diff --git a/codex-rs/core/tests/suite/compact.rs b/codex-rs/core/tests/suite/compact.rs
index 8f3afaea9b..c63b5b9496 100644
--- a/codex-rs/core/tests/suite/compact.rs
+++ b/codex-rs/core/tests/suite/compact.rs
@@ -245,10 +245,72 @@ fn message_text_for_shape(item: &Value) -> String {
         .unwrap_or_else(|| "<NO_TEXT>".to_string())
 }
 
+fn is_non_real_user_text(text: &str) -> bool {
+    text == "<AGENTS_MD>"
+        || text == "<PERMISSIONS_INSTRUCTIONS>"
+        || text == "<SUMMARIZATION_PROMPT>"
+        || text.starts_with("<ENVIRONMENT_CONTEXT")
+        || text.starts_with("<SUMMARY:")
+}
+
+fn is_shape_context_item_text(text: &str) -> bool {
+    text == "<AGENTS_MD>"
+        || text == "<PERMISSIONS_INSTRUCTIONS>"
+        || text.starts_with("<ENVIRONMENT_CONTEXT")
+}
+
+fn user_message_label_for_shape(item: &Value) -> Option<String> {
+    if item.get("type").and_then(Value::as_str) != Some("message") {
+        return None;
+    }
+    if item.get("role").and_then(Value::as_str) != Some("user") {
+        return None;
+    }
+
+    item.get("content")
+        .and_then(Value::as_array)
+        .and_then(|content| {
+            content
+                .iter()
+                .filter_map(|entry| entry.get("text").and_then(Value::as_str))
+                .map(normalize_shape_text)
+                .find(|text| !is_non_real_user_text(text))
+        })
+}
+
+fn previous_user_label_for_shape(items: &[Value], idx: usize) -> Option<String> {
+    items[..idx]
+        .iter()
+        .rev()
+        .find_map(user_message_label_for_shape)
+}
+
+fn next_user_label_for_shape(items: &[Value], idx: usize) -> Option<String> {
+    items
+        .iter()
+        .skip(idx.saturating_add(1))
+        .find_map(user_message_label_for_shape)
+}
+
+fn context_anchor_suffix(items: &[Value], idx: usize, role: &str, text: &str) -> Option<String> {
+    let is_context_message = if role == "developer" {
+        true
+    } else {
+        role == "user" && is_shape_context_item_text(text)
+    };
+    if !is_context_message {
+        return None;
+    }
+
+    let prev = previous_user_label_for_shape(items, idx).unwrap_or_else(|| "<none>".to_string());
+    let next = next_user_label_for_shape(items, idx).unwrap_or_else(|| "<none>".to_string());
+    Some(format!(" [prev_user={prev};next_user={next}]"))
+}
+
 fn request_input_shape(request: &ResponsesRequest) -> String {
-    request
-        .input()
-        .into_iter()
+    let input = request.input();
+    input
+        .iter()
         .enumerate()
         .map(|(idx, item)| {
             let Some(item_type) = item.get("type").and_then(Value::as_str) else {
@@ -257,8 +319,9 @@ fn request_input_shape(request: &ResponsesRequest) -> String {
             match item_type {
                 "message" => {
                     let role = item.get("role").and_then(Value::as_str).unwrap_or("unknown");
-                    let text = message_text_for_shape(&item);
-                    format!("{idx:02}:message/{role}:{text}")
+                    let text = message_text_for_shape(item);
+                    let suffix = context_anchor_suffix(&input, idx, role, &text).unwrap_or_default();
+                    format!("{idx:02}:message/{role}:{text}{suffix}")
                 }
                 "function_call" => {
                     let name = item.get("name").and_then(Value::as_str).unwrap_or("unknown");
diff --git a/codex-rs/core/tests/suite/compact_remote.rs b/codex-rs/core/tests/suite/compact_remote.rs
index a8cf41468a..dcc8a1e3ac 100644
--- a/codex-rs/core/tests/suite/compact_remote.rs
+++ b/codex-rs/core/tests/suite/compact_remote.rs
@@ -113,10 +113,71 @@ fn message_text_for_shape(item: &Value) -> String {
         .unwrap_or_else(|| "<NO_TEXT>".to_string())
 }
 
