[Init] Initial commit - NetMesh terminal manager

application/state/sftp/useSftpConnections.test.ts

@@ -0,0 +1,772 @@
+// Created: 2026-07-21
+// Purpose: Verify SFTP prefers live terminal session reuse before fresh auth.
+
+import test from "node:test";
+import assert from "node:assert/strict";
+import type { Host } from "../../../domain/models";
+import type { SftpPane } from "./types";
+
+import {
+  applyToLiveSftpTabSide,
+  beginSftpTabConnectRequest,
+  buildSftpConnectInFlightKey,
+  buildSftpHomeDirCandidates,
+  clearSftpConnectInFlightForTab,
+  closeSftpTabLifecycle,
+  runSftpConnectOnceByKey,
+  createSftpConnectionId,
+  createPinnedReconnectSideResolver,
+  finishSftpTabConnectRequest,
+  invalidateSftpTabConnectRequest,
+  isSftpHostKeySessionCurrent,
+  isSftpTabConnectRequestCurrent,
+  openSftpConnectionOnce,
+  openSftpWithSessionPreference,
+  rejectHostKeyVerificationRequest,
+  registerOpenedSftpSession,
+  resolveSftpPaneEndpointKey,
+  resolveSftpReconnectAttempt,
+  takeSftpConnectionMetadataForClose,
+  releaseSftpConnectionMetadata,
+  resolvePinnedReconnectSide,
+  resolveSftpReconnectOptions,
+  resolveSftpReconnectSchedule,
+  resolveSftpReconnectHost,
+  runSftpTabDisconnectIfLatest,
+  settleFailedSftpConnectIfCurrent,
+} from "./useSftpConnections.ts";
+
+test("home dir candidates prefer user home then root", () => {
+  assert.deepEqual(buildSftpHomeDirCandidates("deploy"), ["/home/deploy", "/root"]);
+  assert.deepEqual(buildSftpHomeDirCandidates("root"), ["/root"]);
+  assert.deepEqual(buildSftpHomeDirCandidates(undefined), ["/root"]);
+  assert.deepEqual(buildSftpHomeDirCandidates(null), ["/root"]);
+});
+
+test("connection ids stay unique even when connects start in the same millisecond", () => {
+  const ids = ["uuid-a", "uuid-b"];
+  assert.equal(createSftpConnectionId("left", () => ids.shift()!), "left-uuid-a");
+  assert.equal(createSftpConnectionId("left", () => ids.shift()!), "left-uuid-b");
+});
+
+test("runSftpConnectOnceByKey shares an in-flight connect for the same tab and endpoint", async () => {
+  const inFlight = new Map<string, Promise<void>>();
+  let runs = 0;
+  let releaseFirst: (() => void) | undefined;
+
+  const first = runSftpConnectOnceByKey(inFlight, "left:tab-1:host-key:ssh-session-1:/home", async () => {
+    runs += 1;
+    await new Promise<void>((resolve) => {
+      releaseFirst = resolve;
+    });
+  });
+  const second = runSftpConnectOnceByKey(inFlight, "left:tab-1:host-key:ssh-session-1:/home", async () => {
+    runs += 1;
+  });
+
+  assert.equal(runs, 1);
+  releaseFirst?.();
+  await Promise.all([first, second]);
+  assert.equal(runs, 1);
+  assert.equal(inFlight.size, 0);
+});
+
+test("disconnect detaches only that tab's in-flight connects", () => {
+  const pending = Promise.resolve();
+  const inFlight = new Map<string, Promise<void>>([
+    [`tab-a\u0000host-a\u0000`, pending],
+    [`tab-b\u0000host-a\u0000`, pending],
+  ]);
+
+  clearSftpConnectInFlightForTab(inFlight, "tab-a");
+
+  assert.deepEqual([...inFlight.keys()], ["tab-b\u0000host-a\u0000"]);
+});
+
+test("buildSftpConnectInFlightKey uses the allocated tab id for forced new tabs", () => {
+  const first = buildSftpConnectInFlightKey({
+    side: "left",
+    tabId: "new-tab-a",
+    targetConnectionKey: "host-key",
+    sourceSessionId: "ssh-session-1",
+    initialPath: "/home",
+    forceNewTab: true,
+  });
+  const second = buildSftpConnectInFlightKey({
+    side: "left",
+    tabId: "new-tab-b",
