test(id): F11.9 bytes-per-frame baseline for checked-in examples (#542)

doc/2026-10-27T00-00-00Z_baseline_bytes_per_frame.md

@@ -0,0 +1,55 @@
+# F11.9 — Bytes-per-frame baseline table
+
+- Status: baseline record
+- Date: 2026-10-27
+- Issue: developing-today/code#542
+- Measured at commit: `37418e56339c315cf0ddf3e61c9c55c1e9d0c0a2` (main, 2026-10-27)
+- Measurement: `pkgs/id/src/sandbox.rs` test `bytes_per_frame_baseline_for_checked_in_examples`
+
+## What is measured
+
+For each checked-in example wasm in `pkgs/id/examples/`, the guest is
+instantiated in the `Sandbox` with a fixed seed (7) and the full-screen
+frame byte length at rest is recorded via `layout_at(width, height)` at
+the two reference viewports, 80x24 and 200x60.
+
+The baseline is the guest frame bytes **at the sandbox boundary** — the
+number Phase 12 delta frames (F12.11) and server-side redraw batching
+must beat at the source. Presenter wire encodings (surface JSON / ANSI)
+are out of scope for this baseline and are not measured here.
+
+## Baseline table (seed 7, at rest)
+
+| example     | plaza_layout | bytes @ 80x24 | bytes @ 200x60 |
+| ----------- | ------------ | ------------: | -------------: |
+| lounge      | yes          |            29 |             29 |
+| roc-chat    | yes          |            24 |             24 |
+| roc-counter | yes          |             7 |              7 |
+| roc-grid    | yes          |           383 |            383 |
+| roc-screen  | yes          |           179 |            179 |
+| territory   | yes          |          1010 |           1010 |
+| tic-tac-toe | yes          |            25 |             25 |
+
+Notes:
+
+- All seven examples export `plaza_layout`, so no guest used the
+  `view()` fallback in this run. The measurement test asserts the
+  fallback invariant (identical bytes at both viewports, equal to
+  `view()`) for any future guest without the export, and the printed
+  table marks such guests `no (view fallback)`.
+- At rest, every example's frame is the same byte length at both
+  viewports: the initial frames do not fill the larger viewport. That
+  equality is itself a baseline datum — it is the starting point delta
+  frames are compared against, not a measurement error (the test calls
+  `layout_at` separately for each viewport).
+
+## How to rerun
+
+```sh
+cd pkgs/id && cargo test --lib bytes_per_frame_baseline -- --nocapture
+```
+
+The test prints the table above (one row per example) and passes when
+every example instantiates and renders within the default sandbox
+limits. Update this file's table and measured-at commit when a rerun
+produces different numbers.

pkgs/id/src/sandbox.rs

@@ -1264,6 +1264,68 @@ mod tests {
         assert_eq!(width_of(live.view().unwrap()), 20);
     }
 
+    #[test]
+    fn bytes_per_frame_baseline_for_checked_in_examples() {
+        // F11.9 baseline: the full-screen frame size each checked-in example
+        // produces at rest (seed 7), at the two reference viewports. These
+        // numbers are the baseline Phase 12 delta frames (F12.11) must beat;
+        // the committed table lives in
+        // doc/2026-10-27T00-00-00Z_baseline_bytes_per_frame.md.
+        // Rerun with:
+        //   cd pkgs/id && cargo test --lib bytes_per_frame_baseline -- --nocapture
+        const EXAMPLES: [(&str, &[u8]); 7] = [
+            ("lounge", include_bytes!("../examples/lounge/lounge.wasm")),
+            (
+                "roc-chat",
+                include_bytes!("../examples/roc-chat/roc-chat.wasm"),
+            ),
+            (
+                "roc-counter",
+                include_bytes!("../examples/roc-counter/counter.wasm"),
+            ),
+            (
+                "roc-grid",
+                include_bytes!("../examples/roc-grid/roc-grid.wasm"),
+            ),
+            (
+                "roc-screen",
+                include_bytes!("../examples/roc-screen/roc-screen.wasm"),
+            ),
+            (
+                "territory",
+                include_bytes!("../examples/territory/territory.wasm"),
+            ),
+            (
+                "tic-tac-toe",
+                include_bytes!("../examples/tic-tac-toe/tic-tac-toe.wasm"),
+            ),
+        ];
+        println!("| example | plaza_layout | bytes @ 80x24 | bytes @ 200x60 |");
+        for (name, wasm) in EXAMPLES {
+            let runner = Sandbox::compile(wasm, SandboxLimits::default()).unwrap();
+            let mut live = runner.instantiate(7).unwrap();
+            let has_layout = live.layout.is_some();
+            let small = live.layout_at(80, 24).unwrap();
+            let large = live.layout_at(200, 60).unwrap();
+            println!(
+                "| {name} | {} | {} | {} |",
+                if has_layout {
+                    "yes"
+                } else {
+                    "no (view fallback)"
+                },
+                small.len(),
+                large.len()
+            );
+            if !has_layout {
+                // Without `plaza_layout`, layout_at falls back to view():
+                // the frame is the same bytes at both viewports.
+                assert_eq!(small, large, "{name}: view fallback must not reflow");
+                assert_eq!(small, live.view().unwrap(), "{name}: fallback is view()");
+            }
+        }
+    }
+
     #[test]
     fn checked_in_territory_renders_a_styled_screen_within_the_default_fuel() {
         let wasm = include_bytes!("../examples/territory/territory.wasm");