test(core): cover multi-line patch summaries

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

@@ -40,6 +40,7 @@ const layer = Layer.effect(
     const db = (yield* Database.Service).db
     const compaction = yield* SessionCompaction.Service
     const title = yield* SessionTitle.Service
+    const outputs = yield* ToolOutputStore.Service
     // Title generation is a side effect of the first step; it must not delay step continuation.
     // Tracked per process so repeated wakes before the second user message arrives don't
     // re-fire a redundant LLM call; `SessionTitle` itself is idempotent based on durable history.
@@ -116,7 +117,7 @@ const layer = Layer.effect(
       const ownedToolFibers: Array<Fiber.Fiber<void, ToolOutputStore.Error>> = []
       let needsContinuation = false
       const startSnapshot = yield* snapshots.capture()
-      const publisher = createLLMEventPublisher(events, {
+      const publisher = createLLMEventPublisher(events, outputs, {
         sessionID: session.id,
         agent: agent.id,
         // The selected catalog identity, not model.id: route-level ids are provider API
@@ -165,13 +166,25 @@ const layer = Layer.effect(
                     call: event,
                     progress: (update) =>
                       serialized(
-                        events.publish(SessionEvent.Tool.Progress, {
-                          sessionID: session.id,
-                          assistantMessageID,
-                          callID: event.id,
-                          structured: { ...update.structured },
-                          content: [...update.content],
-                        }),
+                        Effect.gen(function* () {
+                          const bounded = yield* outputs.bound({
+                            sessionID: session.id,
+                            callID: event.id,
+                            output: update,
+                          })
+                          const structured = bounded.output.structured
+                          const entries =
+                            typeof structured === "object" && structured !== null && !Array.isArray(structured)
+                              ? Object.entries(structured)
+                              : yield* Effect.die(new Error("Tool progress structured output must be an object"))
+                          yield* events.publish(SessionEvent.Tool.Progress, {
+                            sessionID: session.id,
+                            assistantMessageID,
+                            callID: event.id,
+                            structured: Object.fromEntries(entries),
+                            content: [...bounded.output.content],
+                          })
+                        }).pipe(Effect.orDie),
                       ),
                   }),
                 ).pipe(
@@ -261,6 +274,11 @@ const layer = Layer.effect(
             }
             yield* serialized(publisher.failAssistant(error))
           }
+          if (streamFailure instanceof ToolOutputStore.StorageError) {
+            const error = toSessionError(streamFailure)
+            yield* serialized(publisher.failUnsettledTools(error))
+            yield* serialized(publisher.failAssistant(error))
+          }
           // Provider error events only arrive from the stream, so the flag is final here.
           const providerFailed = publisher.hasProviderError()
 
@@ -287,8 +305,21 @@ const layer = Layer.effect(
           // settles so the model may recover. A typed infrastructure failure (tool output
           // could not be persisted) also fails the assistant and then fails the drain.
           const settledFailure = settledCauses.find((cause) => !Cause.hasInterrupts(cause) && !isUserDeclined(cause))
+          const infrastructureFailure = settledCauses.find(
+            (cause) =>
+              Option.getOrUndefined(Cause.findErrorOption(cause)) instanceof ToolOutputStore.StorageError ||
+              cause.reasons.some(
+                (reason) => Cause.isDieReason(reason) && reason.defect instanceof ToolOutputStore.StorageError,
+              ),
+          )
+          const typedError = infrastructureFailure
+            ? Option.getOrUndefined(Cause.findErrorOption(infrastructureFailure))
+            : undefined
+          const storageDefect = infrastructureFailure?.reasons.find(
+            (reason) => Cause.isDieReason(reason) && reason.defect instanceof ToolOutputStore.StorageError,
+          )
           const infraError =
-            settledFailure === undefined ? undefined : Option.getOrUndefined(Cause.findErrorOption(settledFailure))
+            typedError ?? (storageDefect && Cause.isDieReason(storageDefect) ? storageDefect.defect : undefined)
           if (settledFailure !== undefined) {
             const failure = infraError ?? Cause.squash(settledFailure)
             const error = toSessionError(failure)
@@ -342,8 +373,8 @@ const layer = Layer.effect(
 
           if (stream._tag === "Failure") return yield* Effect.failCause(stream.cause)
           if (userDeclined) return yield* Effect.interrupt
-          if ((toolsInterrupted || infraError !== undefined) && settledFailure)
-            return yield* Effect.failCause(settledFailure)
+          if (infraError !== undefined && infrastructureFailure) return yield* Effect.failCause(infrastructureFailure)
+          if (toolsInterrupted && settledFailure) return yield* Effect.failCause(settledFailure)
           if (toolsInterrupted && settled._tag === "Failure") return yield* Effect.failCause(settled.cause)
           if (stepFailure) return yield* new StepFailedError({ error: stepFailure })
           return {
@@ -500,6 +531,7 @@ export const node = makeLocationNode({
     SessionCompaction.node,
     SessionTitle.node,
     Snapshot.node,
+    ToolOutputStore.node,
     Database.node,
   ],
 })

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

@@ -11,6 +11,7 @@ import { AgentV2 } from "../../agent"
 import { Snapshot } from "../../snapshot"
 import { RelativePath } from "../../schema"
 import { SessionUsage } from "../usage"
+import { ToolOutputStore } from "../../tool-output-store"
 
 type Input = {
   readonly sessionID: SessionSchema.ID
@@ -34,18 +35,22 @@ const message = (value: unknown) => {
 }
 
 type SettledOutput =
-  | { readonly structured: Record<string, unknown>; readonly content: ToolOutput["content"] }
+  | ToolOutput
   | { readonly error: SessionError.Error }
 
 const settledOutput = (value: ToolOutput | undefined, result: ToolResultValue): SettledOutput => {
   if (result.type === "error") return { error: { type: "tool.execution", message: message(result.value) } }
   const settled = value ?? ToolOutput.fromResultValue(result)
   if (!settled) throw new Error(`Unsupported tool result: ${message(result)}`)
-  return { structured: record(settled.structured), content: settled.content }
+  return settled
 }
 
 /** Persist one step without executing tools or starting a continuation step. */
-export const createLLMEventPublisher = (events: Pick<EventV2.Interface, "publish">, input: Input) => {
+export const createLLMEventPublisher = (
+  events: Pick<EventV2.Interface, "publish">,
+  outputs: Pick<ToolOutputStore.Interface, "bound">,
+  input: Input,
+) => {
   const tools = new Map<
     string,
     {
@@ -405,7 +410,6 @@ export const createLLMEventPublisher = (events: Pick<EventV2.Interface, "publish
           if (event.result.type === "error") return
           return yield* Effect.die(new Error(`Duplicate tool result: ${event.id}`))
         }
-        tool.settled = true
         const result = error ? { error } : settledOutput(event.output, event.result)
         const executed = event.providerExecuted === true || tool.providerExecuted
         const resultState = providerState(event.providerMetadata)
@@ -419,17 +423,26 @@ export const createLLMEventPublisher = (events: Pick<EventV2.Interface, "publish
             executed,
             resultState,
           })
+          tool.settled = true
           return
         }
+        const bounded = yield* outputs.bound({
+          sessionID: input.sessionID,
+          callID: event.id,
+          output: { ...result, structured: record(result.structured) },
+        })
         yield* events.publish(SessionEvent.Tool.Success, {
           sessionID: input.sessionID,
           assistantMessageID: tool.assistantMessageID,
           callID: event.id,
-          ...result,
+          structured: record(bounded.output.structured),
+          content: bounded.output.content,
+          // Provider-executed results remain verbatim for provider-history replay.
           ...(executed ? { result: event.result } : {}),
           executed,
           resultState,
         })
+        tool.settled = true
         return
       }
       case "tool-error": {

packages/core/src/tool-output-store.ts

@@ -1,7 +1,7 @@
 export * as ToolOutputStore from "./tool-output-store"
 
 import path from "path"
-import { Context, Duration, Effect, Layer, Option, Schedule, Schema } from "effect"
+import { Context, Duration, Effect, Layer, Option, Predicate, Schedule, Schema } from "effect"
 import { Config } from "./config"
 import { FSUtil } from "./fs-util"
 import { Global } from "./global"
@@ -12,14 +12,21 @@ import type { ToolOutput } from "@opencode-ai/ai"
 
 export const MAX_LINES = 2_000
 export const MAX_BYTES = 50 * 1024
+export const MAX_STRUCTURED_BYTES = 16 * 1024
 export const RETENTION = Duration.days(7)
 
 export const MANAGED_DIRECTORY = "tool-output"
 
+export interface Limits {
+  readonly maxLines: number
+  readonly maxBytes: number
+}
+
 export interface BoundInput {
   readonly sessionID: SessionSchema.ID
   readonly callID: string
   readonly output: ToolOutput
+  readonly propagateTruncation?: boolean
 }
 
 export interface BoundResult {
@@ -40,7 +47,7 @@ export class StorageError extends Schema.TaggedErrorClass<StorageError>()("ToolO
 export type Error = StorageError
 
 export interface Interface {
-  readonly limits: () => Effect.Effect<{ readonly maxLines: number; readonly maxBytes: number }>
+  readonly limits: () => Effect.Effect<Limits>
   readonly bound: (input: BoundInput) => Effect.Effect<BoundResult, Error>
   readonly cleanup: () => Effect.Effect<void>
 }
@@ -49,26 +56,31 @@ export class Service extends Context.Service<Service, Interface>()("@opencode/v2
 
 const takePrefix = (input: string, maximumBytes: number) => {
   let bytes = 0
-  let content = ""
+  let end = 0
   for (const char of input) {
     const size = Buffer.byteLength(char, "utf-8")
     if (bytes + size > maximumBytes) break
-    content += char
+    end += char.length
     bytes += size
   }
-  return content
+  return input.slice(0, end)
 }
 
 const takeSuffix = (input: string, maximumBytes: number) => {
   let bytes = 0
-  const content: string[] = []
-  for (const char of Array.from(input).toReversed()) {
+  let start = input.length
+  while (start > 0) {
+    const codeUnit = input.charCodeAt(start - 1)
+    const previous = start > 1 ? input.charCodeAt(start - 2) : 0
+    const next =
+      codeUnit >= 0xdc00 && codeUnit <= 0xdfff && previous >= 0xd800 && previous <= 0xdbff ? start - 2 : start - 1
+    const char = input.slice(next, start)
     const size = Buffer.byteLength(char, "utf-8")
     if (bytes + size > maximumBytes) break
-    content.unshift(char)
+    start = next
     bytes += size
   }
-  return content.join("")
+  return input.slice(start)
 }
 
 const preview = (text: string, maxLines: number, maxBytes: number) => {
@@ -109,6 +121,27 @@ const lineCount = (text: string) => {
   return count
 }
 
+export const contextualOverflow = (output: ToolOutput, limits: Limits) => {
+  const contextual = output.content
+    .filter((item) => item.type === "text")
+    .map((item) => item.text)
+    .join("")
+  return Buffer.byteLength(contextual, "utf-8") > limits.maxBytes || lineCount(contextual) > limits.maxLines
+}
+
+export const propagateTruncation = (output: ToolOutput, limits: Limits): ToolOutput =>
+  contextualOverflow(output, limits) &&
+  Predicate.isObject(output.structured) &&
+  "truncated" in output.structured &&
+  typeof output.structured.truncated === "boolean"
+    ? { ...output, structured: { ...output.structured, truncated: true } }
+    : output
+
+const record = (value: unknown): Record<string, unknown> =>
+  typeof value === "object" && value !== null && !Array.isArray(value)
+    ? Object.fromEntries(Object.entries(value))
+    : { value }
+
 const layer = Layer.effect(
   Service,
   Effect.gen(function* () {
@@ -128,7 +161,6 @@ const layer = Layer.effect(
 
     const write = Effect.fn("ToolOutputStore.write")(function* (content: string) {
       const file = path.join(directory, `tool_${Identifier.ascending()}`)
-      yield* fs.ensureDir(directory).pipe(Effect.mapError((cause) => new StorageError({ operation: "write", cause })))
       yield* fs
         .writeFileString(file, content, { flag: "wx" })
         .pipe(Effect.mapError((cause) => new StorageError({ operation: "write", cause })))
@@ -139,37 +171,67 @@ const layer = Layer.effect(
       const outputLimits = yield* limits()
       const media = input.output.content.filter((item) => item.type === "file")
       const text = input.output.content.filter((item) => item.type === "text")
-      const contextual =
-        input.output.content.length === 0
-          ? yield* Effect.try({
-              try: () => JSON.stringify(input.output.structured, null, 2) ?? String(input.output.structured),
-              catch: (cause) => new StorageError({ operation: "encode", cause }),
-            })
-          : text.map((item) => item.text).join("")
-      if (
-        lineCount(contextual) <= outputLimits.maxLines &&
-        Buffer.byteLength(contextual, "utf-8") <= outputLimits.maxBytes
-      )
+      const encoded = yield* Effect.try({
+        try: () => JSON.stringify(record(input.output.structured)),
+        catch: (cause) => new StorageError({ operation: "encode", cause }),
+      })
+      const decoded: unknown = JSON.parse(encoded)
+      const structured =
+        typeof decoded === "object" && decoded !== null && !Array.isArray(decoded)
+          ? Object.fromEntries(Object.entries(decoded))
+          : yield* Effect.die(new Error("Durable tool structured output must be an object"))
+      const encodedBytes = Buffer.byteLength(encoded, "utf-8")
+      const contextual = input.output.content.length === 0 ? encoded : text.map((item) => item.text).join("")
+      const contextualBytes = input.output.content.length === 0 ? encodedBytes : Buffer.byteLength(contextual, "utf-8")
+      const structuredOverflow = encodedBytes > MAX_STRUCTURED_BYTES
+      const contentOverflow = contextualBytes > outputLimits.maxBytes || lineCount(contextual) > outputLimits.maxLines
+      if (!structuredOverflow && !contentOverflow)
         return {
-          output: input.output,
+          output: { ...input.output, structured },
           outputPaths: [],
         }
 
