diff --git a/packages/core/src/database/migration/20260804233008_loose_psylocke.ts b/packages/core/src/database/migration/20260804233008_loose_psylocke.ts
index 08c0ebf461..db553c959d 100644
--- a/packages/core/src/database/migration/20260804233008_loose_psylocke.ts
+++ b/packages/core/src/database/migration/20260804233008_loose_psylocke.ts
@@ -1,10 +1,43 @@
 import { Effect } from "effect"
+import { sql } from "drizzle-orm"
 import type { DatabaseMigration } from "../migration.js"
 
+const previousV2Marker = "20260730195856_optional_session_title"
+
 const migration: DatabaseMigration.Migration = {
   id: "20260804233008_loose_psylocke",
   up(tx) {
     return Effect.gen(function* () {
+      // This marker identifies the completed pre-split V2 lineage. Its V2 tables
+      // are canonical, so rename them in place instead of replaying the V1 squash.
+      if (yield* tx.get(sql`SELECT id FROM migration WHERE id = ${previousV2Marker}`)) {
+        const v1Only = yield* tx.get(sql`
+          SELECT 1
+          FROM message
+          WHERE NOT EXISTS (
+            SELECT 1 FROM session_message WHERE session_message.session_id = message.session_id
+          )
+          LIMIT 1
+        `)
+        if (v1Only) return yield* Effect.die(new Error("Previous V2 database contains V1-only session history"))
+
+        yield* tx.run(`DROP INDEX IF EXISTS \`session_project_idx\`;`)
+        yield* tx.run(`DROP INDEX IF EXISTS \`session_workspace_idx\`;`)
+        yield* tx.run(`DROP INDEX IF EXISTS \`session_parent_idx\`;`)
+        yield* tx.run(`DROP INDEX IF EXISTS \`session_time_suspended_idx\`;`)
+        yield* tx.run(`ALTER TABLE \`session\` RENAME TO \`session_v2\`;`)
+        yield* tx.run(`CREATE INDEX \`session_v2_project_idx\` ON \`session_v2\` (\`project_id\`);`)
+        yield* tx.run(`CREATE INDEX \`session_v2_workspace_idx\` ON \`session_v2\` (\`workspace_id\`);`)
+        yield* tx.run(`CREATE INDEX \`session_v2_parent_idx\` ON \`session_v2\` (\`parent_id\`);`)
+        yield* tx.run(
+          `CREATE INDEX \`session_v2_time_suspended_idx\` ON \`session_v2\` (\`time_suspended\`) WHERE "session_v2"."time_suspended" is not null;`,
+        )
+        yield* tx.run(`DROP TABLE IF EXISTS \`data_migration\`;`)
+        yield* tx.run(`DROP TABLE IF EXISTS \`session_context_epoch\`;`)
+        yield* tx.run(`DROP TABLE IF EXISTS \`session_input\`;`)
+        return
+      }
+
       yield* tx.run(`
         CREATE TABLE IF NOT EXISTS \`kv\` (
           \`key\` text PRIMARY KEY,
diff --git a/packages/core/test/database-migration.test.ts b/packages/core/test/database-migration.test.ts
index f36124bb2b..1a5460eb88 100644
--- a/packages/core/test/database-migration.test.ts
+++ b/packages/core/test/database-migration.test.ts
@@ -13,6 +13,10 @@ import { tmpdir } from "./fixture/tmpdir"
 import type { SqlClient } from "effect/unstable/sql/SqlClient"
 import legacyCredentialsMigration from "@opencode-ai/core/database/migration/20260805200742_import_legacy_credentials"
 import worktreeMigration from "@opencode-ai/core/database/migration/20260812213948_worktree"
+import previousV2Migration from "@opencode-ai/core/database/migration/20260804233008_loose_psylocke"
+import workspaceMigration from "@opencode-ai/core/database/migration/20260808023530_workspace_domain"
+import executionClaimsMigration from "@opencode-ai/core/database/migration/20260811161259_execution_claim_attempts"
+import sessionInboxMigration from "@opencode-ai/core/database/migration/20260812181746_session_inbox"
 import { Global } from "@opencode-ai/util/global"
 
 const run = <A, E>(
@@ -128,6 +132,142 @@ describe("DatabaseMigration", () => {
     )
   })
 
