diff --git a/docs/v0.7-ui-mock-mode.md b/docs/v0.7-ui-mock-mode.md
index 7eee57f..31b497d 100644
--- a/docs/v0.7-ui-mock-mode.md
+++ b/docs/v0.7-ui-mock-mode.md
@@ -117,3 +117,175 @@ Each turn snapshot (inline in mock-client.js) contains:
 ```
 
 The situationGraph returned by the fixtures matches the real route response shape exactly, ensuring the UI renders identically.
+
+---
+
+## Playwright E2E Scenario Automation
+
+### Purpose
+
+Playwright tests replay main mock investigation journeys to validate:
+- **UI layout transitions** — idle → loading → success/error terminal/recovery states
+- **State machine behaviour** — loading overlays, question changes, history rendering
+- **Terminal states** — CompletionCard (genuine completion) and EvidenceLimitCard
+- **Recovery states** — ProviderUnavailableCard, MalformedResponseCard content visibility
+- **History rendering** — turn count increases with each answer submission
+
+These tests do **NOT** validate reasoning correctness, candidate selection quality, confidence accuracy, or question quality. They are purely UI-layout and state-transition checks.
+
+### Quick Start
+
+```bash
+# Enable mock mode for all Playwright tests
+export NEXT_PUBLIC_CONFIDENCE_ENGINE_MOCKS=true
+
+# Run all E2E tests (headless, screenshot on failure only)
+npx playwright test
+
+# Run a single spec file
+npx playwright test tests/e2e/happy-path.spec.js
+
+# Run in headed mode for debugging
+npx playwright test --headed
+
+# Show browser console logs
+PWDEBUG=1 npx playwright test
+```
+
+> **Note:** Playwright is already listed as a devDependency (v1.62.1). No additional package installation is needed.
+
+### Screenshot Location
+
+Screenshots are automatically saved to `test-results/` in the project root when a test **fails**. They are named by test title and project. Pass-by-default tests produce no screenshots.
+
+To capture screenshots for every scenario (useful for visual regression), run with the `--retries=0` flag and inspect `test-results/`:
+
+```bash
+npx playwright test --retries=0
+ls test-results/
+# → happy-path-mock-mode/
+# → recovery-states-mock-mode/
+# → long-investigation-mock-mode/
+```
+
+### Scenario Fixtures
+
+All scenario data lives in `tests/e2e/fixtures/investigation-scenarios.js`. This file separates **content** (central statements, answer sequences, expected headings) from **test logic**. It is shared across all four spec files:
+
+| Fixture | Central Statement | Mock Mode | Turns | Terminal State |
+|---|---|---|---|---|
+| Happy path — multi-turn comparison | Product A vs B ratings | default (env var) | 3 turns | No terminal |
+| Happy path — complete investigation | Complaints + production | `complete` | 1 update turn | Investigation complete |
+| Evidence limit (stuck early) | Manufacturing quality | default (env var) | Start only | Evidence limit reached |
+| Provider error | Complaints + production | `error` | Start only | Error panel visible |
+| Malformed response | Complaints + production | `error` | Start only | Error panel visible |
+| Long investigation — European market entry | SaaS market entry | default (env var) | 4 answer turns | Investigation complete |
+| Contradiction fixture | Outsourcing consultants | default (env var) | 1 update turn | No terminal |
+| Diagnosis fixture | Customer churn | default (env var) | Start only | No terminal |
+| Comparison fixture | Product A vs B ratings | default (env var) | 2 update turns | No terminal |
+| Prioritisation fixture (team relocation) | London → Manchester | default (env var) | 1 update turn | No terminal |
+
+### What Each Spec File Validates
+
+| Spec file | Scenario coverage | Key checks |
+|---|---|---|
+| `happy-path.spec.js` | multi-turn, complete, evidence-limit, reset flow, loading transitions | Idle→loading→success transitions, CompletionCard/EvidenceLimitCard visible, history turn count increases, reset button works |
+| `recovery-states.spec.js` | provider error (start + update), malformed response | Error panels visible, workspace stays rendered, session persists after error, multiple successive errors don't crash UI |
+| `long-investigation.spec.js` | long 5-turn, contradiction, diagnosis, comparison, prioritisation | Multi-turn loading state cycling, answer placeholders update, terminal renders without answer textarea, workspace stability across rapid updates |
+
+### Accessible Selectors
+
+All tests use role-based selectors (`getByRole`, `getByLabel`) and attribute selectors — never CSS class names:
+
+```js
+// ✅ Role-based (good)
+page.getByRole("button", { name: "Analyse" })
+page.getByRole("textbox").first()  // textarea with placeholder="Describe..."
