# embedding-abi-m5.3 — time-shard boundary-invisibility proof + friction harvest — Implementation Plan > **Parent spec:** `docs/specs/2026-05-19-embedding-abi-m5.md` > > **For agentic workers:** REQUIRED SUB-SKILL: use `skills/implement` > to run this plan. Steps use `- [ ]` checkboxes for tracking. **Goal:** Prove the chunk/window-boundary-invisibility claim the M4 retirement rests on — one symbol, N disjoint month-windows, each shard's `(acc,n)` bit-exact vs a single-thread host fold of that exact window — and harvest the per-tick-FFI cost at real volume for the P2 decision. The final functional M5 iteration before milestone close. **Architecture:** Builds on shipped+green m5.1/m5.2 (adapter, `Kernel`, `MidPriceStream`, atomic runtime, build.rs runtime-tracking, deterministic leak-proof). Adds a windowed adapter sibling `fold_window`, a new single-responsibility `[[bin]] timeshard_runner` (one thread per disjoint month-window, each owning its `Kernel` — `Ctx: !Send` makes one-ctx-per-thread a compile-time guarantee), and `tests/timeshard.rs` asserting the spec §3 strength-ordered (a)/(b)/(c) plus the (now-deterministic) leak-Σ, with a journal-only friction timing capture. The shipped symbol-fan path (`swarm_runner.rs`, `swarm.rs`) is NOT touched. **Tech Stack:** Rust (edition 2021); `data-server` (`stream_tick_windowed`, `filter_files` month-granularity windowing); `chrono` (dev-dep, `(y,m)→unix_ms` bounds, data-server's own precedent); `std::thread`; `std::time::Instant`; the M3 staticlib via the m5.1 `build.rs`. --- **Files this plan creates or modifies:** - Modify: `ail-embed/Cargo.toml` — add `chrono = "0.4"` to `[dev-dependencies]`; add a second `[[bin]] timeshard_runner` - Modify: `ail-embed/src/adapter.rs` — add `fold_window` (windowed sibling of `fold_symbol`) - Create: `ail-embed/src/bin/timeshard_runner.rs` — one thread per disjoint window; prints `RESULT`/`TIMING` - Test: `ail-embed/tests/timeshard.rs` — boundary-invisibility (a)/(b)/(c) + leak-Σ + friction capture Cross-reference anchors (read-only, do not edit): - `ail-embed/src/adapter.rs:62-69` — `fold_symbol` (the no-window sibling `fold_window` mirrors); `MidPriceStream` `:24-60` - `ail-embed/src/lib.rs:81-100` — `Kernel`/`Kernel::run>` (unchanged; reused) - `ail-embed/src/bin/swarm_runner.rs:1-73` — symbol-fan runner shape `timeshard_runner` parallels (NOT modified) - `ail-embed/tests/swarm.rs:42-44,65-86` — `skip_if_no_data` / `run_swarm_or_skip` idioms `timeshard.rs` mirrors (NOT modified) - `../../libs/data-server/src/lib.rs:241-268` — `stream_tick_windowed(self:&Arc,&str,Option,Option)->Option>`; `filter_files:274-308` (month-granularity inclusive window) - `../../libs/data-server/src/lib.rs:696-699` — the `chrono::NaiveDate::from_ymd_opt(..).and_hms_opt(..).and_utc().timestamp_millis()` bound precedent - `docs/DESIGN.md:2358-2360` — pre-existing "additive M4 concern" drift; spec §"Out of scope" — NOT m5.3's to fix, audit must not charge it here --- ### Task 1: Windowed adapter + chrono dev-dep + bin declaration **Files:** - Modify: `ail-embed/Cargo.toml` - Modify: `ail-embed/src/adapter.rs` - [ ] **Step 1: Add `fold_window` to `ail-embed/src/adapter.rs`** Append to `ail-embed/src/adapter.rs`, immediately after the `fold_symbol` function (currently ends at `:69`), *before* the `#[cfg(test)] mod tests` block: ```rust /// Fold the mid-price stream of `symbol` restricted to the inclusive /// Unix-millisecond window `[from_ms, to_ms]` through the M3 kernel. /// `None` if the symbol has no tick stream in that window. The window /// is the bound (no tick cap): the result is `(Σ mid, count)` over /// exactly the records data-server yields for that window, in stream /// order — identical f64-add sequence to a single-thread host fold of /// the same window, hence bit-exact against it. The windowed sibling /// of `fold_symbol`; same `MidPriceStream` + `Kernel` path, only the /// data-server entry differs (`stream_tick_windowed`). pub fn fold_window( server: &Arc, symbol: &str, from_ms: i64, to_ms: i64, ) -> Option<(f64, i64)> { let it = server.stream_tick_windowed(symbol, Some(from_ms), Some(to_ms))?; Some(Kernel::new().run(MidPriceStream::new(it))) } ``` - [ ] **Step 2: Add `chrono` dev-dep + the `timeshard_runner` bin to `ail-embed/Cargo.toml`** The exact current tail of `ail-embed/Cargo.toml` is: ```toml [dev-dependencies] zip = "2" tempfile = "3" [[bin]] name = "swarm_runner" path = "src/bin/swarm_runner.rs" ``` Replace it verbatim with: ```toml [dev-dependencies] zip = "2" tempfile = "3" # Test-only: the time-shard test derives (year,month) -> Unix-ms # window bounds via chrono (data-server's own bound precedent, # data-server/src/lib.rs:696-699) and passes raw ms to the bin, so # the bin itself stays date-math-free. chrono is already transitively # present via data-server; this is the test-direct declaration. chrono = "0.4" [[bin]] name = "swarm_runner" path = "src/bin/swarm_runner.rs" [[bin]] name = "timeshard_runner" path = "src/bin/timeshard_runner.rs" ``` - [ ] **Step 3: Verify the crate builds and m5.1/m5.2 stay green (no regression)** Run: `cargo test --manifest-path ail-embed/Cargo.toml --lib` Expected: PASS — `kernel_run_sums_prices` + `adapter::tests::tick_to_px_is_mid` `ok`; `0 failed`. (`fold_window` is additive; `[[bin]] timeshard_runner` references a not-yet-created file but `--lib` does not build bins, so this isolates the adapter/lib regression check. The bin + full-suite gate is Task 3 Step 4.) --- ### Task 2: The time-shard E2E test (RED — bin does not exist yet) **Files:** - Create: `ail-embed/tests/timeshard.rs` - [ ] **Step 1: Write `ail-embed/tests/timeshard.rs`** ```rust //! Time-shard boundary-invisibility E2E (spec Architecture §3 //! second assertion / Testing strategy §3). One symbol, N disjoint //! single-month windows, one thread per window (each owning its //! `Kernel` — `Ctx: !Send`). Asserts, in spec strength order: //! (a) each shard's `(acc,n)` == a single-thread host fold of THAT //! EXACT window in stream order, BIT-EXACT — the //! boundary-invisibility proof (the kernel result for a window //! is independent of how data-server chunked it); //! (b) the host-summed `(Σacc,Σn)` == the identically-summed //! reference partials, bit-exact by construction; //! (c) the whole-window single-thread total within an //! f64-reassociation tolerance only (cross-shard re-association //! is host arithmetic, NOT a kernel property — asserting it //! bit-exact would be WRONG, per the spec). //! Plus the global leak-Σ (deterministic since dbd76e5) and a //! journal-only friction timing capture (NO bench gate). //! //! Concrete pin: EURUSD, months 2017-03 / 2017-04 / 2017-05 (all //! present on /mnt, contiguous, no gaps — recon-verified). data-server //! has no public month-listing API, so the months are hard-pinned. //! Skips when /mnt absent — data-server's own precedent. use std::process::Command; use std::sync::Arc; use chrono::{NaiveDate, TimeZone, Utc}; use data_server::{DataServer, DEFAULT_DATA_PATH}; const SYMBOL: &str = "EURUSD"; /// Three disjoint single-month windows. Contiguous so the whole-window /// union is exactly 2017-03-01 .. 