refactor(session): simplify title migration

packages/app/src/components/titlebar-tab-nav.tsx

@@ -11,6 +11,7 @@ import { SessionTabAvatar } from "@/pages/layout/session-tab-avatar"
 import type { Session } from "@opencode-ai/sdk/v2"
 import { canOpenTabRename, forwardTabRef } from "./titlebar-tab-gesture"
 import { TabPreviewPopover } from "./titlebar-tab-popover"
+import { sessionTitle } from "@/utils/session-title"
 import "./titlebar-tab-nav.css"
 
 // MouseEvent.button uses 1 for the middle/wheel button.
@@ -54,7 +55,10 @@ export function TabNavItem(props: {
     if (!session) return
     return projectForSession(session, serverCtx()?.projects.list() ?? [])
   })
-  const title = createMemo(() => props.session()?.title ?? props.fallbackTitle)
+  const title = createMemo(() => {
+    const session = props.session()
+    return session ? sessionTitle(session.title, session.parentID) : props.fallbackTitle
+  })
 
   const projectName = createMemo(() => {
     const session = props.session()
@@ -143,7 +147,7 @@ export function TabNavItem(props: {
     if (!canOpenTabRename(props.dragging, editing(), rename.isPending)) return
     const session = props.session()
     if (!session) return
-    titleEl.textContent = session.title
+    titleEl.textContent = session.title ?? ""
     setEditing(true)
 
     requestAnimationFrame(() => {
@@ -302,7 +306,7 @@ export function TabNavItem(props: {
       }}
       data={{
         projectName: projectName(),
-        title: props.session()?.title,
+        title: title(),
         path: previewPath(),
         serverName: serverLabel(),
       }}

packages/app/src/pages/home/home-session-search-controller.ts

@@ -7,6 +7,7 @@ import { createMemo, onCleanup } from "solid-js"
 import { createStore } from "solid-js/store"
 import type { HomeController } from "./home-controller"
 import { homeSessionSearchKey, type HomeSessionRecord, type HomeSessionsController } from "./home-sessions-controller"
+import { sessionTitle } from "@/utils/session-title"
 
 type HomeSessionSearchSource = Pick<HomeSessionsController, "data" | "session">
 
@@ -23,7 +24,7 @@ export function createHomeSessionSearchController(home: HomeController, sessions
     if (!value) return []
     return sessions.data
       .searchRecords()
-      .filter((record) => `${record.session.title} ${record.projectName}`.toLowerCase().includes(value))
+      .filter((record) => `${sessionTitle(record.session.title)} ${record.projectName}`.toLowerCase().includes(value))
   })
   const active = createMemo(() => {
     const records = results()

packages/app/src/pages/layout/sidebar-items.tsx

@@ -104,7 +104,7 @@ const SessionRow = (props: {
   warmPress: () => void
   warmFocus: () => void
 }): JSX.Element => {
-  const title = () => sessionTitle(props.session.title)
+  const title = () => sessionTitle(props.session.title, props.session.parentID)
 
   return (
     <A
@@ -229,7 +229,7 @@ export const SessionItem = (props: SessionItemProps): JSX.Element => {
               fallback={
                 <Tooltip
                   placement={props.mobile ? "bottom" : "right"}
-                  value={sessionTitle(props.session.title)}
+                  value={sessionTitle(props.session.title, props.session.parentID)}
                   gutter={10}
                   class="min-w-0 w-full"
                 >

