> ## Documentation Index
> Fetch the complete documentation index at: https://e2b.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Collapse envd's own anonymous heap into 2 MiB transparent hugepages before pause, so on resume envd touches fewer distinct guest-physical frames (each a cold fault). Best-effort.



## OpenAPI

````yaml /openapi-public.yml post /collapse
openapi: 3.1.0
info:
  title: E2B API
  version: 0.1.0
  description: >-
    Complete E2B developer API. Platform endpoints are served on api.e2b.app.
    Sandbox endpoints (envd) are served on the shared sandbox host
    (sandbox.e2b.app); target a specific sandbox with the E2b-Sandbox-Id and
    E2b-Sandbox-Port headers.
servers:
  - url: https://api.e2b.app
    description: E2B Platform API
security: []
tags:
  - name: Sandboxes
  - name: Templates
  - name: Tags
  - name: Volumes
  - name: Envd
  - name: Filesystem
  - name: Process
  - name: Teams
paths:
  /collapse:
    servers:
      - url: https://sandbox.{domain}
        description: Sandbox API (envd) - runs inside each sandbox
        variables:
          domain:
            default: e2b.app
            description: E2B domain
    post:
      tags:
        - Envd
      summary: >-
        Collapse envd's own anonymous heap into 2 MiB transparent hugepages
        before pause, so on resume envd touches fewer distinct guest-physical
        frames (each a cold fault). Best-effort.
      operationId: postCollapse
      parameters:
        - name: E2b-Sandbox-Id
          in: header
          required: true
          description: >-
            Identifier of the target sandbox. Routes the request to that
            sandbox's envd over the shared sandbox host.
          schema:
            type: string
        - name: E2b-Sandbox-Port
          in: header
          required: true
          description: Port envd listens on inside the sandbox (default 49983).
          schema:
            type: integer
            default: 49983
      responses:
        '200':
          description: Heap collapsed
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/CollapseResult'
        '500':
          $ref: '#/components/responses/InternalServerError'
        '502':
          description: Sandbox not found
          content:
            application/json:
              schema:
                type: object
                required:
                  - sandboxID
                  - message
                  - code
                properties:
                  message:
                    type: string
                    description: Error message
                  code:
                    type: integer
                    description: Error code
                  sandboxID:
                    type: string
                    description: Identifier of the sandbox
      security:
        - SandboxAccessTokenAuth: []
components:
  schemas:
    CollapseResult:
      type: object
      description: Per-call statistics from a heap collapse
      properties:
        regions:
          type: integer
          description: Anonymous read-write regions scanned
        chunks:
          type: integer
          description: 2 MiB chunks attempted
        collapsed:
          type: integer
          description: >-
            Chunks whose base pages were actually migrated into a new hugepage
            (real work)
        alreadyHuge:
          type: integer
          description: Chunks MADV_COLLAPSE accepted but were already hugepages (no work)
        skipped:
          type: integer
          description: Chunks that could not be collapsed (empty or ineligible)
        elapsedMs:
          type: integer
          format: int64
          description: Wall-clock time spent collapsing, in milliseconds
    Error:
      required:
        - code
        - message
      properties:
        code:
          type: integer
          format: int32
          description: Error code
        message:
          type: string
          description: Error
      type: object
  responses:
    InternalServerError:
      description: Internal server error
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
          example:
            message: 'error opening file ''/home/user/file.txt'': permission denied'
            code: 500
  securitySchemes:
    SandboxAccessTokenAuth:
      type: apiKey
      in: header
      name: X-Access-Token
      description: >-
        Sandbox access token (`envdAccessToken`) for authenticating requests to
        a running sandbox. Returned by: [POST
        /sandboxes](/docs/api-reference/sandboxes/create-a-sandbox) (on create),
        [POST
        /sandboxes/{sandboxID}/connect](/docs/api-reference/sandboxes/connect-to-a-sandbox)
        (on connect), [POST
        /sandboxes/{sandboxID}/resume](/docs/api-reference/sandboxes/resume-a-sandbox)
        (on resume), and [GET
        /sandboxes/{sandboxID}](/docs/api-reference/sandboxes/get-a-sandbox)
        (for running or paused sandboxes).

````