diff --git a/Cargo.lock b/Cargo.lock
index ece10983369..724448f89af 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -7065,11 +7065,14 @@ dependencies = [
  "hash-integrations-definition",
  "pretty_assertions",
  "proptest",
+ "serde",
  "serde_json",
  "simple-mermaid",
  "tempfile",
  "tokio",
  "tracing",
+ "type-system",
+ "uuid",
 ]
 
 [[package]]
diff --git a/libs/@local/integrations/engine/Cargo.toml b/libs/@local/integrations/engine/Cargo.toml
index 169ce41ea2d..b9402070afb 100644
--- a/libs/@local/integrations/engine/Cargo.toml
+++ b/libs/@local/integrations/engine/Cargo.toml
@@ -11,6 +11,7 @@ authors.workspace = true
 # Public workspace dependencies
 error-stack                  = { workspace = true, public = true, features = ["std"] }
 hash-integrations-definition = { workspace = true, public = true }
+type-system                  = { workspace = true, public = true }
 
 # Public third-party dependencies
 duckdb = { workspace = true, public = true, features = ["bundled", "json"] }
@@ -23,10 +24,12 @@ serde_json     = { workspace = true }
 simple-mermaid = { workspace = true }
 tokio          = { workspace = true, features = ["sync"] }
 tracing        = { workspace = true, features = ["attributes"] }
+uuid           = { workspace = true, features = ["v5"] }
 
 [dev-dependencies]
 pretty_assertions = { workspace = true }
 proptest          = { workspace = true, features = ["attr-macro", "std"] }
+serde             = { workspace = true, features = ["derive"] }
 tempfile          = { workspace = true }
 tokio             = { workspace = true, features = ["macros", "rt", "time"] }
 
diff --git a/libs/@local/integrations/engine/README.md b/libs/@local/integrations/engine/README.md
index 7543b32fe3a..29487d7f163 100644
--- a/libs/@local/integrations/engine/README.md
+++ b/libs/@local/integrations/engine/README.md
@@ -3,3 +3,5 @@
 Runs an integration's pipelines in DuckDB.
 
 Each run gets a `Workspace`, a DuckDB database file in which the run's queries execute. A query is a single `SELECT`, and cannot open files, load extensions or change settings.
+
+`derive_entity_id` derives stable entity IDs from an integration namespace, entity type and source record ID using UUID v5.
diff --git a/libs/@local/integrations/engine/docs/task-dependencies.json b/libs/@local/integrations/engine/docs/task-dependencies.json
index e36859a5e10..34f3568fa54 100644
--- a/libs/@local/integrations/engine/docs/task-dependencies.json
+++ b/libs/@local/integrations/engine/docs/task-dependencies.json
@@ -2,7 +2,8 @@
   "package": "hash-integrations-engine",
   "dependencies": [
     "error-stack",
-    "hash-integrations-definition"
+    "hash-integrations-definition",
+    "type-system"
   ],
   "tasks": {
     "doc:dependency-diagram": {
diff --git a/libs/@local/integrations/engine/src/entity_id.rs b/libs/@local/integrations/engine/src/entity_id.rs
new file mode 100644
index 00000000000..3ab0d624df8
--- /dev/null
+++ b/libs/@local/integrations/engine/src/entity_id.rs
@@ -0,0 +1,24 @@
+use type_system::{
+    knowledge::entity::id::{EntityId, EntityUuid},
+    ontology::id::VersionedUrl,
+    principal::actor_group::WebId,
+};
+use uuid::Uuid;
+
+const NAMESPACE: Uuid = Uuid::from_u128(0xD6E2_C7A1_F84B_4E3A_9C0D_5B7F_1E3A_2D4C);
+
+/// Derives a live entity ID from the integration namespace, entity type, and source record ID.
+#[must_use]
+pub fn derive_entity_id(
+    web_id: WebId,
+    namespace: &str,
+    entity_type: &VersionedUrl,
+    source_id: &str,
+) -> EntityId {
+    let name = format!("{namespace}::{entity_type}::{source_id}");
+    EntityId {
+        web_id,
+        entity_uuid: EntityUuid::new(Uuid::new_v5(&NAMESPACE, name.as_bytes())),
+        draft_id: None,
+    }
+}
diff --git a/libs/@local/integrations/engine/src/lib.rs b/libs/@local/integrations/engine/src/lib.rs
index fdb9775bf5a..5f00a9aafd6 100644
--- a/libs/@local/integrations/engine/src/lib.rs
+++ b/libs/@local/integrations/engine/src/lib.rs
@@ -16,12 +16,14 @@
 extern crate alloc;
 
 mod byte_size;
+mod entity_id;
 mod sql;
 mod variant_name;
 mod workspace;
 
