feat: sqlite session storage (#6594)

This PR: - Adds retainedTail to compaction entries in the new agent harness so we don't have to walk up the tree for the 2000 tokens before compaction, - Changes getPathToRoot to getPathToRootOrCompaction to only load until last compaction, as unnecessary to access all nodes where it is called, - Adds a SQLite storage backend, in a separate packages/session-backend-sqlite, with a migration system and schemas as per on-site discussions: sessions to match session header messages (except for metadata, which I couldn't understand what it's used for or where it gets written, so I omitted it), session_entries for shared entry types as columns plus payload as a json for what remains, session_sequences to represent the append-only, serialized nature of the jsonl files, branch_entries to attribute nodes to branches (relationship one-to-many), and session_materialized with the session info (see /session in TUI) to act as a "cache" or quick-access for costs, message count, token info, labels, session name, and model-thinking-level config (e.g. for fast resume). - This is compatible with the new agent harness Session abstraction.
2026-07-21 11:36:31 +02:00
parent 54fad505b9
commit 9e7582aa03
40 changed files with 2659 additions and 145 deletions
@@ -27,6 +27,8 @@
 		"includes": [
 			"packages/*/src/**/*.ts",
 			"packages/*/test/**/*.ts",
+			"packages/storage/*/src/**/*.ts",
+			"packages/storage/*/test/**/*.ts",
 			"packages/coding-agent/examples/**/*.ts",
 			"!**/node_modules/**/*",
 			"!**/test-sessions.ts",
@@ -9,6 +9,7 @@
 			"version": "0.0.3",
 			"workspaces": [
 				"packages/*",
+				"packages/storage/*",
 				"packages/coding-agent/examples/extensions/with-deps",
 				"packages/coding-agent/examples/extensions/custom-provider-anthropic",
 				"packages/coding-agent/examples/extensions/custom-provider-gitlab-duo",
@@ -785,6 +786,10 @@
 			"resolved": "packages/agent",
 			"link": true
 		},
+		"node_modules/@earendil-works/pi-agent-sqlite-node": {
+			"resolved": "packages/storage/sqlite-node",
+			"link": true
+		},
 		"node_modules/@earendil-works/pi-ai": {
 			"resolved": "packages/ai",
 			"link": true
@@ -801,29 +806,6 @@
 			"resolved": "packages/tui",
 			"link": true
 		},
-		"node_modules/@emnapi/core": {
-			"version": "1.10.0",
-			"resolved": "https://registry.npmjs.org/@emnapi/core/-/core-1.10.0.tgz",
-			"integrity": "sha512-yq6OkJ4p82CAfPl0u9mQebQHKPJkY7WrIuk205cTYnYe+k2Z8YBh11FrbRG/H6ihirqcacOgl2BIO8oyMQLeXw==",
-			"dev": true,
-			"license": "MIT",
-			"optional": true,
-			"dependencies": {
-				"@emnapi/wasi-threads": "1.2.1",
-				"tslib": "^2.4.0"
-			}
-		},
-		"node_modules/@emnapi/runtime": {
-			"version": "1.10.0",
-			"resolved": "https://registry.npmjs.org/@emnapi/runtime/-/runtime-1.10.0.tgz",
-			"integrity": "sha512-ewvYlk86xUoGI0zQRNq/mC+16R1QeDlKQy21Ki3oSYXNgLb45GV1P6A0M+/s6nyCuNDqe5VpaY84BzXGwVbwFA==",
-			"dev": true,
-			"license": "MIT",
-			"optional": true,
-			"dependencies": {
-				"tslib": "^2.4.0"
-			}
-		},
 		"node_modules/@emnapi/wasi-threads": {
 			"version": "1.2.1",
 			"resolved": "https://registry.npmjs.org/@emnapi/wasi-threads/-/wasi-threads-1.2.1.tgz",
@@ -1403,9 +1385,6 @@
 			"cpu": [
 				"arm64"
 			],
-			"libc": [
-				"glibc"
-			],
 			"license": "MIT",
 			"optional": true,
 			"os": [
@@ -1422,9 +1401,6 @@
 			"cpu": [
 				"arm64"
 			],
-			"libc": [
-				"musl"
-			],
 			"license": "MIT",
 			"optional": true,
 			"os": [
@@ -1441,9 +1417,6 @@
 			"cpu": [
 				"riscv64"
 			],
-			"libc": [
-				"glibc"
-			],
 			"license": "MIT",
 			"optional": true,
 			"os": [
@@ -1460,9 +1433,6 @@
 			"cpu": [
 				"x64"
 			],
-			"libc": [
-				"glibc"
-			],
 			"license": "MIT",
 			"optional": true,
 			"os": [
@@ -1479,9 +1449,6 @@
 			"cpu": [
 				"x64"
 			],
-			"libc": [
-				"musl"
-			],
 			"license": "MIT",
 			"optional": true,
 			"os": [
@@ -1617,6 +1584,7 @@
 			"resolved": "https://registry.npmjs.org/@opentelemetry/api/-/api-1.9.0.tgz",
 			"integrity": "sha512-3giAOQvZiH5F9bMlMiv8+GSPMeqg0dbaeo58/0SlA9sxSqZhnUtxzX9/2FzyhS9sWQf5S0GJE0AKBrFqjpeYcg==",
 			"license": "Apache-2.0",
+			"peer": true,
 			"engines": {
 				"node": ">=8.0.0"
 			}
@@ -1796,9 +1764,6 @@
 				"arm64"
 			],
 			"dev": true,
-			"libc": [
-				"glibc"
-			],
 			"license": "MIT",
 			"optional": true,
 			"os": [
@@ -1816,9 +1781,6 @@
 				"arm64"
 			],
 			"dev": true,
-			"libc": [
-				"musl"
-			],
 			"license": "MIT",
 			"optional": true,
 			"os": [
@@ -1836,9 +1798,6 @@
 				"ppc64"
 			],
 			"dev": true,
-			"libc": [
-				"glibc"
-			],
 			"license": "MIT",
 			"optional": true,
 			"os": [
@@ -1856,9 +1815,6 @@
 				"s390x"
 			],
 			"dev": true,
-			"libc": [
-				"glibc"
-			],
 			"license": "MIT",
 			"optional": true,
 			"os": [
@@ -1876,9 +1832,6 @@
 				"x64"
 			],
 			"dev": true,
-			"libc": [
-				"glibc"
-			],
 			"license": "MIT",
 			"optional": true,
 			"os": [
@@ -1896,9 +1849,6 @@
 				"x64"
 			],
 			"dev": true,
-			"libc": [
-				"musl"
-			],
 			"license": "MIT",
 			"optional": true,
 			"os": [
@@ -2712,6 +2662,7 @@
 			"dev": true,
 			"hasInstallScript": true,
 			"license": "MIT",
+			"peer": true,
 			"bin": {
 				"esbuild": "bin/esbuild"
 			},
@@ -3607,9 +3558,6 @@
 				"arm64"
 			],
 			"dev": true,
-			"libc": [
-				"glibc"
-			],
 			"license": "MPL-2.0",
 			"optional": true,
 			"os": [
@@ -3631,9 +3579,6 @@
 				"arm64"
 			],
 			"dev": true,
-			"libc": [
-				"musl"
-			],
 			"license": "MPL-2.0",
 			"optional": true,
 			"os": [
@@ -3655,9 +3600,6 @@
 				"x64"
 			],
 			"dev": true,
-			"libc": [
-				"glibc"
-			],
 			"license": "MPL-2.0",
 			"optional": true,
 			"os": [
@@ -3679,9 +3621,6 @@
 				"x64"
 			],
 			"dev": true,
-			"libc": [
-				"musl"
-			],
 			"license": "MPL-2.0",
 			"optional": true,
 			"os": [
@@ -4793,6 +4732,7 @@
 			"integrity": "sha512-QP88BAKvMam/3NxH6vj2o21R6MjxZUAd6nlwAS/pnGvN9IVLocLHxGYIzFhg6fUQ+5th6P4dv4eW9jX3DSIj7A==",
 			"dev": true,
 			"license": "MIT",
+			"peer": true,
 			"engines": {
 				"node": ">=12"
 			},
@@ -4831,6 +4771,7 @@
 			"integrity": "sha512-TvncJykhxAzFCk0VQZKBTClall4Pm7qXDSodb6uxi8QFa8X8mT6ABjxxsQ2opDRYxG7AzcRWXaFtruz5HJKuWg==",
 			"dev": true,
 			"license": "MIT",
+			"peer": true,
 			"dependencies": {
 				"esbuild": "~0.28.0"
 			},
@@ -4911,6 +4852,7 @@
 			"integrity": "sha512-h9bXPmJichP5fLmVQo3PyaGSDE2n3aPuomeAlVRm0JLmt4rY6zmPKd59HYI4LNW8oTK7tlTsuC7l/m7awx9Jcw==",
 			"dev": true,
 			"license": "MIT",
+			"peer": true,
 			"dependencies": {
 				"lightningcss": "^1.32.0",
 				"picomatch": "^4.0.4",
@@ -5100,6 +5042,7 @@
 			"resolved": "https://registry.npmjs.org/zod/-/zod-3.25.76.tgz",
 			"integrity": "sha512-gzUt/qt81nXsFGKIFcC3YnfEAx5NkunCfnDlvuBSSFS02bcXu4Lmea0AFIUwbLWxWPx3d9p8S5QoaujKcNQxcQ==",
 			"license": "MIT",
+			"peer": true,
 			"funding": {
 				"url": "https://github.com/sponsors/colinhacks"
 			}
@@ -5139,6 +5082,7 @@
 			"integrity": "sha512-GUUEShf+PBCGW2KaXwcIt3Yk+e3pkKwWKb9GSyM9WQVE+ep2jzmHdGsHzu4wgcZy5fN9FBdVzjpBQsYlpfpgLA==",
 			"dev": true,
 			"license": "MIT",
+			"peer": true,
 			"dependencies": {
 				"undici-types": "~7.16.0"
 			}
@@ -5149,6 +5093,7 @@
 			"integrity": "sha512-G9/lgqibheLVBDRuya45EbsEXTYcWoSG+TLg7i2axuzx0Eq62eXn+aWXyaVdV5vKvFSWd6ywcX8hA7la9Pvu8g==",
 			"dev": true,
 			"license": "MIT",
+			"peer": true,
 			"dependencies": {
 				"@bcoe/v8-coverage": "^1.0.2",
 				"@vitest/utils": "4.1.9",
@@ -5354,6 +5299,7 @@
 			"integrity": "sha512-nE3/LEyc0z87uHYLZebqCUOaJr2hdtuPp7BQ4BosVFnfltxgAvMG08NyrSGlPpOUWvR27c5flSmYFTNr78L9GQ==",
 			"dev": true,
 			"license": "MIT",
+			"peer": true,
 			"dependencies": {
 				"@vitest/expect": "4.1.9",
 				"@vitest/mocker": "4.1.9",
@@ -5500,6 +5446,7 @@
 			"integrity": "sha512-GUUEShf+PBCGW2KaXwcIt3Yk+e3pkKwWKb9GSyM9WQVE+ep2jzmHdGsHzu4wgcZy5fN9FBdVzjpBQsYlpfpgLA==",
 			"dev": true,
 			"license": "MIT",
+			"peer": true,
 			"dependencies": {
 				"undici-types": "~7.16.0"
 			}
@@ -5867,6 +5814,7 @@
 			"integrity": "sha512-GUUEShf+PBCGW2KaXwcIt3Yk+e3pkKwWKb9GSyM9WQVE+ep2jzmHdGsHzu4wgcZy5fN9FBdVzjpBQsYlpfpgLA==",
 			"dev": true,
 			"license": "MIT",
+			"peer": true,
 			"dependencies": {
 				"undici-types": "~7.16.0"
 			}
@@ -6152,6 +6100,18 @@
 				"node": ">=22.19.0"
 			}
 		},
+		"packages/storage/sqlite-node": {
+			"name": "@earendil-works/pi-agent-sqlite-node",
+			"version": "0.80.10",
+			"license": "MIT",
+			"dependencies": {
+				"@earendil-works/pi-agent-core": "^0.80.10",
+				"@earendil-works/pi-ai": "^0.80.10"
+			},
+			"engines": {
+				"node": ">=22.19.0"
+			}
+		},
 		"packages/tui": {
 			"name": "@earendil-works/pi-tui",
 			"version": "0.80.10",
@@ -4,6 +4,7 @@
 	"type": "module",
 	"workspaces": [
 		"packages/*",
+		"packages/storage/*",
 		"packages/coding-agent/examples/extensions/with-deps",
 		"packages/coding-agent/examples/extensions/custom-provider-anthropic",
 		"packages/coding-agent/examples/extensions/custom-provider-gitlab-duo",
@@ -12,8 +13,8 @@
 	],
 	"scripts": {
 		"clean": "npm run clean --workspaces",
-		"build": "cd packages/tui && npm run build && cd ../ai && npm run build && cd ../agent && npm run build && cd ../coding-agent && npm run build && cd ../orchestrator && npm run build",
-		"build:offline": "cd packages/tui && npm run build && cd ../ai && npm run build:offline && cd ../agent && npm run build && cd ../coding-agent && npm run build && cd ../orchestrator && npm run build",
+		"build": "cd packages/tui && npm run build && cd ../ai && npm run build && cd ../agent && npm run build && cd ../storage/sqlite-node && npm run build && cd ../../coding-agent && npm run build && cd ../orchestrator && npm run build",
+		"build:offline": "cd packages/tui && npm run build && cd ../ai && npm run build:offline && cd ../agent && npm run build && cd ../storage/sqlite-node && npm run build && cd ../../coding-agent && npm run build && cd ../orchestrator && npm run build",
 		"check": "biome check --write --error-on-warnings . && npm run check:pinned-deps && npm run check:ts-imports && npm run check:shrinkwrap && npm run check:install-lock:coding-agent && tsgo --noEmit && npm run check:browser-smoke",
 		"check:browser-smoke": "node scripts/check-browser-smoke.mjs",
 		"check:pinned-deps": "node scripts/check-pinned-deps.mjs",
@@ -8,6 +8,10 @@ Stateful agent with tool execution and event streaming. Built on `@earendil-work
 npm install @earendil-works/pi-agent-core
 ```

+### SQLite session backends
+
+The SQLite session backend and the `node:sqlite` adapter live in a separate package, `@earendil-works/pi-agent-sqlite-node`, so the core package does not pull in runtime builtins or native SQLite dependencies by default. The backend accepts a runtime-specific SQLite factory, allowing other storage backends to ship as their own packages in the future.
+
 ## Quick Start

 ```typescript
@@ -21,12 +21,11 @@
 		"README.md"
 	],
 	"scripts": {
-		"clean": "shx rm -rf dist",
 		"build": "tsgo -p tsconfig.build.json",
 		"test": "vitest --run",
 		"test:harness": "vitest --run --config vitest.harness.config.ts",
 		"coverage:harness": "vitest --run --config vitest.harness.config.ts --coverage",
-		"prepublishOnly": "npm run clean && npm run build"
+		"prepublishOnly": "npm run build"
 	},
 	"dependencies": {
 		"@earendil-works/pi-ai": "^0.80.10",
@@ -730,6 +730,7 @@ export class AgentHarness<
 				result.details,
 				provided !== undefined,
 				result.usage,
+				result.retainedTail,
 			);
 			const entry = await this.session.getEntry(entryId);
 			if (entry?.type === "compaction") {
@@ -97,12 +97,14 @@ function getMessageFromEntryForCompaction(entry: SessionTreeEntry): AgentMessage
 export interface CompactionResult<T = unknown> {
 	/** Summary text that replaces compacted history in future context. */
 	summary: string;
-	/** Entry id where retained history starts. */
-	firstKeptEntryId: string;
+	/** Entry id where retained history starts. Optional during Pi 2.0 transition. */
+	firstKeptEntryId?: string;
 	/** Estimated context tokens before compaction. */
 	tokensBefore: number;
 	/** Usage from the LLM call(s) that generated this summary, if available. */
 	usage?: Usage;
+	/** Retained recent messages stored directly on the compaction entry. Optional during Pi 2.0 transition. */
+	retainedTail?: AgentMessage[];
 	/** Optional implementation-specific details stored with the compaction entry. */
 	details?: T;
 }
@@ -583,6 +585,8 @@ export interface CompactionPreparation {
 	messagesToSummarize: AgentMessage[];
 	/** Prefix messages summarized separately when compaction splits a turn. */
 	turnPrefixMessages: AgentMessage[];
+	/** Recent messages retained after compaction and stored on the compaction entry. */
+	retainedTail: AgentMessage[];
 	/** Whether compaction splits a turn. */
 	isSplitTurn: boolean;
 	/** Estimated context tokens before compaction. */
@@ -617,7 +621,9 @@ export function prepareCompaction(
 	if (prevCompactionIndex >= 0) {
 		const prevCompaction = pathEntries[prevCompactionIndex] as CompactionEntry;
 		previousSummary = prevCompaction.summary;
-		const firstKeptEntryIndex = pathEntries.findIndex((entry) => entry.id === prevCompaction.firstKeptEntryId);
+		const firstKeptEntryIndex = prevCompaction.firstKeptEntryId
+			? pathEntries.findIndex((entry) => entry.id === prevCompaction.firstKeptEntryId)
+			: -1;
 		boundaryStart = firstKeptEntryIndex >= 0 ? firstKeptEntryIndex : prevCompactionIndex + 1;
 	}
 	const boundaryEnd = pathEntries.length;
@@ -644,6 +650,11 @@ export function prepareCompaction(
 			if (msg) turnPrefixMessages.push(msg);
 		}
 	}
+	const retainedTail: AgentMessage[] = [];
+	for (let i = cutPoint.firstKeptEntryIndex; i < boundaryEnd; i++) {
+		const msg = getMessageFromEntryForCompaction(pathEntries[i]);
+		if (msg) retainedTail.push(msg);
+	}
 	const fileOps = extractFileOperations(messagesToSummarize, pathEntries, prevCompactionIndex);
 	if (cutPoint.isSplitTurn) {
 		for (const msg of turnPrefixMessages) {
@@ -655,6 +666,7 @@ export function prepareCompaction(
 		firstKeptEntryId,
 		messagesToSummarize,
 		turnPrefixMessages,
+		retainedTail,
 		isSplitTurn: cutPoint.isSplitTurn,
 		tokensBefore,
 		previousSummary,
@@ -693,6 +705,7 @@ export async function compact(
 		firstKeptEntryId,
 		messagesToSummarize,
 		turnPrefixMessages,
+		retainedTail,
 		isSplitTurn,
 		tokensBefore,
 		previousSummary,
@@ -762,6 +775,7 @@ export async function compact(
 		firstKeptEntryId,
 		tokensBefore,
 		usage: summaryUsage,
+		retainedTail,
 		details: { readFiles, modifiedFiles } as CompactionDetails,
 	});
 }
@@ -1,5 +1,12 @@
 import { uuidv7 } from "@earendil-works/pi-ai";
-import type { FileSystem, JsonlSessionMetadata, LeafEntry, SessionStorage, SessionTreeEntry } from "../types.ts";
+import type {
+	FileSystem,
+	JsonlSessionMetadata,
+	LeafEntry,
+	SessionEntryCursorOptions,
+	SessionStorage,
+	SessionTreeEntry,
+} from "../types.ts";
 import { SessionError, toError } from "../types.ts";
 import { getFileSystemResultOrThrow } from "./repo-utils.ts";

