feat(worktrees): démarrer une session sur la branche principale ou tout worktree

Ajoute le choix « créer un worktree OU bosser sur la branche principale » au
moment de démarrer le travail, sur deux surfaces :
- bouton « Démarrer » (claude/bash) sur chaque WorktreeCard, y compris le
  checkout principal (badge « principal ») — comblait un manque : impossible
  jusqu'ici de lancer une session sur un worktree existant depuis le dashboard ;
- toggle de mode (Worktree / Branche principale) dans le formulaire d'entête
  de RepoSection.

Option git « créer & basculer » : nouvel endpoint POST /api/v1/repos/:id/session
qui lance UNE session dans le checkout principal (repo.path), avec création ou
bascule de branche optionnelle (git switch[-c]) — refusée en 409 si l'arbre est
sale. Pas de hooks ni de pré-trust (c'est le dépôt réel de l'utilisateur).

- shared : type additif StartRepoSessionRequest.
- server : git.switchBranch + WorktreeManager.startMainSession + route.
- web : store worktrees.startMainSession, UI WorktreeCard/RepoSection, i18n fr/en.
- tests : +5 unitaires (switchBranch, startMainSession) ; acceptance-p3 étendue.

packages/server/scripts/acceptance-p3.mjs

@@ -3,7 +3,7 @@
 // Vrai daemon + vrai repo git tmp. Couvre : enregistrement repo, création worktree avec hook
 // post-create, broadcast WS worktree_update, corrélation worktree↔session (bash), suppression.
 import { spawn, execFileSync } from 'node:child_process';
-import { mkdtempSync, rmSync, existsSync } from 'node:fs';
+import { mkdtempSync, rmSync, existsSync, writeFileSync } from 'node:fs';
 import { tmpdir } from 'node:os';
 import { join, dirname, basename } from 'node:path';
 import { fileURLToPath } from 'node:url';
@@ -119,6 +119,24 @@ try {
   const feat = wlist1.worktrees.find((w) => w.branch === 'feat');
   check('corrélation worktree ↔ session (cwd)', feat?.sessions?.some((s) => s.command === 'bash' && s.live));
 
+  // Session sur le checkout principal (« bosser sur la branche principale ») avec création de branche.
+  const mainSess = await j(`/api/v1/repos/${repoSummary.id}/session`, 'POST', cookie, { command: 'bash', branch: 'mainfeat', newBranch: true });
+  const mainBody = await mainSess.json();
+  check('POST repo session → 201 (bash)', mainSess.status === 201 && mainBody.session?.command === 'bash');
+  check('session de branche principale : cwd = checkout principal', mainBody.session?.cwd === repoSummary.path);
+  const mainPush = await c.waitMsg((m) => m.type === 'worktree_update' && m.worktree?.isMain && m.worktree?.branch === 'mainfeat');
+  check('broadcast worktree_update (branche principale basculée)', !!mainPush);
+  await sleep(300);
+  const wlistM = await (await j('/api/v1/worktrees', 'GET', cookie)).json();
+  const mainWt = wlistM.worktrees.find((w) => w.isMain);
+  check('session corrélée au checkout principal', mainWt?.branch === 'mainfeat' && mainWt.sessions.some((s) => s.id === mainBody.session.id));
+
+  // Refus 409 quand le checkout principal est sale.
+  writeFileSync(join(repo, 'scratch.txt'), 'wip\n');
+  const dirtyRefused = await j(`/api/v1/repos/${repoSummary.id}/session`, 'POST', cookie, { command: 'bash', branch: 'other', newBranch: true });
+  check('repo session sur checkout sale → 409', dirtyRefused.status === 409);
+  rmSync(join(repo, 'scratch.txt'), { force: true });
+
   // Suppression forcée (une session vit dans le worktree).
   const refused = await j(`/api/v1/repos/${repoSummary.id}/worktrees?path=${encodeURIComponent(wtPath)}&force=false`, 'DELETE', cookie);
   check('delete sans force (session live) → 409', refused.status === 409);

packages/server/src/core/git.ts

@@ -190,6 +190,16 @@ export async function addWorktree(
   await git(repoPath, args);
 }
 
