Increase default payload size threshold from 1KB to 10KB (#807)

Raises the inline payload threshold to accommodate larger tool responses
before falling back to disk storage.

## Changes

- **Constants**: Updated `DefaultPayloadSizeThreshold` from `1024` to
`10240` in:
  - `internal/config/config_payload.go`
  - `internal/cmd/flags_logging.go`
  
- **Documentation**: Updated comments to reflect 10KB default in
`config_core.go` and `config_payload.go`

- **Tests**: Updated test expectations in `flags_logging_test.go`

## Behavior

Payloads ≤ 10KB now returned inline; larger payloads stored to disk at
`{payloadDir}/{sessionID}/{queryID}/payload.json`.

Threshold remains configurable via `--payload-size-threshold` flag,
`MCP_GATEWAY_PAYLOAD_SIZE_THRESHOLD` env var, or
`payload_size_threshold` config field.

> [!WARNING]
>
> <details>
> <summary>Firewall rules blocked me from connecting to one or more
addresses (expand for details)</summary>
>
> #### I tried to connect to the following addresses, but was blocked by
firewall rules:
>
> - `example.com`
> - Triggering command: `/tmp/go-build2815537700/b275/launcher.test
/tmp/go-build2815537700/b275/launcher.test
-test.testlogfile=/tmp/go-build2815537700/b275/testlog.txt
-test.paniconexit0 -test.timeout=10m0s -test.v=true
/opt/hostedtoolcache/go/1.25.6/x64/src/runtime/cgo1.25.6 cfg
64/pkg/tool/linux_amd64/vet -pthread -Wl,--no-gc-sect-unsafeptr=false
-fmessage-length/tmp/go-build1973070374/b003/vet.cfg
64/pkg/tool/linux_amd64/vet 6552��
/opt/hostedtoolcache/go/1.25.6/x64/src/runtime/c-errorsas cfg
nfig/composer/vendor/bin/as --gdwarf-5 --64 -o as` (dns block)
> - `invalid-host-that-does-not-exist-12345.com`
> - Triggering command: `/tmp/go-build67267443/b001/config.test
/tmp/go-build67267443/b001/config.test
-test.testlogfile=/tmp/go-build67267443/b001/testlog.txt
-test.paniconexit0 -test.timeout=10m0s -test.v=true go --global
64/bin/as user.email` (dns block)
> - `nonexistent.local`
> - Triggering command: `/tmp/go-build2815537700/b275/launcher.test
/tmp/go-build2815537700/b275/launcher.test
-test.testlogfile=/tmp/go-build2815537700/b275/testlog.txt
-test.paniconexit0 -test.timeout=10m0s -test.v=true
/opt/hostedtoolcache/go/1.25.6/x64/src/runtime/cgo1.25.6 cfg
64/pkg/tool/linux_amd64/vet -pthread -Wl,--no-gc-sect-unsafeptr=false
-fmessage-length/tmp/go-build1973070374/b003/vet.cfg
64/pkg/tool/linux_amd64/vet 6552��
/opt/hostedtoolcache/go/1.25.6/x64/src/runtime/c-errorsas cfg
nfig/composer/vendor/bin/as --gdwarf-5 --64 -o as` (dns block)
> - `slow.example.com`
> - Triggering command: `/tmp/go-build2815537700/b275/launcher.test
/tmp/go-build2815537700/b275/launcher.test
-test.testlogfile=/tmp/go-build2815537700/b275/testlog.txt
-test.paniconexit0 -test.timeout=10m0s -test.v=true
/opt/hostedtoolcache/go/1.25.6/x64/src/runtime/cgo1.25.6 cfg
64/pkg/tool/linux_amd64/vet -pthread -Wl,--no-gc-sect-unsafeptr=false
-fmessage-length/tmp/go-build1973070374/b003/vet.cfg
64/pkg/tool/linux_amd64/vet 6552��
/opt/hostedtoolcache/go/1.25.6/x64/src/runtime/c-errorsas cfg
nfig/composer/vendor/bin/as --gdwarf-5 --64 -o as` (dns block)
> - `this-host-does-not-exist-12345.com`
> - Triggering command: `/tmp/go-build2815537700/b284/mcp.test
/tmp/go-build2815537700/b284/mcp.test
-test.testlogfile=/tmp/go-build2815537700/b284/testlog.txt
-test.paniconexit0 -test.timeout=10m0s -test.v=true
/opt/hostedtoolcache/go/1.25.6/x64/src/runtime/c-c=4 cfg
64/pkg/tool/linux_amd64/vet --gdwarf-5 --64 -o
64/pkg/tool/linux_amd64/vet 6552�� ache/go/1.25.6/x64/src/net cfg .test
--gdwarf-5 --64 -o .test` (dns block)
>
> If you need me to access, download, or install something from one of
these locations, you can either:
>
> - Configure [Actions setup
steps](https://gh.io/copilot/actions-setup-steps) to set up my
environment, which run before the firewall is enabled
> - Add the appropriate URLs or hosts to the custom allowlist in this
repository's [Copilot coding agent
settings](https://github.com/github/gh-aw-mcpg/settings/copilot/coding_agent)
(admins only)
>
> </details>

<!-- START COPILOT CODING AGENT TIPS -->
---

💡 You can make Copilot smarter by setting up custom instructions,
customizing its development environment and configuring Model Context
Protocol (MCP) servers. Learn more [Copilot coding agent
tips](https://gh.io/copilot-coding-agent-tips) in the docs.

Author: lpcox

internal/cmd/flags_logging.go

@@ -13,7 +13,7 @@ import (
 const (
 	defaultLogDir               = "/tmp/gh-aw/mcp-logs"
 	defaultPayloadDir           = "/tmp/jq-payloads"
-	defaultPayloadSizeThreshold = 1024 // 1KB default threshold
+	defaultPayloadSizeThreshold = 10240 // 10KB default threshold
 )
 
 // Logging flag variables

internal/cmd/flags_logging_test.go

@@ -71,7 +71,7 @@ func TestPayloadSizeThresholdFlagDefault(t *testing.T) {
 	os.Unsetenv("MCP_GATEWAY_PAYLOAD_SIZE_THRESHOLD")
 
 	result := getDefaultPayloadSizeThreshold()
-	assert.Equal(t, 1024, result, "Default should be 1024 bytes")
+	assert.Equal(t, 10240, result, "Default should be 10240 bytes")
 }
 
 func TestPayloadSizeThresholdEnvVar(t *testing.T) {

internal/config/config_core.go

@@ -57,7 +57,7 @@ type GatewayConfig struct {
 
 	// PayloadSizeThreshold is the size threshold (in bytes) for storing payloads to disk.
 	// Payloads larger than this threshold are stored to disk, smaller ones are returned inline.
-	// Default: 1024 bytes (1KB)
+	// Default: 10240 bytes (10KB)
 	PayloadSizeThreshold int `toml:"payload_size_threshold" json:"payload_size_threshold,omitempty"`
 }
 

internal/config/config_payload.go

@@ -7,8 +7,8 @@ const DefaultPayloadDir = "/tmp/jq-payloads"
 
 // DefaultPayloadSizeThreshold is the default size threshold (in bytes) for storing payloads to disk.
 // Payloads larger than this threshold are stored to disk, smaller ones are returned inline.
-// Default: 1024 bytes (1KB)
-const DefaultPayloadSizeThreshold = 1024
+// Default: 10240 bytes (10KB)
+const DefaultPayloadSizeThreshold = 10240
 
 func init() {
 	// Register default setter for PayloadDir and PayloadSizeThreshold