diff --git a/tests/test_calibration_has_its_own_pane.py b/tests/test_calibration_has_its_own_pane.py
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+"""Calibration is a step in the workflow, so it is a pane in the workflow.
+
+#108. Calibrate used to be a button in the SPIM head's status bar, and its
+result appeared in a different tab entirely. Ryan, 25:30 on the 2026-08-07
+walkthrough: "after setting up the bottom camera and SPIM head, I feel like
+I'm not quite sure what to do in gently at this point." There was no next step
+on screen, because the next step was a button in the corner of the step before.
+
+His own description of the order is the pane order: "you find the embryos on
+the bottom camera, you find them with the SPIM head, you calibrate it, and then
+you set up your acquisition parameters."
+"""
+
+from __future__ import annotations
+
+import re
+from pathlib import Path
+
+ROOT = Path(__file__).resolve().parents[1]
+OPERATE = ROOT / "gently" / "ui" / "web" / "static" / "js" / "operate.js"
+INDEX = ROOT / "gently" / "ui" / "web" / "templates" / "index.html"
+
+
+def test_the_pane_order_is_the_workflow_order() -> None:
+ src = OPERATE.read_text(encoding="utf-8")
+ m = re.search(r"const PANE_ORDER = \[([^\]]+)\]", src)
+ assert m, "PANE_ORDER is gone — the pane list is spelled out in two places again"
+ order = [p.strip().strip("'\"") for p in m.group(1).split(",")]
+ assert order == ["bottom", "spim", "cal", "acquire"], order
+
+
+def test_one_pane_list_not_two() -> None:
+ """It used to be written out in showPane and again in showPaneInitial."""
+ src = OPERATE.read_text(encoding="utf-8")
+ assert "['bottom', 'spim', 'acquire']" not in src
+ assert src.count("PANE_ORDER.forEach") >= 2, (
+ "a caller stopped using PANE_ORDER — adding a pane now means remembering two places again"
+ )
+
+
+def test_the_subtab_sits_between_spim_and_acquisition() -> None:
+ html = INDEX.read_text(encoding="utf-8")
+ views = re.findall(r'#?operate|data-view="(bottom|spim|cal|acquire)"', html)
+ seen = [v for v in views if v]
+ # first occurrence of each, which is the switcher
+ order: list[str] = []
+ for v in seen:
+ if v not in order:
+ order.append(v)
+ assert order[:4] == ["bottom", "spim", "cal", "acquire"], order
+
+
+def test_calibrate_left_the_spim_bar() -> None:
+ """Its result appeared in another tab; the control belonged with the result."""
+ html = INDEX.read_text(encoding="utf-8")
+ spim = html[html.index('id="op-pane-spim"') : html.index('id="op-pane-cal"')]
+ assert 'id="op-calibrate"' not in spim, "Calibrate is back in the SPIM head bar"
+ cal = html[html.index('id="op-pane-cal"') : html.index('id="op-pane-acquire"')]
+ assert 'id="op-calibrate"' in cal
+ assert 'id="op-cal-result"' in cal, "the fit readout should sit with the button"
+
+
+def test_the_pane_declares_its_method_before_running_it() -> None:
+ """Kesavan on the walkthrough: "it should show what is the method it is
+ going to use to calibrate". One method on this rig, so it is named rather
+ than offered as a choice."""
+ html = INDEX.read_text(encoding="utf-8")
+ cal = html[html.index('id="op-pane-cal"') : html.index('id="op-pane-acquire"')]
+ assert 'id="op-cal-method"' in cal
+ # The LED-not-laser confusion is the thing #106 turned on; say it here.
+ assert "laser" in cal.lower()
+
+
+def test_leaving_the_pane_closes_the_led() -> None:
+ """The calibrate path never did, which is half of #106."""
+ src = OPERATE.read_text(encoding="utf-8")
+ block = src[src.index(" cal: {") :]
+ block = block[: block.index("\n }")]
+ assert "forceLedOff()" in block
+
+
+def test_the_rail_shows_which_embryos_lack_a_fit() -> None:
+ """So a refusal at Start is visible beforehand, from any pane."""
+ src = OPERATE.read_text(encoding="utf-8")
+ assert "showFit: true" in src
+ panel = (ROOT / "gently" / "ui" / "web" / "static" / "js" / "panels" / "roster.js").read_text(
+ encoding="utf-8"
+ )
+ # Same field the server-side gate checks.
+ assert "slope_um_per_deg" in panel