replay-theater

1// Copyright 2026 Anthropic PBC
2// SPDX-License-Identifier: Apache-2.0
3//
4// Replay Theater: records the file edits Claude makes in a turn, then lets you
5// step through them in a pane, one diff at a time.
6//
7// Claude Code 2.1.280 function hooks. Load with --plugin-dir.
8
9// cockpit patch: the cockpit accent, instead of magenta and cyan, and no border box.
10const CLAY = "#d97757";
11const PANE_ID = "replay-theater";
12const MAX_DIFF_LINES = 12;
13const MAX_LCS_LINES = 400;
14const EDIT_TOOLS = new Set(["Edit", "Write", "MultiEdit"]);
15
16// Module state. `pending` fills during a turn; `replay` is the last finished
17// turn's steps, the ones the pane shows.
18const state = { pending: [], replay: [], index: 0, isOpen: false, inBand: false, turns: 0 };
19
20function relPath(cwd, path) {
21  if (!path) return "(unknown file)";
22  if (cwd && path.startsWith(cwd + "/")) return path.slice(cwd.length + 1);
23  return path;
24}
25
26function splitLines(text) {
27  if (text === undefined || text === null || text === "") return [];
28  const lines = String(text).split("\n");
29  if (lines.length > 1 && lines[lines.length - 1] === "") lines.pop();
30  return lines;
31}
32
33// A line diff. Small inputs get an LCS diff, so unchanged lines show as
34// context; large ones fall back to all-removed then all-added.
35function diffLines(oldText, newText) {
36  const a = splitLines(oldText);
37  const b = splitLines(newText);
38  if (a.length > MAX_LCS_LINES || b.length > MAX_LCS_LINES) {
39    return [...a.map((t) => ({ op: "-", t })), ...b.map((t) => ({ op: "+", t }))];
40  }
41  const n = a.length, m = b.length;
42  const dp = Array.from({ length: n + 1 }, () => new Array(m + 1).fill(0));
43  for (let i = n - 1; i >= 0; i--)
44    for (let j = m - 1; j >= 0; j--)
45      dp[i][j] = a[i] === b[j] ? dp[i + 1][j + 1] + 1 : Math.max(dp[i + 1][j], dp[i][j + 1]);
46  const out = [];
47  let i = 0, j = 0;
48  while (i < n && j < m) {
49    if (a[i] === b[j]) { out.push({ op: " ", t: a[i] }); i++; j++; }
50    else if (dp[i + 1][j] >= dp[i][j + 1]) out.push({ op: "-", t: a[i++] });
51    else out.push({ op: "+", t: b[j++] });
52  }
53  while (i < n) out.push({ op: "-", t: a[i++] });
54  while (j < m) out.push({ op: "+", t: b[j++] });
55  return trimContext(out);
56}
57
58// Keep one line of context around each change, so a long file's Write shows
59// the changed lines, not the whole file.
60function trimContext(lines) {
61  if (!lines.some((l) => l.op !== " ")) return lines.slice(0, MAX_DIFF_LINES);
62  const keep = lines.map((l, k) =>
63    l.op !== " " || lines[k - 1]?.op && lines[k - 1].op !== " " || lines[k + 1]?.op && lines[k + 1].op !== " ");
64  const out = [];
65  let skipped = false;
66  lines.forEach((l, k) => {
67    if (keep[k]) { if (skipped && out.length) out.push({ op: "~", t: "⋯" }); out.push(l); skipped = false; }
68    else skipped = true;
69  });
70  return out;
71}
72
73function countChanges(diff) {
74  let add = 0, del = 0;
75  for (const l of diff) { if (l.op === "+") add++; else if (l.op === "-") del++; }
76  return { add, del };
77}
78
79// Turns one tool call into one or more steps.
