feat(llm): add replay token metering (PR2 round 1)

packages/compact/compact-basic/README.md

@@ -1,6 +1,6 @@
 # @deepseek-ai/dsh-compact-basic
 
-The **basic compaction backend**: a `BasicCompactService` implementing the `@deepseek-ai/dsh-compact` seam with a chars-per-token heuristic (the `charsPerToken` config, default 4), token-budget retention, and summarization as a direct one-shot `ctx.llm.stream()` call (interceptable at `llm/stream`).
+The **basic compaction backend**: a `BasicCompactService` implementing the `@deepseek-ai/dsh-compact` seam with reusable `ctx.tokenMeter` pressure, token-budget retention, and summarization as a direct one-shot `ctx.llm.stream()` call (interceptable at `llm/stream`).
 
 This is the implementation tier of the compaction capability — see the [interface package](../compact/README.md) for the seam and the [capability-seam RFC](../../../docs/rfc/implemented/feature/2026-06-18-compaction-capability-seam.md) for the design.
 
@@ -8,7 +8,7 @@ This is the implementation tier of the compaction capability — see the [interf
 
 This backend owns the compaction policy:
 
-- **Estimation** — a configurable characters-per-token heuristic counts the current session prefix supplied to pre-step, derived history, and system prompt, matching the next request rather than stale logged prefix state.
+- **Measurement** — the effective conversation model's `ModelTokenMeter` prices the provisional request envelope and current surface at one consumed-log revision. The current prompt and prefix override their logged values; the pre-step boundary reuses logged tools and call config.
 - **Retention** — compact the oldest whole surface units while preserving a recent tail and balanced tool-call/result cuts through the [`dsh-compact` boundary helpers](../compact/README.md#tool-pairing-boundaries). Turn boundaries do not protect old steps inside a runaway turn. An open indivisible tail declines until it closes; a single unit larger than the budget remains out of scope.
 - **Convergence** — retry head-checkpoint compaction up to `compactionRetries`; reject a summary that does not shrink its source, and throw if retries cannot return below threshold.
 - **Summarization** — a direct `llm/stream` call uses the configured model and cap without running the loop-only `agent/request` seam. The input transcript preserves non-text blocks as tagged placeholders; only returned text enters the checkpoint, excluding reasoning and tool calls that would leak private reasoning or create an orphaned call.
@@ -16,41 +16,34 @@ This backend owns the compaction policy:
 - **Lifecycle** — `compactRegion()` records its start, summary, replacement, and end. The serial `agent/pre-step` listener checks pressure before every step, outside an open step, so a tool-heavy turn remains compactable and the loop derives history once after mutation.
 - **Failure handling** — an unmatched `compact/start` is an inert crash marker because no replacement landed. Recoverable failure records an error end and leaves the surface unchanged.
 
-`estimateContentTokens()` and `summarize()` are overridable hooks: a tokenizer-based or template-based backend can subclass `BasicCompactService` and override just those, reusing the retention walk and surface plumbing. `summarize()` returns the summary blocks together with the call envelope it actually used (`{ summary, model, maxTokens? }`) — the caller logs that envelope on the `compact/summary` provenance event, so an overriding backend reports its own envelope honestly.
+`summarize()` is the sole subclass hook. A template- or remote-summarizer subclass can override it while pressure, retention, provenance, shrink validation, and shadowed-token accounting stay on the conversation model's meter. The hook returns the summary blocks together with the call envelope it used (`{ summary, model, maxTokens? }`), which is logged on `compact/summary`.
 
 ## Config (`BasicCompactConfig`)
 
-Every knob is **required** except `auto` — there is no concrete data yet to justify default thresholds/budgets, so a consumer states each value explicitly rather than inherit a guessed default. `auto` alone defaults to `true`.
+Every common setting is optional. Every model known to `ctx.tokenMeter` receives the default compact policy lazily; named overrides merge only the fields supplied and must name a configured meter profile.
 
 | Key | Required | Meaning |
 |---|---|---|
-| `contextWindow` | yes | Context window size in tokens. |
-| `thresholdRatio` | yes | Compact when estimated usage exceeds this fraction of the window. |
-| `retainTokens` | yes | Tokens of recent context to keep intact. |
-| `summarizationModel` | yes | Model for summarization (`''` → use the agent's model). |
-| `maxTokens` | yes | Provider generation cap for the summarization call; may include reasoning tokens. |
-| `compactionRetries` | yes | Extra compaction attempts after the first if the compacted surface remains over threshold. |
-| `auto` | no (default `true`) | Register the `agent/pre-step` auto-compaction listener. Set `false` for manual-only. |
-| `charsPerToken` | no (default `4`) | Token-estimator text density (estimated tokens = chars / `charsPerToken`; may be fractional). The default suits English text; CJK-heavy deployments should set ~1-2 or the estimate undershoots several-fold and compaction fires too late. |
+| `models.<model>.thresholdRatio` | no (default `0.8`) | Compact at `floor(contextWindow × ratio)`. |
+| `models.<model>.retainTokens` | no (default `floor(contextWindow × 0.16)`) | Recent surface budget kept verbatim; must be below the threshold. |
+| `summarizationModel` | no (default `''`) | Empty resolves the latest logged routed model, then `AgentOptions.model`. |
+| `maxTokens` | no (default `8192`) | Provider generation cap for the summarization call; may include reasoning tokens. |
+| `compactionRetries` | no (default `1`) | Extra attempts after the first when pressure remains above threshold. |
+| `auto` | no (default `true`) | Register the `agent/pre-step` automatic listener. Set `false` for manual-only. |
 
 ## Usage
 
 ```ts
 import type { Context } from 'cordis'
 import { BasicCompactService } from '@deepseek-ai/dsh-compact-basic'
+import TokenMeterService from '@deepseek-ai/dsh-token-meter'
 
 export const name = 'compact-basic'
 export const inject = ['llm']
 
 export function apply(ctx: Context): void {
-  ctx.plugin(BasicCompactService, {
-    contextWindow: 128000,
-    thresholdRatio: 0.8,
-    retainTokens: 20480,
-    summarizationModel: '',
-    maxTokens: 8192,
-    compactionRetries: 1,
-  })
+  ctx.plugin(TokenMeterService)
+  ctx.plugin(BasicCompactService)
 }
 ```
 
@@ -122,8 +115,8 @@ Rules:
 
 ## Known Limitations and Deferred Work
 
-- **Token estimation is the chars/`charsPerToken` heuristic** — a marked TODO schedules replacing it with an exact count (a real tokenizer, or provider `usage` fed back) so thresholds track the model's actual budget.
-- **`estimatePressure()` does not count the request's `tools` field** — pressure is underestimated by the size of the serialized tool schemas the request also carries.
+- **Pre-step sees a provisional request envelope** — the current prompt and prefix are exact, but routing and tool changes made later in `agent/request` are not logged yet. A router-only agent with no provisional model skips that check.
+- **Meter accuracy follows the selected profile** — missing provider usage falls back to the token meter's configured character density and structural overhead.
 - **`compactRegion` requires an open turn** — a manual call on a fully-closed session throws ("no open turn") rather than compacting.
 - **Summarization failure fails closed with full, over-budget history** — including truncation at the summarization `maxTokens`, which hidden reasoning tokens can consume; the auto path logs a warning and proceeds.
 - **The summarization call has no transcript-snapshot coverage** — `dsh-llm-replay` derives calls from `assistant/chunk` events, so this chunk-less direct `ctx.llm.stream()` call cannot replay (named deferred replay infrastructure in [the seam RFC](../../../docs/rfc/implemented/feature/2026-06-18-compaction-capability-seam.md)).