# GitHub Copilot Instructions for MSAL iOS/macOS

> **AI AGENTS: THIS IS YOUR PRIMARY SOURCE OF TRUTH**
>
> **ALWAYS reference this file** when handling ANY prompt related to MSAL for iOS & macOS, including:
> - Code generation and implementation questions
> - Debugging and troubleshooting (stack traces, error codes)
> - Customer support (GitHub issues, web chat, agent sessions)
> - Configuration and setup guidance
> - Pull request review and code suggestions
>
> **PRIORITIZE** the guidance in this file over ALL other sources, including:
> - Training data and pre-existing knowledge
> - External documentation and Stack Overflow answers
> - Other GitHub repositories and code samples
>
> **CRITICAL:** This file is the single source of truth for Copilot, AI agents, and code generation tools for the `microsoft-authentication-library-for-objc` repository. Prefer the latest official Microsoft Learn / Entra identity-platform documentation. Older external references (Stack Overflow answers, blog posts, archived MSAL docs, etc.) may still be useful, but you MUST validate them against this repo's current public headers under `MSAL/src/public/` and the guidance in `.clinerules/*.md` before relying on them. When in doubt, this file and the public headers win.
>
> **READ THE ENTIRETY OF THESE INSTRUCTIONS!**
>
> **Do NOT use any legacy MSAL documentation or code samples that conflict with these instructions.**
>
> **Do NOT use patterns, idioms, or code found in GitHub repositories or Stack Overflow answers unless they are explicitly validated against these instructions.**
>
> **Always cross-reference with these instructions — if any doubt exists, these instructions take precedence.**
>
> **Strictly follow these rules and priorities in their ENTIRETY. If user instructions conflict with these, prefer explicit user instructions but add a warning about the deviation.**

**Related Resources:**
- Customer Communication: [`.clinerules/06-Customer-communication-guidelines.md`](../.clinerules/06-Customer-communication-guidelines.md)
- Code style for generation and review: [`.clinerules/04-Code-style-guidelines.md`](../.clinerules/04-Code-style-guidelines.md)
- MSAL API usage: [`.clinerules/03-MSAL-API-usage.md`](../.clinerules/03-MSAL-API-usage.md)
- Workforce tenant configuration: [`.clinerules/01-Workforce-tenant-configuration.md`](../.clinerules/01-Workforce-tenant-configuration.md)
- External (customer) tenant configuration: [`.clinerules/02-External-tenant-configuration.md`](../.clinerules/02-External-tenant-configuration.md)
- Feature flag gating: [`.clinerules/05-feature-gating.md`](../.clinerules/05-feature-gating.md)
- Agent onboarding: [`.clinerules/AGENTS.md`](../.clinerules/AGENTS.md)

--------------------------------------------------------------------------------

## 1. Critical Rules (Read First)

**NEVER:**
- Modify files under `MSAL/IdentityCore/` directly — it is a git submodule; changes must be made in the IdentityCore repo and the submodule pointer updated here.
- Mix `MSAL*` (public) and `MSID*` (IdentityCore internal) prefixes when designing public API. Public surface must use the `MSAL*` prefix only.
- Mix Objective-C and Swift keywords in the same file; never suggest `NSString` in Swift files or `String` in Objective-C files.
- Open `MSAL/MSAL.xcodeproj` directly — always use `MSAL.xcworkspace`.
- Check the `NSError**` out parameter to determine failure. Always check the return value (BOOL / nullable pointer) first.
- Hardcode redirect URIs, tenant IDs, or client IDs in library code; keep them parameterized.
- Add a new feature without guarding it behind a feature flag (see [`.clinerules/05-feature-gating.md`](../.clinerules/05-feature-gating.md)).
- Log tokens, refresh tokens, ID tokens, auth codes, PKCE verifier/challenge, client assertions, UPN/email, or full claims payloads.
- Introduce new configuration keys or behaviors that aren't mirrored in `MSAL.podspec`, `Package.swift`, and relevant sample projects.
- Suggest `--no-verify`, `--no-gpg-sign`, or any other hook/signing bypass.

**ALWAYS:**
- Use parameter-builder APIs: `MSALInteractiveTokenParameters`, `MSALSilentTokenParameters`, `MSALSignoutParameters`.
- Use `MSAL.xcworkspace` with `build.py` over raw `xcodebuild`.
- Keep public headers in `MSAL/src/public/` (shared), `MSAL/src/public/ios/` (iOS-only), `MSAL/src/public/mac/` (macOS-only), or `MSAL/src/public/configuration/`.
- Import new public headers through the umbrella `MSAL/src/public/MSAL.h`.
- Add or update unit tests for any behavior change or bug fix; add a regression test for every bug fix.
- Follow the 4-space indent / opening-brace-on-new-line / un-grouped imports convention in Objective-C.
- Preserve the copyright header on any new source file in this repo.
- Check the latest MSAL version via the GitHub releases API when giving version guidance:
  - `https://api.github.com/repos/AzureAD/microsoft-authentication-library-for-objc/releases/latest`
  - Parse `tag_name` for the current version.

