diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4a1aa4a4..bee2869c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -45,6 +45,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - Prevents timeout errors in Firefox/WebKit caused by strict label matching
 
 ### Fixed
+- **TCP Monitor Creation**: Fixed misleading form UX that caused silent HTTP 500 errors when creating TCP monitors
+  - Corrected URL placeholder to show `host:port` format instead of the incorrect `tcp://host:port` prefix
+  - Added dynamic per-type placeholder and helper text (HTTP monitors show a full URL example; TCP monitors show `host:port`)
+  - Added client-side validation that blocks form submission when a scheme prefix (e.g. `tcp://`) is detected, with an inline error message
+  - Reordered form fields so the monitor type selector appears above the URL input, making the dynamic helper text immediately relevant
+  - i18n: Added 5 new translation keys across en, de, fr, es, and zh locales
 - **CI: Rate Limit Integration Tests**: Hardened test script reliability — login now validates HTTP status, Caddy admin API readiness gated on `/config/` poll, security config failures are fatal with full diagnostics, and poll interval increased to 5s
 - **CI: Rate Limit Integration Tests**: Removed stale GeoIP database SHA256 checksum from Dockerfile non-CI path (hash was perpetually stale due to weekly upstream updates)
 - **CI: Rate Limit Integration Tests**: Fixed Caddy admin API debug dump URL to use canonical trailing slash in workflow
diff --git a/docs/issues/pr5-tcp-monitor-ux-manual-test.md b/docs/issues/pr5-tcp-monitor-ux-manual-test.md
new file mode 100644
index 00000000..4422dd63
--- /dev/null
+++ b/docs/issues/pr5-tcp-monitor-ux-manual-test.md
@@ -0,0 +1,161 @@
+---
+title: "Manual Test Plan - PR-5 TCP Monitor UX Fix"
+labels:
+  - testing
+  - frontend
+  - bug
+priority: high
+---
+
+# Manual Test Plan - PR-5 TCP Monitor UX Fix
+
+## Scope
+
+PR-5 only.
+
+This plan covers manual verification of the five UX fixes applied to the TCP monitor creation form:
+
+1. Corrected URL placeholder (removed misleading `tcp://` prefix)
+2. Dynamic per-type placeholder (HTTP vs TCP)
+3. Per-type helper text below the URL input
+4. Client-side TCP scheme validation with inline error
+5. Form field reorder: type selector now appears before URL input
+
+Out of scope:
+- Backend monitor logic or storage
+- Any other monitor type beyond HTTP and TCP
+- Notification provider changes
+
+## Preconditions
+
+- [ ] Environment is running (Docker E2E or local dev).
+- [ ] Tester can access the Monitors page and open the Create Monitor modal.
+- [ ] Browser DevTools Network tab is available for TC-PR5-007.
+
+---
+
+## Track A — Smoke Tests (Existing HTTP Behaviour)
+
+### TC-PR5-001 HTTP monitor creation still works
+
+- [ ] Open the Create Monitor modal.
+- [ ] Select type **HTTP**.
+- [ ] Enter a valid URL: `https://example.com`.
+- [ ] Fill in remaining required fields and click **Create**.
+- Expected result: monitor is created successfully; no errors shown.
+- Status: [ ] Not run [ ] Pass [ ] Fail
+- Notes:
+
+### TC-PR5-009 Existing HTTP monitors display correctly in the list
+
+- [ ] Navigate to the Monitors list.
+- [ ] Confirm any pre-existing HTTP monitors are still shown with correct URLs.
+- Expected result: no regressions in list display.
+- Status: [ ] Not run [ ] Pass [ ] Fail
+- Notes:
+
+### TC-PR5-010 Existing TCP monitors display correctly in the list
+
+- [ ] Navigate to the Monitors list.
+- [ ] Confirm any pre-existing TCP monitors are still shown with correct host:port values.
+- Expected result: no regressions in list display.
+- Status: [ ] Not run [ ] Pass [ ] Fail
+- Notes:
+
+---
+
+## Track B — Core Fix (TCP Scheme Validation)
+
+### TC-PR5-002 TCP monitor with `tcp://` prefix shows inline error and blocks submission
+
+- [ ] Open the Create Monitor modal.
+- [ ] Select type **TCP**.
