refactor(core): simplify system context into a belief model (#34917)

packages/core/src/session/context-checkpoint.ts

@@ -0,0 +1,131 @@
+export * as SessionContextCheckpoint from "./context-checkpoint"
+
+import { eq } from "drizzle-orm"
+import { DateTime, Effect, Option, Schema } from "effect"
+import type { Database } from "../database/database"
+import { EventV2 } from "../event"
+import { SystemContext } from "../system-context/index"
+import { SessionEvent } from "./event"
+import { SessionHistory } from "./history"
+import { SessionMessage } from "./message"
+import { SessionSchema } from "./schema"
+import { SessionContextCheckpointTable } from "./sql"
+
+type DatabaseService = Database.Interface["db"]
+
+const decodeApplied = Schema.decodeUnknownOption(SystemContext.Applied)
+
+/**
+ * Loads or creates the session's durable context checkpoint, narrating any
+ * drift since the model was last told as a chronological update. Completed
+ * compaction rebaselines; nothing else rewrites the baseline. Runs before
+ * input promotion so a blocked first turn leaves pending inputs untouched.
+ */
+export const prepare = Effect.fn("SessionContextCheckpoint.prepare")(function* (
+  db: DatabaseService,
+  events: EventV2.Interface,
+  context: Effect.Effect<SystemContext.SystemContext>,
+  sessionID: SessionSchema.ID,
+) {
+  const [value, stored, compaction] = yield* Effect.all(
+    [context, find(db, sessionID), SessionHistory.latestCompaction(db, sessionID)],
+    { concurrency: "unbounded" },
+  )
+  if (!stored) {
+    const baseline = yield* SystemContext.initialize(value)
+    const baselineSeq = yield* insert(db, sessionID, baseline)
+    return { baseline: baseline.text, baselineSeq }
+  }
+
+  // The applied record is comparison state only; an undecodable one heals by
+  // treating every source as new, re-announcing baselines as updates.
+  const applied = Option.getOrElse(decodeApplied(stored.snapshot), () => ({}))
+  if (compaction !== undefined && compaction.seq > stored.baseline_seq) {
+    const baseline = yield* SystemContext.rebaseline(value, applied)
+    yield* rewrite(db, sessionID, compaction.seq, baseline)
+    return { baseline: baseline.text, baselineSeq: compaction.seq }
+  }
+  const result = yield* SystemContext.reconcile(value, applied)
+  if (result._tag === "Unchanged") return { baseline: stored.baseline, baselineSeq: stored.baseline_seq }
+
+  yield* events.publish(
+    SessionEvent.ContextUpdated,
+    { sessionID, messageID: SessionMessage.ID.create(), timestamp: yield* DateTime.now, text: result.text },
+    { commit: () => advance(db, sessionID, result.applied).pipe(Effect.orDie) },
+  )
+  return { baseline: stored.baseline, baselineSeq: stored.baseline_seq }
+})
+
+export const reset = Effect.fn("SessionContextCheckpoint.reset")(function* (
+  db: DatabaseService,
+  sessionID: SessionSchema.ID,
+) {
+  yield* db
+    .delete(SessionContextCheckpointTable)
+    .where(eq(SessionContextCheckpointTable.session_id, sessionID))
+    .run()
+    .pipe(Effect.orDie)
+})
+
+const find = Effect.fnUntraced(function* (db: DatabaseService, sessionID: SessionSchema.ID) {
+  return yield* db
+    .select()
+    .from(SessionContextCheckpointTable)
+    .where(eq(SessionContextCheckpointTable.session_id, sessionID))
+    .get()
+    .pipe(Effect.orDie)
+})
+
+const insert = Effect.fnUntraced(function* (
+  db: DatabaseService,
+  sessionID: SessionSchema.ID,
+  baseline: SystemContext.Baseline,
+) {
+  const baselineSeq = yield* EventV2.latestSequence(db, sessionID)
+  yield* db
+    .insert(SessionContextCheckpointTable)
+    .values({
+      session_id: sessionID,
+      baseline: baseline.text,
+      snapshot: baseline.applied,
+      baseline_seq: baselineSeq,
+    })
+    .run()
+    .pipe(Effect.orDie)
+  return baselineSeq
+})
+
+const rewrite = Effect.fnUntraced(function* (
+  db: DatabaseService,
+  sessionID: SessionSchema.ID,
+  baselineSeq: number,
+  baseline: SystemContext.Baseline,
+) {
+  const updated = yield* db
+    .update(SessionContextCheckpointTable)
+    .set({
+      baseline: baseline.text,
+      snapshot: baseline.applied,
+      baseline_seq: baselineSeq,
+    })
+    .where(eq(SessionContextCheckpointTable.session_id, sessionID))
+    .returning({ sessionID: SessionContextCheckpointTable.session_id })
+    .get()
+    .pipe(Effect.orDie)
+  if (!updated) return yield* Effect.die("Context checkpoint not found")
+})
+
+const advance = Effect.fnUntraced(function* (
+  db: DatabaseService,
+  sessionID: SessionSchema.ID,
+  applied: SystemContext.Applied,
+) {
+  const updated = yield* db
+    .update(SessionContextCheckpointTable)
+    .set({ snapshot: applied })
+    .where(eq(SessionContextCheckpointTable.session_id, sessionID))
+    .returning({ sessionID: SessionContextCheckpointTable.session_id })
+    .get()
+    .pipe(Effect.orDie)
+  if (!updated) return yield* Effect.die("Context checkpoint not found")
+})