+/**
+ * Crée/bascule une branche dans le checkout (worktree) en `repoPath` — utilisé pour démarrer une
+ * session sur la branche principale sans worktree dédié. `create` → `git switch -c <branch>` (échoue
+ * si la branche existe) ; sinon `git switch <branch>` (branche existante). Pas de `--` : l'argument
+ * est une réf (pas un pathspec) et le nom est déjà filtré en amont par `isValidBranchName` (anti-flag).
+ */
+export async function switchBranch(repoPath: string, opts: { branch: string; create: boolean }): Promise<void> {
+  await git(repoPath, opts.create ? ['switch', '-c', opts.branch] : ['switch', opts.branch]);
+}
+
 export async function removeWorktree(repoPath: string, worktreePath: string, force: boolean): Promise<void> {
   await git(repoPath, ['worktree', 'remove', ...(force ? ['--force'] : []), '--', worktreePath]);
 }

packages/server/src/core/worktree-manager.ts

@@ -30,6 +30,7 @@ import {
   listWorktrees,
   pruneWorktrees,
   removeWorktree,
+  switchBranch,
   worktreeStatus,
   type ParsedWorktree,
 } from './git.js';
@@ -355,6 +356,41 @@ export class WorktreeManager extends EventEmitter<WorktreeManagerEvents> {
     });
   }
 
+  /**
+   * Lance UNE session dans le checkout principal du repo (`repo.path`) — pour « bosser sur la branche
+   * principale » sans créer de worktree. Si `branch` est fourni, crée/bascule d'abord cette branche
+   * dans ce checkout (`git switch[-c]`), refusé si l'arbre est sale (on n'écrase pas un HEAD modifié).
+   * Volontairement SANS hooks ni pré-trust (contraste avec createWorktree) : le checkout principal
+   * est le dépôt réel de l'utilisateur, déjà configuré/approuvé. Sérialisé par repo (withLock).
+   */
+  async startMainSession(
+    repoId: string,
+    req: { command?: 'claude' | 'bash'; branch?: string; newBranch?: boolean },
+  ): Promise<{ session: SessionSummary; worktree: WorktreeSummary | null }> {
+    const row = this.getRepoRow(repoId);
+    if (!row) throw httpError(404, 'NOT_FOUND', 'No repo with this id');
+    const branch = req.branch?.trim() || undefined;
+    if (branch !== undefined && !isValidBranchName(branch)) throw httpError(400, 'BAD_BRANCH', `Invalid branch name: ${branch}`);
+
+    return this.withLock(repoId, async () => {
+      if (branch !== undefined) {
+        // garde-fou : ne pas basculer le HEAD du checkout principal s'il a des changements non sauvegardés.
+        if ((await worktreeStatus(row.path)).dirtyCount > 0) {
+          throw httpError(409, 'DIRTY_TREE', 'Main checkout has uncommitted changes — commit or stash before switching branch');
+        }
+        try {
+          await switchBranch(row.path, { branch, create: req.newBranch ?? true });
+        } catch (err) {
+          throw httpError(400, 'SWITCH_FAILED', (err as Error).message);
+        }
+        this.factsCache.delete(repoId);
+      }
+      const session = this.ptyManager.spawn({ cwd: row.path, command: req.command ?? 'claude' });
+      const worktree = await this.emitWorktree(row, row.path);
+      return { session, worktree };
+    });
+  }
+
   async adoptWorktree(repoId: string, req: { path: string; runHooks?: boolean; preTrust?: boolean }): Promise<{ worktree: WorktreeSummary; hookResults: HookRunResult[] }> {
     const row = this.getRepoRow(repoId);
     if (!row) throw httpError(404, 'NOT_FOUND', 'No repo with this id');

packages/server/src/routes/worktrees.ts

@@ -3,6 +3,8 @@ import type {
   AdoptWorktreeRequest,
   CreateWorktreeRequest,
   CreateWorktreeResponse,
+  SessionResponse,
+  StartRepoSessionRequest,
   WorktreeResponse,
   WorktreesListResponse,
 } from '@arboretum/shared';
@@ -43,6 +45,33 @@ export function registerWorktreeRoutes(app: FastifyInstance, wt: WorktreeManager
     }
   });
 
