From cb932cfe21ba5b45fd398678598ddce2944f4fd8 Mon Sep 17 00:00:00 2001
From: Jarvis <jarvis@route199.com>
Date: Wed, 28 Jan 2026 04:12:48 +0000
Subject: [PATCH] fix(compaction): resolve model via runtime when ctx.model is
 undefined
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When using the embedded pi-agent runner (createAgentSession path),
extensionRunner.initialize() is never called, leaving ctx.model undefined.

This fix passes the model through the existing WeakMap-based runtime
registry and uses it as a fallback when ctx.model is unavailable.

Fixes #2851

🤖 Generated with Claude Code
---
 src/agents/pi-embedded-runner/extensions.ts              | 1 +
 src/agents/pi-extensions/compaction-safeguard-runtime.ts | 3 +++
 src/agents/pi-extensions/compaction-safeguard.ts         | 7 +++++--
 3 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/agents/pi-embedded-runner/extensions.ts b/src/agents/pi-embedded-runner/extensions.ts
index 270458f2e..fde02652e 100644
--- a/src/agents/pi-embedded-runner/extensions.ts
+++ b/src/agents/pi-embedded-runner/extensions.ts
@@ -79,6 +79,7 @@ export function buildEmbeddedExtensionPaths(params: {
     const compactionCfg = params.cfg?.agents?.defaults?.compaction;
     setCompactionSafeguardRuntime(params.sessionManager, {
       maxHistoryShare: compactionCfg?.maxHistoryShare,
+      model: params.model,
     });
     paths.push(resolvePiExtensionPath("compaction-safeguard"));
   }
diff --git a/src/agents/pi-extensions/compaction-safeguard-runtime.ts b/src/agents/pi-extensions/compaction-safeguard-runtime.ts
index f42cf7abe..3bcbd4edf 100644
--- a/src/agents/pi-extensions/compaction-safeguard-runtime.ts
+++ b/src/agents/pi-extensions/compaction-safeguard-runtime.ts
@@ -1,5 +1,8 @@
+import type { Api, Model } from "@mariozechner/pi-ai";
+
 export type CompactionSafeguardRuntimeValue = {
   maxHistoryShare?: number;
+  model?: Model<Api>;
 };
 
 // Session-scoped runtime registry keyed by object identity.
diff --git a/src/agents/pi-extensions/compaction-safeguard.ts b/src/agents/pi-extensions/compaction-safeguard.ts
index b2fe39884..d2922df63 100644
--- a/src/agents/pi-extensions/compaction-safeguard.ts
+++ b/src/agents/pi-extensions/compaction-safeguard.ts
@@ -146,8 +146,12 @@ export default function compactionSafeguardExtension(api: ExtensionAPI): void {
     const toolFailureSection = formatToolFailuresSection(toolFailures);
     const fallbackSummary = `${FALLBACK_SUMMARY}${toolFailureSection}${fileOpsSummary}`;
 
-    const model = ctx.model;
+    const runtime = getCompactionSafeguardRuntime(ctx.sessionManager);
+    const model = ctx.model ?? runtime?.model;
     if (!model) {
+      console.warn(
+        "Compaction safeguard: no model available (ctx.model and runtime.model both undefined)",
+      );
       return {
         compaction: {
           summary: fallbackSummary,
@@ -175,7 +179,6 @@ export default function compactionSafeguardExtension(api: ExtensionAPI): void {
       const turnPrefixMessages = preparation.turnPrefixMessages ?? [];
       let messagesToSummarize = preparation.messagesToSummarize;
 
-      const runtime = getCompactionSafeguardRuntime(ctx.sessionManager);
       const maxHistoryShare = runtime?.maxHistoryShare ?? 0.5;
 
       const tokensBefore =