Blast Radius

Blast Radius for ServiceNow

Blast Radius provides configuration dependency analysis across a ServiceNow instance. Before making changes to fields, tables, or artifacts, use these tools to understand the full blast radius.

Tool Overview

Coverage

snow_blast_radius_field_references and snow_blast_radius_table_configs scan the following artifact types in parallel. Types backed by plugins that are not activated on the instance fail silently — the tool reports them under errors_by_type and continues.

Table-scoped (queried with the table name as filter):

• Business rules (sys_script) — script + condition + filter_condition + role_conditions
• Client scripts (sys_script_client)
• UI actions (sys_ui_action) — script + condition
• UI policies (sys_ui_policy) — script_true + script_false + conditions
• UI policy actions (sys_ui_policy_action) — exact field match
• Data policies (sys_data_policy2)
• Data policy rules (sys_data_policy_rule) — exact table_field match
• ACLs (sys_security_acl) — field-level name match always included, table-level only when script/condition references the field
• Email notifications (sysevent_email_action) — subject + message_html + message_text + condition + advanced_condition
• Metric definitions (metric_definition) — script + exact field match
• Inbound email actions (sysevent_in_email_action) — script + condition
• Transform entries (sys_transform_entry) — target_field / source_field
• Dictionary dependent / dependent_on_field — UI-level field dependencies

Global (no table column — grep all records, filter client-side by script content mentioning the table name):

• Script includes (sys_script_include)
• Scheduled jobs (sysauto_script)
• Fix scripts (sys_script_fix)
• Script actions (sysevent_script_action)
• Transform scripts (sys_transform_script)
• Processors (sys_processor)
• UI scripts (sys_ui_script)
• Scripted REST resources (sys_ws_operation) — operation_script
• Email scripts (sys_script_email)
• Service Portal widgets (sp_widget) — server script + client script + link
• Catalog client scripts (catalog_script_client)
• Catalog UI policies (catalog_ui_policy)
• ATF step inputs (sys_atf_step)

Table hierarchy: By default the tools walk sys_db_object.super_class up to three levels, so a query on incident also returns artifacts scoped to task. Disable via include_parent_tables: false.

When results are truncated

snow_blast_radius_field_references returns a truncated_types array naming artifact types where the sysparm_limit was hit. Global-scope types (script_includes, scheduled_jobs, widgets, ATF steps) are the usual suspects — they have no table column, so the pre-filter matches any script mentioning the field name anywhere.

What to do when truncated_types is non-empty:

1. Re-run snow_blast_radius_field_references with a higher limit_per_type (e.g. 100) — often enough for medium-size instances.
2. If still truncated, switch to snow_code_search for the affected tables with a tighter pattern. Example for incident.priority references in script includes:

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   snow_code_search({
     query: "current.priority",
     tables: ["sys_script_include"],
     per_table_limit: 100,
   })
   

   Repeat with "'priority'" and '"priority"' to catch setValue('priority') / "priority" patterns. Results are unclassified (no read/write split) but complete.
3. Intersect the snow_code_search hits with the script-analyzer output by running snow_blast_radius_artifact_dependencies on each individual script include for accurate read/write classification.

Treat truncated_types as a signal that blast-radius's structured answer is incomplete, not as a safe zero.

Known Limitations

These gaps are inherent to static regex-based analysis over the REST Table API:

• Reference dotwalks: current.assignment_group.manager is parsed as a reference to assignment_group, not to sys_user_group.manager. Dotwalked field changes are not flagged transitively.
• Dynamic field access: gr.setValue(someVar, value) cannot be resolved because someVar is computed at runtime.
• Dynamic table access: new GlideRecord(tableVar) — global artifacts won't be matched unless the table name appears literally in the script.
• Legacy workflows (wf_workflow, wf_activity) are not scanned — migrating to Flow Designer is recommended anyway.
• Reports/dashboards filter conditions are not scanned.
• Service Portal option schemas / angular providers beyond sp_widget are not scanned.
• Field-level ACLs without scripts that also don't match the name=<table>.<field> exact pattern (e.g., using a regex-like ACL naming) may be missed.
• include_parent_tables adds at most three sys_db_object lookups; deeper hierarchies (incident_task → task → incident) are capped at depth 3.

If the tool reports "0 references", treat it as "no static references found in the artifact types we scan" — not as a proof of safety. For high-risk changes (renaming a widely-used field), combine with grep of the export XML, and consider running a sandboxed test after the change.

