HuangPuStar · 6eanut · Sep 11, 2026
diff --git a/metainfer/tasks/evolve_kernel/server/_state_readers.py b/metainfer/tasks/evolve_kernel/server/_state_readers.py
@@ -5,6 +5,7 @@
 
 from __future__ import annotations
 
+import difflib
 import json
 from pathlib import Path
 from typing import Any, Dict, List, Optional
@@ -213,3 +214,94 @@ def read_reference_kernel(workspace_dir: Path) -> Dict[str, Any]:
         "path": str(path),
         "lines": len(code.splitlines()),
     }
+
+
+# --------------------------------------------------------------------------- #
+# Kernel source & diff
+# --------------------------------------------------------------------------- #
+
+# Metadata carried alongside a single kernel's source (the fields the diff
+# view needs to explain a change: how fast it was, which iteration added it,
+# and which library kernel it was derived from).
+_KERNEL_META_KEYS = (
+    "exec_time_ms",
+    "complexity_score",
+    "combined_score",
+    "iteration_added",
+    "parent_id",
+)
+
+
+def read_kernel_source(workspace_dir: Path, kernel_id: str) -> Dict[str, Any]:
+    """Return the full source + metadata for one library kernel, by id.
+
+    ``read_kernel_library`` ships every kernel's code in one payload; this
+    resolves a single kernel so callers that already know the id (the diff
+    view) don't have to scan the list, and so the lookup has one definition.
+    """
+    for k in read_kernel_library(workspace_dir)["kernels"]:
+        if str(k.get("id")) == str(kernel_id):
+            code = k.get("code") or ""
+            return {
+                "exists": True,
+                "id": k.get("id"),
+                "code": code,
+                "lines": len(code.splitlines()),
+                "meta": {key: k.get(key) for key in _KERNEL_META_KEYS},
+            }
+    return {"exists": False, "id": kernel_id, "code": "", "lines": 0, "meta": {}}
+
+
+def read_kernel_diff(workspace_dir: Path, kernel_id: str,
+                     base: str = "reference") -> Dict[str, Any]:
+    """Unified diff of a library kernel against a baseline.
+
+    ``base`` is ``"reference"`` (the original kernel the task started from)
+    or ``"parent"`` (the library kernel this one was derived from). Returns
+    the diff text plus added/removed line counts; a missing kernel, a root
+    kernel with no parent, or a parent that is no longer in the library
+    (the library evicts past ``MAX_LIBRARY_SIZE``) yields ``exists: False``
+    with an ``error`` reason rather than raising.
+    """
+    src = read_kernel_source(workspace_dir, kernel_id)
+    if not src["exists"]:
+        return _diff_missing(base, f"unknown kernel {kernel_id!r}")
+
+    if base == "parent":
+        parent_id = src["meta"].get("parent_id")
+        if not parent_id:
+            return _diff_missing(base, "kernel has no parent")
+        base_src = read_kernel_source(workspace_dir, parent_id)
+        if not base_src["exists"]:
+            return _diff_missing(
+                base, f"parent {str(parent_id)[:8]} is no longer in the library")
+        base_code = base_src["code"]
+        base_label = f"kernel {str(parent_id)[:8]}"
+    else:
+        ref = read_reference_kernel(workspace_dir)
+        base_code = ref["code"] if ref["exists"] else ""
+        base_label = "reference"
+
+    diff_lines = list(difflib.unified_diff(
+        base_code.splitlines(), (src["code"] or "").splitlines(),
+        fromfile=f"a/{base_label}",
+        tofile=f"b/kernel {str(kernel_id)[:8]}",
+        lineterm="",
+    ))
+    added = sum(1 for ln in diff_lines
+                if ln.startswith("+") and not ln.startswith("+++"))
+    removed = sum(1 for ln in diff_lines
+                  if ln.startswith("-") and not ln.startswith("---"))
+    return {
+        "exists": True,
+        "base": base,
+        "base_label": base_label,
+        "diff": "\n".join(diff_lines),
+        "added": added,
+        "removed": removed,
+    }
+
+
+def _diff_missing(base: str, error: str) -> Dict[str, Any]:
+    return {"exists": False, "base": base, "base_label": base,
+            "diff": "", "added": 0, "removed": 0, "error": error}
diff --git a/metainfer/tasks/evolve_kernel/server/routes.py b/metainfer/tasks/evolve_kernel/server/routes.py
@@ -95,6 +95,16 @@ def ok_reference_kernel(task_id: str) -> Dict[str, Any]:
         require_task_type(entry, PLUGIN_TYPE)
         return _state_readers.read_reference_kernel(workspace_dir_for(entry))
 
