[adr] BiDi is an implementation mechanism, not a public API

[titusfortner]

🔗 Related Issues

ADR process itself depends on #17665 merging

Decision

BiDi is an implementation mechanism, not a public API. New capabilities are exposed as
high-level, protocol-neutral APIs, idiomatic per language, subject to our standard
deprecation policy. Everything in a BiDi namespace is internal: still reachable for
anything not yet wrapped, but not documented and subject to change without warning.

A binding conforms when:

1. The supported API never references BiDi — no types, methods, properties, or entry points.
2. BiDi implementation code (including everything generated from CDDL) is visibly internal — marked per language convention as not intended for public consumption.

Considered options

1. Expose the whole protocol as a public API (Rejected)
   • not user-friendly syntax
2. A supported-but-separate public protocol namespace (Rejected)
   • multiple implementations are confusing
3. Internal implementation mechanism only (Accepted)

[qodo-code-review]

Code Review by Qodo

🐞 Bugs (3) 📘 Rule violations (0)

1. Option 3 ambiguous 🐞 Bug ≡ Correctness ⭐ New

Description

In ADR 0001, considered option #3 lacks an explicit Accepted/Rejected marker and its explanation
reads like the rationale for the *opposite* choice (hiding BiDi from users), leaving the decision
record unclear about what was rejected and why. This makes the ADR less self-contained and increases
the risk of misinterpreting the intended cross-binding direction.

Code

docs/decisions/0001-bidi-is-an-implementation-mechanism.md[R38-40]

+3. Allow methods and classes to reference BiDi
+   * users shouldn't need to know the underlying implementation mechanism, things should just work without additional ceremony
+4. Internal implementation mechanism only (Accepted)

Evidence

Option #3 is missing an Accepted/Rejected label and its supporting bullet reads like an argument for
hiding the implementation mechanism, while the ADR template expects options to state why they were
accepted or rejected.

docs/decisions/0001-bidi-is-an-implementation-mechanism.md[38-40]
docs/decisions/0000-template.md[23-26]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

## Issue description
ADR 0001’s “Considered options” list contains an option (#3) that does not indicate whether it was accepted or rejected, and its rationale text appears to argue for the internal-only approach rather than for allowing BiDi references. This ambiguity reduces the ADR’s usefulness as a durable record.

## Issue Context
The ADR template expects each considered option to state why it was accepted or rejected; the current option #3 neither labels its status nor clearly explains why it lost relative to option #4.

## Fix Focus Areas
- docs/decisions/0001-bidi-is-an-implementation-mechanism.md[38-40]

## Suggested fix
- Mark option #3 explicitly as `(Rejected)`.
- Rewrite its bullet to explain *why* allowing public API surfaces to reference BiDi was rejected (e.g., it exposes protocol details, couples the supported API to an implementation mechanism, harms portability/compatibility), and ensure it no longer reads like support for option #4.

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---

2. Discussion link not PR 🐞 Bug ⚙ Maintainability

Description

ADR 0001’s “Discussion” field uses “PR pending” and links to an issue instead of linking to the
ADR’s PR, which conflicts with the template/process that defines the PR thread as the discussion
record. This weakens traceability from the ADR to its canonical review/discussion history.

Code

docs/decisions/0001-bidi-is-an-implementation-mechanism.md[5]

+- Discussion: _PR pending_, https://github.com/SeleniumHQ/selenium/issues/17628

Evidence

The template explicitly instructs Discussion to link to the record’s PR, and the README states the
PR thread is the discussion record; ADR 0001 currently does not provide that PR link.

docs/decisions/0001-bidi-is-an-implementation-mechanism.md[3-6]
docs/decisions/0000-template.md[6-9]
docs/decisions/README.md[30-36]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

### Issue description
The ADR template/process expects the `Discussion:` field to link to the decision record’s PR (the canonical discussion record). ADR 0001 currently says `_PR pending_` and links to an issue instead.

### Issue Context
It’s fine to reference related issues, but per the template those should go under **Context** (or otherwise be secondary), while `Discussion:` should point at the ADR PR.

### Fix Focus Areas
- docs/decisions/0001-bidi-is-an-implementation-mechanism.md[3-6]
- docs/decisions/0000-template.md[6-9]
- docs/decisions/README.md[30-36]

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---

3. Index entry not linked 🐞 Bug ⚙ Maintainability

Description

docs/decisions/.index.md lists ADR 0001 as plain text instead of a markdown link, so the “Index of
Decisions” is not navigable. Readers can’t click through to the actual record file.

Code

docs/decisions/.index.md[3]

+* 0001 - BiDi is an implementation mechanism, not a public API

Evidence

The index contains only plain text for ADR 0001, while the actual record lives in a separate slugged
markdown file; without a link the index doesn’t provide navigation.

docs/decisions/.index.md[1-3]
docs/decisions/0001-bidi-is-an-implementation-mechanism.md[1-2]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

### Issue description
`docs/decisions/.index.md` is intended to be an index, but the ADR entry is plain text rather than a markdown link to the decision record file, which makes the index non-navigable.

### Issue Context
The ADR itself is stored in a slugged filename (`0001-bidi-is-an-implementation-mechanism.md`), so a link also removes ambiguity about the destination.

### Fix Focus Areas
- docs/decisions/.index.md[1-3]
- docs/decisions/0001-bidi-is-an-implementation-mechanism.md[1-2]

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---

Previous review results

Review updated until commit 3d21495

Results up to commit f32ab0f

🐞 Bugs (2) 📘 Rule violations (0) 📎 Requirement gaps (0) 🎨 UX issues (0) 🔗 Cross-repo conflicts (0)

1. Discussion link not PR 🐞 Bug ⚙ Maintainability

Description

ADR 0001’s “Discussion” field uses “PR pending” and links to an issue instead of linking to the
ADR’s PR, which conflicts with the template/process that defines the PR thread as the discussion
record. This weakens traceability from the ADR to its canonical review/discussion history.

