From da6f65b2477b45299c563e255433deee4661f728 Mon Sep 17 00:00:00 2001
From: ethan <ethan@coder.com>
Date: Wed, 26 Nov 2025 23:37:12 +1100
Subject: [PATCH] =?UTF-8?q?=F0=9F=A4=96=20fix:=20omit=20providerMetadata?=
 =?UTF-8?q?=20from=20compaction=20summary=20to=20fix=20context=20display?=
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The compaction API response's providerMetadata contains cacheCreationInputTokens
from the pre-compaction context, which inflates the context usage display until
the next message is sent. By omitting providerMetadata from the summary message,
context usage correctly shows just the compaction output tokens.

The historicalUsage field still preserves full cost accounting from pre-compaction
messages.

_Generated with mux_
---
 src/node/services/compactionHandler.test.ts | 5 +++--
 src/node/services/compactionHandler.ts      | 6 ++++--
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/src/node/services/compactionHandler.test.ts b/src/node/services/compactionHandler.test.ts
index 175d917007..c5f591de7d 100644
--- a/src/node/services/compactionHandler.test.ts
+++ b/src/node/services/compactionHandler.test.ts
@@ -255,7 +255,7 @@ describe("CompactionHandler", () => {
         model: "claude-3-5-sonnet-20241022",
         usage,
         duration: 2000,
-        providerMetadata: { foo: "bar" },
+        providerMetadata: { anthropic: { cacheCreationInputTokens: 50000 } },
         systemMessageTokens: 100,
       });
       await handler.handleCompletion(event);
@@ -266,14 +266,15 @@ describe("CompactionHandler", () => {
       });
       expect(summaryEvent).toBeDefined();
       const sevt = summaryEvent?.data.message as MuxMessage;
+      // providerMetadata is omitted to avoid inflating context with pre-compaction cacheCreationInputTokens
       expect(sevt.metadata).toMatchObject({
         model: "claude-3-5-sonnet-20241022",
         usage,
         duration: 2000,
-        providerMetadata: { foo: "bar" },
         systemMessageTokens: 100,
         compacted: true,
       });
+      expect(sevt.metadata?.providerMetadata).toBeUndefined();
     });
 
     it("should emit stream-end event to frontend", async () => {
diff --git a/src/node/services/compactionHandler.ts b/src/node/services/compactionHandler.ts
index 3cb9846951..351f6ca5c7 100644
--- a/src/node/services/compactionHandler.ts
+++ b/src/node/services/compactionHandler.ts
@@ -112,7 +112,10 @@ export class CompactionHandler {
     }
     const deletedSequences = clearResult.data;
 
-    // Create summary message with metadata
+    // Create summary message with metadata.
+    // We omit providerMetadata because it contains cacheCreationInputTokens from the
+    // pre-compaction context, which inflates context usage display. The historicalUsage
+    // field preserves full cost accounting from pre-compaction messages.
     const summaryMessage = createMuxMessage(
       `summary-${Date.now()}-${Math.random().toString(36).substring(2, 11)}`,
       "assistant",
@@ -123,7 +126,6 @@ export class CompactionHandler {
         model: metadata.model,
         usage: metadata.usage,
         historicalUsage,
-        providerMetadata: metadata.providerMetadata,
         duration: metadata.duration,
         systemMessageTokens: metadata.systemMessageTokens,
         muxMetadata: { type: "normal" },