Compare stored automation bits across the browser and native hosts

Proposed by Research: render stored session automation in the engine, identically on every
platform (#1058), answer A5, under decision 15 D15-16
(docs/rulings/live-updates-seamless-swaps-and-one-control-plane-2026-10-05.md). A draft for root
to file. Code anchors verified on 6ee64f484. Batch Q.

Product outcome

One fixture session automates every row the engine renders, with every shape, and is seeked once
while it plays. The shipped browser artifact (wasm simd128) and the native browser host on
x86-64 (AVX2) render it to the same bits, and the C ABI renders the same bits as the browser host.
A second fixture does the same for matrix automation. This is the browser and x86-64 half of the
evidence that stored automation renders identically on every platform; #1670 adds AArch64 and
seek-time invariance on the same fixtures. It adds no new digest owner: it extends the direct
oracle's existing pins. Batch Q.

Context

The existing owners.

• The G5 corpus is the single owner of the kernels' cross-target digests
  (tools/wasm-gate-corpus/src/lib.rs:1-20), run natively by wasm-gates and under wasmtime.
  Compile stored automation into per-cell events in node time #1637 adds the evaluator's event values to it.
• The browser direct oracle renders fixed sessions through the shipped simd128 artifact
  (hosts/host-web/tests/browser-v1/direct-oracle.mjs:547-679). Each leg asserts its PCM digest
  equals a native pin before anything prints (the identity leg, :571-583; the command timeline,
  :584-601; the observation timeline, :602-654).
• Each native pin is written by a host-web test that renders the same session and transcript
  through AudioWorkletEngineHost on the host CPU and reads the pin from expected.json
  (native_identity_session_digest_pins_the_wasm_parity, hosts/host-web/src/tests.rs:1632;
  the command and observation twins at :1751 and :6690; the pin reader serde_pin,
  :2255-2300).
• CI runs the oracle in the artifact-gates job through scripts/check-web-audioworklet.sh and
  scripts/check-browser-expected-resources.py --artifacts
  (.github/workflows/qualification.yml:331-343).

What the oracle drives today. The command timeline feeds constant PCM and drives live
commands (direct-oracle.mjs:373-454). No leg has stored automation or a session seek.

The C ABI. No test compares a C ABI render with the browser host's today. #1399 adds the
cross-host harness hosts/host-web/tests/strip_cells_cross_host.rs.

Decisions frozen for this slice

• D1. Two fixtures, beside the existing ones in hosts/host-web/tests/browser-v1/:
  • automation-session.json: two tracks and one submix at 48 kHz, quantum 128. Track 1 automates
    fader, mute, pan, trim, polarity, HPF and LPF on its lanes (one both entry and one
    single-lane entry among them), and has a pre-fader route into the submix with
    follows_mute. Its inserts carry every span-driven launch effect (compressor, delay with its
    time automated, gate/expander, multiband compressor, soft clip, transient shaper, true-peak
    limiter) and a parametric EQ, each with at least one automated Block parameter. Track 2 has
    the same chain with no automation, so a bank holds automated and plain lanes.
  • Across the entries: step, linear and exponential segments (exponential only where a rule
    allows it: Validate builtin automation targets against their rows at preparation #1645's for the input HPF and LPF, Validate builtin automation targets against their rows at preparation #1645's shape rule for an effect frequency, time or
    ratio row), a gap, a step on a sample that is not a grid
    sample, and a segment that starts before the seek target.
  • automation-matrix-session.json: one matrix strip whose four coefficients are automated.
• D2. One transcript. Both fixtures render 96 blocks of PCM generated by an integer formula
  that is exact in f32 in Rust and in JavaScript, for example
  x[i] = ((i·40503) mod 65536 − 32768) / 65536. At block 40 the host makes one session seek to
  timeline 30,000 (Seek the timeline and every source from the browser module export and the headless SDK #1643's export in the oracle, the same control-plane call natively).
• D3. The browser leg. direct-oracle.mjs gains runAutomationTimeline for each fixture. It
  asserts each digest equals expected.directOracle.nativeAutomationPcmF32leSha256 and
  nativeAutomationMatrixPcmF32leSha256 before any print, as the existing legs do. The pins are
  written by two new host-web tests beside :1632, which serde_pin extends to read. Compare stored automation bits on AArch64 and across seek times #1670
  reuses these two tests and pins.
• D4. The C ABI equals the browser host. In Report live_values_superseded in the browser status and prove both hosts drain strip cells alike #1399's cross-host test, both fixtures and the
  transcript render through the C ABI (Seek the timeline and every source in one C ABI call #1642's miso_engine_v1_session_seek) and through
  AudioWorkletEngineHost, and the two outputs are compared bit for bit in the test. No digest.
• D5. One-ulp evidence (PR evidence, not committed). Plant a one-ulp change in Compile stored automation into per-cell events in node time #1637's
  value_at result. Record that the two native pin tests, the oracle's simd128 legs, the
  cross-host test (when the plant reaches only one host's path, as a check of the comparison) and
  the G5 corpus each turn red, then revert.

