The artifact of software development has always been the code. Everything else — commit messages, PR descriptions, documentation, design documents — was secondary, optional, and systematically incomplete. Agent sessions change this. The session trace is not secondary to the code — it is the record of the process that produced the code, automatically generated, complete, and machine-readable. Treating the trace as scaffolding to be discarded after the code is produced has it backwards. The code is the output of the session. The session is the work. First-class treatment means the trace is stored, versioned, and surfaced with the same reliability as the code itself.
(The diff is the residue of thinking · Colocation is what makes context useful · The stream is a transaction log)