docs: remove obsolete migration plan

docs/design/v1-v2-database-migration.md

@@ -1,298 +0,0 @@
-# V1 to V2 Database Migration
-
-## Approach
-
-- Use the `dev` branch database schema and migration registry as the V1 baseline.
-- Remove migrations that exist only on the V2 branch.
-- Generate one canonical migration from the `dev` schema to the final V2 schema.
-- Keep the canonical migration focused on schema changes and dropping obsolete tables.
-- Run the V1 history backfill through an experimental server endpoint invoked by the CLI before it opens the TUI.
-- Show committed session progress while the endpoint runs.
-
-Expose `GET /api/experimental/migration/v1` for status and a blocking `POST /api/experimental/migration/v1` to run or
-resume the backfill. The status is `required`, `running`, or `completed`. On startup, the CLI checks status first and
-renders no migration UI when it is already complete. For required or running status, it shows a spinner and waits for the
-blocking POST without a request timeout. While migration runs, poll GET once per second and render completed and total
-session counts. GET derives total from all session rows and completed from rows through the stored cursor; the count
-advances only after a session transaction commits. The POST returns `{ status: "completed" }`. Do not add a background
-job or streaming progress protocol. Interrupted calls resume from the stored cursor.
-Initially, only interactive TUI startup performs this check; noninteractive run, ACP, raw API, service, health, version,
-and help flows do not trigger the backfill.
-
-Keep migration behavior in Core: status, semaphore, checkpointing, V1 decoding, transformation, and database writes.
-Protocol owns the experimental GET/POST contracts, Server handlers delegate to Core, and the interactive CLI owns only
-the status check and spinner presentation.
-
-Guard the endpoint with one process-local Effect `Semaphore`. Concurrent callers wait; after the active call completes,
-waiting callers acquire the permit, observe the completion key, and return immediately. No distributed lock is required
-for the current single elected server process.
-
-## Preserve
-
-The canonical V1 data remains in its existing tables. In particular, preserve `session`, `message`, and `part` rows.
-
-Preserve `workspace` rows and existing `session.workspace_id` values unchanged. The migration must not clear or rebuild
-workspace relationships.
-
-Preserve existing non-null `session.agent` and `session.model` selections. Fill missing values from the latest ordinary
-V1 user message ordered by `time_created` and `id`, excluding compaction and subtask-only messages. Copy agent, provider
-ID, model ID, and variant, normalizing an absent variant to `default`.
-
-Recompute session usage aggregates from all canonical V1 assistant messages, including compaction or other internal
-assistants omitted from the V2 projection. Overwrite session cost and input, output, reasoning, cache-read, and
-cache-write token totals with those sums.
-
-Clear persisted `session.revert` state. A staged revert is transient operational state and may refer to omitted projection
-rows or unavailable snapshots; it must not resume automatically after upgrading. Preserve the underlying messages,
-parts, and file history.
-
-Clear `session.time_compacting`, leave the new `time_suspended` column as `NULL`, and preserve session creation, update,
-and archive timestamps. Preserve project `time_initialized`; it is unrelated durable state.
-
-Keep the legacy `todo` table and its data physically unchanged, but do not include it in the final V2 Drizzle schema.
-After generation, remove the generated `DROP TABLE todo` statement from the canonical migration so the table remains as
-unmanaged legacy storage.
-
-## Per-Session Replacement
-
-Do not truncate `event`, `event_sequence`, or `session_message` globally before the backfill. A whole-table delete can
-hold SQLite's writer lock long enough to block the running TUI.
-
-Replace each legacy session's V2 state inside that session's checkpointed migration transaction. Delete `event` rows for
-the session aggregate, delete its `session_message` rows, rebuild its projection from canonical V1 `message` and `part`
-rows, and overwrite its `event_sequence` watermark. If migration of that session fails, all replacements roll back and
-the durable cursor remains at the previously committed session. Rows owned by sessions outside the legacy migration set
-remain untouched.
-
-## Message Backfill
-
-Backfill canonical V1 history from `message` and `part` into `session_message`. This is the main data transformation in
-the migration. Preserving the V1 tables alone keeps the data safe but does not make existing history visible through the
-V2 session APIs, which read `session_message`.
-
-Do not fail the whole migration when a V1 message or part payload cannot be decoded. Skip an undecodable message's V2
-projection and log its session and message IDs. Skip an undecodable part while continuing to map its message, and perform
-special-message pairing only with decoded rows. Assign sequences after filtering. Leave every malformed source row
-untouched in the V1 tables.
