fix(opencode): share tool response truncation

packages/opencode/src/session/llm.ts

@@ -29,6 +29,7 @@ import * as OtelTracer from "@effect/opentelemetry/Tracer"
 import { LLMAISDK } from "./llm/ai-sdk"
 import { LLMNativeRuntime } from "./llm/native-runtime"
 import { LLMRequestPrep } from "./llm/request"
+import { Truncate } from "@/tool/truncate"
 
 export const OUTPUT_TOKEN_MAX = ProviderTransform.OUTPUT_TOKEN_MAX
 
@@ -70,6 +71,7 @@ const live: Layer.Layer<
   | EventV2Bridge.Service
   | LLMClientService
   | RuntimeFlags.Service
+  | Truncate.Service
 > = Layer.effect(
   Service,
   Effect.gen(function* () {
@@ -81,6 +83,7 @@ const live: Layer.Layer<
     const events = yield* EventV2Bridge.Service
     const llmClient = yield* LLMClient.Service
     const flags = yield* RuntimeFlags.Service
+    const truncate = yield* Truncate.Service
 
     const run = Effect.fn("LLM.run")(function* (input: StreamRequest) {
       yield* Effect.logInfo("stream", {
@@ -142,7 +145,8 @@ const live: Layer.Layer<
               title: typeof result === "object" ? result?.title : undefined,
             }
           } catch (e: any) {
-            return { result: "", error: e.message ?? String(e) }
+            const error = await bridge.promise(truncate.output(e.message ?? String(e)))
+            return { result: "", error: error.content }
           }
         }
 
@@ -301,11 +305,12 @@ const live: Layer.Layer<
                 toolName: lower,
               }
             }
+            const error = await bridge.promise(truncate.output(failed.error.message))
             return {
               ...failed.toolCall,
               input: JSON.stringify({
                 tool: failed.toolCall.toolName,
-                error: failed.error.message,
+                error: error.content,
               }),
               toolName: "invalid",
             }
@@ -398,6 +403,7 @@ export const node = LayerNode.make({
     EventV2Bridge.node,
     llmClient,
     RuntimeFlags.node,
+    Truncate.node,
   ],
 })
 

packages/opencode/src/session/session.ts

@@ -44,6 +44,7 @@ import { RuntimeFlags } from "@/effect/runtime-flags"
 import { ProviderV2 } from "@opencode-ai/core/provider"
 import { ModelV2 } from "@opencode-ai/core/model"
 import { SessionMessage } from "@opencode-ai/schema/session-message"
+import { Truncate } from "@/tool/truncate"
 
 const parentTitlePrefix = "New session - "
 const childTitlePrefix = "Child session - "
@@ -488,7 +489,7 @@ export type Patch = Omit<Partial<Info>, "time" | "share" | "summary" | "revert"
 const layer: Layer.Layer<
   Service,
   never,
-  BackgroundJob.Service | RuntimeFlags.Service | Database.Service | EventV2Bridge.Service
+  BackgroundJob.Service | RuntimeFlags.Service | Database.Service | EventV2Bridge.Service | Truncate.Service
 > = Layer.effect(
   Service,
   Effect.gen(function* () {
@@ -497,6 +498,7 @@ const layer: Layer.Layer<
     const background = yield* BackgroundJob.Service
     const events = yield* EventV2Bridge.Service
     const flags = yield* RuntimeFlags.Service
+    const truncate = yield* Truncate.Service
 
     const createNext = Effect.fn("Session.createNext")(function* (input: {
       id?: SessionID
@@ -636,6 +638,10 @@ const layer: Layer.Layer<
 
     const updatePart = <T extends SessionV1.Part>(part: T): Effect.Effect<T> =>
       Effect.gen(function* () {
+        if (part.type === "tool" && part.state.status === "error") {
+          const bounded = yield* truncate.output(part.state.error)
+          part.state.error = bounded.content
+        }
         yield* events.publish(SessionV1.Event.PartUpdated, {
           sessionID: part.sessionID,
           part: structuredClone(part),
@@ -1012,7 +1018,7 @@ function listByProject(
 export const node = LayerNode.make({
   service: Service,
   layer: layer,
-  deps: [BackgroundJob.node, RuntimeFlags.node, Database.node, EventV2Bridge.node],
+  deps: [BackgroundJob.node, RuntimeFlags.node, Database.node, EventV2Bridge.node, Truncate.node],
 })
 
