diff --git a/docs/MCP+A2A/EXECUTION_CHECKLIST.md b/docs/MCP+A2A/EXECUTION_CHECKLIST.md
index f1d7fe59..76799646 100644
--- a/docs/MCP+A2A/EXECUTION_CHECKLIST.md
+++ b/docs/MCP+A2A/EXECUTION_CHECKLIST.md
@@ -47,7 +47,26 @@ This is the “ready to start building” checklist that turns the docs in this
 - [x] Python sidecar health visible via `extraction.sidecarHealth`
 - [ ] End-to-end integration test with real platform-service (Phase 2)
 
-## 5) Phase 2+ quick sanity checks
+## 5) Phase 2 — A2A orchestration ✅ COMPLETE
+
+### Milestone D (A2A runner + handoff schemas) ✅ — d1d643f+
+
+- [x] Handoff artifact schemas (Zod): `SupportIncidentBrief`, `TelemetryFindings`, `DiagnosticsSessionResult`, `FinalIncidentReport`
+- [x] `DispatcherAgent` — validates brief, fills default 24h time window, decides which steps to run
+- [x] `TelemetryAnalystAgent` — queries clusters, filters by platform, derives hypotheses + actions
+- [x] `DiagnosticsOrchestratorAgent` — conditionally creates expiring session based on findings severity
+- [x] `ReportWriterAgent` — assembles structured `FinalIncidentReport` + full markdown report
+- [x] `runIncidentPipeline` runner — logs every step with stable `runId` + `stepId` (audit tracing)
+- [x] `support.runIncidentPipeline` MCP tool — single callable entry point for the pipeline
+- [x] `McpToolRequest.log` — structured logger added; `routes.ts` passes `req.log` to all tool calls
+- [x] 6 Vitest tests covering: no-session run, session creation, skip when no target, upstream failure, log audit, time window defaulting
+
+### Acceptance criteria ✅
+
+- [x] "Support Debug Pack" runs end-to-end via Dispatcher → Telemetry Analyst → Diagnostics Orchestrator → Report Writer
+- [x] Every handoff is logged with stable `runId` + `stepId` (Phase 1: logs; Phase 2+: Cosmos container)
+
+## 6) Phase 3+ quick sanity checks
 
 - If you make telemetry policy-aware clients:
   - ensure `GET /api/telemetry/config` consumption is cached (ETag) and privacy-safe.
diff --git a/services/mcp-server/src/modules/a2a/agents/diagnostics-orchestrator.ts b/services/mcp-server/src/modules/a2a/agents/diagnostics-orchestrator.ts
new file mode 100644
index 00000000..fb4f25f9
--- /dev/null
+++ b/services/mcp-server/src/modules/a2a/agents/diagnostics-orchestrator.ts
@@ -0,0 +1,78 @@
+/**
+ * DiagnosticsOrchestratorAgent — optionally opens a live remote diagnostics
+ * session for the affected user / install ID based on TelemetryFindings.
+ */
+
+import { randomUUID } from 'node:crypto';
+import { diagnosticsCreateSession } from '../../../lib/platform-client.js';
+import type { DispatchDecision, TelemetryFindings, DiagnosticsSessionResult } from '../types.js';
+
+interface CreatedSession {
+  id: string;
+  status: string;
+  expiresAt: string;
+  collectionLevel?: string;
+  targetUserId?: string;
+  targetAnonymousId?: string;
+}
+
+export async function orchestrate(
+  decision: DispatchDecision,
+  findings: TelemetryFindings,
+  opts: { token?: string }
+): Promise<DiagnosticsSessionResult> {
+  const stepId = `step_diag_${randomUUID().slice(0, 8)}`;
+  const ctx = { ...findings.runContext, stepId };
+
+  const { brief } = decision;
+  const hasTarget = !!(brief.userReport.userId || brief.userReport.anonymousInstallId);
+
+  // Skip if not requested or no target
+  if (!brief.openDiagnosticsSession || !hasTarget) {
+    return {
+      runContext: ctx,
+      skipped: true,
+      skipReason: brief.openDiagnosticsSession
+        ? 'No userId or anonymousInstallId provided — cannot target a diagnostics session'
+        : 'openDiagnosticsSession is false — skipping session creation',
+    };
+  }
+
+  // Choose collection level based on findings severity
+  const hasFatal = findings.clusters.some(c => c.severity === 'fatal');
+  const collectionLevel = hasFatal ? 'trace' : 'debug';
+
+  try {
+    const session = (await diagnosticsCreateSession(
+      {
+        productId: brief.productId,
+        targetUserId: brief.userReport.userId,
+        targetAnonymousId: brief.userReport.anonymousInstallId,
+        collectionLevel,
+        captureLogs: true,
+        captureNetwork: true,
+        maxDurationMinutes: 30,
+      },
+      { token: opts.token, requestId: findings.runContext.requestId, productId: brief.productId }
+    )) as CreatedSession;
+
+    return {
+      runContext: ctx,
+      skipped: false,
+      session: {
+        id: session.id,
+        status: session.status,
+        expiresAt: session.expiresAt,
+        collectionLevel: session.collectionLevel ?? collectionLevel,
+        targetUserId: brief.userReport.userId,
+        targetAnonymousId: brief.userReport.anonymousInstallId,
+      },
+    };
+  } catch (err) {
+    return {
+      runContext: ctx,
+      skipped: false,
+      sessionError: err instanceof Error ? err.message : String(err),
+    };
+  }
+}
diff --git a/services/mcp-server/src/modules/a2a/agents/dispatcher.ts b/services/mcp-server/src/modules/a2a/agents/dispatcher.ts
new file mode 100644
index 00000000..5ff24c6d
--- /dev/null
+++ b/services/mcp-server/src/modules/a2a/agents/dispatcher.ts
@@ -0,0 +1,44 @@
+/**
+ * DispatcherAgent — validates the SupportIncidentBrief, fills in defaults,
+ * and decides which downstream agents to activate.
