Proxy a HEAD request to a sandbox port

`HEAD` to an app listening on a sandbox port, reached only through `usercontent.b3os.org` port previews. Token check, forwarding and limits are the same as for `GET` (`sandboxesProxyPortGet`).

HEAD /v1/sandboxes/{sandbox_id}/ports/{port}/proxy/{rest}

`HEAD` to an app listening on a sandbox port, reached only through `usercontent.b3os.org` port previews. Token check, forwarding and limits are the same as for `GET` (`sandboxesProxyPortGet`).

Path Parameters

sandbox_id string required path

The sandbox ID (`sbx_…`).

Example: "sbx_01m5t68q1b590rj801nbzsqzkk"

port integer required path

A port declared in the sandbox's `ports`.

Example: 3000

rest string required path

The rest of the path after the usercontent prefix, slashes included, possibly empty (the app's root). Passed to the app as `/<rest>` byte for byte.

Example: "assets/app.js"

Header Parameters

x-b3os-port-token string required header

The port token from the usercontent path (`pt1.<node>.<exp>.<sig>`; see `sandboxesProxyPortGet`), set by the usercontent Worker. Missing, malformed, expired or not matching this sandbox and port: `403 signed_url_invalid`.

Example: "pt1.n1.1792955460.tjsgjiRC3sSYEwneW62TSvNqd-Jo_zzFI5zFYkB_YQBNl0CiBzI9xgoV6EJD_5YEmh3HbzSmb3acL8mY1LmYCg"

Responses

200 The app's response, passed through (any status, headers and body; `Set-Cookie` removed).

No response body

400 The request failed validation (`invalid_request`, `invalid_url`).

application/problem+json

type string (uri) REQUIRED

`https://docs.beta.b3os.org/errors#<code>`.

title string REQUIRED

Short summary of the problem type.

status integer REQUIRED

The HTTP status code, repeated for convenience.

code string REQUIRED

Stable machine-readable error code from the errors catalog.

detail string REQUIRED

Explanation of this occurrence. Never contains secrets.

instance string

The request ID (`req_…`) of the request that failed. Include it when you contact support.

errors object[]

Validation problems, one per field (`invalid_request` and the other codes that list `errors`).

Array of:

pointer string REQUIRED

Where the problem is: a JSON pointer into the request body (`/url`, `/steps/0/uses`), or `#query/<name>`, `#path/<name>` or `#header/<name>` for parameters.

detail string REQUIRED

What is wrong there.

reason string

Finer-grained cause for codes that document one (`unauthorized`, `forbidden`, `egress_denied`, `upstream_unreachable`, …).

required_scope string

The scope that was missing (`forbidden` with `reason: scope`).

retry_after_s integer

Same value as the `Retry-After` header, for clients that only read the body.

limit object

The limit an error refers to. IDs and current values are listed by `GET /v1/limits`.

id string REQUIRED

Limit ID, such as `vision.scrape.rpm` or `sandboxes.concurrent`.

limit number REQUIRED

The limit's value.

unit string REQUIRED

What the limit counts, such as `requests`, `sandboxes`, `vcpu` or `MiB`.

window_s integer

Window length in seconds for rate limits and quotas.

current number

Current usage against the limit, when known.

current_status string

The object's current status, for state conflicts such as `sandbox_not_running`.

upstream_status integer

The HTTP status the upstream returned (`upstream_error`, `action_output_invalid`).

step string

The failed step, as a step ID (routines), an index (`act`) or a path such as `beats/2/do/0` (render).

pack_error object

The error a pack's error mapping chose (`upstream_error` from pack actions).

code string REQUIRED

message string REQUIRED

retryable boolean REQUIRED

403 The port token is missing, malformed, expired, for another sandbox or port, or not signed by this node (`signed_url_invalid`).

application/problem+json

type string (uri) REQUIRED

`https://docs.beta.b3os.org/errors#<code>`.

title string REQUIRED

Short summary of the problem type.

status integer REQUIRED

The HTTP status code, repeated for convenience.

code string REQUIRED

Stable machine-readable error code from the errors catalog.

detail string REQUIRED

Explanation of this occurrence. Never contains secrets.

instance string

The request ID (`req_…`) of the request that failed. Include it when you contact support.

errors object[]

Validation problems, one per field (`invalid_request` and the other codes that list `errors`).

