Perf(renderer): Coalesce contiguous fresh-record inserts in each Phase 2

[jlukic]

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Project	Deployment	Actions	Updated (UTC)
semantic-next	Ready	Preview, Comment	May 23, 2026 1:05am

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[semantic-performance-bot]

✅ Improvement for 10d0f2f on Benchmark Suite 📊

Base: main · Action: #26319233911 · Raw: bench-report.json

^{Perf(renderer): Coalesce contiguous fresh-record inserts in each Phase 2}

Tip

This PR improves ✅ 1 test.

✅ 1 faster · ❌ 0 slower · 🔍 25 unsure · ⚪ 23 no change

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✅ Faster (1)

Metrics where this PR confidently improved performance compared to main.

metric	Improvement
todo:remove-50-back	-10% (0ms)

⚪ No Change (23)

Metrics where this PR measured within ±2% of main — no meaningful performance change detected.

metric	Change
todo:add-20	-0.3% – +1.7%
renderer-micros:build-html-string-10k	-1.8% – +0.6%
todo:bulk-add-500	-0.2% – +1.0%
krausest:clear-10k	-1.9% – +0.8%
todo:clear-completed-250	-1.1% – +1.3%
krausest:create-1k	-0.4% – +1.6%
renderer-micros:dom-walker-1000x15	-1.1% – +1.7%
hydrate:each-100	-0.5% – +0.7%
hydrate:each-100-mount	-1.0% – +0.2%
template:each-mount-1000	-0.8% – +1.8%
todo:edit-start-10	-0.3% – +1.1%
renderer-micros:expr-js-10k	-0.9% – +1.8%
renderer-micros:expr-lisp-50k	-1.7% – +0.4%
renderer-micros:expr-simple-100k	-1.3% – +0.6%
todo:filter-cycle-20	-0.8% – +0.2%
hydrate:helper-100-mount	-1.1% – +0.4%
krausest:replace-1k	-0.4% – +1.3%
krausest:select-40	-0.7% – +1.1%
template:subtemplate-data-blob-100	-0.4% – +0.8%
template:subtemplate-helpers-heavy-100x500	-1.1% – +0.5%
template:subtemplate-helpers-light-100x500	-1.6% – +0.9%
template:subtemplate-shorthand-props-100x500	-1.7% – +0.9%
todo:toggle-all-200	-0.5% – +0.8%

🔍 Unsure (25)

Too Fast to Measure Precisely (25)

On benches this short, OS jitter, GC, and JIT pauses drown out anything under 4%. Bigger changes than that still show up.

metric	Change	Test Time	Expected Noise
template:active-indicator-200	-2.0% – +2.5%	~33ms	±8%
template:active-indicator-nested-200	-2.8% – +1.5%	~17ms	±7%
krausest:append-1k	-2.4% – +2.5%	~90ms	±6%
krausest:create-10k	+1.4% – +2.2%	~906ms	±1%
todo:edit-cycle-5	-1.0% – +2.5%	~64ms	±5%
hydrate:helper-100-state-change-1k	-2.3% – +1.5%	~3ms	±9%
todo:remove-50-front	-5.2% – +0.1%	~3ms	±3%
todo:remove-50-middle	-10.7% – -1.0%	~4ms	±13%
todo:remove-first-100	-2.1% – +3.1%	~14ms	±7%
todo:remove-last-100	-14.2% – +0.3%	~10ms	±20%
todo:remove-middle-100	+0.4% – +7.1%	~10ms	±9%
krausest:remove-row-back-100	-1.1% – +20.2%	~17ms	±26%
krausest:remove-row-front-20	-8.1% – +9.3%	~13ms	±20%
krausest:remove-row-middle-20	-25.4% – +3.7%	~11ms	±39%
todo:rename-500	+1.7% – +7.8%	~16ms	±10%
template:snippet-args-per-key-100x500	-2.1% – +0.2%	~32ms	±4%
template:snippet-in-subtemplate-100x1k	+0.0% – +4.9%	~21ms	±8%
template:stable-ref-mutate-500	-1.5% – +5.3%	~13ms	±11%
template:subtemplate-reactive-data-100x500	-0.6% – +2.1%	~46ms	±4%
krausest:swap-rows-20	-1.0% – +4.0%	~9ms	±6%
todo:toggle-100	-5.2% – +2.5%	~8ms	±11%
todo:toggle-first-100	-3.0% – +4.4%	~13ms	±11%
todo:toggle-last-100	-1.4% – +7.1%	~12ms	±12%
todo:toggle-middle-100	-1.4% – +3.5%	~10ms	±8%
krausest:update-10th-50	-3.8% – +2.9%	~23ms	±8%

