vercel Vercel CLI UX
Canonical front door for making the Vercel CLI consistent, sharp, scriptable, and agent-ready.
Stance
Act like a CLI product engineer, not a string polisher.
- For material changes, define the user job, current friction, desired outcome, success signal, and non-goals before choosing output.
- Inspect the current command source and tests before judging.
- Treat shipped output as evidence, not automatic precedent. Check it against this skill, product behavior, and compatibility contracts.
- Fix the flow when the flow is wrong; copy-only edits are not enough.
- Treat copy changes as symptoms. Inspect the surrounding flow, layout, resolved-state preview, side effects, and tests before stopping.
- Keep human output readable and machine output stable.
- Treat agents as first-class users and untrusted input sources.
- Preserve compatibility unless the migration is explicit and tested.
- Prefer existing command-family helpers and patterns.
Decision Authority
Resolve conflicts in this order:
- The user's explicit goal and constraints.
- Verified product and system truth: API behavior, permissions, billing, data models, reachable states, and compatibility contracts.
- Repository-canonical guidance:
AGENTS.md, this skill, shared helper contracts, and tests that encode intentional behavior. - Accepted command-specific contracts in
command-contracts.md. - Verified adjacent command-family patterns.
- General CLI heuristics.
Do not let a lower source override a higher one. Shipped code proves what exists, not why it is correct.
Workflow
- Outcome map. For material UX changes, name the user and job, current behavior, desired outcome, success signal, and non-goals.
- Surface map. List help, flags, prompts, progress, warnings, success, errors, tables/lists, detail views, JSON, and agent/non-interactive payloads.
- Structure map. For each touched line, identify its surface role, order, vertical rhythm, layout helper, gutter glyph or blank gutter, resolved-state preview, mutation preview, result block, and next action.
- Mode map. Trace TTY, non-TTY,
--non-interactive, JSON/format flags, CI, and pipeable stdout. - State map. Name team, project, cwd/root, environment, config files, framework/services, auth, remote resources, and defaults.
- Question audit. For every prompt, prove the value cannot be inferred and that a flag/arg/payload exists.
- Mutation audit. Identify local writes, remote mutations, polling, retries, idempotency,
--yes,--force, typed confirmation, and--dry-run. - Agent audit. Verify JSON/action payloads, bounded output, safe suggested commands, and no untrusted text in instructions.
- Transcript review. Read the before/after transcript for order, rhythm, duplicated concepts, alignment, and next action.
- Regression lock. Test the new path and lock out old prompts, stale terms, and broken machine contracts.
When to Load References
Load only what the task needs.
| Task surface | Load |
|---|---|
| Any CLI UX/output change | references/core.md |
| User-facing copy or copy review | references/core.md + references/copy.md |
| Prompt/setup flow | copy.md → Prompts; core.md → Flow Design, Prompts, Setup + Mutation Flows |
| Output layout/progress | core.md → Output Surfaces, Layout, Glyphs + Color, Progress + Completion, Terminal Resilience |
| List/detail/resource views | core.md → List + Detail Commands, Layout, Streams + Formats, Machine Introspection |
| Streaming/follow/live commands | core.md → Streaming + Long-Running Commands, Streams + Formats, Terminal Resilience |
| Errors/permissions/rate limits | copy.md → Errors + Warnings; core.md → Errors, Warnings, Remote Work, Secrets |
| JSON/agent/non-interactive paths | core.md → Streams + Formats, Agent + Non-Interactive Output, Machine Introspection, Hardening |
| Help/flags/completions | copy.md → Help; core.md → Commands + Flags, Help + Discoverability, Compatibility |
| Destructive/production mutation | copy.md → Clear + Consistent, Prompts; core.md → Dangerous Actions, Remote Work, Secrets |
vc link or setup/link work |
references/command-contracts.md → Link Flow Contract |
vc env add work |
command-contracts.md → Env Add Flow Contract |
vc, vc deploy, deploy output |
command-contracts.md → Deploy Flow Contract |
| Tests, stale-copy sweeps, review | references/verification.md |
If you add durable guidance, put detailed wording rules in copy.md, keep only the cross-cutting copy baseline plus reusable flow/output rules in core.md, put command-only state machines in command-contracts.md, and put test/review gates in verification.md. Short safety rules may repeat when sections need to stand alone; the canonical reject/fix checklist stays in verification.md.
Quality Bar
Every changed command should answer:
- What target did the CLI resolve?
- What will change?
- What happened?
- What can the user or agent do next?
Top-tier commands:
- make the common path short
- ask only what cannot be inferred
- show detected state before asking for overrides
- show resolved targets in structured output before confirmations
- avoid restating values already visible in argv, prompts, or nearby rows
- show user-facing local and remote side effects in result blocks after mutation
- use gutter glyphs only for semantic state, not decoration
- use one concept per prompt
- support flags or payloads for every prompt path
- behave predictably in TTY, CI, and agent contexts
- expose stable machine-readable contracts for scripted use
- avoid duplicate remote mutations on retry
- make no-op and already-done states explicit
- end with a completed result or exact next command
Review Gates
Apply the canonical Review Checklist in references/verification.md. Keep the checklist there so safety rules do not drift.
Durable skill guidance needs verified current-source evidence, scope and exceptions, rationale tied to user or compatibility consequences, and a concrete bad/good example when the rule is mechanical. One shipped string, screenshot, or review comment is not enough to establish a universal rule.
Minimum Done State
A CLI UX change is not done until:
- the before/after transcript is easier to scan
- copy changes review every user-facing string in the supplied command surface and directly coupled states, not only the edited line
- prompt/result copy changes also checked layout, vertical rhythm, order, and surrounding flow
- resolved target and planned mutation are visible before risky work
- inferred resource confirmations show the resolved target before asking
- mutation results show durable remote resources and user-actionable local artifacts changed
- aligned rows use
printAlignedLabel()with the shared 16-character label column and correct gutter:▲for production rows,✓for the primary completed phase,!for warnings,✗for fatal errors, blank for previews, progress, and secondary receipt rows - every prompt has a flag, argument, or machine-readable action path
- old vague prompts/output are locked out by tests
- JSON/agent output remains valid, bounded, and stdout-clean
- focused tests pass, or unrelated failures are named with evidence
- changes to this skill are checked against at least 2 command families with different surfaces