diff --git a/packages/opencode/src/config/config.ts b/packages/opencode/src/config/config.ts
index c017cf73cd..d2bdc52780 100644
--- a/packages/opencode/src/config/config.ts
+++ b/packages/opencode/src/config/config.ts
@@ -253,20 +253,20 @@ export const Info = Schema.Struct({
     }),
   ),
   tool_output: Schema.optional(
-    Schema.Union([
-      Schema.Literal(false),
-      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.Struct({
+      truncate: Schema.optional(Schema.Boolean).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:
-      "Configure tool output truncation, or set to false to disable it. 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({
diff --git a/packages/opencode/src/skill/prompt/customize-opencode.md b/packages/opencode/src/skill/prompt/customize-opencode.md
index 820195daf5..efb963f6a0 100644
--- a/packages/opencode/src/skill/prompt/customize-opencode.md
+++ b/packages/opencode/src/skill/prompt/customize-opencode.md
@@ -126,7 +126,7 @@ Every field is optional.
     "mcp_timeout": 30000
   },
 
-  "tool_output": false | { "max_lines": 200, "max_bytes": 8192 },
+  "tool_output": { "truncate": false, "max_lines": 200, "max_bytes": 8192 },
 
   "compaction": { "auto": true, "tail_turns": 15 }
 }
@@ -140,7 +140,7 @@ Shape notes worth being explicit about:
 - `plugin` is an array of strings or `[name, options]` tuples, not an object.
 - `mcp[name].command` is an array of strings, never a single string. `type` is required.
 - `permission` is either a string action or an object keyed by tool name.
-- `tool_output: false` disables shared tool output truncation; use an object to override its line and byte thresholds.
+- `tool_output.truncate: false` disables shared tool output truncation; use `max_lines` and `max_bytes` to override its thresholds.
 
 ## Skills
 
diff --git a/packages/opencode/src/tool/truncate.ts b/packages/opencode/src/tool/truncate.ts
index 00b6c327be..0ea9ad08bc 100644
--- a/packages/opencode/src/tool/truncate.ts
+++ b/packages/opencode/src/tool/truncate.ts
@@ -78,9 +78,8 @@ export const layer = Layer.effect(
       const configSvc = yield* Effect.serviceOption(Config.Service)
       if (Option.isNone(configSvc)) return { enabled: true, maxLines: MAX_LINES, maxBytes: MAX_BYTES }
       const cfg = yield* configSvc.value.get().pipe(Effect.catch(() => Effect.succeed(undefined)))
-      if (cfg?.tool_output === false) return { enabled: false, maxLines: MAX_LINES, maxBytes: MAX_BYTES }
       return {
-        enabled: true,
+        enabled: cfg?.tool_output?.truncate !== false,
         maxLines: cfg?.tool_output?.max_lines ?? MAX_LINES,
         maxBytes: cfg?.tool_output?.max_bytes ?? MAX_BYTES,
       }
diff --git a/packages/opencode/test/tool/shell.test.ts b/packages/opencode/test/tool/shell.test.ts
index 96307557b3..7d58120cd7 100644
--- a/packages/opencode/test/tool/shell.test.ts
+++ b/packages/opencode/test/tool/shell.test.ts
@@ -1202,7 +1202,7 @@ 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: false } })
+      const tmp = yield* tmpdirScoped({ config: { tool_output: { truncate: false } } })
       yield* runIn(
         tmp,
         Effect.gen(function* () {
diff --git a/packages/opencode/test/tool/truncation.test.ts b/packages/opencode/test/tool/truncation.test.ts
index 4233dd1b01..b0f946f585 100644
--- a/packages/opencode/test/tool/truncation.test.ts
+++ b/packages/opencode/test/tool/truncation.test.ts
@@ -162,7 +162,7 @@ describe("Truncate", () => {
         }),
       )
 
-      const disabledIt = configuredIt({ tool_output: 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)
diff --git a/packages/sdk/js/src/v2/gen/types.gen.ts b/packages/sdk/js/src/v2/gen/types.gen.ts
index 7393d9d70f..f20f4e8a54 100644
--- a/packages/sdk/js/src/v2/gen/types.gen.ts
+++ b/packages/sdk/js/src/v2/gen/types.gen.ts
@@ -1294,15 +1294,11 @@ export type Config = {
   enterprise?: {
     url?: string
   }
-  /**
-   * Configure tool output truncation, or set to false to disable it. When output exceeds either limit, the full text is written to the truncation directory and a preview is returned.
-   */
-  tool_output?:
-    | false
-    | {
-        max_lines?: number
-        max_bytes?: number
-      }
+  tool_output?: {
+    truncate?: boolean
+    max_lines?: number
+    max_bytes?: number
+  }
   compaction?: {
     auto?: boolean
     prune?: boolean
diff --git a/packages/web/src/content/docs/config.mdx b/packages/web/src/content/docs/config.mdx
index 7aa9ff8934..0be2699d37 100644
--- a/packages/web/src/content/docs/config.mdx
+++ b/packages/web/src/content/docs/config.mdx
@@ -361,23 +361,27 @@ You can control when tool output is truncated using the `tool_output` option. Wh
 {
   "$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 `tool_output` to `false`:
+To disable shared tool output truncation, set `truncate` to `false`:
 
 ```json title="opencode.json"
 {
   "$schema": "https://opencode.ai/config.json",
-  "tool_output": false
+  "tool_output": {
+    "truncate": false
+  }
 }
 ```