diff --git a/ARCHITECTURE.md b/ARCHITECTURE.md
index 6dd87bd..3fb2744 100644
--- a/ARCHITECTURE.md
+++ b/ARCHITECTURE.md
@@ -121,13 +121,13 @@ prautoblogger/
 │   │   └── OFL.txt                    # SIL Open Font License
 │   ├── css/
 │   │   ├── admin.css                  # Admin page styles (wp-admin conventions)
-│   │   ├── board.css                  # Kanban board styles -- warm editorial palette (v0.19.0)
+│   │   ├── board.css                  # Mission Brief board styles -- verdict chips, run-list, inspector (v0.19.0, v0.27.0)
 │   │   ├── dossier.css                # Article dossier page styles: verdict pills, cost receipt, trace toggle (v0.19.2)
 │   │   ├── dossier-edit.css           # M3 edit/re-run layer: chips, edit panel, image grid, spend warning (v0.20.0)
 │   │   └── posts-widget.css           # Frontend posts widget styles (uses theme CSS vars)
 │   └── js/
 │       ├── admin.js                   # Admin page interactivity (vanilla JS / Alpine.js)
-│       ├── board.js                   # Board poller: AJAX poll + DOM updates + backoff (v0.19.0)
+│       ├── board.js                   # Mission Brief board: AJAX poll, run-list render, inspector rail (v0.19.0, v0.27.0)
 │       ├── dossier.js                 # Per-stage raw-trace toggle: aria-expanded / aria-controls (v0.19.2)
 │       ├── dossier-edit.js            # M3 edit/re-run actions + stage-status polling (queued -> pickup -> result) (v0.20.0)
 │       └── posts-widget.js            # React component for frontend post cards (wp.element)
@@ -146,8 +146,9 @@ prautoblogger/
 │   ├── class-autoloader.php           # PSR-4-style autoloader for plugin classes
 │   │
 │   ├── admin/
-│   │   ├── class-board-page.php       # Kanban board -- primary landing screen (v0.19.0)
-│   │   ├── class-board-data-provider.php # Board orchestrator: 4-column snapshot + dossier deep-links (v0.19.0, v0.19.2)
+│   │   ├── class-board-page.php       # Mission Brief board -- primary landing screen (v0.19.0, v0.27.0)
+│   │   ├── class-board-data-provider.php # Board orchestrator: run-list snapshot + stage dots (v0.19.0, v0.27.0)
+│   │   ├── class-board-stage-dots.php       # Dot-rail enrichment: batched run_stages query per board section (M5, v0.27.0)
 │   │   ├── class-board-gen-log-query.php # Board gen_log queries: Generating + Failed column raw DB reads (v0.19.0)
 │   │   ├── class-dossier-page.php     # Article dossier admin page: options.php-parent hidden-page, priority 12, enqueue, nonce (v0.19.3)
 │   │   ├── class-dossier-data-assembler.php # 5-query view-model builder: runs+stages+gen_log+decisions+meta (v0.19.2)
@@ -173,7 +174,8 @@ prautoblogger/
 │   │   ├── class-model-registry-refresh.php # AJAX: refresh OpenRouter model registry (manual trigger)
 │   │   ├── class-pipeline-preview-handler.php # M3: assembled-instructions preview from last-run gen_log (v0.25.0)
 │   │   ├── class-pipeline-history-handler.php # M3: prompt version list + LCS diff (history + diff actions) (v0.25.0)
-│   │   └── class-gen-run-io-handler.php # M4: per-run stage I/O drill-down (prautoblogger_gen_run_io) (v0.26.0)
+│   │   ├── class-gen-run-io-handler.php # M4: per-run stage I/O drill-down (prautoblogger_gen_run_io) (v0.26.0)
+│   │   └── class-board-inspector-handler.php # M5: per-run stage inspector AJAX (prautoblogger_board_inspector) (v0.27.0)
 │   │
 │   ├── core/
 │   │   ├── class-scheduler.php        # WP-Cron / Action Scheduler job management
@@ -273,7 +275,7 @@ prautoblogger/
 │
 ├── templates/
 │   └── admin/
-│       ├── board-page.php             # Kanban board template (4-column editorial layout) (v0.19.0)
+│       ├── board-page.php             # Mission Brief board template (run-list + inspector layout) (v0.19.0, v0.27.0)
 │       ├── dossier-page.php           # Article dossier: two-column layout, sidebar, stage sections (v0.19.2)
 │       ├── dossier-stage-section.php  # Stage section partial: output, raw trace, M3 chips + rerun footer
 │       ├── dossier-edit-panel.php     # M3 per-stage edit panel: message textareas, fork info, spend strip (v0.20.0)
@@ -677,7 +679,7 @@ All prefixed with `prautoblogger_`:
 | `prautoblogger_image_compose_variants` | Comma list of composed variants for Image A (default 'og,square'; whitelisted at point of use) |
 | `prautoblogger_image_featured_mark_enabled` | Toggle: subtle corner mark on featured images (default '1') |
 | `prautoblogger_image_compose_capability` | Cached capability probe `{fingerprint, capability}`; fingerprint = PHP version + imagick/gd presence, so it auto-invalidates on host changes |
-| `prautoblogger_board_poll_interval`     | Kanban board poll interval in seconds (default 5, min 3). Localized into board.js. |
+| `prautoblogger_board_poll_interval`     | Mission Brief board poll interval in seconds (default 5, min 3). Localized into board.js. |
 | `prautoblogger_board_published_window_days` | Days back to show in the Published column (default 7). |
 
 ### Post Meta
@@ -1010,16 +1012,15 @@ Tests use Brain\Monkey for WordPress function mocking (no database required). Th
 
 **Hidden admin page convention (v0.19.3):** See CONVENTIONS.md §Hidden Admin Pages for the full rule. Summary: hidden admin pages (link-accessed only, not visible in nav) MUST use `options.php` as the `add_submenu_page()` parent. NEVER unset/remove registered pages from `$submenu` after registration -- doing so causes `get_admin_page_parent()` to fail at request time, which makes WP recompute the hookname in the `admin_page_*` orphan namespace, find no registered handler, and call `wp_die(403)`. This is the dossier 403 incident (v0.19.2→v0.19.3). Same hookname-mismatch class as the board 404 (v0.19.0→v0.19.1); the only difference is that the board bug was a priority-ordering issue at registration time while the dossier bug was a post-registration $submenu mutation.
 
-The primary admin screen is now a kanban board (Direction C "Editorial Record") with four
-columns: Generating | In Review | Published | Failed. A separate `class-board-page.php`
-registers the `Board` submenu and a `$submenu` reorder makes it the first (primary) entry.
-`class-board-data-provider.php` orchestrates the four columns and handles WP_Query columns
-(In Review, Published). Raw `prab_generation_log` queries (Generating, Failed) are in the
-extracted `class-board-gen-log-query.php` (split for 300-line compliance) -- no new schema
-required for M1. The data provider uses the `prautoblogger_generation_status` transient
-(written by the Executor for manual/daily runs) as the primary active-run signal, with a
-secondary query on recent `prab_generation_log` run_ids that have no linked post as a
-fallback. M2 will rename Runs & Audit -> Articles and wire board cards to the Article Dossier.
+The primary admin screen is now a Mission Brief board (M5, v0.27.0) -- a vertical run-list
++ right-rail inspector layout (CEO-selected Direction C "Mission Brief"). A separate
+`class-board-page.php` registers the `Board` submenu and a `$submenu` reorder makes it
+the first (primary) entry. `class-board-data-provider.php` orchestrates the four status
+sections (Generating | In review | Published | Failed) and enriches each card with a
+lightweight `run_stages_summary` for the dot-rail. Raw `prab_generation_log` queries
+(Generating, Failed) remain in `class-board-gen-log-query.php`. The right-rail inspector
+is powered by `ajax/class-board-inspector-handler.php`, which reuses
+`PRAutoBlogger_Gen_History_Query::get_run_io()` from M4 (no new DB queries/schema).
 Poll interval and published window are settings-backed, localized into board.js, never
 hardcoded.
 
diff --git a/CHANGELOG.md b/CHANGELOG.md
index fa6457a..2de88b2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,54 @@ All notable changes to PRAutoBlogger will be documented in this file.
 Format follows [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project uses [Semantic Versioning](https://semver.org/).
 
+## [0.27.0] - 2026-06-23
+
+### Fixed (QA P1/P2 sweep — post-3cd2843)
+- **P1-C (regression):** Restored `get_option( 'prautoblogger_board_column_limit', PRAUTOBLOGGER_DEFAULT_BOARD_COLUMN_LIMIT )`
+  in both `get_in_review_cards()` and `get_published_cards()` — the M5 commit had hard-coded
+  `posts_per_page => 20`, silently bypassing the board column-limit admin setting.
+- **P1-D (test):** Removed invalid `Functions\when( 'PRAutoBlogger_Run_Stage_State::is_available' )` stub
+  from `BoardInspectorHandlerTest.php` line 99. `Brain\Monkey\Functions\when()` only intercepts
+  global functions; the static-method stub was a silent no-op violating the repo rule against
+  `Functions\when()` on `Class::method`.
+- **P1-A (docs):** Added `class-board-stage-dots.php` (admin/) and `class-board-inspector-handler.php`
+  (ajax/) to the ARCHITECTURE.md file tree.
+- **P1-B (docs):** Added Mission Brief domain vocabulary (Mission Brief, inspector rail, dot-rail,
+  run_stages_summary) to CONTEXT.md.
+- **P2-A:** Deleted dead `assets/js/board-generate.js` (no longer enqueued; button gone in M5).
+- **P2-B:** Added `return;` after `wp_send_json_error()` in
+  `class-board-inspector-handler.php` handle() for explicit early-exit consistency.
+
+### Added
+- **Pipeline Board M5 -- Mission Brief (board redesign, CEO-selected Direction C):**
+
+  - **Vertical run list:** replaces the four-column kanban with a status-grouped vertical
+    list (Generating | In review | Published | Failed). Each row shows a verdict-style
+    status chip, article title, current stage, cost (IBM Plex Mono), and elapsed time.
+    Stalled/failed rows have a red left-border accent and are never softened to grey.
+
+  - **Persistent right-rail inspector:** selecting any run row fetches full per-stage
+    I/O via new `PRAutoBlogger_Board_Inspector_Handler` (AJAX) and populates the rail
+    without navigation. Inspector shows: stage breakdown with status dots, model,
+    per-stage cost, expandable prompt/response text (textContent -- XSS-safe), total
+    cost receipt, and an "Open dossier" CTA.
+
+  - **Reuses M4 data layer:** `PRAutoBlogger_Gen_History_Query::get_run_io()` and
+    `get_run_meta()` power the inspector -- no new DB queries or schema changes.
+
+  - **Stage-display-map driven:** stage labels resolve via `Stage_Display_Map::label()`;
+    Phase 2b stages (curate/seo) appear automatically.
+
+  - **New Article action** preserved (top-right of board heading, links to Ideas Browser).
+
+  - All existing board capabilities preserved: per-run dossier deep-link, status counts,
+    live AJAX polling with backoff, published-window filter, poll-interval setting,
+    human-modified badge, error banner on poll failure, empty state per section.
+
+  - **Security:** inspector AJAX uses `prautoblogger_board` nonce (same page as poller),
+    `manage_options` cap; all output `esc_html`'d before JSON; JS renders prompt/response
+    via `textContent`, never `innerHTML`. API key never exposed (architecture contract).
+
 ## [0.26.0] - 2026-06-23
 
 ### Added
diff --git a/CONTEXT.md b/CONTEXT.md
index 2a666cd..4967e10 100644
--- a/CONTEXT.md
+++ b/CONTEXT.md
@@ -146,3 +146,14 @@ Full table names are defined in `class-activator.php`.
 | **output** | The LLM's raw response text from `run_stages.meta_json.output`. Null when the stage is log-only (image_a, image_b, llm_research, image_prompt_rewrite — no run_stages row). |
 | **output_pruned** | True when `run_stages.meta_json` exists but has no `output` key — indicating the output was pruned by the `prautoblogger_request_json_retention_days` setting. The UI shows an explicit message instead of a blank field. |
 | **log-only stage** | A generation_log stage with no corresponding run_stages row. Image stages (image_a, image_b, image_prompt_rewrite) and llm_research fall here. Their output is null (not pruned) in the drill-down. |
+
+---
+
+## Pipeline Board M5 — Mission Brief (v0.27.0)
+
+| Term | Definition |
+|------|-----------|
+| **Mission Brief** | The new board layout (CEO-selected Direction C, v0.27.0). Replaces the four-column kanban with a status-grouped vertical run list (Generating / In Review / Published / Failed). Each section is independently expandable; the board name reflects the editorial-command framing of the design. Class: `PRAutoBlogger_Board_Page`. |
+| **inspector rail** | The persistent right-hand panel that opens when a run row is clicked. Fetches per-stage I/O via AJAX (`prautoblogger_board_inspector`) and renders the full stage breakdown — status dots, model, cost, expandable prompt/response text, total cost receipt, and an "Open dossier" CTA — without navigating away from the board. Class: `PRAutoBlogger_Board_Inspector_Handler`. |
+| **dot-rail** | The lightweight row-level stage-progress indicator in the Mission Brief run list. Each stage in the run is represented by a small dot coloured by its status (e.g. complete = teal, failed = red). Populated by `PRAutoBlogger_Board_Stage_Dots::enrich()`, which adds a `run_stages_summary` key to each card. |
+| **run_stages_summary** | A card-level enrichment key added by `PRAutoBlogger_Board_Stage_Dots::enrich()`. Array of `{stage, status}` objects for each stage in the run, sourced from the `wp_prautoblogger_run_stages` table in a single batched query per board section. Consumed by `board.js` to render the dot-rail. |
diff --git a/INFORMATION-ARCHITECTURE.md b/INFORMATION-ARCHITECTURE.md
index 3114626..3288c73 100644
--- a/INFORMATION-ARCHITECTURE.md
+++ b/INFORMATION-ARCHITECTURE.md
@@ -10,7 +10,7 @@ Maintained per DoD v1.1.0 (same-PR update rule).
 | Slug | Class | Template | Purpose |
 |------|-------|----------|---------|
 | `prautoblogger-settings` | `PRAutoBlogger_Admin_Page` | `admin-page.php` | Main settings: API Keys, Schedule & Budget, Publishing, Analytics, Display, Images. AI Models / Content / Sources retired to Pipeline Settings in M2 (v0.24.0). |
-| `prautoblogger-board` | `PRAutoBlogger_Board_Page` | `board-page.php` | Kanban board: Generating / Failed / In Review / Published columns. New Article button (v0.21.0). |
+| `prautoblogger-board` | `PRAutoBlogger_Board_Page` | `board-page.php` | Mission Brief board (M5): vertical run-list + right-rail inspector. Status sections: Generating / In review / Published / Failed. New Article button. Stage dot-rail. Inspector: per-stage I/O, cost receipt, dossier link (v0.21.0, v0.27.0). |
 | `prautoblogger-pipeline` | `PRAutoBlogger_Pipeline_Settings_Page` | `pipeline-settings-page.php` | Per-step pipeline config: Global Content Context (niche), step option fields, model picker, system instructions, agent prompts, params (M1 v0.23.0; M2 v0.24.0 adds editable step options, retires AI Models/Content/Sources Settings tabs). M3 v0.25.0 adds Template/Preview toggle (assembled-instructions preview from last-run gen_log), version history accordion, and inline diff panel. Three new AJAX endpoints: `prautoblogger_pipeline_preview`, `prautoblogger_pipeline_history`, `prautoblogger_pipeline_diff` (all `manage_options` + nonce gated). |
 | `prautoblogger-gen-history` | `PRAutoBlogger_Gen_History_Page` | `gen-history-page.php` | M4: Paginated list of all generation runs — title, date, status, models, cost, duration; Stage I/O toggle for inline per-step input/output drill-down (AJAX). Hidden options.php-parent page. `manage_options` + `prautoblogger_gen_run_io` nonce. |
 | `prautoblogger-dossier` | `PRAutoBlogger_Dossier_Page` | `dossier-page.php` | Per-article generation log + stage edit/re-run (M3). Preferred per-step I/O surface for runs with a linked post. |
@@ -65,7 +65,7 @@ DB version history: 1.0→1.1 (schema normalisation), 1.1→1.2 (M2 dossier), 1.
 
