From ad550c544e48d4e3dc3550efcc1ad7a8a30a1af6 Mon Sep 17 00:00:00 2001
From: Aiden Cline <aidenpcline@gmail.com>
Date: Mon, 6 Jul 2026 17:58:17 -0500
Subject: [PATCH] fix(core): preserve text attachments in context estimate

---
 packages/core/src/session/compaction.ts       | 29 ++++++++-----------
 packages/core/test/session-compaction.test.ts | 14 ++-------
 2 files changed, 14 insertions(+), 29 deletions(-)

diff --git a/packages/core/src/session/compaction.ts b/packages/core/src/session/compaction.ts
index da7b71ef40..f1103d0c3a 100644
--- a/packages/core/src/session/compaction.ts
+++ b/packages/core/src/session/compaction.ts
@@ -84,23 +84,18 @@ const estimate = (value: unknown) => Token.estimate(JSON.stringify(value))
 
 const textContext = (request: LLMRequest) => ({
   system: request.system,
-  // TODO: Replace blanket attachment exclusion with model-aware media and file token accounting.
-  messages: request.messages
-    // Text attachments are lowered into dedicated marked messages; the original prompt is emitted separately.
-    .filter((message) => message.metadata?.attachment === undefined)
-    .map((message) => ({
-      id: message.id,
-      role: message.role,
-      content: message.content.flatMap((part) => {
-        if (part.type === "media") return []
-        if (part.type !== "tool-result" || part.result.type !== "content") return [part]
-        return [
-          { ...part, result: { ...part.result, value: part.result.value.filter((item) => item.type === "text") } },
-        ]
-      }),
-      metadata: message.metadata,
-      native: message.native,
-    })),
+  // TODO: Replace media exclusion with model-aware attachment token accounting.
+  messages: request.messages.map((message) => ({
+    id: message.id,
+    role: message.role,
+    content: message.content.flatMap((part) => {
+      if (part.type === "media") return []
+      if (part.type !== "tool-result" || part.result.type !== "content") return [part]
+      return [{ ...part, result: { ...part.result, value: part.result.value.filter((item) => item.type === "text") } }]
+    }),
+    metadata: message.metadata,
+    native: message.native,
+  })),
   tools: request.tools,
 })
 
diff --git a/packages/core/test/session-compaction.test.ts b/packages/core/test/session-compaction.test.ts
index cf24bcf87b..0f9f8e12ec 100644
--- a/packages/core/test/session-compaction.test.ts
+++ b/packages/core/test/session-compaction.test.ts
@@ -72,7 +72,7 @@ test("compaction describes tool media without embedding base64", () => {
   expect(serialized).not.toContain(base64)
 })
 
-it.effect("does not count file attachments as text context", () =>
+it.effect("does not count image attachments as text context", () =>
   Effect.gen(function* () {
     requests = []
     const compaction = yield* SessionCompaction.Service
@@ -84,12 +84,6 @@ it.effect("does not count file attachments as text context", () =>
       source: { type: "inline" },
       name: "screenshot.png",
     })
-    const document = FileAttachment.make({
-      data: Base64.make(Buffer.alloc(64 * 1024, "a").toString("base64")),
-      mime: "text/plain",
-      source: { type: "inline" },
-      name: "notes.txt",
-    })
     const inputModel = Model.make({
       id: "media-model",
       provider: "test",
@@ -110,7 +104,7 @@ it.effect("does not count file attachments as text context", () =>
         id: SessionMessage.ID.create(),
         type: "user",
         text: "Inspect this image",
-        files: [document, image],
+        files: [image],
         time: { created: DateTime.makeUnsafe(1) },
       }),
     ]
@@ -125,10 +119,6 @@ it.effect("does not count file attachments as text context", () =>
       data,
       filename: "screenshot.png",
     })
-    expect(request.messages[1]?.content[0]).toMatchObject({
-      type: "text",
-      text: expect.stringContaining("Attached file: notes.txt"),
-    })
 
     expect(
       yield* compaction.compactIfNeeded({