fix: surface Bash tool image output instead of dropping it (#617)

## What's broken

The Bash branch of `toolUpdateFromToolResult` (`src/tools.ts`) guards
the array-content path on `"text" in result[0]`. When the local Bash
tool produces image content — `[{ type: "image", source: { type:
"base64", ... } }]`, e.g. when a command pipes a base64 data URI — the
guard rejects the array and `output` stays empty. The image is silently
dropped from the ACP `tool_call_update` and the client renders nothing.

## Fix

Distinguish text-only arrays (existing terminal-stream behavior) from
arrays containing non-text blocks. For the latter, bypass the terminal
`_meta` channel (binary payloads can't be streamed through it) and
delegate to `toAcpContentUpdate` so images surface as ACP content
blocks.

The change is contained to the Bash case in `toolUpdateFromToolResult`;
no other tool dispatch is affected.

## Tests

Three regression tests added in `src/tests/tools.test.ts` under a new
`describe("with image array tool_result …")`:

- pure image, `supportsTerminalOutput: false` — image surfaces as ACP
content
- pure image, `supportsTerminalOutput: true` — `_meta` is correctly
bypassed and image still surfaces
- mixed text + image — both blocks surface in order

All existing tests pass. Total: 240 → 243.

## Validation

- `npm run check` ✅
- `npm run build` ✅
- `npm run test:run` ✅ (243 passed, 13 integration skipped)

Co-authored-by: dave <dave@mint.lan>
Co-authored-by: Ben Brandt <benjamin.j.brandt@gmail.com>

src/tests/tools.test.ts

@@ -702,6 +702,77 @@ describe("Bash terminal output", () => {
         });
       });
     });
+
+    describe("with image array tool_result (local Bash image output path)", () => {
+      // The local Bash tool emits image content as
+      // `[{ type: "image", source: { type: "base64", ... } }]` when a
+      // command produces an image (e.g. piping a base64 data URI).
+      const makeImageBashResult = (
+        data: string,
+        media_type: "image/png" | "image/jpeg" | "image/gif" | "image/webp" = "image/png",
+      ): ToolResultBlockParam => ({
+        type: "tool_result",
+        tool_use_id: "toolu_bash",
+        content: [
+          {
+            type: "image",
+            source: { type: "base64", media_type, data },
+          } as ImageBlockParam,
+        ],
+      });
+
+      it("should surface image content as ACP image content (terminal disabled)", () => {
+        const toolResult = makeImageBashResult("iVBORw0KGgo=");
+        const update = toolUpdateFromToolResult(toolResult, bashToolUse, false);
+
+        expect(update.content).toEqual([
+          {
+            type: "content",
+            content: { type: "image", data: "iVBORw0KGgo=", mimeType: "image/png" },
+          },
+        ]);
+        expect(update._meta).toBeUndefined();
+      });
+
+      it("should bypass terminal _meta even when supportsTerminalOutput is true", () => {
+        // Binary content cannot be streamed through the terminal-output
+        // _meta channel, so the fix returns ACP content directly and skips
+        // the terminal info/output/exit triple.
+        const toolResult = makeImageBashResult("iVBORw0KGgo=", "image/jpeg");
+        const update = toolUpdateFromToolResult(toolResult, bashToolUse, true);
+
+        expect(update.content).toEqual([
+          {
+            type: "content",
+            content: { type: "image", data: "iVBORw0KGgo=", mimeType: "image/jpeg" },
+          },
+        ]);
+        expect(update._meta).toBeUndefined();
+      });
+
+      it("should still surface multi-block content with text + image mixed", () => {
+        const toolResult: ToolResultBlockParam = {
+          type: "tool_result",
+          tool_use_id: "toolu_bash",
+          content: [
+            { type: "text", text: "generated:" },
+            {
+              type: "image",
+              source: { type: "base64", media_type: "image/png", data: "AAAA" },
+            } as ImageBlockParam,
+          ],
+        };
+        const update = toolUpdateFromToolResult(toolResult, bashToolUse, false);
+
+        expect(update.content).toEqual([
+          { type: "content", content: { type: "text", text: "generated:" } },
+          {
+            type: "content",
+            content: { type: "image", data: "AAAA", mimeType: "image/png" },
+          },
+        ]);
+      });
+    });
   });
 
   describe("toAcpNotifications with clientCapabilities", () => {

src/tools.ts

@@ -530,7 +530,9 @@ export function toolUpdateFromToolResult(
       // Extract output and exit code from either format:
       // 1. BetaBashCodeExecutionResultBlock: { type: "bash_code_execution_result", stdout, stderr, return_code }
       // 2. Plain string content from a regular tool_result
-      // 3. Array content (e.g. [{ type: "text", text: "..." }])
+      // 3. Array content (e.g. [{ type: "text", text: "..." }] for stdout,
+      //    or [{ type: "image", source: {...} }] when the local Bash tool
+      //    produces an image, e.g. piping a base64 data URI)
       let output = "";
       let exitCode = isError ? 1 : 0;
 
@@ -545,13 +547,20 @@ export function toolUpdateFromToolResult(
         exitCode = bashResult.return_code;
       } else if (typeof result === "string") {
         output = result;
-      } else if (
-        Array.isArray(result) &&
-        result.length > 0 &&
-        "text" in result[0] &&
-        typeof result[0].text === "string"
-      ) {
-        output = result.map((c: any) => c.text).join("\n");
+      } else if (Array.isArray(result) && result.length > 0) {
+        const textOnly = result.every(
+          (c: any) => c && typeof c === "object" && typeof c.text === "string",
+        );
+        if (textOnly) {
+          output = result.map((c: any) => c.text).join("\n");
+        } else {
+          // Image (or mixed non-text) content. Binary payloads can't be
+          // streamed through the terminal-output _meta channel, so bypass
+          // it and surface the blocks as ACP content. This handles the
+          // local Bash tool's image output, which previously failed the
+          // text-only guard and was silently dropped.
+          return toAcpContentUpdate(result, isError);
+        }
       }
 
       if (supportsTerminalOutput) {