diff --git a/crates/ui-egui/tests/panel_snapshots.rs b/crates/ui-egui/tests/panel_snapshots.rs
new file mode 100644
index 000000000..652a670a3
--- /dev/null
+++ b/crates/ui-egui/tests/panel_snapshots.rs
@@ -0,0 +1,257 @@
+//! Snapshot tests of every side panel (M3): each panel opens on one synthetic document and its
+//! AccessKit tree (the roles, labels, values and states a screen reader gets) is compared with a
+//! text file in `tests/snapshots/`. Text rather than pixels: with the reported OS pinned (shortcut
+//! labels follow it) it is the same on every platform and GPU, it is not an asset (AGENTS.md §1),
+//! and a reviewer can read a change in the diff. Positions are left out, so moving a widget is not
+//! a change but adding, removing or renaming one is.
+//!
+//! `UPDATE_SNAPSHOTS=1 cargo test -p pdfcraft-ui-egui --test panel_snapshots` rewrites the files.
+
+use egui::accesskit::{Role, Toggled};
+use egui_kittest::kittest::{NodeT, Queryable};
+use egui_kittest::{Harness, Node};
+use pdfcraft_engine::Session;
+use pdfcraft_ui_egui::{PdfCraftApp, RightPanel};
+
+mod support;
+
+/// Two pages with something for every panel: bookmarks, a layer, an attachment, a text field, an
+/// unsigned signature field, a comment and a structure tree.
+fn fixture() -> Vec<u8> {
+    let page1 = "/P << /MCID 0 >> BDC BT /F1 18 Tf 72 720 Td (Panel sample) Tj ET EMC\n\
+                 /OC /L1 BDC BT /F1 10 Tf 72 690 Td (Draft notes) Tj ET EMC\n";
+    let page2 = "BT /F1 12 Tf 72 720 Td (Second page sample text) Tj ET\n";
+    let objs: Vec<String> = vec![
+        // 1 catalog
+        "<< /Type /Catalog /Pages 2 0 R /Outlines 6 0 R /OCProperties << /OCGs [9 0 R] /D << /ON [9 0 R] /Order [9 0 R] >> >> \
+         /Names << /EmbeddedFiles << /Names [(notes.txt) 11 0 R] >> >> /AcroForm << /Fields [12 0 R 13 0 R] >> \
+         /MarkInfo << /Marked true >> /StructTreeRoot 15 0 R >>"
+            .into(),
+        // 2 page tree, 3 and 4 its pages
+        "<< /Type /Pages /Kids [3 0 R 4 0 R] /Count 2 /MediaBox [0 0 612 792] >>".into(),
+        "<< /Type /Page /Parent 2 0 R /Contents 17 0 R /StructParents 0 /Resources << /Font << /F1 5 0 R >> /Properties << /L1 9 0 R >> >> \
+         /Annots [12 0 R 13 0 R 14 0 R] >>"
+            .into(),
+        "<< /Type /Page /Parent 2 0 R /Contents 18 0 R /Resources << /Font << /F1 5 0 R >> >> >>".into(),
+        // 5 font
+        "<< /Type /Font /Subtype /Type1 /BaseFont /Helvetica >>".into(),
+        // 6 outline, 7 and 8 its items
+        "<< /Type /Outlines /First 7 0 R /Last 8 0 R /Count 2 >>".into(),
+        "<< /Title (Introduction) /Parent 6 0 R /Next 8 0 R /Dest [3 0 R /Fit] >>".into(),
+        "<< /Title (Details) /Parent 6 0 R /Prev 7 0 R /Dest [4 0 R /Fit] >>".into(),
+        // 9 layer
+        "<< /Type /OCG /Name (Draft notes) >>".into(),
+        // 10 embedded file, 11 its file specification
+        "<< /Type /EmbeddedFile /Length 5 >>\nstream\nhello\nendstream".into(),
+        "<< /Type /Filespec /F (notes.txt) /UF (notes.txt) /EF << /F 10 0 R >> >>".into(),
+        // 12 text field, 13 signature field, 14 comment
+        "<< /Type /Annot /Subtype /Widget /FT /Tx /T (Name) /Rect [72 600 272 624] /P 3 0 R /F 4 >>".into(),
+        "<< /Type /Annot /Subtype /Widget /FT /Sig /T (Approval) /Rect [72 520 272 560] /P 3 0 R /F 4 >>".into(),
+        "<< /Type /Annot /Subtype /Text /Rect [400 700 420 720] /P 3 0 R /T (Reviewer) /Contents (Check this heading) \
+         /M (D:20260101120000Z) /CreationDate (D:20260101120000Z) >>"
+            .into(),
+        // 15 structure tree root, 16 its paragraph
