diff --git a/docs/plans/0086-cost-flag-cli-ergonomics.md b/docs/plans/0086-cost-flag-cli-ergonomics.md
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-# Cost-flag CLI ergonomics — Implementation Plan
-
-> **Parent spec:** `docs/specs/0086-cost-flag-cli-ergonomics.md`
->
-> **For agentic workers:** REQUIRED SUB-SKILL: use the `implement` skill to run
-> this plan. Steps use `- [ ]` checkboxes for tracking.
-
-**Goal:** Make the `aura run` cost-flag surface honest — units discoverable, a
-named non-negativity diagnostic, and a refuse-don't-guess rejection of cost flags
-on a non-R harness — with one C10 ledger note, changing no cost-model/R math.
-
-**Architecture:** All code lands in the pure `parse_run_args` grammar (and two
-print sites) in `crates/aura-cli/src/main.rs`; every new rejection is a pure
-`Result::Err` printed by `main`'s existing `eprintln!("aura: {msg}")` + `exit(2)`
-path (main.rs:3273-3279). One realization note is added to contract C10 in the
-ledger. The accepted stage1-r cost path and its eight `net_expectancy_r`/bleed
-goldens stay byte-identical.
-
-**Tech Stack:** Rust; `crates/aura-cli/src/main.rs` (the `aura` binary + its
-`mod tests`), `crates/aura-cli/tests/cli_run.rs` (integration), `docs/design/INDEX.md`.
-
----
-
-**Files this plan creates or modifies:**
-
-- Modify: `crates/aura-cli/src/main.rs` — new private `parse_nonneg_rate` fn + new
-  `const COST_FLAGS_NOTE`; rewire the three cost-flag arms (:3185-3211); insert the
-  non-R-harness guard (between :3215 and :3224); append the note to the `usage`
-  closure (:3137-3140) and the `--help` print (:3265).
-- Test: `crates/aura-cli/src/main.rs` `mod tests` (:3338) — pure `parse_run_args`
-  units (negative-rate, non-R-harness, accepted-path, malformed-regression).
-- Modify: `crates/aura-cli/tests/cli_run.rs` — update the perturbed negative-carry
-  test (:1825-1841); add non-R-harness, negative-cost, and `--help`-note integration
-  tests beside the cost block (:1631-1888) and the help block (:595-663).
-- Modify: `docs/design/INDEX.md` — one C10 realization note at the cost-section tail
-  (after `sweep-path cost. Decision log: #148.`, :831).
-
----
-
-### Task 1: Named non-negativity diagnostic (spec item 2)
-
-**Files:**
-- Modify: `crates/aura-cli/src/main.rs` (new `parse_nonneg_rate`; arms :3185-3211)
-- Test: `crates/aura-cli/src/main.rs` `mod tests` (:3338)
-- Test: `crates/aura-cli/tests/cli_run.rs` (update :1825-1841; add one negative-cost test)
-
-- [ ] **Step 1: Write the failing unit tests**
-
-Add to `mod tests` in `crates/aura-cli/src/main.rs`, beside the existing
-`parse_run_args_*` units (near :4480):
-
-```rust
-#[test]
-fn parse_run_args_negative_cost_rates_are_named_not_usage() {
-    for flag in ["--cost-per-trade", "--slip-vol-mult", "--carry-per-cycle"] {
-        let err = parse_run_args(&["--harness", "stage1-r", flag, "-0.5"])
-            .expect_err("a negative cost rate must be refused");
-        assert!(err.contains("must be non-negative"), "{flag}: {err}");
-        assert!(err.contains(flag), "message must name the offending flag: {err}");
-        assert!(err.contains("-0.5"), "message must carry the value: {err}");
-    }
-}
-
-#[test]
-fn parse_run_args_malformed_cost_rate_stays_grammar_usage() {
-    let err = parse_run_args(&["--harness", "stage1-r", "--cost-per-trade", "x"])
-        .expect_err("a malformed rate is a grammar error");
-    assert!(err.contains("usage"), "a malformed value stays the usage path: {err}");
-}
-```
-
-- [ ] **Step 2: Run the unit tests to verify they fail**
-
-Run: `cargo test -p aura-cli parse_run_args_negative_cost_rates_are_named_not_usage`
-Expected: FAIL — the current arms `return Err(usage())` on a negative value, so the
-message is the usage string and `err.contains("must be non-negative")` is false.