packages/core/src/session/context-epoch.ts

@@ -1,174 +0,0 @@
-export * as SessionContextEpoch from "./context-epoch"
-
-import { eq } from "drizzle-orm"
-import { DateTime, Effect, Schema } from "effect"
-import type { Database } from "../database/database"
-import { EventV2 } from "../event"
-import { SystemContext } from "../system-context/index"
-import { ContextSnapshotDecodeError } from "./error"
-import { SessionEvent } from "./event"
-import { SessionHistory } from "./history"
-import { SessionInput } from "./input"
-import { SessionMessage } from "./message"
-import { SessionSchema } from "./schema"
-import { SessionContextEpochTable } from "./sql"
-
-type DatabaseService = Database.Interface["db"]
-
-interface Prepared {
-  readonly baseline: string
-  readonly baselineSeq: number
-}
-
-export function initialize(
-  db: DatabaseService,
-  context: Effect.Effect<SystemContext.SystemContext>,
-  sessionID: SessionSchema.ID,
-): Effect.Effect<Prepared | undefined, SystemContext.InitializationBlocked> {
-  return initializeOnce(db, context, sessionID).pipe(Effect.withSpan("SessionContextEpoch.initialize"))
-}
-
-export function prepare(
-  db: DatabaseService,
-  events: EventV2.Interface,
-  context: Effect.Effect<SystemContext.SystemContext>,
-  sessionID: SessionSchema.ID,
-): Effect.Effect<Prepared, SystemContext.InitializationBlocked | ContextSnapshotDecodeError> {
-  return prepareOnce(db, events, context, sessionID).pipe(Effect.withSpan("SessionContextEpoch.prepare"))
-}
-
-const prepareOnce = Effect.fnUntraced(function* (
-  db: DatabaseService,
-  events: EventV2.Interface,
-  context: Effect.Effect<SystemContext.SystemContext>,
-  sessionID: SessionSchema.ID,
-) {
-  const [value, stored, compaction] = yield* Effect.all(
-    [context, find(db, sessionID), SessionHistory.latestCompaction(db, sessionID)],
-    { concurrency: "unbounded" },
-  )
-  if (!stored) {
-    const generation = yield* SystemContext.initialize(value)
-    const baselineSeq = yield* insert(db, sessionID, generation)
-    return { baseline: generation.baseline, baselineSeq }
-  }
-
-  const snapshot = yield* Schema.decodeUnknownEffect(SystemContext.Snapshot)(stored.snapshot).pipe(
-    Effect.mapError((error) => new ContextSnapshotDecodeError({ sessionID, details: String(error) })),
-  )
-  const replacementSeq = compaction !== undefined && compaction.seq > stored.baseline_seq ? compaction.seq : undefined
-  const result = replacementSeq
-    ? yield* SystemContext.replace(value, snapshot)
-    : yield* SystemContext.reconcile(value, snapshot)
-  if (result._tag === "Unchanged" || result._tag === "ReplacementBlocked") {
-    return { baseline: stored.baseline, baselineSeq: stored.baseline_seq }
-  }
-  if (result._tag === "ReplacementReady") {
-    const baselineSeq = replacementSeq ?? (yield* EventV2.latestSequence(db, sessionID))
-    yield* replace(db, sessionID, baselineSeq, result.generation)
-    return { baseline: result.generation.baseline, baselineSeq }
-  }
-
-  yield* events.publish(
-    SessionEvent.ContextUpdated,
-    { sessionID, messageID: SessionMessage.ID.create(), timestamp: yield* DateTime.now, text: result.text },
-    { commit: () => advance(db, sessionID, result.snapshot).pipe(Effect.orDie) },
-  )
-  return { baseline: stored.baseline, baselineSeq: stored.baseline_seq }
-})
-
-const initializeOnce = Effect.fnUntraced(function* (
-  db: DatabaseService,
-  context: Effect.Effect<SystemContext.SystemContext>,
-  sessionID: SessionSchema.ID,
-) {
-  if (yield* exists(db, sessionID)) return
-  const generation = yield* context.pipe(Effect.flatMap(SystemContext.initialize))