2017-05-31 23:59:59.999. const SHARDS: [(i32, u32); 3] = [(2017, 3), (2017, 4), (2017, 5)]; /// Relative tolerance for the (c) whole-window cross-check. Derivation: /// recursive f64 summation of n terms has error <= (n-1)*eps*Σ|x_i|. /// One EURUSD month ~250k ticks => 3 shards ~750k adds of O(1) mids; /// Σ|x| ~ 8.3e5, (n-1)*eps ~ 8.3e-11 => abs err ~ 6.8e-5, rel ~ 8e-11. /// 1e-6 is ~4 orders of safety yet still catches any real bug /// (a genuine miscount is off by >> 1 ppm). const REL_TOL: f64 = 1e-6; fn skip_if_no_data() -> bool { !std::path::Path::new(DEFAULT_DATA_PATH).exists() } /// Inclusive Unix-ms bounds for the whole of calendar month `(y, m)`. /// `filter_files` windows at month granularity via /// `unix_ms_to_year_month`, and `filter_chunk` is record-level /// inclusive `[from, to]`; first-instant .. last-instant of the month /// selects exactly that month's file and all its records. fn month_window(y: i32, m: u32) -> (i64, i64) { let from = Utc .from_utc_datetime( &NaiveDate::from_ymd_opt(y, m, 1) .unwrap() .and_hms_opt(0, 0, 0) .unwrap(), ) .timestamp_millis(); let (ny, nm) = if m == 12 { (y + 1, 1) } else { (y, m + 1) }; let next_from = Utc .from_utc_datetime( &NaiveDate::from_ymd_opt(ny, nm, 1) .unwrap() .and_hms_opt(0, 0, 0) .unwrap(), ) .timestamp_millis(); (from, next_from - 1) } /// Single-thread host reference: fold the mid stream over EXACTLY the /// inclusive `[from_ms, to_ms]` window in data-server stream order /// (`acc += mid; n += 1`). Bit-exact with `adapter::fold_window` /// because the f64-add order is identical. fn reference_window(server: &Arc, from_ms: i64, to_ms: i64) -> (f64, i64) { let mut it = server .stream_tick_windowed(SYMBOL, Some(from_ms), Some(to_ms)) .expect("EURUSD has a tick stream in the pinned window"); let (mut acc, mut n) = (0.0_f64, 0_i64); while let Some(chunk) = it.next_chunk() { for r in chunk.iter() { acc += (r.ask + r.bid) / 2.0; n += 1; } } (acc, n) } #[test] fn timeshard_boundary_invisibility_and_leak_free() { if skip_if_no_data() { eprintln!("skipping: {DEFAULT_DATA_PATH} absent (mirrors data-server)"); return; } let windows: Vec<(i64, i64)> = SHARDS.iter().map(|&(y, m)| month_window(y, m)).collect(); // Spawn the time-shard runner: then one // "from:to" arg per shard. It folds each window on its own thread // (own Kernel) and prints `RESULT ` // + a final `TIMING total_ticks= elapsed_ms=` line. let mut cmd = Command::new(env!("CARGO_BIN_EXE_timeshard_runner")); cmd.arg(DEFAULT_DATA_PATH).arg(SYMBOL); for (f, t) in &windows { cmd.arg(format!("{f}:{t}")); } let out = cmd .env("AILANG_RC_STATS", "1") .output() .expect("spawn timeshard_runner"); let stdout = String::from_utf8_lossy(&out.stdout); let stderr = String::from_utf8_lossy(&out.stderr); assert!( out.status.success(), "timeshard_runner exited {:?