@@ -293,13 +300,66 @@ export class JsonlSessionStorage implements SessionStorage<JsonlSessionMetadata>
 		return this.labelsById.get(id);
 	}

-	async getPathToRoot(leafId: string | null): Promise<SessionTreeEntry[]> {
+	async getSessionName(): Promise<string | undefined> {
+		const entries = await this.findEntries("session_info");
+		return entries[entries.length - 1]?.name?.trim() || undefined;
+	}
+
+	async getSessionStats() {
+		let messageCount = 0;
+		let cachedTokens = 0;
+		let uncachedTokens = 0;
+		let totalTokens = 0;
+		let costTotal = 0;
+		for (const entry of this.entries) {
+			if (entry.type === "message") {
+				messageCount += 1;
+			}
+			const usage =
+				entry.type === "message"
+					? entry.message.role === "assistant"
+						? entry.message.usage
+						: undefined
+					: entry.type === "compaction" || entry.type === "branch_summary"
+						? entry.usage
+						: undefined;
+			if (
+				!usage ||
+				typeof usage.input !== "number" ||
+				typeof usage.output !== "number" ||
+				typeof usage.cacheRead !== "number" ||
+				typeof usage.cacheWrite !== "number" ||
+				typeof usage.cost?.total !== "number"
+			) {
+				continue;
+			}
+			cachedTokens += usage.cacheRead;
+			uncachedTokens += usage.input + usage.cacheWrite;
+			totalTokens += usage.input + usage.output + usage.cacheRead + usage.cacheWrite;
+			costTotal += usage.cost.total;
+		}
+		return {
+			messageCount,
+			cachedTokens,
+			uncachedTokens,
+			totalTokens,
+			costTotal,
+		};
+	}
+
+	async getPathToRootOrCompaction(leafId: string | null): Promise<SessionTreeEntry[]> {
 		if (leafId === null) return [];
 		const path: SessionTreeEntry[] = [];
+		let stopAtEntryId: string | null = null;
 		let current = this.byId.get(leafId);
 		if (!current) throw new SessionError("not_found", `Entry ${leafId} not found`);
 		while (current) {
 			path.unshift(current);
+			if (stopAtEntryId !== null && current.id === stopAtEntryId) break;
+			if (current.type === "compaction") {
+				if (current.retainedTail) break;
+				stopAtEntryId = current.firstKeptEntryId ?? null;
+			}
 			if (!current.parentId) break;
 			const parent = this.byId.get(current.parentId);
 			if (!parent) throw new SessionError("invalid_session", `Entry ${current.parentId} not found`);
@@ -308,7 +368,9 @@ export class JsonlSessionStorage implements SessionStorage<JsonlSessionMetadata>
 		return path;
 	}

-	async getEntries(): Promise<SessionTreeEntry[]> {
-		return [...this.entries];
+	async getEntries(options?: SessionEntryCursorOptions): Promise<SessionTreeEntry[]> {
+		const start = options?.afterEntrySeq ?? 0;
+		const end = options?.limit === undefined ? undefined : start + options.limit;
+		return this.entries.slice(start, end);
 	}
 }
@@ -1,6 +1,7 @@
 import { uuidv7 } from "@earendil-works/pi-ai";
 import {
 	type LeafEntry,
+	type SessionEntryCursorOptions,
 	SessionError,
 	type SessionMetadata,
 	type SessionStorage,
@@ -112,13 +113,66 @@ export class InMemorySessionStorage<TMetadata extends SessionMetadata = SessionM
 		return this.labelsById.get(id);
 	}

-	async getPathToRoot(leafId: string | null): Promise<SessionTreeEntry[]> {
+	async getSessionName(): Promise<string | undefined> {
+		const entries = await this.findEntries("session_info");
+		return entries[entries.length - 1]?.name?.trim() || undefined;
+	}
+
+	async getSessionStats() {
+		let messageCount = 0;
+		let cachedTokens = 0;
+		let uncachedTokens = 0;
+		let totalTokens = 0;
+		let costTotal = 0;
+		for (const entry of this.entries) {
+			if (entry.type === "message") {
+				messageCount += 1;
+			}
+			const usage =
+				entry.type === "message"
+					? entry.message.role === "assistant"
+						? entry.message.usage
+						: undefined
+					: entry.type === "compaction" || entry.type === "branch_summary"
+						? entry.usage
+						: undefined;
+			if (
+				!usage ||
+				typeof usage.input !== "number" ||
+				typeof usage.output !== "number" ||
+				typeof usage.cacheRead !== "number" ||
+				typeof usage.cacheWrite !== "number" ||
+				typeof usage.cost?.total !== "number"
+			) {
+				continue;
+			}
+			cachedTokens += usage.cacheRead;
+			uncachedTokens += usage.input + usage.cacheWrite;
+			totalTokens += usage.input + usage.output + usage.cacheRead + usage.cacheWrite;
+			costTotal += usage.cost.total;
+		}
+		return {
+			messageCount,
+			cachedTokens,
+			uncachedTokens,
+			totalTokens,
+			costTotal,
+		};
+	}
+
+	async getPathToRootOrCompaction(leafId: string | null): Promise<SessionTreeEntry[]> {
 		if (leafId === null) return [];
 		const path: SessionTreeEntry[] = [];
+		let stopAtEntryId: string | null = null;
 		let current = this.byId.get(leafId);
 		if (!current) throw new SessionError("not_found", `Entry ${leafId} not found`);
 		while (current) {
 			path.unshift(current);
+			if (stopAtEntryId !== null && current.id === stopAtEntryId) break;
+			if (current.type === "compaction") {
+				if (current.retainedTail) break;
+				stopAtEntryId = current.firstKeptEntryId ?? null;
+			}
 			if (!current.parentId) break;
 			const parent = this.byId.get(current.parentId);
 			if (!parent) throw new SessionError("invalid_session", `Entry ${current.parentId} not found`);
@@ -127,7 +181,9 @@ export class InMemorySessionStorage<TMetadata extends SessionMetadata = SessionM
 		return path;
 	}

-	async getEntries(): Promise<SessionTreeEntry[]> {
-		return [...this.entries];
+	async getEntries(options?: SessionEntryCursorOptions): Promise<SessionTreeEntry[]> {
+		const start = options?.afterEntrySeq ?? 0;
+		const end = options?.limit === undefined ? undefined : start + options.limit;
+		return this.entries.slice(start, end);
 	}
 }
@@ -47,5 +47,5 @@ export async function getEntriesToFork(
 		}
 		effectiveLeafId = target.parentId;
 	}
-	return storage.getPathToRoot(effectiveLeafId);
+	return storage.getPathToRootOrCompaction(effectiveLeafId);
 }
@@ -11,8 +11,10 @@ import type {
 	MessageEntry,
 	ModelChangeEntry,
 	SessionContext,
+	SessionEntryCursorOptions,
 	SessionInfoEntry,
 	SessionMetadata,
+	SessionStats,
 	SessionStorage,
 	SessionTreeEntry,
 	ThinkingLevelChangeEntry,
@@ -67,11 +69,19 @@ export function defaultContextEntryTransform(pathEntries: readonly SessionTreeEn

 	const entries: SessionTreeEntry[] = [compaction];
 	const compactionIdx = pathEntries.findIndex((entry) => entry.type === "compaction" && entry.id === compaction.id);
-	let foundFirstKept = false;
-	for (let i = 0; i < compactionIdx; i++) {
-		const entry = pathEntries[i]!;
-		if (entry.id === compaction.firstKeptEntryId) foundFirstKept = true;
-		if (foundFirstKept) entries.push(entry);
+	if (compaction.retainedTail) {
+		for (let i = compactionIdx + 1; i < pathEntries.length; i++) {
+			entries.push(pathEntries[i]!);
+		}
+		return entries;
+	}
+	if (compaction.firstKeptEntryId) {
+		let foundFirstKept = false;
+		for (let i = 0; i < compactionIdx; i++) {
+			const entry = pathEntries[i]!;
+			if (entry.id === compaction.firstKeptEntryId) foundFirstKept = true;
+			if (foundFirstKept) entries.push(entry);
+		}
 	}
 	for (let i = compactionIdx + 1; i < pathEntries.length; i++) {
 		entries.push(pathEntries[i]!);
@@ -111,7 +121,10 @@ export function sessionEntryToContextMessages(
 		];
 	}
 	if (entry.type === "compaction") {
-		return [createCompactionSummaryMessage(entry.summary, entry.tokensBefore, entry.timestamp)];
+		return [
+			createCompactionSummaryMessage(entry.summary, entry.tokensBefore, entry.timestamp),
+			...(entry.retainedTail ?? []),
+		];
 	}
 	if (entry.type === "branch_summary" && entry.summary) {
 		return [createBranchSummaryMessage(entry.summary, entry.fromId, entry.timestamp)];
@@ -159,13 +172,13 @@ export class Session<TMetadata extends SessionMetadata = SessionMetadata> {
 		return this.storage.getEntry(id);
 	}

-	getEntries(): Promise<SessionTreeEntry[]> {
-		return this.storage.getEntries();
+	getEntries(options?: SessionEntryCursorOptions): Promise<SessionTreeEntry[]> {
+		return this.storage.getEntries(options);
 	}

 	async getBranch(fromId?: string): Promise<SessionTreeEntry[]> {
 		const leafId = fromId ?? (await this.storage.getLeafId());
-		return this.storage.getPathToRoot(leafId);
+		return this.storage.getPathToRootOrCompaction(leafId);
 	}

 	async buildContextEntries(options: SessionContextBuildOptions = {}): Promise<SessionTreeEntry[]> {
@@ -190,9 +203,12 @@ export class Session<TMetadata extends SessionMetadata = SessionMetadata> {
 		return this.storage.getLabel(id);
 	}

+	getSessionStats(): Promise<SessionStats> {
+		return this.storage.getSessionStats();
+	}
+
 	async getSessionName(): Promise<string | undefined> {
-		const entries = await this.storage.findEntries("session_info");
-		return entries[entries.length - 1]?.name?.trim() || undefined;
+		return this.storage.getSessionName();
 	}

 	private async appendTypedEntry<TEntry extends SessionTreeEntry>(entry: TEntry): Promise<string> {
@@ -243,11 +259,12 @@ export class Session<TMetadata extends SessionMetadata = SessionMetadata> {

 	async appendCompaction<T = unknown>(
 		summary: string,
-		firstKeptEntryId: string,
+		firstKeptEntryId: string | undefined,
 		tokensBefore: number,
 		details?: T,
 		fromHook?: boolean,
 		usage?: Usage,
+		retainedTail?: AgentMessage[],
 	): Promise<string> {
 		return this.appendTypedEntry({
 			type: "compaction",
@@ -257,6 +274,7 @@ export class Session<TMetadata extends SessionMetadata = SessionMetadata> {
 			summary,
 			firstKeptEntryId,
 			tokensBefore,
+			retainedTail,
 			details,
 			usage,
 			fromHook,
@@ -370,8 +370,9 @@ export interface ActiveToolsChangeEntry extends SessionTreeEntryBase {
 export interface CompactionEntry<T = unknown> extends SessionTreeEntryBase {
 	type: "compaction";
 	summary: string;
-	firstKeptEntryId: string;
+	firstKeptEntryId?: string;
 	tokensBefore: number;
+	retainedTail?: AgentMessage[];
 	details?: T;
 	usage?: Usage;
 	fromHook?: boolean;
@@ -436,6 +437,14 @@ export interface SessionContext {
 	activeToolNames: string[] | null;
 }

+export interface SessionStats {
+	messageCount: number;
+	cachedTokens: number;
+	uncachedTokens: number;
+	totalTokens: number;
+	costTotal: number;
+}
+
 export interface SessionMetadata {
 	id: string;
 	createdAt: string;
@@ -448,6 +457,11 @@ export interface JsonlSessionMetadata extends SessionMetadata {
 	metadata?: Record<string, unknown>;
 }

+export interface SessionEntryCursorOptions {
+	afterEntrySeq?: number;
+	limit?: number;
+}
+
 export interface SessionStorage<TMetadata extends SessionMetadata = SessionMetadata> {
 	getMetadata(): Promise<TMetadata>;
 	getLeafId(): Promise<string | null>;
@@ -460,8 +474,10 @@ export interface SessionStorage<TMetadata extends SessionMetadata = SessionMetad
 		type: TType,
 	): Promise<Array<Extract<SessionTreeEntry, { type: TType }>>>;
 	getLabel(id: string): Promise<string | undefined>;
-	getPathToRoot(leafId: string | null): Promise<SessionTreeEntry[]>;
-	getEntries(): Promise<SessionTreeEntry[]>;
+	getSessionName(): Promise<string | undefined>;
+	getSessionStats(): Promise<SessionStats>;
+	getPathToRootOrCompaction(leafId: string | null): Promise<SessionTreeEntry[]>;
+	getEntries(options?: SessionEntryCursorOptions): Promise<SessionTreeEntry[]>;
 }

 export type { Session } from "./session/session.ts";
@@ -753,10 +769,11 @@ export interface AbortResult {

 export interface CompactResult {
 	summary: string;
-	firstKeptEntryId: string;
+	firstKeptEntryId?: string;
 	tokensBefore: number;
 	/** Usage from the LLM call(s) that generated this summary, if available. */
 	usage?: Usage;
+	retainedTail?: AgentMessage[];
 	details?: unknown;
 }

@@ -776,6 +793,7 @@ export interface CompactionPreparation {
 	firstKeptEntryId: string;
 	messagesToSummarize: AgentMessage[];
 	turnPrefixMessages: AgentMessage[];
+	retainedTail: AgentMessage[];
 	isSplitTurn: boolean;
 	tokensBefore: number;
 	previousSummary?: string;
@@ -1,4 +1,5 @@
 // Core Agent
+export { uuidv7 } from "@earendil-works/pi-ai";
 export * from "./agent.ts";
 // Loop functions
 export * from "./agent-loop.ts";
@@ -91,6 +91,7 @@ function createCompactionEntry(
 	summary: string,
 	firstKeptEntryId: string,
 	parentId: string | null = null,
+	retainedTail?: AgentMessage[],
 ): CompactionEntry {
 	return {
 		type: "compaction",
@@ -100,6 +101,7 @@ function createCompactionEntry(
 		summary,
 		firstKeptEntryId,
 		tokensBefore: 1234,
+		retainedTail,
 	};
 }

@@ -343,12 +345,38 @@ describe("harness compaction", () => {
 		const a1 = createMessageEntry(createAssistantMessage("a"), u1.id);
 		const u2 = createMessageEntry(createUserMessage("2"), a1.id);
 		const a2 = createMessageEntry(createAssistantMessage("b"), u2.id);
-		const compaction = createCompactionEntry("Summary of 1,a,2,b", u2.id, a2.id);
+		const compaction = createCompactionEntry("Summary of 1,a,2,b", u2.id, a2.id, [
+			createUserMessage("2"),
+			createAssistantMessage("b"),
+		]);
 		const u3 = createMessageEntry(createUserMessage("3"), compaction.id);
 		const a3 = createMessageEntry(createAssistantMessage("c"), u3.id);
 		const loaded = buildSessionContext([u1, a1, u2, a2, compaction, u3, a3]);
 		expect(loaded.messages).toHaveLength(5);
 		expect(loaded.messages[0]?.role).toBe("compactionSummary");
+		expect(loaded.messages.map((message) => message.role)).toEqual([
+			"compactionSummary",
+			"user",
+			"assistant",
+			"user",
+			"assistant",
+		]);
+	});
+
+	it("falls back to firstKeptEntryId when a compaction has no retained tail", () => {
+		const u1 = createMessageEntry(createUserMessage("1"));
+		const a1 = createMessageEntry(createAssistantMessage("a"), u1.id);
+		const u2 = createMessageEntry(createUserMessage("2"), a1.id);
+		const a2 = createMessageEntry(createAssistantMessage("b"), u2.id);
+		const compaction = createCompactionEntry("Summary of 1,a,2,b", u2.id, a2.id);
+		const u3 = createMessageEntry(createUserMessage("3"), compaction.id);
+		const loaded = buildSessionContext([u1, a1, u2, a2, compaction, u3]);
+		expect(loaded.messages.map((message) => message.role)).toEqual([
+			"compactionSummary",
+			"user",
+			"assistant",
+			"user",
+		]);
 	});

 	it("tracks model and thinking level changes in built context", () => {
@@ -374,6 +402,7 @@ describe("harness compaction", () => {
 		expect(preparation).toBeDefined();
 		expect(preparation?.previousSummary).toBe("First summary");
 		expect(preparation?.firstKeptEntryId).toBeTruthy();
+		expect(preparation?.retainedTail.length).toBeGreaterThan(0);
 		expect(preparation?.tokensBefore).toBe(estimateContextTokens(buildSessionContext(pathEntries).messages).tokens);
 	});

