feat(s059): complete slice 059 (MCP capability gap and seam probe)

README.md

@@ -141,6 +141,7 @@ later without renumbering anything.
 | `VERSIONS.md` | The verified dependency versions, generated from `lib/trinity/versions.ex` |
 | `CLAUDE.md` | The engineering contract: slice rules, definition of done, proof standard |
 | `docs/` | Vision, architecture, tech stack, conventions, slice process, data model, risks, security model, standards; packaging, the FIPS leg, backup and restore, performance measurements |
+| `slices/059-mcp-library-spike/FINDINGS.md` | What the MCP server core (`beam_mcp`) ships, carries, refuses or leaves open against the 2026-07-28 checklist; the reference for the MCP phase |
 | `docs/adr/` | Architecture decision records. One is added whenever a decision changes |
 | `slices/` | One folder per slice: specification, notes and proof |
 | `templates/` | The templates a new slice, proof or decision record starts from |
@@ -175,11 +176,12 @@ every project space.
 ## Related projects
 
 [beam_mcp](https://github.com/ScriptKittyOS/beam_mcp) is a Model Context Protocol server core for
-the BEAM from the same organisation, on Hex as `beam_mcp`. Trinity does not depend on it today.
-Trinity's MCP layer (milestone M5a) is chosen by measurement in slice 059, where beam_mcp is one
-of the candidates for the server side; the client side and the authorization server are Trinity's
-own work whichever library is chosen. `docs/adr/0007-mcp-2026-07-28-target-and-library.md`
-records the protocol target and how the choice is made.
+the BEAM from the same organisation, on Hex as `beam_mcp`. Trinity depends on it since slice 059,
+pinned at 0.8.0 and reached only through the `Trinity.MCP` boundary; slice 059's `FINDINGS.md`
+measures what it ships against the 2026-07-28 checklist, and the MCP phase (milestone M5a) builds
+Trinity's client driver, the approval loop and authorization above it. The client side and the
+authorization server are Trinity's own work. `docs/adr/0007-mcp-2026-07-28-target-and-library.md`
+records the protocol target and the layering.
 
 ## License
 

ROADMAP.md

@@ -52,7 +52,7 @@ standards register names the rows that ask for them.
 | 040 | Skills registry + agentskills.io format + progressive disclosure | 4 Skills | M | 020 | approved |
 | 041 | Skill self-management with staged approval + scanner | 4 Skills | M | 040, 021 | approved |
 | 050 | Scheduler: Oban cron agent tasks with delivery targets | 5 Automation | M | 012 | planned |
-| 059 | MCP capability gap against beam_mcp, and the server seam probe | 6 MCP | S/M | 020 | planned |
+| 059 | MCP capability gap against beam_mcp, and the server seam probe | 6 MCP | S/M | 020 | done |
 | 060 | MCP client: Trinity's thin driver (2026-07-28 preferred, 2025-11-25 compat, MRTR, Tasks) | 6 MCP | L | 059, 021 | planned |
 | 061 | MCP server (stateless 2026-07-28 + compat, MRTR approvals, headless profile) | 6 MCP | M | 060, 024 | planned |
 | 062 | MCP authorization: OAuth client role, RS, embedded AS, Enterprise Managed Authorization (ID-JAG) | 6 MCP | L | 061 | planned |

