diff --git a/Cargo.toml b/Cargo.toml
index f94c2a1b3..39df11309 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -125,6 +125,9 @@ image = "0.25"
 # `icons/icon.png` is NOT committed: it is generated from `Oak_Icon.svg`
 # (rsvg-convert) in CD right before packaging, because cargo-packager needs a
 # bitmap (it converts a square PNG into .icns / .ico / hicolor PNGs itself).
+# It must be 512x512: cargo-packager's tauri-icns 0.1.0 maps only 512x512@1x
+# (and 1024x1024@2x) to an ICNS type — a plain 1024x1024 PNG aborts with
+# "No matching IconType".
 # Keep the path here in sync with the CD workflow.
 # ---------------------------------------------------------------------------
 [package.metadata.packager]
diff --git a/build.rs b/build.rs
index 4370ec662..d95f4b192 100644
--- a/build.rs
+++ b/build.rs
@@ -36,15 +36,18 @@
 //! `target/<profile>/deps/`, so dyld finds it by that absolute path at
 //! load time; the `-rpath` flag covers `@rpath`-relative configurations.
 //!
-//! Linux: undefined symbols in a `.so` need no link-time flag; the app's
-//! own link only needs the search path plus `-Wl,--export-dynamic` (the
-//! ELF equivalent of `-export_dynamic`) so the host symbols resolve from
-//! the binary at runtime. An `$ORIGIN`-relative rpath lets a packaged
-//! binary find a sibling `liboakengine.so`.
+//! Linux: the app's own link needs the search path plus
+//! `-Wl,--export-dynamic` (the ELF equivalent of `-export_dynamic`) so
+//! process-global symbol lookups resolve from the binary at runtime. An
+//! `$ORIGIN`-relative rpath lets a packaged binary find a sibling
+//! `liboakengine.so`.
 //!
-//! Windows: NOT SUPPORTED YET — a DLL cannot carry the undefined
-//! `oakcore_*` imports (they need a stub import library or delay-load
-//! plumbing that does not exist yet), so the app does not link there.
+//! Windows: the engine dylib now links there — the `oakcore_*` runtime
+//! imports were folded into the cdylib in M12 P5 (crates/oakengine/src/
+//! stubs.rs, module `audio`), so `liboakengine.dll` carries no undefined
+//! symbols. The app binary itself still has no Windows link
+//! configuration here and the early return stays; that is a separate
+//! effort (gpui win32 support).
 
 use std::path::PathBuf;
 
diff --git a/crates/oakengine/Cargo.toml b/crates/oakengine/Cargo.toml
index ed3842c1a..29baaa38f 100644
--- a/crates/oakengine/Cargo.toml
+++ b/crates/oakengine/Cargo.toml
@@ -29,9 +29,10 @@ libc = "0.2"
 # oakaudio/oakplugin, and clearly marked STUBs for the handle-based
 # oaknode/oaktimeline paths).
 #
-# The remaining undefined imports are the C++ host-provided symbols
-# (`oakcore_audioparams_*` from liboakcore), which build.rs leaves as
-# runtime lookups for the host app (see src/stubs.rs audio module).
+# The `oakcore_audioparams_*` accessors the audio paths read through are
+# implemented inside the dylib too (src/stubs.rs, module `audio`, M12 P5):
+# they used to be C++ liboakcore host-provided symbols left as runtime
+# lookups, which blocked Windows DLL linking.
 #
 # src/linkage.rs anchors every crate (and oakcore-rs) so the linker pulls
 # their object files into the cdylib.
diff --git a/crates/oakengine/README.md b/crates/oakengine/README.md
index c6d25d371..64fc68ad8 100644
--- a/crates/oakengine/README.md
+++ b/crates/oakengine/README.md
@@ -44,10 +44,11 @@ anchors them so their `#[no_mangle]` exports are linked into the
 `liboakengine` cdylib — the dylib carries the module C ABIs (oakundo_*,
 oakcommon_*, oaktimeline_*, oakcodec_*, oakaudio_*, oakrender_*,
 oaktask_*, oakplugin_*, oaknode_*) next to the facade's oakengine_*
-exports. The only remaining imports are the C++ host symbols
-(`oakcore_*` from liboakcore, `fb_*` from ffmpeg_bridge), which
-`build.rs` leaves as runtime lookups (macOS `-undefined dynamic_lookup`)
-resolved from the host Oak process.
+exports. The `oakcore_audioparams_*` accessors the audio paths read
+through are implemented in the dylib too (src/stubs.rs, module `audio`,
+M12 P5) — they used to be C++ host symbols left as runtime lookups
+(macOS `-undefined dynamic_lookup`); the cdylib now carries no undefined
+imports.
 