Array of:

pointer string REQUIRED

Where the problem is: a JSON pointer into the request body (`/url`, `/steps/0/uses`), or `#query/<name>`, `#path/<name>` or `#header/<name>` for parameters.

detail string REQUIRED

What is wrong there.

reason string

Finer-grained cause for codes that document one (`unauthorized`, `forbidden`, `egress_denied`, `upstream_unreachable`, …).

required_scope string

The scope that was missing (`forbidden` with `reason: scope`).

retry_after_s integer

Same value as the `Retry-After` header, for clients that only read the body.

limit object

The limit an error refers to. IDs and current values are listed by `GET /v1/limits`.

id string REQUIRED

Limit ID, such as `vision.scrape.rpm` or `sandboxes.concurrent`.

limit number REQUIRED

The limit's value.

unit string REQUIRED

What the limit counts, such as `requests`, `sandboxes`, `vcpu` or `MiB`.

window_s integer

Window length in seconds for rate limits and quotas.

current number

Current usage against the limit, when known.

current_status string

The object's current status, for state conflicts such as `sandbox_not_running`.

upstream_status integer

The HTTP status the upstream returned (`upstream_error`, `action_output_invalid`).

step string

The failed step, as a step ID (routines), an index (`act`) or a path such as `beats/2/do/0` (render).

pack_error object

The error a pack's error mapping chose (`upstream_error` from pack actions).

code string REQUIRED

message string REQUIRED

retryable boolean REQUIRED

404 No such sandbox, or the port is not declared in its `ports` (`sandbox_not_found`, `port_not_exposed`).

application/problem+json

type string (uri) REQUIRED

`https://docs.beta.b3os.org/errors#<code>`.

title string REQUIRED

Short summary of the problem type.

status integer REQUIRED

The HTTP status code, repeated for convenience.

code string REQUIRED

Stable machine-readable error code from the errors catalog.

detail string REQUIRED

Explanation of this occurrence. Never contains secrets.

instance string

The request ID (`req_…`) of the request that failed. Include it when you contact support.

errors object[]

Validation problems, one per field (`invalid_request` and the other codes that list `errors`).

Array of:

pointer string REQUIRED

Where the problem is: a JSON pointer into the request body (`/url`, `/steps/0/uses`), or `#query/<name>`, `#path/<name>` or `#header/<name>` for parameters.

detail string REQUIRED

What is wrong there.

reason string

Finer-grained cause for codes that document one (`unauthorized`, `forbidden`, `egress_denied`, `upstream_unreachable`, …).

required_scope string

The scope that was missing (`forbidden` with `reason: scope`).

retry_after_s integer

Same value as the `Retry-After` header, for clients that only read the body.

limit object

The limit an error refers to. IDs and current values are listed by `GET /v1/limits`.

id string REQUIRED

Limit ID, such as `vision.scrape.rpm` or `sandboxes.concurrent`.

limit number REQUIRED

The limit's value.

unit string REQUIRED

What the limit counts, such as `requests`, `sandboxes`, `vcpu` or `MiB`.

window_s integer

Window length in seconds for rate limits and quotas.

current number

Current usage against the limit, when known.

current_status string

The object's current status, for state conflicts such as `sandbox_not_running`.

upstream_status integer

The HTTP status the upstream returned (`upstream_error`, `action_output_invalid`).

step string

The failed step, as a step ID (routines), an index (`act`) or a path such as `beats/2/do/0` (render).

pack_error object

The error a pack's error mapping chose (`upstream_error` from pack actions).