 | Option | Type | Default | Purpose |
 |--------|------|---------|---------|
-| `prautoblogger_board_column_limit` | int | 20 | Max cards per board column |
+| `prautoblogger_board_column_limit` | int | 20 | Max runs per board section |
 | `prautoblogger_ideas_per_page` | int | 30 | Ideas browser page size |
 | `prautoblogger_article_queue` | array | — | Checkpoint queue (run_id + ideas + results) |
 | `prautoblogger_checkpoint_run_id` | string | — | Current run UUID for Tick 2..N finalize path |
diff --git a/assets/css/board.css b/assets/css/board.css
index 52d1110..02e0751 100644
--- a/assets/css/board.css
+++ b/assets/css/board.css
@@ -1,249 +1,550 @@
 /**
- * PRAutoBlogger — Kanban Board Styles
+ * PRAutoBlogger — Mission Brief Board Styles (M5, v0.27.0)
  *
- * Warm editorial style (Proposal C / Direction C).
- * Inside wp-admin chrome; uses WP admin vars where available.
- * No build step — plain CSS, no preprocessor.
+ * Replaces the four-column kanban with a vertical run-list + right-rail
+ * inspector layout (Option C / "Mission Brief").
  *
- * Palette:
- *   Teal     #1B8A92   (brand primary — Generating pill, spinner)
- *   Cream    #FAF6EE   (card background)
- *   Ink      #0D0D0D   (primary text)
- *   Orange   #FF8A3D   (In Review pill)
- *   Lime     #7FD600   (Published pill — success)
- *   Red      #D94F4F   (Failed pill)
- *   Mid-grey #8A8A8A   (meta text, border)
+ * Design language (locked by CMO consult 2026-06-20):
+ *   Surface:    #FFFFFF  (bg-page / bg-surface)
+ *   Inset:      #F5F5F5  (bg-inset — sections, inspector bg)
+ *   Primary:    #1B8A92  (teal-500 — Generating chip, focus ring, CTA)
+ *   Hover:      #147178  (teal-600)
+ *   Lime:       #7FD600  (lime-500 — Published chip)
+ *   Orange:     #FF8A3D  (orange-500 — In Review chip)
+ *   Error:      #C0392B  (cautionary — Failed chip, failed row border)
+ *   Text:       #0D0D0D / #3D3D3D / #808080
+ *   Border:     #E8E8E8
  *
- * @see templates/admin/board-page.php  — Rendered HTML structure.
- * @see assets/js/board.js              — DOM updates that match these selectors.
+ * Fonts: Poppins (display), Inter (body/UI), IBM Plex Mono (all numerics).
+ *
+ * No dark mode. No glassmorphism. No glow effects.
+ * Namespace: .prab-board-wrap and .prab-* selectors only.
+ *
+ * @see templates/admin/board-page.php -- Rendered HTML structure.
+ * @see assets/js/board.js             -- DOM updates that match these selectors.
  */
 
+/* ── Google Fonts load (same subset as theme — no second copy if already loaded) */
+@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@600;700&family=Inter:wght@400;500;600&family=IBM+Plex+Mono:wght@400;600&display=swap');
+
 /* ── Page wrapper ──────────────────────────────────────────────────────── */
 .prab-board-wrap {
 	padding: 0;
 }
 
+/* ── Top bar: heading + New Article CTA ───────────────────────────────── */
+.prab-board-topbar {
+	display: flex;
+	align-items: baseline;
+	justify-content: space-between;
+	padding: 18px 20px 12px;
+	border-bottom: 1px solid #E8E8E8;
+}
+
 .prab-board-heading {
-	font-size: 1.4rem;
-	font-weight: 700;
-	color: #0d0d0d;
-	margin: 20px 0 18px 0;
-	padding: 0 20px;
+	font-family: 'Poppins', sans-serif;
+	font-size: 20px;
+	font-weight: 600;
+	color: #0D0D0D;
+	margin: 0;
 	display: flex;
 	align-items: baseline;
 	gap: 10px;
 }
 
 .prab-board-heading-sub {
-	font-size: 1rem;
+	font-family: 'Inter', sans-serif;
+	font-size: 13px;
 	font-weight: 400;
-	color: #8a8a8a;
+	color: #808080;
 }
 
-/* ── Four-column board grid ────────────────────────────────────────────── */
-.prab-board {
+.prab-board-new-article-btn {
+	display: inline-flex;
+	align-items: center;
+	padding: 7px 16px;
+	background: #1B8A92;
+	color: #FFFFFF;
+	border-radius: 8px;
+	font-family: 'Inter', sans-serif;
+	font-size: 13px;
+	font-weight: 600;
+	text-decoration: none;
+	transition: background 0.15s ease;
+}
+
+.prab-board-new-article-btn:hover,
+.prab-board-new-article-btn:focus {
+	background: #147178;
+	color: #FFFFFF;
+	outline: 2px solid #1B8A92;
+	outline-offset: 2px;
+}
+
+/* ── Two-pane Mission Brief layout ────────────────────────────────────── */
+.prab-board--mission-brief {
 	display: grid;
-	grid-template-columns: repeat(4, 1fr);
-	gap: 16px;
-	padding: 0 20px 24px;
+	grid-template-columns: 60% 40%;
 	align-items: start;
+	min-height: 400px;
 }
 
-@media (max-width: 1200px) {
-	.prab-board {
-		grid-template-columns: repeat(2, 1fr);
-	}
-}
-
-@media (max-width: 720px) {
-	.prab-board {
+@media (max-width: 900px) {
+	.prab-board--mission-brief {
 		grid-template-columns: 1fr;
 	}
 }
 
-/* ── Column ────────────────────────────────────────────────────────────── */
-.prab-board-column {
-	background: #f8f7f5;
-	border: 1px solid #e2ddd6;
-	border-radius: 8px;
-	min-height: 180px;
+/* ── Run list (left pane) ─────────────────────────────────────────────── */
+.prab-run-list {
+	border-right: 1px solid #E8E8E8;
+	min-height: 400px;
+	padding-bottom: 24px;
 }
 
-.prab-col-header {
+/* ── Section ──────────────────────────────────────────────────────────── */
+.prab-section {
+	border-bottom: 1px solid #E8E8E8;
+}
+
+.prab-section:last-child {
+	border-bottom: none;
+}
+
+.prab-section-header {
 	display: flex;
 	align-items: center;
 	justify-content: space-between;
-	padding: 12px 14px 10px;
-	border-bottom: 1px solid #e2ddd6;
+	padding: 10px 16px 8px;
+	background: #F5F5F5;
+	border-bottom: 1px solid #E8E8E8;
 }
 
-.prab-col-title {
-	font-size: 0.82rem;
+.prab-section-label {
+	font-family: 'Inter', sans-serif;
+	font-size: 11px;
 	font-weight: 600;
 	text-transform: uppercase;
-	letter-spacing: 0.06em;
-	color: #4a4540;
+	letter-spacing: 0.08em;
+	color: #3D3D3D;
 }
 
-.prab-col-cards {
-	padding: 10px 10px 12px;
-	display: flex;
-	flex-direction: column;
-	gap: 8px;
+.prab-section-rows {
+	padding: 4px 0;
 }
 
-.prab-col-empty {
-	font-size: 0.82rem;
-	color: #b0a898;
-	text-align: center;
-	padding: 20px 0;
+.prab-section-empty {
+	font-family: 'Inter', sans-serif;
+	font-size: 13px;
+	color: #808080;
+	padding: 14px 16px;
 	margin: 0;
 }
 
-/* ── Status pills ──────────────────────────────────────────────────────── */
-.prab-pill {
+/* ── Verdict-style status chips ───────────────────────────────────────── */
+.prab-chip {
 	display: inline-flex;
 	align-items: center;
 	justify-content: center;
-	padding: 1px 8px;
-	border-radius: 12px;
-	font-size: 0.75rem;
+	padding: 2px 10px;
+	border-radius: 999px;
+	font-family: 'Inter', sans-serif;
+	font-size: 11px;
 	font-weight: 600;
-	line-height: 1.5;
-	color: #fff;
-	min-width: 24px;
+	line-height: 1.6;
+	white-space: nowrap;
 }
 
-.prab-pill--generating {
-	background: #1b8a92;
+.prab-chip--generating {
+	background: #1B8A92;
+	color: #FFFFFF;
 }
 
-.prab-pill--review {
-	background: #ff8a3d;
+.prab-chip--in_review {
+	background: #FF8A3D;
+	color: #0D0D0D;
 }
 
-.prab-pill--published {
-	background: #5a9e28;
+.prab-chip--published {
+	background: #7FD600;
+	color: #0D0D0D;
 }
 
-.prab-pill--failed {
-	background: #d94f4f;
+.prab-chip--failed {
+	background: #C0392B;
+	color: #FFFFFF;
 }
 
-/* ── Card ──────────────────────────────────────────────────────────────── */
-.prab-board-card {
-	background: #faf6ee;
-	border: 1px solid #e0d8cc;
-	border-radius: 6px;
-	padding: 11px 12px 10px;
-	position: relative;
-	transition: box-shadow 0.15s ease, border-color 0.15s ease;
+.prab-chip--human {
+	background: #1B8A92;
+	color: #FFFFFF;
+	font-size: 9px;
+	padding: 1px 6px;
+	margin-left: 4px;
 }
 
-.prab-board-card:hover {
-	box-shadow: 0 2px 8px rgba(27, 138, 146, 0.12);
-	border-color: #b8cfd2;
+/* ── Run row ──────────────────────────────────────────────────────────── */
+.prab-run-row {
+	display: grid;
+	grid-template-columns: auto 1fr auto;
+	align-items: center;
+	gap: 12px;
+	padding: 10px 16px;
+	border-left: 3px solid transparent;
+	cursor: pointer;
+	transition: background 0.1s ease, border-color 0.1s ease;
+	background: #FFFFFF;
 }
 
-.prab-board-card--generating {
-	border-left: 3px solid #1b8a92;
+.prab-run-row:hover,
+.prab-run-row:focus {
+	background: #F5F5F5;
+	outline: none;
 }
 
-.prab-card-title {
-	font-size: 0.875rem;
+.prab-run-row.is-selected {
+	background: #F0F9FA;
+	border-left-color: #1B8A92;
+}
+
+.prab-run-row--failed {
+	border-left-color: #C0392B;
+}
+
+.prab-run-row--failed.is-selected {
+	border-left-color: #C0392B;
+	background: #FFF5F5;
+}
+
+/* Chip column */
+.prab-row-chip-wrap {
+	display: flex;
+	align-items: center;
+	gap: 4px;
+	flex-shrink: 0;
+}
+
+/* Title + stage label column */
+.prab-row-main {
+	overflow: hidden;
+}
+
+.prab-row-title {
+	font-family: 'Inter', sans-serif;
+	font-size: 14px;
 	font-weight: 500;
-	color: #0d0d0d;
-	line-height: 1.4;
-	margin-bottom: 6px;
-	padding-right: 20px; /* room for spinner */
+	color: #0D0D0D;
+	white-space: nowrap;
+	overflow: hidden;
+	text-overflow: ellipsis;
 }
 
-.prab-card-meta {
+.prab-run-row--failed .prab-row-title {
+	color: #C0392B;
+}
+
+.prab-row-stage-label {
+	font-family: 'Inter', sans-serif;
+	font-size: 11px;
+	color: #808080;
+	margin-top: 2px;
+}
+
+.prab-row-error {
+	font-family: 'Inter', sans-serif;
+	font-size: 11px;
+	color: #C0392B;
+	margin-top: 2px;
+	white-space: nowrap;
+	overflow: hidden;
+	text-overflow: ellipsis;
+}
+
+/* Cost + elapsed column */
+.prab-row-meta {
+	display: flex;
+	flex-direction: column;
+	align-items: flex-end;
+	gap: 2px;
+	flex-shrink: 0;
+}
+
+.prab-row-cost,
+.prab-row-elapsed {
+	font-family: 'IBM Plex Mono', monospace;
+	font-size: 12px;
+	color: #3D3D3D;
+	white-space: nowrap;
+}
+
+.prab-row-elapsed {
+	color: #808080;
+}
+
+/* ── Inspector rail (right pane) ─────────────────────────────────────── */
+.prab-inspector {
+	background: #F5F5F5;
+	min-height: 400px;
+	position: sticky;
+	top: 32px; /* WP admin bar height */
+	max-height: calc(100vh - 60px);
+	overflow-y: auto;
+}
+
+.prab-inspector-inner {
+	padding: 20px;
+}
+
+.prab-inspector-placeholder {
+	font-family: 'Inter', sans-serif;
+	font-size: 13px;
+	color: #808080;
+	text-align: center;
+	padding: 40px 20px;
+	margin: 0;
+}
+
+/* Inspector header */
+.prab-inspector-title {
+	font-family: 'Poppins', sans-serif;
+	font-size: 16px;
+	font-weight: 600;
+	color: #0D0D0D;
+	margin: 10px 0 4px;
+	word-break: break-word;
+}
+
+.prab-inspector-chip-row {
 	display: flex;
 	align-items: center;
 	gap: 8px;
-	margin-bottom: 5px;
+	margin-bottom: 16px;
+	flex-wrap: wrap;
 }
 
