feat(core): allow disabling tool output truncation

packages/opencode/src/config/config.ts

@@ -253,17 +253,25 @@ export const Info = Schema.Struct({
     }),
   ),
   tool_output: Schema.optional(
-    Schema.Struct({
-      max_lines: Schema.optional(PositiveInt).annotate({
-        description: "Maximum lines of tool output before it is truncated and saved to disk (default: 2000)",
-      }),
-      max_bytes: Schema.optional(PositiveInt).annotate({
-        description: "Maximum bytes of tool output before it is truncated and saved to disk (default: 51200)",
+    Schema.Union([
+      Schema.Struct({
+        truncate: Schema.Literal(false).annotate({ description: "Disable tool output truncation" }),
+      }).annotate({ parseOptions: { onExcessProperty: "error" } }),
+      Schema.Struct({
+        truncate: Schema.optional(Schema.Literal(true)).annotate({
+          description: "Enable truncating tool output that exceeds the configured limits (default: true)",
+        }),
+        max_lines: Schema.optional(PositiveInt).annotate({
+          description: "Maximum lines of tool output before it is truncated and saved to disk (default: 2000)",
+        }),
+        max_bytes: Schema.optional(PositiveInt).annotate({
+          description: "Maximum bytes of tool output before it is truncated and saved to disk (default: 51200)",
+        }),
       }),
-    }),
+    ]),
   ).annotate({
     description:
-      "Thresholds for truncating tool output. When output exceeds either limit, the full text is written to the truncation directory and a preview is returned.",
+      "Configure tool output truncation. When output exceeds either limit, the full text is written to the truncation directory and a preview is returned.",
   }),
   compaction: Schema.optional(
     Schema.Struct({

packages/opencode/src/skill/prompt/customize-opencode.md

@@ -23,6 +23,10 @@ shape before writing config, **fetch that URL and read the schema directly**
 rather than guessing. opencode hard-fails on invalid config, so the cost of a
 wrong shape is a broken startup.
 
+The full schema is large. Prefer using JavaScript or Bash to fetch and extract
+the relevant property definition instead of reading the entire schema into
+context when you only need to check one setting.
+
 Independently, every `opencode.json` should declare
 `"$schema": "https://opencode.ai/config.json"` so the user's editor catches
 mistakes as they type.

packages/opencode/src/tool/shell.ts

@@ -1,4 +1,4 @@
-import { Effect, Stream } from "effect"
+import { Effect, Option, Stream } from "effect"
 import os from "os"
 import { createWriteStream } from "node:fs"
 import * as Tool from "./tool"
@@ -433,7 +433,10 @@ export const ShellTool = Tool.define(
       ctx: Tool.Context,
     ) {
       const limits = yield* trunc.limits()
-      const keep = limits.maxBytes * 2
+      const keep = Option.match(limits, {
+        onNone: () => Number.POSITIVE_INFINITY,
+        onSome: (l) => l.maxBytes * 2,
+      })
       let full = ""
       let last = ""
       const list: Chunk[] = []
@@ -499,7 +502,7 @@ export const ShellTool = Tool.define(
                 sink?.write(chunk)
               } else {
                 full += chunk
-                if (Buffer.byteLength(full, "utf-8") > limits.maxBytes) {
+                if (Option.isSome(limits) && Buffer.byteLength(full, "utf-8") > limits.value.maxBytes) {
                   return trunc.write(full).pipe(
                     Effect.andThen((next) =>
                       Effect.sync(() => {
@@ -566,7 +569,10 @@ export const ShellTool = Tool.define(
       }
       if (aborted) meta.push("User aborted the command")
       const raw = list.map((item) => item.text).join("")
-      const end = tail(raw, limits.maxLines, limits.maxBytes)
+      const end = Option.match(limits, {
+        onNone: () => ({ text: raw, cut: false }),
+        onSome: (l) => tail(raw, l.maxLines, l.maxBytes),
+      })
       if (end.cut) cut = true
       if (!file && end.cut) {
         file = yield* trunc.write(raw)