+fn is_non_real_user_text(text: &str) -> bool {
+    text == "<AGENTS_MD>"
+        || text == "<PERMISSIONS_INSTRUCTIONS>"
+        || text.starts_with("<ENVIRONMENT_CONTEXT")
+        || text.starts_with("<SUMMARY:")
+}
+
+fn is_shape_context_item_text(text: &str) -> bool {
+    text == "<AGENTS_MD>"
+        || text == "<PERMISSIONS_INSTRUCTIONS>"
+        || text.starts_with("<ENVIRONMENT_CONTEXT")
+}
+
+fn user_message_label_for_shape(item: &Value) -> Option<String> {
+    if item.get("type").and_then(Value::as_str) != Some("message") {
+        return None;
+    }
+    if item.get("role").and_then(Value::as_str) != Some("user") {
+        return None;
+    }
+
+    item.get("content")
+        .and_then(Value::as_array)
+        .and_then(|content| {
+            content
+                .iter()
+                .filter_map(|entry| entry.get("text").and_then(Value::as_str))
+                .map(normalize_shape_text)
+                .find(|text| !is_non_real_user_text(text))
+        })
+}
+
+fn previous_user_label_for_shape(items: &[Value], idx: usize) -> Option<String> {
+    items[..idx]
+        .iter()
+        .rev()
+        .find_map(user_message_label_for_shape)
+}
+
+fn next_user_label_for_shape(items: &[Value], idx: usize) -> Option<String> {
+    items
+        .iter()
+        .skip(idx.saturating_add(1))
+        .find_map(user_message_label_for_shape)
+}
+
+fn context_anchor_suffix(items: &[Value], idx: usize, role: &str, text: &str) -> Option<String> {
+    let is_context_message = if role == "developer" {
+        true
+    } else {
+        role == "user" && is_shape_context_item_text(text)
+    };
+    if !is_context_message {
+        return None;
+    }
+
+    let prev = previous_user_label_for_shape(items, idx).unwrap_or_else(|| "<none>".to_string());
+    let next = next_user_label_for_shape(items, idx).unwrap_or_else(|| "<none>".to_string());
+    Some(format!(" [prev_user={prev};next_user={next}]"))
+}
+
 fn request_input_shape(request: &responses::ResponsesRequest) -> String {
-    request
-        .input()
-        .into_iter()
+    let input = request.input();
+    input
+        .iter()
         .enumerate()
         .map(|(idx, item)| {
             let Some(item_type) = item.get("type").and_then(Value::as_str) else {
@@ -125,8 +186,9 @@ fn request_input_shape(request: &responses::ResponsesRequest) -> String {
             match item_type {
                 "message" => {
                     let role = item.get("role").and_then(Value::as_str).unwrap_or("unknown");
-                    let text = message_text_for_shape(&item);
-                    format!("{idx:02}:message/{role}:{text}")
+                    let text = message_text_for_shape(item);
+                    let suffix = context_anchor_suffix(&input, idx, role, &text).unwrap_or_default();
+                    format!("{idx:02}:message/{role}:{text}{suffix}")
                 }
                 "function_call" => {
                     let name = item.get("name").and_then(Value::as_str).unwrap_or("unknown");
diff --git a/codex-rs/core/tests/suite/snapshots/all__suite__compact__manual_compact_with_history_shapes.snap b/codex-rs/core/tests/suite/snapshots/all__suite__compact__manual_compact_with_history_shapes.snap
index e507b79ecc..ff81d79009 100644
--- a/codex-rs/core/tests/suite/snapshots/all__suite__compact__manual_compact_with_history_shapes.snap
+++ b/codex-rs/core/tests/suite/snapshots/all__suite__compact__manual_compact_with_history_shapes.snap
@@ -5,17 +5,17 @@ expression: "sectioned_request_shapes(\"Manual /compact with prior user history
 Scenario: Manual /compact with prior user history compacts existing history and the follow-up turn includes the compact summary plus new user message.
 
