App Handoff Protocol

Takosumi App Handoff is the small URL protocol for creating a Takosumi-managed hosted service from any client: web app, desktop app, mobile app, browser link, or CLI output.

Host Center is a web/dashboard flow. This protocol does not require or imply a standalone Takosumi mobile app; clients return to their own product app or web callback URL.

It is not a mobile-only protocol and it is not a product registry. Takosumi receives a plain OpenTofu/Terraform source, creates a Capsule, runs the normal Takosumi flow, then optionally returns a connection payload to the client.

client
  -> /install URL
  -> Takosumi Host Center
  -> Source / Capsule / ProviderBinding / Run
  -> StateVersion / Output
  -> optional return_uri

Entry URL

The public entrypoint is on the Takosumi origin selected by the operator:

https://<takosumi-origin>/install

The official Takosumi Cloud origin is app.takosumi.com, but the same protocol works at any explicit self-hosted or Operator origin.

The dashboard may canonicalize the flow to /new, but external clients should link /install.

Supported query parameters:

Parameter	Required	Meaning
git	no	HTTPS Git URL for a plain OpenTofu/Terraform module
source	no	Packed module address, for example git::...?...
ref	no	Git branch, tag, or commit
path	no	Module path inside the repository
name	no	Display name for the service
var.<name>	no	Non-secret visible module input
product	no	Client product key, only with return_uri
return_uri	no	Connection payload target, only with product

git or source selects what Takosumi should create. Store nodes are discovery / presentation entrypoints that prefill this URL; they are not the creation target or release-ref authority. product does not select the install target. Use product and return_uri together only when Takosumi should return to a client.

If return_uri is absent, the flow is just a normal hosted-service creation link. In that case, do not include product. If return_uri is present, Takosumi preserves product and return_uri through sign-in, provider connection setup, plan, and apply screens.

These forms do not exist:

/install?=product
/install?product
/install?product=notes-app

They do not specify an OpenTofu source, so there is no install target.

Example:

https://takosumi.example.com/install
  ?git=https%3A%2F%2Fgit.example.com%2Facme%2Fnotes.git
  &ref=v1.2.3
  &path=deploy%2Fopentofu
  &product=notes-app
  &return_uri=notesapp%3A%2F%2Fconnect

OpenTofu-Native Flow

The URL does not install anything by itself. It only pre-fills an explicit dashboard flow:

Git URL / ref / path
  -> Source
  -> Capsule
  -> ProviderBinding review
  -> Run(plan)
  -> Run(apply)
  -> StateVersion / Output

The source repository stays a plain OpenTofu/Terraform module. Takosumi does not require a Takosumi-specific source metadata file or product-specific metadata file.

var.<name> is for non-secret visible inputs only. Secrets, tokens, provider credentials, and private keys must come from Provider Connections, Credential Recipes, Provider Bindings, Secrets, or product-owned setup flows.

Return Payload

After a successful apply, Takosumi builds a connect URL by appending query parameters to return_uri:

<return_uri>
  ?host_url=https%3A%2F%2Fcreated-host.example
  &product=notes-app
  &run_id=run_...
  &capsule_id=cap_...

setup_ticket may be added when a product-owned setup flow needs a one-time handoff token.

The client then discovers the host through:

GET /.well-known/takosumi
GET /v1/capabilities

If the client needs product-specific metadata, it may also read:

GET /.well-known/<product>

Takosumi does not probe for first-party product names.

Product Key And Return URI Rules

product is a generic lower-case key:

^[a-z0-9][a-z0-9._:-]{0,63}$

It is not a Takosumi enum. takos, yurucommu, and future apps all use the same field as ordinary clients.

return_uri may be:

notesapp://connect
https://app.example/connect

It must be absolute, contain no username/password, and contain no existing query or fragment. Takosumi appends the connect payload itself.

Boundary

Takosumi owns the protocol, Host Center flow, Source/Capsule/Run lifecycle, state, output, audit, provider connection review, and capability discovery.

The client owns product UI, custom scheme handling, web callback handling, native plugins, push notification registration, calls, and any product-owned post-connect API calls.

Push notification delivery is not a Takosumi Resource Shape or provider. A client may send a product-owned device token to its own host API after connect, but Takosumi does not advertise a push capability.