@@ -566,6 +595,7 @@ describe("harness compaction", () => {
 			firstKeptEntryId: "entry-keep",
 			messagesToSummarize: messages,
 			turnPrefixMessages: messages,
+			retainedTail: messages,
 			isSplitTurn: true,
 			tokensBefore: 600000,
 			fileOps: { read: new Set(), written: new Set(), edited: new Set() },
@@ -583,6 +613,7 @@ describe("harness compaction", () => {
 			firstKeptEntryId: "entry-keep",
 			messagesToSummarize: messages,
 			turnPrefixMessages: [],
+			retainedTail: messages,
 			isSplitTurn: false,
 			tokensBefore: 100,
 			fileOps: { read: new Set(), written: new Set(), edited: new Set() },
@@ -619,6 +650,7 @@ describe("harness compaction", () => {
 			turnPrefixMessages: messages,
 			isSplitTurn: true,
 			tokensBefore: 100,
+			retainedTail: messages,
 			fileOps: { read: new Set(), written: new Set(), edited: new Set() },
 			settings: { enabled: true, reserveTokens: 2000, keepRecentTokens: 20 },
 		};
@@ -642,6 +674,7 @@ describe("harness compaction", () => {
 			firstKeptEntryId: "entry-keep",
 			messagesToSummarize: [],
 			turnPrefixMessages: messages,
+			retainedTail: messages,
 			isSplitTurn: true,
 			tokensBefore: 100,
 			fileOps: { read: new Set(), written: new Set(), edited: new Set() },
@@ -659,6 +692,7 @@ describe("harness compaction", () => {
 			firstKeptEntryId: "entry-keep",
 			messagesToSummarize: [],
 			turnPrefixMessages: messages,
+			retainedTail: messages,
 			isSplitTurn: true,
 			tokensBefore: 100,
 			fileOps: { read: new Set(), written: new Set(), edited: new Set() },
@@ -697,6 +731,7 @@ describe("harness compaction", () => {
 		expect(result.summary.length).toBeGreaterThan(0);
 		expect(result.firstKeptEntryId).toBeTruthy();
 		expect(result.usage?.totalTokens).toBeGreaterThan(0);
+		expect(result.retainedTail?.length).toBeGreaterThan(0);
 		expect(result.details).toBeDefined();
 	});
 });
@@ -68,11 +68,20 @@ async function runSessionSuite(
 			await session.appendMessage(createAssistantMessage("two"));
 			const user2 = await session.appendMessage(createUserMessage("three"));
 			await session.appendMessage(createAssistantMessage("four"));
-			await session.appendCompaction("summary", user2, 1234);
+			await session.appendCompaction("summary", user2, 1234, undefined, undefined, undefined, [
+				createUserMessage("three"),
+				createAssistantMessage("four"),
+			]);
 			await session.appendMessage(createUserMessage("five"));
 			const context = await session.buildContext();
 			expect(context.messages[0]?.role).toBe("compactionSummary");
 			expect(context.messages).toHaveLength(4);
+			expect(context.messages.map((message) => message.role)).toEqual([
+				"compactionSummary",
+				"user",
+				"assistant",
+				"user",
+			]);
 		});

 		it("supports moving with branch summary entries in context", async () => {
@@ -0,0 +1,441 @@
+import { mkdtempSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { describe, expect, it } from "vitest";
+import {
+	applyMigrations,
+	createNodeSqliteFactory,
+	type SqliteDatabase,
+	type SqliteDatabaseFactory,
+	type SqliteRunResult,
+	type SqliteSessionMetadata,
+	SqliteSessionRepo,
+	SqliteSessionStorage,
+	type SqliteStatement,
+} from "../../../storage/sqlite-node/src/index.ts";
+import { NodeExecutionEnv } from "../../src/harness/env/nodejs.ts";
+import { createAssistantMessage, createUserMessage } from "./session-test-utils.ts";
+
+function createTempDir(): string {
+	return mkdtempSync(join(tmpdir(), "pi-agent-sqlite-"));
+}
+
+class ThrowingStatement implements SqliteStatement {
+	private readonly onRun: () => Promise<SqliteRunResult>;
+
+	constructor(onRun: () => Promise<SqliteRunResult>) {
+		this.onRun = onRun;
+	}
+
+	async run(..._params: unknown[]): Promise<SqliteRunResult> {
+		return this.onRun();
+	}
+
+	async get<TRow extends object>(..._params: unknown[]): Promise<TRow | undefined> {
+		return undefined;
+	}
+
+	async all<TRow extends object>(..._params: unknown[]): Promise<TRow[]> {
+		return [];
+	}
+}
+
+class CountingDatabase implements SqliteDatabase {
+	closeCount = 0;
+	private readonly statementFactory: (sql: string) => SqliteStatement;
+
+	constructor(statementFactory: (sql: string) => SqliteStatement) {
+		this.statementFactory = statementFactory;
+	}
+
+	async exec(_sql: string): Promise<void> {}
+
+	prepare(sql: string): SqliteStatement {
+		return this.statementFactory(sql);
+	}
+
+	async transaction<T>(fn: () => Promise<T>): Promise<T> {
+		return fn();
+	}
+
+	async close(): Promise<void> {
+		this.closeCount += 1;
+	}
+}
+
+describe("SQLite migrations", () => {
+	it("applies file-based migrations and records them", async () => {
+		const root = createTempDir();
+		const databasePath = join(root, "sessions.sqlite");
+		const env = new NodeExecutionEnv({ cwd: root });
+		const sqlite = createNodeSqliteFactory();
+		const repo = new SqliteSessionRepo({ env, sqlite, databasePath });
+		await repo.create({ cwd: root, id: "session-1" });
+
+		const db = await sqlite.open(databasePath);
+		try {
+			const rows = await db.prepare("SELECT id FROM migrations ORDER BY id").all<{ id: string }>();
+			expect(rows.map((row) => row.id)).toEqual(["001_initial.sql"]);
+			const tables = await db
+				.prepare("SELECT name, sql FROM sqlite_master WHERE type = 'table' ORDER BY name")
+				.all<{ name: string; sql: string | null }>();
+			expect(tables.map((row) => row.name)).toEqual(
+				expect.arrayContaining([
+					"migrations",
+					"sessions",
+					"session_entries",
+					"session_sequences",
+					"branch_entries",
+					"session_materialized",
+					"entry_materialized",
+				]),
+			);
+			const sessionColumns = await db.prepare("PRAGMA table_info(sessions)").all<{ name: string }>();
+			expect(sessionColumns.map((column) => column.name)).toContain("active_leaf_id");
+			for (const tableName of [
+				"sessions",
+				"session_sequences",
+				"branch_entries",
+				"session_materialized",
+				"entry_materialized",
+			]) {
+				const table = tables.find((row) => row.name === tableName);
+				expect(table?.sql).toContain("WITHOUT ROWID");
+			}
+		} finally {
+			await db.close();
+		}
+	});
+
+	it("persists session metadata through create, list, open, and fork", async () => {
+		const root = createTempDir();
+		const databasePath = join(root, "sessions.sqlite");
+		const env = new NodeExecutionEnv({ cwd: root });
+		const repo = new SqliteSessionRepo({ env, sqlite: createNodeSqliteFactory(), databasePath });
+		const source = await repo.create({
+			cwd: root,
+			id: "session-1",
+			metadata: { profile: "reviewer" },
+		});
+		const sourceMetadata = await source.getMetadata();
+		expect(sourceMetadata.metadata).toEqual({ profile: "reviewer" });
+		expect((await repo.list({ cwd: root })).map((listed) => listed.metadata)).toEqual([{ profile: "reviewer" }]);
+		expect((await (await repo.open(sourceMetadata)).getMetadata()).metadata).toEqual({ profile: "reviewer" });
+		const fork = await repo.fork(sourceMetadata, { cwd: root, id: "session-2" });
+		expect((await fork.getMetadata()).metadata).toEqual({ profile: "reviewer" });
+		const overridden = await repo.fork(sourceMetadata, {
+			cwd: root,
+			id: "session-3",
+			metadata: { profile: "writer" },
+		});
+		expect((await overridden.getMetadata()).metadata).toEqual({ profile: "writer" });
+	});
+
+	it("materializes active leaf id in sessions transactionally", async () => {
+		const root = createTempDir();
+		const databasePath = join(root, "sessions.sqlite");
+		const env = new NodeExecutionEnv({ cwd: root });
+		const sqlite = createNodeSqliteFactory();
+		const repo = new SqliteSessionRepo({ env, sqlite, databasePath });
+		const session = await repo.create({ cwd: root, id: "session-1" });
+		const rootId = await session.appendMessage(createUserMessage("root"));
+		const childId = await session.appendMessage(createAssistantMessage("child"));
+		await session.getStorage().setLeafId(rootId);
+
+		const db = await sqlite.open(databasePath);
+		try {
+			const row = await db
+				.prepare("SELECT active_leaf_id FROM sessions WHERE id = ?")
+				.get<{ active_leaf_id: string | null }>("session-1");
+			expect(row?.active_leaf_id).toBe(rootId);
+			const latestBranchRow = await db
+				.prepare(
+					"SELECT branch_id, entry_id, entry_seq FROM branch_entries WHERE session_id = ? ORDER BY entry_seq DESC LIMIT 1",
+				)
+				.get<{ branch_id: string; entry_id: string; entry_seq: number }>("session-1");
+			const latestSessionEntry = await db
+				.prepare("SELECT id, type FROM session_entries WHERE session_id = ? ORDER BY entry_seq DESC LIMIT 1")
+				.get<{ id: string; type: string }>("session-1");
+			expect(latestSessionEntry?.type).toBe("leaf");
+			expect(latestBranchRow?.entry_id).toBe(latestSessionEntry?.id);
+		} finally {
+			await db.close();
+		}
+
+		const reopened = await repo.open(await session.getMetadata());
+		expect(await reopened.getLeafId()).toBe(rootId);
+		expect(childId).not.toBe(rootId);
+	});
+
+	it("materializes a new branch when appending from a parent with an existing child", async () => {
+		const root = createTempDir();
+		const databasePath = join(root, "sessions.sqlite");
+		const env = new NodeExecutionEnv({ cwd: root });
+		const sqlite = createNodeSqliteFactory();
+		const repo = new SqliteSessionRepo({ env, sqlite, databasePath });
+		const session = await repo.create({ cwd: root, id: "session-1" });
+		const rootId = await session.appendMessage(createUserMessage("root"));
+		const firstChildId = await session.appendMessage(createAssistantMessage("first child"));
+		await session.getStorage().setLeafId(rootId);
+		const secondChildId = await session.appendMessage(createAssistantMessage("second child"));
+
+		const db = await sqlite.open(databasePath);
+		try {
+			const branchRows = await db
+				.prepare(
+					"SELECT branch_id, entry_id, entry_seq FROM branch_entries WHERE session_id = ? ORDER BY branch_id, entry_seq",
+				)
+				.all<{ branch_id: string; entry_id: string; entry_seq: number }>("session-1");
+			const branchIds = [...new Set(branchRows.map((row) => row.branch_id))];
+			expect(branchIds).toHaveLength(3);
+			expect(branchRows.filter((row) => row.entry_id === rootId)).toHaveLength(3);
+			expect(branchRows.filter((row) => row.entry_id === firstChildId)).toHaveLength(1);
+			expect(branchRows.filter((row) => row.entry_id === secondChildId)).toHaveLength(1);
+		} finally {
+			await db.close();
+		}
+	});
+
+	it("reopens using branch materialization and session summary state", async () => {
+		const root = createTempDir();
+		const databasePath = join(root, "sessions.sqlite");
+		const env = new NodeExecutionEnv({ cwd: root });
+		const repo = new SqliteSessionRepo({ env, sqlite: createNodeSqliteFactory(), databasePath });
+		const session = await repo.create({ cwd: root, id: "session-1" });
+		const rootId = await session.appendMessage(createUserMessage("root"));
+		await session.appendMessage(createAssistantMessage("first child"));
+		await session.appendSessionName("  Reopened Session  ");
+		await session.getStorage().setLeafId(rootId);
+		await session.appendMessage(createAssistantMessage("branched child"));
+
+		const reopened = await repo.open(await session.getMetadata());
+		expect(await reopened.getSessionName()).toBe("Reopened Session");
+		expect((await reopened.buildContext()).messages.map((message) => message.role)).toEqual(["user", "assistant"]);
+		expect((await reopened.buildContext()).messages.at(-1)).toMatchObject({
+			content: [{ type: "text", text: "branched child" }],
+		});
+	});
+
+	it("pages entries by entry_seq cursor", async () => {
+		const root = createTempDir();
+		const databasePath = join(root, "sessions.sqlite");
+		const env = new NodeExecutionEnv({ cwd: root });
+		const repo = new SqliteSessionRepo({ env, sqlite: createNodeSqliteFactory(), databasePath });
+		const session = await repo.create({ cwd: root, id: "session-1" });
+		await session.appendMessage(createUserMessage("one"));
+		await session.appendMessage(createAssistantMessage("two"));
+		await session.appendMessage(createUserMessage("three"));
+
+		expect((await session.getEntries({ limit: 2 })).map((entry) => entry.type)).toEqual(["message", "message"]);
+		expect((await session.getEntries({ afterEntrySeq: 2, limit: 2 })).map((entry) => entry.type)).toEqual([
+			"message",
+			"message",
+		]);
+	});
+
+	it("closes the database when create fails after openDatabase succeeds", async () => {
+		const root = createTempDir();
+		const db = new CountingDatabase((sql) => {
+			if (sql.startsWith("INSERT INTO sessions")) {
+				return new ThrowingStatement(async () => {
+					throw new Error("insert failed");
+				});
+			}
+			return new ThrowingStatement(async () => ({ changes: 1 }));
+		});
+		const sqlite: SqliteDatabaseFactory = {
+			open: async () => db,
+		};
+		const env = new NodeExecutionEnv({ cwd: root });
+		const repo = new SqliteSessionRepo({ env, sqlite, databasePath: join(root, "sessions.sqlite") });
+
+		await expect(repo.create({ cwd: root, id: "session-1" })).rejects.toThrow("insert failed");
+		expect(db.closeCount).toBe(1);
+	});
+
+	it("closes the database when open fails after openDatabase succeeds", async () => {
+		const root = createTempDir();
+		const db = new CountingDatabase((sql) => {
+			if (sql.includes("FROM sessions WHERE id = ?")) {
+				return new ThrowingStatement(async () => ({ changes: 0 }));
+			}
+			return new ThrowingStatement(async () => ({ changes: 1 }));
+		});
+		const sqlite: SqliteDatabaseFactory = {
+			open: async () => db,
+		};
+		const env = new NodeExecutionEnv({ cwd: root });
+		const repo = new SqliteSessionRepo({ env, sqlite, databasePath: join(root, "sessions.sqlite") });
+		const metadata: SqliteSessionMetadata = {
+			id: "missing",
+			createdAt: new Date().toISOString(),
+			cwd: root,
+			path: join(root, "sessions.sqlite"),
+		};
+		writeFileSync(metadata.path, "");
+
+		await expect(repo.open(metadata)).rejects.toThrow("Session not found: missing");
+		expect(db.closeCount).toBe(1);
+	});
+
+	it("closes the source storage after fork reads its entries", async () => {
+		const root = createTempDir();
+		const databasePath = join(root, "sessions.sqlite");
+		const env = new NodeExecutionEnv({ cwd: root });
+		const repo = new SqliteSessionRepo({ env, sqlite: createNodeSqliteFactory(), databasePath });
+		let cleanupCount = 0;
+		const sourceStorage = {
+			async getEntries() {
+				return [];
+			},
+			async getPathToRootOrCompaction() {
+				return [];
+			},
+			async cleanup() {
+				cleanupCount += 1;
+			},
+		} as const;
+		const originalOpen = repo.open.bind(repo);
+		repo.open = async () =>
+			({
+				getStorage() {
+					return sourceStorage;
+				},
+			}) as never;
+
+		try {
+			await repo.fork(
+				{
+					id: "session-1",
+					createdAt: new Date().toISOString(),
+					cwd: root,
+					path: databasePath,
+				},
+				{ cwd: root, id: "session-2" },
+			);
+		} finally {
+			repo.open = originalOpen;
+		}
+
+		expect(cleanupCount).toBe(1);
+	});
+
+	it("restores in-memory state when appendEntry fails after mutating caches", async () => {
+		const root = createTempDir();
+		const databasePath = join(root, "sessions.sqlite");
+		const sqlite = createNodeSqliteFactory();
+		const db = await sqlite.open(databasePath);
+		await applyMigrations(db);
+		const storage = await SqliteSessionStorage.create(db, databasePath, {
+			cwd: root,
+			sessionId: "session-1",
+		});
+		const originalPrepare = db.prepare.bind(db);
+		db.prepare = (sql: string) => {
+			if (sql.startsWith("UPDATE sessions SET active_leaf_id = ?")) {
+				return new ThrowingStatement(async () => {
+					throw new Error("active leaf update failed");
+				});
+			}
+			return originalPrepare(sql);
+		};
+
+		await expect(
+			storage.appendEntry({
+				type: "message",
+				id: "root",
+				parentId: null,
+				timestamp: new Date().toISOString(),
+				message: createUserMessage("root"),
+			}),
+		).rejects.toMatchObject({ code: "storage" });
+		expect(await storage.getLeafId()).toBeNull();
+		expect(await storage.getEntry("root")).toBeUndefined();
+		expect(await storage.getEntries()).toEqual([]);
+		await db.close();
+	});
+
+	it("materializes session summary fields transactionally", async () => {
+		const root = createTempDir();
+		const databasePath = join(root, "sessions.sqlite");
+		const env = new NodeExecutionEnv({ cwd: root });
+		const sqlite = createNodeSqliteFactory();
+		const repo = new SqliteSessionRepo({ env, sqlite, databasePath });
+		const session = await repo.create({ cwd: root, id: "session-1" });
+		const userId = await session.appendMessage(createUserMessage("one"));
+		await session.appendThinkingLevelChange("high");
+		await session.appendModelChange("anthropic", "claude-sonnet-4-5");
+		const assistant = {
+			...createAssistantMessage("two"),
+			provider: "anthropic",
+			model: "claude-sonnet-4-5",
+			usage: {
+				input: 100,
+				output: 25,
+				cacheRead: 40,
+				cacheWrite: 10,
+				totalTokens: 175,
+				cost: { input: 0.1, output: 0.2, cacheRead: 0.03, cacheWrite: 0.04, total: 0.37 },
+			},
+		};
+		await session.appendMessage(assistant);
+		await session.appendCompaction("summary", userId, 200, undefined, false, {
+			input: 1,
+			output: 2,
+			cacheRead: 3,
+			cacheWrite: 4,
+			totalTokens: 10,
+			cost: { input: 0.01, output: 0.02, cacheRead: 0.03, cacheWrite: 0.04, total: 0.1 },
+		});
+		await session.moveTo(userId, {
+			summary: "branch summary",
+			usage: {
+				input: 5,
+				output: 6,
+				cacheRead: 7,
+				cacheWrite: 8,
+				totalTokens: 26,
+				cost: { input: 0.05, output: 0.06, cacheRead: 0.07, cacheWrite: 0.08, total: 0.26 },
+			},
+		});
+		await session.appendSessionName("  My Session  ");
+		await session.appendLabel(userId, "checkpoint");
+
+		const db = await sqlite.open(databasePath);
+		try {
+			const row = await db.prepare("SELECT session_id, payload FROM session_materialized WHERE session_id = ?").get<{
+				session_id: string;
+				payload: string;
+			}>("session-1");
+			expect(row).toBeDefined();
+			expect(row?.session_id).toBe("session-1");
+			expect(JSON.parse(row?.payload ?? "null")).toMatchObject({
+				name: "My Session",
+				messageCount: 2,
+				cachedTokens: 50,
+				uncachedTokens: 128,
+				totalTokens: 211,
+				costTotal: 0.73,
+				currentModel: { provider: "anthropic", modelId: "claude-sonnet-4-5" },
+				currentThinkingLevel: "high",
+			});
+			const entryRows = await db
+				.prepare(
+					"SELECT session_id, entry_seq, type, payload FROM entry_materialized WHERE session_id = ? ORDER BY entry_seq, type",
+				)
+				.all<{
+					session_id: string;
+					entry_seq: number;
+					type: string;
+					payload: string;
+				}>("session-1");
+			expect(
+				entryRows.some((entryRow) => entryRow.type === "label" && JSON.parse(entryRow.payload).targetId === userId),
+			).toBe(true);
+			expect(entryRows.some((entryRow) => entryRow.type === "thinking")).toBe(false);
+			expect(entryRows.some((entryRow) => entryRow.type === "model")).toBe(false);
+		} finally {
+			await db.close();
+		}
+	});
+});
@@ -0,0 +1,21 @@
+import { join } from "node:path";
+import { describe, expect, it } from "vitest";
+import { createNodeSqliteFactory } from "../../../storage/sqlite-node/src/index.ts";
+import { createTempDir } from "./session-test-utils.ts";
+
+describe("sqlite-node adapter", () => {
+	it("supports node:sqlite-style named parameters", async () => {
+		const root = createTempDir();
+		const databasePath = join(root, "adapter.sqlite");
+		const sqlite = createNodeSqliteFactory();
+		const db = await sqlite.open(databasePath);
+		try {
+			await db.exec("CREATE TABLE items (id INTEGER PRIMARY KEY, text TEXT NOT NULL)");
+			await db.prepare("INSERT INTO items (id, text) VALUES ($id, $text)").run({ $id: 1, $text: "hello" });
+			const row = await db.prepare("SELECT text FROM items WHERE id = $id").get<{ text: string }>({ $id: 1 });
+			expect(row).toEqual({ text: "hello" });
+		} finally {
+			await db.close();
+		}
+	});
+});
@@ -4,7 +4,13 @@ import { describe, expect, it } from "vitest";
 import { NodeExecutionEnv } from "../../src/harness/env/nodejs.ts";
 import { JsonlSessionStorage, loadJsonlSessionMetadata } from "../../src/harness/session/jsonl-storage.ts";
 import { InMemorySessionStorage } from "../../src/harness/session/memory-storage.ts";
-import { type MessageEntry, ok, type SessionMetadata } from "../../src/harness/types.ts";
+import {
+	type BranchSummaryEntry,
+	type CompactionEntry,
+	type MessageEntry,
+	ok,
+	type SessionMetadata,
+} from "../../src/harness/types.ts";
 import { createAssistantMessage, createTempDir, createUserMessage } from "./session-test-utils.ts";

