How should security teams let coding agents review pull requests without giving them unrestricted merge access?

Use a review-only credential with the narrowest GitHub permissions needed for inspection and comments, then keep merging behind a separate governed path. That means Contents: read for repository inspection and Pull requests: write for reviews, while keeping Contents: write out of the review token. Also check for other tokens in the shell environment that could bypass the intended control.

Why a review-only credential is the right control boundary

The key design choice is to separate inspection from authority. A coding agent can read repository content, comment on changes, and surface issues without being able to merge, rewrite history, or expand its own access. That keeps the review function useful while preventing the review credential from becoming a general-purpose deployment or release token.

GitHub permissions should reflect that boundary: Contents: read is enough for inspection, and Pull requests: write is enough for reviews and comments. Keeping Contents: write out of the review token avoids accidental or malicious edits being treated as part of the review workflow.

That pattern is especially important when the agent operates in a terminal or CI context, because those environments can expose other secrets that are outside the intended review path. If an agent can see a broader shell environment, the effective privilege is no longer defined only by the GitHub token you issued.

How to preserve separation of duties in the merge path

Review authority and merge authority should not live in the same credential or the same automation step. The review token should support analysis and discussion only, while merging stays behind a separate governed path with human approval, policy checks, or another controlled release mechanism. That prevents a review tool from becoming its own release gatekeeper.

This is the same control logic used in broader access governance: the reviewer should be able to assess, not to execute the final change. When the same principal can inspect, approve, and merge, the workflow loses a meaningful check and turns review into a formality.

AI Coding Agents Security Guide covers why over-scoped tokens, secrets in agent context, and sandboxing matter for coding assistants, while IAM and IGA Basics is a useful companion for the underlying least-privilege and separation-of-duties model.

What teams should check before trusting the agent’s review path

Before you let the agent review pull requests, verify exactly what the token can do in GitHub and what other credentials are present in the environment. The practical test is whether the agent can only read the repository and comment on pull requests, or whether it can also reach write-capable tokens, deploy credentials, or other secrets that bypass the review boundary.

Review environments should be treated as exposed execution surfaces, not as safe analysis sandboxes by default. That means checking repository permissions, runner or shell inheritance, and any credential helper, cached token, or exported environment variable that could silently widen access.

Access Reviews and Certification Guide is useful here because it frames review as a controlled entitlement, not a one-time setup decision, and AI Agent Observability, Audit and Incident Response Guide helps teams decide what evidence to retain if the agent’s actions ever need to be reconstructed.

Risk and Threat Considerations

A review-only credential reduces risk, but the main failure mode is scope creep through adjacent secrets or misconfigured automation. If the agent can inherit a more powerful token from the shell, CI job, or developer environment, an attacker only needs one bypass to turn a comment-capable reviewer into a write-capable actor.

Failure mechanism: A review token is limited, but another credential in the same runtime, such as a cached GitHub token, environment secret, or job-scoped deploy token, allows the agent to act outside the review boundary.

Impact: The agent can approve, alter, or push changes beyond its intended role, which undermines separation of duties and can create unauthorized merges or repository compromise.

Standards & Framework Alignment

This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.

OWASP Non-Human Identity Top 10 and OWASP Agentic AI Top 10 address the attack surface, NIST SP 800-53 Rev 5 sets the technical controls, and ISO/IEC 27001:2022 defines the regulatory obligations.

Framework	Control / Reference	Relevance
OWASP Non-Human Identity Top 10	NHI-05 — Overprivileged NHI	Review tokens must not carry merge or write privilege beyond inspection.
	NHI-07 — Long-Lived Secrets	A review credential should be short-lived to reduce reuse and leakage risk.
	NHI-10 — Human Use of NHI	Human-approved merge authority should stay separate from the agent's review identity.
Recommendation — Limit the agent token to read and comment permissions only. Issue ephemeral review credentials and rotate them after the review task. Keep merge approval on a separate human-controlled path.
OWASP Agentic AI Top 10	ASI03 — Identity & Privilege Abuse	A coding agent must not inherit broader privileges than the review task requires.
Recommendation — Constrain the agent to review-only authority and block privilege escalation.
NIST SP 800-53 Rev 5	IA-9 — Identification and Authentication (Service and External Systems)	Agent and tool interactions rely on non-human system authentication and scoped access.
	AC-6 — Least Privilege	The question is about minimizing permissions for review versus merge actions.
	AC-5 — Separation of Duties	Review and merge should be split so the same principal cannot both approve and execute.
Recommendation — Authenticate the agent with a dedicated service credential and scope it tightly. Grant only the permissions required for comments and inspection. Separate review authority from merge authority.
ISO/IEC 27001:2022	A.5.15 — Access control	The answer depends on restricting repository access to the minimum needed.
	A.5.18 — Access rights	The review token's rights must be provisioned and limited distinctly from merge rights.
Recommendation — Define and enforce access rules for review credentials. Review and periodically verify granted access rights.

Practitioner Guidance

What to prioritize: Make the review token the smallest possible credential and treat every surrounding secret as part of the real trust boundary. If the agent runs in a shell, IDE, or CI job, assume anything exported there may be reachable unless you explicitly remove it.

What to verify: Confirm the agent can read the repo, annotate pull requests, and nothing more. Then test the environment for hidden write paths, including inherited tokens, local credential stores, and any automation that can merge on the agent’s behalf.

Practitioner takeaway: The control works only when review is genuinely non-executive, so the safest design is a narrow inspection token plus a separately governed merge path with no ambient credentials that can bypass it.