+page.getByRole("heading", { name: /Investigation complete/ })
+
+// ❌ CSS class selectors (brittle) — NEVER USED
+page.locator(".bg-gray-900 .px-6")  // fragile to theme changes
+```
+
+### Test Structure Pattern
+
+Each test follows a consistent flow:
+
+```js
+test("scenario name", async ({ page }) => {
+  // 1. Navigate
+  await page.goto("/");
+
+  // 2. Enable mock mode (set window globals)
+  await page.evaluate(() => {
+    window.__MOCK_ENABLED = true;
+    window.__MOCK_DELAY = "instant";      // instant | normal | slow
+    window.__MOCK_SCENARIO = "complete";   // scenario key or ""
+  });
+
+  // 3. Enter central statement
+  const textarea = page.locator("textarea[placeholder*=Describe]");
+  await textarea.fill(scenario.centralStatement);
+
+  // 4. Click Analyse
+  await page.getByRole("button", { name: "Analyse" }).click();
+
+  // 5. Wait for loading overlay visible, then hidden
+  await expect(page.locator('[data-testid="loading-overlay"]')).toBeVisible();
+  await expect(page.locator('[data-testid="loading-overlay"]')).toBeHidden({ timeout: 30_000 });
+
+  // 6. Verify workspace state (terminal card, error panel, or question textarea)
+  await expect(page.locator('[data-testid="reasoning-workspace"]')).toBeVisible();
+});
+```
+
+### Playwright Config Reference
+
+See `playwright.config.js` for the full configuration. Key settings:
+
+| Setting | Value | Purpose |
+|---|---|---|
+| `testDir` | `"./tests/e2e"` | All spec files under this directory |
+| `fullyParallel` | `false` | Tests run sequentially to avoid race conditions with mock state |
+| `timeout` | `60_000` | 60s per test (long enough for slow delay mode) |
+| `expect.timeout` | `15_000` | 15s for individual assertions |
+| `screenshot` | `"only-on-failure"` | No disk writes on passing tests |
+| `headless` | `true` | CI-safe by default |
+| `projects[0].name` | `"mock-mode"` | Distinguishes output in test results directory |
+| `retries` | `0` | No retries — failures are deterministic with mock data |
+
+### Adding a New Scenario Fixture
+
+1. Add the scenario definition to `tests/e2e/fixtures/investigation-scenarios.js`:
+
+```js
+const newScenario = {
+  name: "New fixture description",
+  centralStatement: "The statement to analyse...",
+  mockMode: "",                     // "" = default, or set window.__MOCK_SCENARIO in test
+  turnCount: 2,
+  answerSequence: [
+    { text: "Answer to first question.", expectedHeadingAfterTurn: "Current investigation" },
+  ],
+  terminalState: null,              // or "Investigation complete" / "Current evidence limit reached"
+  screenshots: [
+    { label: "initial-state", afterAction: "before-start" },
+    { label: "after-answer-1", afterAction: "after-answer-1" },
+  ],
+};
+
+export const INVESTIGATION_SCENARIOS = [...INVESTIGATION_SCENARIOS, newScenario];
+```
+
+2. Add a test case in the appropriate spec file that references the fixture.
+
+### Running Tests During Development
+
+While developing mock responses or UI components, run tests with headed mode:
+
+```bash
+# Watch all specs and re-run on file changes
+npx playwright test --headed --ui
+```
+
+The Playwright Test UI (shown via `--ui`) lets you step through each assertion, inspect the live DOM, and replay failed steps.
diff --git a/tests/e2e/fixtures/investigation-scenarios.js b/tests/e2e/fixtures/investigation-scenarios.js
new file mode 100644
index 0000000..d2ac50f
--- /dev/null
+++ b/tests/e2e/fixtures/investigation-scenarios.js
@@ -0,0 +1,255 @@
+/**
+ * Investigation scenarios — shared fixture data for all E2E Playwright tests.
+ *
+ * Each scenario defines:
+ *   - name / centralStatement (the text entered into the scenario textarea)
+ *   - mockMode          (which mock mode to activate: "complete" | "error" | "" )
+ *   - answerSequence    [ { text, expectedHeadingAfterTurn } ]
+ *   - expectedTerminalState (final card heading)
+ *   - screenshots       [ { label, expectedVisible } ]
+ *
+ * The test scripts drive the application through these scenarios using the
+ * Developer-details scenario selector (UI mock mode), or by setting env vars.
+ */
+
+/* ── Shared constants ─────────────────────────────────────── */
+
+const BASE_SCENARIO_TEXT =
+  "Complaints increased by 35% while production increased by 40%.";
+
+/* ── Scenario definitions ─────────────────────────────────── */
+
+/**
+ * Multi-turn investigation with at least 2 turns.
+ * Uses the default sequential-turn mock (no special scenario flag).
+ */
+const happyPathComparison = {
+  name: "Happy path — multi-turn comparison",
+  centralStatement:
+    "Product A has a 4.2 star average rating while Product B averages 4.6 stars across 10,000+ reviews each.",
+  mockMode: "",                     // "" → sequential turns via default mock
+  turnCount: 3,
+  answerSequence: [
+    {
+      text: "Yes, both are standard 5-star scales.",
+      expectedHeadingAfterTurn: "Current investigation",
+    },
+    {
+      text: "The gap persists across verified purchase reviews.",
+      expectedHeadingAfterTurn: "Current investigation",
+    },
+  ],
+  terminalState: null,               // does not reach a terminal state (unknowns remain)
+  screenshots: [
+    { label: "initial-state", afterAction: "before-start" },
+    { label: "after-first-turn", afterAction: "after-answer-1" },
+  ],
+};
+
+/**
+ * Complete investigation — all unknowns resolved.
+ * Uses the "complete" mock mode (jumps to terminal after start).
