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Slack Bet

on Context

Engineering

Samuel Messing
VP of Engineering for Search and AI, Slack
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How Slack AI Agents Accelerate Dev Productivity

with Samuel Messing

Transcript

Chapters

Trailer
[00:00:00]
Podcast Introduction and Guest Welcome
[00:01:12]
The Role of AI in Slack's Development
[00:02:20]
The Challenge of Code Reviews in Large Teams
[00:26:24]
The Future of Development with AI and Slack
[00:31:16]
The Role of Agents in Software Development
[00:35:51]
Preparing for Dreamforce and Final Thoughts
[00:51:14]

In this episode

In this episode, Slack's VP of Engineering for Search and AI, Samuel Messing, joins host Simon Maple to delve into Slack's AI strategy, emphasizing that context is everything. They explore how Slack integrates precise enterprise search with permission-aware generative AI, demonstrating that search and AI are complementary parts of a single system. Discover insights on building reliable AI features, optimizing context over prompts, and the importance of trust and permission in scaling AI across large organizations.

Slack’s VP of Engineering for Search and AI, Samuel Messing, joins host Simon Maple to unpack a central lesson from Slack’s AI journey: context is everything. In a world where developers, execs, and cross-functional teams work inside Slack, the company’s AI strategy hinges on marrying precise enterprise search with trustworthy, permission-aware generative capabilities. The conversation spans scaling AI across massive organizations, where search ends and AI shines, and how to build hybrid features that developers can apply in their own AI-native products and workflows.

Context Is Everything: Slack’s AI Strategy at Enterprise Scale

Sam’s path from individual contributor to leading Search and AI at Slack mirrors the evolution developers are living through: ML and LLMs are only as useful as the context we can safely, efficiently, and correctly pipe into them. For Slack’s largest customers—think IBM (~100k employees) and Salesforce (~75k)—the volume of messages, files, and signals explodes past what any one person (or naive LLM prompt) can manage. That’s why Slack frames its approach as context engineering rather than just prompt engineering.

At enterprise scale, “alignment” is itself an engineering problem. Teams must see across silos without breaking compliance. Slack’s thesis is that search and AI aren’t competing disciplines; they’re a single system. Search is how you retrieve and structure the right context; AI is how you synthesize and explain it. Building reliable features means treating the LLM as one step in a pipeline that includes retrieval, ranking, permission gating, and UI design for trust.

Where Search Ends and AI Begins (and Why It’s a False Dichotomy)

Sam illustrates the limits of pure search with a major news customer. Their Slack channel ingests Associated Press wire updates: dense, frequent info bursts. Searching “Bulgaria” returns a haystack of messages—relevant but hard to digest chronologically. This is where AI shines: Slack’s AI search answers synthesize the top results into a concise, human-readable summary with citations, letting users both understand “what’s going on” and drill into sources. It’s classic retrieval-augmented generation: use search to find the right shards; use an LLM to produce a trustworthy synthesis, backed by links.

Conversely, certain roles demand full recall over synthesis. Support, operations, compliance, or editorial workflows often require “every message” with strict time ordering for triage. For these users, features like saved searches and time-based ranking outperform an LLM’s summary. The lesson for developers: don’t force a generative solution where deterministic, navigable search is the job to be done. Offer both “precision” (synthesis) and “coverage” (recall) modes, and design the UI to help users explicitly choose.

Designing Hybrid Features: Retrieval + Synthesis in Practice

A strong example of Slack’s hybrid design is AI Explain, a message-level action that interprets complex posts—especially helpful in incidents. As a VP, Sam uses it to decode acronyms and implications without interrupting engineers mid-firefight. Under the hood, Explain kicks off a search to gather surrounding context (thread history, related messages, referenced docs) and then uses the LLM to synthesize an explanation. It combines enterprise-specific retrieval with the LLM’s generalized knowledge for a pragmatic, permission-aware explanation.

For developers, this pattern is a blueprint:

  • Scope retrieval to the minimum viable context: thread vicinity, linked artifacts, channel history within a relevant time window.
  • Rank aggressively for relevance, then let the LLM summarize; attach citations to reduce hallucination risk and enable verification.
  • Make it a UI affordance (e.g., “Explain this,” “Summarize channel,” “What changed since yesterday?”) so users can invoke synthesis at the right moment rather than flooding every screen with generated text.
  • Treat this as a system: retrieval, permission checks, LLM synthesis, and UX validation must work as a unit.