}\nstdout:\n{stdout}\nstderr:\n{stderr}", out.status.code() ); let server = Arc::new(DataServer::new(DEFAULT_DATA_PATH)); // Parse RESULT lines into (idx -> (from,to,acc,n)). let mut shards: Vec<(usize, i64, i64, f64, i64)> = Vec::new(); for line in stdout.lines().filter(|l| l.starts_with("RESULT ")) { let mut t = line.split_whitespace(); let _ = t.next(); // RESULT let idx: usize = t.next().unwrap().parse().unwrap(); let from: i64 = t.next().unwrap().parse().unwrap(); let to: i64 = t.next().unwrap().parse().unwrap(); let acc = f64::from_bits( u64::from_str_radix(t.next().unwrap(), 16).unwrap(), ); let n: i64 = t.next().unwrap().parse().unwrap(); shards.push((idx, from, to, acc, n)); } shards.sort_by_key(|s| s.0); assert_eq!( shards.len(), SHARDS.len(), "expected {} shard RESULT lines, got {}", SHARDS.len(), shards.len() ); // (a) Per-shard BIT-EXACT vs a single-thread host fold of that // exact window. THE boundary-invisibility proof. let mut sum_acc = 0.0_f64; let mut sum_n = 0_i64; let mut ref_sum_acc = 0.0_f64; let mut ref_sum_n = 0_i64; for (i, &(idx, from, to, acc, n)) in shards.iter().enumerate() { assert_eq!(idx, i, "shard indices contiguous 0..N"); assert_eq!((from, to), windows[i], "shard {i} window matches pin"); let (r_acc, r_n) = reference_window(&server, from, to); assert_eq!( acc.to_bits(), r_acc.to_bits(), "shard {i} ({from}..{to}): kernel acc BIT-EXACT vs \ single-thread host fold of that exact window \ (boundary-invisibility)" ); assert_eq!(n, r_n, "shard {i}: tick count == reference"); assert!(r_n > 0, "shard {i}: non-empty window"); sum_acc += acc; sum_n += n; ref_sum_acc += r_acc; ref_sum_n += r_n; } // (b) Host-summed partials == identically-summed reference // partials, BIT-EXACT by construction (same values, same // host summation order). assert_eq!( sum_acc.to_bits(), ref_sum_acc.to_bits(), "Σ shard acc bit-exact vs Σ reference partials" ); assert_eq!(sum_n, ref_sum_n, "Σ shard n == Σ reference n"); // (c) Whole-window single-thread total within REL_TOL only — // cross-shard re-association is host arithmetic, NOT a kernel // property; asserting bit-exact here would be WRONG (spec §3). let whole_from = windows.first().unwrap().0; let whole_to = windows.last().unwrap().1; let (whole_acc, whole_n) = reference_window(&server, whole_from, whole_to); assert_eq!( whole_n, sum_n, "whole-window tick count == Σ shard n (windows are an exact \ disjoint partition of the union)" ); let rel = ((whole_acc - sum_acc) / whole_acc).abs(); assert!( rel < REL_TOL, "whole-window total {whole_acc} vs Σ partials {sum_acc}: \ relative diff {rel:e} must be < {REL_TOL:e} (f64 \ reassociation only — NOT a kernel discrepancy)" ); // Global leak-Σ across ALL ailang_rc_stats: lines (deterministic // since dbd76e5: atomic global counters + build.rs runtime-track). let mut allocs: u64 = 0; let mut frees: u64 = 0; let mut seen = 0usize; for line in stderr.lines().filter(|l| l.starts_with("ailang_rc_stats:")) { seen += 1; for tok in line.split_whitespace() { if let Some(v) = tok.strip_prefix("allocs=") { allocs += v.parse::().expect("allocs= u64"); } else if let Some(v) = tok.strip_prefix("frees=") { frees += v.parse::().expect("frees= u64"); } } } assert!(seen > 0, "no ailang_rc_stats line; stderr:\n{stderr}"); assert_eq!( allocs, frees, "globally leak-free: Σallocs==Σfrees across {seen} stat line(s)" ); // Friction harvest: journal-only observation, NO assertion (the // value feeds the P2 batch-crossing decision; it is not a gate). if let Some(tl) = stdout.lines().find(|l| l.starts_with("TIMING ")) { eprintln!