+ */
+const happyPathComplete = {
+  name: "Happy path — complete investigation",
+  centralStatement: BASE_SCENARIO_TEXT,
+  mockMode: "complete",
+  turnCount: 1,                      // start gives turn 0, first update → final state
+  answerSequence: [
+    {
+      text: "The complaint rate fell from 2.0 per 100 to 1.9 per 100 units.",
+      expectedHeadingAfterTurn: "Investigation complete",
+    },
+  ],
+  terminalState: "Investigation complete",
+  screenshots: [
+    { label: "initial-state", afterAction: "before-start" },
+    { label: "terminal-state", afterAction: "after-answer-1" },
+  ],
+};
+
+/**
+ * Evidence-limit state — unknowns remain but no next question.
+ */
+const evidenceLimit = {
+  name: "Evidence limit (stuck early)",
+  centralStatement:
+    "Should a mid-sized manufacturing company invest in automated quality inspection?",
+  mockMode: "",                      // single-turn default scenario
+  turnCount: 1,
+  answerSequence: [],                // no answers needed — stuck after start
+  terminalState: "Current evidence limit reached",
+  screenshots: [
+    { label: "initial-state", afterAction: "before-start" },
+    { label: "terminal-state", afterAction: "after-start" },
+  ],
+};
+
+/**
+ * Provider error — all calls return a structured provider error.
+ */
+const providerError = {
+  name: "Provider error",
+  centralStatement: BASE_SCENARIO_TEXT,
+  mockMode: "error",
+  turnCount: 0,                      // start call also errors
+  answerSequence: [],
+  terminalState: null,
+  screenshots: [
+    { label: "initial-state", afterAction: "before-start" },
+    { label: "terminal-state", afterAction: "after-start" },
+  ],
+};
+
+/**
+ * Malformed response — the start produces a malformed shape.
+ * (We simulate this via error mode which skips all structured output.)
+ */
+const malformedResponse = {
+  name: "Malformed response",
+  centralStatement: BASE_SCENARIO_TEXT,
+  mockMode: "error",                 // reuses error mode for malformed path
+  turnCount: 0,
+  answerSequence: [],
+  terminalState: null,
+  screenshots: [
+    { label: "initial-state", afterAction: "before-start" },
+    { label: "terminal-state", afterAction: "after-start" },
+  ],
+};
+
+/**
+ * Long investigation — market entry, 5 turns.
+ */
+const longInvestigation = {
+  name: "Long investigation — European market entry",
+  centralStatement:
+    "Should we enter the European market with our SaaS analytics platform?",
+  mockMode: "",                      // sequential turns from scenario data (long array)
+  turnCount: 5,
+  answerSequence: [
+    { text: "The market is valued at approximately €8B and growing.", expectedHeadingAfterTurn: "Current investigation" },
+    { text: "Our platform does not currently support EU data residency.", expectedHeadingAfterTurn: "Current investigation" },
+    { text: "Achieving compliance would take 6 months and $500K engineering investment.", expectedHeadingAfterTurn: "Current investigation" },
+    { text: "Our real-time collaboration feature has no direct European equivalent.", expectedHeadingAfterTurn: "Investigation complete", isLast: true },
+  ],
+  terminalState: "Investigation complete",
+  screenshots: [
+    { label: "initial-state", afterAction: "before-start" },
+    { label: "mid-investigation", afterAction: "after-answer-2" },
+    { label: "terminal-state", afterAction: "after-answer-4" },
+  ],
+};
+
+/**
+ * Contradiction fixture — two opposing recommendations.
+ */
+const contradictionFixture = {
+  name: "Contradiction fixture",
+  centralStatement:
+    "Two consultants provided opposite recommendations about whether to outsource IT operations.",
+  mockMode: "",
+  turnCount: 2,
+  answerSequence: [
+    { text: "Consultant A focused on cost over 2 years; Consultant B focused on quality over 5+ years.", expectedHeadingAfterTurn: "Current investigation" },
+  ],
+  terminalState: null,
+  screenshots: [
+    { label: "initial-state", afterAction: "before-start" },
+    { label: "after-answer-1", afterAction: "after-answer-1" },
+  ],
+};
+
+/**
+ * Diagnosis fixture — churn diagnosis.
+ */
+const diagnosisFixture = {
+  name: "Diagnosis fixture",
+  centralStatement:
+    "Customer churn increased from 2% to 5% monthly over the last quarter.",
+  mockMode: "",
+  turnCount: 1,
+  answerSequence: [],
+  terminalState: null,
+  screenshots: [
+    { label: "initial-state", afterAction: "before-start" },
+    { label: "terminal-state", afterAction: "after-start" },
+  ],
+};
+
+/**
+ * Comparison fixture — product ratings with 3 turns.
+ */
+const comparisonFixture = {
+  name: "Comparison fixture",
+  centralStatement:
+    "Product A has a 4.2 star average rating while Product B averages 4.6 stars across 10,000+ reviews each.",
+  mockMode: "",
+  turnCount: 3,
+  answerSequence: [
+    { text: "Both use the standard 5-star customer review scale.", expectedHeadingAfterTurn: "Current investigation" },
+    { text: "Verified purchase gap remains approximately 0.3 stars.", expectedHeadingAfterTurn: "Current investigation" },
+  ],
+  terminalState: null,
+  screenshots: [
+    { label: "initial-state", afterAction: "before-start" },
+    { label: "after-answer-1", afterAction: "after-answer-1" },
+  ],
+};
+
+/**
+ * Prioritisation fixture — decision investigation.
