## What
Wires genuine provider-reported `total_tokens` through the full
buzz-agent → buzz-acp publish chain so kind-44200 events carry real
per-turn and cumulative totals for OpenAI-backed models, while
preserving all existing behaviour for Anthropic and external harnesses
(goose, claude-code).
## Why
Live prod data showed 0 of 1,934 archived reports carry `totalTokens`.
Both hardcoded `total_tokens: None` in `pool.rs` and the absent field in
`buzz-agent`'s parser are root causes. This is the backend half of a
two-track fix; the display-fallback half lands in
[#2035](https://github.com/block/buzz/pull/2035).
## Changes
**`crates/buzz-agent/src/types.rs`**
- Added `total_tokens: Option<u64>` to `LlmResponse` with an explicit
doc comment that NIP-AM forbids deriving it.
- Added `TurnTotalState` enum (`Unseen | Exact(u64) | Unknown`) with
`fold()` and `exact_value()` — the tri-state accumulator that
distinguishes not-yet-observed from permanently poisoned.
**`crates/buzz-agent/src/llm.rs`**
- `parse_responses` and `parse_openai`: read `usage.total_tokens` from
OpenAI Chat Completions (including Databricks routes) and the Responses
API via `sum_usage`.
- Anthropic: explicit `total_tokens: None` — no genuine total available;
NIP-AM forbids summing categories.
**`crates/buzz-agent/src/agent.rs`**
- Added `turn_total_state: &'a mut TurnTotalState` to `RunCtx`.
- Fold `response.total_tokens` into the accumulator after each
usage-bearing response; non-usage-bearing responses (keepalive/stream
frames) do not poison.
**`crates/buzz-agent/src/lib.rs`**
- Added `accumulated_total_state: TurnTotalState` to `Session` (default
`Unseen`).
- Per-turn state passed to `RunCtx`, folded into session cumulative
after each turn.
- Emits `accumulatedTotalTokens` in `usage_update` only when cumulative
is `Exact(n)`.
**`crates/buzz-acp/src/usage.rs`**
- Added `accumulated_total_tokens: Option<u64>` (serde default) to
`UsageUpdatePayload` — optional for goose compat.
- Added `last_total: Option<u64>` to `SessionState`.
- Added `turn_total_tokens` and `cumulative_total_tokens` to `TurnUsage`
(field-local — never affect `delta_reliable`).
- Derive turn-total delta only when prev and current are both `Some` and
monotonic; absence, decrease, or no baseline leaves only the total delta
null without touching input/output reliability.
**`crates/buzz-acp/src/pool.rs`**
- Replaced both hardcoded `total_tokens: None` in
`publish_agent_turn_metric` with `usage.turn_total_tokens` and
`usage.cumulative_total_tokens`.
## Tests
20 new tests across the four touched files:
| File | Tests |
|------|-------|
| `types.rs` | `TurnTotalState` fold, accumulation, exact_value, default
(7 tests) |
| `llm.rs` | Chat present/absent, Responses present/absent, Anthropic
always-None (5 tests) |
| `usage.rs` | First turn no baseline, second-turn delta, cumulative
decrease (field-local), current absent, goose-shaped deserialization,
baseline absent (6 tests) |
| `pool.rs` | Exact turn+cumulative mapping, null totals never derived
(2 tests) |
`cargo test -p buzz-acp -p buzz-agent` — all passing, 0 failures.
## Scope
Boundary: `crates/buzz-agent/**` + `crates/buzz-acp/**` only. Desktop
unchanged.
`costUsd` explicitly out of scope.
Related: [#2035](https://github.com/block/buzz/pull/2035)
---------
Signed-off-by: Will Pfleger <pfleger.will@gmail.com>
Co-authored-by: npub1g8493u0xfsjrvflg4n08ezd7vec99mnwzlv0qgwpr9d7gvjwhuzqx59rhw <41ea58f1e64c243627e8acde7c89be667052ee6e17d8f021c1195be4324ebf04@buzz.block.builderlab.xyz>
