[AI-assisted] Desktop reload fails with Expected JSON value for nested apply_patch metadata #38617

AI-authorship disclosure

This issue was researched and drafted by an AI coding assistant, then submitted under the account owner's direction. The observed symptom was supplied by the human reporter. The source-code findings are linked below; the affected local database has not yet been inspected, and all hypotheses are explicitly marked as such.

Summary

OpenCode Desktop shows the following error whenever it reloads a project/session:

Expected JSON value, got [[{"filePath":...,"type":"update","patch":"Index: ..."}]]

The workload continues to run and files continue to update. The failure is observed specifically during Desktop project/session reload.

Environment

• Client: OpenCode Desktop
• Workload: large, long-lived sessions; multiple sessions used for the same project
• Exact Desktop version, OS/arch, active plugins/MCP configuration: to be added

Observed behavior

• Reopening/reloading the same project reproduces the error.
• The payload resembles patch history.
• Its leading [[{ suggests a nested array.
• The visible object has filePath, type: "update", and a string patch beginning with Index: ....
• Current work is not stopped: tool execution and file writes continue.

Source investigation

Confirmed

• The built-in legacy apply_patch tool emits a flat files array whose items have the observed shape: { filePath, relativePath, type, patch, additions, deletions, movePath }.
  • https://github.com/anomalyco/opencode/blob/dev/packages/opencode/src/tool/apply_patch.ts#L193-L215
• Snapshot PatchPart is not this shape: it is { type: "patch", hash: string, files: string[] }. The snapshot implementation returns a flat list of file path strings.
  • https://github.com/anomalyco/opencode/blob/dev/packages/schema/src/v1/session.ts#L94-L100
  • https://github.com/anomalyco/opencode/blob/dev/packages/opencode/src/snapshot/index.ts#L349-L380
• Session part.data is persisted as JSON text. On legacy message hydration, rows are reconstructed by type assertion rather than a per-row schema decode.
  • https://github.com/anomalyco/opencode/blob/dev/packages/core/src/session/sql.ts#L82-L98
  • https://github.com/anomalyco/opencode/blob/dev/packages/opencode/src/session/message-v2.ts#L80-L121
• Desktop starts a bundled local sidecar server, and the app fetches legacy session messages as a fallback path during reload.
  • https://github.com/anomalyco/opencode/blob/dev/packages/desktop/src/main/sidecar.ts#L51-L69
  • https://github.com/anomalyco/opencode/blob/dev/packages/app/src/context/server-session.ts#L526-L560

Hypothesis, not yet verified against the affected DB

A historical tool part, likely tool.state.metadata.files, may contain Patch[][] / FileChange[][] rather than the flat FileChange[] written by the current apply_patch tool. Reload then reaches an HTTP response JSON/schema boundary that rejects the persisted value.

This is not yet evidence that snapshot PatchPart itself is nested. The source has no declared Patch[][] in the snapshot/revert path.

Related reports

• tools: optional search metadata breaks pending permission listing #37650 / fix(core): drop undefined metadata values from permission requests #37679 show the same general failure class: a permissive metadata field later fails JSON response encoding.
• Parallel terminal sessions overlap when running in the same project directory #28249 reports shared snapshot corruption when multiple OpenCode processes edit the same project concurrently.
• fix(session): prevent cross-session patch contamination #20560 is an unmerged proposal addressing cross-session patch contamination and specifically consumes files[].filePath from apply_patch metadata.

Expected behavior

A malformed or legacy persisted tool part must not prevent a whole session/project from reloading. At minimum, the response should identify the failing part.id and safely isolate or omit that part rather than failing session message retrieval.

Requested guidance

1. Is there a known migration/schema incompatibility for legacy apply_patch metadata or Patch[][]?
2. What is the supported non-destructive recovery path for one malformed session part?
3. Is snapshot: false expected only to prevent future snapshot generation, rather than repair existing persisted metadata?
4. Is there a recommended export/query that maintainers want attached to identify the exact bad row?

I can attach a sanitized session export, relevant part/session_message query results, and a Desktop debug-log archive after guidance on the preferred redaction format.