Add Vercel eve agent adapter (@executor-js/host-eve)

[jackulau]

Expose Executor's codemode surface to a Vercel eve agent as two tools, execute and resume, mirroring the MCP host. Backed by the promise execution engine, so the package has no eve runtime dependency: the factory returns plain objects shaped for eve's defineTool.

Includes unit tests plus integration tests that drive the adapter against the real execution engine and QuickJS sandbox.

[jackulau]

wip - taking feedback.

[greptile-apps]

Greptile Summary

This PR introduces @executor-js/host-eve, a new adapter package that exposes Executor's codemode surface to a Vercel eve agent as two tools (execute and resume), mirroring the existing MCP host design without taking a runtime dependency on eve itself.

• The adapter follows the MCP host pattern closely: shared Promise-based engine instance, runEnvelope for defect isolation, formatExecuteResult/formatPausedExecution for result rendering, and parseJsonContent (Effect Schema) for safe JSON decoding of resume content.
• Unit tests cover all envelope shapes (completed, paused, defect, missing-execution), schema validation, and description override; integration tests drive the real QuickJS sandbox to verify end-to-end execution, tools runtime injection, error surfacing, and resume recovery.

Confidence Score: 4/5

Safe to merge. The new package is private and isolated with no cross-package side effects; the adapter correctly never throws to the agent and the pause/resume wiring is sound.

The adapter is well-structured and the test coverage (unit + real QuickJS integration) is thorough for the core paths. The one notable gap is that emit() output items (files, images, audio) produced during code execution are not included in ExecutorToolEnvelope.data — only a count surfaces in text — which differs from the MCP host's rich-content handling. Whether this matters depends on whether eve-hosted workflows use emit() for binary outputs, but it is a silent data loss rather than a crash.

packages/hosts/eve/src/index.ts — specifically toCompletedEnvelope, which delegates to formatExecuteResult without inspecting result.output[].

Important Files Changed

Filename	Overview
packages/hosts/eve/src/index.ts	Core adapter implementation: clean structure mirroring the MCP host, correct pause/resume wiring, proper defect isolation via runEnvelope. emit() output items (files, images) are dropped from the structured envelope — only the count surfaces in text.
packages/hosts/eve/src/index.test.ts	Unit tests covering completed/paused/defect envelopes, JSON content parsing edge cases, description override, and schema validation. Good use of @effect/vitest throughout.
packages/hosts/eve/src/index.integration.test.ts	Integration tests drive the real QuickJS sandbox and a real Executor; verifies code evaluation, tools runtime injection, error surfacing, and missing-execution recovery. Only tests the { engine } config branch, not { executor, codeExecutor }.
packages/hosts/eve/package.json	Correct workspace dependencies; zod pinned at 4.3.6 matching the MCP host pattern; private: true appropriate for a workspace-only adapter.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant Model as eve Model
    participant ET as execute tool
    participant RT as resume tool
    participant Engine as ExecutionEngine (Promise)
    participant QJS as QuickJS Sandbox

    Model->>ET: "execute({ code })"
    ET->>Engine: executeWithPause(code)
    Engine->>QJS: run code
    alt completed
        QJS-->>Engine: ExecuteResult
        Engine-->>ET: "{ status: completed, result }"
        ET-->>Model: "ExecutorToolEnvelope { status: completed, text, data }"
    else paused (auth/approval)
        QJS-->>Engine: pause (elicitationContext)
        Engine-->>ET: "{ status: paused, execution }"
        ET-->>Model: "ExecutorToolEnvelope { status: waiting_for_interaction, executionId, text }"
        Model->>RT: "resume({ executionId, action, content })"
        RT->>Engine: "resume(executionId, { action, content })"
        Engine->>QJS: continue from pause
        QJS-->>Engine: ExecuteResult
        Engine-->>RT: "{ status: completed, result }"
        RT-->>Model: "ExecutorToolEnvelope { status: completed, text, data }"
    end

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sequenceDiagram
    participant Model as eve Model
    participant ET as execute tool
    participant RT as resume tool
    participant Engine as ExecutionEngine (Promise)
    participant QJS as QuickJS Sandbox

    Model->>ET: "execute({ code })"
    ET->>Engine: executeWithPause(code)
    Engine->>QJS: run code
    alt completed
        QJS-->>Engine: ExecuteResult
        Engine-->>ET: "{ status: completed, result }"
        ET-->>Model: "ExecutorToolEnvelope { status: completed, text, data }"
    else paused (auth/approval)
        QJS-->>Engine: pause (elicitationContext)
        Engine-->>ET: "{ status: paused, execution }"
        ET-->>Model: "ExecutorToolEnvelope { status: waiting_for_interaction, executionId, text }"
        Model->>RT: "resume({ executionId, action, content })"
        RT->>Engine: "resume(executionId, { action, content })"
        Engine->>QJS: continue from pause
        QJS-->>Engine: ExecuteResult
        Engine-->>RT: "{ status: completed, result }"
        RT-->>Model: "ExecutorToolEnvelope { status: completed, text, data }"
    end

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Comments Outside Diff (1)

1. packages/hosts/eve/src/index.ts, line 651-656 (link)

   emit() output items are silently dropped from structured data

   toCompletedEnvelope delegates entirely to formatExecuteResult, which writes only { status, result, emitted (count), logs } into structured. The actual output items in result.output[] (files, images, audio produced by emit()) are never copied into data. The MCP host explicitly branches on result.output && result.output.length > 0 and calls toMcpOutputResult to surface them.

   A consumer relying on data for file content would silently see { emitted: 1 } with no payload. The model only sees "(no return value; 1 item emitted to the user)" — it is told content exists but cannot read it. If any code execution is expected to produce files or images via emit(), those outputs are permanently lost through this host.

   Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

_{Reviews (1): Last reviewed commit: "Add Vercel eve agent adapter (@executor-..." | Re-trigger Greptile}