 describe("InMemorySessionStorage", () => {
@@ -80,7 +86,74 @@ describe("InMemorySessionStorage", () => {
 		expect(await storage.getLabel("entry-1")).toBeUndefined();
 	});

-	it("walks paths to root", async () => {
+	it("includes summary-entry usage in session stats", async () => {
+		const assistant: MessageEntry = {
+			type: "message",
+			id: "assistant",
+			parentId: null,
+			timestamp: "2026-01-01T00:00:00.000Z",
+			message: {
+				role: "assistant",
+				content: [{ type: "text", text: "reply" }],
+				api: "anthropic-messages",
+				provider: "anthropic",
+				model: "claude-sonnet-4-5",
+				usage: {
+					input: 10,
+					output: 20,
+					cacheRead: 30,
+					cacheWrite: 40,
+					totalTokens: 100,
+					cost: { input: 0.1, output: 0.2, cacheRead: 0.3, cacheWrite: 0.4, total: 1 },
+				},
+				stopReason: "stop",
+				timestamp: 0,
+			},
+		};
+		const compaction: CompactionEntry = {
+			type: "compaction",
+			id: "compaction",
+			parentId: "assistant",
+			timestamp: "2026-01-01T00:00:01.000Z",
+			summary: "summary",
+			firstKeptEntryId: "assistant",
+			tokensBefore: 1234,
+			usage: {
+				input: 1,
+				output: 2,
+				cacheRead: 3,
+				cacheWrite: 4,
+				totalTokens: 10,
+				cost: { input: 0.01, output: 0.02, cacheRead: 0.03, cacheWrite: 0.04, total: 0.1 },
+			},
+		};
+		const branchSummary: BranchSummaryEntry = {
+			type: "branch_summary",
+			id: "branch-summary",
+			parentId: "compaction",
+			timestamp: "2026-01-01T00:00:02.000Z",
+			fromId: "assistant",
+			summary: "branch",
+			usage: {
+				input: 5,
+				output: 6,
+				cacheRead: 7,
+				cacheWrite: 8,
+				totalTokens: 26,
+				cost: { input: 0.05, output: 0.06, cacheRead: 0.07, cacheWrite: 0.08, total: 0.26 },
+			},
+		};
+		const storage = new InMemorySessionStorage({ entries: [assistant, compaction, branchSummary] });
+		expect(await storage.getSessionStats()).toEqual({
+			messageCount: 1,
+			cachedTokens: 40,
+			uncachedTokens: 68,
+			totalTokens: 136,
+			costTotal: 1.36,
+		});
+	});
+
+	it("walks paths to root or retained-tail compaction", async () => {
 		const root: MessageEntry = {
 			type: "message",
 			id: "root",
@@ -94,9 +167,29 @@ describe("InMemorySessionStorage", () => {
 			parentId: "root",
 			message: createAssistantMessage("child"),
 		};
-		const storage = new InMemorySessionStorage({ entries: [root, child] });
-		expect((await storage.getPathToRoot("child")).map((entry) => entry.id)).toEqual(["root", "child"]);
-		expect(await storage.getPathToRoot(null)).toEqual([]);
+		const compaction: CompactionEntry = {
+			type: "compaction",
+			id: "compaction",
+			parentId: "child",
+			timestamp: "2026-01-01T00:00:01.000Z",
+			summary: "summary",
+			firstKeptEntryId: "child",
+			tokensBefore: 1234,
+			retainedTail: [createAssistantMessage("child")],
+		};
+		const afterCompaction: MessageEntry = {
+			...root,
+			id: "after-compaction",
+			parentId: "compaction",
+			message: createUserMessage("after"),
+		};
+		const storage = new InMemorySessionStorage({ entries: [root, child, compaction, afterCompaction] });
+		expect((await storage.getPathToRootOrCompaction("child")).map((entry) => entry.id)).toEqual(["root", "child"]);
+		expect((await storage.getPathToRootOrCompaction("after-compaction")).map((entry) => entry.id)).toEqual([
+			"compaction",
+			"after-compaction",
+		]);
+		expect(await storage.getPathToRootOrCompaction(null)).toEqual([]);
 	});
 });

@@ -255,7 +348,7 @@ describe("JsonlSessionStorage", () => {
 		const reloaded = await JsonlSessionStorage.open(env, filePath);
 		expect(await reloaded.getLeafId()).toBe("root");
 		expect((await reloaded.getEntries()).at(-1)).toMatchObject({ type: "leaf", targetId: "root" });
-		expect((await loaded.getPathToRoot("child")).map((entry) => entry.id)).toEqual(["root", "child"]);
+		expect((await loaded.getPathToRootOrCompaction("child")).map((entry) => entry.id)).toEqual(["root", "child"]);
 	});

 	it("finds entries by type", async () => {
@@ -309,6 +402,76 @@ describe("JsonlSessionStorage", () => {
 		expect(await loaded.getLabel("entry-1")).toBeUndefined();
 	});

+	it("includes summary-entry usage in session stats", async () => {
+		const dir = createTempDir();
+		const env = new NodeExecutionEnv({ cwd: dir });
+		const filePath = join(dir, "session.jsonl");
+		const storage = await JsonlSessionStorage.create(env, filePath, { cwd: dir, sessionId: "session-1" });
+		await storage.appendEntry({
+			type: "message",
+			id: "assistant",
+			parentId: null,
+			timestamp: "2026-01-01T00:00:00.000Z",
+			message: {
+				role: "assistant",
+				content: [{ type: "text", text: "reply" }],
+				api: "anthropic-messages",
+				provider: "anthropic",
+				model: "claude-sonnet-4-5",
+				usage: {
+					input: 10,
+					output: 20,
+					cacheRead: 30,
+					cacheWrite: 40,
+					totalTokens: 100,
+					cost: { input: 0.1, output: 0.2, cacheRead: 0.3, cacheWrite: 0.4, total: 1 },
+				},
+				stopReason: "stop",
+				timestamp: 0,
+			},
+		});
+		await storage.appendEntry({
+			type: "compaction",
+			id: "compaction",
+			parentId: "assistant",
+			timestamp: "2026-01-01T00:00:01.000Z",
+			summary: "summary",
+			firstKeptEntryId: "assistant",
+			tokensBefore: 1234,
+			usage: {
+				input: 1,
+				output: 2,
+				cacheRead: 3,
+				cacheWrite: 4,
+				totalTokens: 10,
+				cost: { input: 0.01, output: 0.02, cacheRead: 0.03, cacheWrite: 0.04, total: 0.1 },
+			},
+		});
+		await storage.appendEntry({
+			type: "branch_summary",
+			id: "branch-summary",
+			parentId: "compaction",
+			timestamp: "2026-01-01T00:00:02.000Z",
+			fromId: "assistant",
+			summary: "branch",
+			usage: {
+				input: 5,
+				output: 6,
+				cacheRead: 7,
+				cacheWrite: 8,
+				totalTokens: 26,
+				cost: { input: 0.05, output: 0.06, cacheRead: 0.07, cacheWrite: 0.08, total: 0.26 },
+			},
+		});
+		expect(await storage.getSessionStats()).toEqual({
+			messageCount: 1,
+			cachedTokens: 40,
+			uncachedTokens: 68,
+			totalTokens: 136,
+			costTotal: 1.36,
+		});
+	});
+
 	it("reads session metadata through the line-reading filesystem operation", async () => {
 		const dir = createTempDir();
 		const filePath = join(dir, "session.jsonl");
@@ -3,6 +3,7 @@ import { defineConfig } from "vitest/config";

 const aiSrcIndex = fileURLToPath(new URL("../ai/src/index.ts", import.meta.url));
 const aiSrcCompat = fileURLToPath(new URL("../ai/src/compat.ts", import.meta.url));
+const agentSrcIndex = fileURLToPath(new URL("../agent/src/index.ts", import.meta.url));

 export default defineConfig({
 	test: {
@@ -21,6 +22,7 @@ export default defineConfig({
 	},
 	resolve: {
 		alias: [
+			{ find: /^@earendil-works\/pi-agent-core$/, replacement: agentSrcIndex },
 			{ find: /^@earendil-works\/pi-ai$/, replacement: aiSrcIndex },
 			{ find: /^@earendil-works\/pi-ai\/compat$/, replacement: aiSrcCompat },
 		],
@@ -232,10 +232,18 @@ Created when context is compacted. Stores a summary of earlier messages.
 {"type":"compaction","id":"f6g7h8i9","parentId":"e5f6g7h8","timestamp":"2024-12-03T14:10:00.000Z","summary":"User discussed X, Y, Z...","firstKeptEntryId":"c3d4e5f6","tokensBefore":50000}
 ```

+Newer harness-generated compactions embed the retained post-compaction context directly on the entry, instead of `firstKeptEntryId`:
+
+```json
+{"type":"compaction","id":"f6g7h8i9","parentId":"e5f6g7h8","timestamp":"2024-12-03T14:10:00.000Z","summary":"User discussed X, Y, Z...","tokensBefore":50000,"retainedTail":[{"role":"user","content":"latest request"},{"role":"assistant","content":[{"type":"text","text":"latest reply"}],"provider":"anthropic","model":"claude-sonnet-4-5","usage":{...},"stopReason":"stop"}]}
+```
+
 Optional fields:
 - `usage`: LLM usage from generating the summary; included in session token and cost totals
+- `retainedTail`: Materialized `AgentMessage[]` kept after compaction. This is optional only for backward compatibility with older sessions. Newer harness-generated compactions include it so we can rebuild context from this checkpoint without walking older entries before the compaction entry.
 - `details`: Implementation-specific data (e.g., `{ readFiles: string[], modifiedFiles: string[] }` for default, or custom data for extensions)
 - `fromHook`: `true` if generated by an extension, `false`/`undefined` if pi-generated (legacy field name)
+- `firstKeptEntryId`: for compatibility with old entry format.

 ### BranchSummaryEntry

@@ -314,8 +322,9 @@ Entries form a tree:
 1. Collects all entries on the path
 2. If a `CompactionEntry` is on the path:
   - Includes the compaction entry first
-   - Then entries from `firstKeptEntryId` to compaction
-   - Then entries after compaction
+   - If `retainedTail` is present, it acts as a self-contained checkpoint and entries after the compaction are included
+   - Otherwise entries from `firstKeptEntryId` to the compaction are included
+   - Then entries after compaction are included
 3. Preserves non-message entries in the selected range so interactive mode can render them

 `buildSessionContext()` builds on that entry list to produce the message list for the LLM:
@@ -323,11 +332,13 @@ Entries form a tree:
 1. Extracts current model and thinking level settings from the full path
 2. Converts selected entries to messages:
   - `message` -> stored `AgentMessage`
-   - `compaction` -> `compactionSummary`
+   - `compaction` -> `compactionSummary` plus `retainedTail` when present
   - `branch_summary` -> `branchSummary`
   - `custom_message` -> `CustomMessage`
   - `custom` -> no context message

+This makes newer compactions act like self-contained checkpoints. `retainedTail` is optional only so older sessions that only store `firstKeptEntryId` continue to load correctly.
+
 ## Parsing Example

