feat(core): continue responses after output token limits

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

@@ -1,7 +1,7 @@
 export * as SessionRunnerLLM from "./llm.js"
 
 import { Message } from "@opencode/ai"
-import { and, desc, eq, sql } from "drizzle-orm"
+import { and, desc, eq, inArray, sql } from "drizzle-orm"
 import { Cause, Effect, Exit, FiberMap, Layer } from "effect"
 import { Database } from "../../database/database.js"
 import { Bus } from "../../bus.js"
@@ -35,6 +35,9 @@ import { MAX_STEPS_PROMPT } from "./max-steps.js"
 const CONTINUE_AFTER_INCOMPLETE_STREAM =
   "The previous response was interrupted. Continue from where you left off without repeating completed content."
 
+const CONTINUE_AFTER_OUTPUT_LIMIT =
+  "Your last response hit the output token limit (stop reason: length). Do not apologize, recap, or repeat yourself. Break the remaining work into smaller pieces."
+
 const layer = Layer.effect(
   Service,
   Effect.gen(function* () {
@@ -284,6 +287,36 @@ const layer = Layer.effect(
             yield* bus.publish(SessionEvent.Synthetic, { sessionID, text: CONTINUE_AFTER_INCOMPLETE_STREAM })
             assistantMessageID = SessionMessage.ID.create()
           }),
+          OutputLimit: Effect.fn("SessionRunner.continueOutputLimit")(function* (outcome) {
+            // The current response is included. User input or any other finish breaks the streak.
+            const rows = yield* db
+              .select()
+              .from(SessionMessageTable)
+              .where(
+                and(
+                  eq(SessionMessageTable.session_id, sessionID),
+                  inArray(SessionMessageTable.type, ["user", "assistant"]),
+                ),
+              )
+              .orderBy(desc(SessionMessageTable.seq))
+              .limit(3)
+              .all()
+              .pipe(Effect.orDie)
+            const recent = yield* Effect.forEach(rows, SessionHistory.decodeMessageRow)
+            const exhausted =
+              recent.length === 3 &&
+              recent.every((message) => message.type === "assistant" && message.finish === "length")
+            if (exhausted)
+              return yield* new StepFailedError({
+                error: {
+                  type: "output-limit",
+                  message: "Response still truncated after two output token limit continuations",
+                },
+              })
+            if (outcome.needsContinuation) return true
+            yield* bus.publish(SessionEvent.Synthetic, { sessionID, text: CONTINUE_AFTER_OUTPUT_LIMIT })
+            assistantMessageID = SessionMessage.ID.create()
+          }),
           Compacted: Effect.fnUntraced(function* () {
             recoverOverflow = false
             assistantMessageID = SessionMessage.ID.create()

packages/core/src/session/runner/publish-llm-event.ts

@@ -28,6 +28,32 @@ type Input = {
 const asRecord = (value: unknown): Record<string, unknown> =>
   typeof value === "object" && value !== null && !Array.isArray(value) ? (value as Record<string, unknown>) : { value }
 
+const INPUT_EXCERPT_LIMIT = 2048
+
+type InputExcerpt = {
+  readonly text: string
+  readonly length: number
+}
+
+type InputFailureReason = "malformed" | "length" | "incomplete"
+
+const INPUT_FAILURES = {
+  malformed: {
+    type: "tool.input-json",
+    message:
+      "The tool input could not be parsed as JSON, so the call was not executed. Reissue the call with valid JSON arguments.",
+  },
+  length: {
+    type: "tool.input-incomplete",
+    message:
+      "The tool call was not executed because the output token limit (stop reason: length) was reached before you could complete the arguments. Break large payloads into smaller tool calls and reissue the call with complete arguments.",
+  },
+  incomplete: {
+    type: "tool.input-incomplete",
+    message: "Tool call arguments were not completed and were not executed. Reissue the call with complete arguments.",
+  },
+} satisfies Record<InputFailureReason, SessionError.Error>
+
 /** Immutable fold of the durable facts a step's writer has recorded so far. */
 export interface StepRecord {
   /** The model produced visible output this attempt, which bars transparent retries and overflow recovery. */
@@ -83,6 +109,8 @@ export const createLLMEventPublisher = (bus: Pick<Bus.Interface, "publish">, inp
     settled: boolean
     providerExecuted: boolean
     progress?: Tool.Metadata
+    input?: InputExcerpt
+    malformed?: boolean
   }
   const tools = new Map<string, ToolState>()
   const failureSnapshot = (tool: { readonly progress?: Tool.Metadata }, metadata?: Tool.Metadata) => {
@@ -254,6 +282,7 @@ export const createLLMEventPublisher = (bus: Pick<Bus.Interface, "publish">, inp
     Effect.gen(function* () {
       const tool = tools.get(id)
       if (!tool) return yield* Effect.die(new Error(`Tool input end before start: ${id}`))
+      tool.input = inputExcerpt(value)
       yield* bus.publish(SessionEvent.Tool.Input.Ended, {
         sessionID: input.sessionID,
         assistantMessageID,
@@ -324,21 +353,21 @@ export const createLLMEventPublisher = (bus: Pick<Bus.Interface, "publish">, inp
     if (tool.name !== event.name)
       return yield* Effect.die(new Error(`Tool input name changed for ${event.id}: ${tool.name} -> ${event.name}`))
     if (toolInput.has(event.id)) yield* endToolInput(event, event.raw)
-    tool.settled = true
-    yield* bus.publish(SessionEvent.Tool.Failed, {
-      sessionID: input.sessionID,
-      assistantMessageID,
-      id: event.id,
-      error: {
-        type: "tool.input-json",
-        message: "Tool call arguments were malformed JSON and were not executed. Retry with valid JSON.",
-      },
-      ...failureSnapshot(tool),
-      executed: false,
-    })
+    tool.input = inputExcerpt(event.raw)
+    tool.malformed = true
   })
 