+- [ ] Enter URL: `tcp://192.168.1.1:8080`.
+- [ ] Click **Create** (or attempt to submit).
+- Expected result: an inline error appears on the URL field; the form is not submitted; no new monitor appears in the list.
+- Status: [ ] Not run [ ] Pass [ ] Fail
+- Notes:
+
+### TC-PR5-003 TCP monitor with valid `host:port` format succeeds
+
+- [ ] Open the Create Monitor modal.
+- [ ] Select type **TCP**.
+- [ ] Enter URL: `192.168.1.1:8080`.
+- [ ] Fill in remaining required fields and click **Create**.
+- Expected result: monitor is created successfully; no errors shown.
+- Status: [ ] Not run [ ] Pass [ ] Fail
+- Notes:
+
+---
+
+## Track C — Dynamic Placeholder & Helper Text
+
+### TC-PR5-005 Form field order: Type selector appears above URL input
+
+- [ ] Open the Create Monitor modal.
+- [ ] Inspect the visual layout of the form.
+- Expected result: the monitor **Type** selector is positioned above the **URL** input field.
+- Status: [ ] Not run [ ] Pass [ ] Fail
+- Notes:
+
+### TC-PR5-006 Helper text updates when switching between HTTP and TCP
+
+- [ ] Open the Create Monitor modal.
+- [ ] Select type **HTTP** and note the helper text shown beneath the URL input.
+- [ ] Switch type to **TCP** and note the helper text again.
+- Expected result: helper text differs between HTTP and TCP types, giving format guidance appropriate to each.
+- Status: [ ] Not run [ ] Pass [ ] Fail
+- Notes:
+
+### TC-PR5-006b Placeholder updates when switching between HTTP and TCP
+
+- [ ] Open the Create Monitor modal.
+- [ ] Select type **HTTP** and note the URL input placeholder.
+- [ ] Switch type to **TCP** and note the placeholder again.
+- Expected result: HTTP placeholder shows a full URL (e.g. `https://example.com`); TCP placeholder shows `host:port` format (no scheme).
+- Status: [ ] Not run [ ] Pass [ ] Fail
+- Notes:
+
+---
+
+## Track D — Interaction Edge Cases
+
+### TC-PR5-004 Switching type from TCP (with error) to HTTP clears the inline error
+
+- [ ] Open the Create Monitor modal.
+- [ ] Select type **TCP** and enter `tcp://192.168.1.1:8080` to trigger the inline error.
+- [ ] Switch type to **HTTP**.
+- Expected result: the scheme-prefix inline error disappears immediately after the type change.
+- Status: [ ] Not run [ ] Pass [ ] Fail
+- Notes:
+
+### TC-PR5-007 Submit guard: no API call fires when scheme prefix error is present
+
+- [ ] Open browser DevTools and go to the **Network** tab.
+- [ ] Open the Create Monitor modal.
+- [ ] Select type **TCP** and enter `tcp://192.168.1.1:8080`.
+- [ ] Click **Create**.
+- Expected result: the inline error is shown and no outbound POST/PUT request to the monitors API endpoint appears in the Network tab.
+- Status: [ ] Not run [ ] Pass [ ] Fail
+- Notes:
+
+---
+
+## Track E — Localisation (Optional)
+
+### TC-PR5-008 New translation keys appear correctly in non-English locales
+
+- [ ] Switch the application language to **German**, **French**, **Spanish**, or **Chinese**.
+- [ ] Open the Create Monitor modal and select type **TCP**.
+- [ ] Observe the URL placeholder, helper text, and inline error message (trigger it with `tcp://host:port`).
+- Expected result: all three UI strings appear in the selected language without showing raw translation key strings (e.g. no `urlPlaceholder.tcp` visible to the user).
+- Status: [ ] Not run [ ] Pass [ ] Fail
+- Notes:
+
+---
+
+## Sign-off
+
+| Tester | Date | Environment | Result |
+|--------|------|-------------|--------|
+|        |      |             |        |
diff --git a/frontend/package-lock.json b/frontend/package-lock.json
index 1f5e9062..7c137fc6 100644
--- a/frontend/package-lock.json
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diff --git a/package-lock.json b/package-lock.json
index dda2e129..681a0a62 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -3589,9 +3589,9 @@
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