-      const outputPath = yield* write(contextual)
-      const marker = `... output truncated; full content saved to ${outputPath} ...`
+      yield* fs.ensureDir(directory).pipe(Effect.mapError((cause) => new StorageError({ operation: "write", cause })))
+      const structuredPath = structuredOverflow ? yield* write(encoded) : undefined
+      const contextualPath = contentOverflow
+        ? input.output.content.length === 0 && structuredPath
+          ? structuredPath
+          : yield* write(contextual).pipe(
+              Effect.onError(() =>
+                structuredPath ? fs.remove(structuredPath).pipe(Effect.catch(() => Effect.void)) : Effect.void,
+              ),
+            )
+        : undefined
 
       return {
         output: {
-          structured: input.output.structured,
-          content: [
-            {
-              type: "text" as const,
-              text: boundedPreview(contextual, marker, outputLimits.maxLines, outputLimits.maxBytes),
-            },
-            ...media,
-          ],
+          structured: structuredPath
+            ? { _truncated: true, _bytes: encodedBytes, _outputPath: structuredPath }
+            : contentOverflow &&
+                input.propagateTruncation === true &&
+                Predicate.isObject(structured) &&
+                "truncated" in structured &&
+                typeof structured.truncated === "boolean"
+              ? { ...structured, truncated: true }
+              : structured,
+          content: contentOverflow
+            ? [
+                {
+                  type: "text" as const,
+                  text: boundedPreview(
+                    contextual,
+                    `... output truncated; full content saved to ${contextualPath} ...`,
+                    outputLimits.maxLines,
+                    outputLimits.maxBytes,
+                  ),
+                },
+                ...media,
+              ]
+            : input.output.content.length === 0 && structuredPath
+              ? [{ type: "text" as const, text: contextual }]
+              : input.output.content,
         },
-        outputPaths: [outputPath],
+        outputPaths: [...new Set([structuredPath, contextualPath].filter((value) => value !== undefined))],
       }
     })
 

packages/core/src/tool/edit.ts

@@ -16,6 +16,7 @@ import { FSUtil } from "../fs-util"
 import { LocationMutation } from "../location-mutation"
 import { PermissionV2 } from "../permission"
 import { Tool } from "./tool"
+import { ToolStructured } from "./structured"
 
 export const name = "edit"
 
@@ -103,6 +104,15 @@ export const Plugin = {
                 "Replace exact text in one file. Relative paths resolve within the active Location. Absolute paths inside the Location are accepted. Explicit external absolute paths require external_directory approval before edit approval.",
               input: Input,
               output: Output,
+              structured: Output,
+              toStructuredOutput: ({ output }) =>
+                ToolStructured.fit((maximumBytes) => ({
+                  ...output,
+                  files: output.files.map((file) => ({
+                    ...file,
+                    patch: ToolStructured.patch(file.patch, maximumBytes),
+                  })),
+                })),
               toModelOutput: ({ input, output }) => [
                 { type: "text", text: toModelOutput(output, input.oldString, input.newString) },
               ],

packages/core/src/tool/execute.ts

@@ -49,7 +49,7 @@ export const create = (registrations: ReadonlyMap<string, Registration>) => {
   ) => {
     const tools: Record<string, Tool.Definition<never>> = {}
     for (const [name, registration] of registrations) {
-      const child = definition(name, registration.tool)
+      const child = definition(name, codeModeTool(registration.tool))
       const value = Tool.make({
         description: child.description,
         input: child.inputSchema,
@@ -96,7 +96,7 @@ export const create = (registrations: ReadonlyMap<string, Registration>) => {
             Effect.gen(function* () {
               const index = yield* Ref.getAndUpdate(callIndex, (index) => index + 1)
               const output = yield* settle(
-                registration.tool,
+                codeModeTool(registration.tool),
                 { type: "tool-call", id: context.callID, name, input },
                 {
                   sessionID: context.sessionID,
@@ -141,6 +141,11 @@ export const create = (registrations: ReadonlyMap<string, Registration>) => {
   })
 }
 
+function codeModeTool(tool: AnyTool): AnyTool {
+  if ("jsonSchema" in tool || tool.codeModeOutput !== "output") return tool
+  return { ...tool, structured: undefined }
+}
+
 function displayInput(input: unknown): Record<string, unknown> | undefined {
   if (input === null || input === undefined) return
   if (typeof input !== "object" || Array.isArray(input)) return { input }

packages/core/src/tool/glob.ts

@@ -26,6 +26,7 @@ export const Input = Schema.Struct({
 
 export const Output = Schema.Array(FileSystem.Entry)
 type ModelOutput = typeof Output.Encoded
+const StructuredOutput = Schema.Struct({ count: Schema.Number })
 
 /** Format raw search results into the concise line-oriented output models expect. */
 export const toModelOutput = (output: ModelOutput) => {
@@ -51,6 +52,9 @@ export const Plugin = {
               "Find files by glob pattern within the active Location. Returns concise relative file resources. Use a relative path to narrow the search and limit to bound the result count.",
             input: Input,
             output: Output,
+            structured: StructuredOutput,
+            codeModeOutput: "output",
+            toStructuredOutput: ({ output }) => ({ count: output.length }),
             toModelOutput: ({ output }) => [
               {
                 type: "text",

packages/core/src/tool/grep.ts

@@ -31,6 +31,7 @@ export const Input = Schema.Struct({
 
 export const Output = Schema.Array(FileSystem.Match)
 type ModelOutput = typeof Output.Encoded
+const StructuredOutput = Schema.Struct({ matches: Schema.Number })
 
 /** Format raw search matches into the familiar concise model output. */
 export const toModelOutput = (output: ModelOutput) => {
@@ -65,6 +66,9 @@ export const Plugin = {
               "Search file contents by regular expression within the active Location or an absolute managed tool-output file. Use a path to narrow the search, include to filter files by glob, and limit to bound the match count. Returns concise file resources, line numbers, and bounded line previews.",
             input: Input,
             output: Output,
+            structured: StructuredOutput,
+            codeModeOutput: "output",
+            toStructuredOutput: ({ output }) => ({ matches: output.length }),
             toModelOutput: ({ output }) => [
               {
                 type: "text",

packages/core/src/tool/patch.ts

@@ -11,6 +11,7 @@ import { LocationMutation } from "../location-mutation"
 import { Patch } from "../patch"
 import { PermissionV2 } from "../permission"
 import { Tool } from "./tool"
+import { ToolStructured } from "./structured"
 
 export const name = "patch"
 
@@ -72,6 +73,15 @@ export const Plugin = {
                 "Apply one patch containing add, update, and delete file operations. All targets are resolved and approved before target contents are read. Operations apply sequentially; if a later operation fails, earlier operations remain applied and the failure reports them explicitly. Moves and atomic rollback are not supported yet.",
               input: Input,
               output: Output,
+              structured: Output,
+              toStructuredOutput: ({ output }) =>
+                ToolStructured.fit((maximumBytes) => ({
+                  ...output,
+                  files: output.files.map((file) => ({
+                    ...file,
+                    patch: ToolStructured.patch(file.patch, maximumBytes),
+                  })),
+                })),
               toModelOutput: ({ output }) => [{ type: "text", text: toModelOutput(output) }],
               execute: (input, context) => {
                 const applied: Array<typeof Applied.Type> = []

packages/core/src/tool/question.ts

@@ -7,6 +7,7 @@ import { Form } from "../form"
 import { PermissionV2 } from "../permission"
 import { QuestionV2 } from "../question"
 import { Tool } from "./tool"
+import { ToolStructured } from "./structured"
 
 export const name = "question"
 
@@ -63,6 +64,13 @@ export const Plugin = {
             description,
             input: Input,
             output: Output,
+            structured: Output,
+            toStructuredOutput: ({ output }) =>
+              ToolStructured.fit((maximumBytes) => ({
+                answers: output.answers.map((answers) =>
+                  answers.map((answer) => ToolStructured.truncate(answer, maximumBytes)),
+                ),
+              })),
             toModelOutput: ({ input, output }) => [
               { type: "text", text: toModelOutput(input.questions, output.answers) },
             ],

packages/core/src/tool/read-filesystem.ts

@@ -239,6 +239,7 @@ export const read = Effect.fn("ReadTool.read")(function* (
       let line = 1
       let bytes = 0
       let next: number | undefined
+      let lineTruncated = false
       const append = (input: string) => {
         if (line < offset) {
           line++
@@ -249,6 +250,7 @@ export const read = Effect.fn("ReadTool.read")(function* (
           return false
         }
         const text = input.length > MAX_LINE_LENGTH ? input.slice(0, MAX_LINE_LENGTH) + MAX_LINE_SUFFIX : input
+        if (text !== input) lineTruncated = true
         const size = Buffer.byteLength(text, "utf-8") + (lines.length > 0 ? 1 : 0)
         if (bytes + size > MAX_READ_BYTES) {
           next = line
@@ -314,7 +316,7 @@ export const read = Effect.fn("ReadTool.read")(function* (
         content: lines.join("\n"),
         mime: FSUtil.mimeType(real),
         offset,
-        truncated: next !== undefined,
+        truncated: next !== undefined || lineTruncated,
         ...(next === undefined ? {} : { next }),
       })
     }),

packages/core/src/tool/read.ts

@@ -28,6 +28,31 @@ const LocationInput = Schema.Struct({
 })
 const Input = LocationInput
 const Output = Schema.Union([FileSystem.Content, ReadToolFileSystem.TextPage, ReadToolFileSystem.ListPage])
+const StructuredOutput = Schema.Union([
+  Schema.Struct({
+    type: Schema.Literal("file"),
+    uri: Schema.String,
+    name: Schema.String.pipe(Schema.optional),
+    encoding: FileSystem.Content.fields.encoding,
+    mime: Schema.String,
+    bytes: Schema.Number,
+    truncated: Schema.Boolean,
+  }),
+  Schema.Struct({
+    type: Schema.Literal("text-page"),
+    mime: Schema.String,
+    offset: Schema.Number,
+    bytes: Schema.Number,
+    truncated: Schema.Boolean,
+    next: Schema.Number.pipe(Schema.optional),
+  }),
+  Schema.Struct({
+    type: Schema.Literal("list-page"),
+    count: Schema.Number,
+    truncated: Schema.Boolean,
+    next: Schema.Number.pipe(Schema.optional),
+  }),
+])
 
 export const Plugin = {
   id: "opencode.tool.read",
@@ -48,15 +73,39 @@ export const Plugin = {
               "Read a text file or supported image, page through a large UTF-8 text file by line offset, or list a directory page. Relative paths resolve from the current location; absolute paths inside it are accepted, while external absolute paths require external_directory approval.",
             input: Input,
             output: Output,
-            structured: Schema.toEncoded(Output),
-            // Image base64 reaches the model through content items (normalized generically
-            // at tool settlement); persisting a second copy in structured would store the
-            // original unresized bytes in the message row.
-            toStructuredOutput: ({ output }) =>
-              "encoding" in output && output.encoding === "base64" ? { ...output, content: "" } : output,
+            structured: StructuredOutput,
+            codeModeOutput: "output",
+            contentTruncation: true,
+            toStructuredOutput: ({ output }) => {
+              if ("encoding" in output)
+                return {
+                  type: "file" as const,
+                  uri: output.uri,
+                  name: output.name,
+                  encoding: output.encoding,
+                  mime: output.mime,
+                  bytes: Buffer.byteLength(output.content, output.encoding === "base64" ? "base64" : "utf-8"),
+                  truncated: false,
+                }
+              if ("content" in output)
+                return {
+                  type: output.type,
+                  mime: output.mime,
+                  offset: output.offset,
+                  bytes: Buffer.byteLength(output.content, "utf-8"),
+                  truncated: output.truncated,
+                  next: output.next,
+                }
+              return {
+                type: "list-page" as const,
+                count: output.entries.length,
+                truncated: output.truncated,
+                next: output.next,
+              }
+            },
             toModelOutput: ({ input, output }) => {
               if (!("encoding" in output) || output.encoding !== "base64" || !SUPPORTED_IMAGE_MIMES.has(output.mime))
-                return []
+                return [{ type: "text", text: JSON.stringify(output) }]
               return [
                 { type: "text", text: "Image read successfully" },
                 { type: "file", data: output.content, mime: output.mime, name: input.path },

