T11: dated rates and staleness become data, ahead of the 2026-08-31 flip

The price sheet had two defects of one shape -- a schema that could not
hold the fact it needed, the same criticism the cost survey levelled at
the State Hub.

  CA-16  time-boxed rates are DATA. Sonnet's intro price lived in a
         `# intro ...` comment and was invisible to the collector that
         reads the file. Now promo_input/promo_output/promo_until,
         applied per response at its own timestamp.
  CA-17  the 90-day staleness rule was prose in MetricsAndScenarios 1a
         that every M-D2-CST verdict silently inherited. Now `recorded`
         + `max_age_days` in the sheet, and a stale sheet ABORTS.

Both are exercised by make cost-test: the promo rate must apply before
2026-08-31 and lapse after, and a 102-day-old sheet must trip.

Applying CA-16 moved AC-1 from $93.32 to $93.15 -- the $0.17 CB-EV-0002
predicted, now collected rather than noted. That is a legitimate
retarget under T07's distinction: the instrument disproved the target,
and its output is in this commit. The number has now been stated five
times ($248.46, $92.21, $92.87, $93.32, $93.15), each correction from a
different mechanism.

Evidence tables regenerated from the tool rather than hand-patched,
per CA-15 -- which is the rule that exists because hand-typed tables
were the only thing the adversarial review found wrong.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

benchmarks/baselines/model-prices.toml

@@ -1,6 +1,15 @@
-# USD per million tokens; source: Anthropic pricing, recorded 2026-07-31
+# USD per million tokens. Source: Anthropic pricing.
-# Governed by specs/MetricsAndScenarios.md §1a — refresh on price change or
+# Governed by specs/CostAccounting.md §9 — a stale sheet invalidates new
-# after 90 days, or new M-D2-CST 'better' verdicts are invalid.
+# M-D2-CST `better` verdicts. Staleness is enforced by `make cost-test`,
+# not by this comment.
+#
+# Dated rates are DATA, not comments. A promotional rate written as a
+# comment is invisible to the collector that reads this file: the sonnet
+# intro price sat in a `#` remark and was silently ignored, costing $0.17
+# on a $93.32 pass and heading for a sign flip on 2026-08-31.
+
+recorded = 2026-07-31
+max_age_days = 90
 
 [claude-fable-5]
 input = 10.00
@@ -11,8 +20,13 @@ input = 5.00
 output = 25.00
 
 [claude-sonnet-5]
-input = 3.00    # intro 2.00 through 2026-08-31
+input = 3.00
-output = 15.00  # intro 10.00 through 2026-08-31
+output = 15.00
+# Promotional rate in force through `until` (inclusive); the collector
+# applies it to any response whose timestamp falls on or before that date.
+promo_input = 2.00
+promo_output = 10.00
+promo_until = 2026-08-31
 
 [claude-haiku-4-5]
 input = 1.00

evidence/CB-EV-0002-cost-accounting.md

@@ -17,9 +17,9 @@ transcribed by hand (CA-15).
 
 | ID | Metric | Target | Measured | Verdict |
 |---|---|---|---|---|
-| AC-1 | pinned total, as two components | $93.32 = $92.21 + $1.11 | **$92.21 main + $1.11 subagent = $93.32** | **met** |
+| AC-1 | pinned total, as two components | $93.15 = $92.03 + $1.11 | **$92.03 main + $1.11 subagent = $93.15** | **met** |
 | AC-2 | reconciliation residual | $0.00 | **$0.000000** | **met** |
-| AC-3 | unattributed share reported | present, 33% | **32.5%, own line** | **met** |
+| AC-3 | unattributed share reported | present, 33% | **32.4%, own line** | **met** |
 | AC-4 | composition reported | 5 components | **5 of 5** | **met** |
 | AC-5 | dedup violation aborts | non-zero exit | **abort raised** | **met** |
 | AC-6 | zero responses refuses to report | non-zero exit | **0 rows, no number emitted** | **met** |
@@ -27,7 +27,7 @@ transcribed by hand (CA-15).
 | AC-8 | 5m cache priced at 1.25× | $1.25/100k @ fable | **$1.2500 (1h would be $2.0000)** | **met** |
 | AC-9 | streamed partial output → final | 5,5,195 → 195 | **195** | **met** |
 
-No `unmeasured` rows. AC-1's target was corrected three times before this
+No `unmeasured` rows. AC-1's target was corrected four times before and after this
 run; §4 records why, because the sequence is more useful than the final
 number.
 
