[braindeadz]

Summary

Let Android users rename a remote session from the session list, the action
sheet/popup and the sidebar rail, and stop the shared mobile layer from
inventing placeholder titles for sessions the desktop has not named.

Root cause, verified in code on the base commit: the rename path already
existed end to end — the conversation header dispatched
RemoteSessionIntent.RenameSession, RemoteSessionStore.renameSession handled
it, sending update_session_title — but SessionActionPolicy
never exposed a rename capability, and the action sheet, the session list and
the sidebar never drew a row for it. Separately, three different English
placeholders made an unnamed session look named and made a successful rename
look like it had not been applied:

• shared SessionNaming.fallbackTitle returned "New Session";
• shared RemoteResponseMapper fabricated "Session <id-prefix>" from the id;
• the Android conversation header fell back to "Remote session".

A host that has not named a session sends no title at all. The shared layer now
keeps that title blank and each surface renders its own localized "untitled"
wording (sidebar_untitled on Android).

Fixes #

This PR is related to #3809 but does not close it. #3809 is about the legacy Android APK persisting "Remote Code Session" as a user-edited title on 1.0.7+ hosts. This change stops this client from inventing titles and adds the rename action, but it cannot clear a title the host already holds, and it does not add a host-side compatibility path or ship a new APK. That work remains open in #3809.

Type and Areas

Type:

• Bug fix (with a small feature: a previously unreachable action is now
  surfaced).

Areas:

• Mobile client (Kotlin Multiplatform shared core + Android Compose app).
• No Rust core, desktop, web UI, server or relay changes.

Motivation / Impact

What was broken for a remote-session user. Opening the overflow menu on a
session offered View details, Archive/Export (general chat only) and
Delete — never Rename. To rename, the user had to open the conversation and
use the header's title editor. Worse, a session the desktop had not named yet
showed a fabricated English title ("New Session", "Session <id-prefix>",
"Remote session" depending on the surface), so an untitled session looked
titled, and after a rename the header and the list could disagree until a
refresh.

What changes.

• The action sheet, the anchored popup and the sidebar rail now offer a
  Rename row that opens an inline title field seeded with the current title.
• A blank host title is rendered as the localized sidebar_untitled label on
  every Android surface (list row, rail, header, sheet, home recent row) instead
  of an invented English name.
• The shared layer no longer fabricates a title; it keeps the host's word or an
  empty string.

Design.

• SessionActionCapabilities gains an appended canRename flag rather than
  folding rename into canArchive/canExport. For a remote session rename is a
  round trip to the desktop; for a general chat it rewrites the stored row. It
  is neither of the local-storage operations those flags describe, so a separate
  flag reads correctly in both scopes. Appending it keeps the four existing
  positional arguments meaning what they meant.
• The sheet/popup/sidebar take an optional onRename callback. A shell that
  cannot dispatch a rename renders no row rather than a row that does nothing —
  the same pattern archive and export already use.
• The host keeps authority. The surface only names the new title; the store
  keeps the old title in the list until the desktop answers
  update_session_title (it updates the local row only after the command is
  sent, and re-reads busy so a command that started while the field was open
  cannot submit).
• The editor trims, refuses an empty or unchanged draft, and caps the draft at
  120 characters client-side (the host normalizes and refuses an empty title;
  the cap is the client's own guard against pasting a document into a one-line
  row). A session whose existing host title already exceeds 120 characters
  therefore cannot be saved without shortening it, and Save is disabled with no
  explanation of its own.
• A blank title is rendered per surface via sidebar_untitled, not replaced by
  a fabricated English string.

Verification

All commands were run on Windows with the project's local Android build
environment (node 22.23.5, JDK 17, Android SDK). Test counts are read from the
Gradle JUnit XML reports.

Baseline (base commit, no changes applied)

• From src/apps/mobile/shared:
  .\gradlew.bat --console=plain :core-domain:jvmTest :core-feature:jvmTest
  → 655 tests, 0 failures, 0 errors, 0 skipped (BUILD SUCCESSFUL).
• From src/apps/mobile/android:
  .\gradlew.bat --console=plain :app:testDebugUnitTest
  → 65 tests, 1 failure, 0 errors, 0 skipped. The single failure is
  pre-existing on the official base commit:
  com.openbitfun.mobile.app.ui.chat.ProcessPresentationTest.completedWorkSummarizesWithoutHidingLiveOrFailedTools
  with java.lang.AssertionError: expected:<3> but was:<1>
  (ProcessPresentationTest.kt:44).