+  // Session sur le checkout principal (« bosser sur la branche principale » sans worktree),
+  // avec création/bascule de branche optionnelle côté serveur.
+  app.post('/api/v1/repos/:id/session', async (req, reply) => {
+    const { id } = req.params as { id: string };
+    const body = (req.body as Partial<StartRepoSessionRequest> | null) ?? {};
+    if (body.command != null && body.command !== 'claude' && body.command !== 'bash') {
+      return reply.status(400).send({ error: { code: 'BAD_REQUEST', message: 'command must be claude or bash' } });
+    }
+    if (body.branch != null && typeof body.branch !== 'string') {
+      return reply.status(400).send({ error: { code: 'BAD_REQUEST', message: 'branch must be a string' } });
+    }
+    if (body.newBranch != null && typeof body.newBranch !== 'boolean') {
+      return reply.status(400).send({ error: { code: 'BAD_REQUEST', message: 'newBranch must be a boolean' } });
+    }
+    try {
+      const out = await wt.startMainSession(id, {
+        ...(body.command !== undefined ? { command: body.command } : {}),
+        ...(body.branch !== undefined ? { branch: body.branch } : {}),
+        ...(body.newBranch !== undefined ? { newBranch: body.newBranch } : {}),
+      });
+      const res: SessionResponse = { session: out.session };
+      return reply.status(201).send(res);
+    } catch (err) {
+      return sendManagerError(reply, err);
+    }
+  });
+
   app.post('/api/v1/repos/:id/worktrees/adopt', async (req, reply) => {
     const { id } = req.params as { id: string };
     const body = req.body as Partial<AdoptWorktreeRequest> | null;

packages/server/test/git.test.ts

@@ -13,6 +13,7 @@ import {
   addWorktree,
   removeWorktree,
   pruneWorktrees,
+  switchBranch,
   isDirtyWorktreeError,
 } from '../src/core/git.js';
 
@@ -118,6 +119,20 @@ describe('opérations git (repo tmp réel)', () => {
     expect((await listWorktrees(repo)).some((w) => resolve(w.path) === resolve(wtPath))).toBe(false);
   });
 
+  it('switchBranch : create=true crée une branche, create=false bascule sur une existante', async () => {
+    const repo = makeTmpRepo();
+    const cur = (): string => execFileSync('git', ['branch', '--show-current'], { cwd: repo }).toString().trim();
+
+    await switchBranch(repo, { branch: 'feature/new', create: true });
+    expect(cur()).toBe('feature/new');
+
+    await switchBranch(repo, { branch: 'main', create: false });
+    expect(cur()).toBe('main');
+
+    // créer une branche déjà existante échoue (git refuse).
+    await expect(switchBranch(repo, { branch: 'feature/new', create: true })).rejects.toBeDefined();
+  });
+
   it('prune retire un worktree dont le dossier a disparu', async () => {
     const repo = makeTmpRepo();
     const wtPath = join(dirname(repo), `${basename(repo)}-wt-gone`);

packages/server/test/worktree-manager.test.ts

@@ -116,6 +116,46 @@ describe('WorktreeManager', () => {
     await expect(wt.createWorktree(r.id, { branch: '../evil', newBranch: true })).rejects.toMatchObject({ statusCode: 400 });
   });
 