 ## Local Compaction Request
-00:message/developer:<PERMISSIONS_INSTRUCTIONS>
-01:message/user:<AGENTS_MD>
-02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
+00:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=<none>;next_user=USER_ONE]
+01:message/user:<AGENTS_MD> [prev_user=<none>;next_user=USER_ONE]
+02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>> [prev_user=<none>;next_user=USER_ONE]
 03:message/user:USER_ONE
 04:message/assistant:FIRST_REPLY
 05:message/user:<SUMMARIZATION_PROMPT>
 
 ## Local Post-Compaction History Layout
-00:message/developer:<PERMISSIONS_INSTRUCTIONS>
-01:message/user:<AGENTS_MD>
-02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
+00:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=<none>;next_user=USER_ONE]
+01:message/user:<AGENTS_MD> [prev_user=<none>;next_user=USER_ONE]
+02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>> [prev_user=<none>;next_user=USER_ONE]
 03:message/user:USER_ONE
 04:message/user:<SUMMARY:MANUAL_SUMMARY>
 05:message/user:USER_TWO
diff --git a/codex-rs/core/tests/suite/snapshots/all__suite__compact__manual_compact_without_prev_user_shapes.snap b/codex-rs/core/tests/suite/snapshots/all__suite__compact__manual_compact_without_prev_user_shapes.snap
index b21b68af5b..e10b862de5 100644
--- a/codex-rs/core/tests/suite/snapshots/all__suite__compact__manual_compact_without_prev_user_shapes.snap
+++ b/codex-rs/core/tests/suite/snapshots/all__suite__compact__manual_compact_without_prev_user_shapes.snap
@@ -5,7 +5,7 @@ expression: "sectioned_request_shapes(\"Manual /compact with no prior user turn
 Scenario: Manual /compact with no prior user turn behaves as a no-op and follow-up turn carries only canonical initial context plus the new user message.
 
 ## Local Post-Compaction History Layout
-00:message/developer:<PERMISSIONS_INSTRUCTIONS>
-01:message/user:<AGENTS_MD>
-02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
+00:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=<none>;next_user=<none>]
+01:message/user:<AGENTS_MD> [prev_user=<none>;next_user=<none>]
+02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>> [prev_user=<none>;next_user=<none>]
 03:message/user:<SUMMARIZATION_PROMPT>
diff --git a/codex-rs/core/tests/suite/snapshots/all__suite__compact__mid_turn_compaction_shapes.snap b/codex-rs/core/tests/suite/snapshots/all__suite__compact__mid_turn_compaction_shapes.snap
index 4472ea863d..61fb6dda12 100644
--- a/codex-rs/core/tests/suite/snapshots/all__suite__compact__mid_turn_compaction_shapes.snap
+++ b/codex-rs/core/tests/suite/snapshots/all__suite__compact__mid_turn_compaction_shapes.snap
@@ -5,17 +5,17 @@ expression: "sectioned_request_shapes(\"Mid-turn continuation compaction after t
 Scenario: Mid-turn continuation compaction after tool output: compact request includes tool artifacts and follow-up request includes the summary.
 
 ## Local Compaction Request
-00:message/developer:<PERMISSIONS_INSTRUCTIONS>
-01:message/user:<AGENTS_MD>
-02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
+00:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=<none>;next_user=USER_ONE]
+01:message/user:<AGENTS_MD> [prev_user=<none>;next_user=USER_ONE]
+02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>> [prev_user=<none>;next_user=USER_ONE]
 03:message/user:USER_ONE
 04:function_call/<TOOL_CALL>
 05:function_call_output:<TOOL_ERROR_OUTPUT>
 06:message/user:<SUMMARIZATION_PROMPT>
 