+    targetConnectionKey: "host-key",
+    sourceSessionId: "ssh-session-1",
+    initialPath: "/home",
+    forceNewTab: true,
+  });
+
+  assert.notEqual(first, second);
+});
+
+test("moving an in-flight reconnect does not create a second connection", () => {
+  const base = {
+    tabId: "moving-tab",
+    targetConnectionKey: "host-key",
+    sourceSessionId: "ssh-session-1",
+    initialPath: "/home",
+  };
+  assert.equal(
+    buildSftpConnectInFlightKey({ ...base, side: "left" }),
+    buildSftpConnectInFlightKey({ ...base, side: "right" }),
+  );
+});
+
+test("the newest request for a moved tab wins after an older close finishes", () => {
+  const requests = new Map<string, symbol>();
+  const oldRequest = beginSftpTabConnectRequest(requests, "tab-moving");
+  const newRequest = beginSftpTabConnectRequest(requests, "tab-moving");
+
+  assert.equal(isSftpTabConnectRequestCurrent(requests, "tab-moving", oldRequest), false);
+  assert.equal(isSftpTabConnectRequestCurrent(requests, "tab-moving", newRequest), true);
+
+  finishSftpTabConnectRequest(requests, "tab-moving", oldRequest);
+  assert.equal(isSftpTabConnectRequestCurrent(requests, "tab-moving", newRequest), true);
+
+  invalidateSftpTabConnectRequest(requests, "tab-moving");
+  assert.equal(isSftpTabConnectRequestCurrent(requests, "tab-moving", newRequest), false);
+});
+
+test("a slow disconnect cannot clear a newer connection on the same tab", async () => {
+  const requests = new Map<string, symbol>();
+  let releaseClose: (() => void) | undefined;
+  let clears = 0;
+  const disconnect = runSftpTabDisconnectIfLatest({
+    requests,
+    tabId: "tab-a",
+    disconnect: async () => new Promise<void>((resolve) => {
+      releaseClose = resolve;
+    }),
+    clear: () => {
+      clears += 1;
+    },
+  });
+
+  await Promise.resolve();
+  const newerConnect = beginSftpTabConnectRequest(requests, "tab-a");
+  finishSftpTabConnectRequest(requests, "tab-a", newerConnect);
+  releaseClose?.();
+
+  assert.equal(await disconnect, false);
+  assert.equal(clears, 0);
+});
+
+test("a slow disconnect clears a tab after it moves to the other pane", async () => {
+  const requests = new Map<string, symbol>();
+  let leftTabs: ReadonlyArray<{ id: string }> = [{ id: "tab-moving" }];
+  let rightTabs: ReadonlyArray<{ id: string }> = [];
+  let releaseClose: (() => void) | undefined;
+  let clearedSide: "left" | "right" | null = null;
+  const disconnect = runSftpTabDisconnectIfLatest({
+    requests,
+    tabId: "tab-moving",
+    disconnect: async () => new Promise<void>((resolve) => {
+      releaseClose = resolve;
+    }),
+    clear: () => {
+      applyToLiveSftpTabSide({
+        requestedSide: "left",
+        tabId: "tab-moving",
+        leftTabs,
+        rightTabs,
+        apply: (side) => {
+          clearedSide = side;
+        },
+      });
+    },
+  });
+
+  await Promise.resolve();
+  leftTabs = [];
+  rightTabs = [{ id: "tab-moving" }];
+  releaseClose?.();
+
+  assert.equal(await disconnect, true);
+  assert.equal(clearedSide, "right");
+});
+
+test("closing a tab removes it before a slow connection release", async () => {
+  const requests = new Map<string, symbol>();
+  beginSftpTabConnectRequest(requests, "tab-a");
+  const pending = Promise.resolve();
+  const inFlight = new Map<string, Promise<void>>([
+    ["tab-a\u0000host-a", pending],
+    ["tab-b\u0000host-b", pending],
+  ]);
+  const connectedHosts = new Map<string, Host | "local">([["tab-a", "local"]]);
