diff --git a/src/main/runtime/mobile-subscribe-idle-pane-hydrate.test.ts b/src/main/runtime/mobile-subscribe-idle-pane-hydrate.test.ts
index 023d6d3ba09..219ec7a94e6 100644
--- a/src/main/runtime/mobile-subscribe-idle-pane-hydrate.test.ts
+++ b/src/main/runtime/mobile-subscribe-idle-pane-hydrate.test.ts
@@ -48,12 +48,19 @@ async function screenOn(grid: { cols: number; rows: number }): Promise<string> {
   }
 }
 
-function setup(opts: { paneMounted: boolean; providerSnapshot?: boolean }) {
+function setup(opts: {
+  paneMounted: boolean
+  providerSnapshot?: boolean
+  repaintOnResize?: boolean
+}) {
   const sizes = new Map([[PTY_ID, { ...DESKTOP }]])
-  const serializeBuffer = vi.fn(async () =>
-    opts.paneMounted ? { data: await screenOn(DESKTOP), ...DESKTOP } : null
-  )
   const runtime = new OrcaRuntimeService()
+  // The pane orders its screen against PTY output, as a mounted desktop xterm does.
+  const serializeBuffer = vi.fn(async () =>
+    opts.paneMounted
+      ? { data: await screenOn(DESKTOP), ...DESKTOP, seq: runtime.getPtyOutputSequence(PTY_ID) }
+      : null
+  )
   runtime.setPtyController({
     write: () => true,
     kill: () => true,
@@ -61,6 +68,10 @@ function setup(opts: { paneMounted: boolean; providerSnapshot?: boolean }) {
     getSize: (ptyId: string) => sizes.get(ptyId) ?? null,
     resize: (ptyId: string, cols: number, rows: number) => {
       sizes.set(ptyId, { cols, rows })
+      if (opts.repaintOnResize) {
+        // A TUI answering SIGWINCH before the subscribe reaches its own hydrate.
+        runtime.onPtyData(ptyId, '\x1b[?25h', Date.now())
+      }
       return true
     },
     hasRendererSerializer: () => opts.paneMounted,
@@ -178,6 +189,16 @@ describe('phone subscribe to an idle PTY whose hidden pane sits at desktop size'
     expect({ cols: resubscribed.cols, rows: resubscribed.rows }).toEqual(PHONE)
   })
 
+  it('joins a hydrate the resize repaint already started', async () => {
+    const { runtime, handle, serializeBuffer } = setup({ paneMounted: true, repaintOnResize: true })
+
+    const snapshot = await firstSnapshot(runtime, handle)
+
+    expect({ cols: snapshot.cols, rows: snapshot.rows }).toEqual(PHONE)
+    expect((await paintedRows(snapshot)).slice(0, 4)).toEqual(EXPECTED_PHONE_ROWS)
+    expect(serializeBuffer).toHaveBeenCalledTimes(1)
+  })
+
   it('keeps serving the model on resubscribe without re-reading the pane', async () => {
     const { runtime, handle, serializeBuffer } = setup({ paneMounted: true })
     await firstSnapshot(runtime, handle)
diff --git a/src/main/runtime/orca-runtime-fit-override-listeners.ts b/src/main/runtime/orca-runtime-fit-override-listeners.ts
index 5ef17ce4c2e..f738c81eec5 100644
--- a/src/main/runtime/orca-runtime-fit-override-listeners.ts
+++ b/src/main/runtime/orca-runtime-fit-override-listeners.ts
@@ -130,6 +130,8 @@ export class OrcaRuntimeWithFitOverrideListeners extends OrcaRuntimeWithStopRequ
   // Absent  → hydration has not been considered yet for this PTY.
   // See docs/mobile-prefer-renderer-scrollback.md.
   protected headlessHydrationState = new Map<string, 'pending' | 'done'>()
+  /** The model's renderer seed, resolving true once written; lives as long as the model. */
+  protected rendererSeedsByPtyId = new Map<string, Promise<boolean>>()
 
   // Why: mobile-fit overrides are keyed by ptyId (not terminal handle) because
   // handles can be reissued while the PTY identity is stable. In-memory only —
diff --git a/src/main/runtime/orca-runtime-maybe-hydrate-headless-from-renderer.ts b/src/main/runtime/orca-runtime-maybe-hydrate-headless-from-renderer.ts
index 20139787b3c..37eaf950d82 100644
--- a/src/main/runtime/orca-runtime-maybe-hydrate-headless-from-renderer.ts
+++ b/src/main/runtime/orca-runtime-maybe-hydrate-headless-from-renderer.ts
@@ -110,13 +110,20 @@ export class OrcaRuntimeWithMaybeHydrateHeadlessFromRenderer extends OrcaRuntime
         }
       }
     })
-    return state.writeChain.then(() => seeded)
+    const seed = state.writeChain.then(() => seeded)
+    this.rendererSeedsByPtyId.set(ptyId, seed)
+    return seed
   }
 
   /** Public: a phone fit resizes the PTY, but an idle TUI sends no byte to hydrate on. Resolves
    *  true once the model holds the pane's screen reflowed onto the PTY's current grid. */
   hydrateHeadlessTerminalFromRenderer(ptyId: string): Promise<boolean> {
-    return this.maybeHydrateHeadlessFromRenderer(ptyId) ?? Promise.resolve(false)
+    // Why join: a resize repaint can run the on-data seed first; its result answers this caller too.
+    return (
+      this.maybeHydrateHeadlessFromRenderer(ptyId) ??
+      this.rendererSeedsByPtyId.get(ptyId) ??
+      Promise.resolve(false)
+    )
   }
 
   // Why: seed-derived agent status reflects historical state. Orchestration
diff --git a/src/main/runtime/orca-runtime-serialize-headless-terminal-buffer.ts b/src/main/runtime/orca-runtime-serialize-headless-terminal-buffer.ts
index 673c31167f4..5d985f2c78a 100644
--- a/src/main/runtime/orca-runtime-serialize-headless-terminal-buffer.ts
+++ b/src/main/runtime/orca-runtime-serialize-headless-terminal-buffer.ts
@@ -75,6 +75,7 @@ export class OrcaRuntimeWithSerializeHeadlessTerminalBuffer extends OrcaRuntimeW
 
   protected disposeHeadlessTerminal(ptyId: string): void {
     this.headlessHydrationState.delete(ptyId)
+    this.rendererSeedsByPtyId.delete(ptyId)
     const state = this.headlessTerminals.get(ptyId)
     if (!state) {
       return
diff --git a/src/main/runtime/pty-exit-per-pty-map-reaper-ratchet.test.ts b/src/main/runtime/pty-exit-per-pty-map-reaper-ratchet.test.ts
index 8f1f6035dd8..e8362c0fb94 100644
--- a/src/main/runtime/pty-exit-per-pty-map-reaper-ratchet.test.ts
+++ b/src/main/runtime/pty-exit-per-pty-map-reaper-ratchet.test.ts
@@ -41,6 +41,10 @@ const CLEARED_BY_REAPER_HELPER: Record<string, { helper: string; module: string
   agentPromptPermissionSequenceByPtyId: {
     helper: 'advancePtyLifecycleGeneration',
     module: 'src/main/runtime/orca-runtime-record-agent-prompt-lifecycle-state.ts'
+  },
+  rendererSeedsByPtyId: {
+    helper: 'disposeHeadlessTerminal',
+    module: 'src/main/runtime/orca-runtime-serialize-headless-terminal-buffer.ts'
   }
 }