Show unsupported workspace via the standard session error banner + fit-to-transcript error height (JetBrains)

Goal

1. When a JetBrains workspace directory is unsupported for the host-side CLI runtime (devcontainer / WSL / invalid virtual path), surface it through the existing in-session connection banner (ConnectionPanel) instead of silently showing "Loading…" forever. It gets the same recovery options as other connection errors (Try again → Retry / Restart / Reinstall Core).
2. Change the expanded error/detail area so it fits the whole detail text, capped to the available height of the session transcript area (instead of the current fixed 10-line cap). This becomes the default behavior for all connection error/warning banners, not just unsupported.

Background / Current State

• Detection already works end to end. RemoteDirectory.detect() returns a reason code and KiloBackendWorkspace sets KiloWorkspaceState.Unsupported(reason), mapped to KiloWorkspaceStateDto(status = UNSUPPORTED, error = reason) (KiloWorkspaceRpcApiImpl.kt:507). Reason string is in the DTO error field. Reason codes: devcontainer_virtual_filesystem, wsl_virtual_filesystem, invalid_virtual_path.
• The DTO reaches SessionModel.workspace; syncConnectionState() already runs on every WorkspaceChanged (SessionController.kt:982-984).
• Gap: SessionController.resolveConnectionState() (SessionController.kt:2353-2393) has no UNSUPPORTED branch, so it falls through to ShowConnecting (line 2392) → banner reads "Loading…" indefinitely.
• Banner renderer is ConnectionPanel (session/ui/ConnectionPanel.kt), driven by ConnectionChanged.ShowError/ShowWarning/…. Its "Try again" link opens a popup with Retry / Restart / Reinstall (recoveryGroup()).
• Height cap today: DETAILS_LINES = 10 (line 45). scrollHeight() coerces the row count to 1..DETAILS_LINES (line 304), getPreferredSize() uses it (line 295-301), and maxExpandedHeight() (line 345) exposes the fixed cap.
• Overlay placement: SessionUi.kt:442-452 anchors the banner just above the prompt using child.preferredSize.height as the banner height; bottom edge is promptTop - gap, and it grows upward.

All touched files are Kilo-owned JetBrains frontend paths — no kilocode_change markers required. No backend / shared DTO changes needed.

Design Decisions

• Unsupported reuses the standard ShowError path unchanged — same red banner, same "Try again" popup (Retry / Restart / Reinstall). No new event type and no retry flag. (Reverses the earlier "hide retry" idea per user.)
• Detail area fits the full text, capped to available transcript height. Remove the fixed 10-line cap in ConnectionPanel so preferred height reflects the whole detail text; clamp the rendered banner height to the transcript space above the prompt in the overlay layout (where pane geometry is known). The existing internal JBScrollPane (VERTICAL_SCROLLBAR_AS_NEEDED) scrolls the overflow. This applies to every error/warning banner uniformly.

Implementation Tasks

1. SessionController.resolveConnectionState() (SessionController.kt:2353)

   • Add a branch for workspace.status == KiloWorkspaceStatusDto.UNSUPPORTED (place it next to the workspace ERROR branch, before the READY branches):
     • summary = KiloBundle.message("session.connection.unsupported")
     • detail = reason mapped to a localized string (helper below), falling back to the raw workspace.error
     • source = "workspace" (retry link shows by default; no flag change)
   • Add a private helper (single-word name, e.g. unsupported) mapping the workspace.error reason code to a bundle string:
     • devcontainer_virtual_filesystem → session.connection.unsupported.devcontainer
     • wsl_virtual_filesystem → session.connection.unsupported.wsl
     • invalid_virtual_path → session.connection.unsupported.invalid
     • else → session.connection.unsupported.unknown (or raw reason)

2. KiloBundle.properties (resources/messages/, after line 17)

   • Add (finalize exact copy during implementation):
     • session.connection.unsupported=Workspace not supported
     • session.connection.unsupported.devcontainer=Dev Container virtual filesystem paths can't be reached by the host-side Kilo runtime.
     • session.connection.unsupported.wsl=WSL virtual filesystem paths aren't supported by the host-side Kilo runtime.
     • session.connection.unsupported.invalid=This workspace path can't be resolved on the local filesystem.
     • session.connection.unsupported.unknown=This workspace isn't supported by the host-side Kilo runtime.