Recommended Workflow

1. Instance Overview

Start with snow_blast_radius_apps to see which applications have the most configurations:

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→ snow_blast_radius_apps(include_config_counts: true)

2. Table Deep-Dive

Pick a table and see everything running on it:

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→ snow_blast_radius_table_configs(table_name: "incident")

3. Field Impact Check

Before changing a field, find every artifact that touches it:

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→ snow_blast_radius_field_references(table_name: "incident", field_name: "assignment_group")

4. Artifact Analysis

Analyze what a specific artifact depends on:

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→ snow_blast_radius_artifact_dependencies(artifact_type: "business_rule", artifact_sys_id: "abc123")

Returns fields read/written, tables queried, script includes called, and a complexity rating.

5. Reverse Dependencies

Find what depends on a specific artifact (e.g., a script include):

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→ snow_blast_radius_dependents(artifact_type: "script_include", artifact_identifier: "IncidentUtils")

Common Questions and Which Tool to Use

Script Analysis Patterns

The script analyzer detects these patterns in ServiceNow scripts:

Field reads: current.field, gr.getValue('field'), g_form.getValue('field'), .addQuery('field'), .orderBy('field')

Field writes: current.field = value, gr.setValue('field', value), g_form.setValue('field', value)

Table queries: new GlideRecord('table'), new GlideAggregate('table')

Script include calls: new ClassName() (excludes Glide built-in classes)

What blast-radius does NOT cover — and how to communicate it

Every snow_blast_radius_dependents result includes two fields the user must understand before acting on the data:

• scope_caveat — a single sentence stating that the scan covers script-bearing fields, not the entire instance.
• out_of_scope_surfaces — a list of areas that were NOT searched. Common items: row data inside records, saved filters (sys_filter) and reports (sys_report), pending update sets (sys_update_xml), external consumers (MID server, Integration Hub, REST callers), plain-string properties (sys_property), inactive records, and inactive plugins.

You MUST relay these to the user whenever:

1. The result has zero dependents AND the user is considering deletion — the absence of dependents in script-bearing fields is NOT the same as "safe to delete". Cite out_of_scope_surfaces and recommend manual verification of those surfaces.
2. The user explicitly asks "is it safe to delete X" or "can I remove X" — always include the caveat. Even with 50 dependents, the picture may be incomplete.
3. The user is preparing a refactor that renames or removes an artifact. Mention which out-of-scope surfaces are most likely to break and how to check them (e.g. for a field rename, also run an encoded-query check against sys_filter).

Do not bury the caveat. A one-liner ("Note: this scan does not cover ...") is enough — but it must be visible to the user, not just to you.

Companion tools — RUN ALL OF THESE for delete / rename decisions

When the user asks any of:

• "is it safe to delete X" / "kan ik X verwijderen"
• "what breaks if I rename X" / "wat breekt als ik X hernoem"
• "can I refactor / remove / drop X"
• "blast radius of changing X"

…do NOT stop at snow_blast_radius_dependents. The dependents scan only covers script-bearing fields; three other surfaces silently hold references that gs.getProperty(), saved filters, and pending update sets pull in at runtime. Missing one of them is the difference between a clean refactor and a Monday-morning production incident.

You MUST run the full set in parallel (single response, multiple tool calls). Do not serialize. Do not skip a tool because "the user didn't ask for it" — "is this safe" already implies all of them.

Script include / business rule / widget / scheduled job / processor

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snow_blast_radius_dependents(artifact_type, artifact_identifier)
snow_blast_radius_update_sets(artifact_identifier)
snow_blast_radius_sys_properties(artifact_identifier)

Field deletion or rename

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snow_blast_radius_field_references(table_name, field_name, include_filters: true)
snow_blast_radius_update_sets(field_name)
snow_blast_radius_sys_properties(field_name)

Table deletion

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snow_blast_radius_dependents(artifact_type: "table", artifact_identifier: <table>)
snow_blast_radius_update_sets(<table>)
snow_blast_radius_sys_properties(<table>)

…and if the user is also dropping or renaming columns, add one snow_blast_radius_field_references per column.

Synthesizing the answer

After the tools return, present ONE unified picture to the user. Lead with the totals across surfaces ("33 references across scripts, 2 in update sets, 4 in system properties"), call out cross-scope hits, and end with the out-of-scope surfaces that even the full sweep does NOT cover (row data, external consumers — see out_of_scope_surfaces on the dependents result). The user shouldn't have to mentally aggregate four tool outputs themselves.

If any of the companion tools returns hits in in_progress update sets, in plugin-category sys_properties, or with cross-scope dependents — treat that as a hard "do not delete without addressing these first" and say so in plain language, not buried in a bullet list.