## What
On **first boot** (right after map selection), offer to pre-bake the pathfinding `.swb` cache for the selected maps. This removes first-pathfind-after-boot latency and is now cheap — ~18 MB/facet after the v8 format work (the old ~565 MB is gone). The answer persists in `modernuo.json` as **`pathfinding.prebakeMaps`** (default **false**): asked exactly once, and skipped on headless/CI boots (redirected input) where operators can set the flag directly.
## How — a generic startup phase, not pathfinding hardcoded in the engine
The clean-console (pre-Serilog) prompt window is inside the engine startup, but UOContent isn't loaded until after `ServerConfiguration.Load`. So rather than coupling the engine to pathfinding, this adds a generic lifecycle phase:
- **`Main.cs`**: new `AssemblyHandler.Invoke("ConfigurePrompts")` — runs **after** `LoadAssemblies` (so content can participate) but **before** the first `logger.Information` (so console prompts aren't interleaved with the async console sink). The first log line moves below it. Any class can hook in with `public static void ConfigurePrompts()` and self-gate on first-boot state. No `ServerConfiguration` or pathfinding coupling added to the engine.
- **`PathCacheCommands.ConfigurePrompts()`**: the first-boot prompt (interactive-only, flag-absent-only); persists the answer.
- **`PathCacheCommands.Initialize()`** (`Invoke("Initialize")` phase, after the tile matrix loads — which the bake walks): when the flag is set, bakes any map whose `.swb` is **missing or stale** (tile-data fingerprint mismatch, via `StepCache.ComputeLiveFingerprint` / `TryReadFingerprintFromFile`). A fresh cache is a no-op, so only the first boot — or a post-client-update boot — pays the several-minute cost.
## Docs
Fixed the now-stale "~565 MB / ~1.5–2 GB / do not bake by default" section in `dev-docs/pathfinding.md` (it's 17.9 MB for Trammel, tens of MB for all six facets after v8), added a "First-boot pre-bake prompt" section, and added the `pathfinding.prebakeMaps` lever row.
## Verified
- `dotnet build UOContent -c Release` → 0 errors (rebased on #2474).
- Pathfinding/StepCache tests: **90/90 pass**.
- Bootstrap streamlining of the startup phases is intentionally left as a follow-up.
## Summary
Phase #3b (final roadmap item), stacked on #2470. Compacts the index trailer from 20 to 8 bytes/chunk.
Trammel: 19.2 MB → 17.9 MB. Roadmap total: 565 MB → 17.9 MB (−96.8%).
## Details
- Trailer stores `{ u32 packedKey = (ChunkX << 16) | ChunkY, u32 recordLength }` per chunk, in record write order; the file offset is dropped and reconstructed by cumulative recordLength from HeaderSize.
- No record reordering, no varint; fixed-stride, TryReadChunk unchanged.
- Also simplifies the accumulated `.swb` code comments across the stack.
- Format v8; v7 files rejected and re-baked once.
## Tests
v8 multi-chunk round-trip (cumulative offset reconstruction) + the v6/v7 suite; full pathfinding suite green; Release build clean.
## Summary
Phase #3a, stacked on #2469. Compresses each chunk record independently with libdeflate (random access preserved).
Trammel: 124.7 MB → 19.2 MB (−85%).
## Details
- Whole-record framing `[u32 UncompressedLen][payload]`; records that don't shrink (tiny Uniform) are stored raw, detected as payload length == UncompressedLen.
- Codec chosen by full-Trammel spike: libdeflate VeryHigh (16.5 MB, 1.83 µs/chunk decompress) over zstd L19/22 (17.4 MB) and managed Brotli q11 (16.4 MB) — best native ratio, fastest decompress, already the repo's packet codec (no new dependency).
- Reuses cached thread-static bindings: `Deflate.Maximum` for bake, `Deflate.Standard` for reads.
- Compression is bake-time only; decompression is one-time per chunk (LRU-cached).
- Format v7; v6 files rejected and re-baked once.
## Tests
v7 unit tests + the v6 suite run through the compression path; full pathfinding suite green; Release build clean.
## Summary
Phase #2 of the `.swb` step-cache size-reduction roadmap (after #2465, v5 uniform elision). Stores the 16 base directional Z arrays as masked residuals against each cell's own SourceZ and omits any array that matches its prediction. Lossless, byte-identical reconstruction.
Trammel: 231.9 MB → 124.7 MB (−46%).
## Details
- Predictor: `predict = mask bit ? SourceZ : 0` (matches the baker's 0 on unwalkable directions); residual `Z − predict` via unchecked two's-complement (byte-exact for all inputs); reconstruct `Z = predict + residual`.
- A `u16 ZArrayMask` flags which of the 16 base arrays differ from prediction; matching arrays are omitted and synthesized from mask + SourceZ at read.
