chore(ops): reclaim pre-guard session data from the local database

[LeXwDeX]

This was generated by AI during triage.

Why

The payload-growth defect fixed by #522 left historical data in the local opencode.db. The #523 and #525 code fixes prevent or reduce future growth but cannot remove existing user sessions or return already allocated SQLite pages to the filesystem.

This is a destructive operator task, not a source-code delivery.

Scope

• Identify the exact database path and create a verified backup before any mutation.
• Produce a read-only dry run listing the proposed cutoff, affected session IDs/counts, event/message/part counts, estimated reclaimable bytes, and sessions that will remain.
• Obtain explicit human approval for that exact deletion set.
• Stop every opencode process, delete only approved sessions through a path that also removes event and event_sequence, then run SQLite integrity checks and VACUUM while exclusive access is guaranteed.
• Record before/after counts, database size, integrity result, and application startup smoke result.

Safety constraints

• No agent may execute deletion or VACUUM from this issue without a separate explicit approval after presenting the dry-run evidence and backup location.
• Do not infer consent from approval of chore(core): design bounded event retention and SQLite reclamation #524 or from approval to develop code.
• Abort if the database changes between dry run and maintenance window, backup verification fails, or another opencode process is active.

Acceptance

• The approved backup exists and is restorable.
• The actual deletion set exactly matches the approved dry run.
• PRAGMA integrity_check succeeds after cleanup.
• The database file shrinks materially after offline VACUUM and opencode starts successfully.
• A completion comment records non-sensitive before/after measurements without publishing session contents.

Relations

• fix: message snapshot persists untruncated session diff summary into the event log #522, fix: event append has no idempotency guard so identical payloads are re-persisted #523, fix: summary diff cap discards trailing in-budget diffs when an earlier file exceeds 256KB; summary_diffs column is legacy dead code #525: source fixes already completed
• chore(core): design bounded event retention and SQLite reclamation #524: long-term retention and SQLite reclamation design; independent from this one-time operator action

[LeXwDeX]

This was generated by AI during triage.

Human-only operator brief: first produce a read-only dry run and verified backup, then request explicit approval for the exact session deletion set. Stop all opencode processes before mutation or VACUUM. This issue authorizes planning only; it does not authorize deleting user data.