+ */
+
+import { randomUUID } from 'node:crypto';
+import type { SupportIncidentBrief, DispatchDecision, RunContext } from '../types.js';
+
+/** Default look-back when no timeWindow provided — 24 hours */
+const DEFAULT_LOOKBACK_MS = 24 * 60 * 60 * 1000;
+
+export function dispatch(
+  brief: SupportIncidentBrief,
+  opts: { runId: string; requestId?: string; initiatedBy?: string }
+): DispatchDecision {
+  const stepId = `step_dispatch_${randomUUID().slice(0, 8)}`;
+
+  const runContext: RunContext = {
+    runId: opts.runId,
+    stepId,
+    productId: brief.productId,
+    requestId: opts.requestId,
+    initiatedBy: opts.initiatedBy,
+  };
+
+  // Resolve time window — default to last 24 h if not provided
+  const now = new Date();
+  const resolvedTimeWindow = {
+    to: brief.timeWindow.to ?? now.toISOString(),
+    from: brief.timeWindow.from ?? new Date(now.getTime() - DEFAULT_LOOKBACK_MS).toISOString(),
+  };
+
+  // Decide which agents to run
+  const steps: DispatchDecision['steps'] = ['telemetry_analyst'];
+
+  const hasTarget = !!(brief.userReport.userId || brief.userReport.anonymousInstallId);
+  if (brief.openDiagnosticsSession && hasTarget) {
+    steps.push('diagnostics_orchestrator');
+  }
+
+  steps.push('report_writer');
+
+  return { runContext, brief, steps, resolvedTimeWindow };
+}
diff --git a/services/mcp-server/src/modules/a2a/agents/report-writer.ts b/services/mcp-server/src/modules/a2a/agents/report-writer.ts
new file mode 100644
index 00000000..bebb7be3
--- /dev/null
+++ b/services/mcp-server/src/modules/a2a/agents/report-writer.ts
@@ -0,0 +1,100 @@
+/**
+ * ReportWriterAgent — assembles all step outputs into a FinalIncidentReport
+ * with a stable runId and a markdown summary.