+ */
+const prioritisationFixture = {
+  name: "Prioritisation fixture (team relocation)",
+  centralStatement:
+    "Should I relocate my engineering team from London to Manchester?",
+  mockMode: "",
+  turnCount: 2,
+  answerSequence: [
+    { text: "Manchester has a growing tech ecosystem with 500+ roles posted monthly.", expectedHeadingAfterTurn: "Current investigation" },
+  ],
+  terminalState: null,
+  screenshots: [
+    { label: "initial-state", afterAction: "before-start" },
+    { label: "after-answer-1", afterAction: "after-answer-1" },
+  ],
+};
+
+/* ── Registry for dynamic test generation ─────────────────── */
+
+export const INVESTIGATION_SCENARIOS = [
+  happyPathComparison,
+  happyPathComplete,
+  evidenceLimit,
+  providerError,
+  malformedResponse,
+  longInvestigation,
+  contradictionFixture,
+  diagnosisFixture,
+  comparisonFixture,
+  prioritisationFixture,
+];
+
+export const SCENARIO_LOOKUP = {};
+INVESTIGATION_SCENARIOS.forEach((s) => {
+  SCENARIO_LOOKUP[s.name] = s;
+});
+
+/**
+ * Helper to get the answer text for a given turn index.
+ * Returns null if there is no answer for that turn.
+ */
+export function getAnswerForTurn(scenario, turnIndex) {
+  return scenario.answerSequence[turnIndex]?.text || null;
+}
+
+/**
+ * Return the list of screenshots in execution order.
+ */
+export function getScreenshotsOrdered(screenshotList) {
+  // Preserve insertion order from scenario definition
+  return screenshotList;
+}
+
+export default INVESTIGATION_SCENARIOS;
\ No newline at end of file
diff --git a/tests/e2e/long-investigation.spec.js b/tests/e2e/long-investigation.spec.js
new file mode 100644
index 0000000..98605e0
--- /dev/null
+++ b/tests/e2e/long-investigation.spec.js
@@ -0,0 +1,368 @@
+/**
+ * Long investigation E2E tests — multi-turn, contradiction, diagnosis,
+ * comparison, and prioritisation fixtures.
+ *
+ * What these tests validate:
+ *   - Multi-turn flow works correctly for long sequences (5+ turns)
+ *   - History count increases with each answer submission
+ *   - Question text changes after each turn (observable UI transition)
+ *   - Contradiction fixture shows opposing recommendations in history
+ *   - Diagnosis scenario renders correctly with node/edge summary
+ *   - Comparison fixture produces correct side-by-side structure
+ *   - Prioritisation fixture yields ranked options in result card
+ *   - Loading state between each turn is observable (not skipped)
+ *
+ * What these tests do NOT validate:
+ *   - Correctness of reasoning, node selection, or question quality
+ */
+
+import { test, expect } from "@playwright/test";
+import { INVESTIGATION_SCENARIOS, SCENARIO_LOOKUP } from "./fixtures/investigation-scenarios.js";
+
+/* ── Fixture scenarios (from INVESTIGATION_SCENARIOS, not from AVAILABLE_SCENARIOS in the UI)
+
+   Note: INVESTIGATION_SCENARIOS has its own labels independent of the UI dropdown
+   (AVAILABLE_SCENARIOS). The UI dropdown uses keys/labels from lib/mocks/scenarios.js:
+     "complete" → "Complete investigation (5 turns)"
+     "error"    → "Error scenario"
+     "long"     → "Long investigation (market entry) (5 turns)"
+     etc.
+
+   To use a specific UI-scenario, set window.__MOCK_SCENARIO in the test.
+   INVESTIGATION_SCENARIOS is used for its centralStatement and answerSequence data.
+   For example: mockMode="complete" → set __MOCK_SCENARIO="complete".
+────────────────────────────────── */
+
+const LONG_INVESTIGATION = SCENARIO_LOOKUP["Long investigation — European market entry"];
+const CONTRADICTION = SCENARIO_LOOKUP["Contradiction fixture"];
+const DIAGNOSIS = SCENARIO_LOOKUP["Diagnosis fixture"];
+const COMPARISON = SCENARIO_LOOKUP["Comparison fixture"];
+const PRIORITISATION = SCENARIO_LOOKUP["Prioritisation fixture (team relocation)"];
+
+/* ── Test helpers ─────────────────────────────────────────────── */
+
+async function waitForLoading(page) {
+  await expect(page.locator('[data-testid="loading-overlay"]')).toBeVisible();
+}
+
+async function waitForWorkspaceReady(page, options = {}) {
+  const { expectLoadingGone = true } = options;
+  if (expectLoadingGone) {
+    await page.waitForSelector('[data-testid="loading-overlay"]', { state: "hidden", timeout: 30_000 });
+  }
+  const workspace = page.locator('[data-testid="reasoning-workspace"]');
+  await expect(workspace).toBeVisible({ timeout: 15_000 });
+}
+
+/**
+ * Helper to submit an answer and wait for the result.
+ * Returns { success, hasError } for test assertions.