VERSIONS.md

@@ -91,7 +91,7 @@ never pin a version hex marks as retired or vulnerable.
 | `oban` | ~> 2.24 | 🔍 not yet a dependency | Uses `Oban.Engines.Lite` on SQLite. ⚠️ Oban Pro Workflows/Smart engine are Postgres-only. Added at Slice 050. |
 | `req` | ~> 0.5 | ✅ in `mix.lock` | HTTP client. |
 | `req_llm` | ~> 1.22 | ✅ in `mix.lock` | Provider layer (streaming, tools, structured output, usage). ⚠️ The pin was `~> 1.10` against a recorded latest of 1.10.0; the real latest was twelve minors ahead. Check event shapes against the current version at Slice 011, not against this file's prose. Added at Slice 011. |
-| `beam_mcp` | ~> 0.8 | 🔍 not yet a dependency | MCP server core, Apache-2.0, ADR-0007 decision 5 (owner decision 2026-09-08, recorded 2026-09-20). 0.8.0 on hex.pm, standing before 1.0.0. Server side only: the client, MRTR and OAuth are Trinity's, above it. Added at Slice 059. The earlier candidate list (anubis_mcp, fastest_mcp, gen_mcp) is history. |
+| `beam_mcp` | ~> 0.8 | ✅ in `mix.lock` | MCP server core, Apache-2.0, ADR-0007 decision 5 (owner decision 2026-09-08, recorded 2026-09-20). 0.8.0 on hex.pm, standing before 1.0.0. Server side only: the client, MRTR and OAuth are Trinity's, above it. Added at Slice 059. The earlier candidate list (anubis_mcp, fastest_mcp, gen_mcp) is history. |
 | `jido` | not used (ADR-0009, decided 2026-09-20) | 🔍 not a single package | Measured at the Slice 012 checkpoint and not adopted: the agent runtime duplicates PubSub, Oban and the gateways and adds a second tool executor; the action shape is written in-tree at Slice 020 with `jsv` for its schemas. The row stays so the decision is visible where a reader would look for the package. |
 | `jason` | ~> 1.2 | ✅ in `mix.lock` |  |
 | `boundary` | ~> 0.10 | ✅ in `mix.lock` | Compile-time module dependency enforcement. Measured at Slice 000: it compiles and enforces on Elixir 1.20.4 / OTP 28, and it reports violations as **warnings**, so it enforces only while `--warnings-as-errors` is on the compile step. ⚠️ No release since 2024-09-25. |

coverage.tsv

@@ -18,3 +18,4 @@ slice_id	percent	sha	date
 032	78.99	193800e	2026-09-21
 040	79.86	dc9dc6b	2026-09-21
 041	80.55	ae200d7	2026-09-21
+059	80.54	53c9091	2026-09-21

docs/01-architecture.md

@@ -90,7 +90,7 @@ without anything failing.
 | `Trinity.Memory` | Always-on tiers with their budget and consolidator (030), search (031), semantic store and retrieval (032), compaction (023) | LLM (summaries/embeddings), Repo |
 | `Trinity.Skills` | SKILL.md parsing, registry, loader, manager, scanner (as built at 040: parser, sources, registry, index, the three tools; at 041: staging, promotion, manager, scanner, diff, learn, `skill_manage` and `learn`) | Repo, Permissions, **Effects**, **Receipts**, Sandbox (as built at 041: Tools, Memory, Permissions, Receipts and LLM; Effects is not a dependency: the promotion is not a tool call, it writes its own effect receipt; Tools never depends on Skills) |
 | `Trinity.Scheduler` | Oban workers for agent tasks, delivery | Sessions, Gateways, **Repo** |
-| `Trinity.MCP` | Client manager, tool bridge, server | Tools, **Effects**, **Permissions**, Memory |
+| `Trinity.MCP` | Client manager, tool bridge, server (as built at 059: the boundary alone, holding the core's version, its JSON depth and its telemetry event names) | Tools, **Effects**, **Permissions**, Memory (as built at 059: a top-level boundary, like `Trinity.Smoke`, with `deps: [Trinity, BeamMCP.JSON]`; the boundary compiler checks every call into the `beam_mcp` application and this boundary alone lists its modules) |
 | `Trinity.Gateways` | Adapter behaviour, router, allowlists, pairing | Sessions, **Permissions**, PubSub |
 | `Trinity.Subagents` | Delegation, result collection | Sessions, Tools |
 | `Trinity.Sandbox` | Luerl runners, resource limits | none |