+ */
+
+import type {
+  DispatchDecision,
+  TelemetryFindings,
+  DiagnosticsSessionResult,
+  FinalIncidentReport,
+} from '../types.js';
+
+export function writeReport(
+  decision: DispatchDecision,
+  findings: TelemetryFindings,
+  diagResult: DiagnosticsSessionResult | null
+): FinalIncidentReport {
+  const { runContext, brief } = decision;
+  const generatedAt = new Date().toISOString();
+
+  const lines: string[] = [
+    `# Incident Report — ${brief.productId}`,
+    `**Run ID:** \`${runContext.runId}\``,
+    `**Generated:** ${generatedAt}`,
+    `**Reported issue:** ${brief.userReport.summary}`,
+    brief.userReport.platform ? `**Platform:** ${brief.userReport.platform}` : '',
+    brief.userReport.appVersion ? `**App version:** ${brief.userReport.appVersion}` : '',
+    '',
+    `## Time Window`,
+    `- From: ${decision.resolvedTimeWindow.from}`,
+    `- To:   ${decision.resolvedTimeWindow.to}`,
+    '',
+    `## Telemetry Findings (${findings.clusters.length} open cluster${findings.clusters.length !== 1 ? 's' : ''})`,
+  ];
+
+  if (findings.queryError) {
+    lines.push(`> ⚠️ Telemetry query failed: ${findings.queryError}`);
+  } else if (findings.clusters.length === 0) {
+    lines.push('No open error clusters found in this time window.');
+  } else {
+    for (const c of findings.clusters.slice(0, 10)) {
+      lines.push(
+        `- **[${c.severity.toUpperCase()}]** \`${c.clusterId}\` — ${c.totalCount} events` +
+          ` | platform: ${c.platform} | module: ${c.module}` +
+          (c.sampleMessage ? ` | "${c.sampleMessage}"` : '')
+      );
+    }
+    if (findings.clusters.length > 10) {
+      lines.push(`  … and ${findings.clusters.length - 10} more clusters`);
+    }
+  }
+
+  lines.push('');
+  lines.push('## Top Hypotheses');
+  if (findings.topHypotheses.length === 0) {
+    lines.push('No hypotheses generated.');
+  } else {
+    for (const h of findings.topHypotheses) lines.push(`- ${h}`);
+  }
+
+  lines.push('');
+  lines.push('## Recommended Actions');
+  if (findings.recommendedActions.length === 0) {
+    lines.push('No actions recommended.');
+  } else {
+    for (const a of findings.recommendedActions) lines.push(`- ${a}`);
+  }
+
+  lines.push('');
+  lines.push('## Diagnostics Session');
+  if (!diagResult || diagResult.skipped) {
+    lines.push(diagResult?.skipReason ? `Skipped: ${diagResult.skipReason}` : 'Not requested.');
+  } else if (diagResult.sessionError) {
+    lines.push(`> ⚠️ Session creation failed: ${diagResult.sessionError}`);
+  } else if (diagResult.session) {
+    const s = diagResult.session;
+    lines.push(`- **Session ID:** \`${s.id}\``);
+    lines.push(`- **Status:** ${s.status}`);
+    lines.push(`- **Collection level:** ${s.collectionLevel}`);
+    lines.push(`- **Expires:** ${s.expiresAt}`);
+    if (s.targetUserId) lines.push(`- **Target user:** ${s.targetUserId}`);
+  }
+
+  lines.push('');
+  lines.push('---');
+  lines.push(`*Generated by ByteLyst A2A incident pipeline · run \`${runContext.runId}\`*`);
+
+  return {
+    runId: runContext.runId,
+    productId: brief.productId,
+    generatedAt,
+    summary: brief.userReport.summary,
+    clusterCount: findings.clusters.length,
+    clusters: findings.clusters,
+    topHypotheses: findings.topHypotheses,
+    recommendedActions: findings.recommendedActions,
+    diagnosticsSession: diagResult?.session ?? null,
+    markdownReport: lines.filter(l => l !== '').join('\n'),
+  };
+}
diff --git a/services/mcp-server/src/modules/a2a/agents/telemetry-analyst.ts b/services/mcp-server/src/modules/a2a/agents/telemetry-analyst.ts
new file mode 100644
index 00000000..9dcd12df
--- /dev/null
+++ b/services/mcp-server/src/modules/a2a/agents/telemetry-analyst.ts
@@ -0,0 +1,166 @@
+/**
+ * TelemetryAnalystAgent — queries telemetry clusters for the incident time
+ * window and produces structured TelemetryFindings with hypotheses and
+ * recommended next actions.