packages/app/src/pages/session/timeline/message-timeline.tsx

@@ -297,7 +297,11 @@ export function MessageTimeline(props: {
     return sync().session.get(id)
   })
   const titleValue = createMemo(() => info()?.title)
-  const titleLabel = createMemo(() => sessionTitle(titleValue()))
+  const titleLabel = createMemo(() => {
+    const session = info()
+    if (!session) return
+    return sessionTitle(titleValue(), session.parentID)
+  })
   const shareUrl = createMemo(() => info()?.share?.url)
   const shareEnabled = createMemo(() => sync().data.config.share !== "disabled")
   const parentID = createMemo(() => info()?.parentID)
@@ -311,7 +315,10 @@ export function MessageTimeline(props: {
     if (!id) return emptyMessages
     return sync().data.message[id] ?? emptyMessages
   })
-  const parentTitle = createMemo(() => sessionTitle(parent()?.title) ?? language.t("command.session.new"))
+  const parentTitle = createMemo(() => {
+    const session = parent()
+    return session ? sessionTitle(session.title, session.parentID) : language.t("command.session.new")
+  })
   const getMsgParts = (msgId: string) => sync().data.part[msgId] ?? emptyParts
   const getMsgPart = (messageID: string, partID: string) => getMsgParts(messageID).find((part) => part.id === partID)
   const childTaskDescription = createMemo(() => {
@@ -329,7 +336,7 @@ export function MessageTimeline(props: {
     if (value) return value
     return language.t("command.session.new")
   })
-  const showHeader = createMemo(() => !!(titleValue() || parentID()))
+  const showHeader = createMemo(() => !!(titleLabel() || parentID()))
   const projection = createTimelineProjection({
     messages: sessionMessages,
     userMessages: () => props.userMessages,
@@ -912,9 +919,10 @@ export function MessageTimeline(props: {
   }
 
   function DialogDeleteSession(props: { sessionID: string }) {
-    const name = createMemo(
-      () => sessionTitle(sync().session.get(props.sessionID)?.title) ?? language.t("command.session.new"),
-    )
+    const name = createMemo(() => {
+      const session = sync().session.get(props.sessionID)
+      return session ? sessionTitle(session.title, session.parentID) : language.t("command.session.new")
+    })
     const handleDelete = async () => {
       await deleteSession(props.sessionID)
       dialog.close()

packages/app/src/utils/session-title.test.ts

@@ -0,0 +1,11 @@
+import { describe, expect, test } from "bun:test"
+import { sessionTitle } from "./session-title"
+
+describe("sessionTitle", () => {
+  test("uses a display fallback without persisting it", () => {
+    expect(sessionTitle(undefined)).toBe("New session")
+    expect(sessionTitle(undefined, "ses_parent")).toBe("Child session")
+    expect(sessionTitle("New session - 2026-07-30T18:45:03.662Z")).toBe("New session")
+    expect(sessionTitle("Generated title")).toBe("Generated title")
+  })
+})

packages/app/src/utils/session-title.ts

@@ -1,7 +1,7 @@
 const pattern = /^(New session|Child session) - \d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{3}Z$/
 
-export function sessionTitle(title?: string) {
-  if (!title) return title
+export function sessionTitle(title?: string, parentID?: string) {
+  if (!title) return parentID ? "Child session" : "New session"
   const match = title.match(pattern)
   return match?.[1] ?? title
 }

packages/app/src/utils/session.ts

@@ -13,7 +13,7 @@ export function normalizeSessionInfo(input: SessionInfo | Session): Session {
     parentID: input.parentID,
     cost: input.cost,
     tokens: input.tokens,
-    title: input.title,
+    title: input.title ?? `${input.parentID ? "Child" : "New"} session - ${new Date(input.time.created).toISOString()}`,
     agent: input.agent,
     model: input.model,
     version: "",

packages/cli/src/acp/service.ts

@@ -213,7 +213,9 @@ export function make(input: { readonly client: OpenCodeClient; readonly connecti
         sessions: page.data.map((session) => ({
           sessionId: session.id,
           cwd: session.location.directory,
-          title: session.title,
+          title:
+            session.title ??
+            `${session.parentID ? "Child" : "New"} session - ${new Date(session.time.created).toISOString()}`,
           updatedAt: new Date(session.time.updated).toISOString(),
         })),
         ...(page.cursor.next ? { nextCursor: page.cursor.next } : {}),