Code

docs/decisions/0001-bidi-is-an-implementation-mechanism.md[5]

+- Discussion: _PR pending_, https://github.com/SeleniumHQ/selenium/issues/17628

Evidence

The template explicitly instructs Discussion to link to the record’s PR, and the README states the
PR thread is the discussion record; ADR 0001 currently does not provide that PR link.

docs/decisions/0001-bidi-is-an-implementation-mechanism.md[3-6]
docs/decisions/0000-template.md[6-9]
docs/decisions/README.md[30-36]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

### Issue description
The ADR template/process expects the `Discussion:` field to link to the decision record’s PR (the canonical discussion record). ADR 0001 currently says `_PR pending_` and links to an issue instead.

### Issue Context
It’s fine to reference related issues, but per the template those should go under **Context** (or otherwise be secondary), while `Discussion:` should point at the ADR PR.

### Fix Focus Areas
- docs/decisions/0001-bidi-is-an-implementation-mechanism.md[3-6]
- docs/decisions/0000-template.md[6-9]
- docs/decisions/README.md[30-36]

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---

2. Index entry not linked 🐞 Bug ⚙ Maintainability

Description

docs/decisions/.index.md lists ADR 0001 as plain text instead of a markdown link, so the “Index of
Decisions” is not navigable. Readers can’t click through to the actual record file.

Code

docs/decisions/.index.md[3]

+* 0001 - BiDi is an implementation mechanism, not a public API

Evidence

The index contains only plain text for ADR 0001, while the actual record lives in a separate slugged
markdown file; without a link the index doesn’t provide navigation.

docs/decisions/.index.md[1-3]
docs/decisions/0001-bidi-is-an-implementation-mechanism.md[1-2]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

### Issue description
`docs/decisions/.index.md` is intended to be an index, but the ADR entry is plain text rather than a markdown link to the decision record file, which makes the index non-navigable.

### Issue Context
The ADR itself is stored in a slugged filename (`0001-bidi-is-an-implementation-mechanism.md`), so a link also removes ambiguity about the destination.

### Fix Focus Areas
- docs/decisions/.index.md[1-3]
- docs/decisions/0001-bidi-is-an-implementation-mechanism.md[1-2]

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---

[qodo-code-review]

PR Summary by Qodo

Add ADR process docs and record BiDi as internal implementation detail
📝 Documentation 🕐 10-20 Minutes

Walkthroughs

Description

• Add an ADR/decision-record process, template, and approval rules under docs/decisions.
• Record the decision that BiDi is internal and must not appear in supported public APIs.
• Add a decisions index to make adopted proposals discoverable and citable.

Diagram

graph TD
  A([Contributor]) --> F[["docs/decisions/"]] --> B["ADR template"] --> C["BiDi ADR 0001"] --> D["Index"] --> E["Process README"]

  subgraph Legend
    direction LR
    _p([Person]) ~~~ _dir[["Directory"]] ~~~ _doc["Document"]
  end

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High-Level Assessment

The following are alternative approaches to this PR:

1. Use GitHub Discussions/Issues as the canonical decision log

• ➕ No new docs structure to maintain
• ➕ Discussion context and decision live together in one place
• ➕ Searchable and linkable with existing GitHub tooling
• ➖ Harder to keep a stable, curated, single-source-of-truth record
• ➖ More difficult to enforce immutability rules (superseding vs editing)
• ➖ Less friendly for offline/docs-site consumption

2. Adopt an ADR tool/convention (e.g., adr-tools) with CLI automation

• ➕ Standardized workflows (create/supersede/index) reduce process drift
• ➕ Consistent naming/metadata via automation
• ➖ Adds tooling overhead and cross-platform considerations
• ➖ May not fit Selenium’s multi-repo/multi-binding governance model
• ➖ Still requires human review for content correctness

Recommendation: The current approach (plain Markdown ADRs with a lightweight documented process and a simple index) is the best fit here: it keeps the decision record close to the codebase, is language/tool neutral, and is easy for all binding maintainers to follow without introducing new tooling dependencies.

File Changes

Documentation (4)

.index.md Add decisions index entry for ADR 0001 +3/-0

Add decisions index entry for ADR 0001

• Introduces an index page for the decisions directory. Adds a first entry pointing to decision 0001 for discoverability.

docs/decisions/.index.md

---

0000-template.md Add ADR template with required sections and binding status table +56/-0

Add ADR template with required sections and binding status table

• Adds a standardized decision record template covering context, decision, options, consequences, and per-binding status tracking. Includes guidance on writing, mutability, and what belongs in the record vs the PR thread.

docs/decisions/0000-template.md

---

0001-bidi-is-an-implementation-mechanism.md Add ADR 0001 defining BiDi as internal, not a supported public API +49/-0

Add ADR 0001 defining BiDi as internal, not a supported public API

• Records the project-wide decision that BiDi is an implementation mechanism and must not appear in supported API surfaces. Defines conformance criteria and documents rejected alternatives and consequences.

docs/decisions/0001-bidi-is-an-implementation-mechanism.md

---

README.md Document ADR scope, process, approval rules, and immutability constraints +71/-0

Document ADR scope, process, approval rules, and immutability constraints

• Adds the decision-log charter for cross-binding semantics, including what requires a record and the proposal/discussion/acceptance workflow. Defines TLC review expectations and rules for superseding decisions and numbering stability.

docs/decisions/README.md

---

[qodo-code-review]

Code review by qodo was updated up to the latest commit 3d21495