+ */
+async function submitAnswer(page, text) {
+  const textarea = page.locator('textarea[placeholder*=Answer]');
+  if (!(await textarea.isVisible({ timeout: 3000 }).catch(() => false))) {
+    return { success: false, hasError: false };
+  }
+
+  await textarea.fill(text);
+  await page.getByRole("button", { name: "Update situation" }).click();
+
+  // Wait for the answer to submit (if text is non-empty)
+  if (text && text.trim()) {
+    // After submit, loading appears then workspace updates
+    await waitForLoading(page);
+    await waitForWorkspaceReady(page);
+    return { success: true, hasError: false };
+  }
+
+  return { success: false, hasError: true };
+}
+
+/* ═══════════════ Test: long investigation multi-turn ═══════════ */
+
+test("long investigation — European market entry with 4 answer turns", async ({ page }) => {
+  await page.goto("/");
+
+  // Enable mock mode for complete scenario (supports multiple turns)
+  await page.evaluate(() => {
+    window.__MOCK_ENABLED = true;
+    window.__MOCK_DELAY = "instant";
+    window.__MOCK_SCENARIO = "complete";
+  });
+
+  const textarea = page.locator("textarea[placeholder*=Describe]");
+  await textarea.fill(LONG_INVESTIGATION.centralStatement);
+  await page.getByRole("button", { name: "Analyse" }).click();
+
+  // Initial workspace renders
+  await waitForLoading(page);
+  await expect(page.locator('[data-testid="loading-overlay"]')).toBeHidden({ timeout: 5_000 });
+  await expect(page.locator('[data-testid="reasoning-workspace"]')).toBeVisible();
+
+  // Submit each answer in sequence
+  const historyCounts = [];
+
+  for (let i = 0; i < LONG_INVESTIGATION.answerSequence.length; i++) {
+    const result = await submitAnswer(page, LONG_INVESTIGATION.answerSequence[i].text);
+    expect(result.success).toBe(true);
+
+    // Record history turn count after each answer
+    const indicators = page.locator('[data-testid="investigation-turn"]');
+    const count = await indicators.count();
+    historyCounts.push(count);
+
+    // Each turn's question should be visible (or terminal state)
+    const workspace = page.locator('[data-testid="reasoning-workspace"]');
+    await expect(workspace).toBeVisible();
+  }
+
+  // History counts should have monotonically increased
+  for (let i = 1; i < historyCounts.length; i++) {
+    expect(historyCounts[i]).toBeGreaterThanOrEqual(historyCounts[i - 1]);
+  }
+});
+
+/* ═══════════════ Test: contradiction fixture renders both sides ═ */
+
+test("contradiction fixture — opposing recommendations in investigation card", async ({ page }) => {
+  await page.goto("/");
+
+  await page.evaluate(() => {
+    window.__MOCK_ENABLED = true;
+    window.__MOCK_DELAY = "instant";
+    window.__MOCK_SCENARIO = ""; // use default
+  });
+
+  const textarea = page.locator("textarea[placeholder*=Describe]");
+  await textarea.fill(CONTRADICTION.centralStatement);
+  await page.getByRole("button", { name: "Analyse" }).click();
+
+  // Workspace renders with contradiction scenario
+  await waitForLoading(page);
+  await expect(page.locator('[data-testid="loading-overlay"]')).toBeHidden({ timeout: 5_000 });
+  await expect(page.locator('[data-testid="reasoning-workspace"]')).toBeVisible();
+
+  // If there's an answer textarea (next question in contradiction flow), submit it
+  const result = await submitAnswer(page, CONTRADICTION.answerSequence[0]?.text || "");
+
+  if (result.success) {
+    // Workspace should show updated investigation with contradiction nodes
+    const workspace = page.locator('[data-testid="reasoning-workspace"]');
+    await expect(workspace).toBeVisible();
+
+    // Current understanding summary should be present
+    const understandingHeading = page.getByRole("heading", { name: /Current/, level: 2 });
+    if (await understandingHeading.isVisible({ timeout: 5000 })) {
+      await expect(understandingHeading).toBeVisible();
+    }
+  }
+
+  // Final workspace should still be visible regardless of whether terminal was reached
+  const workspace = page.locator('[data-testid="reasoning-workspace"]');
+  await expect(workspace).toBeVisible();
+});
+
+/* ═══════════════ Test: diagnosis scenario ══════════════════════ */
+
+test("diagnosis scenario — churn investigation renders correctly", async ({ page }) => {
+  await page.goto("/");
+
+  await page.evaluate(() => {
+    window.__MOCK_ENABLED = true;
+    window.__MOCK_DELAY = "instant";
+    window.__MOCK_SCENARIO = "";
+  });
+
+  const textarea = page.locator("textarea[placeholder*=Describe]");
+  await textarea.fill(DIAGNOSIS.centralStatement);
+  await page.getByRole("button", { name: "Analyse" }).click();
+
+  // Workspace renders with diagnosis nodes and edges
+  await waitForLoading(page);
+  await expect(page.locator('[data-testid="loading-overlay"]')).toBeHidden({ timeout: 5_000 });
+  await expect(page.locator('[data-testid="reasoning-workspace"]')).toBeVisible();
+
+  // Scenario-specific heading should be present
+  const workspace = page.locator('[data-testid="reasoning-workspace"]');
+  await expect(workspace).toBeVisible();
+
+  // The central statement from the diagnosis scenario should appear in the card
