[rekram1-node]

Problem

Several paths in packages/core/src/session/ redundantly validate or decode values that are already validated at the boundary or decoded in a downstream projector:

• SessionInbox.publish calls fromRow(row) to read id, type, and delivery before publishing SessionEvent.InboxDelivered, even though those fields are top-level columns on SessionInboxTable and projectDelivered already decodes the deleted row via fromRow(deleted).
• SessionInbox.fromRow and SessionInbox.admitCompaction re-wrap already-typed row.id, row.session_id, and input.delivery values in .make(...) before passing them to schema constructors that validate them again.
• SessionPrompt.prepare spreads Prompt.make(...) into SessionInbox.UserPayload.make(...), validating all prompt fields and base64 attachments twice, and re-wraps event.delivery with SessionInbox.Delivery.make(...).
• SessionMessageUpdater.update rebuilds Schema.decodeUnknownSync(Schema.Array(SessionMessage.AssistantContent)) inside update() on every session.message.content.updated event.

Change

Pass already-typed columns and fields directly to the owning schema constructors, avoid decoding inbox payloads prior to InboxDelivered projection, and hoist the assistant content array decoder to module scope.

 SessionPrompt.prepare
-  Prompt.make({ text, agents, files, skills })
   SessionInbox.UserPayload.make({ text, agents, files, skills, metadata })
-  SessionInbox.Delivery.make(event.delivery)

 SessionInbox.promote -> publish(rows)
-  fromRow(row)                        # decoded payload before publish
+  guard row.type in {move, user, synthetic}
   bus.publish(InboxDelivered, { sessionID, inboxID: row.id })
     projectDelivered
       fromRow(deleted)                # single payload decode on consumption

 SessionMessageUpdater.update
   "session.message.content.updated"
-    Schema.decodeUnknownSync(Schema.Array(AssistantContent))(content)
+    decodeAssistantContent(content)   # hoisted to module scope

Out of scope

• Schema definitions for Prompt and SessionInbox in @opencode/schema.

[opencode-agent]

No problems found; the refactor keeps the same behaviour. Effect make already validates its input, so dropping the nested Prompt.make/Delivery.make/ID make calls still validates each value once. The type check in publish matches the old fromRow plus compaction rejection, and a malformed payload now fails in projectDelivered with the same defect result. Hoisting decodeAssistantContent is safe.

Checked with the session tests in packages/core (prompt, move, compact, skill, execution, runner, owned: 352 pass, 0 fail) and bun run typecheck, which passed.

Public API unchanged (internal packages/core session code only).