promptHandler logs a failing Render's error with the prompt name and
answers the fixed JSON-RPC internal error "pier: the prompt could not be
rendered", as dispatch does for tool calls (A-WR-08), so database or
provider text never reaches the agent or its transcript.
TestPromptRenderError renders a prompt that fails with a database error
naming its host and asserts, on both paths, that the client sees only the
fixed text and the cause is in the log.
Each stateless request now carries an entry-use record on its context;
getServer counts the entry it hands out as active (under the path lock)
and ServeHTTP releases it when the request ends, so a subscriptions/listen
stream keeps its entry active for its whole life. Capacity eviction walks
the LRU from the back and drops only idle entries, so it no longer ends a
quiet listener or cancels a tool call in flight, and a revocation still
finds every open stream. While every entry is busy the LRU stays above
capacity until requests end.
TestStatelessFanOut's LRU subtest now asserts that the listener's server is
spared when the binding past capacity arrives (the oldest idle server goes
instead) and that a revocation then still ends the stream.
catalog.allowedReport returns the allowed lists together with the first
provider error. Widening (stateful) and the stateless refresh leave the
cached server and its recorded fingerprint untouched on an error, so the
next request retries instead of the tools staying hidden until the next
rotation or event. A fan-out recompute still applies its fail-closed diff
but records no fingerprint, so the binding's next request re-filters.
TestWideningGuardError fails the guard during a widening on both paths and
during a permissions recompute, then asserts that the next request lists
every tool once the provider answers again.
The identity fingerprint no longer includes token ids: guards decide on
scopes, subjects and the ceiling, and an OAuth access token's id changes on
every refresh, so a rotation alone no longer re-filters a cached server.
The stateless path's refresh only adds tools and prompts for a fingerprint
new to the entry (remembered until a fan-out recompute) and never removes:
one server serves every live token of a binding, and removing on each
alternation between a wider and a narrower token pulled a tool from under
the wider token's call. The receiving middleware still filters every list
and call per request; fan-out recomputes still narrow. The stateful path
keeps its exact widen, a session serves one client.
TestFingerprintIgnoresTokenID pins the fingerprint; TestStatelessSharedBinding
blocks the wide token's call after its server was chosen, sends a request
of the narrow token and asserts the call still succeeds (it failed with
"unknown tool" before).
Fan-out matching snapshots the sessions (and stateless entries) under the
router-wide lock, releases it, and reads each identity through a small
identity box that is never held across I/O, so an event no longer waits on
a session that is re-filtering while it holds sr.mu or sp.mu.
Widening and the fan-out recomputes run their guard checks with
guardContext: not cancelled with the triggering request, but bounded by
mcp.call_timeout, so a provider that never answers cannot hold a session
lock forever. README and docs/services/mcp.md describe the wider meaning of
mcp.call_timeout.
TestLockScopeUnderWidening blocks a widening guard check, fires a
permission event for that session and asserts that another session's call
still finishes, and that a never-answering check ends at call_timeout.
- pact.MCPSubjectChanged and pier.Event gain TokenID and ClientID; a
narrowed revoked event closes only matching sessions and stateless servers
- cabana fires the admin token revoke with the token row id
- towel.WithClientIP/ClientIP; pier puts the address (surf applies
http.trusted_proxies) on the resolve context and ResolveBackendToken logs it
- pact.MCPPrompt.Writes (additive; the zero value keeps today's listing)
- pier's allowsPrompt hides a prompt declared with Writes from an identity
without write, as it hides a tool that is not read-only (C-IN-01
framework part, P-28)
- a path field must be required in the reflected schema (boot error), and
a missing value, an empty, . or .. segment, or a / inside one segment is
a tool error before dispatch (A-WR-01, A-WR-02)
- a failed guard dispatch logs its cause and answers a fixed tool text;
only an invalid token and an unknown or deactivated account keep their
own fixed texts (A-WR-08)
- path and query scalars decode with UseNumber, so integers above 2^53
keep their digits (A-IN-04)
- the dispatched request carries the outer Host, X-Forwarded-Proto and
X-Forwarded-Host (A-IN-05)
- an embedded struct on a GET or DELETE tool fails boot (A-IN-07)
- a dispatch whose guard list or principal kind contradicts the tool's
guard is refused (A-IN-08)
- Identity.fingerprint covers scopes, both subjects, the ceiling and the
token kind; a stateful lookup or stateless hit whose fingerprint changed
re-filters the server with the event diff under its own mutex (A-WR-04)
- Mount warms a Redis store in the background with a 1 s to 30 s backoff
and every request kicks a pending open without waiting, so stateless-only
instances subscribe to fan-out (A-WR-05)
- a stateless subscriptions/listen POST re-verifies its bearer every
recheck interval; an LRU-evicted stateless server closes its sessions
(A-WR-06)
- resolvePersonalToken refuses a subject with TokenID 0, and the
pact.MCPPersonalTokenResolver contract says one resolver per application,
false means unauthorized and TokenID keys the binding (A-WR-09, A-IN-03)
- a reaper started at Mount checks every local session against the store
every min(idle_ttl/2, 1m) and closes each copy whose record is gone,
logging the expired step (A-CR-01, A-IN-06)
- the GET stream re-check ends the stream when the record is gone (A-IN-01)
- tool calls served without a session on the stateful path log the
session as ephemeral (A-IN-06)
- TestPierReaperSmoke and the ReapNow, LocalSessions, StopReaper seams
- personal tokens only behind mcp.allow_personal_tokens (401 without a
lookup otherwise); an admin token yields a backend-only identity with
its scope limit per dispatched method, a user token a frontend-only one
- read/write ceiling and prompts proven by the tracer's subtests; the
audit line asserted to carry the tool and never the arguments or token
- the mounted *pier.Pier is published on the application (test seams in
export_test.go)
- docs/services/mcp.md with the tested acme.blog example, site.yaml note,
cross-links from authentication.md, registration.md and the surf README
- store_redis.go: records with PX TTLs, per-binding sets, pub/sub events,
opened lazily from redis.url under cooler's prefix (nothing dials at mount)
- events.go: pact.MCPSubjectChanged republished through the store; every
instance recomputes the subject's sessions and stateless servers
(list_changed) or ends them on revocation; the link cache is dropped
- stateless.go: the SDK's stateless handler over per-identity servers for
2026-07-28 clients, routed by the protocol header or server/discover
- prm.go: RFC 9728 metadata at both well-known paths; long GET streams
re-verify their bearer every minute
- TestPierSessionsSmoke, TestPierFanOutSmoke, TestPierStatelessSmoke on
miniredis; README features, configuration and operational notes
- modules/pier: Host contract, mcp.* config, catalog compiled from
pact.HasMCP (prefixing, route binding, guard resolution, schema
reflection, annotations), per-request identity through the published
verifier and resolvers, built-in backend guard provider, in-process
dispatch with the bouncer marker, per-identity SDK server with the
per-request re-filter, stateful session router with rehydration over a
memory store, audit lines
- modules/surf/pier_on.go: the summercms_mcp hook adapting the router to
pier.Host; the untagged hello binary carries no SDK
- go.mod: go-sdk v1.8.0 and jsonschema-go v0.4.3 (decision note committed
before this change)
- TestPierTracerSmoke: SDK client lists and calls acme_echo end to end
through surf's compiled guard chain; README and root table row