 ### Handle mapping
 
@@ -103,8 +104,8 @@ binaries keep the in-crate mocks (ffmpeg_bridge stub / render mocks):
   oaknode/oakundo/oakcommon C ABI symbols as link-time externs, which the
   sibling crate rlibs provide; oaknode itself resolves cross-module
   symbols at runtime with `dlsym(RTLD_DEFAULT)`.
-- `tests/common/mod.rs` defines the `oakcore_*` (liboakcore) and `fb_*`
-  (libffmpeg_bridge) symbols the oakcodec/oakaudio rlibs reference, and
+- `tests/common/mod.rs` re-exports the facade's in-dylib
+  `oakcore_audioparams_*` accessors (M12 P5 folded them in) and
   force-links the oakcommon XML writer/reader + the oakundo command
   factory so the oaknode serializer's dlsym lookups resolve in every test
   binary.
@@ -120,8 +121,8 @@ the module crates' real implementations.
 ```
 cargo test          # lib tests + integration families (undo, common, audio,
                     # plugin, codec, render, linkage, node, timeline, task)
-cargo build         # cdylib embeds the module C ABIs; oakcore_*/fb_* stay
-                    # runtime lookups (see build.rs)
+cargo build         # cdylib embeds the module C ABIs + the folded-in
+                    # oakcore_audioparams_* accessors (no undefined imports)
 ```
 
 ## FFI discipline
diff --git a/crates/oakengine/build.rs b/crates/oakengine/build.rs
index 195e0dd49..9294715dd 100644
--- a/crates/oakengine/build.rs
+++ b/crates/oakengine/build.rs
@@ -16,39 +16,41 @@
 
 //! Build-time link configuration for the `liboakengine` cdylib.
 //!
-//! The dylib now carries the module C ABIs itself (oakundo_*, oakcommon_*,
-//! ... — see Cargo.toml), so the only remaining undefined imports are the
-//! C++ host-provided symbols the modules call directly: `oakcore_*`
-//! (liboakcore's `oakcore_audioparams_*` / `oakcore_rational_*`, called by
-//! oakcodec) and `fb_find_best_pix_fmt_of_list` (ffmpeg_bridge, called by
-//! oakcommon's pixel-format helper). Those live in the host Oak process,
-//! which loads this dylib, so macOS `ld` must accept them as runtime
-//! lookups instead of link-time errors. Only the cdylib gets this flag —
-//! the rlib/staticlib (and the worker/cli consumers) are unaffected.
+//! The dylib carries the module C ABIs itself (oakundo_*, oakcommon_*, ...
+//! — see Cargo.toml). The `oakcore_audioparams_*` accessors the audio
+//! paths read through used to be host-provided C++ liboakcore symbols,
+//! left as runtime lookups via `-undefined,dynamic_lookup`; M12 P5
+//! implemented them inside the dylib (src/stubs.rs, module `audio`), so
+//! no undefined imports remain except system frameworks/libc++, and the
+//! cdylib links on every platform (Windows DLLs reject undefined symbols,
+//! which was the blocker).
 
 fn main() {
-	if std::env::var("CARGO_CFG_TARGET_OS").as_deref() == Ok("macos") {
-		println!("cargo:rustc-cdylib-link-arg=-Wl,-undefined,dynamic_lookup");
+	let os = std::env::var("CARGO_CFG_TARGET_OS").unwrap_or_default();
+	if os == "macos" {
 		// The static FFmpeg's transitive system deps (libz etc.) are
 		// recorded as `@rpath/libz.1.dylib`; the dylib itself carries the
 		// rpath so standalone binaries (and the packaged app) resolve
 		// them without extra host rpaths.
 		println!("cargo:rustc-cdylib-link-arg=-Wl,-rpath,/usr/lib");
 	}
-	// The dlsym codec bridge (M12 P0) resolves `oakcodec_*` from the
-	// process-global scope; the engine's unit-test binary (the former
-	// integration tests live in src/test_support/) statically links the
-	// module crates, so their symbols must be exported from the test
-	// executable. `cargo:rustc-link-arg-tests` is NOT usable: the facade
-	// is cdylib-only, so cargo reports "does not have a test target" for
-	// that directive — use the generic `rustc-link-arg` (harmless no-op
-	// for the cdylib link itself).
-	println!("cargo:rustc-link-arg=-Wl,-export_dynamic");
-	if std::env::var("CARGO_CFG_TARGET_OS").as_deref() == Ok("macos") {
-		// The bundled OpenColorIO's macos system monitor references
-		// IOKit / ColorSync / CoreGraphics display APIs; the engine
-		// dylib links with `-undefined,dynamic_lookup`, so test binaries
-		// must resolve them.
+	if os == "macos" || os == "linux" {
+		// The dlsym codec bridge (M12 P0) resolves `oakcodec_*` from the
+		// process-global scope; the engine's unit-test binary (the former
+		// integration tests live in src/test_support/) statically links the
+		// module crates, so their symbols must be exported from the test
+		// executable. `cargo:rustc-link-arg-tests` is NOT usable: the facade
+		// is cdylib-only, so cargo reports "does not have a test target" for
+		// that directive — use the generic `rustc-link-arg` (a no-op for the
+		// cdylib link itself, and not emitted on Windows where the flag is
+		// meaningless and would break the DLL link).
+		println!("cargo:rustc-link-arg=-Wl,-export_dynamic");
+	}
+	if os == "macos" {
+		// The bundled OpenColorIO's macOS system monitor references
+		// IOKit / ColorSync / CoreGraphics display APIs; link them for
+		// the cdylib link and the unit-test binary (which statically
+		// pulls the same OCIO rlib).
 		for fw in ["IOKit", "ColorSync", "CoreGraphics"] {
 			println!("cargo:rustc-link-arg=-framework");
 			println!("cargo:rustc-link-arg={fw}");
diff --git a/crates/oakengine/src/audio.rs b/crates/oakengine/src/audio.rs
index 037881834..fb1c9e9ed 100644
--- a/crates/oakengine/src/audio.rs
+++ b/crates/oakengine/src/audio.rs
@@ -21,7 +21,9 @@
 //! through [`manager()`] (a borrowed handle; empty when no instance
 //! exists — engine semantics then report `paNoDevice`/error as
 //! documented). The borrowed `OakAudioParams*` handles are read through
-//! the liboakcore `oakcore_audioparams_*` accessors.
+//! the `oakcore_audioparams_*` accessors the facade provides itself
+//! (crate::stubs::audio, folded in M12 P5 — they used to be host-provided
+//! liboakcore symbols).
 