lib/trinity/mcp.ex

@@ -0,0 +1,38 @@
+# SPDX-FileCopyrightText: Sudo Apt Holdings LLC
+# SPDX-License-Identifier: Apache-2.0
+defmodule Trinity.MCP do
+  @moduledoc """
+  The MCP boundary (slice 059, ADR-0007 decisions 4 and 5): the one place in Trinity that may
+  import `BeamMCP`. The boundary compiler checks every call into the `beam_mcp` application
+  (`boundary: [default: [check: [apps: [:beam_mcp]]]]` in mix.exs), and this boundary alone
+  lists `BeamMCP.*` modules among its deps, so a `BeamMCP.*` reference anywhere else is a
+  compile error under `--warnings-as-errors`. Slice 060 puts the client driver here
+  (`Trinity.MCP.Client`), 061 the server (`Trinity.MCP.Server`); at 059 the boundary holds the
+  facts the FINDINGS table measured and nothing that serves.
+  """
+  # beam_mcp defines no boundaries and no `BeamMCP` root module, so each of its modules this
+  # boundary reaches is named as its own implicit boundary (the boundary library's rule for
+  # external apps); 060 and 061 extend the list as they reach more of the core.
+  #
+  # A top-level boundary (as `Trinity.Smoke` is), not a sub-boundary of `Trinity`: the
+  # library lets a nested boundary depend on an external module only when an ancestor does,
+  # and `Trinity` must never list `BeamMCP` (that would open the core to it).
+  use Boundary, top_level?: true, deps: [Trinity, BeamMCP.JSON], exports: []
+
+  @doc "The core's version, from its application spec."
+  @spec core_version() :: String.t()
+  def core_version, do: to_string(Application.spec(:beam_mcp, :vsn))
+
+  @doc "The JSON nesting depth the core's decoder accepts: the first fact 060's driver builds on."
+  @spec json_max_depth() :: pos_integer()
+  def json_max_depth, do: BeamMCP.JSON.max_depth()
+
+  @doc "The core's telemetry events (`[:beam_mcp, :dispatch, :start | :stop | :exception]`), for slice 090's catalogue."
+  @spec core_events() :: [[atom()]]
+  def core_events,
+    do: [
+      [:beam_mcp, :dispatch, :start],
+      [:beam_mcp, :dispatch, :stop],
+      [:beam_mcp, :dispatch, :exception]
+    ]
+end

mix.exs

@@ -26,6 +26,9 @@ defmodule Trinity.MixProject do
       # 90. `mix test --cover` was still exiting 3 on a rule this project does not have, and
       # the comment above it claimed otherwise for the whole of slice 000.
       test_coverage: [summary: [threshold: 0]],
+      # Slice 059: calls into beam_mcp are checked by the boundary compiler everywhere;
+      # only Trinity.MCP lists BeamMCP among its deps (ADR-0007 decision 4 and 5).
+      boundary: [default: [check: [apps: [:beam_mcp]]]],
       releases: releases()
     ]
   end
@@ -157,6 +160,9 @@ defmodule Trinity.MixProject do
         # (Trinity.Skills.Watcher); both were in the lock already as transitive dependencies.
         {:yaml_elixir, "~> 2.12"},
         {:file_system, "~> 1.1"},
+        # Slice 059: the MCP server core (ADR-0007 decision 5), reached only through the
+        # Trinity.MCP boundary; the slice measures its gap, 060 and 061 build on it.
+        {:beam_mcp, "~> 0.8"},
         # Slice 013 (owner decision, 2026-09-20): the linux package builds mdex's NIF from
         # source for musl (MDEX_NATIVE_BUILD=1 and TRINITY_NIF_TARGET in config/config.exs),
         # because neither precompiled artifact loads in Burrito's musl ERTS (NOTES finding 13).

