Summary
A source-based audit of an agent CLI hook configuration found that process churn depended on outer event registrations, runtime boundaries and conditional descendants—not simply the number of listed checks. Transcript synchronization added a different cost: discovering many files even when little content changed. The transferable lesson is to measure launch, console-host and filesystem work separately before consolidating hooks or moving background work elsewhere.
Method and collection date
The October 2026 audit inspected an installed Windows hook configuration, dispatch behavior and relevant child-launch code. It compared these findings with an existing process/allocation trace. No new hook execution, process trace, test run or live configuration change was performed.
The original implementation and trace are not public. This report therefore presents an anonymized case study rather than independently reproducible measurements. Counts below are configuration-derived estimates unless explicitly described as prior trace evidence. They are not defaults for every agent CLI installation.
Findings
A listed check is not necessarily a new process
The inspected runner normally executed compatible Python checks inside an already-started interpreter. External executable entries launched separately; deferred entries entered a queue instead of immediately starting their eventual runtime. Isolation flags, runtime mismatches or failed inline initialization could restore child-process execution.
flowchart TD
L["Listed check"] --> K{"Entry / execution path"}
K -->|"Compatible Python"| I["Inline in already-started interpreter"]
K -->|"External executable"| E["Separate executable launch when matched"]
K -->|"Deferred"| Q["Queue now"]
Q --> A["Eventual runtime executes when admitted"]
K -->|"Isolation flag, runtime mismatch or failed inline initialization"| C["Child-process execution"]
For a successful tool call, the inspected base configuration contained two outer Python runners. Tool matching could add zero, one or two Node launches. Independent write-time checks or additional configuration layers could add further processes.
| Work category | How to account for it | Common attribution mistake |
|---|---|---|
| Compatible inline checks | Work within the outer interpreter | Counting one Python launch per listed check |
| External runtime entry | A separate executable when its matcher applies | Applying the cost to unmatched tools |
| Deferred work | Queueing now; execution when admitted | Counting the eventual runtime on every enqueue |
| Conditional Git or identity lookup | Count only the branch actually reached | Assuming a repeated trace chain is unconditional |
| Console host | Separate from interpreter/executable counts | Treating hidden windows as proof of no host allocation |
A persistent host could theoretically avoid the base two Python and zero-to-two Node starts per successful call. This is an upper-bound opportunity in the inspected configuration, not a measured saving. Consolidation must preserve authoritative denials, isolation, cancellation and ordering; simply combining checks can change security behavior.
Hidden windows and process churn are different concerns
The inspected code already used window-suppression measures in several launch paths. Those measures did not establish that every descendant avoided console-host allocation. Python-side launch handling also did not automatically govern children created inside Node.
Windows documents distinct process-creation flags for console behavior [1]. In this case, console ownership and descendant trees needed direct verification rather than inference from a single flag or the absence of a visible window. Suppressing a console host also does not remove the interpreter process itself.
Trace evidence did not identify a guaranteed per-call Git saving
The supplied trace contained 29 Git metadata-probe chains attributed to Python runners. Inspection did not find an unconditional Git launch in the current runner itself. The responsible loaded check, revision and event therefore remained unresolved; removing an assumed one-per-call probe would not be a supported savings claim.
Caching repository identity is also different from caching mutable publication state. Root discovery may be stable, while HEAD, branch and upstream information can change after checkout or commit. Direct metadata reads require correct handling of worktrees, detached or unborn branches, loose and packed references, and alternative reference storage.
Incremental content parsing can still perform broad discovery
One inspected transcript-sync path recursively discovered all matching files and checked modification metadata before parsing at most 20 candidates. Unchanged files avoided content parsing, not discovery work. Another path selected one conversation but still read its full history before determining what was new.
These are separate scaling dimensions: bounded candidate count does not prove bounded directory enumeration, and exact targeting does not prove incremental byte-offset reading. The actual number of files opened or enumerated in a live run was not measured.
Moving parsing to Linux-native storage could reduce Windows-side import and file-open work, but only if a persistent changed-file collector avoids replacing it with a fresh upload process per tool call. That design was a proposal, not a tested deployment.
Limitations
The audit did not exhaustively inventory plugin or project overlays, dynamic imports, cold dependency repair, all conditional descendants, loaded registrations or current console ownership. Historical trace attribution was not proof that inspected source still produced identical chains. Proposed savings overlap and must not be added together.
No kernel-pool reduction, end-to-end latency gain or deployment readiness was demonstrated. The useful outcome is an accounting method and a bounded set of hypotheses to verify with passive traces during ordinary operation, not a claim that the bottleneck was fixed.
References
- Microsoft process-creation flags, methodological reference: https://learn.microsoft.com/en-us/windows/win32/procthread/process-creation-flags