+        "<< /Type /StructTreeRoot /K [16 0 R] /ParentTree << /Nums [0 [16 0 R]] >> >>".into(),
+        "<< /S /P /P 15 0 R /Pg 3 0 R /K 0 >>".into(),
+        // 17 and 18 page contents
+        format!("<< /Length {} >>\nstream\n{page1}endstream", page1.len()),
+        format!("<< /Length {} >>\nstream\n{page2}endstream", page2.len()),
+    ];
+    let mut out = b"%PDF-1.7\n".to_vec();
+    let mut offs = Vec::new();
+    for (i, o) in objs.iter().enumerate() {
+        offs.push(out.len());
+        out.extend_from_slice(format!("{} 0 obj\n{o}\nendobj\n", i + 1).as_bytes());
+    }
+    let x = out.len();
+    out.extend_from_slice(format!("xref\n0 {}\n0000000000 65535 f \n", objs.len() + 1).as_bytes());
+    for o in offs {
+        out.extend_from_slice(format!("{o:010} 00000 n \n").as_bytes());
+    }
+    out.extend_from_slice(format!("trailer\n<< /Size {} /Root 1 0 R >>\nstartxref\n{x}\n%%EOF\n", objs.len() + 1).as_bytes());
+    out
+}
+
+fn harness(panel: &'static str) -> Harness<'static, PdfCraftApp> {
+    let bytes = fixture();
+    // Shortcut labels follow the reported OS ("Ctrl+B" against "⌘B"), so pin it rather than rely
+    // on kittest's default; the snapshots then match on every host.
+    let mut h = Harness::builder().with_size(egui::vec2(1400.0, 900.0)).with_os(egui::os::OperatingSystem::Nix).build_eframe(move |_cc| {
+        let mut app = PdfCraftApp::new();
+        app.set_option("language", "en").unwrap();
+        app.open_bytes("panels.pdf", None, bytes).expect("opens");
+        app.set_option("panel", panel).unwrap();
+        app
+    });
+    h.run_steps(6);
+    h
+}
+
+/// The side panel's contents: the dock node after the Inspector tab.
+fn panel<'h>(h: &'h Harness<'static, PdfCraftApp>) -> Node<'h> {
+    let tab = h.get_by(|n| n.role() == Role::Tab && n.label().as_deref() == Some("Inspector"));
+    let dock = tab.parent().expect("the Inspector tab sits in a dock node");
+    let mut after = dock.children().skip_while(|n| n.accesskit_node().id() != tab.accesskit_node().id()).skip(1);
+    after.next().expect("the panel follows its tab")
+}
+
+/// One line per node that says something: layout containers are skipped (their children move up a
+/// level) and text runs repeat their label.
+fn describe(node: &Node<'_>, depth: usize, out: &mut String) {
+    let n = node.accesskit_node();
+    let quiet = n.role() == Role::GenericContainer && n.label().is_none() && n.value().is_none();
+    let next = if quiet || n.role() == Role::TextRun {
+        depth
+    } else {
+        let mut line = format!("{:indent$}{:?}", "", n.role(), indent = depth * 2);
+        if let Some(l) = n.label() {
+            line.push_str(&format!(" {l:?}"));
+        }
+        if let Some(v) = n.value().filter(|v| !v.is_empty() && Some(v) != n.label().as_ref()) {
+            line.push_str(&format!(" = {v:?}"));
+        }
+        match n.toggled() {
+            Some(Toggled::True) => line.push_str(" [on]"),
+            Some(Toggled::False) => line.push_str(" [off]"),
+            Some(Toggled::Mixed) => line.push_str(" [mixed]"),
+            None => {}
+        }
+        if n.is_selected() == Some(true) {
+            line.push_str(" [selected]");
+        }
+        if n.is_disabled() {
+            line.push_str(" [disabled]");
+        }
+        out.push_str(&line);
+        out.push('\n');
+        depth + 1
+    };
+    if n.role() == Role::TextRun {
+        return;
+    }
+    for c in node.children() {
+        describe(&c, next, out);
+    }
+}
+
+/// Compares the panel with `tests/snapshots/panel_<name>.txt`, or writes it with `UPDATE_SNAPSHOTS`.