After the change

• Shared, same command → 657 tests, 0 failures, 0 errors, 0 skipped
  (BUILD SUCCESSFUL). The two extra tests are the new/renamed ones below.
• Android unit, same command → 65 tests, 1 failure, 0 errors, 0 skipped.
  The failure is the same ProcessPresentationTest.completedWorkSummarizesWithoutHidingLiveOrFailedTools
  test with the same java.lang.AssertionError: expected:<3> but was:<1>
  message — an unchanged baseline failure, not a regression. This suite is not
  green on the base commit and this PR does not make it green.
• Instrumented tests: the 10 tests in SessionRenameActionTest were executed on a
  real Android device against the original revision of this branch and passed
  10/10 (author-reported; not run by the AI). The amended revision adds
  aSurfaceWithoutARenameCallbackDrawsNoRenameRow and drops the unused
  conversation_title_default string resource; that amended revision is
  compile-verified only, from src/apps/mobile/android,
  .\gradlew.bat --console=plain :app:compileDebugAndroidTestKotlin
  → BUILD SUCCESSFUL. No instrumented test was re-run here, and this does not
  claim the added test passed. AppSidebar's onRenameRemoteSession id+title
  adaptation is covered by compilation only (no widget test renders the sidebar
  rail).

Node guards (from the repo root)

• node scripts/check-mobile-architecture.mjs → PASS:
  "Mobile shared core architecture contracts are satisfied."
• node --test scripts/mobile-client-build.contract.test.mjs → PASS:
  2 tests, 0 failures.
• node scripts/mobile-ui-design-system.mjs --check → PASS:
  "Contract and generated files are in sync."
• node scripts/check-git-object-sizes.mjs --base upstream/main --head HEAD
  → PASS: "Checked 16 Git blobs; no unapproved objects exceed 5242880
  bytes."
• node scripts/mobile-ui-preview.mjs --check → SKIPPED:
  "Missing canonical design-system asset for /design-system-tokens.css." The
  script needs the generated design-system/packages/design-tokens/dist/tokens.css
  (produced by a design-system build); this checkout has no node_modules and
  pnpm is unavailable, so the asset is absent. Nothing was installed.
• node scripts/i18n-audit.mjs → SKIPPED:
  "Failed to load TypeScript for i18n audit: Cannot find module 'typescript'
  … Run pnpm install before running pnpm run i18n:audit." Missing dependency;
  nothing was installed.
• node scripts/audit-frontend-colors.mjs --kind native-mobile → SKIPPED:
  "exclusions[2].path does not exist: src/web-ui/public/monaco-editor". The
  script needs a vendored/generated web-ui asset that a full install would
  provide; absent here.

None of the three skipped scripts read the files changed by this PR (verified by
grep), and all three fail for missing build output or missing packages, not for
anything in this diff.

Verification evidence (for the reviewer)

New/updated shared unit tests:

• SessionListPolicyTest.fallbackTitleStaysBlankForEveryMode (replaces
  fallbackTitleIsIndependentOfMode).
• SessionActionPolicyTest.aRemoteSessionOffersRenameButNeverTheLocalStorageActions
  (renamed from aRemoteSessionNeverOffersTheLocalStorageActions).
• SessionActionPolicyTest.theRenameFlagWasAppendedSoEarlierPositionsKeepTheirMeaning
  (new — pins that the appended flag does not shift the earlier positions).
• SessionActionPolicyTest.archiveAndExportBelongToGeneralChatAlone (updated to
  the new capability shape).
• SessionActionPolicyTest.aCommandInFlightWithdrawsEverything (updated).
• RemoteResponseMapperTest.aHostTitleThatIsMissingStaysBlankAndATitledSessionKeepsItsName
  (new — blank/missing title stays blank, a real title is kept).

New instrumented tests (SessionRenameActionTest, test tags
session-rename-row and session-rename-field):

• theRemoteMenuOffersRenameAndSeedsTheFieldWithTheCurrentTitle
• submittingSendsOneRenameForThisSessionAndDismisses
• theSubmittedTitleIsTheTrimmedDraft
• aBlankHostTitleIsShownAsUntitledAndCanBeGivenAName
• cancellingReturnsToTheActionListAndSendsNothing
• anUnchangedOrBlankTitleCannotBeSubmitted
• aCommandStartingWhileTheEditorIsOpenCannotBeSubmitted
• aCommandInFlightOffersNoRename
• theWideSidebarPopupOffersTheSameStep
• theHomeRecentRowShowsTheUntitledLabelForABlankHostTitle
• aSurfaceWithoutARenameCallbackDrawsNoRenameRow

Updated instrumented test: ConversationHeaderTest now asserts a blank title
renders sidebar_untitled.