80async function stepsFor($, e) {
81  let cwd = "";
82  try { cwd = await $.session.cwd(); } catch { /* keep the full path */ }
83  const file = relPath(cwd, e.file_path);
84  if (e.tool === "Edit") {
85    return [{ tool: "Edit", file, diff: diffLines(e.old_string, e.new_string), note: e.replace_all ? "replace all" : "" }];
86  }
87  if (e.tool === "MultiEdit" && Array.isArray(e.edits)) {
88    return e.edits.map((ed, k) => ({
89      tool: "MultiEdit", file, diff: diffLines(ed.old_string, ed.new_string), note: `edit ${k + 1} of ${e.edits.length}`,
90    }));
91  }
92  if (e.tool === "Write") {
93    let before = "";
94    let isNew = true;
95    try {
96      if (e.file_path && (await $.fs.exists(e.file_path))) {
97        before = await $.fs.read(e.file_path);
98        isNew = false;
99      }
100    } catch { /* unreadable: show it as a new file */ }
101    return [{ tool: "Write", file, diff: diffLines(before, e.content), note: isNew ? "new file" : "rewrite" }];
102  }
103  return [];
104}
105
106function hintText() {
107  const n = state.replay.length;
108  return `▶ Replay: ${n} edit${n === 1 ? "" : "s"} (press r)`;
109}
110
111async function openReplay($) {
112  if (!state.replay.length) return false;
113  state.index = 0;
114  state.isOpen = true;
115  // The pane only takes the keyboard while nothing else holds it. Hide the
116  // band first (it held the keys if its button was pressed), then open.
117  $.ui.invalidate("ui.render");
118  await $.clock.sleep(200);
119  const rows = Math.min(MAX_DIFF_LINES + 8, 22);
120  const placed = await $.ui.open({ id: PANE_ID, title: "Replay Theater", focus: true, closeOnEscape: true, rows, columns: 58 });
121  // No room for a pane (a narrow terminal): draw the replay in the band.
122  state.inBand = placed?.isPlaced === false;
123  $.ui.invalidate("ui.render");
124  return true;
125}
126
127// The replay view: one step at a time. Drawn in the Pane, or in the band
128// above the prompt when the surface can't place a pane.
129function replayView($, e, inBand) {
130    const { Box, Text, Button } = $.ui.resolve(e);
131    const maxDiff = inBand ? Math.max(3, Math.min(MAX_DIFF_LINES, (e.maxRows || 20) - 7)) : MAX_DIFF_LINES;
132    const total = state.replay.length;
133    if (!total) return Text({ dimColor: true, children: "No edits to replay." });
134    const k = Math.max(0, Math.min(state.index, total - 1));
135    const step = state.replay[k];
136    const width = Math.max(40, (e.bodyColumns || 100) - 4);
137    const { add, del } = countChanges(step.diff);
138    const shown = step.diff.slice(0, maxDiff);
139
140    const diffRows = shown.map((l, n) => {
141      const color = l.op === "+" ? "green" : l.op === "-" ? "red" : undefined;
142      const line = `${l.op === "~" ? " " : l.op} ${l.t}`.slice(0, width);
143      return Text({ key: `d${n}`, color, dimColor: l.op === " " || l.op === "~", wrap: "truncate-end", children: line });
144    });
145    if (step.diff.length > maxDiff) diffRows.push(Text({ key: "more", dimColor: true, children: `  … ${step.diff.length - maxDiff} more lines` }));
146    if (!shown.length) diffRows.push(Text({ key: "empty", dimColor: true, children: "  (no line changes)" }));
147
148    // The step list: one cell per step, the current one highlighted.
