diff --git a/CHANGELOG.md b/CHANGELOG.md
index 28d0ef113..9c8155383 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ All notable changes to OriginWeave are documented in this file. The format follo
 - Runtime browser-adapter version binding at the atomic protocol-use boundary: the caller-supplied bounded adapter-version token must exactly match the reviewed descriptor version before runtime revision or capability checks can succeed, preventing adapter-build drift from silently reusing otherwise matching protocol/browser metadata without authenticating or attesting the adapter process.
 - Same-call browser-protocol dispatch gating that validates current protocol family, adapter version, pinned protocol/browser revisions, OriginWeave generation, and required capability before invoking one callback, transferring the non-cloneable validation proof by ownership without turning metadata validation into browser or Agent authority.
 - Context-bound browser-protocol dispatch composition that revalidates the exact OriginWeave browser session/context pair, carries the registry's current document epoch into the immediate callback, and separately requires the same exact runtime protocol metadata/capability checks before dispatch without claiming origin, destination, typed-input, transport-authentication, or post-condition authority.
+- Explicit `BrowserAuthorityRegistry::bind_context_origin` registration that binds one canonical origin to the exact current browser session, browsing context, and document epoch before origin-sensitive protocol use, rejecting cross-session ownership and same-epoch origin changes without granting navigation or action authority.
 - Credential-safe browser-protocol validation evidence that copies only the already validated protocol family, OriginWeave generation, adapter version, pinned protocol/browser revisions, and exact capability into cloneable audit metadata without recreating the non-cloneable validation prerequisite or granting browser/Agent authority.
 - Canonical HTTPS and loopback-origin boundary with case-normalized schemes and hosts, default-port normalization, IPv4/IPv6 handling, browser-special numeric-host rejection, and explicit malformed-input errors.
 - Typed browser actions, capabilities, risk classes, execution modes, robots decisions, secret-delivery contracts, immutable canonical action-intent digests, and intent-bound approval scopes.
@@ -80,4 +81,4 @@ All notable changes to OriginWeave are documented in this file. The format follo
 - The hourly product agent has no Git metadata or repository authority. A separate post-verification publisher opens one PR and cannot approve or merge it.
 - The unprivileged OpenCode user is restricted to loopback egress during model execution, preventing runner-wide allow-listed endpoints from becoming direct source-exfiltration channels.
 
-[Unreleased]: https://github.com/ContextualWisdomLab/OriginWeave/compare/main...HEAD
\ No newline at end of file
+[Unreleased]: https://github.com/ContextualWisdomLab/OriginWeave/compare/main...HEAD
diff --git a/crates/originweave-core/src/browser_registry.rs b/crates/originweave-core/src/browser_registry.rs
index a45da9478..4ec84522b 100644
--- a/crates/originweave-core/src/browser_registry.rs
+++ b/crates/originweave-core/src/browser_registry.rs
@@ -198,6 +198,35 @@ impl BrowserAuthorityRegistry {
         self.current_epoch(browsing_context)
     }
 