-
-- [ ] **Step 3: Add the `parse_nonneg_rate` helper**
-
-Insert immediately above `fn parse_run_args` (currently `crates/aura-cli/src/main.rs:3136`):
-
-```rust
-/// Parse a cost-rate flag value and enforce non-negativity, naming the offending
-/// flag so a sign typo is distinguishable from a mistyped flag name. A *malformed*
-/// value stays a grammar usage error (unchanged); only a parsed-but-negative value
-/// yields the named message. Pure — no I/O, no exit.
-fn parse_nonneg_rate(flag: &str, value: &str, usage: &impl Fn() -> String) -> Result<f64, String> {
-    let v: f64 = value.parse().map_err(|_| usage())?;
-    if v < 0.0 {
-        return Err(format!("{flag} must be non-negative, got {v}"));
-    }
-    Ok(v)
-}
-```
-
-- [ ] **Step 4: Rewire the three cost-flag arms to call the helper**
-
-In `parse_run_args`, replace the `--cost-per-trade` arm (`main.rs:3185-3193`):
-
-```rust
-            "--cost-per-trade" if cost.is_none() => {
-                let (value, t) = t.split_first().ok_or_else(usage)?;
-                cost = Some(parse_nonneg_rate("--cost-per-trade", value, &usage)?);
-                tail = t;
-            }
-```
-
-the `--slip-vol-mult` arm (`main.rs:3194-3202`):
-
-```rust
-            "--slip-vol-mult" if slip_vol_mult.is_none() => {
-                let (value, t) = t.split_first().ok_or_else(usage)?;
-                slip_vol_mult = Some(parse_nonneg_rate("--slip-vol-mult", value, &usage)?);
-                tail = t;
-            }
-```
-
-and the `--carry-per-cycle` arm (`main.rs:3203-3211`):
-
-```rust
-            "--carry-per-cycle" if carry_per_cycle.is_none() => {
-                let (value, t) = t.split_first().ok_or_else(usage)?;
-                carry_per_cycle = Some(parse_nonneg_rate("--carry-per-cycle", value, &usage)?);
-                tail = t;
-            }
-```
-
-- [ ] **Step 5: Run the unit tests to verify they pass**
-
-Run: `cargo test -p aura-cli parse_run_args_negative_cost_rates_are_named_not_usage`
-Expected: PASS.
-Run: `cargo test -p aura-cli parse_run_args_malformed_cost_rate_stays_grammar_usage`
-Expected: PASS (a malformed value still routes through `usage()`).
-
-- [ ] **Step 6: Update the now-perturbed integration test**
-
-The existing `stage1_r_negative_carry_per_cycle_refused_with_usage_exit_2`
-(`crates/aura-cli/tests/cli_run.rs:1825-1841`) asserts `stderr.contains("usage")`,
-which the new named message no longer satisfies. Update its assertion and name.
-
-Replace the assertion line (`cli_run.rs:1838`):
-
-```rust
-    assert!(stderr.contains("must be non-negative"), "negative carry stderr must name the cause: {stderr:?}");
-```
-
-Rename the function (`cli_run.rs:1826`) and adjust the doc line that says
-"usage on stderr":
-
-```rust
-/// Property (cycle 0085 + #153, cost-flag validation symmetry): a NEGATIVE
-/// `--carry-per-cycle` is refused at the binary boundary — exit 2, a named
-/// non-negativity diagnostic on stderr, nothing on stdout, no `runs/` write — the
-/// same shape the sibling `--cost-per-trade`/`--slip-vol-mult` flags enforce. The
-/// `v < 0.0` guard is load-bearing: without it a negative carry reaches
-/// `CarryCost::new` and PANICs, and a negative price-unit carry would CREDIT R —
-/// inverting the accrual sign. Deterministic; the refusal precedes any data access.