packages/core/src/tool/registry.ts

@@ -83,18 +83,16 @@ const registryLayer = Layer.effect(
         const base64 = /^data:[^,]*;base64,(.*)$/s.exec(item.uri)?.[1]
         if (base64 === undefined) return Effect.succeed(item)
         const resource = item.name ?? `${item.mime} tool output`
-        return image
-          .normalize(resource, { uri: resource, content: base64, encoding: "base64", mime: item.mime })
-          .pipe(
-            Effect.map((result) => ({
-              ...item,
-              uri: `data:${result.mime};base64,${result.content}`,
-              mime: result.mime,
-            })),
-            Effect.catchTag("Image.ResizerUnavailableError", () => Effect.succeed(item)),
-            Effect.catchTag("Image.DecodeError", () => Effect.succeed("decode" as const)),
-            Effect.catchTag("Image.SizeError", () => Effect.succeed("size" as const)),
-          )
+        return image.normalize(resource, { uri: resource, content: base64, encoding: "base64", mime: item.mime }).pipe(
+          Effect.map((result) => ({
+            ...item,
+            uri: `data:${result.mime};base64,${result.content}`,
+            mime: result.mime,
+          })),
+          Effect.catchTag("Image.ResizerUnavailableError", () => Effect.succeed(item)),
+          Effect.catchTag("Image.DecodeError", () => Effect.succeed("decode" as const)),
+          Effect.catchTag("Image.SizeError", () => Effect.succeed("size" as const)),
+        )
       })
       const note = (reason: "decode" | "size", text: string) => {
         const count = normalized.filter((item) => item === reason).length
@@ -118,6 +116,7 @@ const registryLayer = Layer.effect(
 
     const settleTool = Effect.fn("ToolRegistry.settleTool")(function* (input: ExecuteInput, tool: AnyTool) {
       // Hooks fire only for hosted/local tools; provider-executed calls never reach settleTool.
+      const propagateTruncation = !("jsonSchema" in tool) && tool.contentTruncation === true
       const beforeEvent: ToolHooks.BeforeEvent = {
         tool: input.call.name,
         sessionID: input.sessionID,
@@ -149,7 +148,28 @@ const registryLayer = Layer.effect(
                       name: part.name,
                     },
               ),
-            ).pipe(Effect.flatMap((content) => progress({ structured: update.structured, content })))
+            ).pipe(
+              Effect.flatMap((content) =>
+                propagateTruncation
+                  ? resources
+                      .limits()
+                      .pipe(
+                        Effect.map((limits) =>
+                          ToolOutputStore.propagateTruncation({ structured: update.structured, content }, limits),
+                        ),
+                      )
+                  : Effect.succeed({ structured: update.structured, content }),
+              ),
+              Effect.flatMap((output) => {
+                const structured = output.structured
+                const entries =
+                  typeof structured === "object" && structured !== null && !Array.isArray(structured)
+                    ? Object.entries(structured)
+                    : undefined
+                if (!entries) return Effect.die(new Error("Tool progress structured output must be an object"))
+                return progress({ structured: Object.fromEntries(entries), content: output.content })
+              }),
+            )
           },
         },
       ).pipe(
@@ -165,21 +185,13 @@ const registryLayer = Layer.effect(
       if ("result" in pending) {
         settlement = pending
       } else {
-        const bounded = yield* resources.bound({
-          sessionID: input.sessionID,
-          callID: input.call.id,
-          output: { structured: pending.output.structured, content: yield* normalizeImages(pending.output.content) },
-        })
-        const result = ToolOutput.toResultValue(bounded.output)
-        settlement =
-          result.type === "error"
-            ? bounded.outputPaths.length > 0
-              ? { result, outputPaths: bounded.outputPaths }
-              : { result }
-            : bounded.outputPaths.length > 0
-              ? { result, output: bounded.output, outputPaths: bounded.outputPaths }
-              : { result, output: bounded.output }
+        const output = {
+          structured: pending.output.structured,
+          content: yield* normalizeImages(pending.output.content),
+        }
+        settlement = { result: ToolOutput.toResultValue(output), output }
       }
+      const initialResult = settlement.result
       const afterEvent: ToolHooks.AfterEvent = {
         tool: input.call.name,
         sessionID: input.sessionID,
@@ -192,10 +204,22 @@ const registryLayer = Layer.effect(
         outputPaths: settlement.outputPaths,
       }
       yield* toolHooks.runAfter(afterEvent)
+      const finalOutput = afterEvent.output
+        ? yield* resources.bound({
+            sessionID: input.sessionID,
+            callID: input.call.id,
+            output: afterEvent.output,
+            propagateTruncation,
+          })
+        : undefined
+      const outputPaths = [...new Set([...(afterEvent.outputPaths ?? []), ...(finalOutput?.outputPaths ?? [])])]
       return {
-        result: afterEvent.result,
-        ...(afterEvent.output !== undefined ? { output: afterEvent.output } : {}),
-        ...(afterEvent.outputPaths !== undefined ? { outputPaths: afterEvent.outputPaths } : {}),
+        result:
+          finalOutput !== undefined && afterEvent.result === initialResult && !("result" in pending)
+            ? ToolOutput.toResultValue(finalOutput.output)
+            : afterEvent.result,
+        ...(finalOutput !== undefined ? { output: finalOutput.output } : {}),
+        ...(outputPaths.length > 0 ? { outputPaths } : {}),
         ...(settlement.error !== undefined ? { error: settlement.error } : {}),
       }
     })

packages/core/src/tool/shell.ts

@@ -148,6 +148,8 @@ export const Plugin = {
             input: Input,
             output: Output,
             structured: StructuredOutput,
+            codeModeOutput: "output",
+            contentTruncation: true,
             toStructuredOutput: ({ output }) => ({
               truncated: output.truncated,
               ...(output.exit === undefined ? {} : { exit: output.exit }),

packages/core/src/tool/skill.ts

@@ -22,6 +22,13 @@ export const Output = Schema.Struct({
   output: Schema.String,
 })
 
+const StructuredOutput = Schema.Struct({
+  name: Schema.String,
+  directory: Schema.String,
+  bytes: Schema.Number,
+  truncated: Schema.Boolean,
+})
+
 export const description = [
   "Load a specialized skill when the task at hand matches one of the available skills in the instructions.",
   "",
@@ -66,6 +73,15 @@ export const Plugin = {
             description,
             input: Input,
             output: Output,
+            structured: StructuredOutput,
+            codeModeOutput: "output",
+            contentTruncation: true,
+            toStructuredOutput: ({ output }) => ({
+              name: output.name,
+              directory: output.directory,
+              bytes: Buffer.byteLength(output.output, "utf-8"),
+              truncated: false,
+            }),
             toModelOutput: ({ output }) => [{ type: "text", text: output.output }],
             execute: (input, context) =>
               Effect.gen(function* () {

packages/core/src/tool/structured.ts

@@ -0,0 +1,70 @@
+export * as ToolStructured from "./structured"
+
+import { formatPatch, parsePatch } from "diff"
+import { ToolOutputStore } from "../tool-output-store"
+
+export function fit<A>(project: (maxStringBytes: number) => A) {
+  const full = project(ToolOutputStore.MAX_STRUCTURED_BYTES)
+  if (Buffer.byteLength(JSON.stringify(full), "utf-8") <= ToolOutputStore.MAX_STRUCTURED_BYTES) return full
+
+  let minimum = 0
+  let maximum = ToolOutputStore.MAX_STRUCTURED_BYTES
+  let result = project(0)
+  while (minimum <= maximum) {
+    const middle = Math.floor((minimum + maximum) / 2)
+    const candidate = project(middle)
+    if (Buffer.byteLength(JSON.stringify(candidate), "utf-8") <= ToolOutputStore.MAX_STRUCTURED_BYTES) {
+      result = candidate
+      minimum = middle + 1
+      continue
+    }
+    maximum = middle - 1
+  }
+  return result
+}
+
+export function truncate(input: string, maximumBytes: number) {
+  if (Buffer.byteLength(input, "utf-8") <= maximumBytes) return input
+  const marker = " ... truncated ..."
+  const markerBytes = Buffer.byteLength(marker, "utf-8")
+  const available = Math.max(0, maximumBytes - markerBytes)
+  let bytes = 0
+  let end = 0
+  for (const char of input) {
+    const size = Buffer.byteLength(char, "utf-8")
+    if (bytes + size > available) break
+    bytes += size
+    end += char.length
+  }
+  return input.slice(0, end).replace(/\r?\n$/, "") + (maximumBytes >= markerBytes ? marker : "")
+}
+
+export function patch(input: string, maximumBytes: number) {
+  if (Buffer.byteLength(input, "utf-8") <= maximumBytes) return input
+  const parsed = parsePatch(input)[0]
+  const hunk = parsed?.hunks[0]
+  if (!parsed || !hunk) return truncate(input, maximumBytes)
+  const changedLines = parsed.hunks.flatMap((item) => item.lines).filter((line) => /^[+-]/.test(line))
+  const removed = changedLines.filter((line) => line.startsWith("-"))
+  const added = changedLines.filter((line) => line.startsWith("+"))
+  const changed = [removed[0], added[0]]
+    .filter((line) => line !== undefined)
+    .map((line) => line[0] + truncate(line.slice(1), Math.max(0, Math.floor(maximumBytes / 2) - 1)))
+  const lines = [
+    ...changed,
+    ...(removed.length > 1 ? [`-... ${removed.length - 1} removed lines omitted ...`] : []),
+    ...(added.length > 1 ? [`+... ${added.length - 1} added lines omitted ...`] : []),
+  ]
+  return formatPatch({
+    ...parsed,
+    hunks: [
+      {
+        oldStart: hunk.oldStart,
+        oldLines: lines.filter((line) => line.startsWith("-") || line.startsWith(" ")).length,
+        newStart: hunk.newStart,
+        newLines: lines.filter((line) => line.startsWith("+") || line.startsWith(" ")).length,
+        lines,
+      },
+    ],
+  })
+}

packages/core/src/tool/subagent.ts

@@ -32,6 +32,13 @@ export const Output = Schema.Struct({
   output: Schema.String,
 })
 
+const StructuredOutput = Schema.Struct({
+  sessionID: Output.fields.sessionID,
+  status: Output.fields.status,
+  bytes: Schema.Number,
+  truncated: Schema.Boolean,
+})
+
 export const description = [
   "Spawn a subagent: a child session running a configured agent with fresh context.",
   "Foreground (default) runs the subagent to completion and returns its final response.",
@@ -115,6 +122,14 @@ export const Plugin = {
             description,
             input: Input,
             output: Output,
+            structured: StructuredOutput,
+            contentTruncation: true,
+            toStructuredOutput: ({ output }) => ({
+              sessionID: output.sessionID,
+              status: output.status,
+              bytes: Buffer.byteLength(output.output, "utf-8"),
+              truncated: false,
+            }),
             toModelOutput: ({ output }) => [{ type: "text", text: output.output }],
             execute: (input, context) =>
               Effect.gen(function* () {

packages/core/src/tool/webfetch.ts

@@ -38,6 +38,14 @@ const Output = Schema.Struct({
   output: Schema.String,
 })
 
+const StructuredOutput = Schema.Struct({
+  url: Schema.String,
+  contentType: Schema.String,
+  format: Input.fields.format,
+  bytes: Schema.Number,
+  truncated: Schema.Boolean,
+})
+
 type Format = (typeof Input.Type)["format"]
 
 const acceptHeader = (format: Format) => {
@@ -126,6 +134,16 @@ export const Plugin = {
             description,
             input: Input,
             output: Output,
+            structured: StructuredOutput,
+            codeModeOutput: "output",
+            contentTruncation: true,
+            toStructuredOutput: ({ input, output }) => ({
+              url: output.url,
+              contentType: output.contentType,
+              format: input.format,
+              bytes: Buffer.byteLength(output.output, "utf-8"),
+              truncated: false,
+            }),
             toModelOutput: ({ output }) => [{ type: "text", text: output.output }],
             execute: (input, context) =>
               Effect.gen(function* () {

packages/core/src/tool/websearch.ts

@@ -187,6 +187,12 @@ const Output = Schema.Struct({
   text: Schema.String,
 })
 
+const StructuredOutput = Schema.Struct({
+  provider: Provider,
+  bytes: Schema.Number,
+  truncated: Schema.Boolean,
+})
+
 export const Plugin = {
   id: "opencode.tool.websearch",
   effect: Effect.fn("WebSearchTool.Plugin")(function* (ctx: PluginContext) {
@@ -202,6 +208,14 @@ export const Plugin = {
             description,
             input: Input,
             output: Output,
+            structured: StructuredOutput,
+            codeModeOutput: "output",
+            contentTruncation: true,
+            toStructuredOutput: ({ output }) => ({
+              provider: output.provider,
+              bytes: Buffer.byteLength(output.text, "utf-8"),
+              truncated: false,
+            }),
             toModelOutput: ({ output }) => [{ type: "text", text: output.text }],
             execute: (input, context) => {
               const provider = selectProvider(context.sessionID, config, config.provider)

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

@@ -12,11 +12,15 @@ import { ProviderV2 } from "@opencode-ai/core/provider"
 import { RelativePath } from "@opencode-ai/core/schema"
 import { Snapshot } from "@opencode-ai/core/snapshot"
 import { createLLMEventPublisher } from "@opencode-ai/core/session/runner/publish-llm-event"
+import { ToolOutputStore } from "@opencode-ai/core/tool-output-store"
 
 const sessionID = SessionV2.ID.make("ses_tool_event_test")
 const base64 = "iVBORw0KGgoAAAANSUhEUgAAAAEAAAAB"
+const outputs: Pick<ToolOutputStore.Interface, "bound"> = {
+  bound: (input) => Effect.succeed({ output: input.output, outputPaths: [] }),
+}
 
