fix: prevent memory leaks from SSE streams, LSP, Bus, and process cleanup

[brendandebeasi]

Issue for this PR

Fixes #15645
Relates to #10913, #9140, #11696, #9156, #14091, #15592

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Fixes multiple memory leaks that cause OpenCode's memory usage to grow unbounded over time, particularly during long-running sessions.

Memory leak fixes (always active)

Fix	Issues	File	Change
SSE cleanup	#15645	server.ts, global.ts, routes.ts	done flag + writeSSE error handling + unsub on abort
LSP shutdown	#10913, #9140	client.ts	diagnostics.clear() + reset files Map in shutdown
Bus dispose	#10913	bus/index.ts	subscriptions.clear() after dispose callback
ACP stdin	#11696	acp.ts	.on() → .once() for end/error listeners
GitHub unsub	#9156	github.ts	Capture + call Bus.subscribe return in finally block
Process exit	#10913, #14091	index.ts	Instance.disposeAll() with 5s timeout before process.exit()

Debug tooling (always available, zero overhead)

• Bus.debug() — subscription count introspection per event type
• Instance.debug() — cache state inspection
• State.debug() — state entry counts
• GET /debug/memory — on-demand runtime memory diagnostics endpoint
• SIGUSR1 signal — captures heap snapshot + diagnostic report to ~/.local/share/opencode/diagnostics/

Memory monitoring (opt-in via OPENCODE_DIAGNOSTICS=1)

The polling monitor and auto-kill are disabled by default. To enable:

OPENCODE_DIAGNOSTICS=1 opencode

When enabled:

• 30s polling interval checks RSS usage
• 2GB warning — logs heap stats + writes periodic diagnostic reports (60s cooldown)
• 4GB kill (configurable via OPENCODE_MEMORY_LIMIT=N in GB) — writes heap snapshot + diagnostic report, then exits
• Kill threshold formula: max(2GB, min(25% total RAM, 4GB))

How did you verify your code works?

• All modified files pass LSP diagnostics
• Type errors are pre-existing (3 TUI errors: Property 'tui' does not exist on type 'Config' — unrelated to this PR)
• Diagnostics opt-in verified: without OPENCODE_DIAGNOSTICS=1, only SIGUSR1 handler is registered (no polling, no kill)
• With OPENCODE_DIAGNOSTICS=1, full monitoring loop activates

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential duplicate/related PRs found:

1. fix: consolidate memory leak fixes from #14650 and #8953 #15435 - "fix: consolidate memory leak fixes from fix: resolve memory leak issues across multiple subsystems #14650 and feat(bash): stream large output to tmpfile with filtering and GC #8953"

   • Related to memory leak fixes with potential overlap in SSE/Bus listener cleanup scope

2. fix: resolve memory leak issues across multiple subsystems #14650 - "fix: resolve memory leak issues across multiple subsystems"

   • Addresses broader memory leak issues that may include SSE stream handling

3. fix(core): add dispose functions to prevent subscription memory leaks #7032 - "fix(core): add dispose functions to prevent subscription memory leaks"

   • Earlier work on subscription memory leak prevention that may be relevant to Bus listener cleanup

These PRs all address memory leak issues in similar areas. Review #15435 and #14650 particularly to ensure the SSE stream cleanup in PR #15646 doesn't duplicate existing fixes or conflict with prior memory leak consolidation efforts.

[brendandebeasi]

Reviewed the related PRs flagged above — this PR is complementary, not duplicative:

• fix: consolidate memory leak fixes from #14650 and #8953 #15435 and fix: resolve memory leak issues across multiple subsystems #14650 address memory leaks in session management, LSP, MCP, event-reducer, and SDK SSE client-side handling. Neither touches the server-side SSE stream handlers in server.ts or routes/global.ts.
• fix(core): add dispose functions to prevent subscription memory leaks #7032 adds dispose() functions and Bus subscription test helpers. It adds _getSubscriptionCount() / _getTotalSubscriptionCount() to bus/index.ts — our Bus.debug() is in the same area but serves a different purpose (runtime diagnostics vs test helpers). Minor merge conflict at worst, easy to resolve.

The core fix in this PR — awaiting writeSSE() calls, catching write errors to detect dead connections, and cleaning up Bus listeners + heartbeat intervals on failure — is not addressed by any of the other open PRs. Those PRs fix leaks in other subsystems; this one fixes the SSE stream handler leak path specifically.

[binarydoubling]

FYI there are now multiple PRs tackling memory leaks from different angles — #16695 (TUI listener cleanup, Maps/Sets eviction, timer cleanup), #16730 (database bloat, SQLite config), #16346 (plugin subscriber stacking, msgs retention), #14650 (subagent deallocation, event-reducer caps). Lots of file overlap across all of these. Might be worth coordinating merges to avoid conflict hell.