editor: show postfix in the prompt preview

The per-scene prompt preview mirrors what Studio encodes, and the postfix is
appended to every scene at generation — so it belongs there. Surface it once
after the scenes as a 'postfix' badge, symmetric to the 'anchor' badge shown
once above them.

- bridge.expand_prompt_fragment: expands a standalone fragment (anchor/postfix)
  the same way generation does, so the previewed text matches exactly.
- server preview: result["postfix"] = expanded effective_postfix(p).
- inspector: postfix badge line; _promptPreviewKey includes postfix so editing
  it refreshes the preview live.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

movie_editor/backend/bridge.py

@@ -68,6 +68,25 @@ def parse_timeline(prompt: str, seed: int = 0) -> dict:
     return {"anchor": s.get("anchor_expanded", ""), "scenes": scenes, "transitions": transitions}
 
 
+def expand_prompt_fragment(text: str) -> str:
+    """Expand shortcuts in a standalone fragment (anchor / postfix) the way generation does —
+    mirrors the _flatten(split_scenes(...)) the chain sampler runs on each, so the preview shows
+    exactly the expanded text Studio will append/prepend. Empty in → empty out."""
+    if not str(text or "").strip():
+        return ""
+    split_fn = _funpack_attr("conditioning", "split_scenes")
+    s = split_fn(str(text))
+    parts = []
+    ae = (s.get("anchor_expanded") or "").strip()
+    if ae:
+        parts.append(ae)
+    for sc in (s.get("scenes", []) or []):
+        e = (sc.get("expanded") or "").strip()
+        if e:
+            parts.append(e)
+    return " ".join(parts).strip()
+
+
 def parse_timeline_raw(prompt: str) -> dict:
     """Split WITHOUT expanding shortcuts — scene texts stay verbatim (shortcuts and
     transition triggers preserved). Used by editing views so the user keeps operating

movie_editor/frontend/inspector.js

@@ -580,6 +580,14 @@
       if (t) l.append(el("span", "pv-badge trans", "→ split"));
       box.append(l);
     });
+    // Postfix is appended to every scene at generation — show it once after the scenes, mirroring
+    // how the anchor (prepended) is shown once above them.
+    if (pv.postfix) {
+      const l = el("div", "pv-line");
+      l.append(el("span", "pv-badge postfix", "postfix"));
+      l.append(el("span", null, pv.postfix));
+      box.append(l);
+    }
     const raw = el("details", "pv-raw"); raw.append(el("summary", null, "generation prompt (sent to Studio)")); raw.append(el("pre", null, pv.combined_prompt || "")); box.append(raw);
     if (pv.display_prompt && pv.display_prompt !== pv.combined_prompt) {
       const disp = el("details", "pv-raw"); disp.append(el("summary", null, "display prompt (timeline view)")); disp.append(el("pre", null, pv.display_prompt)); box.append(disp);

movie_editor/frontend/store.js

@@ -125,6 +125,8 @@
     if (!project) return "";
     return JSON.stringify({
       anchor: project.anchor,
+      postfix: project.postfix,
+      postfix_enabled: project.postfix_enabled,
       global_prompt: project.global_prompt,
       intro_transition: project.intro_transition,
       scenes: (project.scenes || []).map((s) => ({

movie_editor/frontend/styles.css

@@ -550,6 +550,7 @@ input[type=number] { font-family: var(--font-mono); }
 .pv-line { display: flex; gap: 8px; align-items: baseline; padding: 3px 0; font-size: 12.5px; }
 .pv-badge { font-family: var(--font-mono); font-size: 9.5px; letter-spacing: .5px; text-transform: uppercase; color: var(--teal); border: 1px solid #57d0c655; border-radius: 4px; padding: 1px 5px; flex: 0 0 auto; }
 .pv-badge.anchor { color: var(--amber); border-color: #f3a93c55; }
+.pv-badge.postfix { color: var(--amber); border-color: #f3a93c55; }
 .pv-badge.trans { color: var(--faint); border-color: transparent; font-size: 9px; }
 .pv-badge.rkey { color: #c79bf2; border-color: #c79bf255; text-transform: none; letter-spacing: 0; }
 .pv-badge.rkey.default { color: var(--faint); border-color: #ffffff22; }

movie_editor/server.py

@@ -29,6 +29,7 @@ from .backend.timeline import (
     collapse_generative_units,
     continuity_media_refs,
     effective_negative_prompt,
+    effective_postfix,
     gen_unit_id,
     group_generative_units,
     is_video_clip,
@@ -1188,6 +1189,9 @@ if web is not None and PromptServer is not None:
                 result["scene_refinement_keys"] = bridge.scene_refinement_keys(
                     prompt, p.refinement_key)
                 result["refinement_key_pool"] = bridge.refinement_key_pool(prompt)
+                # Postfix is appended to every scene at generation but lives outside the prompt —
+                # surface it (expanded) so the preview mirrors what Studio actually encodes.
+                result["postfix"] = bridge.expand_prompt_fragment(effective_postfix(p))
             except Exception as e:  # noqa: BLE001
                 result["parse_error"] = str(e)
             return web.json_response(result)

tests/test_refinement_keys.py

@@ -34,6 +34,7 @@ sys.modules.setdefault(
 import templates
 import conditioning
 from templates import apply_prompt_shortcuts, normalize_shortcut_item
+from movie_editor.backend import bridge
 
 
 def _db(shortcuts):
@@ -137,6 +138,21 @@ def test_postfix_shortcuts_expand_and_key_folds_into_every_scene(monkeypatch):
         assert "look" in scene["keys"]
 
 
+def test_expand_prompt_fragment_matches_generation_postfix(monkeypatch):
+    """The preview's postfix text must be expanded exactly like generation appends it — same
+    shortcut expansion the chain sampler runs via split_scenes_from_segments."""
+    db = _db({"cine": (["cine"], ["cinematic, shallow depth of field"], "look")})
+    monkeypatch.setattr(templates, "load_shortcut_db", lambda: db)
+    monkeypatch.setattr(templates, "load_custom_transition_triggers", lambda: {})
+
+    preview = bridge.expand_prompt_fragment("cine")
+    generation = conditioning.split_scenes_from_segments(
+        "", ["x"], postfix="cine")["postfix_expanded"]
+    assert preview == "cinematic, shallow depth of field"
+    assert preview == generation                       # preview mirrors generation exactly
+    assert bridge.expand_prompt_fragment("") == ""     # disabled/empty postfix shows nothing
+
+
 def test_split_scenes_no_false_cut_from_generic_label_in_expansion(monkeypatch):
     """A content shortcut whose expansion merely CONTAINS 'scene 2' must NOT cut — only a
     user-defined custom transition phrase does (the generic label is never matched on expansions)."""