docs: how the paid report prices a trial and what stays cost-unknown

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

docs/TESTING_INTERNALS.md

@@ -640,15 +640,36 @@ this checkout to read it)`.
 samples, rationale}` entry per failing dimension (since EVAL_POLICY v3 `mean`
 holds the panel's gating median), each part capped at 200
 characters. `sessions[]` (at most 32) summarizes the trial's session-ledger
-rows. `cost_known: false` marks a record or trial whose harness captured no
-billing: PTY and Codex sessions never bill, and an SDK session bills only with a
-terminal `total_cost_usd`. It also marks a trial no result record could be
-attributed to: a record named by the case id or carrying `case_id` is that
-case's, and a record named by a display label (`/qa fix loop`) is the shard's
-only case's when the shard ran one case, so a multi-case shard whose records
-carry display labels leaves those trials cost-unknown rather than guessing
-which case paid (`junitCensus` in `scripts/lib/paid-report.ts`). An absent
-field means known. Census and marathon cost lines print the known sum and
+rows. `cost_known: false` marks a record or trial whose cost is not fully
+known; an absent field means known. A record carries it when its harness
+captured no billing (a Codex session that completed no turn or whose model has
+no price row). A rule case's trial in the JUnit census (`caseCost` in
+`scripts/lib/paid-report.ts`) costs its records' sum plus what no record
+carries: each ledger session without a terminal result (`billed: false`) adds
+its `streamed_cost_usd`, and a trial with no record adds each billed session's
+own `cost_usd` (Codex). The trial is cost-unknown when any record says
+`cost_known: false`, when any of those sessions has no priced cost (every PTY
+session, a `claude -p` session that ended without a result, an aborted Agent
+SDK session with no usage or an unpriced model), or when it has neither records
+nor sessions. A case in `MODEL_FREE_CASES` (`timeline-event-flow`, which runs
+no model) with neither is a known $0. A panel trial (`behavior`, `judge`) from
+an isolated trial shard keeps the older rule (`trialCostKnown` in
+`test/helpers/eval-store.ts`): known only with at least one record and every
+session billed, and streamed cost is not added.
+
+Records are attributed to a case this way: a record named by the case id or
+carrying `case_id` is that case's, and a record named by a display label
+(`/qa fix loop`) is the shard's only case's when the shard ran one case. In a
+multi-case shard, a display-label record whose `runSkillTest` test name is a
+registered case id carries `cost_case_id` (`recordE2E`), and the census adds
+its cost to that case only: the failed record, failure class and model still
+come from the records named by case id, so no verdict changes. A display-label
+record without `cost_case_id` in a multi-case shard is not attributed rather
+than guessed, and its case is cost-unknown when nothing else prices it
+(`junitCensus`). The report's headline `cost $<x>` adds the streamed session
+cost no collector record carries, so a newly priced trial counts once.
+
+Census and marathon cost lines print the known sum and
 `N of M trial(s) cost unknown`, and a train verdict's `ATTEMPT:` line prints
 `cost=$<known> known + <n> of <m> case(s) cost unknown` when some but not
 every case in the train record has a cost (a record with no priced case prints
@@ -660,13 +681,21 @@ including `runSharedInteractive`, the PTY session and `runRecordedCodexEval`)
 appends one best-effort line per armed session to
 `$GSTACK_EVAL_DIR/session-ledger.jsonl` (`test/helpers/session-ledger.ts`):
 a stable key `<runner>:<label>#n`, the exact `budget_ms` it armed, monotonic
-`elapsed_ms`, the `end` reason, sanitized evidence, `billed`, and a compact
+`elapsed_ms`, the `end` reason, sanitized evidence, `billed`, the billed
+`model`, `cost_usd` and token classes of a Codex session, and a compact
 liveness summary (longest in-request silence, the last event kind, any tool open
 at the end). `claude -p` sessions stream partial messages for this summary;
 transcripts keep their shape and size (full stream diagnostics only with
 `publicStreamDiagnostics`). A failed ledger write never fails a trial; a trial
 without ledger rows has no `sessions` and its headroom is `unknown`, never
-scored. The ledger rides in each slice artifact beside the shard results.
+scored. An Agent SDK session that ends without a terminal result (aborted,
+thrown) also records `streamed_cost_usd`: its streamed assistant usage priced
+by `streamedUsageCostUsd` (`lib/pricing.ts`), each message id once at its
+largest output, subagent turns included, `<synthetic>` messages skipped,
+5-minute cache writes at 1.25x and 1-hour writes at 2x the input rate. The
+field is absent when no message carries usage or any message's model has no
+price row, so an unpriced session stays cost-unknown, never $0. The ledger
+rides in each slice artifact beside the shard results.
 
 **Quarantine** (`CASE_QUARANTINE`, same file). An entry needs: a per-trial rate
 below 95% over at least 10 post-policy trials of the case's current input

docs/evals/census-red.md

@@ -93,7 +93,7 @@ What incomplete data means:
 | headroom `censored` | a sample timed out, so its real duration is at least the budget |
 | cause `unrecorded` | the trial was written before `failure_cause` existed |
 | cause `unknown` | the trial failed with no evidence for any other cause |
-| `cost unknown` | the harness (PTY, Codex) records no billing, or the trial sits in a multi-case shard whose records are named by display label and cannot be attributed to it; only the known sum is shown |
+| `cost unknown` | a session's cost was not captured (a PTY session, an unbilled Codex session, a `claude -p` session without a result, an aborted Agent SDK session with no priced streamed usage), or no record or session can be attributed to the trial (a multi-case shard's display-label record without `cost_case_id`); only the known sum is shown |
 | `history unavailable (...)` | the GitHub history could not be read; `--gate` fails closed |
 
 ## 4. Replay and repair (free)

docs/troubleshooting.md

@@ -2262,12 +2262,21 @@ case with `bun run eval:pass-rates --headroom --case <id>`.
 <a id="cost-unknown"></a>
 ### `cost unknown (no billing captured for any of <N> trial(s))` / `cost $<x> known + <N> of <M> trial(s) cost unknown`
 
-**Meaning.** PTY and Codex sessions record no billing, so their cost is
-unknown. So is a trial in a multi-case shard whose result records are named by
-a display label rather than the case id, because no record can be attributed
-to it (a one-case shard's records are its case's). Only the known sum is
-shown. A train verdict's `ATTEMPT:` line reports the same as `cost=$<x> known
-+ <n> of <m> case(s) cost unknown`, a bare `cost=$<x>` only when every case
+**Meaning.** Some trials' cost was not captured, so only the known sum is
+shown. A trial is cost-unknown when it ran a PTY session (PTY sessions record
+no billing), a Codex session that completed no turn or whose model has no price
+row, a `claude -p` session that ended without a result, or an aborted Agent
+SDK session whose streamed usage could not be priced (no usage, or a model with
+no price row). An aborted Agent SDK session with priced usage counts its
+`streamed_cost_usd` instead. A trial is also unknown when no record and no
+session can be attributed to it, for example a multi-case shard's
+display-label record without `cost_case_id` (a one-case shard's records are
+its case's); a model-free case (`timeline-event-flow`) is a known $0. A panel
+trial (`behavior`, `judge`) is unknown whenever any of its sessions billed
+nothing, even one with a priced `streamed_cost_usd`. The rules are in
+[Failure causes and details](TESTING_INTERNALS.md#failure-causes). A train
+verdict's `ATTEMPT:` line reports the same as `cost=$<x> known + <n> of <m>
+case(s) cost unknown`, a bare `cost=$<x>` only when every case
 in the train record is priced, and no cost at all when none is.
 
 **Fix.** None needed; this is informational.