@@ -35,23 +35,23 @@ number.
 
 ```text
     input                  690 tok  $     0.00    0.0%
-    output             323,643 tok  $    11.15   11.9%
+    output             323,643 tok  $    11.13   11.9%
-    cache_read      80,611,798 tok  $    59.75   64.0%
+    cache_read      80,611,798 tok  $    59.67   64.1%
     write_5m            37,467 tok  $     0.47    0.5%
-    write_1h         1,672,854 tok  $    21.95   23.5%
+    write_1h         1,672,854 tok  $    21.87   23.5%
-    TOTAL                          $    93.32
+    TOTAL                          $    93.15
 ```
 
 **88.0% of spend is cache; 11.9% is output.** The ratio of context re-read
-to text written is 249:1. A single total would have shown $93.32 and
+to text written is 249:1. A single total would have shown $93.15 and
 concealed all of it — which is exactly what CB-WP-0001's `M-D2-TOK` would
 have done, and why that metric is now demoted.
 
 ## 3. Per-task attribution
 
 ```text
-    UNATTRIBUTED        $    30.32   32.5%
+    UNATTRIBUTED        $    30.14   32.4%
-    T08                 $    21.02   22.5%
+    T08                 $    21.02   22.6%
     T07                 $    12.01   12.9%
     T03                 $     9.91   10.6%
     T04                 $     8.00    8.6%
@@ -60,7 +60,7 @@ have done, and why that metric is now demoted.
     T09                 $     1.29    1.4%
 ```
 
-**Stated limit (CA-10):** 32.5% of cost sits in commits whose subject
+**Stated limit (CA-10):** 32.4% of cost sits in commits whose subject
 carries no `T##` tag, so this table is a view over 67.5% of spend. That is
 a property of commit hygiene, not of the collector.
 
@@ -75,14 +75,15 @@ is worth watching, not yet a conclusion from n=1.
 - **The per-task figures are not comparable across passes.** They mix
   models (opus/fable/sonnet) at different price points and different cache
   states. The dollar figure is comparable; a token count is not.
-- **AC-3's 32.5% is a fixture pin, not a quality target.** Improving commit
+- **AC-3's 32.4% is a fixture pin, not a quality target.** Improving commit
   tagging will move it, and that is the desired direction.
 - **This is one session.** Every ratio here (cache share, $/turn, the
   compaction effect in §5) is n=1 and should be treated as a hypothesis
   until a second pass reproduces it.
-- **The price sheet cannot express a time-boxed rate.** Sonnet's intro price
+- ~~**The price sheet cannot express a time-boxed rate.**~~ **Fixed
-  lives in a TOML comment, so sonnet-priced work is off by $0.17 here
+  2026-07-31 by CB-WP-0003 T11** (CA-16/CA-17). Applying the sonnet
-  (0.19%). This becomes a real error on 2026-08-31.
+  promotional rate moved AC-1 from $93.32 to **$93.15** — the $0.17 this
+  section predicted, now collected rather than merely noted.
 - **AC-1 is not invoice-verified.** No admin key exists, so the Anthropic
   billing API could not independently confirm the total. The transcript
   counters are the same ones billing uses, but that is an argument, not a
@@ -145,7 +146,7 @@ largest sample was assumed to hold on the smallest one.** The main
 transcript is 338 of 346 responses, so 206/206 felt conclusive; the
 violation lives entirely in the 8 responses nobody checked separately.
 
-Cost of the adversarial review this pass: **$1.11**, against a $93.32 pass.
+Cost of the adversarial review this pass: **$1.11**, against a $93.15 pass.
 It found three approval-blocking defects, one of which (the subagent
 exclusion) would have made this evidence file certify a broken collector.
 Second consecutive pass where a ~1% spend on review changed the outcome.

specs/CostAccounting.md

@@ -67,6 +67,16 @@ cost = input_tokens              × price.input
 > reported as an unpriced line with its token counts, never dropped and
 > never priced at a default.
 
