[piekstra]

Summary

Adds slck channels join <channel> and slck channels leave <channel>. Joining as yourself (--as-user) is what lets you invite a bot or person to a public channel you are not in; slck could invite but not join.

• join: conversations.join. Slack answers an existing membership with ok plus an already_in_channel warning (alongside others such as missing_charset, in response_metadata.warnings), reported as "Already in channel".
• leave: conversations.leave. Slack answers a missing membership with ok and not_in_channel: true, reported as "Not in channel".

Verification

• Unit tests for both outcomes and an error for each command; make lint clean.
• Against a real workspace with a user token: join, join again (Already in channel), invite a bot, leave, leave again (Not in channel). The warning shape above is what Slack returned.
• integration-tests.md gains the same four steps.

[monit-reviewer]

Automated PR Review

Reviewed commit: c9e34be6068b
Profile: claude-monit-reviewer - Posting as: monit-reviewer

Summary

Reviewer	Findings
go:implementation-tests	0
harness-engineering:repo-health	0
policies:conventions	0
architecture:solid-reviewer-agnostic	1
security:code-auditor	0
documentation:docs	0

architecture:solid-reviewer-agnostic (1 finding)

Minor - internal/client/client.go:973

U-T1: the behavior this PR adds is the membership signal parsed in JoinChannel (already_in_channel in response_metadata.warnings) and LeaveChannel (not_in_channel), but no test checks it. TestRunJoin and TestRunLeave in channels_test.go only assert require.NoError for both the member and non-member replies. If JoinChannel always returned false, or the warning were read from the top-level warning string, every test would still pass and the CLI would print "Joined" for an existing membership. Suggested fix: add TestClient_JoinChannel_* and TestClient_LeaveChannel_* cases to internal/client/client_test.go, matching the existing TestClient_ArchiveChannel_Success pattern, and assert the returned bool for each reply shape. Alternatively (or as well), have the cmd tests capture output the way captureOutput does in internal/cmd/emoji/emoji_test.go and assert "Already in channel" / "Not in channel".

Reviewer Coverage

• go:implementation-tests — complete (broad); inspected 5 assigned files (7 inspected across reviewers): internal/client/client.go, internal/cmd/channels/channels.go, internal/cmd/channels/channels_test.go, internal/cmd/channels/join.go, internal/cmd/channels/leave.go; skipped: none; constraints: none
• harness-engineering:repo-health — complete (constrained); inspected 5 assigned files (7 inspected across reviewers): internal/client/client.go, internal/cmd/channels/channels.go, internal/cmd/channels/channels_test.go, internal/cmd/channels/join.go, internal/cmd/channels/leave.go; skipped: none; constraints: none
• policies:conventions — complete (broad); inspected 5 assigned files (7 inspected across reviewers): README.md, internal/cmd/channels/channels.go, internal/cmd/channels/channels_test.go, internal/cmd/channels/join.go, internal/cmd/channels/leave.go; skipped: none; constraints: Shared cli-common docs and .github automation were not available as sibling checkouts in this workbench; convention check relied on in-repo precedent (internal/cmd/channels/invite.go) rather than canonical external docs.
• architecture:solid-reviewer-agnostic — complete (broad); inspected 4 assigned files (7 inspected across reviewers): internal/client/client.go, internal/cmd/channels/channels.go, internal/cmd/channels/join.go, internal/cmd/channels/leave.go; skipped: none; constraints: Ran go build ./... and go test for internal/cmd/channels and internal/client at the PR head; both pass.
• security:code-auditor — complete (broad); inspected 3 assigned files (7 inspected across reviewers): internal/client/client.go, internal/cmd/channels/join.go, internal/cmd/channels/leave.go; skipped: none; constraints: none
• documentation:docs — complete (broad); inspected 2 assigned files (7 inspected across reviewers): README.md, integration-tests.md; skipped: none; constraints: none

Inspected files (7)

• README.md
• integration-tests.md
• internal/client/client.go
• internal/cmd/channels/channels.go
• internal/cmd/channels/channels_test.go
• internal/cmd/channels/join.go
• internal/cmd/channels/leave.go

0 PR discussion threads considered. 0 summarized; 0 resolved.

---

Completed in 2m 57s | ~$2.43 (est.) | claude-sonnet-5, claude-opus-5-5 | cr 0.10.319

Field	Value
Model	claude-sonnet-5, claude-opus-5-5
Reviewers	go:implementation-tests, harness-engineering:repo-health, policies:conventions, architecture:solid-reviewer-agnostic, security:code-auditor, documentation:docs
Engine	claude_cli · claude-sonnet-5, claude-opus-5-5
Reviewed by	cr · monit-reviewer
Duration	2m 57s wall · 6m 26s compute
Cost	~$2.43 (est.)
Pricing basis	anthropic-public-2026-09-23
Tokens	100 in / 18.4k out

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