packages/client/src/promise/generated/types.ts

@@ -1757,7 +1757,7 @@ export type SessionInfo = {
   cost: MoneyUSD
   tokens: TokenUsageInfo
   time: { created: number; updated: number; archived?: number }
-  title: string
+  title?: string
   location: LocationRef
   subpath?: string
   revert?: SessionRevert
@@ -2006,7 +2006,7 @@ export type SessionV1Info = {
   cost?: number
   tokens?: { input: number; output: number; reasoning: number; cache: { read: number; write: number } }
   share?: { url: string }
-  title: string
+  title?: string
   agent?: string
   model?: { id: string; providerID: string; variant?: string }
   version: string

packages/core/schema.json

@@ -1,9 +1,9 @@
 {
   "version": "7",
   "dialect": "sqlite",
-  "id": "db37a97f-9b5e-4c87-be8b-4feace35136c",
+  "id": "e43ed7e2-b9fc-4178-beae-3646e4a976e1",
   "prevIds": [
-    "a4ba73b4-21bc-41ab-a415-94e2ca38d798"
+    "db37a97f-9b5e-4c87-be8b-4feace35136c"
   ],
   "ddl": [
     {
@@ -1302,7 +1302,7 @@
     },
     {
       "type": "text",
-      "notNull": true,
+      "notNull": false,
       "autoincrement": false,
       "default": null,
       "generated": null,

packages/core/src/database/migration.gen.ts

@@ -58,5 +58,6 @@ export const migrations = (
     import("./migration/20260722011141_delete_tool_progress_events"),
     import("./migration/20260722170000_canonical_tool_results"),
     import("./migration/20260729022634_session_fork_boundary"),
+    import("./migration/20260730195856_optional_session_title"),
   ])
 ).map((module) => module.default) satisfies DatabaseMigration.Migration[]

packages/core/src/database/migration/20260730195856_optional_session_title.ts

@@ -0,0 +1,14 @@
+import { Effect } from "effect"
+import type { DatabaseMigration } from "../migration"
+
+export default {
+  id: "20260730195856_optional_session_title",
+  up(tx) {
+    return Effect.gen(function* () {
+      yield* tx.run(`ALTER TABLE \`session\` RENAME COLUMN \`title\` TO \`title_old\``)
+      yield* tx.run(`ALTER TABLE \`session\` ADD COLUMN \`title\` text`)
+      yield* tx.run(`UPDATE \`session\` SET \`title\` = \`title_old\``)
+      yield* tx.run(`ALTER TABLE \`session\` DROP COLUMN \`title_old\``)
+    })
+  },
+} satisfies DatabaseMigration.Migration

packages/core/src/database/schema.gen.ts

@@ -217,7 +217,7 @@ export default {
           \`slug\` text NOT NULL,
           \`directory\` text NOT NULL,
           \`path\` text,
-          \`title\` text NOT NULL,
+          \`title\` text,
           \`version\` text NOT NULL,
           \`share_url\` text,
           \`summary_additions\` integer,

packages/core/src/session.ts

@@ -374,7 +374,7 @@ const layer = Layer.effect(
           directory: location.directory,
           path: path.relative(project.directory, location.directory).replaceAll("\\", "/"),
           workspaceID: location.workspaceID ? Workspace.ID.make(location.workspaceID) : undefined,
-          title: input.title ?? `New session - ${new Date(now).toISOString()}`,
+          title: input.title,
           agent: input.agent,
           model: input.model
             ? {

packages/core/src/session/info.ts

@@ -17,7 +17,7 @@ export function fromRow(row: typeof SessionTable.$inferSelect): SessionSchema.In
   return SessionSchema.Info.make({
     id: SessionSchema.ID.make(row.id),
     projectID: Project.ID.make(row.project_id),
-    title: row.title,
+    title: row.title ?? undefined,
     parentID: row.parent_id ? SessionSchema.ID.make(row.parent_id) : undefined,
     fork:
       row.fork_session_id && row.fork_boundary

packages/core/src/session/projector.ts

@@ -43,7 +43,8 @@ type Usage = {
 
 const ForkBatchSize = 500
 
-const forkTitle = (value: string) => {
+const forkTitle = (value?: string) => {
+  if (value === undefined) return
   const match = value.match(/^(.+) \(fork #(\d+)\)$/)
   if (match) return `${match[1]} (fork #${Number.parseInt(match[2], 10) + 1})`
   return `${value} (fork #1)`
@@ -216,7 +217,7 @@ const projectFork = Effect.fn("SessionProjector.projectFork")(function* (
       slug: Slug.create(),
       directory: parent.directory,
       path: parent.path,
-      title: forkTitle(parent.title),
+      title: forkTitle(parent.title ?? undefined),
       agent: parent.agent,
       model: parent.model,
       version: parent.version,

