embedded-wallet-constraints

A set of rules describing limits and requirements for Phantom embedded wallets, which are wallets managed inside an application rather than through a separate wallet extension. It covers supported signing methods, spending limits, login sessions, social login, and React Native setup.

In plain words
What is it for?
Use it when building applications with Phantom embedded wallets, especially social login flows, React Native apps, and transaction interfaces.
Why use it?
It helps developers design around unsupported methods, session expiry, daily spending limits, missing app configuration, and mobile cryptography setup errors.

Cursor rule

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add rules/phantom/phantom-agent-kit/embedded-wallet-constraints
Clone the repo
git clone --depth 1 https://github.com/phantom/phantom-agent-kit
Per session 274 This file is loaded in full into every session.
When invoked 274 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00274 $0.00274
Opus 5 $0.00137 $0.00137
Sonnet 5 $0.00055 $0.00055
Haiku 4.5 $0.00027 $0.00027

Measured 2d ago against content hash d319bbffccf4, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

embedded-wallet-constraints scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

rules/embedded-wallet-constraints.mdc · 28 lines

What it actually says

Embedded Wallet Constraints

Unsupported Methods

  • signTransaction and signAllTransactions are NOT supported for embedded wallets. Always use signAndSendTransaction instead. Calling unsupported methods will throw a runtime error.

Spending Limits

  • Default spending limit for embedded wallets is $1,000 USD per day per app per user. Design your UX to account for this limit and provide clear error messages if a transaction exceeds it.

Session Duration

  • Social login sessions persist for 7 days from the last authentication event. After expiry, users must re-authenticate. Handle session expiration gracefully in your UI — check isConnected before operations and prompt re-login when needed.

Social Login Requirements

  • Social login (Google, Apple) requires a valid appId from Phantom Portal. Without an appId, social login options will not appear.

React Native Polyfill

  • React Native apps MUST import react-native-get-random-values as the very first import in the entry file, before any other imports including the Phantom SDK. Failing to do this will cause crypto-related runtime errors.
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 28 lines · 274 tokens per session scan A d319bbffccf4

Subscribe to this mod's changes

embedded-wallet-constraints is a cursor rule published in the GitHub repository phantom/phantom-agent-kit (11 stars, last pushed 14d ago), licensed MIT. It adds 274 tokens to every session, about $0.0014 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.