+> **CA-16.** Promotional and other time-boxed rates are **data**, not
+> comments. A response is priced at the rate in force *at its own
+> timestamp*: `promo_input`/`promo_output` apply on or before
+> `promo_until`, and the standard rate applies after.
+
+> **CA-17.** The price sheet carries `recorded` and `max_age_days`, and a
+> sheet older than `max_age_days` **aborts the run**. A stale sheet
+> invalidates `better` verdicts, so the staleness rule is a command rather
+> than a sentence.
+
 ### 1.3 Scope of a measurement
 
 > **CA-06.** A measurement enumerates **every** transcript for the repo:
@@ -125,9 +135,9 @@ Each row names the command that produces its number, per InnerLoop §Step 4.
 
 | ID | Metric | Target | Instrument |
 |---|---|---|---|
-| **AC-1** | reproduces the pinned CB-WP-0001 total | **$93.32** = $92.21 main + $1.11 subagent | `make cost-pin` |
+| **AC-1** | reproduces the pinned CB-WP-0001 total | **$93.15** = $92.03 main + $1.11 subagent | `make cost-pin` |
 | **AC-2** | reconciliation residual (CA-14) | **$0.00** exactly | same command, `reconciled: ok` line |
-| **AC-3** | unattributed share reported (CA-10) | present, and **33%** on the pinned run | `cb-cost --pin fc76445 --by-task` |
+| **AC-3** | unattributed share reported (CA-10) | present, and **32.4%** on the pinned run | `cb-cost --pin fc76445 --by-task` |
 | **AC-4** | composition reported (CA-13) | all five components present | `cb-cost --pin fc76445 --composition` |
 | **AC-5** | dedup invariant asserted (CA-02) | violation exits non-zero | `make cost-test` |
 | **AC-6** | positive control: refuses to report on zero responses | exits non-zero | `make cost-test` |
@@ -145,7 +155,7 @@ assertion against a fixture whose expected value is known and fails loudly;
 Per InnerLoop §Step 4, the acceptance table is checked against the
 contracts in this same spec:
 
-- AC-1's $93.32 is reachable only if CA-06 holds (both trees enumerated).
+- AC-1's $93.15 is reachable only if CA-06 holds (both trees enumerated).
   Under a main-file-only collector the target is unreachable — this is the
   defect the adversarial review caught, where a target of $92.21 would have
   been hit *only* by a broken collector.
@@ -228,6 +238,31 @@ signal — which is exactly the dead-policy failure this replaces, one level
 up. The mitigation is that it costs nothing to run and is on the one
 command surface.
 
+## 9. The price sheet
+
+`benchmarks/baselines/model-prices.toml` is the single source of rates.
+Two defects were fixed here, both of the same shape — **a schema that
+could not hold the fact it needed**, which is the criticism this
+capability's survey levelled at the State Hub:
+
+1. **A time-boxed rate lived in a comment.** Sonnet's intro price
+   (2.00/10.00 through 2026-08-31) was written as `# intro …` and was
+   therefore invisible to the collector, which used the standard rate. Cost
+   at the pin: **$0.17**, 0.19% of the pass. The real hazard was the
+   date — on **2026-08-31** the promotion expires and a comment-only
+   representation would have been wrong in the opposite direction, with
+   nothing to notice. Now expressed as `promo_*` fields and applied per
+   CA-16.
+2. **The 90-day staleness rule had no check.** It was prose in
+   `MetricsAndScenarios.md` §1a and every M-D2-CST verdict silently
+   inherited it. Now `recorded` + `max_age_days` in the sheet, enforced by
+   CA-17 and exercised by `make cost-test`.
+
+Applying CA-16 moved AC-1 from $93.32 to **$93.15**. This is a *legitimate*
+retarget under the distinction CB-WP-0003 T07 draws: the instrument
+disproved the target, rather than the implementation missing it. The
+instrument's output is in the same commit.
+
 ## 8. Revisions to M-D2-CST
 