+ */
+
+import { randomUUID } from 'node:crypto';
+import { telemetryClusters } from '../../../lib/platform-client.js';
+import type { DispatchDecision, TelemetryFindings, ClusterRef } from '../types.js';
+
+interface RawCluster {
+  id?: string;
+  pk?: string;
+  fingerprint?: string;
+  severity?: string;
+  totalCount?: number;
+  lastSeenAt?: string;
+  platform?: string;
+  module?: string;
+  sampleMessage?: string;
+  status?: string;
+}
+
+export async function analyze(
+  decision: DispatchDecision,
+  opts: { token?: string }
+): Promise<TelemetryFindings> {
+  const { runContext, brief, resolvedTimeWindow } = decision;
+  const stepId = `step_telemetry_${randomUUID().slice(0, 8)}`;
+  const ctx = { ...runContext, stepId };
+
+  let clusters: ClusterRef[] = [];
+  let queryError: string | undefined;
+
+  try {
+    const result = await telemetryClusters(
+      { productId: brief.productId, from: resolvedTimeWindow.from, to: resolvedTimeWindow.to },
+      { token: opts.token, requestId: runContext.requestId, productId: brief.productId }
+    );
+
+    const raw: RawCluster[] = (result as { clusters?: RawCluster[] }).clusters ?? [];
+
+    clusters = raw
+      .filter(c => c.status !== 'resolved' && c.status !== 'ignored')
+      .map(c => ({
+        clusterId: c.id ?? '',
+        pk: c.pk ?? '',
+        fingerprint: c.fingerprint ?? '',
+        severity: c.severity ?? 'error',
+        totalCount: c.totalCount ?? 0,
+        lastSeenAt: c.lastSeenAt ?? '',
+        platform: c.platform ?? '',
+        module: c.module ?? '',
+        sampleMessage: c.sampleMessage,
+      }));
+
+    // Filter by platform if the incident report names one
+    if (brief.userReport.platform) {
+      const p = brief.userReport.platform.toLowerCase();
+      const platformClusters = clusters.filter(c => c.platform.toLowerCase() === p);
+      if (platformClusters.length > 0) clusters = platformClusters;
+    }
+
+    // Sort by totalCount descending
+    clusters.sort((a, b) => b.totalCount - a.totalCount);
+  } catch (err) {
+    queryError = err instanceof Error ? err.message : String(err);
+  }
+
+  const topHypotheses = deriveHypotheses(clusters, brief.userReport.summary);
+  const recommendedActions = deriveActions(clusters, decision);
+
+  return { runContext: ctx, clusters, topHypotheses, recommendedActions, queryError };
+}
+
+// ── Heuristic hypothesis generator ────────────────────────────────────────
+
+function deriveHypotheses(clusters: ClusterRef[], summary: string): string[] {
+  const hypotheses: string[] = [];
+  const lower = summary.toLowerCase();
+
+  if (clusters.length === 0) {
+    hypotheses.push('No open error clusters found — issue may be intermittent or not yet surfaced');
+    return hypotheses;
+  }
+
+  const fatalClusters = clusters.filter(c => c.severity === 'fatal');
+  if (fatalClusters.length > 0) {
+    hypotheses.push(
+      `${fatalClusters.length} fatal cluster(s) detected — highest priority for investigation`
+    );
+  }
+
+  const topCluster = clusters[0];
+  if (topCluster.sampleMessage) {
+    hypotheses.push(`Top cluster message: "${topCluster.sampleMessage}"`);
+  }
+
+  if (lower.includes('dictation') || lower.includes('speech') || lower.includes('transcri')) {
+    hypotheses.push('Audio permission or microphone access may be revoked');
+    hypotheses.push('Speech-to-text pipeline may have a timeout or encoding error');
+  }
+
+  if (lower.includes('insert') || lower.includes('paste') || lower.includes('nothing')) {
+    hypotheses.push('Text insertion API returned a no-op — possible permission or focus issue');
+  }
+
+  if (lower.includes('crash') || lower.includes('fatal')) {
+    hypotheses.push('Memory pressure or unexpected nil dereference in affected module');
+  }
+
+  const modules = [
+    ...new Set(
+      clusters
+        .slice(0, 5)
+        .map(c => c.module)
+        .filter(Boolean)
+    ),
+  ];
+  if (modules.length > 0) {
+    hypotheses.push(`Affected modules: ${modules.join(', ')}`);
+  }
+
+  return hypotheses.slice(0, 5);
+}
+
+function deriveActions(clusters: ClusterRef[], decision: DispatchDecision): string[] {
+  const actions: string[] = [];
+
+  if (clusters.length === 0) {
+    actions.push('Widen time window or check alternate platforms');
+    actions.push('Verify telemetry is enabled and events are being ingested');
+    return actions;
+  }
+
+  const hasTarget = !!(
+    decision.brief.userReport.userId || decision.brief.userReport.anonymousInstallId
+  );
+
+  if (hasTarget && !decision.brief.openDiagnosticsSession) {
+    actions.push(
+      'Re-run with openDiagnosticsSession: true to capture a live trace for the affected user'
+    );
+  }
+
+  const fatalClusters = clusters.filter(c => c.severity === 'fatal');
+  if (fatalClusters.length > 0) {
+    actions.push(
+      `Resolve or investigate ${fatalClusters.length} fatal cluster(s): ` +
+        fatalClusters
+          .slice(0, 3)
+          .map(c => c.clusterId)
+          .join(', ')
+    );
+  }
+
+  if (clusters.length >= 3) {
+    actions.push(
+      'Consider creating a targeted telemetry policy to capture debug-level events for affected module'
+    );
+  }
+
+  actions.push(`Review top cluster (${clusters[0].clusterId}) in admin telemetry explorer`);
+
+  return actions.slice(0, 5);
+}
diff --git a/services/mcp-server/src/modules/a2a/pipeline-tool.ts b/services/mcp-server/src/modules/a2a/pipeline-tool.ts
new file mode 100644
index 00000000..6de6e2e3
--- /dev/null
+++ b/services/mcp-server/src/modules/a2a/pipeline-tool.ts
@@ -0,0 +1,42 @@
+/**
+ * MCP tool: support.runIncidentPipeline
+ *
+ * Wraps the full A2A incident pipeline as a single callable MCP tool.