code string REQUIRED

message string REQUIRED

retryable boolean REQUIRED

409 The sandbox is paused or stopped (`sandbox_not_running`).

application/problem+json

type string (uri) REQUIRED

`https://docs.beta.b3os.org/errors#<code>`.

title string REQUIRED

Short summary of the problem type.

status integer REQUIRED

The HTTP status code, repeated for convenience.

code string REQUIRED

Stable machine-readable error code from the errors catalog.

detail string REQUIRED

Explanation of this occurrence. Never contains secrets.

instance string

The request ID (`req_…`) of the request that failed. Include it when you contact support.

errors object[]

Validation problems, one per field (`invalid_request` and the other codes that list `errors`).

Array of:

pointer string REQUIRED

Where the problem is: a JSON pointer into the request body (`/url`, `/steps/0/uses`), or `#query/<name>`, `#path/<name>` or `#header/<name>` for parameters.

detail string REQUIRED

What is wrong there.

reason string

Finer-grained cause for codes that document one (`unauthorized`, `forbidden`, `egress_denied`, `upstream_unreachable`, …).

required_scope string

The scope that was missing (`forbidden` with `reason: scope`).

retry_after_s integer

Same value as the `Retry-After` header, for clients that only read the body.

limit object

The limit an error refers to. IDs and current values are listed by `GET /v1/limits`.

id string REQUIRED

Limit ID, such as `vision.scrape.rpm` or `sandboxes.concurrent`.

limit number REQUIRED

The limit's value.

unit string REQUIRED

What the limit counts, such as `requests`, `sandboxes`, `vcpu` or `MiB`.

window_s integer

Window length in seconds for rate limits and quotas.

current number

Current usage against the limit, when known.

current_status string

The object's current status, for state conflicts such as `sandbox_not_running`.

upstream_status integer

The HTTP status the upstream returned (`upstream_error`, `action_output_invalid`).

step string

The failed step, as a step ID (routines), an index (`act`) or a path such as `beats/2/do/0` (render).

pack_error object

The error a pack's error mapping chose (`upstream_error` from pack actions).

code string REQUIRED

message string REQUIRED

retryable boolean REQUIRED

429 A rate, concurrency or quota limit applies (`rate_limited`, `concurrency_limited`, `quota_exceeded`).

application/problem+json

type string (uri) REQUIRED

`https://docs.beta.b3os.org/errors#<code>`.

title string REQUIRED

Short summary of the problem type.

status integer REQUIRED

The HTTP status code, repeated for convenience.

code string REQUIRED

Stable machine-readable error code from the errors catalog.

detail string REQUIRED

Explanation of this occurrence. Never contains secrets.

instance string

The request ID (`req_…`) of the request that failed. Include it when you contact support.

errors object[]

Validation problems, one per field (`invalid_request` and the other codes that list `errors`).

Array of:

pointer string REQUIRED

Where the problem is: a JSON pointer into the request body (`/url`, `/steps/0/uses`), or `#query/<name>`, `#path/<name>` or `#header/<name>` for parameters.

detail string REQUIRED

What is wrong there.

reason string

Finer-grained cause for codes that document one (`unauthorized`, `forbidden`, `egress_denied`, `upstream_unreachable`, …).

required_scope string

The scope that was missing (`forbidden` with `reason: scope`).

retry_after_s integer

Same value as the `Retry-After` header, for clients that only read the body.

limit object

The limit an error refers to. IDs and current values are listed by `GET /v1/limits`.

id string REQUIRED

Limit ID, such as `vision.scrape.rpm` or `sandboxes.concurrent`.

limit number REQUIRED

The limit's value.

unit string REQUIRED

What the limit counts, such as `requests`, `sandboxes`, `vcpu` or `MiB`.

window_s integer

Window length in seconds for rate limits and quotas.

current number

Current usage against the limit, when known.

current_status string

The object's current status, for state conflicts such as `sandbox_not_running`.