Deliverables

1. D1-D2's fixtures and transcript.
2. D3: the oracle legs, the two native pin tests and the expected.json pins.
3. D4's test cases.
4. D5's record in the PR.

Authorized paths

• hosts/host-web/tests/browser-v1/ (the two fixtures, direct-oracle.mjs, expected.json).
• hosts/host-web/src/tests.rs (two pin tests and serde_pin).
• hosts/host-web/tests/strip_cells_cross_host.rs (D4's cases).

Non-goals

• Any engine change. A leg that disagrees is a defect for its own issue, recorded here with its
  first differing sample.
• AArch64 and seek-time invariance (Compare stored automation bits on AArch64 and across seek times #1670).
• A new digest owner, or a digest of a rendered session outside expected.json.
• Timing (Build the stored-automation console benchmark row #1671, Record the stored-automation console benchmark baseline #1672). Listening tests.
• Live edits during the fixture: Classify fader automation edits as carried rebuilds #1648, Compose VCA offsets with stored fader automation #1649, Write a following send's route cell from the shared commit #1653, Render stored pan and matrix automation #1657, Render stored input HPF and LPF automation #1660, Classify and carry effect automation edits #1665 and Render stored parametric EQ automation #1667 gate them.

Hazards

• Pin discipline. A pin is written only from a native render the simd128 leg already equals
  (the oracle asserts before it prints). Never mint a pin from one side.
• The browser job. Its Playwright legs replay expected.json; a new key must not break
  scripts/check-browser-expected-resources.py's two-class rule (pins exact, resources
  ceilinged).
• Hot files. hosts/host-web/src/tests.rs and expected.json are stream H's. Root sequences
  the merge.

Objective gates

1. Browser equals native.
   mkdir -p target/ci/qualification-artifacts target/ci/qualification-named-twin && bash scripts/build-web-audioworklet.sh --named-twin target/ci/qualification-named-twin target/ci/qualification-artifacts,
   then
   bash scripts/check-web-audioworklet.sh --without-metadata-regeneration target/ci/qualification-artifacts target/ci/qualification-named-twin/miso-engine-v1-audio-worklet.simd128.named.wasm
   and python3 -B scripts/check-browser-expected-resources.py --artifacts target/ci/qualification-artifacts
   pass with both automation legs.
2. Native pins. cargo test --locked -p host-web --features test-support passes, the two new
   pin tests and D4's cross-host cases included.
3. One ulp turns every leg red (D5, PR evidence).
4. Workspace. The test-debug-a workspace step of qualification.yml;
   cargo test --locked --release -p lane -p math -p wasm-gates --features math/lane (G5);
   cargo fmt --all -- --check;
   cargo clippy --locked --workspace --all-targets --all-features -- -D warnings.

