diff --git a/src/client/app.js b/src/client/app.js
index e5ff503..f249243 100644
--- a/src/client/app.js
+++ b/src/client/app.js
@@ -1248,6 +1248,14 @@ import { mountSidebar } from "./sidebar.js";
     return sink;
   }
   // Pretty value for a tool's args/result (JSON, or a string as-is).
+  // A sandbox tool that promoted files returns { output, artifacts } instead of
+  // the bare text; the documents render from the event, so only the text belongs
+  // in the step's body.
+  function unwrapDelivery(output) {
+    return output && typeof output === "object" && typeof output.output === "string"
+      ? output.output
+      : output;
+  }
   function toolValue(v) {
     if (v == null) return "";
     if (typeof v === "string") return v;
@@ -2370,7 +2378,7 @@ import { mountSidebar } from "./sidebar.js";
   function defaultResult(t, output) {
     var out = document.createElement("div");
     out.className = "tout";
-    out.textContent = toolValue(output);
+    out.textContent = toolValue(unwrapDelivery(output));
     t.body.appendChild(out);
   }
   // A shell run as a terminal card: the command on a `$` prompt line, its output
@@ -2381,11 +2389,7 @@ import { mountSidebar } from "./sidebar.js";
     return i < 0 ? s : s.slice(0, i) + " …";
   }
   function renderShellResult(t, output) {
-    // A command that promoted files returns { output, artifacts } instead of the
-    // bare transcript; the documents render from the event, so only the text
-    // belongs in the terminal card.
-    if (output && typeof output === "object" && typeof output.output === "string")
-      output = output.output;
+    output = unwrapDelivery(output);
     var term = document.createElement("div");
     term.className = "term";
     if (t.input && t.input.command) {
diff --git a/src/tools.ts b/src/tools.ts
index f42e338..32444cf 100644
--- a/src/tools.ts
+++ b/src/tools.ts
@@ -425,10 +425,7 @@ function runShell(executor: Executor, ctx: ToolContext) {
       const result = formatExecResult(
         await executor.run({ command, session, timeoutMs }, abortSignal),
       );
-      const artifacts = session ? await promoteOutputs(executor, ctx, session, abortSignal) : [];
-      // Shape only shifts when there IS something to carry, so the ordinary
-      // command keeps returning the plain transcript it always did.
-      return artifacts.length ? { output: result, artifacts } : result;
+      return deliver(executor, ctx, result, abortSignal);
     },
   });
 }
@@ -521,7 +518,8 @@ export function viewFile(executor: Executor, session: string) {
   });
 }
 
-export function writeFile(executor: Executor, session: string) {
+export function writeFile(executor: Executor, ctx: ToolContext) {
+  const session = ctx.conversationId as string;
   return tool({
     description:
       "Write a text file in the sandbox, creating parent directories and replacing anything " +
@@ -546,14 +544,17 @@ export function writeFile(executor: Executor, session: string) {
       if (before.kind === "directory") return `${full} is a directory, not a file.`;
       await executor.putFile(session, full, new TextEncoder().encode(content), abortSignal);
       const lines = content === "" ? 0 : content.split("\n").length;
-      return before.kind === "file"
-        ? `Overwrote ${full} (${lines} lines, ${content.length} bytes).`
-        : `Created ${full} (${lines} lines, ${content.length} bytes).`;
+      const said =
+        before.kind === "file"
+          ? `Overwrote ${full} (${lines} lines, ${content.length} bytes).`
+          : `Created ${full} (${lines} lines, ${content.length} bytes).`;
+      return deliver(executor, ctx, said, abortSignal);
     },
   });
 }
 
-export function editFile(executor: Executor, session: string) {
+export function editFile(executor: Executor, ctx: ToolContext) {
+  const session = ctx.conversationId as string;
   return tool({
     description:
       "Change part of a text file in the sandbox by exact find-and-replace. old_string must " +
@@ -597,7 +598,8 @@ export function editFile(executor: Executor, session: string) {
       const delta = out.text.split("\n").length - read.text.split("\n").length;
       const shape =
         delta === 0 ? "same line count" : delta > 0 ? `+${delta} lines` : `${delta} lines`;
-      return `Edited ${full} — ${out.replaced} replacement${out.replaced === 1 ? "" : "s"}, ${shape}.`;
+      const said = `Edited ${full} — ${out.replaced} replacement${out.replaced === 1 ? "" : "s"}, ${shape}.`;
+      return deliver(executor, ctx, said, abortSignal);
     },
   });
 }
@@ -606,7 +608,28 @@ export function editFile(executor: Executor, session: string) {
 const DEFAULT_VIEW_LINES = 200;
 
