[rekram1-node]

Problem

Several protocol lowers and response handlers in @opencode/ai re-validated values that were already narrowed by Effect Schema or internal accessors (LLMResponse.toolCalls, ProviderMetadata, MediaPart.metadata, MediaPart.filename, MistralThinkingUnit.text, and ToolChoice validation before ProviderShared.matchToolChoice).

Change

Drop the redundant runtime guards and rely on the existing Schema-decoded types across llm.ts and the protocol adapters:

 LLM.runGenerateObject
-  response.toolCalls.find(event => LLMEvent.is.toolCall(event) && ...)
-  if (!call || !LLMEvent.is.toolCall(call))
+  response.toolCalls.find(event => event.name === GENERATE_OBJECT_TOOL_NAME)
+  if (!call)

 Protocol metadata & event lowers
   open-responses / anthropic-messages / bedrock-converse / gemini / google-interactions
-    ProviderShared.isRecord(providerMetadata?.[key])
+    providerMetadata?.[key]
   anthropic-messages
-    typeof block.content === "object" && block.content !== null && ...
+    ProviderShared.isRecord(block.content) && "type" in block.content
   mistral-chat
-    duplicate request.toolChoice?.type === "tool" && !selected guard
-    typeof unit.text === "string"
+    ProviderShared.matchToolChoice(...)
+    unit.text !== undefined

Out of scope

• Untrusted unknown values inside Record<string, unknown> metadata payloads still retain property-level typeof or ProviderShared.isRecord checks where their values are not schema-decoded.

[opencode-agent]

Looks good. I checked each removed guard against the schema-decoded type it relied on. In packages/ai on the PR head, bun run typecheck passed and bun test gave 1826 passed, 0 failed. The new optional-chained reads still return undefined safely if a metadata entry isn't the expected shape. ProviderShared.matchToolChoice already gives the same Mistral "requires a tool name" error, so removing the guard in mistral-chat.ts loses nothing. The only difference is ordering: if the provider options are also invalid, the options error now comes first.

Public API is unchanged: the changes are internal to packages/ai.