diff --git a/packages/app-bundle/manifest.json b/packages/app-bundle/manifest.json
index c6dfc3db8..2629d5e3c 100644
--- a/packages/app-bundle/manifest.json
+++ b/packages/app-bundle/manifest.json
@@ -287,7 +287,7 @@
     "packages/app/src/pages/new-session.tsx": "c060bbb15569b6da2f67146e6af0879ccb5444345df03dbc2f9b39cb98b9db78",
     "packages/app/src/pages/overlay-content-hash.test.ts": "aa208098213522dcde42434408afe9c8641fad663f44a58c316922dbd0da2f5c",
     "packages/app/src/pages/research-surfaces-absence.test.ts": "9944a8ec5492500eb82548d03b24ea7fb8ccc9c2ae5de14a4d18ddb309378746",
-    "packages/app/src/pages/session.tsx": "7918f8bed4b1bd0932e5e6681546217fa24e5b6e81667163ef4b63439516328f",
+    "packages/app/src/pages/session.tsx": "546262aa8537e9f0229d63fbe7c94179db328568709ec27c44d5de9a374086ee",
     "packages/app/src/utils/amicode-bridge.ts": "3ec87c24c0384d312f7eb644807d9217a53b1b4b97f7fffadab1cc1595603f3b",
     "packages/app/src/utils/amicode-bug-report.test.ts": "b1bbf49230ff3aa6d1a43ffa9165ba5a84ca4ee18a6d49f52ee5cd887c3e6444",
     "packages/app/src/utils/amicode-bug-report.ts": "d55d9cecfe17719c0d4a0ca498345c7eff6fca1de6b645e4bc3fecb40f2f4645",
@@ -1034,7 +1034,9 @@
     "packages/opencode/src/server/routes/instance/httpapi/handlers/session.ts": "b37ff4136c4aea85b23083bf441f03e09820e3e4cdd95e4118ca570d8435b94f",
     "packages/opencode/src/server/routes/instance/httpapi/middleware/file-write-workspace.ts": "665c33633173ee89c6da1d4a0eaacaf4eebe3ccdd04eb36b063515cb4c093e4a",
     "packages/opencode/src/server/routes/instance/httpapi/middleware/gateway-secret.ts": "ec6133ee5d331920ded81042fbeb05221bec0c4b26f5897b3f28bc267d26aefa",
-    "packages/opencode/src/server/routes/instance/httpapi/middleware/workspace-routing.ts": "6ded09e0f424f894e100e1f4904787d97ae1512f25688cfa2f05cbfbd3811a2a"
+    "packages/opencode/src/server/routes/instance/httpapi/middleware/workspace-routing.ts": "6ded09e0f424f894e100e1f4904787d97ae1512f25688cfa2f05cbfbd3811a2a",
+    "packages/app/src/pages/session/work-column-presence.ts": "a6a1485299d602267f91bf821d816f6e97f620fc5e5bb9e946511d111b6fe57e",
+    "packages/app/src/pages/session/work-column-presence.test.ts": "435ded3491681f9274ee1d4f219ce6191e2f374005271844deb12b1c67cb9f1b"
   },
   "symlinks": [
     "packages/app/public/amico.svg"
@@ -1098,7 +1100,7 @@
     }
   },
   "counts": {
-    "overlay_total": 1027,
+    "overlay_total": 1029,
     "deletions": 7,
     "server_coupled": 0
   },
@@ -2129,7 +2131,9 @@
     "packages/opencode/src/server/routes/instance/httpapi/handlers/session.ts": "M",
     "packages/opencode/src/server/routes/instance/httpapi/middleware/file-write-workspace.ts": "A",
     "packages/opencode/src/server/routes/instance/httpapi/middleware/gateway-secret.ts": "A",
-    "packages/opencode/src/server/routes/instance/httpapi/middleware/workspace-routing.ts": "M"
+    "packages/opencode/src/server/routes/instance/httpapi/middleware/workspace-routing.ts": "M",
+    "packages/app/src/pages/session/work-column-presence.ts": "A",
+    "packages/app/src/pages/session/work-column-presence.test.ts": "A"
   },
   "upstream_base_archive_sha256": "4b5f2e5edfc796082a353fd09c1b1dec3e7a108a4b080fe3a86b12d9fa59fae6"
 }
diff --git a/packages/app-bundle/overlay/packages/app/src/pages/session.tsx b/packages/app-bundle/overlay/packages/app/src/pages/session.tsx
index 44a38aabc..26b7c69a0 100644
--- a/packages/app-bundle/overlay/packages/app/src/pages/session.tsx
+++ b/packages/app-bundle/overlay/packages/app/src/pages/session.tsx
@@ -86,6 +86,14 @@ import {
 } from "@/pages/session/session-panel-width"
 import { SessionSidePanel } from "@/pages/session/session-side-panel"
 import { sessionPanelLayout } from "@/pages/session/session-panel-layout"
+import {
+  reduceWorkColumnPhase,
+  WORK_COLUMN_TRANSITION_MS,
+  workColumnExpanded,
+  workColumnMounted,
+  workColumnTransitioning,
+  type WorkColumnPhase,
+} from "@/pages/session/work-column-presence"
 import { SessionReviewEmptyChangesV2 } from "@opencode-ai/session-ui/v2/session-review-empty-changes-v2"
 import { ReviewPanelV2 } from "@/pages/session/v2/review-panel-v2"
 import { createReviewPanelV2State } from "@/pages/session/v2/review-panel-v2-state"
@@ -710,6 +718,39 @@ export default function Page() {
   const workColumnWidth = createMemo(() =>
     clampWorkColumnWidth({ width: layout.panelColumn.width(), available: sessionPanelAvailable() }),
   )
+  // amicode#1610: the work column animates its width on collapse/restore
+  // instead of unmounting in one frame. It stays mounted through `closing`
+  // (width → 0) and `opening` (0 → width); the timers below settle the phase.