-const capture = (providerMetadataKey = "anthropic") => {
+const capture = (providerMetadataKey = "anthropic", outputStore = outputs) => {
   const published: Array<{ readonly type: string; readonly data: unknown }> = []
   const events: Pick<EventV2.Interface, "publish"> = {
     publish: (definition, data) =>
@@ -33,7 +37,7 @@ const capture = (providerMetadataKey = "anthropic") => {
   }
   return {
     published,
-    publisher: createLLMEventPublisher(events, {
+    publisher: createLLMEventPublisher(events, outputStore, {
       sessionID,
       agent: AgentV2.ID.make("build"),
       model: {
@@ -92,6 +96,71 @@ test("provider-executed success retains its raw provider result", async () => {
   expect(success?.data).toHaveProperty("result")
 })
 
+test("provider-executed success bounds output before durable publication", async () => {
+  const guarded: ToolOutputStore.BoundInput[] = []
+  const outputStore: Pick<ToolOutputStore.Interface, "bound"> = {
+    bound: (input) =>
+      Effect.sync(() => guarded.push(input)).pipe(
+        Effect.as({
+          output: {
+            structured: { _truncated: true, _bytes: 20_000, _outputPath: "/managed/provider" },
+            content: [{ type: "text" as const, text: "bounded provider output" }],
+          },
+          outputPaths: ["/managed/provider"],
+        }),
+      ),
+  }
+  const { published, publisher } = capture("anthropic", outputStore)
+  await Effect.runPromise(publisher.publish(LLMEvent.toolCall({ ...call, providerExecuted: true })))
+  await Effect.runPromise(publisher.publish(LLMEvent.toolResult({ ...result, providerExecuted: true })))
+
+  expect(guarded).toHaveLength(1)
+  expect(published.find((event) => event.type === "session.tool.success.1")?.data).toMatchObject({
+    structured: { _truncated: true, _bytes: 20_000, _outputPath: "/managed/provider" },
+    content: [{ type: "text", text: "bounded provider output" }],
+    result: result.result,
+  })
+})
+
+test("normalizes structured output to its durable record shape before bounding", async () => {
+  const guarded: ToolOutputStore.BoundInput[] = []
+  const outputStore: Pick<ToolOutputStore.Interface, "bound"> = {
+    bound: (input) => Effect.sync(() => guarded.push(input)).pipe(Effect.as({ output: input.output, outputPaths: [] })),
+  }
+  const { publisher } = capture("anthropic", outputStore)
+  await Effect.runPromise(publisher.publish(call))
+  await Effect.runPromise(
+    publisher.publish(
+      LLMEvent.toolResult({
+        ...result,
+        output: { structured: "x".repeat(ToolOutputStore.MAX_STRUCTURED_BYTES - 2), content: [] },
+      }),
+    ),
+  )
+
+  expect(guarded[0]?.output.structured).toEqual({
+    value: "x".repeat(ToolOutputStore.MAX_STRUCTURED_BYTES - 2),
+  })
+})
+
+test("a bounding failure leaves the tool eligible for durable failure", async () => {
+  const storage = new ToolOutputStore.StorageError({ operation: "write", cause: new Error("disk full") })
+  const outputStore: Pick<ToolOutputStore.Interface, "bound"> = {
+    bound: () => Effect.fail(storage),
+  }
+  const { published, publisher } = capture("anthropic", outputStore)
+  await Effect.runPromise(publisher.publish(call))
+  const exit = await Effect.runPromiseExit(publisher.publish(result))
+  expect(exit._tag).toBe("Failure")
+
+  await Effect.runPromise(publisher.failUnsettledTools({ type: "unknown", message: storage.message }))
+  expect(published.some((event) => event.type === "session.tool.success.1")).toBe(false)
+  expect(published.find((event) => event.type === "session.tool.failed.1")?.data).toMatchObject({
+    callID: call.id,
+    error: { type: "unknown", message: storage.message },
+  })
+})
+
 test("provider metadata is flattened using the route key", async () => {
   const { published, publisher } = capture()
   await Effect.runPromise(

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

@@ -3,14 +3,18 @@ import { Tool } from "@opencode-ai/core/tool/tool"
 import { AgentV2 } from "@opencode-ai/core/agent"
 import type { PermissionV2 } from "@opencode-ai/core/permission"
 import { AppNodeBuilder } from "@opencode-ai/core/effect/app-node-builder"
+import { LayerNode } from "@opencode-ai/core/effect/layer-node"
+import { Global } from "@opencode-ai/core/global"
 import { Image } from "@opencode-ai/core/image"
 import { SessionV2 } from "@opencode-ai/core/session"
 import { SessionMessage } from "@opencode-ai/core/session/message"
 import { ToolOutputStore } from "@opencode-ai/core/tool-output-store"
+import { ToolHooks } from "@opencode-ai/core/tool/hooks"
 import { ToolRegistry } from "@opencode-ai/core/tool/registry"
 import { executeTool, settleTool, toolDefinitions } from "./lib/tool"
 import { Cause, Deferred, Effect, Exit, Fiber, Layer, Option, Schema, SchemaGetter, SchemaIssue, Scope } from "effect"
 import { testEffect } from "./lib/effect"
+import { tmpdir } from "./fixture/tmpdir"
 
 const bounds: ToolOutputStore.BoundInput[] = []
 const retentionFailure = new ToolOutputStore.StorageError({ operation: "write", cause: new Error("disk full") })
@@ -52,6 +56,7 @@ const registryLayer = AppNodeBuilder.build(ToolRegistry.node, [
   [Image.node, imageStore],
 ])
 const it = testEffect(registryLayer)
+const live = testEffect(Layer.empty)
 const identity = {
   agent: AgentV2.ID.make("build"),
   messageID: SessionMessage.ID.make("msg_registry"),
@@ -84,6 +89,129 @@ const constant = (text: string) =>
   })
 
 describe("ToolRegistry", () => {
+  live.live("bounds structured-only output before deriving the model result", () =>
+    Effect.acquireUseRelease(
+      Effect.promise(() => tmpdir()),
+      (tmp) => {
+        const layer = AppNodeBuilder.build(ToolRegistry.node, [
+          [Global.node, Global.layerWith({ data: tmp.path })],
+          [Image.node, imageStore],
+          [ToolOutputStore.node, ToolOutputStore.nodeWithoutConfig],
+        ])
+        return Effect.gen(function* () {
+          const service = yield* ToolRegistry.Service
+          const text = "x".repeat(ToolOutputStore.MAX_STRUCTURED_BYTES)
+          yield* service.register(
+            {
+              structured_only: Tool.make({
+                description: "Return structured output",
+                input: Schema.Struct({}),
+                output: Schema.Struct({ text: Schema.String }),
+                execute: () => Effect.succeed({ text }),
+              }),
+            },
+            { codemode: false },
+          )
+          const settled = yield* settleTool(service, {
+            sessionID,
+            ...identity,
+            call: { type: "tool-call", id: "call-structured-only", name: "structured_only", input: {} },
+          })
+          const encoded = JSON.stringify({ text })
+
+          expect(settled.result).toEqual({ type: "text", value: encoded })
+          expect(settled.outputPaths).toHaveLength(1)
+          expect(settled.output).toEqual({
+            structured: {
+              _truncated: true,
+              _bytes: Buffer.byteLength(encoded),
+              _outputPath: settled.outputPaths?.[0],
+            },
+            content: [{ type: "text", text: encoded }],
+          })
+        }).pipe(Effect.provide(layer))
+      },
+      (tmp) => Effect.promise(() => tmp[Symbol.asyncDispose]()),
+    ),
+  )
+
+  live.live("bounds output replaced by an execute-after hook", () =>
+    Effect.acquireUseRelease(
+      Effect.promise(() => tmpdir()),
+      (tmp) => {
+        const layer = AppNodeBuilder.build(LayerNode.group([ToolRegistry.node, ToolHooks.node]), [
+          [Global.node, Global.layerWith({ data: tmp.path })],
+          [Image.node, imageStore],
+          [ToolOutputStore.node, ToolOutputStore.nodeWithoutConfig],
+        ])
+        return Effect.gen(function* () {
+          const service = yield* ToolRegistry.Service
+          const hooks = yield* ToolHooks.Service
+          const text = "y".repeat(ToolOutputStore.MAX_STRUCTURED_BYTES)
+          yield* hooks.hook.after((event) => {
+            event.result = { type: "text", value: "hook result" }
+            event.output = { structured: { text }, content: [] }
+          })
+          yield* service.register({ hooked: make() }, { codemode: false })
+          const settled = yield* settleTool(service, {
+            sessionID,
+            ...identity,
+            call: { type: "tool-call", id: "call-hooked", name: "hooked", input: { text: "original" } },
+          })
+          const encoded = JSON.stringify({ text })
+
+          expect(settled.result).toEqual({ type: "text", value: "hook result" })
+          expect(settled.outputPaths).toHaveLength(1)
+          expect(settled.output).toEqual({
+            structured: {
+              _truncated: true,
+              _bytes: Buffer.byteLength(encoded),
+              _outputPath: settled.outputPaths?.[0],
+            },
+            content: [{ type: "text", text: encoded }],
+          })
+        }).pipe(Effect.provide(layer))
+      },
+      (tmp) => Effect.promise(() => tmp[Symbol.asyncDispose]()),
+    ),
+  )
+
+  live.live("allows execute-after hooks to redact output before retention", () =>
+    Effect.acquireUseRelease(
+      Effect.promise(() => tmpdir()),
+      (tmp) => {
+        const layer = AppNodeBuilder.build(LayerNode.group([ToolRegistry.node, ToolHooks.node]), [
+          [Global.node, Global.layerWith({ data: tmp.path })],
+          [Image.node, imageStore],
+          [ToolOutputStore.node, ToolOutputStore.nodeWithoutConfig],
+        ])
+        return Effect.gen(function* () {
+          const service = yield* ToolRegistry.Service
+          const hooks = yield* ToolHooks.Service
+          const text = "sensitive".repeat(ToolOutputStore.MAX_STRUCTURED_BYTES)
+          let observed: unknown
+          yield* hooks.hook.after((event) => {
+            observed = event.output?.structured
+            event.output = { structured: { redacted: true }, content: [{ type: "text", text: "redacted" }] }
+          })
+          yield* service.register({ secret: constant(text) }, { codemode: false })
+          const settled = yield* settleTool(service, {
+            sessionID,
+            ...identity,
+            call: { type: "tool-call", id: "call-secret", name: "secret", input: { text: "ignored" } },
+          })
+
+          expect(observed).toEqual({ text })
+          expect(settled).toEqual({
+            result: { type: "text", value: "redacted" },
+            output: { structured: { redacted: true }, content: [{ type: "text", text: "redacted" }] },
+          })
+        }).pipe(Effect.provide(layer))
+      },
+      (tmp) => Effect.promise(() => tmp[Symbol.asyncDispose]()),
+    ),
+  )
+
   it.effect("rejects invalid dotted namespaces", () =>
     Effect.gen(function* () {
       const service = yield* ToolRegistry.Service
@@ -113,12 +241,15 @@ describe("ToolRegistry", () => {
   it.effect("filters disabled tools with edit aliases and ordered wildcard precedence", () =>
     Effect.gen(function* () {
       const service = yield* ToolRegistry.Service
-      yield* service.register({
-        question: make(),
-        bash: make(),
-        edit: make("edit"),
-        write: make("edit"),
-      }, { codemode: false })
+      yield* service.register(
+        {
+          question: make(),
+          bash: make(),
+          edit: make("edit"),
+          write: make("edit"),
+        },
+        { codemode: false },
+      )
       const names = (permissions: PermissionV2.Ruleset) =>
         toolDefinitions(service, permissions).pipe(Effect.map((definitions) => definitions.map((tool) => tool.name)))
 
@@ -191,14 +322,17 @@ describe("ToolRegistry", () => {
   it.effect("returns model errors without swallowing interruption or defects", () =>
     Effect.gen(function* () {
       const service = yield* ToolRegistry.Service
-      yield* service.register({
-        failed: Tool.make({
-          description: "Failed",
-          input: Schema.Struct({}),
-          output: Schema.Struct({ ok: Schema.Boolean }),
-          execute: () => Effect.fail(new Tool.Failure({ message: "Denied" })),
-        }),
-      }, { codemode: false })
+      yield* service.register(
+        {
+          failed: Tool.make({
+            description: "Failed",
+            input: Schema.Struct({}),
+            output: Schema.Struct({ ok: Schema.Boolean }),
+            execute: () => Effect.fail(new Tool.Failure({ message: "Denied" })),
+          }),
+        },
+        { codemode: false },
+      )
       expect(
         yield* executeTool(service, {
           sessionID,
@@ -214,14 +348,17 @@ describe("ToolRegistry", () => {
         }),
       ).toEqual({ type: "error", value: "Unknown tool: missing" })
 