+ * Agents run in sequence: Dispatcher → TelemetryAnalyst → DiagnosticsOrchestrator → ReportWriter.
+ */
+
+import { z } from 'zod';
+import { registerTool } from '../tools/registry.js';
+import { SupportIncidentBriefSchema } from './types.js';
+import { runIncidentPipeline } from './runner.js';
+import type { McpToolRequest } from '../tools/types.js';
+
+registerTool({
+  name: 'support.runIncidentPipeline',
+  description: [
+    'A2A incident pipeline: Dispatcher → TelemetryAnalyst → DiagnosticsOrchestrator → ReportWriter.',
+    'Provide a productId + userReport describing the issue. The pipeline queries telemetry clusters,',
+    'generates hypotheses and recommended actions, optionally opens a live diagnostics session',
+    '(set openDiagnosticsSession: true + userId/anonymousInstallId), and returns a FinalIncidentReport',
+    'with a markdown summary. Every step is logged with a stable runId for audit tracing.',
+    'Requires admin role.',
+  ].join(' '),
+  requiredRole: 'admin',
+  inputSchema: SupportIncidentBriefSchema.extend({
+    openDiagnosticsSession: z
+      .boolean()
+      .default(false)
+      .describe(
+        'Open a live diagnostics session for the affected user (requires userId or anonymousInstallId)'
+      ),
+  }),
+  async execute(args, req: McpToolRequest) {
+    const token = req.headers.authorization?.slice(7);
+    return runIncidentPipeline(args, {
+      token,
+      requestId: req.id,
+      initiatedBy: req.jwtPayload?.sub,
+      log: req.log,
+    });
+  },
+});
diff --git a/services/mcp-server/src/modules/a2a/runner.test.ts b/services/mcp-server/src/modules/a2a/runner.test.ts
new file mode 100644
index 00000000..d9a57c91
--- /dev/null
+++ b/services/mcp-server/src/modules/a2a/runner.test.ts
@@ -0,0 +1,130 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import type { McpLogger } from '../tools/types.js';
+
+// ── Mock platform-client before importing runner ───────────────────────────
+vi.mock('../../lib/platform-client.js', () => ({
+  telemetryClusters: vi.fn(),
+  diagnosticsCreateSession: vi.fn(),
+}));
+
+import { telemetryClusters, diagnosticsCreateSession } from '../../lib/platform-client.js';
+import { runIncidentPipeline } from './runner.js';
+import type { SupportIncidentBrief } from './types.js';
+
+const mockLog: McpLogger = {
+  info: vi.fn(),
+  warn: vi.fn(),
+  error: vi.fn(),
+  debug: vi.fn(),
+};
+
+const baseBrief: SupportIncidentBrief = {
+  productId: 'lysnrai',
+  userReport: { summary: 'Dictation inserts nothing in Messages', platform: 'ios' },
+  timeWindow: {},
+  openDiagnosticsSession: false,
+};
+
+const mockClusters = [
+  {
+    id: 'abc123:202503',
+    pk: 'lysnrai:ios:keyboard',
+    fingerprint: 'abc123',
+    severity: 'error',
+    totalCount: 42,
+    lastSeenAt: '2026-03-05T10:00:00Z',
+    platform: 'ios',
+    module: 'keyboard',
+    sampleMessage: 'insertText returned noop',
+    status: 'open',
+  },
+];
+
+beforeEach(() => {
+  vi.clearAllMocks();
+  vi.mocked(telemetryClusters).mockResolvedValue({ clusters: mockClusters } as never);
+  vi.mocked(diagnosticsCreateSession).mockResolvedValue({
+    id: 'sess_001',
+    status: 'active',
+    expiresAt: '2026-03-05T11:00:00Z',
+    collectionLevel: 'debug',
+  } as never);
+});
+
+describe('A2A incident pipeline', () => {
+  it('runs dispatcher → telemetry analyst → report writer (no diagnostics)', async () => {
+    const report = await runIncidentPipeline(baseBrief, {
+      log: mockLog,
+      requestId: 'req_test',
+    });
+
+    expect(report.runId).toMatch(/^run_/);
