refactor(core): simplify tool settlement outcomes

packages/core/src/session/runner/llm.ts

@@ -1,37 +1,12 @@
-import {
-  LLM,
-  LLMClient,
-  LLMError,
-  LLMEvent,
-  SystemPart,
-  isContextOverflowFailure,
-  type ProviderErrorEvent,
-} from "@opencode-ai/llm"
-import { Cause, DateTime, Effect, FiberSet, Layer, Option, Schema, Semaphore, Stream } from "effect"
-import { AgentV2 } from "../../agent"
-import { Config } from "../../config"
+import { DateTime, Effect, Layer } from "effect"
 import { Database } from "../../database/database"
 import { EventV2 } from "../../event"
-import { Location } from "../../location"
-import { ModelV2 } from "../../model"
-import { ProviderV2 } from "../../provider"
-import { QuestionV2 } from "../../question"
-import { SystemContext } from "../../system-context/index"
-import { SystemContextRegistry } from "../../system-context/registry"
-import { SkillGuidance } from "../../skill/guidance"
-import { ToolRegistry } from "../../tool/registry"
-import { ToolOutputStore } from "../../tool-output-store"
-import { SessionContextEpoch } from "../context-epoch"
-import { SessionCompaction } from "../compaction"
 import { SessionEvent } from "../event"
-import { SessionHistory } from "../history"
 import { SessionInput } from "../input"
 import { SessionSchema } from "../schema"
 import { SessionStore } from "../store"
-import { type RunError, Service, StepLimitExceededError } from "./index"
-import { SessionRunnerModel } from "./model"
-import { createLLMEventPublisher } from "./publish-llm-event"
-import { toLLMMessages } from "./to-llm-message"
+import { Service, StepLimitExceededError } from "./index"
+import { RunTurn } from "./run-turn"
 
 /**
  * Runs one durable coding-agent Session until it settles.
@@ -75,8 +50,9 @@ import { toLLMMessages } from "./to-llm-message"
  *   - [ ] Coalesce streamed deltas and add covering projected-history indexes.
  *   - [ ] Update title, summaries, compaction state, and cleanup in bounded background work.
  *
- * Use `llm.stream(request)` for each provider turn. Keep tool execution and continuation here.
- * Durable activity recovery remains a separate future slice with an explicit retry policy.
+ * `RunTurn` owns provider-turn preparation, streaming, tool settlement, and continuation signals.
+ * This module owns durable activity scheduling and bounded continuation. Durable activity recovery
+ * remains a separate future slice with an explicit retry policy.
  *
  * The current slice loads V2 history, translates it, resolves a model through a core service, and persists one
  * provider turn. Registry definitions are advertised, local tool calls are settled durably, and a
@@ -90,22 +66,9 @@ export const layer = Layer.effect(
   Service,
   Effect.gen(function* () {
     const events = yield* EventV2.Service
-    const llm = yield* LLMClient.Service
-    const agents = yield* AgentV2.Service
-    const tools = yield* ToolRegistry.Service
-    const models = yield* SessionRunnerModel.Service
     const store = yield* SessionStore.Service
-    const location = yield* Location.Service
-    const systemContext = yield* SystemContextRegistry.Service
-    const skillGuidance = yield* SkillGuidance.Service
-    const config = yield* Config.Service
     const db = (yield* Database.Service).db
-    const compaction = SessionCompaction.make({ events, llm, config: yield* config.entries() })
-    const getSession = Effect.fn("SessionRunner.getSession")(function* (sessionID: SessionSchema.ID) {
-      const session = yield* store.get(sessionID)
-      if (!session) return yield* Effect.die(`Session not found: ${sessionID}`)
-      return session
-    })
+    const runTurn = yield* RunTurn.make
 
     const getContext = Effect.fn("SessionRunner.getContext")(function* (sessionID: SessionSchema.ID) {
       return yield* store.context(sessionID)
@@ -132,242 +95,6 @@ export const layer = Layer.effect(
       }
     })
 
-    const awaitToolFibers = (fibers: FiberSet.FiberSet<void, ToolOutputStore.Error>) =>
-      Effect.raceFirst(FiberSet.join(fibers), FiberSet.awaitEmpty(fibers))
-
-    // Match V1: dismissing a question halts the loop instead of becoming model-facing tool output.
