| 1 | //! Truthful auto-resume of the last valid session (#2934). |
| 2 | //! |
| 3 | //! Plain `codewhale` has always started fresh. Issue #2934 asked for the |
| 4 | //! previous conversation to come back automatically; the review that followed |
| 5 | //! (see the 2026-07-16 comment) landed on a firm constraint: **no surprise |
| 6 | //! resume**. So this is an explicit, opt-in setting, and when it is on it |
| 7 | //! still refuses to guess. |
| 8 | //! |
| 9 | //! The rules, in the order they are applied: |
| 10 | //! |
| 11 | //! 1. An explicit `--resume <id>` or `--continue` always wins. Auto-resume |
| 12 | //! never overrides, reorders, or second-guesses what the user typed. |
| 13 | //! 2. `--fresh` always wins the other way. |
| 14 | //! 3. With the setting off (the default), the decision is |
| 15 | //! [`AutoResumeDecision::Disabled`] and startup is unchanged. |
| 16 | //! 4. With the setting on, the candidate is the newest non-archived session |
| 17 | //! recorded against *this* workspace. If there is none, startup is fresh |
| 18 | //! and says so. |
| 19 | //! 5. The candidate is then **verified**: it must load, and its recorded |
| 20 | //! workspace must still match the workspace we are launching in. A session |
| 21 | //! that fails to load (truncated, hand-edited, half-written) yields |
| 22 | //! [`AutoResumeDecision::Unreadable`] — fresh start, with the reason |
| 23 | //! surfaced rather than swallowed. |
| 24 | //! |
| 25 | //! Rule 5's workspace re-check is the one that matters most. The candidate |
| 26 | //! already came from a workspace-scoped query, but the metadata read there is |
| 27 | //! a 64 KB prefix extraction; re-checking against the fully loaded session is |
| 28 | //! what makes "we will never silently resume a different workspace" a property |
| 29 | //! of the code rather than a claim in a doc. |
| 30 | //! |
| 31 | //! Nothing here contacts a provider or the network. Deciding what to resume, |
| 32 | //! and resuming it, are pure disk operations. |
| 33 | |
| 34 | use std::path::Path; |
| 35 | |
| 36 | use crate::session_manager::{SessionManager, workspace_scope_matches}; |
| 37 | |
| 38 | /// How far down the candidate list auto-resume will walk before giving up. |
| 39 | /// |
| 40 | /// Bounded on purpose: a sessions directory full of damaged files must not |
| 41 | /// turn startup into a long scan, and the receipt's skipped count stays a |
| 42 | /// small, honest number rather than an unbounded tally. |
| 43 | pub const MAX_AUTO_RESUME_CANDIDATES: usize = 10; |
| 44 | |
| 45 | /// Why startup is (or is not) attaching to a previous session. |
| 46 | #[derive(Debug, Clone, PartialEq, Eq)] |
| 47 | pub enum AutoResumeDecision { |
| 48 | /// The user asked for a specific session, or for `--continue`. Auto-resume |
| 49 | /// stands down and the explicit request is carried through untouched. |
| 50 | ExplicitRequest { session_id: String }, |
| 51 | /// `--fresh` was passed. Start clean, no lookup performed. |
| 52 | ForcedFresh, |
| 53 | /// The setting is off. This is the shipped default. |
| 54 | Disabled, |
| 55 | /// A verified session for this workspace. Safe to resume. |
| 56 | /// |
| 57 | /// `skipped_unreadable` counts candidates newer than this one that failed |
| 58 | /// verification. It is reported rather than swallowed: silently landing on |
| 59 | /// an older session while newer ones rot is exactly the kind of quiet |
| 60 | /// degradation a user should be told about. |
| 61 | Resume { |