149    const strip = state.replay.map((s, n) =>
150      Text({ key: `s${n}`, inverse: n === k, color: n === k ? CLAY : undefined, dimColor: n !== k, children: ` ${n + 1} ` }));
151
152    const go = (to) => { state.index = Math.max(0, Math.min(to, total - 1)); $.ui.invalidate("ui.render"); };
153    const close = () => {
154      state.isOpen = false;
155      if (!state.inBand) $.ui.close({ id: PANE_ID });
156      state.inBand = false;
157      $.ui.invalidate("ui.render");
158    };
159
160    return Box({
161      flexDirection: "column", paddingX: 1,
162      children: [
163        Box({ flexDirection: "row", justifyContent: "space-between", children: [
164          Text({ bold: true, color: CLAY, children: "▶ Replay Theater" }),
165          Text({ bold: true, children: `step ${k + 1} of ${total}` }),
166        ] }),
167        Box({ flexDirection: "row", children: strip }),
168        Text({ bold: true, wrap: "truncate-start", children: step.file }),
169        Box({ flexDirection: "row", gap: 2, children: [
170          Text({ dimColor: true, children: `${step.tool}${step.note ? " · " + step.note : ""}` }),
171          Text({ color: "green", children: `+${add}` }),
172          Text({ color: "red", children: `-${del}` }),
173        ] }),
174        Box({ flexDirection: "column", marginTop: 1, children: diffRows }),
175        Box({ flexDirection: "row", gap: 2, marginTop: 1, children: [
176          Button({ key: "prev", label: "◀ Prev", hotkey: "p", onPress: () => go(k - 1) }),
177          Button({ key: "next", label: "Next ▶", hotkey: "n", autoFocus: true, onPress: () => go(k + 1) }),
178          Button({ key: "close", label: "Close", hotkey: "c", onPress: close }),
179        ] }),
180      ],
181    });
182}
183
184export function register(on, options) {
185  // Slash command: /replay opens the pane.
186  on("session.start", async ($, e, next) => {
187    const r = await next(e);
188    await $.command.register({ name: "replay", description: "Replay Theater: step through the last turn's file edits" });
189    return r;
190  });
191
192  on("command.run", { command: "replay" }, async ($, e) => {
193    const opened = await openReplay($);
194    return { text: opened ? `Replay Theater: ${state.replay.length} edits` : "Replay Theater: no edits in the last turn." };
195  });
196
197  // Record each edit, then let it run. Never blocks the call.
198  on("tool.call", async ($, e, next) => {
199    if (EDIT_TOOLS.has(e.tool)) {
200      try {
201        const steps = await stepsFor($, e);
202        state.pending.push(...steps);
203      } catch { /* recording must never stop the edit */ }
204    }
205    return next(e);
206  });
207
208  on("turn.start", ($, e, next) => {
209    if (!e.agentId) state.pending = [];
210    return next(e);
211  });
212
213  // At the end of a main-loop turn, the pending edits become the replay.
214  on("turn.complete", async ($, e, next) => {
215    const r = await next(e);
216    if (e.agentId || !state.pending.length) return r;
217    state.replay = state.pending;
218    state.pending = [];
219    state.index = 0;
220    state.turns++;
221    $.ui.invalidate("ui.render");
222    return r;
223  });
224
225  // The band above the prompt: the hint and a button that opens the pane.
226  // cockpit patch: stack above whatever other plugins draw in this slot instead of replacing it.
227  on("ui.render", { component: "AbovePrompt" }, async ($, e, next) => {
228    const below = await next(e);
229    const { Box, Text, Button } = $.ui.resolve(e);
230    const stack = (mine) => Box({ flexDirection: "column", children: [mine, below].filter(Boolean) });
231    if (state.isOpen && state.inBand) return stack(replayView($, e, true));
232    if (!state.replay.length || state.isOpen) return below;
233    return stack(Box({
234      flexDirection: "row", gap: 2, paddingX: 1,
235      children: [
236        Text({ color: CLAY, bold: true, children: hintText() }),
237        Button({ key: "open-replay", label: "Replay", hotkey: "r", onPress: () => openReplay($) }),
238      ],
239    }));
240  });
241
242  // The pane.
243  on("ui.render", { component: "Pane" }, ($, e, next) => {
244    if (e.requestId !== PANE_ID) return next(e);
245    return replayView($, e, false);
246  });
247
248  // The person closed the pane (Escape): keep our flag in step.
249  on("ui.close", ($, e, next) => {
250    if (e.id === PANE_ID || e.requestId === PANE_ID) state.isOpen = false;
251    $.ui.invalidate("ui.render");
252    return next(e);
253  });
254}
255