-#[test]
-fn stage1_r_negative_carry_per_cycle_refused_non_negative_exit_2() {
-```
-
-- [ ] **Step 7: Add a sibling negative-cost integration test**
-
-Add beside it in `crates/aura-cli/tests/cli_run.rs` (after the carry test, ~:1842):
-
-```rust
-/// Property (#153): a negative `--cost-per-trade` is refused at the binary
-/// boundary — exit 2, a named non-negativity diagnostic on stderr, no `runs/`
-/// write — the sibling of the carry guard, exercising the per-trade arm.
-#[test]
-fn run_negative_cost_per_trade_refused_non_negative_exit_2() {
-    let dir = temp_cwd("cost-per-trade-neg");
-    let out = Command::new(BIN)
-        .current_dir(&dir)
-        .args(["run", "--harness", "stage1-r", "--cost-per-trade", "-0.5"])
-        .output()
-        .expect("spawn aura run --cost-per-trade -0.5");
-    assert_eq!(out.status.code(), Some(2), "negative cost must exit 2; stderr: {}",
-        String::from_utf8_lossy(&out.stderr));
-    assert!(out.stdout.is_empty(), "a refused run must not emit a report: {:?}", out.stdout);
-    let stderr = String::from_utf8_lossy(&out.stderr);
-    assert!(stderr.contains("must be non-negative"), "stderr must name the cause: {stderr:?}");
-    assert!(!dir.join("runs").exists(), "a refused run must not write the registry");
-    let _ = std::fs::remove_dir_all(&dir);
-}
-```
-
-- [ ] **Step 8: Run the integration tests to verify they pass**
-
-Run: `cargo test -p aura-cli --test cli_run stage1_r_negative_carry_per_cycle_refused_non_negative_exit_2`
-Expected: PASS.
-Run: `cargo test -p aura-cli --test cli_run run_negative_cost_per_trade_refused_non_negative_exit_2`
-Expected: PASS.
-
----
-
-### Task 2: Non-R-harness guard (spec item 3 — the spec_gap)
-
-**Files:**
-- Modify: `crates/aura-cli/src/main.rs` (insert guard after :3215)
-- Test: `crates/aura-cli/src/main.rs` `mod tests` (:3338)
-- Test: `crates/aura-cli/tests/cli_run.rs` (new integration test beside :1574-1589)
-
-- [ ] **Step 1: Write the failing unit tests**
-
-Add to `mod tests` in `crates/aura-cli/src/main.rs`, beside the Task-1 units:
-
-```rust
-#[test]
-fn parse_run_args_cost_flags_require_r_harness() {
-    let cases: [(&[&str], &str); 3] = [
-        (&["--harness", "sma"], "--cost-per-trade"),
-        (&["--harness", "macd"], "--slip-vol-mult"),
-        (&["--harness", "sma"], "--carry-per-cycle"),
-    ];
-    for (harness, flag) in cases {
-        let mut argv: Vec<&str> = harness.to_vec();
-        argv.extend_from_slice(&[flag, "0.001"]);
-        let err = parse_run_args(&argv).expect_err("cost flag on a non-R harness must be refused");
-        assert!(err.contains("R-evaluator harness"), "{harness:?}+{flag}: {err}");
-    }
-}
-
-#[test]
-fn parse_run_args_cost_flag_without_harness_defaults_sma_and_is_refused() {
-    let err = parse_run_args(&["--carry-per-cycle", "0.5"])
-        .expect_err("the default harness is sma → cost flag refused");
-    assert!(err.contains("R-evaluator harness"), "{err}");
-}
-
-#[test]
-fn parse_run_args_cost_flags_accepted_on_stage1_r() {
-    let a = parse_run_args(&["--harness", "stage1-r", "--cost-per-trade", "0.001"])
-        .expect("cost flags are accepted on the R harness");
-    assert!(matches!(a.harness, HarnessKind::Stage1R));
-    assert_eq!(a.cost, Some(0.001));
-}
-```
-
-- [ ] **Step 2: Run the unit tests to verify they fail**
-
-Run: `cargo test -p aura-cli parse_run_args_cost_flags_require_r_harness`
-Expected: FAIL — today a cost flag on `--harness sma` is accepted (silently
-ignored downstream), so `parse_run_args` returns `Ok` and `expect_err` panics.
