Fix: compaction now handles branch_summary and custom_message entries

- Add getMessageFromEntry helper to extract AppMessage from any context-producing entry
- Update findValidCutPoints to treat branch_summary/custom_message as valid cut points
- Update findTurnStartIndex to recognize branch_summary/custom_message as turn starters
- Update all message extraction loops to use getMessageFromEntry

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

@@ -9,7 +9,28 @@ import type { AppMessage } from "@mariozechner/pi-agent-core";
 import type { AssistantMessage, Model, Usage } from "@mariozechner/pi-ai";
 import { complete } from "@mariozechner/pi-ai";
 import { messageTransformer } from "./messages.js";
-import type { CompactionEntry, SessionEntry } from "./session-manager.js";
+import { type CompactionEntry, createSummaryMessage, type SessionEntry } from "./session-manager.js";
+
+/**
+ * Extract AppMessage from an entry if it produces one.
+ * Returns null for entries that don't contribute to LLM context.
+ */
+function getMessageFromEntry(entry: SessionEntry): AppMessage | null {
+	if (entry.type === "message") {
+		return entry.message;
+	}
+	if (entry.type === "custom_message") {
+		return {
+			role: "user",
+			content: entry.content,
+			timestamp: new Date(entry.timestamp).getTime(),
+		};
+	}
+	if (entry.type === "branch_summary") {
+		return createSummaryMessage(entry.summary, entry.timestamp);
+	}
+	return null;
+}
 
 /** Result from compact() - SessionManager adds uuid/parentUuid when saving */
 export interface CompactionResult<T = unknown> {
@@ -157,7 +178,10 @@ function findValidCutPoints(entries: SessionEntry[], startIndex: number, endInde
 	const cutPoints: number[] = [];
 	for (let i = startIndex; i < endIndex; i++) {
 		const entry = entries[i];
-		if (entry.type === "message") {
+		// branch_summary and custom_message are user-role messages, valid cut points
+		if (entry.type === "branch_summary" || entry.type === "custom_message") {
+			cutPoints.push(i);
+		} else if (entry.type === "message") {
 			const role = entry.message.role;
 			// user, assistant, and bashExecution are valid cut points
 			// toolResult must stay with its preceding tool call
@@ -177,6 +201,10 @@ function findValidCutPoints(entries: SessionEntry[], startIndex: number, endInde
 export function findTurnStartIndex(entries: SessionEntry[], entryIndex: number, startIndex: number): number {
 	for (let i = entryIndex; i >= startIndex; i--) {
 		const entry = entries[i];
+		// branch_summary and custom_message are user-role messages, can start a turn
+		if (entry.type === "branch_summary" || entry.type === "custom_message") {
+			return i;
+		}
 		if (entry.type === "message") {
 			const role = entry.message.role;
 			if (role === "user" || role === "bashExecution") {
@@ -382,19 +410,15 @@ export function prepareCompaction(entries: SessionEntry[], settings: CompactionS
 	// Messages to summarize (will be discarded after summary)
 	const messagesToSummarize: AppMessage[] = [];
 	for (let i = boundaryStart; i < historyEnd; i++) {
-		const entry = entries[i];
+		const msg = getMessageFromEntry(entries[i]);
-		if (entry.type === "message") {
+		if (msg) messagesToSummarize.push(msg);
-			messagesToSummarize.push(entry.message);
-		}
 	}
 
 	// Messages to keep (recent turns, kept after summary)
 	const messagesToKeep: AppMessage[] = [];
 	for (let i = cutPoint.firstKeptEntryIndex; i < boundaryEnd; i++) {
-		const entry = entries[i];
+		const msg = getMessageFromEntry(entries[i]);
-		if (entry.type === "message") {
+		if (msg) messagesToKeep.push(msg);
-			messagesToKeep.push(entry.message);
-		}
 	}
 
 	return { cutPoint, firstKeptEntryId, messagesToSummarize, messagesToKeep, tokensBefore, boundaryStart };
@@ -460,10 +484,8 @@ export async function compact(
 	const historyEnd = cutResult.isSplitTurn ? cutResult.turnStartIndex : cutResult.firstKeptEntryIndex;
 	const historyMessages: AppMessage[] = [];
 	for (let i = boundaryStart; i < historyEnd; i++) {
-		const entry = entries[i];
+		const msg = getMessageFromEntry(entries[i]);
-		if (entry.type === "message") {
+		if (msg) historyMessages.push(msg);
-			historyMessages.push(entry.message);
-		}
 	}
 
 	// Include previous summary if there was a compaction
@@ -480,10 +502,8 @@ export async function compact(
 	const turnPrefixMessages: AppMessage[] = [];
 	if (cutResult.isSplitTurn) {
 		for (let i = cutResult.turnStartIndex; i < cutResult.firstKeptEntryIndex; i++) {
-			const entry = entries[i];
+			const msg = getMessageFromEntry(entries[i]);
-			if (entry.type === "message") {
+			if (msg) turnPrefixMessages.push(msg);
-				turnPrefixMessages.push(entry.message);
-			}
 		}
 	}