Refactor SessionEventBase to pass sessionManager and modelRegistry

Breaking changes to hook types:
- SessionEventBase now passes sessionManager and modelRegistry directly
- before_compact: passes preparation, previousCompactions (newest first)
- before_switch: has targetSessionFile; switch: has previousSessionFile
- Removed resolveApiKey (use modelRegistry.getApiKey())
- getSessionFile() returns string | undefined for in-memory sessions

Updated:
- All session event emissions in agent-session.ts
- Hook examples (custom-compaction.ts, auto-commit-on-exit.ts, confirm-destructive.ts)
- Tests (compaction-hooks.test.ts, compaction-hooks-example.test.ts)
- export-html.ts guards for in-memory sessions

packages/coding-agent/src/core/agent-session.ts

@@ -395,7 +395,7 @@ export class AgentSession {
 
 	/** Current session file path, or null if sessions are disabled */
 	get sessionFile(): string | null {
-		return this.sessionManager.isPersisted() ? this.sessionManager.getSessionFile() : null;
+		return this.sessionManager.getSessionFile() ?? null;
 	}
 
 	/** Current session ID */
@@ -515,15 +515,13 @@ export class AgentSession {
 	 */
 	async reset(): Promise<boolean> {
 		const previousSessionFile = this.sessionFile;
-		const entries = this.sessionManager.getEntries();
 
 		// Emit before_new event (can be cancelled)
 		if (this._hookRunner?.hasHandlers("session")) {
 			const result = (await this._hookRunner.emit({
 				type: "session",
-				entries,
-				sessionFile: this.sessionFile,
-				previousSessionFile: null,
+				sessionManager: this.sessionManager,
+				modelRegistry: this._modelRegistry,
 				reason: "before_new",
 			})) as SessionEventResult | undefined;
 
@@ -544,9 +542,8 @@ export class AgentSession {
 			this._hookRunner.setSessionFile(this.sessionFile);
 			await this._hookRunner.emit({
 				type: "session",
-				entries: [],
-				sessionFile: this.sessionFile,
-				previousSessionFile,
+				sessionManager: this.sessionManager,
+				modelRegistry: this._modelRegistry,
 				reason: "new",
 			});
 		}
@@ -762,34 +759,22 @@ export class AgentSession {
 				throw new Error("Nothing to compact (session too small)");
 			}
 
-			// Find previous compaction summary if any
-			let previousSummary: string | undefined;
-			for (let i = entries.length - 1; i >= 0; i--) {
-				if (entries[i].type === "compaction") {
-					previousSummary = (entries[i] as CompactionEntry).summary;
-					break;
-				}
-			}
-
 			let hookCompaction: CompactionResult | undefined;
 			let fromHook = false;
 
 			if (this._hookRunner?.hasHandlers("session")) {
+				// Get previous compactions, newest first
+				const previousCompactions = entries.filter((e): e is CompactionEntry => e.type === "compaction").reverse();
+
 				const result = (await this._hookRunner.emit({
 					type: "session",
-					entries,
-					sessionFile: this.sessionFile,
-					previousSessionFile: null,
+					sessionManager: this.sessionManager,
+					modelRegistry: this._modelRegistry,
 					reason: "before_compact",
-					cutPoint: preparation.cutPoint,
-					firstKeptEntryId: preparation.firstKeptEntryId,
-					previousSummary,
-					messagesToSummarize: [...preparation.messagesToSummarize],
-					messagesToKeep: [...preparation.messagesToKeep],
-					tokensBefore: preparation.tokensBefore,
+					preparation,
+					previousCompactions,
 					customInstructions,
 					model: this.model,
-					resolveApiKey: async (m: Model<any>) => (await this._modelRegistry.getApiKey(m)) ?? undefined,
 					signal: this._compactionAbortController.signal,
 				})) as SessionEventResult | undefined;
 
