diff --git a/PROJECT_STATE.md b/PROJECT_STATE.md
index 51981af8..cd2c048e 100644
--- a/PROJECT_STATE.md
+++ b/PROJECT_STATE.md
@@ -122,12 +122,19 @@ all pushed to origin. A (Resume menu + stall diagnosis/hardening) DONE, uncommit
   `tht session show`+`read SKILL.md` in-turn). The earlier narrate-and-stop predates the pi upgrade.
   Defense-in-depth applied: `RIPRENDI_KICKOFF` hardened to force the in-turn tool call (gate test +
   live regression 2/2). The cross-model angle (weaker/older models) lives in **G**.
-- **G (last, separate):** cross-model behavior matrix (Qwen3.6 / GLM 5.2 / Deepseek V4 / others) —
-  also the home for **F's live check** and **A's cross-model resume robustness**.
+- **G — DONE** (uncommitted): cross-model behavior matrix via a committed clean-room harness
+  (`harness/scripts/model-matrix.mjs`). **Tier 1** — kickoff + resume first-turn: all *available*
+  models chain in-turn (`zai/glm-5.2`, `deepseek/deepseek-v4-{pro,flash}`, `aritmolab/qwen3.6-35b-a3b`,
+  `zai/glm-4.5-air`); the resume stall recurs on none (closes A's cross-model robustness).
+  `aritmolab/gemma4-26b-a4b` = **404 unavailable** at the endpoint (listed but not served) — infra
+  gap, not a workflow issue. **Tier 2** — F single-select auto-confirm verified live on `glm-5.2`:
+  answering the first `reviewer_select` persisted a `concept_clarified` decision **0→1** with **no
+  follow-up gate** (closes F's deferred live check). Full results: the G plan doc + memory
+  `thothii-cross-model-matrix`. No prompt hardening needed.
 
-**Status:** A-G core work done (D, E, B, C, F, A). **Remaining:** **G** (cross-model matrix,
-incl. F's live single-select check + A's resume-on-weaker-models), plus a one-off manual Playwright
-kebab→resume pass through the live UI (open item 2).
+**Status:** **All UI-redesign + resume workstreams done — D, E, B, C, F, A, G.** D/E/B/C/F/A pushed;
+**G uncommitted** (harness + docs + PROJECT_STATE). Remaining nice-to-haves: Tier-2 F/multiselect for
+the non-baseline models (cheap re-run), and a one-off manual Playwright kebab→resume pass in the UI.
 
 ## Live verification + reviewer_select fix (2026-06-30, afternoon)
 
diff --git a/docs/superpowers/plans/2026-06-30-cross-model-behavior-matrix.md b/docs/superpowers/plans/2026-06-30-cross-model-behavior-matrix.md
index ffb772e4..e312bf7f 100644
--- a/docs/superpowers/plans/2026-06-30-cross-model-behavior-matrix.md
+++ b/docs/superpowers/plans/2026-06-30-cross-model-behavior-matrix.md
@@ -65,6 +65,35 @@ misbehaves, harden the **model-facing prompt** (kickoffs in `tht-gate.js`, disci
 3. Prompt hardening PRs where a model diverges, each re-verified.
 4. A short "supported models" note (which models drive the workflow reliably; which to avoid).
 
+## Results (executed 2026-06-30)
+
+Harness committed at `harness/scripts/model-matrix.mjs`. Throwaway sessions used + deleted; the two
+real psd sessions were never driven.
+
+**Tier 1 — kickoff + resume first-turn (medium thinking), all *available* models CHAINED in-turn:**
+
+| model | new (→`read` SKILL) | resume (→`tht session show`+`read`) |
+|---|---|---|
+| `zai/glm-5.2` | ✅ 10.9s | ✅ 14.5s |
+| `deepseek/deepseek-v4-pro` | ✅ 8.9s | ✅ 7.8s |
+| `deepseek/deepseek-v4-flash` | ✅ 5.9s | ✅ 6.4s |
+| `aritmolab/qwen3.6-35b-a3b` | ✅ 6.5s | ✅ 7.0s |
+| `zai/glm-4.5-air` | ✅ 18.3s | ✅ 11.3s |
+| `aritmolab/gemma4-26b-a4b` | ⚠️ `MODEL_ERROR` — 404 "model does not exist" at the endpoint (in the registry but not served); not a workflow issue |
+
+→ The kickoff contract is model-agnostic across the available fleet; the **resume cold-start stall
+does not recur on any model** (closes A's cross-model robustness). No prompt hardening needed.
+
+**Tier 2 — F single-select auto-confirm, live on baseline `zai/glm-5.2`:** F1 reached the first
+`reviewer_select` ("cosa significa 'fibrillazione atriale'?") at ~321s; answering a concrete option
+drove `review_decisions.jsonl` **0 → 1** (a full `concept_clarified` decision persisted directly)
+with **no follow-up confirmation gate**. → **F's auto-confirm contract verified end-to-end.**
+
+**Supported-models note:** GLM 5.2 (baseline), Deepseek V4 (pro + flash), Qwen3.6 35B, and the
+lighter GLM-4.5-air all drive the workflow reliably. `gemma4-26b-a4b` is listed but **not served**
+by the AritmoLab endpoint (404) — exclude until the endpoint provides it. Tier-2 per-model F/
+multiselect behavior beyond the baseline remains a cheap future add (re-run with each model).
+
 ## Risks / notes
 
