Missing data migration for tool-part state.input on upgrade 1.14.28 → 1.18.18

Description

Upgrading opencode from 1.14.28 to 1.18.18 lacks a data migration to normalize existing tool-part state.input.

On 1.14.28 a tool part could be persisted with state.input as a JSON string (e.g. an errored/aborted tool call). On 1.18.18 the serialization schema requires state.input to be an object (Schema.Record), so re-encoding the stored part fails and the whole session can no longer be read. The schema/DB migrations run on upgrade, but nothing converts the pre-existing string values.

OpenCode version

Upgraded 1.14.28 → 1.18.18

Steps to reproduce

1. On 1.14.28, run a session where a tool call errors while its arguments are a JSON-encoded string — e.g. the model emits an unavailable/invalid tool name, or todowrite todos arrives as a string (#34652). The errored part is stored with state.input as a string (it can be a truncated partial, so not always valid JSON).
2. Upgrade opencode to 1.18.18 and start it (schema/DB migrations run).
3. GET /session/:id/message for that session.

Observed on step 3 — the whole endpoint returns 400:

{"name":"BadRequest","data":{"kind":"Body",
 "message":"Expected object, got \"{...}\"\n  at [N][\"parts\"][M][\"state\"][\"input\"]"}}

A data migration is needed to coerce legacy state.input string values to objects, falling back to {} when the string isn't valid JSON.

Plugins

none

Operating System

Linux