SeanTAllen · Oct 11, 2026 · Oct 11, 2026
diff --git a/.github/workflows/pr.yml b/.github/workflows/pr.yml
@@ -377,7 +377,7 @@ jobs:
         run: |
           cmake --preset debug
           cmake --build --preset debug
-          cmake --build --preset debug --target pony-doc-tests pony-lint-tests pony-lsp-tests pony-dep-tests
+          cmake --build --preset debug --target pony-doc-tests pony-lint-tests pony-lsp-tests pony-dep-tests pony-agent-server-tests
       - name: Test pony-doc
         run: ctest --preset debug -R pony-doc-tests
       - name: Test pony-lint
@@ -386,6 +386,8 @@ jobs:
         run: ctest --preset debug -R pony-lsp-tests
       - name: Test pony-dep
         run: ctest --preset debug -R pony-dep-tests
+      - name: Test pony-agent-server
+        run: ctest --preset debug -R pony-agent-server-tests
       - name: Lint tools
         run: cd build/debug && PONYPATH=../../tools/lib/ponylang/pony_compiler ./pony-lint ../../tools/
       - name: Lint examples
@@ -418,7 +420,7 @@ jobs:
         run: |
           cmake --preset armv8-debug
           cmake --build --preset armv8-debug
-          cmake --build --preset armv8-debug --target pony-doc-tests pony-lint-tests pony-lsp-tests pony-dep-tests
+          cmake --build --preset armv8-debug --target pony-doc-tests pony-lint-tests pony-lsp-tests pony-dep-tests pony-agent-server-tests
       - name: Test pony-doc
         run: ctest --preset armv8-debug -R pony-doc-tests
       - name: Test pony-lint
@@ -427,6 +429,8 @@ jobs:
         run: ctest --preset armv8-debug -R pony-lsp-tests
       - name: Test pony-dep
         run: ctest --preset armv8-debug -R pony-dep-tests
+      - name: Test pony-agent-server
+        run: ctest --preset armv8-debug -R pony-agent-server-tests
 
   tools-windows:
     needs: [changes, maybe-build-windows]
@@ -459,7 +463,7 @@ jobs:
         run: |
           cmake --preset windows-x86-64
           cmake --build --preset windows-x86-64-debug
-          cmake --build --preset windows-x86-64-debug --target pony-doc-tests pony-lint-tests pony-lsp-tests pony-dep-tests
+          cmake --build --preset windows-x86-64-debug --target pony-doc-tests pony-lint-tests pony-lsp-tests pony-dep-tests pony-agent-server-tests
       - name: Test pony-doc
         run: ctest --preset windows-x86-64-debug -R pony-doc-tests
       - name: Test pony-lint
@@ -468,6 +472,8 @@ jobs:
         run: ctest --preset windows-x86-64-debug -R pony-lsp-tests
       - name: Test pony-dep
         run: ctest --preset windows-x86-64-debug -R pony-dep-tests
+      - name: Test pony-agent-server
+        run: ctest --preset windows-x86-64-debug -R pony-agent-server-tests
 
   # ----- ssl-backends suite -----
 

diff --git a/.gitignore b/.gitignore
@@ -38,6 +38,7 @@ tools/pony-lsp/version.pony
 tools/pony-lint/version.pony
 tools/pony-doc/version.pony
 tools/pony-dep/version.pony
+tools/pony-agent-server/version.pony
 
 # Python bytecode
 __pycache__/

diff --git a/.release-notes/add-pony-agent-server.md b/.release-notes/add-pony-agent-server.md
@@ -0,0 +1,11 @@
+## Add pony-agent-server
+
+A new experimental tool for AI coding agents that need Pony type information while editing code. It compiles a package and answers queries about types, definitions, capabilities, and structure. The query interface is experimental and subject to change.
+
+Start the server on a package directory:
+
+```bash
+pony-agent-server /path/to/my-project
+```
+
+Supported queries: `inspect`, `scope`, `exports`, `type_api`, `check`, `implementors`, `errors`, `reload`, and `status`. The server reads one JSON query per line from stdin and writes one JSON response per line to stdout.
diff --git a/AGENTS.md b/AGENTS.md
@@ -39,7 +39,7 @@ The output goes in `build/debug`. Use `--preset release` for a release build. Th
 Tests are registered with ctest and grouped by label. Two labels matter:
 
 - **`ci-core`** — built by a normal `cmake --build --preset debug`. The C/C++ compiler tests (`libponyc.tests`), the runtime tests (`libponyrt.tests`), the stdlib suite, full-program integration tests, and grammar validation.
-- **`tools`** — **not** built by a normal `cmake --build --preset debug`. The self-hosted tool test suites: pony-compiler, pony-lsp, pony-lint, pony-doc, and pony-dep.
+- **`tools`** — **not** built by a normal `cmake --build --preset debug`. The self-hosted tool test suites: pony-compiler, pony-lsp, pony-lint, pony-doc, pony-dep, and pony-agent-server.
 