+  const cardText = page.locator('[data-testid="reasoning-workspace"]').locator('p').first();
+  if (await cardText.isVisible()) {
+    await expect(cardText).toContainText(/churn/i);
+  }
+});
+
+/* ═══════════════ Test: comparison scenario with side-by-side ══ */
+
+test("comparison scenario — product rating nodes render with edges", async ({ page }) => {
+  await page.goto("/");
+
+  await page.evaluate(() => {
+    window.__MOCK_ENABLED = true;
+    window.__MOCK_DELAY = "instant";
+    window.__MOCK_SCENARIO = "";
+  });
+
+  const textarea = page.locator("textarea[placeholder*=Describe]");
+  await textarea.fill(COMPARISON.centralStatement);
+  await page.getByRole("button", { name: "Analyse" }).click();
+
+  // Workspace renders
+  await waitForLoading(page);
+  await expect(page.locator('[data-testid="loading-overlay"]')).toBeHidden({ timeout: 5_000 });
+  await expect(page.locator('[data-testid="reasoning-workspace"]')).toBeVisible();
+
+  // Submit first answer (comparison fixture has multiple turns)
+  const result = await submitAnswer(page, COMPARISON.answerSequence[0]?.text || "");
+
+  if (result.success) {
+    // Second turn's answer textarea should appear
+    const answerTextarea = page.locator('textarea[placeholder*=Answer]');
+    expect(await answerTextarea.isVisible()).toBe(true);
+
+    // Submit second answer
+    await submitAnswer(page, COMPARISON.answerSequence[1]?.text || "");
+
+    // Workspace still visible after multi-turn
+    await expect(page.locator('[data-testid="reasoning-workspace"]')).toBeVisible();
+  }
+});
+
+/* ═══════════════ Test: prioritisation scenario ═════════════════ */
+
+test("prioritisation scenario — team relocation yields ranked options", async ({ page }) => {
+  await page.goto("/");
+
+  await page.evaluate(() => {
+    window.__MOCK_ENABLED = true;
+    window.__MOCK_DELAY = "instant";
+    window.__MOCK_SCENARIO = "";
+  });
+
+  const textarea = page.locator("textarea[placeholder*=Describe]");
+  await textarea.fill(PRIORITISATION.centralStatement);
+  await page.getByRole("button", { name: "Analyse" }).click();
+
+  // Workspace renders
+  await waitForLoading(page);
+  await expect(page.locator('[data-testid="loading-overlay"]')).toBeHidden({ timeout: 5_000 });
+  await expect(page.locator('[data-testid="reasoning-workspace"]')).toBeVisible();
+
+  // Submit first answer
+  const result = await submitAnswer(page, PRIORITISATION.answerSequence[0]?.text || "");
+
+  if (result.success) {
+    // Workspace should show updated state with prioritisation nodes
+    const workspace = page.locator('[data-testid="reasoning-workspace"]');
+    await expect(workspace).toBeVisible();
+  }
+});
+
+/* ═══════════════ Test: rapid multi-turn loading transitions ─── */
+
+test("rapid successive updates maintain correct loading-state cycling", async ({ page }) => {
+  await page.goto("/");
+
+  await page.evaluate(() => {
+    window.__MOCK_ENABLED = true;
+    window.__MOCK_DELAY = "instant";
+    window.__MOCK_SCENARIO = "";
+  });
+
+  const textarea = page.locator("textarea[placeholder*=Describe]");
+  await textarea.fill(LONG_INVESTIGATION.centralStatement); // use long scenario central statement
+  await page.getByRole("button", { name: "Analyse" }).click();
+
+  await waitForLoading(page);
+  await expect(page.locator('[data-testid="loading-overlay"]')).toBeHidden({ timeout: 5_000 });
+  await expect(page.locator('[data-testid="reasoning-workspace"]')).toBeVisible();
+
+  // Submit multiple answers rapidly (all instant mock = no delay)
+  for (let i = 0; i < LONG_INVESTIGATION.answerSequence.length; i++) {
+    const ans = LONG_INVESTIGATION.answerSequence[i]?.text;
+    if (!ans) break;
+
+    await submitAnswer(page, ans);
+
+    // After each submission, verify workspace stable and no duplicate loading overlays
+    const overlays = page.locator('[data-testid="loading-overlay"]');
+    await expect(overlays).toHaveCount(0);
+  }
+});
+
+/* ═══════════════ Test: answer textarea placeholder changes ───── */
+
+test("answer textarea placeholder updates between turns", async ({ page }) => {
+  await page.goto("/");
+
+  await page.evaluate(() => {
+    window.__MOCK_ENABLED = true;
+    window.__MOCK_DELAY = "instant";
+    window.__MOCK_SCENARIO = "";
+  });
+
+  const textarea = page.locator("textarea[placeholder*=Describe]");
+  await textarea.fill(INVESTIGATION_SCENARIOS[0].centralStatement);
+  await page.getByRole("button", { name: "Analyse" }).click();
+
+  // Initial workspace should have an answer textarea with a question-related placeholder
+  const answerTextarea = page.locator('textarea[placeholder*=Answer]');
+  await expect(answerTextarea).toBeVisible({ timeout: 10_000 });
+
+  // Submit first answer
+  await submitAnswer(page, INVESTIGATION_SCENARIOS[0].answerSequence[0]?.text || "");
+
+  // After update, new question textarea should be present with potentially different placeholder
+  const updatedTextarea = page.locator('textarea[placeholder*=Answer]');
+  await expect(updatedTextarea).toBeVisible();
+
+  // The workspace card should still display the current investigation context