 pub use self::{
     byte_size::ByteSize,
+    entity_id::derive_entity_id,
     workspace::{
         CloseError, DataErrorType, DiskUsageError, OpenError, QueryErrorType, Rows, Setting,
         SnapshotError, StatementError, Workspace, WorkspaceConfig,
diff --git a/libs/@local/integrations/engine/tests/entity_id.rs b/libs/@local/integrations/engine/tests/entity_id.rs
new file mode 100644
index 00000000000..92a284914ca
--- /dev/null
+++ b/libs/@local/integrations/engine/tests/entity_id.rs
@@ -0,0 +1,46 @@
+//! Deterministic entity ID derivation.
+
+use hash_integrations_engine::derive_entity_id;
+use pretty_assertions::assert_eq;
+use serde::Deserialize;
+use type_system::{
+    knowledge::entity::id::EntityUuid, ontology::id::VersionedUrl, principal::actor_group::WebId,
+};
+use uuid::Uuid;
+
+#[derive(Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct Case {
+    ns: String,
+    entity_type: VersionedUrl,
+    entity_id: String,
+    uuid: EntityUuid,
+    composite: String,
+    note: String,
+}
+
+#[test]
+fn derive_entity_id_recorded_vectors() {
+    let web_id = WebId::new(Uuid::from_u128(0xA2C8_E6C7_485D_4B54_A248_53C9_B9B0_14A2));
+    let cases: Vec<Case> =
+        serde_json::from_str(include_str!("fixtures/entity-ids-typescript.json"))
+            .expect("entity ID fixtures should be valid");
+    for case in cases {
+        let entity_id = derive_entity_id(web_id, &case.ns, &case.entity_type, &case.entity_id);
+        assert_eq!(
+            entity_id.entity_uuid, case.uuid,
+            "entity UUID should match the recorded value: {}",
+            case.note
+        );
+        assert_eq!(
+            entity_id.to_string(),
+            case.composite.replace("web-fixture", &web_id.to_string()),
+            "composite ID should match the recorded value: {}",
+            case.note
+        );
+        assert!(
+            entity_id.draft_id.is_none(),
+            "derived entity ID should identify a live entity"
+        );
+    }
+}
diff --git a/libs/@local/integrations/engine/tests/fixtures/README.md b/libs/@local/integrations/engine/tests/fixtures/README.md
new file mode 100644
index 00000000000..532c93c736d
--- /dev/null
+++ b/libs/@local/integrations/engine/tests/fixtures/README.md
@@ -0,0 +1,5 @@
+# Entity ID fixtures
+
+`entity-ids-typescript.json` contains the proof of concept's [recorded UUID vectors](https://github.com/hashintel/labs/blob/40a8d14535cee4020c2cd24c7e513bc209b59e19/pocs/integrations_rs/tests/golden/uuids.json). The two numeric source IDs are stored as text to match the derivation function's input.
+
+`web-fixture` is replaced with a valid web UUID when testing composite entity IDs.
diff --git a/libs/@local/integrations/engine/tests/fixtures/entity-ids-typescript.json b/libs/@local/integrations/engine/tests/fixtures/entity-ids-typescript.json
new file mode 100644
index 00000000000..8911c61f4fb
--- /dev/null
+++ b/libs/@local/integrations/engine/tests/fixtures/entity-ids-typescript.json
@@ -0,0 +1,66 @@
+[
+  {
+    "ns": "conn-a",
+    "entityType": "https://x/@t/types/entity-type/material/v/1",
+    "entityId": "M-0001",
+    "note": "plain string id",
+    "uuid": "fdb92954-9bd5-5558-ae43-40437c693f27",
+    "composite": "web-fixture~fdb92954-9bd5-5558-ae43-40437c693f27"
+  },
+  {
+    "ns": "conn-a",
+    "entityType": "https://x/@t/types/entity-type/material/v/1",
+    "entityId": "1",
+    "note": "numeric ID represented as text",
+    "uuid": "2f37a211-5787-5474-83b3-e3d7cf6bb83a",
+    "composite": "web-fixture~2f37a211-5787-5474-83b3-e3d7cf6bb83a"
+  },
+  {
+    "ns": "conn-a",
+    "entityType": "https://x/@t/types/entity-type/material/v/1",
+    "entityId": "1.5",
+    "note": "decimal ID represented as text",
+    "uuid": "42a6299f-2d8d-5b73-b11f-64badff46a94",
+    "composite": "web-fixture~42a6299f-2d8d-5b73-b11f-64badff46a94"
+  },
+  {
+    "ns": "conn-a",
+    "entityType": "https://x/@t/types/entity-type/material/v/1",
+    "entityId": "Grüße-仓库",
+    "note": "unicode id, hashed as UTF-8 bytes",
+    "uuid": "5aec7f53-3989-5d44-ace4-a78b860193a5",
+    "composite": "web-fixture~5aec7f53-3989-5d44-ace4-a78b860193a5"
+  },
+  {
+    "ns": "conn-a",
+    "entityType": "https://x/@t/types/entity-type/material/v/1",
+    "entityId": "a::b",
+    "note": "id containing the :: separator",
+    "uuid": "b0ed6b55-ea24-512b-97fe-e17e1c7f6861",
+    "composite": "web-fixture~b0ed6b55-ea24-512b-97fe-e17e1c7f6861"
+  },
+  {
+    "ns": "conn-a",
+    "entityType": "https://x/@t/types/entity-type/material/v/1",
+    "entityId": "A|B",
+    "note": "composite-joined id",
+    "uuid": "1ecf2406-4eba-5b0e-93f2-1a08389594d7",
+    "composite": "web-fixture~1ecf2406-4eba-5b0e-93f2-1a08389594d7"
+  },
+  {
+    "ns": "conn-a",
+    "entityType": "https://x/@t/types/entity-type/stored-at/v/1",
+    "entityId": "https://x/@t/types/entity-type/material/v/1::M-0001::https://x/@t/types/entity-type/plant/v/1::P-0100",
+    "note": "link uuid: entityId is sourceType::sourceId::targetType::targetId",
+    "uuid": "25bbb6e3-3e0a-53c2-a2f3-b8b83f7ff314",
+    "composite": "web-fixture~25bbb6e3-3e0a-53c2-a2f3-b8b83f7ff314"
+  },
+  {
+    "ns": "conn-a",
+    "entityType": "https://x/@t/types/entity-type/material/v/1",
+    "entityId": "",
+    "note": "empty-string id",
+    "uuid": "54b1ee67-5978-54fd-81ca-18d4ed3cdb2e",
+    "composite": "web-fixture~54b1ee67-5978-54fd-81ca-18d4ed3cdb2e"
+  }
+]