Alternative: bind Slack HITL from current auth

[remiconnesson]

Summary

This is a channel-only alternative to #142.

• Derive the allowed responder from ctx.session.auth.current inside Slack's default input.requested handler.
• Bind each Slack HITL block to that user and reject mismatched signed button clicks or modal submissions.
• Keep responder identity out of answered cards.
• Fail closed with recovery guidance when the prompt has no Slack-authenticated caller or predates responder binding.

Production changes stay in defaults.ts, hitl.ts, and interactions.ts. This does not change generic send(), harness delivery, or slackChannel.ts.

Hypothesis

This approach works if the verified Slack actor remains the current caller identity through the harness. The default onAppMention and onDirectMessage handlers already satisfy that contract.

Known limitation

Built-in Slack HITL only works when Slack auth remains the current session auth. This includes the default inbound handlers and custom handlers that return defaultSlackAuth(message, ctx) or preserve its slack-webhook authenticator and user_id attribute.

A custom onAppMention or onDirectMessage handler may instead replace session auth with an application principal. In that configuration, input.requested cannot recover the verified Slack actor from ctx.session.auth.current, so it does not render the HITL controls and fails closed. This PR does not support custom session auth and built-in Slack HITL together.

#142 carries the verified Slack actor independently of session auth and supports that combination. The Slack Dev Sandbox screenshots below exercise this PR's supported default-auth path; they do not cover custom session auth.

Verification

Full Slack scenario

packages/eve/test/scenarios/slack-hitl-authorization.scenario.test.ts boots a real eve dev process, sends signed Slack webhook and interaction payloads through the Slack channel route, and records outbound Slack API calls. It verifies that:

• User A creates and answers the first approval prompt.
• User B continues the same durable Slack thread and receives a prompt bound to User B.
• Both turns use the same durable session.
• User A is privately rejected from User B's prompt without updating the card.
• User B answers the prompt and resumes the parked turn.

The scenario was copied from #142. Its fixture now uses the default Slack auth instead of an unrelated shared principal because this PR deliberately derives the responder from current session auth.

Slack Dev Sandbox

[vercel]

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Project	Deployment	Actions	Updated (UTC)
eve-docs	Ready	Preview, Comment, Open in v0	Jun 21, 2026 1:43am

[github-actions]

Bundle + Package Summary: apps/fixtures/weather-agent

Key takeaways

• No notable deltas vs main (c6d04a9).

Delta vs main (c6d04a9)

Area	Metric	Baseline	Current	Delta
Package	Packed tarball	3.24 MB	3.24 MB	+1.0 kB ⚠️
Package	Unpacked publish size	11.61 MB	11.62 MB	+2.9 kB ⚠️
Package	Installed footprint	51.82 MB	51.82 MB	+2.9 kB ⚠️
Package	Published files	2173	2173	0
Package	Installed files	5378	5378	0
Runtime	Unique function payloads	2	2	0
Runtime	Total function bytes	9.34 MB	9.34 MB	-176 B ✅
Runtime	Public routes	9	9	0

Changed function payloads vs main (c6d04a9) (2)

Function	Status	Baseline	Current	Delta	Route changes
functions/__server.func	changed	3.86 MB	3.86 MB	-144 B ✅	none
functions/.well-known/workflow/v1/flow.func	changed	5.48 MB	5.48 MB	-32 B ✅	none

Build Metadata

• Preset: vercel
• Nitro: nitro@3.0.260610-beta
• Output directory: apps/fixtures/weather-agent/.vercel/output
• Build metadata timestamp: 2026-06-21T01:43:28.150Z
• Route aliases: 9 public, 1 internal (10 total aliases)
• Vercel routes in config: 10
• Severity legend: 🔴 dominant/large, 🟠 notable, 🟡 watch, ⚪ small

Package Drill-Down

Package Details

• Package: eve@0.11.10
• Package directory: packages/eve
• Tarball: 3.24 MB (eve-0.11.10.tgz)
• Unpacked payload: 11.62 MB across 2173 published files
• Installed footprint: 51.82 MB across 5378 installed files
• Installed root package: 10.50 MB
• Installed dependencies: 41.32 MB
• Runtime dependencies: 1
• Peer dependencies: 12 (11 optional)

Installed footprint is measured from an isolated temporary npm install of the packed tarball.