-  const flush = Effect.fn("SessionRunner.flush")(flushFragments)
+  const failToolInput = (id: string, tool: ToolState, reason: Exclude<InputFailureReason, "length">) =>
+    failTool(id, inputFailure(tool.input, stepSettlement?.finish === "length" ? "length" : reason))
+
+  const flush = Effect.fn("SessionRunner.flush")(function* () {
+    yield* flushFragments()
+    // The finish reason distinguishes invalid JSON from arguments cut off by the output limit.
+    for (const [id, tool] of tools) {
+      if (!tool.malformed || tool.settled) continue
+      yield* failToolInput(id, tool, "malformed")
+    }
+  })
 
   const failTool = Effect.fnUntraced(function* (id: string, error: SessionError.Error, metadata?: Tool.Metadata) {
     const tool = tools.get(id)
@@ -363,11 +392,18 @@ export const createLLMEventPublisher = (bus: Pick<Bus.Interface, "publish">, inp
     for (const [id, tool] of tools) {
       if (tool.settled || (mode === "hosted" && !tool.providerExecuted) || (mode === "uncalled" && tool.called))
         continue
-      failed = (yield* failTool(id, error)) || failed
+      if (yield* failTool(id, error)) failed = true
     }
     return failed
   })
 
+  const failIncompleteTools = Effect.fn("SessionRunner.failIncompleteTools")(function* () {
+    for (const [id, tool] of tools) {
+      if (tool.called || tool.settled) continue
+      yield* failToolInput(id, tool, "incomplete")
+    }
+  })
+
   const failAssistant = Effect.fnUntraced(function* (error: SessionError.Error) {
     yield* flush()
     yield* failTools(error, "uncalled")
@@ -534,7 +570,7 @@ export const createLLMEventPublisher = (bus: Pick<Bus.Interface, "publish">, inp
         return
       }
       case "step-finish":
-        yield* flush()
+        yield* flushFragments()
         if (stepSettlement) return yield* Effect.die(new Error("Duplicate step finish"))
         stepSettlement = {
           finish: event.reason.normalized,
@@ -604,6 +640,7 @@ export const createLLMEventPublisher = (bus: Pick<Bus.Interface, "publish">, inp
     failTool,
     publishStepFailure,
     failUnsettledTools,
+    failIncompleteTools,
     hasProviderError: () => providerFailed,
     hasStarted: () => stepStarted,
     /** Immutable snapshot of everything recorded for this step so far. */
@@ -621,3 +658,17 @@ export const createLLMEventPublisher = (bus: Pick<Bus.Interface, "publish">, inp
     streamed,
   }
 }
+
+function inputExcerpt(value: string): InputExcerpt {
+  return { text: value.slice(0, INPUT_EXCERPT_LIMIT), length: value.length }
+}
+
+function inputFailure(input: InputExcerpt | undefined, reason: InputFailureReason) {
+  const failure = INPUT_FAILURES[reason]
+  if (!input) return failure
+  const truncated = input.length > input.text.length ? "\n[truncated]" : ""
+  return {
+    ...failure,
+    message: `${failure.message}\n\nInput excerpt (first ${input.text.length} of ${input.length} characters):\n${input.text}${truncated}`,
+  }
+}

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

@@ -38,6 +38,7 @@ export type Outcome = Data.TaggedEnum<{
   }
   RecoverFull: {}
   Compacted: {}
+  OutputLimit: { readonly needsContinuation: boolean }
 }>
 export const Outcome = Data.taggedEnum<Outcome>()
 
@@ -61,11 +62,6 @@ interface Input {
 const TOOLS_INTERRUPTED = { type: "aborted", message: "Tool execution interrupted" } as const
 const STEP_INTERRUPTED = { type: "aborted", message: "Step interrupted" } as const
 const RESULT_MISSING = { type: "tool.result-missing", message: "Provider did not return a tool result" } as const
-const INPUT_INCOMPLETE = {
-  type: "tool.input-incomplete",
-  message:
-    "Tool call arguments were not completed and were not executed. Re-issue the tool call with complete arguments.",
-} as const
 
 /** Captures Location-scoped dependencies without introducing another service or execution loop. */
 export const make = Effect.gen(function* () {
@@ -225,7 +221,7 @@ export const make = Effect.gen(function* () {
         if (llmError || (Exit.isSuccess(stream) && !recorded.providerFailed)) {
           const missing = yield* publisher.failUnsettledTools(RESULT_MISSING, "hosted")
           if (missing && !llmError && !recorded.finish) yield* publisher.failAssistant(RESULT_MISSING)
-          yield* publisher.failUnsettledTools(INPUT_INCOMPLETE, "uncalled")
+          yield* publisher.failIncompleteTools()
         }
 
         const record = publisher.record()
@@ -274,9 +270,9 @@ export const make = Effect.gen(function* () {
         if (tools.interrupted && tools.failure) return yield* Effect.failCause(tools.failure)
         if (tools.interrupted && Exit.isFailure(joined)) return yield* Effect.failCause(joined.cause)
         if (record.failure) return yield* new StepFailedError({ error: record.failure })
-        return Outcome.Completed({
-          needsContinuation: input.prepared.request.toolChoice?.type !== "none" && record.needsContinuation,
-        })
+        const needsContinuation = input.prepared.request.toolChoice?.type !== "none" && record.needsContinuation
+        if (record.finish?.finish === "length") return Outcome.OutputLimit({ needsContinuation })
+        return Outcome.Completed({ needsContinuation })
       }),
     )
   }, Effect.scoped)