upstream_status integer

The HTTP status the upstream returned (`upstream_error`, `action_output_invalid`).

step string

The failed step, as a step ID (routines), an index (`act`) or a path such as `beats/2/do/0` (render).

pack_error object

The error a pack's error mapping chose (`upstream_error` from pack actions).

code string REQUIRED

message string REQUIRED

retryable boolean REQUIRED

500 Something failed inside B3OS (`internal`). Retry with backoff.

application/problem+json

type string (uri) REQUIRED

`https://docs.beta.b3os.org/errors#<code>`.

title string REQUIRED

Short summary of the problem type.

status integer REQUIRED

The HTTP status code, repeated for convenience.

code string REQUIRED

Stable machine-readable error code from the errors catalog.

detail string REQUIRED

Explanation of this occurrence. Never contains secrets.

instance string

The request ID (`req_…`) of the request that failed. Include it when you contact support.

errors object[]

Validation problems, one per field (`invalid_request` and the other codes that list `errors`).

Array of:

pointer string REQUIRED

Where the problem is: a JSON pointer into the request body (`/url`, `/steps/0/uses`), or `#query/<name>`, `#path/<name>` or `#header/<name>` for parameters.

detail string REQUIRED

What is wrong there.

reason string

Finer-grained cause for codes that document one (`unauthorized`, `forbidden`, `egress_denied`, `upstream_unreachable`, …).

required_scope string

The scope that was missing (`forbidden` with `reason: scope`).

retry_after_s integer

Same value as the `Retry-After` header, for clients that only read the body.

limit object

The limit an error refers to. IDs and current values are listed by `GET /v1/limits`.

id string REQUIRED

Limit ID, such as `vision.scrape.rpm` or `sandboxes.concurrent`.

limit number REQUIRED

The limit's value.

unit string REQUIRED

What the limit counts, such as `requests`, `sandboxes`, `vcpu` or `MiB`.

window_s integer

Window length in seconds for rate limits and quotas.

current number

Current usage against the limit, when known.

current_status string

The object's current status, for state conflicts such as `sandbox_not_running`.

upstream_status integer

The HTTP status the upstream returned (`upstream_error`, `action_output_invalid`).

step string

The failed step, as a step ID (routines), an index (`act`) or a path such as `beats/2/do/0` (render).

pack_error object

The error a pack's error mapping chose (`upstream_error` from pack actions).

code string REQUIRED

message string REQUIRED

retryable boolean REQUIRED

502 Nothing in the sandbox accepted a connection on the port (`upstream_unreachable`), or the guest agent did not answer (`guest_unreachable`).

application/problem+json

type string (uri) REQUIRED

`https://docs.beta.b3os.org/errors#<code>`.

title string REQUIRED

Short summary of the problem type.

status integer REQUIRED

The HTTP status code, repeated for convenience.

code string REQUIRED

Stable machine-readable error code from the errors catalog.

detail string REQUIRED

Explanation of this occurrence. Never contains secrets.

instance string

The request ID (`req_…`) of the request that failed. Include it when you contact support.

errors object[]

Validation problems, one per field (`invalid_request` and the other codes that list `errors`).

Array of:

pointer string REQUIRED

Where the problem is: a JSON pointer into the request body (`/url`, `/steps/0/uses`), or `#query/<name>`, `#path/<name>` or `#header/<name>` for parameters.

detail string REQUIRED

What is wrong there.

reason string

Finer-grained cause for codes that document one (`unauthorized`, `forbidden`, `egress_denied`, `upstream_unreachable`, …).

required_scope string

The scope that was missing (`forbidden` with `reason: scope`).

retry_after_s integer

Same value as the `Retry-After` header, for clients that only read the body.

limit object

The limit an error refers to. IDs and current values are listed by `GET /v1/limits`.

id string REQUIRED

Limit ID, such as `vision.scrape.rpm` or `sandboxes.concurrent`.

