diff --git a/packages/api/src/agent-workspace-info.spec.ts b/packages/api/src/agent-workspace-info.spec.ts
new file mode 100644
index 000000000..2c0f7b20b
--- /dev/null
+++ b/packages/api/src/agent-workspace-info.spec.ts
@@ -0,0 +1,35 @@
+/**********************************************************************
+ * Copyright (C) 2026 Red Hat, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ ***********************************************************************/
+
+import { expect, test } from 'vitest';
+
+import { getSandboxNameValidationError, SANDBOX_NAME_MAX_LENGTH } from './agent-workspace-info.js';
+
+test('accepts names at exactly the maximum length', () => {
+  const name = 'a'.repeat(SANDBOX_NAME_MAX_LENGTH);
+
+  expect(getSandboxNameValidationError(name)).toBeUndefined();
+});
+
+test('rejects names exceeding the maximum length', () => {
+  const name = 'a'.repeat(SANDBOX_NAME_MAX_LENGTH + 1);
+
+  expect(getSandboxNameValidationError(name)).toBe(
+    `Workspace name must not exceed ${SANDBOX_NAME_MAX_LENGTH} characters`,
+  );
+});
diff --git a/packages/api/src/agent-workspace-info.ts b/packages/api/src/agent-workspace-info.ts
index 3893fc77b..28041b9ab 100644
--- a/packages/api/src/agent-workspace-info.ts
+++ b/packages/api/src/agent-workspace-info.ts
@@ -58,6 +58,16 @@ export type AgentWorkspaceMcpConfig = configComponents['schemas']['McpConfigurat
 
 export type AgentWorkspaceMount = configComponents['schemas']['Mount'];
 
+/** Maximum sandbox name length for OpenShell. Podman/crun hostname composition leaves a conservative 56-char limit. */
+export const SANDBOX_NAME_MAX_LENGTH = 56;
+
+export function getSandboxNameValidationError(name: string): string | undefined {
+  if (name.length > SANDBOX_NAME_MAX_LENGTH) {
+    return `Workspace name must not exceed ${SANDBOX_NAME_MAX_LENGTH} characters`;
+  }
+  return undefined;
+}
+
 /**
  * Options for creating (initializing) a new workspace via `kdn init`.
  */
diff --git a/packages/main/src/plugin/agent-workspace/agent-workspace-manager.spec.ts b/packages/main/src/plugin/agent-workspace/agent-workspace-manager.spec.ts
index 5fb3efaca..00d568c71 100644
--- a/packages/main/src/plugin/agent-workspace/agent-workspace-manager.spec.ts
+++ b/packages/main/src/plugin/agent-workspace/agent-workspace-manager.spec.ts
@@ -338,6 +338,28 @@ describe('create – OpenShell mode', () => {
     expect(result).toEqual({ id: 'my-project' });
   });
 
+  test('rejects workspace names longer than the hostname limit', async () => {
+    const options: AgentWorkspaceCreateOptions = {
+      ...defaultOptions,
+      name: 'a'.repeat(57),
+    };
+
+    await expect(manager.create(options)).rejects.toThrow(/must not exceed 56 characters/);
+    expect(openshellCli.createSandbox).not.toHaveBeenCalled();
+  });
+
+  test('rejects basename-derived names longer than the hostname limit', async () => {
+    const longBasename = 'a'.repeat(57);
+    const options: AgentWorkspaceCreateOptions = {
+      sourcePath: `/tmp/${longBasename}`,
+      agent: 'claude',
+      model: 'ramalama::granite-4::',
+    };
+
+    await expect(manager.create(options)).rejects.toThrow(/must not exceed 56 characters/);
+    expect(openshellCli.createSandbox).not.toHaveBeenCalled();
+  });
+
   test('passes agent baseImage as from option to createSandbox', async () => {
     vi.mocked(agentRegistry.getAgentRegistration).mockReturnValue({
       ...mockAgent,
diff --git a/packages/main/src/plugin/agent-workspace/agent-workspace-manager.ts b/packages/main/src/plugin/agent-workspace/agent-workspace-manager.ts
index 09594f5d5..12349875a 100644
--- a/packages/main/src/plugin/agent-workspace/agent-workspace-manager.ts
+++ b/packages/main/src/plugin/agent-workspace/agent-workspace-manager.ts
@@ -48,6 +48,7 @@ import type {
   AgentWorkspaceId,
   AgentWorkspaceSummary,
 } from '/@api/agent-workspace-info.js';
+import { getSandboxNameValidationError } from '/@api/agent-workspace-info.js';
 import { ApiSenderType } from '/@api/api-sender/api-sender-type.js';
 import type { IConfigurationNode } from '/@api/configuration/models.js';
 import { IConfigurationRegistry } from '/@api/configuration/models.js';
@@ -200,6 +201,10 @@ export class AgentWorkspaceManager implements Disposable {
     uploads.push(...(await this.buildOpenshellFilesystemUploads(options.sourcePath, workspace)));
 
     const sandboxName = options.name ?? basename(options.sourcePath);
+    const sandboxNameError = getSandboxNameValidationError(sandboxName);
+    if (sandboxNameError) {
+      throw new Error(sandboxNameError);
+    }
     const env = workspace.environment
       ?.filter(entry => typeof entry.value === 'string' && entry.value !== '')
       .reduce<Record<string, string>>((acc, entry) => {
diff --git a/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreate.spec.ts b/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreate.spec.ts
index cdab59e60..485f3a3f6 100644
--- a/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreate.spec.ts
+++ b/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreate.spec.ts
@@ -261,6 +261,31 @@ test('Expect Continue button enabled when name and source are filled', async ()
   expect(screen.getByRole('button', { name: 'Continue' })).not.toBeDisabled();
 });
 