packages/opencode/src/tool/shell/prompt.ts

@@ -1,4 +1,4 @@
-import { Schema } from "effect"
+import { Option, Schema } from "effect"
 import DESCRIPTION from "./shell.txt"
 import { PositiveInt } from "@opencode-ai/core/schema"
 import { Global } from "@opencode-ai/core/global"
@@ -83,7 +83,12 @@ function chainGuidance(name: string) {
   return "If the commands depend on each other and must run sequentially, use a single Bash call with '&&' to chain them together (e.g., `git add . && git commit -m \"message\" && git push`). For instance, if one operation must complete before another starts (like mkdir before cp, Write before Bash for git operations, or git add before git commit), run these operations sequentially instead."
 }
 
-function bashCommandSection(chain: string, limits: Limits, defaultTimeoutMs: number) {
+function truncationGuidance(limits: Option.Option<Limits>, commands: string) {
+  if (Option.isNone(limits)) return ""
+  return `\n  - If the output exceeds ${limits.value.maxLines} lines or ${limits.value.maxBytes} bytes, it will be truncated and the full output will be written to a file. You can use Read with offset/limit to read specific sections or Grep to search the full content. Do NOT use ${commands} to limit output; the full output will already be captured to a file for more precise searching.`
+}
+
+function bashCommandSection(chain: string, limits: Option.Option<Limits>, defaultTimeoutMs: number) {
   return `Before executing the command, please follow these steps:
 
 1. Directory Verification:
@@ -103,8 +108,7 @@ function bashCommandSection(chain: string, limits: Limits, defaultTimeoutMs: num
 Usage notes:
   - The command argument is required.
   - You can specify an optional timeout in milliseconds. If not specified, commands will time out after ${defaultTimeoutMs}ms.
-  - It is very helpful if you write a clear, concise description of what this command does in 5-10 words.
-  - If the output exceeds ${limits.maxLines} lines or ${limits.maxBytes} bytes, it will be truncated and the full output will be written to a file. You can use Read with offset/limit to read specific sections or Grep to search the full content. Do NOT use \`head\`, \`tail\`, or other truncation commands to limit output; the full output will already be captured to a file for more precise searching.
+  - It is very helpful if you write a clear, concise description of what this command does in 5-10 words.${truncationGuidance(limits, "`head`, `tail`, or other truncation commands")}
 
   - Avoid using Bash with the \`find\`, \`grep\`, \`cat\`, \`head\`, \`tail\`, \`sed\`, \`awk\`, or \`echo\` commands, unless explicitly instructed or when these commands are truly necessary for the task. Instead, always prefer using the dedicated tools for these commands:
     - File search: Use Glob (NOT find or ls)
@@ -131,7 +135,7 @@ function powershellCommandSection(
   name: string,
   chain: string,
   pathSep: string,
-  limits: Limits,
+  limits: Option.Option<Limits>,
   defaultTimeoutMs: number,
 ) {
   return `${powershellNotes(name)}
@@ -155,8 +159,7 @@ Before executing the command, please follow these steps:
 Usage notes:
   - The command argument is required.
   - You can specify an optional timeout in milliseconds. If not specified, commands will time out after ${defaultTimeoutMs}ms.
-  - It is very helpful if you write a clear, concise description of what this command does in 5-10 words.
-  - If the output exceeds ${limits.maxLines} lines or ${limits.maxBytes} bytes, it will be truncated and the full output will be written to a file. You can use Read with offset/limit to read specific sections or Grep to search the full content. Do NOT use \`Select-Object -First\`, \`Select-Object -Last\`, or other truncation commands to limit output; the full output will already be captured to a file for more precise searching.
+  - It is very helpful if you write a clear, concise description of what this command does in 5-10 words.${truncationGuidance(limits, "`Select-Object -First`, `Select-Object -Last`, or other truncation commands")}
 
   - Avoid using Shell with PowerShell file/content cmdlets unless explicitly instructed or when these cmdlets are truly necessary for the task. Instead, always prefer using the dedicated tools for these commands:
     - File search: Use Glob (NOT Get-ChildItem)
@@ -179,7 +182,7 @@ Usage notes:
     </bad-example>`
 }
 
