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GL 4.0 folds ARB_transform_feedback2 and _3 into core, and neither existed: glGenTransformFeedbacks, glBindTransformFeedback, glDeleteTransformFeedbacks, glIsTransformFeedback, glPause/ResumeTransformFeedback, the whole glDrawTransformFeedback family and glBegin/EndQueryIndexed were all stubs, and gl_NextBuffer / gl_SkipComponents1..4 failed the link as "not an output of the vertex stage". Seven KHR-GL40.transform_feedback* cases failed on it, three of them by leaving a capture open at deinit and taking the process down. Objects. The capture state and the indexed GL_TRANSFORM_FEEDBACK_BUFFER bindings are object state, but the context keeps one live copy of both, which is what every existing reader - each backend's per-draw sync, the drawing and getter paths - is written against. Rather than teach all of them about objects, a bind saves the live copy into the outgoing object and restores the incoming one's. Object 0 is the default object and needs no seeding; operator[] materialises the rest on first touch. Pause. A paused span captures nothing, and three rules key off that: a draw is exempt from the capture primitive-mode match, it feeds PRIMITIVES_GENERATED but not TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN, and glUseProgram is allowed again (that last one was already refused for an active capture, correctly for GL 3.3, which has no pause). glDrawTransformFeedback replays the vertices the object captured in its last completed span, recorded at End. "Has a completed span" is tracked separately from that count, because a completed empty span draws nothing while an object that never ended one is INVALID_OPERATION. Drawing from the object whose capture is currently open is deliberately allowed - feeding a result straight into the next span is the point of KHR-GL40.transform_feedback.draw_xfb_feedbackk_test. DirectGLES gets a real driver object per frontend object. That is the only reason the default one would not do: several objects can be paused at once, and a paused span lives inside the driver's object. The deferred driver-side Begin (still needed - ES wants the program current and the buffers bound) now also has to be held back while the span is paused, or a pause taken before the first draw would open the span on that draw and subject it to the primitive-mode rule it is exempt from. Special names. gl_NextBuffer and gl_SkipComponents<n> are consumed during varying resolution and never become varyings of their own, so they only move where the following ones land - and stay out of the name list the backend declares on its own driver. ES cannot express the resulting layout at all: it packs every captured varying into one gap-free record. So when the layout has holes or spans several buffers, DirectGLES captures into a scratch buffer bound in place of the application's, and End distributes the records to the offsets GL asked for. Only the bytes a varying occupies are written, which is exactly what makes the holes keep the contents the application left there - the property KHR-GL40.transform_feedback3.skip_components checks. glBegin/EndQueryIndexed and glGetQueryIndexediv differ from the plain forms only in the vertex stream they address, so they validate the index and forward. GL_MAX_VERTEX_STREAMS stays at 1: multi-stream capture needs ARB_gpu_shader5 stream qualifiers that no ES driver implements, and the CTS cases that need more than one stream check the limit and skip. KHR-GL40.transform_feedback, transform_feedback2 and transform_feedback3: 38/38.