+test('Expect Continue button disabled when workspace name exceeds hostname limit', async () => {
+  render(AgentWorkspaceCreate);
+
+  await fireEvent.input(screen.getByPlaceholderText('/path/to/project'), {
+    target: { value: '/home/user/my-repo' },
+  });
+  await fireEvent.input(screen.getByPlaceholderText('e.g., Frontend Refactoring'), {
+    target: { value: 'a'.repeat(57) },
+  });
+
+  expect(screen.getByRole('button', { name: 'Continue' })).toBeDisabled();
+  expect(screen.getByText(/must not exceed 56 characters/)).toBeInTheDocument();
+});
+
+test('Expect Continue button disabled when basename-derived name exceeds hostname limit', async () => {
+  render(AgentWorkspaceCreate);
+
+  await fireEvent.input(screen.getByPlaceholderText('/path/to/project'), {
+    target: { value: `/home/user/${'a'.repeat(57)}` },
+  });
+
+  expect(screen.getByRole('button', { name: 'Continue' })).toBeDisabled();
+  expect(screen.getByText(/must not exceed 56 characters/)).toBeInTheDocument();
+});
+
 test('Expect use-all-defaults button on step 1', async () => {
   render(AgentWorkspaceCreate);
 
diff --git a/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreate.svelte b/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreate.svelte
index 17a7ef2f3..cdc6b3378 100644
--- a/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreate.svelte
+++ b/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreate.svelte
@@ -27,6 +27,7 @@ import type {
   AgentWorkspaceMount,
   NetworkConfiguration,
 } from '/@api/agent-workspace-info';
+import { getSandboxNameValidationError } from '/@api/agent-workspace-info';
 import { NavigationPage } from '/@api/navigation-page';
 import type { DefaultWorkspaceSettings } from '/@api/onboarding-settings-info';
 import type { FilesystemConfiguration, WorkspaceProjectInfo } from '/@api/workspace-project-info';
@@ -212,6 +213,18 @@ function getDefaultSessionName(path: string): string {
   return normalized.split(/[\\/]/).filter(Boolean).at(-1) ?? '';
 }
 
+function getEffectiveWorkspaceName(): string {
+  return wizard.draft.sessionName.trim() || getDefaultSessionName(wizard.draft.sourcePath);
+}
+
+function getEffectiveWorkspaceNameFromSnapshot(draft: { sessionName: string; sourcePath: string }): string {
+  return draft.sessionName.trim() || getDefaultSessionName(draft.sourcePath);
+}
+
+function isWorkspaceNameValid(): boolean {
+  return getSandboxNameValidationError(getEffectiveWorkspaceName()) === undefined;
+}
+
 $effect(() => {
   if (wizard.draft.nameManuallyEdited) return;
   const last = getDefaultSessionName(wizard.draft.sourcePath);
@@ -258,7 +271,12 @@ let validationErrors = $derived.by(() => {
 });
 let isCurrentStepComplete = $derived.by(() => {
   if (currentStepId === 'workspace') {
-    return wizard.draft.sessionName.trim() !== '' && wizard.draft.sourcePath.trim() !== '' && !validationErrors.name;
+    return (
+      getEffectiveWorkspaceName() !== '' &&
+      wizard.draft.sourcePath.trim() !== '' &&
+      isWorkspaceNameValid() &&
+      !validationErrors.name
+    );
   }
   if (currentStepId === 'agent-model') {
     return hasModel;
@@ -406,7 +424,14 @@ function buildMountsFrom(fileAccess: string, mounts: CustomMount[]): AgentWorksp
 }
 
 async function startAsIs(): Promise<void> {
-  if (!wizard.draft.sourcePath.trim() || !wizard.draft.selectedModel) return;
+  if (
+    !wizard.draft.sourcePath.trim() ||
+    !wizard.draft.selectedModel ||
+    !isWorkspaceNameValid() ||
+    validationErrors.name
+  ) {
+    return;
+  }
 
   const draftSnapshot = $state.snapshot(wizard.draft);
 
