Improve branch summarization with preparation and file ops extraction

- Add prepareBranchEntries() to extract messages and file operations
- Extract read/write/edit operations from tool calls
- Append static file operations section to summary
- Improve prompt for branch summarization
- Skip toolResult messages (context already in assistant message)
- Export new types: BranchPreparation, FileOperations

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

@@ -9,8 +9,9 @@ import type { Model } from "@mariozechner/pi-ai";
 import { complete } from "@mariozechner/pi-ai";
 import type { SessionEntry } from "../session-manager.js";
 
-const DEFAULT_INSTRUCTIONS =
-	"Summarize this conversation branch concisely, capturing key decisions, actions taken, and outcomes.";
+// ============================================================================
+// Types
+// ============================================================================
 
 export interface BranchSummaryResult {
 	summary?: string;
@@ -18,6 +19,25 @@ export interface BranchSummaryResult {
 	error?: string;
 }
 
+export interface FileOperations {
+	read: Set<string>;
+	written: Set<string>;
+	edited: Set<string>;
+}
+
+export interface BranchPreparation {
+	/** Messages extracted for summarization */
+	messages: Array<{ role: string; content: string }>;
+	/** File operations extracted from tool calls */
+	fileOps: FileOperations;
+	/** Previous summaries found in entries */
+	previousSummaries: string[];
+}
+
+// ============================================================================
+// Entry Parsing
+// ============================================================================
+
 /**
  * Extract text content from any message type.
  */
@@ -33,6 +53,152 @@ function extractMessageText(message: any): string {
 	return "";
 }
 
+/**
+ * Extract file operations from tool calls in an assistant message.
+ */
+function extractFileOpsFromToolCalls(message: any, fileOps: FileOperations): void {
+	if (!message.content || !Array.isArray(message.content)) return;
+
+	for (const block of message.content) {
+		if (typeof block !== "object" || block === null) continue;
+		if (block.type !== "toolCall") continue;
+
+		const args = block.arguments as Record<string, unknown> | undefined;
+		if (!args) continue;
+
+		const path = typeof args.path === "string" ? args.path : undefined;
+		if (!path) continue;
+
+		switch (block.name) {
+			case "read":
+				fileOps.read.add(path);
+				break;
+			case "write":
+				fileOps.written.add(path);
+				break;
+			case "edit":
+				fileOps.edited.add(path);
+				break;
+		}
+	}
+}
+
+/**
+ * Prepare entries for summarization.
+ *
+ * Extracts:
+ * - Messages (user, assistant text, custom_message)
+ * - File operations from tool calls
+ * - Previous branch summaries
+ *
+ * Skips:
+ * - toolResult messages (context already in assistant message)
+ * - thinking_level_change, model_change, custom, label entries
+ * - compaction entries (these are boundaries, shouldn't be in the input)
+ */
+export function prepareBranchEntries(entries: SessionEntry[]): BranchPreparation {
+	const messages: Array<{ role: string; content: string }> = [];
+	const fileOps: FileOperations = {
+		read: new Set(),
+		written: new Set(),
+		edited: new Set(),
+	};
+	const previousSummaries: string[] = [];
+
+	for (const entry of entries) {
+		switch (entry.type) {
+			case "message": {
+				const role = entry.message.role;
+
+				// Skip tool results - the context is in the assistant's tool call
+				if (role === "toolResult") continue;
+
+				// Extract file ops from assistant tool calls
+				if (role === "assistant") {
+					extractFileOpsFromToolCalls(entry.message, fileOps);
+				}
+
+				// Extract text content
+				const text = extractMessageText(entry.message);
+				if (text) {
+					messages.push({ role, content: text });
+				}
+				break;
+			}
+
+			case "custom_message": {
+				const text =
+					typeof entry.content === "string"
+						? entry.content
+						: entry.content
+								.filter((c): c is { type: "text"; text: string } => c.type === "text")
+								.map((c) => c.text)
+								.join("");
+				if (text) {
+					messages.push({ role: "user", content: text });
+				}
+				break;
+			}
+
+			case "branch_summary": {
+				previousSummaries.push(entry.summary);
+				break;
+			}
+
+			// Skip these entry types - they don't contribute to conversation content
+			case "compaction":
+			case "thinking_level_change":
+			case "model_change":
+			case "custom":
+			case "label":
+				break;
+		}
+	}
+
+	return { messages, fileOps, previousSummaries };
+}
+
+// ============================================================================
+// Summary Generation
+// ============================================================================
+
+const BRANCH_SUMMARY_PROMPT = `Summarize this conversation branch concisely for context when returning later:
+- Key decisions made and actions taken
+- Important context, constraints, or preferences discovered
+- Current state and any pending work
+- Critical information needed to continue from a different point
+
+Be brief and focused on what matters for future reference.`;
+
+/**
+ * Format file operations as a static section to append to summary.
+ */
+function formatFileOperations(fileOps: FileOperations): string {
+	const sections: string[] = [];
+
+	if (fileOps.read.size > 0) {
+		const files = [...fileOps.read].sort();
+		sections.push(`**Read:** ${files.join(", ")}`);
+	}
+
+	if (fileOps.edited.size > 0) {
+		const files = [...fileOps.edited].sort();
+		sections.push(`**Edited:** ${files.join(", ")}`);
+	}
+
+	if (fileOps.written.size > 0) {
+		// Exclude files that were also edited (edit implies write)
+		const writtenOnly = [...fileOps.written].filter((f) => !fileOps.edited.has(f)).sort();
+		if (writtenOnly.length > 0) {
+			sections.push(`**Created:** ${writtenOnly.join(", ")}`);
+		}
+	}
+
+	if (sections.length === 0) return "";
+
+	return `\n\n---\n**Files:**\n${sections.join("\n")}`;
+}
+
 /**
  * Generate a summary of abandoned branch entries.
  *
@@ -49,39 +215,26 @@ export async function generateBranchSummary(
 	signal: AbortSignal,
 	customInstructions?: string,
 ): Promise<BranchSummaryResult> {
-	// Convert entries to messages for summarization
-	const messages: Array<{ role: string; content: string }> = [];
-
-	for (const entry of entries) {
-		if (entry.type === "message") {
-			const text = extractMessageText(entry.message);
-			if (text) {
-				messages.push({ role: entry.message.role, content: text });
-			}
-		} else if (entry.type === "custom_message") {
-			const text =
-				typeof entry.content === "string"
-					? entry.content
-					: entry.content
-							.filter((c): c is { type: "text"; text: string } => c.type === "text")
-							.map((c) => c.text)
-							.join("");
-			if (text) {
-				messages.push({ role: "user", content: text });
-			}
-		} else if (entry.type === "branch_summary") {
-			messages.push({ role: "system", content: `[Previous branch summary: ${entry.summary}]` });
-		}
-	}
+	const { messages, fileOps, previousSummaries } = prepareBranchEntries(entries);
 