+    # ---- Kernel diff ----
+
+    @router.get("/kernels/{kernel_id}/diff")
+    def ok_kernel_diff(task_id: str, kernel_id: str,
+                       base: str = "reference") -> Dict[str, Any]:
+        entry = task_or_404(task_id)
+        require_task_type(entry, PLUGIN_TYPE)
+        return _state_readers.read_kernel_diff(
+            workspace_dir_for(entry), kernel_id, base)
+
     # ---- QA ----
 
     register_qa_routes(router, plugin, prefix="/qa")

diff --git a/metainfer/tasks/evolve_kernel/static/ok-detail.js b/metainfer/tasks/evolve_kernel/static/ok-detail.js
@@ -15,7 +15,7 @@ import { Timeline } from "app/timeline";
 import {
   getIterations, getCharts, getStateGraph,
   getKernelLibrary, getCorrectnessHarness, getPerfHarness,
-  getReferenceKernel,
+  getReferenceKernel, getKernelDiff,
 } from "app/ok-runtime-api";
 
 const withTimeout = (p, ms = 8000) =>
@@ -140,6 +140,101 @@ function HarnessStatus({ harness, label }) {
   return html`<span class="ok-harness-status fail">${label}: not generated</span>`;
 }
 
+// ---- Kernel source / diff inspector ----
+
+// Line-numbered source rendering: the raw string in a <pre> gives no way to
+// cite a line, so emit one <div> per line with a gutter number.
+function SourceLines({ code }) {
+  const lines = (code || "").split("\n");
+  return html`<div class="ok-source">
+    ${lines.map((ln, i) => html`
+      <div class="ok-source-row" key=${i}>
+        <span class="ok-source-num">${i + 1}</span>
+        <span class="ok-source-line">${ln}</span>
+      </div>
+    `)}
+  </div>`;
+}
+
+// Unified-diff rendering: classify each line by prefix so additions and
+// deletions stand out; hunk headers (@@) get their own muted styling.
+function DiffLines({ diff }) {
+  const lines = (diff || "").split("\n");
+  if (!lines.some((l) => l.length > 0)) {
+    return html`<div class="ok-diff empty muted">No differences.</div>`;
+  }
+  return html`<div class="ok-diff">
+    ${lines.map((ln, i) => {
+      let cls = "ok-diff-ctx";
+      if (ln.startsWith("+++") || ln.startsWith("---")) cls = "ok-diff-meta";
+      else if (ln.startsWith("@@")) cls = "ok-diff-hunk";
+      else if (ln.startsWith("+")) cls = "ok-diff-add";
+      else if (ln.startsWith("-")) cls = "ok-diff-del";
+      return html`<div class=${"ok-diff-row " + cls} key=${i}>${ln || " "}</div>`;
+    })}
+  </div>`;
+}
+
+const DIFF_MODES = [
+  { key: "source", label: "Source" },
+  { key: "reference", label: "Diff vs reference" },
+  { key: "parent", label: "Diff vs parent" },
+];
+
+function KernelInspector({ taskId, kernel, onClose }) {
+  const [mode, setMode] = useState("source");
+  const [diff, setDiff] = useState(null);
+  const [diffErr, setDiffErr] = useState(null);
+
+  useEffect(() => {
+    if (mode === "source" || !taskId || !kernel) return;
+    let cancelled = false;
+    setDiff(null);
+    setDiffErr(null);
+    withTimeout(getKernelDiff(taskId, kernel.id, mode))
+      .then((d) => { if (!cancelled) setDiff(d); })
+      .catch((e) => { if (!cancelled) setDiffErr(String(e.message || e)); });
+    return () => { cancelled = true; };
+  }, [taskId, kernel && kernel.id, mode]);
+
+  const code = kernel.code || kernel.code_preview || "";
+  const parentId = kernel.parent_id ? String(kernel.parent_id).slice(0, 8) : null;
+
+  return html`<section class="panel ok-panel-full">
+    <h2>Kernel: ${String(kernel.id).slice(0, 8)}…
+      <button class="btn btn-sm" style="float:right;" onClick=${onClose}>× close</button>
+    </h2>
+    <div class="ok-inspector-toolbar">
+      <div class="ok-inspector-modes">
+        ${DIFF_MODES.map((m) => html`
+          <button key=${m.key}
+            class=${"btn btn-sm" + (mode === m.key ? " active" : "")}
+            disabled=${m.key === "parent" && !parentId}
+            title=${m.key === "parent" && !parentId ? "kernel has no parent" : ""}
+            onClick=${() => setMode(m.key)}>${m.label}</button>
+        `)}
+      </div>
+      ${mode !== "source" && diff && diff.exists ? html`
+        <span class="ok-diff-stat">
+          <span class="ok-diff-stat-add">+${diff.added}</span>
+          <span class="ok-diff-stat-del">−${diff.removed}</span>
+          <span class="muted">vs ${diff.base_label}</span>
+        </span>
+      ` : null}
+    </div>
+
+    ${mode === "source"
+      ? html`<${SourceLines} code=${code} />`
+      : diffErr
+        ? html`<div class="ok-diff empty error">Failed to load diff: ${diffErr}</div>`
+        : !diff
+          ? html`<div class="ok-diff empty muted">Loading diff…</div>`
+          : !diff.exists
+            ? html`<div class="ok-diff empty muted">${diff.error || "No diff available."}</div>`
+            : html`<${DiffLines} diff=${diff.diff} />`}
+  </section>`;
+}
+
 // ---- Main view ----
 
 export default function OptKernelDetailView({
@@ -185,12 +280,10 @@ export default function OptKernelDetailView({
     </div>
 
