Use exhaustive switch on message.role throughout coding-agent

- addMessageToChat: exhaustive switch for all AgentMessage roles
- renderSessionContext: delegates to addMessageToChat, special handling for assistant tool calls and tool results
- export-html formatMessage: exhaustive switch for all AgentMessage roles
- Removed isHookMessage, isBashExecutionMessage type guards in favor of role checks
- Fixed imports and removed unused getLatestCompactionEntry

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

@@ -1,5 +1,5 @@
 import type { AgentMessage } from "@mariozechner/pi-agent-core";
-import type { ImageContent, TextContent } from "@mariozechner/pi-ai";
+import type { ImageContent, Message, TextContent } from "@mariozechner/pi-ai";
 import { randomUUID } from "crypto";
 import {
 	appendFileSync,
@@ -15,6 +15,13 @@ import {
 } from "fs";
 import { join, resolve } from "path";
 import { getAgentDir as getDefaultAgentDir } from "../config.js";
+import {
+	type BashExecutionMessage,
+	createBranchSummaryMessage,
+	createCompactionSummaryMessage,
+	createHookMessage,
+	type HookMessage,
+} from "./messages.js";
 
 export const CURRENT_SESSION_VERSION = 2;
 
@@ -59,9 +66,12 @@ export interface CompactionEntry<T = unknown> extends SessionEntryBase {
 	details?: T;
 }
 
-export interface BranchSummaryEntry extends SessionEntryBase {
+export interface BranchSummaryEntry<T = unknown> extends SessionEntryBase {
 	type: "branch_summary";
+	fromId: string;
 	summary: string;
+	/** Hook-specific data (not sent to LLM) */
+	details?: T;
 }
 
 /**
@@ -145,35 +155,6 @@ export interface SessionInfo {
 	allMessagesText: string;
 }
 
-export const SUMMARY_PREFIX = `The conversation history before this point was compacted into the following summary:
-
-<summary>
-`;
-
-export const SUMMARY_SUFFIX = `
-</summary>`;
-
-/** Exported for compaction.test.ts */
-export function createSummaryMessage(summary: string, timestamp: string): AgentMessage {
-	return {
-		role: "user",
-		content: SUMMARY_PREFIX + summary + SUMMARY_SUFFIX,
-		timestamp: new Date(timestamp).getTime(),
-	};
-}
-
-/** Convert CustomMessageEntry to AgentMessage format */
-function createCustomMessage(entry: CustomMessageEntry): AgentMessage {
-	return {
-		role: "hookMessage",
-		customType: entry.customType,
-		content: entry.content,
-		display: entry.display,
-		details: entry.details,
-		timestamp: new Date(entry.timestamp).getTime(),
-	} as AgentMessage;
-}
-
 /** Generate a unique short ID (8 hex chars, collision-checked) */
 function generateId(byId: { has(id: string): boolean }): string {
 	for (let i = 0; i < 100; i++) {
@@ -328,9 +309,21 @@ export function buildSessionContext(
 	// 3. Emit messages after compaction
 	const messages: AgentMessage[] = [];
 
+	const appendMessage = (entry: SessionEntry) => {
+		if (entry.type === "message") {
+			messages.push(entry.message);
+		} else if (entry.type === "custom_message") {
+			messages.push(
+				createHookMessage(entry.customType, entry.content, entry.display, entry.details, entry.timestamp),
+			);
+		} else if (entry.type === "branch_summary" && entry.summary) {
+			messages.push(createBranchSummaryMessage(entry.summary, entry.fromId, entry.timestamp));
+		}
+	};
+
 	if (compaction) {
 		// Emit summary first
-		messages.push(createSummaryMessage(compaction.summary, compaction.timestamp));
+		messages.push(createCompactionSummaryMessage(compaction.summary, compaction.tokensBefore, compaction.timestamp));
 
 		// Find compaction index in path
 		const compactionIdx = path.findIndex((e) => e.type === "compaction" && e.id === compaction.id);
@@ -343,37 +336,19 @@ export function buildSessionContext(
 				foundFirstKept = true;
 			}
 			if (foundFirstKept) {
-				if (entry.type === "message") {
-					messages.push(entry.message);
-				} else if (entry.type === "custom_message") {
-					messages.push(createCustomMessage(entry));
-				} else if (entry.type === "branch_summary") {
-					messages.push(createSummaryMessage(entry.summary, entry.timestamp));
-				}
+				appendMessage(entry);
 			}
 		}
 
 		// Emit messages after compaction
 		for (let i = compactionIdx + 1; i < path.length; i++) {
 			const entry = path[i];
-			if (entry.type === "message") {
-				messages.push(entry.message);
-			} else if (entry.type === "custom_message") {
-				messages.push(createCustomMessage(entry));
-			} else if (entry.type === "branch_summary") {
-				messages.push(createSummaryMessage(entry.summary, entry.timestamp));
-			}
+			appendMessage(entry);
 		}
 	} else {
 		// No compaction - emit all messages, handle branch summaries and custom messages
 		for (const entry of path) {
-			if (entry.type === "message") {
-				messages.push(entry.message);
-			} else if (entry.type === "custom_message") {
-				messages.push(createCustomMessage(entry));
-			} else if (entry.type === "branch_summary") {
-				messages.push(createSummaryMessage(entry.summary, entry.timestamp));
-			}
+			appendMessage(entry);
 		}
 	}
 
@@ -597,8 +572,13 @@ export class SessionManager {
 		this._persist(entry);
 	}
 
-	/** Append a message as child of current leaf, then advance leaf. Returns entry id. */
-	appendMessage(message: AgentMessage): string {
+	/** Append a message as child of current leaf, then advance leaf. Returns entry id.
+	 * Does not allow writing CompactionSummaryMessage and BranchSummaryMessage directly.
+	 * Reason: we want these to be top-level entries in the session, not message session entries,
+	 * so it is easier to find them.
+	 * These need to be appended via appendCompaction() and appendBranchSummary() methods.
+	 */
+	appendMessage(message: Message | HookMessage | BashExecutionMessage): string {
 		const entry: SessionMessageEntry = {
 			type: "message",
 			id: generateId(this.byId),
@@ -851,6 +831,7 @@ export class SessionManager {
 			id: generateId(this.byId),
 			parentId: branchFromId,
 			timestamp: new Date().toISOString(),
+			fromId: branchFromId,
 			summary,
 		};
 		this._appendEntry(entry);