 use std::ffi::{c_char, c_double, c_int, c_void};
 
@@ -126,6 +128,58 @@ pub extern "C" fn oakengine_audio_set_input_device(device: i64) -> c_int {
 	})
 }
 
+/// `oakengine_audio_output_device_count` — the number of host output
+/// devices; the list index is the device index
+/// `oakengine_audio_set_output_device` takes. Needs no AudioManager
+/// instance.
+#[no_mangle]
+pub extern "C" fn oakengine_audio_output_device_count() -> c_int {
+	guard_int(|| Ok(unsafe { a::oakaudio_output_device_count() }))
+}
+
+/// `oakengine_audio_input_device_count` — the input side of
+/// [`oakengine_audio_output_device_count`].
+#[no_mangle]
+pub extern "C" fn oakengine_audio_input_device_count() -> c_int {
+	guard_int(|| Ok(unsafe { a::oakaudio_input_device_count() }))
+}
+
+/// `oakengine_audio_output_device_name` — the name of output device
+/// `index` (buf/size; the length excludes the NUL).
+#[no_mangle]
+pub unsafe extern "C" fn oakengine_audio_output_device_name(
+	index: c_int,
+	buf: *mut c_char,
+	buf_size: c_int,
+) -> c_int {
+	guard_int(|| unsafe {
+		let rc = a::oakaudio_output_device_name(index, buf, buf_size);
+		if rc < 0 {
+			Err(Error::Module(rc))
+		} else {
+			Ok(crate::handle::string_result(rc))
+		}
+	})
+}
+
+/// `oakengine_audio_input_device_name` — the input side of
+/// [`oakengine_audio_output_device_name`].
+#[no_mangle]
+pub unsafe extern "C" fn oakengine_audio_input_device_name(
+	index: c_int,
+	buf: *mut c_char,
+	buf_size: c_int,
+) -> c_int {
+	guard_int(|| unsafe {
+		let rc = a::oakaudio_input_device_name(index, buf, buf_size);
+		if rc < 0 {
+			Err(Error::Module(rc))
+		} else {
+			Ok(crate::handle::string_result(rc))
+		}
+	})
+}
+
 /// `oakengine_audio_hard_reset` — re-initialize PortAudio and refresh the
 /// device lists.
 #[no_mangle]
diff --git a/crates/oakengine/src/stubs.rs b/crates/oakengine/src/stubs.rs
index 79436f6d1..41d3cafdd 100644
--- a/crates/oakengine/src/stubs.rs
+++ b/crates/oakengine/src/stubs.rs
@@ -3944,7 +3944,7 @@ pub mod node {
 		if params.is_null() {
 			return OAKNODE_E_INVALID;
 		}
-		// SAFETY: the host liboakcore audioparams contract.
+		// SAFETY: the oakcore audioparams contract.
 		let (sample_rate, channel_layout, format) = unsafe {
 			(
 				crate::stubs::audio::oakcore_audioparams_sample_rate(params),
@@ -6064,7 +6064,7 @@ pub mod node {
 			Some(p) => *p,
 			None => return OAKNODE_E_NOT_FOUND,
 		};
-		// SAFETY: the host liboakcore audioparams contract.
+		// SAFETY: the oakcore audioparams contract.
 		let ptr = unsafe {
 			crate::stubs::audio::oakcore_audioparams_create(
 				params.sample_rate,
@@ -6089,7 +6089,7 @@ pub mod node {
 		if params.is_null() || index < 0 {
 			return OAKNODE_E_INVALID;
 		}
-		// SAFETY: the host liboakcore audioparams contract.
+		// SAFETY: the oakcore audioparams contract.
 		let converted = unsafe {
 			oaknode::value::AudioParams {
 				sample_rate: crate::stubs::audio::oakcore_audioparams_sample_rate(params),
@@ -11291,9 +11291,11 @@ pub mod timeline {
 /// bridge functions; the manager CHandle is a borrow-only validity token
 /// (the module owns the process-wide singleton), the processor CHandle
 /// boxes an owned `oakaudio::processor::Processor` with a release
-/// callback. The liboakcore `oakcore_audioparams_*` readers keep their
-/// `extern "C"` declarations — those are host-app-provided symbols
-/// (liboakcore), not module C ABI.
+/// callback. The `oakcore_audioparams_*` C ABI (opaque `AudioParams`
+/// handles in the frozen engine contract) is implemented here, inside the
+/// dylib — the accessors were host-provided (C++ liboakcore, later Rust
+/// mock shims in the app/cli/test binaries) until M12 P5 folded them in
+/// so the cdylib carries no undefined imports.
 pub mod audio {
 	use std::ffi::{c_char, c_double, c_int, c_void, CStr};
 