packages/core/src/session/sql.ts

@@ -36,7 +36,7 @@ export const SessionTable = sqliteTable(
     slug: text().notNull(),
     directory: directoryColumn().notNull(),
     path: pathColumn(),
-    title: text().notNull(),
+    title: text(),
     version: text().notNull(),
     share_url: text(),
     summary_additions: integer(),

packages/core/test/database-migration.test.ts

@@ -26,6 +26,7 @@ import timeSuspendedMigration from "@opencode-ai/core/database/migration/2026070
 import instructionSyncMigration from "@opencode-ai/core/database/migration/20260710025429_instruction_sync"
 import deleteToolProgressEventsMigration from "@opencode-ai/core/database/migration/20260722011141_delete_tool_progress_events"
 import canonicalToolResultsMigration from "@opencode-ai/core/database/migration/20260722170000_canonical_tool_results"
+import optionalSessionTitleMigration from "@opencode-ai/core/database/migration/20260730195856_optional_session_title"
 import { AppNodeBuilder } from "@opencode-ai/core/effect/app-node-builder"
 import { LayerNode } from "@opencode-ai/util/effect/layer-node"
 import { Bus } from "@opencode-ai/core/bus"
@@ -399,6 +400,40 @@ describe("DatabaseMigration", () => {
     ).rejects.toThrow("Database is not empty and has no session table")
   })
 
+  test("makes session titles nullable without deleting dependent rows", async () => {
+    await run(
+      Effect.gen(function* () {
+        const db = yield* makeDb
+        yield* db.run(sql`PRAGMA foreign_keys = ON`)
+        yield* db.run(sql`
+          CREATE TABLE session (
+            id text PRIMARY KEY,
+            title text NOT NULL
+          )
+        `)
+        yield* db.run(sql`
+          CREATE TABLE message (
+            id text PRIMARY KEY,
+            session_id text NOT NULL REFERENCES session(id) ON DELETE CASCADE
+          )
+        `)
+        yield* db.run(sql`INSERT INTO session VALUES ('ses_existing', 'Existing title')`)
+        yield* db.run(sql`INSERT INTO message VALUES ('msg_existing', 'ses_existing')`)
+
+        yield* DatabaseMigration.applyOnly(db, [optionalSessionTitleMigration])
+
+        expect(yield* db.get(sql`SELECT title FROM session WHERE id = 'ses_existing'`)).toEqual({
+          title: "Existing title",
+        })
+        expect(yield* db.get(sql`SELECT id FROM message WHERE id = 'msg_existing'`)).toEqual({ id: "msg_existing" })
+        expect(
+          yield* db.get<{ notnull: number }>(sql`SELECT "notnull" FROM pragma_table_info('session') WHERE name = 'title'`),
+        ).toEqual({ notnull: 0 })
+        expect(yield* db.get<{ foreign_keys: number }>(sql`PRAGMA foreign_keys`)).toEqual({ foreign_keys: 1 })
+      }),
+    )
+  })
+
   test("backfills existing Context Epoch rows to the build agent", async () => {
     await run(
       Effect.gen(function* () {

packages/core/test/session-create.test.ts

@@ -71,6 +71,27 @@ function withTmp<A, E, R>(f: (directory: string) => Effect.Effect<A, E, R>) {
 }
 