| 62 | session_id: String, |
| 63 | title: String, |
| 64 | skipped_unreadable: usize, |
| 65 | }, |
| 66 | /// Auto-resume is on but this workspace has no eligible session yet. |
| 67 | /// Start fresh; this is a normal first-run state, not an error. |
| 68 | NoSession, |
| 69 | /// Every candidate for this workspace failed verification. Start fresh and |
| 70 | /// name the newest failure plus how many were tried. |
| 71 | Unreadable { |
| 72 | session_id: String, |
| 73 | reason: String, |
| 74 | skipped_unreadable: usize, |
| 75 | }, |
| 76 | /// The newest candidate belongs to a different workspace than the one we |
| 77 | /// are launching in. Start fresh — resuming would silently move the user's |
| 78 | /// conversation to another project. |
| 79 | WorkspaceMismatch { session_id: String }, |
| 80 | } |
| 81 | |
| 82 | impl AutoResumeDecision { |
| 83 | /// The session id startup should actually load, if any. |
| 84 | #[must_use] |
| 85 | pub fn session_id(&self) -> Option<&str> { |
| 86 | match self { |
| 87 | Self::ExplicitRequest { session_id } | Self::Resume { session_id, .. } => { |
| 88 | Some(session_id.as_str()) |
| 89 | } |
| 90 | Self::ForcedFresh |
| 91 | | Self::Disabled |
| 92 | | Self::NoSession |
| 93 | | Self::Unreadable { .. } |
| 94 | | Self::WorkspaceMismatch { .. } => None, |
| 95 | } |
| 96 | } |
| 97 | |
| 98 | /// A short, user-facing receipt, or `None` when there is nothing worth |
| 99 | /// saying. Silence is correct for `Disabled` (the default posture) and for |
| 100 | /// `ExplicitRequest` (the existing resume path prints its own receipt). |
| 101 | #[must_use] |
| 102 | pub fn status_message(&self) -> Option<String> { |
| 103 | match self { |
| 104 | Self::ExplicitRequest { .. } | Self::ForcedFresh | Self::Disabled => None, |
| 105 | Self::Resume { |
| 106 | title, |
| 107 | skipped_unreadable: 0, |
| 108 | .. |
| 109 | } => Some(format!("Auto-resumed session: {title}")), |
| 110 | Self::Resume { |
| 111 | title, |
| 112 | skipped_unreadable, |
| 113 | .. |
| 114 | } => Some(format!( |
| 115 | "Auto-resumed session: {title} (skipped {skipped_unreadable} unreadable {} above it)", |
| 116 | plural_sessions(*skipped_unreadable) |
| 117 | )), |
| 118 | Self::NoSession => { |
| 119 | Some("Auto-resume: no previous session for this workspace — starting fresh".into()) |
| 120 | } |
| 121 | Self::Unreadable { |
| 122 | session_id, |
| 123 | reason, |
| 124 | skipped_unreadable, |
| 125 | } => Some(format!( |
| 126 | "Auto-resume found no readable session ({skipped_unreadable} unreadable {}); newest was {}: {reason} — starting fresh", |
| 127 | plural_sessions(*skipped_unreadable), |
| 128 | crate::session_manager::truncate_id(session_id) |
| 129 | )), |
| 130 | Self::WorkspaceMismatch { session_id } => Some(format!( |
| 131 | "Auto-resume skipped session {}: it belongs to a different workspace — starting fresh", |
| 132 | crate::session_manager::truncate_id(session_id) |
| 133 | )), |
| 134 | } |
| 135 | } |
| 136 | |
| 137 | /// True when startup will begin with an empty transcript. |
| 138 | /// |
| 139 | /// Test-only: startup itself branches on [`Self::session_id`], and this is |
| 140 | /// the same fact spelled the way the assertions read. Gating it keeps the |
| 141 | /// shipped surface to what the shipped code calls. |
| 142 | #[cfg(test)] |
| 143 | #[must_use] |
| 144 | pub fn starts_fresh(&self) -> bool { |
| 145 | self.session_id().is_none() |
| 146 | } |
| 147 | } |
| 148 | |
| 149 | /// What the CLI asked for, independent of the persisted setting. |
