T01: cost-accounting survey — and a 2.7x correction to our own numbers

Tier L (structural L, chaos d10=2). Every candidate exercised locally
against the CB-WP-0001 transcript rather than cited.

Verdict: session transcript JSONL is the only exact instrument; git
commits supply the attribution index it lacks; the State Hub is a
durable sink whose schema cannot express cache tokens at all; the
status bar and billing API are eliminated on availability.

Three errors found in this workplan's own Purpose section, all
overstating cost:

  - one API response is written as up to six JSONL lines, each
    repeating the same usage object (657 lines, 346 responses)
  - a multi-model session was priced entirely at Fable 5 rates,
    violating a per-model rule MetricsAndScenarios §1a already had
  - the transcript is a live file, so an unpinned total is not
    repeatable (346 -> 356 responses between two runs minutes apart)

CB-WP-0001 pinned at fc76445: $92.21, not $248.46. The qualitative
finding sharpens rather than weakens — 88.4% of spend is cache, at
256:1 cache-read to output tokens.

Neither error was of the harness-does-nothing class the positive
control was written for; both sums ran over real data. What caught
them was re-deriving a number instead of quoting it. Raised for T07
and for CB-WP-0003 T01.

Also measured: the one subagent (adversarial review) cost $0.66 and is
invisible to a collector reading only the main transcript.

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

.claude/ralph-loop.local.md

@@ -0,0 +1,21 @@
+---
+active: true
+iteration: 1
+session_id: 8cbd5701-a096-45a4-a419-9b7b1c9419bc
+max_iterations: 20
+completion_promise: "HEUREKA"
+workplan_id: CB-WP-0002
+workplan_file: workplans/CB-WP-0002-cost-accounting.md
+started_at: "2026-07-31T02:22:44Z"
+---
+
+Read the workplan at `workplans/CB-WP-0002-cost-accounting.md`.
+
+If every task has `status: done` AND frontmatter `status: done`:
+run `rm -f .claude/ralph-loop.local.md` first (deactivates the loop so the stop hook exits cleanly),
+then output <promise>HEUREKA</promise>.
+
+Otherwise implement the next `todo` task as described in the workplan.
+Set task `in_progress` when starting, `done` when complete.
+When all tasks are done set frontmatter `status: done`.
+