-    const isQuestionRejected = (cause: Cause.Cause<unknown>) =>
-      cause.reasons.some((reason) => Cause.isDieReason(reason) && reason.defect instanceof QuestionV2.RejectedError)
-
-    type TurnTransition =
-      // Request preparation observed a concurrent Session change and must restart from durable state.
-      | { readonly _tag: "RebuildPreparedTurn"; readonly promotion?: SessionInput.Delivery }
-      // Overflow compaction completed; rebuild once through the path without overflow recovery.
-      | { readonly _tag: "ContinueAfterOverflowCompaction" }
-
-    class TurnTransitionError extends Error {
-      constructor(readonly transition: TurnTransition) {
-        super()
-      }
-    }
-
-    const rebuildPreparedTurn = (promotion?: SessionInput.Delivery) =>
-      new TurnTransitionError({ _tag: "RebuildPreparedTurn", promotion })
-    const continueAfterOverflowCompaction = new TurnTransitionError({
-      _tag: "ContinueAfterOverflowCompaction",
-    })
-
-    const retryAgentMismatch = (promotion: SessionInput.Delivery | undefined) =>
-      Effect.catchDefect((defect) =>
-        defect instanceof SessionContextEpoch.AgentMismatch
-          ? Effect.die(rebuildPreparedTurn(promotion))
-          : Effect.die(defect),
-      )
-
-    const sameModel = Schema.toEquivalence(Schema.UndefinedOr(ModelV2.Ref))
-    const loadSystemContext = (agent: AgentV2.Selection) =>
-      Effect.all([systemContext.load(), skillGuidance.load(agent)], { concurrency: "unbounded" }).pipe(
-        Effect.map(SystemContext.combine),
-      )
-
-    const runTurnAttempt = Effect.fn("SessionRunner.runTurn")(function* (
-      sessionID: SessionSchema.ID,
-      promotion: SessionInput.Delivery | undefined,
-      recoverOverflow?: typeof compaction.compactAfterOverflow,
-    ) {
-      const session = yield* getSession(sessionID)
-      if (session.location.directory !== location.directory || session.location.workspaceID !== location.workspaceID)
-        return yield* Effect.interrupt
-      const agent = yield* agents.select(session.agent)
-      const initialized = yield* SessionContextEpoch.initialize(
-        db,
-        loadSystemContext(agent),
-        session.id,
-        session.location,
-        agent.id,
-      ).pipe(retryAgentMismatch(promotion))
-      const toolFibers = yield* FiberSet.make<void, ToolOutputStore.Error>()
-      let needsContinuation = false
-      if (promotion) {
-        const cutoff = yield* SessionInput.latestSeq(db, session.id)
-        if (promotion === "steer") yield* SessionInput.promoteSteers(db, events, session.id, cutoff)
-        if (promotion === "queue") {
-          yield* SessionInput.promoteNextQueued(db, events, session.id)
-          yield* SessionInput.promoteSteers(db, events, session.id, cutoff)
-        }
-      }
-      const system =
-        initialized ??
