compact: summarize is a direct one-shot llm/stream call, not a loop step

The summarization request no longer dispatches agent/request — that seam
shapes the loop's conversation requests; a hand-built one-shot's
interception surface is llm/stream, like every other direct call. The
model comes from summarizationModel falling back to the agent's own. The
turn/step parameters existed on the compact seam only to feed the
agent/request dispatch and leave compactIfNeeded/compactRegion.

Groundwork for making every conversation request a pure function of the
session log (reconstructability RFC, this branch): the seam split keeps
the loop's request path as the single thing the log must explain.

Ported from worktree-prompt-prefix-stability (PR #162) where it was
review-converged; catalog and producer/consumer graphs regenerated.

packages/compact/compact/README.md

@@ -18,8 +18,8 @@ Both methods are **abstract** — the backend owns the entire strategy (token es
 
 | Member | Semantics |
 |---|---|
-| `compactIfNeeded(agent, turn, step, fullSystemPrompt, signal)` | Estimate the surface-derived history size; if over the backend's threshold, compact an older range via `compactRegion`, keeping recent context intact. Returns the `CompactionResult`, or `null` if nothing needed compacting. All parameters required — the loop's `agent/pre-step` checkpoint supplies the agent, lifecycle context, assembled `fullSystemPrompt`, and turn `signal`; router-aware summarizers can use the agent lifecycle context to route their own model call through `agent/request`. |
-| `compactRegion(session, start, end, agent, turn, step, signal?)` | Forcibly summarize surface nodes `[start, end]` (inclusive seqs) into a single replacement node. **Throws** if a compaction is already in progress, if `start`/`end` aren't surface nodes, or if `start` is positioned after `end` on the surface. The range is a SURFACE-POSITION span, not a numeric seq interval — after a prior replace lands a fresh high-seq summary node at the shadowed range's position, surface order no longer tracks seq order. |
+| `compactIfNeeded(agent, fullSystemPrompt, signal)` | Estimate the surface-derived history size; if over the backend's threshold, compact an older range via `compactRegion`, keeping recent context intact. Returns the `CompactionResult`, or `null` if nothing needed compacting. All parameters required — the loop's `agent/pre-step` checkpoint supplies the agent, assembled `fullSystemPrompt`, and turn `signal`. A backend's summarization request is a direct `ctx.llm.stream()` call (not a loop step), so per-call interception happens at `llm/stream`. |
+| `compactRegion(session, start, end, agent, signal?)` | Forcibly summarize surface nodes `[start, end]` (inclusive seqs) into a single replacement node. **Throws** if a compaction is already in progress, if `start`/`end` aren't surface nodes, or if `start` is positioned after `end` on the surface. The range is a SURFACE-POSITION span, not a numeric seq interval — after a prior replace lands a fresh high-seq summary node at the shadowed range's position, surface order no longer tracks seq order. |
 
 `compactIfNeeded` takes a required `signal`; `compactRegion`'s is optional. A backend that summarizes via `ctx.llm.stream()` **must** forward it into the call's `GenerateOptions.signal`, so an abort or fiber dispose tears down the in-flight summarization instead of leaving an orphaned model call running past the cancellation. The session being compacted comes from the agent context; the turn that the `compact/*` events belong to is recoverable from the log (the currently-open turn), so the backend stamps it from the log rather than trusting a caller-supplied value.
 

packages/compact/compact/src/index.ts

@@ -91,8 +91,6 @@ export abstract class CompactService extends Service {
    *   over-budget. Bounding an individual unit's size is a separate concern.
    *
    * @param agent - agent context owning the session surface and model options.
-   * @param turn - turn number of the pre-step checkpoint.
-   * @param step - step number about to start.
    * @param fullSystemPrompt - assembled system prompt, counted toward the estimate.
    * @param signal - cancellation signal. A backend summarizing via
    *   `ctx.llm.stream()` MUST forward this into the call's `GenerateOptions.signal`
@@ -102,8 +100,6 @@ export abstract class CompactService extends Service {
    */
   abstract compactIfNeeded(
     agent: CompactAgentContext,
-    turn: number,
-    step: number,
     fullSystemPrompt: string,
     signal: AbortSignal,
   ): Promise<CompactionResult | null>
@@ -129,8 +125,6 @@ export abstract class CompactService extends Service {
    * @param start - inclusive seq of the first surface node to compact.
    * @param end - inclusive seq of the last surface node to compact.
    * @param agent - agent context used by router-aware summarizers.
-   * @param turn - lifecycle turn forwarded to request-routing seams.
-   * @param step - lifecycle step forwarded to request-routing seams.
    * @param signal - optional cancellation signal. A backend that summarizes via
    *   `ctx.llm.stream()` MUST forward this into the call's `GenerateOptions.signal`
    *   so an abort/dispose tears down the in-flight summarization rather than
@@ -148,8 +142,6 @@ export abstract class CompactService extends Service {
     start: number,
     end: number,
     agent: CompactAgentContext,
-    turn: number,
-    step: number,
     signal?: AbortSignal,
   ): Promise<CompactionResult>
 }

packages/compact/compact/tests/compact.spec.ts

@@ -17,8 +17,6 @@ class StubCompactService extends CompactService {
 
   override async compactIfNeeded(
     _agent: CompactAgentContext,
-    _turn: number,
-    _step: number,
     _fullSystemPrompt: string,
     signal: AbortSignal,
   ): Promise<CompactionResult | null> {
@@ -31,8 +29,6 @@ class StubCompactService extends CompactService {
     start: number,
     end: number,
     _agent: CompactAgentContext,
-    _turn: number,
-    _step: number,
     signal?: AbortSignal,
   ): Promise<CompactionResult> {
     this.lastSignal = signal
@@ -81,7 +77,7 @@ describe('CompactService seam', () => {
     const ctx = new Context()
     const svc = new StubCompactService(ctx)
     const session = new Session(SessionId('s'))
-    expect(await svc.compactIfNeeded(stubAgent(session), 1, 1, '', new AbortController().signal)).toBeNull()
+    expect(await svc.compactIfNeeded(stubAgent(session), '', new AbortController().signal)).toBeNull()
   })
 
   it('compact/* events merge into SessionEventMap and are log-only', async () => {
@@ -89,7 +85,7 @@ describe('CompactService seam', () => {
     const svc = new StubCompactService(ctx)
     const session = new Session(SessionId('s'))
 
-    const result = await svc.compactRegion(session, 0, 0, stubAgent(session, 'm'), 1, 1)
+    const result = await svc.compactRegion(session, 0, 0, stubAgent(session, 'm'))
 
     const startEvent = session.events.find(e => e.type === 'compact/start')
     expect(startEvent).toBeDefined()
@@ -107,10 +103,10 @@ describe('CompactService seam', () => {
     const session = new Session(SessionId('s'))
     const controller = new AbortController()
 
-    await svc.compactRegion(session, 0, 0, stubAgent(session, 'm'), 1, 1, controller.signal)
+    await svc.compactRegion(session, 0, 0, stubAgent(session, 'm'), controller.signal)
     expect(svc.lastSignal).toBe(controller.signal)
 
-    await svc.compactIfNeeded(stubAgent(session), 1, 1, '', controller.signal)
+    await svc.compactIfNeeded(stubAgent(session), '', controller.signal)
     expect(svc.lastSignal).toBe(controller.signal)
   })
 })