docs: add shared agent instructions

.gitignore

@@ -13,3 +13,7 @@ output*.png
 models*
 *.log
 preview.png
+.claude/
+CLAUDE.local.md
+.agents/
+.codex/

AGENTS.md

@@ -0,0 +1,183 @@
+# Instructions for stable-diffusion.cpp
+
+This document is for AI coding agents working in this repository. It should
+describe agent-specific workflow, repository routing, editing boundaries, and
+project-specific pitfalls.
+
+For general contribution rules, including PR scope, commit conventions, code
+style, dependency updates, security hygiene, and AI-assisted contribution policy,
+see `CONTRIBUTING.md`.
+
+---
+
+## Agent Operating Rules
+
+Before analyzing or modifying the repository:
+
+1. Read this file.
+2. Use `rg` / `rg --files` or directory listing commands to confirm the current
+   tree before relying on a path.
+3. Start from `src/` and relevant `docs/` for runtime behavior.
+4. Read the relevant code before editing.
+5. Prefer the smallest change that fits the existing architecture.
+6. Report focused verification and mention any tests not run.
+
+Agents must not:
+
+* Run `git push`, create PRs, or submit issue/PR comments on the user's behalf.
+* Create commits unless the user explicitly requests that specific commit.
+* Modify `ggml/`, `thirdparty/`, or `examples/server/frontend/` unless
+  explicitly requested and necessary.
+* Read large local model files or tokenizer vocabulary files.
+* Rewrite unrelated code for style-only reasons.
+* Add secrets, model weights, generated binaries, local absolute paths, or
+  machine-specific output.
+
+When a change is large, architectural, or likely to affect public behavior,
+pause and present a short plan before editing.
+
+---
+
+## Repository Map and Editing Boundaries
+
+This is a routing map for agents, not a full architecture document. The layout
+can change, so verify paths before using them. Do not inspect excluded
+large-data directories while checking the tree.
+
+### Primary Project Code
+
+Core implementation lives under `src/`.
+
+Current source layout includes:
+
+* `src/core/` - shared tensor, ggml integration, backend, graph, RNG, and utility
+  code.
+* `src/model/` - model families and model components.
+* `src/model_io/` - model file loading, GGUF, safetensors, pickle, and related
+  serialization helpers.
+* `src/runtime/` - sampling, denoising, guidance, caching, preprocessing, and
+  runtime execution helpers.
+* `src/tokenizers/` - tokenizer implementations.
+* `src/conditioning/` - conditioning and prompt-related implementation.
+* `src/extensions/` - optional feature extensions.
+* top-level `src/*.cpp` and `src/*.h` files - public implementation entry
+  points, model loading, conversion, versioning, and shared managers.
+
+`src/tokenizers/vocab/` contains large tokenizer vocabulary data. Do not read or
+parse files in this directory; reference the path only when necessary.
+
+### Public API
+
+`include/` contains the C API exposed by the project. Currently the primary
+public header is `include/stable-diffusion.h`.
+
+Treat public headers as stable API. Avoid breaking compatibility unless the user
+explicitly requests it. If public behavior changes, update relevant examples or
+documentation.
+
+### Examples
+
+`examples/` contains programs demonstrating library usage.
+
+* `examples/cli/` - command line program for running models, testing features,
+  and debugging.
+* `examples/common/` - shared example support code.
+* `examples/server/` - server application built on top of the library.
+* `examples/server/frontend/` - git submodule containing independent frontend
+  code. Avoid modifying it unless explicitly requested.
+
+### Documentation and Tooling
+
+* `docs/` - documentation for supported models, build options, behavior, and
+  workflows.
+* `scripts/` - development, model processing, build automation, formatting, and
+  tooling scripts.
+* `cmake/` - CMake support modules.
+* `docker/` - Docker-related project files.
+* `assets/` - documentation assets; not runtime code.
+
+### External, Local, and Generated State
+
+* `ggml/` - git submodule for the ggml dependency.
+* `thirdparty/` - vendored third-party dependencies.
+* `models/` - local model storage. Ignore this directory and do not read model
+  files.
+* `test/` - local testing scripts. Use only when relevant to the task.
+* `build/`, `build_*`, and similar directories - generated build outputs.
+  Inspect them only when debugging a build result.
+
+---
+
+## Agent Workflow for Code Changes
+
+1. Identify the relevant modules under `src/`.
+2. Check whether the change touches the public API in `include/`.
+3. Consult relevant `docs/` and examples before changing user-facing behavior.
+4. Follow existing local patterns before adding new abstractions.
+5. Keep edits scoped to the requested behavior.
+6. Run the narrowest useful build, test, or inspection command available.
+
+Follow `CONTRIBUTING.md` for formatting, naming, PR expectations, dependency
+update policy, and security rules.
+
+---
+
+## Code Comments
+
+Keep comments rare and useful.
+
+Do not add comments that only describe what the code does. Add comments only
+when the code cannot fully express the logic, the logic is unusually complex, or
+there are historical reasons, invariants, constraints, compatibility concerns,
+or known pitfalls that future maintainers need to understand.
+
+Do not add task-specific comments that will be meaningless after review.
+
+Examples from the current codebase:
+
+```cpp
+// GOOD: explains a safety constraint that is not obvious from the assignment.
+// From src/model_io/pickle_io.cpp.
+// Non-tensor checkpoint metadata can use REDUCE for arbitrary
+// Python objects. Do not execute it; keep stack shape only.
+stack.push_back(make_none_value());
+
+// BAD: describes only what the next line does.
+// Set the token count to zero.
+token_count = 0;
+```
+
+---
+
+## Text File Encoding
+
+When reading or editing repository text files:
+
+* Prefer UTF-8 with LF for Markdown, frontend source, JSON, and other text-first
+  project files unless the file already clearly uses a different encoding.
+* Do not assume terminal output encoding matches file encoding on Windows.
+* A file that looks garbled in PowerShell output may still be valid UTF-8.
+* When inspecting UTF-8 files in PowerShell, prefer explicit UTF-8 reads such as:
+  * `[Console]::OutputEncoding = [System.Text.Encoding]::UTF8`
+  * `Get-Content -Encoding utf8 <path>`
+* Avoid rewriting a file purely because console output looked garbled; verify
+  the actual file encoding first.
+
+---
+
+## Tensor and Layout Notes
+
+Additional tensor/layout rules for this codebase:
+
+* `sd::Tensor` shape order is not PyTorch/NumPy-style. `shape()[0]` is the
+  lowest and most contiguous dimension, and higher indices are higher
+  dimensions.
+* Broadcasting for `sd::Tensor` must align dimensions from low to high dimension
+  indices. If one tensor has fewer dimensions, append implicit `1`s at the
+  higher-dimension end.
+* `ggml_n_dims` / `ggml_n_dims(tensor)` can drop trailing singleton high
+  dimensions. Do not assume a logical trailing dimension of `1` will still be
+  counted in ggml metadata.
+* Internal tensor-returning interfaces use an empty `sd::Tensor` to represent
+  null, absent, or failure states. Do not add `std::optional<sd::Tensor<...>>`
+  for internal APIs unless a distinct semantic state is truly required.

CLAUDE.md

@@ -0,0 +1,11 @@
+@AGENTS.md
+
+## Claude Code
+
+Follow `AGENTS.md` as the shared repository instructions.
+
+Do not duplicate contribution, style, PR, dependency, or security policy here;
+use `CONTRIBUTING.md` as the canonical source for those rules.
+
+Keep Claude-specific project notes in this file only when they do not apply to
+other coding agents.