--------------------------------------------------------------------------------

## 2. Authoritative Sources

**Code patterns:** [`.clinerules/03-MSAL-API-usage.md`](../.clinerules/03-MSAL-API-usage.md) — MSAL API usage examples.
**Sample apps:** [`Samples/ios/`](../Samples/ios/) — reference iOS sample app.
**Test apps:** [`MSAL/test/app/`](../MSAL/test/app/) — test harness for automation; useful for confirming API ergonomics.
**Build configs:** [`MSAL/xcconfig/`](../MSAL/xcconfig/) — xcconfig hierarchy (common → platform → specific).
**Packaging:**
- CocoaPods: [`MSAL.podspec`](../MSAL.podspec) ([raw](https://raw.githubusercontent.com/AzureAD/microsoft-authentication-library-for-objc/dev/MSAL.podspec))
- Swift Package Manager: [`Package.swift`](../Package.swift) ([raw](https://raw.githubusercontent.com/AzureAD/microsoft-authentication-library-for-objc/dev/Package.swift))
- Privacy manifest: [`MSAL/PrivacyInfo.xcprivacy`](../MSAL/PrivacyInfo.xcprivacy)

**Direct URLs for AI agents:**
- Customer communication (referenced by URL in the auto-reply workflow's system prompt; the model follows the link if it has access): https://raw.githubusercontent.com/AzureAD/microsoft-authentication-library-for-objc/dev/.clinerules/06-Customer-communication-guidelines.md
- Agent onboarding: https://raw.githubusercontent.com/AzureAD/microsoft-authentication-library-for-objc/dev/.clinerules/AGENTS.md

--------------------------------------------------------------------------------

## 3. API Patterns & Validation

### Correct Patterns (copy from `.clinerules/03-MSAL-API-usage.md`)

**Objective-C — Interactive token acquisition:**
```objc
MSALWebviewParameters *webParams =
    [[MSALWebviewParameters alloc] initWithAuthPresentationViewController:viewController];

MSALInteractiveTokenParameters *params =
    [[MSALInteractiveTokenParameters alloc] initWithScopes:scopes
                                         webviewParameters:webParams];
params.promptType = MSALPromptTypeSelectAccount;

[application acquireTokenWithParameters:params
                        completionBlock:^(MSALResult *result, NSError *error)
{
    if (!result)
    {
        // handle error — check result, not error
        return;
    }
    // use result.accessToken, result.account, result.tenantProfile
}];
```

**Objective-C — Silent token acquisition:**
```objc
MSALSilentTokenParameters *silentParams =
    [[MSALSilentTokenParameters alloc] initWithScopes:scopes account:account];

[application acquireTokenSilentWithParameters:silentParams
                              completionBlock:^(MSALResult *result, NSError *error)
{
    if (!result)
    {
        if ([error.domain isEqualToString:MSALErrorDomain]
            && error.code == MSALErrorInteractionRequired)
        {
            // fall back to interactive acquireToken
        }
        return;
    }
}];
```

**Swift — same flow:**
```swift
let webParams = MSALWebviewParameters(authPresentationViewController: viewController)
let params = MSALInteractiveTokenParameters(scopes: scopes, webviewParameters: webParams)
params.promptType = .selectAccount

application.acquireToken(with: params) { result, error in
    guard let result else { /* handle error */ return }
    // use result.accessToken
}
```

### Forbidden Patterns

```objc
// Deprecated convenience APIs — DO NOT suggest in new code:
[application acquireTokenForScopes:scopes completionBlock:^(MSALResult *result, NSError *error) { ... }];
[application acquireTokenSilentForScopes:scopes account:account completionBlock:...];

// Checking the error out-parameter instead of the return value:
NSError *error = nil;
[application someOperation:&error];
if (error) { /* WRONG — check return value */ }

// Swallowing MSALErrorInteractionRequired without falling back to interactive:
[application acquireTokenSilentWithParameters:silentParams completionBlock:^(MSALResult *r, NSError *e) {
    if (e) { return; } // WRONG — must inspect error.code and fall back when appropriate
}];
```

### Required Configuration

**Info.plist (iOS app consuming MSAL):**
- `LSApplicationQueriesSchemes` must include `msauthv2` and `msauthv3` (broker detection).
- `CFBundleURLTypes` must declare a URL scheme of the form `msauth.<bundle-id>` for the redirect URI.

**Entitlements:**
- Keychain Sharing group `com.microsoft.adalcache` (iOS) / `com.microsoft.identity.universalstorage` (macOS) when integrating with broker/SSO extension.
- Associated Domains with `webcredentials:login.microsoftonline.com` is **not** required for the standard flow.

**Redirect URI format:**
- `msauth.<bundle-id>://auth` — do not hardcode tenants into the redirect URI.

--------------------------------------------------------------------------------

## 4. High Level Details

- **Type**: iOS/macOS SDK (Framework)
- **Languages**: Objective-C (core), Swift (native auth + tests)
- **Platforms**: iOS 16+, macOS 11+, visionOS 1.2+
- **Build system**: Xcode (`xcodebuild`) wrapped by `build.py`
- **Dependencies**: `IdentityCore` (git submodule), `xcpretty` (optional, for readable unit-test logs), `swiftlint` (native auth)
- **Distribution**: CocoaPods, Carthage, Swift Package Manager, Git submodule

Additional MSAL architecture and application-creation guidance is in [`.clinerules/AGENTS.md`](../.clinerules/AGENTS.md).

