🧊 feat: Persist Context Fading Tier Across Agent Runs (#15505)

* 🧊 feat: Persist Context Fading Tier Across Agent Runs

Carry the pruner's latched context-fading tier from `@librechat/agents`
through `contextMeta` the way `calibrationRatio` already travels, so a
historical tool result keeps the same truncated bytes from one run to the
next and Anthropic's prefix-based prompt cache survives across turns
(danny-avila/agents#497).

- Add `IAgentFadingTier` to the message and conversation `contextMeta`
  types, schemas and the data-provider zod schema
- Add `isAgentFadingTier`, `resolvePersistableFadingTier` and
  `resolveRunContextMeta` in `packages/api`; a tier is persisted once it
  carries information (masking active or a budget below the window), and
  a latched tier is kept even at a neutral calibration ratio
- Seed `createRun({ fadingTier })` from the parent response's contextMeta
  regardless of encoding, since caps are character-based; the field rides
  the existing forward-compatible `runConfig` variable and older SDK
  versions ignore it, as does `Run.getFadingTier` being absent
- Accept a valid `fading` field in event actor context and reject a
  malformed one, matching the calibration checks
- Capture run context meta through one module-level helper for both
  completion paths instead of two inline copies

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 fix: Seed Fading Tier Across HITL Resume, Validate at the DB Layer

Address review findings on fading tier persistence:

- Leave the "is this tier worth persisting" decision to the SDK, whose
  `Run.getFadingTier()` now returns only informative tiers; comparing
  against the client's window misclassified untouched conversations
  whenever a reserve ratio was configured
- Carry `contextMeta` through the HITL pause projection (staged approval,
  job metadata, resume state) and seed the rebuilt client from it, so a
  paused turn resumes with the same tier and calibration instead of
  re-deriving a shallower one and rewriting the prefix
- Share run seeding between `chatCompletion` and `resumeCompletion`, and
  make capture tolerate partial runs and bare resume contexts
- Validate `contextMeta.fading` in `commitAgentEventActorState` with a
  shared `isAgentFadingTier` guard in data-schemas, so a malformed tier is
  rejected at the DB layer instead of silently cold-starting the actor
- Reuse `IAgentEventActorContextMeta` for `IMessage.contextMeta` instead of
  extending an inline duplicate

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 test: Cover Resume Seeding From Paused Context Meta

Assert the resume controller seeds the rebuilt client from the context meta
captured at the pause before rebuilding the run, and move the capture
helper's JSDoc back above its function.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧹 style: Sort Imports in Fading Tier Plumbing

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 fix: Persist Fading Tier Through Redis Jobs and Branches

Address Codex and Copilot review findings on fading tier persistence:

- Deserialize `contextMeta` in `RedisJobStore`, whose explicit read mapper
  rebuilt every other pause field but this one, so Redis-backed
  deployments resumed with no tier to seed after every HITL pause
- Copy server-private `contextMeta` onto the assistant message created by
  `POST /api/messages/branch`, so the next turn seeds its pruner the same
  way it would from the parallel source response
- Constrain the `fading` subdocuments in both Mongoose schemas (version
  enum, positive budget, required fields) to match the zod schema
- Throw a distinct "fading tier is invalid" error from both context meta
  validators instead of reporting a calibration failure

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 fix: Carry Context Meta Through Stop and Re-Pause

Addresses the second Codex pass on the fading-tier persistence:

- A re-pause whose resumed segment has nothing persistable now clears the
  job's `contextMeta` in the same transition instead of leaving the first
  pause's calibration and tier for the next resume to seed from.
- The client publishes the run's live calibration and fading tier onto the
  job after each pre-invoke context snapshot (deduplicated on value), and
  the Stop path copies `jobData.contextMeta` onto the stopped response, so
  a follow-up from a stopped turn keeps the prompt prefix stable.
- Mid-run captures (HITL pause, Stop) read the graph's live state; `Run`
  refreshes its own getters only after the stream settles, so the pause
  used to persist the seeds it started from.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 fix: Fence Context Meta Publication Ahead of Stop

A Stop handled by another replica reads the job before the owner is
signaled, so a fire-and-forget publish could lose the race, and a run
stopped before its first context snapshot never published the tier it
inherited. The client now publishes the inherited seed before the run
streams or resumes, and the context-usage handler awaits each
snapshot's publish so the write lands before the model call it
describes begins. Failures still only log; the pre-run publish is
optional-called so bare resume contexts keep working.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 fix: Read Back Context Meta After the Abort Claim