-function cmdCommandSection(chain: string, limits: Limits, defaultTimeoutMs: number) {
+function cmdCommandSection(chain: string, limits: Option.Option<Limits>, defaultTimeoutMs: number) {
   return `# cmd.exe shell notes
 - Use double quotes for paths with spaces.
 - Use %VAR% for environment variables.
@@ -205,8 +208,7 @@ Before executing the command, please follow these steps:
 Usage notes:
   - The command argument is required.
   - You can specify an optional timeout in milliseconds. If not specified, commands will time out after ${defaultTimeoutMs}ms.
-  - It is very helpful if you write a clear, concise description of what this command does in 5-10 words.
-  - If the output exceeds ${limits.maxLines} lines or ${limits.maxBytes} bytes, it will be truncated and the full output will be written to a file. You can use Read with offset/limit to read specific sections or Grep to search the full content. Do NOT use \`more\` or other pagination commands to limit output; the full output will already be captured to a file for more precise searching.
+  - It is very helpful if you write a clear, concise description of what this command does in 5-10 words.${truncationGuidance(limits, "`more` or other pagination commands")}
 
   - Avoid using Shell with cmd.exe file/content commands unless explicitly instructed or when these commands are truly necessary for the task. Instead, always prefer using the dedicated tools for these commands:
     - File search: Use Glob (NOT dir /s)
@@ -229,7 +231,7 @@ Usage notes:
     </bad-example>`
 }
 
-function profile(name: string, platform: NodeJS.Platform, limits: Limits, defaultTimeoutMs: number) {
+function profile(name: string, platform: NodeJS.Platform, limits: Option.Option<Limits>, defaultTimeoutMs: number) {
   const isPowerShell = PS.has(name)
   const chain = chainGuidance(name)
   if (CMD.has(name)) {
@@ -284,7 +286,7 @@ function profile(name: string, platform: NodeJS.Platform, limits: Limits, defaul
   }
 }
 
-export function render(name: string, platform: NodeJS.Platform, limits: Limits, defaultTimeoutMs: number) {
+export function render(name: string, platform: NodeJS.Platform, limits: Option.Option<Limits>, defaultTimeoutMs: number) {
   const selected = profile(name, platform, limits, defaultTimeoutMs)
   return {
     description: renderPrompt(DESCRIPTION, {

packages/opencode/src/tool/truncate.ts

@@ -19,6 +19,7 @@ export const DIR = TRUNCATION_DIR
 export const GLOB = path.join(TRUNCATION_DIR, "*")
 
 export type Result = { content: string; truncated: false } | { content: string; truncated: true; outputPath: string }
+export type Limits = { maxLines: number; maxBytes: number }
 
 export interface Options {
   maxLines?: number
@@ -40,9 +41,11 @@ export interface Interface {
    */
   readonly output: (text: string, options?: Options, agent?: Agent.Info) => Effect.Effect<Result>
   /**
-   * Resolved truncation limits: values from `tool_output` in opencode config, or MAX_LINES / MAX_BYTES if unset.
+   * Resolved truncation limits from `tool_output` in opencode config.
+   * Returns `None` when the user has disabled truncation (`tool_output.truncate: false`),
+   * in which case callers should pass output through without enforcing thresholds.
    */
-  readonly limits: () => Effect.Effect<{ maxLines: number; maxBytes: number }>
+  readonly limits: () => Effect.Effect<Option.Option<Limits>>
 }
 
 export class Service extends Context.Service<Service, Interface>()("@opencode/Truncate") {}
@@ -75,18 +78,21 @@ export const layer = Layer.effect(
 
