectTest.php b/tests/Feature/Api/TaskStreamProjectTest.php
index 04862bd..d20e157 100644
--- a/tests/Feature/Api/TaskStreamProjectTest.php
+++ b/tests/Feature/Api/TaskStreamProjectTest.php
@@ -18,8 +18,8 @@ use Tests\FakesPireon;
 use Tests\TestCase;
 
 /**
- * `taskstream: true` on a new project opens its board in TaskStream too, and
- * the answer carries the link.
+ * `taskstream: true` on a new project, or on one without a board yet, opens
+ * its board in TaskStream too, and the answer carries the link.
  */
 class TaskStreamProjectTest extends TestCase
 {
@@ -211,23 +211,64 @@ class TaskStreamProjectTest extends TestCase
     }
 
     #[Test]
-    public function an_update_ignores_the_flag(): void
+    public function an_update_opens_a_board_for_a_project_without_one(): void
+    {
+        $this->fakeTaskStream();
+        $this->withHeaders($this->apiHeadersFor($this->editor()));
+        $project = Project::factory()->create(['slug' => ['es' => 'catalogo']]);
+
+        $this->patchJson("/api/v1/projects/{$project->id}", ['taskstream' => true, 'needs_help' => true])
+            ->assertOk()
+            ->assertJsonPath('data.taskstream_key', 'CATALOGO')
+            ->assertJsonPath('data.taskstream_url', 'https://taskstream.test/p/CATALOGO')
+            ->assertJsonPath('data.needs_help', true);
+
+        $this->assertSame('ts-1', $project->fresh()->taskstream_project_id);
+    }
+
+    #[Test]
+    public function a_project_with_a_board_keeps_it(): void
+    {
+        $this->fakeTaskStream();
+        $this->withHeaders($this->apiHeadersFor($this->editor()));
+        $project = Project::factory()->create(['taskstream_project_id' => 'ts-0', 'taskstream_key' => 'CAT']);
+
+        $this->patchJson("/api/v1/projects/{$project->id}", ['taskstream' => true, 'taskstream_key' => 'OTRA'])
+            ->assertOk()
+            ->assertJsonPath('data.taskstream_key', 'CAT');
+
+        $this->assertSame(0, $this->sentToTaskStream());
+    }
+
+    #[Test]
+    public function an_update_without_the_flag_ignores_the_key(): void
     {
         $this->fakeTaskStream();
         $this->withHeaders($this->apiHeadersFor($this->editor()));
         $project = Project::factory()->create();
 
-        $this->patchJson("/api/v1/projects/{$project->id}", [
-            'taskstream' => true,
-            'taskstream_key' => 'OTRA',
-            'needs_help' => true,
-        ])
+        // What a client sends back after reading a project.
+        $this->patchJson("/api/v1/projects/{$project->id}", ['taskstream_key' => 'OTRA', 'needs_help' => true])
             ->assertOk()
             ->assertJsonPath('data.taskstream_key', null);
 
         $this->assertSame(0, $this->sentToTaskStream());
     }
 
+    #[Test]
+    public function a_refused_board_leaves_the_update_unsaved(): void
+    {
+        $this->fakeTaskStream(409, ['statusCode' => 409, 'message' => 'Project key WEB is already in use']);
+        $this->withHeaders($this->apiHeadersFor($this->editor()));
+        $project = Project::factory()->create(['needs_help' => false]);
+
+        $this->patchJson("/api/v1/projects/{$project->id}", ['taskstream' => true, 'taskstream_key' => 'WEB', 'needs_help' => true])
+            ->assertUnprocessable()
+            ->assertJsonValidationErrors('taskstream_key');
+
+        $this->assertFalse($project->fresh()->needs_help);
+    }
+
     #[Test]
     public function keys_are_made_from_the_slug_in_taskstreams_style(): void
     {
diff --git a/tests/Feature/Panel/TaskStreamPanelTest.php b/tests/Feature/Panel/TaskStreamPanelTest.php
index e9c27d5..609cfc5 100644
--- a/tests/Feature/Panel/TaskStreamPanelTest.php
+++ b/tests/Feature/Panel/TaskStreamPanelTest.php
@@ -19,8 +19,9 @@ use Tests\FakesPireon;
 use Tests\TestCase;
 
 /**
- * The panel's way to open a project's board in TaskStream: a toggle on the
- * create form, as the person signed in.
+ * The panel's way to open a project's board in TaskStream, as the person
+ * signed in: a toggle on the create form, or an action on a project that
+ * has none yet.
  */
 class TaskStreamPanelTest extends TestCase
 {
@@ -131,4 +132,41 @@ class TaskStreamPanelTest extends TestCase
 
         $this->assertSame(0, Project::withTrashed()->count());
     }
+
+    #[Test]
+    public function a_project_without_a_board_can_get_one_later(): void
+    {
+        $this->fakeTaskStream();
+        $project = Project::factory()->create(['slug' => ['es' => 'catalogo']]);
+
+        Livewire::test(EditProject::class, ['record' => $project->getRouteKey()])
+            ->assertActionHidden('taskstream')
+            ->assertActionVisible('createInTaskStream')
+            ->callAction('createInTaskStream', data: ['key' => 'cat'])
+            ->assertHasNoActionErrors()
+            ->assertNotified();
+
+        Http::assertSent(fn (Request $request) => $request->hasHeader('Authorization', 'Bearer session-token')
+            && $request['key'] === 'CAT'
+            && $request['isPublic'] === true);
+
+        $this->assertSame('CAT', $project->fresh()->taskstream_key);
+
+        Livewire::test(EditProject::class, ['record' => $project->getRouteKey()])
+            ->assertActionVisible('taskstream')
+            ->assertActionHidden('createInTaskStream');
+    }
+
+    #[Test]
+    public function a_refusal_later_keeps_the_project_without_a_board(): void
+    {
+        $this->fakeTaskStream(409, ['statusCode' => 409, 'message' => 'Project key WEB is already in use']);
+        $project = Project::factory()->create();
+
+        Livewire::test(EditProject::class, ['record' => $project->getRouteKey()])
+            ->callAction('createInTaskStream', data: ['key' => 'WEB'])
+            ->assertNotified(__('rules.taskstream.refused', ['reason' => 'Project key WEB is already in use']));
+
+        $this->assertNull($project->fresh()->taskstream_key);
+    }
 }