The run owner publishes its context meta ahead of each model call and
awaits the write, so a publish landing between the abort's initial job
read and its terminal claim describes the call whose partial output the
abort snapshot carries. abortJob now reads the same-epoch job back after
the claim and content re-read and takes its context meta, so the stopped
response persists the tier that produced its bytes. The refresh is
best-effort and logs on failure like the content refresh beside it.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 fix: Share In-Flight Context Meta Writes and Clear Neutral Live State

Two snapshot callbacks in a parallel-agent run can capture the same tier
before the first write settles; the publisher now caches the in-flight
promise per serialized value so the second caller awaits the same
durable write instead of treating an uncommitted value as published.
A live snapshot with nothing left to persist after an earlier publish now
writes a neutral record (ratio 1, no tier), since a running job's fields
cannot be deleted through the metadata writer, so a Stop no longer
persists an earlier non-neutral state onto the response. The pre-run
seed publish is unchanged and is told apart from live snapshots by a
flag from the context-usage sink.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 chore: Drop Unused Rest Parameter in Context Meta Test

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 feat: Persist Per-Agent Fading Tiers as Compact Context Meta

Reconciles the host with @librechat/agents at 9aacad1a, where graph
history stays canonical and each Run derives a provider-only projection
from the latched tiers. LibreChat therefore persists only compact state:
the calibration ratio, the default agent's tier, and now the per-agent
tiers from Run.getFadingTiers(), stored as validated entries so agent IDs
never become MongoDB field names and restored onto a null-prototype
record for RunConfig.fadingTiers. Truncated messages, canonical tool
content, projection provenance and per-message truncation state are
never persisted; the SDK's latched flag is stripped on capture.

The per-agent map travels everywhere the single tier already did:
response contextMeta, event-actor checkpoint state, HITL pause and
resume job metadata in both stores, the Stop path, and branch creation.
A shared Mongoose definition keeps the message and conversation schemas
identical, the zod schema validates entries, and commitAgentEventActorState
rejects malformed maps. Comments no longer describe graph messages as
truncated; only the provider projection is.

Tests cover: tool results and inputs reach the persisted content parts
at full size; contextMeta carries exactly the compact tier and
calibration fields; a persisted snapshot round-trips into the seeded
RunConfig unchanged and prototype-safe; per-agent tiers survive pause,
Redis job round-trips, and event-actor context validation.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 fix: Restore Event Actor Types and Publish Seeds Before Abortable Setup

The previous commit's doc rewording in the conversation types dropped the
event-actor interfaces that precede the fading tier, which broke the
declaration bundle in CI; they are restored unchanged.

The inherited context meta is now published onto the job as soon as the
parent's state is loaded and awaited at the top of chatCompletion and
resumeCompletion, ahead of run creation and the other abortable setup
stages, so a Stop during setup still persists the parent's tiers onto the
stopped response. The partial response saved when every subscriber
disconnects now carries the job's context meta like the Stop and pause
paths do. The branch route keeps the source's context meta in the saved
message but strips it from the HTTP response, matching client reads.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 fix: Serialize Distinct Context Meta Publications

Overlapping snapshots from parallel agents could carry different tiers;
each started its own write and both job stores keep whichever write
finished last, so an older snapshot could overwrite a newer one. Each
distinct publication is now issued after the previous one settles, in
call order, so the newest snapshot is what a Stop reads back. Equal
values still share one write.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 fix: Project Root Message Reads and Keep Inherited Meta on Setup Failure

The root GET /api/messages paths returned raw documents: the
single-message query read called getMessages without a projection and the
cursor page performed an unprojected find. Both now apply
CLIENT_MESSAGE_SELECT, with getMessagesByCursor accepting a select option,
so the persisted fading tiers never reach the client through the
paginated endpoint; the search-hydration read projects the same way.

A turn that loads a parent's context meta but fails before its run exists
used to replace the inherited meta with the capture of a missing run, so
the persisted error response lost the last valid tiers. Both finalizers
now keep the inherited meta when no run was created while a created run's
neutral state may still clear it.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 refactor: Move Context Meta Publication Into packages/api

The publication coordinator (ordering, deduplication, in-flight sharing,
failure state) now lives in packages/api as createContextMetaPublisher,
with selectRunContextMetaToPublish deciding what a publication carries;
the legacy client keeps only the wiring to the job metadata writer. A
transiently failing write is retried with a short backoff before the
publication is reported and forgotten, so a snapshot's model call no
longer proceeds on the first rejection while the job holds the previous
record. The SDK swallows handler errors, so retrying is the only way to
strengthen the fence without failing the turn.