@@ -847,12 +832,10 @@ export class AgentSession {
 			if (this._hookRunner && savedCompactionEntry) {
 				await this._hookRunner.emit({
 					type: "session",
-					entries: newEntries,
-					sessionFile: this.sessionFile,
-					previousSessionFile: null,
+					sessionManager: this.sessionManager,
+					modelRegistry: this._modelRegistry,
 					reason: "compact",
 					compactionEntry: savedCompactionEntry,
-					tokensBefore,
 					fromHook,
 				});
 			}
@@ -948,34 +931,22 @@ export class AgentSession {
 				return;
 			}
 
-			// Find previous compaction summary if any
-			let previousSummary: string | undefined;
-			for (let i = entries.length - 1; i >= 0; i--) {
-				if (entries[i].type === "compaction") {
-					previousSummary = (entries[i] as CompactionEntry).summary;
-					break;
-				}
-			}
-
 			let hookCompaction: CompactionResult | undefined;
 			let fromHook = false;
 
 			if (this._hookRunner?.hasHandlers("session")) {
+				// Get previous compactions, newest first
+				const previousCompactions = entries.filter((e): e is CompactionEntry => e.type === "compaction").reverse();
+
 				const hookResult = (await this._hookRunner.emit({
 					type: "session",
-					entries,
-					sessionFile: this.sessionFile,
-					previousSessionFile: null,
+					sessionManager: this.sessionManager,
+					modelRegistry: this._modelRegistry,
 					reason: "before_compact",
-					cutPoint: preparation.cutPoint,
-					firstKeptEntryId: preparation.firstKeptEntryId,
-					previousSummary,
-					messagesToSummarize: [...preparation.messagesToSummarize],
-					messagesToKeep: [...preparation.messagesToKeep],
-					tokensBefore: preparation.tokensBefore,
+					preparation,
+					previousCompactions,
 					customInstructions: undefined,
 					model: this.model,
-					resolveApiKey: async (m: Model<any>) => (await this._modelRegistry.getApiKey(m)) ?? undefined,
 					signal: this._autoCompactionAbortController.signal,
 				})) as SessionEventResult | undefined;
 
@@ -1034,12 +1005,10 @@ export class AgentSession {
 			if (this._hookRunner && savedCompactionEntry) {
 				await this._hookRunner.emit({
 					type: "session",
-					entries: newEntries,
-					sessionFile: this.sessionFile,
-					previousSessionFile: null,
+					sessionManager: this.sessionManager,
+					modelRegistry: this._modelRegistry,
 					reason: "compact",
 					compactionEntry: savedCompactionEntry,
-					tokensBefore,
 					fromHook,
 				});
 			}
@@ -1337,16 +1306,15 @@ export class AgentSession {
 	 */
 	async switchSession(sessionPath: string): Promise<boolean> {
 		const previousSessionFile = this.sessionFile;
-		const oldEntries = this.sessionManager.getEntries();
 
 		// Emit before_switch event (can be cancelled)
 		if (this._hookRunner?.hasHandlers("session")) {
 			const result = (await this._hookRunner.emit({
 				type: "session",
-				entries: oldEntries,
-				sessionFile: this.sessionFile,
-				previousSessionFile: null,
+				sessionManager: this.sessionManager,
+				modelRegistry: this._modelRegistry,
 				reason: "before_switch",
+				targetSessionFile: sessionPath,
 			})) as SessionEventResult | undefined;
 
 			if (result?.cancel) {
@@ -1362,7 +1330,6 @@ export class AgentSession {
 		this.sessionManager.setSessionFile(sessionPath);
 
 		// Reload messages
-		const entries = this.sessionManager.getEntries();
 		const sessionContext = this.sessionManager.buildSessionContext();
 
 		// Emit session event to hooks
@@ -1370,10 +1337,10 @@ export class AgentSession {
 			this._hookRunner.setSessionFile(sessionPath);
 			await this._hookRunner.emit({
 				type: "session",
-				entries,
-				sessionFile: sessionPath,
-				previousSessionFile,
+				sessionManager: this.sessionManager,
+				modelRegistry: this._modelRegistry,
 				reason: "switch",
+				previousSessionFile,
 			});
 		}
 
