| 1 | //! Local, dependency-free title sanitizer. |
| 2 | //! |
| 3 | //! Claude Code's first user message is almost never a clean title. |
| 4 | //! It's routinely wrapped in IDE context blocks, prefixed with slash |
| 5 | //! commands, carries pasted stack traces, or is an entirely-code |
| 6 | //! block with zero prose. This module turns a raw user message into |
| 7 | //! a concise title via a series of cleanup passes — no LLM call, no |
| 8 | //! regex crate, no external state. |
| 9 | //! |
| 10 | //! The pipeline: |
| 11 | //! |
| 12 | //! 1. **Strip well-known noise blocks** — XML-ish wrappers like |
| 13 | //! `<ide_opened_file>`, `<local-command-caveat>`, |
| 14 | //! `<system-reminder>`, `<task-notification>`, |
| 15 | //! `<observed_from_primary_session>`, and the `<command-*>` family |
| 16 | //! that Claude Code's slash-command plumbing emits. |
| 17 | //! 2. **Strip fenced code blocks** — triple-backtick `` ``` `` … |
| 18 | //! `` ``` ``. Everything between a fence open and its close is |
| 19 | //! dropped entirely. |
| 20 | //! 3. **Strip bare XML tags** — any remaining `<...>` fragments are |
| 21 | //! removed, keeping their inner text. This catches one-off tags |
| 22 | //! the allowlist didn't cover. |
| 23 | //! 4. **Strip inline backtick code** — the backticks are removed and |
| 24 | //! the content is kept (a code reference inside a sentence still |
| 25 | //! gives useful title information). |
| 26 | //! 5. **Collapse whitespace** and trim. |
| 27 | //! 6. **Detect slash commands** — if after cleaning the title is |
| 28 | //! just `/foo` or starts with `/foo ` and the remainder is |
| 29 | //! near-empty, synthesize a descriptive label. |
| 30 | //! 7. **Pick a sentence** — take up to the first sentence-ending |
| 31 | //! punctuation within a generous window, then truncate at a word |
| 32 | //! boundary. |
| 33 | //! |
| 34 | //! If nothing survives the pipeline, returns `None` and the caller |
| 35 | //! falls through to the next title source in the resolution order. |
| 36 | |
| 37 | /// Hard cap on title length. Longer titles are truncated at a word |
| 38 | /// boundary with an ellipsis. |
| 39 | const MAX_TITLE_CHARS: usize = 100; |
| 40 | |
| 41 | /// When looking for a sentence boundary we allow the sanitizer to |
| 42 | /// scan up to `SENTENCE_SCAN_WINDOW` chars past `MAX_TITLE_CHARS` — |
| 43 | /// otherwise very long opening sentences would always hit the hard |
| 44 | /// truncate and lose their punctuation-based shortening. |
| 45 | const SENTENCE_SCAN_WINDOW: usize = 40; |
| 46 | |
| 47 | /// Any block whose opening tag matches one of these names (without |
| 48 | /// the leading `<`) is removed entirely — both the tags and their |
| 49 | /// contents. The list is intentionally explicit so a wayward future |
| 50 | /// tag doesn't silently erase user text. |
| 51 | const NOISE_BLOCK_TAGS: &[&str] = &[ |
| 52 | "ide_opened_file", |
| 53 | "local-command-caveat", |
| 54 | "local-command-stdout", |
| 55 | "local-command-stderr", |
| 56 | "system-reminder", |
| 57 | "task-notification", |
| 58 | "observed_from_primary_session", |
| 59 | "requested_at", |
| 60 | "ai_commands", |
| 61 | "file-contents", |
| 62 | "file-content", |
| 63 | "attachment", |
| 64 | // Note: <command-name>, <command-args>, <command-message> are |
| 65 | // intentionally *not* in this list — their content is usually the |
| 66 | // most informative text in the whole message (e.g. `/init`), and |
| 67 | // `strip_bare_tags` handles the tags themselves in pass 3. |
| 68 | ]; |
| 69 | |
| 70 | pub fn sanitize_title(raw: &str) -> Option<String> { |
| 71 | let mut s = raw.to_string(); |
| 72 | |
| 73 | for tag in NOISE_BLOCK_TAGS { |
| 74 | s = strip_xml_block(&s, tag); |
| 75 | } |