-  const baselineSeq = yield* insert(db, sessionID, generation)
-  return { baseline: generation.baseline, baselineSeq }
-})
-
-const exists = Effect.fn("SessionContextEpoch.exists")(function* (db: DatabaseService, sessionID: SessionSchema.ID) {
-  return (
-    (yield* db
-      .select({ sessionID: SessionContextEpochTable.session_id })
-      .from(SessionContextEpochTable)
-      .where(eq(SessionContextEpochTable.session_id, sessionID))
-      .get()
-      .pipe(Effect.orDie)) !== undefined
-  )
-})
-
-const find = Effect.fn("SessionContextEpoch.find")(function* (db: DatabaseService, sessionID: SessionSchema.ID) {
-  return yield* db
-    .select()
-    .from(SessionContextEpochTable)
-    .where(eq(SessionContextEpochTable.session_id, sessionID))
-    .get()
-    .pipe(Effect.orDie)
-})
-
-export const reset = Effect.fn("SessionContextEpoch.reset")(function* (
-  db: DatabaseService,
-  sessionID: SessionSchema.ID,
-) {
-  yield* db
-    .delete(SessionContextEpochTable)
-    .where(eq(SessionContextEpochTable.session_id, sessionID))
-    .run()
-    .pipe(Effect.orDie)
-})
-
-const insert = Effect.fnUntraced(function* (
-  db: DatabaseService,
-  sessionID: SessionSchema.ID,
-  generation: SystemContext.Generation,
-) {
-  const baselineSeq = yield* EventV2.latestSequence(db, sessionID)
-  yield* db
-    .insert(SessionContextEpochTable)
-    .values({
-      session_id: sessionID,
-      baseline: generation.baseline,
-      snapshot: generation.snapshot,
-      baseline_seq: baselineSeq,
-    })
-    .run()
-    .pipe(Effect.orDie)
-  return baselineSeq
-})
-
-const replace = Effect.fnUntraced(function* (
-  db: DatabaseService,
-  sessionID: SessionSchema.ID,
-  baselineSeq: number,
-  generation: SystemContext.Generation,
-) {
-  const updated = yield* db
-    .update(SessionContextEpochTable)
-    .set({
-      baseline: generation.baseline,
-      snapshot: generation.snapshot,
-      baseline_seq: baselineSeq,
-    })
-    .where(eq(SessionContextEpochTable.session_id, sessionID))
-    .returning({ sessionID: SessionContextEpochTable.session_id })
-    .get()
-    .pipe(Effect.orDie)
-  if (!updated) return yield* Effect.die("Context Epoch not found")
-})
-
-const advance = Effect.fnUntraced(function* (
-  db: DatabaseService,
-  sessionID: SessionSchema.ID,
-  snapshot: SystemContext.Snapshot,
-) {
-  const updated = yield* db
-    .update(SessionContextEpochTable)
-    .set({ snapshot })
-    .where(eq(SessionContextEpochTable.session_id, sessionID))
-    .returning({ sessionID: SessionContextEpochTable.session_id })
-    .get()
-    .pipe(Effect.orDie)
-  if (!updated) return yield* Effect.die("Context Epoch not found")
-})

packages/core/src/session/error.ts

@@ -10,15 +10,3 @@ export class MessageDecodeError extends Schema.TaggedErrorClass<MessageDecodeErr
     return `Failed to decode message ${this.messageID} in session ${this.sessionID}`
   }
 }
-
-export class ContextSnapshotDecodeError extends Schema.TaggedErrorClass<ContextSnapshotDecodeError>()(
-  "Session.ContextSnapshotDecodeError",
-  {
-    sessionID: SessionSchema.ID,
-    details: Schema.String,
-  },
-) {
-  override get message() {
-    return `Failed to decode context snapshot for session ${this.sessionID}: ${this.details}`
-  }
-}

packages/core/src/session/history.ts

@@ -4,7 +4,7 @@ import { Database } from "../database/database"
 import { MessageDecodeError } from "./error"
 import { SessionMessage } from "./message"
 import { SessionSchema } from "./schema"
-import { SessionContextEpochTable, SessionMessageTable } from "./sql"
+import { SessionContextCheckpointTable, SessionMessageTable } from "./sql"
 
 type DatabaseService = Database.Interface["db"]
 
