fix(image): disable attachment resizing by default

packages/opencode/src/config/attachment.ts

@@ -4,8 +4,13 @@ import { Schema } from "effect"
 import { PositiveInt } from "@opencode-ai/core/schema"
 
 export const Image = Schema.Struct({
+  enforce_limits: Schema.optional(Schema.Boolean).annotate({
+    description:
+      "Enforce image attachment size limits before sending images to the model. When false, images pass through unchanged (default: false)",
+  }),
   auto_resize: Schema.optional(Schema.Boolean).annotate({
-    description: "Resize images before sending them to the model when they exceed configured limits (default: true)",
+    description:
+      "Resize images before sending them to the model when they exceed configured limits. Requires enforce_limits to be true (default: false)",
   }),
   max_width: Schema.optional(PositiveInt).annotate({
     description: "Maximum image width before resizing or rejecting the attachment (default: 2000)",

packages/opencode/src/image/image.ts

@@ -6,7 +6,8 @@ import { Context, Effect, Layer, Schema } from "effect"
 const MAX_BASE64_BYTES = 4.5 * 1024 * 1024
 const MAX_WIDTH = 2000
 const MAX_HEIGHT = 2000
-const AUTO_RESIZE = true
+const ENFORCE_LIMITS = false
+const AUTO_RESIZE = false
 const JPEG_QUALITIES = [80, 85, 70, 55, 40]
 const log = Log.create({ service: "image" })
 
@@ -76,11 +77,13 @@ export const layer = Layer.effect(
     const normalize = Effect.fn("Image.normalize")(function* (input: MessageV2.FilePart) {
       const image = (yield* config.get()).attachment?.image
       const info = {
+        enforceLimits: image?.enforce_limits ?? ENFORCE_LIMITS,
         autoResize: image?.auto_resize ?? AUTO_RESIZE,
         maxWidth: image?.max_width ?? MAX_WIDTH,
         maxHeight: image?.max_height ?? MAX_HEIGHT,
         maxBase64Bytes: image?.max_base64_bytes ?? MAX_BASE64_BYTES,
       }
+      if (!info.enforceLimits) return input
       if (!input.url.startsWith("data:") || !input.url.includes(";base64,"))
         return yield* new InvalidDataUrlError({ url: input.url })
 

packages/opencode/test/image/image.test.ts

@@ -6,11 +6,24 @@ import { TestConfig } from "../fixture/config"
 import { testEffect } from "../lib/effect"
 
 const it = testEffect(Layer.mergeAll(Image.layer.pipe(Layer.provide(TestConfig.layer()))))
+const enforcing = testEffect(
+  Layer.mergeAll(
+    Image.layer.pipe(
+      Layer.provide(
+        TestConfig.layer({
+          get: () => Effect.succeed({ attachment: { image: { enforce_limits: true, auto_resize: true } } }),
+        }),
+      ),
+    ),
+  ),
+)
 const tiny = testEffect(
   Layer.mergeAll(
     Image.layer.pipe(
       Layer.provide(
-        TestConfig.layer({ get: () => Effect.succeed({ attachment: { image: { max_base64_bytes: 1 } } }) }),
+        TestConfig.layer({
+          get: () => Effect.succeed({ attachment: { image: { enforce_limits: true, max_base64_bytes: 1 } } }),
+        }),
       ),
     ),
   ),
@@ -28,7 +41,16 @@ function part(mime: string, data: string) {
 }
 
 describe("Image", () => {
-  it.effect("normalizes generated png and jpeg attachments", () =>
+  it.effect("passes images through by default without loading the resizer", () =>
+    Effect.gen(function* () {
+      const image = yield* Image.Service
+      const input = part("image/png", "not-valid-image-data")
+
+      expect(yield* image.normalize(input)).toEqual(input)
+    }),
+  )
+
+  enforcing.effect("normalizes generated png and jpeg attachments when limit enforcement is enabled", () =>
     Effect.gen(function* () {
       const photon = yield* Effect.promise(() => import("@silvia-odwyer/photon-node"))
       const source = new photon.PhotonImage(

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

@@ -1143,6 +1143,7 @@ export type McpRemoteConfig = {
 export type LayoutConfig = "auto" | "stretch"
 
 export type ImageAttachmentConfig = {
+  enforce_limits?: boolean
   auto_resize?: boolean
   max_width?: number
   max_height?: number

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

@@ -345,6 +345,39 @@ You can manage the tools an LLM can use through the `tools` option.
 
 ---
 
+### Attachments
+
+You can configure how image attachments are processed before they are sent to the model through the `attachment.image` option.
+
+By default OpenCode does not enforce image attachment limits and does not resize images. Images pass through unchanged unless you explicitly enable limit enforcement.
+
+```json title="opencode.json"
+{
+  "$schema": "https://opencode.ai/config.json",
+  "attachment": {
+    "image": {
+      "enforce_limits": true,
+      "auto_resize": false,
+      "max_width": 2000,
+      "max_height": 2000,
+      "max_base64_bytes": 4718592
+    }
+  }
+}
+```
+
+Available options:
+
+- `enforce_limits` - Enforce configured image limits before sending images to the model. Defaults to `false`, which passes images through unchanged.
+- `auto_resize` - Resize images that exceed configured limits. This only applies when `enforce_limits` is `true`. Defaults to `false`.
+- `max_width` - Maximum image width when limit enforcement is enabled. Defaults to `2000`.
+- `max_height` - Maximum image height when limit enforcement is enabled. Defaults to `2000`.
+- `max_base64_bytes` - Maximum base64 payload size when limit enforcement is enabled. Defaults to `4718592`.
+
+When `enforce_limits` is `true` and `auto_resize` is `false`, images over the configured limits are omitted. When both are `true`, OpenCode attempts to resize oversized images before omitting them.
+
+---
+
 ### Models
 
 You can configure the providers and models you want to use in your OpenCode config through the `provider`, `model` and `small_model` options.