-        (yield* SessionContextEpoch.prepare(
-          db,
-          events,
-          loadSystemContext(agent),
-          session.id,
-          session.location,
-          agent.id,
-        ).pipe(retryAgentMismatch(undefined)))
-      const current = yield* getSession(sessionID)
-      if ((yield* agents.select(current.agent)).id !== agent.id || !sameModel(current.model, session.model))
-        return yield* Effect.die(rebuildPreparedTurn())
-      const model = yield* models.resolve(session)
-      const entries = yield* SessionHistory.entriesForRunner(db, session.id, system.baselineSeq)
-      const context = entries.map((entry) => entry.message)
-      const toolMaterialization = yield* tools.materialize(agent.info?.permissions)
-      const promptCacheKey = /^ses_[0-9a-f]{64}$/.test(session.id) ? session.id.slice(4) : session.id
-      const request = LLM.request({
-        model,
-        providerOptions: { openai: { promptCacheKey } },
-        system: [agent.info?.system, system.baseline]
-          .filter((part): part is string => part !== undefined && part.length > 0)
-          .map(SystemPart.make),
-        messages: toLLMMessages(context, model),
-        tools: toolMaterialization.definitions,
-      })
-      if (yield* compaction.compactIfNeeded({ sessionID: session.id, entries, model, request }))
-        return yield* Effect.die(rebuildPreparedTurn())
-      const publisher = createLLMEventPublisher(events, {
-        sessionID: session.id,
-        agent: agent.id,
-        model: {
-          id: ModelV2.ID.make(model.id),
-          providerID: ProviderV2.ID.make(model.provider),
-          ...(session.model?.variant === undefined ? {} : { variant: session.model.variant }),
-        },
-      })
-      const withPublication = Semaphore.makeUnsafe(1).withPermit
-      const publish = (event: LLMEvent, outputPaths: ReadonlyArray<string> = []) =>
-        withPublication(publisher.publish(event, outputPaths))
-      let overflowFailure: ProviderErrorEvent | undefined
-      if (!(yield* SessionContextEpoch.current(db, session.id, agent.id, system.revision)))
-        return yield* Effect.die(rebuildPreparedTurn())
-      const providerStream = llm.stream(request).pipe(
-        Stream.runForEach((event) =>
-          Effect.gen(function* () {
-            if (overflowFailure || publisher.hasProviderError()) return
-            if (LLMEvent.is.providerError(event)) {
-              if (isContextOverflowFailure(event) && !publisher.hasAssistantStarted()) {
-                overflowFailure = event
-                return
-              }
-            }
-            yield* publish(event)
-            if (event.type !== "tool-call" || event.providerExecuted) return
-            needsContinuation = true
-            const assistantMessageID = yield* publisher.assistantMessageID(event.id)
-            yield* Effect.uninterruptibleMask((restore) =>
-              restore(
-                toolMaterialization.settle({
-                  sessionID: session.id,
-                  agent: agent.id,
-                  assistantMessageID,
-                  call: event,
-                }),
-              ).pipe(
-                Effect.flatMap((settlement) =>
-                  publish(
-                    LLMEvent.toolResult({
-                      id: event.id,
-                      name: event.name,
-                      result: settlement.result,
-                      output: settlement.output,
-                    }),
-                    settlement.outputPaths ?? [],
-                  ),
-                ),
-              ),
-            ).pipe(FiberSet.run(toolFibers))
-          }),
-        ),
-        Effect.ensuring(withPublication(publisher.flush())),
-      )
-
-      return yield* Effect.uninterruptibleMask((restore) =>
-        Effect.gen(function* () {
-          const stream = yield* restore(providerStream).pipe(Effect.exit)
-          const failure =
-            stream._tag === "Failure" ? Option.getOrUndefined(Cause.findErrorOption(stream.cause)) : undefined
-          if (
-            recoverOverflow &&
-            !publisher.hasAssistantStarted() &&
-            isContextOverflowFailure(overflowFailure ?? failure) &&
-            (yield* restore(recoverOverflow({ sessionID: session.id, entries, model, request })))
-          )
-            return yield* Effect.die(continueAfterOverflowCompaction)
-          if (overflowFailure) yield* publish(overflowFailure)
-          const llmFailure = failure instanceof LLMError ? failure : undefined
-          if (llmFailure && !publisher.hasProviderError()) {