+fn check(h: &Harness<'static, PdfCraftApp>, name: &str) -> Result<(), String> {
+    let mut got = String::new();
+    describe(&panel(h), 0, &mut got);
+    let path = std::path::Path::new(env!("CARGO_MANIFEST_DIR")).join("tests/snapshots").join(format!("panel_{name}.txt"));
+    if std::env::var_os("UPDATE_SNAPSHOTS").is_some() {
+        std::fs::create_dir_all(path.parent().unwrap()).unwrap();
+        std::fs::write(&path, &got).unwrap();
+        return Ok(());
+    }
+    match std::fs::read_to_string(&path) {
+        Ok(want) if want == got => Ok(()),
+        Ok(want) => Err(format!(
+            "{name} panel differs from {}
+--- want
+{want}
+--- got
+{got}",
+            path.display()
+        )),
+        Err(e) => Err(format!(
+            "{}: {e}
+--- got
+{got}",
+            path.display()
+        )),
+    }
+}
+
+/// Every panel, in the order of the rail.
+const ALL: [RightPanel; 11] = [
+    RightPanel::Comments,
+    RightPanel::Bookmarks,
+    RightPanel::Pages,
+    RightPanel::Fields,
+    RightPanel::Layers,
+    RightPanel::Attachments,
+    RightPanel::Signatures,
+    RightPanel::Accessibility,
+    RightPanel::Tags,
+    RightPanel::Search,
+    RightPanel::Compare,
+];
+
+/// Opens `p` with something in it and names its snapshot. No wildcard on purpose: a new
+/// `RightPanel` stops this file compiling until it is set up here (and listed in [`ALL`]).
+fn open(p: RightPanel) -> (Harness<'static, PdfCraftApp>, &'static str) {
+    let name = match p {
+        RightPanel::Comments => "comments",
+        RightPanel::Bookmarks => "bookmarks",
+        RightPanel::Pages => "pages",
+        RightPanel::Fields => "fields",
+        RightPanel::Layers => "layers",
+        RightPanel::Attachments => "attachments",
+        RightPanel::Signatures => "signatures",
+        RightPanel::Tags => "tags",
+        RightPanel::Accessibility => {
+            let mut h = harness("none");
+            assert!(h.state_mut().execute("a11y.check"));
+            h.run_steps(2);
+            h.get_by_label("Start Checking").click();
+            h.run_steps(3);
+            return (h, "accessibility");
+        }
+        RightPanel::Search => {
+            let mut h = harness("none");
+            assert!(h.state_mut().execute("edit.advanced_search"));
+            h.run_steps(2);
+            h.state_mut().views[0].find.as_mut().expect("Advanced Search opens a search").query = "sample".into();
+            support::wait_until(&mut h, "both pages searched", |app| app.views[0].find.as_ref().is_some_and(|f| f.matches.len() == 2));
+            h.run_steps(2);
+            return (h, "search");
+        }
+        RightPanel::Compare => {
+            let s = Session::new();
+            let old = s.create_from_text("t", "Delivery within five days. Returns accepted.").unwrap().to_vec();
+            let new = s.create_from_text("t", "Delivery within three days. Returns accepted for a week.").unwrap().to_vec();
+            let mut h = Harness::builder().with_size(egui::vec2(1400.0, 900.0)).build_eframe(move |_cc| {
+                let mut app = PdfCraftApp::new();
+                app.set_option("language", "en").unwrap();
+                app.open_bytes("old.pdf", None, old.clone()).unwrap();
+                app.open_bytes("new.pdf", None, new.clone()).unwrap();
+                app
+            });
+            h.run_steps(4);
+            assert!(h.state_mut().execute("doc.compare"));
+            h.run_steps(2);
+            h.get_by_label("Compare").click();
+            h.run_steps(3);
+            return (h, "compare");
+        }
+    };
+    (harness(name), name)
+}
+
+/// Every panel matches its snapshot. All of them are checked before failing, so one run shows
+/// every panel a change touched.
