fix(copilot): keep prose a tag wrapped instead of a JSON payload

Third real case from a trace (1206fd8a): `<workspace_resource>the gmail-agent
workflow</workspace_resource>` — a matched pair whose body is plain prose. The
sentence rendered as "...once I wired up to handle the welcome sequence" with
its subject silently removed.

The marker test could not fire (prose contains no tag markers), so it fell to
the deliberate drop-malformed-payload path. But that path exists for an agent
emitting BROKEN JSON, not for a tag wrapping prose.

The distinction is whether the body was ever an attempted payload, which
isViableJsonPrefix already answers: `{"type":"single_select"}` is a well-formed
JSON value failing its shape guard and keeps being dropped; `the gmail-agent
workflow` was never a payload and is emitted.

Author: j15z

apps/sim/app/workspace/[workspaceId]/home/components/message-content/components/special-tags/special-tags.test.ts

@@ -176,6 +176,19 @@ describe('parseSpecialTags with <question>', () => {
     )
   })
 
+  it('keeps prose a tag wrapped instead of a payload', () => {
+    // Verbatim from a real message (trace 1206fd8a): a matched pair whose body
+    // is plain prose, never an attempted JSON payload. The sentence read
+    // "...once I wired up to handle the welcome sequence" with the subject gone.
+    const raw =
+      'once I wired up <workspace_resource>the gmail-agent workflow</workspace_resource> to handle the welcome sequence.'
+    const rendered = parseSpecialTags(raw, false)
+      .segments.map((segment) => ('content' in segment ? segment.content : ''))
+      .join('')
+    expect(rendered).toContain('the gmail-agent workflow')
+    expect(rendered).toContain('to handle the welcome sequence')
+  })
+
   it('still drops a marker-free malformed payload rather than showing raw JSON', () => {
     // The complement of the case above: no tag markers in the body, so this is
     // a genuinely broken emission from the agent, not swallowed prose.

apps/sim/app/workspace/[workspaceId]/home/components/message-content/components/special-tags/special-tags.tsx

@@ -685,17 +685,21 @@ export function parseSpecialTags(content: string, isStreaming: boolean): ParsedS
     const parsedTag = parseSpecialTagData(nearestTagName, body)
     if (parsedTag) {
       segments.push(parsedTag)
-    } else if (TAG_SHAPED_MARKER.test(body)) {
-      // The body failed to parse AND contains tag markers, which means the
-      // close we matched was not this opener's — the model was explaining tag
-      // syntax and a later example like `<workspace_resource>...</workspace_resource>`
-      // closed an earlier opener, making paragraphs of prose the "body".
-      // Dropping that silently loses the text and resumes mid-sentence, so emit
-      // it verbatim. Streamdown escapes the markers, so it reads as literal text.
+    } else if (
+      // The close we matched was not this opener's: the model was explaining tag
+      // syntax and a later example closed an earlier opener, making paragraphs
+      // of prose the "body".
+      TAG_SHAPED_MARKER.test(body) ||
+      // Or the tag wrapped prose that was never an attempted payload at all.
+      (JSON_BODY_TAG_NAMES.has(nearestTagName) && !isViableJsonPrefix(body))
+    ) {
+      // Either way the markers were literal text, so dropping the span loses
+      // real content and resumes mid-sentence. Emit it verbatim — Streamdown
+      // escapes the markers, so it reads as literal text.
       //
-      // A marker-free body that merely fails validation is a genuinely
-      // malformed payload from the agent; that keeps being dropped rather than
-      // showing the user raw JSON.
+      // A body that IS a well-formed JSON value and merely fails its shape
+      // guard keeps being dropped: that is a genuinely malformed payload from
+      // the agent, and showing the user raw JSON there would be a regression.
       const literal = content.slice(nearestStart, closeIdx + closeTag.length)
       if (literal.trim()) {
         segments.push({ type: 'text', content: literal })