📖 Bench glossary (49 metrics)

metric	what it tests
hydrate:each-100	Reassigns the items of a hydrated 1000-item list to a fresh array with the same keys and data.
hydrate:each-100-mount	Hydrates a server-rendered 1000-item list and waits for it to become interactive without re-rendering.
hydrate:helper-100-mount	Hydrates a 1000-item list where each item calls a helper that reads state shared across the list.
hydrate:helper-100-state-change-1k	Walks the shared activeID across every item in a hydrated 1000-item list so two items repaint per cycle.
krausest:append-1k	Appends 1000 new rows onto an existing 1000-row table.
krausest:clear-10k	Clears a 10000-row table back to empty in a single operation.
krausest:create-10k	Renders a fresh 10000-row table into an empty parent at ten times the create-1k scale.
krausest:create-1k	Renders a fresh 1000-row table into an empty parent.
krausest:remove-row-back-100	Removes the last row 100 times from a 1000-row table, with no other rows needing to move.
krausest:remove-row-front-20	Removes the first row 20 times from a 1000-row table, with all remaining rows sliding up each time.
krausest:remove-row-middle-20	Removes the middle row 20 times from a 1000-row table, with the rows below it sliding up each time.
krausest:replace-1k	Replaces 1000 rows with a fresh 1000-row set, diffing the keyed list against a populated table.
krausest:select-40	Highlights one row at a time across 40 rows so only the previous and newly highlighted rows update.
krausest:swap-rows-20	Swaps the second and second-to-last rows in a 1000-row table, repeated 20 times.
krausest:update-10th-50	Updates the label on every tenth row of a 1000-row table, looped 50 times to lift the work above noise.
renderer-micros:build-html-string-10k	Builds the HTML string for a realistic card AST 10000 times. Raw assembly throughput.
renderer-micros:dom-walker-1000x15	Runs bindMarkers across a 1000-node card fragment 15 times. TreeWalker pass and binding dispatch.
renderer-micros:expr-js-10k	Evaluates one arithmetic expression and one ternary 10000 times each. JS-eval hot path.
renderer-micros:expr-lisp-50k	Evaluates one Lisp-style helper call 50000 times. Parse-cache lookup and helper dispatch.
renderer-micros:expr-simple-100k	Evaluates one simple identifier and one dotted path 100000 times each. Property-lookup hot path.
template:active-indicator-200	Cycles selectedId across 200 list items. Only the previously and newly active items update their class.
template:active-indicator-nested-200	Cycles currentUrl through 50 leaf urls in a 5×10×4 nav. Only the previously and newly active leaves should update their…
template:each-mount-1000	Mounts a fresh 1000-item each block with five-field items so per-record allocation cost dominates the wall clock.
template:snippet-args-per-key-100x500	Mutates one snippet arg's source across 100 invocations, 500 cycles. Adjacent no-signal expressions stay quiet.
template:snippet-in-subtemplate-100x1k	Mutates one subtemplate prop's source across 25 cards each invoking 4 inner snippets, 1000 cycles. Snippet bodies shoul…
template:stable-ref-mutate-500	Replaces one item by index in a 500-item list across 100 cycles. Only that item's expressions re-render.
template:subtemplate-data-blob-100	Mutates one field inside data=expression on 100 children. Every child re-renders by design.
template:subtemplate-helpers-heavy-100x500	100 subtemplates, 4 inner bindings where three call helpers shaped like userland reality — Intl.NumberFormat, Array.fin…
template:subtemplate-helpers-light-100x500	100 subtemplates, 4 inner bindings each calling formatDate / classIf / capitalize, 500 cycles. Mutates one source signa…
template:subtemplate-reactive-data-100x500	Mutates one verbose reactiveData field across 100 child subtemplates, 500 cycles. Only the changed field re-evaluates.
template:subtemplate-shorthand-props-100x500	Mutates one shorthand prop's source across 100 child subtemplates, 500 cycles. Only that prop re-evaluates.
todo:add-20	Appends 20 todo items one at a time, like a user typing entries in a row.
todo:bulk-add-500	Renders 500 todo items added at once from a single data load.
todo:clear-completed-250	Clears 250 completed items from a 500-item list in one action, like clicking clear completed.
todo:edit-cycle-5	Runs 5 full edit-then-save cycles on different items, like editing a row and saving it.
todo:edit-start-10	Enters edit mode on 10 different items in a row, like double-clicking each one.
todo:filter-cycle-20	Cycles through active, completed, and all filters 20 times on a 100-item list.
todo:remove-50-back	Deletes 50 items from the end of a 100-item list, one click at a time.
todo:remove-50-front	Deletes 50 items from the front of a 100-item list, one click at a time.
todo:remove-50-middle	Deletes 50 items from the middle of a 100-item list, one click at a time.
todo:remove-first-100	Deletes the first item 100 times from a 200-item list, with remaining items moving up each time.
todo:remove-last-100	Deletes the last item 100 times from a 200-item list, with no other items needing to move.
todo:remove-middle-100	Deletes the middle item 100 times from a 200-item list, walking halfway through to find each target.
todo:rename-500	Renames items in a 100-item list 500 times via single-field setProperty without editingId co-fires.
todo:toggle-100	Cycles through the first 10 items 10 times each, like a user toggling items repeatedly down a list.
todo:toggle-all-200	Toggles all 100 items completed and back across 200 cycles via the master checkbox.
todo:toggle-first-100	Toggles the first item in a 100-item list 100 times, alternating completed on and off.
todo:toggle-last-100	Toggles the last item in a 100-item list 100 times, alternating completed on and off.
todo:toggle-middle-100	Toggles a middle item in a 100-item list 100 times, alternating completed on and off.

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_{Sample size: 80 floor / 280 max · Noise floor: ±2% · Timeout: 3min · Wall-clock: 9m39s}