@@ -1428,9 +1395,8 @@ export class AgentSession {
 		if (this._hookRunner?.hasHandlers("session")) {
 			const result = (await this._hookRunner.emit({
 				type: "session",
-				entries,
-				sessionFile: this.sessionFile,
-				previousSessionFile: null,
+				sessionManager: this.sessionManager,
+				modelRegistry: this._modelRegistry,
 				reason: "before_branch",
 				targetTurnIndex: entryIndex,
 			})) as SessionEventResult | undefined;
@@ -1454,7 +1420,6 @@ export class AgentSession {
 		}
 
 		// Reload messages from entries (works for both file and in-memory mode)
-		const newEntries = this.sessionManager.getEntries();
 		const sessionContext = this.sessionManager.buildSessionContext();
 
 		// Emit branch event to hooks (after branch completes)
@@ -1462,9 +1427,8 @@ export class AgentSession {
 			this._hookRunner.setSessionFile(newSessionFile);
 			await this._hookRunner.emit({
 				type: "session",
-				entries: newEntries,
-				sessionFile: newSessionFile,
-				previousSessionFile,
+				sessionManager: this.sessionManager,
+				modelRegistry: this._modelRegistry,
 				reason: "branch",
 				targetTurnIndex: entryIndex,
 			});

packages/coding-agent/src/core/export-html.ts

@@ -1343,6 +1343,9 @@ export function exportSessionToHtml(
 	const opts: ExportOptions = typeof options === "string" ? { outputPath: options } : options || {};
 
 	const sessionFile = sessionManager.getSessionFile();
+	if (!sessionFile) {
+		throw new Error("Cannot export in-memory session to HTML");
+	}
 	const content = readFileSync(sessionFile, "utf8");
 	const data = parseSessionFile(content);
 

packages/coding-agent/src/core/hooks/types.ts

@@ -7,8 +7,9 @@
 
 import type { AppMessage, Attachment } from "@mariozechner/pi-agent-core";
 import type { ImageContent, Model, TextContent, ToolResultMessage } from "@mariozechner/pi-ai";
-import type { CompactionResult, CutPointResult } from "../compaction.js";
-import type { CompactionEntry, SessionEntry } from "../session-manager.js";
+import type { CompactionPreparation, CompactionResult } from "../compaction.js";
+import type { ModelRegistry } from "../model-registry.js";
+import type { CompactionEntry, SessionManager } from "../session-manager.js";
 import type {
 	BashToolDetails,
 	FindToolDetails,
@@ -95,12 +96,10 @@ export interface HookEventContext {
  */
 interface SessionEventBase {
 	type: "session";
-	/** All session entries (including pre-compaction history) */
-	entries: SessionEntry[];
-	/** Current session file path, or null in --no-session mode */
-	sessionFile: string | null;
-	/** Previous session file path, or null for "start" and "new" */
-	previousSessionFile: string | null;
+	/** Session manager instance - use for entries, session file, etc. */
+	sessionManager: SessionManager;
+	/** Model registry - use for API key resolution */
+	modelRegistry: ModelRegistry;
 }
 