Test value

• The automation legs turn red if any row's events, designs or ramps differ between wasm and
  native: a platform transcendental in the evaluator, a fused multiply-add, an FP environment left
  unpinned at preparation (finding F11), or a grid on the render clock.
• The cross-host test turns red if the C ABI and the browser host prepare or seek a session
  differently, which no test compares today.

Dependencies

Batch Q. Direct dependencies:

• Write a following send's route cell from the shared commit #1653 Write a following send's route cell from the shared commit (it brings Render stored mute automation on the strip #1651 and Follow an automated mute on following sends in render #1652).
• Render stored pan and matrix automation #1657 Render stored pan and matrix automation.
• Render stored input trim and polarity automation #1658 Render stored input trim and polarity automation.
• Render stored input HPF and LPF automation #1660 Render stored input HPF and LPF automation.
• Render stored parametric EQ automation #1667 Render stored parametric EQ automation.
• Report live_values_superseded in the browser status and prove both hosts drain strip cells
  alike (Report live_values_superseded in the browser status and prove both hosts drain strip cells alike #1399): the cross-host harness.

#1651, #1642 Seek the timeline and every source in one C ABI call, #1643 Seek the
timeline and every source from the browser module export and the headless SDK and #1637
Compile stored automation into per-cell events in node time (D5's plant, G5's case) arrive
through those drafts. #1670 Compare stored automation bits on AArch64 and across seek times
depends on this draft.

Amendment (controls coordinator, 2026-10-14)

Checked against 12d4a4f9d.

• The cross-host harness is hosts/host-web/tests/control_parity.rs (Prove that both hosts give the same result for the same control edits #1560);
  strip_cells_cross_host.rs is gone. Report live_values_superseded in the browser status and prove both hosts drain strip cells alike #1399 has landed.
• The fixtures add a fader offset (Store a hand move on an automated fader as a dB offset #1650), a hand mute over a mute curve (Render stored mute automation on the strip #1651 amended) and a send
  ride (Render stored send gain, mute and matrix automation #1654); depend on Store a hand move on an automated fader as a dB offset #1650 and Render stored send gain, mute and matrix automation #1654.
• Native pin tests in hosts/host-web/src/tests.rs have moved; re-read at filing.

Amendment (controls coordinator, batch 20, 2026-10-17): narrowed to the delivered rows

Checked against e7722bd19. The owner narrowed this issue on 2026-10-17. This amendment replaces
D1-D5, the authorized paths, the gates, the test value and the dependencies above, and the
amendment of 2026-10-14.

Product outcome (narrowed)

One fixture session automates the rows that the engine renders today: the strip fader, the strip
mute, the VCA offset, the VCA mute, and a following send that tracks its source's mute and its
VCA's mute. It uses every shape that each row accepts, and it is seeked once while it plays. The
shipped simd128 artifact (the direct oracle), the native browser host on x86-64
(AudioWorkletEngineHost) and the C ABI render the same bits. There is no new digest owner. The
oracle leg adds one pin beside the existing pins in expected.json.

What the code accepts (anchors at e7722bd19)