| 150 | #[derive(Debug, Clone, Default)] |
| 151 | pub struct ResumeRequest { |
| 152 | /// `--resume <id>` (or a `--continue`-resolved id). |
| 153 | pub explicit_session_id: Option<String>, |
| 154 | /// `--fresh`. |
| 155 | pub force_fresh: bool, |
| 156 | } |
| 157 | |
| 158 | /// Decide what, if anything, to auto-resume. |
| 159 | /// |
| 160 | /// `manager` is borrowed rather than opened here so tests and the `main` |
| 161 | /// startup path share one session directory, and so a caller that already has |
| 162 | /// a manager does not pay for a second directory resolution. |
| 163 | pub fn decide_auto_resume( |
| 164 | enabled: bool, |
| 165 | request: &ResumeRequest, |
| 166 | workspace: &Path, |
| 167 | manager: &SessionManager, |
| 168 | ) -> AutoResumeDecision { |
| 169 | if let Some(session_id) = request |
| 170 | .explicit_session_id |
| 171 | .as_deref() |
| 172 | .map(str::trim) |
| 173 | .filter(|id| !id.is_empty()) |
| 174 | { |
| 175 | return AutoResumeDecision::ExplicitRequest { |
| 176 | session_id: session_id.to_string(), |
| 177 | }; |
| 178 | } |
| 179 | if request.force_fresh { |
| 180 | return AutoResumeDecision::ForcedFresh; |
| 181 | } |
| 182 | if !enabled { |
| 183 | return AutoResumeDecision::Disabled; |
| 184 | } |
| 185 | |
| 186 | let listed = match manager.list_sessions() { |
| 187 | Ok(listed) => listed, |
| 188 | // A sessions directory we cannot enumerate is not a reason to fail |
| 189 | // startup; it is a reason not to resume. |
| 190 | Err(err) => { |
| 191 | return AutoResumeDecision::Unreadable { |
| 192 | session_id: String::new(), |
| 193 | reason: format!("sessions directory unreadable ({err})"), |
| 194 | skipped_unreadable: 0, |
| 195 | }; |
| 196 | } |
| 197 | }; |
| 198 | |
| 199 | // Candidates newest-first, scoped through the *same* matcher the picker, |
| 200 | // the rail, and the API use. `list_sessions` already sorts by `updated_at` |
| 201 | // descending. |
| 202 | let candidates = candidate_ids(&listed, workspace); |
| 203 | if candidates.is_empty() { |
| 204 | return AutoResumeDecision::NoSession; |
| 205 | } |
| 206 | |
| 207 | let mut skipped_unreadable = 0usize; |
| 208 | let mut newest_failure: Option<(String, String)> = None; |
| 209 | |
| 210 | // One corrupt newest session must not cost the user every older one. Walk |
| 211 | // down until something verifies, bounded so a directory full of damaged |
| 212 | // files cannot turn startup into a long scan. |
| 213 | for id in candidates.into_iter().take(MAX_AUTO_RESUME_CANDIDATES) { |
| 214 | // Verify against the real file before trusting it: the listing above |
| 215 | // only parsed each session's bounded metadata prefix. The probe only |
| 216 | // needs durable metadata — repair belongs to the resume that follows, |
| 217 | // so read the snapshot without running or logging it here. |
| 218 | let saved = match manager.load_session_snapshot(&id) { |
| 219 | Ok(saved) => saved, |
| 220 | Err(err) => { |
| 221 | skipped_unreadable += 1; |
| 222 | if newest_failure.is_none() { |
| 223 | newest_failure = Some((id, describe_load_error(&err))); |
| 224 | } |
| 225 | continue; |
| 226 | } |
| 227 | }; |
| 228 | |
| 229 | // A workspace mismatch is a different failure from corruption: it means |
| 230 | // the candidate is fine but is not ours. Report it rather than counting |
| 231 | // it as damage, and stop — resuming past it would be guessing. |
| 232 | if !workspace_scope_matches(&saved.metadata.workspace, workspace) { |