- Serializer-layer only: StepChunk, the cache, the algorithm, and the baker are unchanged.
- Format v6; v5 files rejected and re-baked once.
## Tests
21 v6 unit tests; full pathfinding suite green; Release build clean.
## Summary
Sub-project #1 of the `.swb` step-cache size-reduction roadmap (`dev-docs/pathfinding.md` § Future work). Adds **uniform-chunk elision** to the `StepCacheFile` format, bumping it **v4 → v5**.
A fully-uniform 16×16 chunk — no strata, **no swim layer**, all 19 base arrays constant (open ocean, Green Acres, void) — serializes to a **~28-byte record** (`KindUniform`) instead of ~5,393, and reconstructs **byte-identically** via `Array.Fill`. Non-uniform chunks use the existing v4 body (`KindFull`) with the swim-layer and strata trailers **fully preserved** — the Kind byte is just prepended.
## Calibrated result (measured, not projected)
Baked Trammel via `SaveToFile`:
| | |
|---|---:|
| Chunks | 114,688 |
| Uniform (swim-aware) → elided | 62.7% |
| Swim-layer chunks (stay Full) | 8.9% |
| Strata chunks (stay Full) | 1.8% |
| Baseline (full records) | 592.2 MB |
| **Actual v5 `.swb`** | **231.9 MB (−61%)** |
The residual is ~150 MB of non-uniform land Z-blocks (targeted by #2 predictive-Z) + ~81 MB of swim-layer trailers (#2/#3). #2 and #3 are separate follow-up PRs.
## Implementation
- `StepChunk.IsUniform()` — false if it has strata **or a swim layer**, else true only when all 19 base arrays are constant (the "all-same" check uses the SIMD-accelerated `ContainsAnyExcept`).
- `StepCacheFile` v5 — `Kind` byte (`KindFull=0`/`KindUniform=2`, 1 reserved); uniform write/read; `FormatVersion`/`MinSupportedVersion` → 5 (v4 files rejected on open and re-baked). No `StepCache`/algorithm/index changes; fingerprint logic untouched.
## Tests
7 `StepCacheFileV5Tests` (uniform round-trip + `<200 B` compactness, varied-full, swim-layer-full, strata-full, swim+strata combined, v4 version-gate rejection) + the existing StepCache/pathfinding suite — **70 pass**, including the prior `SwimLayer_RoundTrips`. An independent review verified write/read symmetry, cast round-tripping, swim/strata preservation, and the version gate (READY TO MERGE).
## Summary
Adds `dev-docs/pathfinding.md` — a reference for how creature pathfinding works in ModernUO, written so a future contributor (human or AI) can reason about it without re-deriving it from the code.
Covers:
- **The stack** end to end: `ApproachTarget` → `PathFollower` → `MovementPath` → `BitmapAStarAlgorithm` → `StepCache` → `MovementImpl` slow path (and that the removed FastAStar survives as the slow path).
- **Windowed-A* limits** (`AreaSize=38`, `MaxSearchNodes`, Z planes) and what they mean (2D-adjacent-but-obstacle-separated / a-floor-up goals are unsolvable by design).
- **StepCache**: second-touch warming, LRU-bounded memory, lazy `.swb` backing stores — with **measured** disk sizes (~565 MB/Trammel; ~1.5–2 GB all facets).
- **Four config levers** in a table: `pathfinding.enable`, `bitmap_pathfinding_cache`, `pathfinding.maxResidentChunks`, `pathfinding.maxSearchNodes`.
- **Small/crappy-hardware shard spectrum** (cache off ≈ FastAStar at ~1× with zero warming memory, up through baked `.swb`).
- **Diagnostics & tooling** (`[PathCacheStats`/`[PathRecord`/`[PathBake`, the MapDump tool, the benchmark suite) and the Debug/Release test note.
- **Future work**: background-thread bake, long-traverse BDN scenario, swim `SourceZ` bake, and the `.swb` size-reduction roadmap.
## Note on scope
This is docs-only. It documents the *complete* pathfinding system, so it references a couple of pieces that ride in separate PRs (the `ApproachTarget` AI fix and the `pathfinding.maxSearchNodes` setting). If those havent merged yet, sequence this after them so the doc doesnt describe unshipped code. The StepCache/`.swb`/provider material it documents is already on `main`.
## Summary
Captures the durable learnings from the message-interpolation work (PRs #2434, #2436, #2437, #2438, #2440) as reference documentation. **Doc-only PR — no code changes.**
The original Phase 2 audit (PR #2435) was development scaffolding and was closed unmerged once Phase 3 consumed it. This PR replaces it with proper reference docs that future authors can consult.
## What's added
### `dev-docs/string-handling.md`
- Promote `RawInterpolatedStringHandler` from a one-line note to a proper section listing all APIs that accept it (messages, OPL, gumps, packets).
