> For the complete documentation index, see [llms.txt](https://faction-os.gitbook.io/faction-os-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://faction-os.gitbook.io/faction-os-docs/.spec_system/archive/sessions/phase21-session02-shared-expansion-host/implementation_summary.md). # Implementation Summary **Session ID**: `phase21-session02-shared-expansion-host` **Package**: apps/web **Completed**: 2026-06-29 **Duration**: 3-4 hours *** ## Overview Session 02 delivered the shared bottom-rail expansion host for Quest Board, Orchestration, and War Room. The web cockpit now promotes one existing mounted panel instance into a focused working surface, with explicit Focus controls, guarded background expansion, backdrop and close recovery, Escape handling, focus restoration, dialog ARIA semantics, and stable test ids. *** ## Deliverables ### Files Created | File | Purpose | Lines | | -------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ | ----- | | `apps/web/src/components/BottomRailExpansionHost.tsx` | Shared compact/focused bottom-rail host with store-backed singleton expansion behavior. | 200 | | `apps/web/tests/BottomRailExpansionHost.test.tsx` | Component coverage for open, close, backdrop, Escape, focus restore, listener cleanup, guard selectors, and same-child preservation. | 252 | | `.spec_system/specs/phase21-session02-shared-expansion-host/spec.md` | Session specification. | 222 | | `.spec_system/specs/phase21-session02-shared-expansion-host/tasks.md` | Completed task checklist. | 78 | | `.spec_system/specs/phase21-session02-shared-expansion-host/implementation-notes.md` | Implementation task log and evidence. | 634 | | `.spec_system/specs/phase21-session02-shared-expansion-host/code-review.md` | Code-review findings and repair evidence. | 65 | | `.spec_system/specs/phase21-session02-shared-expansion-host/security-compliance.md` | Security and GDPR review. | 70 | | `.spec_system/specs/phase21-session02-shared-expansion-host/validation.md` | Validation report. | 191 | | `.spec_system/specs/phase21-session02-shared-expansion-host/IMPLEMENTATION_SUMMARY.md` | Session completion summary. | 111 | ### Files Modified | File | Changes | | --------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `apps/web/src/App.tsx` | Wrapped Quest Board, Orchestration, and War Room bottom-rail surfaces in the shared expansion host while preserving shell notes and one panel instance per surface. | | `apps/web/tests/CockpitShell.test.tsx` | Added app-shell coverage for all three focus controls, one-at-a-time replacement, close recovery, shell-note preservation, and no duplicate mocked panel trees. | | `.spec_system/state.json` | Marked the session complete, cleared `current_session`, and appended completion history for `apps/web`. | | `.spec_system/PRD/phase_21/PRD_phase_21.md` | Updated Session 02 status and Phase 21 progress to 2/7 sessions. | | `.spec_system/PRD/phase_21/session_02_shared_expansion_host.md` | Marked Session 02 complete and checked prerequisites and success criteria. | | `apps/web/package.json` | Incremented package version from `0.1.49` to `0.1.50`. | | `package-lock.json` | Synchronized the `apps/web` workspace version to `0.1.50`. | *** ## Technical Decisions 1. **Same-instance promotion**: The host changes wrapper layout and ARIA semantics instead of rendering a duplicate panel tree, preserving local panel state across compact and focused modes. 2. **Store-backed singleton expansion**: The host uses the existing transient `expandedBottomRailSurfaceId` setting so opening one bottom surface replaces the previous focused surface. 3. **Guarded background expansion**: Background clicks open a surface only when the target is outside buttons, links, form fields, tab roles, editable content, and `[data-no-panel-expand]`. 4. **Focus recovery by default**: Explicit close, backdrop close, Escape close, and open-time focus handoff avoid leaving keyboard focus outside the focused dialog. *** ## Test Results | Metric | Value | | ------------- | ---------------------- | | Focused tests | 32 passed | | Full tests | 3138 passed, 1 skipped | | Test files | 274 passed, 1 skipped | | Failed | 0 | | Coverage | Not collected | Additional gates passed: `npm run lint`, `npm run format:check`, `npm run typecheck --workspace @factionos/web`, and `npm run typecheck --workspaces --if-present`. *** ## Lessons Learned 1. Shared shell expansion needs focus movement on background-click open, not only focus restoration on close. 2. Same-instance promotion is the simplest way to avoid panel state forks while expanding constrained cockpit surfaces. 3. Guard selectors need broad coverage because the bottom panels already contain nested controls, tabs, and secondary inspectors. *** ## Future Considerations Items for future sessions: 1. Route Orchestration's primary command-center entry through the expanded host in Session 03. 2. Define nested overlay precedence for shortcuts, drawers, detail portals, and the shared host in Session 04. 3. Reconcile Quest Board and War Room secondary detail portals with focused host parity in Session 05. 4. Capture desktop and mobile viewport accessibility evidence in Session 06. *** ## Session Statistics * **Tasks**: 22 completed * **Files Created**: 9 * **Files Modified**: 7 * **Tests Added**: 32 focused assertions across host and shell coverage * **Blockers**: 0 resolved --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://faction-os.gitbook.io/faction-os-docs/.spec_system/archive/sessions/phase21-session02-shared-expansion-host/implementation_summary.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.