+  let releaseClose: (() => void) | undefined;
+  let closedSide: "left" | "right" | null = null;
+  const closing = closeSftpTabLifecycle({
+    requestedSide: "left",
+    tabId: "tab-a",
+    leftTabs: [{ id: "tab-a" }],
+    rightTabs: [],
+    connectRequests: requests,
+    connectInFlight: inFlight,
+    connectedHosts,
+    closeTab: (side) => {
+      closedSide = side;
+    },
+    releaseConnection: async () => new Promise<void>((resolve) => {
+      releaseClose = resolve;
+    }),
+  });
+
+  assert.equal(closedSide, "left");
+  assert.equal(requests.has("tab-a"), false);
+  assert.deepEqual([...inFlight.keys()], ["tab-b\u0000host-b"]);
+  assert.equal(connectedHosts.has("tab-a"), false);
+  releaseClose?.();
+  await closing;
+});
+
+test("a slow failed-request cleanup cannot overwrite a newer successful connection", async () => {
+  let current = true;
+  let releaseClose: (() => void) | undefined;
+  let failuresWritten = 0;
+  const settlement = settleFailedSftpConnectIfCurrent({
+    isCurrent: () => current,
+    close: async () => new Promise<void>((resolve) => {
+      releaseClose = resolve;
+    }),
+    updateFailure: () => {
+      failuresWritten += 1;
+    },
+  });
+
+  await Promise.resolve();
+  current = false;
+  releaseClose?.();
+
+  assert.equal(await settlement, false);
+  assert.equal(failuresWritten, 0);
+});
+
+test("stale host-key prompts do not belong to a replacement connection", () => {
+  const requests = new Map<string, symbol>();
+  const oldToken = beginSftpTabConnectRequest(requests, "tab-a");
+  const oldOwner = { tabId: "tab-a", connectRequestToken: oldToken };
+  assert.equal(isSftpHostKeySessionCurrent(requests, oldOwner), true);
+
+  beginSftpTabConnectRequest(requests, "tab-a");
+  assert.equal(isSftpHostKeySessionCurrent(requests, oldOwner), false);
+});
+
+test("reconnect state only follows the endpoint that originally failed", () => {
+  assert.equal(resolveSftpReconnectAttempt({
+    isPinnedBackgroundReconnect: false,
+    previousPaneReconnecting: true,
+    previousConnectionKey: "host-a",
+    targetConnectionKey: "host-a",
+  }), true);
+  assert.equal(resolveSftpReconnectAttempt({
+    isPinnedBackgroundReconnect: false,
+    previousPaneReconnecting: true,
+    previousConnectionKey: "host-a",
+    targetConnectionKey: "host-b",
+  }), false);
+  assert.equal(resolveSftpReconnectAttempt({
+    isPinnedBackgroundReconnect: true,
+    initialPath: "/srv/app",
+    previousPaneReconnecting: false,
+    previousConnectionKey: null,
+    targetConnectionKey: "host-a",
+  }), true);
+});
+
+test("reconnect keeps its endpoint identity after released connection metadata is gone", () => {
+  const hostA = {
+    id: "host-a",
+    label: "A",
+    hostname: "a.example",
+    port: 22,
+    username: "alice",
+    protocol: "ssh",
+  } as Host;
+  const hostB = {
+    id: "host-b",
+    label: "B",
+    hostname: "b.example",
+    port: 22,
+    username: "bob",
+    protocol: "ssh",
+  } as Host;
+  const pane = {
+    id: "tab-a",
+    reconnecting: true,
+    connection: {
+      id: "released-connection-a",
+      hostId: hostA.id,
+      hostLabel: hostA.label,
+      isLocal: false,
+      status: "disconnected",
+      currentPath: "/srv/app",
+    },
+  } as SftpPane;
+
+  const previousConnectionKey = resolveSftpPaneEndpointKey({
+    connection: pane.connection,
+    cachedConnectionKey: null,
+    connectedHost: hostA,
+  });
+  const hostAKey = resolveSftpPaneEndpointKey({
+    connection: pane.connection,
