v1.21.0 ERC-4337 Session Keys — caps enforced BY THE CHAIN

[ceoguy]

What this is

Roadmap item 7, complete implementation (was: PR A libs only — now the full feature per .plans/erc4337-session-keys.md). The trust story graduates from "our code enforces the caps" to "the chain enforces the caps even if the machine is compromised."

The user's ERC-7579 smart account grants the agent's existing EOA a scoped on-chain session via the audited, vendor-neutral Smart Sessions module: cumulative per-token spend caps, mandatory expiry, optional usage caps — validated by the EntryPoint on every operation. Zero new dependencies (deterministic module addresses + viem encoders; no AGPL code vendored).

Surface (135 → 140 tools)

• chaingpt_aa_session_build_grant / _build_revoke — UNSIGNED payloads; the account OWNER signs externally; unbounded grants refused by construction; revoke = chain-level kill.
• chaingpt_aa_session_status — chain-authoritative state (account kind, module installed, permission enabled, caps).
• chaingpt_aa_submit_userop — custody-free eth_sendUserOperation (refuses empty signatures).
• chaingpt_agent_wallet_4337_sign_and_send — local gates first (fail-closed erc4337 who/where sub-policy, OFF by default everywhere + standard per-tx/velocity checks on the inner call), then the agent signs in the Smart Sessions USE envelope and the chain enforces the granted caps. Bundler cap-rejections render as the chain-side refusal they are — never retried around.

v1 account support: Biconomy Nexus 1.x (Kernel v3 / Safe7579 follow — the module layer is shared). PreToolUse guard asks on both new signing/submitting tools.

Verification

• 8/8 local layers; 428 vitest (+29: encoder round-trips, permissionId determinism, USE-signature layout, full gate matrix incl. type-strict migration guarantee, tool-surface custody invariant, offline refusal paths with zero-network assertions, hook coverage).
• Tag gate: v1.21.0 is tagged only after the live Base Sepolia loop in TESTING.md passes — including the headline proof: local policy set to unrestricted and the chain still refuses the over-cap transfer. The CHANGELOG carries this gate explicitly.
• Merge-risk note: the entire surface is opt-in fail-closed (erc4337.enabled absent/false in every default and template), so merging ahead of the live loop changes nothing for any existing user.

🤖 Generated with Claude Code

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: db712987-f966-4450-bcd7-197e269a3388

📥 Commits

Reviewing files that changed from the base of the PR and between 3b913af and fb5dddc.

📒 Files selected for processing (5)

• mcp-server/src/__tests__/erc4337_gate.test.ts
• mcp-server/src/__tests__/smart_sessions.test.ts
• mcp-server/src/lib/agent-policy.ts
• mcp-server/src/lib/erc7579.ts
• mcp-server/src/lib/smart-sessions.ts

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/erc4337-session-keys

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