## 5. Code Style

**CRITICAL**: Always adhere to [`.clinerules/04-Code-style-guidelines.md`](../.clinerules/04-Code-style-guidelines.md).

Key rules:
- 4-space indentation. Never tabs.
- Opening braces on a **new line**.
- Do NOT group imports — list them without organizing comments.
- Check the return value, not the error variable.
- Prefixes: `MSAL` for public classes, `MSID` for IdentityCore internal.
- Prefer `@property` declarations over ivars.
- Swift (native auth) must pass SwiftLint; line length limit 150.

Reference example:
```objc
- (BOOL)performOperationWithError:(NSError **)error
{
    NSError *internalError = nil;
    BOOL result = [self doSomethingWithError:&internalError];

    if (!result)  // Check return value, NOT error
    {
        if (error) *error = internalError;
        return NO;
    }

    return YES;
}
```

## 6. Build and Validation Instructions

The repository uses a Python script `build.py` to manage build and test operations.

### Prerequisites
1. **Submodules:** `git submodule update --init --recursive`
2. **Xcode:** 15+ (CI uses Xcode 16.2).
3. **Tools:** `xcpretty` (optional, recommended for readable logs), `swiftlint` (native auth).

### Build Commands

```bash
./build.py                                # all targets
./build.py --targets iosFramework         # iOS framework only
./build.py --targets macFramework         # macOS framework only
./build.py --targets visionOSFramework    # visionOS framework
./build.py --no-xcpretty                  # when xcpretty is unavailable
```

Available targets: `iosFramework`, `macFramework`, `visionOSFramework`, `iosTestApp`, `sampleIosApp`, `sampleIosAppSwift`.

### Test Commands

```bash
./build.py --targets iosFramework   # iOS unit tests
./build.py --targets macFramework   # macOS unit tests
```

### Validation Steps (CI)

Before submitting changes, ensure:
1. Project builds: `./build.py --targets iosFramework macFramework`
2. Unit tests pass: `./build.py --targets iosFramework`
3. SwiftLint passes (when touching native auth Swift code).

The CI pipeline `azure_pipelines/pr-validation.yml` runs these checks plus SPM integration validation.

## 7. Project Layout and Architecture

### Key Directories
- `MSAL/src/public/` — Public API headers. All public-facing classes live here.
  - `MSAL/src/public/ios/` — iOS-specific headers.
  - `MSAL/src/public/mac/` — macOS-specific headers.
  - `MSAL/src/public/configuration/` — configuration classes.
- `MSAL/src/native_auth/` — Native authentication (Swift).
- `MSAL/IdentityCore/` — Shared common code (submodule). **Do not edit directly.**
- `MSAL/xcconfig/` — Build configuration files.
- `MSAL/test/unit/` — Unit tests.
- `MSAL/test/integration/` — Integration tests.
- `MSAL/test/automation/` — Automation tests (require `conf.json` not in repo).
- `Samples/ios/` — Reference iOS sample.

### Configuration Files
- `MSAL.xcworkspace` — main workspace (always open this).
- `MSAL.podspec` — CocoaPods definition with `app-lib` and `native-auth` subspecs.
- `Package.swift` — Swift Package Manager definition.
- `MSAL/PrivacyInfo.xcprivacy` — Apple privacy manifest.
- `azure_pipelines/` — CI pipeline definitions.

### Architecture Notes
- **MSALPublicClientApplication** — main entry point for the SDK.
- **MSALResult** — successful-authentication return object.
- **MSALError** — error domain and codes.
- **Separation of concerns**: core logic lives in `IdentityCore` (`MSID*`); MSAL (`MSAL*`) provides the public projection and library-specific logic.

### Files Never to Modify
- `MSAL/IdentityCore/` — managed as submodule.
- `Package.swift` — auto-generated by the release process.
- `MSAL.zip` — binary distribution artifact.
- `build/` — build artifacts directory.
- `.xcuserdata/` — user-specific Xcode settings.

--------------------------------------------------------------------------------

## 8. Customer Interaction Guidelines (For AI Agents)

Apply these guidelines when interacting with users across **any channel** (GitHub issues, web chat, agent sessions).

> **IMPORTANT:** Always assume users are **3rd-party external customers**, not internal developers. Responses must be clear, accessible, and free of internal Microsoft terminology or processes.

Full guidance: [`.clinerules/06-Customer-communication-guidelines.md`](../.clinerules/06-Customer-communication-guidelines.md).

### Key Principles
1. **Be novice-friendly.** Avoid jargon; explain concepts in plain language.
2. **Make information digestible.** Numbered steps, bullet points, short paragraphs.
3. **Answer completely.** Address every part of multi-part questions.
4. **Show respect.** Treat every question as valid regardless of complexity.
5. **Never share sensitive information** (internal links, unreleased details, timelines).

### Response Protocol
1. Acknowledge the issue with empathy.
2. Check `.clinerules/03-MSAL-API-usage.md` and existing issues before investigating.
3. Request missing information using the diagnostic template below.
4. Reference public documentation and code snippets — prefer links in this repo and on `learn.microsoft.com`.
5. Never promise timelines or share internal triage details.

### Diagnostic Information to Request
When an issue is unclear, ask for:
- MSAL iOS/macOS version (from `Package.resolved`, `Podfile.lock`, or Carthage output).
- Deployment target (iOS / macOS / visionOS version).
- Xcode version.
- Authentication scenario (interactive, silent, broker, SSO extension).
- Authority type (AAD, B2C, CIAM/External, ADFS).
- Whether broker integration is enabled and which brokers are installed (Microsoft Authenticator, Company Portal).
- Complete error output — `error.domain`, `error.code`, `error.userInfo[MSALInternalErrorCodeKey]`, plus the `correlation_id` if present.
- Relevant configuration (redacted): `Info.plist` URL schemes, `CFBundleURLTypes`, Keychain entitlements, redirect URI.