("m5.3 friction-harvest: {tl} (Σn={sum_n})"); } } ``` - [ ] **Step 2: Run the test — verify it is RED (bin does not exist)** Run: `cargo test --manifest-path ail-embed/Cargo.toml --test timeshard` Expected: FAIL to compile — `error: environment variable \`CARGO_BIN_EXE_timeshard_runner\` not defined at compile time` (the `[[bin]] timeshard_runner` target's source file does not exist yet, so Cargo does not set the env var `env!` reads). This is the deterministic RED. --- ### Task 3: The `timeshard_runner` bin (GREEN) **Files:** - Create: `ail-embed/src/bin/timeshard_runner.rs` - [ ] **Step 1: Write `ail-embed/src/bin/timeshard_runner.rs`** ```rust //! Time-shard swarm harness (spec §3). Run as a subprocess by //! `tests/timeshard.rs` under `AILANG_RC_STATS=1`. //! //! argv: ` [ ...]` — one //! inclusive Unix-ms window per shard. Date math lives in the test //! (chrono); this bin is date-math-free. Spawns one thread per //! window, each building its OWN `Kernel` (`Ctx: !Send` forces //! one-ctx-per-thread — a shared-ctx design is `error[E0277]`). //! Prints, in shard order, `RESULT //! `, then one `TIMING total_ticks=<Σn> elapsed_ms=` line //! (the friction-harvest observation; the test records it in the //! close-out journal, it is not asserted). use std::sync::Arc; use std::time::Instant; use ail_embed::adapter::fold_window; use data_server::DataServer; fn main() { let mut args = std::env::args().skip(1); let data_dir = args.next().expect("argv[1] = data dir"); let symbol = args.next().expect("argv[2] = symbol"); let windows: Vec<(i64, i64)> = args .map(|a| { let (f, t) = a.split_once(':').expect("window arg is from:to"); ( f.parse::().expect("from_ms i64"), t.parse::().expect("to_ms i64"), ) }) .collect(); assert!( windows.len() >= 2, "need >= 2 disjoint windows for a time-shard, got {}", windows.len() ); let server = Arc::new(DataServer::new(&data_dir)); let started = Instant::now(); let handles: Vec<_> = windows .iter() .copied() .enumerate() .map(|(idx, (from, to))| { let srv = Arc::clone(&server); let sym = symbol.clone(); // Each thread builds its own Kernel inside the closure — // Kernel/Ctx are !Send, so this is the ONLY shape that // compiles (one ctx per thread, type-enforced). std::thread::spawn(move || { let (acc, n) = fold_window(&srv, &sym, from, to) .expect("window has a tick stream"); (idx, from, to, acc, n) }) }) .collect(); let mut results: Vec<(usize, i64, i64, f64, i64)> = handles .into_iter() .map(|h| h.join().expect("shard thread panicked")) .collect(); let elapsed_ms = started.elapsed().as_millis(); results.sort_by_key(|r| r.0); let mut total_ticks: i64 = 0; for (idx, from, to, acc, n) in &results { total_ticks += *n; println!("RESULT {idx} {from} {to} {:016x} {n}", acc.to_bits()); } println!("TIMING total_ticks={total_ticks} elapsed_ms={elapsed_ms}"); } ``` - [ ] **Step 2: Run the time-shard test — verify GREEN** Run: `cargo test --manifest-path ail-embed/Cargo.toml --test timeshard` Expected: PASS — `test timeshard_boundary_invisibility_and_leak_free ... ok`; `1 passed; 0 failed`. The `eprintln!