diff --git a/docs/agent-log.md b/docs/agent-log.md
index bf2ff66..5171a81 100644
--- a/docs/agent-log.md
+++ b/docs/agent-log.md
@@ -4,6 +4,16 @@ What agents have done, newest first. Add an entry for every piece of work: the d
 note or request it was for, what changed, the files touched, the tests run, and anything left
 open or not verified. Keep each entry short; the git history has the details.
 
+## 2026-10-29: t79 preserve progress before world import (Codex)
+
+- importWorldFile uses GAME.running to await saveWorld('auto', true) before reading
+  the file or starting loading. Save failure cancels import with a toast.
+- Files: src/ui/saves.js, test/t_import_save.js, tasks/t79_importing_world_mid.md
+  and this log. Regression failed first; seven focused checks, build.py and all
+  headless suites passed (python3 test/run_all.py; /tmp/t79-headless.log).
+- Browser suite and screenshots not run as requested; owner playtesting remains
+  open. No simulation/worldgen changes; no commit.
+
 ## 2026-10-29: t78 damaged blueprint code validation (Codex)
 
 - bpValid checks block codes, non-fixed machine types and mold kinds against their
diff --git a/src/ui/saves.js b/src/ui/saves.js
index 6e90901..821a2fb 100644
--- a/src/ui/saves.js
+++ b/src/ui/saves.js
@@ -184,6 +184,10 @@ async function exportWorld() {
   catch (e) { if (e && e.code !== 'declined') toast('The world file was not saved.'); }
 }
 async function importWorldFile(file) {
+  if (GAME.running && !await saveWorld('auto', true)) {
+    toast('The current world could not be saved. Import cancelled.');
+    return;
+  }
   const progress = (f, s) => showLoading(true, f, s, 'Loading world');
   progress(0.05, 'Reading the save');
   try {
diff --git a/test/t_import_save.js b/test/t_import_save.js
new file mode 100644
index 0000000..caea677
--- /dev/null
+++ b/test/t_import_save.js
@@ -0,0 +1,83 @@
+// Import must preserve the running world before reading or replacing it.
+const fs = require('fs');
+const path = require('path');
+const { load, suite, flatWorld } = require('./harness');
+const { run } = load(), { check, done } = suite();
+run(fs.readFileSync(path.join(__dirname, '../src/ui/saves.js'), 'utf8'));
+run(`
+  globalThis.GAME = { running: true, paused: true, worldId: 'current', worldName: 'Current', playTime: 42 };
+  globalThis.messages = [];
+  globalThis.toast = text => messages.push(text);
+  globalThis.$ = () => ({});
+  globalThis.showLoading = () => {};
+  globalThis.stored = new Map();
+  globalThis.failStorage = false;
+  globalThis.releaseWrite = null;
+  DB.get = async key => stored.get(key);
+  DB.op = async (mode, fn) => {
+    if (failStorage) throw new Error('Storage full');
+    await new Promise(resolve => { releaseWrite = resolve; });
+    fn({ put: (value, key) => stored.set(key, value) });
+  };
+  globalThis.loads = 0;
+  globalThis.startFromSave = async sv => {
+    loads++;
+    deserializeWorld(sv.meta, sv.buffers);
+    GAME.worldId = sv.worldId; GAME.worldName = sv.worldName;
+    return true;
+  };
+`);
+
+async function main() {
+  flatWorld(run, 64, 64, 48);
+  const incoming = run('serializeWorld()');
+  const buffers = {};
+  for (const [key, arr] of Object.entries(incoming.buffers)) {
+    buffers[key] = { type: arr.constructor.name, gz: false,
+      b64: Buffer.from(arr.buffer, arr.byteOffset, arr.byteLength).toString('base64') };
+  }
+  const text = JSON.stringify({ format: 'deepgrain-world', meta: incoming.meta, buffers });
+  run('money = 12345; setCell(10 * W + 10, CUORE, AMB[10], 0);');
+  let reads = 0, savedBeforeRead = false;
+  // Release each storage transaction on the next turn, after observing whether
+  // the importer tried to read the file while the first save was still pending.
+  const pending = run('importWorldFile')({ text: async () => {
+    reads++;
+    savedBeforeRead = run("stored.has('current:auto')");
+    return text;
+  } });
+  await new Promise(resolve => setImmediate(resolve));
+  check('file waits for the running world save to commit', reads === 0);
+  let settled = false;
+  pending.finally(() => { settled = true; });
+  const deadline = Date.now() + 10000;
+  while (!settled && Date.now() < deadline) {
+    if (run('releaseWrite !== null')) run('releaseWrite(); releaseWrite = null;');
+    await new Promise(resolve => setTimeout(resolve, 1));
+  }
+  if (!settled) throw new Error('Import timed out');
+  await pending;
+  check('current world is saved before reading the import', savedBeforeRead);
+  check('autosave contains latest money and grains', run(`(() => {
+    const sv = stored.get('current:auto');
+    return !!sv && sv.meta.economy.money === 12345;
+  })()`) && (await run("worldNewest('current')"))?.buffers.mat[650] === run('CUORE'));
+  check('good import loads and saves under its own id', run(`loads === 1 && GAME.worldId !== 'current'
+    && stored.has(GAME.worldId + ':auto') && messages.includes('World imported.')`));
+
+  run('failStorage = true; messages.length = 0; loads = 0;');
+  const before = run('mat');
+  reads = 0;
+  await run('importWorldFile')({ text: async () => { reads++; return text; } });
+  check('failed save stops before reading or replacing the world', reads === 0 && run('loads') === 0 && before === run('mat'));
+  check('failed save explains that the current world could not be saved',
+    run("messages.some(s => /current world/i.test(s) && /could not be saved/i.test(s))"));
+
+  // Title-screen import must not attempt to save a nonexistent running world.
+  run('GAME.running = false; messages.length = 0; loads = 0;');
+  reads = 0;
+  await run('importWorldFile')({ text: async () => { reads++; return text; } });
+  check('title-screen import still reads and loads without a pre-save', reads === 1 && run('loads') === 1);
+  done();
+}
+main().catch(e => { console.error(e); process.exitCode = 1; });