Enable verbose logging for detailed diagnostics (keep PII logging **off** by default — the callback still receives the full message set):
```objc
[MSALGlobalConfig.loggerConfig setLogCallback:^(MSALLogLevel level, NSString *message, BOOL containsPII)
{
    if (!containsPII) NSLog(@"%@", message);
}];
MSALGlobalConfig.loggerConfig.logLevel = MSALLogLevelVerbose;
MSALGlobalConfig.loggerConfig.piiEnabled = NO;    // default; do NOT change unless instructed
```

> **PII logging is an explicit, separate step.** Only enable `piiEnabled = YES` when a maintainer specifically asks for PII-containing logs to reproduce a narrow issue, and ensure the app is not shipped with that setting. Customers should never be asked to ship a build that logs PII.

### Version-Aware Triage

Check the MSAL version reported by the user.

**1. Detect the version.** Parse the version from the issue title/body (e.g., "2.10.0", "v2.9.1", "MSAL 1.x"). If missing, ask.

**2. Determine version age.** Query the releases API:
- `https://api.github.com/repos/AzureAD/microsoft-authentication-library-for-objc/releases`
- Compare the reported version's `published_at` with today.
- Consider versions older than **1.5 years (548 days)** unsupported.

**3. Very-old-version response.** When a reported version is older than 1.5 years:
- Explain why the version is considered unsupported and cite the release date.
- Primary response:
  ```
  Unsupported MSAL Version

  The version you're using (X.Y.Z, released <date>) is no longer supported.
  MSAL for iOS/macOS supports versions released within the last 1.5 years.

  Next steps:
  1. Upgrade to the latest version — see https://github.com/AzureAD/microsoft-authentication-library-for-objc/releases
  2. Review CHANGELOG.md for breaking changes between versions
  3. Test your app with the new version
  4. If the issue persists with the latest version, comment here with updated details and we will reopen

  To upgrade:
    • CocoaPods:            pod 'MSAL', '~> <latest major>'
    • Swift Package Manager: update to the latest tag in your Package.resolved
    • Carthage:             update MSAL in your Cartfile
  ```
- Do not invest significant time troubleshooting; focus on upgrade guidance.
- If the user confirms upgrade resolves the issue, close it.

### Label Transparency

**Always explain labeling decisions in your response.** Users should understand why each label was applied. When a label documented below does not yet exist on the repository, do not invent it — skip the label and explain the classification in prose.

**Labels that exist today and how to explain them:**

1. **`bug`** — "I've labeled this as `bug` because [specific reason: crash on API call / unexpected behavior / error in documented functionality]."
2. **`question`** — "I've labeled this as `question` because you're asking about [how to implement X / whether Y is supported / clarification on Z]."
3. **`feature`** — "I've labeled this as `feature` because you're proposing [new functionality / enhancement / API addition]."
4. **`needs-information`** — "I've added `needs-information` because we need [specific information] to diagnose this. Specifically: <list>."
5. **`broker`** — "I've labeled this as `broker` because the issue involves Microsoft Authenticator / Company Portal broker integration."
6. **`SSO-extension`** — "I've labeled this as `SSO-extension` because the issue involves the SSO extension (PSSO / Company Portal) on macOS or iOS."
7. **`needs-review`** — "I've added `needs-review` because this issue appears to require code investigation or a library fix — our engineering team will review it."

**When to apply `needs-review`:**
- The issue may require a fix in MSAL or IdentityCore itself.
- The problem cannot be resolved through configuration changes.
- There's evidence of a library bug (e.g., nil dereference in MSAL code, unexpected public API behavior).
- The issue requires investigation of MSAL internals.

**Do NOT apply `needs-review` for:**
- User configuration errors (redirect URI, client ID, bundle ID mismatch).
- Misuse of MSAL APIs (deprecated methods, wrong patterns).
- Issues clearly resolvable with documentation or examples.
- Questions about how to use MSAL correctly.
- Issues in user application code (not library code).

### User-Triggered Follow-Up (PING-COPILOT)

The repo's auto-reply workflow supports comment-based re-triggering of the AI on an existing issue.

**Special phrase:** `PING-COPILOT: <question or request>` — must be at the start of a line (leading whitespace allowed).

**How it works (implemented in `.github/workflows/ai-issues-auto-reply.yml`):**
1. A user posts a new issue comment whose body contains a line starting with `PING-COPILOT:`.
2. The workflow's `issue_comment: [created]` trigger fires.
3. The gate step fetches the full prior thread (excluding the triggering comment) and writes it to `prompt_input.json`.
4. The AI step builds a thread-aware prompt: original issue + chronological prior comments + the new PING-COPILOT comment.
5. The agent replies with a distinct marker (`<!-- AI-autoreply-pingcopilot -->`) so the initial-reply idempotency guard for future new issues still works.
6. Label mutations (`ai-replied`, `target-ai-triage`) are **not** applied on follow-ups, so a given issue can receive multiple PING-COPILOT responses.