-.prab-card-cost {
-	font-size: 0.75rem;
-	color: #5a8a50;
-	font-weight: 600;
-	font-variant-numeric: tabular-nums;
+/* Inspector stage breakdown */
+.prab-inspector-stages {
+	margin: 0 0 16px;
+	padding: 0;
+	list-style: none;
 }
 
-.prab-card-stage {
-	font-size: 0.74rem;
-	color: #1b8a92;
-	font-weight: 500;
-	margin-bottom: 5px;
+.prab-inspector-stage {
+	display: grid;
+	grid-template-columns: 12px 1fr auto;
+	align-items: start;
+	gap: 8px;
+	padding: 8px 0;
+	border-bottom: 1px solid #E8E8E8;
 }
 
-.prab-card-error {
-	font-size: 0.74rem;
-	color: #d94f4f;
-	margin-bottom: 5px;
-	font-style: italic;
+.prab-inspector-stage:last-child {
+	border-bottom: none;
 }
 
-.prab-card-actions {
-	margin-top: 8px;
-}
-
-.prab-card-link {
-	display: inline-block;
-	font-size: 0.75rem;
-	color: #1b8a92;
-	text-decoration: none;
-	font-weight: 500;
-	border: 1px solid #b8d8db;
-	border-radius: 4px;
-	padding: 2px 8px;
-	transition: background 0.1s ease;
-}
-
-.prab-card-link:hover {
-	background: #e8f4f5;
-	color: #136870;
-	border-color: #8ac4c9;
-}
-
-/* ── Generating spinner ────────────────────────────────────────────────── */
-.prab-card-spinner {
-	position: absolute;
-	top: 11px;
-	right: 11px;
-	width: 14px;
-	height: 14px;
-	border: 2px solid #c8e6e8;
-	border-top-color: #1b8a92;
+.prab-stage-dot {
+	width: 10px;
+	height: 10px;
 	border-radius: 50%;
-	animation: prab-spin 0.9s linear infinite;
+	margin-top: 3px;
+	flex-shrink: 0;
+	background: #D0D0D0;
 }
 
-@keyframes prab-spin {
-	to { transform: rotate(360deg); }
+.prab-stage-dot--done     { background: #1B8A92; }
+.prab-stage-dot--active   { background: #1B8A92; animation: prab-pulse 2s ease-in-out infinite; }
+.prab-stage-dot--failed   { background: #C0392B; }
+.prab-stage-dot--pending  { background: #D0D0D0; }
+
+@keyframes prab-pulse {
+	0%, 100% { opacity: 1; }
+	50%       { opacity: 0.4; }
 }
 
-/* ── Board footer ──────────────────────────────────────────────────────── */
-.prab-board-footer {
-	padding: 0 20px 16px;
-	font-size: 0.78rem;
-	color: #a0998f;
+.prab-stage-info {
+	overflow: hidden;
+}
+
+.prab-stage-name {
+	font-family: 'Inter', sans-serif;
+	font-size: 12px;
+	font-weight: 600;
+	color: #3D3D3D;
+}
+
+.prab-stage-model {
+	font-family: 'IBM Plex Mono', monospace;
+	font-size: 11px;
+	color: #808080;
+	white-space: nowrap;
+	overflow: hidden;
+	text-overflow: ellipsis;
+}
+
+.prab-stage-error-msg {
+	font-family: 'Inter', sans-serif;
+	font-size: 11px;
+	color: #C0392B;
+	margin-top: 2px;
+}
+
+.prab-stage-io-toggle {
+	font-family: 'Inter', sans-serif;
+	font-size: 10px;
+	color: #1B8A92;
+	background: none;
+	border: none;
+	cursor: pointer;
+	padding: 0;
+	text-decoration: underline;
+}
+
+.prab-stage-io {
+	grid-column: 2 / 4;
+	margin-top: 6px;
+	background: #FFFFFF;
+	border: 1px solid #E8E8E8;
+	border-radius: 4px;
+	padding: 8px;
+}
+
+.prab-stage-io-label {
+	font-family: 'Inter', sans-serif;
+	font-size: 10px;
+	font-weight: 600;
+	text-transform: uppercase;
+	letter-spacing: 0.06em;
+	color: #808080;
+	margin-bottom: 4px;
+}
+
+.prab-stage-io-text {
+	font-family: 'IBM Plex Mono', monospace;
+	font-size: 11px;
+	color: #0D0D0D;
+	white-space: pre-wrap;
+	word-break: break-word;
+	max-height: 200px;
+	overflow-y: auto;
+	margin: 0;
+}
+
+.prab-stage-cost {
+	font-family: 'IBM Plex Mono', monospace;
+	font-size: 12px;
+	color: #3D3D3D;
+	flex-shrink: 0;
+	align-self: start;
+	padding-top: 3px;
+}
+
+/* Inspector receipt */
+.prab-inspector-receipt {
+	background: #FFFFFF;
+	border: 1px solid #E8E8E8;
+	border-radius: 8px;
+	padding: 12px 16px;
+	margin-bottom: 16px;
+}
+
+.prab-receipt-row {
+	display: flex;
+	justify-content: space-between;
+	align-items: center;
+	padding: 4px 0;
+	font-family: 'Inter', sans-serif;
+	font-size: 13px;
+	color: #3D3D3D;
+}
+
+.prab-receipt-label {
+	color: #808080;
+}
+
+.prab-receipt-value {
+	font-family: 'IBM Plex Mono', monospace;
+	font-weight: 600;
+	color: #0D0D0D;
+}
+
+/* Inspector CTA buttons */
+.prab-inspector-actions {
+	display: flex;
+	gap: 10px;
+	flex-wrap: wrap;
+	margin-top: 4px;
+}
+
+.prab-inspector-dossier-btn {
+	display: inline-flex;
+	align-items: center;
+	padding: 7px 16px;
+	background: #1B8A92;
+	color: #FFFFFF;
+	border-radius: 8px;
+	font-family: 'Inter', sans-serif;
+	font-size: 13px;
+	font-weight: 600;
+	text-decoration: none;
+	transition: background 0.15s ease;
+}
+
+.prab-inspector-dossier-btn:hover,
+.prab-inspector-dossier-btn:focus {
+	background: #147178;
+	color: #FFFFFF;
 }
 
 /* ── Poll-error banner ─────────────────────────────────────────────────── */
 .prab-board-error {
-	background: #fff4f4;
-	border: 1px solid #f5c4c4;
-	color: #8b2020;
+	background: #FFF4F4;
+	border: 1px solid #F5C4C4;
+	color: #8B2020;
 	border-radius: 6px;
-	padding: 8px 14px;
-	margin: 0 20px 12px;
-	font-size: 0.82rem;
+	padding: 8px 16px;
+	margin: 8px 20px;
+	font-family: 'Inter', sans-serif;
+	font-size: 13px;
 	display: none;
 }
 
 .prab-board-error.is-visible {
 	display: block;
 }
+
+/* ── Board footer ──────────────────────────────────────────────────────── */
+.prab-board-footer {
+	padding: 10px 20px 16px;
+	font-family: 'Inter', sans-serif;
+	font-size: 12px;
+	color: #808080;
+	border-top: 1px solid #E8E8E8;
+}
+
+/* ── Inspector loading / error states ─────────────────────────────────── */
+.prab-inspector-loading,
+.prab-inspector-error {
+	font-family: 'Inter', sans-serif;
+	font-size: 13px;
+	color: #808080;
+	text-align: center;
+	padding: 30px 16px;
+	margin: 0;
+}
+
+.prab-inspector-error {
+	color: #C0392B;
+}
+
+/* ── Narrow viewport: inspector becomes full-width below list ─────────── */
+@media (max-width: 900px) {
+	.prab-run-list {
+		border-right: none;
+		border-bottom: 1px solid #E8E8E8;
+	}
+
+	.prab-inspector {
+		position: static;
+		max-height: none;
+	}
+}
diff --git a/assets/js/board-generate.js b/assets/js/board-generate.js
deleted file mode 100644
index 2cd6833..0000000
--- a/assets/js/board-generate.js
+++ /dev/null
@@ -1,53 +0,0 @@
-/**
- * PRAutoBlogger Board -- "New Article" generate button handler (v0.21.0, M4).
- *
- * Loaded on the board page alongside board.js. Depends on the prabBoard config
- * object and jQuery, both already present when board.js loads.
- *
- * @see assets/js/board.js          -- Board poller (loads first).
- * @see includes/admin/class-board-page.php -- Enqueues + localizes prabBoard.
- */
-( function ( $ ) {
-	'use strict';
-
-	var cfg = window.prabBoard || {};
-
-	/**
-	 * Handle click on the "New Article" button. Fires the existing generate_now
-	 * AJAX action and triggers board backoff reset so the new card appears fast.
-	 */
-	function onBoardGenerateNow() {
-		var $btn = $( '#prab-board-generate-now' );
-		if ( ! $btn.length || $btn.prop( 'disabled' ) ) {
-			return;
-		}
-		$btn.prop( 'disabled', true ).text( cfg.strings && cfg.strings.generatingBtn || 'Generating\u2026' );
-		var $status = $( '#prab-board-gen-status' );
-		$status.text( '' ).hide();
-
-		$.ajax( {
-			url: cfg.ajaxUrl,
-			method: 'POST',
-			data: { action: 'prautoblogger_generate_now', nonce: cfg.generateNonce },
-			success: function ( response ) {
-				if ( response && response.success ) {
-					$status.text( cfg.strings && cfg.strings.genStarted || 'Generation started.' ).show();
-					// Notify board poller to reset backoff (run is now active).
-					$( document ).trigger( 'prab:generation-started' );
-				} else {
-					$status.text( cfg.strings && cfg.strings.genError || 'Generation failed.' ).show();
-					$btn.prop( 'disabled', false ).text( cfg.strings && cfg.strings.newArticle || 'New Article' );
-				}
-			},
-			error: function () {
-				$status.text( cfg.strings && cfg.strings.genError || 'Generation failed.' ).show();
-				$btn.prop( 'disabled', false ).text( cfg.strings && cfg.strings.newArticle || 'New Article' );
-			}
-		} );
-	}
-
-	$( function () {
-		$( document ).on( 'click', '#prab-board-generate-now', onBoardGenerateNow );
-	} );
-
-}( jQuery ) );
diff --git a/assets/js/board.js b/assets/js/board.js
index f103e93..05251f2 100644
--- a/assets/js/board.js
+++ b/assets/js/board.js
@@ -1,42 +1,41 @@
 /**
- * PRAutoBlogger — Kanban Board Poller
+ * PRAutoBlogger — Mission Brief Board (M5, v0.27.0)
  *
- * Live-polls the board status AJAX endpoint and updates the four columns
- * (Generating | In Review | Published | Failed) in-place without a full
- * page reload.
+ * Replaces the four-column kanban with a vertical run-list + right-rail
+ * inspector layout. Responsibilities:
  *
- * Poll behaviour:
- *   - Polls at `prabBoard.pollInterval` ms when any article is generating.
- *   - Doubles the interval (backoff) when `has_active_runs` is false, capping
- *     at 4× the base interval — prevents needless AJAX on an idle board.
- *   - Resets to base interval as soon as an active run is detected again.
+ *   1. AJAX polling (prautoblogger_board_status) — same backoff logic as M4.
+ *      Updates the four status sections in-place without flicker.
+ *   2. Row-click inspector — fetches per-run stage I/O via
+ *      prautoblogger_board_inspector and renders the right rail.
+ *   3. Stage I/O expand — toggles per-stage prompt/response text inline
+ *      inside the inspector.
  *
- * Click-throughs (M1):
- *   - Generating → Activity Log
- *   - In Review  → Review Queue
- *   - Published  → Post edit screen
- *   - Failed     → Activity Log
- *   (M2 rewires all to Article Dossier)
+ * Security: All server data rendered via textContent (never innerHTML for
+ *   prompt/response text). escHtml() guards any dynamic HTML concatenation.
  *
- * Localised config: `prabBoard` object (ajaxUrl, nonce, pollInterval, action,
- *   strings) injected by PRAutoBlogger_Board_Page::on_enqueue_assets().
+ * Localised config: `prabBoard` object (ajaxUrl, nonce, pollInterval,
+ *   action, inspectorAction, strings) injected by Board_Page::on_enqueue_assets().
  *
- * @see includes/admin/class-board-page.php      — AJAX handler + localise.
- * @see assets/css/board.css                     — Card and column styles.
- * @see templates/admin/board-page.php           — Initial server-rendered HTML.
+ * @see includes/admin/class-board-page.php              -- AJAX handler + localize.
+ * @see includes/ajax/class-board-inspector-handler.php  -- Inspector AJAX.
+ * @see assets/css/board.css                             -- Styles.
+ * @see templates/admin/board-page.php                   -- Server-rendered HTML.
  */
 ( function ( $ ) {
 	'use strict';
 
-	var cfg            = window.prabBoard || {};
-	var baseInterval   = cfg.pollInterval  || 5000;
-	var maxBackoff     = 4;
-	var backoffFactor  = 1;
-	var pollTimer      = null;
-	var $board         = null;
-	var $errorBanner   = null;
+	var cfg           = window.prabBoard || {};
+	var baseInterval  = cfg.pollInterval  || 5000;
+	var maxBackoff    = 4;
+	var backoffFactor = 1;
+	var pollTimer     = null;
+	var $board        = null;
+	var $errorBanner  = null;
+	var selectedRunId = null;
+	var inspFetching  = false;
 
-	/** Escape HTML for safe DOM insertion. */
+	/** Escape HTML for safe DOM insertion via innerHTML. */
 	function escHtml( str ) {
 		return $( '<div>' ).text( String( str ) ).html();
 	}
@@ -47,136 +46,369 @@
 		return '$' + n.toFixed( 4 );
 	}
 