-      yield* service.register({
-        defect: Tool.make({
-          description: "Defect",
-          input: Schema.Struct({}),
-          output: Schema.Struct({}),
-          execute: () => Effect.die("unexpected executor defect"),
-        }),
-      }, { codemode: false })
+      yield* service.register(
+        {
+          defect: Tool.make({
+            description: "Defect",
+            input: Schema.Struct({}),
+            output: Schema.Struct({}),
+            execute: () => Effect.die("unexpected executor defect"),
+          }),
+        },
+        { codemode: false },
+      )
       expect(
         yield* service.materialize().pipe(
           Effect.flatMap((materialized) =>
@@ -264,22 +401,23 @@ describe("ToolRegistry", () => {
     Effect.gen(function* () {
       const service = yield* ToolRegistry.Service
       const contexts: Tool.Context[] = []
-      yield* service.register({
-        context: Tool.make({
-          description: "Context",
-          input: Schema.Struct({}),
-          output: Schema.Struct({ ok: Schema.Boolean }),
-          execute: (_, context) => Effect.sync(() => contexts.push(context)).pipe(Effect.as({ ok: true })),
-        }),
-      }, { codemode: false })
+      yield* service.register(
+        {
+          context: Tool.make({
+            description: "Context",
+            input: Schema.Struct({}),
+            output: Schema.Struct({ ok: Schema.Boolean }),
+            execute: (_, context) => Effect.sync(() => contexts.push(context)).pipe(Effect.as({ ok: true })),
+          }),
+        },
+        { codemode: false },
+      )
       yield* executeTool(service, {
         sessionID,
         ...identity,
         call: { type: "tool-call", id: "call-context", name: "context", input: {} },
       })
-      expect(contexts).toEqual([
-        { sessionID, ...identity, callID: "call-context", progress: expect.any(Function) },
-      ])
+      expect(contexts).toEqual([{ sessionID, ...identity, callID: "call-context", progress: expect.any(Function) }])
     }),
   )
 
@@ -306,20 +444,23 @@ describe("ToolRegistry", () => {
   it.effect("normalizes image tool output at settlement and drops unresizable images", () =>
     Effect.gen(function* () {
       const service = yield* ToolRegistry.Service
-      yield* service.register({
-        snapshot: Tool.make({
-          description: "Return images",
-          input: Schema.Struct({ text: Schema.String }),
-          output: Schema.Struct({ text: Schema.String }),
-          execute: ({ text }) => Effect.succeed({ text }),
-          toModelOutput: ({ output }) => [
-            { type: "file", data: "aW1hZ2U=", mime: "image/png", name: "frame.png" },
-            { type: "file", data: "aW1hZ2U=", mime: "image/png", name: "too-large.png" },
-            { type: "file", data: "aW1hZ2U=", mime: "image/png", name: "corrupt.png" },
-            { type: "text", text: output.text },
-          ],
-        }),
-      }, { codemode: false })
+      yield* service.register(
+        {
+          snapshot: Tool.make({
+            description: "Return images",
+            input: Schema.Struct({ text: Schema.String }),
+            output: Schema.Struct({ text: Schema.String }),
+            execute: ({ text }) => Effect.succeed({ text }),
+            toModelOutput: ({ output }) => [
+              { type: "file", data: "aW1hZ2U=", mime: "image/png", name: "frame.png" },
+              { type: "file", data: "aW1hZ2U=", mime: "image/png", name: "too-large.png" },
+              { type: "file", data: "aW1hZ2U=", mime: "image/png", name: "corrupt.png" },
+              { type: "text", text: output.text },
+            ],
+          }),
+        },
+        { codemode: false },
+      )
 
       const settlement = yield* settleTool(service, call("snapshot"))
       expect(settlement.output?.content).toEqual([
@@ -334,23 +475,26 @@ describe("ToolRegistry", () => {
   it.effect("normalizes image progress content before it is published", () =>
     Effect.gen(function* () {
       const service = yield* ToolRegistry.Service
-      yield* service.register({
-        progressive: Tool.make({
-          description: "Emit image progress",
-          input: Schema.Struct({ text: Schema.String }),
-          output: Schema.Struct({ text: Schema.String }),
-          execute: ({ text }, context) =>
-            context
-              .progress({
-                structured: { stage: "capture" },
-                content: [
-                  { type: "file", data: "aW1hZ2U=", mime: "image/png", name: "frame.png" },
-                  { type: "file", data: "aW1hZ2U=", mime: "image/png", name: "too-large.png" },
-                ],
-              })
-              .pipe(Effect.as({ text })),
-        }),
-      }, { codemode: false })
+      yield* service.register(
+        {
+          progressive: Tool.make({
+            description: "Emit image progress",
+            input: Schema.Struct({ text: Schema.String }),
+            output: Schema.Struct({ text: Schema.String }),
+            execute: ({ text }, context) =>
+              context
+                .progress({
+                  structured: { stage: "capture" },
+                  content: [
+                    { type: "file", data: "aW1hZ2U=", mime: "image/png", name: "frame.png" },
+                    { type: "file", data: "aW1hZ2U=", mime: "image/png", name: "too-large.png" },
+                  ],
+                })
+                .pipe(Effect.as({ text })),
+          }),
+        },
+        { codemode: false },
+      )
 
       const updates: ToolRegistry.Progress[] = []
       yield* settleTool(service, {
@@ -382,15 +526,18 @@ describe("ToolRegistry", () => {
           encode: SchemaGetter.transform((value) => value === "yes"),
         }),
       )
-      yield* service.register({
-        transformed: Tool.make({
-          description: "Transform values",
-          input: Schema.Struct({ value: Transformed }),
-          output: Schema.Struct({ value: Transformed }),
-          execute: ({ value }) => Effect.sync(() => executed.push(value)).pipe(Effect.as({ value })),
-          toModelOutput: ({ output }) => [{ type: "text", text: String(output.value) }],
-        }),
-      }, { codemode: false })
+      yield* service.register(
+        {
+          transformed: Tool.make({
+            description: "Transform values",
+            input: Schema.Struct({ value: Transformed }),
+            output: Schema.Struct({ value: Transformed }),
+            execute: ({ value }) => Effect.sync(() => executed.push(value)).pipe(Effect.as({ value })),
+            toModelOutput: ({ output }) => [{ type: "text", text: String(output.value) }],
+          }),
+        },
+        { codemode: false },
+      )
 
       expect(
         yield* executeTool(service, {
@@ -409,25 +556,28 @@ describe("ToolRegistry", () => {
       ).toMatchObject({ type: "error", value: expect.stringContaining("Invalid tool input") })
       expect(executed).toEqual(["yes"])
 
-      yield* service.register({
-        invalid_output: Tool.make({
-          description: "Return invalid output",
-          input: Schema.Struct({}),
-          output: Schema.Struct({
-            value: Schema.Boolean.pipe(
-              Schema.decodeTo(Schema.String, {
-                decode: SchemaGetter.transform((value) => String(value)),
-                encode: SchemaGetter.transformOrFail((value) =>
-                  value === "valid"
-                    ? Effect.succeed(true)
-                    : Effect.fail(new SchemaIssue.InvalidValue(Option.some(value), { message: "invalid output" })),
-                ),
-              }),
-            ),
+      yield* service.register(
+        {
+          invalid_output: Tool.make({
+            description: "Return invalid output",
+            input: Schema.Struct({}),
+            output: Schema.Struct({
+              value: Schema.Boolean.pipe(
+                Schema.decodeTo(Schema.String, {
+                  decode: SchemaGetter.transform((value) => String(value)),
+                  encode: SchemaGetter.transformOrFail((value) =>
+                    value === "valid"
+                      ? Effect.succeed(true)
+                      : Effect.fail(new SchemaIssue.InvalidValue(Option.some(value), { message: "invalid output" })),
+                  ),
+                }),
+              ),
+            }),
+            execute: () => Effect.succeed({ value: "invalid" }),
           }),
-          execute: () => Effect.succeed({ value: "invalid" }),
-        }),
-      }, { codemode: false })
+        },
+        { codemode: false },
+      )
       expect(
         yield* executeTool(service, {
           sessionID,

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

@@ -239,43 +239,46 @@ const permission = Layer.succeed(
 )
 const echo = Layer.effectDiscard(
   ToolRegistry.Service.use((registry) =>
-    registry.register({
-      echo: Tool.make({
-        description: "Echo text",
-        input: Schema.Struct({ text: Schema.String }),
-        output: Schema.Struct({ text: Schema.String }),
-        toModelOutput: ({ output }) => [{ type: "text", text: output.text }],
-        execute: ({ text }, context) =>
-          Effect.gen(function* () {
-            authorizations.push(context)
-            executions.push(text)
-            activeToolExecutions++
-            maxActiveToolExecutions = Math.max(maxActiveToolExecutions, activeToolExecutions)
-            if (activeToolExecutions === toolExecutionsReady && toolExecutionsStarted) {
-              yield* Deferred.succeed(toolExecutionsStarted, undefined)
-            }
-            if (toolExecutionGate) yield* Deferred.await(toolExecutionGate)
-            return { text }
-          }).pipe(Effect.ensuring(Effect.sync(() => activeToolExecutions--))),
-      }),
-      defect: Tool.make({
-        description: "Fail unexpectedly",
-        input: Schema.Struct({}),
-        output: Schema.Struct({}),
-        execute: () =>
-          (toolExecutionGate ? Deferred.await(toolExecutionGate) : Effect.void).pipe(
-            Effect.andThen(Effect.die("unexpected tool defect")),
-          ),
-      }),
-      // BigInt output with no model content forces ToolOutputStore.bound onto its
-      // JSON.stringify encode path, which fails with a typed StorageError.
-      storefail: Tool.make({
-        description: "Produce output that cannot be persisted",
-        input: Schema.Struct({}),
-        output: Schema.Any,
-        execute: () => Effect.succeed({ big: 1n }),
-      }),
-    }, { codemode: false }),
+    registry.register(
+      {
+        echo: Tool.make({
+          description: "Echo text",
+          input: Schema.Struct({ text: Schema.String }),
+          output: Schema.Struct({ text: Schema.String }),
+          toModelOutput: ({ output }) => [{ type: "text", text: output.text }],
+          execute: ({ text }, context) =>
+            Effect.gen(function* () {
+              authorizations.push(context)
+              executions.push(text)
+              activeToolExecutions++
+              maxActiveToolExecutions = Math.max(maxActiveToolExecutions, activeToolExecutions)
+              if (activeToolExecutions === toolExecutionsReady && toolExecutionsStarted) {
+                yield* Deferred.succeed(toolExecutionsStarted, undefined)
+              }
+              if (toolExecutionGate) yield* Deferred.await(toolExecutionGate)
+              return { text }
+            }).pipe(Effect.ensuring(Effect.sync(() => activeToolExecutions--))),
+        }),
+        defect: Tool.make({
+          description: "Fail unexpectedly",
+          input: Schema.Struct({}),
+          output: Schema.Struct({}),
+          execute: () =>
+            (toolExecutionGate ? Deferred.await(toolExecutionGate) : Effect.void).pipe(
+              Effect.andThen(Effect.die("unexpected tool defect")),
+            ),
+        }),
+        // BigInt output with no model content forces ToolOutputStore.bound onto its
+        // JSON.stringify encode path, which fails with a typed StorageError.
+        storefail: Tool.make({
+          description: "Produce output that cannot be persisted",
+          input: Schema.Struct({}),
+          output: Schema.Any,
+          execute: () => Effect.succeed({ big: 1n }),
+        }),
+      },
+      { codemode: false },
+    ),
   ),
 )
 const echoNode = makeLocationNode({ name: "test/session-runner-tools", layer: echo, deps: [ToolRegistry.node] })
@@ -840,19 +843,23 @@ describe("SessionRunnerLLM", () => {
       const session = yield* setup
       const registry = yield* ToolRegistry.Service
       const contexts: Tool.Context[] = []
-      yield* registry.register({
-        location_context: Tool.make({
-          description: "Read application context",
-          input: Schema.Struct({ query: Schema.String }),
-          output: Schema.Struct({ answer: Schema.String }),
-          execute: ({ query }, context) =>
-            Effect.gen(function* () {
-              contexts.push(context)
-              yield* context.progress({ structured: { phase: "reading" } })
-              return { answer: query.toUpperCase() }
-            }),
-        }),
-      }, { codemode: false })
+      const progress = "x".repeat(ToolOutputStore.MAX_STRUCTURED_BYTES)
+      yield* registry.register(
+        {
+          location_context: Tool.make({
+            description: "Read application context",
+            input: Schema.Struct({ query: Schema.String }),
+            output: Schema.Struct({ answer: Schema.String }),
+            execute: ({ query }, context) =>
+              Effect.gen(function* () {
+                contexts.push(context)
+                yield* context.progress({ structured: { phase: progress } })
+                return { answer: query.toUpperCase() }
+              }),
+          }),
+        },
+        { codemode: false },
+      )
       yield* admit(session, "Use application context")
       responses = [reply.tool("call-location", "location_context", { query: "hello" }), []]
       const events = yield* EventV2.Service
@@ -875,7 +882,13 @@ describe("SessionRunnerLLM", () => {
           progress: expect.any(Function),
         },
       ])
-      expect(Array.from(yield* Fiber.join(progressFiber))[0]?.data.structured).toEqual({ phase: "reading" })
+      const update = Array.from(yield* Fiber.join(progressFiber))[0]?.data
+      expect(update?.structured).toMatchObject({
+        _truncated: true,
+        _bytes: Buffer.byteLength(JSON.stringify({ phase: progress })),
+        _outputPath: expect.any(String),
+      })
+      expect(update?.content).toEqual([{ type: "text", text: JSON.stringify({ phase: progress }) }])
       expect(yield* session.context(sessionID)).toMatchObject([
         { type: "user", text: "Use application context" },
         {
@@ -899,14 +912,17 @@ describe("SessionRunnerLLM", () => {
       const scope = yield* Scope.make()
       const executions: string[] = []
       yield* registry
-        .register({
-          reloaded: Tool.make({
-            description: "Record the advertised tool",
-            input: Schema.Struct({}),
-            output: Schema.Struct({ value: Schema.String }),
-            execute: () => Effect.sync(() => executions.push("advertised")).pipe(Effect.as({ value: "advertised" })),
-          }),
-        }, { codemode: false })
+        .register(
+          {
+            reloaded: Tool.make({
+              description: "Record the advertised tool",
+              input: Schema.Struct({}),
+              output: Schema.Struct({ value: Schema.String }),
+              execute: () => Effect.sync(() => executions.push("advertised")).pipe(Effect.as({ value: "advertised" })),
+            }),
+          },
+          { codemode: false },
+        )
         .pipe(Scope.provide(scope))
       yield* admit(session, "Use the reloaded tool")
       responses = [
@@ -924,14 +940,17 @@ describe("SessionRunnerLLM", () => {
       const run = yield* session.resume(sessionID).pipe(Effect.forkChild)
       yield* Deferred.await(streamStarted)
       yield* Scope.close(scope, Exit.void)
-      yield* registry.register({
-        reloaded: Tool.make({
-          description: "Record the replacement tool",
-          input: Schema.Struct({}),
-          output: Schema.Struct({ value: Schema.String }),
-          execute: () => Effect.sync(() => executions.push("replacement")).pipe(Effect.as({ value: "replacement" })),
-        }),
-      }, { codemode: false })
+      yield* registry.register(
+        {
+          reloaded: Tool.make({
+            description: "Record the replacement tool",
+            input: Schema.Struct({}),
+            output: Schema.Struct({ value: Schema.String }),
+            execute: () => Effect.sync(() => executions.push("replacement")).pipe(Effect.as({ value: "replacement" })),
+          }),
+        },
+        { codemode: false },
+      )
       yield* Deferred.succeed(streamGate, undefined)
       yield* Fiber.join(run)
 