limit number REQUIRED

The limit's value.

unit string REQUIRED

What the limit counts, such as `requests`, `sandboxes`, `vcpu` or `MiB`.

window_s integer

Window length in seconds for rate limits and quotas.

current number

Current usage against the limit, when known.

current_status string

The object's current status, for state conflicts such as `sandbox_not_running`.

upstream_status integer

The HTTP status the upstream returned (`upstream_error`, `action_output_invalid`).

step string

The failed step, as a step ID (routines), an index (`act`) or a path such as `beats/2/do/0` (render).

pack_error object

The error a pack's error mapping chose (`upstream_error` from pack actions).

code string REQUIRED

message string REQUIRED

retryable boolean REQUIRED

503 The node or the product is not available right now (`node_unavailable`, `product_unavailable`, `capacity_unavailable`).

application/problem+json

type string (uri) REQUIRED

`https://docs.beta.b3os.org/errors#<code>`.

title string REQUIRED

Short summary of the problem type.

status integer REQUIRED

The HTTP status code, repeated for convenience.

code string REQUIRED

Stable machine-readable error code from the errors catalog.

detail string REQUIRED

Explanation of this occurrence. Never contains secrets.

instance string

The request ID (`req_…`) of the request that failed. Include it when you contact support.

errors object[]

Validation problems, one per field (`invalid_request` and the other codes that list `errors`).

Array of:

pointer string REQUIRED

Where the problem is: a JSON pointer into the request body (`/url`, `/steps/0/uses`), or `#query/<name>`, `#path/<name>` or `#header/<name>` for parameters.

detail string REQUIRED

What is wrong there.

reason string

Finer-grained cause for codes that document one (`unauthorized`, `forbidden`, `egress_denied`, `upstream_unreachable`, …).

required_scope string

The scope that was missing (`forbidden` with `reason: scope`).

retry_after_s integer

Same value as the `Retry-After` header, for clients that only read the body.

limit object

The limit an error refers to. IDs and current values are listed by `GET /v1/limits`.

id string REQUIRED

Limit ID, such as `vision.scrape.rpm` or `sandboxes.concurrent`.

limit number REQUIRED

The limit's value.

unit string REQUIRED

What the limit counts, such as `requests`, `sandboxes`, `vcpu` or `MiB`.

window_s integer

Window length in seconds for rate limits and quotas.

current number

Current usage against the limit, when known.

current_status string

The object's current status, for state conflicts such as `sandbox_not_running`.

upstream_status integer

The HTTP status the upstream returned (`upstream_error`, `action_output_invalid`).

step string

The failed step, as a step ID (routines), an index (`act`) or a path such as `beats/2/do/0` (render).

pack_error object

The error a pack's error mapping chose (`upstream_error` from pack actions).

code string REQUIRED

message string REQUIRED

retryable boolean REQUIRED

curl -X HEAD 'https://beta-api.b3os.org/v1/sandboxes/sbx_01m5t68q1b590rj801nbzsqzkk/ports/3000/proxy/assets/app.js' \  -H 'Authorization: Bearer YOUR_API_TOKEN' \  -H 'x-b3os-port-token: pt1.n1.1792955460.tjsgjiRC3sSYEwneW62TSvNqd-Jo_zzFI5zFYkB_YQBNl0CiBzI9xgoV6EJD_5YEmh3HbzSmb3acL8mY1LmYCg'

const response = await fetch('https://beta-api.b3os.org/v1/sandboxes/sbx_01m5t68q1b590rj801nbzsqzkk/ports/3000/proxy/assets/app.js', {  method: 'HEAD',  headers: {      "Authorization": "Bearer YOUR_API_TOKEN",      "x-b3os-port-token": "pt1.n1.1792955460.tjsgjiRC3sSYEwneW62TSvNqd-Jo_zzFI5zFYkB_YQBNl0CiBzI9xgoV6EJD_5YEmh3HbzSmb3acL8mY1LmYCg"  }});const data = await response.json();console.log(data);