     ${selectedKernel ? html`
-      <section class="panel ok-panel-full">
-        <h2>Kernel: ${selectedKernel.id.slice(0, 8)}…
-          <button class="btn btn-sm" style="float:right;" onClick=${() => setSelectedKernel(null)}>× close</button>
-        </h2>
-        <div class="ok-code-preview large">${selectedKernel.code || selectedKernel.code_preview || "Code not available"}</div>
-      </section>
+      <${KernelInspector}
+        taskId=${taskId}
+        kernel=${selectedKernel}
+        onClose=${() => setSelectedKernel(null)} />
     ` : null}
 
     <div class="ok-grid">

diff --git a/metainfer/tasks/evolve_kernel/static/ok-runtime-api.js b/metainfer/tasks/evolve_kernel/static/ok-runtime-api.js
@@ -51,6 +51,14 @@ export async function getReferenceKernel(taskId) {
   return res.json();
 }
 
+export async function getKernelDiff(taskId, kernelId, base = "reference") {
+  const res = await fetch(
+    `${BASE(taskId)}/kernels/${encodeURIComponent(kernelId)}/diff` +
+    `?base=${encodeURIComponent(base)}`);
+  if (!res.ok) throw new Error(`kernel diff: ${res.status}`);
+  return res.json();
+}
+
 export async function getRetrospective(taskId, n) {
   const res = await fetch(`${BASE(taskId)}/iterations/${n}/retrospective`);
   if (!res.ok) throw new Error(`retrospective ${n}: ${res.status}`);

diff --git a/metainfer/tasks/evolve_kernel/static/ok.css b/metainfer/tasks/evolve_kernel/static/ok.css
@@ -162,3 +162,107 @@
   color: var(--muted, #8b949e);
   margin-top: 0.25rem;
 }
+
+/* ---- Kernel source / diff inspector ---- */
+
+.ok-inspector-toolbar {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  gap: 0.75rem;
+  margin-bottom: 0.75rem;
+  flex-wrap: wrap;
+}
+
+.ok-inspector-modes {
+  display: flex;
+  gap: 0.4rem;
+}
+
+.ok-inspector-modes .btn.active {
+  background: var(--accent-bg, rgba(88, 166, 255, 0.15));
+  color: var(--accent, #58a6ff);
+  border-color: var(--accent, #58a6ff);
+}
+
+.ok-diff-stat {
+  display: inline-flex;
+  align-items: center;
+  gap: 0.4rem;
+  font-size: 0.8rem;
+  font-family: monospace;
+}
+
+.ok-diff-stat-add {
+  color: #3fb950;
+  font-weight: 600;
+}
+
+.ok-diff-stat-del {
+  color: #f85149;
+  font-weight: 600;
+}
+
+.ok-source,
+.ok-diff {
+  max-height: 600px;
+  overflow: auto;
+  background: var(--code-bg, #0d1117);
+  border: 1px solid var(--border-color, #30363d);
+  border-radius: 6px;
+  font-family: monospace;
+  font-size: 0.8rem;
+  line-height: 1.45;
+}
+
+.ok-diff.empty {
+  padding: 1rem;
+}
+
+.ok-diff.empty.error {
+  color: #f85149;
+}
+
+.ok-source-row,
+.ok-diff-row {
+  display: flex;
+  white-space: pre;
+}
+
+.ok-source-num {
+  flex: 0 0 auto;
+  width: 3.5rem;
+  padding: 0 0.6rem;
+  text-align: right;
+  color: var(--muted, #8b949e);
+  user-select: none;
+  border-right: 1px solid var(--border-color, #30363d);
+}
+
+.ok-source-line {
+  flex: 1 1 auto;
+  padding: 0 0.6rem;
+}
+
+.ok-diff-row {
+  padding: 0 0.75rem;
+}
+
+.ok-diff-add {
+  background: rgba(63, 185, 80, 0.15);
+  color: #3fb950;
+}
+
+.ok-diff-del {
+  background: rgba(248, 81, 73, 0.15);
+  color: #f85149;
+}
+
+.ok-diff-hunk {
+  color: var(--accent, #58a6ff);
+  background: var(--accent-bg, rgba(88, 166, 255, 0.08));
+}
+
+.ok-diff-meta {
+  color: var(--muted, #8b949e);
+}