diff --git a/src/renderer/types/sessionReport.ts b/src/renderer/types/sessionReport.ts
new file mode 100644
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--- /dev/null
+++ b/src/renderer/types/sessionReport.ts
@@ -0,0 +1,306 @@
+/**
+ * Session analysis report types.
+ * Output of analyzeSession() — one interface per report section.
+ */
+
+// =============================================================================
+// Pricing
+// =============================================================================
+
+export interface ModelPricing {
+  input: number;
+  output: number;
+  cache_read: number;
+  cache_creation: number;
+}
+
+// =============================================================================
+// Report Sections
+// =============================================================================
+
+export interface ReportOverview {
+  sessionId: string;
+  projectId: string;
+  projectPath: string;
+  firstMessage: string;
+  messageCount: number;
+  hasSubagents: boolean;
+  contextConsumption: number;
+  contextConsumptionPct: number | null;
+  contextAssessment: 'critical' | 'high' | 'moderate' | 'healthy' | null;
+  compactionCount: number;
+  gitBranch: string;
+  startTime: Date | null;
+  endTime: Date | null;
+  durationSeconds: number;
+  durationHuman: string;
+  totalMessages: number;
+}
+
+export interface ModelTokenStats {
+  apiCalls: number;
+  inputTokens: number;
+  outputTokens: number;
+  cacheCreation: number;
+  cacheRead: number;
+  costUsd: number;
+}
+
+export interface TokenTotals {
+  inputTokens: number;
+  outputTokens: number;
+  cacheCreation: number;
+  cacheRead: number;
+  grandTotal: number;
+  cacheReadPct: number;
+}
+
+export interface ReportTokenUsage {
+  byModel: Record<string, ModelTokenStats>;
+  totals: TokenTotals;
+}
+
+export interface ReportCostAnalysis {
+  parentCostUsd: number;
+  subagentCostUsd: number;
+  totalSessionCostUsd: number;
+  costByModel: Record<string, number>;
+  costPerCommit: number | null;
+  costPerLineChanged: number | null;
+}
+
+export interface ReportCacheEconomics {
+  cacheCreation5m: number;
+  cacheCreation1h: number;
+  cacheRead: number;
+  cacheEfficiencyPct: number;
+  coldStartDetected: boolean;
+  cacheReadToWriteRatio: number;
+}
+
+export interface ToolSuccessRate {
+  totalCalls: number;
+  errors: number;
+  successRatePct: number;
+}
+
+export interface ReportToolUsage {
+  counts: Record<string, number>;
+  totalCalls: number;
+  successRates: Record<string, ToolSuccessRate>;
+}
+
+export interface SubagentEntry {
+  description: string;
+  subagentType: string;
+  model: string;
+  totalTokens: number;
+  totalDurationMs: number;
+  totalToolUseCount: number;
+  costUsd: number;
+  costNote?: string;
+}
+
+export interface ReportSubagentMetrics {
+  count: number;
+  totalTokens: number;
+  totalDurationMs: number;
+  totalToolUseCount: number;
+  totalCostUsd: number;
+  byAgent: SubagentEntry[];
+}
+
+export interface ToolError {
+  tool: string;
+  inputPreview: string;
+  error: string;
+  messageIndex: number;
+  isPermissionDenial: boolean;
+}
+
+export interface ReportErrors {
+  errors: ToolError[];
+  permissionDenials: {
+    count: number;
+    denials: ToolError[];
+    affectedTools: string[];
+  };
+}
+
+export interface GitCommit {
+  messagePreview: string;
+  messageIndex: number;
+}
+
+export interface ReportGitActivity {
+  commitCount: number;
+  commits: GitCommit[];
+  pushCount: number;
+  branchCreations: string[];
+  linesAdded: number;
+  linesRemoved: number;
+  linesChanged: number;
+}
+
+export interface FrictionCorrection {
+  messageIndex: number;
+  keyword: string;
+  preview: string;
+}
+
+export interface ReportFrictionSignals {
+  correctionCount: number;
+  corrections: FrictionCorrection[];
+  frictionRate: number;
+}
+
+export interface ReportThrashingSignals {
+  bashNearDuplicates: { prefix: string; count: number }[];