 describe("Session.create", () => {
+  it.effect("persists a missing title until one is generated or supplied", () =>
+    Effect.gen(function* () {
+      const session = yield* Session.Service
+      const { db } = yield* Database.Service
+
+      const created = yield* session.create({ location })
+      const row = yield* db.select().from(SessionTable).where(eq(SessionTable.id, created.id)).get().pipe(Effect.orDie)
+      const event = yield* db
+        .select({ data: EventTable.data })
+        .from(EventTable)
+        .where(eq(EventTable.aggregate_id, created.id))
+        .get()
+        .pipe(Effect.orDie)
+
+      expect(created.title).toBeUndefined()
+      expect(row?.title).toBeNull()
+      expect(event?.data).not.toHaveProperty("info.title")
+      expect((yield* session.create({ location, title: "Explicit title" })).title).toBe("Explicit title")
+    }),
+  )
+
   it.effect("creates a fresh projected session when the ID is omitted", () =>
     Effect.gen(function* () {
       const session = yield* Session.Service
@@ -296,6 +317,23 @@ describe("Session.create", () => {
     }),
   )
 
+  it.effect("keeps a fork untitled when its parent is untitled", () =>
+    Effect.gen(function* () {
+      const session = yield* Session.Service
+      const bus = yield* Bus.Service
+      const { db } = yield* Database.Service
+      const parent = yield* session.create({ location })
+      yield* session.prompt({ sessionID: parent.id, text: "First", resume: false })
+      yield* SessionPending.promote(db, bus, parent.id, "steer")
+
+      const forked = yield* session.fork({ sessionID: parent.id, boundary: { type: "through" } })
+      const row = yield* db.select().from(SessionTable).where(eq(SessionTable.id, forked.id)).get().pipe(Effect.orDie)
+
+      expect(forked.title).toBeUndefined()
+      expect(row?.title).toBeNull()
+    }),
+  )
+
   it.effect("rejects forking an empty session", () =>
     Effect.gen(function* () {
       const session = yield* Session.Service

packages/core/test/tool-subagent.test.ts

@@ -47,7 +47,7 @@ const executionNode = makeGlobalNode({
       const completed = new Set<Session.ID>()
       const complete = Effect.fn("SubagentTest.complete")(function* (sessionID: Session.ID) {
         if (completed.has(sessionID)) return
-        if ((yield* store.get(sessionID))?.title.includes("fail")) {
+        if ((yield* store.get(sessionID))?.title?.includes("fail")) {
           yield* new SessionRunnerModel.ModelNotSelectedError({ sessionID })
           return
         }

packages/enterprise/src/routes/share/[shareID].tsx

@@ -167,7 +167,8 @@ export default function () {
               }
             }
             const modelIDs = Array.from(models)
-            const encodedTitle = encodeURIComponent(Base64.encode(encodeURIComponent(info().title.substring(0, 700))))
+            const title = info().title ?? `New session - ${new Date(info().time.created).toISOString()}`
+            const encodedTitle = encodeURIComponent(Base64.encode(encodeURIComponent(title.substring(0, 700))))
             let modelParam: string
             if (modelIDs.length === 1) {
               modelParam = modelIDs[0]

packages/schema/src/session.ts

@@ -42,7 +42,7 @@ export const Info = Schema.Struct({
     updated: DateTimeUtcFromMillis,
     archived: DateTimeUtcFromMillis.pipe(optional),
   }),
-  title: Schema.String,
+  title: Schema.String.pipe(optional),
   location: Location.Ref,
   subpath: RelativePath.pipe(optional),
   revert: Revert.pipe(optional),

packages/schema/src/v1/session.ts

@@ -552,7 +552,7 @@ export const SessionInfo = Schema.Struct({
   cost: optional(Schema.Finite),
   tokens: optional(SessionTokens),
   share: optional(SessionShare),
-  title: Schema.String,
+  title: optional(Schema.String),
   agent: optional(Schema.String),
   model: optional(SessionModel),
   version: Schema.String,

packages/schema/test/contract-hygiene.test.ts

@@ -17,7 +17,7 @@ import { Money } from "../src/money.js"
 import { Skill } from "../src/skill.js"
 import { Shell } from "../src/shell.js"
 import { PersistedRevert } from "../src/session-revert.js"
-import { optional } from "../src/schema.js"
+import { AbsolutePath, optional } from "../src/schema.js"
 
