feat(slack-researcher): add Slack organizational context research agent (#495)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

plugins/compound-engineering/skills/ce-brainstorm/SKILL.md

@@ -96,6 +96,8 @@ If nothing obvious appears after a short scan, say so and continue. Two rules go
 
 2. **Defer design decisions to planning** — Implementation details like schemas, migration strategies, endpoint structure, or deployment topology belong in planning, not here — unless the brainstorm is itself about a technical or architectural decision, in which case those details are the subject of the brainstorm and should be explored.
 
+**Slack context** (Standard and Deep only) — If any `slack_*` tool is available in the tool list, dispatch `compound-engineering:research:slack-researcher` with a brief summary of the brainstorm topic. If the agent returns an error or reports Slack MCP unavailable, log a warning ("Slack context unavailable: {reason}. Proceeding without organizational context.") and continue. Coordinate this dispatch at the start of Phase 1.1 alongside the inline Constraint Check and Topic Scan. Wait for all to complete before proceeding to Phase 1.2. Incorporate any Slack findings into the constraint and context awareness for the brainstorm session. Skip for Lightweight scope.
+
 #### 1.2 Product Pressure Test
 
 Before generating approaches, challenge the request to catch misframing. Match depth to scope:

plugins/compound-engineering/skills/ce-ideate/SKILL.md

@@ -117,11 +117,16 @@ Run agents in parallel in the **foreground** (do not use background dispatch —
 
    If the agent reports fewer than 5 total issues, note "Insufficient issue signal for theme analysis" and proceed with default ideation frames in Phase 2.
 
+4. **Slack context** (conditional) — if any `slack_*` tool is available in the tool list, dispatch `compound-engineering:research:slack-researcher` with the focus hint as context. Run this in parallel with agents 1-3.
+
+   If the agent returns an error or reports Slack MCP unavailable, log a warning ("Slack context unavailable: {reason}. Proceeding without organizational context.") and continue.
+
 Consolidate all results into a short grounding summary. When issue intelligence is present, keep it as a distinct section so ideation sub-agents can distinguish between code-observed and user-reported signals:
 
 - **Codebase context** — project shape, notable patterns, obvious pain points, likely leverage points
 - **Past learnings** — relevant institutional knowledge from docs/solutions/
 - **Issue intelligence** (when present) — theme summaries from the issue intelligence agent, preserving theme titles, descriptions, issue counts, and trend directions
+- **Slack context** (when present) — relevant organizational context, team discussions, and decisions from Slack channels surfaced by the slack-researcher agent
 
 Do **not** do external research in v1.
 

plugins/compound-engineering/skills/ce-plan/SKILL.md

@@ -158,6 +158,7 @@ Run these agents in parallel:
 
 - Task compound-engineering:research:repo-research-analyst(Scope: technology, architecture, patterns. {planning context summary})
 - Task compound-engineering:research:learnings-researcher(planning context summary)
+- (conditional) Task compound-engineering:research:slack-researcher({planning context summary}. If the origin document contains a Slack context section, include it verbatim so the researcher can focus on gaps rather than re-searching.) — if any `slack_*` tool is available in the tool list. If the agent returns an error or reports Slack MCP unavailable, log a warning ("Slack context unavailable: {reason}. Proceeding without organizational context.") and continue.
 
 Collect:
 - Technology stack and versions (used in section 1.2 to make sharper external research decisions)
@@ -165,6 +166,7 @@ Collect:
 - Implementation patterns, relevant files, modules, and tests
 - AGENTS.md guidance that materially affects the plan, with CLAUDE.md used only as compatibility fallback when present
 - Institutional learnings from `docs/solutions/`
+- Organizational context from Slack (if the slack-researcher agent ran successfully)
 
 #### 1.1b Detect Execution Posture Signals
 
@@ -229,6 +231,7 @@ If Step 1.2 indicates external research is useful, run these agents in parallel:
 Summarize:
 - Relevant codebase patterns and file paths
 - Relevant institutional learnings
+- Organizational context from Slack conversations, if gathered (prior discussions, decisions, or domain knowledge relevant to the feature)
 - External references and best practices, if gathered
 - Related issues, PRs, or prior art
 - Any constraints that should materially shape the plan