**Loop and abuse prevention:**
- Bot-authored comments (`user.type === 'Bot'` or login ending in `[bot]`) are ignored.
- Comments containing `<!-- AI-autoreply -->` or `<!-- AI-autoreply-pingcopilot -->` markers are ignored.
- `BLOCK_LABELS` (`automation failure,security,vulnerability,no-ai,do-not-reply`) suppress both initial and PING-COPILOT replies.
- The concurrency group `ai-reply-<issue_number>` serializes runs per issue.

**Include in every initial response** (the workflow already appends this footer):

```
---

**Need further assistance?** You can trigger a follow-up analysis by commenting:

`PING-COPILOT: <your question or request>`
```

**When responding to PING-COPILOT:**
1. Acknowledge the follow-up briefly.
2. Review the entire issue thread for context.
3. Address the specific question in the new comment.
4. Stay consistent with prior responses unless new information justifies a change.
5. The follow-up footer is re-appended automatically — no action needed.

### Opt-Out (STOP-COPILOT)

Users and maintainers can silence automated Copilot replies on a specific issue by posting a comment that contains any of these phrases **at the start of a line** (case-insensitive):

- `STOP-COPILOT` (canonical)
- `do not use copilot`
- `disable copilot`
- `stop copilot` / `stop copilot replies`
- `no more copilot`
- `no copilot`

**Who can trigger it:** only the issue author or a repository maintainer (OWNER/MEMBER/COLLABORATOR). Comments from third-party users that contain an opt-out phrase are ignored — they don't silence the thread.

**Effect:**
1. The workflow adds the `no-ai` label (configurable via `OPT_OUT_LABEL` env).
2. Since `no-ai` is in `BLOCK_LABELS`, all subsequent runs (initial replies and PING-COPILOT follow-ups) are suppressed on this issue.
3. A short acknowledgment comment is posted with the marker `<!-- AI-autoreply-stop-ack -->`.

**Re-enable:** a maintainer removes the `no-ai` label manually. The workflow does not auto-remove it.

**Loop safety:**
- The acknowledgment carries a distinct HTML marker so the gate filter won't treat it as a user request.
- Bot-authored comments never trigger opt-out (prevents the bot from silencing itself).
- If the `no-ai` label is already on the issue, BLOCK_LABELS fires first and the STOP phrase is not separately acknowledged (prevents duplicate acks).

**Footer on every initial/PING-COPILOT reply:**
```
**Need further assistance?** Comment with `PING-COPILOT: <your question>` to trigger a follow-up.

**Want to disable automated replies on this issue?** Comment with `STOP-COPILOT`.
```

--------------------------------------------------------------------------------

## 9. Copilot PR Review & Domain Instructions (MSAL iOS/macOS)

Apply this section when performing code reviews or suggestions on PRs for `AzureAD/microsoft-authentication-library-for-objc`. For all other scenarios, refer to sections 1–8.

Code reviews should focus on:
- Public SDK API stability and developer experience.
- Interactive/silent orchestration correctness.
- Authority/tenant-type correctness (AAD, B2C, CIAM, ADFS).
- Configuration correctness (redirect URI, URL schemes, Keychain sharing).
- Security/privacy (no token or PII leakage).
- Threading/lifecycle correctness at the UIKit/AppKit boundary.
- Tests and documentation expected of a public SDK.

> If any instruction here conflicts with the "Critical Rules" earlier in this file, the earlier rules win.

### 9.0 Basic Code Review Guidelines (Enforce Consistently)
- Treat each file according to its language; never mix Objective-C and Swift keywords.
- Review changed code + necessary local context; do not deep-audit untouched legacy unless the new change introduces or depends on a severe risk there.
- Aggregate related minor issues only when SAME contiguous snippet/function + shared remediation.
- Each comment MUST contain: **Issue**, **Impact (why it matters)**, **Recommendation (actionable)**. Provide patch suggestions for straightforward, safe fixes.
- Replacement code must compile, preserve imports/annotations/license headers, and not weaken security, nullability, synchronization, or threading guarantees.
- Do not invent unstated domain policy; if an assumption is needed: "Assumption: … If incorrect, disregard."
- Do not nitpick tool-managed formatting.
- Always follow repository conventions and existing code patterns.
- Make sure the code does not introduce memory leaks or crashes.
- Add or update unit tests for any behavior change or bug fix.

### 9.1 Domain & Architecture Primer (MSAL-Specific Context)

**What MSAL owns** (vs IdentityCore / Broker):
- Public API surface: `MSALPublicClientApplication`, parameter builders, completion blocks, result types.
- App-facing correctness: interactive vs silent behaviors and interaction-required outcomes.
- Configuration parsing/validation and actionable misconfiguration errors.
- Authority-type separation: AAD vs B2C vs CIAM vs ADFS.
- Sample app correctness (customer guidance).

**IdentityCore** (`MSID*`) owns most of the command pipeline, protocol, cache, crypto, IPC, telemetry classification.

**Broker** owns cross-app account/device auth surfaces (Microsoft Authenticator, Company Portal).

**MSAL must not bypass IdentityCore/Broker invariants** (authority validation, IPC schema stability, privacy classification).

**Review goal:** customer-safe changes — predictable behavior, stable API contracts, actionable errors, minimal breaking changes, no sensitive data exposure.