 ```typescript
@@ -638,9 +638,6 @@
 			"cpu": [
 				"arm64"
 			],
-			"libc": [
-				"glibc"
-			],
 			"optional": true
 		},
 		"node_modules/@mariozechner/clipboard-linux-arm64-musl": {
@@ -657,9 +654,6 @@
 			"cpu": [
 				"arm64"
 			],
-			"libc": [
-				"musl"
-			],
 			"optional": true
 		},
 		"node_modules/@mariozechner/clipboard-linux-riscv64-gnu": {
@@ -676,9 +670,6 @@
 			"cpu": [
 				"riscv64"
 			],
-			"libc": [
-				"glibc"
-			],
 			"optional": true
 		},
 		"node_modules/@mariozechner/clipboard-linux-x64-gnu": {
@@ -695,9 +686,6 @@
 			"cpu": [
 				"x64"
 			],
-			"libc": [
-				"glibc"
-			],
 			"optional": true
 		},
 		"node_modules/@mariozechner/clipboard-linux-x64-musl": {
@@ -714,9 +702,6 @@
 			"cpu": [
 				"x64"
 			],
-			"libc": [
-				"musl"
-			],
 			"optional": true
 		},
 		"node_modules/@mariozechner/clipboard-win32-arm64-msvc": {
@@ -790,7 +775,8 @@
 			"license": "Apache-2.0",
 			"engines": {
 				"node": ">=8.0.0"
-			}
+			},
+			"peer": true
 		},
 		"node_modules/@opentelemetry/semantic-conventions": {
 			"version": "1.41.1",
@@ -1834,7 +1820,8 @@
 			"license": "MIT",
 			"funding": {
 				"url": "https://github.com/sponsors/colinhacks"
-			}
+			},
+			"peer": true
 		},
 		"node_modules/zod-to-json-schema": {
 			"version": "3.25.2",
@@ -628,9 +628,6 @@
 			"cpu": [
 				"arm64"
 			],
-			"libc": [
-				"glibc"
-			],
 			"optional": true
 		},
 		"node_modules/@mariozechner/clipboard-linux-arm64-musl": {
@@ -647,9 +644,6 @@
 			"cpu": [
 				"arm64"
 			],
-			"libc": [
-				"musl"
-			],
 			"optional": true
 		},
 		"node_modules/@mariozechner/clipboard-linux-riscv64-gnu": {
@@ -666,9 +660,6 @@
 			"cpu": [
 				"riscv64"
 			],
-			"libc": [
-				"glibc"
-			],
 			"optional": true
 		},
 		"node_modules/@mariozechner/clipboard-linux-x64-gnu": {
@@ -685,9 +676,6 @@
 			"cpu": [
 				"x64"
 			],
-			"libc": [
-				"glibc"
-			],
 			"optional": true
 		},
 		"node_modules/@mariozechner/clipboard-linux-x64-musl": {
@@ -704,9 +692,6 @@
 			"cpu": [
 				"x64"
 			],
-			"libc": [
-				"musl"
-			],
 			"optional": true
 		},
 		"node_modules/@mariozechner/clipboard-win32-arm64-msvc": {
@@ -780,7 +765,8 @@
 			"license": "Apache-2.0",
 			"engines": {
 				"node": ">=8.0.0"
-			}
+			},
+			"peer": true
 		},
 		"node_modules/@opentelemetry/semantic-conventions": {
 			"version": "1.41.1",
@@ -1824,7 +1810,8 @@
 			"license": "MIT",
 			"funding": {
 				"url": "https://github.com/sponsors/colinhacks"
-			}
+			},
+			"peer": true
 		},
 		"node_modules/zod-to-json-schema": {
 			"version": "3.25.2",
@@ -0,0 +1,5 @@
+# @earendil-works/pi-agent-sqlite-node
+
+Node sqlite storage backend for `@earendil-works/pi-agent-core` sessions. Provides the
+`node:sqlite` adapter (`SqliteDatabase` implementation) and the SQLite session
+repo/storage implementation (`SqliteSessionRepo`, migrations, materialized views).
@@ -0,0 +1,37 @@
+{
+	"name": "@earendil-works/pi-agent-sqlite-node",
+	"version": "0.80.10",
+	"description": "Node sqlite storage backend for @earendil-works/pi-agent-core sessions",
+	"type": "module",
+	"main": "./dist/index.js",
+	"types": "./dist/index.d.ts",
+	"exports": {
+		".": {
+			"types": "./dist/index.d.ts",
+			"import": "./dist/index.js"
+		}
+	},
+	"files": [
+		"dist",
+		"README.md"
+	],
+	"scripts": {
+		"clean": "node -e \"import('node:fs/promises').then(fs=>fs.rm('dist',{recursive:true,force:true}))\"",
+		"build": "tsgo -p tsconfig.build.json && node ./scripts/prepare-dist.mjs copy-sqlite-migrations",
+		"prepublishOnly": "npm run clean && npm run build"
+	},
+	"author": "Earendil Works",
+	"license": "MIT",
+	"repository": {
+		"type": "git",
+		"url": "git+https://github.com/earendil-works/pi.git",
+		"directory": "packages/storage/sqlite-node"
+	},
+	"engines": {
+		"node": ">=22.19.0"
+	},
+	"dependencies": {
+		"@earendil-works/pi-ai": "^0.80.10",
+		"@earendil-works/pi-agent-core": "^0.80.10"
+	}
+}
@@ -0,0 +1,35 @@
+#!/usr/bin/env node
+
+import { cp, mkdir, rm } from "node:fs/promises";
+import { dirname, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const scriptDir = dirname(fileURLToPath(import.meta.url));
+const packageDir = resolve(scriptDir, "..");
+const distDir = resolve(packageDir, "dist");
+const migrationSourceDir = resolve(packageDir, "src/sqlite/migrations");
+const migrationDestDir = resolve(distDir, "sqlite/migrations");
+
+async function clean() {
+	await rm(distDir, { recursive: true, force: true });
+}
+
+async function copySqliteMigrations() {
+	await mkdir(migrationDestDir, { recursive: true });
+	await cp(migrationSourceDir, migrationDestDir, { recursive: true });
+}
+
+const command = process.argv[2];
+
+if (command === "clean") {
+	await clean();
+	process.exit(0);
+}
+
+if (command === "copy-sqlite-migrations") {
+	await copySqliteMigrations();
+	process.exit(0);
+}
+
+console.error("Usage: node scripts/prepare-dist.mjs <clean|copy-sqlite-migrations>");
+process.exit(1);
@@ -0,0 +1,97 @@
+import type { SQLInputValue } from "node:sqlite";
+import { DatabaseSync } from "node:sqlite";
+import type { SqliteDatabase, SqliteDatabaseFactory, SqliteRunResult, SqliteStatement } from "./sqlite/types.ts";
+
+function isNamedParameters(value: unknown): value is Record<string, SQLInputValue> {
+	if (value === null || typeof value !== "object") return false;
+	if (Array.isArray(value) || ArrayBuffer.isView(value)) return false;
+	return true;
+}
+
+class NodeSqliteStatement implements SqliteStatement {
+	private readonly statement: ReturnType<DatabaseSync["prepare"]>;
+
+	constructor(statement: ReturnType<DatabaseSync["prepare"]>) {
+		this.statement = statement;
+	}
+
+	async run(...params: unknown[]): Promise<SqliteRunResult> {
+		const [first, ...rest] = params;
+		const result = isNamedParameters(first)
+			? this.statement.run(first, ...(rest as SQLInputValue[]))
+			: this.statement.run(...(params as SQLInputValue[]));
+		return {
+			changes: Number(result.changes),
+			lastInsertRowid: result.lastInsertRowid === undefined ? undefined : Number(result.lastInsertRowid),
+		};
+	}
+
+	async get<TRow extends object>(...params: unknown[]): Promise<TRow | undefined> {
+		const [first, ...rest] = params;
+		return (
+			isNamedParameters(first)
+				? this.statement.get(first, ...(rest as SQLInputValue[]))
+				: this.statement.get(...(params as SQLInputValue[]))
+		) as TRow | undefined;
+	}
+
+	async all<TRow extends object>(...params: unknown[]): Promise<TRow[]> {
+		const [first, ...rest] = params;
+		return (
+			isNamedParameters(first)
+				? this.statement.all(first, ...(rest as SQLInputValue[]))
+				: this.statement.all(...(params as SQLInputValue[]))
+		) as TRow[];
+	}
+}
+
+class NodeSqliteDatabase implements SqliteDatabase {
+	private readonly db: DatabaseSync;
+
+	constructor(db: DatabaseSync) {
+		this.db = db;
+	}
+
+	async exec(sql: string): Promise<void> {
+		this.db.exec(sql);
+	}
+
+	prepare(sql: string): SqliteStatement {
+		return new NodeSqliteStatement(this.db.prepare(sql));
+	}
+
+	async transaction<T>(fn: () => Promise<T>): Promise<T> {
+		this.db.exec("BEGIN");
+		try {
+			const result = await fn();
+			this.db.exec("COMMIT");
+			return result;
+		} catch (error) {
+			try {
+				this.db.exec("ROLLBACK");
+			} catch {
+				// Ignore rollback errors to rethrow original error.
+			}
+			throw error;
+		}
+	}
+
+	async close(): Promise<void> {
+		this.db.close();
+	}
+}
+
+export function wrapNodeSqliteDatabase(db: DatabaseSync): SqliteDatabase {
+	return new NodeSqliteDatabase(db);
+}
+
+export function createNodeSqliteFactory(): SqliteDatabaseFactory {
+	return {
+		async open(path: string): Promise<SqliteDatabase> {
+			return new NodeSqliteDatabase(new DatabaseSync(path));
+		},
+	};
+}
+
+// Re-export the SQLite session storage backend and types so this package is a complete node-sqlite backend.
+export * from "./sqlite/index.ts";
@@ -0,0 +1,4 @@
+export * from "./migrations.ts";
+export * from "./repo.ts";
+export * from "./storage/index.ts";
+export * from "./types.ts";
@@ -0,0 +1,50 @@
+import { readFile } from "node:fs/promises";
+import { fileURLToPath } from "node:url";
+import type { SqliteDatabase } from "./types.ts";
+
+export interface SqliteMigration {
+	id: string;
+	order: number;
+	sql: string;
+}
+
+async function loadMigrationSql(relativePath: string): Promise<string> {
+	return readFile(fileURLToPath(new URL(relativePath, import.meta.url)), "utf8");
+}
+
+export async function loadMigrations(): Promise<SqliteMigration[]> {
+	return [
+		{
+			id: "001_initial.sql",
+			order: 1,
+			sql: await loadMigrationSql("./migrations/001_initial.sql"),
+		},
+	];
+}
+
+async function ensureMigrationsTable(db: SqliteDatabase): Promise<void> {
+	await db.exec(`
+CREATE TABLE IF NOT EXISTS migrations (
+	id TEXT PRIMARY KEY,
+	applied_at TEXT NOT NULL
+);
+`);
+}
+
+export async function applyMigrations(db: SqliteDatabase): Promise<void> {
+	await ensureMigrationsTable(db);
+	const migrations = await loadMigrations();
+	const appliedRows = await db.prepare("SELECT id FROM migrations ORDER BY applied_at, id").all<{ id: string }>();
+	const applied = new Set(appliedRows.map((row) => row.id));
+
+	for (const migration of migrations) {
+		if (applied.has(migration.id)) continue;
+		await db.transaction(async () => {
+			await db.exec(migration.sql);
+			await db
+				.prepare("INSERT INTO migrations (id, applied_at) VALUES (?, ?)")
+				.run(migration.id, new Date().toISOString());
+		});
+		applied.add(migration.id);
+	}
+}
@@ -0,0 +1,59 @@
+CREATE TABLE IF NOT EXISTS sessions (
+	id TEXT PRIMARY KEY,
+	created_at TEXT NOT NULL,
+	cwd TEXT NOT NULL,
+	parent_session_id TEXT NULL,
+	metadata TEXT NULL,
+	active_leaf_id TEXT NULL
+) WITHOUT ROWID;
+
+CREATE INDEX IF NOT EXISTS idx_sessions_created_at ON sessions(created_at DESC);
+CREATE INDEX IF NOT EXISTS idx_sessions_cwd ON sessions(cwd);
+CREATE INDEX IF NOT EXISTS idx_sessions_parent ON sessions(parent_session_id);
+
+CREATE TABLE IF NOT EXISTS session_entries (
+	session_id TEXT NOT NULL,
+	id TEXT NOT NULL,
+	entry_seq INTEGER NOT NULL,
+	parent_id TEXT NULL,
+	type TEXT NOT NULL,
+	timestamp TEXT NOT NULL,
+	payload TEXT NOT NULL,
+	PRIMARY KEY (session_id, id)
+);
+
+CREATE UNIQUE INDEX IF NOT EXISTS idx_session_entries_session_seq ON session_entries(session_id, entry_seq);
+CREATE INDEX IF NOT EXISTS idx_session_entries_session_parent ON session_entries(session_id, parent_id);
+CREATE INDEX IF NOT EXISTS idx_session_entries_session_type ON session_entries(session_id, type);
+
+CREATE TABLE IF NOT EXISTS session_sequences (
+	session_id TEXT PRIMARY KEY,
+	next_seq INTEGER NOT NULL
+) WITHOUT ROWID;
+
+CREATE TABLE IF NOT EXISTS branch_entries (
+	session_id TEXT NOT NULL,
+	branch_id TEXT NOT NULL,
+	entry_id TEXT NOT NULL,
+	entry_seq INTEGER NOT NULL,
+	PRIMARY KEY (session_id, branch_id, entry_id)
+) WITHOUT ROWID;
+
+CREATE INDEX IF NOT EXISTS idx_branch_entries_session_branch ON branch_entries(session_id, branch_id);
+CREATE INDEX IF NOT EXISTS idx_branch_entries_session_branch_seq ON branch_entries(session_id, branch_id, entry_seq);
+CREATE INDEX IF NOT EXISTS idx_branch_entries_session_entry ON branch_entries(session_id, entry_id);
+
+CREATE TABLE IF NOT EXISTS session_materialized (
+	session_id TEXT PRIMARY KEY,
+	payload TEXT NOT NULL
+) WITHOUT ROWID;
+
+CREATE TABLE IF NOT EXISTS entry_materialized (
+	session_id TEXT NOT NULL,
+	entry_seq INTEGER NOT NULL,
+	type TEXT NOT NULL,
+	payload TEXT NOT NULL,
+	PRIMARY KEY (session_id, entry_seq, type)
+) WITHOUT ROWID;
+
+CREATE INDEX IF NOT EXISTS idx_entry_materialized_session_type_seq ON entry_materialized(session_id, type, entry_seq);
@@ -0,0 +1,192 @@
+import type { Session, SessionStorage, SessionTreeEntry } from "@earendil-works/pi-agent-core";
+import {
+	createSessionId,
+	getEntriesToFork,
+	getFileSystemResultOrThrow,
+	SessionError,
+	toSession,
+} from "@earendil-works/pi-agent-core";
+import { applyMigrations } from "./migrations.ts";
+import { SqliteSessionStorage } from "./storage/index.ts";
+import { rowToMetadata, type SessionRow } from "./storage/sessions.ts";
+import type {
+	SqliteDatabase,
+	SqliteDatabaseFactory,
+	SqliteSessionCreateOptions,
+	SqliteSessionListOptions,
+	SqliteSessionMetadata,
+	SqliteSessionRepoApi,
+	SqliteSessionRepoEnv,
+} from "./types.ts";
+
+function getParentPath(path: string): string {
+	const normalized = path.replace(/[\\/]+$/, "");
+	const lastSlash = Math.max(normalized.lastIndexOf("/"), normalized.lastIndexOf("\\"));
+	if (lastSlash < 0) return ".";
+	if (lastSlash === 0) return normalized.slice(0, 1);
+	return normalized.slice(0, lastSlash);
+}
+
+async function configureSqliteDatabase(db: SqliteDatabase): Promise<void> {
+	await db.exec("PRAGMA journal_mode=WAL");
+	await db.exec("PRAGMA synchronous=FULL");
+	await db.exec("PRAGMA busy_timeout=5000");
+}
+
+async function cleanupSessionStorage(storage: SessionStorage): Promise<void> {
+	const maybeClosable = storage as SessionStorage & { cleanup?: () => Promise<void> };
+	if (typeof maybeClosable.cleanup === "function") {
+		await maybeClosable.cleanup();
+	}
+}
+
+export class SqliteSessionRepo implements SqliteSessionRepoApi {
+	private readonly env: SqliteSessionRepoEnv;
+	private readonly sqlite: SqliteDatabaseFactory;
+	private readonly databasePathInput: string;
+	private databasePath: string | undefined;
+
+	constructor(options: { env: SqliteSessionRepoEnv; sqlite: SqliteDatabaseFactory; databasePath: string }) {
+		this.env = options.env;
+		this.sqlite = options.sqlite;
+		this.databasePathInput = options.databasePath;
+	}
+
+	private async getDatabasePath(): Promise<string> {
+		if (!this.databasePath) {
+			this.databasePath = getFileSystemResultOrThrow(
+				await this.env.absolutePath(this.databasePathInput),
+				`Failed to resolve SQLite sessions database ${this.databasePathInput}`,
+			);
+		}
+		return this.databasePath;
+	}
+
+	private async ensureDatabaseDir(): Promise<void> {
+		const path = await this.getDatabasePath();
+		const directory = getParentPath(path);
+		getFileSystemResultOrThrow(
+			await this.env.createDir(directory, { recursive: true }),
+			`Failed to create SQLite sessions directory ${directory}`,
+		);
+	}
+
+	private async openDatabase(): Promise<SqliteDatabase> {
+		await this.ensureDatabaseDir();
+		const db = await this.sqlite.open(await this.getDatabasePath());
+		try {
+			await configureSqliteDatabase(db);
+			await applyMigrations(db);
+			return db;
+		} catch (error) {
+			await db.close();
+			throw error;
+		}
+	}
+
+	async create(options: SqliteSessionCreateOptions): Promise<Session<SqliteSessionMetadata>> {
+		const db = await this.openDatabase();
+		try {
+			const id = options.id ?? createSessionId();
+			const storage = await SqliteSessionStorage.create(db, await this.getDatabasePath(), {
+				cwd: options.cwd,
+				sessionId: id,
+				parentSessionId: options.parentSessionId,
+				metadata: options.metadata,
+			});
+			return toSession(storage);
+		} catch (error) {
+			await db.close();
+			throw error;
+		}
+	}
+
+	async open(metadata: SqliteSessionMetadata): Promise<Session<SqliteSessionMetadata>> {
+		if (
+			!getFileSystemResultOrThrow(await this.env.exists(metadata.path), `Failed to check database ${metadata.path}`)
+		) {
+			throw new SessionError("not_found", `Session not found: ${metadata.id}`);
+		}
+		const db = await this.openDatabase();
+		try {
+			const storage = await SqliteSessionStorage.open(db, metadata);
+			return toSession(storage);
+		} catch (error) {
+			await db.close();
+			throw error;
+		}
+	}
+
+	async list(options: SqliteSessionListOptions = {}): Promise<SqliteSessionMetadata[]> {
+		const path = await this.getDatabasePath();
+		if (!getFileSystemResultOrThrow(await this.env.exists(path), `Failed to check database ${path}`)) {
+			return [];
+		}
+		const db = await this.openDatabase();
+		try {
+			const rows = options.cwd