 ## Local Post-Compaction History Layout
-00:message/developer:<PERMISSIONS_INSTRUCTIONS>
-01:message/user:<AGENTS_MD>
-02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
+00:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=<none>;next_user=USER_ONE]
+01:message/user:<AGENTS_MD> [prev_user=<none>;next_user=USER_ONE]
+02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>> [prev_user=<none>;next_user=USER_ONE]
 03:message/user:USER_ONE
 04:message/user:<SUMMARY:MID_TURN_SUMMARY>
diff --git a/codex-rs/core/tests/suite/snapshots/all__suite__compact__pre_turn_compaction_context_window_exceeded_shapes.snap b/codex-rs/core/tests/suite/snapshots/all__suite__compact__pre_turn_compaction_context_window_exceeded_shapes.snap
index c2452c67fa..16eb0ecf14 100644
--- a/codex-rs/core/tests/suite/snapshots/all__suite__compact__pre_turn_compaction_context_window_exceeded_shapes.snap
+++ b/codex-rs/core/tests/suite/snapshots/all__suite__compact__pre_turn_compaction_context_window_exceeded_shapes.snap
@@ -5,9 +5,9 @@ expression: "sectioned_request_shapes(\"Pre-turn auto-compaction context-window
 Scenario: Pre-turn auto-compaction context-window failure on main: compaction request excludes the incoming user message and the turn errors.
 
 ## Local Compaction Request (Incoming User Excluded on main)
-00:message/developer:<PERMISSIONS_INSTRUCTIONS>
-01:message/user:<AGENTS_MD>
-02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
+00:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=<none>;next_user=USER_ONE]
+01:message/user:<AGENTS_MD> [prev_user=<none>;next_user=USER_ONE]
+02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>> [prev_user=<none>;next_user=USER_ONE]
 03:message/user:USER_ONE
 04:message/assistant:FIRST_REPLY
 05:message/user:<SUMMARIZATION_PROMPT>
diff --git a/codex-rs/core/tests/suite/snapshots/all__suite__compact__pre_turn_compaction_including_incoming_shapes.snap b/codex-rs/core/tests/suite/snapshots/all__suite__compact__pre_turn_compaction_including_incoming_shapes.snap
index e8bb19a4cd..1ba966469a 100644
--- a/codex-rs/core/tests/suite/snapshots/all__suite__compact__pre_turn_compaction_including_incoming_shapes.snap
+++ b/codex-rs/core/tests/suite/snapshots/all__suite__compact__pre_turn_compaction_including_incoming_shapes.snap
@@ -5,20 +5,20 @@ expression: "sectioned_request_shapes(\"Pre-turn auto-compaction with a context
 Scenario: Pre-turn auto-compaction with a context override emits the context diff in the compact request while the incoming user message is still excluded on main.
 
 ## Local Compaction Request
-00:message/developer:<PERMISSIONS_INSTRUCTIONS>
-01:message/user:<AGENTS_MD>
-02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
+00:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=<none>;next_user=USER_ONE]
+01:message/user:<AGENTS_MD> [prev_user=<none>;next_user=USER_ONE]
+02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>> [prev_user=<none>;next_user=USER_ONE]
 03:message/user:USER_ONE
 04:message/assistant:FIRST_REPLY
 05:message/user:USER_TWO
 06:message/assistant:SECOND_REPLY
-07:message/user:<ENVIRONMENT_CONTEXT:cwd=PRETURN_CONTEXT_DIFF_CWD>
+07:message/user:<ENVIRONMENT_CONTEXT:cwd=PRETURN_CONTEXT_DIFF_CWD> [prev_user=USER_TWO;next_user=<none>]
 08:message/user:<SUMMARIZATION_PROMPT>
 
 ## Local Post-Compaction History Layout
-00:message/developer:<PERMISSIONS_INSTRUCTIONS>
-01:message/user:<AGENTS_MD>
-02:message/user:<ENVIRONMENT_CONTEXT:cwd=PRETURN_CONTEXT_DIFF_CWD>
+00:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=<none>;next_user=USER_ONE]
+01:message/user:<AGENTS_MD> [prev_user=<none>;next_user=USER_ONE]
+02:message/user:<ENVIRONMENT_CONTEXT:cwd=PRETURN_CONTEXT_DIFF_CWD> [prev_user=<none>;next_user=USER_ONE]
 03:message/user:USER_ONE
 04:message/user:USER_TWO
 05:message/user:<SUMMARY:PRE_TURN_SUMMARY>
diff --git a/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_manual_compact_with_history_shapes.snap b/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_manual_compact_with_history_shapes.snap
index 5814c71c3a..e40d8c8b29 100644
--- a/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_manual_compact_with_history_shapes.snap
+++ b/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_manual_compact_with_history_shapes.snap
@@ -5,16 +5,16 @@ expression: "sectioned_request_shapes(\"Remote manual /compact with prior user h
 Scenario: Remote manual /compact with prior user history compacts existing history and follow-up includes compact summary plus new user message.
 