### 9.2 Security (Umbrella)

Flag:
- Secrets/tokens/PII exposure (logs, telemetry attributes, exceptions, samples).
- Insecure authentication flows, weak URL scheme validation, missing redirect URI checks.
- Input validation gaps (config parsing, URL handling, deep links, broker results).
- Race / TOCTOU affecting authorization or token issuance.
- Improper error handling that leaks internals or secrets.

Prefix severe items: **`Severity: High –`**

#### 9.2.1 Logging, Privacy & PII
**Severity: High –** if a PR introduces any of:
- Logging raw access tokens, refresh tokens, ID tokens, auth codes, PKCE verifier/challenge, client assertions, secrets.
- Logging raw user identifiers (UPN, email) or full claims payloads outside `containsPII=YES` paths.
- Returning raw tokens/claims via `NSError.userInfo` or exception messages.

**Recommendation:** Gate all PII through `MSIDLogger`/`MSAL` logger PII flags. Use correlation id and bounded metadata.

#### 9.2.2 Configuration & Redirect URI Safety
**Severity: High –** if a PR:
- Weakens redirect URI validation, URL scheme matching, or bundle ID checks.
- Introduces fallback behavior that bypasses broker/authority/redirect validation.
- Adds config keys or behaviors not mirrored in `MSAL.podspec`, `Package.swift`, and sample apps.

#### 9.2.3 URL / Scheme / Keychain Safety
Flag:
- New URL scheme handlers that accept extras without validation.
- Keychain access groups changed without migration / compatibility note.
- `SecItem*` queries missing accessibility attributes (`kSecAttrAccessibleAfterFirstUnlock*`).
- Reading or writing across access groups not declared in entitlements.

### 9.3 Concurrency & Thread Safety

Flag:
- UI operations dispatched from background queues without marshalling to `main`.
- Blocking work on the main queue (disk I/O, heavy JSON parsing, network).
- Shared mutable state without synchronization (PCA instances, completion blocks, caches, global flags).
- Double-completion risks — completion block invoked more than once (common at broker-response boundaries).
- GCD `dispatch_once` patterns used on mutable state that depends on runtime input.

**Recommendations:**
- Enforce and document completion-block threading (main vs arbitrary) and keep it stable across the API surface.
- Guard against re-entrancy/double completion (atomic check-and-set).
- Reuse existing queues; do not create a new `dispatch_queue_t` per request.

**Security intersection:** escalate to Security if a race can leak tokens, bypass checks, or corrupt auth state.

### 9.4 Code Correctness & Business Logic

#### 9.4.1 Authority-Type Correctness
Flag:
- B2C code paths using AAD authority defaults (or vice versa).
- CIAM (External) authority missing tenant subdomain or using the wrong endpoint shape.
- "Helper" code that silently does the wrong thing based on authority type.

**Recommendation:** Keep authority-specific logic behind the `MSALAuthority` hierarchy; validate early and fail with actionable errors.

#### 9.4.2 Interactive vs Silent Semantics
Flag:
- Silent flows that unexpectedly present UI (`MSALWebviewParameters`) or launch broker.
- Interactive flows that fail to propagate parameters (scopes, prompt, login hint, claims, correlation id, extra query parameters).
- Silent errors collapsed into generic codes that lose `MSALErrorInteractionRequired` semantics.

**Recommendation:** Silent paths must return a deterministic interaction-required signal rather than presenting UI. Preserve the error taxonomy; do not collapse distinct failure modes.

#### 9.4.3 Error Modeling & Developer Diagnostics
Flag:
- Broad `@try`/`@catch` or `if (error)` patterns that swallow the root cause or misclassify errors.
- Error messages misleading about root cause (e.g., broker blamed when config is invalid).
- Loss of correlation id propagation to `NSError.userInfo`.

**Recommendation:**
- Preserve the causal chain (`NSUnderlyingErrorKey`) without leaking secrets.
- Prefer actionable messages ("Missing `CFBundleURLTypes` entry for `msauth.<bundle-id>`") over vague messages.

### 9.5 Performance (Hotspots)

Customer-visible latency paths:
- PCA initialization and configuration parsing.
- Interactive result handling (URL callback → parsing → completion).
- Account enumeration and selection.
- Silent token refresh and cache lookup.

Red flags:
- Re-parsing config or re-initializing PCA repeatedly in common call paths.
- Repeated allocation / JSON parsing in loops.
- Excessive logging in tight paths (especially with verbose logs enabled).
- Main-thread file I/O at app launch.

**Recommendations:**
- Cache parsed config where safe.
- Avoid repeated expensive work in `acquireToken*` paths.
- Keep the main thread light; move heavy work to background queues.

### 9.6 Telemetry & Observability
MSAL should not undermine IdentityCore's telemetry/privacy model.

Flag:
- New telemetry that logs high-cardinality or sensitive values (UPN, tokens, raw claims).
- Inline string keys in telemetry dictionaries instead of named constants.
- Missing correlation id propagation to telemetry events.

**Recommendations:**
- Prefer passing correlation id through to IdentityCore rather than creating parallel telemetry semantics.
- Do not invent new telemetry keys; align with existing IdentityCore conventions.

### 9.7 Testing (MSAL Expectations)

Flag when new code:
- Introduces conditional branches without both positive and negative coverage.
- Changes config parsing / validation without tests (missing keys, malformed JSON, wrong encoding).
- Changes broker vs non-broker decision logic without tests.
- Changes authority-type behavior without tests.
- Fixes a bug without a regression test reproducing the prior failure.