+				? await db
+						.prepare(
+							"SELECT id, created_at, metadata, cwd, parent_session_id, active_leaf_id FROM sessions WHERE cwd = ? ORDER BY created_at DESC",
+						)
+						.all<SessionRow>(options.cwd)
+				: await db
+						.prepare(
+							"SELECT id, created_at, metadata, cwd, parent_session_id, active_leaf_id FROM sessions ORDER BY created_at DESC",
+						)
+						.all<SessionRow>();
+			return rows.map((row) => rowToMetadata(row, path));
+		} finally {
+			await db.close();
+		}
+	}
+
+	async delete(metadata: SqliteSessionMetadata): Promise<void> {
+		const db = await this.openDatabase();
+		try {
+			await db.transaction(async () => {
+				await db.prepare("DELETE FROM branch_entries WHERE session_id = ?").run(metadata.id);
+				await db.prepare("DELETE FROM session_entries WHERE session_id = ?").run(metadata.id);
+				await db.prepare("DELETE FROM entry_materialized WHERE session_id = ?").run(metadata.id);
+				await db.prepare("DELETE FROM session_materialized WHERE session_id = ?").run(metadata.id);
+				await db.prepare("DELETE FROM session_sequences WHERE session_id = ?").run(metadata.id);
+				const result = await db.prepare("DELETE FROM sessions WHERE id = ?").run(metadata.id);
+				if (result.changes === 0) {
+					throw new SessionError("not_found", `Session not found: ${metadata.id}`);
+				}
+			});
+		} finally {
+			await db.close();
+		}
+	}
+
+	async fork(
+		sourceMetadata: SqliteSessionMetadata,
+		options: SqliteSessionCreateOptions & { entryId?: string; position?: "before" | "at"; id?: string },
+	): Promise<Session<SqliteSessionMetadata>> {
+		const source = await this.open(sourceMetadata);
+		let forkedEntries: SessionTreeEntry[];
+		try {
+			forkedEntries = await getEntriesToFork(source.getStorage(), options);
+		} finally {
+			await cleanupSessionStorage(source.getStorage());
+		}
+		const db = await this.openDatabase();
+		try {
+			const id = options.id ?? createSessionId();
+			const storage = await SqliteSessionStorage.create(db, await this.getDatabasePath(), {
+				cwd: options.cwd,
+				sessionId: id,
+				parentSessionId: options.parentSessionId ?? sourceMetadata.id,
+				metadata: options.metadata ?? sourceMetadata.metadata,
+			});
+			for (const entry of forkedEntries) {
+				await storage.appendEntry(entry);
+			}
+			return toSession(storage);
+		} catch (error) {
+			await db.close();
+			throw error;
+		}
+	}
+}
@@ -0,0 +1,57 @@
+import type { SessionTreeEntry } from "@earendil-works/pi-agent-core";
+import type { SqliteDatabase } from "../types.ts";
+import { decodeEntry, type SessionEntryRow } from "./session-entries.ts";
+import { invalidSession } from "./shared.ts";
+
+export interface BranchEntryRow {
+	entry_id: string;
+	entry_seq: number;
+}
+
+export async function getMaterializedBranchPathOrCompaction(
+	db: SqliteDatabase,
+	sessionId: string,
+	branchId: string,
+	byId: Map<string, SessionTreeEntry>,
+): Promise<SessionTreeEntry[]> {
+	const branchRows = await db
+		.prepare(
+			"SELECT entry_id, entry_seq FROM branch_entries WHERE session_id = ? AND branch_id = ? ORDER BY entry_seq",
+		)
+		.all<BranchEntryRow>(sessionId, branchId);
+	if (branchRows.length === 0) {
+		return [];
+	}
+	const entryIds = branchRows.map((row) => row.entry_id);
+	const placeholders = entryIds.map(() => "?").join(", ");
+	const entryRows = await db
+		.prepare(
+			`SELECT session_id, id, entry_seq, parent_id, type, timestamp, payload FROM session_entries WHERE session_id = ? AND id IN (${placeholders})`,
+		)
+		.all<SessionEntryRow>(sessionId, ...entryIds);
+	const entryRowsById = new Map(entryRows.map((row) => [row.id, row]));
+	const entries: SessionTreeEntry[] = [];
+	for (const branchRow of branchRows) {
+		// leaf entries are navigation markers used to mark which branch became active;
+		// they are not part of the model/context path reconstructed from branch_entries.
+		const cached = byId.get(branchRow.entry_id);
+		if (cached) {
+			if (cached.type !== "leaf") {
+				entries.push(cached);
+			}
+			continue;
+		}
+		const entryRow = entryRowsById.get(branchRow.entry_id);
+		if (!entryRow) throw invalidSession(`missing entry row for branch entry ${branchRow.entry_id}`);
+		try {
+			const entry = decodeEntry(entryRow);
+			byId.set(entry.id, entry);
+			if (entry.type !== "leaf") {
+				entries.push(entry);
+			}
+		} catch {
+			throw invalidSession(`invalid entry row for branch entry ${branchRow.entry_id}`);
+		}
+	}
+	return entries;
+}
@@ -0,0 +1,449 @@
+import type {
+	LeafEntry,
+	SessionEntryCursorOptions,
+	SessionStorage,
+	SessionTreeEntry,
+} from "@earendil-works/pi-agent-core";
+import { SessionError } from "@earendil-works/pi-agent-core";
+import { uuidv7 } from "@earendil-works/pi-ai";
+import type { SqliteDatabase, SqliteSessionMetadata } from "../types.ts";
+import { getMaterializedBranchPathOrCompaction } from "./branch-entries.ts";
+import { decodeEntry, encodeEntry, type SessionEntryRow } from "./session-entries.ts";
+import {
+	applyEntryToMaterializedState,
+	createEmptyMaterializedState,
+	type EntryMaterializedRow,
+	entryMaterializedValues,
+	materializedStateFromRows,
+	materializedStateValues,
+	type SessionMaterializedRow,
+	type SessionMaterializedState,
+	serializeSummary,
+	sessionStatsFromMaterializedState,
+} from "./session-materialized.ts";
+import { advanceSequence, getNextSequence } from "./session-sequences.ts";
+import { rowToMetadata, type SessionRow } from "./sessions.ts";
+import { generateEntryId, invalidSession, leafIdAfterEntry } from "./shared.ts";
+
+async function decodeEntryRows(entryRows: SessionEntryRow[]): Promise<{
+	entries: SessionTreeEntry[];
+	leafId: string | null;
+}> {
+	const entries: SessionTreeEntry[] = [];
+	let leafId: string | null = null;
+	for (const entryRow of entryRows) {
+		try {
+			const entry = decodeEntry(entryRow);
+			entries.push(entry);
+			leafId = leafIdAfterEntry(entry);
+		} catch {
+			// Keep JSONL-like permissive resume behavior: skip malformed entries.
+		}
+	}
+	return { entries, leafId };
+}
+
+async function loadEntryRowsByIds(
+	db: SqliteDatabase,
+	sessionId: string,
+	entryIds: string[],
+): Promise<Map<string, SessionEntryRow>> {
+	if (entryIds.length === 0) return new Map<string, SessionEntryRow>();
+	const placeholders = entryIds.map(() => "?").join(", ");
+	const rows = await db
+		.prepare(
+			`SELECT session_id, id, entry_seq, parent_id, type, timestamp, payload FROM session_entries WHERE session_id = ? AND id IN (${placeholders})`,
+		)
+		.all<SessionEntryRow>(sessionId, ...entryIds);
+	return new Map(rows.map((row) => [row.id, row]));
+}
+
+async function loadActiveBranchId(db: SqliteDatabase, sessionId: string): Promise<string | null> {
+	// branch_entries includes leaf navigation entries for the active branch, so the
+	// newest branch_entries row identifies the branch that was most recently made active.
+	const row = await db
+		.prepare(
+			"SELECT branch_id FROM branch_entries WHERE session_id = ? ORDER BY entry_seq DESC, branch_id DESC LIMIT 1",
+		)
+		.get<{ branch_id: string }>(sessionId);
+	return row?.branch_id ?? null;
+}
+
+async function hasExistingChild(db: SqliteDatabase, sessionId: string, parentId: string | null): Promise<boolean> {
+	const row =
+		parentId === null
+			? await db
+					.prepare("SELECT 1 AS found FROM session_entries WHERE session_id = ? AND parent_id IS NULL LIMIT 1")
+					.get<{ found: number }>(sessionId)
+			: await db
+					.prepare("SELECT 1 AS found FROM session_entries WHERE session_id = ? AND parent_id = ? LIMIT 1")
+					.get<{ found: number }>(sessionId, parentId);
+	return row !== undefined;
+}
+
+async function loadSqliteStorage(
+	db: SqliteDatabase,
+	sessionId: string,
+): Promise<{
+	row: SessionRow;
+	leafId: string | null;
+	activeBranchId: string | null;
+	materializedState: SessionMaterializedState;
+}> {
+	const row = await db
+		.prepare("SELECT id, created_at, metadata, cwd, parent_session_id, active_leaf_id FROM sessions WHERE id = ?")
+		.get<SessionRow>(sessionId);
+	if (!row) throw new SessionError("not_found", `Session not found: ${sessionId}`);
+
+	const leafId = row.active_leaf_id;
+	const materializedRow = await db
+		.prepare("SELECT session_id, payload FROM session_materialized WHERE session_id = ?")
+		.get<SessionMaterializedRow>(sessionId);
+	if (!materializedRow) throw invalidSession(`missing materialized row for session ${sessionId}`);
+	const entryMaterializedRows = await db
+		.prepare(
+			"SELECT session_id, entry_seq, type, payload FROM entry_materialized WHERE session_id = ? ORDER BY entry_seq, type",
+		)
+		.all<EntryMaterializedRow>(sessionId);
+	return {
+		row,
+		leafId,
+		activeBranchId: await loadActiveBranchId(db, sessionId),
+		materializedState: materializedStateFromRows(materializedRow, entryMaterializedRows),
+	};
+}
+
+export class SqliteSessionStorage implements SessionStorage<SqliteSessionMetadata> {
+	private readonly db: SqliteDatabase;
+	private readonly metadata: SqliteSessionMetadata;
+	private byId: Map<string, SessionTreeEntry>;
+	private labelsById: Map<string, string>;
+	private currentLeafId: string | null;
+	private activeBranchId: string | null;
+	private materializedState: SessionMaterializedState;
+
+	private async getPathToRootOrCompactionEntries(leafId: string | null): Promise<SessionTreeEntry[]> {
+		if (leafId === null) return [];
+		const path: SessionTreeEntry[] = [];
+		let stopAtEntryId: string | null = null;
+		let current = await this.getEntry(leafId);
+		if (!current) throw new SessionError("not_found", `Entry ${leafId} not found`);
+		while (current) {
+			path.unshift(current);
+			if (stopAtEntryId !== null && current.id === stopAtEntryId) break;
+			if (current.type === "compaction") {
+				if (current.retainedTail) break;
+				stopAtEntryId = current.firstKeptEntryId ?? null;
+			}
+			if (!current.parentId) break;
+			const parent = await this.getEntry(current.parentId);
+			if (!parent) throw new SessionError("invalid_session", `Entry ${current.parentId} not found`);
+			current = parent;
+		}
+		return path;
+	}
+
+	private async materializeBranch(leafId: string | null): Promise<void> {
+		const branchId = uuidv7();
+		// Rebuild the branch path only when branch membership changes: branch switch
+		// (leaf navigation) or a new fork from a parent that already has a child.
+		// Linear appends stay cheap and extend the active branch incrementally.
+		const path = await this.getPathToRootOrCompactionEntries(leafId);
+		const entryRowsById = await loadEntryRowsByIds(
+			this.db,
+			this.metadata.id,
+			path.map((entry) => entry.id),
+		);
+		for (const entry of path) {
+			const entryRow = entryRowsById.get(entry.id);
+			if (!entryRow) throw invalidSession(`missing entry row for session ${this.metadata.id} entry ${entry.id}`);
+			await this.db
+				.prepare("INSERT INTO branch_entries (session_id, branch_id, entry_id, entry_seq) VALUES (?, ?, ?, ?)")
+				.run(this.metadata.id, branchId, entry.id, entryRow.entry_seq);
+		}
+		this.activeBranchId = branchId;
+	}
+
+	private async appendToActiveBranch(entryId: string, parentId: string | null): Promise<void> {
+		if (!this.activeBranchId) {
+			await this.materializeBranch(parentId);
+		}
+		// After a branch is materialized/resynced, subsequent linear appends only add the
+		// new tip entry. We do not rebuild the full branch on every append.
+		if (!this.activeBranchId) {
+			throw invalidSession(`active branch missing for session ${this.metadata.id}`);
+		}
+		const entryRow = await this.db
+			.prepare("SELECT entry_seq FROM session_entries WHERE session_id = ? AND id = ?")
+			.get<{ entry_seq: number }>(this.metadata.id, entryId);
+		if (!entryRow) throw invalidSession(`missing entry row for session ${this.metadata.id} entry ${entryId}`);
+		await this.db
+			.prepare("INSERT INTO branch_entries (session_id, branch_id, entry_id, entry_seq) VALUES (?, ?, ?, ?)")
+			.run(this.metadata.id, this.activeBranchId, entryId, entryRow.entry_seq);
+	}
+
+	private constructor(
+		db: SqliteDatabase,
+		metadata: SqliteSessionMetadata,
+		entries: SessionTreeEntry[] | null,
+		leafId: string | null,
+		activeBranchId: string | null,
+		materializedState: SessionMaterializedState,
+	) {
+		this.db = db;
+		this.metadata = metadata;
+		this.byId = new Map((entries ?? []).map((entry) => [entry.id, entry]));
+		this.materializedState = materializedState;
+		this.labelsById = materializedState.labelsById;
+		this.currentLeafId = leafId;
+		this.activeBranchId = activeBranchId;
+	}
+
+	static async open(db: SqliteDatabase, metadata: SqliteSessionMetadata): Promise<SqliteSessionStorage> {
+		const loaded = await loadSqliteStorage(db, metadata.id);
+		return new SqliteSessionStorage(
+			db,
+			rowToMetadata(loaded.row, metadata.path),
+			null,
+			loaded.leafId,
+			loaded.activeBranchId,
+			loaded.materializedState,
+		);
+	}
+
+	static async create(
+		db: SqliteDatabase,
+		path: string,
+		options: {
+			cwd: string;
+			sessionId: string;
+			parentSessionId?: string;
+			metadata?: Record<string, unknown>;
+		},
+	): Promise<SqliteSessionStorage> {
+		const createdAt = new Date().toISOString();
+		await db
+			.prepare(
+				"INSERT INTO sessions (id, created_at, metadata, cwd, parent_session_id, active_leaf_id) VALUES (?, ?, ?, ?, ?, ?)",
+			)
+			.run(
+				options.sessionId,
+				createdAt,
+				options.metadata === undefined ? null : JSON.stringify(options.metadata),
+				options.cwd,
+				options.parentSessionId ?? null,
+				null,
+			);
+		await db.prepare("INSERT INTO session_sequences (session_id, next_seq) VALUES (?, ?)").run(options.sessionId, 1);
+		await db
+			.prepare("INSERT INTO session_materialized (session_id, payload) VALUES (?, ?)")
+			.run(...materializedStateValues(options.sessionId, createEmptyMaterializedState()));
+		return new SqliteSessionStorage(
+			db,
+			{
+				id: options.sessionId,
+				createdAt,
+				cwd: options.cwd,
+				path,
+				parentSessionId: options.parentSessionId,
+				metadata: options.metadata,
+			},
+			[],
+			null,
+			null,
+			createEmptyMaterializedState(),
+		);
+	}
+
+	async getMetadata(): Promise<SqliteSessionMetadata> {
+		return this.metadata;
+	}
+
+	async getLeafId(): Promise<string | null> {
+		return this.currentLeafId;
+	}
+
+	async setLeafId(leafId: string | null): Promise<void> {
+		if (leafId !== null && !(await this.getEntry(leafId))) {
+			throw new SessionError("not_found", `Entry ${leafId} not found`);
+		}
+		const entry: LeafEntry = {
+			type: "leaf",
+			id: await this.createEntryId(),
+			parentId: this.currentLeafId,
+			timestamp: new Date().toISOString(),
+			targetId: leafId,
+		};
+		await this.appendEntry(entry);
+	}
+
+	async createEntryId(): Promise<string> {
+		for (let i = 0; i < 100; i++) {
+			const id = generateEntryId(this.byId);
+			const existing = await this.db
+				.prepare("SELECT 1 AS found FROM session_entries WHERE session_id = ? AND id = ? LIMIT 1")
+				.get<{ found: number }>(this.metadata.id, id);
+			if (!existing) return id;
+		}
+		return uuidv7();
+	}
+
+	async appendEntry(entry: SessionTreeEntry): Promise<void> {
+		const encoded = encodeEntry(entry);
+		const previousMaterializedState: SessionMaterializedState = {
+			...this.materializedState,
+			labelsById: new Map(this.materializedState.labelsById),
+			modelThinkingConfigs: [...this.materializedState.modelThinkingConfigs],
+			currentModel: this.materializedState.currentModel ? { ...this.materializedState.currentModel } : null,
+		};
+		const previousById = new Map(this.byId);
+		const previousLeafId = this.currentLeafId;
+		const previousActiveBranchId = this.activeBranchId;
+		try {
+			applyEntryToMaterializedState(this.materializedState, entry);
+			await this.db.transaction(async () => {
+				const parentHadExistingChild = await hasExistingChild(this.db, this.metadata.id, entry.parentId);
+				const nextSeq = await getNextSequence(this.db, this.metadata.id);