- Document the `:L` lowercase format specifier.
- New comprehensive **"Interpolation Anti-Patterns"** section covering 8 patterns with before/after examples — applies to any handler-aware API:
1. Ternary with interpolated branches
2. Switch expression with interpolated arms
3. Pre-built local typed as `string`
4. `.ToString()` (or any string-returning method) inside a hole
5. String concatenation inside a hole
6. `string.Format` feeding a handler-aware API
7. LINQ-built strings inside a hole
8. Pre-built concat var
### `dev-docs/networking-packets.md`
- Add **"Player-Facing Message APIs"** section listing `Mobile` / `Item` / `NetState` message methods with their handler overloads.
- Note the `IBroadcastFilter` pattern for new spatial-broadcast helpers.
### `dev-docs/property-lists.md`, `dev-docs/gump-system.md`
- Cross-reference the new anti-patterns section.
- Add explicit `.ToString()` inside holes warning to property-lists (it had no such guidance before).
### `dev-docs/claude-skills/`
- Mirror the same content (condensed) in `modernuo-string-handling.md`, `modernuo-networking.md`, `modernuo-property-lists.md`, `modernuo-gump-system.md`.
- Add audit rule #17 to `modernuo-code-audit.md` covering all 8 anti-patterns with severity WARNING, plus the `:L` format spec.
### `CLAUDE.md`
- Add audit rule #18 summarizing the interpolation anti-patterns + `:L`, pointing to `dev-docs/string-handling.md` for details.
## Why this matters
Before this PR there was no documentation explaining when an interpolated string call site silently allocates a string despite the receiving API providing a handler overload. The Phase 3 cleanup (PRs #2436/#2437/#2438) discovered ~28 such sites in the codebase; without these docs the same patterns would re-emerge. The new audit rule + CLAUDE.md entry will catch them at write time.
BaseCreatures are deleted on death (Mobile.OnDeath calls Delete for non-players), so after save/restart the corpse's _owner reference resolves to null. CorpseNotoriety gated its entire creature branch on `target.Owner is BaseCreature`, falling through to player-corpse logic once the reference vanished. That made monster corpses turn red (body.IsMonster -> Murderer) and innocent NPC corpses turn grey (null is not PlayerMobile -> CanBeAttacked) on the next restart.
Snapshots the relevant owner state into CorpseFlag at corpse creation: OwnerWasBaseCreature, OwnerWasSummoned, OwnerWasAnimatedDead. Folds the standalone _murderer bool into CorpseFlag.Murderer for consistency with Criminal. CorpseNotoriety now consults the flags so the creature branch stays correct without a live mobile reference.
Bumps Corpse serialization to v16 with a MigrateFrom(V15Content) that maps the old Murderer bool onto the new flag. Pre-fix corpses already on disk decay within 7 minutes; their first post-restart color may be wrong, which is acceptable.
Also documents that the schema generator must be run after every version bump (`dotnet tool run ModernUOSchemaGenerator -- ModernUO.slnx`) since `dotnet build` does not emit migration JSON files.
## Summary
- **Add a self-referencing `InterpolationHandler` to `ValueStringBuilder`** that writes directly into the builder's buffer — zero intermediate allocation, works with `stackalloc`-backed builders
- **Replace all `System.Text.StringBuilder` usage** across the codebase with `ValueStringBuilder`
- **Convert `ValueStringBuilder.Create()` to `stackalloc`** at 10 sites where output length is provably bounded
- **Convert manual `Dispose()` to `using var`** where possible, and hoist loop-scoped builders outside loops with `Reset()`
- **Convert verbose `Append()` chains to `Append($"...")`** interpolation for readability
- **Add comprehensive documentation** for string handling patterns
## InterpolationHandler Design
`ValueStringBuilder` is a `ref struct`, which creates challenges for C#'s interpolated string handler pattern:
- **`ref` fields to ref structs are not allowed** (CS9050)
- **`[InterpolatedStringHandlerArgument("")]` passes struct receivers by value**, not by ref
- **`ISelfInterpolatedStringHandler` requires boxing** ref structs into interface fields
**Solution: Copy-and-reconcile pattern.** The handler receives a value copy of the builder. The copy shares the same underlying `char` buffer (`Span` points to the same `stackalloc`/pooled memory), so writes go to the original buffer. `Append()` reconciles by `this = handler._builder`, updating `_length` and any buffer references changed by `Grow()`.
