Agentic LLM systems that generate code through multi-turn tool use face a fundamental context problem: each session starts from zero, discarding the configuration choices, domain constraints, data schemas, and tool-use patterns that made previous sessions productive. Naively persisting entire conversation histories is both token-inefficient and counterproductive—irrelevant context degrades generation quality. We introduce shared selective persistent memory, a memory architecture for agentic systems that identifies and retains four categories of reusable context—task specifications, data schemas, tool configurations, and output constraints—while discarding session-specific reasoning traces. Crucially, this memory is shared: workspaces encapsulating selective memory can be transferred across users with role-based access control, enabling collaborative reuse of accumulated context without redundant specification. We implement this architecture in a deployed collaborative workspace platform where LLM agents produce, edit, and maintain git-versioned artifacts—including interactive dashboards, structured reports, and data-driven documents—from heterogeneous data sources accessed via multiple connector types (CSV upload, SQL, REST APIs, and MCP servers). Git-backed versioning with draft isolation enables users to explore modifications risk-free and restore to any prior state without re-invoking the model. A complementary zero-token data refresh mechanism decouples generated programs from runtime data, enabling artifact reuse without re-invocation. Across three enterprise deployment scenarios, shared selective persistent memory achieves 96% task completion (vs. 79% without memory and 71% with full history). A complementary zero-token data refresh mechanism eliminates LLM re-invocation entirely for recurring data updates (14×task time reduction), while summary-driven generation reduces per-invocation token cost by 97×versus raw data injection. A replication on four public datasets confirms generalizability, with zero-token refresh succeeding in 12/12 trials.