• Grammar. An entry is {id, target, segments, offset} (crates/session/src/parse.rs:1569-1604).
  The target is {owner, owner_id, section, control, lane} (:1606-1646). A segment is
  {shape, start_sample, end_sample, start_value, end_value, unit} (:1690). Sample times are
  JSON strings.
• Rows. Strip fader: strip, builtins, control 5. Strip mute: control 6
  (crates/controls/src/builtin_rows.rs:29-30). VCA offset: vca, own, control 1. VCA mute:
  control 2 (crates/controls/src/vca.rs:14-15). Only these four rows compile to cells
  (crates/controls/src/automation.rs:394-408). A route-row entry is kept but inert (Render stored send gain, mute and matrix automation #1654).
• Shapes. step is always valid. linear needs a continuous row. exponential needs a
  continuous row above 0 that is not in dB (crates/controls/src/automation.rs:255-266). So the
  fader and the VCA offset take step and linear, the two mutes take step only (unit
  linear, values 0 and 1), and exponential is refused on all five rows with
  control.automation.shape.
• Structure (crates/session/src/validate.rs). Segments are ordered and do not overlap
  (:1023, :1031). Gaps are valid. The jumps of one entry are at least 64 samples apart
  (:1070-1134). One entry per lane, and both claims the two lanes (:1141-1185). The hold
  rule is in docs/SESSION_SCHEMA_V1.md:339-345: a step holds start_value and takes
  end_value at end_sample.
• Offsets. The stored hand-move offset (Store a hand move on an automated fader as a dB offset #1650) is offset.{left_db,right_db}. A lane that the
  entry drives on the fader or VCA offset row takes a value in [-144, 24] dB. Every other lane
  holds exactly +0.0 (docs/SESSION_SCHEMA_V1.md:363-371).
• Known-good shapes. fixtures/session/v1/builtins-automation.json (fader :174-197, VCA
  offset :294-318, VCA members :106-118, a following send :129-148). Mute entries:
  hosts/host-web/tests/stored_mute_automation.rs:184-207. VCA mute:
  crates/host-core/tests/stored_vca_automation.rs:161-184.

D1 (replaced). One fixture: hosts/host-web/tests/browser-v1/automation-session.json

Copy the frame of command-session.json (48 kHz, quantum 128, profiles, main-out, default
smoothing). Then:

• Sources. src-t1 and src-t2, 2 channels, 32f, frames "48000". A seek clamps a
  source to [0, frames] (crates/host-core/src/source.rs:37-39), so the frames must be more
  than 37,168.
• Tracks. t1 on src-t1 and t2 on src-t2. No console slot, no insert, no input
  filter. Static faders at 0 dB, all hand mutes false.
• Submix. bus, with the plain builtins of builtins-automation.json:68-118.
• VCA. vca, members ["t1", "t2"], static fader.left_db -2.0 (the static offset on the
  left lanes), all other static values zero or false.
• Routes. t1-main and t2-main (post_pan to main-out). t1-bus (pre_fader to bus,
  follows_mute: true). t2-bus (pre_fader to bus, follows_mute: false, the
  non-following contrast). bus-main (post_pan to main-out).
• Entries (values in dB for the dB rows, 0 or 1 for the mutes):
  • t1-fader, t1 control 5, lane both, offset {left_db: -1.5, right_db: 0.0}:
    linear 256-2304, 0 to -12; a gap; step 3001-3601, -6 then -9 (3001 and 3601 are not grid
    samples); linear 29000-33000, -9 to +3; step 34000-35000, 0 then -3.
  • t1-mute, t1 control 6, lane left: step 0-1000, 0 then 1; step 1600-4200, 0 then 1;
    step 4800-29800, 0 then 1; step 30600-33500, 0 then 1; step 34000-36000, 0 then 0. Muted over
    1000-1600, 4200-4800, 29800-30600 and 33500-34000.
  • t2-fader, t2 control 5, lane right, offset {left_db: 0.0, right_db: 0.0}: linear
    1024-4096, -3 to 0; linear 29900-32000, 0 to -18.
  • vca-offset, vca control 1, lane right, offset {left_db: 0.0, right_db: -0.5}: linear
    512-3584, 0 to -6; step 4096-4352, +2 then 0; linear 29500-31500, -4 to +2; step 33000-35500,
    -3 then -3.
  • vca-mute, vca control 2, lane both: step 0-2000, 0 then 1; step 2400-30200, 0 then 1;
    step 30400-35000, 0 then 1; step 35500-36000, 0 then 0. Muted over 2000-2400, 30200-30400
    and 35000-35500 (review fold 1, M1: the seek target 30,000 and the step at 3001 are outside
    every VCA mute hold, so their landings are heard).
• What this covers. A both entry and single-lane entries. Lanes driven by their own curve,
  by a VCA curve, by both, and plain lanes. Linear segments, steps on and off the grid, gaps, a
  hold before the first segment and after the last one, and non-zero stored offsets. Each entry
  has a segment that starts before the seek target 30,000 and ends after it, and events after the
  seek. The following send closes for the strip mute (left lane only) and for the VCA mute. The
  non-following send stays open.
• Dropped. The matrix fixture, effect inserts, and every other row (phase 2, below).

