feat: Android host adapter (android/truapi-host) + hosts/android submodule by TarikGul · Pull Request #289 · paritytech/truapi

TarikGul · 2026-07-17T18:24:58Z

Android TrUAPI host adapter

Brings Android to parity with the iOS host adapter (ios/truapi-host): the truapi repo owns a Kotlin host-adapter package, and vendors the Android app as a submodule so the core can be built and diagnosed against it.

What this adds

android/truapi-host/ — the Kotlin host-adapter package over the truapi-server UniFFI core, the analogue of ios/truapi-host. TrUAPIHost.kt exposes the current FFI surface: HostBridge (device/remote permission split, a single confirmUserAction, chainConnect/Send/Close, lookupPreimage, theme, feature support), HostStorage + HostCoreStorage, TrUAPIHostCore (WS-bridge lifecycle, local-session activation, permission-authorization status, native change notifications), and LocalhostBridgeBootstrap. Products in a WebView reach the core over the localhost WebSocket bridge; the core signs on-device (signing-host role) with no separate phone.
Build tooling (Makefile): uniffi-kotlin (generate Kotlin bindings), android-jni (cargo-ndk cross-compile of libtruapi_server.so per ABI), and android-publish-local. check-android-parity fails if the canonical TrUAPIHost.kt shell drifts from the copy vendored in the app (skips cleanly when the submodule is uninitialized). Generated bindings and jniLibs are gitignored.
hosts/android submodule — vendors polkadot-app-android-v2 (branch tg/truapi-rust-core), mirroring hosts/ios. .gitmodules uses the HTTPS URL. Its app-side integration (a bindings/truapi-host rust-android module, a functional DefaultHostBridge + WebSocketChainProvider, and an instrumented diagnostics harness) lives in that repo's companion PR.

Verified on an Android emulator

The vendored app drives the host playground through the core end-to-end: the built-in Diagnosis sweep runs every TrUAPI method, with on-device signing/ permission approval prompts (no phone). All Signing methods pass and sign
locally; Account/Entropy/Local Storage/Notifications/Permissions pass. Remaining failures are funding/allowance-gated (Payment needs a balance; Preimage/Resource Allocation need on-chain allowances) or unimplemented on this host (Chat), consistent with the deployed-host diagnosis.

Notes

The canonical package is shell-only, matching ios/truapi-host (no default-host/chain-provider helpers — those are app-side).
TrUAPIHost.kt is duplicated between here and the vendored app copy; make check-android-parity guards against drift until it's single-sourced.
JitPack distribution is documented as the target but is not yet wired (no root jitpack.yml); local integration uses make android-publish-local + mavenLocal(). Noted in android/truapi-host/README.md.

pgherveou · 2026-07-23T09:33:56Z

will test it out

One note before before I look into the code.
We have to be make sure the mobile integration is using the signing host logic and not the pairing host logic as mobile apps are accounts holder.

I am a bit surprised that this work without some of the changes to the signing host that I pushed to
#264 and backported in #288

TarikGul · 2026-07-23T14:52:02Z

@pgherveou Calrification: so signing did fail with the ring-vrf path which was expected but for sr25519 signing worked fine. I only used the signing host - no pairing at all.

This is the list of pass fail:

✅ Passed (37)

Account
- Account/connection_status_subscribe
- Account/get_account
- Account/get_account_alias
- Account/get_legacy_accounts
- Account/get_user_id
- Account/request_login

Chain (all)
- Chain/get_head_header, get_head_body, get_head_storage
- Chain/call_head
- Chain/unpin_head, continue_head, stop_head_operation
- Chain/get_spec_genesis_hash, get_spec_chain_name, get_spec_properties
- Chain/broadcast_transaction, stop_transaction

Signing (all — on-device sr25519)
- Signing/create_transaction
- Signing/create_transaction_with_legacy_account
- Signing/sign_raw, sign_payload
- Signing/sign_raw_with_legacy_account, sign_payload_with_legacy_account

Entropy — Entropy/derive
Local Storage — read, write, clear
Notifications — send_push_notification, cancel_push_notification
Permissions — request_device_permission, request_remote_permission
System — handshake, feature_supported, navigate_to
Theme — Theme/subscribe

❌ Failed (27)

Chat (all — not implemented in core)
- create_room, register_bot, list_subscribe, post_message, action_subscribe, custom_message_render_subscri

Coin Payment (all — need a funded balance)
- create_purse, query_purse, rebalance_purse, delete_purse, create_receivable, listen_for_payment

Payment (all — need a funded balance)
- balance_subscribe, top_up, request, status_subscribe

Statement Store (all — not implemented in core)
- subscribe, create_proof, submit, create_proof_authenticated

Preimage — lookup_subscribe, submit (allowance-gated)
Resource Allocation — request (allowance-gated / native-only)
Account — create_account_proof (ring-VRF; comes from  #288)

TarikGul · 2026-07-23T18:03:36Z

Holding this until #288 lands. Two things depend on it:

Signing host: mobile is an account holder, so it signs through the signing host. The respondToPairing surface isn't exposed over the native binding yet, and that's part of the signing-host work in feat(core): implement missing signing host fn #288.
create_account_proof: this is the ring-VRF path, which is the one method that fails right now on the emulator. feat(core): implement missing signing host fn #288 backports the signing-host ring-VRF changes that make it work.

Once #288 is in the mobile base I'll wire respondToPairing.

…eview

…igning

…uapi into feat/signing-host-ring-vrf

Use codec-derived runtime payloads and metadata-aware storage projections so field ordering and variant encoding stay aligned with chain types. Derive SSO message labels once and keep normal transcript events at debug.

