Make the instance actor discoverable through WebFinger - #46
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📝 WalkthroughWalkthroughThis change reserves the instance actor username and maps the instance actor through WebFinger in multi-bot instances. Tests cover default and renamed identifiers, case-insensitive conflicts, and compatibility mode behavior. ChangesInstance actor WebFinger support
Estimated code review effort: 2 (Simple) | ~10 minutes Merge Risk: 🔵 Low · up to Multi-bot instances gain WebFinger discovery for the instance actor and reserve its username. The behavior change is narrowly scoped, but release notes currently overstate the compatibility-mode behavior and the new regression test should validate its response payload. Suggested reviewers: 🚥 Pre-merge checks | ✅ 5✅ Passed checks (5 passed)
Full details: Linked Issues checkExplanation The changes satisfy issue Full details: Docstring CoverageExplanation Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files. (2 skipped: 2 unsupported.) ✨ Finishing Touches🧪 Generate unit tests (beta)
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Multi-bot instances sign the requests they make on their own behalf with the instance actor's key, but mapHandle() resolved only registered bots, so that actor had no WebFinger record. Servers that dereference a signature's key owner through WebFinger rather than by URI, such as GoToSocial, answered 401 to every such request, so follows from those servers never completed. Mastodon resolves key owners by URI, which is why this went unnoticed. Map the reserved instance-actor identifier ahead of the bots, and reserve it against bot usernames too. Only the identifier was reserved before, so a bot could take the name and then silently lose its own WebFinger mapping once the actor started resolving first. fedify-dev#45 fedify-dev#46 Assisted-by: Claude Code:claude-opus-5
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Inline comments:
In `@CHANGES.md`:
- Around line 15-18: Qualify the reserved instance-actor username and resulting
createBot() TypeError in CHANGES.md (lines 15-18) and
changes.d/botkit/instance-actor-webfinger.md (lines 5-8) as applying only to
multi-bot instances; make clear single-bot compatibility mode remains allowed.
In `@packages/botkit/src/instance-impl.ts`:
- Line 380: Update the error message in the instance actor username validation
to end with a period, preserving the existing message text and interpolation.
In `@packages/botkit/src/instance-multi.test.ts`:
- Line 163: Update the response parsing in the test’s JRD-loading flow to treat
response.json() as unknown, then validate and narrow the payload’s links array
and each link entry before calling jrd.links.find(...). Preserve the declared
JRD contract by returning only the validated structure.
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CHANGES.mdchanges.d/botkit/instance-actor-webfinger.mdpackages/botkit/src/instance-impl.tspackages/botkit/src/instance-multi.test.ts
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Multi-bot instances sign the requests they make on their own behalf with the instance actor's key, but mapHandle() resolved only registered bots, so that actor had no WebFinger record. Servers that dereference a signature's key owner through WebFinger rather than by URI, such as GoToSocial, answered 401 to every such request, so follows from those servers never completed. Mastodon resolves key owners by URI, which is why this went unnoticed. Map the reserved instance-actor identifier ahead of the bots, and reserve it against bot usernames too. Only the identifier was reserved before, so a bot could take the name and then silently lose its own WebFinger mapping once the actor started resolving first. fedify-dev#45 fedify-dev#46 Assisted-by: Claude Code:claude-opus-5
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Multi-bot instances sign the requests they make on their own behalf with the instance actor's key, but mapHandle() resolved only registered bots, so that actor had no WebFinger record. Servers that dereference a signature's key owner through WebFinger rather than by URI, such as GoToSocial, answered 401 to every such request, so follows from those servers never completed. Mastodon resolves key owners by URI, which is why this went unnoticed. Resolve the reserved instance-actor name in mapHandle(), after the static bots and the dynamic groups. Resolving it last keeps a mapping something else already owns: addBot() can reject the name outright for static bots because registration is synchronous, but a group's mapUsername() is evaluated per request, and one that claims the name resolved to its own bot before mapHandle() knew about the instance actor at all. Deferring keeps that mapping rather than silently redirecting the handle away from a bot that is still dereferenceable under its own identifier. fedify-dev#45 fedify-dev#46 Assisted-by: Claude Code:claude-opus-5
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This fix is shipped with BotKit 0.5.3. |
2 participants
What
Multi-bot instances now give their instance actor a WebFinger record, and reserve that actor's name against bot usernames as well as bot identifiers. Both live in packages/botkit/src/instance-impl.ts.