+  const workColumnVisible = createMemo(() => isDesktop() && desktopV2PanelLayout().visible)
+  const [workColumnPhase, setWorkColumnPhase] = createSignal<WorkColumnPhase>(
+    untrack(workColumnVisible) ? "open" : "unmounted",
+  )
+  createEffect(
+    on(
+      workColumnVisible,
+      (visible, previous) => {
+        if (previous === undefined || visible === previous) return
+        setWorkColumnPhase((phase) => reduceWorkColumnPhase(phase, visible ? "show" : "hide"))
+      },
+      { defer: true },
+    ),
+  )
+  createEffect(() => {
+    const phase = workColumnPhase()
+    if (!workColumnTransitioning(phase)) return
+    let live = true
+    const settle = () => {
+      if (live) setWorkColumnPhase((current) => reduceWorkColumnPhase(current, "settled"))
+    }
+    // closing: wait out the width transition. opening: let the collapsed
+    // width paint first (two frames), then expand so the transition runs.
+    const timer = phase === "closing" ? setTimeout(settle, WORK_COLUMN_TRANSITION_MS) : undefined
+    if (phase === "opening") requestAnimationFrame(() => requestAnimationFrame(settle))
+    onCleanup(() => {
+      live = false
+      if (timer !== undefined) clearTimeout(timer)
+    })
+  })
   const sessionPanelWidth = createMemo(() => {
     if (chatTakesRemainder()) return undefined
     if (!desktopSidePanelOpen()) return "100%"
@@ -2846,14 +2887,25 @@ export default function Page() {
           </Suspense>
         </Show>
         <Show when={newSessionDesign()}>
-          <Show when={isDesktop() ? desktopV2PanelLayout().visible : terminalOpen()}>
+          <Show when={isDesktop() ? workColumnMounted(workColumnPhase()) : terminalOpen()}>
             <div
               classList={{
                 "min-w-0 h-full flex flex-col relative": true,
                 "flex-1": !isDesktop(),
                 "flex-none": isDesktop(),
+                // amicode#1610: animate collapse/restore only — never during a
+                // manual drag (size.active()), which must track the pointer 1:1.