 export * as Session from "./session"

packages/opencode/src/tool/truncate.ts

@@ -1,6 +1,6 @@
 import { LayerNode } from "@opencode-ai/core/effect/layer-node"
 import { NodePath } from "@effect/platform-node"
-import { Cause, Duration, Effect, Layer, Option, Schedule, Context } from "effect"
+import { Cause, Duration, Effect, Exit, Layer, Option, Schedule, Context } from "effect"
 import path from "path"
 import type { Agent } from "../agent/agent"
 import { FSUtil } from "@opencode-ai/core/fs-util"
@@ -13,11 +13,11 @@ import { TRUNCATION_DIR } from "./truncation-dir"
 const RETENTION = Duration.days(7)
 
 export const MAX_LINES = 2000
-export const MAX_BYTES = 50 * 1024
+export const MAX_BYTES = 40 * 1024
 export const DIR = TRUNCATION_DIR
 export const GLOB = path.join(TRUNCATION_DIR, "*")
 
-export type Result = { content: string; truncated: false } | { content: string; truncated: true; outputPath: string }
+export type Result = { content: string; truncated: false } | { content: string; truncated: true; outputPath?: string }
 
 export interface Options {
   maxLines?: number
@@ -124,19 +124,25 @@ const layer = Layer.effect(
       const removed = hitBytes ? totalBytes - bytes : lines.length - out.length
       const unit = hitBytes ? "bytes" : "lines"
       const preview = out.join("\n")
-      const file = yield* write(text)
+      const saved = yield* write(text).pipe(Effect.exit)
+      const file = Exit.isSuccess(saved) ? saved.value : undefined
+      if (Exit.isFailure(saved)) {
+        yield* Effect.logWarning("failed to save full truncated tool response", { cause: Cause.pretty(saved.cause) })
+      }
 
-      const hint = hasTaskTool(agent)
-        ? `The tool call succeeded but the output was truncated. Full output saved to: ${file}\nUse the Task tool to have explore agent process this file with Grep and Read (with offset/limit). Do NOT read the full file yourself - delegate to save context.`
-        : `The tool call succeeded but the output was truncated. Full output saved to: ${file}\nUse Grep to search the full content or Read with offset/limit to view specific sections.`
+      const hint = file
+        ? hasTaskTool(agent)
+          ? `The tool response was truncated. Full content saved to: ${file}\nUse the Task tool to have explore agent process this file with Grep and Read (with offset/limit). Do NOT read the full file yourself - delegate to save context.`
+          : `The tool response was truncated. Full content saved to: ${file}\nUse Grep to search the full content or Read with offset/limit to view specific sections.`
+        : "The tool response was truncated, and the full content could not be saved."
 
       return {
         content:
           direction === "head"
             ? `${preview}\n\n...${removed} ${unit} truncated...\n\n${hint}`
             : `...${removed} ${unit} truncated...\n\n${hint}\n\n${preview}`,
         truncated: true,
-        outputPath: file,
+        ...(file ? { outputPath: file } : {}),
       } as const
     })
 

packages/opencode/test/tool/truncation.test.ts

@@ -1,9 +1,10 @@
 import { describe, test, expect } from "bun:test"
+import { JSONParseError } from "@ai-sdk/provider"
 import { ConfigV1 } from "@opencode-ai/core/v1/config/config"
 import { LayerNode } from "@opencode-ai/core/effect/layer-node"
 import { filesystem } from "@opencode-ai/core/effect/app-node-platform"
 import { FSUtil } from "@opencode-ai/core/fs-util"
-import { Effect, FileSystem } from "effect"
+import { Effect, FileSystem, Layer } from "effect"
 import { Truncate } from "@/tool/truncate"
 import { Config } from "@/config/config"
 import { Identifier } from "../../src/id/id"
@@ -12,11 +13,26 @@ import path from "path"
 import { testEffect } from "../lib/effect"
 import { writeFileStringScoped } from "../lib/filesystem"
 import { TestConfig } from "../fixture/config"
+import { InvalidToolInputError } from "ai"
 
 const FIXTURES_DIR = path.join(import.meta.dir, "fixtures")
 const ROOT = path.resolve(import.meta.dir, "..", "..")
 