@@ -11315,23 +11317,116 @@ pub mod audio {
 		StretchOffsetResult,
 	};
 
-	extern "C" {
-		/// `oakcore_audioparams_create` (host liboakcore).
-		pub fn oakcore_audioparams_create(
-			sample_rate: c_int,
-			channel_layout: u64,
-			format: c_int,
-		) -> *mut c_void;
-		/// `oakcore_audioparams_free` (host liboakcore).
-		pub fn oakcore_audioparams_free(params: *mut c_void);
-		/// `oakcore_audioparams_sample_rate` (host liboakcore).
-		pub fn oakcore_audioparams_sample_rate(params: *const c_void) -> c_int;
-		/// `oakcore_audioparams_set_time_base` (host liboakcore).
-		pub fn oakcore_audioparams_set_time_base(params: *mut c_void, num: c_int, den: c_int);
-		/// `oakcore_audioparams_channel_layout` (host liboakcore).
-		pub fn oakcore_audioparams_channel_layout(params: *const c_void) -> u64;
-		/// `oakcore_audioparams_format` (host liboakcore).
-		pub fn oakcore_audioparams_format(params: *const c_void) -> c_int;
+	/// The liboakcore `AudioParams` object layout
+	/// (`oakcore_audioparams.h`): sample rate, ffmpeg channel-layout mask,
+	/// sample format, stream index, duration and time base. Mirrors
+	/// `olive::core::AudioParams` (and the app/cli mock shims it replaces),
+	/// so the engine contract's borrowed/owned `AudioParams*` handles
+	/// round-trip unchanged.
+	#[repr(C)]
+	struct HostAudioParams {
+		sample_rate: c_int,
+		channel_layout: u64,
+		format: c_int,
+		stream_index: c_int,
+		duration: i64,
+		time_base_num: c_int,
+		time_base_den: c_int,
+	}
+
+	/// `oakcore_audioparams_create` — new owned audio params (release with
+	/// `oakcore_audioparams_free`). The time base defaults to 1/sample_rate,
+	/// exactly like the liboakcore constructor.
+	#[no_mangle]
+	pub extern "C" fn oakcore_audioparams_create(
+		sample_rate: c_int,
+		channel_layout: u64,
+		format: c_int,
+	) -> *mut c_void {
+		let den = if sample_rate > 0 { sample_rate } else { 1 };
+		Box::into_raw(Box::new(HostAudioParams {
+			sample_rate,
+			channel_layout,
+			format,
+			stream_index: 0,
+			duration: 0,
+			time_base_num: 1,
+			time_base_den: den,
+		})) as *mut c_void
+	}
+
+	/// `oakcore_audioparams_free` — NULL no-op.
+	///
+	/// # Safety
+	/// `params` must come from [`oakcore_audioparams_create`] or be NULL.
+	#[no_mangle]
+	pub extern "C" fn oakcore_audioparams_free(params: *mut c_void) {
+		if params.is_null() {
+			return;
+		}
+		// SAFETY: produced by `oakcore_audioparams_create`; we hold the only
+		// reference after the box is dropped.
+		unsafe { drop(Box::from_raw(params as *mut HostAudioParams)) };
+	}
+
+	/// `oakcore_audioparams_sample_rate` — 0 for NULL (liboakcore contract).
+	///
+	/// # Safety
+	/// `params` must come from [`oakcore_audioparams_create`] or be NULL.
+	#[no_mangle]
+	pub extern "C" fn oakcore_audioparams_sample_rate(params: *const c_void) -> c_int {
+		if params.is_null() {
+			return 0;
+		}
+		// SAFETY: contract above.
+		unsafe { (*(params as *const HostAudioParams)).sample_rate }
+	}
+
+	/// `oakcore_audioparams_channel_layout` — 0 for NULL.
+	///
+	/// # Safety
+	/// `params` must come from [`oakcore_audioparams_create`] or be NULL.
+	#[no_mangle]
+	pub extern "C" fn oakcore_audioparams_channel_layout(params: *const c_void) -> u64 {
+		if params.is_null() {
+			return 0;
+		}
+		// SAFETY: contract above.
+		unsafe { (*(params as *const HostAudioParams)).channel_layout }
+	}
+
+	/// `oakcore_audioparams_format` — 0 for NULL.
+	///
+	/// # Safety
+	/// `params` must come from [`oakcore_audioparams_create`] or be NULL.
+	#[no_mangle]
+	pub extern "C" fn oakcore_audioparams_format(params: *const c_void) -> c_int {
+		if params.is_null() {
+			return 0;
+		}
+		// SAFETY: contract above.
+		unsafe { (*(params as *const HostAudioParams)).format }
+	}
+
+	/// `oakcore_audioparams_set_time_base` — NULL no-op.
+	///
+	/// # Safety
+	/// `params` must come from [`oakcore_audioparams_create`] or be NULL.
+	#[no_mangle]
+	pub extern "C" fn oakcore_audioparams_set_time_base(
+		params: *mut c_void,
+		num: c_int,
+		den: c_int,
+	) {
+		if params.is_null() {
+			return;
+		}
+		// SAFETY: contract above.
+		unsafe {
+			let p = &mut *(params as *mut HostAudioParams);
+			p.time_base_num = num;
+			p.time_base_den = den;
+		}
 	}
 