| 233 | return AutoResumeDecision::WorkspaceMismatch { |
| 234 | session_id: saved.metadata.id, |
| 235 | }; |
| 236 | } |
| 237 | if saved.metadata.archived { |
| 238 | continue; |
| 239 | } |
| 240 | |
| 241 | return AutoResumeDecision::Resume { |
| 242 | title: saved.metadata.title.clone(), |
| 243 | session_id: saved.metadata.id, |
| 244 | skipped_unreadable, |
| 245 | }; |
| 246 | } |
| 247 | |
| 248 | match newest_failure { |
| 249 | Some((session_id, reason)) => AutoResumeDecision::Unreadable { |
| 250 | session_id, |
| 251 | reason, |
| 252 | skipped_unreadable, |
| 253 | }, |
| 254 | None => AutoResumeDecision::NoSession, |
| 255 | } |
| 256 | } |
| 257 | |
| 258 | /// Newest-first eligible session ids for `workspace`. |
| 259 | /// |
| 260 | /// Uses [`crate::session_projection::select_sessions`] so "which sessions |
| 261 | /// belong to this workspace" is answered by the same code the browse surfaces |
| 262 | /// use — auto-resume cannot pick something the rail would not have listed. |
| 263 | fn candidate_ids( |
| 264 | sessions: &[crate::session_manager::SessionMetadata], |
| 265 | workspace: &Path, |
| 266 | ) -> Vec<String> { |
| 267 | let query = crate::session_projection::SessionQuery::default() |
| 268 | .with_filter(crate::session_manager::SessionListFilter::ActiveOnly) |
| 269 | .with_sort(crate::session_projection::SessionSortMode::Recent) |
| 270 | .scoped_to(workspace) |
| 271 | .with_limit(MAX_AUTO_RESUME_CANDIDATES); |
| 272 | crate::session_projection::select_sessions(sessions, &query) |
| 273 | .into_iter() |
| 274 | .filter(|metadata| !is_empty_placeholder(metadata)) |
| 275 | .map(|metadata| metadata.id.clone()) |
| 276 | .collect() |
| 277 | } |
| 278 | |
| 279 | /// An auto-created, never-used session is not something to resume into. |
| 280 | /// Mirrors the filter `get_latest_session_for_workspace` applies. |
| 281 | fn is_empty_placeholder(metadata: &crate::session_manager::SessionMetadata) -> bool { |
| 282 | metadata.message_count == 0 |
| 283 | && metadata |
| 284 | .title |
| 285 | .trim() |
| 286 | .eq_ignore_ascii_case(crate::session_manager::DEFAULT_SESSION_TITLE) |
| 287 | } |
| 288 | |
| 289 | fn plural_sessions(count: usize) -> &'static str { |
| 290 | if count == 1 { "session" } else { "sessions" } |
| 291 | } |
| 292 | |
| 293 | fn describe_load_error(err: &std::io::Error) -> String { |
| 294 | match err.kind() { |
| 295 | std::io::ErrorKind::NotFound => "session file is missing".to_string(), |
| 296 | std::io::ErrorKind::InvalidData => "session file is corrupt".to_string(), |
| 297 | std::io::ErrorKind::PermissionDenied => "session file is not readable".to_string(), |
| 298 | _ => err.to_string(), |
| 299 | } |
| 300 | } |
| 301 | |
| 302 | #[cfg(test)] |
| 303 | mod tests { |
| 304 | use super::*; |
| 305 | use crate::session_manager::{SavedSession, create_saved_session_with_id_and_mode}; |
| 306 | use codewhale_models::Role; |
| 307 | use codewhale_models::{ContentBlock, Message}; |
| 308 | use std::path::PathBuf; |
| 309 | use tempfile::TempDir; |
| 310 | |
| 311 | struct Fixture { |
| 312 | _dir: TempDir, |
| 313 | workspace: PathBuf, |
| 314 | manager: SessionManager, |
| 315 | } |
| 316 | |
| 317 | fn fixture() -> Fixture { |
| 318 | let dir = TempDir::new().expect("tempdir"); |
| 319 | let workspace = dir.path().join("workspace"); |
| 320 | std::fs::create_dir_all(&workspace).expect("workspace dir"); |
| 321 | let manager = SessionManager::new(dir.path().join("sessions")).expect("session manager"); |
