满庭芳·源流归一

结论：LinuxCNC rs274ngc 源码移植边界继续收拢。已将 rs274ngc 头文件纳入 manifest 跟踪，core 编译组仍只包含可编译源文件；启用 CNC_SIM_ENABLE_LINUXCNC_RS274_BACKEND 时 API 默认使用 LinuxCNC rs274 后端；M428/M429/M430 与 5axis/TRT/TDR/RTCP 相关路径继续保持来自 LinuxCNC 源码或 remap 配置的薄桥接。

验证：./test-linuxcnc-source-syntax.sh；./test-linuxcnc-api-native.sh；./test-native.sh；./test-linuxcnc-source-link.sh。

docs/architecture.md

@@ -18,6 +18,9 @@ The event callback emits normalized `CncSimEvent` records. JavaScript can transf
 
 ## LinuxCNC integration plan
 
+Functional behavior must come from LinuxCNC source code, not independently
+designed project code. See `docs/linuxcnc-source-policy.md`.
+
 1. Build a native `CanonEventSink` that implements all functions declared in `canon.hh`.
 2. Link the sink with `src/emc/rs274ngc` and `src/emc/nml_intf` instead of the task controller.
 3. Stub or remove Python remap support for the first browser target.
@@ -58,10 +61,18 @@ Feature parity needs more than G-code parsing:
 
 ## Five-axis and RTCP
 
-The first RTCP implementation is a geometry kernel, not the full LinuxCNC motion
-controller. It treats programmed XYZ as the tool-center point, applies A/B/C
-orientation to a local tool vector, and computes the compensated pivot/spindle
-point needed to keep the tool tip fixed.
+RTCP pivot events are emitted only for known LinuxCNC switchkins modes. These
+paths must use formulas copied from LinuxCNC source code, not independently
+derived geometry. The current source mapping is:
+
+- `M428` / `XYZBC_TRT`: `linuxcnc/src/emc/kinematics/trtfuncs.c`,
+  `xyzbcKinematicsForward()` and `xyzbcKinematicsInverse()`
+- `M430` / `USERK_IDENTITY`: `linuxcnc/src/emc/kinematics/userkfuncs.c`,
+  delegating to `identityKinematicsForward()` and
+  `identityKinematicsInverse()` in `kins_util.c`
+- The retained `5axiskins` helpers map to
+  `linuxcnc/src/emc/kinematics/5axiskins.c`,
+  `fiveaxis_KinematicsForward()` and `fiveaxis_KinematicsInverse()`
 
 RTCP is opt-in through config JSON. When enabled, the original motion events
 remain programmed tool-tip motion and an additional `rtcp-pivot` event is emitted
@@ -74,7 +85,5 @@ Current files:
 - `core/src/rtcp_kinematics.cpp`
 - `core/tests/rtcp_kinematics_smoke.cpp`
 
-The next integration step is to add machine configuration for rotary topology,
-pivot offsets, tool length sources, and rotation order, then apply RTCP
-compensation while converting LinuxCNC Canon motion events into renderable
-machine/tool-tip trajectories.
+The next integration step is to add more LinuxCNC source-backed kinematics for
+additional switchkins or machine topologies.

docs/linuxcnc-porting.md

@@ -19,7 +19,7 @@ g++ -std=c++17 -I core/include core/src/cnc_sim_api.cpp core/tests/cnc_sim_api_s
 
 Status: in progress.
 
-This parser only exists to test the ABI and UI before Emscripten and LinuxCNC are wired in. It currently handles:
+This parser only exists to test the ABI and UI before Emscripten and LinuxCNC are wired in. It is not a production feature implementation. Do not extend it with independently designed G-code behavior; when a behavior needs to change, first locate the LinuxCNC source implementation and either route to that source-backed backend or port the corresponding source logic. It currently handles:
 
 - multiple G/M words on one line
 - `G0`, `G1`, `G2`, `G3`
@@ -39,7 +39,7 @@ This parser only exists to test the ABI and UI before Emscripten and LinuxCNC ar
 - canned cycles `G73`, `G74`, `G81`, `G82`, `G83`, `G84`, `G85`, `G86`, `G87`, `G88`, `G89` with `G80`, `G98`, `G99`, `L`
 - coordinate offset events for `G10 L2`, `G10 L20`, `G54`-`G59.3`, `G52`, `G92`, `G92.1`, `G92.2`, and `G92.3`
 
-It is not the production interpreter.
+It is not the production interpreter. Any remaining smoke-only behavior is technical debt to replace with LinuxCNC source-backed code.
 
 ## Step 2: Canon event sink
 

docs/linuxcnc-source-policy.md

@@ -0,0 +1,32 @@
+# LinuxCNC Source Policy
+
+The simulator must not grow independently designed functional behavior.
+Functional behavior must come from LinuxCNC source code.
+
+Allowed project code:
+
+- Thin adapters between LinuxCNC source code and the simulator C API.
+- Platform shims needed to compile LinuxCNC code for native tests or wasm.
+- Event serialization, test fixtures, build scripts, and documentation.
+- Temporary smoke scaffolding only when it is explicitly marked as temporary.
+
+Not allowed as final behavior:
+
+- Hand-written G-code interpretation semantics.
+- Hand-derived kinematics, RTCP, coordinate transform, cutter compensation, canned cycle, modal, parameter, or expression behavior.
+- Behavior copied from documentation, controller intuition, or examples without checking the LinuxCNC implementation.
+
+Required workflow for every functional change:
+
+1. Identify the LinuxCNC source file and function that defines the behavior.
+2. Add or update a test that demonstrates the LinuxCNC behavior.
+3. Port, wrap, or route to that LinuxCNC implementation.
+4. Record the source file/function in code comments or nearby documentation when the mapping is not obvious.
+5. Run `./test-native.sh` and `./test-linuxcnc-source-link.sh`.
+
+Current temporary exceptions:
+
+- The smoke parser exists only to exercise the public API and UI while the LinuxCNC RS274 backend is being wired in.
+- RTCP pivot behavior is limited to LinuxCNC source-backed switchkins paths; unsupported switchkins types must not fall back to hand-derived geometry.
+
+Both exceptions should shrink over time. New functional behavior should not be added to them unless it is directly copied from, or routed to, LinuxCNC source code.