diff --git a/dashboard/observablehq.config.js b/dashboard/observablehq.config.js
index e30abbe..9fdcfb2 100644
--- a/dashboard/observablehq.config.js
+++ b/dashboard/observablehq.config.js
@@ -10,7 +10,9 @@ const _configDir = dirname(fileURLToPath(import.meta.url));
 const _modalScript = readFileSync(
   join(_configDir, "src/components/improvement-modal.js"), "utf-8"
 )
-  .replace(/^export function /gm, "function ")   // strip ES module export
+  // Strip ES module exports so the file can run as a plain <script>.
+  .replace(/^export function /gm, "function ")
+  .replace(/^export const /gm, "const ")
   + "\ninitImprovementModal();\n";               // auto-initialise
 
 export default {
diff --git a/dashboard/src/components/improvement-modal.js b/dashboard/src/components/improvement-modal.js
index c2cdb51..133bc00 100644
--- a/dashboard/src/components/improvement-modal.js
+++ b/dashboard/src/components/improvement-modal.js
@@ -12,10 +12,59 @@
  * Submissions are stored as technical-debt items with debt_type="dashboard-improvement".
  *
  * Interaction:
- *   - Hold Shift → cursor changes to crosshair across the entire page
+ *   - Hold Shift 1s → cursor changes to copy/highlight mode (shift-wait-click)
  *   - Shift+click any element (except form controls) → opens suggestion modal
  */
 
+/** Domain slug for dashboard-improvement TD records (state-hub lives under infotech). */
+export const DEFAULT_IMPROVEMENT_DOMAIN = "infotech";
+const DEFAULT_API = "http://127.0.0.1:8000";
+const API_STORAGE_KEY = "stateHubApiBase";
+
+/**
+ * Resolve API base when init is called without an explicit apiBase.
+ * Mirrors dashboard/src/components/config.js so the modal works when the
+ * dashboard is not on 127.0.0.1 (remote host, tunnel, storage override).
+ */
+export function resolveImprovementApiBase({
+  location = globalThis.location,
+  storage = globalThis.localStorage,
+} = {}) {
+  const clean = (value) => {
+    if (typeof value !== "string") return null;
+    const cleaned = value.trim().replace(/\/+$/, "");
+    return cleaned || null;
+  };
+  try {
+    if (location?.href) {
+      const url = new URL(location.href);
+      for (const name of ["api_base", "apiBase"]) {
+        const q = clean(url.searchParams.get(name));
+        if (q) return q;
+      }
+    }
+  } catch { /* ignore */ }
+  const fromGlobal = clean(globalThis.STATE_HUB_API_BASE);
+  if (fromGlobal) return fromGlobal;
+  try {
+    const fromStorage = clean(storage?.getItem?.(API_STORAGE_KEY));
+    if (fromStorage) return fromStorage;
+  } catch { /* ignore */ }
+  try {
+    if (location?.href) {
+      const url = new URL(location.href);
+      if (!["http:", "https:"].includes(url.protocol)) return DEFAULT_API;
+      if (url.hostname === "::1" || url.hostname === "[::1]") return DEFAULT_API;
+      url.port = globalThis.STATE_HUB_API_PORT || "8000";
+      url.pathname = "";
+      url.search = "";
+      url.hash = "";
+      return url.origin;
+    }
+  } catch { /* ignore */ }
+  return DEFAULT_API;
+}
+
 const _STYLE_ID = "improvement-modal-styles";
 
 function _ensureStyles() {
@@ -239,10 +288,13 @@ let _initialized = false;
  * Safe to call multiple times — only the first call takes effect.
  *
  * @param {object} opts
- * @param {string} opts.apiBase  State Hub API base URL (default: "http://127.0.0.1:8000")
- * @param {string} opts.domain   Domain slug for the TD record  (default: "custodian")
+ * @param {string} [opts.apiBase]  State Hub API base URL (resolved like config.js if omitted)
+ * @param {string} [opts.domain]   Domain slug for the TD record (default: "infotech")
  */
-export function initImprovementModal({ apiBase = "http://127.0.0.1:8000", domain = "custodian" } = {}) {
+export function initImprovementModal({
+  apiBase = resolveImprovementApiBase(),
+  domain = DEFAULT_IMPROVEMENT_DOMAIN,
+} = {}) {
   if (_initialized) return;
   _initialized = true;
   _ensureStyles();
@@ -391,7 +443,10 @@ export function initImprovementModal({ apiBase = "http://127.0.0.1:8000", domain
       try {
         const r = await fetch(`${apiBase}/technical-debt/`, {
           method: "POST",
-          headers: { "Content-Type": "application/json" },
+          headers: {
+            "Content-Type": "application/json",
+            "X-StateHub-Component": "state-hub.dashboard.improvement-modal",
+          },
           body: JSON.stringify(payload),
         });
         if (r.ok) {
@@ -400,7 +455,13 @@ export function initImprovementModal({ apiBase = "http://127.0.0.1:8000", domain
         } else {
           submitBtn.disabled = false;
           submitBtn.textContent = "Submit suggestion";
-          _toast(`⚠ Submission failed (HTTP ${r.status})`);
+          let detail = `HTTP ${r.status}`;
+          try {
+            const body = await r.json();
+            if (typeof body?.detail === "string") detail = body.detail;
+            else if (body?.detail != null) detail = JSON.stringify(body.detail);
+          } catch { /* keep status-only detail */ }
+          _toast(`⚠ Submission failed (${detail})`);
         }
       } catch {
         submitBtn.disabled = false;
diff --git a/dashboard/test/improvement-modal.test.mjs b/dashboard/test/improvement-modal.test.mjs
new file mode 100644
index 0000000..8fe6019
--- /dev/null
+++ b/dashboard/test/improvement-modal.test.mjs
@@ -0,0 +1,46 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import {readFileSync} from "node:fs";
+import {dirname, join} from "node:path";
+import {fileURLToPath} from "node:url";
+
+import {
+  DEFAULT_IMPROVEMENT_DOMAIN,
+  resolveImprovementApiBase,
+} from "../src/components/improvement-modal.js";
+
+const root = dirname(fileURLToPath(import.meta.url));
+const modalSource = readFileSync(
+  join(root, "../src/components/improvement-modal.js"),
+  "utf-8",
+);
+
+test("dashboard-improvement default domain is the live infotech slug", () => {
+  assert.equal(DEFAULT_IMPROVEMENT_DOMAIN, "infotech");
+  // Regression: custodian was retired from the domain registry; POST /technical-debt/
+  // returns 422 for unknown domain, so the shift-wait-click modal must not use it.
+  assert.doesNotMatch(modalSource, /domain\s*=\s*["']custodian["']/);
+  assert.match(modalSource, /domain\s*=\s*DEFAULT_IMPROVEMENT_DOMAIN/);
+  assert.match(modalSource, /debt_type:\s*["']dashboard-improvement["']/);
+});
+
+test("improvement modal api base mirrors dashboard config resolution", () => {
+  assert.equal(
+    resolveImprovementApiBase({location: null, storage: null}),
+    "http://127.0.0.1:8000",
+  );
+  assert.equal(
+    resolveImprovementApiBase({
+      location: new URL("http://localhost:3000/workstreams"),
+      storage: null,
+    }),
+    "http://localhost:8000",
+  );
+  assert.equal(
+    resolveImprovementApiBase({
+      location: new URL("http://localhost:3000/?api_base=http%3A%2F%2F127.0.0.1%3A18000%2F"),
+      storage: {getItem: () => "http://ignored.example:8000"},
+    }),
+    "http://127.0.0.1:18000",
+  );
+});