-
-Skip and log orphan parts whose source message does not exist and parts with unknown or unsupported types. Continue
-migrating the owning message and other valid parts. Include session, message, part ID, and observed type in warnings, and
-leave skipped source rows unchanged.
-
-Reuse each V1 `message.id` as the corresponding `session_message.id`. Stable IDs keep the migration deterministic and
-avoid rewriting other persisted state that may refer to a message.
-
-For ordinary user and assistant rows, preserve source `message.time_created` and `message.time_updated`. Entirely
-synthetic messages preserve their source timestamps, and synthetic rows split from mixed messages use the source user
-timestamps. A collapsed compaction uses the compaction user creation time and the later update time of the compaction
-user and summary assistant. Keep payload creation/completion times consistent with row timestamps.
-
-Within each session, order V1 messages by `time_created` and then `id`, matching the existing V1 message index. Assign
-contiguous `session_message.seq` values starting at `0`.
-
-Map ordinary V1 messages one-to-one by role. Each ordinary V1 user message becomes one V2 `user` row, and each ordinary
-V1 assistant message becomes one V2 `assistant` row. Fold the source message's ordered V1 parts into that row's V2
-payload.
-
-Keep ordinary messages even when their transformed payload becomes empty after filtering. Preserve an empty V2 user row
-with `text: ""` and an empty V2 assistant row with `content: []` so IDs, chronology, and conversation structure remain
-stable. Omit only explicitly dropped internal concepts and undecodable messages.
-
-Handle semantic marker parts before applying the ordinary mapping. In particular, a V1 user message containing a
-`compaction` part and its paired assistant summary represent one compaction operation, not two ordinary messages. Special
-part mappings must be decided explicitly before implementing the backfill.
-
-Do not carry the V1 subtask concept into the V2 projection. Omit user messages containing only `subtask` parts and omit
-the paired assistant task-tool messages generated from those markers. For mixed user messages, ignore the `subtask`
-parts while preserving ordinary content, and still omit assistant task-tool messages generated by the skipped subtasks.
-Keep all source rows unchanged in the V1 `message` and `part` tables.
-
-Map ordinary V1 assistant `text` and `reasoning` parts into the V2 assistant `content` array in part order. Preserve text,
-including empty assistant text parts used as structural separators. Map V1 part metadata to optional V2 provider state.
-For reasoning, map `time.start` to `time.created` and optional `time.end` to `time.completed`.
-
-Preserve V1 tool parts that are `pending` or `running`, but convert them to terminal V2 tool error states. Preserve the
-call ID, tool name, parsed input, metadata, and available start time. Use the assistant message creation time when the V1
-state has no start time. Set the error to type `tool.interrupted` with message
-`Tool execution was interrupted before V2 migration`. Never resume migrated tool executions.
-
-For a completed V1 tool part, use `callID` as the V2 tool content ID and preserve the tool name and parsed input. Set the
-state to `completed`. Convert V1 output into the first text content item and convert stored output attachments into
-following file content items with their URI, MIME type, and filename. Preserve state metadata. Map `time.start` to
-`time.created` and `time.end` to `time.completed`. When `time.compacted` exists, use
-`[Old tool result content cleared]` as the only output and omit attachments.
-
-For a failed V1 tool part, preserve the call ID, tool name, parsed input, metadata, and timestamps, and set the V2 state
-to `error`. Convert the V1 error string to a structured error with type `tool.execution`. If V1 metadata contains a string
-`output`, preserve it as optional V2 text content. Map `time.start` to `time.created` and `time.end` to `time.completed`.
-
-For an ordinary V1 assistant message, preserve agent, provider ID, model ID, optional variant, creation and completion
-times, cost, and input/output/reasoning/cache token counts. Use `default` when the V1 variant is absent. Ignore V1
-`tokens.total` because it is derivable and V2 does not persist it.
-
-Use V1 assistant `parentID` only while pairing compactions and skipped subtasks with their originating user messages. Do
-not persist it in ordinary V2 assistant rows; V2 uses ordered history rather than user/assistant parent links.
-
-Ignore the optional V1 assistant `structured` output value. V2 has no equivalent top-level assistant field, and visible
-text and tool content are migrated separately. Retain the original structured value only in the V1 `message` row.
-
-Ignore V1 assistant `mode` and historical `path` (`cwd` and `root`). Mode is redundant with the preserved assistant
-agent, and historical filesystem paths do not belong to the V2 assistant message contract. Retain them only in the V1
-`message` row.