 describe("contract hygiene", () => {
   test("restricts agent colors to six-digit hex values", () => {
@@ -52,6 +52,18 @@ describe("contract hygiene", () => {
         metadata: undefined,
       }),
     ).toEqual({ text: "completed" })
+
+    expect(
+      Schema.encodeSync(Session.Info)({
+        id: Session.ID.make("ses_untitled"),
+        projectID: Project.ID.make("global"),
+        cost: Money.USD.zero,
+        tokens: { input: 0, output: 0, reasoning: 0, cache: { read: 0, write: 0 } },
+        time: { created: DateTime.makeUnsafe(0), updated: DateTime.makeUnsafe(0) },
+        title: undefined,
+        location: { directory: AbsolutePath.make("/project") },
+      }),
+    ).not.toHaveProperty("title")
   })
 
   test("pending session items omit the internal admission sequence", () => {

packages/tui/src/app.tsx

@@ -536,13 +536,13 @@ function App(props: { pair?: DialogPairCredentials }) {
 
     if (route.data.type === "session") {
       const session = data.session.get(route.data.sessionID)
-      if (!session || isDefaultTitle(session.title)) {
+      const title = session?.title
+      if (!title || isDefaultTitle(title)) {
         renderer.setTerminalTitle("OpenCode")
         return
       }
 
-      const title = session.title.length > 40 ? session.title.slice(0, 37) + "..." : session.title
-      renderer.setTerminalTitle(`OC | ${title}`)
+      renderer.setTerminalTitle(`OC | ${title.length > 40 ? title.slice(0, 37) + "..." : title}`)
       return
     }
 

packages/tui/src/component/dialog-session-list.tsx

@@ -17,6 +17,7 @@ import { DialogSessionRename } from "./dialog-session-rename"
 import { Spinner } from "./spinner"
 import { errorMessage } from "../util/error"
 import { useSessionTabs } from "../context/session-tabs"
+import { sessionTitle } from "../util/session"
 
 export function DialogSessionList() {
   const dialog = useDialog()
@@ -75,7 +76,7 @@ export function DialogSessionList() {
           (session.projectID === current?.project.id && session.location.directory === current.directory),
       )
     if (!query) return sessions
-    return sessions.filter((session) => !session.parentID && session.title.toLowerCase().includes(query))
+    return sessions.filter((session) => !session.parentID && sessionTitle(session).toLowerCase().includes(query))
   })
   const sessions = createMemo(() => {
     const query = filter().trim()
@@ -137,7 +138,7 @@ export function DialogSessionList() {
       const slot = sessionTabs.enabled() ? undefined : slotByID.get(session.id)
       const deleting = toDelete() === session.id
       return {
-        title: deleting ? `Press ${shortcuts.get("session.delete")} again to confirm` : session.title,
+        title: deleting ? `Press ${shortcuts.get("session.delete")} again to confirm` : sessionTitle(session),
         value: session.id,
         category,
         footer,