Adoption Patterns, Trust, and Enterprise Guardrails

Slack sees adoption vary by role and company stage. Some features are universally sticky—message translation, for instance, which auto-detects language mismatches and translates inline so globally distributed teams can move faster. Others appeal to AI-forward orgs building specialized workflows. Sam highlights Plaintiff, a customer using Salesforce’s Agentforce to deploy a constellation of agents (call prep, customer research, call summary) that run in parallel to halve sales prep time and lift upsell bookings by roughly 50%. It’s a compelling pattern for developers: break complex journeys into composable agents with clear interfaces and handoffs.

Trust is the adoption unlock. Slack leans on two differentiators: unparalleled context (since work happens in Slack) and deeply integrated permissions. Their AI features respect existing enterprise controls, with just-in-time permission enforcement so users never see content they lack rights to access. They’re HIPAA compliant and designing for job-role-based empowerment—treating groups like HR and Sales as “protective communities” with internal and shared surfaces. For developers, the message is clear: permission-aware retrieval and output are non-negotiable in enterprise AI. Bake them into your RAG stack and UX from day one.

A Practical Playbook: Context Engineering for AI-Native Dev Teams

If you’re building AI features for developers or knowledge workers, adopt a context-engineering mindset:

  • Map your context sources: messages, tickets, code, docs, CRM activities. Decide which are searchable and which must remain siloed. Create a graph of relationships (message ↔ thread ↔ document ↔ incident).
  • Design recall vs synthesis surfaces: provide time-ordered, saveable searches for triage workflows; offer “AI answer” or “Explain this” for interpretive tasks. Let users toggle or pin their preferred view.
  • Implement permission-aware RAG: perform retrieval with ACL filters before generation and ensure just-in-time checks before display. Return citations to primary sources. Consider redaction strategies for sensitive spans.
  • Optimize for scale: compact chunks, sliding time windows, semantic + lexical hybrid ranking, and de-duplication. Be intentional about how much you feed the LLM; more tokens aren’t always better.
  • Instrument trust and ROI: measure false exposure attempts blocked by permissions, citation click-throughs, time-to-understanding during incidents, and business outcomes (e.g., prep time reduced, conversion lift).
  • Localize and normalize: automatic message translation unlocks cross-border collaboration with near-zero friction; it’s a low-lift feature with outsized impact.
  • Respect change management: roll features by role and team; document boundaries of LLM outputs; pair new AI features with “show work” links and opt-out controls to build confidence.

Slack’s framing is useful for any AI-native product: search and AI are two halves of one system. Retrieval gives you control, determinism, and safety; LLMs provide synthesis, language understanding, and speed. When you design them together—and respect permissions throughout—you enable teams to move faster without sacrificing trust.

Key Takeaways

  • Treat search and AI as a single pipeline: retrieve, permission-check, synthesize, cite, display.
  • Offer dual modes: synthesis (precision and speed) and recall (coverage and auditability) based on role and task.
  • Build permission-aware RAG: enforce ACLs at retrieval and display; return citations for verification; stay compliant.
  • Ship “moment-of-need” AI: message-level Explain, channel summaries, “what changed” views—invoked where work happens.
  • Optimize context, not just prompts: hybrid ranking, time windows, chunking, and de-duplication beat brute-force token stuffing.
  • Prove value with metrics: time-to-understanding, reduced prep time, and business outcomes (e.g., Plaintiff’s ~50% lift in upsell).
  • Start with high-utility features: automatic translation is a fast path to global velocity with minimal friction.
  • Plan adoption by role: empower “protective communities” (e.g., HR vs Sales) differently and communicate boundaries clearly.

Chapters

Trailer
[00:00:00]
Podcast Introduction and Guest Welcome
[00:01:12]
The Role of AI in Slack's Development
[00:02:20]
The Challenge of Code Reviews in Large Teams
[00:26:24]
The Future of Development with AI and Slack
[00:31:16]
The Role of Agents in Software Development
[00:35:51]
Preparing for Dreamforce and Final Thoughts
[00:51:14]