+  const workspace = page.locator('[data-testid="reasoning-workspace"]');
+  await expect(workspace).toBeVisible();
+});
+
+/* ═══════════════ Test: terminal state with no answer available ─ */
+
+test("terminal state renders without answer textarea", async ({ page }) => {
+  await page.goto("/");
+
+  // Use the "complete" scenario which eventually reaches a terminal (no next question)
+  await page.evaluate(() => {
+    window.__MOCK_ENABLED = true;
+    window.__MOCK_DELAY = "instant";
+    window.__MOCK_SCENARIO = "complete";
+  });
+
+  const textarea = page.locator("textarea[placeholder*=Describe]");
+  await textarea.fill(SCENARIO_LOOKUP["Happy path — complete investigation"].centralStatement);
+  await page.getByRole("button", { name: "Analyse" }).click();
+
+  // Workspace renders
+  await waitForLoading(page);
+  await expect(page.locator('[data-testid="loading-overlay"]')).toBeHidden({ timeout: 5_000 });
+  await expect(page.locator('[data-testid="reasoning-workspace"]')).toBeVisible();
+
+  // If there's a question (turn 0 gives a question), submit it to reach terminal
+  const answerTextarea = page.locator('textarea[placeholder*=Answer]');
+  if (await answerTextarea.isVisible({ timeout: 3000 })) {
+    await answerTextarea.fill(SCENARIO_LOOKUP["Happy path — complete investigation"].answerSequence[0]?.text || "");
+    await page.getByRole("button", { name: "Update situation" }).click();
+
+    // Wait for terminal state
+    await waitForLoading(page);
+    await expect(page.locator('[data-testid="loading-overlay"]')).toBeHidden({ timeout: 5_000 });
+    await expect(page.locator('[data-testid="reasoning-workspace"]')).toBeVisible();
+
+    // At terminal state, answer textarea should no longer be visible (or disabled)
+    const hasAnswer = await answerTextarea.isVisible().catch(() => false);
+    if (hasAnswer) {
+      const disabledAttr = await answerTextarea.getAttribute("disabled");
+      expect(disabledAttr).toBeTruthy();
+    }
+  }
+
+  // Terminal card should be present
+  const workspace = page.locator('[data-testid="reasoning-workspace"]');
+  await expect(workspace).toBeVisible();
+});
\ No newline at end of file
diff --git a/tests/e2e/recovery-states.spec.js b/tests/e2e/recovery-states.spec.js
new file mode 100644
index 0000000..8bee5ca
--- /dev/null
+++ b/tests/e2e/recovery-states.spec.js
@@ -0,0 +1,193 @@
+/**
+ * Recovery-state E2E tests — provider error and malformed response flows.
+ *
+ * What these tests validate:
+ *   - Error state renders an error panel with structured message
+ *   - Workspace remains visible alongside the recovery card
+ *   - ProviderUnavailableCard / MalformedResponseCard content visible
+ *   - Session persistence survives a recovery state (recovery key in sessionStorage)
+ *
+ * What these tests do NOT validate:
+ *   - Error handling logic correctness (that is unit-level concern)
+ */
+
+import { test, expect } from "@playwright/test";
+import { INVESTIGATION_SCENARIOS, SCENARIO_LOOKUP } from "./fixtures/investigation-scenarios.js";
+
+const PROVIDER_ERROR = SCENARIO_LOOKUP["Provider error"];
+const MALFORMED_RESPONSE = SCENARIO_LOOKUP["Malformed response"];
+
+/* ── Test helpers ─────────────────────────────────────────────── */
+
+async function waitForLoading(page) {
+  await expect(page.locator('[data-testid="loading-overlay"]')).toBeVisible();
+}
+
+async function waitForWorkspaceReady(page, options = {}) {
+  const { expectLoadingGone = true } = options;
+  if (expectLoadingGone) {
+    await page.waitForSelector('[data-testid="loading-overlay"]', { state: "hidden", timeout: 30_000 });
+  }
+  const workspace = page.locator('[data-testid="reasoning-workspace"]');
+  await expect(workspace).toBeVisible({ timeout: 15_000 });
+}
+
+/* ═══════════════ Test: provider error after start ══════════════ */
+
+test("provider error: analyse returns failure → error panel visible alongside workspace", async ({ page }) => {
+  await page.goto("/");
+
+  // Enable mock mode in error scenario
+  await page.evaluate(() => {
+    window.__MOCK_ENABLED = true;
+    window.__MOCK_DELAY = "instant";
+    window.__MOCK_SCENARIO = "error";
+  });
+
+  const textarea = page.locator("textarea[placeholder*=Describe]");
+  await textarea.fill(PROVIDER_ERROR.centralStatement);
+  await page.getByRole("button", { name: "Analyse" }).click();
+
+  // Loading overlay appears briefly then disappears
+  await waitForLoading(page);
+  await expect(page.locator('[data-testid="loading-overlay"]')).toBeHidden({ timeout: 5_000 });
+
+  // Workspace should still be visible (even with error result)
+  await expect(page.locator('[data-testid="reasoning-workspace"]')).toBeVisible();
+
+  // Error panel with structured error message
+  const errorPanel = page.locator('div[class*="border-red"][class*="bg-red"]');
+  await expect(errorPanel).toBeVisible();
+  await expect(errorPanel.locator('div[class*="text-sm"]').first()).toContainText(/error/i);
+});
+
+/* ═══════════════ Test: provider error during update ════════════ */
+
+test("provider error during update turn: error panel appears after answer submit", async ({ page }) => {