packages/tui/src/context/session-tabs.tsx

@@ -3,6 +3,7 @@ import { isDeepEqual } from "remeda"
 import { createSimpleContext } from "./helper"
 import { useClient } from "./client"
 import { useData } from "./data"
+import { sessionTitle } from "../util/session"
 import { useEvent } from "./event"
 import { useRoute } from "./route"
 import { useConfig } from "../config"
@@ -114,7 +115,8 @@ export const { use: useSessionTabs, provider: SessionTabsProvider } = createSimp
       if (route.data.type !== "session" || route.data.sessionID === "dummy") return
       const sessionID = root(route.data.sessionID)
       history = recordSessionTabHistory(history, sessionID)
-      const title = data.session.get(sessionID)?.title ?? (newTab() ? NEW_SESSION_TAB_TITLE : undefined)
+      const session = data.session.get(sessionID)
+      const title = session?.title ?? (newTab() ? NEW_SESSION_TAB_TITLE : session ? sessionTitle(session) : undefined)
       const tabs = openSessionTab(state().tabs, { sessionID, title })
       if (tabs === state().tabs && !state().unread[sessionID]) return
       update((draft) => {
@@ -127,7 +129,8 @@ export const { use: useSessionTabs, provider: SessionTabsProvider } = createSimp
       if (!enabled()) return
       const next = state().tabs.reduce<SessionTab[]>((tabs, tab) => {
         const sessionID = root(tab.sessionID)
-        return openSessionTab(tabs, { sessionID, title: data.session.get(sessionID)?.title ?? tab.title })
+        const session = data.session.get(sessionID)
+        return openSessionTab(tabs, { sessionID, title: session ? sessionTitle(session) : tab.title })
       }, [])
       const unread = Object.entries(state().unread).reduce<Record<string, SessionTabUnread>>((result, entry) => {
         const sessionID = root(entry[0])
@@ -138,7 +141,8 @@ export const { use: useSessionTabs, provider: SessionTabsProvider } = createSimp
       update((draft) => {
         draft.tabs = draft.tabs.reduce<SessionTab[]>((tabs, tab) => {
           const sessionID = root(tab.sessionID)
-          return openSessionTab(tabs, { sessionID, title: data.session.get(sessionID)?.title ?? tab.title })
+          const session = data.session.get(sessionID)
+          return openSessionTab(tabs, { sessionID, title: session ? sessionTitle(session) : tab.title })
         }, [])
         draft.unread = Object.entries(draft.unread).reduce<Record<string, SessionTabUnread>>((result, entry) => {
           const sessionID = root(entry[0])

packages/tui/src/routes/session/composer/subagents-tab.tsx

@@ -8,6 +8,7 @@ import { useTheme } from "../../../context/theme"
 import { Locale } from "../../../util/locale"
 import { Keymap } from "../../../context/keymap"
 import { useComposerTab } from "./index"
+import { sessionTitle } from "../../../util/session"
 
 interface SubagentEntry {
   sessionID: string
@@ -38,13 +39,14 @@ export function SubagentsTab(props: { sessionID: string }) {
     if (current.parentID) {
       const siblings = data.session.list().filter((s) => s.parentID === current.parentID)
       for (const sibling of siblings) {
-        const agentMatch = sibling.title.match(/@(\w+) subagent/)
+        const title = sessionTitle(sibling)
+        const agentMatch = title.match(/@(\w+) subagent/)
         const agent = sibling.agent
           ? Locale.titlecase(sibling.agent)
           : agentMatch
             ? Locale.titlecase(agentMatch[1])
             : "Subagent"
-        const name = agentMatch ? sibling.title.replace(agentMatch[0], "").trim() || sibling.title : sibling.title
+        const name = agentMatch ? title.replace(agentMatch[0], "").trim() || title : title
         result.push({
           sessionID: sibling.id,
           agent,
@@ -56,13 +58,14 @@ export function SubagentsTab(props: { sessionID: string }) {
     } else {
       const children = data.session.list().filter((s) => s.parentID === props.sessionID)
       for (const child of children) {
-        const agentMatch = child.title.match(/@(\w+) subagent/)
+        const title = sessionTitle(child)
+        const agentMatch = title.match(/@(\w+) subagent/)
         const agent = child.agent
           ? Locale.titlecase(child.agent)
           : agentMatch
             ? Locale.titlecase(agentMatch[1])
             : "Subagent"
-        const name = agentMatch ? child.title.replace(agentMatch[0], "").trim() || child.title : child.title
+        const name = agentMatch ? title.replace(agentMatch[0], "").trim() || title : title
         result.push({
           sessionID: child.id,
           agent,

packages/tui/src/routes/session/index.tsx

@@ -92,6 +92,7 @@ import { switchLabel } from "../../util/model"
 import { findMessageBoundary, messageNavigationSlack } from "./message-navigation"
 import { stringWidth } from "../../util/string-width"
 import { useArgs } from "../../context/args"
+import { sessionTitle } from "../../util/session"
 
 addDefaultParsers(parsers.parsers)
 