 ## Remote Compaction Request
-00:message/developer:<PERMISSIONS_INSTRUCTIONS>
-01:message/user:<AGENTS_MD>
-02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
+00:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=<none>;next_user=USER_ONE]
+01:message/user:<AGENTS_MD> [prev_user=<none>;next_user=USER_ONE]
+02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>> [prev_user=<none>;next_user=USER_ONE]
 03:message/user:USER_ONE
 04:message/assistant:REMOTE_MANUAL_FIRST_REPLY
 
 ## Remote Post-Compaction History Layout
 00:message/user:USER_ONE
-01:message/developer:<PERMISSIONS_INSTRUCTIONS>
-02:message/user:<AGENTS_MD>
-03:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
+01:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=USER_ONE;next_user=USER_TWO]
+02:message/user:<AGENTS_MD> [prev_user=USER_ONE;next_user=USER_TWO]
+03:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>> [prev_user=USER_ONE;next_user=USER_TWO]
 04:message/user:<SUMMARY:REMOTE_MANUAL_WITH_HISTORY_SUMMARY>
 05:message/user:USER_TWO
diff --git a/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_manual_compact_without_prev_user_shapes.snap b/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_manual_compact_without_prev_user_shapes.snap
index 4e4c7098ca..4978a9aa74 100644
--- a/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_manual_compact_without_prev_user_shapes.snap
+++ b/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_manual_compact_without_prev_user_shapes.snap
@@ -5,12 +5,12 @@ expression: "sectioned_request_shapes(\"Remote manual /compact with no prior use
 Scenario: Remote manual /compact with no prior user turn still issues a compact request on main; follow-up turn carries canonical context and new user message.
 
 ## Remote Compaction Request
-00:message/developer:<PERMISSIONS_INSTRUCTIONS>
-01:message/user:<AGENTS_MD>
-02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
+00:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=<none>;next_user=<none>]
+01:message/user:<AGENTS_MD> [prev_user=<none>;next_user=<none>]
+02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>> [prev_user=<none>;next_user=<none>]
 
 ## Remote Post-Compaction History Layout
-00:message/developer:<PERMISSIONS_INSTRUCTIONS>
-01:message/user:<AGENTS_MD>
-02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
+00:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=<none>;next_user=USER_ONE]
+01:message/user:<AGENTS_MD> [prev_user=<none>;next_user=USER_ONE]
+02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>> [prev_user=<none>;next_user=USER_ONE]
 03:message/user:USER_ONE
diff --git a/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_mid_turn_compaction_shapes.snap b/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_mid_turn_compaction_shapes.snap
index 979c122b15..9c7b22a306 100644
--- a/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_mid_turn_compaction_shapes.snap
+++ b/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_mid_turn_compaction_shapes.snap
@@ -5,16 +5,16 @@ expression: "sectioned_request_shapes(\"Remote mid-turn continuation compaction
 Scenario: Remote mid-turn continuation compaction after tool output: compact request includes tool artifacts and follow-up request includes the summary.
 
 ## Remote Compaction Request
-00:message/developer:<PERMISSIONS_INSTRUCTIONS>
-01:message/user:<AGENTS_MD>
-02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
+00:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=<none>;next_user=USER_ONE]
+01:message/user:<AGENTS_MD> [prev_user=<none>;next_user=USER_ONE]
+02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>> [prev_user=<none>;next_user=USER_ONE]
 03:message/user:USER_ONE
 04:function_call/<TOOL_CALL>
 05:function_call_output:<TOOL_ERROR_OUTPUT>
 
