Better context is a product decision, not a bigger prompt
Relevant context is selected, bounded and connected to the work an agent is asked to perform.
Giving a coding agent more text is not the same as giving it better context. Useful context is relevant to a bounded objective and grounded in the current product and codebase.
Start with the work item
A clear work item connects the outcome, constraints and acceptance criteria to the implementation run. Architecture notes, repository files and prior decisions can then be selected because they help with that specific work.
Preserve provenance
Context should remain reviewable. A later reviewer should be able to see which requirement revision and supporting artifacts shaped the run. That provenance makes an agent result easier to understand, reproduce and challenge.