+    cachedConnectionKey: null,
+    connectedHost: hostA,
+  });
+  const hostBKey = resolveSftpPaneEndpointKey({
+    connection: {
+      ...pane.connection!,
+      hostId: hostB.id,
+    },
+    cachedConnectionKey: null,
+    connectedHost: hostB,
+  });
+
+  assert.equal(resolveSftpReconnectAttempt({
+    isPinnedBackgroundReconnect: false,
+    previousPaneReconnecting: pane.reconnecting,
+    previousConnectionKey,
+    targetConnectionKey: hostAKey!,
+  }), true);
+  assert.equal(resolveSftpReconnectAttempt({
+    isPinnedBackgroundReconnect: false,
+    previousPaneReconnecting: pane.reconnecting,
+    previousConnectionKey,
+    targetConnectionKey: hostBKey!,
+  }), false);
+});
+
+test("forced terminal rebinds never merge into an older in-flight route", () => {
+  const base = {
+    side: "left" as const,
+    tabId: "tab-1",
+    targetConnectionKey: "host-key",
+    initialPath: "/srv/app",
+  };
+  const oldRoute = buildSftpConnectInFlightKey(base);
+  const newRouteDrop = buildSftpConnectInFlightKey({
+    ...base,
+    connectRequestKey: "drop-route-b",
+  });
+
+  assert.notEqual(oldRoute, newRouteDrop);
+});
+
+const openOptions = {
+  sessionId: "sftp-request-1",
+  hostname: "192.168.9.138",
+  username: "zhlrs",
+  port: 22,
+} as NetcattySSHOptions;
+
+test("openSftpWithSessionPreference opens session-backed SFTP before authing again", async () => {
+  const calls: string[] = [];
+  let expectedEndpoint: NetcattySSHOptions | undefined;
+  const sftpId = await openSftpWithSessionPreference({
+    bridge: {
+      openSftpForSession: async (sessionId: string, endpoint?: NetcattySSHOptions) => {
+        calls.push(`openForSession:${sessionId}`);
+        expectedEndpoint = endpoint;
+        return "session-backed-sftp";
+      },
+      openSftp: async () => {
+        calls.push("openSftp");
+        return "fresh-sftp";
+      },
+    },
+    sourceSessionId: "ssh-session-1",
+    openOptions,
+  });
+
+  assert.equal(sftpId, "session-backed-sftp");
+  assert.deepEqual(calls, ["openForSession:ssh-session-1"]);
+  assert.equal(expectedEndpoint, openOptions);
+});
+
+test("openSftpWithSessionPreference falls back to normal SFTP when session reuse fails", async () => {
+  const calls: string[] = [];
+  const sftpId = await openSftpWithSessionPreference({
+    bridge: {
+      openSftpForSession: async (sessionId: string) => {
+        calls.push(`openForSession:${sessionId}`);
+        throw new Error("channel unavailable");
+      },
+      openSftp: async (options: NetcattySSHOptions) => {
+        calls.push(`openSftp:${options.sessionId}`);
+        return "fresh-sftp";
+      },
+    },
+    sourceSessionId: "ssh-session-1",
+    openOptions,
+  });
+
+  assert.equal(sftpId, "fresh-sftp");
+  assert.deepEqual(calls, ["openForSession:ssh-session-1", "openSftp:sftp-request-1"]);
+});
+
+test("strict source-session reuse never dials a different route after reuse fails", async () => {
+  const calls: string[] = [];
+  let receivedOptions: NetcattySSHOptions | undefined;
+  await assert.rejects(
+    openSftpWithSessionPreference({
+      bridge: {
+        openSftpForSession: async (sessionId: string, options?: NetcattySSHOptions) => {
+          calls.push(`openForSession:${sessionId}`);
+          receivedOptions = options;
+          throw new Error("channel unavailable");
+        },
+        openSftp: async () => {
+          calls.push("openSftp");
+          return "fresh-sftp";
+        },
+      },