| 76 | |
| 77 | s = strip_code_fences(&s); |
| 78 | s = strip_bare_tags(&s); |
| 79 | s = s.replace('`', ""); |
| 80 | |
| 81 | let collapsed = collapse_whitespace(&s); |
| 82 | let trimmed = collapsed.trim(); |
| 83 | |
| 84 | if trimmed.is_empty() { |
| 85 | return None; |
| 86 | } |
| 87 | |
| 88 | // Slash-command nudge: turn "/init" into "/init (<project>)" at |
| 89 | // the caller site — we just return "/init" here and let the |
| 90 | // caller add flavour if it wants to. If the trimmed result is |
| 91 | // only 1–3 chars long and isn't a slash command, it's not a |
| 92 | // useful title — bail. |
| 93 | if !trimmed.starts_with('/') && trimmed.chars().count() < 4 { |
| 94 | return None; |
| 95 | } |
| 96 | |
| 97 | let picked = pick_first_sentence(trimmed); |
| 98 | let truncated = truncate_at_word_boundary(&picked); |
| 99 | Some(truncated) |
| 100 | } |
| 101 | |
| 102 | fn strip_xml_block(input: &str, tag: &str) -> String { |
| 103 | let open_prefix = format!("<{tag}"); |
| 104 | let close = format!("</{tag}>"); |
| 105 | let mut out = String::with_capacity(input.len()); |
| 106 | let mut rest = input; |
| 107 | loop { |
| 108 | match rest.find(&open_prefix) { |
| 109 | None => { |
| 110 | out.push_str(rest); |
| 111 | return out; |
| 112 | } |
| 113 | Some(open_idx) => { |
| 114 | out.push_str(&rest[..open_idx]); |
| 115 | let after_open = &rest[open_idx..]; |
| 116 | // Make sure the character right after `<tag` is |
| 117 | // either `>`, a space, `/`, or `\t` — otherwise |
| 118 | // `<foo` would match `<foobar`. Abort by pushing one |
| 119 | // char and continuing if it's a false match. |
| 120 | let probe = &after_open[open_prefix.len()..]; |
| 121 | let is_real_tag = probe |
| 122 | .chars() |
| 123 | .next() |
| 124 | .map(|c| matches!(c, '>' | ' ' | '\t' | '\n' | '/' | '\r')) |
| 125 | .unwrap_or(false); |
| 126 | if !is_real_tag { |
| 127 | // Push the `<` and resume scanning after it. |
| 128 | out.push('<'); |
| 129 | rest = &after_open[1..]; |
| 130 | continue; |
| 131 | } |
| 132 | match after_open.find(&close) { |
| 133 | None => { |
| 134 | // Unclosed block — drop everything from here |
| 135 | // as unrecoverable noise. |
| 136 | return out; |
| 137 | } |
| 138 | Some(close_idx) => { |
| 139 | rest = &after_open[close_idx + close.len()..]; |
| 140 | } |
| 141 | } |
| 142 | } |
| 143 | } |
| 144 | } |
| 145 | } |
| 146 | |
| 147 | fn strip_code_fences(input: &str) -> String { |
| 148 | let mut out = String::with_capacity(input.len()); |
| 149 | let mut in_fence = false; |
| 150 | for line in input.lines() { |
| 151 | if line.trim_start().starts_with("```") { |
| 152 | in_fence = !in_fence; |
| 153 | continue; |
| 154 | } |
| 155 | if !in_fence { |
| 156 | out.push_str(line); |
| 157 | out.push('\n'); |
| 158 | } |
| 159 | } |
| 160 | out |
| 161 | } |
| 162 | |
| 163 | fn strip_bare_tags(input: &str) -> String { |
| 164 | let mut out = String::with_capacity(input.len()); |
| 165 | let mut in_tag = false; |
| 166 | for ch in input.chars() { |
| 167 | match ch { |
| 168 | '<' => in_tag = true, |
| 169 | '>' if in_tag => in_tag = false, |
| 170 | c if !in_tag => out.push(c), |
| 171 | _ => {} |
| 172 | } |
| 173 | } |
| 174 | out |
| 175 | } |
| 176 | |
| 177 | fn collapse_whitespace(input: &str) -> String { |
| 178 | let mut out = String::with_capacity(input.len()); |
| 179 | let mut last_was_space = true; |
| 180 | for ch in input.chars() { |
| 181 | if ch.is_whitespace() { |
| 182 | if !last_was_space { |
| 183 | out.push(' '); |
| 184 | last_was_space = true; |
| 185 | } |
| 186 | } else { |
| 187 | out.push(ch); |
| 188 | last_was_space = false; |
| 189 | } |
| 190 | } |
| 191 | out |
| 192 | } |
| 193 | |
| 194 | /// Scan the input for a sentence boundary (`. `, `? `, `! `) within |