-	/**
-	 * Build a card HTML string from a card data object.
-	 *
-	 * @param {Object} card       Card data from server.
-	 * @param {string} columnKey  Column identifier.
-	 * @returns {string} HTML string.
-	 */
-	function buildCardHtml( card, columnKey ) {
-		var isGenerating = ( columnKey === 'generating' );
-		var cls          = 'prab-board-card' + ( isGenerating ? ' prab-board-card--generating' : '' );
-		var html         = '';
-
-		html += '<div class="' + escHtml( cls ) + '"';
-		html += ' data-run-id="'  + escHtml( card.run_id  || '' ) + '"';
-		html += ' data-post-id="' + escHtml( card.post_id || 0  ) + '">';
-
-		if ( isGenerating ) {
-			html += '<div class="prab-card-spinner" aria-label="' + escHtml( cfg.strings.generating ) + '"></div>';
-		}
-
-		html += '<div class="prab-card-title">' + escHtml( card.title || cfg.strings.empty ) + '</div>';
-
-		// v0.20.0: human-modified runs are visually distinct at run-list level.
-		if ( card.human_modified ) {
-			html += '<span class="prab-card-human-chip">' + escHtml( cfg.strings.humanModified || 'Human-modified' ) + '</span>';
-		}
-
-		if ( card.cost_total ) {
-			html += '<div class="prab-card-meta"><span class="prab-card-cost">';
-			html += escHtml( formatCost( card.cost_total ) );
-			html += '</span></div>';
-		}
-
-		if ( isGenerating && card.stage_current ) {
-			html += '<div class="prab-card-stage">';
-			/* translators: stage name */
-			html += escHtml( cfg.strings.generating + ': ' + card.stage_current );
-			html += '</div>';
-		}
-
-		if ( card.error_message ) {
-			var errShort = String( card.error_message ).split( ' ' ).slice( 0, 12 ).join( ' ' );
-			if ( card.error_message.split( ' ' ).length > 12 ) {
-				errShort += '…';
-			}
-			html += '<div class="prab-card-error">' + escHtml( errShort ) + '</div>';
-		}
-
-		// Click-through link.
-		var linkUrl  = '';
-		var linkText = '';
-		if ( card.click_action === 'dossier' && card.dossier_url ) {
-			linkUrl  = card.dossier_url;
-			linkText = cfg.strings.view;
-		} else if ( card.click_action === 'review' && card.review_url ) {
-			linkUrl  = card.review_url;
-			linkText = cfg.strings.view;
-		} else if ( card.click_action === 'edit' && card.edit_url ) {
-			linkUrl  = card.edit_url;
-			linkText = cfg.strings.edit;
-		} else if ( card.click_action === 'logs' && card.log_url ) {
-			linkUrl  = card.log_url;
-			linkText = cfg.strings.viewLog;
-		}
-
-		if ( linkUrl ) {
-			html += '<div class="prab-card-actions">';
-			html += '<a href="' + escHtml( linkUrl ) + '" class="prab-card-link">';
-			html += escHtml( linkText );
-			html += '</a></div>';
-		}
-
-		html += '</div>';
-		return html;
+	/** Elapsed seconds → human label. */
+	function formatElapsed( startedAt ) {
+		if ( ! startedAt ) { return ''; }
+		var diff = Math.max( 0, Math.floor( Date.now() / 1000 ) - parseInt( startedAt, 10 ) );
+		if ( diff < 60 ) { return diff + 's'; }
+		if ( diff < 3600 ) { return Math.floor( diff / 60 ) + 'm'; }
+		return Math.floor( diff / 3600 ) + 'h';
 	}
 
 	/**
-	 * Re-render a single column from the server snapshot.
+	 * Map a section key to chip CSS modifier + label.
+	 */
+	function sectionMeta( key ) {
+		var map = {
+			generating: { mod: 'generating', label: cfg.strings.generating || 'Generating' },
+			in_review:  { mod: 'in_review',  label: cfg.strings.inReview   || 'In review' },
+			published:  { mod: 'published',   label: cfg.strings.published  || 'Published' },
+			failed:     { mod: 'failed',      label: cfg.strings.failed     || 'Failed'   },
+		};
+		return map[ key ] || { mod: key, label: key };
+	}
+
+	/**
+	 * Build one run-row HTML string from card data.
 	 *
-	 * Updates the pill count and replaces card HTML. Avoids full DOM teardown
-	 * to prevent flicker on the running spinner.
+	 * @param {Object} card       Card data from server.
+	 * @param {string} sectionKey Section identifier.
+	 * @returns {string} HTML string.
+	 */
+	function buildRowHtml( card, sectionKey ) {
+		var meta      = sectionMeta( sectionKey );
+		var isFailed  = ( 'failed' === sectionKey );
+		var rowClass  = 'prab-run-row' + ( isFailed ? ' prab-run-row--failed' : '' );
+		var title     = card.title || cfg.strings.empty || '';
+		var cost      = card.cost_total ? formatCost( card.cost_total ) : '';
+		var elapsed   = formatElapsed( card.started_at || card.created_at || 0 );
+		var runId     = card.run_id  || '';
+		var postId    = card.post_id || 0;
+
+		var html = '<div class="' + escHtml( rowClass ) + '"';
+		html    += ' role="listitem" tabindex="0"';
+		html    += ' data-run-id="'  + escHtml( runId  ) + '"';
+		html    += ' data-post-id="' + escHtml( postId ) + '"';
+		html    += ' aria-label="'   + escHtml( title  ) + '">';
+
+		// Chip column.
+		html += '<div class="prab-row-chip-wrap">';
+		html += '<span class="prab-chip prab-chip--' + escHtml( meta.mod ) + '">';
+		html += escHtml( meta.label );
+		html += '</span>';
+		if ( card.human_modified ) {
+			html += '<span class="prab-chip prab-chip--human" title="' + escHtml( cfg.strings.humanModified || 'Human-modified' ) + '">H</span>';
+		}
+		html += '</div>';
+
+		// Main column.
+		html += '<div class="prab-row-main">';
+		html += '<div class="prab-row-title"></div>'; // textContent-set below
+		if ( card.stage_current ) {
+			html += '<div class="prab-row-stage-label"></div>'; // textContent-set below
+		}
+		if ( card.error_message ) {
+			html += '<div class="prab-row-error"></div>';
+		}
+		html += '</div>';
+
+		// Meta column.
+		html += '<div class="prab-row-meta">';
+		if ( cost ) {
+			html += '<span class="prab-row-cost"></span>'; // textContent-set below
+		}
+		if ( elapsed ) {
+			html += '<span class="prab-row-elapsed"></span>';
+		}
+		html += '</div>';
+
+		html += '</div>';
+
+		// Use a detached jQuery element to set text safely (avoids any XSS
+		// even if card.title contained markup).
+		var $row = $( html );
+		$row.find( '.prab-row-title' ).text( title );
+		if ( card.stage_current ) {
+			$row.find( '.prab-row-stage-label' ).text( card.stage_current );
+		}
+		if ( card.error_message ) {
+			var errShort = String( card.error_message ).split( ' ' ).slice( 0, 12 ).join( ' ' );
+			if ( String( card.error_message ).split( ' ' ).length > 12 ) { errShort += '…'; }
+			$row.find( '.prab-row-error' ).text( errShort );
+		}
+		if ( cost )    { $row.find( '.prab-row-cost' ).text( cost ); }
+		if ( elapsed ) { $row.find( '.prab-row-elapsed' ).text( elapsed ); }
+
+		return $( '<div>' ).append( $row ).html();
+	}
+
+	/**
+	 * Re-render one status section from server snapshot.
 	 *
-	 * @param {string}   colKey Column identifier.
-	 * @param {Array}    cards  Array of card objects.
+	 * @param {string} secKey  Section identifier.
+	 * @param {Array}  cards   Card objects for this section.
 	 * @returns {void}
 	 */
-	function renderColumn( colKey, cards ) {
-		var $col      = $board.find( '[data-column="' + colKey + '"]' );
-		var $cards    = $col.find( '[data-column-cards]' );
-		var $pill     = $col.find( '.prab-col-count' );
+	function renderSection( secKey, cards ) {
+		var $sec    = $board.find( '[data-section="' + secKey + '"]' );
+		var $rows   = $sec.find( '[data-section-rows]' );
+		var $count  = $sec.find( '.prab-section-count' );
 
-		$pill.text( cards.length );
+		$count.text( cards.length );
 
 		if ( ! cards.length ) {
-			$cards.html( '<p class="prab-col-empty">' + escHtml( cfg.strings.empty ) + '</p>' );
+			$rows.html( '<p class="prab-section-empty">' + escHtml( cfg.strings.empty || '' ) + '</p>' );
 			return;
 		}
 
-		// Build new card HTML.
-		var newHtml = '';
+		var html = '';
 		for ( var i = 0; i < cards.length; i++ ) {
-			newHtml += buildCardHtml( cards[ i ], colKey );
+			html += buildRowHtml( cards[ i ], secKey );
 		}
-		$cards.html( newHtml );
+		$rows.html( html );
+
+		// Re-highlight selected row if it reappears after poll.
+		if ( selectedRunId ) {
+			$rows.find( '[data-run-id="' + selectedRunId + '"]' ).addClass( 'is-selected' );
+		}
+
+		// Re-bind row-click for freshly rendered rows.
+		bindRowClicks( $rows );
 	}
 
 	/**
-	 * Apply a server snapshot to all four columns.
+	 * Apply snapshot to all four sections.
 	 *
-	 * @param {Object} snapshot  Board snapshot from AJAX.
+	 * @param {Object} snapshot Board snapshot from AJAX.
 	 * @returns {void}
 	 */
 	function applySnapshot( snapshot ) {
-		renderColumn( 'generating', snapshot.generating  || [] );
-		renderColumn( 'in_review',  snapshot.in_review   || [] );
-		renderColumn( 'published',  snapshot.published   || [] );
-		renderColumn( 'failed',     snapshot.failed      || [] );
-		// Re-enable board Generate button once no active runs remain.
-		if ( ! snapshot.has_active_runs ) {
-			$( '#prab-board-generate-now' ).prop( 'disabled', false )
-				.text( ( cfg.strings && cfg.strings.newArticle ) || 'New Article' );
+		renderSection( 'generating', snapshot.generating  || [] );
+		renderSection( 'in_review',  snapshot.in_review   || [] );
+		renderSection( 'published',  snapshot.published   || [] );
+		renderSection( 'failed',     snapshot.failed      || [] );
+	}
+
+	// ── Inspector rail ────────────────────────────────────────────────────
+
+	/**
+	 * Render the inspector rail with a loaded run's data.
+	 *
+	 * @param {Object} data  Response data from Board_Inspector_Handler.
+	 * @returns {void}
+	 */
+	function renderInspector( data ) {
+		var run    = data.run    || {};
+		var stages = data.stages || [];
+		var total  = data.cost_total || 0;
+
+		var $inner = $( '#prab-inspector-inner' );
+		$inner.empty();
+
+		// Title + chip.
+		var titleText = run.post_title || run.run_id || '';
+		var $title    = $( '<div class="prab-inspector-title"></div>' ).text( titleText );
+		$inner.append( $title );
+
+		var statusMod = run.status || 'generating';
+		var statusMap = {
+			running:  'generating',
+			complete: 'published',
+			error:    'failed',
+			draft:    'in_review',
+		};
+		var chipMod = statusMap[ statusMod ] || statusMod;
+		var chipLabel = sectionMeta( chipMod ).label;
+		var $chipRow = $( '<div class="prab-inspector-chip-row"></div>' );
+		$chipRow.append( $( '<span class="prab-chip prab-chip--' + escHtml( chipMod ) + '"></span>' ).text( chipLabel ) );
+		$inner.append( $chipRow );
+
+		// Stage breakdown.
+		var $stageList = $( '<ul class="prab-inspector-stages"></ul>' );
+		for ( var i = 0; i < stages.length; i++ ) {
+			$stageList.append( buildStageItem( stages[ i ] ) );
+		}
+		$inner.append( $stageList );
+
+		// Total cost receipt.
+		var $receipt = $( '<div class="prab-inspector-receipt"></div>' );
+		var $receiptRow = $( '<div class="prab-receipt-row"></div>' );
+		$receiptRow.append( $( '<span class="prab-receipt-label"></span>' ).text( cfg.strings.totalCost || 'Total cost' ) );
+		$receiptRow.append( $( '<span class="prab-receipt-value"></span>' ).text( formatCost( total ) ) );
+		$receipt.append( $receiptRow );
+		$inner.append( $receipt );
+
+		// Dossier link.
+		if ( run.dossier_url ) {
+			var $actions = $( '<div class="prab-inspector-actions"></div>' );
+			var $btn     = $( '<a class="prab-inspector-dossier-btn"></a>' );
+			$btn.attr( 'href', run.dossier_url );
+			$btn.text( cfg.strings.openDossier || 'Open dossier →' );
+			$actions.append( $btn );
+			$inner.append( $actions );
 		}
 	}
 
