fix(compaction): handle pi-agent-core toolResult format in truncation and pruning

The pre-emptive truncation, tool result pruning, and summary fallback
only checked for Anthropic-style `role: "user"` messages with
`type: "tool_result"` blocks. The actual runtime uses pi-agent-core
format with `role: "toolResult"`, `toolCallId`, and `toolName` on the
message itself. This caused truncation and pruning to silently skip
all tool results in real agent runs.

Add handlers for the pi-agent-core format in all four affected modules:
- session-manager.ts: check both "user" and "toolResult" roles
- tool-result-truncation.ts: new handler for toolResult format
- tool-result-pruning.ts: new processToolResultMessage() + updated loops
- summary-fallback.ts: include "toolResult" in artifact ref extraction

Verified via agent-driven E2E tests (5 test sessions, 6 artifacts).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/core/src/agent/context-window/summary-fallback.ts

@@ -105,7 +105,8 @@ function extractArtifactRefs(messages: AgentMessage[]): string[] {
   const pattern = /Full result (?:saved to|available at) (artifacts\/[^\s.]+\.txt)/g;
 
   for (const msg of messages) {
-    if (msg.role !== "user") continue;
+    const role = msg.role as string;
+    if (role !== "user" && role !== "toolResult") continue;
     const content = (msg as any).content;
     if (typeof content === "string") {
       for (const match of content.matchAll(pattern)) {

packages/core/src/agent/context-window/tool-result-pruning.ts

@@ -318,7 +318,51 @@ function softTrimText(
 }
 
 /**
- * Process a user message containing tool results.
+ * Process a pi-agent-core "toolResult" message.
+ * These have role="toolResult" with content as text blocks and toolCallId/toolName on the message.
+ */
+function processToolResultMessage(
+  message: AgentMessage,
+  settings: ToolResultPruningSettings,
+  mode: "soft" | "hard",
+): { message: AgentMessage; changed: boolean; charsSaved: number } {
+  const msgAny = message as any;
+  const toolName = msgAny.toolName ?? "unknown";
+
+  if (!isToolPrunable(toolName, settings)) {
+    return { message, changed: false, charsSaved: 0 };
+  }
+
+  if (hasImageContent(msgAny.content)) {
+    return { message, changed: false, charsSaved: 0 };
+  }
+
+  const originalText = extractToolResultText(msgAny.content);
+
+  if (mode === "soft") {
+    const result = softTrimText(originalText, settings);
+    if (!result) return { message, changed: false, charsSaved: 0 };
+    return {
+      message: { ...message, content: [{ type: "text", text: result.trimmed }] } as AgentMessage,
+      changed: true,
+      charsSaved: result.saved,
+    };
+  }
+
+  // Hard clear
+  const artifactRef = extractArtifactRef(originalText);
+  const placeholder = artifactRef
+    ? `${settings.hardClear.placeholder} Full result available at ${artifactRef}.`
+    : settings.hardClear.placeholder;
+  return {
+    message: { ...message, content: [{ type: "text", text: placeholder }] } as AgentMessage,
+    changed: true,
+    charsSaved: originalText.length - placeholder.length,
+  };
+}
+
+/**
+ * Process a user message containing tool results (Anthropic format).
  * Returns modified message if any tool results were trimmed/cleared.
  */
 function processUserMessageToolResults(
@@ -467,7 +511,26 @@ export function pruneToolResults(params: {
   // Phase 1: Soft Trim
   for (let i = pruneStartIndex; i < cutoffIndex; i++) {
     const msg = result[i];
-    if (!msg || msg.role !== "user") continue;
+    if (!msg) continue;
+
+    const msgRole = msg.role as string;
+
+    // pi-agent-core "toolResult" format
+    if (msgRole === "toolResult") {
+      prunableIndexes.push(i);
+      const processed = processToolResultMessage(msg, settings, "soft");
+      if (processed.changed) {
+        result[i] = processed.message;
+        changed = true;
+        softTrimmed++;
+        charsSaved += processed.charsSaved;
+        totalChars -= processed.charsSaved;
+      }
+      continue;
+    }
+
+    // Anthropic-style "user" format with tool_result blocks
+    if (msgRole !== "user") continue;
 
     const msgAny = msg as any;
     if (!Array.isArray(msgAny.content)) continue;
@@ -506,9 +569,10 @@ export function pruneToolResults(params: {
         if (ratio < settings.hardClearRatio) break;
 
         const msg = result[i]!;
-        const beforeChars = estimateMessageChars(msg);
 
-        const processed = processUserMessageToolResults(msg, settings, "hard");
+        const processed = (msg.role as string) === "toolResult"
+          ? processToolResultMessage(msg, settings, "hard")
+          : processUserMessageToolResults(msg, settings, "hard");
         if (processed.changed) {
           result[i] = processed.message;
           changed = true;

packages/core/src/agent/context-window/tool-result-truncation.ts

@@ -150,9 +150,34 @@ export function truncateOversizedToolResults(params: {
   };
 
   const msgAny = params.message as any;
+  const role = params.message.role as string;
 
-  // Only process user messages with array content (tool results come as user messages)
-  if (params.message.role !== "user" || !Array.isArray(msgAny.content)) {
+  // Handle pi-agent-core "toolResult" format:
+  //   { role: "toolResult", content: [{ type: "text", text: "..." }], toolCallId, toolName }
+  if (role === "toolResult" && Array.isArray(msgAny.content)) {
+    const maxChars = computeMaxChars(params.contextWindowTokens, settings);
+    if (hasImages(msgAny.content)) {
+      return { message: params.message, truncated: false, artifacts: [] };
+    }
+    const text = extractText(msgAny.content);
+    const effectiveMax = Math.max(maxChars, settings.minKeepChars);
+    if (text.length <= effectiveMax) {
+      return { message: params.message, truncated: false, artifacts: [] };
+    }
+    const toolCallId = msgAny.toolCallId ?? "unknown";
+    const toolName = msgAny.toolName ?? "unknown";
+    const artifactRelPath = params.saveArtifact(toolCallId, text);
+    const truncatedText = truncateText(text, maxChars, artifactRelPath, settings);
+    return {
+      message: { ...params.message, content: [{ type: "text", text: truncatedText }] } as AgentMessage,
+      truncated: true,
+      artifacts: [{ toolCallId, toolName, originalChars: text.length, artifactRelPath }],
+    };
+  }
+
+  // Handle Anthropic-style "user" format with tool_result blocks:
+  //   { role: "user", content: [{ type: "tool_result", tool_use_id, content: "..." }] }
+  if (role !== "user" || !Array.isArray(msgAny.content)) {
     return { message: params.message, truncated: false, artifacts: [] };
   }
 

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

@@ -252,7 +252,7 @@ export class SessionManager {
     // Pre-emptive truncation: save oversized tool results as artifacts
     // and persist a truncated version in the JSONL session file.
     let persistMessage = message;
-    if (this.enableToolResultTruncation && message.role === "user") {
+    if (this.enableToolResultTruncation && (message.role === "user" || message.role === "toolResult")) {
       const result = truncateOversizedToolResults({
         message,
         contextWindowTokens: this.contextWindowTokens,