+				await this.db
+					.prepare(
+						"INSERT INTO session_entries (session_id, id, entry_seq, parent_id, type, timestamp, payload) VALUES (?, ?, ?, ?, ?, ?, ?)",
+					)
+					.run(this.metadata.id, entry.id, nextSeq, entry.parentId, entry.type, entry.timestamp, encoded.payload);
+				await advanceSequence(this.db, this.metadata.id, nextSeq);
+				await this.db
+					.prepare("UPDATE session_materialized SET payload = ? WHERE session_id = ?")
+					.run(serializeSummary(this.materializedState), this.metadata.id);
+				for (const materializedEntry of entryMaterializedValues(entry)) {
+					await this.db
+						.prepare("INSERT INTO entry_materialized (session_id, entry_seq, type, payload) VALUES (?, ?, ?, ?)")
+						.run(this.metadata.id, nextSeq, materializedEntry.type, materializedEntry.payload);
+				}
+				this.byId.set(entry.id, entry);
+				this.currentLeafId = leafIdAfterEntry(entry);
+				await this.db
+					.prepare("UPDATE sessions SET active_leaf_id = ? WHERE id = ?")
+					.run(this.currentLeafId, this.metadata.id);
+				if (entry.type === "leaf") {
+					this.activeBranchId = null;
+					await this.materializeBranch(entry.targetId);
+					await this.appendToActiveBranch(entry.id, entry.parentId);
+				} else {
+					if (parentHadExistingChild) {
+						await this.materializeBranch(entry.parentId);
+					}
+					await this.appendToActiveBranch(entry.id, entry.parentId);
+				}
+			});
+		} catch (error) {
+			this.materializedState = previousMaterializedState;
+			this.labelsById = previousMaterializedState.labelsById;
+			this.byId = previousById;
+			this.currentLeafId = previousLeafId;
+			this.activeBranchId = previousActiveBranchId;
+			if (error instanceof SessionError) throw error;
+			throw new SessionError("storage", `Failed to append SQLite session entry ${entry.id}`);
+		}
+	}
+
+	async getEntry(id: string): Promise<SessionTreeEntry | undefined> {
+		const cached = this.byId.get(id);
+		if (cached) return cached;
+		const row = await this.db
+			.prepare(
+				"SELECT session_id, id, entry_seq, parent_id, type, timestamp, payload FROM session_entries WHERE session_id = ? AND id = ?",
+			)
+			.get<SessionEntryRow>(this.metadata.id, id);
+		if (!row) return undefined;
+		try {
+			const entry = decodeEntry(row);
+			this.byId.set(entry.id, entry);
+			return entry;
+		} catch {
+			return undefined;
+		}
+	}
+
+	async findEntries<TType extends SessionTreeEntry["type"]>(
+		type: TType,
+	): Promise<Array<Extract<SessionTreeEntry, { type: TType }>>> {
+		const rows = await this.db
+			.prepare(
+				"SELECT session_id, id, entry_seq, parent_id, type, timestamp, payload FROM session_entries WHERE session_id = ? AND type = ? ORDER BY entry_seq",
+			)
+			.all<SessionEntryRow>(this.metadata.id, type);
+		const entries: Array<Extract<SessionTreeEntry, { type: TType }>> = [];
+		for (const row of rows) {
+			try {
+				const entry = decodeEntry(row) as Extract<SessionTreeEntry, { type: TType }>;
+				this.byId.set(entry.id, entry);
+				entries.push(entry);
+			} catch {
+				// Keep JSONL-like permissive resume behavior: skip malformed entries.
+			}
+		}
+		return entries;
+	}
+
+	async getLabel(id: string): Promise<string | undefined> {
+		return this.labelsById.get(id);
+	}
+
+	async getSessionName(): Promise<string | undefined> {
+		return this.materializedState.name;
+	}
+
+	async getSessionStats() {
+		return sessionStatsFromMaterializedState(this.materializedState);
+	}
+
+	async getPathToRootOrCompaction(leafId: string | null): Promise<SessionTreeEntry[]> {
+		if (leafId === null) return [];
+		if (leafId === this.currentLeafId) {
+			if (!this.activeBranchId) {
+				throw invalidSession(`missing active branch for session ${this.metadata.id} leaf ${leafId}`);
+			}
+			return getMaterializedBranchPathOrCompaction(this.db, this.metadata.id, this.activeBranchId, this.byId);
+		}
+		return this.getPathToRootOrCompactionEntries(leafId);
+	}
+
+	async getEntries(options?: SessionEntryCursorOptions): Promise<SessionTreeEntry[]> {
+		const limit = options?.limit;
+		if (limit !== undefined) {
+			const beforeOrAtEntrySeq =
+				options?.afterEntrySeq ??
+				(
+					await this.db
+						.prepare("SELECT entry_seq FROM session_entries WHERE session_id = ? ORDER BY entry_seq DESC LIMIT 1")
+						.get<{ entry_seq: number }>(this.metadata.id)
+				)?.entry_seq;
+			if (beforeOrAtEntrySeq === undefined) {
+				return [];
+			}
+			const rows = await this.db
+				.prepare(
+					"SELECT session_id, id, entry_seq, parent_id, type, timestamp, payload FROM session_entries WHERE session_id = ? AND entry_seq <= ? ORDER BY entry_seq DESC LIMIT ?",
+				)
+				.all<SessionEntryRow>(this.metadata.id, beforeOrAtEntrySeq, limit);
+			const entries = (await decodeEntryRows(rows)).entries;
+			for (const entry of entries) {
+				this.byId.set(entry.id, entry);
+			}
+			return entries.reverse();
+		}
+		const rows = await this.db
+			.prepare(
+				"SELECT session_id, id, entry_seq, parent_id, type, timestamp, payload FROM session_entries WHERE session_id = ? ORDER BY entry_seq",
+			)
+			.all<SessionEntryRow>(this.metadata.id);
+		const entries = (await decodeEntryRows(rows)).entries;
+		for (const entry of entries) {
+			this.byId.set(entry.id, entry);
+		}
+		return entries;
+	}
+
+	async cleanup(): Promise<void> {
+		await this.db.close();
+	}
+}
@@ -0,0 +1,217 @@
+import type { SessionTreeEntry, SessionTreeEntryBase } from "@earendil-works/pi-agent-core";
+import { invalidEntry, isRecord } from "./shared.ts";
+
+export interface SessionEntryRow {
+	session_id: string;
+	id: string;
+	entry_seq: number;
+	parent_id: string | null;
+	type: SessionTreeEntry["type"];
+	timestamp: string;
+	payload: string;
+}
+
+export type EncodedEntry = {
+	payload: string;
+};
+
+type EntryPayload<TEntry extends SessionTreeEntry> = Omit<TEntry, keyof SessionTreeEntryBase | "type">;
+
+type MessagePayload = EntryPayload<Extract<SessionTreeEntry, { type: "message" }>>;
+type ThinkingLevelChangePayload = EntryPayload<Extract<SessionTreeEntry, { type: "thinking_level_change" }>>;
+type ModelChangePayload = EntryPayload<Extract<SessionTreeEntry, { type: "model_change" }>>;
+type ActiveToolsChangePayload = EntryPayload<Extract<SessionTreeEntry, { type: "active_tools_change" }>>;
+type CompactionPayload = EntryPayload<Extract<SessionTreeEntry, { type: "compaction" }>>;
+type BranchSummaryPayload = EntryPayload<Extract<SessionTreeEntry, { type: "branch_summary" }>>;
+type CustomPayload = EntryPayload<Extract<SessionTreeEntry, { type: "custom" }>>;
+type CustomMessagePayload = EntryPayload<Extract<SessionTreeEntry, { type: "custom_message" }>>;
+type LabelPayload = EntryPayload<Extract<SessionTreeEntry, { type: "label" }>>;
+type SessionInfoPayload = EntryPayload<Extract<SessionTreeEntry, { type: "session_info" }>>;
+type LeafPayload = EntryPayload<Extract<SessionTreeEntry, { type: "leaf" }>>;
+
+function parsePayload(row: SessionEntryRow): unknown {
+	try {
+		return JSON.parse(row.payload);
+	} catch (error) {
+		throw invalidEntry(`entry ${row.id} payload is not valid JSON`, error instanceof Error ? error : undefined);
+	}
+}
+
+function isTextImageContentArray(value: unknown): boolean {
+	return (
+		Array.isArray(value) &&
+		value.every(
+			(item) =>
+				isRecord(item) && typeof item.type === "string" && (item.type !== "text" || typeof item.text === "string"),
+		)
+	);
+}
+
+export function validateSessionTreeEntry(entry: SessionTreeEntry): void {
+	if (typeof entry.id !== "string" || !entry.id) throw invalidEntry("entry is missing id");
+	if (entry.parentId !== null && typeof entry.parentId !== "string") {
+		throw invalidEntry(`entry ${entry.id} has invalid parentId`);
+	}
+	if (typeof entry.timestamp !== "string" || !entry.timestamp) {
+		throw invalidEntry(`entry ${entry.id} is missing timestamp`);
+	}
+
+	switch (entry.type) {
+		case "message":
+			if (!isRecord(entry.message) || typeof entry.message.role !== "string") {
+				throw invalidEntry(`entry ${entry.id} is missing message payload`);
+			}
+			break;
+		case "thinking_level_change":
+			if (typeof entry.thinkingLevel !== "string") throw invalidEntry(`entry ${entry.id} is missing thinkingLevel`);
+			break;
+		case "model_change":
+			if (typeof entry.provider !== "string" || typeof entry.modelId !== "string") {
+				throw invalidEntry(`entry ${entry.id} has invalid model_change payload`);
+			}
+			break;
+		case "active_tools_change":
+			if (
+				!Array.isArray(entry.activeToolNames) ||
+				entry.activeToolNames.some((value) => typeof value !== "string")
+			) {
+				throw invalidEntry(`entry ${entry.id} has invalid active_tools_change payload`);
+			}
+			break;
+		case "compaction":
+			if (
+				typeof entry.summary !== "string" ||
+				typeof entry.firstKeptEntryId !== "string" ||
+				typeof entry.tokensBefore !== "number" ||
+				(entry.retainedTail !== undefined && !Array.isArray(entry.retainedTail))
+			) {
+				throw invalidEntry(`entry ${entry.id} has invalid compaction payload`);
+			}
+			break;
+		case "branch_summary":
+			if (typeof entry.fromId !== "string" || typeof entry.summary !== "string") {
+				throw invalidEntry(`entry ${entry.id} has invalid branch_summary payload`);
+			}
+			break;
+		case "custom":
+			if (typeof entry.customType !== "string") throw invalidEntry(`entry ${entry.id} has invalid custom payload`);
+			break;
+		case "custom_message":
+			if (
+				typeof entry.customType !== "string" ||
+				typeof entry.display !== "boolean" ||
+				!(typeof entry.content === "string" || isTextImageContentArray(entry.content))
+			) {
+				throw invalidEntry(`entry ${entry.id} has invalid custom_message payload`);
+			}
+			break;
+		case "label":
+			if (typeof entry.targetId !== "string" || (entry.label !== undefined && typeof entry.label !== "string")) {
+				throw invalidEntry(`entry ${entry.id} has invalid label payload`);
+			}
+			break;
+		case "session_info":
+			if (entry.name !== undefined && typeof entry.name !== "string") {
+				throw invalidEntry(`entry ${entry.id} has invalid session_info payload`);
+			}
+			break;
+		case "leaf":
+			if (entry.targetId !== null && typeof entry.targetId !== "string") {
+				throw invalidEntry(`entry ${entry.id} has invalid leaf payload`);
+			}
+			break;
+		default: {
+			const exhaustive: never = entry;
+			throw invalidEntry(`unknown entry type ${(exhaustive as { type?: string }).type ?? "unknown"}`);
+		}
+	}
+}
+
+function entryToPayload<TEntry extends SessionTreeEntry>(entry: TEntry): EntryPayload<TEntry> {
+	const { type: _type, id: _id, parentId: _parentId, timestamp: _timestamp, ...payload } = entry;
+	return payload as EntryPayload<TEntry>;
+}
+
+export function encodeEntry(entry: SessionTreeEntry): EncodedEntry {
+	validateSessionTreeEntry(entry);
+	return { payload: JSON.stringify(entryToPayload(entry)) };
+}
+
+export function decodeEntry(row: SessionEntryRow): SessionTreeEntry {
+	const payload = parsePayload(row);
+	if (!isRecord(payload)) throw invalidEntry(`entry ${row.id} payload is not an object`);
+	const base = {
+		id: row.id,
+		parentId: row.parent_id,
+		timestamp: row.timestamp,
+	};
+
+	switch (row.type) {
+		case "message": {
+			if (!("message" in payload)) throw invalidEntry(`entry ${row.id} is missing message payload`);
+			const messagePayload = payload as MessagePayload;
+			return { ...base, type: "message", ...messagePayload };
+		}
+		case "thinking_level_change":
+			if (typeof payload.thinkingLevel !== "string") throw invalidEntry(`entry ${row.id} is missing thinkingLevel`);
+			return { ...base, type: "thinking_level_change", ...(payload as ThinkingLevelChangePayload) };
+		case "model_change":
+			if (typeof payload.provider !== "string" || typeof payload.modelId !== "string") {
+				throw invalidEntry(`entry ${row.id} has invalid model_change payload`);
+			}
+			return { ...base, type: "model_change", ...(payload as ModelChangePayload) };
+		case "active_tools_change":
+			if (
+				!Array.isArray(payload.activeToolNames) ||
+				payload.activeToolNames.some((value) => typeof value !== "string")
+			) {
+				throw invalidEntry(`entry ${row.id} has invalid active_tools_change payload`);
+			}
+			return { ...base, type: "active_tools_change", ...(payload as ActiveToolsChangePayload) };
+		case "compaction":
+			if (
+				typeof payload.summary !== "string" ||
+				typeof payload.firstKeptEntryId !== "string" ||
+				typeof payload.tokensBefore !== "number" ||
+				(payload.retainedTail !== undefined && !Array.isArray(payload.retainedTail))
+			) {
+				throw invalidEntry(`entry ${row.id} has invalid compaction payload`);
+			}
+			return { ...base, type: "compaction", ...(payload as CompactionPayload) };
+		case "branch_summary":
+			if (typeof payload.fromId !== "string" || typeof payload.summary !== "string") {
+				throw invalidEntry(`entry ${row.id} has invalid branch_summary payload`);
+			}
+			return { ...base, type: "branch_summary", ...(payload as BranchSummaryPayload) };
+		case "custom":
+			if (typeof payload.customType !== "string") throw invalidEntry(`entry ${row.id} has invalid custom payload`);
+			return { ...base, type: "custom", ...(payload as CustomPayload) };
+		case "custom_message":
+			if (
+				typeof payload.customType !== "string" ||
+				typeof payload.display !== "boolean" ||
+				!("content" in payload)
+			) {
+				throw invalidEntry(`entry ${row.id} has invalid custom_message payload`);
+			}
+			return { ...base, type: "custom_message", ...(payload as CustomMessagePayload) };
+		case "label":
+			if (typeof payload.targetId !== "string") throw invalidEntry(`entry ${row.id} has invalid label payload`);
+			if (payload.label !== undefined && typeof payload.label !== "string") {
+				throw invalidEntry(`entry ${row.id} has invalid label payload`);
+			}
+			return { ...base, type: "label", ...(payload as LabelPayload) };
+		case "session_info":
+			if (payload.name !== undefined && typeof payload.name !== "string") {
+				throw invalidEntry(`entry ${row.id} has invalid session_info payload`);
+			}
+			return { ...base, type: "session_info", ...(payload as SessionInfoPayload) };
+		case "leaf":
+			if (payload.targetId !== null && typeof payload.targetId !== "string") {
+				throw invalidEntry(`entry ${row.id} has invalid leaf payload`);
+			}
+			return { ...base, type: "leaf", ...(payload as LeafPayload) };
+		default:
+			throw invalidEntry(`unknown entry type ${row.type}`);
+	}
+}
@@ -0,0 +1,368 @@
+import type { SessionStats, SessionTreeEntry, ThinkingLevel } from "@earendil-works/pi-agent-core";
+import { invalidSession, isRecord } from "./shared.ts";
+
+export interface SessionMaterializedRow {
+	session_id: string;
+	payload: string;
+}
+
+export interface EntryMaterializedRow {
+	session_id: string;
+	entry_seq: number;
+	type: string;
+	payload: string;
+}
+
+export interface ModelThinkingConfig {
+	provider: string;
+	modelId: string;
+	thinkingLevel: ThinkingLevel;
+}
+
+export interface SessionMaterializedState {
+	name: string | undefined;
+	messageCount: number;
+	cachedTokens: number;
+	uncachedTokens: number;
+	totalTokens: number;
+	costTotal: number;
+	labelsById: Map<string, string>;
+	modelThinkingConfigs: ModelThinkingConfig[];
+	currentModel: { provider: string; modelId: string } | null;
+	currentThinkingLevel: ThinkingLevel | null;
+}
+
+interface SessionMaterializedSummary {
+	name?: string;
+	messageCount: number;
+	cachedTokens: number;
+	uncachedTokens: number;
+	totalTokens: number;
+	costTotal: number;
+	currentModel?: { provider: string; modelId: string } | null;
+	currentThinkingLevel?: ThinkingLevel | null;
+}
+
+function compareModelThinkingConfig(left: ModelThinkingConfig, right: ModelThinkingConfig): number {
+	return (
+		left.provider.localeCompare(right.provider) ||
+		left.modelId.localeCompare(right.modelId) ||
+		left.thinkingLevel.localeCompare(right.thinkingLevel)
+	);
+}
+