 ### Core tests (ci-core)
 
@@ -87,6 +87,7 @@ Tool test binaries must be built explicitly before running. Build one target, th
 - `cmake --build --preset debug --target pony-lint-tests && ctest --preset debug -R pony-lint-tests`
 - `cmake --build --preset debug --target pony-doc-tests && ctest --preset debug -R pony-doc-tests`
 - `cmake --build --preset debug --target pony-dep-tests && ctest --preset debug -R pony-dep-tests`
+- `cmake --build --preset debug --target pony-agent-server-tests && ctest --preset debug -R pony-agent-server-tests`
 
 Build all tool test binaries at once with `cmake --build --preset debug --target tool-tests`, then run them with `ctest --preset debug -L tools`.
 
@@ -100,7 +101,7 @@ Run the `pony-lint` binary (built by a normal `cmake --build --preset debug`) ag
 cd build/debug && PONYPATH=../../tools/lib/ponylang/pony_compiler ./pony-lint ../../tools/pony-lint/
 ```
 
-The same works for `../../tools/pony-lsp/`, `../../tools/pony-doc/`, and `../../tools/pony-dep/`.
+The same works for `../../tools/pony-lsp/`, `../../tools/pony-doc/`, `../../tools/pony-dep/`, and `../../tools/pony-agent-server/`.
 
 ## Opening PRs
 

diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -859,6 +859,7 @@ else()
     add_subdirectory(tools/pony-lint)
     add_subdirectory(tools/pony-doc)
     add_subdirectory(tools/pony-dep)
+    add_subdirectory(tools/pony-agent-server)
 
     # Test binaries compiled with the just-built ponyc. Built on demand, NOT under
     # ALL: each runs ponyc to compile builtin and the stdlib packages, so building
@@ -897,12 +898,18 @@ else()
         PATHS ${CMAKE_SOURCE_DIR}/tools/lib/ponylang/pony_compiler ${PONY_SSL_LIB_DIR}
         WATCH ${CMAKE_SOURCE_DIR}/tools/pony-dep)
 
+    add_pony_binary(pony-agent-server-tests
+        NAME pony-agent-server-tests
+        SOURCE ${CMAKE_SOURCE_DIR}/tools/pony-agent-server/test
+        PATHS ${CMAKE_SOURCE_DIR}/tools/lib/ponylang/pony_compiler
+        WATCH ${CMAKE_SOURCE_DIR}/tools/pony-agent-server)
+
     # On-demand aggregate: build every self-hosted tool test in one target. Run
     # `cmake --build <dir> --target tool-tests` before `ctest -L tools`.
     add_custom_target(tool-tests)
     add_dependencies(tool-tests
         pony-compiler-tests pony-doc-tests pony-lint-tests pony-lsp-tests
-        pony-dep-tests)
+        pony-dep-tests pony-agent-server-tests)
 
     # ctest registration. Every test binary builds under ALL, so ctest only runs
     # them. Labels group the suites: `ci-core` is the core CI suite (the old
@@ -944,6 +951,9 @@ else()
     add_test(NAME pony-dep-tests
         COMMAND ${PONY_OUTPUT_DIR}/pony-dep-tests${CMAKE_EXECUTABLE_SUFFIX} --sequential
         WORKING_DIRECTORY ${PONY_OUTPUT_DIR})
+    add_test(NAME pony-agent-server-tests
+        COMMAND ${PONY_OUTPUT_DIR}/pony-agent-server-tests${CMAKE_EXECUTABLE_SUFFIX} --sequential
+        WORKING_DIRECTORY ${PONY_OUTPUT_DIR})
     set_tests_properties(pony-lint-tests PROPERTIES
         ENVIRONMENT "PONYPATH=${CMAKE_SOURCE_DIR}/packages;PONYTEST_DB_DIR=${CMAKE_SOURCE_DIR}/.ponytest/pony-lint-tests")
     set_tests_properties(pony-doc-tests PROPERTIES
@@ -952,6 +962,8 @@ else()