 	/// Map an oakaudio `Box<dyn Error>` result to its public module code
@@ -11546,6 +11641,67 @@ pub mod audio {
 		}
 	}
 
+	/// The number of host output devices (enumeration order == the device
+	/// index `set_output_device` takes). Needs no manager instance.
+	pub fn oakaudio_output_device_count() -> c_int {
+		oakaudio::manager::output_device_names().len() as c_int
+	}
+
+	/// The number of host input devices (see [`oakaudio_output_device_count`]).
+	pub fn oakaudio_input_device_count() -> c_int {
+		oakaudio::manager::input_device_names().len() as c_int
+	}
+
+	/// The name of output device `index` (two-stage buf/size; reports the
+	/// required size INCLUDING the NUL, the module convention the facade
+	/// converts with `string_result`).
+	///
+	/// # Safety
+	/// `buf` must point to `buf_size` writable bytes when non-NULL.
+	pub unsafe fn oakaudio_output_device_name(
+		index: c_int,
+		buf: *mut c_char,
+		buf_size: c_int,
+	) -> c_int {
+		unsafe { device_name_result(oakaudio::manager::output_device_names(), index, buf, buf_size) }
+	}
+
+	/// The name of input device `index` (see [`oakaudio_output_device_name`]).
+	///
+	/// # Safety
+	/// `buf` must point to `buf_size` writable bytes when non-NULL.
+	pub unsafe fn oakaudio_input_device_name(
+		index: c_int,
+		buf: *mut c_char,
+		buf_size: c_int,
+	) -> c_int {
+		unsafe { device_name_result(oakaudio::manager::input_device_names(), index, buf, buf_size) }
+	}
+
+	/// Shared two-stage string write for the device-name getters: reports
+	/// `len + 1` (the required buffer size including the NUL), writes the
+	/// NUL-terminated name when it fits. `OAKAUDIO_E_NOT_FOUND` for an
+	/// out-of-range index.
+	unsafe fn device_name_result(
+		names: Vec<String>,
+		index: c_int,
+		buf: *mut c_char,
+		buf_size: c_int,
+	) -> c_int {
+		let Some(name) = names.get(index.max(0) as usize).filter(|_| index >= 0) else {
+			return OAKAUDIO_E_NOT_FOUND;
+		};
+		// SAFETY: `buf` points to `buf_size` writable bytes when non-NULL.
+		unsafe {
+			if !buf.is_null() && buf_size > 0 {
+				let copy = name.len().min((buf_size as usize).saturating_sub(1));
+				std::ptr::copy_nonoverlapping(name.as_ptr(), buf as *mut u8, copy);
+				*buf.add(copy) = 0;
+			}
+		}
+		name.len() as c_int + 1
+	}
+
 	/// Close the output stream and reset the playback state.
 	pub fn oakaudio_manager_hard_reset(_self: CHandle) -> c_int {
 		match with_manager(_self).and_then(|mut m| m.hard_reset().map_err(|e| audio_code(&*e))) {
@@ -12413,13 +12569,13 @@ pub mod render {
 		let sample_rate = if params.is_null() {
 			48000
 		} else {
-			// SAFETY: the host liboakcore audioparams contract.
+			// SAFETY: the oakcore audioparams contract.
 			unsafe { crate::stubs::audio::oakcore_audioparams_sample_rate(params) }
 		};
 		let channel_layout = if params.is_null() {
 			0x3
 		} else {
-			// SAFETY: the host liboakcore audioparams contract.
+			// SAFETY: the oakcore audioparams contract.
 			unsafe { crate::stubs::audio::oakcore_audioparams_channel_layout(params) }
 		};
 		let audio_params = oakrender::ticket::AudioTicketParams {
diff --git a/crates/oakengine/src/test_support/common/mod.rs b/crates/oakengine/src/test_support/common/mod.rs
index b0d7ad602..272899081 100644
--- a/crates/oakengine/src/test_support/common/mod.rs
+++ b/crates/oakengine/src/test_support/common/mod.rs
@@ -25,19 +25,16 @@
 //!    would otherwise drop the dev-dependency rlibs from the link and
 //!    leave the imports undefined.
 //!
-//! 2. **Provide the `oakcore_*` symbols** that the
-//!    oakcodec rlib references: `oakcore_audioparams_*` /
-//!    `oakcore_rational_*` live in the C++ liboakcore (only linked in the
-//!    real build), so cargo tests define minimal in-memory mocks — the
-//!    same mock the oakcodec crate itself compiles under `#[cfg(test)]`
-//!    (src/bridge/test_stubs.rs). The real dylib behavior is required
-//!    for actual media decode; those facade tests are `#[ignore]`.
+//! 2. **Re-export the folded-in `oakcore_audioparams_*` accessors** for
+//!    the former mock call sites (`common::oakcore_audioparams_*`). The
+//!    facade used to leave those symbols as runtime lookups for a C++
+//!    liboakcore host, and the tests defined in-memory mocks; M12 P5
+//!    implemented them inside the dylib (crates/oakengine/src/stubs.rs,
+//!    module `audio`), so the tests just use those implementations.
 
