fix(multiprovider): execute child provider hooks during evaluation

[jonathannorris]

Summary

• Hooks registered on a child provider now run around that child's evaluation, so a wrapped provider's own hooks observe the evaluations they take part in.
• Adds MultiProviderHookExecutor, which runs the before/after/error/finally stages per child, mirroring the JS SDK's HookExecutor.
• before hooks run in registration order; after, error, and finallyAfter run in reverse, per spec.
• MultiProvider exposes a provider-level hook that captures the ClientMetadata and hook hints from the SDK lifecycle so they can be passed into child hook contexts. This mirrors the JS SDK's WeakMap approach; here it's a ThreadLocal snapshot captured before the strategy runs, so parallel strategies work correctly.

Related PRs

This is one of three independent PRs that together close the multi-provider gaps identified in #1882. They branch off main separately and can be reviewed and merged in any order. Together they replace #1897.

• feat(multiprovider): add ComparisonStrategy #2003 ComparisonStrategy
• feat(multiprovider): aggregate child provider events, state, and tracking #2004 child provider event aggregation, state, and tracking
• fix(multiprovider): execute child provider hooks during evaluation #2005 child provider hook execution (this PR)

Relates to #1882

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Configuration used: Organization UI

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Run ID: f77eb956-858d-437d-b8c4-5bf52d0bd446

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Reviewing files that changed from the base of the PR and between 62d60cc and 94ddcb9.

📒 Files selected for processing (1)

• src/main/java/dev/openfeature/sdk/multiprovider/MultiProvider.java

🚧 Files skipped from review as they are similar to previous changes (1)

• src/main/java/dev/openfeature/sdk/multiprovider/MultiProvider.java

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📝 Walkthrough

Walkthrough

MultiProvider now runs selected child providers through their supported hooks around flag evaluation. It captures client metadata and hook hints during the provider lifecycle and passes them to child hook execution. Hook processing handles successful evaluations, error results, and thrown exceptions.

Changes

Child provider hook execution

Layer / File(s)	Summary
Hook lifecycle execution src/main/java/dev/openfeature/sdk/MultiProviderHookExecutor.java, src/main/java/dev/openfeature/sdk/multiprovider/HookExecutionContext.java, src/test/java/dev/openfeature/sdk/MultiProviderHookExecutorTest.java	The executor bypasses hooks when none apply to the flag type. Otherwise, it runs hook stages around evaluation, handles errors and exceptions, and runs final callbacks. Tests cover stage order, context merging, metadata, hints, and error details.
MultiProvider hook context and child routing src/main/java/dev/openfeature/sdk/multiprovider/MultiProvider.java, src/test/java/dev/openfeature/sdk/multiprovider/MultiProviderHooksTest.java	MultiProvider captures client metadata and a defensive hint snapshot in its provider hook. All five flag types route selected providers through child hook execution. Tests cover callback behavior, provider-specific contexts, metadata, hints, and thread behavior.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant OpenFeatureClient
  participant MultiProvider
  participant MultiProviderHookExecutor
  participant ChildProvider
  participant ChildProviderHooks
  OpenFeatureClient->>MultiProvider: evaluate flag
  MultiProvider->>MultiProviderHookExecutor: execute selected child evaluation
  MultiProviderHookExecutor->>ChildProviderHooks: before
  ChildProviderHooks-->>MultiProviderHookExecutor: enriched evaluation context
  MultiProviderHookExecutor->>ChildProvider: evaluate flag with context
  alt evaluation succeeds
    ChildProvider-->>MultiProviderHookExecutor: evaluation result
    MultiProviderHookExecutor->>ChildProviderHooks: after
  else evaluation returns an error or throws
    ChildProvider-->>MultiProviderHookExecutor: error result or exception
    MultiProviderHookExecutor->>ChildProviderHooks: error
  end
  MultiProviderHookExecutor->>ChildProviderHooks: finallyAfter
  MultiProviderHookExecutor-->>MultiProvider: evaluation result or rethrown exception
  MultiProvider-->>OpenFeatureClient: evaluation result

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Suggested reviewers: toddbaert

Merge Risk: ⚪ Minimal · up to 94ddc

No actionable issue introduced by this change remains; it is ready to merge after normal checks.

Security Architecture Review

Security architecture risk: 🟡 Moderate · up to 62d60

Child hooks may receive incomplete request context when an evaluation uses a worker thread or re-enters the same MultiProvider. This matters if an application relies on those hooks to make security-sensitive decisions. The built-in strategies use the same thread, and no exploitable deployment was established.

