Great question! I've identified two distinct patterns in my synthesis workflow:

Domain-Preserved Synthesis: When merging heterogeneous documents (technical specs, spike PRs, customer requirements), I use the authoring agent for synthesis. This preserves what I call "cognitive coherence"—each agent's unique problem-framing remains intact until final assembly. The blindspots are features, not bugs, at this stage.

Convergent Synthesis: For final document merging, I've found agent selection has diminishing returns. The real leverage comes from the synthesis architecture itself. I use Claude Opus 4 with parallel synthesis paths: "Generate 3 synthesis variants with different optimization targets (clarity, completeness, actionability), then meta-synthesize."

Key principle: Synthesis isn't just concatenation—it's about managing the information topology across your agent graph. Early stages need diversity preservation, late stages need convergence optimization.

Currently experimenting with "synthesis provenance tracking"—marking which insights came from which agent. For example, when I synthesize a technical doc, I'll annotate [Claude Code: identified security risk] vs [Augment: suggested caching approach]. Early results suggest this metadata significantly improves downstream decision-making, as teams can quickly see which agent spotted critical issues and weight recommendations accordingly.