+    /// Bind the canonical origin observed for the exact current browser document.
+    ///
+    /// This boundary lets a trusted browser adapter establish current document-origin state before
+    /// semantic-node discovery begins. The supplied session must own the context. Rebinding the
+    /// same canonical origin in the same document epoch is idempotent, while a different origin
+    /// fails closed until [`Self::advance_document`] rotates the document epoch and clears the old
+    /// binding. The returned epoch is descriptive immediate-use state, not reusable capability.
+    ///
+    /// This method does not authenticate the adapter, derive an origin from Chromium, authorize a
+    /// destination or action, or prove that any browser I/O occurred.
+    pub fn bind_context_origin(
+        &mut self,
+        browser_session: BrowserSessionId,
+        browsing_context: BrowsingContextId,
+        origin: &Origin,
+    ) -> Result<DocumentEpoch, BrowserRegistryError> {
+        let epoch = self.current_context_epoch(browser_session, browsing_context)?;
+        match self.context_origin.get(&browsing_context) {
+            Some(expected_origin) if expected_origin != origin => {
+                return Err(BrowserRegistryError::OriginChangedWithoutDocumentAdvance);
+            }
+            Some(_expected_origin) => {}
+            None => {
+                self.context_origin.insert(browsing_context, origin.clone());
+            }
+        }
+        Ok(epoch)
+    }
+
     /// Advance a browsing context to the next document epoch and invalidate old node bindings.
     ///
     /// Call this whenever navigation or document replacement invalidates actionable node identity.
diff --git a/crates/originweave-core/tests/browser_context_origin_binding.rs b/crates/originweave-core/tests/browser_context_origin_binding.rs
new file mode 100644
index 000000000..9d404ff3c
--- /dev/null
+++ b/crates/originweave-core/tests/browser_context_origin_binding.rs
@@ -0,0 +1,91 @@
+use std::error::Error;
+use std::io;
+
+use originweave_core::{
+    BrowserAuthorityRegistry, BrowserRegistryError, BrowserSessionId, BrowsingContextId,
+    DocumentEpoch, Origin,
+};
+
+fn first_origin() -> Result<Origin, Box<dyn Error>> {
+    Origin::parse("http://127.0.0.1:43127")
+        .map_err(|_error| io::Error::other("controlled first origin must be valid").into())
+}
+
+fn second_origin() -> Result<Origin, Box<dyn Error>> {
+    Origin::parse("http://localhost:43127")
+        .map_err(|_error| io::Error::other("controlled second origin must be valid").into())
+}
+
+#[test]
+fn context_origin_can_be_bound_before_node_discovery() -> Result<(), Box<dyn Error>> {
+    let mut registry = BrowserAuthorityRegistry::new();
+    let session = registry.register_session("webdriver-session")?;
+    let context = registry.register_context(session, "top-level-context")?;
+    let origin = first_origin()?;
+
+    let epoch = registry.bind_context_origin(session, context, &origin)?;
+    assert_eq!(epoch, DocumentEpoch::new(1)?);
+    assert_eq!(
+        registry.bind_context_origin(session, context, &origin)?,
+        epoch
+    );
+
+    let node = registry.bind_node(session, context, &origin, "backend-node-17")?;
+    assert_eq!(node.document_epoch(), epoch);
+    assert_eq!(node.origin(), &origin);
+    Ok(())
+}
+
+#[test]
+fn context_origin_change_requires_document_rotation() -> Result<(), Box<dyn Error>> {
+    let mut registry = BrowserAuthorityRegistry::new();
+    let session = registry.register_session("webdriver-session")?;
+    let context = registry.register_context(session, "top-level-context")?;
+    let first = first_origin()?;
+    let second = second_origin()?;
+
+    registry.bind_context_origin(session, context, &first)?;
+    assert_eq!(
+        registry.bind_context_origin(session, context, &second),
+        Err(BrowserRegistryError::OriginChangedWithoutDocumentAdvance)
+    );
+
+    let next_epoch = registry.advance_document(context)?;
+    assert_eq!(next_epoch, DocumentEpoch::new(2)?);
+    assert_eq!(
+        registry.bind_context_origin(session, context, &second)?,
+        next_epoch
+    );
+    Ok(())
+}
+
+#[test]
+fn context_origin_binding_rejects_cross_session_and_unknown_authority() -> Result<(), Box<dyn Error>>
+{
+    let mut registry = BrowserAuthorityRegistry::new();
+    let owner = registry.register_session("owner-session")?;
+    let attacker = registry.register_session("attacker-session")?;
+    let context = registry.register_context(owner, "top-level-context")?;
+    let origin = first_origin()?;
+
+    assert_eq!(
+        registry.bind_context_origin(attacker, context, &origin),
+        Err(BrowserRegistryError::ContextSessionMismatch {
+            expected: owner,
+            actual: attacker,
+        })
+    );
+
+    let unknown_session = BrowserSessionId::new(999)?;
+    assert_eq!(
+        registry.bind_context_origin(unknown_session, context, &origin),
+        Err(BrowserRegistryError::UnknownBrowserSession)
+    );
+
+    let unknown_context = BrowsingContextId::new(999)?;
+    assert_eq!(
+        registry.bind_context_origin(owner, unknown_context, &origin),
+        Err(BrowserRegistryError::UnknownBrowsingContext)
+    );
+    Ok(())
+}
diff --git a/tests/test_repository_contract.py b/tests/test_repository_contract.py
index 360e11143..07ddea2d5 100644
--- a/tests/test_repository_contract.py
+++ b/tests/test_repository_contract.py
@@ -175,6 +175,12 @@ def test_product_name_is_consistent_in_binding_documents(self) -> None:
             self.assertNotIn("TraceWeave", text, relative)
             self.assertNotIn("ProofRail", text, relative)
 
+    def test_context_origin_binding_is_recorded_in_the_changelog(self) -> None:
+        """The public origin-binding boundary must remain visible in release history."""
+
+        changelog = (ROOT / "CHANGELOG.md").read_text(encoding="utf-8")
+        self.assertIn("BrowserAuthorityRegistry::bind_context_origin", changelog)
+
     def test_database_contract_requires_two_word_snake_case(self) -> None:
         """Persistent naming policy must include the mandated canonical form."""
 
@@ -185,4 +191,4 @@ def test_database_contract_requires_two_word_snake_case(self) -> None:
 
 
 if __name__ == "__main__":
-    unittest.main()
\ No newline at end of file
+    unittest.main()