 ## Remote Post-Compaction History Layout
 00:message/user:USER_ONE
-01:message/developer:<PERMISSIONS_INSTRUCTIONS>
-02:message/user:<AGENTS_MD>
-03:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
+01:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=USER_ONE;next_user=<none>]
+02:message/user:<AGENTS_MD> [prev_user=USER_ONE;next_user=<none>]
+03:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>> [prev_user=USER_ONE;next_user=<none>]
 04:message/user:<SUMMARY:REMOTE_MID_TURN_SUMMARY>
diff --git a/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_pre_turn_compaction_failure_shapes.snap b/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_pre_turn_compaction_failure_shapes.snap
index 2cac4940b1..daf7378fc5 100644
--- a/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_pre_turn_compaction_failure_shapes.snap
+++ b/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_pre_turn_compaction_failure_shapes.snap
@@ -5,8 +5,8 @@ expression: "sectioned_request_shapes(\"Remote pre-turn auto-compaction parse fa
 Scenario: Remote pre-turn auto-compaction parse failure on main: compaction request excludes the incoming user message and the turn stops.
 
 ## Remote Compaction Request (Incoming User Excluded on main)
-00:message/developer:<PERMISSIONS_INSTRUCTIONS>
-01:message/user:<AGENTS_MD>
-02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
+00:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=<none>;next_user=USER_ONE]
+01:message/user:<AGENTS_MD> [prev_user=<none>;next_user=USER_ONE]
+02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>> [prev_user=<none>;next_user=USER_ONE]
 03:message/user:USER_ONE
 04:message/assistant:REMOTE_FIRST_REPLY
diff --git a/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_pre_turn_compaction_including_incoming_shapes.snap b/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_pre_turn_compaction_including_incoming_shapes.snap
index 48346aebab..def3975e0d 100644
--- a/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_pre_turn_compaction_including_incoming_shapes.snap
+++ b/codex-rs/core/tests/suite/snapshots/all__suite__compact_remote__remote_pre_turn_compaction_including_incoming_shapes.snap
@@ -5,21 +5,21 @@ expression: "sectioned_request_shapes(\"Remote pre-turn auto-compaction with a c
 Scenario: Remote pre-turn auto-compaction with a context override emits the context diff in the compact request while excluding the incoming user message on main.
 
 ## Remote Compaction Request
-00:message/developer:<PERMISSIONS_INSTRUCTIONS>
-01:message/user:<AGENTS_MD>
-02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>>
+00:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=<none>;next_user=USER_ONE]
+01:message/user:<AGENTS_MD> [prev_user=<none>;next_user=USER_ONE]
+02:message/user:<ENVIRONMENT_CONTEXT:cwd=<CWD>> [prev_user=<none>;next_user=USER_ONE]
 03:message/user:USER_ONE
 04:message/assistant:REMOTE_FIRST_REPLY
 05:message/user:USER_TWO
 06:message/assistant:REMOTE_SECOND_REPLY
-07:message/user:<ENVIRONMENT_CONTEXT:cwd=PRETURN_CONTEXT_DIFF_CWD>
+07:message/user:<ENVIRONMENT_CONTEXT:cwd=PRETURN_CONTEXT_DIFF_CWD> [prev_user=USER_TWO;next_user=<none>]
 
 ## Remote Post-Compaction History Layout
 00:message/user:USER_ONE
 01:message/user:USER_TWO
 02:message/user:USER_THREE
-03:message/developer:<PERMISSIONS_INSTRUCTIONS>
-04:message/user:<AGENTS_MD>
-05:message/user:<ENVIRONMENT_CONTEXT:cwd=PRETURN_CONTEXT_DIFF_CWD>
+03:message/developer:<PERMISSIONS_INSTRUCTIONS> [prev_user=USER_THREE;next_user=USER_THREE]
+04:message/user:<AGENTS_MD> [prev_user=USER_THREE;next_user=USER_THREE]
+05:message/user:<ENVIRONMENT_CONTEXT:cwd=PRETURN_CONTEXT_DIFF_CWD> [prev_user=USER_THREE;next_user=USER_THREE]
 06:message/user:<SUMMARY:REMOTE_PRE_TURN_SUMMARY>
 07:message/user:USER_THREE