@@ -3367,17 +3386,20 @@ describe("SessionRunnerLLM", () => {
     Effect.gen(function* () {
       const session = yield* setup
       const registry = yield* ToolRegistry.Service
-      yield* registry.register({
-        blocked: Tool.make({
-          description: "Fail because policy blocked execution",
-          input: Schema.Struct({}),
-          output: Schema.Struct({}),
-          execute: () =>
-            Effect.fail(new PermissionV2.BlockedError({ rules: [], permission: "blocked", resources: ["*"] })).pipe(
-              Effect.mapError(() => new Tool.Failure({ message: "Permission blocked" })),
-            ),
-        }),
-      }, { codemode: false })
+      yield* registry.register(
+        {
+          blocked: Tool.make({
+            description: "Fail because policy blocked execution",
+            input: Schema.Struct({}),
+            output: Schema.Struct({}),
+            execute: () =>
+              Effect.fail(new PermissionV2.BlockedError({ rules: [], permission: "blocked", resources: ["*"] })).pipe(
+                Effect.mapError(() => new Tool.Failure({ message: "Permission blocked" })),
+              ),
+          }),
+        },
+        { codemode: false },
+      )
       yield* admit(session, "Call blocked")
 
       responses = [reply.tool("call-blocked", "blocked", {}), reply.stop()]
@@ -3402,14 +3424,17 @@ describe("SessionRunnerLLM", () => {
     Effect.gen(function* () {
       const session = yield* setup
       const registry = yield* ToolRegistry.Service
-      yield* registry.register({
-        declined: Tool.make({
-          description: "Fail because the user declined approval",
-          input: Schema.Struct({}),
-          output: Schema.Struct({}),
-          execute: () => Effect.die(new PermissionV2.DeclinedError()),
-        }),
-      }, { codemode: false })
+      yield* registry.register(
+        {
+          declined: Tool.make({
+            description: "Fail because the user declined approval",
+            input: Schema.Struct({}),
+            output: Schema.Struct({}),
+            execute: () => Effect.die(new PermissionV2.DeclinedError()),
+          }),
+        },
+        { codemode: false },
+      )
       yield* admit(session, "Call declined")
 
       response = reply.tool("call-declined", "declined", {})
@@ -3439,17 +3464,20 @@ describe("SessionRunnerLLM", () => {
     Effect.gen(function* () {
       const session = yield* setup
       const registry = yield* ToolRegistry.Service
-      yield* registry.register({
-        corrected: Tool.make({
-          description: "Fail with user correction feedback",
-          input: Schema.Struct({}),
-          output: Schema.Struct({}),
-          execute: () =>
-            Effect.fail(new PermissionV2.CorrectedError({ feedback: "Use another tool" })).pipe(
-              Effect.mapError(() => new Tool.Failure({ message: "Use another tool" })),
-            ),
-        }),
-      }, { codemode: false })
+      yield* registry.register(
+        {
+          corrected: Tool.make({
+            description: "Fail with user correction feedback",
+            input: Schema.Struct({}),
+            output: Schema.Struct({}),
+            execute: () =>
+              Effect.fail(new PermissionV2.CorrectedError({ feedback: "Use another tool" })).pipe(
+                Effect.mapError(() => new Tool.Failure({ message: "Use another tool" })),
+              ),
+          }),
+        },
+        { codemode: false },
+      )
       yield* admit(session, "Call corrected")
 
       responses = [reply.tool("call-corrected", "corrected", {}), reply.stop()]
@@ -3505,6 +3533,36 @@ describe("SessionRunnerLLM", () => {
     }),
   )
 
+  it.effect("does not hide output persistence failure behind another concurrent tool defect", () =>
+    Effect.gen(function* () {
+      const session = yield* setup
+      yield* admit(session, "Call defect and storefail")
+      responses = [
+        [
+          LLMEvent.stepStart({ index: 0 }),
+          LLMEvent.toolCall({ id: "call-defect", name: "defect", input: {} }),
+          LLMEvent.toolCall({ id: "call-storefail", name: "storefail", input: {} }),
+          LLMEvent.stepFinish({ index: 0, reason: "tool-calls" }),
+          LLMEvent.finish({ reason: "tool-calls" }),
+        ],
+        [],
+      ]
+
+      const exit = yield* session.resume(sessionID).pipe(Effect.exit)
+
+      expect(Exit.isFailure(exit)).toBe(true)
+      expect(requests).toHaveLength(1)
+      expect(yield* session.context(sessionID)).toMatchObject([
+        { type: "user", text: "Call defect and storefail" },
+        {
+          type: "assistant",
+          finish: "error",
+          error: { type: "unknown", message: expect.stringContaining("Failed to encode tool output") },
+        },
+      ])
+    }),
+  )
+
   it.effect("returns configured permission denials to the model and continues", () =>
     Effect.gen(function* () {
       const session = yield* setup
@@ -3547,14 +3605,17 @@ describe("SessionRunnerLLM", () => {
     Effect.gen(function* () {
       const session = yield* setup
       const registry = yield* ToolRegistry.Service
-      yield* registry.register({
-        question: Tool.make({
-          description: "Ask the user",
-          input: Schema.Struct({}),
-          output: Schema.Struct({}),
-          execute: () => Effect.die(new QuestionTool.CancelledError()),
-        }),
-      }, { codemode: false })
+      yield* registry.register(
+        {
+          question: Tool.make({
+            description: "Ask the user",
+            input: Schema.Struct({}),
+            output: Schema.Struct({}),
+            execute: () => Effect.die(new QuestionTool.CancelledError()),
+          }),
+        },
+        { codemode: false },
+      )
       yield* admit(session, "Ask then stop")
 
       responses = [reply.tool("call-question", "question", {}), []]

packages/core/test/tool-edit.test.ts

@@ -2,7 +2,8 @@ import fs from "fs/promises"
 import path from "path"
 import { fileURLToPath } from "url"
 import { describe, expect, test } from "bun:test"
-import { Effect, Layer } from "effect"
+import { Effect, Layer, Schema } from "effect"
+import { parsePatch } from "diff"
 import { AppNodeBuilder } from "@opencode-ai/core/effect/app-node-builder"
 import { LayerNode } from "@opencode-ai/core/effect/layer-node"
 import { FileMutation } from "@opencode-ai/core/file-mutation"
@@ -174,6 +175,48 @@ describe("EditTool", () => {
     ),
   )
 
+  it.live("retains a bounded patch for large edits", () =>
+    Effect.acquireUseRelease(
+      Effect.promise(() => tmpdir()),
+      (tmp) => {
+        reset()
+        const target = path.join(tmp.path, "large.txt")
+        const before = "x".repeat(20_000)
+        const after = "y".repeat(20_000)
+        return Effect.promise(() => fs.writeFile(target, before)).pipe(
+          Effect.andThen(
+            withTool(tmp.path, (registry) =>
+              Effect.gen(function* () {
+                const settled = yield* settleTool(
+                  registry,
+                  call({ path: "large.txt", oldString: before, newString: after }),
+                )
+                const structured = Schema.decodeUnknownSync(EditTool.Output)(settled.output?.structured)
+                expect(Buffer.byteLength(JSON.stringify(structured))).toBeLessThanOrEqual(
+                  ToolOutputStore.MAX_STRUCTURED_BYTES,
+                )
+                const hunk = parsePatch(structured.files[0]?.patch ?? "")[0]?.hunks[0]
+                expect(hunk?.lines.some((line) => line.startsWith("-"))).toBe(true)
+                expect(hunk?.lines.some((line) => line.startsWith("+"))).toBe(true)
+                expect(hunk).toMatchObject({ oldLines: 1, newLines: 1 })
+                expect(structured).toMatchObject({
+                  replacements: 1,
+                  files: [
+                    {
+                      file: "large.txt",
+                      patch: expect.stringContaining("... truncated ..."),
+                    },
+                  ],
+                })
+              }),
+            ),
+          ),
+        )
+      },
+      (tmp) => Effect.promise(() => tmp[Symbol.asyncDispose]()),
+    ),
+  )
+
   it.live("accepts an absolute file path inside the active Location", () =>
     Effect.acquireUseRelease(
       Effect.promise(() => tmpdir()),

packages/core/test/tool-execute.test.ts

@@ -93,3 +93,70 @@ test("execute supports callable namespace tools", async () => {
   })
   expect(result.content).toEqual([{ type: "text", text: '[\n  "admin",\n  "created"\n]' }])
 })
+
+test("execute exposes typed internal output instead of the persisted receipt", async () => {
+  const child = Tool.make({
+    description: "Fetch content",
+    input: Schema.Struct({}),
+    output: Schema.Struct({ content: Schema.String, bytes: Schema.Number }),
+    structured: Schema.Struct({ bytes: Schema.Number }),
+    codeModeOutput: "output",
+    toStructuredOutput: ({ output }) => ({ bytes: output.bytes }),
+    toModelOutput: ({ output }) => [{ type: "text", text: output.content }],
+    execute: () => Effect.succeed({ content: "full payload", bytes: 12 }),
+  })
+  const execute = ExecuteTool.create(new Map([["fetch", { tool: child, name: "fetch" }]]))
+  const result = await Effect.runPromise(
+    Tool.settle(
+      execute,
+      {
+        type: "tool-call",
+        id: "call_execute",
+        name: "execute",
+        input: { code: "return (await tools.fetch({})).content" },
+      },
+      {
+        sessionID: Session.ID.make("ses_execute"),
+        agent: Agent.ID.make("build"),
+        messageID: SessionMessage.ID.make("msg_execute"),
+        callID: "call_execute",
+        progress: () => Effect.void,
+      },
+    ),
+  )
+
+  expect(result.structured).toEqual({ toolCalls: [{ tool: "fetch", status: "completed" }] })
+  expect(result.content).toEqual([{ type: "text", text: "full payload" }])
+})
+
+test("execute keeps the structured projection unless a tool opts into internal output", async () => {
+  const child = Tool.make({
+    description: "Fetch content",
+    input: Schema.Struct({}),
+    output: Schema.Struct({ content: Schema.String, bytes: Schema.Number }),
+    structured: Schema.Struct({ bytes: Schema.Number }),
+    toStructuredOutput: ({ output }) => ({ bytes: output.bytes }),
+    execute: () => Effect.succeed({ content: "internal", bytes: 8 }),
+  })
+  const execute = ExecuteTool.create(new Map([["fetch", { tool: child, name: "fetch" }]]))
+  const result = await Effect.runPromise(
+    Tool.settle(
+      execute,
+      {
+        type: "tool-call",
+        id: "call_execute",
+        name: "execute",
+        input: { code: "return await tools.fetch({})" },
+      },
+      {
+        sessionID: Session.ID.make("ses_execute"),
+        agent: Agent.ID.make("build"),
+        messageID: SessionMessage.ID.make("msg_execute"),
+        callID: "call_execute",
+        progress: () => Effect.void,
+      },
+    ),
+  )
+
+  expect(result.content).toEqual([{ type: "text", text: '{\n  "bytes": 8\n}' }])
+})

packages/core/test/tool-output-store.test.ts

@@ -75,7 +75,14 @@ describe("ToolOutputStore", () => {
       Effect.gen(function* () {
         const structured = { text: "x".repeat(ToolOutputStore.MAX_BYTES) }
         const result = yield* store.bound({ sessionID, callID: "call-json", output: { structured, content: [] } })
-        expect(result.output.structured).toEqual(structured)
+        expect(result.output.structured).toEqual({
+          _truncated: true,
+          _bytes: Buffer.byteLength(JSON.stringify(structured)),
+          _outputPath: result.outputPaths[0],
+        })
+        expect(Buffer.byteLength(JSON.stringify(result.output.structured))).toBeLessThanOrEqual(
+          ToolOutputStore.MAX_STRUCTURED_BYTES,
+        )
         expect(result.outputPaths).toHaveLength(1)
         expect(JSON.parse(yield* fs.readFileString(result.outputPaths[0]))).toEqual(structured)
         expect(result.output.content).toHaveLength(1)
@@ -83,6 +90,131 @@ describe("ToolOutputStore", () => {
     ),
   )
 
