[rekram1-node]

Problem

Several paths in packages/core/src/tool and packages/core/src/mcp re-validated, re-branded, or wrapped values already guaranteed by schemas or upstream helpers:

• SubagentTool re-branded Agent.ID.make(input.agent) when agent.id was already resolved and branded.
• ReadTool checked for encoding === "base64" with a non-media MIME after ReadToolFileSystem.read, which only produces encoding: "base64" inside if (MEDIA_MIMES.has(media)).
• McpTool used a manual try { return JSON.parse(text) } catch {} block instead of Schema.decodeUnknownOption(Schema.fromJsonString(Schema.Unknown)).
• Mcp.connect, Mcp.disconnect, and Mcp.remove called ServerName.make(server) before passing the already-branded name into requireServer, which called ServerName.make a second time.

Change

Drop the dead binary MIME check, use Schema.decodeUnknownOption(Schema.fromJsonString(Schema.Unknown)) in McpTool, reuse agent.id in SubagentTool, and have requireServer accept name: ServerName in Mcp:

 packages/core/src/
 ├── mcp/index.ts
-│   └── requireServer(server: ServerName | string) -> ServerName.make(server)
+│   └── requireServer(name: ServerName)
 └── tool/
     ├── mcp.ts
-    │   └── try { return JSON.parse(text) } catch {}
+    │   └── Option.getOrElse(decodeJson(text), () => text)
     └── plugin/
         ├── read.ts
-        │   └── dead base64 && !MEDIA_MIMES.has(mime) check
         └── subagent.ts
-            └── agent: Agent.ID.make(input.agent)
+            └── agent: agent.id

Out of Scope

• Changing tool input schemas or MCP connection lifecycle semantics.

[opencode-agent]

Two of the five cleanups change behaviour, so the PR can't land as a pure refactor yet. The read.ts, subagent.ts and tool/mcp.ts changes look fine.

How I checked: I ran a temporary probe calling glob with path: "undefined" on the base and on this branch. I also ran the nearby core tests and typecheck. Type checking passes. The tests pass except one MCP test (terminates MCP descendants after the wrapper exits successfully), which also fails on the base.

Public API: unchanged.

Concerns:

• glob: RelativePath is only a branded String, so it doesn't reject "undefined" or "null". The check you removed was live: on the base, glob with path: "undefined" searches the working directory; with this PR it fails with Search path does not exist: undefined.
• MCP connect/disconnect: these now look up the server entry before taking the per-server lock, which reintroduces a race (details inline).

[opencode-agent]

Both earlier points are fixed. The glob "undefined"/"null" normalisation is back, and connect/disconnect look up the server inside the per-server lock again. The rest of the change keeps behaviour the same.

Type checking in packages/core passes. The nearby tool and MCP tests pass except one MCP test, which also fails on the base.

The public API is unchanged.