+#[test]
+fn every_panel_matches_its_snapshot() {
+    let mut failures = Vec::new();
+    for p in ALL {
+        let (h, name) = open(p);
+        assert_eq!(h.state().right, Some(p), "{name} opens its own panel");
+        if let Err(e) = check(&h, name) {
+            failures.push(e);
+        }
+    }
+    assert!(
+        failures.is_empty(),
+        "{} of {} panels differ (UPDATE_SNAPSHOTS=1 rewrites them)
+
+{}",
+        failures.len(),
+        ALL.len(),
+        failures.join(
+            "
+
+"
+        )
+    );
+}
diff --git a/crates/ui-egui/tests/snapshots/panel_accessibility.txt b/crates/ui-egui/tests/snapshots/panel_accessibility.txt
new file mode 100644
index 000000000..33d04008d
--- /dev/null
+++ b/crates/ui-egui/tests/snapshots/panel_accessibility.txt
@@ -0,0 +1,85 @@
+Label = "Accessibility Checker"
+Button "Close" [off]
+Label = "7 issues"
+Button "Check again"
+Button "Report"
+Label = "Needs manual check: 5"
+Button "Collapse" [off]
+Label = "Document (2 issues)"
+Image
+Label = "Accessibility permission flag - Passed"
+Image
+Label = "Image-only PDF - Passed"
+Image
+Label = "Tagged PDF - Passed"
+Image
+Label = "Logical Reading Order - Needs manual check"
+Image
+Label = "Primary language - Failed"
+Image
+Label = "Title - Failed"
+Image
+Label = "Bookmarks - Passed"
+Image
+Label = "Color contrast - Skipped"
+Button "Collapse" [off]
+Label = "Page Content (3 issues)"
+Image
+Label = "Tagged content - Failed"
+Image
+Label = "Tagged annotations - Failed"
+Image
+Label = "Tab order - Failed"
+Image
+Label = "Character encoding - Passed"
+Image
+Label = "Tagged multimedia - Passed"
+Image
+Label = "Screen flicker - Needs manual check"
+Image
+Label = "Scripts - Needs manual check"
+Image
+Label = "Timed responses - Needs manual check"
+Image
+Label = "Navigation links - Needs manual check"
+Button "Collapse" [off]
+Label = "Forms (2 issues)"
+Image
+Label = "Tagged form fields - Failed"
+Image
+Label = "Field descriptions - Failed"
+Button "Collapse" [off]
+Label = "Alternate Text"
+Image
+Label = "Figures alternate text - Passed"
+Image
+Label = "Nested alternate text - Passed"
+Image
+Label = "Associated with content - Passed"
+Image
+Label = "Hides annotation - Passed"
+Image
+Label = "Other elements alternate text - Passed"
+Button "Collapse" [off]
+Label = "Tables"
+Image
+Label = "Rows - Passed"
+Image
+Label = "TH and TD - Passed"
+Image
+Label = "Headers - Passed"
+Image
+Label = "Regularity - Passed"
+Image
+Label = "Summary - Passed"
+Button "Collapse" [off]
+Label = "Lists"
+Image
+Label = "List items - Passed"
+Image
+Label = "Lbl and LBody - Passed"
+Button "Collapse" [off]
+Label = "Headings"
+Image
+Label = "Appropriate nesting - Passed"
+ScrollBar
diff --git a/crates/ui-egui/tests/snapshots/panel_attachments.txt b/crates/ui-egui/tests/snapshots/panel_attachments.txt
new file mode 100644
index 000000000..c61b2f860
--- /dev/null
+++ b/crates/ui-egui/tests/snapshots/panel_attachments.txt
@@ -0,0 +1,7 @@
+Label = "Attachments"
+Label = "1"
+Button "Close" [off]
+Image
+Label = "notes.txt"
+Label = "5 bytes"
+Button "Save attachment…" [off]
diff --git a/crates/ui-egui/tests/snapshots/panel_bookmarks.txt b/crates/ui-egui/tests/snapshots/panel_bookmarks.txt
new file mode 100644
index 000000000..7ee13c4e6
--- /dev/null
+++ b/crates/ui-egui/tests/snapshots/panel_bookmarks.txt
@@ -0,0 +1,9 @@
+Label = "Bookmarks"
+Button "Close" [off]
+Button "Bookmark options" [off]
+Button "New bookmark (Ctrl+B)" [off]
+Label = "Search"
+TextInput "Search"
+Button "Clear" [off]
+Button "Introduction"
+Button "Details"
diff --git a/crates/ui-egui/tests/snapshots/panel_comments.txt b/crates/ui-egui/tests/snapshots/panel_comments.txt
new file mode 100644
index 000000000..c5bed5873
--- /dev/null
+++ b/crates/ui-egui/tests/snapshots/panel_comments.txt
@@ -0,0 +1,14 @@
+Label = "Comments"
+Label = "1"