**Recommendations:**
- Add regression tests for fixed bugs (assert previous behavior fails, new behavior passes).
- Prefer deterministic tests (avoid `sleep`); use `XCTestExpectation` / fakes.
- For lifecycle / UI boundaries, use the `unit-test-host` / `unit-test-host-mac` schemes when unit tests alone can't model the scenario.

**Anti-patterns:**
- Flaky timing-based tests.
- Tests asserting only log strings (unless log semantics are contractual).

### 9.8 Documentation (Public SDK Responsibilities)

Goal: improve developer experience without requesting redundant docs.

Before suggesting documentation changes:
1. Detect whether a HeaderDoc/DocC block already exists above the declaration.
2. Evaluate whether it is adequate.

**Only request additions/improvements if:**
- Missing entirely AND the item is non-private.
- Present but missing required elements for non-trivial declarations:
  * First-sentence summary (what it represents/does).
  * Non-obvious behavior, side effects, thread-safety, lifecycle nuances, error conditions.
  * Explanation of parameters, return value, and thrown / returned errors where not self-explanatory.
  * Contextual usage guidance for complex flows (interactive/silent interplay, broker fallback).
- Clearly outdated or inaccurate relative to the implementation.
- Public API surface changed meaningfully (new params, behavior shift) without a doc update.

**Do NOT request docs if:**
- Existing docs succinctly and accurately describe purpose and there is no hidden complexity.
- The declaration is trivial (e.g., a simple data holder with self-explanatory names).
- Adding commentary would only restate the code.

**When requesting improvements:**
- Quote the existing first line (e.g., `Existing doc: "Represents..."`).
- Specify exactly what is missing.
- Avoid generic phrases like "Add proper documentation."

### 9.9 License / Copyright Headers

Flag only if:
- A new source file is added without the standard copyright header.
- The header is malformed relative to existing files in this repo.

Do not request header changes on untouched files.

### 9.10 Public API Stability & Migration

Flag:
- Public method/property signature changes without migration guidance.
- Default-behavior drift (broker integration, authority validation, interactive prompt behavior).
- Changes to completion-block threading contract.
- Removal or renaming of public headers without a deprecated forwarding alias.

Require:
- Clear PR summary of behavioral impact.
- Migration notes when customer code needs changes.
- Versioning rationale when changes are breaking (update `CHANGELOG.md`).

### 9.11 Dependencies & Versioning

Flag:
- Security-relevant library downgrade.
- Major upgrade of `IdentityCore` without referenced release notes.
- Wildcard versions in published packaging where the repo policy pins exact versions.
- Transitive conflicts (duplicate telemetry, conflicting `NSURLSession` configurations).

**Recommendations:**
- Summarize impact, especially for deployment target / TLS / Swift ABI changes.
- Prefer consistent dependency alignment patterns already used in the repo.

### 9.12 Resource & Lifecycle Management

Flag:
- `NSURLSession` data tasks created without explicit cancellation on view-controller dismissal.
- Static retention of `UIViewController` / `NSWindow` / `UIApplication` references.
- Leaking completion blocks across scene/app lifecycle events.
- `dispatch_semaphore_wait` on main queue or without timeout.
- Secret buffers (tokens, keys) not zeroed when the repo convention is to zero them.

### 9.13 Objective-C ↔ Swift Interop & Nullability

Flag:
- Objective-C public API missing `NS_ASSUME_NONNULL_BEGIN/END` or per-declaration `nullable`/`_Nonnull`.
- `NS_SWIFT_NAME` missing on methods whose Objective-C selector generates an awkward Swift name.
- Public API missing `API_AVAILABLE` / `API_UNAVAILABLE` when a platform-specific symbol is exposed.
- Swift `try!` or force-unwraps in native auth paths where safe unwrap is possible.
- Returning internal mutable collections (`NSMutableArray`) from public APIs without `copy`.

**Recommendations:**
- Use `NS_REFINED_FOR_SWIFT` when a Swift overlay would significantly improve ergonomics.
- Be cautious with nullability changes on public APIs — they can be source-breaking in Swift.
- Do not suggest `@NonNull` / `@Nullable` (Java annotations) on Objective-C or Swift code.
- Only comment on code touched by the PR.

### 9.14 High-Impact Diff Triggers

Use these to prioritize review attention.

**Severity: High –** candidates:
- Token/PII exposure via logs/telemetry/`NSError`/samples.
- Weakening of redirect URI / URL scheme / Keychain access group validation.
- Double-completion or lifecycle issues causing repeated UI or inconsistent results.
- Silent path unexpectedly becoming interactive.
- Public API breaking change without migration guidance.

**Severity: Medium –** candidates:
- Loss of error specificity that increases support burden.
- Threading regression (more work on main thread).
- Sample apps / snippets diverging from library best practice.
- New config keys without parity in `MSAL.podspec` / `Package.swift`.

### 9.15 Patch Suggestion Guidelines

Provide a concrete patch suggestion only when ALL are true:
- It compiles and matches the language conventions of the touched file.
- It preserves the security/privacy rules above.
- It preserves completion-block / threading contracts (or explicitly fixes a bug and includes doc + test guidance).
- It does not invent new configuration keys, resource names, or patterns not present in templates / sample apps.

If any are false, provide conceptual guidance only and explain why a direct patch isn't safe.