-
-- [ ] **Step 3: Insert the non-R-harness guard**
-
-In `parse_run_args`, immediately after `let harness = harness.unwrap_or(HarnessKind::Sma);`
-(`main.rs:3215`) and before the `// --from/--to require --real.` comment:
-
-```rust
-    let harness = harness.unwrap_or(HarnessKind::Sma);
-    // Cost flags are defined only against the R chain (gross-R -> net-R); a non-R
-    // harness produces no R to charge against, so a cost flag there is a usage error,
-    // not a silent no-op (refuse-don't-guess, C10).
-    if !matches!(harness, HarnessKind::Stage1R)
-        && (cost.is_some() || slip_vol_mult.is_some() || carry_per_cycle.is_some())
-    {
-        return Err(
-            "cost flags require an R-evaluator harness (stage1-r); \
-             --harness sma/macd produces no R to charge against"
-                .to_string(),
-        );
-    }
-```
-
-- [ ] **Step 4: Run the unit tests to verify they pass**
-
-Run: `cargo test -p aura-cli parse_run_args_cost_flags_require_r_harness`
-Expected: PASS.
-Run: `cargo test -p aura-cli parse_run_args_cost_flags_accepted_on_stage1_r`
-Expected: PASS (the accepted path is unchanged).
-
-- [ ] **Step 5: Write the failing integration test**
-
-Add to `crates/aura-cli/tests/cli_run.rs`, beside `run_harness_sma_is_pip_only_no_r_block`
-(~:1589):
-
-```rust
-/// Property (#153): a cost flag on a non-R harness (sma/macd, which produce no R)
-/// is a usage error — exit 2 with a named diagnostic, no silent no-op, no `runs/`
-/// write. The pre-#153 behaviour silently ignored the flag and exited 0.
-#[test]
-fn run_cost_flag_on_non_r_harness_is_refused_exit_2() {
-    let dir = temp_cwd("sma-cost-refused");
-    let out = Command::new(BIN)
-        .current_dir(&dir)
-        .args(["run", "--harness", "sma", "--cost-per-trade", "0.001"])
-        .output()
-        .expect("spawn aura run --harness sma --cost-per-trade");
-    assert_eq!(out.status.code(), Some(2), "cost on a non-R harness must exit 2; stderr: {}",
-        String::from_utf8_lossy(&out.stderr));
-    assert!(out.stdout.is_empty(), "a refused run must not emit a report: {:?}", out.stdout);
-    let stderr = String::from_utf8_lossy(&out.stderr);
-    assert!(stderr.contains("R-evaluator harness"), "stderr must name the cause: {stderr:?}");
-    assert!(!dir.join("runs").exists(), "a refused run must not write the registry");
-    let _ = std::fs::remove_dir_all(&dir);
-}
-```
-
-- [ ] **Step 6: Run the integration test to verify it passes**
-
-Run: `cargo test -p aura-cli --test cli_run run_cost_flag_on_non_r_harness_is_refused_exit_2`
-Expected: PASS.
-
----
-
-### Task 3: Cost-flag units note (spec item 1)
-
-**Files:**
-- Modify: `crates/aura-cli/src/main.rs` (new `const COST_FLAGS_NOTE`; usage closure :3137; `--help` print :3265)
-- Test: `crates/aura-cli/tests/cli_run.rs` (new `--help` note test beside :595-663)
-
-- [ ] **Step 1: Write the failing integration test**
-
-Add to `crates/aura-cli/tests/cli_run.rs`, beside the help tests (~:663):
-
-```rust
-/// Property (#153): the cost-flag units/constraints are discoverable from
-/// `aura run --help` — the appended note states the in-R charge, the per-ENGINE-
-/// cycle carry semantics, the `>= 0` constraint, and that cost flags are stage1-r
-/// only. Pre-#153 the usage listed the flags with no unit or scale guidance.