The now-unreferenced conversation_title_default string was deleted from both
src/apps/mobile/android/app/src/main/res/values/strings.xml and
src/apps/mobile/android/app/src/main/res/values-zh/strings.xml; no production
or test code reads it any more.

Reviewer Notes

This PR closes no issue. (Fixes # is deliberately left empty; see the Summary note about #3809.)

Compatibility (this touches shared code used by other clients)

• SessionActionCapabilities is a Kotlin data class consumed only by Kotlin
  code (the Android app and shared tests). The HarmonyOS client has its own
  parallel SessionActionCapabilities class in
  pages/policy/SessionActionPolicy.ets and does not consume the Kotlin one, so
  the appended field does not touch it. The iOS client has no caller of the
  Kotlin SessionActionCapabilities, so the appended field is not a compile
  break for it.
• SessionNaming.fallbackTitle now returns "". Its only Kotlin caller is the
  shared RemoteSessionStore (when a new session has no title). HarmonyOS uses
  its own ArkTS RemoteResponseMapper and is unaffected. On iOS, several
  surfaces already render an empty title as a localized "untitled" label
  (SessionActionComponents, MobileAppModel+RemoteSession,
  ConversationHeader), but a few raw Text(session.title) sites (e.g. the
  home recent row and some sidebar rows) will now show a blank line where a
  fabricated "Session <id>" used to appear. That is a rendering difference on
  iOS, not a crash or compile break; a follow-up may want to route those raw
  sites through the same localized "untitled" label.
• RemoteSessionUiState.Ready(...) is constructed only inside the shared store
  and shared tests; iOS/HarmonyOS reach it through their bridges, not by
  constructing it directly, so no break.
• RemoteSessionIntent.RenameSession already existed on the base commit
  (handled in RemoteSessionStore.renameSession, dispatched by the Android
  conversation header, sending update_session_title). The claim of this PR is
  therefore "the rename path existed but no list/sheet/sidebar UI offered it",
  not "rename was implemented".

What a remote-session user sees

• Before: an untitled session showed a fabricated English name; rename was only
  reachable from the conversation header.
• After: an untitled session reads as the localized "Untitled session" on every
  Android surface; Rename is available from the list, the sheet, the popup and
  the sidebar rail; the row keeps its old title until the desktop acknowledges
  the change; if the desktop refuses, the title is unchanged and the failure is
  reported only through the connection state (see Limitations).

Limitations / risks to attack

• No live host round trip was run by the AI. The AI did not run a live desktop host, so update_session_title against a real (and especially an older or third-party) host is unverified here. A host that rejects update_session_title does not merely leave the old title: the store's shared handleFailure discards the rejection message and, for a RemoteRejected/CLI_NOT_IMPLEMENTED answer, sets the connection phase to FAILED (RemoteSessionStore.kt:2215-2233). The session list survives, but until the 10 s health probe recovers, the status bar reads as a connection error and the remote composer is disabled. The user is told nothing about the rename itself. This is pre-existing store behaviour that this PR makes reachable from the list, and it is not fixed here.
• The amendment is the unverified delta. The real-device run covers the
  original revision (10/10 SessionRenameActionTest tests, author-reported). The
  amended revision — the added aSurfaceWithoutARenameCallbackDrawsNoRenameRow
  test and the removed conversation_title_default resource — has only been
  compile-verified here, not re-run on a device, so changes in that delta are not
  device-proven.
• The rename editor caps drafts at 120 characters, while
  ui/chat/ConversationHeader.TitleEditor caps nothing. The two editors differ
  here; that inconsistency is known and deliberately not widened by this PR.
• A pre-existing delete-confirmation branch reads no capability (so an
  already-open confirmation can still submit after busy flips). It is out of
  scope and is left untouched, with a code comment marking it.
• Three node guards are skipped for missing build output / missing packages (see
  Verification); none read the files in this diff.

Honesty disclosure

AI-assisted implementation; testing level: lightly tested. The AI ran no
device and no live desktop host. A real-device run of the original instrumented
suite exists and is author-reported (see Verification and Limitations); the AI
only compiled the amended revision.

Author-reported (not independently verified by the AI): the contributor
manually smoke-tested the rename on a real desktop host from one Android device,
and the new title appeared both in the session list and in the conversation
header. A screenshot of that run is withheld because it shows a private
workspace name.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.