` shows the friction-harvest `TIMING` line (captured for the journal). - [ ] **Step 3: Determinism — run the time-shard test ×5** Run: `for i in 1 2 3 4 5; do cargo test --manifest-path ail-embed/Cargo.toml --test timeshard 2>&1 | grep 'test result:'; done` Expected: `test result: ok. 1 passed; 0 failed; 0 ignored; ...` **every** run (5/5). The leak-Σ is deterministic post-`dbd76e5`; per-shard bit-exactness is deterministic by same-order f64 adds. Any FAIL here is a hard stop (the leak-proof saga's lesson: one green run is insufficient). - [ ] **Step 4: Full ail-embed suite + the M5 acceptance gates** Run: `cargo test --manifest-path ail-embed/Cargo.toml` Expected: PASS — lib (`kernel_run_sums_prices`, `adapter::tests::tick_to_px_is_mid`), `smoke` (`hermetic_smoke_data_server_roundtrip`), `swarm` (`symbol_fan_swarm_bit_exact`, `symbol_fan_swarm_leak_free`), `timeshard` (`timeshard_boundary_invisibility_and_leak_free`), `rt_archive_freshness` all `ok`; **0 failed, 0 ignored** across all test binaries (the m5.2 leak-proof stays green; nothing re-quarantined). - [ ] **Step 5: Invariant 1 + no-compiler-surface-diff gate** Run: `cargo metadata --format-version 1 --manifest-path Cargo.toml --no-deps 2>/dev/null | grep -c data-server | cat` Expected: `0` — the AILang workspace graph has no `data-server` (adding `chrono` as an `ail-embed` dev-dep does not enter it; `ail-embed` is its own workspace root). Run: `git status --porcelain | grep -E '^\?\?|^ ?M' | grep -vE '^.. (ail-embed/|docs/|bench/orchestrator-stats/)'` Expected: empty output — m5.3 touches **only** `ail-embed/**`, `docs/`, and the stats file. **Zero** diff to `crates/ailang-*`, `crates/ail/`, `runtime/`, `examples/*.ail`, root `Cargo.toml`. - [ ] **Step 6: Isolated runtime RED still green (no regression)** Run: `cargo test -p ail --test embed_rc_global_stats_race 2>&1 | grep 'test result:'` Expected: `test result: ok. 1 passed; 0 failed; ...` — the runtime/build are untouched by m5.3; the audit-trail RED stays GREEN. --- ## Boss decisions (recorded for the audit) - **Friction-harvest is journal-only.** `timeshard_runner` emits a `TIMING total_ticks=N elapsed_ms=M` line; the test `eprintln!`s it and the **Boss records the derived per-tick-FFI cost (elapsed / total_ticks) in the m5.3 close-out journal** as the P2 flat-array-decision input. There is NO timing assertion and NO `bench/` baseline touched (recon confirmed no bench harness is invoked by `ail-embed`) — a wall-clock gate would flake; the spec (`:302-305`) is explicit it is an observation, not a perf gate. - **`chrono` is a dev-dependency only.** The date math lives in the test; the bin takes raw `from:to` ms args and is date-math-free. Invariant 1 is unaffected (compiler crates untouched; the AILang workspace graph stays `data-server`/`chrono`-free since `ail-embed` is its own workspace root — gated in Task 3 Step 5). - **New bin, not an arg-mode on `swarm_runner`.** Keeps the now-green m5.2 symbol-fan path byte-untouched (no regression surface) and each runner single-responsibility; its own `CARGO_BIN_EXE_timeshard_runner` is the established subprocess wiring. - **(c) is a tolerance check, never bit-exact.** Cross-shard re-association is host f64 arithmetic, not a kernel property; the spec and the m5-spec self-review are explicit. `REL_TOL = 1e-6` is derived from the recursive-summation error bound with ~4 orders of safety margin (shown in the test). - **Pre-existing DESIGN.md drift out of scope.