fix(kotlin): stop public extensions from swallowing coroutine cancellation

[ayaangazali]

What

Follow-up to the pattern from #563: four public extension sites catch Throwable, which also traps kotlinx.coroutines.CancellationException (and JVM Errors). This breaks Kotlin's cooperative cancellation contract, a cancelled coroutine should stop, not keep going.

Sites

1. loadModel (RunAnywhereModelLifecycle.kt:51): the ensureServicesReady() guard ate the caller's cancellation, so task.cancel() during init still ran the heavy native load afterwards. Now rethrows cancellation and swallows only Exception, same as the reviewed #563 registry fix.
2. transcribeStream (RunAnywhereSTT.kt:112): collector cancellation got converted into a synthetic "STT stream failed" final partial. Now cancellation propagates; real errors still produce the failure partial and close the flow.
3. synthesizeStream (RunAnywhereTTS.kt:131): normal cancellation logged a spurious "synthesizeStream errored" warning. Now rethrows; teardown is unchanged because close() lives in the finally.
4. downloadModel cleanup (RunAnywhereDownload.kt:149): being honest, this one is NOT a cancellation bug. The block runs under NonCancellable and the original CancellationException keeps propagating after the finally either way. I only narrowed Throwable to Exception so the best-effort native cancel doesn't log-and-ignore JVM Errors. Happy to drop this hunk if you'd rather keep the change minimal.

Why the two-clause pattern

On the JVM CancellationException extends Exception (via java.util.concurrent.CancellationException), so just narrowing Throwable to Exception would still swallow it. The explicit catch (e: CancellationException) { throw e } clause first is required. Import used is kotlinx.coroutines.CancellationException, matching the existing usage in NativeUnaryRequest.kt:8 and ToolCallingOrchestrator.kt:31.

Testing

From a clean worktree of main: :compileDebugKotlin (no local natives), :ktlintCheck, :testDebugUnitTest, :detekt all pass.

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Small note for transparency: I'm a freshman learning by contributing here. I found these by systematically comparing the Kotlin extensions against the Swift ones after you merged my earlier registry fix, and I bounced my reasoning off Claude Code before writing anything. If any of these catches were intentionally broad, tell me and I'll adjust or revert those hunks. Thanks for the quick reviews so far, it genuinely made my week :)

Summary by CodeRabbit

• Bug Fixes
  • Improved cancellation handling across model loading, speech-to-text streaming, speech synthesis, and model downloads.
  • Canceled operations now stop cleanly instead of being reported as generic failures.
  • Preserved existing error reporting for non-cancellation failures.

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[coderabbitai]

📝 Walkthrough

Walkthrough

Kotlin SDK exception handling now preserves coroutine cancellation in model loading, STT streaming, and TTS streaming, while native download cancellation narrows its catch block from Throwable to Exception.

Changes

Coroutine cancellation handling

Layer / File(s)	Summary
Propagate cancellation across SDK operations sdk/runanywhere-kotlin/src/main/kotlin/com/runanywhere/sdk/public/extensions/{Models,STT,TTS,Storage}/*	Model loading, STT streaming, and TTS streaming rethrow CancellationException; native download cancellation catches Exception instead of Throwable.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: copilot, sanchitmonga22

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Description check	⚠️ Warning	The description covers the change, but it does not follow the repository template sections or required checklists.	Add the required template sections: Description, Type of Change, Testing, platform-specific testing, Labels, Checklist, and Screenshots.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the main change: preserving coroutine cancellation in public Kotlin extensions.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

🧹 Nitpick comments (1)

sdk/runanywhere-kotlin/src/main/kotlin/com/runanywhere/sdk/public/extensions/TTS/RunAnywhereTTS.kt (1)

151-151: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Narrow exception handling to avoid swallowing JVM errors.

Consider replacing catch (t: Throwable) with catch (t: Exception) for the native stop() call, aligning with the native download cancellation changes in this PR. Based on learnings, you should avoid catching Throwable/Error to ensure that critical JVM Error subclasses (like OutOfMemoryError) are allowed to propagate.

♻️ Proposed refactor

-                    } catch (t: Throwable) {
+                    } catch (t: Exception) {

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In
`@sdk/runanywhere-kotlin/src/main/kotlin/com/runanywhere/sdk/public/extensions/TTS/RunAnywhereTTS.kt`
at line 151, Update the exception handler around the native TTS stop call in
RunAnywhereTTS to catch Exception instead of Throwable, allowing critical JVM
Error subclasses to propagate while preserving handling of ordinary operation
failures.

Source: Learnings

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In
`@sdk/runanywhere-kotlin/src/main/kotlin/com/runanywhere/sdk/public/extensions/TTS/RunAnywhereTTS.kt`:
- Line 151: Update the exception handler around the native TTS stop call in
RunAnywhereTTS to catch Exception instead of Throwable, allowing critical JVM
Error subclasses to propagate while preserving handling of ordinary operation
failures.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 6fdd15c9-0e93-44a1-a24a-d9488b8b0524

📥 Commits

Reviewing files that changed from the base of the PR and between 541842a and 129461a.

📒 Files selected for processing (4)

• sdk/runanywhere-kotlin/src/main/kotlin/com/runanywhere/sdk/public/extensions/Models/RunAnywhereModelLifecycle.kt
• sdk/runanywhere-kotlin/src/main/kotlin/com/runanywhere/sdk/public/extensions/STT/RunAnywhereSTT.kt
• sdk/runanywhere-kotlin/src/main/kotlin/com/runanywhere/sdk/public/extensions/Storage/RunAnywhereDownload.kt
• sdk/runanywhere-kotlin/src/main/kotlin/com/runanywhere/sdk/public/extensions/TTS/RunAnywhereTTS.kt