# Session- and auth-bound task context cache

Key and lifecycle in-process task-context caches by session id and live auth generation so shared-process sessions and mid-session auth replace cannot leak or reuse stale context.

Exact reference: {"kind":"skill_version","skill_id":"skl_wCKU3ytdp9mfmqZocBWzrA","version_id":"skv_EFATM4Hj1j8RhU9FchsXbg"}

Applicability: []

# Session- and auth-bound task context cache

## When to use
Use when an agent plugin caches task context before a system-message transform, multiple root or child sessions share one process, and authorization may be revoked or replaced while that process and root session stay alive.

## Steps
1. Key every entry as sessionId plus authGeneration. If a process-wide epoch or auth-lineage identity is used to survive counter restart, fold that epoch or lineage id into the same composite key. Carry only sessionId in request scope such as AsyncLocalStorage. Resolve authGeneration from the live authorization handle for that auth lineage at write, read, and inject time—never from a module-level current pointer and never from an ALS-cached generation alone.
2. Look up by the full composite key. Do not select by sessionId alone. After any await on a read or inject path, re-resolve live generation immediately before the composite lookup. Missing or generation mismatch injects empty or default. Never fall back to parent, sibling, last-writer, or a prior generation.
3. After a successful fetch and immediately before mutating prompt state, re-validate that entry.authGeneration equals live.authGeneration while holding the revoke critical section through prompt mutation, or an otherwise indivisible load-check-mutate sequence with respect to bump and credential publish. A bare check-then-inject without that indivisibility is not equivalent. On mismatch, abort to empty or default.
4. Default-isolate child sessions. If inheritance is required, copy-on-create a snapshot into the child key; never share a mutable object with the parent. Children must read the live parent auth handle for generation checks. Maintain a parent-to-child or auth-lineage index so revoke sweeps every tied key.
5. Sample generation once at the start of a write. Key and tag the entry only with that sampled generation. On commit, inside the same critical section used for revoke or an equivalent compare-and-set, require sampled equals live; only then insert or replace. On mismatch, abort and delete any provisional entry under the sampled key. Never re-resolve live into the composite key after a bump.
6. Serialize child snapshot creation and lineage-index registration with that same critical section. Treat entry install and lineage registration as one atomic unit. If using post-insert re-validation instead, on mismatch delete the child entry and remove the index edge so revoke cannot mis-sweep or skip.
7. On revoke or replace: compare-and-set live.authGeneration from expected to expected plus one (or hold one critical section for the whole bump, lineage delete or tombstone including indexed children, and credential publish). On CAS failure, retry or abort without publishing.
8. Treat injected context as prompt data only—never as a network credential. Every outbound network or tool call must mint or present a capability from an atomic snapshot of the live handle so credentials and generation cannot tear across a concurrent replace; mismatch fails closed. Cancel work that will take another hop; do not assume already-gated single-shot I/O is recalled. Re-check live generation before applying response side effects.
9. Bound memory: cap entry count, bytes per entry, and total bytes; prefer delete-on-bump and session dispose; use LRU plus TTL for orphans; store slim summaries. Do not recycle a sessionId while an orphaned composite entry for that id may remain. When using a process-wide epoch, keep it in the key from step 1 so restarted counters cannot alias orphans.

## Limits
- Does not scrub prompt text already injected into an in-flight model turn before a bump.
- Cannot recall bytes already on the wire; re-check live generation before applying response side effects.
- Completed single-shot I/O under an old generation is not undone.
- Support for this guidance is reasoned analysis and independent design review, not executed tests.

## Failure prevented
Prevents cross-session context injection, inject of a payload loaded before a concurrent revoke, cross-generation prompt and credential mix from non-indivisible inject, stale-generation miss after await, torn outbound capability minting across auth replace, late-writer orphan or reinstall of a revoked generation, write-key poison onto a post-bump generation, child snapshot and lineage-index races across parent auth replace, and same-session auth-rotate paths where stale cache entries authorize network activity or reappear under a recycled session identity or restarted generation counter.

## Supporting basis and limitations

Update grounded in reasoned design analysis from the cited native conversation on this root covering session isolation, composite sessionId plus authGeneration keys, revoke compare-and-set invalidation, and fail-closed network capabilities; plus an independent native subagent review in the same conversation that found four concrete gaps—torn credential and generation reads when minting outbound capabilities, process-wide epoch omitted from the composite key, load-check-inject that is not indivisible with bump and publish, and async read paths that look up a stale sampled generation after await. No repository inspection and no executed tests were performed.

## Change and rationale

Close four races from independent review: atomic outbound credential-plus-generation minting, fold process epoch into the composite key when used, require inject check and prompt mutation indivisible with revoke, and re-resolve live generation immediately before read lookup after any await.

Session-only keys leak under concurrency. Without indivisible inject, post-await re-resolve, epoch-in-key when epochs are used, and atomic outbound credential-plus-generation minting, stale or torn state can still inject or authorize after mid-session auth replace.