send images to opencode, which never needed the fork

B4 properly. The composer gate was the honest stopgap; this is the fix. opencode run takes
attachments with --file, so images work on the subprocess path we already use — the parity
doc had them down as phase 4, behind the serve migration, and they were not.

The bug was one omission: handleOpenCodeChat`s msg type had no images field, so the browser
sent them, the bubble rendered them, and they stopped at that signature. Nothing reported a
loss anywhere.

Attachments are paths, not inline data, so the sidecar spills each image to a temp file for
the length of the turn and removes it in settle — the same place every other per-turn
resource is released, so a killed or superseded turn cleans up too.

The load-bearing detail is `--` before the prompt: --file is an array option, so without the
separator the prompt is eaten as another filename and the turn dies with "File not found:"
followed by the entire message. Confirmed against the binary, and pinned by a test that
records argv from a stub.

list-models now reports each model own capability instead of a hardcoded false — opencode
publishes capabilities.input.image per model and nothing had ever read it. Defaults to false,
so a model that does not declare it keeps the affordance hidden.

Verified end to end: a red png sent over the chat socket to opencode/claude-sonnet-4-6 came
back "Red".

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/servers/api/chat/list-models.ts

@@ -39,8 +39,12 @@ export function invalidateModelCache(): void {
   openCodeCache = null;
 }
 
+type OpenCodeModel = {
+  capabilities?: { input?: { image?: boolean }; reasoning?: boolean };
+};
+
 type ProvidersResponse = {
-  providers?: Array<{ id?: string; models?: Record<string, unknown> }>;
+  providers?: Array<{ id?: string; models?: Record<string, OpenCodeModel> }>;
 };
 
 // Enumerate OpenCode models from the fixed server's GET /config/providers (reliable — no subprocess).
@@ -58,19 +62,20 @@ async function listOpenCodeModels(): Promise<ModelInfo[]> {
     const models: ModelInfo[] = [];
     for (const provider of data.providers ?? []) {
       const providerId = provider.id ?? '';
-      for (const modelId of Object.keys(provider.models ?? {})) {
+      for (const [modelId, model] of Object.entries(provider.models ?? {})) {
         models.push({
           id: `${providerId}/${modelId}`,
           name: modelId,
           provider: providerId,
           contextWindow: 200000,
           maxTokens: 8192,
-          reasoning: false,
-          // False because nothing carries them: `handleOpenCodeChat`'s message type has no `images`
-          // field, so an attached image is rendered in the bubble, never sent, and silently dropped.
-          // The composer gates on this flag, so advertising `true` offered a capability that did not
-          // exist. Flip it back when images are plumbed through OpenCodeRunParams (parity doc, Phase 4).
-          images: false,
+          reasoning: model?.capabilities?.reasoning ?? false,
+          // Was hardcoded `false`, correctly, while nothing carried images — the composer gates on this
+          // flag, so advertising `true` offered a capability that did not exist. Images are now plumbed
+          // through `OpenCodeRunParams` to `opencode run --file`, so the honest answer is the model's
+          // own: OpenCode publishes it per model and we had never read it. Defaults to false, so a model
+          // that does not declare the capability keeps the affordance hidden rather than offering it.
+          images: model?.capabilities?.input?.image ?? false,
         });
       }
     }

src/servers/api/chat/websocket.ts

@@ -396,6 +396,10 @@ async function handleOpenCodeChat(
     cwd?: string;
     cwdRoot?: string;
     resumeSessionId?: string;
+    // The whole of B4 lived in this omission. The browser sent images, the bubble rendered them, and
+    // they stopped at this signature — so they were never passed on and never reached the model, with
+    // nothing anywhere reporting a loss.
+    images?: PromptImage[];
   },
   effectivePrompt: string,
 ): Promise<void> {
@@ -457,6 +461,7 @@ async function handleOpenCodeChat(
       cwd,
       model,
       resumeSessionId: msg.resumeSessionId,
+      images: msg.images,
       onMessage,
     });