Known Limitations

Features that are designed but not yet fully implemented, and constraints of the current implementation.

What you'll learn: What to expect from the current Grove release and what's coming next.

Area 2: Workflows

Workflow orchestration (Area 2) is designed and parsed but the runtime implementation is in progress:

Feature	Status
Workflow declarations	Parsed and checked
Activity declarations	Parsed and checked
Service declarations	Parsed and checked
Route declarations	Parsed and checked
Query declarations	Parsed and checked
Trigger declarations	Parsed and checked
Schedule declarations	Parsed and checked
Webhook declarations	Parsed and checked
In-process orchestrator	In development
Temporal backend	In development

You can write and type-check workflow code today. Runtime execution is being implemented.

Agent System

The agent system is in preview:

Feature	Status
Agent declarations	Design finalized
Tool declarations	Design finalized
MCP server	Design finalized
Agent runtime	In development
Prompt evaluation	In development

Temporal Integration

Feature	Status
Bridge architecture	Designed
Activity registration	In development
Signal/cancel/await	Not yet implemented
SDK interop	Not yet implemented

Runtime Limits

Event payload size

Individual event payloads are capped at 256 KiB. The runtime enforces this on the write path; oversized events return HTTP 413 Payload Too Large with code Z4004 (see Error Reference).

The ceiling is chosen to fit comfortably under the smallest downstream delivery mechanism Grove targets (SQS/SNS/Lambda-async all accept 256 KiB body payloads) while leaving margin inside the 6 MiB TiDB transaction budget for the surrounding commit.

When you hit the limit. Store the bulk payload in blob/object storage (S3, R2, GCS) and put only the reference (URL, key, ETag) in the event. The runtime offers the File type for records that need large attachments — see File Uploads. For event-level attachments, include a URL field in the event and upload separately.

Language Limitations

Limitation	Details
No block comments	Only `// line comments` are supported
No mutable variables	All `let` bindings are immutable
For loop restrictions	Only in action apply blocks, max 3 levels deep
No nested type declarations	Types must be declared at module top level
Single record per module	Each module can have at most one `record` block
No generic functions	Functions cannot have type parameters
No recursive types	Type declarations cannot reference themselves

Runtime Gotchas

These issues compile successfully but cause unexpected behavior at runtime:

Issue	Symptom	Workaround
`??` null coalesce	Compiles but fails at runtime with "unknown function 'coalesce'"	Use sentinel defaults with `if` conditionals instead
State machine field co-declaration	`state status { ... }` in a record requires a matching field declaration `status: Status = Status.draft`	Always declare both the field with its default and the state machine
Duration literals in assertions	`assert record.prep_time == 2m` fails even when the value matches	Use the string form: `assert record.prep_time == "2m"`
Events must set state field explicitly	Emitting a state-transition event like `published` without a `status` field in the event doesn't update the status	Add `status: Status = Status.published` with a default value to the event declaration

Null Coalesce Workaround

Instead of:

// Does NOT work at runtime:
let name = input.name ?? "default"

Use:

// Works:
if input.name != null {
  let name = input.name
} else {
  let name = "default"
}

State Machine Co-declaration

The state block and the field it controls must both be declared:

record {
  kind "post"
  status: ArticleStatus = ArticleStatus.draft   // Required field declaration

  state status {                                  // State machine references the field
    ArticleStatus.draft -> ArticleStatus.published on published
  }
}

Event Status Field

State-transition events must explicitly include the status field with a default:

event published {
  status: ArticleStatus = ArticleStatus.published   // Required for state transition
}

Database Backends

Backend	Status
SQLite	Implemented
PostgreSQL	Implemented
MySQL	Implemented
TiDB	Implemented
DynamoDB	Not planned
MongoDB	Not planned