         ENVIRONMENT "PONYPATH=${CMAKE_SOURCE_DIR}/packages;PONYTEST_DB_DIR=${CMAKE_SOURCE_DIR}/.ponytest/pony-dep-tests")
     set_tests_properties(pony-lsp-tests PROPERTIES
         ENVIRONMENT "PONYTEST_DB_DIR=${CMAKE_SOURCE_DIR}/.ponytest/pony-lsp-tests")
+    set_tests_properties(pony-agent-server-tests PROPERTIES
+        ENVIRONMENT "PONYPATH=${CMAKE_SOURCE_DIR}/packages;PONYTEST_DB_DIR=${CMAKE_SOURCE_DIR}/.ponytest/pony-agent-server-tests")
     add_test(NAME pony-compiler-tests
         COMMAND ${PONY_OUTPUT_DIR}/pony-compiler-tests${CMAKE_EXECUTABLE_SUFFIX} --sequential
         WORKING_DIRECTORY ${PONY_OUTPUT_DIR})
@@ -967,7 +979,7 @@ else()
             ENVIRONMENT "PONYPATH=${CMAKE_SOURCE_DIR}/tools/lib/ponylang/pony_compiler:${CMAKE_SOURCE_DIR}/packages;PONYTEST_DB_DIR=${CMAKE_SOURCE_DIR}/.ponytest/pony-compiler-tests")
     endif()
     set_tests_properties(pony-doc-tests pony-lsp-tests pony-lint-tests pony-compiler-tests
-        pony-dep-tests PROPERTIES LABELS tools)
+        pony-dep-tests pony-agent-server-tests PROPERTIES LABELS tools)
 
     # Compile-then-run ci-core tests. Each compiles Pony sources with the freshly
     # built ponyc and then runs (or diffs) the result, so they depend on ponyc
@@ -1045,6 +1057,7 @@ else()
         ${PONY_OUTPUT_DIR}/pony-lint${CMAKE_EXECUTABLE_SUFFIX}
         ${PONY_OUTPUT_DIR}/pony-doc${CMAKE_EXECUTABLE_SUFFIX}
         ${PONY_OUTPUT_DIR}/pony-dep${CMAKE_EXECUTABLE_SUFFIX}
+        ${PONY_OUTPUT_DIR}/pony-agent-server${CMAKE_EXECUTABLE_SUFFIX}
         DESTINATION ${PONY_VERSIONED_DIR}/bin)
 
     # Runtime + compiler static libs, into the lib dir ponyc searches at run time
@@ -1138,7 +1151,7 @@ else()
                 endif()
             endforeach()
             file(MAKE_DIRECTORY \"\${_prefix}/bin\" \"\${_prefix}/lib\")
-            foreach(_tool ponyc pony-lsp pony-lint pony-doc pony-dep)
+            foreach(_tool ponyc pony-lsp pony-lint pony-doc pony-dep pony-agent-server)
                 set(_t \"\${_prefix}/${PONY_VERSIONED_DIR}/bin/\${_tool}\")
                 if(EXISTS \"\${_t}\")
                     file(CREATE_LINK \"\${_t}\" \"\${_prefix}/bin/\${_tool}\" SYMBOLIC)
@@ -1152,7 +1165,7 @@ else()
             endforeach()
         ")
     elseif(PONY_INSTALL_SYMLINKS AND WIN32)
-        foreach(_tool ponyc pony-lsp pony-lint pony-doc pony-dep)
+        foreach(_tool ponyc pony-lsp pony-lint pony-doc pony-dep pony-agent-server)
             install(PROGRAMS $<TARGET_FILE:ponyc-shim>
                 DESTINATION bin RENAME ${_tool}.exe)
         endforeach()

diff --git a/src/libponyc/CMakeLists.txt b/src/libponyc/CMakeLists.txt
@@ -94,6 +94,7 @@ add_library(libponyc STATIC
     type/sanitise.c
     type/subtype.c
     type/subtype_cache.c
+    type/subtype_ffi.c
     type/type_assume.c
     type/typealias.c
     type/typeparam.c

diff --git a/src/libponyc/type/subtype_ffi.c b/src/libponyc/type/subtype_ffi.c
@@ -0,0 +1,22 @@
+#include "subtype_ffi.h"
+#include "assemble.h"
+#include "subtype.h"
+
+bool is_subtype_for_defs(ast_t* sub_def, token_id sub_cap,
+  ast_t* super_def, token_id super_cap, pass_opt_t* opt)
+{
+  ast_t* sub_type =