 #![allow(dead_code, unused_variables)]
 
-use std::collections::HashMap;
-use std::ffi::{c_int, c_void};
-use std::sync::{Mutex, OnceLock};
+use std::sync::Mutex;
 
 /// One public direct-Rust symbol per module crate (the module C ABIs are
 /// deleted; this mirrors the anchors in `crates/oakengine/src/linkage.rs`).
@@ -106,201 +103,14 @@ pub fn storage_off_guard() -> std::sync::MutexGuard<'static, ()> {
 }
 
 // ---------------------------------------------------------------------------
-// oakcore_* stubs (see module docs)
+// oakcore_audioparams_* (see module docs)
 // ---------------------------------------------------------------------------
 
-/// Opaque `OakAudioParams` handle type (the real one lives in liboakcore).
-#[repr(C)]
-pub struct OakAudioParams {
-	_opaque: [u8; 0],
-}
-
-/// Per-`OakAudioParams` backing state.
-#[derive(Debug, Clone, Default, PartialEq, Eq)]
-struct MockAudioParams {
-	sample_rate: i32,
-	channel_layout: u64,
-	format: i32,
-	stream_index: i32,
-	duration: i64,
-	time_base_num: i32,
-	time_base_den: i32,
-}
-
-fn audio_params_store() -> &'static Mutex<HashMap<usize, MockAudioParams>> {
-	static S: OnceLock<Mutex<HashMap<usize, MockAudioParams>>> = OnceLock::new();
-	S.get_or_init(|| Mutex::new(HashMap::new()))
-}
-
-fn audio_params_get(ctx: *const c_void) -> MockAudioParams {
-	let store = audio_params_store().lock().unwrap();
-	store.get(&(ctx as usize)).cloned().unwrap_or_default()
-}
-
-fn audio_params_set(ctx: *mut c_void, f: impl FnOnce(&mut MockAudioParams)) {
-	let mut store = audio_params_store().lock().unwrap();
-	if let Some(p) = store.get_mut(&(ctx as usize)) {
-		f(p);
-	}
-}
-
-/// Per-`OakRational` backing state (an owned `(num, den)` pair).
-fn rational_store() -> &'static Mutex<HashMap<usize, (i32, i32)>> {
-	static S: OnceLock<Mutex<HashMap<usize, (i32, i32)>>> = OnceLock::new();
-	S.get_or_init(|| Mutex::new(HashMap::new()))
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_create(
-	sample_rate: c_int,
-	channel_layout: u64,
-	format: c_int,
-) -> *mut OakAudioParams {
-	let p = MockAudioParams {
-		sample_rate,
-		channel_layout,
-		format,
-		stream_index: 0,
-		duration: 0,
-		time_base_num: 1,
-		time_base_den: sample_rate,
-	};
-	let raw = Box::into_raw(Box::new(p.clone()));
-	audio_params_store().lock().unwrap().insert(raw as usize, p);
-	raw as *mut OakAudioParams
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_free(params: *mut OakAudioParams) {
-	if params.is_null() {
-		return;
-	}
-	audio_params_store()
-		.lock()
-		.unwrap()
-		.remove(&(params as usize));
-	// SAFETY: produced by `oakcore_audioparams_create`; we hold the only
-	// reference after removal.
-	unsafe { drop(Box::from_raw(params as *mut MockAudioParams)) };
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_sample_rate(params: *const OakAudioParams) -> c_int {
-	audio_params_get(params as *const c_void).sample_rate
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_set_sample_rate(
-	params: *mut OakAudioParams,
-	sample_rate: c_int,
-) {
-	audio_params_set(params as *mut c_void, |p| p.sample_rate = sample_rate);
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_channel_layout(params: *const OakAudioParams) -> u64 {
-	audio_params_get(params as *const c_void).channel_layout
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_set_channel_layout(params: *mut OakAudioParams, layout: u64) {
-	audio_params_set(params as *mut c_void, |p| p.channel_layout = layout);
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_set_time_base(
-	params: *mut OakAudioParams,
-	num: c_int,
-	den: c_int,
-) {