+  it('startMainSession : session dans le checkout principal (branche actuelle, sans mutation git)', async () => {
+    const repo = makeTmpRepo();
+    const r = await wt.addRepo({ path: repo });
+    const out = await wt.startMainSession(r.id, { command: 'bash' });
+    expect(resolve(out.session.cwd)).toBe(resolve(repo));
+    expect(out.session).toMatchObject({ command: 'bash', live: true });
+    // pas de bascule de branche → toujours sur main.
+    expect(execFileSync('git', ['branch', '--show-current'], { cwd: repo }).toString().trim()).toBe('main');
+    const main = (await wt.listRepoWorktrees(r.id, true)).find((w) => w.isMain);
+    expect(main?.sessions.some((s) => s.id === out.session.id)).toBe(true);
+  });
+
+  it('startMainSession : newBranch crée et bascule la branche dans le checkout principal + event', async () => {
+    const repo = makeTmpRepo();
+    const r = await wt.addRepo({ path: repo });
+    const events: Array<{ worktree: WorktreeSummary }> = [];
+    wt.on('worktree_update', (e) => events.push(e));
+    const out = await wt.startMainSession(r.id, { command: 'bash', branch: 'feature/x', newBranch: true });
+    expect(execFileSync('git', ['branch', '--show-current'], { cwd: repo }).toString().trim()).toBe('feature/x');
+    expect(out.worktree?.branch).toBe('feature/x');
+    expect(events.some((e) => e.worktree.isMain && e.worktree.branch === 'feature/x')).toBe(true);
+  });
+
+  it('startMainSession : checkout principal sale → 409 DIRTY_TREE (pas de bascule)', async () => {
+    const repo = makeTmpRepo();
+    const r = await wt.addRepo({ path: repo });
+    writeFileSync(join(repo, 'scratch.txt'), 'wip\n'); // arbre sale
+    await expect(wt.startMainSession(r.id, { command: 'bash', branch: 'feature/y', newBranch: true })).rejects.toMatchObject({
+      statusCode: 409,
+      code: 'DIRTY_TREE',
+    });
+    expect(execFileSync('git', ['branch', '--show-current'], { cwd: repo }).toString().trim()).toBe('main');
+  });
+
+  it('startMainSession : branche invalide → 400', async () => {
+    const repo = makeTmpRepo();
+    const r = await wt.addRepo({ path: repo });
+    await expect(wt.startMainSession(r.id, { command: 'bash', branch: '../evil', newBranch: true })).rejects.toMatchObject({ statusCode: 400 });
+  });
+
   it('deleteWorktree : main refusé (400), dirty refusé (409) puis force OK', async () => {
     const repo = makeTmpRepo();
     const r = await wt.addRepo({ path: repo });

packages/shared/src/api.ts

@@ -128,6 +128,20 @@ export interface AdoptWorktreeRequest {
   preTrust?: boolean;
 }
 
+/**
+ * POST /api/v1/repos/:id/session — lance UNE session dans le checkout principal du repo
+ * (`repo.path`) pour « bosser sur la branche principale » sans créer de worktree.
+ * Réponse : `SessionResponse`.
+ */
+export interface StartRepoSessionRequest {
+  /** binaire à lancer — défaut "claude" ; "bash" sert aux tests sans quota. */
+  command?: 'claude' | 'bash';
+  /** si fourni : crée/bascule cette branche dans le checkout principal avant la session. */
+  branch?: string;
+  /** true (défaut quand `branch` fourni) : `git switch -c` ; false : bascule sur une branche existante. */
+  newBranch?: boolean;
+}
+
 // ---- Groupes de travail (P5) ----
 export interface GroupsListResponse {
   groups: GroupSummary[];

packages/web/src/components/RepoSection.vue

@@ -5,7 +5,7 @@
       <BaseBadge v-if="!repo.valid" tone="red">{{ t('repos.invalid') }}</BaseBadge>
       <span class="truncate font-mono text-xs text-zinc-500" :title="repo.path">{{ repo.path }}</span>
       <div class="ml-auto flex items-center gap-2">
-        <BaseButton size="sm" :icon="Plus" @click="creating = !creating">{{ t('worktrees.new') }}</BaseButton>
+        <BaseButton size="sm" :icon="Plus" @click="creating = !creating">{{ t('worktrees.startWork') }}</BaseButton>
         <BaseButton size="sm" :icon="Scissors" :loading="busy" @click="onPrune">{{ t('worktrees.prune') }}</BaseButton>
         <BaseButton
           size="sm"
@@ -18,23 +18,58 @@
       </div>
     </header>
 