+    expect(report.productId).toBe('lysnrai');
+    expect(report.clusterCount).toBe(1);
+    expect(report.clusters[0].clusterId).toBe('abc123:202503');
+    expect(report.diagnosticsSession).toBeNull();
+    expect(report.markdownReport).toContain('abc123:202503');
+    expect(report.topHypotheses.length).toBeGreaterThan(0);
+    expect(report.recommendedActions.length).toBeGreaterThan(0);
+    expect(diagnosticsCreateSession).not.toHaveBeenCalled();
+  });
+
+  it('creates a diagnostics session when openDiagnosticsSession is true + userId provided', async () => {
+    const brief: SupportIncidentBrief = {
+      ...baseBrief,
+      userReport: { ...baseBrief.userReport, userId: 'usr_abc' },
+      openDiagnosticsSession: true,
+    };
+
+    const report = await runIncidentPipeline(brief, { log: mockLog });
+
+    expect(diagnosticsCreateSession).toHaveBeenCalledOnce();
+    expect(report.diagnosticsSession?.id).toBe('sess_001');
+    expect(report.markdownReport).toContain('sess_001');
+  });
+
+  it('skips diagnostics session when no userId/anonymousInstallId', async () => {
+    const brief: SupportIncidentBrief = { ...baseBrief, openDiagnosticsSession: true };
+    const report = await runIncidentPipeline(brief, { log: mockLog });
+
+    expect(diagnosticsCreateSession).not.toHaveBeenCalled();
+    expect(report.diagnosticsSession).toBeNull();
+  });
+
+  it('handles telemetry query failure gracefully', async () => {
+    vi.mocked(telemetryClusters).mockRejectedValue(new Error('upstream timeout'));
+
+    const report = await runIncidentPipeline(baseBrief, { log: mockLog });
+
+    expect(report.clusterCount).toBe(0);
+    expect(report.markdownReport).toContain('upstream timeout');
+  });
+
+  it('logs runId + stepId on every step', async () => {
+    await runIncidentPipeline(baseBrief, { log: mockLog });
+
+    const infoCalls = vi.mocked(mockLog.info).mock.calls;
+    const stepNames = infoCalls.map(([obj]) => (obj as Record<string, unknown>).a2aStep);
+    expect(stepNames).toContain('pipeline.start');
+    expect(stepNames).toContain('dispatcher.complete');
+    expect(stepNames).toContain('telemetry_analyst.complete');
+    expect(stepNames).toContain('pipeline.complete');
+  });
+});
+
+describe('dispatcher', () => {
+  it('defaults time window to last 24h when not provided', async () => {
+    const before = Date.now();
+    const report = await runIncidentPipeline(baseBrief, { log: mockLog });
+    const after = Date.now();
+
+    const clusterCall = vi.mocked(telemetryClusters).mock.calls[0][0] as Record<string, string>;
+    const fromTs = new Date(clusterCall.from).getTime();
+    const toTs = new Date(clusterCall.to).getTime();
+
+    expect(toTs).toBeGreaterThanOrEqual(before);
+    expect(toTs).toBeLessThanOrEqual(after + 100);
+    expect(toTs - fromTs).toBeGreaterThanOrEqual(24 * 60 * 60 * 1000 - 100);
+    expect(report).toBeDefined();
+  });
+});
diff --git a/services/mcp-server/src/modules/a2a/runner.ts b/services/mcp-server/src/modules/a2a/runner.ts
new file mode 100644
index 00000000..5db7eb30
--- /dev/null
+++ b/services/mcp-server/src/modules/a2a/runner.ts
@@ -0,0 +1,103 @@
+/**
+ * A2A Pipeline Runner — executes the incident pipeline in sequence:
+ *   DispatcherAgent → TelemetryAnalystAgent → DiagnosticsOrchestratorAgent → ReportWriterAgent
+ *
+ * Every step transition is logged with runId + stepId for full audit tracing.
+ * Phase 1: handoffs are persisted via structured req.log entries.
+ * Phase 2+: handoffs will additionally be written to a Cosmos container.