+      sourceSessionId: "ssh-session-1",
+      requireSourceSessionReuse: true,
+      openOptions,
+    }),
+    /channel unavailable/,
+  );
+
+  assert.deepEqual(calls, ["openForSession:ssh-session-1"]);
+  assert.equal(receivedOptions?.requireExactSourceSession, true);
+});
+
+test("openSftpWithSessionPreference tries session reuse for sudo SFTP before fresh auth", async () => {
+  const calls: string[] = [];
+  let passedOptions: NetcattySSHOptions | undefined;
+  const sftpId = await openSftpWithSessionPreference({
+    bridge: {
+      openSftpForSession: async (sessionId: string, options?: NetcattySSHOptions) => {
+        calls.push(`openForSession:${sessionId}`);
+        passedOptions = options;
+        return "sudo-session-backed-sftp";
+      },
+      openSftp: async () => {
+        calls.push("openSftp");
+        return "fresh-sftp";
+      },
+    },
+    sourceSessionId: "ssh-session-1",
+    openOptions: {
+      ...openOptions,
+      sudo: true,
+      password: "sudo-pass",
+    },
+  });
+
+  assert.equal(sftpId, "sudo-session-backed-sftp");
+  assert.deepEqual(calls, ["openForSession:ssh-session-1"]);
+  assert.equal(passedOptions?.sudo, true);
+  assert.equal(passedOptions?.password, "sudo-pass");
+});
+
+test("openSftpWithSessionPreference opens normal SFTP without a source session", async () => {
+  const calls: string[] = [];
+  const sftpId = await openSftpWithSessionPreference({
+    bridge: {
+      openSftpForSession: async () => {
+        calls.push("openForSession");
+        return "session-backed-sftp";
+      },
+      openSftp: async (options: NetcattySSHOptions) => {
+        calls.push(`openSftp:${options.sessionId}`);
+        return "fresh-sftp";
+      },
+    },
+    sourceSessionId: undefined,
+    openOptions,
+  });
+
+  assert.equal(sftpId, "fresh-sftp");
+  assert.deepEqual(calls, ["openSftp:sftp-request-1"]);
+});
+
+test("one connect attempt never repeats a failed fresh SFTP dial after reuse fails", async () => {
+  const calls: string[] = [];
+  await assert.rejects(
+    openSftpConnectionOnce({
+      bridge: {
+        openSftpForSession: async () => {
+          calls.push("openForSession");
+          throw new Error("shared channel unavailable");
+        },
+        openSftp: async () => {
+          calls.push("openSftp");
+          throw new Error("authentication failed");
+        },
+      },
+      sourceSessionId: "ssh-session-1",
+      openOptions,
+    }),
+    /authentication failed/,
+  );
+
+  assert.deepEqual(calls, ["openForSession", "openSftp"]);
+});
+
+test("closing connections releases their session and cache-key metadata", () => {
+  const sessions = new Map<string, string>();
+  const cacheKeys = new Map<string, string>();
+  const cleared: string[] = [];
+  for (let index = 0; index < 1_000; index += 1) {
+    const connectionId = `connection-${index}`;
+    sessions.set(connectionId, `sftp-${index}`);
+    cacheKeys.set(connectionId, `endpoint-${index}`);
+    assert.equal(takeSftpConnectionMetadataForClose({
+      connectionId,
+      sftpSessions: sessions,
+      connectionCacheKeys: cacheKeys,
+      clearCacheForConnection: (id) => { cleared.push(id); },
+    }), `sftp-${index}`);
+  }
+  assert.equal(sessions.size, 0);
+  assert.equal(cacheKeys.size, 0);
+  assert.equal(cleared.length, 1_000);
+});
+
+test("release metadata closes the backend before a failed connection is retained as an error", async () => {
+  const sessions = new Map([["connection-1", "sftp-1"]]);
