fix(core): honor compaction agent model for summaries (#53276)

Co-authored-by: Padure Sergio <70955746+sergiopadure@users.noreply.github.com>

packages/core/src/session/compaction.ts

@@ -19,9 +19,11 @@ import type { SessionCompactionResult } from "@opencode/plugin/effect/session"
 import type { SessionError } from "@opencode/schema/session-error"
 import { makeLocationNode } from "@opencode/util/effect/app-node"
 import { Context, Effect, Layer, Result, Stream } from "effect"
+import { Agent } from "../agent.js"
 import { Bus } from "../bus.js"
 import { Database } from "../database/database.js"
 import { llmClient } from "../effect/app-node-platform.js"
+import { Model } from "../model.js"
 import { State } from "../state.js"
 import { Token } from "../util/token.js"
 import type { SessionContext } from "./context.js"
@@ -30,6 +32,7 @@ import { SessionHistory } from "./history.js"
 import type { SessionMessage } from "./message.js"
 import { SessionModelRequest } from "./model-request.js"
 import { SessionProviderContext } from "./provider-context.js"
+import { SessionRunnerModel } from "./runner/model.js"
 import { SessionRunnerRetry } from "./runner/retry.js"
 import { toLLMMessages } from "./runner/to-llm-message.js"
 import { contentFilterError, toSessionError } from "./to-session-error.js"
@@ -181,8 +184,11 @@ const LEGACY_HEADING = "## Additional Context"
 export const layer = Layer.effect(
   Service,
   Effect.gen(function* () {
+    const agents = yield* Agent.Service
     const bus = yield* Bus.Service
     const llm = yield* LLMClient.Service
+    const catalog = yield* Model.Service
+    const models = yield* SessionRunnerModel.Service
     const db = (yield* Database.Service).db
     const requests = yield* SessionModelRequest.Service
 
@@ -202,24 +208,33 @@ export const layer = Layer.effect(
 
       // Only the user compacts when automatic compaction is off, overflow included.
       if (trigger.reason !== "manual" && !settings.auto) return { status: "skipped" }
-      const ceiling = calculateCeiling(context.model.limit, settings.buffer)
-      if (trigger.reason === "auto" && !due(context, ceiling)) return { status: "skipped" }
+      if (trigger.reason === "auto" && !due(context, calculateCeiling(context.model.limit, settings.buffer)))
+        return { status: "skipped" }
+      const native = context.model.compaction?.type === "native"
+      const agent = native ? undefined : yield* agents.get(Agent.ID.make("compaction"))
+      const model =
+        (agent?.model &&
+          (yield* models
+            .resolve({ ...context.session, model: agent.model }, catalog.available)
+            .pipe(Effect.orElseSucceed(() => undefined)))) ??
+        context.model
+      const ceiling = calculateCeiling(model.limit, settings.buffer)
       // An unknown window never triggers auto compaction, but the compaction request still needs a size to aim for.
       const cap = Number.isFinite(ceiling)
         ? ceiling
-        : calculateCeiling({ ...context.model.limit, context: UNKNOWN_WINDOW }, settings.buffer)
+        : calculateCeiling({ ...model.limit, context: UNKNOWN_WINDOW }, settings.buffer)
       // The provider just rejected this context, so the estimate ran low; the first attempt already aims below it.
       const budget =
         trigger.reason === "overflow" ? Math.min(cap, Math.floor(estimateContext(context) * SHRINK_STEPS[0])) : cap
 
-      const compaction =
-        context.model.compaction?.type === "native"
-          ? compactNatively(trigger, budget, settings.keep)
-          : summarize(trigger, budget, settings.keep)
+      const selected = model === context.model ? trigger : { ...trigger, context: { ...context, model } }
+      const compaction = native
+        ? compactNatively(selected, budget, settings.keep)
+        : summarize(selected, budget, settings.keep)
       return yield* compaction.pipe(
         Effect.matchEffect({
-          onSuccess: (result) => publish(trigger, result),
-          onFailure: (failure) => publish(trigger, failure),
+          onSuccess: (result) => publish(selected, result),
+          onFailure: (failure) => publish(selected, failure),
         }),
       )
     })
@@ -662,7 +677,7 @@ export const layer = Layer.effect(
 export const node = makeLocationNode({
   service: Service,
   layer,
-  deps: [Bus.node, Database.node, llmClient, SessionModelRequest.node],
+  deps: [Agent.node, Bus.node, Database.node, llmClient, Model.node, SessionModelRequest.node, SessionRunnerModel.node],
 })
 
 /** History loads from the latest completed compaction, so a previous one is always the first message. */

packages/core/test/config/compaction.test.ts

@@ -46,6 +46,7 @@ const it = testEffect(
         }),
       ),
       Config.node.replace(config),
+      Location.node.replace(Location.boundNode({ directory: AbsolutePath.make("/tmp") })),
     ]),
   ),
 )

packages/core/test/session-compaction.test.ts

@@ -18,6 +18,7 @@ import { SessionRunnerModel } from "@opencode/core/session/runner/model"
 import { SessionTable } from "@opencode/core/session/sql"
 import { SessionStore } from "@opencode/core/session/store"
 import { Session } from "@opencode/core/session"
+import { Location } from "@opencode/core/location"
 import { Project } from "@opencode/core/project"
 import { ProjectTable } from "@opencode/core/project/sql"
 import { App } from "@opencode/core/app"
@@ -87,7 +88,11 @@ const it = testEffect(
       SessionModelRequest.node,
       PluginHooks.node,
     ]),
-    [Bus.node.replace(Bus.configured({ persist: true })), llmClient.replace(client)],
+    [
+      Bus.node.replace(Bus.configured({ persist: true })),
+      llmClient.replace(client),
+      Location.node.replace(Location.boundNode({ directory: AbsolutePath.make("/project") })),
+    ],
   ),
 )
 

packages/core/test/session-native-compaction.test.ts

@@ -8,6 +8,7 @@ import { AppNodeBuilder } from "@opencode/core/effect/app-node-builder"
 import { llmClient } from "@opencode/core/effect/app-node-platform"
 import { Instructions } from "@opencode/core/instructions/index"
 import { PluginHooks } from "@opencode/core/plugin/hooks"
+import { Location } from "@opencode/core/location"
 import { Project } from "@opencode/core/project"
 import { ProjectTable } from "@opencode/core/project/sql"
 import { AbsolutePath } from "@opencode/core/schema"
@@ -40,7 +41,10 @@ const it = testEffect(
       PluginHooks.node,
       llmClient,
     ]),
-    [Bus.node.replace(Bus.configured({ persist: true }))],
+    [
+      Bus.node.replace(Bus.configured({ persist: true })),
+      Location.node.replace(Location.boundNode({ directory: AbsolutePath.make("/project") })),
+    ],
   ),
 )