Summary

Closes Gap A of #126 — adds a new cdp_interact action=\"setFieldValue\" for the case where typeText's descendant walk can't find a typeable handler because the field's state flows through React Hook Form's field.onChange → FormProvider context → setValue, with no inner TextInput-shaped fiber for typeText to find.

Gap B (action-sheet portal modal invisibility) is a different fiber-root iteration problem — deferred to a follow-up.

API

cdp_interact({
  action: 'setFieldValue',
  testID: 'email-field',          // anchor inside the form subtree
  name: 'email',                  // RHF field name (matches useController/Controller name)
  value: 'a@b.com',               // any string | number | boolean, passed verbatim
  shouldValidate: true,           // default true; pass-through to setValue options
  shouldDirty: true,              // default true; pass-through to setValue options
})

Algorithm (injected-helpers.ts)

1. Match the testID anchor (existing infrastructure).
2. Walk UP via node.return, bounded at 32 levels / 100 fiber visits.
3. Find the first Provider fiber whose memoizedProps.value duck-types as UseFormReturn: typeof value.setValue === 'function' && typeof value.getValues === 'function' && value.control && typeof value.control === 'object'.
4. Call value.setValue(name, value, { shouldValidate, shouldDirty }).
5. Surface the thrown message if setValue rejects (bad field name, value type mismatch, transitioning state).

Closest ancestor wins → nested forms behave like natural React context resolution.

Design decisions

Why explicit action, not implicit typeText fallback. Implicit fallback would change the meaning of an existing tool call and risk surprising users who expected the existing 'no handler' error. Explicit setFieldValue is opt-in, self-contained, and documented in the tool description.

Why walk-up via fiber.return instead of useFormContext(). Injected helpers run OUTSIDE React's rendering cycle, so hooks can't be called. The codebase already uses this fiber-walk pattern for nav state and store context — adding setFieldValue follows the established convention.

Why a strict duck-type (setValue + getValues + control all required). Many Providers expose value objects with one or two look-alike fields. ThemeProvider with .value.theme.setValue (a custom setter) shouldn't be mistaken for a form. Requiring all three RHF surface markers gives a clean signal.

Test plan

8 new tests in gh-126-set-field-value.test.js, all using a VM sandbox with synthetic fiber trees (consistent with existing injected-helpers tests):

• Happy path — walks up to FormProvider, calls setValue with defaults
• Options pass-through — shouldValidate=false and shouldDirty=false reach setValue verbatim
• No coercion — numeric and boolean values pass through unchanged
• Nested forms — closest provider wins (proves React context semantics)
• Validation — missing opts.name returns clear error without walking the tree
• No form ancestor — returns actionable hint pointing at <FormProvider>
• Throwing setValue — caught and thrown message surfaced (bad field name etc.)
• Strict duck-type — rejects Providers whose value lacks setValue

Total: 1514/1514 cdp-bridge unit tests passing (+8 net new).

Other changes:

• Helpers bundle version bumped 21 → 22 (existing source-guard tests + version-pin assertion both updated)
• cdp_interact action enum gains 'setFieldValue' AND 'longPress' (latter was in the description string but missing from the TypeScript type union — fixed for consistency)
• 4 new args: name, value, shouldValidate, shouldDirty (all optional; required only for setFieldValue, enforced at handler boundary)

Note on review

codex-pair did not review this commit — the ask-codex MCP server appears disconnected this session (no log entries since May 20). The 8-test coverage + the explicit design approval before implementation are the safety net. Manual /codex-review welcome from reviewers if a deeper second-opinion is wanted.

Refs

• bug: dual CDP gap blocks Maestro automation through TextField wrappers and action-sheet portal modals #126 — dual CDP gap (TextField wrappers + portal modals); this PR addresses Gap A only
• scripts/cdp-bridge/src/injected-helpers.ts:1250 — new setFieldValue handler
• scripts/cdp-bridge/src/tools/interact.ts — handler args extension + validation
• scripts/cdp-bridge/src/index.ts:509 — Zod schema + tool description

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