Evidence-first dev loop for Slack

Stop asking AI to guess what your code does.

Beacon turns Slack into a codebase control room: ask a question, retrieve evidence, answer with citations, review a PR, diagnose CI, and open the fix PR without leaving the thread.

Start setup Compare the options

Cursor Slack Agent answers in Slack. Useful, but editor-first context is still the center.

CodeRabbit-style agents review PRs. Helpful, but the loop starts after code is written.

Beacon starts with the team question and keeps going until there is a cited answer or a fix PR.

The anti-hallucination contract

Every answer enters with a badge, a source, and an escape hatch.

01 / Grounded

Cited or silent.

Beacon builds answers only from retrieved code chunks and returns file-line citations. If the evidence is missing, it refuses the answer instead of filling the gap with confidence.

verified source workers/slack-bot/src/signature.ts:21-44

02 / Multi-hop

It traces why.

Lexical search, vectors, and code-graph expansion work together, then an agent runs follow-up reads when the first pass is thin.

03 / Slack-native

The thread is the UI.

Channels, DMs, mentions, slash commands, emoji triggers, and assistant pane follow-ups all preserve team context.

abstention gate

NO SOURCE

NO ANSWER

Not a bot. A loop.

Beacon connects the moments other Slack agents leave scattered.

  1. Ask

    A question lands where the team already is.

    @beacon or /ask-code in channels, DMs, and the Slack assistant pane.

  2. Retrieve

    The index fans out for evidence.

    BM25, Vectorize, and one-hop call/import graph expansion retrieve the surrounding code context.

  3. Answer

    The reply arrives with source lines.

    Streaming answers cite paths and line ranges so the team can verify the claim immediately.

  4. Review

    PR review sees more than the diff.

    Paste a PR URL or react to a link and Beacon reviews against indexed repo context.

  5. Fix

    The thread can become a pull request.

    Describe the issue, react, and Beacon proposes file edits and opens a PR.

  6. Triage

    Red CI loops back to Slack.

    GitHub Actions failures become cited diagnoses, with transient flakes separated from real fixes.

Against current Slack-agent options

Beacon is built for engineering leads who need the whole loop, not one more clever reply.

Cursor Slack Agent

Good when the ask starts near an editor.

Beacon's pitch is different: the team thread is the center, and the agent can continue from question to review, CI diagnosis, and fix PR.

Beacon edge: team-wide loop ownership.

CodeRabbit-style Slack agent

Strong around PR review events.

Beacon covers review, but it also handles the question before the PR and the failed build after it.

Beacon edge: pre-PR and post-CI workflow.

Generic AI in Slack

Fast answers, weak provenance.

Beacon is deliberately narrower: no retrieved evidence means no answer. The product earns trust by showing its working.

Beacon edge: evidence over fluency.
Beacon verdict Answers + reviews + triages + opens the fix PR, with receipts.

Infrastructure posture

Runs on your Cloudflare. Indexed by your GitHub Actions. MIT licensed.

Two Workers, D1 with SQLite FTS5, Vectorize, Queues, Workers AI, tree-sitter chunking, secret redaction, and an indexing pipeline you can inspect.

Slack slack-bot Worker D1 + Vectorize
GitHub App webhook Worker Actions indexer
signature verification prompt-injection boundary secret redaction

Bring receipts to every Slack answer

Point Beacon at the repo. Let the thread prove itself.

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