-            yield* withPublication(publisher.failUnsettledTools("Provider did not return a tool result", true))
-            yield* withPublication(
-              events.publish(SessionEvent.Step.Failed, {
-                sessionID: session.id,
-                timestamp: yield* DateTime.now,
-                assistantMessageID: yield* publisher.startAssistant(),
-                error: { type: "unknown", message: llmFailure.reason.message },
-              }),
-            )
-          }
-          if (stream._tag === "Failure" && Cause.hasInterrupts(stream.cause)) yield* FiberSet.clear(toolFibers)
-          const settled = yield* restore(awaitToolFibers(toolFibers)).pipe(Effect.exit)
-          if (settled._tag === "Failure" && isQuestionRejected(settled.cause)) {
-            yield* FiberSet.clear(toolFibers)
-            yield* withPublication(publisher.failUnsettledTools("Tool execution interrupted"))
-            return yield* Effect.interrupt
-          }
-          if (
-            (stream._tag === "Failure" && Cause.hasInterrupts(stream.cause)) ||
-            (settled._tag === "Failure" && Cause.hasInterrupts(settled.cause))
-          ) {
-            yield* FiberSet.clear(toolFibers)
-            yield* withPublication(publisher.failUnsettledTools("Tool execution interrupted"))
-          }
-          if (settled._tag === "Failure" && !Cause.hasInterrupts(settled.cause)) {
-            const failure = Cause.squash(settled.cause)
-            const message = failure instanceof Error ? failure.message : String(failure)
-            yield* withPublication(publisher.failUnsettledTools(`Tool execution failed: ${message}`))
-          }
-          if (publisher.hasProviderError())
-            yield* withPublication(publisher.failUnsettledTools("Tool execution interrupted"))
-          if (stream._tag === "Success" && !publisher.hasProviderError())
-            yield* withPublication(publisher.failUnsettledTools("Provider did not return a tool result", true))
-          if (stream._tag === "Failure") return yield* Effect.failCause(stream.cause)
-          if (settled._tag === "Failure") return yield* Effect.failCause(settled.cause)
-          return !publisher.hasProviderError() && needsContinuation
-        }),
-      )
-    }, Effect.scoped)
-    type RunTurn = (
-      sessionID: SessionSchema.ID,
-      promotion: SessionInput.Delivery | undefined,
-    ) => Effect.Effect<boolean, RunError>
-
-    const runAfterOverflowCompaction: RunTurn = Effect.fnUntraced(function* (sessionID, promotion) {
-      return yield* runTurnAttempt(sessionID, promotion).pipe(
-        Effect.catchDefect(
-          Effect.fnUntraced(function* (defect) {
-            if (!(defect instanceof TurnTransitionError)) return yield* Effect.die(defect)
-            if (defect.transition._tag === "ContinueAfterOverflowCompaction")
-              return yield* Effect.die("Post-compaction provider attempt cannot recover another overflow")
-            yield* Effect.yieldNow
-            return yield* runAfterOverflowCompaction(sessionID, defect.transition.promotion)
-          }),
-        ),
-      )
-    })
-
-    const runTurn: RunTurn = Effect.fnUntraced(function* (sessionID, promotion) {
-      return yield* runTurnAttempt(sessionID, promotion, compaction.compactAfterOverflow).pipe(
-        Effect.catchDefect(
-          Effect.fnUntraced(function* (defect) {
-            if (!(defect instanceof TurnTransitionError)) return yield* Effect.die(defect)
-            yield* Effect.yieldNow
-            if (defect.transition._tag === "ContinueAfterOverflowCompaction")
-              return yield* runAfterOverflowCompaction(sessionID, undefined)
-            return yield* runTurn(sessionID, defect.transition.promotion)
-          }),
-        ),
-      )
-    })
-
     const run = Effect.fn("SessionRunner.run")(function* (input: {
       readonly sessionID: SessionSchema.ID
       readonly force?: boolean
@@ -381,7 +108,7 @@ export const layer = Layer.effect(
       while (openActivity) {
         let needsContinuation = true
         for (let step = 0; step < MAX_STEPS; step++) {
-          needsContinuation = yield* runTurn(input.sessionID, promotion)
+          needsContinuation = yield* runTurn({ sessionID: input.sessionID, delivery: promotion })
           promotion = "steer"
           if (!needsContinuation) needsContinuation = yield* SessionInput.hasPending(db, input.sessionID, "steer")
           if (!needsContinuation) break

packages/core/src/session/runner/run-turn.ts

@@ -0,0 +1,332 @@
+export * as RunTurn from "./run-turn"
+
+/**
+ * Sends the next request to the model and finishes every tool call it starts.