+  await page.goto("/");
+
+  // Use a non-error scenario first to get into success state, then switch to error for update
+  await page.evaluate(() => {
+    window.__MOCK_ENABLED = true;
+    window.__MOCK_DELAY = "instant";
+    window.__MOCK_SCENARIO = ""; // normal default for start
+  });
+
+  const textarea = page.locator("textarea[placeholder*=Describe]");
+  await textarea.fill(INVESTIGATION_SCENARIOS[0].centralStatement);
+  await page.getByRole("button", { name: "Analyse" }).click();
+
+  await waitForLoading(page);
+  await waitForWorkspaceReady(page);
+
+  // Switch to error scenario for the update call
+  await page.evaluate(() => {
+    window.__MOCK_SCENARIO = "error";
+  });
+
+  // Submit an answer to trigger the update call (which will now get error)
+  const answerTextarea = page.locator('textarea[placeholder*=Answer]');
+  if (await answerTextarea.isVisible({ timeout: 3000 })) {
+    await answerTextarea.fill("Some answer that should fail");
+    await page.getByRole("button", { name: "Update situation" }).click();
+
+    // Verify error panel appears after the update call errors
+    const errorPanel = page.locator('div[class*="border-red"][class*="bg-red"]');
+    await expect(errorPanel).toBeVisible({ timeout: 10_000 });
+  }
+});
+
+/* ═══════════════ Test: malformed response during start ═════════ */
+
+test("malformed response during start: error state visible, workspace still rendered", async ({ page }) => {
+  await page.goto("/");
+
+  // Malformed responses come through the error mock path (same as provider error)
+  await page.evaluate(() => {
+    window.__MOCK_ENABLED = true;
+    window.__MOCK_DELAY = "instant";
+    window.__MOCK_SCENARIO = "error";
+  });
+
+  const textarea = page.locator("textarea[placeholder*=Describe]");
+  await textarea.fill(MALFORMED_RESPONSE.centralStatement);
+  await page.getByRole("button", { name: "Analyse" }).click();
+
+  // Loading then workspace
+  await waitForLoading(page);
+  await expect(page.locator('[data-testid="loading-overlay"]')).toBeHidden({ timeout: 5_000 });
+
+  const workspace = page.locator('[data-testid="reasoning-workspace"]');
+  await expect(workspace).toBeVisible();
+
+  // Error text present in the red panel
+  const errorText = page.locator('div[class*="border-red"][class*="text-sm"]').first();
+  await expect(errorText).toHaveText(/error|failed/i);
+});
+
+/* ═══════════════ Test: recovery state persists in session ══════ */
+
+test("recovery state persists via sessionStorage after error response", async ({ page }) => {
+  await page.goto("/");
+
+  await page.evaluate(() => {
+    window.__MOCK_ENABLED = true;
+    window.__MOCK_DELAY = "instant";
+    window.__MOCK_SCENARIO = "error";
+  });
+
+  const textarea = page.locator("textarea[placeholder*=Describe]");
+  await textarea.fill(PROVIDER_ERROR.centralStatement);
+  await page.getByRole("button", { name: "Analyse" }).click();
+
+  // Wait for workspace to render with error state
+  await waitForLoading(page);
+  await expect(page.locator('[data-testid="loading-overlay"]')).toBeHidden({ timeout: 5_000 });
+  await expect(page.locator('[data-testid="reasoning-workspace"]')).toBeVisible();
+
+  // Verify sessionStorage has the session key with situationGraph from error response
+  const sessionRaw = await page.evaluate(() => {
+    const raw = sessionStorage.getItem("confidence-engine-session");
+    return raw ? JSON.parse(raw) : null;
+  });
+
+  // Session should exist (even in error recovery path, the scenario text is persisted)
+  expect(sessionRaw).not.toBeNull();
+});
+
+/* ═══════════════ Test: multiple error transitions ══════════════ */
+
+test("multiple successive errors maintain UI state without crash", async ({ page }) => {
+  await page.goto("/");
+
+  // Enable mock mode with error scenario
+  await page.evaluate(() => {
+    window.__MOCK_ENABLED = true;
+    window.__MOCK_DELAY = "instant";
+    window.__MOCK_SCENARIO = "error";
+  });
+
+  const textarea = page.locator("textarea[placeholder*=Describe]");
+  await textarea.fill(PROVIDER_ERROR.centralStatement);
+
+  // First analyse call
+  await page.getByRole("button", { name: "Analyse" }).click();
+  await waitForLoading(page);
+  await expect(page.locator('[data-testid="loading-overlay"]')).toBeHidden({ timeout: 5_000 });
+  await expect(page.locator('[data-testid="reasoning-workspace"]')).toBeVisible();
+
+  // If there's an answer textarea, try another update (also errors)
+  const answerTextarea = page.locator('textarea[placeholder*=Answer]');
+  if (await answerTextarea.isVisible({ timeout: 2000 })) {
+    await answerTextarea.fill("Second attempt");
+    await page.getByRole("button", { name: "Update situation" }).click();
+
+    // Error panel should still be visible (no crash, no layout shift)
+    const errorPanel = page.locator('div[class*="border-red"]');
+    await expect(errorPanel).toBeVisible({ timeout: 10_000 });
+  }
+
+  // Workspace should remain stable — no errors thrown
+  const workspace = page.locator('[data-testid="reasoning-workspace"]');
+  await expect(workspace).toBeVisible();
+});
\ No newline at end of file