+  it.live("projects guarded structured-only output into the bounded content channel", () =>
+    withStore(({ store, fs }) =>
+      Effect.gen(function* () {
+        const structured = { text: "x".repeat(ToolOutputStore.MAX_STRUCTURED_BYTES) }
+        const result = yield* store.bound({
+          sessionID,
+          callID: "call-structured-content",
+          output: { structured, content: [] },
+        })
+        expect(result.output.structured).toEqual({
+          _truncated: true,
+          _bytes: Buffer.byteLength(JSON.stringify(structured)),
+          _outputPath: result.outputPaths[0],
+        })
+        expect(result.output.content).toEqual([{ type: "text", text: JSON.stringify(structured) }])
+        expect(JSON.parse(yield* fs.readFileString(result.outputPaths[0]))).toEqual(structured)
+      }),
+    ),
+  )
+
+  it.live("measures the structured boundary in UTF-8 bytes", () =>
+    withStore(({ store }) =>
+      Effect.gen(function* () {
+        const structured = { text: "é".repeat(ToolOutputStore.MAX_STRUCTURED_BYTES / 2) }
+        const encoded = JSON.stringify(structured)
+        expect(structured.text.length).toBeLessThan(ToolOutputStore.MAX_STRUCTURED_BYTES)
+        expect(Buffer.byteLength(encoded)).toBeGreaterThan(ToolOutputStore.MAX_STRUCTURED_BYTES)
+
+        const result = yield* store.bound({
+          sessionID,
+          callID: "call-structured-utf8",
+          output: { structured, content: [] },
+        })
+
+        expect(result.output.structured).toMatchObject({
+          _truncated: true,
+          _bytes: Buffer.byteLength(encoded),
+        })
+      }),
+    ),
+  )
+
+  it.live("retains independent structured and contextual overflow", () =>
+    withStore(({ store, fs }) =>
+      Effect.gen(function* () {
+        const structured = { detail: "s".repeat(ToolOutputStore.MAX_STRUCTURED_BYTES) }
+        const content = "c".repeat(ToolOutputStore.MAX_BYTES + 1)
+        const result = yield* store.bound({
+          sessionID,
+          callID: "call-two-channel-overflow",
+          output: { structured, content: [{ type: "text", text: content }] },
+        })
+
+        expect(result.outputPaths).toHaveLength(2)
+        expect(JSON.parse(yield* fs.readFileString(result.outputPaths[0]))).toEqual(structured)
+        expect(yield* fs.readFileString(result.outputPaths[1])).toBe(content)
+      }),
+    ),
+  )
+
+  it.live("keeps structured output at the receipt boundary inline", () =>
+    withStore(({ store }) =>
+      Effect.gen(function* () {
+        const empty = JSON.stringify({ text: "" })
+        const structured = { text: "x".repeat(ToolOutputStore.MAX_STRUCTURED_BYTES - Buffer.byteLength(empty)) }
+        expect(Buffer.byteLength(JSON.stringify(structured))).toBe(ToolOutputStore.MAX_STRUCTURED_BYTES)
+
+        const result = yield* store.bound({
+          sessionID,
+          callID: "call-structured-boundary",
+          output: { structured, content: [] },
+        })
+
+        expect(result).toEqual({ output: { structured, content: [] }, outputPaths: [] })
+      }),
+    ),
+  )
+
+  it.live("normalizes structured values to their durable JSON record", () =>
+    withStore(({ store }) =>
+      Effect.gen(function* () {
+        const primitive = yield* store.bound({
+          sessionID,
+          callID: "call-primitive",
+          output: { structured: "value", content: [] },
+        })
+        const nonFinite = yield* store.bound({
+          sessionID,
+          callID: "call-non-finite",
+          output: { structured: { value: Number.NaN }, content: [] },
+        })
+        const omitted = yield* store.bound({
+          sessionID,
+          callID: "call-omitted",
+          output: { structured: undefined, content: [] },
+        })
+
+        expect(primitive.output.structured).toEqual({ value: "value" })
+        expect(nonFinite.output.structured).toEqual({ value: null })
+        expect(omitted.output.structured).toEqual({})
+      }),
+    ),
+  )
+
+  it.live("measures primitive overflow after durable record normalization", () =>
+    withStore(({ store, fs }) =>
+      Effect.gen(function* () {
+        const value = "x".repeat(ToolOutputStore.MAX_STRUCTURED_BYTES)
+        const encoded = JSON.stringify({ value })
+        const result = yield* store.bound({
+          sessionID,
+          callID: "call-primitive-overflow",
+          output: { structured: value, content: [] },
+        })
+
+        expect(result.output.structured).toEqual({
+          _truncated: true,
+          _bytes: Buffer.byteLength(encoded),
+          _outputPath: result.outputPaths[0],
+        })
+        expect(yield* fs.readFileString(result.outputPaths[0])).toBe(encoded)
+      }),
+    ),
+  )
+
   it.live("preserves native media and structured metadata without applying a settlement media limit", () =>
     withStore(({ store }) =>
       Effect.gen(function* () {
@@ -131,15 +263,52 @@ describe("ToolOutputStore", () => {
     ),
   )
 
-  it.live("does not double-count structured data duplicated in projected text", () =>
+  it.live("marks projected receipt metadata truncated when bounding its contextual output", () =>
     withStore(({ store }) =>
+      Effect.gen(function* () {
+        const result = yield* store.bound({
+          sessionID,
+          callID: "call-receipt",
+          propagateTruncation: true,
+          output: {
+            structured: { bytes: ToolOutputStore.MAX_BYTES + 1, truncated: false },
+            content: [{ type: "text", text: "x".repeat(ToolOutputStore.MAX_BYTES + 1) }],
+          },
+        })
+        expect(result.output.structured).toEqual({ bytes: ToolOutputStore.MAX_BYTES + 1, truncated: true })
+      }),
+    ),
+  )
+
+  it.live("preserves ordinary truncated metadata when bounding contextual output", () =>
+    withStore(({ store }) =>
+      Effect.gen(function* () {
+        const result = yield* store.bound({
+          sessionID,
+          callID: "call-ordinary-truncated",
+          output: {
+            structured: { truncated: false },
+            content: [{ type: "text", text: "x".repeat(ToolOutputStore.MAX_BYTES + 1) }],
+          },
+        })
+        expect(result.output.structured).toEqual({ truncated: false })
+      }),
+    ),
+  )
+
+  it.live("bounds structured data duplicated in projected text independently", () =>
+    withStore(({ store, fs }) =>
       Effect.gen(function* () {
         const text = "x".repeat(30_000)
         const output = { structured: { output: text }, content: [{ type: "text" as const, text }] }
-        expect(yield* store.bound({ sessionID, callID: "call-duplicated", output })).toEqual({
-          output,
-          outputPaths: [],
+        const result = yield* store.bound({ sessionID, callID: "call-duplicated", output })
+        expect(result.output.content).toEqual(output.content)
+        expect(result.output.structured).toEqual({
+          _truncated: true,
+          _bytes: Buffer.byteLength(JSON.stringify(output.structured)),
+          _outputPath: result.outputPaths[0],
         })
+        expect(JSON.parse(yield* fs.readFileString(result.outputPaths[0]))).toEqual(output.structured)
       }),
     ),
   )
@@ -162,14 +331,17 @@ describe("ToolOutputStore", () => {
     ),
   )
 
-  it.live("does not encode ignored structured metadata when projected content exists", () =>
+  it.live("rejects unencodable structured metadata even when projected content exists", () =>
     withStore(({ store }) =>
       Effect.gen(function* () {
         const output = { structured: { value: 1n }, content: [{ type: "text" as const, text: "readable text" }] }
-        expect(yield* store.bound({ sessionID, callID: "call-unencodable", output })).toEqual({
-          output,
-          outputPaths: [],
-        })
+        const exit = yield* store.bound({ sessionID, callID: "call-unencodable", output }).pipe(Effect.exit)
+        expect(Exit.isFailure(exit)).toBe(true)
+        if (Exit.isFailure(exit))
+          expect(Option.getOrUndefined(Cause.findErrorOption(exit.cause))).toMatchObject({
+            _tag: "ToolOutputStore.StorageError",
+            operation: "encode",
+          })
       }),
     ),
   )

packages/core/test/tool-patch.test.ts

@@ -1,7 +1,8 @@
 import fs from "fs/promises"
 import path from "path"
-import { describe, expect } from "bun:test"
-import { Deferred, Effect, Exit, Fiber, Layer } from "effect"
+import { describe, expect, test } from "bun:test"
+import { Deferred, Effect, Exit, Fiber, Layer, Schema } from "effect"
+import { createTwoFilesPatch, parsePatch } from "diff"
 import { AppNodeBuilder } from "@opencode-ai/core/effect/app-node-builder"
 import { LayerNode } from "@opencode-ai/core/effect/layer-node"
 import { FileMutation } from "@opencode-ai/core/file-mutation"
@@ -14,6 +15,7 @@ import { SessionV2 } from "@opencode-ai/core/session"
 import { ToolRegistry } from "@opencode-ai/core/tool/registry"
 import { ToolOutputStore } from "@opencode-ai/core/tool-output-store"
 import { PatchTool } from "@opencode-ai/core/tool/patch"
+import { ToolStructured } from "@opencode-ai/core/tool/structured"
 import { location } from "./fixture/location"
 import { tmpdir } from "./fixture/tmpdir"
 import { makeLocationNode } from "@opencode-ai/core/effect/app-node"
@@ -145,6 +147,22 @@ const exists = (target: string) =>
 const it = testEffect(Layer.empty)
 
 describe("PatchTool", () => {
+  test("summarizes multi-line truncation without fabricating unchanged context", () => {
+    const before = Array.from({ length: 100 }, (_, index) => `old-${index}`).join("\n")
+    const after = Array.from({ length: 100 }, (_, index) => `new-${index}`).join("\n")
+    const summary = ToolStructured.patch(createTwoFilesPatch("large.txt", "large.txt", before, after), 500)
+    const hunk = parsePatch(summary)[0]?.hunks[0]
+
+    expect(hunk?.lines.some((line) => line.startsWith(" "))).toBe(false)
+    expect(hunk?.lines).toEqual([
+      "-old-0",
+      "+new-0",
+      "-... 99 removed lines omitted ...",
+      "+... 99 added lines omitted ...",
+    ])
+    expect(hunk).toMatchObject({ oldLines: 2, newLines: 2 })
+  })
+
   it.live("registers and sequentially applies add, update, and delete hunks", () =>
     Effect.acquireUseRelease(
       Effect.promise(() => tmpdir()),
@@ -217,6 +235,43 @@ describe("PatchTool", () => {
     ),
   )
 
+  it.live("retains a bounded patch for large changes", () =>
+    Effect.acquireUseRelease(
+      Effect.promise(() => tmpdir()),
+      (tmp) => {
+        reset()
+        const target = path.join(tmp.path, "large.txt")
+        const before = "x".repeat(20_000)
+        const after = "y".repeat(20_000)
+        return Effect.promise(() => fs.writeFile(target, `${before}\n`)).pipe(
+          Effect.andThen(
+            withTool(tmp.path, (registry) =>
+              Effect.gen(function* () {
+                const settled = yield* settleTool(
+                  registry,
+                  call(`*** Begin Patch\n*** Update File: large.txt\n@@\n-${before}\n+${after}\n*** End Patch`),
+                )
+                const structured = Schema.decodeUnknownSync(PatchTool.Output)(settled.output?.structured)
+                expect(Buffer.byteLength(JSON.stringify(structured))).toBeLessThanOrEqual(
+                  ToolOutputStore.MAX_STRUCTURED_BYTES,
+                )
+                const hunk = parsePatch(structured.files[0]?.patch ?? "")[0]?.hunks[0]
+                expect(hunk?.lines.some((line) => line.startsWith("-"))).toBe(true)
+                expect(hunk?.lines.some((line) => line.startsWith("+"))).toBe(true)
+                expect(hunk).toMatchObject({ oldLines: 1, newLines: 1 })
+                expect(structured).toMatchObject({
+                  applied: [{ type: "update", resource: "large.txt" }],
+                  files: [{ file: "large.txt", patch: expect.stringContaining("... truncated ...") }],
+                })
+              }),
+            ),
+          ),
+        )
+      },
+      (tmp) => Effect.promise(() => tmp[Symbol.asyncDispose]()),
+    ),
+  )
+
   it.live("rejects moves before applying any hunk", () =>
     Effect.acquireUseRelease(
       Effect.promise(() => tmpdir()),

packages/core/test/tool-question.test.ts

@@ -19,6 +19,7 @@ const assertions: PermissionV2.AssertInput[] = []
 let captured: Form.CreateInput | undefined
 let reject = false
 let deny = false
+let firstAnswer = "Build"
 const capturedInput = () => captured
 const questionInput = {
   questions: [
@@ -63,7 +64,7 @@ const form = Layer.succeed(
         Effect.andThen(
           Effect.sync(
             (): Form.TerminalState =>
-              reject ? { status: "cancelled" } : { status: "answered", answer: { q0: "Build", q1: ["Dev"] } },
+              reject ? { status: "cancelled" } : { status: "answered", answer: { q0: firstAnswer, q1: ["Dev"] } },
           ),
         ),
       ),
@@ -122,6 +123,7 @@ describe("QuestionTool", () => {
       captured = undefined
       reject = false
       deny = false
+      firstAnswer = "Build"
       const registry = yield* ToolRegistry.Service
       const questions = [
         {
@@ -200,6 +202,27 @@ describe("QuestionTool", () => {
     }),
   )
 