A terminal save now supplies contextMeta: null when the finished run has
nothing to carry, and saveMessage unsets a previously stored value in
that case, so a disconnect snapshot's record cannot outlive the run that
completed neutrally.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 fix: Widen the saveMessage Method Type for the Null Unset

The exported method interface still typed contextMeta as the message
field, so the spec exercising the null unset failed typechecking; it now
mirrors the implementation signature.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 fix: Publish Every Agent's Snapshot, Sanitize Search Hits, Unbound Agent IDs

The context-usage handler now awaits the run's context meta publish for
every ON_CONTEXT_USAGE event, hidden sequential agents included, while
the visible-snapshot bookkeeping and the client emission keep their gate;
a Stop before the next visible snapshot finds the tier a hidden agent's
model call latched. Search results are built from the hydrated hit minus
its server-private contextMeta, since Meilisearch hydration projects every
schema field. The per-agent tier entry guard no longer caps the agent ID
length: ephemeral agent IDs encode endpoint, model and sender without a
bound, and dropping such an entry would let that agent alone re-derive
its tier on the next turn. Also formats the publication spec so the
static checks pass.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 fix: Unset Context Meta Atomically, Keep Publication State After a Failed Write

- `saveMessage` folds the `contextMeta` unset into the same update that
  persists the terminal response, on both the plain and the provenance-merge
  paths, so a failure between two writes can no longer leave a completed row
  carrying a disconnect snapshot's state.
- `createContextMetaPublisher` tracks whether any record has committed
  separately from the retryable latest publication, so `hasPublished` stays
  true after a later publication exhausts its retries and a following neutral
  snapshot still overwrites the earlier record on the job.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 fix: Carry Context Meta Through the Resumable Stop Route and Neutral Resumed Completions

- The resumable Stop route copies the refreshed `jobData.contextMeta` onto the
  terminal assistant message it persists, as the abort middleware already
  does, so a stopped resumable response keeps the tiers that produced its
  partial output.
- A resumed run that completes with neutral context state now saves
  `contextMeta: null`, which unsets the paused segment's record instead of
  letting an omitted field keep it on the completed row.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 fix: Trust Only Server-Authored Context Meta, Unset It on a Neutral Stop, Read It From the Job on Disconnect

- `POST /api/messages/:conversationId` and conversation imports drop any
  client-supplied `contextMeta`, and the run seeds its calibration and fading
  tiers only from a server-authored parent response, so a forged tier can never
  shape a provider projection.
- Both Stop paths save `contextMeta: jobData.contextMeta ?? null`, so a job that
  re-paused with neutral state unsets what an earlier pause stored on the row
  instead of leaving it behind.
- The disconnect partial save reads the same-epoch job record for the run's
  published context meta, since the client-facing resume snapshot never carries
  server-private state.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧪 test: Mock the Job Store in the Resume Metadata Spec

The disconnect partial save now reads the same-epoch job record through
`GenerationJobManager.getJobStore()`, so the resume metadata spec's manager
mock provides it as the other disconnect spec already does.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 🧊 fix: Keep Context Meta Off the POST Message Response

`POST /api/messages/:conversationId` returned the saved row verbatim, so a
client write against an existing server-authored message echoed the row's
stored context meta. The route now projects the row through the same client
projection the branch route uses, which drops the server-private field.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

* 📦 chore: Bump @librechat/agents to 3.7.16 for Persisted Fading Tiers

3.7.16 is the first release that carries danny-avila/agents#497, so
`Run.getFadingTier()` / `getFadingTiers()` now report the latched tier
this branch persists and `RunConfig.fadingTier` / `fadingTiers` seed the
next run from it. The dependency set is unchanged from 3.7.15; only the
package entry moves.

Adds an SDK-backed round trip to the fading spec: a first pruner latches
an informative tier, `resolveRunContextMeta` reduces it to the persisted
shape, and a second pruner seeded from that shape reproduces the first
run's projected tool-exchange bytes under instruction and calibration
drift, while an unseeded pruner under the same drift relaxes its tier and
rewrites them.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WNbgMeR2aZDyhsqAy4L8gF

---------

Co-authored-by: Claude <noreply@anthropic.com>