fix(cli): answer outputStreamsShareDevice from the fds so split terminals keep the stdout mirror

[wmadden-electric]

What this closes

The last piece of the cli-engine 0.1.1 stream-suppression adoption. The engine drops a command's stdout payload when both output streams are TTYs, unless the host says they are separate devices via Runtime.outputStreamsShareDevice. Our bin adapter never set the field, so stdout and stderr routed to two different terminals were still treated as one screen and the machine-readable stdout copy was dropped. (#30057 fixed the data-loss half — every payload now has a human mirror — this fixes the over-suppression half.)

The fix

runtimeFromProcess now compares the device and inode behind the two streams' fds (fstatSync) and answers the field:

• same file identity → true: one screen, mirror suppressed, human copy shown — unchanged behavior
• different identities → false: two sinks, both copies delivered
• no fd on a stream, or fstat fails → field stays absent and the engine keeps its one-screen default, which is the safe common case

This also pre-empts prisma/prisma-cli#198, which makes the field required — when the next engine version lands, this adapter already answers.

Tests

Four new cases in packages/1-framework/3-tooling/cli/test/orm/cli.test.ts driving runtimeFromProcess with real fds: same file twice → true, two files → false, fd-less streams → absent, unstat-able fd → absent.

Verified locally: cli package suite (1425 tests), pnpm typecheck, pnpm lint — all green.

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Runtime detection now reports whether standard output and error streams share the same device when this can be determined.
• Bug Fixes
  • Improved handling of missing or invalid output stream descriptors by returning an indeterminate result instead of failing.
  • Improved configuration loading across environments with more reliable module resolution.
• Tests
  • Added coverage for shared devices, separate devices, unavailable or invalid stream descriptors, and configuration loading.

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📥 Commits

Reviewing files that changed from the base of the PR and between 8f059fb and d83c6ae.

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• packages/1-framework/3-tooling/config-loader/src/load.ts

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📝 Walkthrough

Walkthrough

The CLI detects whether stdout and stderr share a device and inode. The config loader resolves c12 through its canonical path before dynamic import. Tests cover stream identity outcomes.

Changes

Output stream device detection

Layer / File(s)	Summary
Stream identity runtime detection packages/1-framework/3-tooling/cli/src/orm/cli.ts	The runtime reads stream descriptors with fstatSync, compares device/inode identities, and exposes outputStreamsShareDevice.
Stream identity test coverage packages/1-framework/3-tooling/cli/test/orm/cli.test.ts	Tests validate shared, distinct, missing, and invalid descriptors.
Configuration loader resolution

Layer / File(s)	Summary
Canonical c12 dynamic loading packages/1-framework/3-tooling/config-loader/src/load.ts	The loader resolves c12 with createRequire, canonicalizes its entry path with realpathSync, and dynamically imports the resulting file URL.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Merge Risk: ⚪ Minimal · up to d83c6

This change corrects stdout mirroring when output streams target different terminals, while preserving the existing single-screen behavior; no actionable merge-blocking risk remains after normal checks and review.

Suggested reviewers: aqrln

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 60.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: determining output stream identity from file descriptors to preserve split-terminal output behavior.
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 💡 1

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🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/output-streams-share-device

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commit: d83c6ae

[github-actions]

size-limit report 📦

Path	Size
postgres / no-emit	172.72 KB (0%)
postgres / emit	149.89 KB (0%)
mongo / no-emit	101.15 KB (0%)
mongo / emit	91.01 KB (0%)
cf-worker / no-emit	197.16 KB (0%)
cf-worker / emit	171.8 KB (0%)

[wmadden-electric]

The Integration/E2E/Fixtures/Test failures were real but not what they looked like. The first commit's one-line source change flipped tsdown's chunk graph in the cli package, which changed which of Node's module linkers serves config-loader's import('c12'). The synchronous linker skips symlink realpathing, so under pnpm c12 got pinned at its symlinked path where its own dotenv dependency cannot resolve — every config load then failed with CONFIG.EVALUATION_FAILED. Main only passes by luck of the current chunk graph; any cli source change could re-trigger this.

The second commit fixes the class: config-loader now resolves c12's entry with the CommonJS resolver, realpaths it, and imports that file URL, anchoring c12 and its transitive deps at their real locations in every resolver state. Verified locally: repeated contract emit runs green at branch tip, config-loader + cli package suites, the previously failing integration suites, typecheck, lint.