perf: avoid discarded replay and scrollback splice results

[onmax]

After their buffers fill, RPC replay and terminal scrollback discard an array returned by splice on each new chunk. Use shift when exactly one entry must be removed. Keep splice for other overflows, including fractional replay windows and oversized supplied scrollback buffers.

 buffer exceeds its limit by one
-  splice(0, 1), discard the returned array
+  shift()
 other overflow values
   keep splice()

For each buffer, 10,000 writes with a 1,000-entry limit produce 9,000 discarded splice results before and 0 after. The retained entries, order, and buffer identity stay the same.

Reproduction	Before	After
RPC replay	Before	After
Terminal scrollback	Before	After

Run locally on Node 24.19.0 with Corepack. Each pair tests the same published package version with and without a committed package patch. The terminal fixture drives the real stream pump with a recording sink; it does not spawn a PTY.

Copy and run both comparisons

for repro in devframe-replay-buffer-eviction devframe-terminal-scrollback; do
  (
    set -e
    git clone --depth 1 --filter=blob:none --sparse --branch "repro/$repro" https://github.com/onmax/repros.git "$repro-repro"
    cd "$repro-repro"
    git sparse-checkout set "$repro" "$repro-fix"
    cd "$repro"
    corepack pnpm install --frozen-lockfile --ignore-scripts
    corepack pnpm verify
    cd "../$repro-fix"
    corepack pnpm install --frozen-lockfile --ignore-scripts
    corepack pnpm verify
  ) || exit 1
done

[coldtea-pr-lens]

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🟢 +0 new · 🟠 ~2 changed · 🔴 -0 removed · 1 flow · 4 files · commit 618e1cb

Architecture

2 components touched across 3 lanes.

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Data flow

Terminal stream output and buffer eviction

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Drill down

Hub Orchestration — 1 component

🟡 CHANGED Hub Terminals Subsystem

Drains terminal process and PTY output into session scrollback buffers and RPC streaming channels, using shift for single-chunk eviction.

• packages/hub/src/node/host-terminals.ts:159-166
• packages/hub/src/node/__tests__/host-terminals.test.ts:182-230

Devframe Core — 1 component

🟡 CHANGED Streaming Channel Sink

Implements server-side stream sinks with bounded replay buffers, evicting single overflow chunks via shift to prevent splice allocations.

• packages/devframe/src/utils/streaming-channel.ts:151-160
• packages/devframe/src/utils/streaming-channel.test.ts:64-82

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1 Skipped Deployment

Project	Deployment	Actions	Updated
devframe	Skipped		Sep 5, 2026 6:40am UTC