fix(core): respect automatic compaction opt-out on overflow (#45036)

Co-authored-by: rekram1-node <rekram1-node@users.noreply.github.com>

packages/core/src/session/compaction.ts

@@ -103,6 +103,7 @@ export type Outcome =
   | Pick<SessionMessage.CompactionFailed, "status" | "error">
 
 export interface Interface extends State.Transformable<Draft> {
+  readonly enabled: () => boolean
   readonly required: (input: RequiredInput) => boolean
   readonly compact: (input: AutoInput) => Effect.Effect<Outcome>
   readonly compactManual: (input: ManualInput) => Effect.Effect<Outcome>
@@ -405,6 +406,7 @@ const make = (dependencies: Dependencies) => {
   return Service.of({
     transform: state.transform,
     reload: state.reload,
+    enabled: () => state.get().auto,
     required,
     compact,
     compactManual,

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

@@ -508,6 +508,7 @@ const layer = Layer.effect(
           // restart the step instead of surfacing the provider error.
           if (
             recoverOverflow &&
+            compaction.enabled() &&
             !publisher.record().outputStarted &&
             isContextOverflowFailure(overflowFailure ?? streamFailure) &&
             (yield* restore(compaction.compact(compactionInput))).status === "completed"

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

@@ -33,6 +33,7 @@ import { Session } from "@opencode-ai/core/session"
 import { Snapshot } from "@opencode-ai/core/snapshot"
 import { SessionEvent } from "@opencode-ai/core/session/event"
 import { SessionContext } from "@opencode-ai/core/session/context"
+import { SessionCompaction } from "@opencode-ai/core/session/compaction"
 import { SessionInbox } from "@opencode-ai/core/session/inbox"
 import { SessionMessage } from "@opencode-ai/core/session/message"
 import { SessionModelRequest } from "@opencode-ai/core/session/model-request"
@@ -458,6 +459,7 @@ const it = testEffect(
       Config.node,
       Snapshot.node,
       SessionContext.node,
+      SessionCompaction.node,
       SessionModelRequest.node,
       SessionRunnerLLM.node,
       SessionExecution.node,
@@ -2560,6 +2562,34 @@ describe("SessionRunnerLLM", () => {
     }),
   )
 
+  it.effect("does not recover provider context overflow when automatic compaction is disabled", () =>
+    Effect.gen(function* () {
+      const session = yield* setupOverflowRecovery
+      const compaction = yield* SessionCompaction.Service
+      yield* compaction.transform((draft) => draft.configure({ auto: false }))
+      yield* TestLLM.push(
+        [LLMEvent.providerError({ message: "prompt too long", classification: "context-overflow" })],
+        TestLLM.text("Must not compact", "text-unexpected-summary"),
+        TestLLM.text("Must not retry", "text-unexpected-retry"),
+      )
+      yield* admit(session, "Continue")
+      expect((yield* session.resume(sessionID).pipe(Effect.flip)).message).toBe("prompt too long")
+
+      expect(requests).toHaveLength(1)
+      expect(yield* session.context(sessionID)).toContainEqual(
+        expect.objectContaining({
+          type: "assistant",
+          finish: "error",
+          error: expect.objectContaining({ message: "prompt too long" }),
+        }),
+      )
+      expect(yield* session.context(sessionID)).not.toContainEqual(expect.objectContaining({ type: "compaction" }))
+      expect(yield* recordedEventTypes(sessionID)).not.toContain(
+        Bus.versionedType(SessionEvent.Compaction.Started.type, 1),
+      )
+    }),
+  )
+
   it.effect("recovers from provider context overflow without a configured context limit", () =>
     Effect.gen(function* () {
       const session = yield* setupOverflowRecovery

packages/www/src/docs/content/compaction.mdx

@@ -67,7 +67,7 @@ Add `compaction` to any [OpenCode configuration file](/config):
 
 | Field         | Default | V2 behavior                                                                                                                                   |
 | ------------- | ------: | --------------------------------------------------------------------------------------------------------------------------------------------- |
-| `auto`        |  `true` | Runs the preflight context-size check. It does not disable manual compaction or one-shot provider-overflow recovery.                          |
+| `auto`        |  `true` | Enables preflight context-size checks and one-shot provider-overflow recovery. Disabling it does not affect manual compaction.                |
 | `keep.tokens` | `15000` | Approximate number of tokens from the newest serialized conversation context to retain beside the summary.                                    |
 | `buffer`      | `20000` | Safety reserve below an explicit input limit. Without one, it is the minimum context reserve and the model output allowance wins when larger. |
 

specs/v2/session.md

@@ -73,7 +73,7 @@ Before each Step, the runner estimates the complete model-visible request agains
 
 The full transcript remains durable. Active model history after the compaction boundary contains the summary and retained recent context; provider-native continuation state does not cross that boundary.
 
-If the provider reports context overflow before durable assistant output or tool execution, the runner may perform one overflow-triggered compaction and rebuild the same logical Step. A second overflow or any overflow after durable output is terminal.
+If automatic compaction is enabled and the provider reports context overflow before durable assistant output or tool execution, the runner may perform one overflow-triggered compaction and rebuild the same logical Step. A second overflow, any overflow after durable output, or an overflow when automatic compaction is disabled is terminal.
 
 ## Durable Events Are Session-Scoped