+  it.effect("retains bounded answers for long custom responses", () =>
+    Effect.gen(function* () {
+      reject = false
+      deny = false
+      firstAnswer = "x".repeat(ToolOutputStore.MAX_STRUCTURED_BYTES)
+      const registry = yield* ToolRegistry.Service
+      const settled = yield* settleTool(registry, {
+        sessionID,
+        ...toolIdentity,
+        call: { type: "tool-call", id: "call-question-large", name: "question", input: questionInput },
+      })
+
+      expect(Buffer.byteLength(JSON.stringify(settled.output?.structured))).toBeLessThanOrEqual(
+        ToolOutputStore.MAX_STRUCTURED_BYTES,
+      )
+      expect(settled.output?.structured).toMatchObject({
+        answers: [[expect.stringContaining("... truncated ...")]],
+      })
+    }).pipe(Effect.ensuring(Effect.sync(() => (firstAnswer = "Build")))),
+  )
+
   it.effect("does not invent tool ownership metadata without a durable registry source", () =>
     Effect.gen(function* () {
       captured = undefined

packages/core/test/tool-read-filesystem.test.ts

@@ -100,6 +100,21 @@ describe("ReadToolFileSystem", () => {
     }),
   )
 
+  it.effect("reports a shortened long line as truncated", () =>
+    Effect.gen(function* () {
+      const { fs, files, directory } = yield* fixture
+      const file = path.join(directory, "long-line.txt")
+      yield* files.writeFileString(file, "x".repeat(3_000))
+
+      const result = yield* ReadToolFileSystem.read(fs, file, "long-line.txt", { limit: 1 })
+
+      expect(result).toMatchObject({ type: "text-page", truncated: true })
+      if (!(result instanceof ReadToolFileSystem.TextPage)) throw new Error("expected text page")
+      expect(result.next).toBeUndefined()
+      expect(result.content).toEndWith("... (line truncated to 2000 chars)")
+    }),
+  )
+
   it.effect("preserves the media ingestion limit message", () =>
     Effect.gen(function* () {
       const { fs, files, directory } = yield* fixture

packages/core/test/tool-read.test.ts

@@ -206,14 +206,14 @@ describe("ReadTool", () => {
           call: { type: "tool-call", id: "call-read", name: "read", input: { path: "README.md" } },
         }),
       ).toEqual({
-        type: "json",
-        value: {
+        type: "text",
+        value: JSON.stringify({
           uri: "file:///README.md",
           name: "README.md",
           content: "hello",
           encoding: "utf8",
           mime: "text/plain",
-        },
+        }),
       })
       expect(assertions).toMatchObject([{ sessionID, action: "read", resources: ["README.md"], save: ["*"] }])
       expect(readCalls).toEqual([
@@ -236,7 +236,7 @@ describe("ReadTool", () => {
           ...toolIdentity,
           call: { type: "tool-call", id: "call-external-read", name: "read", input: { path: external } },
         }),
-      ).toMatchObject({ type: "json" })
+      ).toMatchObject({ type: "text" })
       expect(assertions).toMatchObject([
         {
           sessionID,
@@ -287,14 +287,15 @@ describe("ReadTool", () => {
         call: { type: "tool-call", id: "call-image-settle", name: "read", input: { path: "pixel.png" } },
       })
       expect(settled.output?.structured).toMatchObject({
+        type: "file",
         uri: "file:///pixel.png",
         name: "pixel.png",
         mime: "image/png",
         encoding: "base64",
-        // Image base64 is carried by the content file item only; structured is slimmed
-        // so the original bytes are never persisted twice.
-        content: "",
+        bytes: Buffer.byteLength(png, "base64"),
+        truncated: false,
       })
+      expect(settled.output?.structured).not.toHaveProperty("content")
       expect(settled.output?.content).toMatchObject([
         { type: "text", text: "Image read successfully" },
         { type: "file", mime: "image/png", uri: `data:image/png;base64,${png}` },
@@ -626,7 +627,7 @@ describe("ReadTool", () => {
             input: { path: "src", offset: 2, limit: 10 },
           },
         }),
-      ).toEqual({ type: "json", value: { entries: [], truncated: false } })
+      ).toEqual({ type: "text", value: JSON.stringify({ entries: [], truncated: false }) })
       expect(assertions).toMatchObject([{ sessionID, action: "read", resources: ["src"], save: ["*"] }])
       expect(listCalls).toEqual([{ offset: 2, limit: 10 }])
     }),
@@ -692,8 +693,15 @@ describe("ReadTool", () => {
           },
         }),
       ).toEqual({
-        type: "json",
-        value: { type: "text-page", content: "hello", mime: "text/plain", offset: 2, truncated: true, next: 3 },
+        type: "text",
+        value: JSON.stringify({
+          type: "text-page",
+          content: "hello",
+          mime: "text/plain",
+          offset: 2,
+          truncated: true,
+          next: 3,
+        }),
       })
       expect(readCalls).toEqual([
         { input: AbsolutePath.make(path.join(process.cwd(), "large.txt")), page: { offset: 2, limit: 1 } },

packages/core/test/tool-search.test.ts

@@ -86,8 +86,8 @@ describe("search tools", () => {
               const glob = yield* settleTool(registry, call("glob", { pattern: "*" }))
               const grep = yield* settleTool(registry, call("grep", { pattern: "needle" }))
 
-              expect(glob.output?.structured).toHaveLength(FileSystem.DEFAULT_SEARCH_LIMIT)
-              expect(grep.output?.structured).toHaveLength(FileSystem.DEFAULT_SEARCH_LIMIT)
+              expect(glob.output?.structured).toEqual({ count: FileSystem.DEFAULT_SEARCH_LIMIT })
+              expect(grep.output?.structured).toEqual({ matches: FileSystem.DEFAULT_SEARCH_LIMIT })
             }),
           )
         }),

packages/core/test/tool-shell.test.ts

@@ -223,6 +223,30 @@ describe("ShellTool", () => {
     ),
   )
 
+  it.live("marks output truncated when generic settlement limits are lower than shell capture limits", () =>
+    Effect.acquireUseRelease(
+      Effect.promise(() => tmpdir()),
+      (tmp) => {
+        reset()
+        return withSession(tmp.path, (registry) =>
+          Effect.gen(function* () {
+            const settled = yield* settleTool(
+              registry,
+              call({ command: overflowCommand(ToolOutputStore.MAX_BYTES + 1_000) }),
+            )
+
+            expect(settled.output?.structured).toMatchObject({ exit: 0, truncated: true })
+            expect(settled.output?.content[0]).toMatchObject({
+              type: "text",
+              text: expect.stringContaining("output truncated; full content saved to"),
+            })
+          }),
+        )
+      },
+      (tmp) => Effect.promise(() => tmp[Symbol.asyncDispose]().then(() => undefined)),
+    ),
+  )
+
   it.live("resolves a relative workdir from the active Location", () =>
     Effect.acquireUseRelease(
       Effect.promise(() => tmpdir()),
@@ -439,7 +463,10 @@ describe("ShellTool", () => {
                     if (update.structured.truncated !== true) return
                     const content = update.content[0]
                     if (content?.type !== "text") return
-                    if (content.text.indexOf("\n\n[output truncated; full output saved to:") !== ShellTool.MAX_CAPTURE_BYTES)
+                    if (
+                      content.text.indexOf("\n\n[output truncated; full output saved to:") !==
+                      ShellTool.MAX_CAPTURE_BYTES
+                    )
                       return
                     yield* Deferred.succeed(observed, update)
                     yield* Effect.promise(() => fs.writeFile(releasePath, ""))

packages/core/test/tool-skill.test.ts

@@ -121,7 +121,14 @@ describe("SkillTool", () => {
               }),
             ).toMatchObject({
               result: { type: "text", value: SkillTool.toModelOutput(info, [reference]) },
-              output: { structured: { name: "Effect" } },
+              output: {
+                structured: {
+                  name: "Effect",
+                  directory,
+                  bytes: Buffer.byteLength(SkillTool.toModelOutput(info, [reference])),
+                  truncated: false,
+                },
+              },
             })
             expect(assertions).toMatchObject([
               { sessionID, action: "skill", resources: ["effect"], save: ["effect"] },

packages/core/test/tool-subagent.test.ts

@@ -35,7 +35,8 @@ const childModel = ModelV2.Ref.make({ id: ModelV2.ID.make("child"), providerID:
 const parentModel = ModelV2.Ref.make({ id: ModelV2.ID.make("parent"), providerID: ProviderV2.ID.make("test") })
 const tokens = { input: 0, output: 0, reasoning: 0, cache: { read: 0, write: 0 } }
 
-const outputSessionID = (value: unknown) => Schema.decodeUnknownSync(SubagentTool.Output)(value).sessionID
+const outputSessionID = (value: unknown) =>
+  Schema.decodeUnknownSync(Schema.Struct({ sessionID: SessionV2.ID }))(value).sessionID
 
 const executionNode = makeGlobalNode({
   service: SessionExecution.Service,
@@ -229,7 +230,12 @@ describe("SubagentTool", () => {
             },
           })
 
-          expect(settled.output?.structured).toMatchObject({ status: "completed", output: childText })
+          expect(settled.output?.structured).toMatchObject({
+            status: "completed",
+            bytes: Buffer.byteLength(childText),
+            truncated: false,
+          })
+          expect(settled.output?.structured).not.toHaveProperty("output")
           expect((yield* sessions.get(outputSessionID(settled.output?.structured))).parentID).toBe(parent.id)
         }),
       ),
@@ -264,7 +270,13 @@ describe("SubagentTool", () => {
             },
           })
 
-          expect(settled.output?.structured).toMatchObject({ status: "completed", output: childText })
+          expect(settled.result).toEqual({ type: "text", value: childText })
+          expect(settled.output?.structured).toMatchObject({
+            status: "completed",
+            bytes: Buffer.byteLength(childText),
+            truncated: false,
+          })
+          expect(settled.output?.structured).not.toHaveProperty("output")
           const child = yield* sessions.get(outputSessionID(settled.output?.structured))
           expect(progress[0]?.structured).toEqual({ sessionID: child.id, status: "running" })
           expect(child).toMatchObject({
@@ -358,8 +370,10 @@ describe("SubagentTool", () => {
           const childID = outputSessionID(settled.output?.structured)
           expect(settled.output?.structured).toMatchObject({
             status: "running",
-            output: expect.stringContaining(`id: ${childID}`),
+            bytes: expect.any(Number),
+            truncated: false,
           })
+          expect(settled.output?.structured).not.toHaveProperty("output")
 
           const admission = Array.from(yield* Fiber.join(admitted))[0]
           expect(admission?.data.input.data.text).toContain(`<subagent id="${childID}" state="completed"`)

packages/core/test/tool-webfetch.test.ts

@@ -96,7 +96,7 @@ describe("WebFetchTool registration", () => {
       expect(yield* settleTool(registry, call({ url, format: "text", timeout: 4 }))).toEqual({
         result: { type: "text", value: "hello" },
         output: {
-          structured: { url, contentType: "text/plain", format: "text", output: "hello" },
+          structured: { url, contentType: "text/plain", format: "text", bytes: 5, truncated: false },
           content: [{ type: "text", text: "hello" }],
         },
       })

packages/core/test/tool-websearch.test.ts

@@ -244,7 +244,7 @@ describe("WebSearchTool registration", () => {
       expect(settled).toEqual({
         result: { type: "text", value: "parallel results" },
         output: {
-          structured: { provider: "parallel", text: "parallel results" },
+          structured: { provider: "parallel", bytes: 16, truncated: false },
           content: [{ type: "text", text: "parallel results" }],
         },
       })

packages/plugin/src/v2/effect/tool.ts

@@ -97,6 +97,10 @@ export type Definition<
   readonly input: Input
   readonly output: Output
   readonly structured?: Structured
+  /** Expose encoded output to CodeMode instead of the persisted structured projection. */
+  readonly codeModeOutput?: "output"
+  /** Mark a receipt's `truncated` field when its model-facing text is bounded. */
+  readonly contentTruncation?: true
   readonly permission?: string
   readonly toStructuredOutput?: (input: {
     readonly input: InputValue<Input>