-#[test]
-fn run_help_surfaces_cost_flag_units_note() {
-    let out = Command::new(BIN).args(["run", "--help"]).output().expect("spawn aura run --help");
-    assert_eq!(out.status.code(), Some(0), "run --help exits 0: {:?}", out.status);
-    let stdout = String::from_utf8(out.stdout).expect("utf-8 stdout");
-    assert!(stdout.contains("per ENGINE cycle"), "help must explain carry units: {stdout}");
-    assert!(stdout.contains("stage1-r only"), "help must state the R-harness requirement: {stdout}");
-}
-```
-
-- [ ] **Step 2: Run the integration test to verify it fails**
-
-Run: `cargo test -p aura-cli --test cli_run run_help_surfaces_cost_flag_units_note`
-Expected: FAIL — the current `--help` output (`USAGE`) carries no cost-flag note,
-so `stdout.contains("per ENGINE cycle")` is false.
-
-- [ ] **Step 3: Add the `COST_FLAGS_NOTE` const**
-
-Insert immediately above `const USAGE: &str` (`main.rs:3244`):
-
-```rust
-/// One-line note appended to the `aura run` usage surfaces (the grammar-error
-/// usage closure and `--help`) so the cost-flag units, scale, per-engine-cycle
-/// semantics, non-negativity, and R-harness requirement are discoverable at the
-/// point of use (#153). A leading newline puts it on its own line under the usage.
-const COST_FLAGS_NOTE: &str = "\ncost flags (stage1-r only; all >= 0, charged in R as cost/|entry−stop|): \
---cost-per-trade = per-trade cost in price units; --slip-vol-mult = slippage multiplier on realized vol; \
---carry-per-cycle = carry in price units per ENGINE cycle (not per day, not an overnight swap)";
-```
-
-- [ ] **Step 4: Append the note to the `parse_run_args` usage closure**
-
-Replace the `usage` closure (`main.rs:3137-3140`):
-
-```rust
-    let usage = || {
-        format!(
-            "usage: aura run [--harness <sma|macd|stage1-r>] [--real <SYMBOL> [--from <ms>] [--to <ms>]] [--trace <name>] [--cost-per-trade <f64>] [--slip-vol-mult <f64>] [--carry-per-cycle <f64>]{COST_FLAGS_NOTE}"
-        )
-    };
-```
-
-- [ ] **Step 5: Append the note to the `--help` print**
-
-Replace the `--help` short-circuit print (`main.rs:3265`):
-
-```rust
-    if args.iter().any(|a| a == "--help" || a == "-h") {
-        println!("{USAGE}{COST_FLAGS_NOTE}");
-        return;
-    }
-```
-
-- [ ] **Step 6: Run the integration test to verify it passes**
-
-Run: `cargo test -p aura-cli --test cli_run run_help_surfaces_cost_flag_units_note`
-Expected: PASS.
-
-- [ ] **Step 7: Regression — the uniform help/usage pins still hold**
-
-Run: `cargo test -p aura-cli --test cli_run per_subcommand_help_is_uniform_stdout_exit_zero`
-Expected: PASS (the appended note keeps `contains("usage")` true and stderr empty).
-
----
-
-### Task 4: C10 ledger note + full-suite gate
-
-**Files:**
-- Modify: `docs/design/INDEX.md` (C10 cost-section tail, after :831)
-
-- [ ] **Step 1: Add the C10 realization note**
-
-In `docs/design/INDEX.md`, replace the boundary between the cycle-0085 cost note
-and the #117 HISTORY reframe (`:831-833`):
-
-```markdown
-sweep-path cost. Decision log: #148.
-
-**Realization (cost-flag harness scoping, #153).** Cost flags are defined only
-against an R-evaluator harness (the gross-R → net-R chain). On a non-R harness
-(`--harness sma`/`macd`, which produce no R) a cost flag is a **usage error
-(exit 2)**, not a silent no-op — refuse-don't-guess. Negative cost rates are
-likewise rejected (exit 2) with a named diagnostic that identifies the offending
-flag. CLI ergonomics only; the cost-model graph and the R math are untouched.