Retained concerns

• Medium · security · inferred: A Strategy that evaluates a child on another thread loses captured client metadata and hints; the child hook instead receives MultiProvider metadata and empty hints. This can weaken a hook that depends on request-specific information.
• Medium · security · inferred: Nested evaluation of the same MultiProvider overwrites its single thread-local context; nested cleanup removes it rather than restoring the outer evaluation’s context. Subsequent outer child hooks can therefore lose their request metadata and hints.

Security review details

Security Blast Radius

• inferred — Potential context loss is scoped to evaluations through a MultiProvider instance using off-thread child callbacks or same-instance re-entry; evidence does not establish tenant, service, or deployment-wide exposure.

Security Findings and Attack Paths

• inferred — If an application’s child hook relies on client metadata or hints as a control input, losing those inputs could change its decision. No attacker-controlled registration path, affected control, or realized bypass was verified.

Trust Boundaries and Controls

• observed — Child before hooks can enrich a layered evaluation context for their own provider. Child hook exceptions can affect strategy selection: FirstSuccessfulStrategy may try another provider, whereas FirstMatchStrategy does not generally swallow them.

Resilience and Maintainability Implications

• observed — The executor runs child finally hooks after successful or caught exceptional execution, and the outer provider hook removes its thread-local value in finallyAfter. This supports sequential cleanup but does not restore an overwritten outer value.

Hardening Proposals

• proposed — Pass an immutable request snapshot explicitly through the strategy callback, or define and enforce a same-thread strategy contract; restore the prior snapshot when a nested lifecycle ends. Exercise both cases with security-sensitive hook inputs.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 8.11% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 74 functions across 5 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely states the main change: child provider hooks now execute during multi-provider evaluation.
Description check	✅ Passed	The description directly explains child provider hook execution, hook stages, context propagation, and the related multi-provider objectives.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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[codecov]

Codecov Report

❌ Patch coverage is 97.53086% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.45%. Comparing base (098a594) to head (94ddcb9).

Files with missing lines	Patch %	Lines
...dev/openfeature/sdk/MultiProviderHookExecutor.java	97.61%	0 Missing and 1 partial ⚠️
...v/openfeature/sdk/multiprovider/MultiProvider.java	97.14%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #2005      +/-   ##
============================================
+ Coverage     92.70%   93.45%   +0.74%     
- Complexity      730      757      +27     
============================================
  Files            60       62       +2     
  Lines          1741     1817      +76     
  Branches        203      210       +7     
============================================
+ Hits           1614     1698      +84     
+ Misses           77       69       -8     
  Partials         50       50              

Flag	Coverage Δ
unittests	93.45% <97.53%> (+0.74%)	⬆️

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[sonarqubecloud]

Quality Gate passed

Issues
6 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[toddbaert]

I'll take this over.

[coderabbitai]

Actionable comments posted: 1

---

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🤖 Prompt to fix review comments

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Inline comments:
In `@src/main/java/dev/openfeature/sdk/multiprovider/MultiProvider.java`:
- Around line 283-291: Resolve the HookExecutionContext on the caller thread in
each getXxxEvaluation method before invoking strategy.evaluate, then pass that
captured context into evaluateChild. Update evaluateChild to use the supplied
context rather than calling currentHookExecutionContext inside the provider
function, so child hooks retain the caller’s metadata and hints when custom
strategies run providers on worker threads.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Advanced

Run ID: 043b2031-ed4b-4cdd-989b-f4eaf018b4fe

📥 Commits

Reviewing files that changed from the base of the PR and between 098a594 and 62d60cc.

📒 Files selected for processing (5)

• src/main/java/dev/openfeature/sdk/MultiProviderHookExecutor.java
• src/main/java/dev/openfeature/sdk/multiprovider/HookExecutionContext.java
• src/main/java/dev/openfeature/sdk/multiprovider/MultiProvider.java
• src/test/java/dev/openfeature/sdk/MultiProviderHookExecutorTest.java
• src/test/java/dev/openfeature/sdk/multiprovider/MultiProviderHooksTest.java

Included review availability: Your plan provides up to 2 included reviews per hour; 1 remains after this review.

[sonarqubecloud]

Quality Gate passed

Issues
4 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[toddbaert]

I fundamentally didn't change @jonathannorris ' draft here, except I leveraged the already existing HookSupport from the SDK with a bridging-class, which saved ~300 lines. Tests still passed and haven't changed much.