diff --git a/src/main/runtime/headless-hydration-live-overlap.test.ts b/src/main/runtime/headless-hydration-live-overlap.test.ts
new file mode 100644
index 00000000000..0f05f06f4ff
--- /dev/null
+++ b/src/main/runtime/headless-hydration-live-overlap.test.ts
@@ -0,0 +1,28 @@
+import { expect, it } from 'vitest'
+import { deferred } from './orca-runtime-test-fixtures.spec'
+import { createHydrationRuntime, PTY_ID, SIZE } from './headless-hydration-ownership-test-fixture'
+
+it('does not replay live bytes the renderer seed already painted', async () => {
+  const runtime = createHydrationRuntime()
+  const rendered = deferred<{ data: string; cols: number; rows: number; seq: number }>()
+  runtime.setPtyController({
+    write: () => true,
+    kill: () => true,
+    getForegroundProcess: async () => null,
+    getSize: () => SIZE,
+    hasRendererSerializer: () => true,
+    serializeBuffer: () => rendered.promise
+  })
+
+  // The renderer parses these while main awaits its serialization.
+  runtime.onPtyData(PTY_ID, 'LIVE-ONE\r\n', 1)
+  runtime.onPtyData(PTY_ID, '\x1b[38;5', 2)
+  runtime.onPtyData(PTY_ID, ';242mLIVE-TWO\x1b[0m\r\n', 3)
+  rendered.resolve({ data: 'HISTORY\r\nLIVE-ONE\r\n', ...SIZE, seq: 16 })
+  await runtime.model().writeChain
+
+  const screen = runtime.model().emulator.getVisibleLines().join('\n')
+  expect(screen.match(/LIVE-ONE/g)).toHaveLength(1)
+  expect(screen).toContain('LIVE-TWO')
+  expect(screen).not.toContain(';242m')
+})
diff --git a/src/main/runtime/runtime-terminal-state-records.ts b/src/main/runtime/runtime-terminal-state-records.ts
index b4841e2c8e1..e1cd456abed 100644
--- a/src/main/runtime/runtime-terminal-state-records.ts
+++ b/src/main/runtime/runtime-terminal-state-records.ts
@@ -158,6 +158,10 @@ export type RuntimeHeadlessTerminal = {
   outputSequence: number
   writeChain: Promise<void>
   ownership: PtyShellOwnershipMirror
+  /** Output seq a renderer hydration seed already painted; queued live chunks at/below it are not rewritten. */
+  rendererSeedSeq?: number
+  /** Unfinished escape from skipped seed-covered chunks, written before the next uncovered chunk. */
+  rendererSeedEscapeTail?: string
   /** The grid a reattach reflowed the model onto, until a PTY resize off it repaints the TUI. */
   unrepaintedReflowGrid?: { cols: number; rows: number }
 }
diff --git a/src/main/runtime/terminal/output/headless-terminal-hydration.ts b/src/main/runtime/terminal/output/headless-terminal-hydration.ts
index 6c8549cee89..62f26925f6a 100644
--- a/src/main/runtime/terminal/output/headless-terminal-hydration.ts
+++ b/src/main/runtime/terminal/output/headless-terminal-hydration.ts
@@ -12,6 +12,7 @@ import {
   normalizeTerminalTitle
 } from '../../../../shared/agent-detection'
 import { shouldModelAnswerHiddenPtyQueries } from '../../terminal-model-query-authority'
+import { advancePartialEscapeTail } from '../../../../shared/terminal-partial-escape-tail'
 
 export abstract class OrcaRuntimeWithMaybeHydrateHeadlessFromRenderer extends OrcaRuntimeWithSerializeMainTerminalBuffer {
   protected abstract getOrCreateHeadlessTerminal(ptyId: string): RuntimeHeadlessTerminal
@@ -84,6 +85,10 @@ export abstract class OrcaRuntimeWithMaybeHydrateHeadlessFromRenderer extends Or
         if (this.headlessTerminals.get(ptyId) !== state) {
           return
         }
+        // Why: the renderer parsed live bytes queued behind this seed while serializing; writing them again doubles TUI frames and splits escapes.
+        if (typeof rendered.seq === 'number') {
+          state.rendererSeedSeq = rendered.seq
+        }
         const ptyDims = this.getTerminalSize(ptyId)
         if (ptyDims && (ptyDims.cols !== rendered.cols || ptyDims.rows !== rendered.rows)) {
           state.emulator.resize(ptyDims.cols, ptyDims.rows)
@@ -187,6 +192,22 @@ export abstract class OrcaRuntimeWithMaybeHydrateHeadlessFromRenderer extends Or
     const completion = state.writeChain.then(async () => {
       // Capture reply ownership at ingestion, then scan inside the chain so live bytes and seeds retain total order.
       state.ownership.scan(data)
+      if (state.rendererSeedSeq !== undefined) {
+        if (outputSequence <= state.rendererSeedSeq) {
+          state.rendererSeedEscapeTail = advancePartialEscapeTail(
+            state.rendererSeedEscapeTail ?? '',
+            data
+          )
+          state.outputSequence = outputSequence
+          return
+        }
+        const escapeTail = state.rendererSeedEscapeTail
+        state.rendererSeedSeq = undefined
+        state.rendererSeedEscapeTail = undefined
+        if (escapeTail) {
+          await state.emulator.write(escapeTail)
+        }
+      }
       for (const chunk of splitFreebuffScreenUpdates(data, state.emulator.partialEscapeTailAnsi)) {
         await state.emulator.write(chunk, { forwardQueryReplies })
         const pty = this.ptysById.get(ptyId)