fix(images): render agent-generated images in chat (#2809)

* fix(images): render agent-generated images in chat

When a chat model calls generate_image mid-conversation (agentic flow), the image does
not display — it survives only as a URL the model echoes in prose. generate_image runs
as a text-only MCP server, so result['image_url'] is never populated and the existing
buildImageBubble render path never fires. Promote the image URL out of the tool's stdout
in tool_execution so the agent loop's existing forwarding renders it via buildImageBubble
— deterministically, no dependence on the model echoing the URL. Backend-only; reuses
dev's image bubble, forwarding, and the tool's existing parseable output.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* feat(images): fully-qualified, valid generated-image links

The chat model often mangled the generated-image URL it echoed in prose (relative path,
or copying the 'image_url:' label into the link href). Build a fully-qualified link by
prefixing the existing app_public_url setting (empty default keeps relative paths), and
present it as a clean 'Direct link:' the model can echo verbatim (the frontend auto-links
bare https URLs). One file; independent of how the image is rendered.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* test(images): cover _promote_image_fields; make exit-code guard self-contained

Adds the unit tests requested in review on #2809: absolute URL, relative URL,
no URL (result unchanged), and non-zero exit_code (not promoted). Moves the
dict/exit_code==0 guard from the call site into _promote_image_fields so the
function is self-contained and the failure case is unit-testable; call-site
behavior is unchanged.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

mcp_servers/image_gen_server.py

@@ -115,6 +115,10 @@ async def call_tool(name: str, arguments: dict) -> list[TextContent]:
 
             img = images[0]
             image_url = None
+            # Prefix the instance's public base URL (existing app_public_url setting) so the
+            # link is fully-qualified and clickable when the model echoes it. Empty = relative
+            # same-origin path (unchanged default).
+            _pub_base = (get_setting("app_public_url", "") or "").rstrip("/")
 
             if img.get("b64_json"):
                 img_dir = Path("data/generated_images")
@@ -122,7 +126,7 @@ async def call_tool(name: str, arguments: dict) -> list[TextContent]:
                 filename = f"{uuid.uuid4().hex[:12]}.png"
                 img_path = img_dir / filename
                 img_path.write_bytes(base64.b64decode(img["b64_json"]))
-                image_url = f"/api/generated-image/{filename}"
+                image_url = f"{_pub_base}/api/generated-image/{filename}"
 
                 # Save to gallery
                 try:
@@ -146,7 +150,13 @@ async def call_tool(name: str, arguments: dict) -> list[TextContent]:
             else:
                 return [TextContent(type="text", text="Error: Unexpected image API response format")]
 
-            result = f"Generated image for: {prompt[:100]}\nimage_url: {image_url}\nmodel: {model_id}\nsize: {size}"
+            # "Direct link:" rather than an "image_url:" label — small models copied the
+            # label token ("image_url") into the link href, producing a broken link.
+            result = (
+                f"Generated image for: {prompt[:100]}\n"
+                f"Direct link: {image_url}\n"
+                f"model: {model_id}\nsize: {size}"
+            )
             return [TextContent(type="text", text=result)]
 
     except httpx.TimeoutException:

src/tool_execution.py

@@ -13,6 +13,7 @@ import json
 import logging
 import os
 import pathlib
+import re
 import sys
 import time
 from typing import Any, Awaitable, Callable, Dict, Optional, Tuple
@@ -594,9 +595,40 @@ async def _call_mcp_tool(
         if fallback:
             return fallback
 
+    # generate_image runs as a text-only MCP tool, so the saved image URL never
+    # reaches the agent loop's structured forwarding (which renders the image via
+    # buildImageBubble on result["image_url"]). Lift it out of the tool's stdout so
+    # the image renders deterministically — no dependence on the model echoing the
+    # URL into its prose (which it mangles/hallucinates).
+    if tool == "generate_image":
+        _promote_image_fields(result)
+
     return result
 
 
+def _promote_image_fields(result: Dict) -> None:
+    """Lift the image URL (+ prompt/model/size) from a successful generate_image MCP
+    text result into structured fields the agent loop already forwards to
+    buildImageBubble. Only acts on a dict result with exit_code 0; matches the
+    generated-image URL by pattern (absolute or relative) so it's robust to the
+    result's wording."""
+    if not isinstance(result, dict) or result.get("exit_code") != 0:
+        return
+    out = result.get("stdout") or ""
+    m = re.search(r'(?:https?://[^\s)\]]+)?/api/generated-image/[A-Za-z0-9._-]+', out)
+    if not m:
+        return
+    result["image_url"] = m.group(0).strip()
+    for field, pat in (
+        ("image_prompt", r'^Generated image for:\s*(.+)$'),
+        ("image_model", r'^model:\s*(.+)$'),
+        ("image_size", r'^size:\s*(.+)$'),
+    ):
+        fm = re.search(pat, out, re.M)
+        if fm:
+            result[field] = fm.group(1).strip()
+
+
 _BG_MARKERS = {"#!bg", "#bg", "# bg", "#background", "# background", "@background", "# @background"}
 
 

tests/test_promote_image_fields.py

@@ -0,0 +1,57 @@
+"""Unit tests for `_promote_image_fields` (PR #2809).
+
+`generate_image` is a text-only MCP tool, so the saved image URL never reaches
+the agent loop's structured forwarding (which renders the image via
+`buildImageBubble` on `result["image_url"]`). `_promote_image_fields` lifts the
+URL — plus prompt/model/size — out of the tool's stdout into structured fields so
+the image renders deterministically, without relying on the model echoing the URL
+into prose. These cases cover the absolute-URL, relative-URL, no-URL, and
+non-success-exit paths.
+"""
+from src.tool_execution import _promote_image_fields
+
+
+def _result(stdout, exit_code=0):
+    return {"exit_code": exit_code, "stdout": stdout}
+
+
+def test_absolute_url_promoted_with_fields():
+    """An absolute https URL in stdout is lifted into image_url, along with the
+    prompt/model/size lines."""
+    r = _result(
+        "Generated image for: a red fox in snow\n"
+        "Direct link: https://odysseus.example.com/api/generated-image/abc123.png\n"
+        "model: qwen-image\n"
+        "size: 1024x1024"
+    )
+    _promote_image_fields(r)
+    assert r["image_url"] == "https://odysseus.example.com/api/generated-image/abc123.png"
+    assert r["image_prompt"] == "a red fox in snow"
+    assert r["image_model"] == "qwen-image"
+    assert r["image_size"] == "1024x1024"
+
+
+def test_relative_url_promoted():
+    """A relative /api/generated-image/... path (no host) is still matched."""
+    r = _result(
+        "Generated image for: a cat\n"
+        "Direct link: /api/generated-image/def456.png"
+    )
+    _promote_image_fields(r)
+    assert r["image_url"] == "/api/generated-image/def456.png"
+    assert r["image_prompt"] == "a cat"
+
+
+def test_no_url_leaves_result_unchanged():
+    """No generated-image URL anywhere -> no image_url key is added."""
+    r = _result("Generated image for: a dog\n(no link produced)")
+    _promote_image_fields(r)
+    assert "image_url" not in r
+    assert "image_prompt" not in r
+
+
+def test_nonzero_exit_not_promoted():
+    """A non-success result is never promoted, even if stdout contains a URL."""
+    r = _result("https://host/api/generated-image/zzz.png", exit_code=1)
+    _promote_image_fields(r)
+    assert "image_url" not in r