-
-**Reframe (2026-06-23, #117 — exposure → bias, R as the signal-quality unit).**
-```
-
-- [ ] **Step 2: Full aura-cli suite gate — new tests pass, goldens byte-green**
-
-Run: `cargo test -p aura-cli`
-Expected: PASS — the whole `aura-cli` suite is green, including the eight accepted-path
-cost goldens (`stage1_r_flat_cost_net_expectancy_r_golden` et al., cli_run.rs
-:1686/1714/1736/1757/...) byte-unchanged, since only the grammar/usage strings and the
-previously-unguarded sma-cost path changed.
-
-- [ ] **Step 3: Lint gate**
-
-Run: `cargo clippy -p aura-cli --all-targets -- -D warnings`
-Expected: PASS — no warnings (the new helper, const, and guard are idiomatic).
diff --git a/docs/specs/0086-cost-flag-cli-ergonomics.md b/docs/specs/0086-cost-flag-cli-ergonomics.md
deleted file mode 100644
index f11b3c9..0000000
--- a/docs/specs/0086-cost-flag-cli-ergonomics.md
+++ /dev/null
@@ -1,210 +0,0 @@
-# Cost-flag CLI ergonomics — Design Spec
-
-**Date:** 2026-06-29
-**Status:** Draft — awaiting user spec review
-**Authors:** orchestrator + Claude
-
-## Goal
-
-Close the three non-blocking ergonomics/diagnostic gaps the milestone-close
-fieldtest of #148 surfaced on the `aura run` cost-flag surface
-(`--cost-per-trade`, `--slip-vol-mult`, `--carry-per-cycle`), plus the one
-named spec_gap. The cost-model-graph capability already ships end-to-end; this
-cycle only makes its CLI surface *honest and self-describing*, changing no
-cost-model node, no R chain, and no `net_r_equity` / `summarize_r` math.
-
-Three observable defects, all instances of one anti-pattern (a misuse that
-produces no actionable feedback):
-
-1. **Units undiscoverable.** The usage string lists the three cost flags with no
-   unit, scale, or per-close-vs-per-held-cycle note. A user must trial magnitudes
-   to find one that moves net-R.
-2. **Negative-rate diagnostic is mute.** A negative rate already exits 2, but the
-   message is the bare 1-line usage dump — it never names the cause, and the
-   usage never states the non-negativity constraint, so a sign typo is
-   indistinguishable from a mistyped flag.
-3. **Silent no-op on a non-R harness (the spec_gap).** `aura run --harness sma
-   --cost-per-trade 0.001` exits 0 with output byte-identical to the no-cost run:
-   the flag is silently ignored. C10 defines cost only against the R chain and
-   never constrained what a cost flag does on a harness that produces no R.
-
-## Architecture
-
-All three changes live in `crates/aura-cli/src/main.rs`, in and around the
-**pure** `parse_run_args` grammar (line 3136) — the function the codebase
-deliberately keeps side-effect-free so the grammar is unit-testable; `main`
-already maps its `Err(String)` to `eprintln!("aura: {msg}")` + `exit(2)` (line
-3277). Keeping every new rejection inside `parse_run_args` means each is a pure,
-unit-testable `Result::Err`, and the fail-loud exit path is the existing one —
-no new exit site, no new I/O. One ledger note pins the decision in C10.
-
-**Decision recorded (reference issue #153, 2026-06-29 — derived, not preference):**
-item 3 resolves to **reject, exit 2** (not warn-and-continue). Basis: aura's
-settled *refuse-don't-guess / fail-loud* discipline — C10 refuse-don't-guess
-(exit 2 on absent geometry), the "every error path exits 2, never panics" rule
-(#107), and the negative-rate guard in this very surface already exits 2. A
-silent no-op is the lone exception in an otherwise fail-loud surface; rejecting
-is the only behaviour consistent with every sibling guard.
-
-## Concrete code shapes
-
-### Worked user-facing surface (the acceptance evidence)
-
-```text
-# Item 1 — units/constraints discoverable at the point of use (--help, exit 0)
-$ aura run --help
-usage: aura run [--harness <sma|macd|stage1-r>] [--real <SYMBOL> [--from <ms>] [--to <ms>]] [--trace <name>] [--cost-per-trade <f64>] [--slip-vol-mult <f64>] [--carry-per-cycle <f64>] | aura chart ...