@@ -33,6 +33,9 @@ const messageRows = Effect.fnUntraced(function* (
     .where(
       and(
         eq(SessionMessageTable.session_id, sessionID),
+        // Keep system updates visible in the gap between a completed compaction
+        // and the next prepared turn's rebaseline, when their content is not yet
+        // folded into a new baseline.
         compaction
           ? or(
               gte(SessionMessageTable.seq, compaction.seq),
@@ -67,9 +70,9 @@ export const load = Effect.fn("SessionHistory.load")(function* (db: DatabaseServ
   const [epoch, compaction] = yield* Effect.all(
     [
       db
-        .select({ baselineSeq: SessionContextEpochTable.baseline_seq })
-        .from(SessionContextEpochTable)
-        .where(eq(SessionContextEpochTable.session_id, sessionID))
+        .select({ baselineSeq: SessionContextCheckpointTable.baseline_seq })
+        .from(SessionContextCheckpointTable)
+        .where(eq(SessionContextCheckpointTable.session_id, sessionID))
         .get()
         .pipe(Effect.orDie),
       latestCompaction(db, sessionID),
@@ -79,14 +82,6 @@ export const load = Effect.fn("SessionHistory.load")(function* (db: DatabaseServ
   return yield* Effect.forEach(yield* messageRows(db, sessionID, compaction, epoch?.baselineSeq), decodeMessageRow)
 })
 
-export const loadForRunner = Effect.fn("SessionHistory.loadForRunner")(function* (
-  db: DatabaseService,
-  sessionID: SessionSchema.ID,
-  baselineSeq: number,
-) {
-  return (yield* entriesForRunner(db, sessionID, baselineSeq)).map((entry) => entry.message)
-})
-
 export const entriesForRunner = Effect.fn("SessionHistory.entriesForRunner")(function* (
   db: DatabaseService,
   sessionID: SessionSchema.ID,

packages/core/src/session/projector.ts

@@ -12,8 +12,15 @@ import { SessionMessage } from "./message"
 import { SessionMessageUpdater } from "./message-updater"
 import { SessionInput } from "./input"
 import { WorkspaceV2 } from "../workspace"
-import { SessionContextEpoch } from "./context-epoch"
-import { MessageTable, PartTable, SessionInputTable, SessionMessageTable, SessionTable } from "./sql"
+import { SessionContextCheckpoint } from "./context-checkpoint"
+import {
+  MessageTable,
+  PartTable,
+  SessionContextCheckpointTable,
+  SessionInputTable,
+  SessionMessageTable,
+  SessionTable,
+} from "./sql"
 import type { DeepMutable } from "../schema"
 import { Slug } from "../util/slug"
 
@@ -156,12 +163,16 @@ const projectFork = Effect.fn("SessionProjector.projectFork")(function* (
         .select({ seq: SessionMessageTable.seq })
         .from(SessionMessageTable)
         .where(
-          and(eq(SessionMessageTable.session_id, event.data.parentID), eq(SessionMessageTable.id, event.data.messageID)),
+          and(
+            eq(SessionMessageTable.session_id, event.data.parentID),
+            eq(SessionMessageTable.id, event.data.messageID),
+          ),
         )
         .get()
         .pipe(Effect.orDie)
     : undefined
-  if (event.data.messageID && !boundary) return yield* Effect.die(`Fork boundary message not found: ${event.data.messageID}`)
+  if (event.data.messageID && !boundary)
+    return yield* Effect.die(`Fork boundary message not found: ${event.data.messageID}`)
   const copied = yield* db
     .select({ seq: SessionMessageTable.seq })
     .from(SessionMessageTable)
@@ -206,6 +217,23 @@ const projectFork = Effect.fn("SessionProjector.projectFork")(function* (
     .pipe(Effect.orDie)
   if (!stored) return yield* Effect.die(new SessionAlreadyProjected())
 