 	if (messages.length === 0) {
 		return { summary: "No content to summarize" };
 	}
 
-	// Build prompt for summarization
-	const conversationText = messages.map((m) => `${m.role}: ${m.content}`).join("\n\n");
-	const instructions = customInstructions ? `${customInstructions}\n\n` : `${DEFAULT_INSTRUCTIONS}\n\n`;
-	const prompt = `${instructions}Conversation:\n${conversationText}`;
+	// Build conversation text
+	const parts: string[] = [];
+
+	// Include previous summaries as context
+	if (previousSummaries.length > 0) {
+		parts.push(`[Previous context: ${previousSummaries.join(" | ")}]`);
+	}
+
+	// Add conversation
+	parts.push(messages.map((m) => `${m.role}: ${m.content}`).join("\n\n"));
+
+	const conversationText = parts.join("\n\n");
+	const instructions = customInstructions || BRANCH_SUMMARY_PROMPT;
+	const prompt = `${instructions}\n\nConversation:\n${conversationText}`;
 
 	// Call LLM for summarization
 	const response = await complete(
@@ -106,10 +259,13 @@ export async function generateBranchSummary(
 		return { error: response.errorMessage || "Summarization failed" };
 	}
 
-	const summary = response.content
+	let summary = response.content
 		.filter((c): c is { type: "text"; text: string } => c.type === "text")
 		.map((c) => c.text)
 		.join("\n");
 
+	// Append static file operations section
+	summary += formatFileOperations(fileOps);
+
 	return { summary: summary || "No summary generated" };
 }

packages/coding-agent/src/index.ts

@@ -12,6 +12,7 @@ export {
 export { type ApiKeyCredential, type AuthCredential, AuthStorage, type OAuthCredential } from "./core/auth-storage.js";
 // Compaction
 export {
+	type BranchPreparation,
 	type BranchSummaryResult,
 	type CompactionResult,
 	type CutPointResult,
@@ -19,11 +20,13 @@ export {
 	compact,
 	DEFAULT_COMPACTION_SETTINGS,
 	estimateTokens,
+	type FileOperations,
 	findCutPoint,
 	findTurnStartIndex,
 	generateBranchSummary,
 	generateSummary,
 	getLastAssistantUsage,
+	prepareBranchEntries,
 	shouldCompact,
 } from "./core/compaction/index.js";
 // Custom tools