-
-For assistant finish reasons, preserve `stop`, `length`, `tool-calls`, `content-filter`, `error`, and `unknown`. Map every
-other nonempty V1 finish value to `unknown`, and leave the field absent when V1 omitted it. Do not retain unrecognized raw
-finish values in metadata.
-
-Map V1 assistant errors into the current V2 `{ type, message }` storage shape. Normalize Auth, content-filter, context
-overflow, structured-output, output-length, aborted, API, and unknown errors to the established V2 string conventions,
-preserve the message, and discard V1-only retryability and raw provider details.
-
-Ignore V1 `retry` parts. Do not populate the V2 assistant `retry` field during migration; historical retry state is not
-useful enough to preserve. The original retry rows remain in the V1 `part` table.
-
-Do not emit V2 assistant content for V1 `step-start` and `step-finish` parts. Use the first available
-`step-start.snapshot` as `assistant.snapshot.start` and the last available `step-finish.snapshot` as
-`assistant.snapshot.end`. Continue to source finish, cost, and tokens from the assistant message itself. Ignore step
-markers without snapshots.
-
-Do not emit assistant content for standalone V1 `snapshot` or `patch` parts. If no start snapshot came from `step-start`,
-use the first standalone snapshot value, then the first patch hash as a final fallback. Only `step-finish.snapshot` may
-populate the end snapshot. Merge patch file lists into `assistant.snapshot.files` in first-seen order with duplicates
-removed.
-
-V2 follow-up: replace the open `SessionError.Error` string shape with a properly typed persisted error union. This is not
-a blocker for the V1 migration, which should target the current storage contract.
-
-V1 synthetic content is represented by user text parts with `synthetic: true`, not by a separate message role. A V1 user
-message whose visible text parts are all synthetic should become a V2 `synthetic` message. If a V1 user message mixes
-ordinary and synthetic content, preserve the ordinary content in the V2 `user` row and emit the synthetic content as an
-adjacent V2 `synthetic` row. Ignore text parts marked `ignored`, matching V1 model-history behavior.
-
-For an ordinary V2 user message, take visible V1 text parts that are neither ignored nor synthetic, preserve part order,
-and join their text with `"\n\n"`. Use an empty string when the message contains attachments but no ordinary text.
-
-Ignore the optional V1 user-message `system` override. Do not create a V2 system message or preserve the override in
-metadata. The original value remains in the V1 `message` row.
-
-Ignore the optional V1 user-message `tools` map. It represented request-time tool enablement for a historical step and
-must not affect future V2 execution. The original value remains in the V1 `message` row.
-
-Ignore the optional V1 user-message `format` field and its schema. It controlled structured-output behavior for a
-historical request and must not affect future V2 runs. Preserve visible assistant text normally; retain the original
-format only in the V1 `message` row.
-
-Ignore V1 user-message `summary` metadata, including title, body, and diffs. V2 user messages have no equivalent field,
-and session-level summary data is already persisted separately. Retain the original summary only in the V1 `message`
-row.
-
-Map V1 `agent` parts into the V2 user message's `agents` array in part order. Preserve `name`. When the V1 part has
-`source`, map its `value`, `start`, and `end` into the V2 attachment's `mention.text`, `mention.start`, and `mention.end`.
-Omit `agents` when there are no agent parts.
-
-Do not read the filesystem or network while migrating V1 file attachments. Attachment migration must be deterministic
-from database contents alone. Convert persisted `data:` URLs; represent non-embedded `file:`, HTTP, and other external
-URLs with deterministic text rather than fetching them. Keep the original V1 `part` rows unchanged.
-
-For a V1 file backed by a `data:` URL, decode the URL and normalize its payload to base64 for the V2 attachment's `data`.
-Preserve `mime` and optional `filename` as `name`. Use a V2 `uri` source with the original URI for a V1 resource source;
-otherwise use an `inline` source. When V1 source text metadata exists, map its `value`, `start`, and `end` into the V2
-attachment mention. Leave `description` unset and preserve file-part order in the V2 `files` array.
-
-For a non-embedded V1 file, do not create a V2 file attachment. Append
-`[Attachment unavailable after migration: <name-or-url> (<mime>)]` to the V2 user text in original part order, separated
-by blank lines. Prefer the V1 filename, then resource URI, then part URL for the label. The original URL remains only in
-the preserved V1 `part` row.
-
-For a synthetic row split from a mixed user message, derive a generated-looking ID from the source message ID. Preserve
-the source ID's 12-character timestamp component and replace its 14-character random component with a deterministic
-base-62 encoding of a hash of `v1-synthetic:` plus the source message ID. If that candidate collides with an existing or
-derived message ID, deterministically retry with an incrementing salt. Place the synthetic row immediately after its
-source user row. Entirely synthetic messages continue to reuse their original message ID.
