Chat with your Letta agents from your phone: pick an agent, watch it think, run tools, and ask you for permission before it does anything consequential. Works against Letta Cloud or your own machine running a Letta app-server.
It is also a worked example. Every screen maps to a small number of files, and the whole SDK story — resuming a session, reducing the stream into a transcript, approvals, aborting, queued follow-ups — lives in one readable file you can lift into your own app.
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Built with Expo (React Native), TypeScript, and
@letta-ai/letta-agent-sdk.
Install Expo Go on your iPhone or Android device, then run:
git clone https://github.com/letta-ai/agent-sdk-mobile-app.git
cd agent-sdk-mobile-app
bun install
bunx expo start --tunnelScan the QR code shown in the terminal with your phone.
To build the native app locally instead:
bun run ios # requires macOS and Xcode
bun run android # requires Android StudioThen connect it to one of two things.
Letta Cloud — choose Letta Cloud on the first screen, then continue in your browser
with OAuth or paste an API key from platform.letta.com.
The reference build includes the general-purpose Letta Mobile public OAuth client and
uses letta-mobile://oauth/callback. Apps that need a separate OAuth identity can set
EXPO_PUBLIC_LETTA_OAUTH_CLIENT_ID and configure their own scheme. Access tokens,
refresh tokens, and API keys stay in the device keychain (expo-secure-store). Cloud
requests always use https://api.letta.com.
The distributed OAuth client is ci-let-94bf2d5e34984a684fb6b18880b6bc7d. It is a
public identifier, not a client secret. The registered redirect is
letta-mobile://oauth/callback, and the app always uses Authorization Code with PKCE.
Your own machine — run an app-server wherever your code lives:
npm install -g @letta-ai/letta-code
openssl rand -hex 24 > /tmp/ws-token
letta server --listen ws://0.0.0.0:4610 --ws-auth capability-token --ws-token-file /tmp/ws-tokenChoose Your own server, enter ws://<your-machine>:4610, and paste that token. The
token is required from a phone: React Native always sends an Origin header, and
app-servers only accept those on token-authenticated upgrades.
This is a real terminal on that machine. An agent connected to your own server can read files and run commands there. For anything beyond your own LAN, put it behind TLS (
wss://) or a private network such as Tailscale, and treat the endpoint as a credential.
Requires Agent SDK 0.7.x with letta-code ≥ 0.30.5; the single-socket transport means those two move together.
- Agents and conversations — browse, search, create, rename, delete; cursor pagination on both lists and on message history.
- Streaming chat — assistant text as it arrives, collapsible reasoning with live think time, markdown with fenced code and tappable links, long-press to copy.
- Tool calls — status from running to settled with durations, a detail sheet with the full input and output, unified diffs coloured, and consecutive calls collapsed into one "Ran 5 tools" row so a long agentic turn stays readable.
- Approvals — when the agent wants to run something, you get the full command, the working directory, one-tap "always allow" suggestions, and allow/deny with a reason.
- Permission modes — strict, standard, accept-edits, unrestricted, switchable mid-conversation.
- Interrupt and queue — stop a running turn, or send follow-ups that queue behind it.
- Attachments — send screenshots and photos, downscaled on device.
- Reconnect — background the app and come back mid-turn; state reconciles against the server rather than guessing.
Two rules run through the whole app:
- The server is the truth. Run phase, queue order, and approvals render only what the runtime confirms. Mutations show pending, never pretend.
- Opening a conversation is free. History hydrates over REST; the SDK session — and on Cloud, its sandbox — is created lazily on the first send.
| Layer | Files | What it teaches |
|---|---|---|
| SDK ↔ UI | src/lib/letta/ChatSession.ts |
The whole story: resumeSession, reducing stream(), canUseTool approvals, abort, queue |
| Transcript rows | src/lib/letta/transcriptProjection.ts |
Turning the SDK's createTranscriptAccumulator() rows into render state |
| Domain model | src/lib/letta/model.ts |
The snapshot vocabulary the UI renders — the mock and real transports both speak it |
| Data layer | src/lib/letta/api.ts |
Agents, conversations, models, history via the portable client |
| Mock transport | src/lib/letta/mockSession.ts |
A fixture-driven fake session, so every UI state is reachable with no server |
| Design system | src/theme/tokens.ts |
Colour, type, space, motion — everything visual resolves through tokens |
A note on idiom, since it is the point of the repo: row identity, delta accumulation and replay suppression are not hand-rolled here. They belong to the SDK's transcript accumulator, and this app keeps only what the SDK cannot know — which row is live, how long a think took, and the two tool states the approval flow owns. Earlier versions of this app did hand-roll them and got them subtly wrong; the shape you see is the second answer, not the first.
Two dev-only routes are worth opening: /gallery renders every component in every
state against the mock transport (no server, no credentials), and /stills renders
the press screenshots.
Deeper detail lives in docs/design-doc.md (visual system,
screen map, and the screen→SDK operation map) and
docs/architecture.md.
The name Bloop and its blue-sphere mark are placeholders, so the repo ships with
nobody's trademarks in it. To rebrand: edit name, scheme, and the bundle identifiers
in app.json, change the two colours in src/theme/tokens.ts, and run
python3 scripts/make-icons.py to regenerate the icon, adaptive icon, and splash mark.
Agent avatars derive their colour from the agent id using the same palette.
Apache-2.0, assets included — there is no separate artwork carve-out, because the app ships no third-party marks.
"Letta", "Letta Cloud" and "Letta Code" identify the service this client connects to. That is nominative use and grants no rights in those marks; Apache-2.0 §6 grants none either. Give a published fork its own name and icon.