D2 (replaced). One transcript

• 96 blocks of 128 frames. Blocks 0-39 render timeline 0-5,119. Before block 40 renders, the host
  makes one plain session seek: generation 2, timeline 30,000. Blocks 40-95 render timeline
  30,000-37,167.
• Before each render, submit exactly one 128-frame chunk per source (the oracle's ring holds one
  quantum, direct-oracle.mjs:96). Block k < 40: generation 1, start frame k*128. Block
  k >= 40: generation 2, start frame 30000 + (k-40)*128. final is always false. Do not
  submit a generation-1 chunk for block 40. A seek discards stale chunks and needs contiguous new
  chunks from the seek frame (crates/source/src/lib.rs:1162-1168, :1355-1381).
• PCM at source frame f: ((f*m) mod 65536 - 32768) / 65536, with m = 40503 (src-t1 left),
  30011 (src-t1 right), 52153 (src-t2 left), 18749 (src-t2 right). The value is exact in
  f32. In Rust, compute (f as u32).wrapping_mul(m) & 0xffff in integers, then subtract 32768
  and divide by 65536.0 (plain i32 multiplication overflows). In JavaScript,
  (Math.imul(f, m) >>> 0) & 0xffff gives the same integer.
• The seek: miso_engine_web_v1_session_seek(handle, 2, 30000n) in the oracle
  (hosts/host-web/src/ffi.rs:3351), host.session_seek(None, 2, 30000, None) natively
  (hosts/host-web/src/lib.rs:3756), and miso_engine_v1_session_seek(session, 2, 30000) on the
  C ABI (crates/capi/src/ffi.rs:660). All three reach SessionState::session_seek
  (crates/control-plane/src/control.rs:4327). A plain seek declares a discontinuity and
  publishes a successor plan, on every host alike. Every seek and every submit must return 0.

D3 (replaced). One oracle leg and one pin

• direct-oracle.mjs gains runAutomationTimeline. It boots automation-session.json, runs D2
  and digests the PCM as the other legs do (pcmSha256, every left block then every right block).
  It records actual.automationTimeline = {blocks: 96, seekBlock: 40, seekTimelineSample: 30000, beforeDisposeStatus, pcmF32leSha256}. Before the print branch, it asserts that the digest
  equals expected.directOracle.nativeAutomationPcmF32leSha256, as the other legs do
  (:493-576).
• The pin key is directOracle.nativeAutomationPcmF32leSha256. Put automationTimeline and
  the pin after observationTimeline in expected.json.
• The native pin test is native_automation_timeline_digest_pins_the_wasm_parity in
  hosts/host-web/src/tests.rs, beside its twin at :2016. It copies that twin: include_str!
  of the fixture, AudioWorkletEngineHost::boot with source_ring_frames: QUANTUM,
  submit_source, render_next, the same digest. It asserts against both pins.
• serde_pin (:2120-2164) gains two fields: the text after "nativeAutomationPcmF32leSha256":,
  and the "pcmF32leSha256": after the anchor "automationTimeline".
• scripts/check-browser-expected-resources.py adds ("automationTimeline", "pcmF32leSha256")
  to DIGEST_PATHS (:121-125) and says four PCM digests in its docstring (:33-35). The two-class
  rule covers resource rows only, so the new key needs no class. The oracle (:599) and the
  script (:274-283) compare the whole document, so expected.json, the oracle and the script
  change in one commit. No other reader breaks: qualification/qualification.js:1131-1132 and
  run.mjs:204-207 read only the identity pins.