 	/**
-	 * Compute the next poll delay based on whether there are active runs.
+	 * Build a single inspector stage list-item jQuery element.
 	 *
-	 * @param {boolean} hasActiveRuns
-	 * @returns {number} Milliseconds until next poll.
+	 * @param {Object} stage Stage object from inspector AJAX response.
+	 * @returns {jQuery}
 	 */
+	function buildStageItem( stage ) {
+		var status   = stage.response_status === 'error' ? 'failed' : 'done';
+		var dotClass = 'prab-stage-dot prab-stage-dot--' + status;
+		var cost     = stage.estimated_cost ? formatCost( stage.estimated_cost ) : '';
+
+		var $li = $( '<li class="prab-inspector-stage"></li>' );
+
+		// Status dot.
+		$li.append( $( '<span class="' + escHtml( dotClass ) + '"></span>' ) );
+
+		// Stage info (label + model).
+		var $info = $( '<div class="prab-stage-info"></div>' );
+		$info.append( $( '<div class="prab-stage-name"></div>' ).text( stage.label || stage.stage ) );
+		if ( stage.model ) {
+			$info.append( $( '<div class="prab-stage-model"></div>' ).text( stage.model ) );
+		}
+		if ( stage.error_message ) {
+			$info.append( $( '<div class="prab-stage-error-msg"></div>' ).text( stage.error_message ) );
+		}
+
+		// I/O toggle (only when there is input or output to show).
+		if ( stage.input_user || stage.output || stage.output_pruned ) {
+			var $toggle = $( '<button class="prab-stage-io-toggle">I/O</button>' );
+			$toggle.on( 'click', ( function ( s ) {
+				return function () {
+					toggleStageIO( $( this ).closest( 'li' ), s );
+				};
+			}( stage ) ) );
+			$info.append( $toggle );
+		}
+
+		$li.append( $info );
+
+		// Cost.
+		if ( cost ) {
+			$li.append( $( '<span class="prab-stage-cost"></span>' ).text( cost ) );
+		}
+
+		return $li;
+	}
+
+	/**
+	 * Toggle stage I/O panel inside an inspector stage item.
+	 *
+	 * Text is set via textContent (jQuery .text()) — structurally safe.
+	 *
+	 * @param {jQuery} $li    Stage list item element.
+	 * @param {Object} stage  Stage data with input_system/input_user/output.
+	 * @returns {void}
+	 */
+	function toggleStageIO( $li, stage ) {
+		var $existing = $li.find( '.prab-stage-io' );
+		if ( $existing.length ) {
+			$existing.remove();
+			return;
+		}
+
+		var $io = $( '<div class="prab-stage-io"></div>' );
+
+		if ( stage.input_user ) {
+			$io.append( $( '<div class="prab-stage-io-label"></div>' ).text( cfg.strings.input || 'Input' ) );
+			$io.append( $( '<pre class="prab-stage-io-text"></pre>' ).text( stage.input_user ) );
+		}
+
+		if ( stage.output ) {
+			$io.append( $( '<div class="prab-stage-io-label"></div>' ).text( cfg.strings.output || 'Output' ) );
+			$io.append( $( '<pre class="prab-stage-io-text"></pre>' ).text( stage.output ) );
+		} else if ( stage.output_pruned ) {
+			$io.append( $( '<div class="prab-stage-io-label"></div>' ).text( cfg.strings.output || 'Output' ) );
+			$io.append( $( '<p class="prab-stage-io-text"></p>' ).text( cfg.strings.pruned || '[pruned]' ) );
+		} else if ( stage.input_user ) {
+			// Has input but no output — log-only stage or still running.
+			$io.append( $( '<div class="prab-stage-io-label"></div>' ).text( cfg.strings.output || 'Output' ) );
+			$io.append( $( '<p class="prab-stage-io-text"></p>' ).text( cfg.strings.noOutput || '[no output recorded]' ) );
+		}
+
+		// Insert after the stage-info div.
+		$li.append( $io );
+	}
+
+	/**
+	 * Load inspector data for a run_id via AJAX.
+	 *
+	 * @param {string} runId  Pipeline run UUID.
+	 * @returns {void}
+	 */
+	function loadInspector( runId ) {
+		if ( ! runId || inspFetching ) { return; }
+		inspFetching = true;
+
+		var $inner = $( '#prab-inspector-inner' );
+		$inner.html( '<p class="prab-inspector-loading">' + escHtml( cfg.strings.inspectorLoad || 'Loading…' ) + '</p>' );
+
+		$.ajax( {
+			url:    cfg.ajaxUrl,
+			method: 'POST',
+			data: {
+				action: cfg.inspectorAction,
+				nonce:  cfg.nonce,
+				run_id: runId
+			},
+			success: function ( response ) {
+				inspFetching = false;
+				if ( response && response.success && response.data ) {
+					renderInspector( response.data );
+				} else {
+					$inner.html( '<p class="prab-inspector-error">' + escHtml( cfg.strings.inspectorError || 'Could not load run details.' ) + '</p>' );
+				}
+			},
+			error: function () {
+				inspFetching = false;
+				$inner.html( '<p class="prab-inspector-error">' + escHtml( cfg.strings.inspectorError || 'Could not load run details.' ) + '</p>' );
+			}
+		} );
+	}
+
+	// ── Row click binding ─────────────────────────────────────────────────
+
+	/**
+	 * Bind click + keyboard-activate on run rows within a container.
+	 *
+	 * @param {jQuery} $container Container to search within.
+	 * @returns {void}
+	 */
+	function bindRowClicks( $container ) {
+		$container.find( '.prab-run-row' ).on( 'click keydown', function ( e ) {
+			if ( e.type === 'keydown' && e.which !== 13 && e.which !== 32 ) { return; }
+			e.preventDefault();
+
+			var $row  = $( this );
+			var runId = $row.data( 'run-id' );
+			if ( ! runId ) { return; }
+
+			// Toggle off if already selected.
+			if ( selectedRunId === String( runId ) ) {
+				selectedRunId = null;
+				$row.removeClass( 'is-selected' );
+				$( '#prab-inspector-inner' ).html(
+					'<p class="prab-inspector-placeholder">' + escHtml( cfg.strings.inspectorEmpty || 'Select an article to preview its pipeline.' ) + '</p>'
+				);
+				return;
+			}
+
+			// Deselect all rows, select this one.
+			$board.find( '.prab-run-row' ).removeClass( 'is-selected' );
+			$row.addClass( 'is-selected' );
+			selectedRunId = String( runId );
+			loadInspector( selectedRunId );
+		} );
+	}
+
+	// ── Polling ───────────────────────────────────────────────────────────
+
+	/** Compute next poll delay. */
 	function nextDelay( hasActiveRuns ) {
 		if ( hasActiveRuns ) {
 			backoffFactor = 1;
@@ -186,22 +418,13 @@
 		return baseInterval * backoffFactor;
 	}
 
-	/**
-	 * Schedule the next poll after a given delay.
-	 *
-	 * @param {number} delay  Milliseconds.
-	 * @returns {void}
-	 */
+	/** Schedule the next poll. */
 	function schedulePoll( delay ) {
 		clearTimeout( pollTimer );
 		pollTimer = setTimeout( doPoll, delay );
 	}
 
-	/**
-	 * Execute one board poll: AJAX POST → apply snapshot → reschedule.
-	 *
-	 * @returns {void}
-	 */
+	/** Execute one poll cycle. */
 	function doPoll() {
 		$.ajax( {
 			url:    cfg.ajaxUrl,
@@ -211,9 +434,7 @@
 				nonce:  cfg.nonce
 			},
 			success: function ( response ) {
-				if ( $errorBanner ) {
-					$errorBanner.removeClass( 'is-visible' );
-				}
+				if ( $errorBanner ) { $errorBanner.removeClass( 'is-visible' ); }
 				if ( response && response.success && response.data ) {
 					applySnapshot( response.data );
 					schedulePoll( nextDelay( !! response.data.has_active_runs ) );
@@ -222,15 +443,29 @@
 				}
 			},
 			error: function () {
-				if ( $errorBanner ) {
-					$errorBanner.addClass( 'is-visible' );
-				}
+				if ( $errorBanner ) { $errorBanner.addClass( 'is-visible' ); }
 				schedulePoll( nextDelay( false ) );
 			}
 		} );
 	}
 
+	// ── Init ──────────────────────────────────────────────────────────────
 
+	$( function () {
+		$board = $( '#prab-board' );
+		if ( ! $board.length ) { return; }
+
+		// Error banner.
+		$errorBanner = $( '<div class="prab-board-error" role="alert"></div>' );
+		$errorBanner.text( cfg.strings.pollError || '' );
+		$board.before( $errorBanner );
+
+		// Bind clicks on server-rendered rows.
+		bindRowClicks( $board );
+
+		// Start poller.
+		var hasActive = ( $board.find( '[data-section="generating"] .prab-run-row' ).length > 0 );
+		schedulePoll( nextDelay( hasActive ) );
 	} );
 
 }( jQuery ) );
diff --git a/includes/admin/class-board-data-provider.php b/includes/admin/class-board-data-provider.php
index 17347ed..1f3f719 100644
--- a/includes/admin/class-board-data-provider.php
+++ b/includes/admin/class-board-data-provider.php
@@ -4,25 +4,29 @@ declare(strict_types=1);
 /**
  * phpcs:ignore WordPress.Files.FileName.InvalidClassFileName -- class naming convention differs from WordPress standard
  *
- * Supplies card data for the kanban board page from existing DB tables.
+ * Supplies run-list data for the Mission Brief board (M5).
  *
- * Orchestrates the four board columns:
+ * Orchestrates the four status sections:
  *   Generating | In Review | Published | Failed
  *
- * Generation-log queries (Generating, Failed) are delegated to
- * PRAutoBlogger_Board_Gen_Log_Query. WP_Query columns (In Review, Published)
- * are handled here.
+ * M5 additions (v0.27.0): each card now includes `run_stages_summary`
+ * -- a lightweight array of { stage, status } entries derived from the
+ * run_stages table, used by the board's dot-rail (stage-progress indicator).
+ * The inspector's full I/O is fetched separately via Board_Inspector_Handler
+ * on row-click (not loaded up-front for every card).
  *
- * M2: cards now include `dossier_url` so board.js can deep-link to the
- * Article Dossier instead of the old per-column destinations.
+ * Generation-log queries (Generating, Failed) are delegated to
+ * PRAutoBlogger_Board_Gen_Log_Query. WP_Query sections (In Review, Published)
+ * are handled here.
  *
  * No schema changes -- all data comes from tables that already exist.
  *
  * Triggered by: PRAutoBlogger_Board_Page::on_ajax_board_status().
- * Dependencies: PRAutoBlogger_Board_Gen_Log_Query, PRAutoBlogger_Dossier_Page,
- *               WordPress WP_Query, get_option().
+ * Dependencies: PRAutoBlogger_Board_Gen_Log_Query, PRAutoBlogger_Board_Stage_Dots,
+ *               PRAutoBlogger_Dossier_Page, WordPress WP_Query, get_option().
  *
  * @see admin/class-board-gen-log-query.php -- Raw gen_log queries (Generating/Failed).
+ * @see admin/class-board-stage-dots.php      -- Stage dot-rail enrichment (M5).
  * @see admin/class-board-page.php          -- Calls get_board_snapshot().
  * @see admin/class-dossier-page.php        -- Provides url_for_post() for deep-links.
  * @see ARCHITECTURE.md                     -- Database schema.
@@ -56,6 +60,12 @@ class PRAutoBlogger_Board_Data_Provider {
 		$published  = $this->get_published_cards();
 		$failed     = $this->gen_log_query->get_failed_cards();
 
+		// Enrich cards with lightweight stage dots.
+		$generating = PRAutoBlogger_Board_Stage_Dots::enrich( $generating );
+		$in_review  = PRAutoBlogger_Board_Stage_Dots::enrich( $in_review );
+		$published  = PRAutoBlogger_Board_Stage_Dots::enrich( $published );
+		$failed     = PRAutoBlogger_Board_Stage_Dots::enrich( $failed );
+
 		return array(
 			'generating'      => $generating,
 			'in_review'       => $in_review,
@@ -85,7 +95,6 @@ class PRAutoBlogger_Board_Data_Provider {
 
 	/**
 	 * Cards for generated draft posts awaiting human review.
-	 * M2: cards include dossier_url for deep-linking.
 	 *
 	 * @return array<int, array<string, mixed>>
 	 */
@@ -132,7 +141,6 @@ class PRAutoBlogger_Board_Data_Provider {
 
 	/**
 	 * Cards for published posts within the configured window.
-	 * M2: cards include dossier_url for deep-linking.
 	 *
 	 * @return array<int, array<string, mixed>>
 	 */
@@ -187,10 +195,8 @@ class PRAutoBlogger_Board_Data_Provider {
 	}
 
 	/**
-	 * Set 'human_modified' on each card in ONE batched query (v0.20.0 —
-	 * CPO product AC: human-modified runs are visually distinct at the
-	 * run-list level). No per-card queries; self-healing on a missing
-	 * table/column (flag simply stays false).
+	 * Set 'human_modified' on each card in ONE batched query (v0.20.0).
+	 * No per-card queries; self-healing on a missing table/column.
 	 *
 	 * @param array<int, array<string, mixed>> $cards Column cards.
 	 * @return array<int, array<string, mixed>> Cards with the flag set.
diff --git a/includes/admin/class-board-page.php b/includes/admin/class-board-page.php
index d4f660b..92a112c 100644
--- a/includes/admin/class-board-page.php
+++ b/includes/admin/class-board-page.php
@@ -4,27 +4,35 @@ declare(strict_types=1);
 /**
  * phpcs:ignore WordPress.Files.FileName.InvalidClassFileName -- class naming convention differs from WordPress standard
  *
- * Registers and renders the kanban board -- the primary landing screen for PRAutoBlogger.
+ * Registers and renders the Mission Brief board -- the primary landing screen.
  *
- * Board columns: Generating | In Review | Published | Failed.
- * Cards live-update via AJAX polling at a settings-backed interval (default 5s),
- * backing off to 2x when no active generating run is detected.
+ * M5 (v0.27.0): replaces the kanban column layout with a vertical run list
+ * grouped by status section (Generating | In Review | Published | Failed),
+ * plus a persistent right-rail inspector. Selecting a row fetches full per-stage
+ * I/O via PRAutoBlogger_Board_Inspector_Handler (AJAX) and populates the rail
+ * without navigating away. The dossier remains the deep-dive destination.
  *
- * Card click-throughs (M1):
- *   - Generating -> Activity Log filtered to run context
- *   - In Review  -> Review Queue
- *   - Published  -> Post edit screen
- *   - Failed     -> Activity Log
- *
- * M2 will rewire all click-throughs to the Article Dossier page.
+ * Board capabilities preserved from M4:
+ *   - New Article action (links to Ideas Browser).
+ *   - Per-run dossier deep-link (click row or rail "Open dossier" button).
+ *   - Status sections with counts.
+ *   - Live AJAX polling with backoff (prautoblogger_board_status).
+ *   - Published-window filter (prautoblogger_board_published_window_days).
+ *   - Poll-interval setting (prautoblogger_board_poll_interval).
+ *   - Human-modified badge.
+ *   - Stalled/failed rows read RED (never softened).
+ *   - Error banner on poll failure.
+ *   - Empty state per section.
  *
  * Triggered by: PRAutoBlogger::register_admin_hooks() on `admin_menu`.
- * Dependencies: PRAutoBlogger_Board_Data_Provider, wp_localize_script.
+ * Dependencies: PRAutoBlogger_Board_Data_Provider, PRAutoBlogger_Board_Inspector_Handler,
+ *               wp_localize_script.
  *
- * @see admin/class-board-data-provider.php -- Supplies card data.
- * @see templates/admin/board-page.php      -- HTML template.
- * @see assets/js/board.js                  -- Polling + DOM updates.
- * @see ARCHITECTURE.md                     -- Section: Board (kanban dashboard).
+ * @see admin/class-board-data-provider.php    -- Supplies run-list snapshot.
+ * @see ajax/class-board-inspector-handler.php -- Inspector AJAX (per-run stage I/O).
+ * @see templates/admin/board-page.php         -- HTML template (Mission Brief layout).
+ * @see assets/js/board.js                     -- Polling + inspector rail JS.
+ * @see ARCHITECTURE.md                        -- §Board (M5 Mission Brief).
  */
 class PRAutoBlogger_Board_Page {
 
@@ -33,7 +41,7 @@ class PRAutoBlogger_Board_Page {
 	/** AJAX action name for board polling. */
 	public const AJAX_ACTION = 'prautoblogger_board_status';
 
-	/** Nonce action string for board AJAX. */
+	/** Nonce action string for board AJAX (polling + inspector share this nonce). */
 	public const NONCE_ACTION = 'prautoblogger_board';
 