 /**
- * Drain /workspace/outputs into blobs after a command.
+ * A sandbox tool's reply, plus whatever it left in the outbox.
+ *
+ * Promotion follows the outbox, not the tool that filled it: a report written
+ * with write_file is as finished as one a shell command copied there, and the
+ * model shouldn't have to run a stray `ls` to make it arrive. The shape only
+ * shifts when there IS something to carry, so an ordinary call keeps returning
+ * the plain string it always did.
+ */
+async function deliver(
+  executor: Executor,
+  ctx: ToolContext,
+  output: string,
+  signal?: AbortSignal,
+): Promise<string | { output: string; artifacts: ArtifactRef[] }> {
+  const session = ctx.conversationId;
+  if (!session) return output;
+  const artifacts = await promoteOutputs(executor, ctx, session, signal);
+  return artifacts.length ? { output, artifacts } : output;
+}
+
+/**
+ * Drain /workspace/outputs into blobs.
  *
  * The spec's promotion rule, in one place: if it wasn't promoted, it was
  * scratch. Auto-harvesting means a model that writes a chart to the outbox gets
@@ -1030,7 +1053,7 @@ const REGISTRY: Array<{
     executor: "sandbox",
     create: (ctx) => {
       const e = getExecutor();
-      return e && ctx.conversationId ? writeFile(e, ctx.conversationId) : null;
+      return e && ctx.conversationId ? writeFile(e, ctx) : null;
     },
   },
   {
@@ -1038,7 +1061,7 @@ const REGISTRY: Array<{
     executor: "sandbox",
     create: (ctx) => {
       const e = getExecutor();
-      return e && ctx.conversationId ? editFile(e, ctx.conversationId) : null;
+      return e && ctx.conversationId ? editFile(e, ctx) : null;
     },
   },
 ];
diff --git a/tests/filetools.test.ts b/tests/filetools.test.ts
index 28765d4..196fdf3 100644
--- a/tests/filetools.test.ts
+++ b/tests/filetools.test.ts
@@ -1,4 +1,9 @@
 import { expect, test } from "bun:test";
+import { mkdtempSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { FsBlobStore } from "../src/blobs";
+import type { ArtifactRef } from "../src/events";
 import type { ExecResult, Executor, HarvestedFile, ReadResult } from "../src/executor";
 import { editFile, viewFile, writeFile } from "../src/tools";
 
@@ -40,8 +45,18 @@ class FakeSandbox implements Executor {
     if (text === undefined) return { kind: "missing" };
     return { kind: "file", text, bytes: text.length };
   }
+  /** Drains the outbox, like the real one: what's taken is gone. */
   async harvest(): Promise<HarvestedFile[]> {
-    return [];
+    const out: HarvestedFile[] = [];
+    for (const [path, text] of this.files) {
+      if (!path.startsWith("/workspace/outputs/")) continue;
+      out.push({
+        path: path.slice("/workspace/outputs/".length),
+        bytes: new TextEncoder().encode(text),
+      });
+      this.files.delete(path);
+    }
+    return out;
   }
   disposeSession(): void {}
 }
@@ -94,7 +109,7 @@ test("each way a read fails names a different fix", async () => {
 
 test("writing reports whether it created or replaced, and writes it verbatim", async () => {
   const box = new FakeSandbox();
-  const write = writeFile(box, "c1");
+  const write = writeFile(box, { conversationId: "c1" });
   // Content that would need escaping through a shell, passed through untouched.
   const tricky = "line 'one'\n$(echo hi) `date`\n\"two\"\n";
 
@@ -111,7 +126,7 @@ test("writing reports whether it created or replaced, and writes it verbatim", a
 test("an edit writes back exactly the replacement it computed", async () => {
   const box = new FakeSandbox();
   box.files.set("/workspace/app.py", "def main():\n    return 1\n");
-  const edit = editFile(box, "c1");
+  const edit = editFile(box, { conversationId: "c1" });
 
   const out = (await call(edit, {
     path: "app.py",
@@ -127,7 +142,7 @@ test("a failed edit changes nothing and explains itself", async () => {
   const box = new FakeSandbox();
   const before = "a = 1\nb = 2\na = 1\n";
   box.files.set("/workspace/c.py", before);
-  const edit = editFile(box, "c1");
+  const edit = editFile(box, { conversationId: "c1" });
 
   const ambiguous = (await call(edit, {
     path: "c.py",
@@ -158,7 +173,7 @@ test("a failed edit changes nothing and explains itself", async () => {
 
 test("editing a file that isn't there says so instead of creating it", async () => {
   const box = new FakeSandbox();
-  const out = (await call(editFile(box, "c1"), {
+  const out = (await call(editFile(box, { conversationId: "c1" }), {
     path: "ghost.py",
     old_string: "a",
     new_string: "b",
@@ -166,3 +181,32 @@ test("editing a file that isn't there says so instead of creating it", async ()
   expect(out).toContain("No file at /workspace/ghost.py");
   expect(box.files.size).toBe(0);
 });
+
+test("a file written into the outbox is promoted, whichever tool put it there", async () => {
+  // The model is told to prefer write_file over a heredoc, so the outbox has to
+  // drain after a write too — a report that arrives only if a later `ls` happens
+  // to run is a report that usually doesn't arrive.
+  const dir = mkdtempSync(join(tmpdir(), "kloe-ft-"));
+  const box = new FakeSandbox();
+  const ctx = { conversationId: "c1", blobs: new FsBlobStore(join(dir, "blobs")) };
+
+  const wrote = (await call(writeFile(box, ctx), {
+    path: "outputs/report.md",
+    content: "# Findings\n",
+  })) as { output: string; artifacts: ArtifactRef[] };
+  expect(wrote.output).toContain("Created");
+  expect(wrote.artifacts).toMatchObject([{ name: "report.md", mime: "text/markdown" }]);
+
+  // A file kept in the workspace is scratch: writing it promotes nothing.
+  expect(await call(writeFile(box, ctx), { path: "notes.md", content: "x" })).toBeString();
+
+  // An edit delivers too — the finished version is the one worth handing over.
+  box.files.set("/workspace/outputs/chart.html", "<p>old</p>");
+  const edited = (await call(editFile(box, ctx), {
+    path: "outputs/chart.html",
+    old_string: "old",
+    new_string: "new",
+  })) as { output: string; artifacts: ArtifactRef[] };
+  expect(edited.artifacts).toMatchObject([{ name: "chart.html", mime: "text/html" }]);
+  expect(await (await ctx.blobs.get(edited.artifacts[0]!.sha256))?.text()).toBe("<p>new</p>");
+});