D4 (replaced). One cross-host case in hosts/host-web/tests/control_parity.rs

• the_automation_fixture_renders_alike_on_both_hosts_across_one_session_seek. The browser side
  boots the fixture bytes through Rig::boot (tests/common/mod.rs:363-385). The C ABI side
  parses the same bytes with parse_session_json and builds CAbi::new
  (control_parity.rs:922-975).
• It runs D2 with CAbi::session_seek (:4949-4972) and direct submits, as
  a_composed_stored_mute_renders_alike_on_both_hosts does (:3694-3741). Do not use step():
  it hard-codes generation 1 (common/mod.rs:454-475).
• It compares every block's two planes with bits() (common/mod.rs:287-289) and assert_eq!.
  No digest. The case is under test-support.

D5 (replaced). The plants (PR evidence, not committed)

A plain one-ulp change to the result of value_at alone is not valid. The program builder
compares value_before with value_at to find jumps (crates/automation/src/program.rs:330), so
the change adds jumps and can make preparation refuse the session. Use these three plants, one at
a time, and record each leg's result:

• P1, the evaluator (every row). Put f32::from_bits(v.to_bits() + 1) on every return of
  value_at (crates/automation/src/evaluate.rs:18-44) and of value_before
  (crates/automation/src/program.rs:338-358). The jumps stay the same. A mute value of 0.0
  becomes the least subnormal, so every open mute span, VCA mute span and follow gate closes
  (value != 0.0: crates/builtins-compiler/src/lib.rs:3252;
  crates/graph/src/runtime.rs:1480-1481, :2196). The FP environment keeps subnormals on every
  target (crates/lane/src/fpenv.rs:518-530). Expected red: the native pin test, the oracle leg,
  and G5 (g5_native_digests_match_pins and the wasm leg; crates/automation/src/corpus.rs:245).
  Expected green: D4 (the path is shared).
• P2, the dB rows. On a dB row a P1 ulp can disappear (in db_gain, or in
  vca_compose_db). Put next_up on the output of db_gain
  (crates/builtins/src/lib.rs:6472-6479). It reaches every fader and VCA offset lane. Expected
  red: the native pin test and the oracle leg.
• P3, one host only (does D4 compare?). After state.render returns Ok in
  miso_engine_v1_render_f32_planar (crates/capi/src/ffi.rs:1133), flip the low bit of the
  first left sample when absolute_sample >= 5120. Expected red: D4 at block 40. Expected green:
  the pin test and the oracle leg.

Hand-written tests that compute their expected values with value_at stay green under P1 (for
example crates/host-core/tests/stored_fader_automation.rs:578). Do not count them.

Authorized paths (replaced)

• hosts/host-web/tests/browser-v1/automation-session.json (new), direct-oracle.mjs,
  expected.json.
• hosts/host-web/src/tests.rs (one pin test, serde_pin).
• hosts/host-web/tests/control_parity.rs (D4).
• scripts/check-browser-expected-resources.py (DIGEST_PATHS and the docstring only).

Objective gates (replaced)

1. Browser equals native. As on main (.github/workflows/qualification.yml:132, :345-348):
   mkdir -p target/ci/qualification-artifacts target/ci/qualification-named-twin && bash scripts/build-web-audioworklet.sh --named-twin target/ci/qualification-named-twin target/ci/qualification-artifacts,
   then
   bash scripts/check-web-audioworklet.sh --without-metadata-regeneration target/ci/qualification-artifacts target/ci/qualification-named-twin/miso-engine-v1-audio-worklet.simd128.named.wasm
   and python3 -B scripts/check-browser-expected-resources.py --artifacts target/ci/qualification-artifacts
   pass with the automation leg. python3 -B scripts/check-browser-expected-resources.py --self-test
   passes.
2. Native pin and cross-host. cargo test --locked -p host-web --features test-support passes,
   with the new pin test and the D4 case.
3. Plants (D5, PR evidence): P1, P2 and P3 each give the expected red legs.
4. Workspace. The test-debug-a step (qualification.yml:631-638); G5,
   cargo test --locked --release -p lane -p math -p wasm-gates --features math/lane (:705-706);
   cargo fmt --all -- --check;
   cargo clippy --locked --workspace --all-targets --all-features -- -D warnings.

