feat: add Application Runtime docs and Sandbox snapshots/fork page

[devin-ai-integration]

Summary

Adds customer-facing documentation for the new Application Runtime feature (ENG-2908) and sandbox snapshot/fork capabilities.

New pages:

• Applications/Overview.mdx — single comprehensive page covering:

  • CRUD operations (create, get, list, update, delete) with TypeScript, Python, Go SDK, CLI, and HTTP API examples for each
  • Revision management (list revisions, traffic splitting 0/1-99/100, sticky sessions)
  • Custom URL configuration (direct and wildcard domains)
  • Environment variables, memory/compute allocation, deployment statuses

• Sandboxes/Snapshots-and-fork.mdx — snapshot and fork operations:

  • Create/list/delete snapshots via SDK and HTTP API
  • Fork sandbox → sandbox or sandbox → application with SDK, CLI (bl fork sbx/... app/...), and HTTP API
  • Canary fork and snapshot-based fork

Navigation (docs.json):

• "Applications" group added after "Batch Jobs", before "Agents Hosting"
• "Snapshots & fork" page added to Sandboxes group before "best-practices"

Link to Devin session: https://app.devin.ai/sessions/2d9e244c4263469c8020ddff54347def
Requested by: @drappier-charles

---

Note

New commit adds a prefix fork parameter to the Sandboxes doc and a dedicated custom domain creation endpoint example for applications.

^{Written by Mendral for commit 0f7d99a.}

[devin-ai-integration]

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[mintlify]

Preview deployment for your docs. Learn more about Mintlify Previews.

Project	Status	Preview	Updated (UTC)
blaxel	🟢 Ready	View Preview	Jun 17, 2026, 9:50 PM

[mendral-app]

🧪 Testing Guide

What this PR addresses

Adds new documentation pages for the Application Runtime feature (ENG-2908) and Sandbox Snapshots & Fork capabilities. This includes:

• Applications/Overview.mdx — comprehensive docs covering CRUD operations, revision management, traffic splitting, sticky sessions, custom URLs, env vars, and deployment statuses with TypeScript, Python, Go SDK, CLI, and HTTP API examples.
• Sandboxes/Snapshots-and-fork.mdx — docs for creating/listing/deleting snapshots and forking sandboxes into new sandboxes or applications.
• Navigation updates in docs.json to register both new pages.

Steps to verify

1. Local docs site renders correctly

   • Run the docs site locally (e.g., mintlify dev or equivalent).
   • Navigate to the Applications → Overview page and confirm it renders without errors.
   • Navigate to the Sandboxes → Snapshots & fork page and confirm it renders without errors.

2. Navigation structure

   • Verify the sidebar shows "Snapshots & fork" under the Sandboxes group (after "Templates").
   • Verify a new "Applications" group appears in the sidebar with an "Overview" page.

3. Content accuracy

   • Confirm all code examples (TypeScript, Python, Go, CLI, HTTP API) render properly within <CodeGroup> tabs.
   • Check that internal links work: the cross-references between Applications and Snapshots pages (e.g., [application](/Applications/Overview) and the <Card> links at the bottom of each page) navigate correctly.
   • Verify the <Note> component renders (e.g., "Application Runtime is currently in preview").

4. No regressions

   • Confirm existing pages (Sandboxes/Volumes, Sandboxes/Templates, Jobs, etc.) still render and navigate correctly.
   • Ensure docs.json is valid JSON (no syntax errors).

What to verify (expected behavior)

• Both new pages load and display all sections, code blocks, tables, and callouts without rendering issues.
• Sidebar navigation correctly reflects the new entries in their expected positions.
• All internal cross-links between the two new pages and existing docs resolve properly.
• No broken layout or missing content in surrounding pages due to the docs.json changes.

Note

Posted by PR Testing Guide · Tag @mendral-app with feedback.

[mendral-app]

✅ Linked to Linear issue ENG-2908 — status already In Progress

• Assignee: Charles Drappier
• PR linked: ✅ Issue will auto-close when this PR merges

Note

Posted by Linear Issue Enforcer · Tag @mendral-app with feedback.

[mendral-app]

📄 Documentation PR — Interaction Flow

This PR is documentation-only (new .mdx pages + nav config), so there are no code-level component interactions to diagram. However, here's a sequence diagram illustrating the user interaction flows documented by these new pages:

sequenceDiagram
    participant User as User/Developer
    participant SDK as SDK / CLI / HTTP API
    participant App as Applications Service
    participant Rev as Revision Manager
    participant Sandbox as Sandbox Service
    participant Snap as Snapshot Store

    Note over User, App: Applications Lifecycle (Overview.mdx)
    User->>SDK: Create Application (name, env vars, compute)
    SDK->>App: Deploy application
    App->>Rev: Create initial revision
    Rev-->>App: Revision active (status: serving)
    App-->>User: Public endpoint URL

    User->>SDK: Update Application (new config)
    SDK->>App: Deploy new revision
    App->>Rev: Traffic split (canary %)
    Rev-->>App: Gradual rollout
    App-->>User: Sticky session / custom URL

    Note over User, Snap: Snapshots & Fork (Snapshots-and-fork.mdx)
    User->>SDK: Create Snapshot (sandbox_id)
    SDK->>Sandbox: Capture state
    Sandbox->>Snap: Store snapshot
    Snap-->>User: Snapshot ID

    User->>SDK: Fork Sandbox or Application
    SDK->>Snap: Load snapshot (optional)
    Snap->>Sandbox: Restore state → new sandbox
    Snap->>App: Restore state → new application
    App-->>User: Forked resource with traffic control

Loading

Summary

New Page	Covers
Applications/Overview.mdx	Full CRUD, revisions, traffic splitting, custom URLs, env vars, compute config
Sandboxes/Snapshots-and-fork.mdx	Snapshot lifecycle, forking to sandbox or application, canary deploys
docs.json	Navigation entries for both new sections

No code changes to review — only documentation content and structure.

Note

Posted by PR Sequence Diagram · Tag @mendral-app with feedback.