[FEATURE]:add session/delete method to ACP for programmatic session cleanup #54478

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Description

OpenCode’s ACP protocol already supports session-related methods such as session/new, session/load, session/list, session/fork, session/prompt, and session/cancel. The CLI also supports deleting sessions, for example opencode session delete <id>.

However, ACP currently does not expose a session/delete method. This makes it impossible for IDE clients, editor plugins, or automation tools to delete a session purely through the ACP protocol. Clients that want to clean up sessions must fall back to CLI commands or other APIs, which breaks the consistency of ACP as a unified session management protocol.

Adding session/delete would complete the ACP session lifecycle and allow clients to create, load, list, fork, cancel, and delete sessions through the same interface.

Motivation

• Make the ACP session lifecycle complete and symmetric.
• Allow IDE/editor clients to delete sessions without shelling out to the CLI.
• Improve automation scenarios such as tests, CI workflows, and multi-session orchestration.
• Keep ACP consistent with existing OpenCode session capabilities.

Proposed API

Request:

{
  "jsonrpc": "2.0",
  "id": 42,
  "method": "session/delete",
  "params": {
    "sessionId": "ses_xxx"
  }
}

Response:

{
  "jsonrpc": "2.0",
  "id": 42,
  "result": {
    "deleted": true
  }
}

Optional extensions:

• Support all: true to delete all sessions, similar to opencode session delete --all.
• Return a clear error if the session does not exist, is locked, or cannot be deleted.
• If the target session is actively running, either reject the request or automatically cancel it via session/cancel before deletion.

Acceptance Criteria

• ACP exposes a session/delete method.
• After deletion, the session no longer appears in session/list.
• Deleting an active session produces a predictable and documented behavior.
• Errors are returned for invalid or missing session IDs.
• Documentation and error codes are updated alongside the implementation.

References

• ACP already supports session/new, session/load, session/list, session/fork, session/prompt, and session/cancel.
• The OpenCode CLI supports opencode session delete <id> and opencode session delete --all.
• ACP currently lacks a matching delete method for programmatic session cleanup.