+ *
+ * Before sending, it makes admitted input visible, loads the latest Session
+ * history and instructions, and compacts oversized history. If the model rejects
+ * the request for being too large before producing output, it may compact and
+ * try once more. Returns `true` when tool results require another model request.
+ */
+
+import {
+  LLM,
+  LLMClient,
+  LLMError,
+  LLMEvent,
+  SystemPart,
+  isContextOverflowFailure,
+  type ProviderErrorEvent,
+} from "@opencode-ai/llm"
+import { Cause, DateTime, Effect, Exit, FiberSet, Option, Schema, Semaphore, Stream } from "effect"
+import { AgentV2 } from "../../agent"
+import { Config } from "../../config"
+import { Database } from "../../database/database"
+import { EventV2 } from "../../event"
+import { Location } from "../../location"
+import { ModelV2 } from "../../model"
+import { ProviderV2 } from "../../provider"
+import { QuestionV2 } from "../../question"
+import { SkillGuidance } from "../../skill/guidance"
+import { SystemContext } from "../../system-context/index"
+import { SystemContextRegistry } from "../../system-context/registry"
+import { ToolOutputStore } from "../../tool-output-store"
+import { ToolRegistry } from "../../tool/registry"
+import { SessionCompaction } from "../compaction"
+import { SessionContextEpoch } from "../context-epoch"
+import { SessionEvent } from "../event"
+import { SessionHistory } from "../history"
+import { SessionInput } from "../input"
+import { SessionSchema } from "../schema"
+import { SessionStore } from "../store"
+import type { RunError } from "./index"
+import { SessionRunnerModel } from "./model"
+import { createLLMEventPublisher } from "./publish-llm-event"
+import { toLLMMessages } from "./to-llm-message"
+
+export interface Input {
+  readonly sessionID: SessionSchema.ID
+  readonly delivery?: SessionInput.Delivery
+}
+
+const AttemptResult = Schema.TaggedUnion({
+  Complete: { needsContinuation: Schema.Boolean },
+  CompactedOverflow: {},
+})
+
+const isQuestionRejected = (cause: Cause.Cause<unknown>) =>
+  cause.reasons.some((reason) => Cause.isDieReason(reason) && reason.defect instanceof QuestionV2.RejectedError)
+
+const awaitTools = (fibers: FiberSet.FiberSet<void, ToolOutputStore.Error>) =>
+  Effect.raceFirst(FiberSet.join(fibers), FiberSet.awaitEmpty(fibers))
+
+export const make = Effect.gen(function* () {
+  const events = yield* EventV2.Service
+  const llm = yield* LLMClient.Service
+  const agents = yield* AgentV2.Service
+  const tools = yield* ToolRegistry.Service
+  const models = yield* SessionRunnerModel.Service
+  const store = yield* SessionStore.Service
+  const location = yield* Location.Service
+  const systemContext = yield* SystemContextRegistry.Service
+  const skillGuidance = yield* SkillGuidance.Service
+  const config = yield* Config.Service
+  const db = (yield* Database.Service).db
+  const compaction = SessionCompaction.make({ events, llm, config: yield* config.entries() })
+
+  const getSession = Effect.fn("SessionRunner.getSession")(function* (sessionID: SessionSchema.ID) {
+    const session = yield* store.get(sessionID)
+    if (!session) return yield* Effect.die(`Session not found: ${sessionID}`)
+    return session
+  })
+  const stale = Symbol("stale turn preparation")
+  const retryAgentMismatch = <A, E, R>(effect: Effect.Effect<A, E, R>) =>
+    effect.pipe(
+      Effect.catchDefect((defect) =>