+  const cacheKeys = new Map([["connection-1", "endpoint-1"]]);
+  const closed: string[] = [];
+  const cleared: string[] = [];
+
+  await releaseSftpConnectionMetadata({
+    connectionId: "connection-1",
+    sftpSessions: sessions,
+    connectionCacheKeys: cacheKeys,
+    clearCacheForConnection: (id) => { cleared.push(id); },
+    closeSftp: async (id) => { closed.push(id); },
+  });
+
+  assert.deepEqual(closed, ["sftp-1"]);
+  assert.deepEqual(cleared, ["connection-1"]);
+  assert.equal(sessions.size, 0);
+  assert.equal(cacheKeys.size, 0);
+});
+
+test("a connection that finishes after its owner unmounts is closed instead of registered", async () => {
+  const sftpSessions = new Map<string, string>();
+  const closed: string[] = [];
+  const notified: string[] = [];
+  const disposedRef = { current: true };
+
+  const registered = await registerOpenedSftpSession({
+    disposedRef,
+    connectionId: "connection-late",
+    sftpId: "sftp-late",
+    sftpSessions,
+    closeSftp: async (sftpId) => { closed.push(sftpId); },
+    onRemoteSessionClosed: (sftpId) => { notified.push(sftpId); },
+  });
+
+  assert.equal(registered, false);
+  assert.equal(sftpSessions.size, 0);
+  assert.deepEqual(closed, ["sftp-late"]);
+  assert.deepEqual(notified, ["sftp-late"]);
+});
+
+test("a connection that finishes after browse parking is closed instead of registered", async () => {
+  const sftpSessions = new Map<string, string>();
+  const closed: string[] = [];
+  const lifecycle = { generation: 1, interactive: true };
+  const openedGeneration = lifecycle.generation;
+  lifecycle.generation += 1;
+  lifecycle.interactive = false;
+
+  const registered = await registerOpenedSftpSession({
+    disposedRef: { current: false },
+    canRegister: () => (
+      lifecycle.interactive && lifecycle.generation === openedGeneration
+    ),
+    connectionId: "connection-parked",
+    sftpId: "sftp-parked",
+    sftpSessions,
+    closeSftp: async (sftpId) => { closed.push(sftpId); },
+  });
+
+  assert.equal(registered, false);
+  assert.equal(sftpSessions.size, 0);
+  assert.deepEqual(closed, ["sftp-parked"]);
+});
+
+test("releaseSftpConnectionMetadata notifies after a remote session closes", async () => {
+  const sessions = new Map([["connection-1", "sftp-1"]]);
+  const cacheKeys = new Map([["connection-1", "cache-1"]]);
+  const notified: string[] = [];
+
+  await releaseSftpConnectionMetadata({
+    connectionId: "connection-1",
+    sftpSessions: sessions,
+    connectionCacheKeys: cacheKeys,
+    clearCacheForConnection: () => {},
+    closeSftp: async () => {},
+    onRemoteSessionClosed: (sftpId) => { notified.push(sftpId); },
+  });
+
+  assert.deepEqual(notified, ["sftp-1"]);
+});
+
+test("resolvePinnedReconnectSide follows a tab moved to the other side", () => {
+  assert.equal(
+    resolvePinnedReconnectSide("left", "tab-1", [], [{ id: "tab-1" }]),
+    "right",
+  );
+  assert.equal(
+    resolvePinnedReconnectSide("right", "tab-1", [{ id: "tab-1" }], []),
+    "left",
+  );
+  assert.equal(
+    resolvePinnedReconnectSide("left", "tab-1", [{ id: "tab-1" }], []),
+    "left",
+  );
+  assert.equal(
+    resolvePinnedReconnectSide("left", undefined, [], [{ id: "tab-1" }]),
+    "left",
+  );
+  assert.throws(
+    () => resolvePinnedReconnectSide("left", "gone", [], []),
+    /SFTP tab is no longer available/,
+  );
+});
+
+test("rejectHostKeyVerificationRequest rejects an orphaned verification", () => {
+  const responses: Array<[string, boolean, boolean]> = [];