-	audio_params_set(params as *mut c_void, |p| {
-		p.time_base_num = num;
-		p.time_base_den = den;
-	});
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_set_format(params: *mut OakAudioParams, format: c_int) {
-	audio_params_set(params as *mut c_void, |p| p.format = format);
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_set_stream_index(params: *mut OakAudioParams, index: c_int) {
-	audio_params_set(params as *mut c_void, |p| p.stream_index = index);
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_set_duration(params: *mut OakAudioParams, duration: i64) {
-	audio_params_set(params as *mut c_void, |p| p.duration = duration);
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_channel_count(params: *const OakAudioParams) -> c_int {
-	audio_params_get(params as *const c_void)
-		.channel_layout
-		.count_ones() as c_int
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_format(params: *const OakAudioParams) -> c_int {
-	audio_params_get(params as *const c_void).format
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_stream_index(params: *const OakAudioParams) -> c_int {
-	audio_params_get(params as *const c_void).stream_index
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_duration(params: *const OakAudioParams) -> i64 {
-	audio_params_get(params as *const c_void).duration
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_is_valid(params: *const OakAudioParams) -> c_int {
-	let p = audio_params_get(params as *const c_void);
-	(p.sample_rate > 0 && p.channel_layout != 0 && p.format >= 0) as c_int
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_audioparams_time_base(params: *const OakAudioParams) -> *mut c_void {
-	let p = audio_params_get(params as *const c_void);
-	let r = (p.time_base_num, p.time_base_den);
-	let raw = Box::into_raw(Box::new(r));
-	rational_store().lock().unwrap().insert(raw as usize, r);
-	raw as *mut c_void
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_rational_numerator(rational: *const c_void) -> c_int {
-	rational_store()
-		.lock()
-		.unwrap()
-		.get(&(rational as usize))
-		.map(|r| r.0)
-		.unwrap_or(0)
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_rational_denominator(rational: *const c_void) -> c_int {
-	rational_store()
-		.lock()
-		.unwrap()
-		.get(&(rational as usize))
-		.map(|r| r.1)
-		.unwrap_or(0)
-}
-
-#[no_mangle]
-pub extern "C" fn oakcore_rational_free(rational: *mut c_void) {
-	if rational.is_null() {
-		return;
-	}
-	rational_store()
-		.lock()
-		.unwrap()
-		.remove(&(rational as usize));
-	// SAFETY: produced by `oakcore_audioparams_time_base` as a boxed
-	// `(i32, i32)` pair; we hold the only reference after removal.
-	unsafe { drop(Box::from_raw(rational as *mut (i32, i32))) };
-}
+/// The facade's in-dylib `oakcore_audioparams_*` C ABI (see
+/// `crate::stubs::audio`): the accessors were host-provided mocks until
+/// M12 P5 folded them into the engine, so the tests now share the real
+/// implementations instead of defining per-binary duplicates. Only the
+/// two entry points the test files call (`create`/`free`) are re-exported;
+/// the read accessors are reached through `crate::stubs::audio` where the
+/// tests need them.
+pub use crate::stubs::audio::{oakcore_audioparams_create, oakcore_audioparams_free};
diff --git a/crates/oakengine/src/test_support/it_audio.rs b/crates/oakengine/src/test_support/it_audio.rs
index d7b30eebb..4d9d70f77 100644
--- a/crates/oakengine/src/test_support/it_audio.rs
+++ b/crates/oakengine/src/test_support/it_audio.rs
@@ -108,9 +108,10 @@ fn alive() -> c_int {
 	crate::stubs::audio::oakaudio_debug_alive_count()
 }
 