Heavy installed dependencies

• @rolldown/binding-linux-x64-gnu: 20.61 MB (39.8%)
• eve: 10.50 MB (20.3%)
• ai: 6.20 MB (12.0%)
• zod: 4.97 MB (9.6%)
• nitro: 2.41 MB (4.6%)

Publish payload breakdown

Published file size
🟠 dist/src/compiled/experimental-ai-sdk-code-mo... [#####...................] 1.51 MB 13.0%
🟡 dist/src/compiled/@workflow/core/runtime.js      [##......................] 775.4 kB 6.7%
🟡 dist/src/compiled/@vercel/sandbox/index.js       [##......................] 632.0 kB 5.4%
🟡 dist/src/compiled/@chat-adapter/slack/index.js   [#.......................] 436.9 kB 3.8%
🟡 dist/src/compiled/_chunks/workflow/attribute-... [#.......................] 370.9 kB 3.2%
🔴 Other published files                            [########################] 7.90 MB 68.0%

Installed footprint breakdown

Installed package size
🔴 @rolldown/binding-linux-x64-gnu [########################] 20.61 MB 39.8%
🔴 eve                             [############............] 10.50 MB 20.3%
🔴 ai                              [#######.................] 6.20 MB 12.0%
🟠 zod                             [######..................] 4.97 MB 9.6%
🟠 nitro                           [###.....................] 2.41 MB 4.6%
🟡 rolldown                        [#.......................] 771.0 kB 1.5%
🔴 Other installed packages        [#######.................] 6.37 MB 12.3%

Runtime dependencies (1)

Package	Range	Notes
nitro	3.0.260610-beta

Peer dependencies (12)

Package	Range	Notes
@opentelemetry/api	^1.0.0	optional peer
@sveltejs/kit	^2.0.0	optional peer
ai	catalog:
braintrust	^3.0.0	optional peer
just-bash	^3.0.0	optional peer
microsandbox	^0.5.0	optional peer
next	^16.0.0	optional peer
nuxt	^4.0.0	optional peer
react	^19.0.0	optional peer
svelte	^5.0.0	optional peer
vite	^8.0.0	optional peer
vue	^3.5.0	optional peer

Function Drill-Down

Payload Size Graph

Unique function payload size and share of total
🔴 functions/.well-known/workflow/v1/flow.func     [########################] 5.48 MB 58.6%
🔴 functions/__server.func                         [#################.......] 3.86 MB 41.4%

Top Function Payloads

🟠 functions/.well-known/workflow/v1/flow.func • 1 public route • 5.48 MB

Metric	Value
Public routes	/.well-known/workflow/v1/flow
Runtime	nodejs24.x
Handler	index.mjs
Payload	5.48 MB
Function files	5.48 MB across 27 files
Traced dependencies	0 B
Signal	🟠 Bundled file __eve_nitro_handler__.mjs is 1.51 MB (27.5%)

🟠 🔎 Dependency Analysis

📦 Bundled files:

Bundled file size
🟠 __eve_nitro_handler__.mjs              [########################] 1.51 MB 27.5%
🟠 _chunks/runtime.mjs                    [###############.........] 958.4 kB 17.5%
🟡 _chunks/sandbox.mjs                    [############............] 766.0 kB 14.0%
🟡 _chunks/attribute-changes-Bi5DLT8S.mjs [########................] 472.2 kB 8.6%
🟡 _chunks/dist-DTchiX0N.mjs              [#######.................] 460.6 kB 8.4%
🟠 Other bundled files                    [#####################...] 1.31 MB 24.0%

🧾 Vercel Config

{
  "handler": "index.mjs",
  "launcherType": "Nodejs",
  "shouldAddHelpers": false,
  "supportsResponseStreaming": true,
  "runtime": "nodejs24.x",
  "environment": {
    "NODE_OPTIONS": "--experimental-require-module",
    "WORKFLOW_QUEUE_NAMESPACE": "eve"
  },
  "maxDuration": "max",
  "experimentalTriggers": [
    {
      "type": "queue/v2beta",
      "topic": "__eve_wkf_workflow_*",
      "consumer": "default",
      "retryAfterSeconds": 5,
      "initialDelaySeconds": 0
    }
  ]
}

---

🟠 functions/__server.func • 8 public routes, 1 internal alias • 3.86 MB

Metric	Value
Public routes	/ /eve/v1/callback/[token] /eve/v1/connections/[name]/callback/[token] /eve/v1/health /eve/v1/info /eve/v1/session /eve/v1/session/[sessionId] /eve/v1/session/[sessionId]/stream
Internal aliases	/__server
Runtime	nodejs24.x
Handler	index.mjs
Payload	3.86 MB
Function files	3.86 MB across 21 files
Traced dependencies	0 B
Signal	🟠 Bundled file index.mjs is 1.40 MB (36.3%)

🟠 🔎 Dependency Analysis

📦 Bundled files:

Bundled file size
🟠 index.mjs                              [########################] 1.40 MB 36.3%
🟠 _chunks/runtime.mjs                    [###############.........] 875.8 kB 22.7%
🟠 _chunks/sandbox.mjs                    [#############...........] 766.0 kB 19.8%
🟡 _chunks/attribute-changes-Bi5DLT8S.mjs [########................] 448.5 kB 11.6%
⚪ _libs/zod.mjs                          [##......................] 114.2 kB 3.0%
🟡 Other bundled files                    [####....................] 258.8 kB 6.7%

🧾 Vercel Config

{
  "handler": "index.mjs",
  "launcherType": "Nodejs",
  "shouldAddHelpers": false,
  "supportsResponseStreaming": true,
  "runtime": "nodejs24.x"
}