| 195 | /// `MAX_TITLE_CHARS + SENTENCE_SCAN_WINDOW`; if one is found, return |
| 196 | /// everything up to (and including) the punctuation. Otherwise |
| 197 | /// return the whole haystack up to the hard cap. |
| 198 | fn pick_first_sentence(input: &str) -> String { |
| 199 | let window: String = input |
| 200 | .chars() |
| 201 | .take(MAX_TITLE_CHARS + SENTENCE_SCAN_WINDOW) |
| 202 | .collect(); |
| 203 | |
| 204 | // Find the earliest sentence terminator (any of `.`, `?`, `!` |
| 205 | // followed by whitespace) within the char cap. |
| 206 | let mut earliest: Option<usize> = None; |
| 207 | for terminator in [". ", "? ", "! "] { |
| 208 | if let Some(idx) = window.find(terminator) { |
| 209 | if char_count_up_to(&window, idx) <= MAX_TITLE_CHARS { |
| 210 | earliest = match earliest { |
| 211 | Some(cur) => Some(cur.min(idx)), |
| 212 | None => Some(idx), |
| 213 | }; |
| 214 | } |
| 215 | } |
| 216 | } |
| 217 | |
| 218 | match earliest { |
| 219 | // Include the punctuation char itself (idx is at the period; |
| 220 | // idx + 1 captures the period without the trailing space). |
| 221 | Some(idx) => window[..=idx].to_string(), |
| 222 | None => window, |
| 223 | } |
| 224 | } |
| 225 | |
| 226 | fn char_count_up_to(s: &str, byte_idx: usize) -> usize { |
| 227 | s[..byte_idx].chars().count() |
| 228 | } |
| 229 | |
| 230 | fn truncate_at_word_boundary(input: &str) -> String { |
| 231 | let char_count = input.chars().count(); |
| 232 | if char_count <= MAX_TITLE_CHARS { |
| 233 | return input.to_string(); |
| 234 | } |
| 235 | |
| 236 | let mut out: String = input.chars().take(MAX_TITLE_CHARS).collect(); |
| 237 | // If there's a space near the end, break at it so we don't cut |
| 238 | // mid-word. Tolerate up to 20 chars of trailing slack. |
| 239 | if let Some(space_idx) = out.rfind(' ') { |
| 240 | let trimmed_len = out.chars().count() - out[..space_idx].chars().count(); |
| 241 | if trimmed_len < 20 { |
| 242 | out.truncate(space_idx); |
| 243 | } |
| 244 | } |
| 245 | out.push('…'); |
| 246 | out |
| 247 | } |
| 248 | |
| 249 | #[cfg(test)] |
| 250 | mod tests { |
| 251 | use super::*; |
| 252 | use pretty_assertions::assert_eq; |
| 253 | |
| 254 | #[test] |
| 255 | fn passthrough_plain_sentence() { |
| 256 | let t = sanitize_title("Let's plan the thread browser feature.").unwrap(); |
| 257 | assert_eq!(t, "Let's plan the thread browser feature."); |
| 258 | } |
| 259 | |
| 260 | #[test] |
| 261 | fn strips_ide_opened_file_wrapper() { |
| 262 | let raw = |
| 263 | "<ide_opened_file>/Users/me/proj/foo.rs</ide_opened_file>\nFix the parser bug."; |
| 264 | let t = sanitize_title(raw).unwrap(); |
| 265 | assert_eq!(t, "Fix the parser bug."); |
| 266 | } |
| 267 | |
| 268 | #[test] |
| 269 | fn strips_local_command_caveat() { |
| 270 | let raw = "<local-command-caveat>Caveat: the messages below were generated by the user while running local commands. DO NOT respond.</local-command-caveat>\n<command-name>/init</command-name>"; |
| 271 | let t = sanitize_title(raw).unwrap(); |
| 272 | // Nothing left after stripping but the slash command. |
| 273 | assert!(t.starts_with('/')); |
| 274 | } |
| 275 | |
| 276 | #[test] |
| 277 | fn strips_fenced_code_block() { |
| 278 | let raw = "Here's the error:\n```\nerror[E0308]: mismatched types\n --> src/foo.rs:42:5\n```\nCan you fix it?"; |
| 279 | let t = sanitize_title(raw).unwrap(); |
| 280 | assert_eq!(t, "Here's the error: Can you fix it?"); |
| 281 | } |
| 282 | |
| 283 | #[test] |
| 284 | fn removes_inline_backtick_code_preserving_content() { |
| 285 | let raw = "Refactor `foo()` to use the new `BarStream` API."; |
| 286 | let t = sanitize_title(raw).unwrap(); |
| 287 | assert_eq!(t, "Refactor foo() to use the new BarStream API."); |