-    <form v-if="creating" class="card-inset flex flex-wrap items-end gap-2" @submit.prevent="onCreate">
+    <form v-if="creating" class="card-inset flex flex-col gap-2" @submit.prevent="onCreate">
-      <label class="flex flex-1 flex-col gap-1 text-xs text-zinc-400">
+      <!-- mode : créer un worktree dédié, ou bosser directement sur le checkout principal -->
-        {{ t('worktrees.branch') }}
+      <div class="flex flex-wrap items-center gap-3 text-xs text-zinc-400">
-        <input v-model="branch" class="input font-mono" placeholder="feature/…" required />
+        {{ t('worktrees.modeLabel') }}
-      </label>
+        <label class="flex items-center gap-1.5"><input v-model="mode" type="radio" value="worktree" /> {{ t('worktrees.modeWorktree') }}</label>
-      <label class="flex flex-col gap-1 text-xs text-zinc-400">
+        <label class="flex items-center gap-1.5"><input v-model="mode" type="radio" value="main" /> {{ t('worktrees.modeMain') }}</label>
-        {{ t('worktrees.start') }}
+      </div>
-        <select v-model="startSession" class="input">
+
-          <option :value="null">{{ t('worktrees.startNone') }}</option>
+      <div class="flex flex-wrap items-end gap-2">
-          <option value="claude">claude</option>
+        <!-- mode worktree : branche + créer/existante -->
-          <option value="bash">bash</option>
+        <template v-if="mode === 'worktree'">
-        </select>
+          <label class="flex flex-1 flex-col gap-1 text-xs text-zinc-400">
-      </label>
+            {{ t('worktrees.branch') }}
-      <label class="flex items-center gap-1 text-xs text-zinc-400"><input v-model="newBranch" type="checkbox" /> {{ t('worktrees.newBranch') }}</label>
+            <input v-model="branch" class="input font-mono" placeholder="feature/…" required />
-      <BaseButton type="submit" variant="primary" size="sm" :loading="busy" :disabled="branch.trim() === ''">
+          </label>
-        {{ t('worktrees.create') }}
+          <label class="flex flex-col gap-1 text-xs text-zinc-400">
-      </BaseButton>
+            {{ t('worktrees.start') }}
+            <select v-model="startSession" class="input">
+              <option :value="null">{{ t('worktrees.startNone') }}</option>
+              <option value="claude">claude</option>
+              <option value="bash">bash</option>
+            </select>
+          </label>
+          <label class="flex items-center gap-1 text-xs text-zinc-400"><input v-model="newBranch" type="checkbox" /> {{ t('worktrees.newBranch') }}</label>
+        </template>
+
+        <!-- mode branche principale : option git (branche actuelle ou nouvelle branche) + commande -->
+        <template v-else>
+          <label class="flex flex-col gap-1 text-xs text-zinc-400">
+            {{ t('worktrees.branchModeLabel') }}
+            <select v-model="mainBranchMode" class="input">
+              <option value="current">{{ t('worktrees.currentBranch') }}</option>
+              <option value="new">{{ t('worktrees.newBranchOpt') }}</option>
+            </select>
+          </label>
+          <label v-if="mainBranchMode === 'new'" class="flex flex-1 flex-col gap-1 text-xs text-zinc-400">
+            {{ t('worktrees.branch') }}
+            <input v-model="branch" class="input font-mono" placeholder="feature/…" />
+          </label>
+          <label class="flex flex-col gap-1 text-xs text-zinc-400">
+            {{ t('worktrees.commandLabel') }}
+            <select v-model="mainCommand" class="input">
+              <option value="claude">claude</option>
+              <option value="bash">bash</option>
+            </select>
+          </label>
+        </template>
+
+        <BaseButton type="submit" variant="primary" size="sm" :loading="busy" :disabled="!canSubmit">
+          {{ mode === 'worktree' ? t('worktrees.create') : t('worktrees.start') }}
+        </BaseButton>
+      </div>
     </form>
     <p v-if="error" class="text-sm text-red-400">{{ error }}</p>
 
@@ -66,20 +101,37 @@ const toasts = useToastsStore();
 // applique le tri/filtre/recherche partagé (toolbar du dashboard) aux worktrees de ce repo.
 const worktrees = computed(() => view.apply(store.worktreesForRepo(props.repo.id)));
 const creating = ref(false);
+const mode = ref<'worktree' | 'main'>('worktree');
 const branch = ref('');
 const newBranch = ref(true);
 const startSession = ref<'claude' | 'bash' | null>(null);
+const mainBranchMode = ref<'current' | 'new'>('current');
+const mainCommand = ref<'claude' | 'bash'>('claude');
 const busy = ref(false);
 const error = ref<string | null>(null);
 