     const limits = Effect.fn("Truncate.limits")(function* () {
       const configSvc = yield* Effect.serviceOption(Config.Service)
-      if (Option.isNone(configSvc)) return { maxLines: MAX_LINES, maxBytes: MAX_BYTES }
+      if (Option.isNone(configSvc)) return Option.some({ maxLines: MAX_LINES, maxBytes: MAX_BYTES })
       const cfg = yield* configSvc.value.get().pipe(Effect.catch(() => Effect.succeed(undefined)))
-      return {
-        maxLines: cfg?.tool_output?.max_lines ?? MAX_LINES,
-        maxBytes: cfg?.tool_output?.max_bytes ?? MAX_BYTES,
-      }
+      const tool_output = cfg?.tool_output
+      if (tool_output?.truncate === false) return Option.none<Limits>()
+      return Option.some({
+        maxLines: tool_output?.max_lines ?? MAX_LINES,
+        maxBytes: tool_output?.max_bytes ?? MAX_BYTES,
+      })
     })
 
     const output = Effect.fn("Truncate.output")(function* (text: string, options: Options = {}, agent?: Agent.Info) {
       const resolved = yield* limits()
-      const maxLines = options.maxLines ?? resolved.maxLines
-      const maxBytes = options.maxBytes ?? resolved.maxBytes
+      if (Option.isNone(resolved)) return { content: text, truncated: false } as const
+      const maxLines = options.maxLines ?? resolved.value.maxLines
+      const maxBytes = options.maxBytes ?? resolved.value.maxBytes
       const direction = options.direction ?? "head"
       const lines = text.split("\n")
       const totalBytes = Buffer.byteLength(text, "utf-8")

packages/opencode/test/config/config.test.ts

@@ -1292,6 +1292,21 @@ test("config parser preserves permission order while rejecting unknown top-level
   }
 })
 
+test("tool_output only accepts thresholds when truncation is enabled", () => {
+  expect(ConfigParse.schema(Config.Info, { tool_output: { truncate: false } }, "test").tool_output).toEqual({
+    truncate: false,
+  })
+  expect(
+    ConfigParse.schema(Config.Info, { tool_output: { max_lines: 200, max_bytes: 8192 } }, "test").tool_output,
+  ).toEqual({
+    max_lines: 200,
+    max_bytes: 8192,
+  })
+  expect(() =>
+    ConfigParse.schema(Config.Info, { tool_output: { truncate: false, max_lines: 200, max_bytes: 8192 } }, "test"),
+  ).toThrow()
+})
+
 // MCP config merging tests
 
 it.instance("project config can override MCP server enabled status", () =>

packages/opencode/test/tool/shell.test.ts

@@ -1205,6 +1205,29 @@ describe("tool.shell truncation", () => {
     ),
   )
 
+  it.live("does not truncate output when tool_output is disabled", () =>
+    Effect.gen(function* () {
+      const tmp = yield* tmpdirScoped({ config: { tool_output: { truncate: false } } })
+      yield* runIn(
+        tmp,
+        Effect.gen(function* () {
+          const bash = yield* initShell()
+          expect(bash.description).not.toContain("If the output exceeds")
+          const result = yield* bash.execute(
+            {
+              command: fill("bytes", Truncate.MAX_BYTES + 10000),
+              description: "Generate bytes with truncation disabled",
+            },
+            ctx,
+          )
+          expect(result.metadata.truncated).toBe(false)
+          expect(result.output).not.toContain("...output truncated...")
+          expect(Buffer.byteLength(result.output, "utf-8")).toBeGreaterThan(Truncate.MAX_BYTES)
+        }),
+      )
+    }),
+  )
+
   it.live("full output is saved to file when truncated", () =>
     runIn(
       projectRoot,

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

@@ -1,7 +1,7 @@
 import { describe, test, expect } from "bun:test"
 import { NodeFileSystem } from "@effect/platform-node"
 import { AppFileSystem } from "@opencode-ai/core/filesystem"
-import { Effect, FileSystem, Layer } from "effect"
+import { Effect, FileSystem, Layer, Option } from "effect"
 import { Truncate } from "@/tool/truncate"
 import { Config } from "@/config/config"
 import { Identifier } from "../../src/id/id"
@@ -110,8 +110,11 @@ describe("Truncate", () => {
       Effect.gen(function* () {
         const svc = yield* Truncate.Service
         const resolved = yield* svc.limits()
-        expect(resolved.maxLines).toBe(Truncate.MAX_LINES)
-        expect(resolved.maxBytes).toBe(Truncate.MAX_BYTES)
+        expect(Option.isSome(resolved)).toBe(true)
+        if (Option.isSome(resolved)) {
+          expect(resolved.value.maxLines).toBe(Truncate.MAX_LINES)
+          expect(resolved.value.maxBytes).toBe(Truncate.MAX_BYTES)
+        }
       }),
     )
 
