diff --git a/crates/forge-docs-check/src/extindex.rs b/crates/forge-docs-check/src/extindex.rs
new file mode 100644
index 0000000..20041e4
--- /dev/null
+++ b/crates/forge-docs-check/src/extindex.rs
@@ -0,0 +1,94 @@
+//! Rule `ext-index`: every `crates/ext_*` extension is listed in the
+//! `architecture.md` "Extension Crates" overview table.
+//!
+//! This is the index/module-list guard (Phase 2.5). It is a **completeness
+//! check**, not a generator: the table's `Purpose` column is hand-authored prose
+//! and only 13/37 crates carry a `Cargo.toml` description, so generating that
+//! column would either fabricate text or replace good labels with inconsistent
+//! doc-first-lines. Instead the rule ensures the authored table can never go
+//! silently incomplete — which it had (it listed 27 of 37 extensions, missing
+//! `console`, `dock`, `encoding`, `image_tools`, `svelte`, `web_inspector`,
+//! `codesign`, …). Adding a new extension now requires adding its row, the same
+//! way `crate-page` requires its dedicated page.
+
+use crate::checks::read_optional;
+use crate::discovery::Workspace;
+use crate::Finding;
+
+/// The overview page whose extension table must list every extension crate.
+const INDEX_PAGE: &str = "architecture.md";
+
+pub fn check(ws: &Workspace) -> Vec<Finding> {
+    let page = match read_optional(&ws.docs_dir().join(INDEX_PAGE)) {
+        Some(p) => p,
+        None => return Vec::new(),
+    };
+    let mut findings = Vec::new();
+    for krate in ws.extension_crates() {
+        // The table references each extension by its crate name in a code span,
+        // e.g. `| `ext_console` | … |`. Require that exact token to be present.
+        let needle = format!("`{}`", krate.dir_name);
+        if !page.contains(&needle) {
+            findings.push(Finding::new(
+                "ext-index",
+                format!(
+                    "extension crate `{}` is not listed in {}'s extension overview table",
+                    krate.dir_name, INDEX_PAGE
+                ),
+            ));
+        }
+    }
+    findings
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs;
+
+    fn ws_with(arch: &str, ext_crates: &[&str]) -> (tempfile::TempDir, Workspace) {
+        let tmp = tempfile::tempdir().unwrap();
+        let root = tmp.path();
+        fs::create_dir_all(root.join("sdk")).unwrap();
+        fs::create_dir_all(root.join("site/src/content/docs")).unwrap();
+        fs::write(root.join("site/src/content/docs/architecture.md"), arch).unwrap();
+        let mut members = String::new();
+        for c in ext_crates {
+            let dir = root.join("crates").join(c);
+            fs::create_dir_all(&dir).unwrap();
+            fs::write(
+                dir.join("Cargo.toml"),
+                format!("[package]\nname = \"{c}\"\nversion = \"0.1.0\"\nedition = \"2021\"\n"),
+            )
+            .unwrap();
+            members.push_str(&format!("  \"crates/{c}\",\n"));
+        }
+        fs::write(
+            root.join("Cargo.toml"),
+            format!("[workspace]\nmembers = [\n{members}]\nresolver = \"2\"\n"),
+        )
+        .unwrap();
+        let ws = Workspace::discover_at(root).unwrap();
+        (tmp, ws)
+    }
+
+    #[test]
+    fn flags_extension_missing_from_table() {
+        let arch = "| `ext_fs` | runtime:fs | files |\n";
+        let (_t, ws) = ws_with(arch, &["ext_fs", "ext_console"]);
+        let findings = check(&ws);
+        assert!(
+            findings.iter().any(|f| f.message.contains("ext_console")),
+            "missing ext_console must be flagged: {:?}",
+            findings.iter().map(|f| &f.message).collect::<Vec<_>>()
+        );
+        assert!(!findings.iter().any(|f| f.message.contains("ext_fs")));
+    }
+
+    #[test]
+    fn passes_when_all_listed() {
+        let arch = "| `ext_fs` | x |\n| `ext_console` | y |\n";
+        let (_t, ws) = ws_with(arch, &["ext_fs", "ext_console"]);
+        assert!(check(&ws).is_empty());
+    }
+}
diff --git a/crates/forge-docs-check/src/lib.rs b/crates/forge-docs-check/src/lib.rs
index c6f0cfc..6089663 100644
--- a/crates/forge-docs-check/src/lib.rs
+++ b/crates/forge-docs-check/src/lib.rs
@@ -18,6 +18,7 @@ pub mod checks;
 pub mod cratepage;
 pub mod discovery;
 pub mod exampleblock;
+pub mod extindex;
 pub mod markers;
 
 use discovery::Workspace;
@@ -93,5 +94,6 @@ pub fn run_all_checks(ws: &Workspace) -> Report {
     report.extend(checks::forge_docs::check(ws));
     report.extend(apiblock::check(ws));
     report.extend(exampleblock::check(ws));
+    report.extend(extindex::check(ws));
     report
 }
diff --git a/site/src/content/docs/architecture.md b/site/src/content/docs/architecture.md
index a497335..25c4e68 100644
--- a/site/src/content/docs/architecture.md
+++ b/site/src/content/docs/architecture.md
@@ -563,6 +563,13 @@ All extension crates use forge-weld macros for automatic TypeScript SDK generati
 | `ext_protocol` | `runtime:protocol` | Custom protocol handlers |
 | `ext_os_compat` | `runtime:os_compat` | OS compatibility layer |
 | `ext_debugger` | `runtime:debugger` | Debugging support |
+| `ext_console` | `runtime:console` | Console output capture (Deno + renderer) |
+| `ext_dock` | `runtime:dock` | macOS dock customization (badge, bounce, menu) |
+| `ext_encoding` | `runtime:encoding` | Text encoding/decoding |
+| `ext_image_tools` | `runtime:image_tools` | Image conversion (PNG, SVG, WebP, ICO) |
+| `ext_svelte` | `runtime:svelte` | SvelteKit integration |
+| `ext_web_inspector` | `runtime:web_inspector` | Chrome DevTools Protocol bridge |
+| `ext_codesign` | `runtime:codesign` | Code signing (macOS / Windows / Linux) |
 
 ### Forge Tool Extension Crates
 
@@ -570,6 +577,7 @@ All extension crates use forge-weld macros for automatic TypeScript SDK generati
 |-------|--------|---------|
 | `ext_weld` | `forge:weld` | Runtime code generation, TypeScript transpilation |
 | `ext_bundler` | `forge:bundler` | Icon management, manifest parsing, bundling utilities |
+| `ext_etcher` | `forge:etcher` | Documentation generation (forge-etch access) |
 
 ---