+  // The fork inherits the parent's transcript, so it inherits the context
+  // checkpoint that transcript was built against: copied message seqs keep
+  // folding at the same baseline horizon.
+  const checkpoint = yield* db
+    .select()
+    .from(SessionContextCheckpointTable)
+    .where(eq(SessionContextCheckpointTable.session_id, event.data.parentID))
+    .get()
+    .pipe(Effect.orDie)
+  if (checkpoint) {
+    yield* db
+      .insert(SessionContextCheckpointTable)
+      .values({ ...checkpoint, session_id: event.data.sessionID })
+      .run()
+      .pipe(Effect.orDie)
+  }
+
   const usage = emptyUsage()
   let cursor = -1
   while (true) {
@@ -452,7 +480,7 @@ const layer = Layer.effectDiscard(
           .where(eq(SessionTable.id, event.data.sessionID))
           .run()
           .pipe(Effect.orDie)
-        yield* SessionContextEpoch.reset(db, event.data.sessionID)
+        yield* SessionContextCheckpoint.reset(db, event.data.sessionID)
       }),
     )
     yield* events.project(SessionV1.Event.Deleted, (event) =>
@@ -666,7 +694,7 @@ const layer = Layer.effectDiscard(
           .where(eq(SessionTable.id, event.data.sessionID))
           .run()
           .pipe(Effect.orDie)
-        yield* SessionContextEpoch.reset(db, event.data.sessionID)
+        yield* SessionContextCheckpoint.reset(db, event.data.sessionID)
       }),
     )
   }),

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

@@ -3,7 +3,7 @@ export * as SessionRunner from "./index"
 import type { LLMError } from "@opencode-ai/llm"
 import { Context, Effect } from "effect"
 import { SessionSchema } from "../schema"
-import type { ContextSnapshotDecodeError, MessageDecodeError } from "../error"
+import type { MessageDecodeError } from "../error"
 import { SessionRunnerModel } from "./model"
 import type { SystemContext } from "../../system-context/index"
 import type { ToolOutputStore } from "../../tool-output-store"
@@ -12,7 +12,6 @@ export type RunError =
   | LLMError
   | SessionRunnerModel.Error
   | MessageDecodeError
-  | ContextSnapshotDecodeError
   | SystemContext.InitializationBlocked
   | ToolOutputStore.Error
 

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

@@ -18,13 +18,14 @@ 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 { SystemContextBuiltIns } from "../../system-context/builtins"
+import { InstructionContext } from "../../instruction-context"
 import { SkillGuidance } from "../../skill/guidance"
 import { ReferenceGuidance } from "../../reference/guidance"
 import { McpGuidance } from "../../mcp/guidance"
 import { ToolRegistry } from "../../tool/registry"
 import { ToolOutputStore } from "../../tool-output-store"
-import { SessionContextEpoch } from "../context-epoch"
+import { SessionContextCheckpoint } from "../context-checkpoint"
 import { SessionCompaction } from "../compaction"
 import { SessionEvent } from "../event"
 import { SessionHistory } from "../history"
@@ -102,7 +103,8 @@ const layer = Layer.effect(
     const models = yield* SessionRunnerModel.Service
     const store = yield* SessionStore.Service
     const location = yield* Location.Service
-    const systemContext = yield* SystemContextRegistry.Service
+    const builtins = yield* SystemContextBuiltIns.Service
+    const instructions = yield* InstructionContext.Service
     const skillGuidance = yield* SkillGuidance.Service
     const referenceGuidance = yield* ReferenceGuidance.Service
     const mcpGuidance = yield* McpGuidance.Service
@@ -170,9 +172,16 @@ const layer = Layer.effect(
       new TurnTransitionError({ _tag: "ContinueAfterOverflowCompaction", step })
 
     const loadSystemContext = (agent: AgentV2.Selection) =>
-      Effect.all([systemContext.load(), skillGuidance.load(agent), referenceGuidance.load(), mcpGuidance.load(agent)], {
-        concurrency: "unbounded",
-      }).pipe(Effect.map(SystemContext.combine))
+      Effect.all(
+        [
+          builtins.load(),
+          instructions.load(),
+          skillGuidance.load(agent),
+          referenceGuidance.load(),
+          mcpGuidance.load(agent),
+        ],
+        { concurrency: "unbounded" },
+      ).pipe(Effect.map(SystemContext.combine))
 