 /**
@@ -120,7 +119,17 @@ interface SessionEventBase {
  */
 export type SessionEvent =
 	| (SessionEventBase & {
-			reason: "start" | "switch" | "new" | "before_switch" | "before_new" | "shutdown";
+			reason: "start" | "new" | "before_new" | "shutdown";
+	  })
+	| (SessionEventBase & {
+			reason: "before_switch";
+			/** Session file we're switching to */
+			targetSessionFile: string;
+	  })
+	| (SessionEventBase & {
+			reason: "switch";
+			/** Session file we came from */
+			previousSessionFile: string | null;
 	  })
 	| (SessionEventBase & {
 			reason: "branch" | "before_branch";
@@ -129,27 +138,20 @@ export type SessionEvent =
 	  })
 	| (SessionEventBase & {
 			reason: "before_compact";
-			cutPoint: CutPointResult;
-			/** ID of first entry to keep (for hooks that return CompactionEntry) */
-			firstKeptEntryId: string;
-			/** Summary from previous compaction, if any. Include this in your summary to preserve context. */
-			previousSummary?: string;
-			/** Messages that will be summarized and discarded */
-			messagesToSummarize: AppMessage[];
-			/** Messages that will be kept after the summary (recent turns) */
-			messagesToKeep: AppMessage[];
-			tokensBefore: number;
+			/** Compaction preparation with cut point, messages to summarize/keep, etc. */
+			preparation: CompactionPreparation;
+			/** Previous compaction entries, newest first. Use for iterative summarization. */
+			previousCompactions: CompactionEntry[];
+			/** Optional user-provided instructions for the summary */
 			customInstructions?: string;
+			/** Current model */
 			model: Model<any>;
-			/** Resolve API key for any model (checks settings, OAuth, env vars) */
-			resolveApiKey: (model: Model<any>) => Promise<string | undefined>;
 			/** Abort signal - hooks should pass this to LLM calls and check it periodically */
 			signal: AbortSignal;
 	  })
 	| (SessionEventBase & {
 			reason: "compact";
 			compactionEntry: CompactionEntry;
-			tokensBefore: number;
 			/** Whether the compaction entry was provided by a hook */
 			fromHook: boolean;
 	  });

packages/coding-agent/src/core/session-manager.ts

@@ -421,7 +421,7 @@ export function findMostRecentSession(sessionDir: string): string | null {
  */
 export class SessionManager {
 	private sessionId: string = "";
-	private sessionFile: string = "";
+	private sessionFile: string | undefined;
 	private sessionDir: string;
 	private cwd: string;
 	private persist: boolean;
@@ -434,10 +434,10 @@ export class SessionManager {
 	private constructor(cwd: string, sessionDir: string, sessionFile: string | null, persist: boolean) {
 		this.cwd = cwd;
 		this.sessionDir = sessionDir;
+		this.persist = persist;
 		if (persist && sessionDir && !existsSync(sessionDir)) {
 			mkdirSync(sessionDir, { recursive: true });
 		}
-		this.persist = persist;
 
 		if (sessionFile) {
 			this.setSessionFile(sessionFile);
@@ -479,8 +479,8 @@ export class SessionManager {
 		this.byId.clear();
 		this.leafId = "";
 		this.flushed = false;
-		// Only generate filename if not already set (e.g., via --session flag)
-		if (!this.sessionFile) {
+		// Only generate filename if persisting and not already set (e.g., via --session flag)
+		if (this.persist && !this.sessionFile) {
 			const fileTimestamp = timestamp.replace(/[:.]/g, "-");
 			this.sessionFile = join(this.getSessionDir(), `${fileTimestamp}_${this.sessionId}.jsonl`);
 		}
@@ -505,7 +505,7 @@ export class SessionManager {
 	}
 
 	private _rewriteFile(): void {
-		if (!this.persist) return;
+		if (!this.persist || !this.sessionFile) return;
 		const content = `${this.fileEntries.map((e) => JSON.stringify(e)).join("\n")}\n`;
 		writeFileSync(this.sessionFile, content);
 	}
@@ -526,12 +526,12 @@ export class SessionManager {
 		return this.sessionId;
 	}
 
-	getSessionFile(): string {
+	getSessionFile(): string | undefined {
 		return this.sessionFile;
 	}
 
 	_persist(entry: SessionEntry): void {
-		if (!this.persist) return;
+		if (!this.persist || !this.sessionFile) return;
 
 		const hasAssistant = this.fileEntries.some((e) => e.type === "message" && e.message.role === "assistant");
 		if (!hasAssistant) return;