diff --git a/hive-c0re/src/dashboard/approvals.rs b/hive-c0re/src/dashboard/approvals.rs
index c523f728..8604483c 100644
--- a/hive-c0re/src/dashboard/approvals.rs
+++ b/hive-c0re/src/dashboard/approvals.rs
@@ -16,7 +16,7 @@ use axum::{
 use hive_sh4re::Approval;
 use serde::Deserialize;
 
-use super::{AppState, error_response};
+use super::{AppState, error_response, problem_response};
 use crate::actions;
 use crate::coordinator::Coordinator;
 use crate::lifecycle;
@@ -209,7 +209,12 @@ pub(super) async fn get_approval_diff(
                 .max()
                 .map(|n| format!("refs/tags/proposal/{n}"))
         }
-        other => return error_response(&format!("unknown diff base {other:?}")),
+        other => {
+            return problem_response(
+                StatusCode::BAD_REQUEST,
+                &format!("unknown diff base {other:?}"),
+            );
+        }
     };
     let Some(base_ref) = base_ref else {
         return plain_text(match base {
diff --git a/hive-c0re/src/dashboard/journal.rs b/hive-c0re/src/dashboard/journal.rs
index cdcba9fb..5a661d51 100644
--- a/hive-c0re/src/dashboard/journal.rs
+++ b/hive-c0re/src/dashboard/journal.rs
@@ -13,7 +13,7 @@ use axum::{
 };
 use serde::Deserialize;
 
-use super::{error_response, strip_container_prefix, validate_agent_name};
+use super::{error_response, problem_response, strip_container_prefix, validate_agent_name};
 use crate::lifecycle;
 
 #[derive(Deserialize)]
@@ -48,7 +48,10 @@ pub(super) async fn get_journal(
     let prefixed = format!("{}{container}", lifecycle::AGENT_PREFIX);
     let live = lifecycle::list().await.unwrap_or_default();
     if !live.iter().any(|c| c == &prefixed) {
-        return error_response(&format!("journal: no managed container {prefixed:?}"));
+        return problem_response(
+            StatusCode::NOT_FOUND,
+            &format!("journal: no managed container {prefixed:?}"),
+        );
     }
     let lines = q.lines.unwrap_or(500).min(5000);
     let unit = match q.unit.as_deref().filter(|s| !s.is_empty()) {
@@ -61,7 +64,10 @@ pub(super) async fn get_journal(
                 format!("{u}.service")
             };
             if !allowed.contains(&unit.as_str()) {
-                return error_response(&format!("journal: unknown unit {unit:?}"));
+                return problem_response(
+                    StatusCode::BAD_REQUEST,
+                    &format!("journal: unknown unit {unit:?}"),
+                );
             }
             Some(unit)
         }
@@ -121,7 +127,10 @@ pub(super) async fn get_journal_host(
             format!("{u}.service")
         };
         if !allowed.contains(&unit.as_str()) {
-            return error_response(&format!("journal-host: unknown unit {unit:?}"));
+            return problem_response(
+                StatusCode::BAD_REQUEST,
+                &format!("journal-host: unknown unit {unit:?}"),
+            );
         }
         cmd.args(["-u", &unit]);
     }
diff --git a/hive-c0re/src/dashboard/permissions.rs b/hive-c0re/src/dashboard/permissions.rs
index 60044b4b..ff379188 100644
--- a/hive-c0re/src/dashboard/permissions.rs
+++ b/hive-c0re/src/dashboard/permissions.rs
@@ -12,7 +12,7 @@ use axum::{
 };
 use serde::{Deserialize, Serialize};
 
-use super::{AppState, error_response, guard_agent_name, strip_container_prefix};
+use super::{AppState, guard_agent_name, problem_response, strip_container_prefix};
 
 #[derive(Serialize)]
 pub(super) struct ToolGroupsSnapshot {
@@ -120,7 +120,10 @@ pub(super) async fn post_tool_groups(
     // Validate group names before queuing — fail fast so the operator
     // sees the error immediately rather than waiting for the worker.
     if let Err(e) = crate::tool_groups::validate_groups(&body.groups) {
-        return error_response(&format!("invalid tool-groups for {logical}: {e}"));
+        return problem_response(
+            StatusCode::BAD_REQUEST,
+            &format!("invalid tool-groups for {logical}: {e}"),
+        );
     }
     // Enqueue a PermChange so the JSON file write is serialised through
     // the FIFO worker. Prevents concurrent batch-apply actions for
@@ -204,7 +207,10 @@ pub(super) async fn post_capabilities(
         .collect();
     for cap in &body.caps {
         if !known.contains(&cap.as_str()) {
-            return error_response(&format!("unknown capability: {cap}"));
+            return problem_response(
+                StatusCode::BAD_REQUEST,
+                &format!("unknown capability: {cap}"),
+            );
         }
     }
     // Enqueue a PermChange so the JSON file write is serialised through
@@ -272,12 +278,18 @@ pub(super) async fn post_permissions(
         if let Some(groups) = &change.tool_groups
             && let Err(e) = crate::tool_groups::validate_groups(groups)
         {
-            return error_response(&format!("invalid tool-groups for {logical}: {e}"));
+            return problem_response(
+                StatusCode::BAD_REQUEST,
+                &format!("invalid tool-groups for {logical}: {e}"),
+            );
         }
         if let Some(caps) = &change.capabilities {
             for cap in caps {
                 if !known_caps.contains(&cap.as_str()) {
-                    return error_response(&format!("unknown capability for {logical}: {cap}"));
+                    return problem_response(
+                        StatusCode::BAD_REQUEST,
+                        &format!("unknown capability for {logical}: {cap}"),
+                    );
                 }
             }
         }
diff --git a/hive-c0re/src/dashboard/questions.rs b/hive-c0re/src/dashboard/questions.rs
index 5d6530e0..ef50aff8 100644
--- a/hive-c0re/src/dashboard/questions.rs
+++ b/hive-c0re/src/dashboard/questions.rs
@@ -13,7 +13,7 @@ use axum::{
 };
 use serde::Deserialize;
 