     const runTurnAttempt = Effect.fn("SessionRunner.runTurn")(function* (
       sessionID: SessionSchema.ID,
@@ -184,7 +193,9 @@ const layer = Layer.effect(
       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)
+      // Establish what the model knows before admitting what the user said, so
+      // a blocked first turn leaves pending inputs untouched.
+      const checkpoint = yield* SessionContextCheckpoint.prepare(db, events, loadSystemContext(agent), session.id)
       const toolFibers = yield* FiberSet.make<void, ToolOutputStore.Error>()
       let needsContinuation = false
       let currentStep = step
@@ -198,10 +209,8 @@ const layer = Layer.effect(
         }
         if (promoted > 0) currentStep = 1
       }
-      const system =
-        initialized ?? (yield* SessionContextEpoch.prepare(db, events, loadSystemContext(agent), session.id))
       const model = yield* models.resolve(session)
-      const entries = yield* SessionHistory.entriesForRunner(db, session.id, system.baselineSeq)
+      const entries = yield* SessionHistory.entriesForRunner(db, session.id, checkpoint.baselineSeq)
       const context = entries.map((entry) => entry.message)
       const isLastStep = agent.info?.steps !== undefined && currentStep >= agent.info.steps
       const toolMaterialization = isLastStep
@@ -211,7 +220,10 @@ const layer = Layer.effect(
       const request = LLM.request({
         model,
         providerOptions: { openai: { promptCacheKey } },
-        system: [agent.info?.system ? agent.info.system : SessionRunnerSystemPrompt.provider(model), system.baseline]
+        system: [
+          agent.info?.system ? agent.info.system : SessionRunnerSystemPrompt.provider(model),
+          checkpoint.baseline,
+        ]
           .filter((part): part is string => part !== undefined && part.length > 0)
           .map(SystemPart.make),
         messages: [...toLLMMessages(context, model), ...(isLastStep ? [Message.assistant(MAX_STEPS_PROMPT)] : [])],
@@ -462,7 +474,8 @@ export const node = makeLocationNode({
     SessionRunnerModel.node,
     SessionStore.node,
     Location.node,
-    SystemContextRegistry.node,
+    SystemContextBuiltIns.node,
+    InstructionContext.node,
     SkillGuidance.node,
     ReferenceGuidance.node,
     McpGuidance.node,

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

@@ -103,7 +103,9 @@ const withDefaults = (model: ModelV2.Info, route: AnyRoute) => {
   })
 }
 
-const providerOptions = (model: ModelV2.Info) => {
+const providerOptions = (
+  model: ModelV2.Info,
+): { readonly [key: string]: { readonly [key: string]: unknown } } | undefined => {
   if (Object.keys(model.request.settings).length === 0) return undefined
   if (model.api.type !== "aisdk") return undefined
   if (model.api.package === "@ai-sdk/openai") return { openai: model.request.settings }

packages/core/src/session/sql.ts

@@ -165,12 +165,12 @@ export const SessionInputTable = sqliteTable(
   ],
 )
 
-export const SessionContextEpochTable = sqliteTable("session_context_epoch", {
+export const SessionContextCheckpointTable = sqliteTable("session_context_epoch", {
   session_id: text()
     .$type<SessionSchema.ID>()
     .primaryKey()
     .references(() => SessionTable.id, { onDelete: "cascade" }),
   baseline: text().notNull(),
-  snapshot: text({ mode: "json" }).notNull().$type<SystemContext.Snapshot>(),
+  snapshot: text({ mode: "json" }).notNull().$type<SystemContext.Applied>(),
   baseline_seq: integer().notNull(),
 })

packages/core/src/session/store.ts

@@ -14,10 +14,6 @@ import { fromRow } from "./info"
 export interface Interface {
   readonly get: (sessionID: SessionSchema.ID) => Effect.Effect<SessionSchema.Info | undefined>
   readonly context: (sessionID: SessionSchema.ID) => Effect.Effect<SessionMessage.Message[], MessageDecodeError>
-  readonly runnerContext: (
-    sessionID: SessionSchema.ID,
-    baselineSeq: number,
-  ) => Effect.Effect<SessionMessage.Message[], MessageDecodeError>
   readonly message: (
     messageID: SessionMessage.ID,
   ) => Effect.Effect<{ readonly sessionID: SessionSchema.ID; readonly message: SessionMessage.Message } | undefined>
@@ -39,9 +35,6 @@ const layer = Layer.effect(
       context: Effect.fn("SessionStore.context")(function* (sessionID) {
         return yield* SessionHistory.load(db, sessionID)
       }),
-      runnerContext: Effect.fn("SessionStore.runnerContext")(function* (sessionID, baselineSeq) {
-        return yield* SessionHistory.loadForRunner(db, sessionID, baselineSeq)
-      }),
       message: Effect.fn("SessionStore.message")(function* (messageID) {
         const row = yield* db
           .select()