+    type_for_class(opt, sub_def, sub_def, sub_cap, TK_NONE, false);
+  ast_setdata(sub_type, sub_def);
+
+  ast_t* super_type =
+    type_for_class(opt, super_def, super_def, super_cap, TK_NONE, false);
+  ast_setdata(super_type, super_def);
+
+  bool result = is_subtype(sub_type, super_type, NULL, opt);
+
+  ast_free_unattached(sub_type);
+  ast_free_unattached(super_type);
+
+  return result;
+}
diff --git a/src/libponyc/type/subtype_ffi.h b/src/libponyc/type/subtype_ffi.h
@@ -0,0 +1,15 @@
+#ifndef SUBTYPE_FFI_H
+#define SUBTYPE_FFI_H
+
+#include <platform.h>
+#include "../ast/ast.h"
+#include "../pass/pass.h"
+
+PONY_EXTERN_C_BEGIN
+
+bool is_subtype_for_defs(ast_t* sub_def, token_id sub_cap,
+  ast_t* super_def, token_id super_cap, pass_opt_t* opt);
+
+PONY_EXTERN_C_END
+
+#endif
diff --git a/tools/corral.json b/tools/corral.json
@@ -8,7 +8,9 @@
     "pony-doc",
     "pony-doc/test",
     "pony-dep",
-    "pony-dep/test"
+    "pony-dep/test",
+    "pony-agent-server",
+    "pony-agent-server/test"
   ],
   "deps": [
     {

diff --git a/tools/lib/ponylang/pony_compiler/pony_compiler/compile_session.pony b/tools/lib/ponylang/pony_compiler/pony_compiler/compile_session.pony
@@ -96,6 +96,29 @@ class CompileSession
     _pass_opt.limit = limit()
     @ast_passes_program(_raw, _pass_opt)
 
+  fun box is_sendable(type_ast: AST box): Bool =>
+    """
+    True when the given type is sendable (iso, val, or tag).
+    Handles nominal, union, intersection, tuple, and arrow types.
+    """
+    @sendable(type_ast.raw, _pass_opt)
+
+  fun box is_subtype(
+    sub_def: AST box,
+    sub_cap: TokenId,
+    super_def: AST box,
+    super_cap: TokenId)
+    : Bool
+  =>
+    """
+    True when a nominal type built from `sub_def` at `sub_cap` is a
+    subtype of a nominal type built from `super_def` at `super_cap`.
+    Both definitions must be entity AST nodes (TK_CLASS, TK_ACTOR,
+    TK_PRIMITIVE, TK_TRAIT, TK_INTERFACE, TK_STRUCT).
+    """
+    @is_subtype_for_defs(
+      sub_def.raw, sub_cap, super_def.raw, super_cap, _pass_opt)
+
   fun ref dispose() =>
     """
     Release pass_opt resources. Must be called when the session is no longer

diff --git a/tools/lib/ponylang/pony_compiler/pony_compiler/types.pony b/tools/lib/ponylang/pony_compiler/pony_compiler/types.pony
@@ -1,3 +1,11 @@
+use @sendable[Bool](type_ast: Pointer[_AST] box, opt: _PassOpt box)
+use @is_subtype_for_defs[Bool](
+  sub_def: Pointer[_AST] box,
+  sub_cap: I32,
+  super_def: Pointer[_AST] box,
+  super_cap: I32,
+  opt: _PassOpt box)
+
 primitive Types
   """
   AST type extraction utilities.

diff --git a/tools/pony-agent-server/CMakeLists.txt b/tools/pony-agent-server/CMakeLists.txt
@@ -0,0 +1,11 @@
+project(tools.pony-agent-server)
+
+# Generate version.pony from template
+# (.gitignore prevents version.pony from dirtying the git tree)
+configure_file(version.pony.in ${CMAKE_CURRENT_SOURCE_DIR}/version.pony @ONLY)
+
+add_pony_binary(tools.pony-agent-server ALL
+    NAME pony-agent-server
+    SOURCE ${CMAKE_CURRENT_SOURCE_DIR}
+    PATHS ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_CURRENT_SOURCE_DIR}/../lib/ponylang/pony_compiler
+    WATCH ${CMAKE_CURRENT_SOURCE_DIR})