Monosecret 0.12: audit logs and coding agents

Jun 8, 2026

Domen Kožar

Historical upstream article

This article is preserved from the upstream Monosecret 0.12 release. For current usage, use monosecret, monosecret.toml, and MONOSECRET_*; see the Monosecret audit documentation.

A coding agent reaches for the same secrets you do, but on its own initiative and many times a session: a read looks identical whether it came from you running a deploy or an agent exploring the codebase.

Monosecret 0.12 makes that access accountable. It ships three things:

• Audit log — every secret read and write is appended to a local, per-user JSONL log. On by default. Values are never recorded.
• Reason-on-access — secret access can require a human-readable reason, enforced for coding agents by default.
• monosecret audit command — filter and summarize the log, or pipe raw JSON Lines to jq.

Behavior change in 0.12

If you run Monosecret inside a coding agent, secret access now fails until a reason is supplied. This is the new default (require_reason = "agents"). Opt out with require_reason = false in the [project] table. Existing providers and library callers keep working unchanged. See Upgrading.

The audit log

Every secret read and write, from the CLI and the Rust SDK, is appended to a local log as JSON Lines, one event per line. Secret values are never written, only metadata: the secret name, the profile, the provider that served it (with any embedded credentials redacted), the outcome, the reason, and who was asking, including the detected coding agent.

{
  "v": 1,
  "ts": "2026-06-04T17:04:00.893Z",
  "action": "get",
  "project": "my-app",
  "profile": "production",
  "key": "DATABASE_URL",
  "provider": "keyring://",
  "outcome": "found",
  "reason": "deploy web frontend",
  "actor": { "user": "alice", "agent": "claude-code", "is_agent": true },
  "version": "0.12.0"
}

The log lives in your per-user state directory (~/.local/state/monosecret/audit.log) and is created readable only by you. Read it with any tool, or use the new monosecret audit command for filtering and a readable summary:

# Last 20 entries, formatted
monosecret audit -n 20

# Only `run` events for one project
monosecret audit --project my-app --action run

# Raw JSON Lines, piped to jq
monosecret audit --json | jq 'select(.outcome == "missing")'

It is configured in your user-global config (~/.config/monosecret/config.toml), not the project’s monosecret.toml, so a repository you clone can’t quietly turn off or redirect your audit log. The log is a single file capped at 1 MiB, a size-bounded recent record rather than permanent compliance history; forward it to a central system if you need that. To turn it off entirely:

~/.config/monosecret/config.toml

[audit]
enabled = false

See Audit Logging for the full record schema and options.

Supplying a reason

When a coding agent like Claude Code reaches for a secret without a reason, the access is refused and the agent is told exactly what to do next:

$ monosecret run -- npm test
Error: Accessing secrets requires a reason. Provide one with --reason
"<why you are accessing these secrets>", the MONOSECRET_REASON environment
variable, or Secrets::with_reason() in the SDK. (Policy: require_reason in
[project] of monosecret.toml — defaults to "agents"; set it to false to
disable.)

Claude Code reads that message, states why it needs the secret, and retries:

monosecret run --reason "run the test suite before opening a PR" -- npm test

Both the refusal and the successful retry land in the audit log, so the reason is tied to the access. There are three ways to supply a reason:

Source	Scope	Precedence
--reason flag	CLI	highest
Secrets::with_reason()	SDK	overrides env
MONOSECRET_REASON	CLI + SDK + derive	lowest

# CLI: the most explicit option, overrides the others
monosecret run --reason "deploying release 0.12" -- ./deploy.sh

// SDK: the programmatic equivalent of --reason
let secrets = Secrets::load(/* ... */)?.with_reason("nightly backup job");

# Env: lowest precedence, but honored everywhere
export MONOSECRET_REASON="nightly backup job"

MONOSECRET_REASON is resolved by Secrets::load / load_from, which means monosecret_derive-generated code and other library callers satisfy the policy and supply an audit reason without any code changes.

Whichever path you use, blank or whitespace-only reasons are ignored, so they can’t quietly satisfy the policy. Under the hood this is backed by a new Provider::set_reason trait method (a no-op by default), so existing providers keep working unchanged.

Configuring when a reason is required

The new require_reason policy in the [project] table controls when a reason is mandatory:

[project]
name = "my-app"
require_reason = "agents" # require it from agents (default), or true / false

• "agents" (the default): require a reason only when a coding agent is detected.
• true: require it from every caller.
• false: never require it.

Because the policy lives in monosecret.toml and is enforced by Monosecret, it applies to everyone and every CI runner, and is inherited through extends. Coding agents are spotted by the detect-coding-agent crate (Claude Code, Cursor, Codex, Gemini CLI, Copilot, and more); set MONOSECRET_AGENT for a harness it doesn’t recognize.

Upgrading

cargo install monosecret

Remember the new default: agents must pass a reason: set require_reason = false to opt out.

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Secrets Don’t Belong in Config