** `docs/DESIGN.md:2358-2360` ("additive M4 concern") is pre-existing M4-retirement drift, NOT m5.3's to fix; the audit must not charge it to m5.3 (spec §"Out of scope"). m5.3 ships zero `runtime/`/`crates/`/DESIGN.md change. - **Milestone close next.** m5.3 is the last functional M5 iteration; after Boss-verification the milestone closes and `audit` (mandatory) runs separately. ## Self-review (planner Step 5) 1. **Spec coverage.** Architecture §3 time-shard second assertion → Task 2/3 (per-shard bit-exact (a), Σ bit-exact (b), whole-window tolerance (c)). Testing §3 → `tests/timeshard.rs`. Friction-harvest (`:302-305`, Acceptance `:331-332`) → `TIMING` line + journal record (Boss decision). Leak-Σ acceptance (`:323-324`) → the leak-Σ block. Invariant 1 / no-surface-diff (`:309-314`, `:328-330`) → Task 3 Step 5. skip-if-absent (`:326-327`) → `skip_if_no_data`. Symbol-fan / hermetic smoke already shipped (m5.2/m5.1) — not re-implemented; verified non-regressed in Task 3 Step 4. Audit runs separately (not an m5.3 task). 2. **Placeholder scan.** No "TBD/TODO/implement later/similar to/add appropriate". `SYMBOL`/`SHARDS`/`REL_TOL` are concrete pinned constants with recon-verified data + a derived tolerance, not placeholders. 3. **Type/name consistency.** `fold_window`, `MidPriceStream`, `Kernel`, `timeshard_runner`, `CARGO_BIN_EXE_timeshard_runner`, `RESULT ` (written in Task 3 / parsed in Task 2), `TIMING total_ticks= elapsed_ms=`, `month_window`, `reference_window`, `SHARDS=[(2017,3),(2017,4),(2017,5)]`, `SYMBOL="EURUSD"`, `REL_TOL=1e-6`, `timeshard_boundary_invisibility_and_leak_free` — identical across tasks and verification filters. 4. **Step granularity.** Each step is one file write or one command; 2-5 min. Largest paste (Task 2 Step 1) is a single verbatim test. 5. **No commit steps.** None. Work stays in the working tree. 6. **Pin/replacement substring contiguity.** The one verbatim replacement (Task 1 Step 2, the `[dev-dependencies]`/`[[bin]]` block) is not paired with any `contains(...)`/grep over its own body. The greps (Task 3 Step 5) assert over `cargo metadata` / `git status` output, not over a verbatim text body this plan writes — no contiguity hazard. 7. **Compile-gate vs deferred-caller.** No signature change to an existing function (only the additive `fold_window`; `fold_symbol` and all callers untouched). Task 1 Step 3 uses `--lib` precisely because the `[[bin]] timeshard_runner` path does not exist until Task 3 — a full `cargo test` in Task 1 would fail to build the declared bin. The full-suite/bin gate is correctly placed in Task 3 Step 4 (after the bin exists). This ordering is deliberate and internally consistent — `--lib` is satisfiable at Task 1 (bins are not built by `--lib`); the RED in Task 2 Step 2 is the *intended* `env!` compile failure, not a plan defect. 8. **Verification filter strings resolve.** `--lib`, `--test timeshard`, `--test embed_rc_global_stats_race`, `timeshard_boundary_invisibility_and_leak_free` are all defined *by this plan* (or are the shipped isolated RED) in the same tasks that filter on them — resolve by construction. Task 3 Steps 4/5/6 use the unfiltered suite or explicit `grep -c … == 0` / empty-output / `1 passed` assertions, so "nothing ran" cannot masquerade as success. Task 2 Step 2's "RED" is a *compile* failure (deterministic, not a 0-filtered false-green).