 const it = testEffect(LayerNode.compile(LayerNode.group([Truncate.node, FSUtil.node, filesystem])))
+const failedWriteFS = Layer.effect(
+  FSUtil.Service,
+  FSUtil.Service.pipe(
+    Effect.map((fs) =>
+      FSUtil.Service.of({
+        ...fs,
+        writeFileString: () => Effect.die("blocked test write"),
+      }),
+    ),
+  ),
+).pipe(Layer.provide(LayerNode.compile(FSUtil.node)))
+const failedWriteIt = testEffect(
+  LayerNode.compile(LayerNode.group([Truncate.node, FSUtil.node, filesystem]), [[FSUtil.node, failedWriteFS]]),
+)
 
 const configuredLayer = (cfg: ConfigV1.Info) =>
   LayerNode.compile(LayerNode.group([Truncate.node, FSUtil.node, filesystem, Config.node]), [
@@ -102,7 +118,7 @@ describe("Truncate", () => {
 
     test("uses default MAX_LINES and MAX_BYTES", () => {
       expect(Truncate.MAX_LINES).toBe(2000)
-      expect(Truncate.MAX_BYTES).toBe(50 * 1024)
+      expect(Truncate.MAX_BYTES).toBe(40 * 1024)
     })
 
     it.live("limits() falls back to MAX_LINES/MAX_BYTES when Config is not provided", () =>
@@ -180,7 +196,7 @@ describe("Truncate", () => {
         const result = yield* svc.output(lines, { maxLines: 10 })
 
         expect(result.truncated).toBe(true)
-        expect(result.content).toContain("The tool call succeeded but the output was truncated")
+        expect(result.content).toContain("The tool response was truncated")
         expect(result.content).toContain("Grep")
         if (!result.truncated) throw new Error("expected truncated")
         expect(result.outputPath).toBeDefined()
@@ -192,6 +208,45 @@ describe("Truncate", () => {
       }),
     )
 
+    it.live("archives the production-shaped malformed tool error", () =>
+      Effect.gen(function* () {
+        const malformed =
+          '{"description":"Test resumed player extraction","code":"const x=1;' + "\n\t".repeat(118_000) + '"}'
+        let cause: unknown
+        try {
+          JSON.parse(malformed)
+        } catch (error) {
+          cause = error
+        }
+        if (!cause) throw new Error("expected malformed input to fail JSON parsing")
+
+        const failed = new InvalidToolInputError({
+          toolName: "browser_execute",
+          toolInput: malformed,
+          cause: new JSONParseError({ text: malformed, cause }),
+        })
+        const result = yield* (yield* Truncate.Service).output(failed.message)
+        expect(result.truncated).toBe(true)
+        if (!result.truncated || !result.outputPath) throw new Error("expected archived malformed-tool error")
+
+        const stored = JSON.stringify({ tool: "browser_execute", error: result.content })
+        expect(stored.length).toBeLessThanOrEqual(Truncate.MAX_BYTES)
+        expect(JSON.parse(stored).error).toContain(result.outputPath)
+        expect(yield* (yield* FSUtil.Service).readFileString(result.outputPath)).toBe(failed.message)
+      }),
+    )
+
+    failedWriteIt.live("keeps a bounded response when the full content cannot be saved", () =>
+      Effect.gen(function* () {
+        const result = yield* (yield* Truncate.Service).output("x".repeat(Truncate.MAX_BYTES + 1))
+
+        expect(result.truncated).toBe(true)
+        if (!result.truncated) throw new Error("expected truncated output")
+        expect(result.outputPath).toBeUndefined()
+        expect(result.content).toContain("full content could not be saved")
+      }),
+    )
+
     it.live("suggests Task tool when agent has task permission", () =>
       Effect.gen(function* () {
         const svc = yield* Truncate.Service