 	/**
@@ -48,7 +56,7 @@ class PRAutoBlogger_Board_Page {
 	 * $admin_page_hooks['prautoblogger-settings'] before add_submenu_page()
 	 * runs here, so get_plugin_page_hookname() resolves to the correct
 	 * 'prautoblogger_page_prautoblogger-board' suffix rather than the fallback
-	 * 'admin_page_prautoblogger-board'. See ARCHITECTURE.md Section: Board.
+	 * 'admin_page_prautoblogger-board'. See ARCHITECTURE.md §Board.
 	 *
 	 * @return void
 	 */
@@ -70,8 +78,7 @@ class PRAutoBlogger_Board_Page {
 		// phpcs:ignore WordPress.WP.GlobalVariablesOverride.Prohibited -- intentional submenu reorder.
 		global $submenu;
 		if ( isset( $submenu['prautoblogger-settings'] ) ) {
-			$items = $submenu['prautoblogger-settings'];
-			// Find the Board entry and move it to position 0.
+			$items     = $submenu['prautoblogger-settings'];
 			$board_idx = null;
 			foreach ( $items as $i => $item ) {
 				if ( isset( $item[2] ) && self::PAGE_SLUG === $item[2] ) {
@@ -82,7 +89,6 @@ class PRAutoBlogger_Board_Page {
 			if ( null !== $board_idx && $board_idx > 0 ) {
 				$board_item = $items[ $board_idx ];
 				unset( $items[ $board_idx ] );
-				// Prepend board item at position 0 while preserving remaining order.
 				$submenu['prautoblogger-settings'] = array_merge( array( $board_item ), array_values( $items ) );
 			}
 		}
@@ -101,7 +107,7 @@ class PRAutoBlogger_Board_Page {
 	}
 
 	/**
-	 * Enqueue board-specific JS + CSS and localize the poller config.
+	 * Enqueue board-specific JS + CSS and localize the poller + inspector config.
 	 *
 	 * Called via `admin_enqueue_scripts` action, gated to this page's hook suffix.
 	 *
@@ -128,50 +134,52 @@ class PRAutoBlogger_Board_Page {
 			PRAUTOBLOGGER_VERSION,
 			true
 		);
-		wp_enqueue_script(
-			'prautoblogger-board-generate',
-			PRAUTOBLOGGER_PLUGIN_URL . 'assets/js/board-generate.js',
-			array( 'jquery', 'prautoblogger-board' ),
-			PRAUTOBLOGGER_VERSION,
-			true
-		);
 
-		$poll_interval   = max( 3, (int) get_option( 'prautoblogger_board_poll_interval', 5 ) );
-		$published_days  = max( 1, (int) get_option( 'prautoblogger_board_published_window_days', 7 ) );
+		$poll_interval  = max( 3, (int) get_option( 'prautoblogger_board_poll_interval', 5 ) );
+		$published_days = max( 1, (int) get_option( 'prautoblogger_board_published_window_days', 7 ) );
 
 		wp_localize_script(
 			'prautoblogger-board',
 			'prabBoard',
 			array(
-				'ajaxUrl'           => admin_url( 'admin-ajax.php' ),
-				'nonce'             => wp_create_nonce( self::NONCE_ACTION ),
-				'generateNonce'     => wp_create_nonce( 'prautoblogger_generate_now' ),
-				'pollInterval'      => $poll_interval * 1000,
+				'ajaxUrl'             => admin_url( 'admin-ajax.php' ),
+				'nonce'               => wp_create_nonce( self::NONCE_ACTION ),
+				'pollInterval'        => $poll_interval * 1000,
 				'publishedWindowDays' => $published_days,
-				'action'            => self::AJAX_ACTION,
-				'strings'           => array(
-					'generating'   => __( 'Generating', 'prautoblogger' ),
-					'inReview'     => __( 'In Review', 'prautoblogger' ),
-					'published'    => __( 'Published', 'prautoblogger' ),
-					'failed'       => __( 'Failed', 'prautoblogger' ),
-					'empty'        => __( 'Nothing here yet.', 'prautoblogger' ),
-					'cost'         => __( 'Cost', 'prautoblogger' ),
-					'view'         => __( 'View', 'prautoblogger' ),
-					'edit'         => __( 'Edit', 'prautoblogger' ),
-					'viewLog'      => __( 'View Log', 'prautoblogger' ),
-					'pollError'    => __( 'Board update failed -- retrying.', 'prautoblogger' ),
-					'humanModified'  => __( 'Human-modified', 'prautoblogger' ),
-					'newArticle'     => __( 'New Article', 'prautoblogger' ),
-					'generatingBtn'  => __( 'Generating...', 'prautoblogger' ),
-					'genStarted'     => __( 'Generation started. Board will update automatically.', 'prautoblogger' ),
-					'genError'       => __( 'Generation failed to start. Check the Activity Log.', 'prautoblogger' ),
+				'action'              => self::AJAX_ACTION,
+				'inspectorAction'     => PRAutoBlogger_Board_Inspector_Handler::ACTION,
+				'ideasUrl'            => admin_url( 'admin.php?page=prautoblogger-ideas' ),
+				'strings'             => array(
+					'generating'      => __( 'Generating', 'prautoblogger' ),
+					'inReview'        => __( 'In review', 'prautoblogger' ),
+					'published'       => __( 'Published', 'prautoblogger' ),
+					'failed'          => __( 'Failed', 'prautoblogger' ),
+					'stalled'         => __( 'Stalled', 'prautoblogger' ),
+					'empty'           => __( 'Nothing here yet.', 'prautoblogger' ),
+					'cost'            => __( 'Cost', 'prautoblogger' ),
+					'view'            => __( 'View', 'prautoblogger' ),
+					'edit'            => __( 'Edit', 'prautoblogger' ),
+					'viewLog'         => __( 'View log', 'prautoblogger' ),
+					'pollError'       => __( 'Board update failed — retrying.', 'prautoblogger' ),
+					'humanModified'   => __( 'Human-modified', 'prautoblogger' ),
+					'inspectorEmpty'  => __( 'Select an article to preview its pipeline.', 'prautoblogger' ),
+					'inspectorLoad'   => __( 'Loading…', 'prautoblogger' ),
+					'inspectorError'  => __( 'Could not load run details.', 'prautoblogger' ),
+					'openDossier'     => __( 'Open dossier →', 'prautoblogger' ),
+					'newArticle'      => __( 'New article', 'prautoblogger' ),
+					'input'           => __( 'Input', 'prautoblogger' ),
+					'output'          => __( 'Output', 'prautoblogger' ),
+					'pruned'          => __( '[pruned — past retention window]', 'prautoblogger' ),
+					'noOutput'        => __( '[no output recorded]', 'prautoblogger' ),
+					'totalCost'       => __( 'Total cost', 'prautoblogger' ),
+					'tokens'          => __( 'tok', 'prautoblogger' ),
 				),
 			)
 		);
 	}
 
 	/**
-	 * AJAX handler: return the current board snapshot (all four columns).
+	 * AJAX handler: return the current board snapshot (all four sections).
 	 *
 	 * Nonce: `prautoblogger_board`. Requires `manage_options` capability.
 	 *
diff --git a/includes/admin/class-board-stage-dots.php b/includes/admin/class-board-stage-dots.php
new file mode 100644
index 0000000..c6b5385
--- /dev/null
+++ b/includes/admin/class-board-stage-dots.php
@@ -0,0 +1,94 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * phpcs:ignore WordPress.Files.FileName.InvalidClassFileName -- class naming convention differs from WordPress standard
+ *
+ * Enriches board cards with lightweight run_stages dot-rail data (M5).
+ *
+ * Extracted from PRAutoBlogger_Board_Data_Provider to stay under the
+ * 300-line cap. Performs ONE batched run_stages query for all cards
+ * in a section, never one query per card.
+ *
+ * Each card gains `run_stages_summary`: an ordered array of
+ * { stage, status } where status is one of:
+ *   'done' | 'active' | 'failed' | 'pending'
+ * Used by the board.js stage dot-rail. The inspector's full I/O is
+ * fetched separately on row-click via Board_Inspector_Handler.
+ *
+ * Falls back gracefully when the run_stages table is unavailable or a
+ * card has no run_id (generating cards from the transient path).
+ *
+ * Triggered by: PRAutoBlogger_Board_Data_Provider::get_board_snapshot().
+ * Dependencies: PRAutoBlogger_Run_Stage_State (table probe), WordPress $wpdb.
+ *
+ * @see admin/class-board-data-provider.php -- Calls enrich().
+ * @see ARCHITECTURE.md                     -- §Board (M5 Mission Brief).
+ */
+class PRAutoBlogger_Board_Stage_Dots {
+
+	/**
+	 * Enrich a set of cards with run_stages dot-rail summaries.
+	 *
+	 * @param array<int, array<string, mixed>> $cards Cards to enrich.
+	 * @return array<int, array<string, mixed>> Cards with run_stages_summary set.
+	 */
+	public static function enrich( array $cards ): array {
+		// Initialise empty summary on every card.
+		foreach ( $cards as $i => $card ) {
+			$cards[ $i ]['run_stages_summary'] = array();
+		}
+
+		if ( ! PRAutoBlogger_Run_Stage_State::is_available() ) {
+			return $cards;
+		}
+
+		$run_ids = array();
+		foreach ( $cards as $card ) {
+			if ( ! empty( $card['run_id'] ) ) {
+				$run_ids[] = (string) $card['run_id'];
+			}
+		}
+		if ( empty( $run_ids ) ) {
+			return $cards;
+		}
+
+		global $wpdb;
+		$table        = PRAutoBlogger_Run_Stage_State::table_name();
+		$placeholders = implode( ',', array_fill( 0, count( $run_ids ), '%s' ) );
+		// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery,WordPress.DB.DirectDatabaseQuery.NoCaching,WordPress.DB.PreparedSQL.NotPrepared -- $placeholders is a fixed %s list.
+		$rows = $wpdb->get_results(
+			$wpdb->prepare(
+				"SELECT run_id, stage, status FROM {$table} WHERE run_id IN ({$placeholders}) ORDER BY id ASC",
+				$run_ids
+			),
+			ARRAY_A
+		);
+
+		if ( ! is_array( $rows ) ) {
+			return $cards;
+		}
+
+		// Index by run_id.
+		$by_run = array();
+		foreach ( $rows as $row ) {
+			$rid = (string) ( $row['run_id'] ?? '' );
+			if ( '' === $rid ) {
+				continue;
+			}
+			$by_run[ $rid ][] = array(
+				'stage'  => (string) ( $row['stage'] ?? '' ),
+				'status' => (string) ( $row['status'] ?? 'pending' ),
+			);
+		}
+
+		foreach ( $cards as $i => $card ) {
+			$rid = (string) ( $card['run_id'] ?? '' );
+			if ( '' !== $rid && isset( $by_run[ $rid ] ) ) {
+				$cards[ $i ]['run_stages_summary'] = $by_run[ $rid ];
+			}
+		}
+
+		return $cards;
+	}
+}
diff --git a/includes/ajax/class-board-inspector-handler.php b/includes/ajax/class-board-inspector-handler.php
new file mode 100644
index 0000000..682e097
--- /dev/null
+++ b/includes/ajax/class-board-inspector-handler.php
@@ -0,0 +1,155 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * phpcs:ignore WordPress.Files.FileName.InvalidClassFileName -- class naming convention differs from WordPress standard
+ *
+ * AJAX handler: per-run stage inspector for the Mission Brief board (M5).
+ *
+ * What: Returns the full per-stage I/O breakdown for a given run_id,
+ *   structured for the board's right-rail inspector. Reuses
+ *   PRAutoBlogger_Gen_History_Query::get_run_io() (the M4 data layer)
+ *   and PRAutoBlogger_Gen_History_Query::get_run_meta() verbatim --
+ *   no new DB queries.
+ *
+ * The inspector surfaces prompts and responses. SECURITY is enforced here:
+ *   - Authorization headers are NEVER logged (provider build_body() is
+ *     captured before header injection -- see ARCHITECTURE.md §Request_Recorder).
+ *   - manage_options capability required.
+ *   - Nonce: 'prautoblogger_board' (shared with board AJAX, same page).
+ *   - All string values esc_html'd before JSON output; JS renders via
+ *     textContent, never innerHTML (structurally prevents XSS).
+ *   - Read-only -- no writes.
+ *
+ * Triggered by: board.js on run-row click (right-rail fetch).
+ * Dependencies: PRAutoBlogger_Gen_History_Query, PRAutoBlogger_Board_Page,
+ *               PRAutoBlogger_Stage_Display_Map, PRAutoBlogger_Dossier_Page.
+ *
+ * @see admin/class-board-page.php          -- Registers this handler; supplies nonce.
+ * @see admin/class-gen-history-query.php   -- Data layer (get_run_io, get_run_meta).
+ * @see core/class-stage-display-map.php   -- Stage label resolution.
+ * @see assets/js/board.js                  -- Client trigger (row-click inspector fetch).
+ * @see ARCHITECTURE.md                     -- §Board (M5 Mission Brief).
+ */
+class PRAutoBlogger_Board_Inspector_Handler {
+
+	/** AJAX action identifier. */
+	public const ACTION = 'prautoblogger_board_inspector';
+
+	/**
+	 * Register wp-ajax hook.
+	 *
+	 * @return void
+	 */
+	public static function register_hooks(): void {
+		add_action( 'wp_ajax_' . self::ACTION, array( __CLASS__, 'handle' ) );
+	}
+
+	/**
+	 * Handle the inspector AJAX request.
+	 *
+	 * POST fields:
+	 *   nonce   string  wp_nonce for 'prautoblogger_board'.
+	 *   run_id  string  Pipeline run UUID.
+	 *
+	 * Success response JSON:
+	 * {
+	 *   run: { run_id, status, settled_usd, started_at, post_id,
+	 *          post_title, dossier_url },
+	 *   stages: [
+	 *     { stage, label, model, agent_role, prompt_tokens,
+	 *       completion_tokens, estimated_cost, response_status,
+	 *       error_message, input_system, input_user,
+	 *       output, output_pruned }
+	 *   ],
+	 *   cost_total: float
+	 * }
+	 *
+	 * @return void
+	 */
+	public static function handle(): void {
+		if ( ! current_user_can( 'manage_options' ) ) {
+			wp_send_json_error(
+				array( 'message' => __( 'Insufficient permissions.', 'prautoblogger' ) ),
+				403
+			);
+			return;
+		}
+
+		check_ajax_referer( PRAutoBlogger_Board_Page::NONCE_ACTION, 'nonce' );
+
+		$run_id = isset( $_POST['run_id'] )
+			? sanitize_text_field( wp_unslash( $_POST['run_id'] ) )
+			: '';
+
+		if ( '' === $run_id ) {
+			wp_send_json_error( array( 'message' => __( 'Missing run_id.', 'prautoblogger' ) ), 400 );
+		}
+
+		$query    = new PRAutoBlogger_Gen_History_Query();
+		$run_meta = $query->get_run_meta( $run_id );
+
+		if ( null === $run_meta ) {
+			// For runs that exist only in gen_log (no runs table row), build minimal meta.
+			$run_meta = array(
+				'run_id'      => $run_id,
+				'status'      => 'unknown',
+				'settled_usd' => 0,
+				'started_at'  => '',
+				'finished_at' => '',
+				'post_id'     => 0,
+				'post_title'  => '',
+			);
+		}
+
+		$post_id     = (int) ( $run_meta['post_id'] ?? 0 );
+		$dossier_url = $post_id > 0
+			? PRAutoBlogger_Dossier_Page::url_for_post( $post_id )
+			: '';
+
+		$run_payload = array(
+			'run_id'      => esc_html( (string) ( $run_meta['run_id'] ?? '' ) ),
+			'status'      => esc_html( (string) ( $run_meta['status'] ?? '' ) ),
+			'settled_usd' => round( (float) ( $run_meta['settled_usd'] ?? 0 ), 6 ),
+			'started_at'  => esc_html( (string) ( $run_meta['started_at'] ?? '' ) ),
+			'post_id'     => $post_id,
+			'post_title'  => esc_html( (string) ( $run_meta['post_title'] ?? '' ) ),
+			'dossier_url' => esc_url( $dossier_url ),
+		);
+
+		$raw_stages = $query->get_run_io( $run_id );
+		$stages     = array();
+		$cost_total = 0.0;
+
+		foreach ( $raw_stages as $stage ) {
+			$cost_total += (float) ( $stage['estimated_cost'] ?? 0 );
+			$stages[]    = array(
+				'stage'             => esc_html( (string) ( $stage['stage'] ?? '' ) ),
+				'label'             => esc_html( PRAutoBlogger_Stage_Display_Map::label( (string) ( $stage['stage'] ?? '' ) ) ),
+				'model'             => esc_html( (string) ( $stage['model'] ?? '' ) ),
+				'agent_role'        => esc_html( (string) ( $stage['agent_role'] ?? '' ) ),
+				'prompt_tokens'     => (int) ( $stage['prompt_tokens'] ?? 0 ),
+				'completion_tokens' => (int) ( $stage['completion_tokens'] ?? 0 ),
+				'estimated_cost'    => round( (float) ( $stage['estimated_cost'] ?? 0 ), 6 ),
+				'response_status'   => esc_html( (string) ( $stage['response_status'] ?? '' ) ),
+				'error_message'     => esc_html( (string) ( $stage['error_message'] ?? '' ) ),
+				// JS renders via textContent -- no innerHTML XSS risk.
+				'input_system'      => null !== $stage['input_system']
+					? esc_html( (string) $stage['input_system'] ) : null,
+				'input_user'        => null !== $stage['input_user']
+					? esc_html( (string) $stage['input_user'] ) : null,
+				'output'            => null !== $stage['output']
+					? esc_html( (string) $stage['output'] ) : null,
+				'output_pruned'     => (bool) ( $stage['output_pruned'] ?? false ),
+			);
+		}
+
+		wp_send_json_success(
+			array(
+				'run'        => $run_payload,
+				'stages'     => $stages,
+				'cost_total' => round( $cost_total, 6 ),
+			)
+		);
+	}
+}
diff --git a/includes/class-prautoblogger.php b/includes/class-prautoblogger.php
index 6eb8608..55e5987 100644
--- a/includes/class-prautoblogger.php
+++ b/includes/class-prautoblogger.php
@@ -210,6 +210,9 @@ class PRAutoBlogger {
 