import requestsheaders = {    'Authorization': 'Bearer YOUR_API_TOKEN',    'x-b3os-port-token': 'pt1.n1.1792955460.tjsgjiRC3sSYEwneW62TSvNqd-Jo_zzFI5zFYkB_YQBNl0CiBzI9xgoV6EJD_5YEmh3HbzSmb3acL8mY1LmYCg'}response = requests.head('https://beta-api.b3os.org/v1/sandboxes/sbx_01m5t68q1b590rj801nbzsqzkk/ports/3000/proxy/assets/app.js', headers=headers)print(response.json())

400 Response

{  "type": "https://docs.beta.b3os.org/errors#invalid_request",  "title": "Invalid request",  "status": 400,  "code": "invalid_request",  "detail": "1 field failed validation",  "instance": "req_01m5t4yg394wegr3j4y01qb363",  "errors": [    {      "pointer": "/url",      "detail": "must be an absolute http or https URL"    }  ]}

403 Response

{  "type": "https://docs.beta.b3os.org/errors#signed_url_invalid",  "title": "Invalid or expired signed URL",  "status": 403,  "code": "signed_url_invalid",  "detail": "The preview URL expired at 2026-10-25T19:11:00Z; request a new one with POST /v1/sandboxes/sbx_01m5t68q1b590rj801nbzsqzkk/ports/3000/url",  "instance": "req_01m5t4yg394wegr3j4y01qb363",  "reason": "expired"}

404 Response

{  "type": "https://docs.beta.b3os.org/errors#port_not_exposed",  "title": "Port not exposed",  "status": 404,  "code": "port_not_exposed",  "detail": "Port 8080 is not in the ports of sbx_01m5t68q1b590rj801nbzsqzkk",  "instance": "req_01m5t4yg394wegr3j4y01qb363"}

409 Response

{  "type": "https://docs.beta.b3os.org/errors#sandbox_not_running",  "title": "Sandbox not running",  "status": 409,  "code": "sandbox_not_running",  "detail": "sbx_01m5t68q1b590rj801nbzsqzkk is paused; resume it first",  "instance": "req_01m5t4yg394wegr3j4y01qb363",  "current_status": "paused"}

429 Response

{  "type": "https://docs.beta.b3os.org/errors#rate_limited",  "title": "Rate limited",  "status": 429,  "code": "rate_limited",  "detail": "60 scrapes per minute allowed; retry in 12 seconds",  "instance": "req_01m5t4yg394wegr3j4y01qb363",  "retry_after_s": 12,  "limit": {    "id": "vision.scrape.rpm",    "limit": 60,    "unit": "requests",    "window_s": 60,    "current": 60  }}

500 Response

{  "type": "https://docs.beta.b3os.org/errors#internal",  "title": "Internal error",  "status": 500,  "code": "internal",  "detail": "internal error",  "instance": "req_01m5t4yg394wegr3j4y01qb363"}

502 Response

{  "type": "https://docs.beta.b3os.org/errors#upstream_unreachable",  "title": "Upstream unreachable",  "status": 502,  "code": "upstream_unreachable",  "detail": "Nothing is listening on port 3000 in sbx_01m5t68q1b590rj801nbzsqzkk",  "instance": "req_01m5t4yg394wegr3j4y01qb363",  "reason": "connect"}

503 Response

{  "type": "https://docs.beta.b3os.org/errors#node_unavailable",  "title": "Node unavailable",  "status": 503,  "code": "node_unavailable",  "detail": "Node n1 is not reachable; retry in 5 seconds",  "instance": "req_01m5t4yg394wegr3j4y01qb363",  "retry_after_s": 5}

HEAD /v1/sandboxes/{sandbox_id}/ports/{port}/proxy/{rest}

Base URL

Bearer Token

Path Parameters

sandbox_id string required

port integer required

rest string required

Headers

x-b3os-port-token string required

Response

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