+  test("preserves previous V2 state through the current migration lineage", async () => {
+    await run(
+      Effect.gen(function* () {
+        const db = yield* makeDb
+        yield* db.run(sql`PRAGMA foreign_keys = ON`)
+        yield* db.run(sql`CREATE TABLE migration (id text PRIMARY KEY, time_completed integer NOT NULL)`)
+        yield* db.run(sql`
+          INSERT INTO migration (id, time_completed)
+          VALUES ('20260730195856_optional_session_title', 1)
+        `)
+        yield* db.run(sql`CREATE TABLE project (id text PRIMARY KEY)`)
+        yield* db.run(sql`
+          CREATE TABLE project_directory (
+            project_id text NOT NULL,
+            directory text NOT NULL,
+            type text,
+            strategy text,
+            time_created integer NOT NULL,
+            PRIMARY KEY (project_id, directory)
+          )
+        `)
+        yield* db.run(sql`
+          CREATE TABLE workspace (
+            id text PRIMARY KEY,
+            type text NOT NULL,
+            name text NOT NULL,
+            project_id text NOT NULL,
+            time_used integer NOT NULL
+          )
+        `)
+        yield* db.run(sql`
+          CREATE TABLE session (
+            id text PRIMARY KEY,
+            project_id text NOT NULL REFERENCES project(id) ON DELETE CASCADE,
+            workspace_id text,
+            parent_id text,
+            time_suspended integer
+          )
+        `)
+        yield* db.run(sql`CREATE INDEX session_project_idx ON session (project_id)`)
+        yield* db.run(sql`CREATE INDEX session_workspace_idx ON session (workspace_id)`)
+        yield* db.run(sql`CREATE INDEX session_parent_idx ON session (parent_id)`)
+        yield* db.run(
+          sql`CREATE INDEX session_time_suspended_idx ON session (time_suspended) WHERE "session"."time_suspended" IS NOT NULL`,
+        )
+        yield* db.run(sql`
+          CREATE TABLE session_message (
+            id text PRIMARY KEY,
+            session_id text NOT NULL REFERENCES session(id) ON DELETE CASCADE,
+            data text NOT NULL
+          )
+        `)
+        yield* db.run(sql`CREATE TABLE message (id text PRIMARY KEY, session_id text NOT NULL)`)
+        yield* db.run(sql`
+          CREATE TABLE session_pending (
+            id text PRIMARY KEY,
+            session_id text NOT NULL REFERENCES session(id) ON DELETE CASCADE
+          )
+        `)
+        yield* db.run(sql`CREATE TABLE event_sequence (aggregate_id text PRIMARY KEY, seq integer NOT NULL)`)
+        yield* db.run(sql`
+          CREATE TABLE event (
+            id text PRIMARY KEY,
+            aggregate_id text NOT NULL REFERENCES event_sequence(aggregate_id) ON DELETE CASCADE,
+            seq integer NOT NULL,
+            created integer NOT NULL,
+            type text NOT NULL,
+            data text NOT NULL
+          )
+        `)
+        yield* db.run(sql`CREATE TABLE data_migration (name text PRIMARY KEY)`)
+        yield* db.run(sql`INSERT INTO project VALUES ('project')`)
+        yield* db.run(sql`INSERT INTO project_directory VALUES ('project', '/repo', 'main', NULL, 1)`)
+        yield* db.run(sql`INSERT INTO session VALUES ('session', 'project', NULL, NULL, NULL)`)
+        yield* db.run(sql`INSERT INTO session_message VALUES ('message', 'session', '{"text":"preserved"}')`)
+        yield* db.run(sql`INSERT INTO session_pending VALUES ('pending', 'session')`)
+        yield* db.run(sql`INSERT INTO event_sequence VALUES ('session', 41)`)
+        yield* db.run(sql`INSERT INTO event VALUES ('event', 'session', 41, 1, 'session.text.ended.1', '{}')`)
+
+        yield* DatabaseMigration.applyOnly(db, [
+          previousV2Migration,
+          workspaceMigration,
+          executionClaimsMigration,
+          sessionInboxMigration,
+          worktreeMigration,
+        ])
+
+        expect(yield* db.get(sql`SELECT id, resume_attempts FROM session_v2`)).toEqual({
+          id: "session",
+          resume_attempts: 0,
+        })
+        expect(yield* db.get(sql`SELECT id, data FROM session_message`)).toEqual({
+          id: "message",
+          data: '{"text":"preserved"}',
+        })
+        expect(yield* db.get(sql`SELECT id FROM session_pending`)).toEqual({ id: "pending" })
+        expect(yield* db.get(sql`SELECT seq FROM event_sequence`)).toEqual({ seq: 41 })
+        expect(yield* db.get(sql`SELECT id, seq FROM event`)).toEqual({ id: "event", seq: 41 })
+        expect(
+          yield* db.get(sql`SELECT name FROM sqlite_master WHERE type = 'table' AND name = 'session'`),
+        ).toBeUndefined()
+        expect(yield* db.get(sql`SELECT directory FROM worktree`)).toEqual({ directory: "/repo" })
+        expect(yield* db.all<{ table: string }>(sql`PRAGMA foreign_key_list(session_message)`)).toContainEqual(
+          expect.objectContaining({ table: "session_v2" }),
+        )
+        expect(yield* db.all<{ table: string }>(sql`PRAGMA foreign_key_list(session_pending)`)).toContainEqual(
+          expect.objectContaining({ table: "session_v2" }),
+        )
+      }),
+    )
+  })
+
+  test("rejects previous V2 databases with V1-only session history", async () => {
+    await run(
+      Effect.gen(function* () {
+        const db = yield* makeDb
+        yield* db.run(sql`CREATE TABLE migration (id text PRIMARY KEY, time_completed integer NOT NULL)`)
+        yield* db.run(sql`
+          INSERT INTO migration (id, time_completed)
+          VALUES ('20260730195856_optional_session_title', 1)
+        `)
+        yield* db.run(sql`CREATE TABLE session (id text PRIMARY KEY)`)
+        yield* db.run(sql`CREATE TABLE session_message (id text PRIMARY KEY, session_id text NOT NULL)`)
+        yield* db.run(sql`CREATE TABLE message (id text PRIMARY KEY, session_id text NOT NULL)`)
+        yield* db.run(sql`INSERT INTO session VALUES ('session')`)
+        yield* db.run(sql`INSERT INTO message VALUES ('message', 'session')`)
+
+        expect((yield* Effect.exit(DatabaseMigration.applyOnly(db, [previousV2Migration])))._tag).toBe("Failure")
+        expect(yield* db.get(sql`SELECT name FROM sqlite_master WHERE type = 'table' AND name = 'session'`)).toEqual({
+          name: "session",
+        })
+        expect(yield* db.get(sql`SELECT id FROM migration WHERE id = ${previousV2Migration.id}`)).toBeUndefined()
+      }),
+    )
+  })
+
   test("copies project directories into worktrees without removing the old table", async () => {
     await run(
       Effect.gen(function* () {