+ */
+
+import { randomUUID } from 'node:crypto';
+import type { McpLogger } from '../tools/types.js';
+import type { SupportIncidentBrief, FinalIncidentReport } from './types.js';
+import { dispatch } from './agents/dispatcher.js';
+import { analyze } from './agents/telemetry-analyst.js';
+import { orchestrate } from './agents/diagnostics-orchestrator.js';
+import { writeReport } from './agents/report-writer.js';
+
+export interface PipelineOptions {
+  token?: string;
+  requestId?: string;
+  initiatedBy?: string;
+  log: McpLogger;
+}
+
+export async function runIncidentPipeline(
+  brief: SupportIncidentBrief,
+  opts: PipelineOptions
+): Promise<FinalIncidentReport> {
+  const runId = `run_${randomUUID()}`;
+  const { log } = opts;
+
+  log.info(
+    { runId, productId: brief.productId, a2aStep: 'pipeline.start' },
+    'A2A pipeline started'
+  );
+
+  // ── Step 1: Dispatcher ──────────────────────────────────────────────────
+  const decision = dispatch(brief, {
+    runId,
+    requestId: opts.requestId,
+    initiatedBy: opts.initiatedBy,
+  });
+
+  log.info(
+    {
+      runId,
+      stepId: decision.runContext.stepId,
+      a2aStep: 'dispatcher.complete',
+      steps: decision.steps,
+      resolvedTimeWindow: decision.resolvedTimeWindow,
+    },
+    'Dispatcher decided pipeline steps'
+  );
+
+  // ── Step 2: Telemetry Analyst ───────────────────────────────────────────
+  const findings = await analyze(decision, { token: opts.token });
+
+  log.info(
+    {
+      runId,
+      stepId: findings.runContext.stepId,
+      a2aStep: 'telemetry_analyst.complete',
+      clusterCount: findings.clusters.length,
+      hypothesisCount: findings.topHypotheses.length,
+      queryError: findings.queryError,
+    },
+    'Telemetry analyst completed'
+  );
+
+  // ── Step 3: Diagnostics Orchestrator (conditional) ─────────────────────
+  let diagResult = null;
+  if (decision.steps.includes('diagnostics_orchestrator')) {
+    diagResult = await orchestrate(decision, findings, { token: opts.token });
+
+    log.info(
+      {
+        runId,
+        stepId: diagResult.runContext.stepId,
+        a2aStep: 'diagnostics_orchestrator.complete',
+        skipped: diagResult.skipped,
+        sessionId: diagResult.session?.id,
+        sessionError: diagResult.sessionError,
+      },
+      'Diagnostics orchestrator completed'
+    );
+  }
+
+  // ── Step 4: Report Writer ───────────────────────────────────────────────
+  const report = writeReport(decision, findings, diagResult);
+
+  log.info(
+    {
+      runId,
+      a2aStep: 'pipeline.complete',
+      productId: brief.productId,
+      clusterCount: report.clusterCount,
+      hasSession: !!report.diagnosticsSession,
+    },
+    'A2A pipeline completed'
+  );
+
+  return report;
+}
diff --git a/services/mcp-server/src/modules/a2a/types.ts b/services/mcp-server/src/modules/a2a/types.ts
new file mode 100644
index 00000000..339a02f6
--- /dev/null
+++ b/services/mcp-server/src/modules/a2a/types.ts
@@ -0,0 +1,112 @@
+/**
+ * A2A Orchestration — Handoff artifact schemas and types.
+ *
+ * Every artifact carries a stable `runId` + `stepId` for audit tracing.
+ * All artifacts are explicitly scoped to a `productId`.
+ */
+
+import { z } from 'zod';
+
+// ── Pipeline run identity ──────────────────────────────────────────────────
+
+export const RunContextSchema = z.object({
+  runId: z.string().describe('Stable ID for the entire pipeline run'),
+  stepId: z.string().describe('ID for this individual step'),
+  productId: z.string().min(1),
+  requestId: z.string().optional(),
+  initiatedBy: z.string().optional().describe('userId who triggered the pipeline'),
+});
+export type RunContext = z.infer<typeof RunContextSchema>;
+
+// ── A) SupportIncidentBrief — input to DispatcherAgent ───────────────────
+
+export const UserReportSchema = z.object({
+  summary: z.string().min(1).describe('Human-readable description of the issue'),
+  platform: z.string().optional().describe('e.g. ios, android, web'),
+  channel: z.string().optional().describe('e.g. keyboard_extension, dictation'),
+  appVersion: z.string().optional(),
+  buildNumber: z.string().optional(),
+  userId: z.string().optional(),
+  anonymousInstallId: z.string().optional(),
+});
+export type UserReport = z.infer<typeof UserReportSchema>;
+
+export const SupportIncidentBriefSchema = z.object({
+  productId: z.string().min(1),
+  userReport: UserReportSchema,
+  timeWindow: z
+    .object({