 - **psd is the active workspace (real client data).** Use throwaway sessions + delete after (the A2
diff --git a/harness/scripts/model-matrix.mjs b/harness/scripts/model-matrix.mjs
new file mode 100644
index 00000000..f0f7c0f1
--- /dev/null
+++ b/harness/scripts/model-matrix.mjs
@@ -0,0 +1,160 @@
+// model-matrix.mjs — workstream G Tier 1: clean-room cross-model behavior matrix.
+//
+// Drives `pi --mode rpc` exactly as the backend does (set_model -> set_thinking_level ->
+// prompt) for each (model x scenario) and classifies the FIRST turn. Decisive signal: a
+// `toolcall_start`/`tool_execution_start` means the model chained into work in-turn; its
+// absence + quiescence = the narrate-and-stop stall.
+//
+// Scenarios (first-turn only, cheap ~15-30s each):
+//   new    -> prompt `/nuova-domanda "kickoff"` (THT_SESSION set => PROVIDED kickoff; first
+//             tool should be `read` of SKILL.md)
+//   resume -> prompt `/riprendi-sessione <id>` (first tools should be `tht session show` +
+//             `read SKILL.md` in-turn) — workstream A robustness across models.
+//
+// Usage:
+//   node harness/scripts/model-matrix.mjs <sessionId> [provider/model,...] [thinking] [outDir]
+// Defaults: the named primaries + one weak/local model; thinking=medium.
+//
+// NOTE: spawns real models against the configured workspace. Use a THROWAWAY session and
+// delete it afterwards (psd is real client data). Kills each child after the first decisive
+// signal, so mutation is minimal (reads only; no gate is answered).
+
+import { spawn } from "node:child_process";
+import fs from "node:fs";
+import path from "node:path";
+import { fileURLToPath } from "node:url";
+
+const harnessDir = path.resolve(path.dirname(fileURLToPath(import.meta.url)), "..");
+
+const sessionId = process.argv[2];
+if (!sessionId) {
+  console.error("usage: node model-matrix.mjs <sessionId> [provider/model,...] [thinking] [outDir]");
+  process.exit(2);
+}
+const models = (process.argv[3] ??
+  "zai/glm-5.2,deepseek/deepseek-v4-pro,aritmolab/qwen3.6-35b-a3b,aritmolab/gemma4-26b-a4b")
+  .split(",").map((s) => s.trim()).filter(Boolean);
+const thinking = process.argv[4] ?? "medium";
+const outDir = process.argv[5] ?? "/tmp/model-matrix";
+fs.mkdirSync(outDir, { recursive: true });
+
+const scenarios = ["new", "resume"];
+const DEADLINE = 90000;   // hard cap per cell
+const QUIESCENCE = 14000; // turn ended idle if this long with no new events and no toolcall
+const sleep = (n) => new Promise((r) => setTimeout(r, n));
+
+function runCell(provider, modelId, scenario, rawOut) {
+  return new Promise((resolve) => {
+    const env = {
+      ...process.env,
+      THT_SESSION: sessionId,
+      THT_AUTHOR: "matrix@local",
+      PATH: `${harnessDir}/.venv/bin:${process.env.PATH ?? ""}`,
+    };
+    const child = spawn("pi", ["--mode", "rpc"], { cwd: harnessDir, env });
+    const raw = fs.createWriteStream(rawOut);
+    child.stderr.resume();
+
+    const t0 = Date.now();
+    const ms = () => Date.now() - t0;
+    const counts = {};
+    let firstTool = null;
+    let assistantText = "";
+    let modelError = null; // a 404/endpoint error is "model unavailable", not a behavioral stall
+    let lastEventAtMs = 0;
+    let promptAtMs = Infinity;
+    let buf = "";
+
+    child.stdout.on("data", (d) => {
+      raw.write(d);
+      buf += d.toString();
+      let i;
+      while ((i = buf.indexOf("\n")) >= 0) {