| 322 | Fixture { |
| 323 | _dir: dir, |
| 324 | workspace, |
| 325 | manager, |
| 326 | } |
| 327 | } |
| 328 | |
| 329 | fn saved(id: &str, workspace: &Path, title: &str) -> SavedSession { |
| 330 | let messages = vec![Message { |
| 331 | role: Role::User, |
| 332 | content: vec![ContentBlock::Text { |
| 333 | text: "hello".to_string(), |
| 334 | cache_control: None, |
| 335 | }], |
| 336 | }]; |
| 337 | let mut session = create_saved_session_with_id_and_mode( |
| 338 | id.to_string(), |
| 339 | &messages, |
| 340 | "deepseek-chat", |
| 341 | workspace, |
| 342 | 12, |
| 343 | None, |
| 344 | Some("agent"), |
| 345 | ); |
| 346 | session.metadata.title = title.to_string(); |
| 347 | session |
| 348 | } |
| 349 | |
| 350 | #[test] |
| 351 | fn disabled_by_default_never_looks_at_disk() { |
| 352 | let fx = fixture(); |
| 353 | fx.manager |
| 354 | .save_session(&saved("s1", &fx.workspace, "Prior work")) |
| 355 | .expect("save"); |
| 356 | |
| 357 | let decision = |
| 358 | decide_auto_resume(false, &ResumeRequest::default(), &fx.workspace, &fx.manager); |
| 359 | |
| 360 | assert_eq!(decision, AutoResumeDecision::Disabled); |
| 361 | assert!(decision.starts_fresh()); |
| 362 | assert_eq!(decision.status_message(), None); |
| 363 | } |
| 364 | |
| 365 | #[test] |
| 366 | fn enabled_resumes_the_newest_valid_session_for_this_workspace() { |
| 367 | let fx = fixture(); |
| 368 | fx.manager |
| 369 | .save_session(&saved("older", &fx.workspace, "Older work")) |
| 370 | .expect("save older"); |
| 371 | let mut newer = saved("newer", &fx.workspace, "Newer work"); |
| 372 | newer.metadata.updated_at = chrono::Utc::now() + chrono::Duration::minutes(5); |
| 373 | fx.manager.save_session(&newer).expect("save newer"); |
| 374 | |
| 375 | let decision = |
| 376 | decide_auto_resume(true, &ResumeRequest::default(), &fx.workspace, &fx.manager); |
| 377 | |
| 378 | assert_eq!(decision.session_id(), Some("newer")); |
| 379 | assert_eq!( |
| 380 | decision.status_message().as_deref(), |
| 381 | Some("Auto-resumed session: Newer work") |
| 382 | ); |
| 383 | } |
| 384 | |
| 385 | #[test] |
| 386 | fn missing_session_starts_fresh_with_a_receipt() { |
| 387 | let fx = fixture(); |
| 388 | |
| 389 | let decision = |
| 390 | decide_auto_resume(true, &ResumeRequest::default(), &fx.workspace, &fx.manager); |
| 391 | |
| 392 | assert_eq!(decision, AutoResumeDecision::NoSession); |
| 393 | assert!(decision.starts_fresh()); |
| 394 | assert!( |
| 395 | decision |
| 396 | .status_message() |
| 397 | .expect("receipt") |
| 398 | .contains("starting fresh") |
| 399 | ); |
| 400 | } |
| 401 | |
| 402 | #[test] |
| 403 | fn corrupt_session_falls_back_to_fresh_instead_of_failing_startup() { |
| 404 | let fx = fixture(); |
| 405 | fx.manager |
| 406 | .save_session(&saved("broken", &fx.workspace, "Broken work")) |
| 407 | .expect("save"); |
| 408 | // Drop the closing brace: the metadata block still parses from the |
| 409 | // file prefix (so listing still surfaces the session), but the full |
| 410 | // load fails. That is exactly the shape auto-resume must survive. |
| 411 | let path = fx.manager.sessions_dir().join("broken.json"); |
| 412 | let content = std::fs::read_to_string(&path).expect("read session"); |
| 413 | let truncated = content |
| 414 | .trim_end() |
| 415 | .strip_suffix('}') |
| 416 | .expect("session JSON ends with }"); |
| 417 | std::fs::write(&path, truncated).expect("truncate session"); |
| 418 | |
| 419 | let decision = |
| 420 | decide_auto_resume(true, &ResumeRequest::default(), &fx.workspace, &fx.manager); |
