From fe188f87224200f67fd76c7a587b4fba65afd58c Mon Sep 17 00:00:00 2001
From: Kit Langton <kit.langton@gmail.com>
Date: Fri, 28 Aug 2026 13:29:41 -0400
Subject: [PATCH] fix(core): normalize directory page headings (#45641)

---
 .changeset/directory-page-heading.md  |  5 ++++
 packages/core/src/tool/plugin/read.ts |  2 +-
 packages/core/test/tool-read.test.ts  | 34 +++++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 .changeset/directory-page-heading.md

diff --git a/.changeset/directory-page-heading.md b/.changeset/directory-page-heading.md
new file mode 100644
index 00000000000..f23be6e7d76
--- /dev/null
+++ b/.changeset/directory-page-heading.md
@@ -0,0 +1,5 @@
+---
+"@opencode-ai/core": patch
+---
+
+Correct directory page headings when the read offset is zero.
diff --git a/packages/core/src/tool/plugin/read.ts b/packages/core/src/tool/plugin/read.ts
index ea1643fe564..ee4d488c61b 100644
--- a/packages/core/src/tool/plugin/read.ts
+++ b/packages/core/src/tool/plugin/read.ts
@@ -169,7 +169,7 @@ export const toModelContent = (path: string, offset: number | undefined, output:
     ] as const
 
   if (output.type === "list-page") {
-    const start = offset ?? 1
+    const start = offset || 1
     const content = [
       output.entries.length === 0
         ? `Read directory ${path}, 0 entries`
diff --git a/packages/core/test/tool-read.test.ts b/packages/core/test/tool-read.test.ts
index 107b62ea319..391129672fa 100644
--- a/packages/core/test/tool-read.test.ts
+++ b/packages/core/test/tool-read.test.ts
@@ -678,6 +678,40 @@ describe("ReadTool", () => {
     }),
   )
 
+  it.effect("normalizes a zero directory offset in the model heading", () =>
+    Effect.gen(function* () {
+      readResult = new ReadToolFileSystem.ListPage({
+        type: "list-page",
+        entries: [FileSystem.Entry.make({ path: RelativePath.make("index.ts"), type: "file" })],
+        truncated: true,
+        next: 2,
+      })
+      const registry = yield* Tool.Service
+
+      const result = yield* executeTool(registry, {
+        sessionID,
+        ...toolIdentity,
+        call: {
+          type: "tool-call",
+          id: "call-read-directory-zero",
+          name: "read",
+          input: { path: "src", offset: 0, limit: 1 },
+        },
+      })
+      expect(result.status).toBe("completed")
+      if (result.status !== "completed") return
+      expect(result.content).toEqual([
+        {
+          type: "text",
+          text: "Read directory src, entries 1-1\nindex.ts\n[Output truncated. Continue reading with offset: 2]",
+        },
+      ])
+      expect(readCalls).toEqual([
+        { input: AbsolutePath.make(path.join(process.cwd(), "src")), page: { offset: 0, limit: 1 } },
+      ])
+    }),
+  )
+
   it.effect("does not list a directory when permission is denied", () =>
     Effect.gen(function* () {
       allow = false