-use super::{AppState, error_response};
+use super::{AppState, error_response, problem_response};
 
 #[derive(Deserialize)]
 pub(super) struct AnswerForm {
@@ -41,7 +41,10 @@ pub(super) async fn post_answer_question(
 ) -> Response {
     let answer = form.answer.trim();
     if answer.is_empty() {
-        return with_cors(error_response("answer: required"));
+        return with_cors(problem_response(
+            StatusCode::BAD_REQUEST,
+            "answer: required",
+        ));
     }
     let resp = match state
         .coord
diff --git a/hive-c0re/src/dashboard/reminders.rs b/hive-c0re/src/dashboard/reminders.rs
index e29e885c..75789b0f 100644
--- a/hive-c0re/src/dashboard/reminders.rs
+++ b/hive-c0re/src/dashboard/reminders.rs
@@ -10,7 +10,7 @@ use axum::{
     response::{IntoResponse, Response},
 };
 
-use super::{AppState, error_response};
+use super::{AppState, error_response, problem_response};
 
 pub(super) async fn api_reminders(State(state): State<AppState>) -> Response {
     match state.coord.broker.list_pending_reminders() {
@@ -24,7 +24,10 @@ pub(super) async fn post_cancel_reminder(
     AxumPath(id): AxumPath<i64>,
 ) -> Response {
     match state.coord.broker.cancel_reminder(id) {
-        Ok(0) => error_response(&format!("reminder {id} not pending (already delivered?)")),
+        Ok(0) => problem_response(
+            StatusCode::NOT_FOUND,
+            &format!("reminder {id} not pending (already delivered?)"),
+        ),
         Ok(_) => {
             tracing::info!(%id, "operator cancelled reminder");
             state.coord.emit_reminders_snapshot();
@@ -44,7 +47,10 @@ pub(super) async fn post_retry_reminder(
     AxumPath(id): AxumPath<i64>,
 ) -> Response {
     match state.coord.broker.reset_reminder_failure(id) {
-        Ok(0) => error_response(&format!("reminder {id} not pending (already delivered?)")),
+        Ok(0) => problem_response(
+            StatusCode::NOT_FOUND,
+            &format!("reminder {id} not pending (already delivered?)"),
+        ),
         Ok(_) => {
             tracing::info!(%id, "operator reset reminder failure for retry");
             state.coord.emit_reminders_snapshot();
diff --git a/hive-c0re/src/dashboard/schedules.rs b/hive-c0re/src/dashboard/schedules.rs
index 535ae9c0..ccabe878 100644
--- a/hive-c0re/src/dashboard/schedules.rs
+++ b/hive-c0re/src/dashboard/schedules.rs
@@ -11,7 +11,7 @@ use axum::{
     response::{IntoResponse, Response},
 };
 
-use super::{AppState, error_response};
+use super::{AppState, error_response, problem_response};
 
 /// `GET /api/schedules` — snapshot of every schedule for the
 /// scheduled-prompts tab. Returns the wire shape directly
@@ -51,13 +51,19 @@ pub(super) async fn post_schedule_new(
     axum::Json(payload): axum::Json<hive_sh4re::SchedulePromptPayload>,
 ) -> Response {
     if payload.targets.is_empty() {
-        return error_response("schedule must have at least one target");
+        return problem_response(
+            StatusCode::BAD_REQUEST,
+            "schedule must have at least one target",
+        );
     }
     if payload.body.trim().is_empty() {
-        return error_response("schedule body must be non-empty");
+        return problem_response(StatusCode::BAD_REQUEST, "schedule body must be non-empty");
     }
     if let Some(0) = payload.interval_seconds {
-        return error_response("interval_seconds must be > 0 (use None for one-shot)");
+        return problem_response(
+            StatusCode::BAD_REQUEST,
+            "interval_seconds must be > 0 (use None for one-shot)",
+        );
     }
     let new = crate::scheduled_prompts::NewSchedule {
         owner: hive_sh4re::OPERATOR_RECIPIENT.to_owned(),
diff --git a/hive-c0re/src/dashboard/topology.rs b/hive-c0re/src/dashboard/topology.rs
index 7482a846..5751d9a0 100644
--- a/hive-c0re/src/dashboard/topology.rs
+++ b/hive-c0re/src/dashboard/topology.rs
@@ -13,7 +13,7 @@ use axum::{
 };
 use serde::Deserialize;
 
-use super::{AppState, error_response};
+use super::{AppState, error_response, problem_response};
 
 /// `POST /api/topology/set-parent` body. `child` is required.
 /// `new_parent` may be:
@@ -53,7 +53,7 @@ pub(super) async fn post_set_parent(
 ) -> Response {
     let child = form.child.trim().to_owned();
     if child.is_empty() {
-        return error_response("set-parent: `child` required");
+        return problem_response(StatusCode::BAD_REQUEST, "set-parent: `child` required");
     }
     // Empty / whitespace-only `new_parent` ⇒ promote to root. Web
     // forms submit the empty string for a "no value" radio button,