diff --git a/03-DESIGN/01-to-be/28-building-the-bus.md b/03-DESIGN/01-to-be/28-building-the-bus.md
index 6576b08..abd5e32 100644
--- a/03-DESIGN/01-to-be/28-building-the-bus.md
+++ b/03-DESIGN/01-to-be/28-building-the-bus.md
@@ -557,16 +557,40 @@ it, and the beds that need a mesh living on NATS can finally run.
       that forgot it. The check earned itself at once: the composer was granting a role's whole event
       branch *and* the one event it follows, and the wider grant wins — so only the submitting half of
       a role is granted now, and what comes back is named exactly.
-- [~] 4.4 a person's client — **the account is done**: a person is not a module and holds no
-      seat, so their authority is a list of tools (or `*` for an administrator) and nothing else.
-      Held to four properties, each a way of being wrong that would not announce itself: nothing
-      but tools, so a person cannot claim a module said something; no ack subject, because
-      authority over a consumer that does not exist is authority nobody audits; no ability to
-      answer, because a person who can answer a request is impersonating a module on a bus where
-      anyone may serve a tool; and two people do not share an inbox.
+- [x] 4.4 a person's client — **the account and the program are both in.**
+
+      **The account**: a person is not a module and holds no seat, so their authority is a list of
+      tools (or `*` for an administrator) and nothing else. Held to four properties, each a way of
+      being wrong that would not announce itself: nothing but tools, so a person cannot claim a
+      module said something; no ack subject, because authority over a consumer that does not exist
+      is authority nobody audits; no ability to answer, because a person who can answer a request is
+      impersonating a module on a bus where anyone may serve a tool; and two people do not share an
+      inbox. Issued, listed and revoked by command; stating what somebody may call replaces what was
+      there, because a list that could only grow is a permission nobody can take back; and forgetting
+      somebody takes their credential with them, or it is not a revocation.
+
+      **The program**: two surfaces over one thing — a command line and an MCP server — both adapters
+      over the same three calls, because a second way of reaching a tool is a second thing to keep
+      correct. It uses the client a module's runtime uses, so what a person may do is answered by the
+      same permission list that answers it for a module and an audit has nothing separate to read.
+
+      Three decisions in it worth keeping. It lists what the **catalogue** has rather than what this
+      credential may call: somebody seeing only their own tools cannot tell "not installed" from "not
+      yours", and those need different people to fix them. A failed call says which of three things
+      happened — nobody serves it, this credential may not, or the tool was slow — because the
+      remedies are in three different places and without that they are one timeout and a stack trace.
+      And the MCP surface decides nothing: the names are the ones a person types, the schemas are the
+      modules' own, an answer is passed through unshaped, and a tool that fails comes back as a tool
+      error rather than a protocol error, because the request was well-formed and the mesh answered it.
+
+      Both surfaces are driven against a running bus, including a host's notification being answered
+      with nothing and an unknown method refused.
+
+      > **Design 25 §7 says "nothing is built of this before §10's bed passes", and this was built
+      > before.** Recorded rather than quietly ignored: the operator asked for it, it is on the
+      > critical path for nothing and blocked by nothing, and the bed it waits for is 4.1's. If the
+      > bed changes what a person's client should be, this is what gets changed.
 
-      Still to build: the client program itself — the command line and the MCP surface over it.
-      It needs nothing from the consume side, so it is not blocked by step 3.
 - [~] 4.5 reports and catch-up: a node that was unreachable catches up rather than losing them —
       **the reports half is in and proved against a server** (3.4): held through the store's absence
       by the server rather than by the controller, superseded ones settled by the digest they carry.