diff --git a/src/client/components/browser.tsx b/src/client/components/browser.tsx
index 68c1459..1700153 100644
--- a/src/client/components/browser.tsx
+++ b/src/client/components/browser.tsx
@@ -896,8 +896,7 @@ export function makeContextBrowser(
         </div>
 
         {/* The block map sits in the card's fixed zone, right under the head: the rows region below is the
-            only scroller, so the map never rides a scroll, whether it is shown or not. The squarified panel
-            re-measures whatever box the cap leaves it, folding in height under pane pressure (browser.css). */}
+            only scroller, and the map keeps the height it opens at (browser.css). */}
         {mapOn
           ? (
             <BrowserTreemap
diff --git a/src/client/styles/browser.css b/src/client/styles/browser.css
index 5ce96da..c532171 100644
--- a/src/client/styles/browser.css
+++ b/src/client/styles/browser.css
@@ -21,10 +21,12 @@
 .lc-br-map-btn:hover { color: var(--dsw-alias-label-primary); border-color: var(--dsw-alias-border-l1); }
 .lc-br-map-btn-on, .lc-br-map-btn-on:hover { color: var(--dsw-alias-brand-primary); border-color: var(--dsw-alias-brand-primary); background: color-mix(in srgb, var(--dsw-alias-brand-primary) 10%, transparent); }
 
-/* The block map: a measured squarified treemap (browserTreemap.tsx) in the card's fixed zone, reflowing to
-   whatever box the cap leaves it — under pane pressure it folds in height down to its floor, so the rows
-   region below keeps a readable slice. */
-.lc-br > .lc-map { flex: 0 1 auto; min-height: 40px; }
+/* The block map: a measured squarified treemap (browserTreemap.tsx) in the card's fixed zone. It keeps the
+   height it opens at: opened rows scroll the rows region below instead of squeezing the map, whose own flex
+   base no longer follows the content. The percentage ceiling folds it only when a capped card is genuinely
+   too short — it also leaves room for the head, the map's margin and the rows region's floor — and a
+   content-sized card ignores the percentage. */
+.lc-br > .lc-map { flex: none; min-height: 40px; max-height: calc(100% - 140px); }
 .lc-map { position: relative; height: 240px; margin-top: 8px; }
 /* Narrow panes stack taller so regions stay legible instead of crushing into slivers. */
 @container lc-card (max-width: 560px) { .lc-map { height: 320px; } }
diff --git a/src/client/styles/modal.css b/src/client/styles/modal.css
index c7cf69b..091ab57 100644
--- a/src/client/styles/modal.css
+++ b/src/client/styles/modal.css
@@ -1,7 +1,7 @@
 /* Fixed positioning escapes the composer anchor; the card's percentage width resolves against the backdrop, so a docked mask clamps it inside the main column. */
 .lc-modal-backdrop { position: fixed; inset: 0; z-index: 200; background: var(--dsw-alias-bg-mask-1, rgba(0, 0, 0, 0.45)); display: flex; align-items: center; justify-content: center; }
 /* Side margins keep 2/3 of the old fixed-720px cap's (pane/3 + 480 ⇒ margin = pane/3 − 240); the 32px floor is the old 24px gutter cut to 16. */
-.lc-modal-card { width: min(calc(33.333% + 480px), calc(100% - 32px)); max-height: min(82vh, 760px); overflow-y: auto; box-sizing: border-box; background: var(--dsw-alias-bg-layer-1); border: 1px solid var(--dsw-alias-border-l2); border-radius: 12px; box-shadow: var(--dsw-shadow-lv3, 0 12px 32px rgba(0, 0, 0, 0.4)); padding: 16px 18px 18px; color: var(--dsw-alias-label-primary); font-size: 13px; }
+.lc-modal-card { width: min(calc(33.333% + 480px), calc(100% - 32px)); --lc-modal-h: min(82vh, 760px); max-height: var(--lc-modal-h); overflow-y: auto; box-sizing: border-box; background: var(--dsw-alias-bg-layer-1); border: 1px solid var(--dsw-alias-border-l2); border-radius: 12px; box-shadow: var(--dsw-shadow-lv3, 0 12px 32px rgba(0, 0, 0, 0.4)); padding: 16px 18px 18px; color: var(--dsw-alias-label-primary); font-size: 13px; }
 .lc-modal-head { display: flex; align-items: baseline; gap: 8px; margin-bottom: 12px; }
 .lc-modal-title { font-weight: 600; font-size: 14px; }
 .lc-modal-close { margin-left: auto; border: 0; background: transparent; color: var(--dsw-alias-label-secondary); font-size: 18px; line-height: 1; padding: 2px 6px; border-radius: 6px; cursor: pointer; font-family: inherit; transition: color var(--ds-transition-duration, 0.2s) var(--ds-ease-in-out, ease-in-out), background-color var(--ds-transition-duration, 0.2s) var(--ds-ease-in-out, ease-in-out); }
@@ -14,6 +14,13 @@
 .lc-modal-body { flex: 1 1 auto; min-height: 0; display: flex; flex-direction: column; }
 .lc-modal-body > * { flex: none; }
 .lc-modal-body > .lc-br { flex: 0 1 auto; }
+/* While the map is shown, fill the dialog's viewport cap and give the body's leftover to the browser card
+   and its rows region: opened rows never squeeze the map, and the map folds exactly to the remaining height,
+   which the fixed head reserve of browser.css's ceiling cannot track. */
+.lc-modal-fill:has(.lc-map) { height: var(--lc-modal-h); }
+.lc-modal-fill:has(.lc-map) .lc-modal-body > .lc-br { flex: 1 1 0; }
+.lc-modal-fill:has(.lc-map) .lc-br-scroll { flex: 1 1 0; }
+.lc-modal-fill:has(.lc-map) .lc-map { flex: 0 1 auto; max-height: none; }
 
 /* ---- the baseline-gate dialog (upgradeGate.tsx) ---- */
 .lc-gate-card { width: min(440px, calc(100vw - 48px)); }