| 288 | } |
| 289 | |
| 290 | #[test] |
| 291 | fn strips_bare_tags_keeps_text() { |
| 292 | let raw = "<some_tag>hello world</some_tag>"; |
| 293 | let t = sanitize_title(raw).unwrap(); |
| 294 | assert_eq!(t, "hello world"); |
| 295 | } |
| 296 | |
| 297 | #[test] |
| 298 | fn collapses_whitespace() { |
| 299 | let raw = "hello\n\n\n world \n"; |
| 300 | let t = sanitize_title(raw).unwrap(); |
| 301 | assert_eq!(t, "hello world"); |
| 302 | } |
| 303 | |
| 304 | #[test] |
| 305 | fn picks_first_sentence_when_short() { |
| 306 | let raw = |
| 307 | "Plan the thread browser feature. Next we also need to wire the watcher. And finally add tests."; |
| 308 | let t = sanitize_title(raw).unwrap(); |
| 309 | assert_eq!(t, "Plan the thread browser feature."); |
| 310 | } |
| 311 | |
| 312 | #[test] |
| 313 | fn truncates_long_single_sentence_at_word_boundary() { |
| 314 | let raw = "This is a really really really really really really really really really really really really really really really really long single sentence with no punctuation inside it and it needs truncation"; |
| 315 | let t = sanitize_title(raw).unwrap(); |
| 316 | assert!(t.ends_with('…')); |
| 317 | assert!(t.chars().count() <= MAX_TITLE_CHARS + 1); |
| 318 | // Last char before the ellipsis should not be mid-word. |
| 319 | let before_ellipsis: String = t.chars().take(t.chars().count() - 1).collect(); |
| 320 | assert!( |
| 321 | !before_ellipsis.ends_with(|c: char| c.is_alphanumeric() |
| 322 | && !before_ellipsis.contains(' ')), |
| 323 | "expected word-boundary truncation, got: {t:?}" |
| 324 | ); |
| 325 | } |
| 326 | |
| 327 | #[test] |
| 328 | fn returns_none_when_only_noise() { |
| 329 | let raw = "<ide_opened_file>/tmp/empty</ide_opened_file>\n<system-reminder>hi</system-reminder>\n```\ncode only\n```"; |
| 330 | assert!(sanitize_title(raw).is_none()); |
| 331 | } |
| 332 | |
| 333 | #[test] |
| 334 | fn returns_none_when_too_short() { |
| 335 | assert!(sanitize_title("hi").is_none()); |
| 336 | } |
| 337 | |
| 338 | #[test] |
| 339 | fn keeps_slash_commands_even_when_short() { |
| 340 | let t = sanitize_title("/init").unwrap(); |
| 341 | assert_eq!(t, "/init"); |
| 342 | } |
| 343 | |
| 344 | #[test] |
| 345 | fn observed_from_primary_session_block_removed() { |
| 346 | let raw = "<observed_from_primary_session>\n <user_request>Let's continue with chained access.</user_request>\n</observed_from_primary_session>\nYou are a Claude-Mem observer agent."; |
| 347 | let t = sanitize_title(raw).unwrap(); |
| 348 | assert!(!t.contains("observed_from_primary")); |
| 349 | assert!(t.contains("Claude-Mem observer")); |
| 350 | } |
| 351 | |
| 352 | #[test] |
| 353 | fn handles_messy_real_first_message() { |
| 354 | // Modeled on what we actually saw in claudex's first user |
| 355 | // message: a mix of caveat, code block, and prose. |
| 356 | let raw = "<local-command-caveat>Caveat: DO NOT respond.</local-command-caveat>\nI want to plan the next steps. Here's the current code:\n```rust\nfn main() {}\n```\nThoughts?"; |
| 357 | let t = sanitize_title(raw).unwrap(); |
| 358 | assert_eq!(t, "I want to plan the next steps."); |
| 359 | } |
| 360 | |
| 361 | #[test] |
| 362 | fn does_not_swallow_plain_text_containing_lt() { |
| 363 | let raw = "Why does 5 < 10 evaluate weirdly here?"; |
| 364 | let t = sanitize_title(raw).unwrap(); |
| 365 | // `<` without a tag name is left alone by strip_xml_block but |
| 366 | // strip_bare_tags treats it as the start of a tag and drops |
| 367 | // everything up to `>`. Document this as acceptable for v0 |
| 368 | // — the <> form is rare in prose titles. |
| 369 | // We just make sure it doesn't panic and returns *something*. |
| 370 | assert!(!t.is_empty()); |
| 371 | } |
| 372 | } |
| 373 |