+                "transition-[width] duration-200 ease-[cubic-bezier(0.22,1,0.36,1)] motion-reduce:transition-none":
+                  isDesktop() && !size.active(),
+                "overflow-hidden": isDesktop() && workColumnPhase() !== "open",
+              }}
+              style={{
+                width: isDesktop()
+                  ? workColumnExpanded(workColumnPhase())
+                    ? `${workColumnWidth()}px`
+                    : "0px"
+                  : undefined,
               }}
-              style={{ width: isDesktop() ? `${workColumnWidth()}px` : undefined }}
             >
               {/* amicode#105: the work column's own resize handle (its left
                   edge), sizing layout.panelColumn within the policy bounds —
diff --git a/packages/app-bundle/overlay/packages/app/src/pages/session/work-column-presence.test.ts b/packages/app-bundle/overlay/packages/app/src/pages/session/work-column-presence.test.ts
new file mode 100644
index 000000000..6a9e71c61
--- /dev/null
+++ b/packages/app-bundle/overlay/packages/app/src/pages/session/work-column-presence.test.ts
@@ -0,0 +1,62 @@
+import { describe, expect, test } from "bun:test"
+import {
+  reduceWorkColumnPhase,
+  WORK_COLUMN_TRANSITION_EASING,
+  WORK_COLUMN_TRANSITION_MS,
+  workColumnExpanded,
+  workColumnMounted,
+  workColumnTransitioning,
+  type WorkColumnPhase,
+} from "./work-column-presence"
+
+describe("reduceWorkColumnPhase", () => {
+  test("collapse animates through closing before unmounting", () => {
+    let phase: WorkColumnPhase = "open"
+    phase = reduceWorkColumnPhase(phase, "hide")
+    expect(phase).toBe("closing")
+    expect(workColumnMounted(phase)).toBe(true)
+    expect(workColumnExpanded(phase)).toBe(false)
+    phase = reduceWorkColumnPhase(phase, "settled")
+    expect(phase).toBe("unmounted")
+    expect(workColumnMounted(phase)).toBe(false)
+  })
+
+  test("restore mounts collapsed, then expands once settled", () => {
+    let phase: WorkColumnPhase = "unmounted"
+    phase = reduceWorkColumnPhase(phase, "show")
+    expect(phase).toBe("opening")
+    expect(workColumnMounted(phase)).toBe(true)
+    expect(workColumnExpanded(phase)).toBe(false)
+    phase = reduceWorkColumnPhase(phase, "settled")
+    expect(phase).toBe("open")
+    expect(workColumnExpanded(phase)).toBe(true)
+  })
+
+  test("reversing mid-animation keeps the column mounted and retargets", () => {
+    expect(reduceWorkColumnPhase("opening", "hide")).toBe("closing")
+    expect(reduceWorkColumnPhase("closing", "show")).toBe("opening")
+  })
+
+  test("events that do not apply to the current phase are no-ops", () => {
+    expect(reduceWorkColumnPhase("open", "show")).toBe("open")
+    expect(reduceWorkColumnPhase("unmounted", "hide")).toBe("unmounted")
+    expect(reduceWorkColumnPhase("unmounted", "settled")).toBe("unmounted")
+    expect(reduceWorkColumnPhase("open", "settled")).toBe("open")
+  })
+})
+
+describe("transition constants", () => {
+  test("uses a ~200ms ease-out style curve, not linear", () => {
+    expect(WORK_COLUMN_TRANSITION_MS).toBe(200)
+    expect(WORK_COLUMN_TRANSITION_EASING).toBe("cubic-bezier(0.22,1,0.36,1)")
+  })
+})
+
+describe("workColumnTransitioning", () => {
+  test("is true only while opening or closing", () => {
+    expect(workColumnTransitioning("opening")).toBe(true)
+    expect(workColumnTransitioning("closing")).toBe(true)
+    expect(workColumnTransitioning("open")).toBe(false)
+    expect(workColumnTransitioning("unmounted")).toBe(false)
+  })
+})
diff --git a/packages/app-bundle/overlay/packages/app/src/pages/session/work-column-presence.ts b/packages/app-bundle/overlay/packages/app/src/pages/session/work-column-presence.ts
new file mode 100644
index 000000000..bfcebd8fa
--- /dev/null
+++ b/packages/app-bundle/overlay/packages/app/src/pages/session/work-column-presence.ts
@@ -0,0 +1,42 @@
+// Presence state for the Work Column's collapse/restore animation (#1610).
+// The column is kept mounted while its width animates to 0 (closing) or from 0
+// (opening), then unmounted (or expanded) once the transition settles. Pure
+// reducer: the Solid wiring (timers, frames) lives in session.tsx.
+
+export const WORK_COLUMN_TRANSITION_MS = 200
+export const WORK_COLUMN_TRANSITION_EASING = "cubic-bezier(0.22,1,0.36,1)"
+
+export type WorkColumnPhase = "unmounted" | "opening" | "open" | "closing"
+export type WorkColumnEvent = "show" | "hide" | "settled"
+
+export function reduceWorkColumnPhase(phase: WorkColumnPhase, event: WorkColumnEvent): WorkColumnPhase {
+  switch (phase) {
+    case "unmounted":
+      return event === "show" ? "opening" : phase
+    case "opening":
+      if (event === "hide") return "closing"
+      if (event === "settled") return "open"
+      return phase
+    case "open":
+      return event === "hide" ? "closing" : phase
+    case "closing":
+      if (event === "show") return "opening"
+      if (event === "settled") return "unmounted"
+      return phase
+  }
+}
+
+/** The column stays in the DOM for every phase except fully collapsed. */
+export function workColumnMounted(phase: WorkColumnPhase): boolean {
+  return phase !== "unmounted"
+}
+
+/** Only the settled open state renders at the full column width; opening
+ * starts at 0 so the width transition has a start point, closing ends at 0. */
+export function workColumnExpanded(phase: WorkColumnPhase): boolean {
+  return phase === "open"
+}
+
+export function workColumnTransitioning(phase: WorkColumnPhase): boolean {
+  return phase === "opening" || phase === "closing"
+}