Terminal output buffers can grow unbounded causing memory leaks

[hannesrudolph]

Problem

Terminal process implementations retain command output buffers for too long. When commands produce large output, these buffers can grow unbounded and keep large strings in memory, leading to steadily increasing memory usage and causing grey screens.

Expected behavior

After a command completes, large output buffers should be trimmed and/or cleared so finished commands do not keep large output in memory.

Impact

Running commands with large output can cause significant memory growth over time (potentially a leak-like behavior).

Repro Steps

Run this commend in code mode

This is a test. Use execute_command with `seq 1 2000000`, wait for it to complete, then repeat this 40 more times. Do not attempt to do this all in one go. execute_command needs to be called 41 times before we are considered complete.

Related

Originated from PR #7666.

[roomote]

I've analyzed this issue and reviewed the existing PR #7666 along with the feedback from daniel-lxs about the timing issue. Here's my proposed implementation plan:

Problem Analysis

The fullOutput buffer in TerminalProcess and ExecaTerminalProcess is never cleared after output has been consumed. This causes memory to grow unbounded when running commands with large output.

The existing PR #7666 attempted to fix this by setting lastRetrievedIndex = fullOutput.length when the command completes, but this incorrectly marks output as "retrieved" before getEnvironmentDetails() has a chance to actually consume it via getUnretrievedOutput().

Proposed Solution

Add a trimRetrievedOutput() method to BaseTerminalProcess that trims only the output that has actually been consumed (i.e., output before lastRetrievedIndex):

1. Add trimRetrievedOutput() to BaseTerminalProcess:

   • Trim fullOutput to remove characters before lastRetrievedIndex
   • Reset lastRetrievedIndex to 0 after trimming
   • This only clears memory for output that has been read via getUnretrievedOutput()

2. Call trimRetrievedOutput() in getUnretrievedOutput() for both TerminalProcess and ExecaTerminalProcess:

   • After advancing lastRetrievedIndex, call trimRetrievedOutput() to release memory
   • This ensures memory is freed as output is consumed, not prematurely

3. Call trimRetrievedOutput() in BaseTerminal.getUnretrievedOutput():

   • After iterating through completed processes, trim their buffers

This approach:

• Prevents memory leaks by clearing consumed output
• Preserves the timing contract - output is only cleared after being consumed
• Does not break the "Inactive Terminals with Completed Process Output" feature in getEnvironmentDetails.ts

Please mention @roomote in a comment saying that you approve this plan, and I'll proceed with the implementation.