-cost flags (stage1-r only; all >= 0, charged in R as cost/|entry−stop|): --cost-per-trade = per-trade cost in price units; --slip-vol-mult = slippage multiplier on realized vol; --carry-per-cycle = carry in price units per ENGINE cycle (not per day, not an overnight swap)
-
-# Item 2 — a negative rate names the cause + flag (exit 2, stderr), no runs/ write
-$ aura run --harness stage1-r --cost-per-trade -0.5
-aura: --cost-per-trade must be non-negative, got -0.5
-$ echo $?
-2
-
-# Item 3 — a cost flag on a non-R harness is a usage error (exit 2, stderr), no runs/ write
-$ aura run --harness sma --cost-per-trade 0.001
-aura: cost flags require an R-evaluator harness (stage1-r); --harness sma/macd produces no R to charge against
-$ echo $?
-2
-
-# Unchanged: the accepted path is byte-identical to today
-$ aura run --harness stage1-r --cost-per-trade 2          # → net_expectancy_r as before
-$ aura run --harness stage1-r --carry-per-cycle 0         # → exactly free (zero-rate boundary)
-```
-
-### Implementation shape (before → after, secondary)
-
-**(a) Non-negativity guard — named cause, factored (items 2).** The three
-flags currently restate an identical guard that returns the bare usage:
-
-```rust
-// BEFORE (×3, lines 3188 / 3197 / 3206):
-"--cost-per-trade" if cost.is_none() => {
-    let (value, t) = t.split_first().ok_or_else(usage)?;
-    let v: f64 = value.parse().map_err(|_| usage())?;
-    if v < 0.0 { return Err(usage()); }      // mute: bare usage dump
-    cost = Some(v);
-    tail = t;
-}
-
-// AFTER: one helper, named diagnostic; the three arms call it.
-fn parse_nonneg_rate(flag: &str, value: &str, usage: &impl Fn() -> String) -> Result<f64, String> {
-    let v: f64 = value.parse().map_err(|_| usage())?;     // malformed → grammar usage error (unchanged)
-    if v < 0.0 {
-        return Err(format!("{flag} must be non-negative, got {v}"));  // named cause + offending flag
-    }
-    Ok(v)
-}
-// arm:
-"--cost-per-trade" if cost.is_none() => {
-    let (value, t) = t.split_first().ok_or_else(usage)?;
-    cost = Some(parse_nonneg_rate("--cost-per-trade", value, &usage)?);
-    tail = t;
-}
-```
-
-A *malformed* value (`--cost-per-trade x`) stays a grammar usage error
-(unchanged); only the *parsed-but-negative* case gets the named message.
-
-**(b) Non-R-harness guard — post-parse, pure (item 3).** After the parse loop,
-once `harness` is resolved (line 3215), before constructing `RunArgs`:
-
-```rust
-let harness = harness.unwrap_or(HarnessKind::Sma);
-// Cost flags are defined only against the R chain; a non-R harness produces no R
-// to charge against, so a cost flag there is a usage error (refuse-don't-guess).
-if !matches!(harness, HarnessKind::Stage1R)
-    && (cost.is_some() || slip_vol_mult.is_some() || carry_per_cycle.is_some())
-{
-    return Err(
-        "cost flags require an R-evaluator harness (stage1-r); \
-         --harness sma/macd produces no R to charge against".to_string(),
-    );
-}
-```
-
-**(c) Usage note — units + constraints, one appended line (item 1).** A
-`const COST_FLAGS_NOTE: &str` appended to both the `parse_run_args` `usage`
-closure (line 3137) and the top-level `USAGE` (line 3244), so the same note
-shows on a grammar error and on `--help`:
-
-```rust
-const COST_FLAGS_NOTE: &str = "\ncost flags (stage1-r only; all >= 0, charged in R as cost/|entry−stop|): \
---cost-per-trade = per-trade cost in price units; --slip-vol-mult = slippage multiplier on realized vol; \
---carry-per-cycle = carry in price units per ENGINE cycle (not per day, not an overnight swap)";
-```
-
-### Ledger note (C10) — pin the spec_gap decision
-
-Add one note to contract C10 in `docs/design/INDEX.md` (cost-model area), e.g.:
-
-> **Realization (cost-flag harness scoping, #153).** Cost flags are defined
-> only against an R-evaluator harness (the gross-R → net-R chain). On a non-R
-> harness (`--harness sma`/`macd`, which produce no R) a cost flag is a **usage
-> error (exit 2)**, not a silent no-op — refuse-don't-guess. Negative cost rates
-> are likewise rejected (exit 2) with a named diagnostic.