+  editReworkFiles: { filePath: string; editIndices: number[] }[];
+}
+
+export interface ReportConversationTree {
+  totalNodes: number;
+  maxDepth: number;
+  sidechainCount: number;
+  branchPoints: number;
+  branchDetails: {
+    parentUuid: string;
+    childCount: number;
+    parentMessageIndex: number | undefined;
+  }[];
+}
+
+export interface IdleGap {
+  gapSeconds: number;
+  gapHuman: string;
+  afterMessageIndex: number;
+}
+
+export interface ReportIdleAnalysis {
+  idleThresholdSeconds: number;
+  idleGapCount: number;
+  totalIdleSeconds: number;
+  totalIdleHuman: string;
+  wallClockSeconds: number;
+  activeWorkingSeconds: number;
+  activeWorkingHuman: string;
+  idlePct: number;
+  longestGaps: IdleGap[];
+}
+
+export interface ModelSwitch {
+  from: string;
+  to: string;
+  messageIndex: number;
+  timestamp: Date | null;
+}
+
+export interface ReportModelSwitches {
+  count: number;
+  switches: ModelSwitch[];
+  modelsUsed: string[];
+}
+
+export interface ReportWorkingDirectories {
+  uniqueDirectories: string[];
+  directoryCount: number;
+  changes: { from: string; to: string; messageIndex: number }[];
+  changeCount: number;
+  isMultiDirectory: boolean;
+}
+
+export interface TestSnapshot {
+  messageIndex: number;
+  passed: number;
+  failed: number;
+  total: number;
+  raw: string;
+}
+
+export interface ReportTestProgression {
+  snapshotCount: number;
+  snapshots: TestSnapshot[];
+  trajectory: 'improving' | 'regressing' | 'stable' | 'insufficient_data';
+  firstSnapshot: TestSnapshot | null;
+  lastSnapshot: TestSnapshot | null;
+}
+
+export interface ReportStartupOverhead {
+  messagesBeforeFirstWork: number;
+  tokensBeforeFirstWork: number;
+  pctOfTotal: number;
+}
+
+export interface ReportTokenDensityTimeline {
+  quartiles: { q: number; avgTokens: number; messageCount: number }[];
+}
+
+export interface ReportPromptQuality {
+  firstMessageLengthChars: number;
+  userMessageCount: number;
+  correctionCount: number;
+  frictionRate: number;
+  assessment: 'underspecified' | 'verbose_but_unclear' | 'well_specified' | 'moderate_friction';
+  note: string;
+}
+
+export interface ThinkingBlockAnalysis {
+  messageIndex: number;
+  preview: string;
+  charLength: number;
+  signals: Record<string, boolean>;
+}
+
+export interface ReportThinkingBlocks {
+  count: number;
+  analyzedCount: number;
+  signalSummary: Record<string, number>;
+  notableBlocks: ThinkingBlockAnalysis[];
+}
+
+export interface KeyEvent {
+  timestamp: Date;
+  label: string;
+  deltaSeconds?: number;
+  deltaHuman?: string;
+}
+
+export interface ReportFileReadRedundancy {
+  totalReads: number;
+  uniqueFiles: number;
+  readsPerUniqueFile: number;
+  redundantFiles: Record<string, number>;
+}
+
+// =============================================================================
+// Combined Report
+// =============================================================================
+
+export interface SessionReport {
+  overview: ReportOverview;
+  tokenUsage: ReportTokenUsage;
+  costAnalysis: ReportCostAnalysis;
+  cacheEconomics: ReportCacheEconomics;
+  toolUsage: ReportToolUsage;
+  subagentMetrics: ReportSubagentMetrics;
+  errors: ReportErrors;
+  gitActivity: ReportGitActivity;
+  frictionSignals: ReportFrictionSignals;
+  thrashingSignals: ReportThrashingSignals;
+  conversationTree: ReportConversationTree;
+  idleAnalysis: ReportIdleAnalysis;
+  modelSwitches: ReportModelSwitches;
+  workingDirectories: ReportWorkingDirectories;
+  testProgression: ReportTestProgression;
+  startupOverhead: ReportStartupOverhead;
+  tokenDensityTimeline: ReportTokenDensityTimeline;
+  promptQuality: ReportPromptQuality;
+  thinkingBlocks: ReportThinkingBlocks;
+  keyEvents: KeyEvent[];
+  messageTypes: Record<string, number>;
+  serviceTiers: Record<string, number>;
+  fileReadRedundancy: ReportFileReadRedundancy;
+  compactionCount: number;
+  gitBranches: string[];
+}