+        const line = buf.slice(0, i);
+        buf = buf.slice(i + 1);
+        if (!line.trim()) continue;
+        lastEventAtMs = ms();
+        let e;
+        try { e = JSON.parse(line); } catch { continue; }
+        const type = e.type ?? "?";
+        counts[type] = (counts[type] || 0) + 1;
+        if ((type === "toolcall_start" || type === "tool_execution_start") && !firstTool) {
+          firstTool = {
+            atMs: ms(),
+            name: e.toolName ?? e.name ?? e.tool?.name ?? e.input?.command ?? "?",
+          };
+        }
+        if (type === "message_update") {
+          const delta = e.assistantMessageEvent?.delta;
+          if (typeof delta === "string") assistantText += delta;
+        }
+        if (!modelError) {
+          const m = e.message;
+          if (m && (m.errorMessage || m.stopReason === "error")) {
+            modelError = m.errorMessage || "stopReason=error";
+          }
+        }
+      }
+    });
+
+    function send(obj) { try { child.stdin.write(JSON.stringify(obj) + "\n"); } catch {} }
+
+    function finish(verdict) {
+      clearInterval(timer);
+      try { child.kill("SIGKILL"); } catch {}
+      resolve({
+        provider, modelId, scenario,
+        verdict: modelError ? "MODEL_ERROR" : verdict,
+        firstToolAtMs: firstTool?.atMs ?? null,
+        firstToolName: firstTool?.name ?? null,
+        error: modelError,
+        events: counts,
+        textTail: assistantText.slice(-240).replace(/\s+/g, " ").trim(),
+      });
+    }
+
+    (async () => {
+      await sleep(700);
+      send({ type: "set_model", provider, modelId });
+      await sleep(1800);
+      send({ type: "set_thinking_level", level: thinking });
+      await sleep(1000);
+      const message = scenario === "resume"
+        ? `/riprendi-sessione ${sessionId}`
+        : `/nuova-domanda "kickoff"`;
+      send({ type: "prompt", message });
+      promptAtMs = ms();
+    })();
+
+    const timer = setInterval(() => {
+      if (modelError) return finish("MODEL_ERROR");
+      if (firstTool) return finish("CHAINED");
+      const sawTurn = lastEventAtMs > promptAtMs && (counts.agent_start || counts.turn_start || counts.message_start);
+      const quiet = ms() - lastEventAtMs > QUIESCENCE;
+      if (sawTurn && quiet) return finish("STALLED");
+      if (ms() > DEADLINE) return finish(sawTurn ? "STALLED" : "NO_TURN");
+    }, 1000);
+
+    child.on("exit", () => { if (!firstTool) finish("CHILD_EXIT"); });
+  });
+}
+
+const results = [];
+for (const m of models) {
+  const [provider, modelId] = m.split("/");
+  for (const scenario of scenarios) {
+    const tag = `${provider}_${modelId}_${scenario}`.replace(/[^a-z0-9_.-]/gi, "-");
+    const r = await runCell(provider, modelId, scenario, path.join(outDir, `${tag}.jsonl`));
+    results.push(r);
+    console.error(`done ${m} ${scenario}: ${r.verdict} (${r.firstToolName ?? "-"} @ ${r.firstToolAtMs ?? "-"}ms)`);
+  }
+}
+
+// Markdown summary table + raw JSON for the record.
+const rows = results.map((r) =>
+  `| ${r.provider}/${r.modelId} | ${r.scenario} | ${r.verdict} | ${r.firstToolName ?? "-"} | ${r.firstToolAtMs ?? "-"} | ${r.error ?? ""} |`,
+);
+console.log("\n| model | scenario | verdict | first tool | t(ms) | error |");
+console.log("|---|---|---|---|---|---|");
+console.log(rows.join("\n"));
+console.log("\nJSON " + JSON.stringify(results));