+Button "Close" [off]
+Button "More options" [off]
+Button "Filter comments" [off]
+Button "Search comments" [off]
+TextInput
+Button "Collapse" [off]
+Label = "Page 1"
+Label = "1"
+Label = "Reviewer"
+Label = "2026-01-01 12:00"
+Label = "Check this heading"
+Unknown
diff --git a/crates/ui-egui/tests/snapshots/panel_compare.txt b/crates/ui-egui/tests/snapshots/panel_compare.txt
new file mode 100644
index 000000000..a2d8cc5a6
--- /dev/null
+++ b/crates/ui-egui/tests/snapshots/panel_compare.txt
@@ -0,0 +1,16 @@
+Label = "Compare"
+Label = "2"
+Button "Close" [off]
+Label = "2 Replaced"
+Label = "0 Inserted"
+Label = "0 Deleted"
+Label = "1 Visual"
+Button "Side by side"
+Button "New file only"
+Button "Mark as comments"
+Button "Report…"
+Button "Clear"
+Label = "Replaced · page 1"
+Button "\"five\" → \"three\"" [off]
+Label = "Replaced · page 1"
+Button "\"accepted.\" → \"accepted for a week.\"" [off]
diff --git a/crates/ui-egui/tests/snapshots/panel_fields.txt b/crates/ui-egui/tests/snapshots/panel_fields.txt
new file mode 100644
index 000000000..9fa61404e
--- /dev/null
+++ b/crates/ui-egui/tests/snapshots/panel_fields.txt
@@ -0,0 +1,6 @@
+Label = "Fields"
+Label = "2"
+Button "Close" [off]
+Label = "Page 1"
+Button "Name" [off]
+Button "Approval" [off]
diff --git a/crates/ui-egui/tests/snapshots/panel_layers.txt b/crates/ui-egui/tests/snapshots/panel_layers.txt
new file mode 100644
index 000000000..1e75f6bf6
--- /dev/null
+++ b/crates/ui-egui/tests/snapshots/panel_layers.txt
@@ -0,0 +1,4 @@
+Label = "Layers"
+Label = "1"
+Button "Close" [off]
+CheckBox "Draft notes" [on]
diff --git a/crates/ui-egui/tests/snapshots/panel_pages.txt b/crates/ui-egui/tests/snapshots/panel_pages.txt
new file mode 100644
index 000000000..726d58208
--- /dev/null
+++ b/crates/ui-egui/tests/snapshots/panel_pages.txt
@@ -0,0 +1,7 @@
+Label = "Pages"
+Label = "2"
+Button "Close" [off]
+Button "Page 1" [off]
+Label = "1"
+Button "Page 2" [off]
+Label = "2"
diff --git a/crates/ui-egui/tests/snapshots/panel_search.txt b/crates/ui-egui/tests/snapshots/panel_search.txt
new file mode 100644
index 000000000..d031afac6
--- /dev/null
+++ b/crates/ui-egui/tests/snapshots/panel_search.txt
@@ -0,0 +1,11 @@
+Label = "Search"
+Button "Close" [off]
+Label = "What word or phrase would you like to search for?"
+TextInput "What word or phrase would you like to search for?" = "sample"
+CheckBox "Whole words only" [off]
+CheckBox "Case-sensitive" [off]
+Label = "2 instances"
+Label = "Page 1"
+Button "…Panel sample Draft notes…" [on]
+Label = "Page 2"
+Button "…Second page sample text…" [off]
diff --git a/crates/ui-egui/tests/snapshots/panel_signatures.txt b/crates/ui-egui/tests/snapshots/panel_signatures.txt
new file mode 100644
index 000000000..8b7038738
--- /dev/null
+++ b/crates/ui-egui/tests/snapshots/panel_signatures.txt
@@ -0,0 +1,7 @@
+Label = "Signatures"
+Label = "0"
+Button "Close" [off]
+Button "Validate all"
+Button "Expand" [off]
+Image
+Label = "Unsigned signature field: Approval"
diff --git a/crates/ui-egui/tests/snapshots/panel_tags.txt b/crates/ui-egui/tests/snapshots/panel_tags.txt
new file mode 100644
index 000000000..7c694e0b5
--- /dev/null
+++ b/crates/ui-egui/tests/snapshots/panel_tags.txt
@@ -0,0 +1,24 @@
+Label = "Tags"
+Button "Close" [off]
+Label = "Find a tag"
+TextInput "Find a tag"
+Label = "1 tags"
+Button "P · 16" [on]
+Label = "16 0 R"
+Button "Go to page 1"
+Label = "Tag type"
+TextInput "Tag type" = "P"
+Label = "Title"
+TextInput "Title"
+Label = "Actual text"
+MultilineTextInput "Actual text"
+Label = "Alternate text"
+MultilineTextInput "Alternate text"
+Label = "Language"
+TextInput "Language"
+Button "Save tag properties" [disabled]
+Button "Revert changes" [disabled]
+Button "Move tag earlier" [disabled]
+Button "Move tag later" [disabled]
+Button "Mark as artifact"
+Button "MCID 0 · Go to page 1 · Panel sample"