migration: V1 to V2 session import reports completed but orphans sessions created after it ran #55493

Summary

After updating to OpenCode 2.0.29, recent chat history is missing from the app. The one-shot V1→V2 data migration (kv.migration.v1-v2) had already been marked {"phase":"completed"} and never runs again, so sessions that were written to the legacy session / message / part tables after that migration are never imported into session_v2 / session_message. GET /api/experimental/migration/v1 still reports {"status":"completed"} even though 15 sessions exist in session with no corresponding session_v2 row.

Environment

• opencode version: 2.0.29 (desktop app ai.opencode.desktop 2.0.29; bundled CLI 2.0.29)
• OS: Windows 11 (Windows_NT 10.0.26300.9550, win32 x64)
• Terminal: Warp (TERM=xterm-256color)
• Shell: cmd.exe
• Install/channel: latest (desktop, packaged) + pnpm-installed CLI 2.0.29
• Active plugins: none

Reproduction

1. Install an OpenCode 2.x build so ~/.local/share/opencode/opencode.db contains the V2 tables and the V1→V2 data migration completes (kv.migration.v1-v2 = {"phase":"completed"}).
2. Run a pre-2.0 client (in my case the desktop app on versions 1.18.33–1.19.0) and create/resume sessions. Those rows are written to the legacy session / message / part tables.
3. Update to OpenCode 2.0.29 and open the app.
4. Observe: the sessions created in step 2 do not appear, and:
   • SELECT COUNT(*) FROM session = 71 vs SELECT COUNT(*) FROM session_v2 = 59
   • opencode api get /api/experimental/migration/v1 → {"status":"completed"}

Expected Behavior

On startup (or when the status endpoint is queried), OpenCode should detect legacy session rows that have no session_v2 counterpart and import them, so upgrading to 2.0 never hides existing history.

Actual Behavior

Sessions that exist only in the legacy tables are silently orphaned and the app shows no history for them. The migration is effectively one-shot: when kv.migration.v1-v2 phase is completed, the migration returns early, and the status endpoint reports completed based on that flag without comparing session against session_v2.

Observed counts before the workaround:

session          = 71
session_v2       = 59      (15 legacy sessions had no session_v2 row)
message          = 4520
session_message  = 2886

The 15 missing sessions all had version between 1.18.33 and 1.19.0. Sessions with version 1.18.15–1.18.32 (present when the migration first ran) were imported correctly, so the gap is specifically sessions created after the migration completed.

Additional Context

• No data was actually lost: all 15 sessions had full message and part rows in the legacy tables.
• Workaround that restored everything: set kv.migration.v1-v2 to {"phase":"sessions"} and restart the service. The startup migration re-ran (INSERT OR IGNORE into session_v2 plus a rebuild of session_message for each session), and session_v2 went 59 → 74 with 0 remaining un-imported sessions; migration.v1-v2 then returned to {"phase":"completed"}.
• The workaround also repaired one already-migrated session that had been truncated (session_message rows for it went from 9 to 102, matching its 99 legacy messages).
• Suggestion: make the startup/status path compare the legacy session table against session_v2 and re-import any missing ids, instead of trusting the phase flag alone. The migration already supports resuming with {"phase":"sessions"} and uses INSERT OR IGNORE, so a re-check should be cheap.
• Standalone database (SQLite): ~/.local/share/opencode/opencode.db.

Related Issues

• V1→V2 migration loses/hides history: corrupt-part migrator 500s, undecodable rows report no field detail, >9k-message imports 500 with empty body, project picker is a hidden shortcut #42671 — V1→V2 migration loses/hides history (corrupt rows, >9k-message sessions, hidden project picker). Different root cause: this report is only about the one-shot phase flag skipping legacy sessions created after the migration ran.
• V1→V2 migration silently drops legacy messages missing required fields (agent/model/parentID) — old sessions show empty history #53971 — migration silently drops legacy messages missing required fields.
• v2: V1 sessions in non-git directories invisible after migration (legacy catch-all project) #50800 — V1 sessions in non-git directories invisible after migration (legacy catch-all project).