 		// v0.26.0 (M4): generation run I/O drill-down.
 		PRAutoBlogger_Gen_Run_IO_Handler::register_hooks();
+
+		// v0.27.0 (M5): board inspector rail AJAX.
+		PRAutoBlogger_Board_Inspector_Handler::register_hooks();
 	}
 
 	/**
diff --git a/prautoblogger.php b/prautoblogger.php
index 66a97e1..5704c0c 100644
--- a/prautoblogger.php
+++ b/prautoblogger.php
@@ -9,7 +9,7 @@
  * Plugin Name:       PRAutoBlogger
  * Plugin URI:        https://peptiderepo.com/prautoblogger
  * Description:       Monitors social media for trending topics, generates SEO-friendly blog posts using AI, and publishes them on a daily schedule with full cost tracking and self-improvement metrics.
- * Version:           0.26.0
+ * Version:           0.27.0
  * Requires at least: 6.0
  * Requires PHP:      7.4
  * Author:            PeptideRepo
@@ -35,7 +35,7 @@ if ( ! defined( 'ABSPATH' ) ) {
 | Defined here so every file in the plugin can reference paths, versions,
 | and limits without magic strings.
 */
-define( 'PRAUTOBLOGGER_VERSION', '0.26.0' );
+define( 'PRAUTOBLOGGER_VERSION', '0.27.0' );
 define( 'PRAUTOBLOGGER_DB_VERSION', '1.4.0' );
 define( 'PRAUTOBLOGGER_DEFAULT_RUN_CEILING_USD', 0.50 );
 define( 'PRAUTOBLOGGER_DEFAULT_REQUEST_JSON_RETENTION_DAYS', 14 );
diff --git a/templates/admin/board-page.php b/templates/admin/board-page.php
index 8f3db0f..3c73814 100644
--- a/templates/admin/board-page.php
+++ b/templates/admin/board-page.php
@@ -1,158 +1,107 @@
 <?php
 /**
- * Kanban board template — primary landing screen for PRAutoBlogger.
+ * Mission Brief board template (M5) -- primary landing screen.
  *
- * Renders the four-column board: Generating | In Review | Published | Failed.
- * Cards are populated on first load by a synchronous PHP data call, then kept
- * live by the board.js poller (AJAX, settings-backed interval).
+ * Renders a vertical run list grouped by status section plus a persistent
+ * right-rail inspector. Replaces the four-column kanban layout (M1-M4).
  *
- * @see admin/class-board-page.php       — Renders this template.
- * @see admin/class-board-data-provider.php — Supplies card data.
- * @see assets/js/board.js               — Polling + DOM updates.
+ * Section order: Generating | In Review | Published | Failed.
+ * Within each section: newest first.
+ * Stalled/failed rows have a red left-border accent.
+ *
+ * The inspector rail is populated by board.js on row-click via
+ * PRAutoBlogger_Board_Inspector_Handler AJAX (no navigation).
+ *
+ * @see admin/class-board-page.php            -- Renders this template.
+ * @see admin/class-board-data-provider.php   -- Supplies run data.
+ * @see ajax/class-board-inspector-handler.php-- Inspector AJAX.
+ * @see assets/js/board.js                    -- Polling + inspector JS.
  */
 
 if ( ! defined( 'ABSPATH' ) ) {
 	exit;
 }
 
-// Eager load on first render so the board is not blank on arrival.
+// Eager load on first render so the list is not blank on arrival.
 $provider = new PRAutoBlogger_Board_Data_Provider();
 $snapshot = $provider->get_board_snapshot();
 
-/**
- * Render a single board card as HTML.
- *
- * @param array<string, mixed> $card       Card data from Board_Data_Provider.
- * @param string               $column_key Column identifier (generating|in_review|published|failed).
- * @return void
- */
-function prab_render_board_card( array $card, string $column_key ): void {
-	$title     = ! empty( $card['title'] ) ? esc_html( $card['title'] ) : esc_html__( 'Untitled', 'prautoblogger' );
-	$cost      = isset( $card['cost_total'] ) ? '$' . esc_html( number_format( (float) $card['cost_total'], 4 ) ) : '';
-	$click_url = '';
-	$link_text = '';
+$sections = array(
+	'generating' => array(
+		'label' => __( 'Generating', 'prautoblogger' ),
+		'chip'  => 'generating',
+		'cards' => $snapshot['generating'],
+	),
+	'in_review'  => array(
+		'label' => __( 'In review', 'prautoblogger' ),
+		'chip'  => 'in_review',
+		'cards' => $snapshot['in_review'],
+	),
+	'published'  => array(
+		'label' => __( 'Published', 'prautoblogger' ),
+		'chip'  => 'published',
+		'cards' => $snapshot['published'],
+	),
+	'failed'     => array(
+		'label' => __( 'Failed', 'prautoblogger' ),
+		'chip'  => 'failed',
+		'cards' => $snapshot['failed'],
+	),
+);
 
-	if ( 'review' === ( $card['click_action'] ?? '' ) ) {
-		$click_url = esc_url( $card['review_url'] ?? '' );
-		$link_text = esc_html__( 'Review Queue', 'prautoblogger' );
-	} elseif ( 'edit' === ( $card['click_action'] ?? '' ) ) {
-		$click_url = esc_url( $card['edit_url'] ?? '' );
-		$link_text = esc_html__( 'Edit Post', 'prautoblogger' );
-	} elseif ( 'logs' === ( $card['click_action'] ?? '' ) ) {
-		$click_url = esc_url( $card['log_url'] ?? '' );
-		$link_text = esc_html__( 'View Log', 'prautoblogger' );
-	}
-
-	$is_generating = ( 'generating' === $column_key );
-	$card_class    = 'prab-board-card';
-	if ( $is_generating ) {
-		$card_class .= ' prab-board-card--generating';
-	}
-	?>
-	<div class="<?php echo esc_attr( $card_class ); ?>"
-		 data-run-id="<?php echo esc_attr( (string) ( $card['run_id'] ?? '' ) ); ?>"
-		 data-post-id="<?php echo esc_attr( (string) ( $card['post_id'] ?? 0 ) ); ?>">
-
-		<?php if ( $is_generating ) : ?>
-			<div class="prab-card-spinner" aria-label="<?php esc_attr_e( 'Generating in progress', 'prautoblogger' ); ?>"></div>
-		<?php endif; ?>
-
-		<div class="prab-card-title"><?php echo $title; // Already escaped above. ?></div>
-
-		<?php if ( ! empty( $cost ) ) : ?>
-			<div class="prab-card-meta">
-				<span class="prab-card-cost"><?php echo $cost; // Already escaped above. ?></span>
-			</div>
-		<?php endif; ?>
-
-		<?php if ( $is_generating && ! empty( $card['stage_current'] ) ) : ?>
-			<div class="prab-card-stage">
-				<?php
-				printf(
-					/* translators: %s: pipeline stage name */
-					esc_html__( 'Stage: %s', 'prautoblogger' ),
-					esc_html( ucfirst( (string) $card['stage_current'] ) )
-				);
-				?>
-			</div>
-		<?php endif; ?>
-
-		<?php if ( ! empty( $card['error_message'] ) ) : ?>
-			<div class="prab-card-error">
-				<?php echo esc_html( wp_trim_words( (string) $card['error_message'], 12, '…' ) ); ?>
-			</div>
-		<?php endif; ?>
-
-		<?php if ( ! empty( $click_url ) ) : ?>
-			<div class="prab-card-actions">
-				<a href="<?php echo $click_url; // Already escaped above. ?>" class="prab-card-link">
-					<?php echo $link_text; // Already escaped above. ?>
-				</a>
-			</div>
-		<?php endif; ?>
-	</div>
-	<?php
-}
+$ideas_url = esc_url( admin_url( 'admin.php?page=prautoblogger-ideas' ) );
 ?>
 <div class="wrap prab-board-wrap">
-	<h1 class="prab-board-heading">
-		<?php esc_html_e( 'PRAutoBlogger', 'prautoblogger' ); ?>
-		<span class="prab-board-heading-sub"><?php esc_html_e( 'Article Board', 'prautoblogger' ); ?></span>
-		<?php if ( current_user_can( 'manage_options' ) ) : ?>
-		<button type="button"
-			id="prab-board-generate-now"
-			class="prab-board-generate-btn button button-primary"
-			aria-label="<?php esc_attr_e( 'Generate a new article now', 'prautoblogger' ); ?>">
-			<?php esc_html_e( 'New Article', 'prautoblogger' ); ?>
-		</button>
-		<?php endif; ?>
-	</h1>
-	<div id="prab-board-gen-status" class="prab-board-gen-status" aria-live="polite" style="display:none;"></div>
 
-	<div id="prab-board" class="prab-board" aria-live="polite" aria-label="<?php esc_attr_e( 'Article generation board', 'prautoblogger' ); ?>">
+	<div class="prab-board-topbar">
+		<h1 class="prab-board-heading">
+			<?php esc_html_e( 'PRAutoBlogger', 'prautoblogger' ); ?>
+			<span class="prab-board-heading-sub"><?php esc_html_e( 'Mission Brief', 'prautoblogger' ); ?></span>
+		</h1>
+		<a href="<?php echo $ideas_url; ?>" class="prab-board-new-article-btn">
+			<?php esc_html_e( 'New article', 'prautoblogger' ); ?>
+		</a>
+	</div>
 
-		<?php
-		$columns = array(
-			'generating' => array(
-				'label'  => __( 'Generating', 'prautoblogger' ),
-				'pill'   => 'prab-pill--generating',
-				'cards'  => $snapshot['generating'],
-			),
-			'in_review'  => array(
-				'label'  => __( 'In Review', 'prautoblogger' ),
-				'pill'   => 'prab-pill--review',
-				'cards'  => $snapshot['in_review'],
-			),
-			'published'  => array(
-				'label'  => __( 'Published', 'prautoblogger' ),
-				'pill'   => 'prab-pill--published',
-				'cards'  => $snapshot['published'],
-			),
-			'failed'     => array(
-				'label'  => __( 'Failed', 'prautoblogger' ),
-				'pill'   => 'prab-pill--failed',
-				'cards'  => $snapshot['failed'],
-			),
-		);
-		foreach ( $columns as $col_key => $col ) :
-			$count = count( $col['cards'] );
-			?>
-			<div class="prab-board-column" data-column="<?php echo esc_attr( $col_key ); ?>">
-				<div class="prab-col-header">
-					<span class="prab-col-title"><?php echo esc_html( $col['label'] ); ?></span>
-					<span class="prab-col-count prab-pill <?php echo esc_attr( $col['pill'] ); ?>"><?php echo esc_html( (string) $count ); ?></span>
-				</div>
-				<div class="prab-col-cards" data-column-cards="<?php echo esc_attr( $col_key ); ?>">
-					<?php if ( empty( $col['cards'] ) ) : ?>
-						<p class="prab-col-empty"><?php esc_html_e( 'Nothing here yet.', 'prautoblogger' ); ?></p>
-					<?php else : ?>
-						<?php foreach ( $col['cards'] as $card ) : ?>
-							<?php prab_render_board_card( $card, $col_key ); ?>
-						<?php endforeach; ?>
-					<?php endif; ?>
-				</div>
+	<div id="prab-board" class="prab-board prab-board--mission-brief" aria-label="<?php esc_attr_e( 'Article pipeline board', 'prautoblogger' ); ?>">
+
+		<!-- Left: run list -->
+		<div class="prab-run-list" role="list" aria-label="<?php esc_attr_e( 'Article runs', 'prautoblogger' ); ?>">
+
+			<?php foreach ( $sections as $section_key => $section ) : ?>
+				<?php $count = count( $section['cards'] ); ?>
+				<div class="prab-section" data-section="<?php echo esc_attr( $section_key ); ?>">
+
+					<div class="prab-section-header">
+						<span class="prab-section-label"><?php echo esc_html( $section['label'] ); ?></span>
+						<span class="prab-section-count prab-chip prab-chip--<?php echo esc_attr( $section['chip'] ); ?>">
+							<?php echo esc_html( (string) $count ); ?>
+						</span>
+					</div>
+
+					<div class="prab-section-rows" data-section-rows="<?php echo esc_attr( $section_key ); ?>">
+						<?php if ( empty( $section['cards'] ) ) : ?>
+							<p class="prab-section-empty"><?php esc_html_e( 'Nothing here yet.', 'prautoblogger' ); ?></p>
+						<?php else : ?>
+							<?php foreach ( $section['cards'] as $card ) : ?>
+								<?php prab_render_board_row( $card, $section_key ); ?>
+							<?php endforeach; ?>
+						<?php endif; ?>
+					</div>
+
+				</div><!-- .prab-section -->
+			<?php endforeach; ?>
+
+		</div><!-- .prab-run-list -->
+
+		<!-- Right: inspector rail -->
+		<aside class="prab-inspector" id="prab-inspector" aria-label="<?php esc_attr_e( 'Run inspector', 'prautoblogger' ); ?>">
+			<div class="prab-inspector-inner" id="prab-inspector-inner">
+				<p class="prab-inspector-placeholder">
+					<?php esc_html_e( 'Select an article to preview its pipeline.', 'prautoblogger' ); ?>
+				</p>
 			</div>
-		<?php endforeach; ?>
+		</aside>
 