+        defect instanceof SessionContextEpoch.AgentMismatch ? Effect.succeed(stale) : Effect.die(defect),
+      ),
+    )
+  const loadSystemContext = (agent: AgentV2.Selection) =>
+    Effect.all([systemContext.load(), skillGuidance.load(agent)], { concurrency: "unbounded" }).pipe(
+      Effect.map(SystemContext.combine),
+    )
+  const promoteDelivery = Effect.fnUntraced(function* (sessionID: SessionSchema.ID, delivery: SessionInput.Delivery) {
+    const cutoff = yield* SessionInput.latestSeq(db, sessionID)
+    if (delivery === "queue") yield* SessionInput.promoteNextQueued(db, events, sessionID)
+    yield* SessionInput.promoteSteers(db, events, sessionID, cutoff)
+  })
+
+  /**
+   * Builds the next model request from durable Session state.
+   *
+   * Initial instructions must be available before admitted input becomes visible.
+   * Once input is promoted, retries load it from history instead of promoting
+   * again. This matters for queued input because promotion opens the next item.
+   */
+  const buildRequest = Effect.fn("SessionRunner.buildRequest")(function* (
+    sessionID: SessionSchema.ID,
+    delivery: SessionInput.Delivery | undefined,
+  ) {
+    let pendingDelivery = delivery
+    while (true) {
+      const session = yield* getSession(sessionID)
+      if (session.location.directory !== location.directory || session.location.workspaceID !== location.workspaceID)
+        return yield* Effect.interrupt
+      const agent = yield* agents.select(session.agent)
+      const initialized = yield* retryAgentMismatch(
+        SessionContextEpoch.initialize(db, loadSystemContext(agent), session.id, session.location, agent.id),
+      )
+      if (initialized === stale) continue
+      if (pendingDelivery) {
+        yield* promoteDelivery(session.id, pendingDelivery)
+        pendingDelivery = undefined
+      }
+      const prepared =
+        initialized ??
+        (yield* retryAgentMismatch(
+          SessionContextEpoch.prepare(db, events, loadSystemContext(agent), session.id, session.location, agent.id),
+        ))
+      if (prepared === stale) continue
+      const system = prepared
+      const model = yield* models.resolve(session)
+      const entries = yield* SessionHistory.entriesForRunner(db, session.id, system.baselineSeq)
+      const toolMaterialization = yield* tools.materialize(agent.info?.permissions)
+      const request = LLM.request({
+        model,
+        providerOptions: {
+          openai: { promptCacheKey: /^ses_[0-9a-f]{64}$/.test(session.id) ? session.id.slice(4) : session.id },
+        },
+        system: [agent.info?.system, system.baseline]
+          .filter((part): part is string => part !== undefined && part.length > 0)
+          .map(SystemPart.make),
+        messages: toLLMMessages(
+          entries.map((entry) => entry.message),
+          model,
+        ),
+        tools: toolMaterialization.definitions,
+      })
+      if (yield* compaction.compactIfNeeded({ sessionID: session.id, entries, model, request })) {
+        continue
+      }
+      if (!(yield* SessionContextEpoch.current(db, session.id, agent.id, system.revision))) {
+        continue
+      }
+      return { session, agent, model, entries, request, toolMaterialization }
+    }
+  })
+
+  type RequestSnapshot = Effect.Success<ReturnType<typeof buildRequest>>
+
+  /**
+   * Reads one model response and finishes every tool it starts.