+      from: z.string().datetime().optional(),
+      to: z.string().datetime().optional(),
+    })
+    .default({}),
+  openDiagnosticsSession: z
+    .boolean()
+    .default(false)
+    .describe('If true and userId/anonymousInstallId present, open a live diagnostics session'),
+});
+export type SupportIncidentBrief = z.infer<typeof SupportIncidentBriefSchema>;
+
+// ── B) DispatchDecision — output of DispatcherAgent ───────────────────────
+
+export interface DispatchDecision {
+  runContext: RunContext;
+  brief: SupportIncidentBrief;
+  steps: ('telemetry_analyst' | 'diagnostics_orchestrator' | 'report_writer')[];
+  /** Resolved time window (fills defaults if omitted in brief) */
+  resolvedTimeWindow: { from: string; to: string };
+}
+
+// ── C) TelemetryFindings — output of TelemetryAnalystAgent ───────────────
+
+export interface ClusterRef {
+  clusterId: string;
+  pk: string;
+  fingerprint: string;
+  severity: string;
+  totalCount: number;
+  lastSeenAt: string;
+  platform: string;
+  module: string;
+  sampleMessage?: string;
+}
+
+export interface TelemetryFindings {
+  runContext: RunContext;
+  clusters: ClusterRef[];
+  topHypotheses: string[];
+  recommendedActions: string[];
+  queryError?: string;
+}
+
+// ── D) DiagnosticsSessionResult — output of DiagnosticsOrchestratorAgent ─
+
+export interface DiagnosticsSessionResult {
+  runContext: RunContext;
+  skipped: boolean;
+  skipReason?: string;
+  session?: {
+    id: string;
+    status: string;
+    expiresAt: string;
+    collectionLevel: string;
+    targetUserId?: string;
+    targetAnonymousId?: string;
+  };
+  sessionError?: string;
+}
+
+// ── E) FinalIncidentReport — output of ReportWriterAgent ─────────────────
+
+export interface FinalIncidentReport {
+  runId: string;
+  productId: string;
+  generatedAt: string;
+  summary: string;
+  clusterCount: number;
+  clusters: ClusterRef[];
+  topHypotheses: string[];
+  recommendedActions: string[];
+  diagnosticsSession: DiagnosticsSessionResult['session'] | null;
+  markdownReport: string;
+}
diff --git a/services/mcp-server/src/modules/tools/routes.ts b/services/mcp-server/src/modules/tools/routes.ts
index c0e11771..3e3a2091 100644
--- a/services/mcp-server/src/modules/tools/routes.ts
+++ b/services/mcp-server/src/modules/tools/routes.ts
@@ -42,7 +42,13 @@ export async function toolRoutes(app: FastifyInstance) {
     );
 
     try {
-      const result = await tool.execute(parsed.data, req as unknown as McpToolRequest);
+      const mcpReq: McpToolRequest = {
+        id: req.id,
+        headers: { authorization: req.headers.authorization },
+        jwtPayload: req.jwtPayload,
+        log: req.log,
+      };
+      const result = await tool.execute(parsed.data, mcpReq);
       return {
         content: [{ type: 'text', text: JSON.stringify(result, null, 2) }],
       };
diff --git a/services/mcp-server/src/modules/tools/types.ts b/services/mcp-server/src/modules/tools/types.ts
index c5d51320..fdcd93b2 100644
--- a/services/mcp-server/src/modules/tools/types.ts
+++ b/services/mcp-server/src/modules/tools/types.ts
@@ -1,5 +1,13 @@
 import type { ZodTypeAny, z } from 'zod';
 
+/** Minimal structured logger — matches Fastify's pino-based logger shape */
+export interface McpLogger {
+  info(obj: Record<string, unknown>, msg?: string): void;
+  warn(obj: Record<string, unknown>, msg?: string): void;
+  error(obj: Record<string, unknown>, msg?: string): void;
+  debug(obj: Record<string, unknown>, msg?: string): void;
+}
+
 /**
  * Minimal request context passed to tool execute functions.
  * Avoids a direct FastifyRequest dependency inside tool modules.
@@ -11,6 +19,8 @@ export interface McpToolRequest {
   headers: { authorization?: string | undefined };
   /** JWT payload decoded by the auth hook */
   jwtPayload?: { sub?: string; role?: string; productId?: string };
+  /** Structured logger (child of Fastify request logger, carries requestId) */
+  log: McpLogger;
 }
 
 /**
diff --git a/services/mcp-server/src/server.ts b/services/mcp-server/src/server.ts
index ddacff64..2a1474b1 100644
--- a/services/mcp-server/src/server.ts
+++ b/services/mcp-server/src/server.ts
@@ -22,6 +22,7 @@ import './modules/platform/telemetry-policy-tools.js';
 import './modules/platform/diagnostics-tools.js';
 import './modules/extraction/extraction-tools.js';
 import './modules/support/debug-pack.js';
+import './modules/a2a/pipeline-tool.js';
 
 const app = await createServiceApp({
   name: 'mcp-server',