Move guardian prompt composition into the reviewer crate (#57488)

## What changed

Export `GuardianPromptItems` and `compose_guardian_prompt` from `codex-guardian-reviewer`, and delegate prompt composition from core to the new helper. Core continues to collect context sections and choose the history version.

Preserve full and delta transcript selection, empty-transcript placeholders, cursor accounting, and Node REPL evidence sequencing.

GitOrigin-RevId: e3e2b2a87a42709ddb5441f47cbb7461b0130579

codex-rs/core/src/guardian/prompt.rs

@@ -1,9 +1,8 @@
 use codex_extension_api::ConversationHistorySnapshot;
 use codex_features::Feature;
+#[cfg(test)]
 use codex_guardian_context::Budgeted;
 use codex_guardian_context::CollectedContext;
-use codex_guardian_context::ComposedContext;
-use codex_guardian_context::ContextPresentation;
 use codex_guardian_context::ContextProfile;
 #[cfg(test)]
 use codex_guardian_context::ConversationTranscriptEntry;
@@ -13,10 +12,11 @@ use codex_guardian_context::PlannedActionKind;
 use codex_guardian_context::SectionError;
 use codex_guardian_context::SectionHistory;
 use codex_guardian_context::SectionInput;
+#[cfg(test)]
 pub(crate) use codex_guardian_context::TranscriptCursor as GuardianTranscriptCursor;
 pub(crate) use codex_guardian_context::TranscriptMode as GuardianPromptMode;
-use codex_guardian_context::TranscriptSelection;
 use codex_guardian_context::default_registry;
+use codex_guardian_reviewer::GuardianPromptItems;
 use codex_protocol::models::ResponseItem;
 
 use crate::context::GuardianPermissionContext;
@@ -45,12 +45,6 @@ pub(crate) enum GuardianTranscriptHistory<'a> {
     LoadedParentCheckpoint(&'a dyn ConversationHistorySnapshot),
 }
 
-pub(crate) struct GuardianPromptItems {
-    pub(crate) context: ComposedContext,
-    pub(crate) transcript_cursor: GuardianTranscriptCursor,
-    pub(crate) node_repl_evidence_sequence: u64,
-}
-
 /// Builds the guardian user content items from:
 /// - a compact transcript for authorization and local context
 /// - the exact action JSON being proposed for approval
@@ -210,45 +204,18 @@ pub(crate) async fn build_guardian_prompt_items_with_parent_turn(
         permissions.as_ref(),
         node_repl_context.as_ref(),
     )?;
-    let (selection, transcript_cursor) = mode.select(
-        sections.transcript_entries(),
+    codex_guardian_reviewer::compose_guardian_prompt(
+        sections,
+        &profile,
+        mode,
         if use_parent_checkpoint {
             history.history_version()
         } else {
             history.review_history_version()
         },
-    );
-    let session_id = session.thread_id.to_string();
-    let (transcript_entries, offset, placeholder, presentation) = match selection {
-        TranscriptSelection::Full(entries) => (
-            entries,
-            0,
-            "<no retained transcript entries>",
-            ContextPresentation::SyncFull {
-                session_id: &session_id,
-            },
-        ),
-        TranscriptSelection::Delta { entries, offset } => (
-            entries,
-            offset,
-            "<no retained transcript delta entries>",
-            ContextPresentation::SyncDelta {
-                session_id: &session_id,
-            },
-        ),
-    };
-    let mut transcript = profile.prepare_transcript(transcript_entries, offset);
-    if transcript_entries.is_empty() {
-        transcript.items.push(Budgeted::required(
-            codex_guardian_context::TranscriptContent::Text(placeholder.to_owned()),
-        ));
-    }
-    let context = sections.compose(presentation, transcript)?;
-    Ok(GuardianPromptItems {
-        context,
-        transcript_cursor,
+        &session.thread_id.to_string(),
         node_repl_evidence_sequence,
-    })
+    )
 }
 
 /// Exercises the sync profile through the host's existing transcript tests.

codex-rs/ext/guardian-reviewer/src/lib.rs

@@ -19,6 +19,7 @@ mod metrics;
 mod model;
 mod outcome;
 mod pool;
+mod prompt;
 mod reporting;
 mod retry;
 mod review;
@@ -58,6 +59,8 @@ pub use pool::ReviewerRequest;
 pub use pool::ReviewerSession;
 pub use pool::ReviewerTasks;
 pub use pool::SessionDisposition;
+pub use prompt::GuardianPromptItems;
+pub use prompt::compose_guardian_prompt;
 
 pub use review::ReviewHost;
 

codex-rs/ext/guardian-reviewer/src/prompt.rs

@@ -0,0 +1,55 @@
+//! Composes synchronous review prompts from the host's captured context sections.
+//! Full/delta selection, empty-transcript text, and cursor accounting preserve the existing layout.
+
+use codex_guardian_context::Budgeted;
+use codex_guardian_context::CollectedContext;
+use codex_guardian_context::ComposedContext;
+use codex_guardian_context::ContextPresentation;
+use codex_guardian_context::ContextProfile;
+use codex_guardian_context::TranscriptCursor as GuardianTranscriptCursor;
+use codex_guardian_context::TranscriptMode as GuardianPromptMode;
+use codex_guardian_context::TranscriptSelection;
+
+pub struct GuardianPromptItems {
+    pub context: ComposedContext,
+    pub transcript_cursor: GuardianTranscriptCursor,
+    pub node_repl_evidence_sequence: u64,
+}
+
+pub fn compose_guardian_prompt(
+    sections: CollectedContext,
+    profile: &ContextProfile,
+    mode: GuardianPromptMode,
+    history_version: u64,
+    session_id: &str,
+    node_repl_evidence_sequence: u64,
+) -> anyhow::Result<GuardianPromptItems> {
+    let (selection, transcript_cursor) =
+        mode.select(sections.transcript_entries(), history_version);
+    let (transcript_entries, offset, placeholder, presentation) = match selection {
+        TranscriptSelection::Full(entries) => (
+            entries,
+            0,
+            "<no retained transcript entries>",
+            ContextPresentation::SyncFull { session_id },
+        ),
+        TranscriptSelection::Delta { entries, offset } => (
+            entries,
+            offset,
+            "<no retained transcript delta entries>",
+            ContextPresentation::SyncDelta { session_id },
+        ),
+    };
+    let mut transcript = profile.prepare_transcript(transcript_entries, offset);
+    if transcript_entries.is_empty() {
+        transcript.items.push(Budgeted::required(
+            codex_guardian_context::TranscriptContent::Text(placeholder.to_owned()),
+        ));
+    }
+    let context = sections.compose(presentation, transcript)?;
+    Ok(GuardianPromptItems {
+        context,
+        transcript_cursor,
+        node_repl_evidence_sequence,
+    })
+}