+   *
+   * Provider events and tool results share one permit so durable events stay in
+   * order. Tool calls are recorded before their side effects begin. A pre-output
+   * overflow is held back so successful compaction does not leave a terminal
+   * error in Session history.
+   */
+  const streamAndSettle = Effect.fn("SessionRunner.streamAndSettle")(function* (
+    prepared: RequestSnapshot,
+    canRecoverOverflow: boolean,
+  ) {
+    const publisher = createLLMEventPublisher(events, {
+      sessionID: prepared.session.id,
+      agent: prepared.agent.id,
+      model: {
+        id: ModelV2.ID.make(prepared.model.id),
+        providerID: ProviderV2.ID.make(prepared.model.provider),
+        ...(prepared.session.model?.variant === undefined ? {} : { variant: prepared.session.model.variant }),
+      },
+    })
+    const withPublication = Semaphore.makeUnsafe(1).withPermit
+    const publish = (event: LLMEvent, outputPaths: ReadonlyArray<string> = []) =>
+      withPublication(publisher.publish(event, outputPaths))
+    const failUnsettled = (message: string, providerExecuted = false) =>
+      withPublication(publisher.failUnsettledTools(message, providerExecuted))
+    let needsContinuation = false
+    let overflowFailure: ProviderErrorEvent | undefined
+    const toolEffect = Effect.fnUntraced(function* (event: Extract<LLMEvent, { readonly type: "tool-call" }>) {
+      needsContinuation = true
+      const assistantMessageID = yield* publisher.assistantMessageID(event.id)
+      return yield* prepared.toolMaterialization
+        .settle({
+          sessionID: prepared.session.id,
+          agent: prepared.agent.id,
+          assistantMessageID,
+          call: event,
+        })
+        .pipe(
+          Effect.flatMap((settlement) =>
+            publish(
+              LLMEvent.toolResult({
+                id: event.id,
+                name: event.name,
+                result: settlement.result,
+                output: settlement.output,
+              }),
+              settlement.outputPaths ?? [],
+            ),
+          ),
+        )
+    })
+    const handleProviderEvent = Effect.fnUntraced(function* (
+      event: LLMEvent,
+      tools: FiberSet.FiberSet<void, ToolOutputStore.Error>,
+    ) {
+      if (overflowFailure || publisher.hasProviderError()) return
+      if (LLMEvent.is.providerError(event) && isContextOverflowFailure(event) && !publisher.hasAssistantStarted()) {
+        overflowFailure = event
+        return
+      }
+      yield* publish(event)
+      if (event.type !== "tool-call" || event.providerExecuted) return
+      yield* toolEffect(event).pipe(FiberSet.run(tools))
+    })
+    const providerStream = (tools: FiberSet.FiberSet<void, ToolOutputStore.Error>) =>
+      llm.stream(prepared.request).pipe(
+        Stream.runForEach((event) => handleProviderEvent(event, tools)),
+        Effect.ensuring(withPublication(publisher.flush())),
+      )
+    const projectProviderFailure = Effect.fnUntraced(function* (failure: unknown) {
+      if (overflowFailure) yield* publish(overflowFailure)
+      if (!(failure instanceof LLMError) || publisher.hasProviderError()) return
+      yield* failUnsettled("Provider did not return a tool result", true)
+      yield* withPublication(
+        events.publish(SessionEvent.Step.Failed, {
+          sessionID: prepared.session.id,
+          timestamp: yield* DateTime.now,
+          assistantMessageID: yield* publisher.startAssistant(),
+          error: { type: "unknown", message: failure.reason.message },
+        }),
+      )
+    })
+    const finishToolsSuccessfully = Effect.fnUntraced(function* <A, E>(stream: Exit.Exit<A, E>) {
+      if (Exit.hasInterrupts(stream) || publisher.hasProviderError()) yield* failUnsettled("Tool execution interrupted")