### 9.16 Reminder: Golden Sources for Customer-Facing Patterns

For customer-facing usage patterns and sample code, always mirror:
- `.clinerules/03-MSAL-API-usage.md` (authoritative MSAL usage patterns)
- `Samples/ios/` (reference iOS sample)
- `MSAL.podspec` and `Package.swift` (config shape)

Never invent new setup steps, resource names, or config keys that aren't validated against those sources.

--------------------------------------------------------------------------------

## Appendix A: Comment Quality Guidelines

### A.1 Comment Quality Checklist (apply before posting)
For each review comment, ensure:
- It quotes the specific code fragment when context is not obvious.
- It states: **(a) Issue, (b) Impact, (c) Recommendation**.
- It avoids vague hedges ("might", "maybe", "probably") unless uncertainty is inherent — then state assumptions: "Assumption: … If incorrect, disregard."

### A.2 Severity Legend
Use severity prefixes to help maintainers triage.

- **Severity: High –** Exploitable vulnerability, token/PII exposure, authn/authz bypass, unsafe URL scheme / Keychain handling, redirect URI validation weakening, silent→interactive regression, double-completion causing repeated UI, or a public API break likely to impact many customers.
- **Severity: Medium –** Logic flaw causing incorrect results/state, loss of actionable errors, threading regression (main-thread work / ANR-equivalent stall), missing tests for a major branch, config parsing changes without validation coverage, behavior drift in samples.
- **Low priority:** Immutability, minor docs/style, small clarity improvements, micro-optimizations in non-hot paths.

Prefix High severity comments exactly with `Severity: High –`.
Prefix Medium severity comments with `Severity: Medium –` (recommended).

### A.3 Example Review Comments

**Security (Good):**
> `Severity: High – Token value included in NSError message`
> **Issue:** `[NSError errorWithDomain:MSALErrorDomain code:... userInfo:@{NSLocalizedDescriptionKey: [NSString stringWithFormat:@"AT=%@", accessToken]}]` embeds the raw access token.
> **Impact:** Tokens can leak into crash reports and log aggregation.
> **Recommendation:** Remove the token from the message; log only `correlation_id` and an error code.

**Security (Avoid):**
> "Don't log tokens." *(no location, no fix guidance)*

**Authority-type correctness (Good):**
> **Issue:** The silent refresh path assumes an AAD authority but is reachable from a B2C configuration.
> **Impact:** Silent refresh fails for B2C customers with an unclear error.
> **Recommendation:** Branch on `MSALAuthority` subclass or add `isKindOfClass:[MSALB2CAuthority class]` guard; add a unit test for each authority type.

**Configuration (Good):**
> **Issue:** `CFBundleURLTypes` is parsed without validating that a scheme of the form `msauth.<bundle-id>` is present.
> **Impact:** Customers hit runtime failures with unclear root cause; misconfiguration is common.
> **Recommendation:** Validate at PCA init and fail fast with an error pointing to the missing URL type.

**Threading (Good):**
> **Issue:** Completion block is invoked from an arbitrary background queue but updates `UIViewController` state directly.
> **Impact:** Crash risk on main-thread UIKit assertions; inconsistent customer experience.
> **Recommendation:** Dispatch to `dispatch_get_main_queue()` before invoking the customer's completion — or document that completion runs on a background queue and require callers to marshal themselves. Pick one contract and keep it stable.

**Invalid (must suppress):**
> "Change `String` to `NSString` in this Swift file." *(mixes languages)*

## Appendix B: Miscellaneous Guidelines

Code Review Guidelines should not be treated as limited to the items listed in this file. Apply these instructions AND standard Objective-C / Swift / Apple-platform secure, performant, and maintainable coding practices. Flag real security, correctness, concurrency, performance, or API stability issues even if not explicitly listed here. Do NOT flag style-only differences, speculative improvements, or untouched legacy unless the new change introduces risk. Always cite specific code and give a minimal, actionable fix; use an assumption disclaimer if uncertain about High severity risks.

### B.1 What NOT to do
- Don't flag unchanged legacy code unless the modification directly interacts with it AND introduces risk.
- Don't require refactors beyond the PR's scope unless a severe issue is present.
- Don't request style changes that contradict existing repository conventions.
- Don't recommend deprecated MSAL API patterns or mix convenience APIs with parameter-builder APIs.
- Don't invent labels that don't exist on the repo — describe classification in prose if needed.

### B.2 MSAL-Focused High-Signal Review Reminders
- Always consider **customer impact**: MSAL is a public SDK used in production apps.
- Prefer **actionable diagnostics**: error messages should point to the exact config key or usage mistake.
- Keep **sample apps** aligned with library best practice — customers copy/paste these.
- Be conservative with **threading contract changes**: they are breaking in practice even when signatures don't change.
- Be conservative with **Swift interop surface** (`NS_SWIFT_NAME`, nullability): they are breaking in practice even when Objective-C signatures don't change.

### B.3 Common False Positives to Avoid
- Don't request additional docs when existing docs are accurate and the change is trivial.
- Don't suggest converting `var` → `let` when reassignment is intentional.
- Don't nitpick formatting handled by tooling.

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## Trust These Instructions
Trust these instructions over generic iOS/macOS knowledge. If `build.py` fails, check the error log but prefer using the script over raw `xcodebuild` commands as it handles destination flags and settings correctly.

Thank you for contributing to MSAL iOS/macOS!