mix.lock

@@ -2,6 +2,7 @@
   "abnf_parsec": {:hex, :abnf_parsec, "2.1.0", "c4e88d5d089f1698297c0daced12be1fb404e6e577ecf261313ebba5477941f9", [:mix], [{:nimble_parsec, "~> 1.4", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "e0ed6290c7cc7e5020c006d1003520390c9bdd20f7c3f776bd49bfe3c5cd362a"},
   "axon": {:hex, :axon, "0.8.1", "c4a975e62a14ab6c374997b77367ec3a4c2740952ac474d3b0f202c91b7f75c4", [:mix], [{:kino, "~> 0.7", [hex: :kino, repo: "hexpm", optional: true]}, {:kino_vega_lite, "~> 0.1.7", [hex: :kino_vega_lite, repo: "hexpm", optional: true]}, {:nx, "~> 0.10", [hex: :nx, repo: "hexpm", optional: false]}, {:polaris, "~> 0.1", [hex: :polaris, repo: "hexpm", optional: false]}, {:table_rex, "~> 3.1 or ~> 4.1", [hex: :table_rex, repo: "hexpm", optional: true]}], "hexpm", "682a3517489300507ac9345f28341e7fa95bc5b4960d645816074ce551795d37"},
   "bandit": {:hex, :bandit, "1.12.5", "af205a8e550f304caae09a97d29fd3c79a7f337526ea7cd772d2ff11d2f7c800", [:mix], [{:hpax, "~> 1.0", [hex: :hpax, repo: "hexpm", optional: false]}, {:plug, "~> 1.18", [hex: :plug, repo: "hexpm", optional: false]}, {:telemetry, "~> 0.4 or ~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}, {:thousand_island, "~> 1.5", [hex: :thousand_island, repo: "hexpm", optional: false]}, {:websock, "~> 0.5", [hex: :websock, repo: "hexpm", optional: false]}], "hexpm", "c5684ca062fa407cac115aec3256383f3e2ec9fdced7904d59cf5a7bb7ed6181"},
+  "beam_mcp": {:hex, :beam_mcp, "0.8.0", "49f2607a92da4137cd1d11fc8669c396e1d93eedf7a3e29aaab1531dd41bd9c2", [:mix], [{:bandit, "~> 1.5", [hex: :bandit, repo: "hexpm", optional: true]}, {:jason, "~> 1.4", [hex: :jason, repo: "hexpm", optional: false]}, {:plug, "~> 1.16", [hex: :plug, repo: "hexpm", optional: true]}, {:telemetry, "~> 1.0", [hex: :telemetry, repo: "hexpm", optional: false]}], "hexpm", "b5a1beba2c936c2c50e164c43240ac31bc8b159a994980083ec0f6562392801e"},
   "boundary": {:hex, :boundary, "0.10.4", "5fec5d2736c12f9bfe1720c3a2bd8c48c3547c24d6002ebf8e087570afd5bd2f", [:mix], [], "hexpm", "8baf6f23987afdb1483033ed0bde75c9c703613c22ed58d5f23bf948f203247c"},
   "bumblebee": {:hex, :bumblebee, "0.7.1", "0d6a757f955671a379ebcf4ed07565513fa767b1869169b989f65ba7958a80f4", [:mix], [{:axon, "~> 0.8.0", [hex: :axon, repo: "hexpm", optional: false]}, {:jason, "~> 1.4.0", [hex: :jason, repo: "hexpm", optional: false]}, {:nx, "~> 0.12.0 or ~> 0.13.0", [hex: :nx, repo: "hexpm", optional: false]}, {:nx_image, "~> 0.1.0", [hex: :nx_image, repo: "hexpm", optional: false]}, {:nx_signal, "~> 0.2.0", [hex: :nx_signal, repo: "hexpm", optional: false]}, {:safetensors, "~> 0.1.3", [hex: :safetensors, repo: "hexpm", optional: false]}, {:tokenizers, "~> 0.4", [hex: :tokenizers, repo: "hexpm", optional: false]}, {:unpickler, "~> 0.1.0", [hex: :unpickler, repo: "hexpm", optional: false]}, {:unzip, "~> 0.12.0 or ~> 0.13.0", [hex: :unzip, repo: "hexpm", optional: false]}], "hexpm", "f26b3355700e3c7580014d41ce477d87d9fd71a60b76d5b64701dacb07830a58"},
   "bunt": {:hex, :bunt, "1.0.0", "081c2c665f086849e6d57900292b3a161727ab40431219529f13c4ddcf3e7a44", [:mix], [], "hexpm", "dc5f86aa08a5f6fa6b8096f0735c4e76d54ae5c9fa2c143e5a1fc7c1cd9bb6b5"},