-
-## Components
-
-- `parse_nonneg_rate` (new, pure, private) — parse + non-negativity, named error.
-- `parse_run_args` (edited) — three arms call the helper; one post-parse R-harness
-  guard; the `usage` closure appends `COST_FLAGS_NOTE`.
-- `COST_FLAGS_NOTE` (new const) + `USAGE` (edited to append it).
-- C10 ledger note (one paragraph).
-
-## Data flow
-
-Unchanged at runtime. `parse_run_args` either returns `Ok(RunArgs)` (the
-accepted path → `run_dispatch` → identical to today) or `Err(String)` (the new
-named messages → `main`'s existing `eprintln!` + `exit(2)`). No cost-model node,
-harness, tap, or metric is touched.
-
-## Error handling
-
-Every misuse is a single, named, fail-loud stderr line + `exit(2)`, no `runs/`
-write, no panic — the established CLI convention. Three messages:
-malformed value → existing grammar usage; negative rate → `<flag> must be
-non-negative, got <v>`; cost flag on non-R harness → `cost flags require an
-R-evaluator harness (stage1-r); …`.
-
-## Testing strategy
-
-**Unit (pure `parse_run_args`, in `main.rs` tests):**
-- `parse_run_args(["--cost-per-trade","-0.5"])` → `Err` containing `non-negative`
-  and `-0.5`.
-- `parse_run_args(["--carry-per-cycle","-0.001"])` and `["--slip-vol-mult","-1"]`
-  → `Err` containing `non-negative` (guard symmetry across all three).
-- `parse_run_args(["--harness","sma","--cost-per-trade","0.001"])` → `Err`
-  containing `R-evaluator harness`.
-- `parse_run_args(["--harness","macd","--slip-vol-mult","0.5"])` → `Err`.
-- `parse_run_args(["--carry-per-cycle","0.5"])` (no `--harness`, defaults to sma)
-  → `Err` (R-evaluator requirement).
-- `parse_run_args(["--harness","stage1-r","--cost-per-trade","0.001"])` → `Ok`
-  (the accepted path is unchanged).
-- Malformed value still maps to the grammar usage error (regression).
-
-**CLI integration (`crates/aura-cli/tests/cli_run.rs`):**
-- `aura run --harness sma --cost-per-trade 0.001` → exit 2, stderr contains
-  `R-evaluator harness`, no `runs/` write.
-- `aura run --cost-per-trade -0.5` → exit 2, stderr contains `non-negative`.
-- `aura run --help` → exit 0, stdout contains the cost-flags note (units +
-  per-engine-cycle + `>= 0` + stage1-r-only).
-- **Regression:** the existing stage1-r cost tests (cli_run.rs:1635/1688/1716/
-  1738/1759/1830/1879) stay green byte-for-byte — the accepted and negative-rate
-  exit-code paths are unchanged in code-behaviour; only message text and the
-  previously-unguarded sma path change.
-
-## Acceptance criteria
-
-Judged against aura's feature-acceptance criterion (improves correctness /
-removes a foot-gun; reintroduces no failure class the core constraints forbid):
-
-- The cost-flag units, scale, per-engine-cycle semantics, non-negativity, and
-  R-harness requirement are all discoverable from `aura run --help`.
-- No cost-flag misuse is silent: a negative rate and a cost flag on a non-R
-  harness each produce a named stderr diagnostic + exit 2, never a silent no-op
-  and never a bare usage dump for these two named causes.
-- The accepted stage1-r cost path and all its goldens are byte-unchanged.
-- C10 carries a one-line note pinning "cost flags require an R-evaluator harness;
-  non-R harness ⇒ usage error (exit 2)", closing the spec_gap.