[debugmcpdev]

What

Removes ChildSessionManager's own "cannot adopt → release undebugged" branch — #501's original lever — and the bookkeeping that existed only for it: releasedTargets, releaseUndebugged, waitForReadySignal, the 'released'/'release-failed' outcomes, and MinimalDapClient's rollback on those outcomes (−426/+73 over 6 files). Pure refactor: no reachable path changes behaviour.

Why it is unreachable

Since #1094 every js-debug startDebugging report after the program's own is relayed as a child report before it can reach ChildSessionManager.createChildSession:

• on the root connection, adapter-policy-js.ts handleReverseRequest returns childReport for every report once context.adoptedTargets.size > 0 (the id is added before the first adoption runs);
• on every other connection, createChildSafePolicy returns childReport for every report.

The worker's holder then adopts or releases the report (throwaway-release.ts). createChildSession is called from minimal-dap.ts only (two sites), and only for the program's own first target. The manager's second copy of the release therefore had no caller left.

What replaces it

An invariant: a second pending target reaching the manager while a child is active or being adopted is a routing bug, so the manager logs it and throws by name instead of acking it with nothing attached — the ack-with-nothing is exactly what parks the process forever (#501). MinimalDapClient's existing catch rolls the id back.

Tests

• Five js attach to a Node process that forks children strands those children (second startDebugging target ignored, child waits forever) #501 manager cases and two minimal-dap client cases that pinned the deleted outcomes are removed; the DAP trace: no parent/child connection discriminator — frames from all sockets interleave with independent seq spaces #518 trace case keeps its adoption half.
• Two new cases pin the invariant throw.
• The session tree M2: js-debug forks as debug sessions — N targets per tree, #501's release stays the fallback (#1005 part B) #1082 relay cases assert that no connection is opened for a fork (instances length 1).
• docs/javascript/spike-notes-forks.md now points at throwaway-release.ts for the lever.

Gates run locally: the two unit files (178/178), npm run lint, npm run typecheck:all, and the JS tree/attach/cascade/launch-config integration suites (32/32) against build:ci; the pre-push hook ran the full unit and integration projects on push.

No changelog fragment: pure refactor (no-changelog).

Refs #1082, #1094, #501.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 80.00000% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/proxy/minimal-dap.ts	50.00%	1 Missing ⚠️

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