+      if (Exit.isSuccess(stream) && !publisher.hasProviderError())
+        yield* failUnsettled("Provider did not return a tool result", true)
+      if (Exit.isFailure(stream)) return yield* Effect.failCause(stream.cause)
+    })
+    const finishToolsAfterFailure = Effect.fnUntraced(function* <A, E>(
+      stream: Exit.Exit<A, E>,
+      tools: FiberSet.FiberSet<void, ToolOutputStore.Error>,
+      cause: Cause.Cause<ToolOutputStore.Error>,
+    ) {
+      if (isQuestionRejected(cause)) {
+        yield* FiberSet.clear(tools)
+        yield* failUnsettled("Tool execution interrupted")
+        return yield* Effect.interrupt
+      }
+      const interrupted = Cause.hasInterrupts(cause)
+      if (interrupted) yield* FiberSet.clear(tools)
+      if (Exit.hasInterrupts(stream) || interrupted || publisher.hasProviderError())
+        yield* failUnsettled("Tool execution interrupted")
+      if (!interrupted) {
+        const failure = Cause.squash(cause)
+        yield* failUnsettled(`Tool execution failed: ${failure instanceof Error ? failure.message : String(failure)}`)
+      }
+      if (Exit.isFailure(stream)) return yield* Effect.failCause(stream.cause)
+      return yield* Effect.failCause(cause)
+    })
+    const finishTools = Effect.fnUntraced(function* <A, E>(
+      stream: Exit.Exit<A, E>,
+      tools: FiberSet.FiberSet<void, ToolOutputStore.Error>,
+      wait: Effect.Effect<void, ToolOutputStore.Error>,
+    ) {
+      if (Exit.hasInterrupts(stream)) yield* FiberSet.clear(tools)
+      return yield* wait.pipe(
+        Effect.matchCauseEffect({
+          onFailure: (cause) => finishToolsAfterFailure(stream, tools, cause),
+          onSuccess: () => finishToolsSuccessfully(stream),
+        }),
+      )
+    })
+    const settleProviderTurn = Effect.fnUntraced(function* () {
+      const tools = yield* FiberSet.make<void, ToolOutputStore.Error>()
+      return yield* Effect.uninterruptibleMask((restore) =>
+        Effect.gen(function* () {
+          const stream = yield* restore(providerStream(tools)).pipe(Effect.exit)
+          const failure =
+            stream._tag === "Failure" ? Option.getOrUndefined(Cause.findErrorOption(stream.cause)) : undefined
+          const recovered =
+            canRecoverOverflow &&
+            !publisher.hasAssistantStarted() &&
+            isContextOverflowFailure(overflowFailure ?? failure) &&
+            (yield* restore(
+              compaction.compactAfterOverflow({
+                sessionID: prepared.session.id,
+                entries: prepared.entries,
+                model: prepared.model,
+                request: prepared.request,
+              }),
+            ))
+          if (recovered) return AttemptResult.cases.CompactedOverflow.make({})
+
+          yield* projectProviderFailure(failure)
+          yield* finishTools(stream, tools, restore(awaitTools(tools)))
+          return AttemptResult.cases.Complete.make({
+            needsContinuation: !publisher.hasProviderError() && needsContinuation,
+          })
+        }),
+      )
+    })
+    return yield* settleProviderTurn()
+  }, Effect.scoped)
+
+  const run = Effect.fn("SessionRunner.runTurn")(function* (input: Input): Effect.fn.Return<boolean, RunError> {
+    let pendingDelivery = input.delivery
+    let canRecoverOverflow = true
+    while (true) {
+      const request = yield* buildRequest(input.sessionID, pendingDelivery)
+      pendingDelivery = undefined
+      const result = yield* streamAndSettle(request, canRecoverOverflow)
+      const next = AttemptResult.match(result, {
+        Complete: (completed) => completed.needsContinuation,
+        CompactedOverflow: () => undefined,
+      })
+      if (next !== undefined) return next
+      canRecoverOverflow = false
+    }
+  })
+
+  return run
+})