+function normalizeModelThinkingConfigs(configs: readonly ModelThinkingConfig[]): ModelThinkingConfig[] {
+	const unique = new Map<string, ModelThinkingConfig>();
+	for (const config of configs) {
+		unique.set(`${config.provider}\u0000${config.modelId}\u0000${config.thinkingLevel}`, config);
+	}
+	return [...unique.values()].sort(compareModelThinkingConfig);
+}
+
+function addModelThinkingConfig(
+	state: SessionMaterializedState,
+	provider: string,
+	modelId: string,
+	thinkingLevel: ThinkingLevel,
+): void {
+	state.modelThinkingConfigs = normalizeModelThinkingConfigs([
+		...state.modelThinkingConfigs,
+		{ provider, modelId, thinkingLevel },
+	]);
+}
+
+export function isThinkingLevel(value: unknown): value is ThinkingLevel {
+	return (
+		value === "off" ||
+		value === "minimal" ||
+		value === "low" ||
+		value === "medium" ||
+		value === "high" ||
+		value === "xhigh"
+	);
+}
+
+function getAssistantUsage(message: unknown):
+	| {
+			provider: string;
+			modelId: string;
+			input: number;
+			output: number;
+			cacheRead: number;
+			cacheWrite: number;
+			costTotal: number;
+	  }
+	| undefined {
+	if (!isRecord(message) || message.role !== "assistant") return undefined;
+	if (typeof message.provider !== "string" || typeof message.model !== "string") return undefined;
+	if (!isRecord(message.usage) || !isRecord(message.usage.cost)) return undefined;
+	const { input, output, cacheRead, cacheWrite } = message.usage;
+	const costTotal = message.usage.cost.total;
+	if (
+		typeof input !== "number" ||
+		typeof output !== "number" ||
+		typeof cacheRead !== "number" ||
+		typeof cacheWrite !== "number" ||
+		typeof costTotal !== "number"
+	) {
+		return undefined;
+	}
+	return {
+		provider: message.provider,
+		modelId: message.model,
+		input,
+		output,
+		cacheRead,
+		cacheWrite,
+		costTotal,
+	};
+}
+
+export function createEmptyMaterializedState(): SessionMaterializedState {
+	return {
+		name: undefined,
+		messageCount: 0,
+		cachedTokens: 0,
+		uncachedTokens: 0,
+		totalTokens: 0,
+		costTotal: 0,
+		labelsById: new Map<string, string>(),
+		modelThinkingConfigs: [],
+		currentModel: null,
+		currentThinkingLevel: null,
+	};
+}
+
+export function applyEntryToMaterializedState(state: SessionMaterializedState, entry: SessionTreeEntry): void {
+	switch (entry.type) {
+		case "session_info":
+			state.name = entry.name?.trim() || undefined;
+			break;
+		case "label": {
+			const label = entry.label?.trim();
+			if (label) {
+				state.labelsById.set(entry.targetId, label);
+			} else {
+				state.labelsById.delete(entry.targetId);
+			}
+			break;
+		}
+		case "model_change":
+			state.currentModel = { provider: entry.provider, modelId: entry.modelId };
+			if (state.currentThinkingLevel) {
+				addModelThinkingConfig(state, entry.provider, entry.modelId, state.currentThinkingLevel);
+			}
+			break;
+		case "thinking_level_change":
+			if (!isThinkingLevel(entry.thinkingLevel)) break;
+			state.currentThinkingLevel = entry.thinkingLevel;
+			if (state.currentModel) {
+				addModelThinkingConfig(state, state.currentModel.provider, state.currentModel.modelId, entry.thinkingLevel);
+			}
+			break;
+		case "message": {
+			state.messageCount += 1;
+			const usage = getAssistantUsage(entry.message);
+			if (!usage) break;
+			state.cachedTokens += usage.cacheRead;
+			state.uncachedTokens += usage.input + usage.cacheWrite;
+			state.totalTokens += usage.input + usage.output + usage.cacheRead + usage.cacheWrite;
+			state.costTotal += usage.costTotal;
+			state.currentModel = { provider: usage.provider, modelId: usage.modelId };
+			if (state.currentThinkingLevel) {
+				addModelThinkingConfig(state, usage.provider, usage.modelId, state.currentThinkingLevel);
+			}
+			break;
+		}
+		case "compaction":
+		case "branch_summary": {
+			const usage = entry.usage;
+			if (
+				!isRecord(usage) ||
+				!isRecord(usage.cost) ||
+				typeof usage.input !== "number" ||
+				typeof usage.output !== "number" ||
+				typeof usage.cacheRead !== "number" ||
+				typeof usage.cacheWrite !== "number" ||
+				typeof usage.cost.total !== "number"
+			) {
+				break;
+			}
+			state.cachedTokens += usage.cacheRead;
+			state.uncachedTokens += usage.input + usage.cacheWrite;
+			state.totalTokens += usage.input + usage.output + usage.cacheRead + usage.cacheWrite;
+			state.costTotal += usage.cost.total;
+			break;
+		}
+		case "active_tools_change":
+		case "custom":
+		case "custom_message":
+		case "leaf":
+			break;
+		default: {
+			const exhaustive: never = entry;
+			void exhaustive;
+			break;
+		}
+	}
+}
+
+export function serializeSummary(state: SessionMaterializedState): string {
+	const summary: SessionMaterializedSummary = {
+		name: state.name,
+		messageCount: state.messageCount,
+		cachedTokens: state.cachedTokens,
+		uncachedTokens: state.uncachedTokens,
+		totalTokens: state.totalTokens,
+		costTotal: state.costTotal,
+		currentModel: state.currentModel,
+		currentThinkingLevel: state.currentThinkingLevel,
+	};
+	return JSON.stringify(summary);
+}
+
+function parseSummary(json: string): SessionMaterializedSummary {
+	let parsed: unknown;
+	try {
+		parsed = JSON.parse(json);
+	} catch (error) {
+		throw invalidSession(
+			`materialized session summary is not valid JSON`,
+			error instanceof Error ? error : undefined,
+		);
+	}
+	if (!isRecord(parsed) || Array.isArray(parsed)) {
+		throw invalidSession("materialized session summary is not an object");
+	}
+	const currentModel = parsed.currentModel;
+	const currentThinkingLevel = parsed.currentThinkingLevel;
+	if (
+		(parsed.name !== undefined && typeof parsed.name !== "string") ||
+		typeof parsed.messageCount !== "number" ||
+		typeof parsed.cachedTokens !== "number" ||
+		typeof parsed.uncachedTokens !== "number" ||
+		typeof parsed.totalTokens !== "number" ||
+		typeof parsed.costTotal !== "number" ||
+		(currentModel !== undefined &&
+			currentModel !== null &&
+			(!isRecord(currentModel) ||
+				typeof currentModel.provider !== "string" ||
+				typeof currentModel.modelId !== "string")) ||
+		(currentThinkingLevel !== undefined && currentThinkingLevel !== null && !isThinkingLevel(currentThinkingLevel))
+	) {
+		throw invalidSession("materialized session summary has invalid fields");
+	}
+	return {
+		name: parsed.name?.trim() || undefined,
+		messageCount: parsed.messageCount,
+		cachedTokens: parsed.cachedTokens,
+		uncachedTokens: parsed.uncachedTokens,
+		totalTokens: parsed.totalTokens,
+		costTotal: parsed.costTotal,
+		currentModel:
+			currentModel && isRecord(currentModel)
+				? { provider: currentModel.provider as string, modelId: currentModel.modelId as string }
+				: (currentModel ?? undefined),
+		currentThinkingLevel: (currentThinkingLevel as ThinkingLevel | null | undefined) ?? undefined,
+	};
+}
+
+function parseEntryMaterializedPayload(row: EntryMaterializedRow): unknown {
+	try {
+		return JSON.parse(row.payload);
+	} catch (error) {
+		throw invalidSession(
+			`materialized entry row ${row.entry_seq} is not valid JSON`,
+			error instanceof Error ? error : undefined,
+		);
+	}
+}
+
+export function materializedStateFromRows(
+	summaryRow: SessionMaterializedRow,
+	entryRows: EntryMaterializedRow[],
+): SessionMaterializedState {
+	const summary = parseSummary(summaryRow.payload);
+	const state: SessionMaterializedState = {
+		name: summary.name,
+		messageCount: summary.messageCount,
+		cachedTokens: summary.cachedTokens,
+		uncachedTokens: summary.uncachedTokens,
+		totalTokens: summary.totalTokens,
+		costTotal: summary.costTotal,
+		labelsById: new Map<string, string>(),
+		modelThinkingConfigs: [],
+		currentModel: summary.currentModel ?? null,
+		currentThinkingLevel: summary.currentThinkingLevel ?? null,
+	};
+	for (const row of entryRows) {
+		const payload = parseEntryMaterializedPayload(row);
+		if (!isRecord(payload)) throw invalidSession(`materialized entry row ${row.entry_seq} is not an object`);
+		if (row.type === "label") {
+			if (typeof payload.targetId !== "string") {
+				throw invalidSession(`materialized label row ${row.entry_seq} is missing targetId`);
+			}
+			if (payload.label !== null && payload.label !== undefined && typeof payload.label !== "string") {
+				throw invalidSession(`materialized label row ${row.entry_seq} has invalid label`);
+			}
+			const label = typeof payload.label === "string" ? payload.label.trim() : "";
+			if (label) {
+				state.labelsById.set(payload.targetId, label);
+			} else {
+				state.labelsById.delete(payload.targetId);
+			}
+			continue;
+		}
+		if (row.type !== "label") {
+		}
+	}
+	return state;
+}
+
+export function sessionStatsFromMaterializedState(state: SessionMaterializedState): SessionStats {
+	return {
+		messageCount: state.messageCount,
+		cachedTokens: state.cachedTokens,
+		uncachedTokens: state.uncachedTokens,
+		totalTokens: state.totalTokens,
+		costTotal: state.costTotal,
+	};
+}
+
+export function materializedStateValues(
+	sessionId: string,
+	state: SessionMaterializedState,
+): [sessionId: string, payload: string] {
+	return [sessionId, serializeSummary(state)];
+}
+
+export function entryMaterializedValues(
+	entry: SessionTreeEntry,
+): Array<{ type: EntryMaterializedRow["type"]; payload: string }> {
+	switch (entry.type) {
+		case "label":
+			return [
+				{
+					type: "label",
+					payload: JSON.stringify({ targetId: entry.targetId, label: entry.label ?? null }),
+				},
+			];
+		case "model_change":
+		case "thinking_level_change":
+		case "message":
+			return [];
+		case "active_tools_change":
+		case "branch_summary":
+		case "compaction":
+		case "custom":
+		case "custom_message":
+		case "leaf":
+		case "session_info":
+			return [];
+		default: {
+			const exhaustive: never = entry;
+			void exhaustive;
+			return [];
+		}
+	}
+}
@@ -0,0 +1,16 @@
+import type { SqliteDatabase } from "../types.ts";
+import { invalidSession } from "./shared.ts";
+
+export async function getNextSequence(db: SqliteDatabase, sessionId: string): Promise<number> {
+	const sequenceRow = await db
+		.prepare("SELECT next_seq FROM session_sequences WHERE session_id = ?")
+		.get<{ next_seq: number }>(sessionId);
+	if (!sequenceRow) {
+		throw invalidSession(`missing sequence row for session ${sessionId}`);
+	}
+	return sequenceRow.next_seq;
+}
+
+export async function advanceSequence(db: SqliteDatabase, sessionId: string, nextSeq: number): Promise<void> {
+	await db.prepare("UPDATE session_sequences SET next_seq = ? WHERE session_id = ?").run(nextSeq + 1, sessionId);
+}
@@ -0,0 +1,40 @@
+import { SessionError } from "@earendil-works/pi-agent-core";
+import type { SqliteSessionMetadata } from "../types.ts";
+
+export interface SessionRow {
+	id: string;
+	created_at: string;
+	metadata: string | null;
+	cwd: string;
+	parent_session_id: string | null;
+	active_leaf_id: string | null;
+}
+
+function parseMetadata(metadata: string | null, sessionId: string): Record<string, unknown> | undefined {
+	if (metadata === null) return undefined;
+	let parsed: unknown;
+	try {
+		parsed = JSON.parse(metadata);
+	} catch (error) {
+		throw new SessionError(
+			"invalid_session",
+			`Invalid SQLite session ${sessionId}: metadata is not valid JSON`,
+			error instanceof Error ? error : undefined,
+		);
+	}
+	if (typeof parsed !== "object" || parsed === null || Array.isArray(parsed)) {
+		throw new SessionError("invalid_session", `Invalid SQLite session ${sessionId}: metadata must be an object`);
+	}
+	return parsed as Record<string, unknown>;
+}
+
+export function rowToMetadata(row: SessionRow, path: string): SqliteSessionMetadata {
+	return {
+		id: row.id,
+		createdAt: row.created_at,
+		cwd: row.cwd,
+		path,
+		parentSessionId: row.parent_session_id ?? undefined,
+		metadata: parseMetadata(row.metadata, row.id),
+	};
+}
@@ -0,0 +1,29 @@
+import type { SessionTreeEntry } from "@earendil-works/pi-agent-core";
+import { SessionError } from "@earendil-works/pi-agent-core";
+import { uuidv7 } from "@earendil-works/pi-ai";
+
+export function generateEntryId(byId: { has(id: string): boolean }): string {
+	for (let i = 0; i < 100; i++) {
+		// The uuidv7 prefix is timestamp-derived and nearly constant between calls,
+		// so short ids must come from the random tail.
+		const id = uuidv7().slice(0, 8);
+		if (!byId.has(id)) return id;
+	}
+	return uuidv7();
+}
+
+export function isRecord(value: unknown): value is Record<string, unknown> {
+	return typeof value === "object" && value !== null;
+}
+
+export function invalidSession(message: string, cause?: Error): SessionError {
+	return new SessionError("invalid_session", `Invalid SQLite session: ${message}`, cause);
+}
+
+export function invalidEntry(message: string, cause?: Error): SessionError {
+	return new SessionError("invalid_entry", `Invalid SQLite session entry: ${message}`, cause);
+}
+
+export function leafIdAfterEntry(entry: SessionTreeEntry): string | null {
+	return entry.type === "leaf" ? entry.targetId : entry.id;
+}
@@ -0,0 +1,55 @@
+import type { FileSystem, SessionCreateOptions, SessionMetadata, SessionRepo } from "@earendil-works/pi-agent-core";
+
+/** Result of a prepared SQLite statement execution. */
+export interface SqliteRunResult {
+	/** Number of rows changed by the statement. */
+	changes: number;
+	/** Inserted row id when the backend exposes one. */
+	lastInsertRowid?: number;
+}
+
+/** Prepared SQLite statement capability used by the SQLite session backend. */
+export interface SqliteStatement {
+	run(...params: unknown[]): Promise<SqliteRunResult>;
+	get<TRow extends object>(...params: unknown[]): Promise<TRow | undefined>;
+	all<TRow extends object>(...params: unknown[]): Promise<TRow[]>;
+}
+
+/** SQLite database capability used by the SQLite session backend. */
+export interface SqliteDatabase {
+	exec(sql: string): Promise<void>;
+	prepare(sql: string): SqliteStatement;
+	transaction<T>(fn: () => Promise<T>): Promise<T>;
+	close(): Promise<void>;
+}
+
+export interface SqliteDatabaseFactory {
+	open(path: string): Promise<SqliteDatabase>;
+}
+
+export interface SqliteSessionMetadata extends SessionMetadata {
+	cwd: string;
+	path: string;
+	parentSessionId?: string;
+	metadata?: Record<string, unknown>;
+}
+
+export interface SqliteSessionCreateOptions extends SessionCreateOptions {
+	cwd: string;
+	parentSessionId?: string;
+	metadata?: Record<string, unknown>;
+}
+
+export interface SqliteSessionListOptions {
+	cwd?: string;
+}
+
+export interface SqliteSessionBackendOptions {
+	kind: "sqlite";
+	databasePath: string;
+}
+
+export interface SqliteSessionRepoApi
+	extends SessionRepo<SqliteSessionMetadata, SqliteSessionCreateOptions, SqliteSessionListOptions> {}
+
+export type SqliteSessionRepoEnv = Pick<FileSystem, "absolutePath" | "createDir" | "exists">;
@@ -0,0 +1,11 @@
+{
+	"extends": "../../../tsconfig.base.json",
+	"compilerOptions": {
+		"rootDir": "src",
+		"outDir": "dist",
+		"declaration": true,
+		"emitDeclarationOnly": false,
+		"noEmit": false
+	},
+	"include": ["src/**/*.ts"]
+}
@@ -12,6 +12,7 @@
 			"@earendil-works/pi-ai/dist/*": ["./packages/ai/src/*"],
 			"@earendil-works/pi-agent-core": ["./packages/agent/src/index.ts"],
 			"@earendil-works/pi-agent-core/*": ["./packages/agent/src/*"],
+			"@earendil-works/pi-agent-sqlite-node": ["./packages/storage/sqlite-node/src/index.ts"],
 			"@earendil-works/pi-coding-agent": ["./packages/coding-agent/src/index.ts"],
 			"@earendil-works/pi-coding-agent/hooks": ["./packages/coding-agent/src/core/hooks/index.ts"],
 			"@earendil-works/pi-coding-agent/*": ["./packages/coding-agent/src/*"],
@@ -24,6 +25,6 @@
 			"@earendil-works/pi-agent-old/*": ["./packages/agent-old/src/*"]
 		}
 	},
-	"include": ["packages/*/src/**/*", "packages/*/test/**/*", "packages/coding-agent/examples/**/*"],
+	"include": ["packages/*/src/**/*", "packages/*/test/**/*", "packages/storage/*/src/**/*", "packages/storage/*/test/**/*", "packages/coding-agent/examples/**/*"],
 	"exclude": ["**/dist/**", "packages/coding-agent/examples/extensions/gondolin/**"]
 }