Closes #45.
Why
A multi-bot instance signs the requests it makes on its own behalf with the instance actor's key:
dispatchSharedKey()returnsinstanceActorIdentifierwhenever the instance is not incompatMode. The actor dispatcher serves that actor, butmapHandle()resolved only registered bots and dynamic groups, and the instance actor is synthesized by#dispatchInstanceActor()rather than stored in#bots. So it was dereferenceable by URI and invisible to WebFinger.That distinction matters to peers that dereference a signature's key owner through WebFinger rather than by URI. GoToSocial does: its
enrichAccountstep WebFingers the key owner, got a 404, fell back to /.well-known/host-meta — which BotKit does not serve either — and answered 401 to every request the instance actor signed. AFollowfrom GoToSocial was accepted, but the follow could never complete, because BotKit could not then dereference the follower's actor.Mastodon resolves key owners by URI and never asks, which is why this went unnoticed. No configuration avoided it:
createBot(DEFAULT_INSTANCE_ACTOR_IDENTIFIER, …)throws because the identifier is reserved, andinstanceActorIdentifieronly renames the actor without registering it.How
mapHandle()resolves the reserved instance-actor name before iterating the bots, returninginstanceActorIdentifierso the actor gets the same WebFinger treatment a bot does. It readsthis.instanceActorIdentifierrather than the default constant, so a renamed actor resolves under its new name, and it stays inert incompatMode, where the shared key already belongs to a real bot.Resolving ahead of the bots is what makes the second half necessary. Only the instance actor's identifier was reserved; a bot could still take the name as its username, and would then have silently lost its own WebFinger mapping once the actor began resolving first.
addBot()now rejects that collision, matched case-insensitively against the same lowercased username the existing duplicate-username check already computes. With both halves in place the ordering cannot shadow a bot, which is the invariant the comment inmapHandle()now cites.This is a behaviour change for anyone registering a bot whose username equals the instance actor's name:
createBot()now throws aTypeError. The changelog carries it as its own entry.Testing
Two regression tests in packages/botkit/src/instance-multi.test.ts, both of which fail before this change and pass after. The first checks that the instance actor resolves through WebFinger with a
selflink pointing at its actor URI, under both the default identifier and a renamed one. The second checks the username collision, its case-insensitive form, and that the reservation followsinstanceActorIdentifierrather than the default name — a renamed actor reserves its own name and frees the default. I confirmed the second test is meaningful by removing theaddBot()guard and watching it fail before restoring it.mise run checkandmise run testboth pass. The PostgreSQL and Redis integration suites skip, as no server is running locally.I also verified the WebFinger half against a live GoToSocial instance, with two bots behind a tunnel. Before, GoToSocial answered 401 with
keyOwnerFetchErrorwhen BotKit fetched the follower's actor. After, WebFinger returns 200, the actor fetch returns 200 signed with__botkit_instance__#main-key, GoToSocial processes theAccept, and a subsequent mention gets a reply delivered and accepted. The username reservation has no live path to exercise — it only rejects a configuration at startup — so that half is covered by tests alone.AI disclosure
Root-caused, patched, and tested with AI assistance (Claude Code, claude-opus-5). I reviewed every line, ran the tests myself, and confirmed the fix end to end against my own GoToSocial instance. The commit carries an
Assisted-bytrailer.Assisted-by: Claude Code:claude-opus-5
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