+// worktree : branche obligatoire ; branche principale + nouvelle branche : branche obligatoire ; sinon OK.
+const canSubmit = computed(() =>
+  mode.value === 'worktree' ? branch.value.trim() !== '' : mainBranchMode.value === 'current' || branch.value.trim() !== '',
+);
+
 async function onCreate(): Promise<void> {
   busy.value = true;
   error.value = null;
   try {
-    await store.createWorktree(props.repo.id, { branch: branch.value.trim(), newBranch: newBranch.value, startSession: startSession.value });
+    if (mode.value === 'worktree') {
+      await store.createWorktree(props.repo.id, { branch: branch.value.trim(), newBranch: newBranch.value, startSession: startSession.value });
+      toasts.success(t('toast.worktreeCreated'));
+    } else {
+      // bosser sur la branche principale : session dans le checkout principal, avec création de branche optionnelle.
+      await store.startMainSession(props.repo.id, {
+        command: mainCommand.value,
+        ...(mainBranchMode.value === 'new' ? { branch: branch.value.trim(), newBranch: true } : {}),
+      });
+      toasts.success(t('toast.sessionCreated'));
+    }
     branch.value = '';
     creating.value = false;
-    toasts.success(t('toast.worktreeCreated'));
   } catch (err) {
     error.value = err instanceof Error ? err.message : String(err);
   } finally {

packages/web/src/components/WorktreeCard.vue

@@ -26,6 +26,30 @@
       </RouterLink>
       <span v-if="worktree.sessions.length === 0" class="text-xs text-zinc-600">{{ t('worktrees.noSession') }}</span>
 
+      <!-- lancement d'une session sur ce worktree ; carte principale = bosser sur la branche principale -->
+      <button v-if="hasLiveSession && !showLauncher" class="btn text-xs" @click="showLauncher = true">+ {{ t('worktrees.start') }}</button>
+      <form v-if="!hasLiveSession || showLauncher" class="flex flex-wrap items-center gap-1" @submit.prevent="onStart">
+        <template v-if="worktree.isMain">
+          <select v-model="branchMode" class="input text-xs" :aria-label="t('worktrees.branchModeLabel')">
+            <option value="current">{{ t('worktrees.currentBranch') }}</option>
+            <option value="new">{{ t('worktrees.newBranchOpt') }}</option>
+          </select>
+          <input v-if="branchMode === 'new'" v-model="newBranchName" class="input w-32 font-mono text-xs" placeholder="feature/…" />
+        </template>
+        <select v-model="startCommand" class="input text-xs" :aria-label="t('worktrees.commandLabel')">
+          <option value="claude">claude</option>
+          <option value="bash">bash</option>
+        </select>
+        <button
+          type="submit"
+          class="btn-primary text-xs"
+          :disabled="starting || (worktree.isMain && branchMode === 'new' && newBranchName.trim() === '')"
+        >
+          {{ starting ? t('worktrees.starting') : t('worktrees.start') }}
+        </button>
+      </form>
+      <span v-if="startError" class="text-xs text-amber-400">{{ startError }}</span>
+
       <div v-if="!worktree.isMain" class="ml-auto flex items-center gap-2">
         <template v-if="confirming">
           <span v-if="error" class="text-xs text-amber-400">{{ error }}</span>
@@ -74,6 +98,39 @@ const forceNeeded = ref(false);
 const error = ref<string | null>(null);
 const busy = ref(false);
 
