diff --git a/crates/worker-runtime/src/worker_backend.rs b/crates/worker-runtime/src/worker_backend.rs
index cc53a20c..2fdcabe4 100644
--- a/crates/worker-runtime/src/worker_backend.rs
+++ b/crates/worker-runtime/src/worker_backend.rs
@@ -653,18 +653,22 @@ impl RuntimeWorkerFactory for ProfileRuntimeWorkerFactory {
         };
         if let Some(bundle) = request.config_bundle.as_ref() {
             if let Some(prompt_catalog) = bundle.prompt_catalog.clone() {
-                let source_digest = bundle
-                    .metadata
-                    .provenance
-                    .detail
-                    .as_deref()
-                    .and_then(|detail| {
-                        detail
-                            .split(';')
-                            .find_map(|part| part.strip_prefix("source_tree_digest="))
-                    })
-                    .unwrap_or(&prompt_catalog.catalog_digest)
-                    .to_string();
+                let source_digest = if prompt_catalog.source_digest.is_empty() {
+                    bundle
+                        .metadata
+                        .provenance
+                        .detail
+                        .as_deref()
+                        .and_then(|detail| {
+                            detail
+                                .split(';')
+                                .find_map(|part| part.strip_prefix("source_tree_digest="))
+                        })
+                        .unwrap_or(&prompt_catalog.catalog_digest)
+                        .to_string()
+                } else {
+                    prompt_catalog.source_digest.clone()
+                };
                 let projection = worker::WorkspacePromptProjection::new(
                     bundle.metadata.workspace_id.clone(),
                     source_digest,
diff --git a/crates/worker/src/prompt/catalog.rs b/crates/worker/src/prompt/catalog.rs
index 28e748e9..9c5d187a 100644
--- a/crates/worker/src/prompt/catalog.rs
+++ b/crates/worker/src/prompt/catalog.rs
@@ -31,6 +31,8 @@ const BUILTIN_TOOLCHAIN_FINGERPRINT: &str = "builtin:prompts:decodal-0.4";
 pub struct EffectivePromptCatalog {
     pub templates: BTreeMap<String, String>,
     pub config_revision: u64,
+    #[serde(default, skip_serializing_if = "String::is_empty")]
+    pub source_digest: String,
     pub schema_fingerprint: String,
     pub toolchain_fingerprint: String,
     pub catalog_digest: String,
@@ -48,6 +50,7 @@ impl EffectivePromptCatalog {
         Ok(Self {
             templates,
             config_revision,
+            source_digest: String::new(),
             schema_fingerprint: schema_fingerprint.into(),
             toolchain_fingerprint: toolchain_fingerprint.into(),
             catalog_digest,
@@ -208,6 +211,11 @@ impl WorkspacePromptProjection {
                 "Workspace Prompt projection digest must not be empty".to_string(),
             ));
         }
+        if !catalog.source_digest.is_empty() && catalog.source_digest != source_digest {
+            return Err(CatalogError::InvalidTemplateCatalog(
+                "Workspace Prompt projection source digest does not match its catalog".to_string(),
+            ));
+        }
         Ok(Self {
             workspace_id,
             config_revision: catalog.config_revision,
diff --git a/crates/workspace-server/src/prompt_settings.rs b/crates/workspace-server/src/prompt_settings.rs
index 376e53e1..81f1415b 100644
--- a/crates/workspace-server/src/prompt_settings.rs
+++ b/crates/workspace-server/src/prompt_settings.rs
@@ -215,13 +215,15 @@ pub fn project_prompts_from_workspace_config(
             "active Workspace config projection has no prompts namespace".to_string(),
         )
     })?;
-    EffectivePromptCatalog::from_projection(
+    let mut catalog = EffectivePromptCatalog::from_projection(
         prompts,
         state.snapshot.revision,
         state.contract.schema_bundle.fingerprint.clone(),
         state.contract.fingerprint.clone(),
     )
-    .map_err(|error| Error::RegistryInconsistency(error.to_string()))
+    .map_err(|error| Error::RegistryInconsistency(error.to_string()))?;
+    catalog.source_digest = state.snapshot.digest.clone();
+    Ok(catalog)
 }
 
 pub fn project_workspace_prompt_projection(