diff --git a/bun.lock b/bun.lock
index fae6c5a2..0909270f 100644
--- a/bun.lock
+++ b/bun.lock
@@ -52,10 +52,10 @@
         "vite-plugin-pwa": "^1.2.0",
       },
       "optionalDependencies": {
-        "@gbasin/agentboard-darwin-arm64": "0.4.3",
-        "@gbasin/agentboard-darwin-x64": "0.4.3",
-        "@gbasin/agentboard-linux-arm64": "0.4.3",
-        "@gbasin/agentboard-linux-x64": "0.4.3",
+        "@gbasin/agentboard-darwin-arm64": "0.4.4",
+        "@gbasin/agentboard-darwin-x64": "0.4.4",
+        "@gbasin/agentboard-linux-arm64": "0.4.4",
+        "@gbasin/agentboard-linux-x64": "0.4.4",
       },
     },
   },
diff --git a/src/server/__tests__/isolated/terminalProxy.test.ts b/src/server/__tests__/isolated/terminalProxy.test.ts
index dbeb1d71..1aa2a9e4 100644
--- a/src/server/__tests__/isolated/terminalProxy.test.ts
+++ b/src/server/__tests__/isolated/terminalProxy.test.ts
@@ -647,4 +647,49 @@ describe('TerminalProxy', () => {
       options: expect.objectContaining({ timeout: 15000 }),
     })
   })
+
+  test('disposes the grouped session when tmux attach spawn fails', async () => {
+    const harness = createSpawnHarness()
+    const failingSpawn = (
+      args: string[],
+      options: Parameters<typeof Bun.spawn>[1]
+    ) => {
+      harness.spawnCalls.push({ args, options })
+      throw new Error('pty exhausted')
+    }
+
+    const proxy = new TerminalProxy({
+      connectionId: 'attach-fail',
+      sessionName: 'agentboard-ws-attach-fail',
+      baseSession: 'agentboard',
+      onData: () => {},
+      spawn: failingSpawn,
+      spawnSync: harness.spawnSync,
+      wait: async () => {},
+    })
+
+    await expect(proxy.start()).rejects.toMatchObject({
+      code: 'ERR_TMUX_ATTACH_FAILED',
+    })
+
+    // new-session created the grouped session before attach; dispose must
+    // kill it so a failed spawn cannot orphan a pty-holding session.
+    expect(harness.spawnSyncCalls).toContainEqual({
+      args: [
+        'tmux',
+        'new-session',
+        '-d',
+        '-t',
+        'agentboard',
+        '-s',
+        'agentboard-ws-attach-fail',
+      ],
+      options: expect.objectContaining({ timeout: 15000 }),
+    })
+    expect(harness.spawnSyncCalls).toContainEqual({
+      args: ['tmux', 'kill-session', '-t', 'agentboard-ws-attach-fail'],
+      options: expect.objectContaining({ timeout: 15000 }),
+    })
+    expect(proxy.isReady()).toBe(false)
+  })
 })
diff --git a/src/server/terminal/PtyTerminalProxy.ts b/src/server/terminal/PtyTerminalProxy.ts
index bed7eb7a..be6bdb14 100644
--- a/src/server/terminal/PtyTerminalProxy.ts
+++ b/src/server/terminal/PtyTerminalProxy.ts
@@ -240,7 +240,10 @@ class PtyTerminalProxy extends TerminalProxyBase {
         },
       })
     } catch (error) {
-      this.state = TerminalState.DEAD
+      // Tear down the grouped session created just above; otherwise a failed
+      // attach orphans a `…-ws-<uuid>` session that holds a pty until the next
+      // restart's reaper.
+      await this.dispose()
       throw new TerminalProxyError(
         'ERR_TMUX_ATTACH_FAILED',
         error instanceof Error ? error.message : 'Failed to attach tmux client',