Struct KvAllocId 

pub struct KvAllocId(/* private fields */);

A process-unique, never-recycled identity for one KV allocation — the set of storage buffers a held decode plan is welded to.

Why a held plan needs this at all

DecodeSession keeps a base_cache holding the KV storage Arcs bound on the first decode token, and the per-token rebind overwrites only the data Consts — token_ids, RoPE tables, mask, offset. It never rebinds kv_nodes. So a held plan does not read the &mut KvCache it is handed; it reads the buffers it was built against, forever.

Geometry cannot see that. Two same-shaped caches key identically, so the slot-pooled serving happy path — retire request A, admit B on a fresh cache of the same shape, reuse the plan for speed — silently decodes B over A’s KV. Full speed, plausible distribution, nothing to report. That is why this id exists and why it is in the validity key.

The id names the ALLOCATION, not the conversation

This distinction is the entire design, and getting it backwards breaks one of the two directions that matter:

• Re-allocate ⇒ new id. Constructing a cache, and any operation that replaces storage under it (KvCache::clear / KvCache::set_layer), mints a fresh id. A plan welded to the old buffers must be rebuilt.
• Rewind ⇒ SAME id. KvCache::truncate_to — speculative decoding’s reject path — moves cached_len and touches no storage. The plan is still welded to exactly the right buffers, so invalidating there would forfeit plan reuse (223× on CUDA) on every rejected draft batch, for no correctness gain.

Over-keying is the failure mode with no error message: an “always stale” predicate passes every correctness test while quietly disabling the optimization. The tests assert both halves for that reason.

Never recycled, for the same reason ModelInstanceId is: pointer identity would be sound only while something pins the allocation, and a session outliving its cache is exactly the case this guards. See the module docs.

Implementations

impl KvAllocId

pub fn next() -> Self

Mint the next id. Monotonic and never recycled.

pub fn get(self) -> u64

Trait Implementations

impl Clone for KvAllocId

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for KvAllocId

impl Debug for KvAllocId

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for KvAllocId

impl Hash for KvAllocId

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for KvAllocId

fn eq(&self, other: &Self) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for KvAllocId