[Bug] PKPs cannot authenticate with protocols requiring ERC-1271

[ulixes]

Is there an existing issue for this?

• I have searched the existing issues

SDK version

• @lit-protocol/lit-client: 8.0.0-alpha.18
• @lit-protocol/auth: 8.0.0
• @lit-protocol/networks: 8.0.0-alpha.27

Lit Network

naga-dev

Description of the bug/issue

PKPs cannot be used as signers/managers with protocols that require ERC-1271 implementation (e.g., Lens Protocol v3, Safe, other AA wallets).

The Issue:

• PKPs are EOA-like addresses with no on-chain bytecode (returns 0x)
• Protocols like Lens Protocol v3 check if manager addresses implement ERC-1271's isValidSignature()
• PKP addresses fail this check with error: "The provided address is not a valid ERC1271 address"
• PKPs can sign messages perfectly, but cannot validate their own signatures on-chain

Error:
Invalid signature: The provided address is not a valid ERC1271 address: 0x400Eb86D988A1aBFC7Fc9275f9FD88f70Fa03595

Root Cause:
PKPs have no bytecode on-chain, so they cannot implement the isValidSignature(bytes32, bytes) function required by ERC-1271.

Severity of the bug

High - Blocks integration with major Web3 protocols

This prevents PKPs from being used with:

• Lens Protocol v3 account managers
• Safe multisig wallets
• Account Abstraction wallets requiring ERC-1271
• Any protocol that validates signatures via smart contract calls

Many modern Web3 protocols expect signers to be ERC-1271 compatible smart contracts rather than EOAs.

Steps To Reproduce

Run our reproduction app:: https://lit-pkp-lens-issue.vercel.app/

1. Mint a PKP using EOA auth from https://naga-v8-interactive-docs.vercel.app/eoa-auth
2. Create PKP auth context and get PKP Viem Account (following V8 docs)
3. Attempt to authenticate with a protocol requiring ERC-1271 (e.g., Lens Protocol)
4. See error: "not a valid ERC1271 address"

Link to code

https://github.com/ulixes/lit-pkp-lens-issue

Full reproduction with side-by-side comparison:
- Direct wallet authentication (works)
- PKP authentication (fails with ERC-1271 error)


### Anything else?

Run our reproduction app:: https://lit-pkp-lens-issue.vercel.app/