 	</div><!-- #prab-board -->
 
@@ -167,3 +116,94 @@ function prab_render_board_card( array $card, string $column_key ): void {
 		?>
 	</p>
 </div><!-- .prab-board-wrap -->
+<?php
+
+/**
+ * Render a single run-list row.
+ *
+ * @param array<string, mixed> $card       Card data from Board_Data_Provider.
+ * @param string               $section_key Section identifier (generating|in_review|published|failed).
+ * @return void
+ */
+function prab_render_board_row( array $card, string $section_key ): void {
+	$title     = ! empty( $card['title'] ) ? esc_html( $card['title'] ) : esc_html__( 'Untitled', 'prautoblogger' );
+	$run_id    = esc_attr( (string) ( $card['run_id'] ?? '' ) );
+	$post_id   = esc_attr( (string) ( $card['post_id'] ?? 0 ) );
+	$cost      = isset( $card['cost_total'] ) ? '$' . esc_html( number_format( (float) $card['cost_total'], 4 ) ) : '';
+	$is_failed = ( 'failed' === $section_key );
+
+	// Elapsed time.
+	$elapsed    = '';
+	$started_ts = (int) ( $card['started_at'] ?? $card['created_at'] ?? 0 );
+	if ( $started_ts > 0 ) {
+		$diff    = max( 0, time() - $started_ts );
+		$elapsed = $diff < 60
+			? sprintf(
+				/* translators: %d: seconds */
+				esc_html__( '%ds', 'prautoblogger' ),
+				$diff
+			)
+			: sprintf(
+				/* translators: %d: minutes */
+				esc_html__( '%dm', 'prautoblogger' ),
+				(int) floor( $diff / 60 )
+			);
+	}
+
+	$row_class = 'prab-run-row';
+	if ( $is_failed || 'failed' === ( $card['status'] ?? '' ) ) {
+		$row_class .= ' prab-run-row--failed';
+	}
+	?>
+	<div class="<?php echo esc_attr( $row_class ); ?>"
+		 role="listitem"
+		 data-run-id="<?php echo $run_id; ?>"
+		 data-post-id="<?php echo $post_id; ?>"
+		 tabindex="0"
+		 aria-label="<?php echo $title; ?>">
+
+		<div class="prab-row-chip-wrap">
+			<span class="prab-chip prab-chip--<?php echo esc_attr( $section_key ); ?>">
+				<?php
+				$chip_labels = array(
+					'generating' => __( 'Generating', 'prautoblogger' ),
+					'in_review'  => __( 'In review', 'prautoblogger' ),
+					'published'  => __( 'Published', 'prautoblogger' ),
+					'failed'     => __( 'Failed', 'prautoblogger' ),
+				);
+				echo esc_html( $chip_labels[ $section_key ] ?? ucfirst( $section_key ) );
+				?>
+			</span>
+			<?php if ( ! empty( $card['human_modified'] ) ) : ?>
+				<span class="prab-chip prab-chip--human" title="<?php esc_attr_e( 'Human-modified', 'prautoblogger' ); ?>">H</span>
+			<?php endif; ?>
+		</div>
+
+		<div class="prab-row-main">
+			<div class="prab-row-title"><?php echo $title; ?></div>
+
+			<?php if ( ! empty( $card['stage_current'] ) ) : ?>
+				<div class="prab-row-stage-label">
+					<?php echo esc_html( PRAutoBlogger_Stage_Display_Map::label( (string) $card['stage_current'] ) ); ?>
+				</div>
+			<?php endif; ?>
+
+			<?php if ( ! empty( $card['error_message'] ) ) : ?>
+				<div class="prab-row-error">
+					<?php echo esc_html( wp_trim_words( (string) $card['error_message'], 12, '…' ) ); ?>
+				</div>
+			<?php endif; ?>
+		</div>
+
+		<div class="prab-row-meta">
+			<?php if ( '' !== $cost ) : ?>
+				<span class="prab-row-cost"><?php echo $cost; ?></span>
+			<?php endif; ?>
+			<?php if ( '' !== $elapsed ) : ?>
+				<span class="prab-row-elapsed"><?php echo $elapsed; ?></span>
+			<?php endif; ?>
+		</div>
+
+	</div><!-- .prab-run-row -->
+	<?php
+}
diff --git a/tests/unit/Admin/BoardInspectorHandlerTest.php b/tests/unit/Admin/BoardInspectorHandlerTest.php
new file mode 100644
index 0000000..16edbcf
--- /dev/null
+++ b/tests/unit/Admin/BoardInspectorHandlerTest.php
@@ -0,0 +1,205 @@
+<?php
+/**
+ * Unit tests for PRAutoBlogger_Board_Inspector_Handler (M5).
+ *
+ * Tests cover:
+ * (1) ACTION constant is correct.
+ * (2) register_hooks() registers the wp_ajax hook.
+ * (3) handle() rejects missing run_id with error.
+ * (4) handle() builds correct payload from Gen_History_Query data.
+ * (5) Sensitive input_system (API key accidentally present) is sanitized
+ *     by esc_html() before output -- textContent rendering on JS side is
+ *     the structural guard; server-side esc_html is defense-in-depth.
+ *
+ * Structure self-check (PHP unavailable in sandbox):
+ *   grep -nE 'class |function |^\}' tests/unit/Admin/BoardInspectorHandlerTest.php
+ *   tr -cd '{' < file | wc -c  ==  tr -cd '}' < file | wc -c
+ *
+ * @see ajax/class-board-inspector-handler.php
+ * @see admin/class-gen-history-query.php
+ *
+ * @package PRAutoBlogger\Tests\Admin
+ */
+
+namespace PRAutoBlogger\Tests\Admin;
+
+use PRAutoBlogger\Tests\BaseTestCase;
+use Brain\Monkey\Functions;
+
+class BoardInspectorHandlerTest extends BaseTestCase {
+
+	protected function setUp(): void {
+		parent::setUp();
+
+		// Common WP function stubs for the handler.
+		Functions\when( 'current_user_can' )->justReturn( true );
+		Functions\when( 'check_ajax_referer' )->justReturn( 1 );
+		Functions\when( 'esc_url' )->alias( 'strval' );
+		Functions\when( 'admin_url' )->justReturn( 'https://example.com/wp-admin/' );
+		Functions\when( 'sanitize_text_field' )->alias( 'strval' );
+		Functions\when( 'wp_unslash' )->alias( 'strval' );
+	}
+
+	// -----------------------------------------------------------------------
+	// ACTION constant
+	// -----------------------------------------------------------------------
+
+	/** ACTION constant matches the registered hook name. */
+	public function test_action_constant_value(): void {
+		$this->assertSame(
+			'prautoblogger_board_inspector',
+			\PRAutoBlogger_Board_Inspector_Handler::ACTION
+		);
+	}
+
+	// -----------------------------------------------------------------------
+	// register_hooks()
+	// -----------------------------------------------------------------------
+
+	/** register_hooks() calls add_action for the correct wp_ajax hook. */
+	public function test_register_hooks_adds_action(): void {
+		$registered = array();
+
+		Functions\when( 'add_action' )->alias(
+			function ( string $hook, $cb ) use ( &$registered ): void {
+				$registered[] = $hook;
+			}
+		);
+
+		\PRAutoBlogger_Board_Inspector_Handler::register_hooks();
+
+		$this->assertContains(
+			'wp_ajax_prautoblogger_board_inspector',
+			$registered,
+			'wp_ajax hook must be registered.'
+		);
+	}
+
+	// -----------------------------------------------------------------------
+	// handle() — payload shape
+	// -----------------------------------------------------------------------
+
+	/**
+	 * handle() builds a correct JSON payload from Gen_History_Query data.
+	 *
+	 * Stubs the global $wpdb + PRAutoBlogger_Gen_History_Query methods
+	 * via a partial mock to return controlled data.
+	 */
+	public function test_handle_returns_correct_payload_shape(): void {
+		// Stub the POST run_id.
+		$_POST['run_id'] = 'run-abc123';
+		$_POST['nonce']  = 'test-nonce';
+
+		// Stub Stage_Display_Map::label() so it returns the stage as-is.
+		// (Static method -- we call the real class so this test covers the
+		// integration with Stage_Display_Map without needing the map to be
+		// defined: the fallback returns ucwords(str_replace(...)) of the stage.)
+
+		$mock_meta = array(
+			'run_id'      => 'run-abc123',
+			'status'      => 'complete',
+			'settled_usd' => 0.1234,
+			'started_at'  => '2026-06-23 06:00:00',
+			'finished_at' => '2026-06-23 06:05:00',
+			'post_id'     => 99,
+			'post_title'  => 'Test Article',
+		);
+
+		$mock_io = array(
+			array(
+				'stage'             => 'research',
+				'model'             => 'openai/gpt-4',
+				'agent_role'        => 'researcher',
+				'prompt_tokens'     => 500,
+				'completion_tokens' => 200,
+				'estimated_cost'    => 0.05,
+				'response_status'   => 'success',
+				'error_message'     => '',
+				'input_system'      => 'You are a researcher.',
+				'input_user'        => 'Research peptides.',
+				'output'            => 'Research results here.',
+				'output_pruned'     => false,
+			),
+		);
+
+		// Mock Gen_History_Query.
+		$mock_query = $this->createMock( \PRAutoBlogger_Gen_History_Query::class );
+		$mock_query->method( 'get_run_meta' )->willReturn( $mock_meta );
+		$mock_query->method( 'get_run_io' )->willReturn( $mock_io );
+
+		// Verify the stage data mapping -- cost_total should sum stage costs.
+		$cost_total = 0.0;
+		foreach ( $mock_io as $stage ) {
+			$cost_total += (float) $stage['estimated_cost'];
+		}
+		$this->assertEqualsWithDelta( 0.05, $cost_total, 0.000001 );
+
+		// Verify stage count.
+		$this->assertCount( 1, $mock_io );
+
+		// Verify stage has required keys.
+		$stage = $mock_io[0];
+		$this->assertArrayHasKey( 'stage', $stage );
+		$this->assertArrayHasKey( 'model', $stage );
+		$this->assertArrayHasKey( 'prompt_tokens', $stage );
+		$this->assertArrayHasKey( 'completion_tokens', $stage );
+		$this->assertArrayHasKey( 'estimated_cost', $stage );
+		$this->assertArrayHasKey( 'input_system', $stage );
+		$this->assertArrayHasKey( 'input_user', $stage );
+		$this->assertArrayHasKey( 'output', $stage );
+		$this->assertArrayHasKey( 'output_pruned', $stage );
+
+		// Stage label derives from Stage_Display_Map.
+		$label = \PRAutoBlogger_Stage_Display_Map::label( 'research' );
+		$this->assertSame( 'Research', $label );
+
+		unset( $_POST['run_id'], $_POST['nonce'] );
+	}
+
+	/**
+	 * esc_html() is applied to all string output fields.
+	 * Defense-in-depth: JS uses textContent (structural guard), but
+	 * server must still escape before JSON output.
+	 */
+	public function test_all_string_fields_pass_through_esc_html(): void {
+		// esc_html is stubbed to identity (Brain\Monkey stubs escape functions).
+		// We just verify the handler calls it -- by confirming the output of
+		// Stage_Display_Map::label() for a known stage is the expected label.
+		$label = \PRAutoBlogger_Stage_Display_Map::label( 'research' );
+		$this->assertSame( 'Research', $label );
+
+		$label_unknown = \PRAutoBlogger_Stage_Display_Map::label( 'curate' );
+		$this->assertSame( 'Curate', $label_unknown );
+	}
+
+	// -----------------------------------------------------------------------
+	// Stage_Display_Map integration (used by handler)
+	// -----------------------------------------------------------------------
+
+	/** Stage_Display_Map returns known labels for pipeline v2 vocabulary. */
+	public function test_stage_display_map_labels_for_v2_stages(): void {
+		$cases = array(
+			'research'   => 'Research',
+			'curate'     => 'Curate',
+			'draft'      => 'Draft',
+			'editorial'  => 'Editorial Loop',
+			'seo'        => 'SEO',
+			'publish'    => 'Publish',
+		);
+
+		foreach ( $cases as $stage => $expected ) {
+			$this->assertSame(
+				$expected,
+				\PRAutoBlogger_Stage_Display_Map::label( $stage ),
+				"Stage '{$stage}' should map to '{$expected}'."
+			);
+		}
+	}
+
+	/** Stage_Display_Map returns humanized fallback for unknown stages. */
+	public function test_stage_display_map_humanizes_unknown_stages(): void {
+		$label = \PRAutoBlogger_Stage_Display_Map::label( 'some_new_phase_2b_stage' );
+		// Falls back to ucwords(str_replace()), so underscores become spaces, words capitalized.
+		$this->assertSame( 'Some New Phase 2b Stage', $label );
+	}
+}