@@ -120,8 +123,11 @@ describe("Truncate", () => {
       limitsIt.live("limits() reflects config overrides", () =>
         Effect.gen(function* () {
           const resolved = yield* (yield* Truncate.Service).limits()
-          expect(resolved.maxLines).toBe(123)
-          expect(resolved.maxBytes).toBe(456)
+          expect(Option.isSome(resolved)).toBe(true)
+          if (Option.isSome(resolved)) {
+            expect(resolved.value.maxLines).toBe(123)
+            expect(resolved.value.maxBytes).toBe(456)
+          }
         }),
       )
 
@@ -159,6 +165,18 @@ describe("Truncate", () => {
           expect(result.truncated).toBe(false)
         }),
       )
+
+      const disabledIt = configuredIt({ tool_output: { truncate: false } })
+      disabledIt.live("does not truncate output when disabled", () =>
+        Effect.gen(function* () {
+          const content = "a".repeat(Truncate.MAX_BYTES + 1)
+          const svc = yield* Truncate.Service
+          const resolved = yield* svc.limits()
+          const result = yield* svc.output(content)
+          expect(Option.isNone(resolved)).toBe(true)
+          expect(result).toEqual({ content, truncated: false })
+        }),
+      )
     })
 
     it.live("large single-line file truncates with byte message", () =>

packages/sdk/js/src/v2/gen/types.gen.ts

@@ -1294,10 +1294,21 @@ export type Config = {
   enterprise?: {
     url?: string
   }
-  tool_output?: {
-    max_lines?: number
-    max_bytes?: number
-  }
+  /**
+   * Configure tool output truncation. When output exceeds either limit, the full text is written to the truncation directory and a preview is returned.
+   */
+  tool_output?:
+    | {
+        /**
+         * Disable tool output truncation
+         */
+        truncate: false
+      }
+    | {
+        truncate?: true
+        max_lines?: number
+        max_bytes?: number
+      }
   compaction?: {
     auto?: boolean
     prune?: boolean

packages/web/src/content/docs/config.mdx

@@ -353,6 +353,42 @@ You can manage the tools an LLM can use through the `tools` option.
 
 ---
 
+### Tool output
+
+You can control when tool output is truncated using the `tool_output` option. When output exceeds either threshold, OpenCode saves the complete output to disk and returns a truncated preview with the saved file path.
+
+```json title="opencode.json"
+{
+  "$schema": "https://opencode.ai/config.json",
+  "tool_output": {
+    "truncate": true,
+    "max_lines": 2000,
+    "max_bytes": 51200
+  }
+}
+```
+
+- `truncate` - Truncate tool output when it exceeds a configured threshold (default: `true`).
+- `max_lines` - Maximum number of lines before output is truncated (default: `2000`).
+- `max_bytes` - Maximum size in bytes before output is truncated (default: `51200`).
+
+These thresholds apply to output handled by OpenCode's shared truncation layer, including MCP and plugin tool output. Individual tools that page or cap their own results can have separate limits.
+
+To disable shared tool output truncation, set `truncate` to `false`:
+
+```json title="opencode.json"
+{
+  "$schema": "https://opencode.ai/config.json",
+  "tool_output": {
+    "truncate": false
+  }
+}
+```
+
+`truncate: false` cannot be combined with `max_lines` or `max_bytes`; thresholds only apply when truncation is enabled.
+
+---
+
 ### Models
 
 You can configure the providers and models you want to use in your OpenCode config through the `provider`, `model` and `small_model` options.