 `specs/MetricsAndScenarios.md` §1a is superseded by this spec. M-D2-CST is

tools/cb-cost.py

@@ -72,16 +72,53 @@ def components(usage):
     }
 
 
-def price_of(prices, model, toks):
+def rates_at(prices, model, when=None):
+    """Input/output rate in force for `model` at ISO instant `when` (CA-16).
+
+    Promotional rates are data, not comments. A response is priced at the
+    promo rate when its timestamp falls on or before `promo_until`.
+    """
+    pr = prices.get(model)
+    if not pr:
+        return None
+    if "promo_until" in pr and when:
+        until = pr["promo_until"]
+        # tomllib returns a datetime.date for a bare TOML date.
+        if str(when)[:10] <= str(until)[:10]:
+            return pr["promo_input"], pr["promo_output"]
+    return pr["input"], pr["output"]
+
+
+def check_price_sheet_age(prices, today=None):
+    """CA-17: a stale sheet invalidates verdicts, so it fails a command."""
+    import datetime as _dt
+
+    recorded = prices.get("recorded")
+    if recorded is None:
+        return "price sheet has no `recorded` date"
+    max_age = prices.get("max_age_days", 90)
+    today = today or _dt.date.today()
+    if isinstance(recorded, _dt.datetime):
+        recorded = recorded.date()
+    age = (today - recorded).days
+    if age > max_age:
+        return (f"price sheet is {age} days old (max {max_age}); refresh "
+                f"benchmarks/baselines/model-prices.toml or new M-D2-CST "
+                f"`better` verdicts are invalid")
+    return None
+
+
+def price_of(prices, model, toks, when=None):
     """USD for one response. Returns None when the model is unpriced (CA-05)."""
     pr = prices.get(model)
     if not pr:
         return None
+    rin, rout = rates_at(prices, model, when)
     cache = prices["cache"]
-    unit = pr["input"] / 1e6
+    unit = rin / 1e6
     return (
         toks["input"] * unit
-        + toks["output"] * pr["output"] / 1e6
+        + toks["output"] * rout / 1e6
         + toks["cache_read"] * unit * cache["read"]
         + toks["write_5m"] * unit * cache["write_5m"]
         + toks["write_1h"] * unit * cache["write_1h"]
@@ -281,8 +318,12 @@ def collect(slug, pin_ref=None):
         # as though it were an answer.
         raise Abort(f"no responses in {len(paths)} transcript(s) — refusing to report")
 
+    stale = check_price_sheet_age(prices)
+    if stale:
+        raise Abort(stale)
+
     for r in responses:
-        r["cost"] = price_of(prices, r["model"], r["toks"])
+        r["cost"] = price_of(prices, r["model"], r["toks"], r["timestamp"])
 
     attribute(responses, commit_index(pin))
 
@@ -298,11 +339,11 @@ def collect(slug, pin_ref=None):
             continue
         by_task[r["task"]] += r["cost"]
         by_model[r["model"]] += r["cost"]
-        pr = prices[r["model"]]
+        rin, rout = rates_at(prices, r["model"], r["timestamp"])
-        unit = pr["input"] / 1e6
+        unit = rin / 1e6
         rates = {
             "input": unit,
-            "output": pr["output"] / 1e6,
+            "output": rout / 1e6,
             "cache_read": unit * cache["read"],
             "write_5m": unit * cache["write_5m"],
             "write_1h": unit * cache["write_1h"],
@@ -456,6 +497,21 @@ def self_test():
     finally:
         os.unlink(partial)
 
+    # CA-16: a dated promo rate must apply before its expiry and lapse after.
+    pr = prices
+    before = rates_at(pr, "claude-sonnet-5", "2026-07-31T00:00:00Z")
+    after = rates_at(pr, "claude-sonnet-5", "2026-09-01T00:00:00Z")
+    check("CA-16 promo rate applies before expiry and lapses after",
+          before == (2.0, 10.0) and after == (3.0, 15.0),
+          f"{before} -> {after}")
+
+    # CA-17: staleness must actually trip, or the rule is decorative again.
+    import datetime as _dt
+    fresh = check_price_sheet_age(pr, _dt.date(2026, 8, 1))
+    stale = check_price_sheet_age(pr, _dt.date(2026, 11, 10))
+    check("CA-17 staleness detected past max_age_days",
+          fresh is None and stale is not None, "fresh ok, 102d trips")
+
     # CB-02: thresholds must be ordered, or the budget silently never fires.
     ap_defaults = {"soft": 10.00, "hard": 22.00}
     check("CB-02 budget thresholds ordered and positive",

workplans/CB-WP-0003-loop-hardening.md

@@ -325,7 +325,7 @@ now price the evaluation itself.
 
 ```task
 id: CB-WP-0003-T11
-status: todo
+status: done
 priority: medium
 state_hub_task_id: "809215d8-8a5c-4b10-9445-9bc6db9bda42"
 ```