+
+  rejectHostKeyVerificationRequest({
+    respondHostKeyVerification: async (requestId, accept, addToKnownHosts) => {
+      responses.push([requestId, accept, addToKnownHosts]);
+      return { success: true };
+    },
+  }, "hostkey-1");
+
+  assert.deepEqual(responses, [["hostkey-1", false, false]]);
+});
+
+test("a newly allocated forced-connect tab follows moves across async boundaries", async () => {
+  let leftTabs: ReadonlyArray<{ id: string }> = [{ id: "tab-1" }];
+  let rightTabs: ReadonlyArray<{ id: string }> = [];
+  const resolveSide = createPinnedReconnectSideResolver(
+    "left",
+    "tab-1",
+    () => leftTabs,
+    () => rightTabs,
+  );
+
+  assert.equal(resolveSide(), "left");
+
+  await Promise.resolve();
+  leftTabs = [];
+  rightTabs = [{ id: "tab-1" }];
+
+  assert.equal(resolveSide(), "right");
+
+  rightTabs = [];
+  assert.equal(resolveSide(), "right");
+});
+
+test("a just-allocated connect tab uses its known side until React state commits", () => {
+  let leftTabs: ReadonlyArray<{ id: string }> = [];
+  let rightTabs: ReadonlyArray<{ id: string }> = [];
+  const resolveSide = createPinnedReconnectSideResolver(
+    "left",
+    "new-tab",
+    () => leftTabs,
+    () => rightTabs,
+  );
+
+  assert.equal(resolveSide(), "left");
+  leftTabs = [{ id: "new-tab" }];
+  assert.equal(resolveSide(), "left");
+  leftTabs = [];
+  rightTabs = [{ id: "new-tab" }];
+  assert.equal(resolveSide(), "right");
+});
+
+test("reconnect uses the active tab host instead of the side's previous host", () => {
+  const hostA = {
+    id: "host-a",
+    label: "A",
+    hostname: "a.example",
+    port: 22,
+    username: "alice",
+    protocol: "ssh",
+  } as Host;
+  const hostB = {
+    id: "host-b",
+    label: "B",
+    hostname: "b.example",
+    port: 22,
+    username: "bob",
+    protocol: "ssh",
+  } as Host;
+  const activePane = {
+    id: "tab-a-moved-right",
+    connection: {
+      id: "connection-a",
+      hostId: "host-a",
+      hostLabel: "A",
+      isLocal: false,
+      status: "disconnected",
+      currentPath: "/home/alice",
+    },
+  } as SftpPane;
+
+  assert.equal(resolveSftpReconnectHost({
+    pane: activePane,
+    lastHost: hostB,
+    connectedHostByTabId: new Map([[activePane.id, hostA]]),
+    hosts: [hostA, hostB],
+  }), hostA);
+});
+
+test("a reconnecting tab moved to the other pane still schedules recovery", () => {
+  const movedPane = {
+    id: "tab-a",
+    reconnecting: true,
+    connection: {
+      id: "connection-a",
+      hostId: "host-a",
+      hostLabel: "A",
+      isLocal: false,
+      status: "disconnected",
+      currentPath: "/home/alice",
+    },
+  } as SftpPane;
+
+  assert.deepEqual(resolveSftpReconnectSchedule({
+    requestedSide: "left",
+    pane: movedPane,
+    leftTabs: [],
+    rightTabs: [movedPane],
+  }), { side: "right", tabId: "tab-a" });
+});
+
+test("automatic reconnect retries the source session then allows a fresh open", () => {
+  const pane = {
+    id: "tab-a",
+    connection: {
+      id: "connection-a",
+      hostId: "host-a",
+      hostLabel: "A",
+      isLocal: false,
+      status: "disconnected",
+      currentPath: "/home/alice",
+      sourceSessionId: "ssh-a",
+    },
+  } as SftpPane;
+
+  assert.deepEqual(resolveSftpReconnectOptions(pane), {
+    tabId: "tab-a",
+    sourceSessionId: "ssh-a",
+  });
+  assert.equal(
+    "requireSourceSessionReuse" in resolveSftpReconnectOptions(pane),
+    false,
+  );
+});