This is safe because:
- The game loop is single-threaded — no concurrent access between handler construction and reconciliation
- If `Grow()` occurs in the copy, the original's stale buffer isn't accessed until `Append()` replaces it
- `Dispose()` correctly returns the reconciled buffer to the pool
## Changes by Category
### ValueStringBuilder (`Projects/Server/Buffers/ValueStringBuilder.cs`)
- Added nested `InterpolationHandler` ref struct with copy-and-reconcile pattern
- Added `Append([InterpolatedStringHandlerArgument("")] scoped ref InterpolationHandler)` method
- Removed `RawInterpolatedStringHandler` overloads (new handler replaces them)
- All `AppendFormatted` overloads delegate to existing `Append` methods (no code duplication)
- Alignment support via direct private field access (nested type privilege)
### StringBuilder → ValueStringBuilder (15 files)
Replaced all `new StringBuilder()` with `ValueStringBuilder.Create()` or `stackalloc`:
- ConPVP games: KingOfTheHill, DoubleDom, CTF, BombingRun, TourneyMatch
- ConPVP infrastructure: Tournament, Participant, TourneyParticipant
- ConPVP gumps: ArenaGump, TournamentBracketGump, AcceptTeamGump, ConfirmSignupGump
- Commands: Handlers, Logging, Add
- Other: TownCrier, SpeechLogGump, TestCenter
Key patterns:
- `sb = new StringBuilder()` reassignment → `sb.Reset()`
- `sb.AppendFormat("{0:N0}", value)` → `sb.Append($"{value:N0}")`
- `sb.Append(x).Append(y)` chains → separate statements (VSB returns void)
### Create() → stackalloc (10 files)
Converted heap-allocated builders to stackalloc where output is bounded:
- ClientVersion (32), MapSelection (160), HouseRaffleStone (48)
- HolySense (96), UnholySense (96), ClientVerification (192)
- AcceptTeamGump (64), ConfirmSignupGump (64)
- BaseWeapon (160), BaseArmor (128)
### Loop optimizations (2 files)
Hoisted `ValueStringBuilder` creation outside loops with `Reset()` per iteration:
- TourneyMatch.cs: `using var` inside for loop → stackalloc before loop
- ArenaGump.cs: `Create()` + `Dispose()` per iteration → stackalloc before loop
### Append chain → interpolation (5 files)
Converted multi-line `Append()` chains to `Append($"...")`:
- BountyMessage.cs: title switch (6 cases), paragraph (15→1 Append), description lines, closing
- AcceptTeamGump, ConfirmSignupGump, TournamentBracketGump: tournament type strings
- AdminGump: comment/tag formatting in loops
### Documentation
- `dev-docs/string-handling.md`: Full reference — construction, interpolation, disposal, decision guide
- `dev-docs/claude-skills/modernuo-string-handling.md`: Claude skill with quick reference
- `CLAUDE.md`: Added rule 17 (no StringBuilder), dev-docs table entry, skills table entry
- `dev-docs/code-standards.md`: Updated memory management section
## Test Plan
- [x] `dotnet build` — 0 errors, 0 warnings
- [x] `dotnet test` — 940/940 tests pass
- [x] 28 ValueStringBuilder tests covering all reconciliation scenarios:
- Stackalloc no-grow, stackalloc with grow (→pool transition)
- Heap no-grow, heap with grow, heap double grow
- Pre-existing content with and without grow
- Sequential multiple `Append($"...")` calls
- Mixed plain + interpolated Append
- Empty interpolation, literal-only, format specifiers
- Null string holes, ISpanFormattable types
- Dispose after stackalloc→pool grow
Summary
- Adds CLAUDE.md at repo root with 14 terse code audit rules (always loaded, low token cost)
- Adds pointer files for other AI tools: AGENTS.md (Codex), GEMINI.md, .github/COPILOT-INSTRUCTIONS.md (Copilot), .cursorrules (Cursor) — all redirect to CLAUDE.md as single source of truth
- Gitignores /.claude so personal AI config isn't distributed
- Moves Claude skills to dev-docs/claude-skills/ (opt-in, not auto-loaded)
- Adds 14 dev-docs covering codebase conventions
Code Audit Rules (in CLAUDE.md)
1. LINQ tiered rules (Tier 1 free, Tier 2 warm, Tier 3 forbidden)
2. No Console.WriteLine — use LogFactory.GetLogger()
3. No concurrency primitives in game code
4. No World.Mobiles/World.Items iteration
5. Clean up refs in OnDelete()/OnAfterDelete()
6. Cancel timers in OnDelete()/OnAfterDelete()
7. STArrayPool<T>.Shared not ArrayPool<T>.Shared
8. PooledRefList<T> not new List<T>() on hot paths
9. Serialization: partial class, [Constructible], no serialized TimerExecutionToken
10. No Task.Run/new Thread() in game code
11. Never assume era — ask which expansion
12. _camelCase fields, PascalCase properties/methods
13. No empty gumps — use DisplayTo() pattern
14. PropertyList string literals must be {} holes, cliloc-as-argument uses :#