-
-Use the V1 compaction user message ID as the ID of the collapsed V2 compaction message. This matches V2's use of the
-admitted compaction input ID and preserves references to the initiating message.
-
-For a completed compaction, create one V2 `compaction` row with `status: "completed"`. Set `reason` from the V1
-compaction part's `auto` flag, join the paired summary assistant's nonempty text parts with blank lines for `summary`, and
-serialize the retained V1 tail beginning at `tail_start_id` for `recent`. Use an empty `recent` value when no tail was
-retained, and use the compaction user message creation time. Do not emit the paired summary assistant as a separate V2
-assistant row.
-
-Do not project incomplete or failed V1 compactions into `session_message`. Omit both the internal compaction user marker
-and its paired summary assistant when no successful summary was completed. Assign final sequence numbers after filtering
-so omitted compactions leave no gaps. Their source rows remain preserved in the V1 `message` and `part` tables.
-
-After rebuilding a session's `session_message`, replace its `event_sequence` watermark with that session's maximum
-backfilled `session_message.seq`. This prevents new V2 events from reusing sequence numbers or sorting before migrated
-history. The migrated session's prior `event` rows are removed in the same transaction.
-
-## Drop
-
-Drop these pre-launch V2 tables without preserving or transforming their rows:
-
-- `session_input`
-- `session_context_epoch`
-- `data_migration`
-
-Do not transfer `session_input` rows into `session_pending`.
-
-## Create Empty
-
-Let the generated migration create these tables empty:
-
-- `instruction_blob`
-- `instruction_entry`
-- `instruction_state`
-- `session_pending`
-- `kv`
-
-V1 has no canonical data to backfill into these tables. V2 initializes their state as it runs.
-
-## Fork Storage
-
-V1 has no fork-boundary state to backfill. New V2 forks use a required message boundary and persist it in
-`session.fork_boundary`. The durable fork event contains no parent sequence. Its resolved boundary is one of:
-
-- `before`: copy messages before the identified message.
-- `through`: copy messages through the identified message.
-
-Forking an empty session is not supported. `session.fork_seq` and `session.fork_message_id` are not part of the final V2
-schema.
-
-New nullable session columns, including `fork_session_id`, `fork_boundary`, and `time_suspended`, require no explicit
-backfill. Existing rows naturally receive `NULL` when the generated migration adds the columns.
-
-## Execution
-
-Before transforming V1 rows, look for `opencode-next.db` in the data directory. This file was used by pre-launch V2
-builds. Open it read-only with Bun SQLite and copy its `project`, `session`, and `session_message` rows directly into the
-current `project`, `session_v2`, and `session_message` tables. Existing current projects and Sessions win ID collisions.
-Do not copy its durable events or runtime caches; initialize each imported Session's `event_sequence` watermark from its
-maximum message sequence. Commit each imported Session independently and leave the source database untouched.
-
-The previous V2 import is part of this migration and uses the same completion marker. It needs no source-specific cursor:
-the destination Session row is the per-Session idempotency boundary, so a retry skips transactions that already committed.
-
-Store V1 backfill state in `kv`; do not retain a dedicated `data_migration` table. Store the last successfully migrated
-session ID under `migration.v1-v2.session.cursor` and write `migration.v1-v2.completed` with value `true` after every
-session finishes. Delete the cursor key on completion and return immediately on later calls when the completion key
-exists.
-
-Absence of the completion key means migration is required, including on a fresh database. Running the endpoint against a
-database with no sessions completes immediately and writes the completion key; fresh database initialization does not
-seed migration state specially.
-
-Process sessions in stable ID order. Rebuild one session in one transaction, including its `session_message` rows,
-session-level backfills, `event_sequence` watermark, and cursor update. If interrupted during a session, that transaction
-rolls back and the next endpoint call retries the same session. If it committed, the next call continues after the stored
-cursor. Mark the migration complete after the final session and return immediately on later calls.
-
-Ensure the global project exists using the current platform's filesystem root as its worktree. Process every `session`
-row, including archived, root, child, and empty sessions, as well as sessions whose messages are all skipped or internal.
-Reassign beta and V1 Sessions whose referenced project row is missing to the global project and log a warning. Each
-successfully committed session advances the cursor.
-
-## Testing
-
-Detailed migration test design is deferred until after the canonical migration is implemented.