| 421 | |
| 422 | assert!(decision.starts_fresh()); |
| 423 | assert!( |
| 424 | matches!(&decision, AutoResumeDecision::Unreadable { session_id, .. } if session_id == "broken"), |
| 425 | "expected an Unreadable decision, got {decision:?}" |
| 426 | ); |
| 427 | assert!( |
| 428 | decision |
| 429 | .status_message() |
| 430 | .expect("receipt") |
| 431 | .contains("starting fresh") |
| 432 | ); |
| 433 | } |
| 434 | |
| 435 | #[test] |
| 436 | fn a_session_from_another_workspace_is_never_resumed() { |
| 437 | let fx = fixture(); |
| 438 | let other = fx._dir.path().join("other-workspace"); |
| 439 | std::fs::create_dir_all(&other).expect("other workspace"); |
| 440 | fx.manager |
| 441 | .save_session(&saved("elsewhere", &other, "Someone else's project")) |
| 442 | .expect("save"); |
| 443 | |
| 444 | let decision = |
| 445 | decide_auto_resume(true, &ResumeRequest::default(), &fx.workspace, &fx.manager); |
| 446 | |
| 447 | assert!(decision.starts_fresh()); |
| 448 | assert_eq!(decision, AutoResumeDecision::NoSession); |
| 449 | } |
| 450 | |
| 451 | #[test] |
| 452 | fn archived_sessions_are_not_auto_resume_candidates() { |
| 453 | let fx = fixture(); |
| 454 | let mut session = saved("put-away", &fx.workspace, "Put away"); |
| 455 | session.metadata.archived = true; |
| 456 | fx.manager.save_session(&session).expect("save"); |
| 457 | |
| 458 | let decision = |
| 459 | decide_auto_resume(true, &ResumeRequest::default(), &fx.workspace, &fx.manager); |
| 460 | |
| 461 | assert_eq!(decision, AutoResumeDecision::NoSession); |
| 462 | } |
| 463 | |
| 464 | #[test] |
| 465 | fn explicit_resume_wins_over_the_setting_in_both_directions() { |
| 466 | let fx = fixture(); |
| 467 | fx.manager |
| 468 | .save_session(&saved("auto", &fx.workspace, "Auto candidate")) |
| 469 | .expect("save"); |
| 470 | |
| 471 | let explicit = ResumeRequest { |
| 472 | explicit_session_id: Some("chosen".to_string()), |
| 473 | force_fresh: false, |
| 474 | }; |
| 475 | // Setting off: the explicit id still resumes. |
| 476 | assert_eq!( |
| 477 | decide_auto_resume(false, &explicit, &fx.workspace, &fx.manager).session_id(), |
| 478 | Some("chosen") |
| 479 | ); |
| 480 | // Setting on: the explicit id is not replaced by the auto candidate. |
| 481 | assert_eq!( |
| 482 | decide_auto_resume(true, &explicit, &fx.workspace, &fx.manager).session_id(), |
| 483 | Some("chosen") |
| 484 | ); |
| 485 | } |
| 486 | |
| 487 | #[test] |
| 488 | fn fresh_flag_suppresses_auto_resume() { |
| 489 | let fx = fixture(); |
| 490 | fx.manager |
| 491 | .save_session(&saved("auto", &fx.workspace, "Auto candidate")) |
| 492 | .expect("save"); |
| 493 | |
| 494 | let decision = decide_auto_resume( |
| 495 | true, |
| 496 | &ResumeRequest { |
| 497 | explicit_session_id: None, |
| 498 | force_fresh: true, |
| 499 | }, |
| 500 | &fx.workspace, |
| 501 | &fx.manager, |
| 502 | ); |
| 503 | |
| 504 | assert_eq!(decision, AutoResumeDecision::ForcedFresh); |
| 505 | assert_eq!(decision.status_message(), None); |
| 506 | } |
| 507 | |
| 508 | #[test] |
| 509 | fn blank_explicit_id_is_treated_as_absent() { |
| 510 | let fx = fixture(); |
| 511 | let decision = decide_auto_resume( |
| 512 | false, |
| 513 | &ResumeRequest { |
| 514 | explicit_session_id: Some(" ".to_string()), |
| 515 | force_fresh: false, |
| 516 | }, |
| 517 | &fx.workspace, |
| 518 | &fx.manager, |
| 519 | ); |
| 520 | assert_eq!(decision, AutoResumeDecision::Disabled); |
| 521 | } |
| 522 | } |
| 523 |