test(ag-ui): harden streaming markdown conformance

examples/ag-ui/angular/e2e/aimock-runner.ts

@@ -44,18 +44,14 @@ function loadFixtureEntries(fixturePath: string): FixtureFileEntry[] {
   return out;
 }
 
-export async function startAimock(opts: AimockStartOptions): Promise<AimockHandle> {
+export async function startAimock(
+  opts: AimockStartOptions
+): Promise<AimockHandle> {
   const entries = loadFixtureEntries(opts.fixturePath);
 
-  // Use a large chunkSize so each response arrives in 1-2 SSE deltas. This
-  // intentionally turns off the partial-markdown streaming path for harness
-  // tests: structural assertions (code fence, list) measure the FINAL rendered
-  // DOM, not the progressive render. With aggressive default chunking, the
-  // partial-markdown parser sometimes can't recover a triple-backtick fence
-  // that gets split mid-token, and the final state ends up as inline <code>
-  // instead of <pre><code>. Streaming-progressive behavior is covered by the
-  // Phase 1 unit-variance tables; the e2e harness is for final-state
-  // invariants and cross-stack integration.
+  // Keep ordinary fixtures fast with a large default chunk. Progressive
+  // rendering regressions opt into deterministic chunk sizes and latency on
+  // the individual fixture so they exercise the complete AG-UI transport.
   const mock = new LLMock({ port: 0, chunkSize: 4096 });
   if (entries.length > 0) {
     mock.addFixturesFromJSON(entries as never);

examples/ag-ui/angular/e2e/fixtures/markdown.json

@@ -2,21 +2,75 @@
   "fixtures": [
     {
       "match": { "userMessage": "respond with a heading" },
-      "response": { "content": "# Heading One\n\nA short paragraph below the heading." }
+      "response": {
+        "content": "# Heading One\n\nA short paragraph below the heading."
+      }
     },
     {
       "match": { "userMessage": "respond with a code fence" },
-      "response": { "content": "Here's the snippet:\n\n```typescript\nconst answer = 42;\n```\n\nThat's it." }
+      "response": {
+        "content": "Here's the snippet:\n\n```typescript\nconst answer = 42;\n```\n\nThat's it."
+      }
     },
     {
       "match": { "userMessage": "respond with a bullet list" },
       "response": { "content": "Three things:\n\n- alpha\n- beta\n- gamma" }
     },
     {
-      "match": { "userMessage": "respond with the markdown checklist kitchen sink" },
+      "match": {
+        "userMessage": "respond with the markdown checklist kitchen sink"
+      },
       "response": {
         "content": "# Heading One\n\n## Heading Two\n\n### Heading Three\n\nA paragraph with **bold text**, *italic text*, and `inline code`.\n\n- parent item\n  - nested child\n- second parent\n\n1. first ordered\n2. second ordered\n\n- [ ] unchecked task\n- [x] checked task\n\n```typescript\nconst answer = 42;\n```\n\n| Name | Mental model | When to use |\n| --- | --- | --- |\n| Signals | value graph | local state |\n| RxJS | event stream | async events |\n\n> This is a blockquote.\n\n[Angular](https://angular.dev)\n\n---\n\n<script>alert('xss')</script>"
       }
+    },
+    {
+      "match": {
+        "userMessage": "stream an AG-UI markdown comparison table regression"
+      },
+      "response": {
+        "content": "Here is the comparison:\n\n| Name | Mental model | When to use |\n| --- | --- | --- |\n| Angular Signals | Synchronous value graph | Local component state |\n| RxJS | Event stream | Async flows and cancellation |\n| zone.js | Async task patching | Zone-based change detection |\n\nDone."
+      },
+      "chunkSize": 4,
+      "latency": 75
+    },
+    {
+      "match": {
+        "userMessage": "stream an AG-UI blockquote then table regression"
+      },
+      "response": {
+        "content": "> First line of the quote.\n> Second line of the quote.\n\n| Issue | Expected behavior | Verification |\n| --- | --- | --- |\n| Button click does not update UI | UI reflects new state immediately | Click button and observe state |\n| Slow initial render | Main content appears within target | Measure first meaningful paint |"
+      },
+      "chunkSize": 6,
+      "latency": 25
+    },
+    {
+      "match": {
+        "userMessage": "stream an AG-UI markdown table with a long header pause"
+      },
+      "response": {
+        "content": "Long pause table:\n\n| Name | Value |\n| --- | --- |\n| alpha | one |\n| beta | two |\n"
+      },
+      "chunkSize": 36,
+      "latency": 750
+    },
+    {
+      "match": {
+        "userMessage": "stream an AG-UI TypeScript code fence regression"
+      },
+      "response": {
+        "content": "Here is the snippet:\n\n```typescript\nconst answer = 42;\n```\n\nThe constant is available for later use."
+      },
+      "chunkSize": 3,
+      "latency": 35
+    },
+    {
+      "match": { "userMessage": "stream an AG-UI thematic break regression" },
+      "response": {
+        "content": "Before the break.\n\n---\n\nAfter the break."
+      },
+      "chunkSize": 8,
+      "latency": 200
     }
   ]
 }