3. ConnectionPanel.kt (session/ui/) — remove the fixed cap so details fit the whole text:

   • Delete DETAILS_LINES (line 45) usage in scrollHeight() (line 303-306): compute rows from the full logical line count (coerceAtLeast(1)), no upper bound. getPreferredSize() (line 295-301) then reports the full detail height when expanded.
   • Remove maxExpandedHeight() (line 345) or repurpose it; it encodes the 10-line cap and is only used by the outgoing test.
   • Leave the JBScrollPane policies as-is so overflow scrolls when the overlay clamps the banner shorter than preferred.
   • Note (known limitation, keep behavior parity): row count uses logical lines, not wrapped visual lines, so a wrapped long line may under-estimate height; the scrollbar still covers overflow. Optional follow-up only.

4. SessionUi.kt overlay layout for connection (lines 442-452) — clamp the banner height to the transcript area above the prompt:

   • full = child.preferredSize.height
   • avail = (point.y - gap).coerceAtLeast(0) (space from pane top to just above the prompt)
   • h = full.coerceAtMost(avail)
   • Rectangle: x = point.x + gap, y = point.y - h - gap, width = (prompt.width - gap*2).coerceAtLeast(0), height = h
   • This keeps the bottom anchored at promptTop - gap (unchanged) while preventing the top from overflowing above the transcript region; the panel's internal scroll pane handles the remainder. Applies to every banner state.

Tests

• ConnectionDelayTest.kt (session/controller/): add a test mirroring test persistent workspace error is delayed — set projectRpc.state.value = KiloWorkspaceStateDto(status = UNSUPPORTED, error = "wsl_virtual_filesystem"), assert a ShowError with summary "Workspace not supported", the mapped WSL detail, and source == "workspace"; assert it no longer resolves to ShowConnecting.
• ConnectionPanelTest.kt (session/ui/):
  • Replace test expanded details height is capped at ten lines (lines 140-150) with a test asserting the expanded preferred height grows with the full text (e.g. 30 lines yields a preferred height clearly larger than the old 10-line height / a computed full-text height), i.e. no fixed cap.
  • Optionally add a small test that an unsupported-style ShowError still shows the retry link and uses the Core recovery group (parity with existing test retry popup group uses core recovery actions).
• SessionUiLayoutTest.kt: add a test that with a large detail body and a constrained root/pane height, the expanded banner is clamped to the transcript area — connection.y >= 0 (does not overflow above the transcript), bottom still anchored at promptTop - gap, detailsVisible() true, and the internal JBScrollPane shows/needs its vertical scrollbar. Reuse the anchoring assertions from test expanded connection panel remains anchored above prompt (lines 261-276).

Validation

From packages/kilo-jetbrains/:

• ./gradlew typecheck
• ./gradlew test (or targeted: ConnectionPanelTest, ConnectionDelayTest, SessionUiLayoutTest)

Requires Java 21; only check Java if Gradle fails with a Java-version error.

Risks / Notes

• Removing the fixed cap changes sizing for all connection banners; the overlay clamp is what bounds it, so verify very long errors scroll rather than push the banner off the top of the transcript.
• No backend / shared DTO changes; UNSUPPORTED + error=reason already reach the frontend.
• Reason codes live only in RemoteDirectory.kt today; the new bundle keys are the first human-readable mapping. New reason codes fall back to unknown.

Open Questions

• Exact user-facing wording for the five session.connection.unsupported* strings (placeholder copy above).