Test value (replaced)

• The oracle leg and its pin turn red if the simd128 artifact renders an event, a
  composition (fader with VCA offsets, mute OR, the follow gate) or the landing of a plain session
  seek differently from x86-64 native. Today the only artifact-versus-native renders have empty
  automation (session.json:62, command-session.json:141, observation-session.json:159).
• The D4 case turns red if the C ABI and the browser host prepare the whole fixture or land
  its seek differently. Today the only cross-host case with a seek automates the mute row only
  (control_parity.rs:3571), and the VCA cases do not seek (:6916-7395).

Dependencies (replaced): all on main

• Compile stored automation into per-cell events in node time #1637 and Hold the automation jump lengths in a plan cell #1639 (PR Controls batch 13b: stored-automation start (#1635-#1639), core-owned observation addressing and limits (#1676-#1678) #1687), Validate builtin automation targets against their rows at preparation #1645 (PR Controls batch 14a: exact-byte observation admission, automation target checks at preparation, master strip after boot (#1685, #1645, #1686, #1683) #1692), Seek the timeline and every source in one C ABI call #1642 and Seek the timeline and every source from the browser module export and the headless SDK #1643 (PR Controls batch 16b: seek the session in one step on both hosts, behind a publish fence #1708), Prepare stored fader automation and render it flat #1646-Store a hand move on an automated fader as a dB offset #1650 (PR
  Controls batch 17: stored fader automation renders on both hosts, with VCA offsets and hand moves #1712), Render stored mute automation on the strip #1651-Write a following send's route cell from the shared commit #1653 (PR Controls batch 18: stored mute automation, and following sends that track it in render #1715), Render stored VCA offset and mute automation #1655 (PR Controls batch 19b: stored VCA offset and mute automation, composed with each member's own curves #1719). The harness work Report live_values_superseded in the browser status and prove both hosts drain strip cells alike #1399 and Prove that both hosts give the same result for the same control edits #1560 is closed.
  All of these issues are closed on GitHub.
• The fixture has no live edit. A stored offset (Store a hand move on an automated fader as a dB offset #1650) is a field of the entry. A hand mute
  (Render stored mute automation on the strip #1651) is the static fader.*_mute and would OR to a constant mute, so the fixture keeps it
  false. The live hand mute over a curve is already compared across hosts at :3571.
• Compare stored automation bits on AArch64 and across seek times #1670 depends on this issue. Its spec names two fixtures and two pin tests; it needs a matching
  amendment (one fixture, one pin test).

Phase-2 extensions (not in this issue)

• The matrix fixture automation-matrix-session.json and pan and matrix automation (Render stored pan and matrix automation #1657).
• Input trim and polarity (Render stored input trim and polarity automation #1658), input HPF and LPF (Render stored input HPF and LPF automation #1660), parametric EQ (Render stored parametric EQ automation #1667), and every
  other effect-parameter row, with effect inserts in the fixture.
• Send-row (route-row) automation (Render stored send gain, mute and matrix automation #1654, behind Land a removed send row exactly across a live move #1718).
• A following send at a latent tap (an insert with latency) in the oracle fixture.
• AArch64 and seek-time invariance stay in Compare stored automation bits on AArch64 and across seek times #1670.