@@ -415,7 +440,7 @@ async function startAsIs(): Promise<void> {
       sourcePath: draftSnapshot.sourcePath,
       agent: draftSnapshot.selectedAgent,
       model: getModelId(draftSnapshot.selectedModel!),
-      name: draftSnapshot.sessionName || getDefaultSessionName(draftSnapshot.sourcePath),
+      name: getEffectiveWorkspaceNameFromSnapshot(draftSnapshot),
       project: draftSnapshot.selectedProjectId,
     });
     resetDraft();
@@ -435,7 +460,15 @@ async function startAsIs(): Promise<void> {
 }
 
 async function startWorkspace(): Promise<void> {
-  if (!wizard.draft.sessionName.trim() || !wizard.draft.sourcePath.trim() || !wizard.draft.selectedModel) return;
+  if (
+    !getEffectiveWorkspaceName() ||
+    !wizard.draft.sourcePath.trim() ||
+    !wizard.draft.selectedModel ||
+    !isWorkspaceNameValid() ||
+    validationErrors.name
+  ) {
+    return;
+  }
 
   const draftSnapshot = $state.snapshot(wizard.draft);
 
@@ -467,7 +500,7 @@ async function startWorkspace(): Promise<void> {
       sourcePath: draftSnapshot.sourcePath,
       agent: draftSnapshot.selectedAgent,
       model: getModelId(draftSnapshot.selectedModel!),
-      name: draftSnapshot.sessionName,
+      name: getEffectiveWorkspaceNameFromSnapshot(draftSnapshot),
       skills: selectedSkillPaths.length > 0 ? selectedSkillPaths : undefined,
       network,
       secrets: draftSnapshot.selectedSecretIds.length > 0 ? [...draftSnapshot.selectedSecretIds] : undefined,
diff --git a/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreateStepWorkspace.spec.ts b/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreateStepWorkspace.spec.ts
index 8e667da6e..70cc93c58 100644
--- a/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreateStepWorkspace.spec.ts
+++ b/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreateStepWorkspace.spec.ts
@@ -103,6 +103,36 @@ test('Expect workspace name input renders initial value', () => {
   expect((screen.getByPlaceholderText('e.g., Frontend Refactoring') as HTMLInputElement).value).toBe('my-workspace');
 });
 
+test('shows validation error when workspace name exceeds hostname limit', () => {
+  render(AgentWorkspaceCreateStepWorkspace, {
+    ...defaultProps,
+    sessionName: 'a'.repeat(57),
+  });
+
+  expect(screen.getByText(/must not exceed 56 characters/)).toBeInTheDocument();
+  expect(screen.getByPlaceholderText('e.g., Frontend Refactoring')).toHaveAttribute('aria-invalid', 'true');
+});
+
+test('shows validation error when basename-derived name exceeds hostname limit', () => {
+  render(AgentWorkspaceCreateStepWorkspace, {
+    ...defaultProps,
+    sourcePath: `/home/user/${'a'.repeat(57)}`,
+    sessionName: '',
+  });
+
+  expect(screen.getByText(/must not exceed 56 characters/)).toBeInTheDocument();
+});
+
+test('accepts workspace name at exactly the hostname limit', () => {
+  render(AgentWorkspaceCreateStepWorkspace, {
+    ...defaultProps,
+    sessionName: 'a'.repeat(56),
+  });
+
+  expect(screen.queryByText(/must not exceed 56 characters/)).not.toBeInTheDocument();
+  expect(screen.getByPlaceholderText('e.g., Frontend Refactoring')).toHaveAttribute('aria-invalid', 'false');
+});
+
 test('shows config-exists notification when configExists is true', () => {
   render(AgentWorkspaceCreateStepWorkspace, {
     ...defaultProps,
diff --git a/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreateStepWorkspace.svelte b/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreateStepWorkspace.svelte
index e1aa53bcc..df9e07bce 100644
--- a/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreateStepWorkspace.svelte
+++ b/packages/renderer/src/lib/agent-workspaces/AgentWorkspaceCreateStepWorkspace.svelte
@@ -4,6 +4,7 @@ import { Button, Input } from '@podman-desktop/ui-svelte';
 import { Icon } from '@podman-desktop/ui-svelte/icons';
 
 import { Textarea } from '/@/lib/chat/components/ui/textarea';
+import { getSandboxNameValidationError } from '/@api/agent-workspace-info';
 import type { WorkspaceProjectInfo } from '/@api/workspace-project-info';
 
 interface Props {
@@ -53,6 +54,18 @@ function toggleDescription(): void {
 function toggleProject(): void {
   projectOpen = !projectOpen;
 }
+
+function getEffectiveWorkspaceName(name: string, path: string): string {
+  const trimmed = name.trim();
+  if (trimmed) {
+    return trimmed;
+  }
+  const normalized = path.trim().replace(/[\\/]+$/, '');
+  return normalized.split(/[\\/]/).filter(Boolean).at(-1) ?? '';
+}
+
+let sessionNameError = $derived(getSandboxNameValidationError(getEffectiveWorkspaceName(sessionName, sourcePath)));
+let nameInputError = $derived(sessionNameError ?? errors?.name ?? '');
 </script>
 
 <h2 class="text-lg font-semibold text-[var(--pd-modal-text)] mb-1">Workspace</h2>
@@ -133,8 +146,8 @@ function toggleProject(): void {
       placeholder="e.g., Frontend Refactoring"
       class="w-full"
       oninput={markNameEdited}
-      error={errors?.name ?? ''}
-      aria-invalid={!!errors?.name}
+      error={nameInputError}
+      aria-invalid={nameInputError !== ''}
     />
   </div>