Add the android/truapi-host package (Kotlin host adapter shell over the truapi-server UniFFI core, localhost WebSocket bridge transport) matched to the current core FFI surface: HostCoreStorage, a single confirmUserAction, local signing session activation, and LocalhostBridgeBootstrap. Add Makefile targets uniffi-kotlin (Kotlin binding generation), android-jni (cargo-ndk cross-compile of libtruapi_server.so per ABI), and android-publish-local; gitignore the generated bindings and jniLibs.

- android-publish-local no longer depends on android-jni: the AAR does not bundle the cdylib, so publishing only needs the Kotlin bindings (JitPack has no NDK). - README: flag that the JitPack distribution is not yet wired up (no jitpack.yml at the repo root) and document the INTERNET permission the consuming app must declare.

…dule Mirror hosts/ios: vendor the Android app at hosts/android (tracking branch tg/truapi-rust-core) so the truapi repo can build and diagnose the app against its own core. .gitmodules uses the HTTPS URL to match hosts/ios; document the mobile host adapter packages and host submodules in the README layout.

Advance the submodule pin to include DefaultHostBridge + WebSocketChainProvider and the connected-session diagnostics test, so the vendored app builds and diagnoses against a working host.

Advance the hosts/android submodule to the hardened host bridge (deny-by-default confirmations, lifecycle/storage fixes) and add a check-android-parity make target that fails if the canonical android/truapi-host TrUAPIHost.kt shell drifts from the copy vendored in the app (hosts/android). The target skips cleanly when the submodule is not initialized, so it is safe to run in any checkout and to wire into CI.

TarikGul · 2026-07-24T22:53:12Z

Depends on #215 — that needs to land before this one.

The Kotlin package in android/truapi-host/ binds to the UniFFI surface that #215 carries:

rust/crates/truapi-server/src/native.rs - the HostCallbacks callback interface and NativeTrUApiCore
rust/crates/truapi-server/src/ws_bridge.rs - the localhost WebSocket transport the product WebView dials
rust/crates/uniffi-bindgen-cli/ - generates the Kotlin bindings from the compiled cdylib
the ws-bridge feature on truapi-server

This PR's base (feat/signing-host-ring-vrf) is core-only and carries none of them, so on the base alone import uniffi.truapi_server.* in TrUAPIHost.kt has no source, and make uniffi-kotlin, make android-jni and make android-publish-local cannot run - they require both the ws-bridge feature and the bindgen crate. Everything here is otherwise self-contained; the dependency is purely on that shared surface.

Merge order: #288 → #215 → this.

To build the Android host before #215 lands, point the consuming app's truapi.dir at a checkout that carries the FFI surface rather than at this branch.

pgherveou and others added 3 commits July 17, 2026 19:07

feat(core): implement ring-vrf signing

ddf0786

Merge branch 'main' into feat/signing-host-ring-vrf

d59fdb1

Merge branch 'main' into feat/signing-host-ring-vrf

5911457

TarikGul changed the title ~~Android wiring~~ feat: Android host adapter (android/truapi-host) + hosts/android submodule Jul 23, 2026

update

01513f9

pgherveou added 6 commits July 23, 2026 13:45

analyse and fix diff with ~/github/polkadot-app-android-v2/

bc2a5fe

fixup

1aed8f4

fixes

5489b13

fix(core): align host compatibility

132f667

Merge main into feat/signing-host-ring-vrf

7c96e27

ci: refresh generated fixture and licenses

5dd8ef1

TarikGul and others added 9 commits July 23, 2026 21:23

fix(sso-responder): bound the replay-dedup set to cap memory

6868f0b

chore(codegen): refresh stale host-callbacks golden

f7999e3

fix(signing-host): name the beneficiary product in the allocation review

eaaa22b

chore(codegen): refresh host-callbacks golden for ResourceAllocationR…

d8168ad

…eview

fix(signing-host): use a dedicated review for statement-store proof s…

0bed52d

…igning

Clippy / fmt

16009a1

Merge branch 'feat/signing-host-ring-vrf' of github.com:paritytech/tr…

a4e8e40

…uapi into feat/signing-host-ring-vrf

fix(server): align runtime SCALE codecs

103431c

Use codec-derived runtime payloads and metadata-aware storage projections so field ordering and variant encoding stay aligned with chain types. Derive SSO message labels once and keep normal transcript events at debug.

update

0e7e96e

pgherveou force-pushed the worktree-issue-96-mobile-followup branch from 45bb321 to 8f8255d Compare July 24, 2026 11:30

TarikGul changed the base branch from worktree-issue-96-mobile-followup to feat/signing-host-ring-vrf July 24, 2026 13:56

TarikGul added 5 commits July 24, 2026 10:18

add local android env to gitignore

51d9568

chore(android): bump hosts/android to the functional host bridge

f9baf3b

Advance the submodule pin to include DefaultHostBridge + WebSocketChainProvider and the connected-session diagnostics test, so the vendored app builds and diagnoses against a working host.

TarikGul added 3 commits July 24, 2026 10:20

chore(android): bump hosts/android to the chain-race fix

8c2ba3e

fix(android): address host-adapter review — codegen, lint, equals, docs

1c73b49

TarikGul force-pushed the tg/truapi-rust-core branch from 75f288d to 1c73b49 Compare July 24, 2026 14:32

chore(android): bump hosts/android to the equals-contract fix

41e9c34

Base automatically changed from feat/signing-host-ring-vrf to main July 28, 2026 16:53

TarikGul requested a review from a team July 28, 2026 16:53

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feat: Android host adapter (android/truapi-host) + hosts/android submodule - #289

feat: Android host adapter (android/truapi-host) + hosts/android submodule#289
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Android TrUAPI host adapter

What this adds

Verified on an Android emulator

Notes

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