Decision record: T1+T2 (batch 20)

• D1 shipped as written. hosts/host-web/tests/browser-v1/automation-session.json has the
  amendment's sources, tracks, submix, VCA, five routes and five entries with no departure. Every
  value was accepted: the "0 then 0" and "-3 then -3" steps, the 64-sample jump spacing and the
  VCA both mute lane all parse, validate and prepare (the native pin test boots the file
  verbatim). Track pan is left -1.0, right 1.0, smoothing_samples 0 and the bus matrix is the
  identity with smoothing_samples 0, as in command-session.json and builtins-automation.json.
  The two content digests are placeholders of the valid form (the engine streams the PCM).
• D2. One transcript helper, automation_transcript in hosts/host-web/src/tests.rs, and its
  JS twin in runAutomationTimeline: the same integer formula and chunk schedule. Every seek,
  submit and render returns 0 and is asserted on both sides.
• D3. Pin test native_automation_timeline_digest_pins_the_wasm_parity; serde_pin reads
  nativeAutomationPcmF32leSha256 and the pcmF32leSha256 after "automationTimeline". The test
  also asserts the automation is heard: the same session with automation cleared renders other
  bits before the seek (blocks 0-39) and after it (blocks 40-95).
• Pin discipline. The native digest and the simd128 oracle digest were read independently
  before any pin was written (the oracle run against a scratch copy of expected.json with a
  probe pin). Both are
  6f82e4668836ea2c7b977f2c322882aea98d73c0dd285caf41e13ccd18186cb6. The leg's
  beforeDisposeStatus.memoryBytes is 2,949,120 (one 64 KiB page above the other legs; the
  seek's successor plan is control work).
• Script. DIGEST_PATHS gains ("automationTimeline", "pcmF32leSha256"); the docstring and the
  comment above it say four digests.
• Gates (all green). cargo fmt --all; cargo clippy --locked -p host-web --all-targets --all-features -- -D warnings; cargo check --locked -p host-web --all-targets;
  cargo test --locked -p host-web --features test-support native_ (the four pin tests);
  bash scripts/check-web-audioworklet.sh --without-metadata-regeneration ...;
  python3 -B scripts/check-browser-expected-resources.py --artifacts target/ci/qualification-artifacts
  and --self-test (32 red mutations); node direct-oracle.mjs in compare mode.

T3

• D4 shipped. the_automation_fixture_renders_alike_on_both_hosts_across_one_session_seek in
  hosts/host-web/tests/control_parity.rs (under test-support). The browser side boots the
  fixture bytes with Rig::boot; the C ABI side builds CAbi::new from parse_session_json of
  the same bytes. Both run the D2 schedule with direct submits and session_seek; every seek,
  submit and render returns OK, and each block's left and right planes are compared with bits().
  Both hosts agree on all 96 blocks.
• Ring. Rig::boot and limits() both use a ring of two quanta, not one; the transcript
  submits one quantum per block, so the ring size does not change what renders.
• Probe (not committed). Flipping the low bit of the first C ABI sample at blocks >= 40 in the
  test's read path turns the case red at block 40, left plane.

Review fold 1

• M1. At timeline 30,000 every member lane was inside a closed mute (VCA mute 29900-30100;
  t1 left 29800-30600). A mute hold only remembers a seek's value (docs/SESSION_SCHEMA_V1.md,
  the fader-row paragraph), so the fader and VCA-offset landings were never heard, and the step
  at 3001 sat inside the VCA unmute hold. The vca-mute segments are now step 0-2000, 2400-30200,
  30400-35000 and 35500-36000 (D1 above is edited in place); t1 left still lands inside a closed
  mute. Re-minted pin, measured on both sides independently and equal:
  a81d883b3f83eaf629bd78db149d1a39825c821c6cb2e9a53506341a97ed1363 (native pin test, and the
  oracle against the unchanged artifact). The pin test now also asserts the landing is heard:
  two copies whose t1-fader holds -6 dB or +20 dB over 30000-30064 only render other bits in
  block 40. It is red on the fixture before this fold and green after it. The expected-resources self-test gains the automationTimeline digest mutation.