+// --- lancement de session sur ce worktree ---
+const hasLiveSession = computed(() => props.worktree.sessions.some((s) => liveSession(s).live));
+const showLauncher = ref(false);
+const startCommand = ref<'claude' | 'bash'>('claude');
+const branchMode = ref<'current' | 'new'>('current'); // carte principale uniquement
+const newBranchName = ref('');
+const starting = ref(false);
+const startError = ref<string | null>(null);
+
+async function onStart(): Promise<void> {
+  if (starting.value) return;
+  starting.value = true;
+  startError.value = null;
+  try {
+    if (props.worktree.isMain && branchMode.value === 'new') {
+      // bosser sur la branche principale en créant d'abord une branche dans le checkout principal.
+      await store.startMainSession(props.worktree.repoId, { command: startCommand.value, branch: newBranchName.value.trim(), newBranch: true });
+    } else {
+      // worktree existant (ou branche principale actuelle) : session directe dans son cwd.
+      await sessions.createSession(props.worktree.path, startCommand.value);
+    }
+    // resynchronise les worktrees du repo pour que la nouvelle session apparaisse sur la carte.
+    await store.refreshRepoWorktrees(props.worktree.repoId);
+    showLauncher.value = false;
+    newBranchName.value = '';
+    branchMode.value = 'current';
+  } catch (err) {
+    startError.value = err instanceof Error ? err.message : String(err);
+  } finally {
+    starting.value = false;
+  }
+}
+
 const branchLabel = computed(() =>
   props.worktree.branch ?? (props.worktree.detached ? `${t('worktrees.detached')} ${props.worktree.head.slice(0, 7)}` : '—'),
 );

packages/web/src/i18n/en.ts

@@ -141,7 +141,16 @@ export default {
     branch: 'Branch',
     newBranch: 'create branch',
     start: 'Start',
+    starting: 'Starting…',
     startNone: 'no session',
+    startWork: 'Start work',
+    modeLabel: 'Mode',
+    modeWorktree: 'Worktree',
+    modeMain: 'Main branch',
+    branchModeLabel: 'Branch',
+    currentBranch: 'current branch',
+    newBranchOpt: 'new branch',
+    commandLabel: 'Command',
     delete: 'Delete',
     confirmDelete: 'Confirm delete',
     forceDelete: 'Force delete',

packages/web/src/i18n/fr.ts

@@ -143,7 +143,16 @@ const fr: typeof en = {
     branch: 'Branche',
     newBranch: 'créer la branche',
     start: 'Démarrer',
+    starting: 'Démarrage…',
     startNone: 'aucune session',
+    startWork: 'Démarrer le travail',
+    modeLabel: 'Mode',
+    modeWorktree: 'Worktree',
+    modeMain: 'Branche principale',
+    branchModeLabel: 'Branche',
+    currentBranch: 'branche actuelle',
+    newBranchOpt: 'nouvelle branche',
+    commandLabel: 'Commande',
     delete: 'Supprimer',
     confirmDelete: 'Confirmer',
     forceDelete: 'Forcer la suppression',

packages/web/src/stores/worktrees.ts

@@ -7,6 +7,9 @@ import type {
   RepoResponse,
   ReposListResponse,
   RepoSummary,
+  SessionResponse,
+  SessionSummary,
+  StartRepoSessionRequest,
   WorktreeSummary,
   WorktreesListResponse,
 } from '@arboretum/shared';
@@ -104,6 +107,16 @@ export const useWorktreesStore = defineStore('worktrees', () => {
     return res;
   }
 
+  /**
+   * Lance une session sur le checkout principal du repo (« bosser sur la branche principale » sans
+   * worktree). Avec `branch`, le serveur crée/bascule la branche d'abord. La session et le worktree
+   * mis à jour arrivent aussi par WS ; on retourne la session pour permettre la navigation immédiate.
+   */
+  async function startMainSession(repoId: string, req: StartRepoSessionRequest = {}): Promise<SessionSummary> {
+    const res = await api.post<SessionResponse>(`/api/v1/repos/${repoId}/session`, req);
+    return res.session;
+  }
+
   async function deleteWorktree(repoId: string, path: string, force: boolean): Promise<void> {
     await api.delete<{ ok: true }>(`/api/v1/repos/${repoId}/worktrees?path=${encodeURIComponent(path)}&force=${force}`);
     removeWorktreeLocal(path);
@@ -135,6 +148,7 @@ export const useWorktreesStore = defineStore('worktrees', () => {
     discover,
     refreshRepoWorktrees,
     createWorktree,
+    startMainSession,
     deleteWorktree,
     prune,
     startRealtime,