A retired Bot can still be reached from outside: its shared grant survives archive_bot #1801

Implementation: FlyBot (ours) — PR follows within 24h. Do not pick up without a pickup-ok comment on this issue.

Written-by: FlyBot Lead
Claimed-by: FlyBot Lead
Claim-Id: e235ecb932d34d92bfb93b810f64c70a
Branch: dev/4-retired-inbound-grant
Base: 7b8f81e
At: 2026-10-30T05:29:25Z

Implementation: FlyBot (ours) — PR follows within 24h. Do not pick up without a pickup-ok comment.

Written-by: FlyBot Lead

What a person sees

A Bot that was shared with a friend's Bot and later retired still accepts messages from that friend's Bot: the retired Bot runs a turn, reads the memory it kept, and spends the owner's model budget — with nothing on screen telling the owner it happened. From the friend's side it looks like the Bot is still there.

Where (main 7b8f81e15a803d54a13fe32d2c0bc2119e7f9333, and the same code at 92a4cf26)

• core/src/host/roster.js:519-540 archiveBot writes retired/hidden, stops the timers and files a failure card — but leaves state.grants untouched; only the delete path clears sharing (roster.js:584 rt.forgetBotSecrets).
• core/src/host/hooks.js:733-736 send checks that the target exists, not that it is retired.
• core/src/host/reach.js:323-353 reach() never looks at retiredBot.

Reproduction

1. grantTo('b', '@bob.bot'); the friend's Bot sends one message → {"action":"allow"}, delivered: 1.
2. archive_bot Writer → retired: true; the grant survives: grants: ["b"], [{"id":"b:@bob.bot::0","grantee":"@bob.bot"}].
3. The same message again → {"action":"allow"}, delivered: 2, and it lands as [Message from Bob] <untrusted-message from="Bob"> hello after </…>.

Expected: after retirement the outside sender is refused, the same way message_bot refuses a retired Bot's name ("No Bot named …").

This is not the channel.js send case: that is the owner typing in their own chat, which docs/subsystems/core-host.md:217 explicitly keeps ("opens the chat again"). This one is triggered by an outside party and is invisible to the owner, and the docs do not keep it.

Expected

A retired Bot cannot be reached from outside: the shared grant either stops resolving (the clean fix — clear state.grants[id] in archiveBot and rt.reachChanged(id), symmetric with the delete path) or reach()/send refuses a retired target with the same No Bot named-shaped refusal.

Scope

5-10 lines plus one case in core/test/retired-bot-paths.test.js; regenerated patches/ds-bot/0001/0002. It is a generate face, so the PR queues behind the ones already in flight.

Dedupe (searched 2026-10-30, open + closed)

• retired grant → 4 hits: Sharing to a home member that was deleted reports success and can never deliver #1125 (a deleted home member's share stops working — different surface) and docs/self-test material.
• retired shared bot inbound → 1 hit, A friend's Bot added to a local group shows the raw FLYBOT-ROOM-SHARE envelope on its approval cards #847 (a face-room card).
• archive_bot grant → 0.