@@ -3307,7 +3308,7 @@ function formatSessionTranscript(session: SessionInfo, messages: SessionMessageI
     })
     return [`## Assistant\n\n${content.join("\n\n")}`]
   })
-  return `# ${session.title}\n\n**Session ID:** ${session.id}\n**Created:** ${new Date(session.time.created).toLocaleString()}\n**Updated:** ${new Date(session.time.updated).toLocaleString()}\n\n---\n\n${body.join("\n\n---\n\n")}\n`
+  return `# ${sessionTitle(session)}\n\n**Session ID:** ${session.id}\n**Created:** ${new Date(session.time.created).toLocaleString()}\n**Updated:** ${new Date(session.time.updated).toLocaleString()}\n\n---\n\n${body.join("\n\n---\n\n")}\n`
 }
 
 export function parseApplyPatchFiles(value: unknown) {

packages/tui/src/routes/session/sidebar.tsx

@@ -3,6 +3,7 @@ import { createMemo, Show } from "solid-js"
 import { useTheme } from "../../context/theme"
 import { useConfig } from "../../config"
 import { PluginSlot } from "../../plugin/context"
+import { sessionTitle } from "../../util/session"
 
 import { getScrollAcceleration } from "../../util/scroll"
 
@@ -38,7 +39,7 @@ export function Sidebar(props: { sessionID: string; overlay?: boolean }) {
           <box flexShrink={0} gap={1} paddingRight={1}>
             <box paddingRight={1}>
               <text fg={theme.text.default}>
-                <b>{session()!.title}</b>
+                <b>{sessionTitle(session()!)}</b>
               </text>
               <Show when={session()!.location.workspaceID}>
                 <text fg={theme.text.subdued}>{session()!.location.workspaceID}</text>

packages/tui/src/util/session.ts

@@ -1,8 +1,16 @@
-import type { ModelInfo, SessionMessageAssistant, SessionMessageInfo } from "@opencode-ai/client"
+import type { ModelInfo, SessionInfo, SessionMessageAssistant, SessionMessageInfo } from "@opencode-ai/client"
 import { Locale } from "./locale"
 
-export function isDefaultTitle(title: string) {
-  return /^(New session - |Child session - )\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{3}Z$/.test(title)
+export function isDefaultTitle(title?: string) {
+  return (
+    title === undefined || /^(New session - |Child session - )\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{3}Z$/.test(title)
+  )
+}
+
+export function sessionTitle(session: Pick<SessionInfo, "parentID" | "time" | "title">) {
+  return (
+    session.title ?? `${session.parentID ? "Child" : "New"} session - ${new Date(session.time.created).toISOString()}`
+  )
 }
 
 export function lastAssistantWithUsage(messages: ReadonlyArray<SessionMessageInfo>, boundary?: string) {

packages/tui/test/util/session.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, test } from "bun:test"
 import type { SessionMessageInfo } from "@opencode-ai/client"
-import { isDefaultTitle, lastAssistantWithUsage } from "../../src/util/session"
+import { isDefaultTitle, lastAssistantWithUsage, sessionTitle } from "../../src/util/session"
 
 const assistant = (id: string, input: number): SessionMessageInfo => ({
   id,
@@ -14,11 +14,21 @@ const assistant = (id: string, input: number): SessionMessageInfo => ({
 
 describe("util.session", () => {
   test("recognizes generated parent and child titles", () => {
+    expect(isDefaultTitle(undefined)).toBeTrue()
     expect(isDefaultTitle("New session - 2026-06-06T12:34:56.789Z")).toBeTrue()
     expect(isDefaultTitle("Child session - 2026-06-06T12:34:56.789Z")).toBeTrue()
     expect(isDefaultTitle("New session - custom")).toBeFalse()
   })
 
+  test("derives display-only titles for untitled sessions", () => {
+    expect(sessionTitle({ title: undefined, time: { created: 0, updated: 0 } })).toBe(
+      "New session - 1970-01-01T00:00:00.000Z",
+    )
+    expect(sessionTitle({ title: undefined, parentID: "ses_parent", time: { created: 0, updated: 0 } })).toBe(
+      "Child session - 1970-01-01T00:00:00.000Z",
+    )
+  })
+
   test("tracks usage across undo and redo boundaries", () => {
     const messages = [assistant("msg_z", 10), assistant("msg_a", 30)]