-/// A borrowed `OakAudioParams*` mock handle (tests/common/mod.rs provides
-/// the `oakcore_audioparams_*` accessors the facade reads through).
-fn audio_params(rate: c_int, layout: u64, format: c_int) -> *mut common::OakAudioParams {
+/// A borrowed `OakAudioParams*` handle created through the facade's
+/// in-dylib `oakcore_audioparams_*` accessors (tests/common/mod.rs
+/// re-exports them; see `crate::stubs::audio`).
+fn audio_params(rate: c_int, layout: u64, format: c_int) -> *mut c_void {
 	common::oakcore_audioparams_create(rate, layout, format)
 }
 
diff --git a/crates/oakengine/src/test_support/it_export.rs b/crates/oakengine/src/test_support/it_export.rs
index 243fb3307..525ac878a 100644
--- a/crates/oakengine/src/test_support/it_export.rs
+++ b/crates/oakengine/src/test_support/it_export.rs
@@ -20,8 +20,9 @@
 //!
 //! Coverage rules (see the family test charter):
 //!   1. no mocks — every call goes through the real facade into the real
-//!      module crates (the only stubs are the host-provided `oakcore_*`
-//!      symbols in `tests/common`); the output file is a REAL mp4 written
+//!      module crates (the `oakcore_audioparams_*` accessors the facade
+//!      reads through are its own in-dylib implementations, re-exported by
+//!      `tests/common`); the output file is a REAL mp4 written
 //!      by the statically linked FFmpeg (oakcodec encoder), asserted by
 //!      its `ftyp` box;
 //!   2. every exporter-family export is exercised on a legal path with the
diff --git a/crates/oakengine/src/test_support/it_task.rs b/crates/oakengine/src/test_support/it_task.rs
index bd63ef104..205a7cb59 100644
--- a/crates/oakengine/src/test_support/it_task.rs
+++ b/crates/oakengine/src/test_support/it_task.rs
@@ -19,9 +19,10 @@
 //!
 //! Coverage rules (see the family test charter):
 //!   1. no mocks — every call goes through the real facade into the real
-//!      oaktask/oaknode/oakundo/oakcodec module crates (the only stubs are
-//!      the host-provided `oakcore_*` symbols in `tests/common`,
-//!      the same mechanism the other family tests use);
+//!      oaktask/oaknode/oakundo/oakcodec module crates (the
+//!      `oakcore_audioparams_*` accessors the facade reads through are its
+//!      own in-dylib implementations, re-exported by `tests/common`, the
+//!      same mechanism the other family tests use);
 //!   2. every one of the 27 `oakengine_task_*` / `oakengine_cli_task_*`
 //!      exports is exercised on a legal path with the result asserted;
 //!   3. legal-input matrix (compression flags, url counts, indices, buffer
diff --git a/crates/oakengine/src/test_support/it_timeline.rs b/crates/oakengine/src/test_support/it_timeline.rs
index 3119b9a30..af8e6bdbf 100644
--- a/crates/oakengine/src/test_support/it_timeline.rs
+++ b/crates/oakengine/src/test_support/it_timeline.rs
@@ -21,8 +21,9 @@
 //! undoable). Coverage rules (see the family test charter):
 //!
 //! 1. no mocks — every call goes through the real facade into the real
-//!    module crates; the only stubs are the host-provided `oakcore_*`
-//!    symbols in `tests/common` (no media is decoded, so no FFmpeg);
+//!    module crates (the `oakcore_audioparams_*` accessors the facade
+//!    reads through are its own in-dylib implementations, re-exported by
+//!    `tests/common`; no media is decoded, so no FFmpeg);
 //! 2. every export under test is exercised on a legal path with the
 //!    result asserted;
 //! 3. illegal inputs (NULL seq, bad track types, out-of-range indices,
diff --git a/crates/oakengine/src/test_support/mod.rs b/crates/oakengine/src/test_support/mod.rs
index 7bd216244..731705aea 100644
--- a/crates/oakengine/src/test_support/mod.rs
+++ b/crates/oakengine/src/test_support/mod.rs
@@ -21,8 +21,8 @@
 //! They moved here (`src/test_support/`, pulled in by `src/lib.rs` under
 //! `#[cfg(test)]`) and run as unit tests against `crate::*` instead of
 //! `oakengine::*`. The old `#[path = "common/mod.rs"] mod common;` include
-//! is replaced by the single [`common`] declaration below — the
-//! `oakcore_*` mock symbols it defines may exist only once per binary.
+//! is replaced by the single [`common`] declaration below — its
+//! `oakcore_audioparams_*` re-exports may exist only once per binary.
 //!
 //! The node/timeline/render-graph families (and the graph-op tests that
 //! built fixtures through the deleted handle-based module C ABIs) are