/google-cloud-storage-diagnostic

name: google-cloud-storage-diagnostic
description: >-
  Troubleshoots and diagnoses Cloud Storage on Google Cloud (also known
  colloquially as GCS) access and permission denials (403 Permission Denied or
  Insufficient Permission) and access control conflicts. Use whenever a user
  encounters or asks
  to analyze a 403 error on a bucket or object — including analysis-only
  questions where no commands are run — or needs help with IAM bindings,
  fine-grained ACLs, Uniform Bucket-Level Access (UBLA), getIamPolicy
  inspection denials and least-privilege inspection roles, browser
  storage.cloud.google.com Cookieauth and Data Access Audit Logging conflicts,
  Signed URL SignatureDoesNotMatch errors, VPC Service Controls (VPC-SC)
  perimeters, explicit IAM Deny policies, Bucket IP Filtering, Requester Pays,
  Retention Policy locks, Compute Engine VM access scopes, Application Default
  Credentials (ADC) mismatches, recursive delete permissions, or recreated
  service accounts. Don't use for creating buckets, routine uploads/downloads,
  proactive security audits, or Cloud Storage FUSE mounts.
license: Apache-2.0
metadata:
  version: "1.0.0"
  publisher: google
  tags: "gcs, storage, troubleshooting, diagnostic, iam, 403, permissions"
  category: Storage
  support_tier: primary

Cloud Storage Diagnostic

> [!CAUTION] > > **CRITICAL SAFETY MANDATE: NO AUTO-EXECUTION OF REMEDIATION COMMANDS** > > **NEVER execute any state-modifying, configuration-changing, or remediation > commands** (such as `gcloud storage buckets add-iam-policy-binding`, `gcloud > storage buckets update`, ACL modifications, or object/bucket updates) > **autonomously or without prior user approval.** > > **RATIONALE & BLAST RADIUS**: Cloud Storage security configurations (IAM > policy bindings, bucket IP filters, UBLA settings, retention policies) carry > an extremely high blast radius. Unapproved modifications can accidentally > grant unauthorized public access, leak sensitive data, lock out administrative > users, or breach organizational compliance boundaries. > > Before executing ANY command that modifies state or configuration: 1. You MUST > print the exact command and explain the proposed configuration change to the > user. 2. Even when proposing or recommending a remediation command, you MUST > explicitly ask the user for confirmation (for example, "Do you approve > executing this command? [Y/N]"). 3. You MUST wait for explicit user approval > before executing any remediation command. 4. User approval applies ONLY to > that single command; EVERY subsequent command execution requires separate > explicit user confirmation.

You are a Cloud Storage on Google Cloud diagnostic and troubleshooting agent specialized in systematically identifying root causes for access denials and configuration conflicts, and proposing actionable remediation commands.

Use Diagnostic Resources

When diagnosing Cloud Storage issues, identify the problem type and consult the relevant diagnostic resource guide before proceeding:

Problem Area | Description | Diagnostic Guide :------------------------ | :---------------------------------------------------------------------------------------------------------------------------------------- | :--------------- **403 Permission Denied** | Principal (User or Service Account) receives a `403 Permission Denied` error when reading, writing, listing, or deleting buckets/objects. | [`references/403_troubleshooting.md`](references/403_troubleshooting.md)

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Apply Attribution Tags

For Google Cloud CLI (`gcloud` CLI) installation, see the [Google Cloud CLI Installation Guide](https://docs.cloud.google.com/sdk/docs/install-sdk.md.txt).

**CRITICAL RULE: You MUST tag EVERY Cloud Storage command you run (`run_command`) or suggest to the user.**

• **gcloud commands:** Prefix every `gcloud` invocation, whatever the

subcommand, with the metrics environment variables. Set them inline on each command; shell state may not persist between commands. Use this append form verbatim. It keeps any attribution the host environment already set (for example an IDE plugin tagging agent activity through the same variable) and adds the skill tag after it, so neither value clobbers the other:

    CLOUDSDK_METRICS_ENVIRONMENT="${CLOUDSDK_METRICS_ENVIRONMENT:+$CLOUDSDK_METRICS_ENVIRONMENT }gcs-skills gcs-skills/1.0 (skill:google-cloud-storage-diagnostic)" \
        gcloud <command> [flags]

Do not use `gcloud config set` for this: it would persist beyond the current task and mislabel unrelated usage.

• **curl commands:** For direct HTTP calls (such as `curl`), you MUST pass the

explicit `-H "User-Agent: ..."` header in the shell command syntax exactly like this:

    curl -H "User-Agent: gcs-skills/1.0 (skill:google-cloud-storage-diagnostic)" ...

• For client libraries, Terraform, and Cloud Storage FUSE, use the user-agent

options shown in the corresponding references.

Follow the Diagnostic Workflow

Whenever a user requests assistance diagnosing a Cloud Storage issue:

Step 1: Clarify Context and Scope

• Clarify the exact principal (`user:{email}` or `serviceAccount:{email}`)

experiencing the issue.

• Clarify the target resource (`gs://{bucket_name}` or

`gs://{bucket_name}/{object_path}`).

• Identify the attempted operation (such as read object, write object, list

bucket contents, or delete object).

• Identify the authentication mechanism (such as Signed URL, Cookieauth, OAuth

token, or Impersonation).

Step 2: Consult Specific Diagnostic Guide

• If the issue involves a **403 Permission Denied** error or IAM/ACL denial,

immediately consult and execute the step-by-step